WO2020012809A1 - Nickel metal hydride battery - Google Patents

Nickel metal hydride battery Download PDF

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Publication number
WO2020012809A1
WO2020012809A1 PCT/JP2019/021270 JP2019021270W WO2020012809A1 WO 2020012809 A1 WO2020012809 A1 WO 2020012809A1 JP 2019021270 W JP2019021270 W JP 2019021270W WO 2020012809 A1 WO2020012809 A1 WO 2020012809A1
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active material
electrode active
positive electrode
negative electrode
hydrogen storage
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PCT/JP2019/021270
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French (fr)
Japanese (ja)
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佐々木　博之
岳太 岡西
正人 穂積
素宜 奥村
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株式会社豊田自動織機
トヨタ自動車株式会社
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/24—Alkaline accumulators
    • H01M10/30—Nickel accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a nickel metal hydride battery.
  • a nickel metal hydride battery is a secondary battery including a positive electrode having a nickel oxide compound such as nickel hydroxide as a positive electrode active material, a negative electrode having a hydrogen storage alloy as a negative electrode active material, and an electrolytic solution comprising an aqueous alkali metal solution. It is.
  • Cobalt added to the positive electrode contacts an electrolytic solution that is a strongly basic aqueous solution to form cobalt complex ions, and then precipitates on the positive electrode as cobalt hydroxide.
  • the cobalt hydroxide is oxidized to produce cobalt oxyhydroxide having excellent conductivity. It is believed that a conductive network is formed on the positive electrode due to the cobalt oxyhydroxide generated here.
  • Patent Literature 1 discloses that a nickel metal hydride battery containing metal cobalt and cobalt hydroxide in the positive electrode is charged, so that the metal cobalt and the cobalt hydroxide contained in the positive electrode are oxidized to form oxywater. It is stated that cobalt oxide was formed (see paragraphs 0030 and 0032 for the examples).
  • Patent Literature 2 discloses a technique in which a nickel metal hydride battery containing metal cobalt in a positive electrode is charged to change cobalt contained in the positive electrode into cobalt oxyhydroxide having high conductivity. (Eg paragraph 0007).
  • Patent Document 3 discloses that a hydrogen storage alloy having a CaCu 5- type crystal structure and comprising a rare earth element and an alloy containing Ni, Co, Mn, and Al is immersed in an aqueous sodium hydroxide solution. A technique for washing with water is described. The document describes that by immersing the above-described hydrogen storage alloy in an aqueous sodium hydroxide solution, the hydrogen storage alloy becomes in a state of being coated with nickel.
  • the industry is eager for a nickel metal hydride battery that exhibits excellent properties.
  • the present invention has been made in view of such circumstances, and has as its object to provide a new nickel metal hydride battery exhibiting excellent battery characteristics.
  • the present inventor has proposed that a nickel metal hydride battery containing metal cobalt in the positive electrode be charged to convert cobalt contained in the positive electrode into cobalt oxyhydroxide having high conductivity.
  • a technique in which a layer of cobalt oxyhydroxide is previously formed around the positive electrode active material was recalled.
  • the layer of cobalt oxyhydroxide is doped with an alkali metal, particularly lithium or sodium. By doing so, it was found that the conductivity of the positive electrode active material was significantly improved.
  • the present inventor studied a negative electrode simultaneously with a positive electrode, and surprisingly, a nickel metal hydride battery employing a hydrogen storage alloy having a high oxygen content as a negative electrode active material was effective in reducing battery resistance. I found that there is.
  • the nickel metal hydride battery of the present invention A cathode active material coated with a cobalt oxyhydroxide layer containing lithium or sodium, A negative electrode active material having an oxygen concentration of 1000 ppm or more before charge and discharge, It is characterized by having.
  • the nickel metal hydride battery of the present invention has excellent battery characteristics.
  • FIG. 6 is a schematic cross-sectional view of a bipolar nickel metal hydride battery of Application Example 1.
  • FIG. 6 is a schematic cross-sectional view of a bipolar nickel metal hydride battery of Application Example 1.
  • the numerical range “ab” described herein includes the lower limit a and the upper limit b.
  • a numerical range can be formed by arbitrarily combining these upper and lower limits and the numerical values listed in the examples.
  • numerical values arbitrarily selected from within these numerical ranges can be used as new upper and lower numerical values.
  • the nickel metal hydride battery of the present invention A cathode active material coated with a cobalt oxyhydroxide layer containing lithium or sodium (hereinafter, may be referred to as a cathode active material of the present invention); A negative electrode active material having an oxygen concentration of 1000 ppm or more before charge and discharge (hereinafter, sometimes referred to as a negative electrode active material of the present invention); It is characterized by having.
  • the positive electrode active material of the present invention includes a cobalt oxyhydroxide layer containing lithium or sodium and cobalt oxyhydroxide, and a positive electrode active material body coated with the cobalt oxyhydroxide layer (in the present specification, simply referred to as a “positive electrode”). Active material ”).
  • the positive electrode active material is not limited as long as it is used as a positive electrode active material of a nickel metal hydride battery.
  • Specific examples of the positive electrode active material include nickel hydroxide and nickel hydroxide doped with a metal.
  • Examples of the metal to be doped into nickel hydroxide include Group 2 elements such as magnesium and calcium, Group 9 elements such as cobalt, rhodium and iridium, and Group 12 elements such as zinc and cadmium.
  • the method of forming a cobalt oxyhydroxide layer containing lithium or sodium and cobalt oxyhydroxide on the positive electrode active material main body includes the following steps P-1) and P-2).
  • a step of forming a cobalt hydroxide layer on the surface of the positive electrode active material P-2) The positive electrode active material on which the cobalt hydroxide layer is formed is heated to convert the cobalt hydroxide layer to a cobalt oxyhydroxide layer And doping the cobalt hydroxide layer or the cobalt oxyhydroxide layer with lithium or sodium.
  • P-1-1) A step of preparing a dispersion in which the positive electrode active material is dispersed in an aqueous solution of a cobalt salt, making the pH of the dispersion alkaline, and depositing cobalt hydroxide on the surface of the positive electrode active material.
  • 1-2) a step of producing a dispersion in which the positive electrode active material is dispersed in an alkaline aqueous solution, and adding an aqueous cobalt salt solution to the dispersion to precipitate cobalt hydroxide on the surface of the positive electrode active material
  • cobalt salt examples include cobalt sulfate, cobalt nitrate, and cobalt chloride.
  • the heating temperature in the step can be, for example, 70 to 230 ° C. or 80 to 200 ° C.
  • the atmosphere in the step P-2) is an oxygen-containing atmosphere.
  • the step P-2) is preferably performed in the presence of air from the viewpoint of cost.
  • lithium or sodium may be doped with respect to the cobalt hydroxide layer before heating, or to the cobalt hydroxide layer or cobalt oxyhydroxide layer during heating.
  • a method of spraying a lithium salt aqueous solution or a sodium salt aqueous solution on the positive electrode active material is preferable.
  • the surface of the positive electrode active material is heated.
  • Lithium or sodium is doped into the cobalt oxyhydroxide layer (or the cobalt hydroxide layer before conversion to the cobalt oxyhydroxide layer).
  • the heating temperature in the method of doping with lithium or sodium it is reasonable to perform the heating at the same temperature as the heating temperature in converting the cobalt hydroxide layer to the cobalt oxyhydroxide layer in the step P-2).
  • lithium salts include lithium hydroxide, lithium sulfate, lithium nitrate, lithium chloride, lithium acetate, lithium trifluoromethanesulfonate, and lithium bis (trifluoromethanesulfonyl) imide.
  • sodium salts include sodium hydroxide, sodium sulfate, sodium nitrate, sodium chloride, sodium acetate, sodium trifluoromethanesulfonate, and sodium bis (trifluoromethanesulfonyl) imide.
  • step P-2 not only lithium or sodium but also lithium and sodium may be doped, or another alkali metal may be doped.
  • another alkali metal potassium can be exemplified.
  • a method of doping other alkali metals a method of spraying an aqueous solution of an alkali metal salt is preferable, similarly to the method of doping lithium or sodium.
  • the cobalt oxyhydroxide layer has a conductive property together with ⁇ -CoOOH, which has poor conductivity among CoOOH. It is considered that Co 3 O 4 having poor properties is formed. In Co 3 O 4 , cobalt exists in both divalent and trivalent states.
  • the cobalt oxyhydroxide layer when a cobalt oxyhydroxide layer is formed on the positive electrode active material by using a method of doping an alkali metal other than lithium, the cobalt oxyhydroxide layer has ⁇ -CoOOH, which is superior in conductivity among CoOOH. Are formed, but it is considered that Co 3 O 4 having poor conductivity is also formed.
  • the cobalt oxyhydroxide layer is formed on the positive electrode active material by using a lithium doping method, even if Co 3 O 4 having poor conductivity is formed, at least Co 3 O 4 is formed due to the presence of lithium. It is considered that a part of 3 O 4 is converted to LiCoO 2 having excellent conductivity. Then, when the cobalt oxyhydroxide layer is formed on the positive electrode active material using the lithium doping method, the cobalt oxyhydroxide layer contains a large amount of ⁇ -CoOOH having excellent conductivity among CoOOH, Although there is LiCoO 2 having relatively excellent conductivity, the proportion of Co 3 O 4 having poor conductivity is considered to be extremely low.
  • the resistivity of ⁇ -CoOOH is about 2 ⁇ ⁇ cm
  • the resistivity of LiCoO 2 is about 1 ⁇ 10 2 ⁇ ⁇ cm
  • the resistivity of Co 3 O 4 is about 1 ⁇ 10 6 ⁇ ⁇ cm
  • ⁇ -The resistivity of CoOOH is approximately 1 ⁇ 10 8 ⁇ ⁇ cm.
  • Both ⁇ -CoOOH and LiCoO 2 which are excellent in conductivity, are trivalent.
  • cobalt of the raw material cobalt hydroxide is divalent, and that Co 3 O 4 has both divalent and trivalent cobalt
  • the oxyhydroxide of the positive electrode active material of the present invention is considered. The higher the valence of cobalt in the cobalt layer, the better.
  • the valence of cobalt in the cobalt oxyhydroxide layer of the positive electrode active material of the present invention is preferably 2.9 to 3.2, more preferably 2.95 to 3.1, and further preferably 2.98 to 3.07. preferable.
  • the valence of cobalt is a value obtained by measuring the valence of cobalt in the cobalt oxyhydroxide layer present on the surface of the positive electrode active material of the present invention by an iodometry method.
  • the content of cobalt in the positive electrode active material of the present invention is preferably 1 to 10% by mass, more preferably 2 to 7% by mass, and still more preferably 3 to 7% by mass.
  • the content of lithium in the positive electrode active material of the present invention is preferably 0.01 to 0.3% by mass, more preferably 0.04 to 0.2% by mass, and still more preferably 0.07 to 0.1% by mass.
  • the content of sodium in the positive electrode active material of the present invention is preferably 0.01 to 1% by mass, more preferably 0.1 to 0.6% by mass, and further preferably 0.2 to 0.5% by mass.
  • the content of the alkali metal other than lithium and sodium in the positive electrode active material of the present invention is 0% by mass, 0.01 to 1% by mass, 0.1 to 0.6% by mass, 0.2 to 0.5% by mass. % Can be exemplified.
  • the positive electrode active material of the present invention is preferably in a powder state, and has an average particle diameter of preferably 3 to 40 ⁇ m, more preferably 5 to 30 ⁇ m, and further preferably 7 to 20 ⁇ m.
  • the average particle diameter means a value of D 50 in the measurement using a conventional laser diffraction particle size distribution analyzer.
  • the BET specific surface area of the positive electrode active material of the present invention preferably 5 ⁇ 30m 2 / g, more preferably from 10 ⁇ 20m 2 / g, more preferably 12 ⁇ 18m 2 / g.
  • the resistivity of the positive electrode active material of the present invention is preferably 0.1 to 40 ⁇ ⁇ cm, more preferably 0.1 to 10 ⁇ ⁇ cm, further preferably 0.1 to 7 ⁇ ⁇ cm, and 0.1 to 5 ⁇ ⁇ cm. Is particularly preferable, and 0.1 to 4 ⁇ ⁇ cm is most preferable.
  • the negative electrode active material of the present invention is substantially a material obtained by oxidizing the surface of a hydrogen storage alloy.
  • the negative electrode active material of the present invention has an oxygen concentration of 1000 ppm or more before charge and discharge.
  • the oxygen concentration is preferably in the range of 1000 to 90000 ppm, more preferably in the range of 5000 to 80000 ppm, still more preferably in the range of 10,000 to 60000 ppm, particularly preferably in the range of 15,000 to 50,000 ppm, and more preferably in the range of 18,000 to 45,000 ppm. Within the range is most preferred.
  • the oxygen concentration of the negative electrode active material may be such that the oxygen concentration before charging / discharging the nickel metal hydride battery including the negative electrode active material is within the above range. Note that during charging and discharging of the nickel metal hydride battery, the oxygen concentration of the negative electrode active material may fluctuate.
  • the oxygen concentration of the negative electrode active material of the present invention may be interpreted as a value “before battery production” or “at the time of battery production”, or “before electrode production” or “at the time of electrode production”.
  • the average particle size of the negative electrode active material of the present invention is preferably in the range of 1 to 40 ⁇ m, more preferably in the range of 3 to 30 ⁇ m, further preferably in the range of 4 to 20 ⁇ m, and particularly preferably in the range of 5 to 15 ⁇ m. Most preferably in the range of 5 to 12 ⁇ m.
  • the BET specific surface area of the negative electrode active material of the present invention preferably 0.2 ⁇ 10.0m 2 / g, more preferably 0.5 ⁇ 8.0m 2 / g, 1.0 ⁇ 6.0m 2 / g Is more preferred.
  • the saturation magnetization of those containing Ni is preferably 0.2 to 10 emu / g, more preferably 0.5 to 9 emu / g, and still more preferably 1 to 8 emu / g. , 1.5 to 7 emu / g are particularly preferred.
  • the hydrogen storage alloy in the negative electrode active material is not limited as long as it is used as a negative electrode active material of a nickel metal hydride battery.
  • the hydrogen storage alloy is basically an alloy of a metal A, which easily reacts with hydrogen but is inferior in hydrogen releasing ability, and a metal B which hardly reacts with hydrogen but has excellent hydrogen releasing ability.
  • Metal hereinafter, may be abbreviated as Mm), Pd and the like can be exemplified.
  • Mm Metal
  • Pd and the like can be exemplified.
  • B include Fe, Co, Ni, Cr, Pt, Cu, Ag, Mn, Zn, and Al.
  • Specific hydrogen-absorbing alloy AB 5 type showing a hexagonal CaCu 5 type crystal structure, hexagonal MgZn 2 type or AB 2 type showing a cubic MgCu 2 type crystal structure, AB type indicating the cubic CsCl-type crystal structure , a 2 B type denoting hexagonal Mg 2 Ni-type crystal structure, solid solution showing a body-centered cubic structure, and, AB 5 type and AB 2 type AB 3 type crystal structure are combined in, a 2 B 7 It can be exemplified of a type and a 5 B 19 type.
  • the hydrogen storage alloy may have one of the above crystal structures, or may have a plurality of the above crystal structures.
  • AB 5 type hydrogen storage alloy can be exemplified by LaNi 5, CaCu 5, MmNi 5 .
  • Examples of the AB 2 type hydrogen storage alloy include MgZn 2 , ZrNi 2 , and ZrCr 2 .
  • Examples of the AB-type hydrogen storage alloy include TiFe and TiCo.
  • Examples of the A 2 B type hydrogen storage alloy include Mg 2 Ni and Mg 2 Cu.
  • Examples of solid solution type hydrogen storage alloys include Ti-V, V-Nb, and Ti-Cr.
  • CeNi 3 can be exemplified as the AB 3 type hydrogen storage alloy.
  • Ce 2 Ni 7 can be exemplified as the A 2 B 7 type hydrogen storage alloy.
  • Examples of the A 5 B 19 type hydrogen storage alloy include Ce 5 Co 19 and Pr 5 Co 19 . In each of the above crystal structures, some metals may be replaced with one or more other metals or elements.
  • an A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni is preferable.
  • the negative electrode active material of the present invention having a high oxygen concentration, it is preferable to positively oxidize the surface of the hydrogen storage alloy.
  • the A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni is used as an example, and the hydrogen storage alloy is processed by a suitable method (hereinafter referred to as a hydrogen storage alloy processing method). The procedure for producing the negative electrode active material of the present invention will be described.
  • the processing method of the hydrogen storage alloy is as follows: N-1) a step of treating the hydrogen storage alloy with an aqueous alkali solution; N-2) oxidizing the surface of the hydrogen storage alloy after the N-1) step.
  • the step N-1) is not an essential step for oxidizing the hydrogen storage alloy.
  • a more suitable negative electrode active material of the present invention can be obtained by going through these steps.
  • the step N-1) preferably includes the following steps a) and b). a) a step of treating an A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni with a first alkaline aqueous solution in which a hydroxide of an alkali metal is dissolved b) a) a first alkaline aqueous solution after the step a) Of separating hydrogen storage alloy from water and treating it with a second aqueous alkali solution in which alkali metal hydroxide is dissolved
  • a) a step of treating an A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni with a first aqueous alkali solution in which an alkali metal hydroxide is dissolved (hereinafter simply referred to as “a) step” That. ) Will be described.
  • the hydrogen storage alloy used in the step a) is an A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni. It is considered that rare earth elements and Mg belong to metal A, and Ni belongs to metal B. Examples of rare earth elements include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Other metal elements may be present in the hydrogen storage alloy used in the step a), and as other metal elements, Mn, Fe, Co, Cu, Zn, Al, Cr, Pt, Cu, Ag, Ti , Zr, V, and Ta. As the hydrogen storage alloy used in the step a), a hydrogen storage alloy containing 60 to 70% by mass of Ni is preferable.
  • the hydrogen storage alloy is preferably in the form of a powder which is pulverized and adjusted to a certain particle size.
  • the average particle size of the hydrogen storage alloy is preferably in the range of 1 to 40 ⁇ m, more preferably in the range of 3 to 30 ⁇ m, still more preferably in the range of 4 to 20 ⁇ m, particularly preferably in the range of 5 to 15 ⁇ m. Most preferably, it is within the range of 12 ⁇ m.
  • the rare earth element having high solubility in the alkali aqueous solution elutes from the surface of the hydrogen storage alloy.
  • the Ni concentration on the surface of the hydrogen storage alloy becomes higher than that inside the hydrogen storage alloy.
  • a portion of the hydrogen storage alloy where the Ni concentration is higher than the inside is referred to as a Ni-enriched layer. It is considered that the performance of the negative electrode active material is improved due to the presence of the Ni enriched layer.
  • alkali metal hydroxide examples include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and among them, sodium hydroxide is preferable.
  • the battery characteristics of the nickel metal hydride battery of the present invention are optimized by using an aqueous sodium hydroxide solution as the first alkaline aqueous solution, as compared with the case of using lithium hydroxide or potassium hydroxide as the first alkaline aqueous solution There is.
  • the first alkaline aqueous solution is preferably a strong base.
  • concentration of the alkali metal hydroxide in the first aqueous alkali solution include 10 to 60% by mass, 20 to 55% by mass, 30 to 50% by mass, and 40 to 50% by mass.
  • Step (a) is preferably performed by a method of immersing the hydrogen storage alloy in a first alkaline aqueous solution.
  • the reaction is preferably performed under stirring conditions, and more preferably, under heating conditions.
  • Examples of the range of the heating temperature include 50 to 150 ° C., 70 to 140 ° C., and 90 to 130 ° C.
  • the heating time may be appropriately determined according to the concentration of the first alkaline aqueous solution and the heating temperature, and examples thereof include 0.1 to 10 hours, 0.2 to 5 hours, and 0.5 to 3 hours.
  • the relationship between the hydrogen storage alloy and the amount of the first alkaline aqueous solution is preferably 1: 0.5 to 1:10, more preferably 1: 0.7 to 1: 5, and more preferably 1: 0.9 to 1: 1 by mass ratio. 3 is more preferred. If the amount of the first alkali aqueous solution is too small, the Ni-enriched layer may not be formed sufficiently on the surface of the hydrogen storage alloy. On the other hand, if the amount of the first alkali aqueous solution is too large, it is disadvantageous in terms of cost. .
  • step b) after the step a), a step of separating the hydrogen storage alloy from the first aqueous alkali solution and treating it with a second aqueous alkali solution in which a hydroxide of an alkali metal is dissolved (hereinafter, simply referred to as “b) step”. ) Will be described.
  • Step b) Rare earth elements eluted from the hydrogen storage alloy are present in the first alkaline aqueous solution at the time when the step is completed.
  • the rare earth element can adhere to the surface of the hydrogen storage alloy as a hydroxide of the rare earth element when the first aqueous alkali solution and the hydrogen storage alloy are separated.
  • Step b) can be said to be a step of removing the hydroxide of the rare earth element attached to the surface of the hydrogen storage alloy separated from the first alkali aqueous solution with the second alkali aqueous solution.
  • Rare earth element hydroxides precipitate under neutral conditions, but are easily soluble in basic aqueous solutions. The step b) utilizes this property.
  • filtration or centrifugation is preferable, and suction filtration is particularly preferable.
  • the method of treating the hydrogen storage alloy with the second alkali aqueous solution include a method of immersing the hydrogen storage alloy in the second alkali aqueous solution and a method of immersing the second alkali aqueous solution in the hydrogen storage alloy. It is reasonable to select a method in which the second alkaline aqueous solution is immersed in the hydrogen storage alloy subsequent to or while performing the filtration described above.
  • alkali metal hydroxide dissolved in the second alkali aqueous solution examples include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and among them, sodium hydroxide is preferable.
  • a step is performed. Since the alkali aqueous solution having a low concentration has a low viscosity, the operation of the step b) proceeds smoothly under the condition that C 1 > C 2 is satisfied.
  • concentration of the alkali metal hydroxide in the second aqueous alkali solution include 0.01 to 10% by mass, 0.03 to 5% by mass, 0.05 to 1% by mass, and 0.1 to 0.5% by mass. it can.
  • the step b) is preferably performed under lower temperature conditions than the step a).
  • Examples of the temperature range of the step b) include 0 to 100 ° C., 10 to 70 ° C., and 20 to 50 ° C.
  • the temperature in the step b) may be defined by the temperature of the environment where the hydrogen storage alloy is present, or may be defined by the temperature of the second alkaline aqueous solution.
  • the relationship between the hydrogen storage alloy and the amount of the second alkali aqueous solution is preferably 1: 0.5 to 1:50, more preferably 1: 1 to 1:30, and more preferably 1: 1.5 to 1:10 in terms of mass ratio. More preferred. If the amount of the second alkali aqueous solution is too small, the removal of the hydroxide of the rare earth element may be insufficient, while if the amount of the second alkali aqueous solution is too large, it is disadvantageous in terms of cost.
  • the hydrogen storage alloy may be washed with water after the treatment with the second alkaline aqueous solution.
  • the second alkaline aqueous solution attached to the surface of the hydrogen storage alloy can be removed.
  • the relationship between the hydrogen storage alloy and the amount of water at the time of washing with water is preferably 1: 1 to 1:50, more preferably 1: 2 to 1:30, and more preferably 1: 3 to 1:10 in terms of mass ratio. preferable.
  • N-2) a step of oxidizing the surface of the hydrogen storage alloy after the N-1) step (hereinafter, simply referred to as an "N-2) step”. ) Will be described.
  • a method of exposing the hydrogen storage alloy to air and oxidizing it with oxygen in the air may be used, or a method of oxidizing the hydrogen storage alloy by contacting it with an oxide such as hydrogen peroxide may be used.
  • the hydrogen storage alloy is cooled while being cooled by immersing the hydrogen storage alloy in water, or the hydrogen storage alloy is disposed in water, or the hydrogen storage alloy is stored in an aqueous solution of an oxide such as hydrogen peroxide. It is preferable to carry out the method after disposing the alloy.
  • the washing of the hydrogen storage alloy with water which can be performed after the treatment with the second alkaline aqueous solution in the above-described step b), may be performed in the air to form the step N-2).
  • the preferable negative electrode active material of the present invention which is manufactured through the steps (N-1) and (N-2), contains a hydrogen storage alloy whose surface Ni concentration is increased as compared with the internal Ni concentration.
  • the internal Ni concentration is synonymous with the Ni concentration in the hydrogen storage alloy before the treatment used in the N-1) step. Further, it can be said that the preferable negative electrode active material of the present invention has a Ni-enriched layer on the surface.
  • Examples of the thickness of the Ni-enriched layer include 5 to 200 nm, 10 to 150 nm, and 30 to 100 nm.
  • the thickness of the Ni-enriched layer can be confirmed by observing the cross section of the particles of the negative electrode active material of the present invention with various electron microscopes.
  • step a) of step N-1 a rare earth element that is easily dissolved in an aqueous alkaline solution is eluted. A concentrated layer is formed.
  • step b) the hydroxide of the rare earth element attached to the surface of the hydrogen storage alloy is removed with a second alkaline aqueous solution, so that the Ni concentration on the surface of the hydrogen storage alloy after step b) further increases. I can say that.
  • the present inventor measured the surface of the hydrogen storage alloy after the step b) by X-ray photoelectron spectroscopy, the Ni ratio was significantly higher than the composition of the hydrogen storage alloy before the treatment used in the step a). It was confirmed that it was higher. Therefore, the following can be grasped as one preferred embodiment of the negative electrode active material of the present invention.
  • One embodiment of the negative electrode active material of the present invention contains an A 2 B 7 type hydrogen storage alloy containing La, Mg, and Ni, and containing 60 to 70% by mass of Ni, and has an internal Ni / La element ratio.
  • the value of the Ni / La element ratio on the surface with respect to is 1.3 or more.
  • the internal Ni / La element ratio means the Ni / La element ratio inside the hydrogen storage alloy, for example, at the center of the particles of the negative electrode active material of the present invention. Is the same as the Ni / La element ratio in the hydrogen storage alloy before the treatment used in step a).
  • Examples of the value of the Ni / La element ratio on the surface with respect to the Ni / La element ratio inside are 1.3 to 2, 1.31 to 1.5, and 1.34 to 1.4.
  • the nickel metal hydride battery of the present invention includes a positive electrode active material layer containing the positive electrode active material of the present invention, and a negative electrode active material layer containing the negative electrode active material of the present invention.
  • the nickel metal hydride battery of the present invention is a normal nickel metal hydride battery including the positive electrode of the present invention having the positive electrode active material layer and the negative electrode of the present invention having the negative electrode active material layer.
  • a bipolar nickel metal hydride battery comprising a positive electrode active material layer on one surface of a current collector foil and a bipolar electrode having the negative electrode active material layer on the other surface. May be.
  • the positive electrode of the present invention and the negative electrode of the present invention will be described.
  • the description of the bipolar electrode the description of the positive electrode of the present invention and the negative electrode of the present invention will be appropriately used.
  • the positive electrode of the present invention includes a current collector and a positive electrode active material layer formed on the surface of the current collector.
  • a current collector refers to a chemically inert electronic conductor that keeps current flowing through electrodes during discharging or charging of a nickel metal hydride battery.
  • the material of the current collector is not particularly limited as long as the metal can withstand a voltage suitable for the active material to be used.
  • As a material of the current collector at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel And other metal materials.
  • the current collector may be covered with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector.
  • nickel or a metal material plated with nickel is preferable.
  • the current collector may be in the form of foil, sheet, film, wire, rod, mesh, sponge, or the like.
  • the thickness is preferably in the range of 1 ⁇ m to 100 ⁇ m.
  • the positive electrode active material of the present invention has excellent conductivity, it is reasonable to adopt a foil-shaped current collector. For the same reason, it can be said that the positive electrode active material of the present invention is suitable for a bipolar electrode using a current collector foil.
  • the positive electrode active material layer contains the positive electrode active material of the present invention, and optionally contains a positive electrode additive, a binder, and a conductive auxiliary.
  • the amount of one positive electrode active material layer present on the current collector of the positive electrode is preferably 20 mg / cm 2 or more, more preferably 25 to 50 mg / cm 2 , and further preferably 27 to 40 mg / cm 2 .
  • the density of the positive electrode active material layer is preferably 2.5 g / cm 3 or more, more preferably 2.6 to 3.2 g / cm 3, still more preferably 2.7 to 3.1 g / cm 3. Particularly preferred is ⁇ 3.0 g / cm 3 .
  • the positive electrode active material layer preferably contains the positive electrode active material of the present invention in an amount of 75 to 99% by mass, more preferably 80 to 97% by mass, based on the total mass of the positive electrode active material layer. More preferably, the content is 85 to 95% by mass.
  • the positive electrode additive is added to the positive electrode in order to improve the battery characteristics of the nickel metal hydride battery.
  • the positive electrode additive is not limited as long as it is used as a positive electrode additive of a nickel metal hydride battery.
  • Specific positive electrode additives niobium compound, such as Nb 2 O 5, WO 2, WO 3, Li 2 WO 4, a tungsten compound such as Na 2 WO 4 and K 2 WO 4, ytterbium compound such as Yb 2 O 3 titanium compounds such as TiO 2, yttrium compound, such as Y 2 O 3, zinc compounds such as ZnO, CaO, Ca (OH) calcium compounds such as 2 and CaF 2, and can be exemplified by other rare earth oxides.
  • the positive electrode active material layer preferably contains the positive electrode additive in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total mass of the positive electrode active material layer. .
  • the binder plays a role of binding the active material and the like to the surface of the current collector.
  • the binder is not limited as long as it is used as a binder for an electrode of a nickel metal hydride battery.
  • Specific binders include polyvinylidene fluoride, fluorine-containing resins such as polytetrafluoroethylene and fluororubber, polyolefin resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, carboxymethylcellulose, methylcellulose and hydroxypropyl.
  • Cellulose derivatives such as cellulose, copolymers such as styrene-butadiene rubber, and (meth) acrylic acid derivatives containing as monomer units, such as polyacrylic acid, polyacrylic acid ester, polymethacrylic acid and polymethacrylic acid ester ( A (meth) acrylic resin can be exemplified.
  • the active material layer preferably contains the binder in an amount of 0.1 to 15% by mass, more preferably 0.3 to 10% by mass, based on the mass of the entire active material layer. More preferably, it is contained at 0.5 to 7% by mass. This is because if the amount of the binder is too small, the moldability of the electrode decreases, and if the amount of the binder is too large, the energy density of the electrode decreases.
  • the conductive additive is added to increase the conductivity of the electrode. Therefore, the conductive assistant may be arbitrarily added when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent.
  • Specific conductive assistants include metals such as cobalt, nickel and copper, metal oxides such as cobalt oxide, metal hydroxides such as cobalt hydroxide, and carbon materials such as carbon black, graphite and carbon fiber. Is exemplified.
  • the active material layer preferably contains the conductive additive in an amount of 0.1 to 20% by mass based on the total mass of the active material layer.
  • the positive electrode active material layer preferably contains the conductive additive in an amount of 1 to 15% by mass, more preferably 3 to 12% by mass, and more preferably 5 to 10% by mass, based on the total mass of the positive electrode active material layer. More preferably, it is contained by mass%.
  • the negative electrode active material layer preferably contains the conductive auxiliary in an amount of 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, based on the total mass of the negative electrode active material layer. , 0.3 to 1% by mass. If the amount of the conductive auxiliary agent is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary agent is too large, the moldability of the active material layer deteriorates and the energy density of the electrode decreases.
  • the negative electrode of the present invention includes the negative electrode active material of the present invention.
  • the negative electrode of the present invention includes a current collector and a negative electrode active material layer formed on a surface of the current collector.
  • the negative electrode active material layer contains the negative electrode active material of the present invention, and optionally contains a negative electrode additive, a binder, and a conductive auxiliary.
  • the binder and the conductive assistant are as described above.
  • the negative electrode active material layer preferably contains the negative electrode active material in an amount of 85 to 99% by mass, more preferably 90 to 98% by mass, based on the mass of the entire negative electrode active material layer.
  • the negative electrode additive is added to the negative electrode in order to improve the battery characteristics of the nickel metal hydride battery.
  • the negative electrode additive is not limited as long as it is used as a negative electrode additive of a nickel metal hydride battery.
  • specific negative electrode additives fluorides of rare earth elements such as CeF 3 and YF 3 , bismuth compounds such as Bi 2 O 3 and BiF 3 , indium compounds such as In 2 O 3 and InF 3 , and positive electrode additives And the compounds exemplified above.
  • the negative electrode active material layer preferably contains the negative electrode additive in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total mass of the negative electrode active material layer. .
  • the current is collected using a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method.
  • the active material may be applied to the surface of the body.
  • an active material, a solvent, and, if necessary, a binder, a conductive auxiliary agent, and an additive are mixed to form a slurry, and the slurry is applied to the surface of the current collector and then dried.
  • the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water.
  • the dried product may be compressed to increase the electrode density.
  • the nickel metal hydride battery of the present invention also includes an electrolyte and a separator.
  • the electrolytic solution is an aqueous solution in which an alkali metal hydroxide is dissolved.
  • the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
  • the electrolytic solution may contain one kind of alkali metal hydroxide, or may contain plural kinds of alkali metal hydroxides. Particularly, those containing three kinds of alkali metal hydroxides of lithium hydroxide, sodium hydroxide and potassium hydroxide are preferable.
  • the concentration of the alkali metal hydroxide in the electrolyte is preferably 2 to 10 mol / L, more preferably 3 to 9 mol / L, and still more preferably 4 to 8 mol / L.
  • the electrolyte may contain a known additive employed in the electrolyte for nickel metal hydride batteries.
  • the additive include alkali metal halides such as lithium chloride and sodium chloride, and alkali metal tungstates such as sodium tungstate.
  • an electrolytic solution composed of an aqueous solution containing an alkali metal hydroxide and an alkali metal halide is preferable.
  • the reason why the presence of an alkali metal halide is preferable is as follows.
  • the alkali metal halide is ionized into the alkali metal cation and the halogen anion in the electrolytic solution. Then, the negatively charged halogen anion is electrically adsorbed to the positive electrode, so that the positive electrode is coated with the halogen anion. In the positive electrode coated with the halogen anion, direct contact of water molecules with the positive electrode body is suppressed, so that it is considered that generation of oxygen in the positive electrode is suppressed.
  • the alkali metal cation is coordinated with water molecules in the electrolytic solution in the electrolytic solution.
  • the water molecule is in a state of being strongly coordinated with the alkali metal cation, thereby improving the oxidation resistance and increasing the oxygen generation potential.
  • the halogen anion adsorbed on the positive electrode is oxidized to become a simple halogen.
  • Oxidation resistance of the halogen anions, F -> Cl -> Br -> I - are known to be in the order of. Therefore, from the viewpoint of oxidation resistance, the alkali metal halide is most preferably an alkali metal fluoride, the alkali metal chloride is more preferred, and the alkali metal bromide is the second most preferred.
  • alkali metal halide examples include LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr and KI. From the viewpoint of coordination with water molecules and oxidation resistance, LiF, LiCl, NaF, and NaCl are preferable as the alkali metal halide. From the viewpoint of solubility, it can be said that LiCl and NaCl are preferable as alkali metal halides.
  • the concentration of the alkali metal halide in the electrolyte is preferably 0.01 to 1 mol / L, more preferably 0.03 to 0.5 mol / L, still more preferably 0.05 to 0.3 mol / L. 0.05 to 0.1 mol / L is particularly preferred.
  • the separator separates the positive electrode and the negative electrode, and provides a storage space and a passage for the electrolyte while preventing a short circuit due to contact between the two electrodes.
  • Known separators may be used as the separator, and synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic @ polyamide), polyester, and polyacrylonitrile; polysaccharides such as cellulose and amylose; and fibroin.
  • Natural polymers such as keratin, lignin and suberin, and porous bodies, non-woven fabrics and woven fabrics using one or more electrically insulating materials such as ceramics.
  • the separator may have a multilayer structure.
  • the surface of the separator is preferably subjected to a hydrophilic treatment.
  • a hydrophilic treatment include a sulfonation treatment, a corona treatment, a fluorine gas treatment, and a plasma treatment.
  • a separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. After connecting from the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collecting lead or the like, an electrolytic solution is added to the electrode body to obtain a nickel metal hydride battery. .
  • the shape of the nickel metal hydride battery of the present invention is not particularly limited, and various shapes such as a prismatic shape, a cylindrical shape, a coin shape, and a laminate shape can be adopted.
  • the nickel metal hydride battery of the present invention may be mounted on a vehicle.
  • the vehicle may be any vehicle that uses electric energy from a nickel metal hydride battery for all or a part of its power source, such as an electric vehicle or a hybrid vehicle.
  • a nickel metal hydride battery is mounted on a vehicle, a plurality of nickel metal hydride batteries may be connected in series to form an assembled battery.
  • devices on which the nickel metal hydride battery is mounted include various types of battery-driven home appliances, office devices, industrial devices, and the like, such as personal computers and portable communication devices, in addition to vehicles.
  • the nickel metal hydride battery of the present invention is a power storage device and a power smoothing device for wind power generation, solar power generation, hydroelectric power generation and other power systems, power sources for ships and the like and / or power supply sources for auxiliary equipment, aircraft, Power supply for spacecraft and other power supplies and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply,
  • the present invention may be applied to a power storage device that temporarily stores electric power required for charging at a charging station for an electric vehicle or the like.
  • Example 1 Manufacture of positive electrode active material
  • Nickel sulfate, cobalt sulfate, and zinc sulfate were weighed so that the molar ratio of nickel, cobalt, and zinc became 94.5: 4.5: 1.1, and these were added to an aqueous solution of sodium hydroxide containing ammonium ions.
  • To prepare a mixed aqueous solution An aqueous sodium hydroxide solution was gradually added to the mixed aqueous solution under stirring to adjust the pH of the mixed aqueous solution to 13 to 14.
  • precursor particles containing nickel hydroxide as a main component and solid solution of cobalt and zinc were produced.
  • the obtained precursor particles (positive electrode active material body) were washed with water and then dried.
  • Step P-1) The obtained precursor particles were put into an aqueous ammonia solution to form a suspension.
  • An aqueous solution of cobalt sulfate was added to the suspension while maintaining the pH of the suspension at 9-10.
  • cobalt hydroxide was deposited on the surface of the precursor particles to obtain particles having a layer of cobalt hydroxide.
  • Step P-2) The particles having the layer of cobalt hydroxide obtained in the preceding paragraph are sprayed with an aqueous solution of sodium hydroxide and an aqueous solution of lithium hydroxide while being convected in high-temperature air containing oxygen. gave. Thereby, the cobalt hydroxide on the surface of the particles becomes cobalt oxyhydroxide having high conductivity, and sodium and lithium are taken into the layer of cobalt oxyhydroxide, and the cobalt oxyhydroxide containing sodium and lithium is contained. A layer is formed. Thereafter, the particles provided with the cobalt oxyhydroxide layer were collected by filtration, washed with water, and dried at 60 ° C. Thus, the positive electrode active material of Example 1 covered with the cobalt oxyhydroxide layer containing sodium and lithium was produced.
  • An A 2 B 7 type hydrogen storage alloy represented by (La, Sm, Mg, Zr) 1.0 (Ni, Al) 3.6 was prepared as a rare earth-Mg—Ni hydrogen storage alloy.
  • the Ni content was 62% by mass.
  • a coarse powder of the hydrogen storage alloy and polyvinyl alcohol were mixed with distilled water so that the concentration of the hydrogen storage alloy was 10% by mass, and mixed with a mixer to form a mixture.
  • the content of polyvinyl alcohol was 0.5% by mass with respect to the hydrogen storage alloy.
  • the mixture was transferred to a bead mill in the atmosphere, mixed in the bead mill, and then discharged from the bead mill.
  • the beads used in the bead mill were made of zirconia.
  • the mixture discharged from the bead mill was transported to the mixer via a circulation pipe, and then returned to the bead mill again.
  • the hydrogen storage alloy and water circulated between the bead mill and the mixer, and the hydrogen storage alloy was repeatedly pulverized by the bead mill.
  • the pulverized product obtained in the above steps was collected by filtration to obtain a pulverized filtered product of Example 1 containing the hydrogen storage alloy powder and a small amount of water.
  • the crushed and filtered product of Example 1 was subjected to the following alkali treatment step.
  • the average particle size (D 50 ) of the hydrogen storage alloy powder in the pulverized filtration product of Example 1 was 7 ⁇ m.
  • Step N-1 Alkali treatment step of negative electrode active material: step N-1
  • a) Step As an aqueous first alkali solution an aqueous sodium hydroxide solution containing 40% by mass of sodium hydroxide was prepared. Under stirring conditions, 50 parts by mass of the pulverized and filtered product of Example 1 was added to 50 parts by mass of the first alkaline aqueous solution to form a suspension. The suspension was heated to 90 ° C. and held for 1 hour, then cooled to room temperature.
  • Step As an aqueous second alkali solution an aqueous sodium hydroxide solution containing 0.4% by mass of sodium hydroxide was prepared. a) The suspension after completion of the step was subjected to suction filtration to separate the hydrogen storage alloy from the first aqueous alkali solution. While suction filtration was continued, 50 parts by mass of a second alkaline aqueous solution was poured over the hydrogen storage alloy to wash the hydrogen storage alloy.
  • Step b) While the suction filtration in the step b) was continued, 300 parts by mass of water was poured from above the hydrogen storage alloy, and the hydrogen storage alloy was washed with water.
  • a nickel metal hydride battery of Example 1 was manufactured as follows.
  • the nickel foil coated with the slurry was dried to remove water, and then the nickel foil was pressed to produce a positive electrode having a positive electrode active material layer formed on a current collector.
  • the amount of the positive electrode active material layer present on the current collector of the positive electrode was 28 mg / cm 2 , and the density of the positive electrode active material layer was 2.9 g / cm 3 .
  • Example 1 97.8 parts by mass of the negative electrode active material of Example 1, 1.5 parts by mass of an acrylic resin emulsion as a solid content as a binder, 0.7 parts by mass of carboxymethyl cellulose as a binder, and an appropriate amount of ions Exchanged water was mixed to produce a slurry.
  • a nickel foil having a thickness of 20 ⁇ m was prepared as a negative electrode current collector. The slurry was applied in the form of a film to the surface of the nickel foil. The nickel foil coated with the slurry was dried to remove water, and then the nickel foil was pressed to produce a negative electrode in which a negative electrode active material layer was formed on a current collector.
  • the concentration of potassium hydroxide is 5.4 mol / L
  • the concentration of sodium hydroxide is 0.8 mol / L
  • the concentration of lithium hydroxide is 0.5 mol / L
  • the concentration of lithium chloride is Was prepared at 0.05 mol / L.
  • a non-woven fabric made of sulfonated polyolefin fiber and having a thickness of 104 ⁇ m was prepared as a separator.
  • a separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group.
  • the nickel metal hydride battery of Example 1 was manufactured by disposing the electrode group in a resin housing, further injecting the above-mentioned electrolyte solution, and sealing the housing.
  • Example 2 was carried out in substantially the same manner as in Example 1 except that the amount of the aqueous solution of cobalt sulfate added in the step P-1) and the spray amount of the aqueous solution of sodium hydroxide in the step P-2) were slightly changed.
  • a nickel metal hydride battery of Example 2 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Example 2 was used.
  • Example 3 A method similar to that of Example 1 except that the amount of the aqueous solution of cobalt sulfate added in the step P-1) and the amount of the aqueous sodium hydroxide solution and the aqueous solution of lithium hydroxide in the step P-2) were slightly changed. Thus, the positive electrode active material of Example 3 was manufactured. A nickel metal hydride battery of Example 3 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Example 3 was used.
  • Example 4 In the production of the positive electrode active material main body, the molar ratio of nickel, cobalt and zinc was slightly changed, and the addition amount of the aqueous solution of cobalt sulfate in the step P-1) and the spray amount of the aqueous sodium hydroxide solution in the step P-2) were changed.
  • a positive electrode active material of Example 4 was manufactured in substantially the same manner as in Example 1, except for a slight change.
  • a nickel metal hydride battery of Example 4 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Example 4 was used.
  • Example 5 In the production of the negative electrode active material, the negative electrode active material of Example 5 was produced in substantially the same manner as in Example 1, except that the steps N-1) and N-2) were not performed. A nickel metal hydride battery of Example 5 was manufactured in the same manner as in Example 1, except that the negative electrode active material of Example 5 was used. Note that the negative electrode active material of Example 5 was not oxidized with hydrogen peroxide in the step N-2), but was oxidized to a certain extent because it was in contact with the atmosphere.
  • Example 6 In the production of the negative electrode active material, the method of Example 6 was repeated in substantially the same manner as in Example 1, except that the grinding conditions were relaxed and that oxidation with hydrogen peroxide was not performed in the step N-2). A negative electrode active material was manufactured. A nickel metal hydride battery of Example 6 was manufactured in the same manner as in Example 1, except that the negative electrode active material of Example 6 was used. The average particle size (D 50 ) of the hydrogen storage alloy powder of Example 6 was 15 ⁇ m. Further, although the negative electrode active material of Example 6 was not oxidized with hydrogen peroxide in Step N-2), it was oxidized to a certain extent because it came into contact with the atmosphere in Step b) in Step N-1). ing.
  • Example 7 The positive electrode active material of Example 7 was produced in substantially the same manner as in Example 1 except that the aqueous lithium hydroxide solution was not sprayed in the step P-2) in the production of the positive electrode active material body.
  • a nickel metal hydride battery of Example 7 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Example 7 was used.
  • Example 8 In the step a) of the step N-1) in the production of the negative electrode active material, except that the suspension was heated to 90 ° C. and held for 3 hours, the negative electrode of the example 8 was produced in substantially the same manner as in the example 1. An active material was manufactured. The average particle diameter (D 50 ) of the hydrogen storage alloy powder of Example 8 was 9 ⁇ m. As the electrolyte, the concentration of potassium hydroxide is 5.4 mol / L, the concentration of sodium hydroxide is 0.8 mol / L, the concentration of lithium hydroxide is 0.5 mol / L, and tungstic acid is used. An aqueous solution having a sodium concentration of 0.01 mol / L was prepared. A nickel metal hydride battery of Example 8 was manufactured in the same manner as in Example 7, except that the negative electrode active material of Example 8 and the above-mentioned electrolyte solution were used.
  • Comparative Example 1 Except that the molar ratio of nickel, cobalt and zinc was slightly changed in the production of the positive electrode active material body, and that the aqueous sodium hydroxide solution and the aqueous lithium hydroxide solution were not sprayed in the step P-2).
  • a positive electrode active material of Comparative Example 1 was produced in the same manner as in Example 1.
  • a nickel metal hydride battery of Comparative Example 1 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Comparative Example 1 was used.
  • Comparative Example 2 In the production of the negative electrode active material, the negative electrode of Comparative Example 2 was produced in substantially the same manner as in Example 1 except that the grinding conditions were relaxed and the steps N-1) and N-2) were not performed. An active material was manufactured. A nickel metal hydride battery of Comparative Example 2 was manufactured in the same manner as in Example 1, except that the negative electrode active material of Comparative Example 2 was used. The average particle diameter (D 50 ) of the hydrogen storage alloy powder of Comparative Example 2 was 15 ⁇ m.
  • Comparative Example 3 The positive electrode active material of Comparative Example 3 was manufactured in substantially the same manner as in Example 1 except that the aqueous lithium hydroxide solution was not sprayed in the step P-2) in the manufacture of the positive electrode active material body. Note that the positive electrode active material of Comparative Example 3 is one embodiment of the positive electrode active material of the present invention, but is referred to as “the positive electrode active material of Comparative Example 3” for convenience to avoid confusion.
  • a nickel metal hydride battery of Comparative Example 3 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Comparative Example 3 and the negative electrode active material of Comparative Example 2 were used.
  • Table 1 shows a list of nickel metal hydride batteries of Examples 1 to 7 and Comparative Examples 1 to 3.
  • the lithium and sodium contents were analyzed by atomic absorption spectrometry using a solution in which each positive electrode active material was dissolved.
  • the lithium content in the positive electrode active materials of Examples 1 to 4 was approximately 0.1% by mass.
  • the sodium content was about 0.2 to 0.6% by mass.
  • No lithium was detected from the positive electrode active materials of Example 7, Comparative Examples 1 and 3.
  • Some amount of sodium was detected from the positive electrode active material of Comparative Example 1.
  • the sodium contents in the positive electrode active materials of Example 7 and Comparative Example 3 were almost the same as those of the positive electrode active materials of Examples 1 to 4.
  • the average particle diameter (D 50 ) was measured using a general laser diffraction type particle size distribution analyzer.
  • the measurement of the BET specific surface area was performed using a general BET specific surface area measuring device.
  • the valence of cobalt was measured by an iodometry method.
  • the resistivity was measured using a powder resistivity measuring system (Mitsubishi Analytech Co., Ltd.) at 20 kN under the conditions of 25 ° C. and a relative humidity of 40 to 50% for 2.0 g of the powder of the positive electrode active material. The measurement was performed after applying a load. Table 2 shows the above results.
  • Table 2 shows that the valence of cobalt of the positive electrode active material increases and the resistivity of the positive electrode active material decreases due to the presence of the alkali metal, particularly lithium. Further, the positive electrode active materials of Example 7 and Comparative Example 3 having the same sodium content as the positive electrode active materials of Examples 1 to 4 exhibited more preferable physical property values than the positive electrode active material of Comparative Example 1. However, it did not reach the physical properties of the positive electrode active materials of Examples 1 to 4 containing lithium together with sodium.
  • Table 4 shows that the nickel metal hydride batteries of Examples 1 to 8 including both the lithium or sodium doped positive electrode active material and the high oxygen concentration negative electrode active material have low discharge resistance. Understand. Further, the values of the discharge resistors of Examples 1 to 4, the values of the discharge resistors of Examples 5 and 6, the values of the discharge resistors of Comparative Example 2, and the values of the discharge resistors of Examples 7 and 8 were used. From the value of the resistance, it is found that the higher the oxygen concentration of the negative electrode active material, the smaller the value of the discharge resistance.
  • KCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing 0.05 mol / L of KCl.
  • the aqueous solution produced as described above was used as the electrolyte of Reference Example 4.
  • KCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing KCl at 0.5 mol / L.
  • the aqueous solution produced as described above was used as the electrolyte of Reference Example 5.
  • Reference evaluation example 1 The electrolyte solutions of Reference Examples 1 to 5 were stored at 25 ° C., 0 ° C., or ⁇ 40 ° C. for 20 hours, and the properties were observed. Table 6 shows the results.
  • Reference Example 1-h alf As follows, to produce a half cell of Reference Example 1-h alf comprising the electrolytic solution of Example 1.
  • Fluorine resin container was poured an electrolyte solution of Example 1, further working electrode, by placing the counter electrode and a reference electrode, and the half cell of Reference Example 1-h alf. Note that a Ni mesh was used as a working electrode, a Pt line was used as a counter electrode, and a mercury-mercury oxide electrode was used as a reference electrode.
  • Reference Example 2-h alf instead of the electrolyte of Example 1, except for using an electrolytic solution of Reference Example 2, in Reference Example 1-h alf a similar manner was prepared the half cell of Reference Example 2-h alf.
  • Nion-exchanged water 83.3 parts by mass of nickel hydroxide powder as a positive electrode active material, 5 parts by mass of cobalt powder as a conduction aid, 5 parts by mass of carbon black as a conduction aid, and an acrylic resin emulsion (Joncryl PDX 7341; BASF) as a solid content, 5 parts by mass of carboxymethylcellulose as a binder, 1 part by mass of Y 2 O 3 as a positive electrode additive, and an appropriate amount of ion-exchanged water.
  • a nickel foil having a thickness of 10 ⁇ m was prepared as a positive electrode current collector. The slurry was applied to the surface of the nickel foil in the form of a film using a doctor blade.
  • the nickel foil to which the slurry was applied was dried to remove water, and then the nickel foil was pressed to obtain a bonded product.
  • the obtained bonded article was dried by heating at 70 ° C. for 1 hour using a drier to produce a positive electrode having a positive electrode active material layer formed on a current collector.
  • a slurry was prepared by mixing 2 parts by mass as a solid content, 0.7 parts by mass of carboxymethyl cellulose as a binder, and an appropriate amount of ion-exchanged water.
  • a nickel foil having a thickness of 10 ⁇ m was prepared as a current collector for the negative electrode. The slurry was applied to the surface of the nickel foil in the form of a film using a doctor blade.
  • the nickel foil to which the slurry was applied was dried to remove water, and then the nickel foil was pressed to obtain a bonded product.
  • the obtained bonded article was dried by heating at 70 ° C. for 1 hour using a drier to produce a negative electrode having a negative electrode active material layer formed on a current collector.
  • a 120 ⁇ m-thick nonwoven polypropylene fiber nonwoven fabric that had been subjected to a sulfonation treatment was prepared as a separator.
  • a separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group.
  • the electrode group was arranged in a resin housing, the electrolyte of Reference Example 1 was further injected, and the housing was sealed to produce a nickel metal hydride battery of Reference Example 1- Full .
  • Reference Example 2-F ull A nickel metal hydride battery of Reference Example 2- Full was manufactured in the same manner as in Reference Example 1- Full except that the electrolyte of Reference Example 2 was used instead of the electrolyte of Reference Example 1.
  • Reference Example 3-F ull A nickel metal hydride battery of Reference Example 3- Full was manufactured in the same manner as in Reference Example 1- Full , except that the electrolyte of Reference Example 1 was used instead of the electrolyte of Reference Example 1.
  • Reference Example 4-F ull A nickel metal hydride battery of Reference Example 4- Full was manufactured in the same manner as in Reference Example 1- Full , except that the electrolyte of Reference Example 4 was used instead of the electrolyte of Reference Example 1.
  • Reference Comparative Example 1-F ull The nickel metal hydride battery of Reference Comparative Example 1- Full was manufactured in the same manner as in Reference Example 1- Full except that the electrolytic solution of Reference Comparative Example 1 was used instead of the electrolytic solution of Reference Example 1. did.
  • KCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing 0.05 mol / L of KCl.
  • the aqueous solution produced as described above was used as the electrolyte of Reference Example 8.
  • the half cell of Reference Example 8 was manufactured in the same manner as in Reference Example 6.
  • Reference Comparative Example 2 An aqueous solution in which the concentration of potassium hydroxide was 5.5 mol / L, the concentration of sodium hydroxide was 0.5 mol / L, and the concentration of lithium hydroxide was 0.5 mol / L was obtained as Reference Comparative Example 2. Electrolyte solution. Hereinafter, the half cell of Reference Comparative Example 2 was manufactured in the same manner as in Reference Example 6.
  • FIG. 1 shows a schematic cross-sectional view of the bipolar nickel metal hydride battery of Application Example 1, observed from the thickness side of the electrode.
  • the bipolar nickel metal hydride battery 1 of the application example 1 is: A positive electrode 2 in which a positive electrode active material layer 21 is formed on one surface of a current collector foil 20; A negative electrode 3 in which a negative electrode active material layer 31 is formed on one surface of a current collector foil 30; A bipolar electrode 4 having a positive electrode active material layer 41 formed on one surface of a current collector foil 40 and a negative electrode active material layer 42 formed on the other surface; And a polyolefin separator 5 that has been subjected to a hydrophilic treatment.
  • the current collector foil 20 of the positive electrode 2 is made of nickel and is a rectangular foil having a thickness of 20 ⁇ m.
  • a positive electrode active material layer 21 including the positive electrode active material of the present invention, a conductive auxiliary agent, a binder, and an additive is formed on the upper surface of the current collector foil 20, a positive electrode active material layer 21 including the positive electrode active material of the present invention, a conductive auxiliary agent, a binder, and an additive is formed.
  • the peripheral edge of the current collector foil 20 is fixed by an outer frame 7 made of synthetic resin, and a seal portion 6 made of a fluorine-containing resin is arranged inside the outer frame 7. The seal portion 6 is bound to the upper and lower surfaces of the current collector foil 20.
  • the separator 5 is arranged on the upper surface of the positive electrode active material layer 21 of the positive electrode 2.
  • the separator 5 is impregnated with an electrolytic solution.
  • the area of the surface of the separator 5 is larger than the area of the surface of the positive electrode active material layer 21 that is in contact.
  • the bipolar electrode 4 is disposed on the upper surface of the separator 5 disposed on the upper surface of the positive electrode active material layer 21 of the positive electrode 2 in the direction in which the negative electrode active material layer 42 faces.
  • the positive electrode active material layer 41 is formed on the upper surface of the current collector foil 40, and the negative electrode active material layer 42 is formed on the lower surface.
  • the current collector foil 40 is the same as the current collector foil 20 of the positive electrode 2
  • the positive electrode active material layer 41 is also the same as the positive electrode active material layer 21 of the positive electrode 2.
  • the negative electrode active material layer 42 of the bipolar electrode 4 contains the negative electrode active material of the present invention and a binder.
  • the periphery of the current collecting foil 40 is fixed by an outer frame 7 made of synthetic resin, and a seal portion 6 made of a fluorine-containing resin is arranged inside the outer frame 7.
  • the sealing portion 6 is bonded to the upper and lower surfaces of the current collecting foil 40, and the sealing portion 6 on the upper surface of the current collecting foil 40 is further bonded to the lower surface of the current collecting foil 40 of the other bipolar electrode 4 above.
  • the sealing portion 6 on the lower surface of the current collector foil 40 is also bonded to the upper surface of the current collector foil 20 of the positive electrode 2. That is, the positive electrode active material layer 21, the separator 5, the electrolytic solution, and the negative electrode active material layer 42 are in a sealed state by the seal portion 6.
  • the separator 5 On the upper surface of the bipolar electrode 4 laminated on the positive electrode 2 via the separator 5, a plurality of bipolar electrodes 4 are laminated via the separator 5.
  • the separator 5 is disposed on the upper surface of the positive electrode active material layer 41 of the uppermost bipolar electrode 4, and the negative electrode 3 is disposed on the upper surface of the separator 5 in the direction in which the negative electrode active material layer 31 faces.
  • the negative electrode active material layer 31 is formed on the lower surface of the current collector foil 30.
  • the current collector foil 30 is the same as the current collector foil 20 of the positive electrode 2 and the current collector foil 40 of the bipolar electrode 4, and the negative electrode active material layer 31 is the same as the negative electrode active material layer 42 of the bipolar electrode 4. is there.
  • the peripheral edge of the current collector foil 30 is fixed by an outer frame 7 made of a synthetic resin, and a seal portion 6 made of a fluorine-containing resin is arranged inside the outer frame 7.
  • the sealing portion 6 is bonded to the upper surface and the lower surface of the current collecting foil 30, and the sealing portion 6 on the lower surface of the current collecting foil 30 is also bonded to the upper surface of the current collecting foil 40 of the bipolar electrode 4.
  • Cooling units 8 are arranged above and below the thickness of the battery module including the positive electrode 2, the bipolar electrode 4, the negative electrode 3 and the separator 5.
  • the cooling unit 8 is a rectangular plate made of aluminum, and is provided with a plurality of through holes 80 capable of air cooling.
  • a module positive electrode 22 and a module negative electrode 32 for supplying electricity to the outside are arranged outside the cooling unit 8.
  • the module positive electrode 22 and the module negative electrode 32 are rectangular plates made of metal.
  • the restraining tools 9 are arranged outside the module positive electrode 22 and the module negative electrode 32, respectively.
  • the restraint 9 is a rectangular plate made of synthetic resin.
  • the two restraints 9 are fastened with a plurality of bolts and nuts (not shown), and press and restrain the battery module in the thickness direction of the electrodes.
  • the separator 5 is compressed by pressurization by the two restraints 9.

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Abstract

Provided is a novel nickel metal hydride battery which exhibits excellent battery characteristics. This nickel metal hydride battery is characterized by including: a positive electrode active material coated with a cobalt oxyhydroxide layer containing lithium or sodium; and a negative electrode active material having an oxygen concentration of 1000 ppm or more before charge and discharge.

Description

ニッケル金属水素化物電池Nickel metal hydride battery
　本発明は、ニッケル金属水素化物電池に関するものである。 The present invention relates to a nickel metal hydride battery.
　ニッケル金属水素化物電池は、正極活物質として水酸化ニッケルなどのニッケル酸化化合物を有する正極と、負極活物質として水素吸蔵合金を有する負極と、アルカリ金属水溶液からなる電解液とを具備する二次電池である。 A nickel metal hydride battery is a secondary battery including a positive electrode having a nickel oxide compound such as nickel hydroxide as a positive electrode active material, a negative electrode having a hydrogen storage alloy as a negative electrode active material, and an electrolytic solution comprising an aqueous alkali metal solution. It is.
　ニッケル金属水素化物電池の正極に、導電性向上の目的で、コバルトを添加する技術が知られている。正極に添加されたコバルトは、強塩基性の水溶液である電解液と接触することで、コバルト錯イオンを形成した後に、正極に水酸化コバルトとして析出する。その後の充電時に、水酸化コバルトが酸化されて、導電性に優れるオキシ水酸化コバルトが生成される。ここで生成されたオキシ水酸化コバルトに因り、正極に導電ネットワークが形成されると考えられている。 技術 A technique of adding cobalt to the positive electrode of a nickel metal hydride battery for the purpose of improving conductivity is known. Cobalt added to the positive electrode contacts an electrolytic solution that is a strongly basic aqueous solution to form cobalt complex ions, and then precipitates on the positive electrode as cobalt hydroxide. During subsequent charging, the cobalt hydroxide is oxidized to produce cobalt oxyhydroxide having excellent conductivity. It is believed that a conductive network is formed on the positive electrode due to the cobalt oxyhydroxide generated here.
　特許文献１には、正極に金属コバルト及び水酸化コバルトを含有するニッケル金属水素化物電池に対して、充電を行うことに因り、正極に含まれる金属コバルト及び水酸化コバルトが酸化して、オキシ水酸化コバルトが生成したことが記載されている（実施例に関する００３０及び００３２段落を参照）。 Patent Literature 1 discloses that a nickel metal hydride battery containing metal cobalt and cobalt hydroxide in the positive electrode is charged, so that the metal cobalt and the cobalt hydroxide contained in the positive electrode are oxidized to form oxywater. It is stated that cobalt oxide was formed (see paragraphs 0030 and 0032 for the examples).
　特許文献２には、正極に金属コバルトを含有するニッケル金属水素化物電池に対して、充電を行うことに因り、正極中に含まれるコバルトを高い導電性を持つオキシ水酸化コバルトに変化させる技術が記載されている（０００７段落など）。 Patent Literature 2 discloses a technique in which a nickel metal hydride battery containing metal cobalt in a positive electrode is charged to change cobalt contained in the positive electrode into cobalt oxyhydroxide having high conductivity. (Eg paragraph 0007).
　また、負極に関して、水素吸蔵合金の負極活物質としての性能を向上させるため、様々な技術が提案されている。例えば、特許文献３には、ＣａＣｕ５型の結晶構造を有し、かつ、希土類元素並びにＮｉ、Ｃｏ、Ｍｎ及びＡｌを含む合金からなる水素吸蔵合金を、水酸化ナトリウム水溶液に浸漬処理した後に、水洗する技術が記載されている。そして、同文献には、上述の水素吸蔵合金を水酸化ナトリウム水溶液に浸漬処理することで、水素吸蔵合金はニッケルで被覆されたような状態になることが記載されている。 Various techniques have been proposed for the negative electrode in order to improve the performance of the hydrogen storage alloy as a negative electrode active material. For example, Patent Document 3 discloses that a hydrogen storage alloy having a CaCu 5- type crystal structure and comprising a rare earth element and an alloy containing Ni, Co, Mn, and Al is immersed in an aqueous sodium hydroxide solution. A technique for washing with water is described. The document describes that by immersing the above-described hydrogen storage alloy in an aqueous sodium hydroxide solution, the hydrogen storage alloy becomes in a state of being coated with nickel.
特開２００２－２６０７１９号公報JP-A-2002-260719 特開２００３－６８２９１号公報JP-A-2003-68291 特開２００２－２５６３０１号公報JP-A-2002-256301
　さて、産業界は、優れた特性を示すニッケル金属水素化物電池を切望している。
　本発明はかかる事情に鑑みて為されたものであり、優れた電池特性を示す新たなニッケル金属水素化物電池を提供することを目的とする。 The industry is eager for a nickel metal hydride battery that exhibits excellent properties.
The present invention has been made in view of such circumstances, and has as its object to provide a new nickel metal hydride battery exhibiting excellent battery characteristics.
　本発明者は、正極に金属コバルトを含有するニッケル金属水素化物電池に対して、充電を行うことに因り、正極中に含まれるコバルトを高い導電性を持つオキシ水酸化コバルトに変化させるとの従来の技術ではなく、あらかじめ、正極活物質の周りにオキシ水酸化コバルトの層を形成させておく技術を想起した。 The present inventor has proposed that a nickel metal hydride battery containing metal cobalt in the positive electrode be charged to convert cobalt contained in the positive electrode into cobalt oxyhydroxide having high conductivity. Instead of the technique described in the above, a technique in which a layer of cobalt oxyhydroxide is previously formed around the positive electrode active material was recalled.
　そして、本発明者の鋭意検討の結果、あらかじめ、正極活物質の周りにオキシ水酸化コバルトの層を形成させておく場合において、オキシ水酸化コバルトの層にアルカリ金属、特にリチウム又はナトリウムをドープしておくことで、正極活物質の導電性が著しく向上することを見出した。 As a result of the inventor's intensive studies, in advance, when a layer of cobalt oxyhydroxide is formed around the positive electrode active material, the layer of cobalt oxyhydroxide is doped with an alkali metal, particularly lithium or sodium. By doing so, it was found that the conductivity of the positive electrode active material was significantly improved.
　また、本発明者は、正極の検討と同時に負極の検討も行い、意外にも、酸素含有量が高い水素吸蔵合金を負極活物質として採用したニッケル金属水素化物電池が、電池抵抗の低減に効果があることを見出した。 In addition, the present inventor studied a negative electrode simultaneously with a positive electrode, and surprisingly, a nickel metal hydride battery employing a hydrogen storage alloy having a high oxygen content as a negative electrode active material was effective in reducing battery resistance. I found that there is.
　これらの知見に基づき、本発明者は本発明を完成させた。 Based on these findings, the present inventors have completed the present invention.
　本発明のニッケル金属水素化物電池は、
　リチウム又はナトリウムを含有するオキシ水酸化コバルト層で被覆された正極活物質と、
　充放電前における酸素濃度が１０００ｐｐｍ以上の負極活物質と、
　を備えることを特徴とする。 The nickel metal hydride battery of the present invention,
A cathode active material coated with a cobalt oxyhydroxide layer containing lithium or sodium,
A negative electrode active material having an oxygen concentration of 1000 ppm or more before charge and discharge,
It is characterized by having.
　本発明のニッケル金属水素化物電池は、電池特性に優れる。 ニ ッ ケ ル The nickel metal hydride battery of the present invention has excellent battery characteristics.
応用例１の双極型ニッケル金属水素化物電池の模式断面図である。6 is a schematic cross-sectional view of a bipolar nickel metal hydride battery of Application Example 1. FIG.
　以下に、本発明を実施するための形態を説明する。なお、特に断らない限り、本明細書に記載された数値範囲「ａ～ｂ」は、下限ａ及び上限ｂをその範囲に含む。そして、これらの上限値及び下限値、ならびに実施例中に列記した数値も含めてそれらを任意に組み合わせることで数値範囲を構成し得る。さらに、これらの数値範囲内から任意に選択した数値を、新たな上限や下限の数値とすることができる。 Hereinafter, embodiments for carrying out the present invention will be described. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit a and the upper limit b. A numerical range can be formed by arbitrarily combining these upper and lower limits and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from within these numerical ranges can be used as new upper and lower numerical values.
　本発明のニッケル金属水素化物電池は、
　リチウム又はナトリウムを含有するオキシ水酸化コバルト層で被覆された正極活物質（以下、本発明の正極活物質ということがある。）と、
　充放電前における酸素濃度が１０００ｐｐｍ以上の負極活物質（以下、本発明の負極活物質ということがある。）と、
　を備えることを特徴とする。 The nickel metal hydride battery of the present invention,
A cathode active material coated with a cobalt oxyhydroxide layer containing lithium or sodium (hereinafter, may be referred to as a cathode active material of the present invention);
A negative electrode active material having an oxygen concentration of 1000 ppm or more before charge and discharge (hereinafter, sometimes referred to as a negative electrode active material of the present invention);
It is characterized by having.
　まず、本発明の正極活物質について説明する。
　本発明の正極活物質は、リチウム又はナトリウム、及びオキシ水酸化コバルトを含有するオキシ水酸化コバルト層と、オキシ水酸化コバルト層で被覆された正極活物質本体（本明細書中では、単に「正極活物質」ということがある。）を含む。 First, the positive electrode active material of the present invention will be described.
The positive electrode active material of the present invention includes a cobalt oxyhydroxide layer containing lithium or sodium and cobalt oxyhydroxide, and a positive electrode active material body coated with the cobalt oxyhydroxide layer (in the present specification, simply referred to as a “positive electrode”). Active material ”).
　正極活物質としては、ニッケル金属水素化物電池の正極活物質として用いられるものであれば限定されない。具体的な正極活物質として、水酸化ニッケル、金属をドープした水酸化ニッケルを例示できる。水酸化ニッケルにドープする金属として、マグネシウム、カルシウムなどの第２族元素、コバルト、ロジウム、イリジウムなどの第９族元素、亜鉛、カドミウムなどの第１２族元素を例示できる。 The positive electrode active material is not limited as long as it is used as a positive electrode active material of a nickel metal hydride battery. Specific examples of the positive electrode active material include nickel hydroxide and nickel hydroxide doped with a metal. Examples of the metal to be doped into nickel hydroxide include Group 2 elements such as magnesium and calcium, Group 9 elements such as cobalt, rhodium and iridium, and Group 12 elements such as zinc and cadmium.
　正極活物質本体に、リチウム又はナトリウム、及びオキシ水酸化コバルトを含有するオキシ水酸化コバルト層を形成する方法は、以下のＰ－１）工程及びＰ－２）工程である。 方法 The method of forming a cobalt oxyhydroxide layer containing lithium or sodium and cobalt oxyhydroxide on the positive electrode active material main body includes the following steps P-1) and P-2).
　Ｐ－１）正極活物質の表面に水酸化コバルト層を形成させる工程
　Ｐ－２）前記水酸化コバルト層が形成された正極活物質を加熱して、前記水酸化コバルト層をオキシ水酸化コバルト層に変換する工程であって、さらに、前記水酸化コバルト層又は前記オキシ水酸化コバルト層にリチウム又はナトリウムをドープする工程 P-1) A step of forming a cobalt hydroxide layer on the surface of the positive electrode active material P-2) The positive electrode active material on which the cobalt hydroxide layer is formed is heated to convert the cobalt hydroxide layer to a cobalt oxyhydroxide layer And doping the cobalt hydroxide layer or the cobalt oxyhydroxide layer with lithium or sodium.
　Ｐ－１）工程としては、以下のＰ－１－１）工程、又は、Ｐ－１－２）工程を例示できる。
　Ｐ－１－１）コバルト塩水溶液中に正極活物質を分散させた分散液を製造した上で、分散液のｐＨをアルカリ性にして、正極活物質の表面に水酸化コバルトを析出させる工程
　Ｐ－１－２）正極活物質をアルカリ性水溶液に分散させた分散液を製造した上で、分散液にコバルト塩水溶液を添加して、正極活物質の表面に水酸化コバルトを析出させる工程 As the P-1) step, the following P-1-1) step or P-1-2) step can be exemplified.
P-1-1) A step of preparing a dispersion in which the positive electrode active material is dispersed in an aqueous solution of a cobalt salt, making the pH of the dispersion alkaline, and depositing cobalt hydroxide on the surface of the positive electrode active material. 1-2) a step of producing a dispersion in which the positive electrode active material is dispersed in an alkaline aqueous solution, and adding an aqueous cobalt salt solution to the dispersion to precipitate cobalt hydroxide on the surface of the positive electrode active material
　コバルト塩としては、硫酸コバルト、硝酸コバルト、塩化コバルトを例示できる。 Examples of the cobalt salt include cobalt sulfate, cobalt nitrate, and cobalt chloride.
　Ｐ－２）工程における加熱温度としては、７０～２３０℃、８０～２００℃を例示できる。Ｐ－２）工程における雰囲気は酸素含有雰囲気である。Ｐ－２）工程は、費用の点から、空気存在下で行うのが好ましい。 加熱 P-2) The heating temperature in the step can be, for example, 70 to 230 ° C. or 80 to 200 ° C. The atmosphere in the step P-2) is an oxygen-containing atmosphere. The step P-2) is preferably performed in the presence of air from the viewpoint of cost.
　Ｐ－２）工程において、リチウム又はナトリウムをドープする時期は、加熱前の水酸化コバルト層に対してでも良いし、加熱中の水酸化コバルト層又はオキシ水酸化コバルト層に対してでも良い。 In the step (P-2), lithium or sodium may be doped with respect to the cobalt hydroxide layer before heating, or to the cobalt hydroxide layer or cobalt oxyhydroxide layer during heating.
　Ｐ－２）工程において、リチウム又はナトリウムをドープする方法としては、正極活物質に対して、リチウム塩水溶液又はナトリウム塩水溶液を噴霧する方法が好ましい。正極活物質に対してリチウム塩水溶液又はナトリウム塩水溶液を噴霧しつつ加熱すること、又は、正極活物質に対してリチウム塩水溶液又はナトリウム塩水溶液を噴霧した後に加熱することで、正極活物質表面のオキシ水酸化コバルト層（又は、オキシ水酸化コバルト層に変換前の水酸化コバルト層）に対して、リチウム又はナトリウムがドープされる。
　リチウム又はナトリウムをドープする方法における加熱温度としては、Ｐ－２）工程において、水酸化コバルト層をオキシ水酸化コバルト層に変換する際の加熱温度と同様の温度で行うのが合理的である。 In the step P-2), as a method of doping with lithium or sodium, a method of spraying a lithium salt aqueous solution or a sodium salt aqueous solution on the positive electrode active material is preferable. By heating while spraying a lithium salt aqueous solution or a sodium salt aqueous solution on the positive electrode active material, or by heating after spraying a lithium salt aqueous solution or a sodium salt aqueous solution on the positive electrode active material, the surface of the positive electrode active material is heated. Lithium or sodium is doped into the cobalt oxyhydroxide layer (or the cobalt hydroxide layer before conversion to the cobalt oxyhydroxide layer).
As the heating temperature in the method of doping with lithium or sodium, it is reasonable to perform the heating at the same temperature as the heating temperature in converting the cobalt hydroxide layer to the cobalt oxyhydroxide layer in the step P-2).
　リチウム塩としては、水酸化リチウム、硫酸リチウム、硝酸リチウム、塩化リチウム、酢酸リチウム、トリフルオロメタンスルホン酸リチウム、リチウムビス(トリフルオロメタンスルホニル)イミドを例示できる。 Examples of lithium salts include lithium hydroxide, lithium sulfate, lithium nitrate, lithium chloride, lithium acetate, lithium trifluoromethanesulfonate, and lithium bis (trifluoromethanesulfonyl) imide.
　ナトリウム塩としては、水酸化ナトリウム、硫酸ナトリウム、硝酸ナトリウム、塩化ナトリウム、酢酸ナトリウム、トリフルオロメタンスルホン酸ナトリウム、ナトリウムビス(トリフルオロメタンスルホニル)イミドを例示できる。 Examples of sodium salts include sodium hydroxide, sodium sulfate, sodium nitrate, sodium chloride, sodium acetate, sodium trifluoromethanesulfonate, and sodium bis (trifluoromethanesulfonyl) imide.
　Ｐ－２）工程においては、リチウム又はナトリウムのみではなく、リチウム及びナトリウムをドープしてもよいし、他のアルカリ金属をドープしてもよい。他のアルカリ金属として、カリウムを例示できる。
　他のアルカリ金属のドープ方法としては、リチウム又はナトリウムをドープする方法と同様に、アルカリ金属塩水溶液を噴霧する方法が好ましい。 In the step P-2), not only lithium or sodium but also lithium and sodium may be doped, or another alkali metal may be doped. As another alkali metal, potassium can be exemplified.
As a method of doping other alkali metals, a method of spraying an aqueous solution of an alkali metal salt is preferable, similarly to the method of doping lithium or sodium.
　リチウムを含有するオキシ水酸化コバルト層で被覆された本発明の正極活物質が優れた導電性を示す理由は、以下のとおりと考えられる。 The reason why the positive electrode active material of the present invention coated with the lithium-containing cobalt oxyhydroxide layer exhibits excellent conductivity is considered as follows.
　まず、リチウムなどのアルカリ金属をドープせずに、オキシ水酸化コバルト層を正極活物質に形成させる場合には、オキシ水酸化コバルト層には、ＣｏＯＯＨのうち導電性に劣るβ－ＣｏＯＯＨとともに、導電性に劣るＣｏ３Ｏ４が形成されると考えられる。なお、Ｃｏ３Ｏ４においては、コバルトは２価と３価の両者で存在する。 First, in the case where a cobalt oxyhydroxide layer is formed on the positive electrode active material without doping with an alkali metal such as lithium, the cobalt oxyhydroxide layer has a conductive property together with β-CoOOH, which has poor conductivity among CoOOH. It is considered that Co 3 O 4 having poor properties is formed. In Co 3 O 4 , cobalt exists in both divalent and trivalent states.
　次に、リチウム以外のアルカリ金属をドープする方法を用いて、オキシ水酸化コバルト層を正極活物質に形成させる場合には、オキシ水酸化コバルト層には、ＣｏＯＯＨのうち導電性に優れるγ－ＣｏＯＯＨが多く形成されるものの、導電性に劣るＣｏ３Ｏ４も形成されると考えられる。 Next, when a cobalt oxyhydroxide layer is formed on the positive electrode active material by using a method of doping an alkali metal other than lithium, the cobalt oxyhydroxide layer has γ-CoOOH, which is superior in conductivity among CoOOH. Are formed, but it is considered that Co 3 O 4 having poor conductivity is also formed.
　しかしながら、リチウムをドープする方法を用いて、オキシ水酸化コバルト層を正極活物質に形成させる場合には、導電性に劣るＣｏ３Ｏ４が形成されたとしても、リチウムの存在に因り、少なくともＣｏ３Ｏ４の一部が導電性に優れるＬｉＣｏＯ２に変換されると考えられる。そうすると、リチウムをドープする方法を用いて、オキシ水酸化コバルト層を正極活物質に形成させる場合には、オキシ水酸化コバルト層には、ＣｏＯＯＨのうち導電性に優れるγ－ＣｏＯＯＨが多く存在し、比較的導電性に優れるＬｉＣｏＯ２も存在するものの、導電性に劣るＣｏ３Ｏ４の存在する割合は著しく低いと考えられる。 However, in the case where the cobalt oxyhydroxide layer is formed on the positive electrode active material by using a lithium doping method, even if Co 3 O 4 having poor conductivity is formed, at least Co 3 O 4 is formed due to the presence of lithium. It is considered that a part of 3 O 4 is converted to LiCoO 2 having excellent conductivity. Then, when the cobalt oxyhydroxide layer is formed on the positive electrode active material using the lithium doping method, the cobalt oxyhydroxide layer contains a large amount of γ-CoOOH having excellent conductivity among CoOOH, Although there is LiCoO 2 having relatively excellent conductivity, the proportion of Co 3 O 4 having poor conductivity is considered to be extremely low.
　なお、γ－ＣｏＯＯＨの抵抗率は概ね２Ω・ｃｍ程度、ＬｉＣｏＯ２の抵抗率は概ね１×１０２Ω・ｃｍ程度、Ｃｏ３Ｏ４の抵抗率は概ね１×１０６Ω・ｃｍ程度、β－ＣｏＯＯＨの抵抗率は概ね１×１０８Ω・ｃｍ程度である。 The resistivity of γ-CoOOH is about 2Ω · cm, the resistivity of LiCoO 2 is about 1 × 10 2 Ω · cm, the resistivity of Co 3 O 4 is about 1 × 10 6 Ω · cm, β -The resistivity of CoOOH is approximately 1 × 10 8 Ω · cm.
　導電性に優れるγ－ＣｏＯＯＨ及びＬｉＣｏＯ２のコバルトは、いずれも３価である。原料の水酸化コバルトのコバルトは２価であること、及び、Ｃｏ３Ｏ４においては、コバルトは２価と３価の両者で存在することを考慮すると、本発明の正極活物質のオキシ水酸化コバルト層におけるコバルトの価数は、高い方が好ましいといえる。 Both γ-CoOOH and LiCoO 2 , which are excellent in conductivity, are trivalent. Considering that cobalt of the raw material cobalt hydroxide is divalent, and that Co 3 O 4 has both divalent and trivalent cobalt, the oxyhydroxide of the positive electrode active material of the present invention is considered. The higher the valence of cobalt in the cobalt layer, the better.
　本発明の正極活物質のオキシ水酸化コバルト層におけるコバルトの価数としては、２．９～３．２が好ましく、２．９５～３．１がより好ましく、２．９８～３．０７がさらに好ましい。
　ここでのコバルトの価数は、本発明の正極活物質の表面に存在するオキシ水酸化コバルト層におけるコバルトの価数を、ヨードメトリー法で測定した値である。 The valence of cobalt in the cobalt oxyhydroxide layer of the positive electrode active material of the present invention is preferably 2.9 to 3.2, more preferably 2.95 to 3.1, and further preferably 2.98 to 3.07. preferable.
Here, the valence of cobalt is a value obtained by measuring the valence of cobalt in the cobalt oxyhydroxide layer present on the surface of the positive electrode active material of the present invention by an iodometry method.
　本発明の正極活物質におけるコバルトの含有量は、１～１０質量％が好ましく、２～７質量％がより好ましく、３～７質量％がさらに好ましい。
　本発明の正極活物質におけるリチウムの含有量は、０．０１～０．３質量％が好ましく、０．０４～０．２質量％がより好ましく、０．０７～０．１質量％がさらに好ましい。
　本発明の正極活物質におけるナトリウムの含有量は、０．０１～１質量％が好ましく、０．１～０．６質量％がより好ましく、０．２～０．５質量％がさらに好ましい。
　本発明の正極活物質におけるリチウム及びナトリウム以外のアルカリ金属の含有量としては、０質量％、０．０１～１質量％、０．１～０．６質量％、０．２～０．５質量％を例示できる。 The content of cobalt in the positive electrode active material of the present invention is preferably 1 to 10% by mass, more preferably 2 to 7% by mass, and still more preferably 3 to 7% by mass.
The content of lithium in the positive electrode active material of the present invention is preferably 0.01 to 0.3% by mass, more preferably 0.04 to 0.2% by mass, and still more preferably 0.07 to 0.1% by mass. .
The content of sodium in the positive electrode active material of the present invention is preferably 0.01 to 1% by mass, more preferably 0.1 to 0.6% by mass, and further preferably 0.2 to 0.5% by mass.
The content of the alkali metal other than lithium and sodium in the positive electrode active material of the present invention is 0% by mass, 0.01 to 1% by mass, 0.1 to 0.6% by mass, 0.2 to 0.5% by mass. % Can be exemplified.
　本発明の正極活物質は粉末状態が好ましく、また、その平均粒子径としては３～４０μｍの範囲内が好ましく、５～３０μｍの範囲内がより好ましく、７～２０μｍの範囲内がさらに好ましい。なお、本明細書において、平均粒子径とは、一般的なレーザー回折式粒度分布測定装置を用いた測定におけるＤ５０の値を意味する。 The positive electrode active material of the present invention is preferably in a powder state, and has an average particle diameter of preferably 3 to 40 μm, more preferably 5 to 30 μm, and further preferably 7 to 20 μm. In the present specification, the average particle diameter means a value of D 50 in the measurement using a conventional laser diffraction particle size distribution analyzer.
　本発明の正極活物質のＢＥＴ比表面積としては、５～３０ｍ２／ｇが好ましく、１０～２０ｍ２／ｇがより好ましく、１２～１８ｍ２／ｇがさらに好ましい。 The BET specific surface area of the positive electrode active material of the present invention, preferably 5 ~ 30m 2 / g, more preferably from 10 ~ 20m 2 / g, more preferably 12 ~ 18m 2 / g.
　本発明の正極活物質の抵抗率は、０．１～４０Ω・ｃｍが好ましく、０．１～１０Ω・ｃｍがより好ましく、０．１～７Ω・ｃｍがさらに好ましく、０．１～５Ω・ｃｍが特に好ましく、０．１～４Ω・ｃｍが最も好ましい。 The resistivity of the positive electrode active material of the present invention is preferably 0.1 to 40 Ω · cm, more preferably 0.1 to 10 Ω · cm, further preferably 0.1 to 7 Ω · cm, and 0.1 to 5 Ω · cm. Is particularly preferable, and 0.1 to 4 Ω · cm is most preferable.
　次に、本発明の負極活物質について説明する。本発明の負極活物質とは、実質的に、水素吸蔵合金の表面が酸化されたものである。 Next, the negative electrode active material of the present invention will be described. The negative electrode active material of the present invention is substantially a material obtained by oxidizing the surface of a hydrogen storage alloy.
　本発明の負極活物質は、充放電前における酸素濃度が１０００ｐｐｍ以上である。酸素濃度の範囲としては、１０００～９００００ｐｐｍの範囲内が好ましく、５０００～８００００ｐｐｍの範囲内がより好ましく、１００００～６００００ｐｐｍの範囲内がさらに好ましく、１５０００～５００００ｐｐｍの範囲内が特に好ましく、１８０００～４５０００ｐｐｍの範囲内が最も好ましい。 負極 The negative electrode active material of the present invention has an oxygen concentration of 1000 ppm or more before charge and discharge. The oxygen concentration is preferably in the range of 1000 to 90000 ppm, more preferably in the range of 5000 to 80000 ppm, still more preferably in the range of 10,000 to 60000 ppm, particularly preferably in the range of 15,000 to 50,000 ppm, and more preferably in the range of 18,000 to 45,000 ppm. Within the range is most preferred.
　負極活物質の酸素濃度は、当該負極活物質を備えるニッケル金属水素化物電池を充放電する前における酸素濃度が上記範囲内であればよい。なお、ニッケル金属水素化物電池の充放電時には、負極活物質の酸素濃度が変動し得る。
　本発明の負極活物質の酸素濃度を、「電池製造前」若しくは「電池製造時」、又は、「電極製造前」若しくは「電極製造時」の値であると解釈してもよい。 The oxygen concentration of the negative electrode active material may be such that the oxygen concentration before charging / discharging the nickel metal hydride battery including the negative electrode active material is within the above range. Note that during charging and discharging of the nickel metal hydride battery, the oxygen concentration of the negative electrode active material may fluctuate.
The oxygen concentration of the negative electrode active material of the present invention may be interpreted as a value “before battery production” or “at the time of battery production”, or “before electrode production” or “at the time of electrode production”.
　本発明の負極活物質の平均粒子径としては１～４０μｍの範囲内が好ましく、３～３０μｍの範囲内がより好ましく、４～２０μｍの範囲内がさらに好ましく、５～１５μｍの範囲内が特に好ましく、５～１２μｍの範囲内が最も好ましい。 The average particle size of the negative electrode active material of the present invention is preferably in the range of 1 to 40 μm, more preferably in the range of 3 to 30 μm, further preferably in the range of 4 to 20 μm, and particularly preferably in the range of 5 to 15 μm. Most preferably in the range of 5 to 12 μm.
　本発明の負極活物質のＢＥＴ比表面積としては、０．２～１０．０ｍ２／ｇが好ましく、０．５～８．０ｍ２／ｇがより好ましく、１．０～６．０ｍ２／ｇがさらに好ましい。 The BET specific surface area of the negative electrode active material of the present invention, preferably 0.2 ~ 10.0m 2 / g, more preferably 0.5 ~ 8.0m 2 / g, 1.0 ~ 6.0m 2 / g Is more preferred.
　本発明の負極活物質のうち、Ｎｉを含有するものについての飽和磁化としては、０．２～１０ｅｍｕ／ｇが好ましく、０．５～９ｅｍｕ／ｇがより好ましく、１～８ｅｍｕ／ｇがさらに好ましく、１．５～７ｅｍｕ／ｇが特に好ましい。 Among the negative electrode active materials of the present invention, the saturation magnetization of those containing Ni is preferably 0.2 to 10 emu / g, more preferably 0.5 to 9 emu / g, and still more preferably 1 to 8 emu / g. , 1.5 to 7 emu / g are particularly preferred.
　負極活物質における水素吸蔵合金としては、ニッケル金属水素化物電池の負極活物質として用いられるものであれば限定されない。水素吸蔵合金とは、基本的に、容易に水素と反応するものの、水素の放出能力に劣る金属Ａと、水素と反応しにくいものの、水素の放出能力に優れる金属Ｂとの合金である。Ａとしては、Ｍｇなどの第２族元素、Ｓｃ、ランタノイドなどの第３族元素、Ｔｉ、Ｚｒなどの第４族元素、Ｖ、Ｔａなどの第５族元素、複数の希土類元素を含有するミッシュメタル（以下、Ｍｍと略すことがある。）、Ｐｄなどを例示できる。また、Ｂとしては、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｐｔ、Ｃｕ、Ａｇ、Ｍｎ、Ｚｎ、Ａｌなどを例示できる。 水 素 The hydrogen storage alloy in the negative electrode active material is not limited as long as it is used as a negative electrode active material of a nickel metal hydride battery. The hydrogen storage alloy is basically an alloy of a metal A, which easily reacts with hydrogen but is inferior in hydrogen releasing ability, and a metal B which hardly reacts with hydrogen but has excellent hydrogen releasing ability. A misch containing a Group 2 element such as Mg, a Group 3 element such as Sc and lanthanoid, a Group 4 element such as Ti and Zr, a Group 5 element such as V and Ta, and a plurality of rare earth elements. Metal (hereinafter, may be abbreviated as Mm), Pd and the like can be exemplified. Examples of B include Fe, Co, Ni, Cr, Pt, Cu, Ag, Mn, Zn, and Al.
　具体的な水素吸蔵合金として、六方晶ＣａＣｕ5型結晶構造を示すＡＢ5型、六方晶ＭｇＺｎ2型若しくは立方晶ＭｇＣｕ2型結晶構造を示すＡＢ2型、立方晶ＣｓＣｌ型結晶構造を示すＡＢ型、六方晶Ｍｇ2Ｎｉ型結晶構造を示すＡ2Ｂ型、体心立方晶構造を示す固溶体型、並びに、ＡＢ5型及びＡＢ2型の結晶構造が組み合わされたＡＢ3型、Ａ2Ｂ7型及びＡ5Ｂ19型のものを例示できる。水素吸蔵合金は、以上の結晶構造のうち、１種類を有するものでもよいし、また、以上の結晶構造の複数を有するものでもよい。 Specific hydrogen-absorbing alloy, AB 5 type showing a hexagonal CaCu 5 type crystal structure, hexagonal MgZn 2 type or AB 2 type showing a cubic MgCu 2 type crystal structure, AB type indicating the cubic CsCl-type crystal structure , a 2 B type denoting hexagonal Mg 2 Ni-type crystal structure, solid solution showing a body-centered cubic structure, and, AB 5 type and AB 2 type AB 3 type crystal structure are combined in, a 2 B 7 It can be exemplified of a type and a 5 B 19 type. The hydrogen storage alloy may have one of the above crystal structures, or may have a plurality of the above crystal structures.
　ＡＢ5型水素吸蔵合金として、ＬａＮｉ5、ＣａＣｕ5、ＭｍＮｉ5を例示できる。ＡＢ2型水素吸蔵合金として、ＭｇＺｎ2、ＺｒＮｉ2、ＺｒＣｒ2を例示できる。ＡＢ型水素吸蔵合金として、ＴｉＦｅ、ＴｉＣｏを例示できる。Ａ2Ｂ型水素吸蔵合金として、Ｍｇ2Ｎｉ、Ｍｇ2Ｃｕを例示できる。固溶体型水素吸蔵合金として、Ｔｉ－Ｖ、Ｖ－Ｎｂ、Ｔｉ－Ｃｒを例示できる。ＡＢ3型水素吸蔵合金として、ＣｅＮｉ3を例示できる。Ａ2Ｂ7型水素吸蔵合金として、Ｃｅ2Ｎｉ7を例示できる。Ａ5Ｂ19型水素吸蔵合金として、Ｃｅ5Ｃｏ19、Ｐｒ5Ｃｏ19を例示できる。上記の各結晶構造において、一部の金属を、他の１種類若しくは複数種類の金属又は元素で置換してもよい。 As AB 5 type hydrogen storage alloy can be exemplified by LaNi 5, CaCu 5, MmNi 5 . Examples of the AB 2 type hydrogen storage alloy include MgZn 2 , ZrNi 2 , and ZrCr 2 . Examples of the AB-type hydrogen storage alloy include TiFe and TiCo. Examples of the A 2 B type hydrogen storage alloy include Mg 2 Ni and Mg 2 Cu. Examples of solid solution type hydrogen storage alloys include Ti-V, V-Nb, and Ti-Cr. CeNi 3 can be exemplified as the AB 3 type hydrogen storage alloy. Ce 2 Ni 7 can be exemplified as the A 2 B 7 type hydrogen storage alloy. Examples of the A 5 B 19 type hydrogen storage alloy include Ce 5 Co 19 and Pr 5 Co 19 . In each of the above crystal structures, some metals may be replaced with one or more other metals or elements.
　水素吸蔵合金としては、希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金が好ましい。 As the hydrogen storage alloy, an A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni is preferable.
　酸素濃度が高い本発明の負極活物質を得るには、積極的に、水素吸蔵合金の表面を酸化させるのがよい。以下、希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金を例として、水素吸蔵合金に対して好適な方法で処理（以下、水素吸蔵合金の処理方法という。）を行い、本発明の負極活物質を製造する手順を説明する。 In order to obtain the negative electrode active material of the present invention having a high oxygen concentration, it is preferable to positively oxidize the surface of the hydrogen storage alloy. Hereinafter, the A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni is used as an example, and the hydrogen storage alloy is processed by a suitable method (hereinafter referred to as a hydrogen storage alloy processing method). The procedure for producing the negative electrode active material of the present invention will be described.
　水素吸蔵合金の処理方法は、
　Ｎ－１）水素吸蔵合金をアルカリ水溶液で処理する工程、
　Ｎ－２）前記Ｎ－１）工程後の水素吸蔵合金の表面を酸化する工程、を有する。
　Ｎ－１）工程は、水素吸蔵合金を酸化させるための必須の工程ではないが、後述するとおり、かかる工程を経ることに因り、より好適な本発明の負極活物質を得ることができる。 The processing method of the hydrogen storage alloy is as follows:
N-1) a step of treating the hydrogen storage alloy with an aqueous alkali solution;
N-2) oxidizing the surface of the hydrogen storage alloy after the N-1) step.
The step N-1) is not an essential step for oxidizing the hydrogen storage alloy. However, as described later, a more suitable negative electrode active material of the present invention can be obtained by going through these steps.
　Ｎ－１）工程としては、以下のａ）工程及びｂ）工程を有するのが好ましい。
　ａ）希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金を、アルカリ金属の水酸化物を溶解した第１アルカリ水溶液で処理する工程
　ｂ）ａ）工程後、第１アルカリ水溶液から水素吸蔵合金を分離し、アルカリ金属の水酸化物を溶解した第２アルカリ水溶液で処理する工程 The step N-1) preferably includes the following steps a) and b).
a) a step of treating an A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni with a first alkaline aqueous solution in which a hydroxide of an alkali metal is dissolved b) a) a first alkaline aqueous solution after the step a) Of separating hydrogen storage alloy from water and treating it with a second aqueous alkali solution in which alkali metal hydroxide is dissolved
　まず、ａ）希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金を、アルカリ金属の水酸化物を溶解した第１アルカリ水溶液で処理する工程（以下、単に「ａ）工程」という。）について、説明する。 First, a) a step of treating an A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni with a first aqueous alkali solution in which an alkali metal hydroxide is dissolved (hereinafter simply referred to as “a) step” That. ) Will be described.
　ａ）工程に用いられる水素吸蔵合金は、希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金である。希土類元素及びＭｇは金属Ａに属し、Ｎｉは金属Ｂに属すると考えられる。希土類元素としては、Ｓｃ、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕを例示できる。ａ）工程に用いられる水素吸蔵合金には、その他の金属元素が存在してもよく、その他の金属元素として、Ｍｎ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ａｌ、Ｃｒ、Ｐｔ、Ｃｕ、Ａｇ、Ｔｉ、Ｚｒ、Ｖ、Ｔａを例示できる。ａ）工程に用いられる水素吸蔵合金としては、Ｎｉを６０～７０質量％で含有する水素吸蔵合金が好ましい。 The hydrogen storage alloy used in the step a) is an A 2 B 7 type hydrogen storage alloy containing a rare earth element, Mg and Ni. It is considered that rare earth elements and Mg belong to metal A, and Ni belongs to metal B. Examples of rare earth elements include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Other metal elements may be present in the hydrogen storage alloy used in the step a), and as other metal elements, Mn, Fe, Co, Cu, Zn, Al, Cr, Pt, Cu, Ag, Ti , Zr, V, and Ta. As the hydrogen storage alloy used in the step a), a hydrogen storage alloy containing 60 to 70% by mass of Ni is preferable.
　水素吸蔵合金は、粉砕されて、一定程度の粒子径に調製された粉末状のものが好ましい。水素吸蔵合金の平均粒子径としては１～４０μｍの範囲内が好ましく、３～３０μｍの範囲内がより好ましく、４～２０μｍの範囲内がさらに好ましく、５～１５μｍの範囲内が特に好ましく、５～１２μｍの範囲内が最も好ましい。 The hydrogen storage alloy is preferably in the form of a powder which is pulverized and adjusted to a certain particle size. The average particle size of the hydrogen storage alloy is preferably in the range of 1 to 40 μm, more preferably in the range of 3 to 30 μm, still more preferably in the range of 4 to 20 μm, particularly preferably in the range of 5 to 15 μm. Most preferably, it is within the range of 12 μm.
　ａ）工程で水素吸蔵合金をアルカリ金属の水酸化物を溶解した第１アルカリ水溶液で処理すると、アルカリ水溶液に対して溶解性の高い希土類元素が水素吸蔵合金の表面から溶出することになる。ここで、Ｎｉはアルカリ水溶液に対して溶解性が低いため、結果的に、水素吸蔵合金の表面のＮｉ濃度は、水素吸蔵合金の内部と比較して高くなる。以下、水素吸蔵合金において、Ｎｉ濃度が内部と比較して高い部分を、Ｎｉ濃縮層という。Ｎｉ濃縮層の存在に因り、負極活物質の性能が向上すると考えられる。 When the hydrogen storage alloy is treated with the first alkali aqueous solution in which the alkali metal hydroxide is dissolved in the step a), the rare earth element having high solubility in the alkali aqueous solution elutes from the surface of the hydrogen storage alloy. Here, since Ni has low solubility in the alkaline aqueous solution, as a result, the Ni concentration on the surface of the hydrogen storage alloy becomes higher than that inside the hydrogen storage alloy. Hereinafter, a portion of the hydrogen storage alloy where the Ni concentration is higher than the inside is referred to as a Ni-enriched layer. It is considered that the performance of the negative electrode active material is improved due to the presence of the Ni enriched layer.
　アルカリ金属の水酸化物としては、水酸化リチウム、水酸化ナトリウム、水酸化カリウムを例示でき、中でも、水酸化ナトリウムが好ましい。第１アルカリ水溶液として水酸化ナトリウム水溶液を用いることで、第１アルカリ水溶液として水酸化リチウムや水酸化カリウムを用いる場合と比較して、本発明のニッケル金属水素化物電池の電池特性が好適化する場合がある。 Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and among them, sodium hydroxide is preferable. When the battery characteristics of the nickel metal hydride battery of the present invention are optimized by using an aqueous sodium hydroxide solution as the first alkaline aqueous solution, as compared with the case of using lithium hydroxide or potassium hydroxide as the first alkaline aqueous solution There is.
　第１アルカリ水溶液としては強塩基のものが好ましい。第１アルカリ水溶液におけるアルカリ金属の水酸化物の濃度として、１０～６０質量％、２０～５５質量％、３０～５０質量％、４０～５０質量％を例示できる。 強 The first alkaline aqueous solution is preferably a strong base. Examples of the concentration of the alkali metal hydroxide in the first aqueous alkali solution include 10 to 60% by mass, 20 to 55% by mass, 30 to 50% by mass, and 40 to 50% by mass.
　ａ）工程は、水素吸蔵合金を第１アルカリ水溶液に浸ける方法で行うのが好ましい。その際には、撹拌条件下で行うのが好ましく、また、加熱条件下で行うのが好ましい。加熱温度の範囲としては、５０～１５０℃、７０～１４０℃、９０～１３０℃を例示できる。加熱時間は、第１アルカリ水溶液の濃度や加熱温度に応じて適宜決定すればよいが、０．１～１０時間、０．２～５時間、０．５～３時間を例示できる。 Step (a) is preferably performed by a method of immersing the hydrogen storage alloy in a first alkaline aqueous solution. In this case, the reaction is preferably performed under stirring conditions, and more preferably, under heating conditions. Examples of the range of the heating temperature include 50 to 150 ° C., 70 to 140 ° C., and 90 to 130 ° C. The heating time may be appropriately determined according to the concentration of the first alkaline aqueous solution and the heating temperature, and examples thereof include 0.1 to 10 hours, 0.2 to 5 hours, and 0.5 to 3 hours.
　水素吸蔵合金と第１アルカリ水溶液の量の関係は、質量比で１：０．５～１：１０が好ましく、１：０．７～１：５がより好ましく、１：０．９～１：３がさらに好ましい。第１アルカリ水溶液の量が過少であれば、水素吸蔵合金の表面にＮｉ濃縮層が十分に形成されない場合があり、他方、第１アルカリ水溶液の量が過多であれば、コスト面で不利になる。 The relationship between the hydrogen storage alloy and the amount of the first alkaline aqueous solution is preferably 1: 0.5 to 1:10, more preferably 1: 0.7 to 1: 5, and more preferably 1: 0.9 to 1: 1 by mass ratio. 3 is more preferred. If the amount of the first alkali aqueous solution is too small, the Ni-enriched layer may not be formed sufficiently on the surface of the hydrogen storage alloy. On the other hand, if the amount of the first alkali aqueous solution is too large, it is disadvantageous in terms of cost. .
　次に、ｂ）ａ）工程後、第１アルカリ水溶液から水素吸蔵合金を分離し、アルカリ金属の水酸化物を溶解した第２アルカリ水溶液で処理する工程（以下、単に「ｂ）工程」という。）について、説明する。 Next, b) after the step a), a step of separating the hydrogen storage alloy from the first aqueous alkali solution and treating it with a second aqueous alkali solution in which a hydroxide of an alkali metal is dissolved (hereinafter, simply referred to as “b) step”. ) Will be described.
　ａ）工程が終了した時点における第１アルカリ水溶液には、水素吸蔵合金から溶出した希土類元素が存在する。そして、当該希土類元素は、第１アルカリ水溶液と水素吸蔵合金の分離時に、水素吸蔵合金の表面に、希土類元素の水酸化物として付着し得る。
　ｂ）工程は、第１アルカリ水溶液から分離した水素吸蔵合金の表面に付着した、希土類元素の水酸化物を、第２アルカリ水溶液で除去する工程であるといえる。希土類元素の水酸化物は中性条件下においては析出するものの、塩基性水溶液には溶解しやすいとの性質を示す。ｂ）工程は、この性質を利用したものである。 a) Rare earth elements eluted from the hydrogen storage alloy are present in the first alkaline aqueous solution at the time when the step is completed. The rare earth element can adhere to the surface of the hydrogen storage alloy as a hydroxide of the rare earth element when the first aqueous alkali solution and the hydrogen storage alloy are separated.
Step b) can be said to be a step of removing the hydroxide of the rare earth element attached to the surface of the hydrogen storage alloy separated from the first alkali aqueous solution with the second alkali aqueous solution. Rare earth element hydroxides precipitate under neutral conditions, but are easily soluble in basic aqueous solutions. The step b) utilizes this property.
　第１アルカリ水溶液から水素吸蔵合金を分離する方法としては、濾過や遠心分離が好ましく、特に吸引濾過が好ましい。水素吸蔵合金を第２アルカリ水溶液で処理する方法としては、水素吸蔵合金を第２アルカリ水溶液に浸ける方法、第２アルカリ水溶液を水素吸蔵合金に浴びせる方法を例示できる。上述した濾過に引き続き又は濾過を行いつつ、第２アルカリ水溶液を水素吸蔵合金に浴びせる方法を選択するのが合理的である。 濾過 As a method for separating the hydrogen storage alloy from the first aqueous alkali solution, filtration or centrifugation is preferable, and suction filtration is particularly preferable. Examples of the method of treating the hydrogen storage alloy with the second alkali aqueous solution include a method of immersing the hydrogen storage alloy in the second alkali aqueous solution and a method of immersing the second alkali aqueous solution in the hydrogen storage alloy. It is reasonable to select a method in which the second alkaline aqueous solution is immersed in the hydrogen storage alloy subsequent to or while performing the filtration described above.
　第２アルカリ水溶液に溶解したアルカリ金属の水酸化物としては、水酸化リチウム、水酸化ナトリウム、水酸化カリウムを例示でき、中でも、水酸化ナトリウムが好ましい。 ア ル カ リ Examples of the alkali metal hydroxide dissolved in the second alkali aqueous solution include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and among them, sodium hydroxide is preferable.
　また、第１アルカリ水溶液のアルカリ金属の水酸化物の濃度Ｃ１と、第２アルカリ水溶液のアルカリ金属の水酸化物の濃度Ｃ２の関係が、Ｃ１＞Ｃ２を満足する条件でｂ）工程を行うのが好ましい。濃度が低いアルカリ水溶液は粘度が低いため、Ｃ１＞Ｃ２を満足する条件においては、ｂ）工程の作業が円滑に進行する。第２アルカリ水溶液におけるアルカリ金属の水酸化物の濃度として、０．０１～１０質量％、０．０３～５質量％、０．０５～１質量％、０．１～０．５質量％を例示できる。 Further, b under the conditions and concentration C 1 of alkali metal hydroxide in the first aqueous alkaline solution, the relationship of the concentration C 2 of an alkali metal hydroxide in the second aqueous alkaline solution, which satisfies C 1> C 2) Preferably, a step is performed. Since the alkali aqueous solution having a low concentration has a low viscosity, the operation of the step b) proceeds smoothly under the condition that C 1 > C 2 is satisfied. Examples of the concentration of the alkali metal hydroxide in the second aqueous alkali solution include 0.01 to 10% by mass, 0.03 to 5% by mass, 0.05 to 1% by mass, and 0.1 to 0.5% by mass. it can.
　製造コストなどの観点から、ｂ）工程はａ）工程よりも低温条件下で行うのが好ましい。ｂ）工程の温度範囲としては、０～１００℃、１０～７０℃、２０～５０℃を例示できる。ｂ）工程の温度は、水素吸蔵合金が存在する環境の温度で規定してもよいし、第２アルカリ水溶液の温度で規定してもよい。 か ら From the viewpoint of manufacturing cost and the like, the step b) is preferably performed under lower temperature conditions than the step a). Examples of the temperature range of the step b) include 0 to 100 ° C., 10 to 70 ° C., and 20 to 50 ° C. The temperature in the step b) may be defined by the temperature of the environment where the hydrogen storage alloy is present, or may be defined by the temperature of the second alkaline aqueous solution.
　水素吸蔵合金と第２アルカリ水溶液の量の関係は、質量比で１：０．５～１：５０が好ましく、１：１～１：３０がより好ましく、１：１．５～１：１０がさらに好ましい。第２アルカリ水溶液の量が過少であれば、希土類元素の水酸化物の除去が不十分となる場合があり、他方、第２アルカリ水溶液の量が過多であれば、コスト面で不利になる。 The relationship between the hydrogen storage alloy and the amount of the second alkali aqueous solution is preferably 1: 0.5 to 1:50, more preferably 1: 1 to 1:30, and more preferably 1: 1.5 to 1:10 in terms of mass ratio. More preferred. If the amount of the second alkali aqueous solution is too small, the removal of the hydroxide of the rare earth element may be insufficient, while if the amount of the second alkali aqueous solution is too large, it is disadvantageous in terms of cost.
　ｂ）工程においては、第２アルカリ水溶液での処理に引き続き、水素吸蔵合金に対する水での洗浄を行ってもよい。水での洗浄を行うことで水素吸蔵合金の表面に付着する第２アルカリ水溶液を除去できる。水での洗浄時における水素吸蔵合金と水の量の関係は、質量比で１：１～１：５０が好ましく、１：２～１：３０がより好ましく、１：３～１：１０がさらに好ましい。 In step b), the hydrogen storage alloy may be washed with water after the treatment with the second alkaline aqueous solution. By performing washing with water, the second alkaline aqueous solution attached to the surface of the hydrogen storage alloy can be removed. The relationship between the hydrogen storage alloy and the amount of water at the time of washing with water is preferably 1: 1 to 1:50, more preferably 1: 2 to 1:30, and more preferably 1: 3 to 1:10 in terms of mass ratio. preferable.
　次に、Ｎ－２）前記Ｎ－１）工程後の水素吸蔵合金の表面を酸化する工程（以下、単に「Ｎ－２）工程」という。）について説明する。 Next, N-2) a step of oxidizing the surface of the hydrogen storage alloy after the N-1) step (hereinafter, simply referred to as an "N-2) step". ) Will be described.
　Ｎ－２）工程としては、空気中に水素吸蔵合金を曝して、空気中の酸素で酸化させる方法でもよいし、水素吸蔵合金を過酸化水素などの酸化物と接触させて酸化させる方法でもよい。ただし、いずれの方法においても、水素吸蔵合金の過剰な発熱を抑制するために、水素吸蔵合金を冷却しながら実施するのが好ましい。具体的には、水素吸蔵合金に水を浴びせて水素吸蔵合金を冷却しながら実施するか、水中に水素吸蔵合金を配置した上で、又は、過酸化水素などの酸化物の水溶液中に水素吸蔵合金を配置した上で実施するのが好ましい。上述したｂ）工程における第２アルカリ水溶液での処理後に実施され得る水素吸蔵合金に対する水での洗浄を、大気下で実施することで、Ｎ－２）工程としてもよい。 As the N-2) step, a method of exposing the hydrogen storage alloy to air and oxidizing it with oxygen in the air may be used, or a method of oxidizing the hydrogen storage alloy by contacting it with an oxide such as hydrogen peroxide may be used. . However, in either method, in order to suppress excessive heat generation of the hydrogen storage alloy, it is preferable to perform the method while cooling the hydrogen storage alloy. Specifically, the hydrogen storage alloy is cooled while being cooled by immersing the hydrogen storage alloy in water, or the hydrogen storage alloy is disposed in water, or the hydrogen storage alloy is stored in an aqueous solution of an oxide such as hydrogen peroxide. It is preferable to carry out the method after disposing the alloy. The washing of the hydrogen storage alloy with water, which can be performed after the treatment with the second alkaline aqueous solution in the above-described step b), may be performed in the air to form the step N-2).
　Ｎ－１）及びＮ－２）工程を経て製造される、好適な本発明の負極活物質は、表面のＮｉ濃度が、内部のＮｉ濃度と比較して増加された水素吸蔵合金を含有する。内部のＮｉ濃度とは、Ｎ－１）工程で用いる処理前の水素吸蔵合金におけるＮｉ濃度と同義である。また、好適な本発明の負極活物質は、表面にＮｉ濃縮層を具備すると表現することもできる。 The preferable negative electrode active material of the present invention, which is manufactured through the steps (N-1) and (N-2), contains a hydrogen storage alloy whose surface Ni concentration is increased as compared with the internal Ni concentration. The internal Ni concentration is synonymous with the Ni concentration in the hydrogen storage alloy before the treatment used in the N-1) step. Further, it can be said that the preferable negative electrode active material of the present invention has a Ni-enriched layer on the surface.
　Ｎｉ濃縮層の厚みとしては、５～２００ｎｍ、１０～１５０ｎｍ、３０～１００ｎｍを例示できる。Ｎｉ濃縮層の厚みは、本発明の負極活物質の粒子の断面を各種の電子顕微鏡で観察して確認できる。 Examples of the thickness of the Ni-enriched layer include 5 to 200 nm, 10 to 150 nm, and 30 to 100 nm. The thickness of the Ni-enriched layer can be confirmed by observing the cross section of the particles of the negative electrode active material of the present invention with various electron microscopes.
　水素吸蔵合金の処理方法においては、まず、Ｎ－１）工程のうちのａ）工程で、アルカリ水溶液に溶解しやすい希土類元素が溶出するため、ａ）工程後の水素吸蔵合金の表面にはＮｉ濃縮層が形成される。次に、ｂ）工程で、水素吸蔵合金の表面に付着した、希土類元素の水酸化物を、第２アルカリ水溶液で除去するため、ｂ）工程後の水素吸蔵合金の表面のＮｉ濃度はさらに増加するといえる。 In the method for treating a hydrogen storage alloy, first, in step a) of step N-1), a rare earth element that is easily dissolved in an aqueous alkaline solution is eluted. A concentrated layer is formed. Next, in step b), the hydroxide of the rare earth element attached to the surface of the hydrogen storage alloy is removed with a second alkaline aqueous solution, so that the Ni concentration on the surface of the hydrogen storage alloy after step b) further increases. I can say that.
　実際に、本発明者がｂ）工程後の水素吸蔵合金の表面をＸ線光電子分光法で測定したところ、ａ）工程で用いた処理前の水素吸蔵合金の組成よりも、大幅にＮｉ比率が高くなっていることが確認された。そこで、好適な本発明の負極活物質の一態様として、以下のものを把握できる。 Actually, when the present inventor measured the surface of the hydrogen storage alloy after the step b) by X-ray photoelectron spectroscopy, the Ni ratio was significantly higher than the composition of the hydrogen storage alloy before the treatment used in the step a). It was confirmed that it was higher. Therefore, the following can be grasped as one preferred embodiment of the negative electrode active material of the present invention.
　本発明の負極活物質の一態様は、Ｌａ、Ｍｇ及びＮｉを含有し、Ｎｉを６０～７０質量％で含有するＡ２Ｂ７型の水素吸蔵合金を含有し、内部のＮｉ／Ｌａ元素比に対する表面のＮｉ／Ｌａ元素比の値が１．３以上であることを特徴とする。
　ここで、内部のＮｉ／Ｌａ元素比とは、水素吸蔵合金の内部、例えば本発明の負極活物質の粒子の中心におけるＮｉ／Ｌａ元素比を意味し、また、内部のＮｉ／Ｌａ元素比とは、ａ）工程で用いる処理前の水素吸蔵合金におけるＮｉ／Ｌａ元素比と同義である。 One embodiment of the negative electrode active material of the present invention contains an A 2 B 7 type hydrogen storage alloy containing La, Mg, and Ni, and containing 60 to 70% by mass of Ni, and has an internal Ni / La element ratio. Wherein the value of the Ni / La element ratio on the surface with respect to is 1.3 or more.
Here, the internal Ni / La element ratio means the Ni / La element ratio inside the hydrogen storage alloy, for example, at the center of the particles of the negative electrode active material of the present invention. Is the same as the Ni / La element ratio in the hydrogen storage alloy before the treatment used in step a).
　内部のＮｉ／Ｌａ元素比に対する表面のＮｉ／Ｌａ元素比の値としては、１．３～２、１．３１～１．５、１．３４～１．４の範囲を例示できる。内部のＮｉ／Ｌａ元素比に対する表面のＮｉ／Ｌａ元素比の値が大きいほど、表面からの希土類元素の除去が好適に行われたことを意味する。 Examples of the value of the Ni / La element ratio on the surface with respect to the Ni / La element ratio inside are 1.3 to 2, 1.31 to 1.5, and 1.34 to 1.4. The larger the value of the Ni / La element ratio on the surface relative to the internal Ni / La element ratio, the better the removal of the rare earth element from the surface.
　本発明のニッケル金属水素化物電池は、本発明の正極活物質を含む正極活物質層と、本発明の負極活物質を含む負極活物質層を具備する。
　ここで、本発明のニッケル金属水素化物電池は、上記正極活物質層を備える本発明の正極及び上記負極活物質層を備える本発明の負極を具備する、通常のニッケル金属水素化物電池であってもよいし、または、集電箔の一面に上記正極活物質層を備え、かつ、他面に上記負極活物質層を備える双極型の電極を具備する、双極型のニッケル金属水素化物電池であってもよい。 The nickel metal hydride battery of the present invention includes a positive electrode active material layer containing the positive electrode active material of the present invention, and a negative electrode active material layer containing the negative electrode active material of the present invention.
Here, the nickel metal hydride battery of the present invention is a normal nickel metal hydride battery including the positive electrode of the present invention having the positive electrode active material layer and the negative electrode of the present invention having the negative electrode active material layer. Or a bipolar nickel metal hydride battery comprising a positive electrode active material layer on one surface of a current collector foil and a bipolar electrode having the negative electrode active material layer on the other surface. May be.
　以下、本発明の正極及び本発明の負極についての説明を行うが、双極型の電極の説明については、本発明の正極及び本発明の負極についての説明を適宜適切に援用することとする。 Hereinafter, the positive electrode of the present invention and the negative electrode of the present invention will be described. For the description of the bipolar electrode, the description of the positive electrode of the present invention and the negative electrode of the present invention will be appropriately used.
　本発明の正極について説明する。なお、本発明の負極の構成と重複するものについては、正極との限定を付さずに説明する。 正極 The positive electrode of the present invention will be described. In addition, what overlaps with the configuration of the negative electrode of the present invention will be described without limiting the positive electrode.
　本発明の正極は、集電体と集電体の表面に形成された正極活物質層とを含む。 正極 The positive electrode of the present invention includes a current collector and a positive electrode active material layer formed on the surface of the current collector.
　集電体は、ニッケル金属水素化物電池の放電又は充電の間、電極に電流を流し続けるための化学的に不活性な電子伝導体をいう。集電体の材料は、使用する活物質に適した電圧に耐え得る金属であれば特に制限はない。集電体の材料としては、銀、銅、金、アルミニウム、タングステン、コバルト、亜鉛、ニッケル、鉄、白金、錫、インジウム、チタン、ルテニウム、タンタル、クロム、モリブデンから選ばれる少なくとも一種、並びにステンレス鋼などの金属材料を例示することができる。集電体は公知の保護層で被覆されていても良い。集電体の表面を公知の方法で処理したものを集電体として用いても良い。集電体の材料としては、ニッケル、又は、ニッケルめっきを施した金属材料が好ましい。 A current collector refers to a chemically inert electronic conductor that keeps current flowing through electrodes during discharging or charging of a nickel metal hydride battery. The material of the current collector is not particularly limited as long as the metal can withstand a voltage suitable for the active material to be used. As a material of the current collector, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel And other metal materials. The current collector may be covered with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector. As a material of the current collector, nickel or a metal material plated with nickel is preferable.
　集電体は箔、シート、フィルム、線状、棒状、メッシュ、スポンジ状などの形態をとることができる。集電体が箔、シート、フィルム形態の場合は、その厚みが１μｍ～１００μｍの範囲内であることが好ましい。 The current collector may be in the form of foil, sheet, film, wire, rod, mesh, sponge, or the like. When the current collector is in the form of a foil, sheet, or film, the thickness is preferably in the range of 1 μm to 100 μm.
　本発明の正極活物質は導電性に優れるため、箔状の集電体を採用するのが合理的といえる。同じ理由で、本発明の正極活物質は、集電箔を用いる双極型の電極に適しているといえる。 正極 Since the positive electrode active material of the present invention has excellent conductivity, it is reasonable to adopt a foil-shaped current collector. For the same reason, it can be said that the positive electrode active material of the present invention is suitable for a bipolar electrode using a current collector foil.
　正極活物質層は、本発明の正極活物質を含み、必要に応じて正極添加剤、結着剤及び導電助剤を含む。
　正極の集電体上に存在する一の正極活物質層の量としては、２０ｍｇ／ｃｍ２以上が好ましく、２５～５０ｍｇ／ｃｍ２がより好ましく、２７～４０ｍｇ／ｃｍ２がさらに好ましい。
　正極活物質層の密度としては、２．５ｇ／ｃｍ３以上が好ましく、２．６～３．２ｇ／ｃｍ３がより好ましく、２．７～３．１ｇ／ｃｍ３がさらに好ましく、２．８～３．０ｇ／ｃｍ３が特に好ましい。 The positive electrode active material layer contains the positive electrode active material of the present invention, and optionally contains a positive electrode additive, a binder, and a conductive auxiliary.
The amount of one positive electrode active material layer present on the current collector of the positive electrode is preferably 20 mg / cm 2 or more, more preferably 25 to 50 mg / cm 2 , and further preferably 27 to 40 mg / cm 2 .
The density of the positive electrode active material layer is preferably 2.5 g / cm 3 or more, more preferably 2.6 to 3.2 g / cm 3, still more preferably 2.7 to 3.1 g / cm 3. Particularly preferred is ～ 3.0 g / cm 3 .
　正極活物質層には、本発明の正極活物質が正極活物質層全体の質量に対して、７５～９９質量％で含まれるのが好ましく、８０～９７質量％で含まれるのがより好ましく、８５～９５質量％で含まれるのがさらに好ましい。 The positive electrode active material layer preferably contains the positive electrode active material of the present invention in an amount of 75 to 99% by mass, more preferably 80 to 97% by mass, based on the total mass of the positive electrode active material layer. More preferably, the content is 85 to 95% by mass.
　正極添加剤は、ニッケル金属水素化物電池の電池特性を向上させるために正極に添加されるものである。正極添加剤としては、ニッケル金属水素化物電池の正極添加剤として用いられるものであれば限定されない。具体的な正極添加剤として、Ｎｂ２Ｏ５などのニオブ化合物、ＷＯ２、ＷＯ３、Ｌｉ２ＷＯ４、Ｎａ２ＷＯ４及びＫ２ＷＯ４などのタングステン化合物、Ｙｂ２Ｏ３などのイッテルビウム化合物、ＴｉＯ２などのチタン化合物、Ｙ２Ｏ３などのイットリウム化合物、ＺｎＯなどの亜鉛化合物、ＣａＯ、Ｃａ（ＯＨ）２及びＣａＦ２などのカルシウム化合物、並びに、その他の希土類酸化物を例示できる。 The positive electrode additive is added to the positive electrode in order to improve the battery characteristics of the nickel metal hydride battery. The positive electrode additive is not limited as long as it is used as a positive electrode additive of a nickel metal hydride battery. Specific positive electrode additives, niobium compound, such as Nb 2 O 5, WO 2, WO 3, Li 2 WO 4, a tungsten compound such as Na 2 WO 4 and K 2 WO 4, ytterbium compound such as Yb 2 O 3 titanium compounds such as TiO 2, yttrium compound, such as Y 2 O 3, zinc compounds such as ZnO, CaO, Ca (OH) calcium compounds such as 2 and CaF 2, and can be exemplified by other rare earth oxides.
　正極活物質層には、正極添加剤が正極活物質層全体の質量に対して、０．１～１０質量％で含まれるのが好ましく、０．５～５質量％で含まれるのがより好ましい。 The positive electrode active material layer preferably contains the positive electrode additive in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total mass of the positive electrode active material layer. .
　結着剤は活物質などを集電体の表面に繋ぎ止める役割を果たすものである。結着剤としては、ニッケル金属水素化物電池の電極用結着剤として用いられるものであれば限定されない。具体的な結着剤として、ポリフッ化ビニリデン、ポリテトラフルオロエチレン及びフッ素ゴムなどの含フッ素樹脂、ポリプロピレン及びポリエチレンなどのポリオレフィン樹脂、ポリイミド及びポリアミドイミドなどのイミド系樹脂、カルボキシメチルセルロース、メチルセルロース及びヒドロキシプロピルセルロースなどのセルロース誘導体、スチレンブタジエンゴムなどの共重合体、並びに、（メタ）アクリル酸誘導体をモノマー単位として含有する、ポリアクリル酸、ポリアクリル酸エステル、ポリメタクリル酸及びポリメタクリル酸エステルなどの（メタ）アクリル系樹脂を例示できる。 (4) The binder plays a role of binding the active material and the like to the surface of the current collector. The binder is not limited as long as it is used as a binder for an electrode of a nickel metal hydride battery. Specific binders include polyvinylidene fluoride, fluorine-containing resins such as polytetrafluoroethylene and fluororubber, polyolefin resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, carboxymethylcellulose, methylcellulose and hydroxypropyl. Cellulose derivatives such as cellulose, copolymers such as styrene-butadiene rubber, and (meth) acrylic acid derivatives containing as monomer units, such as polyacrylic acid, polyacrylic acid ester, polymethacrylic acid and polymethacrylic acid ester ( A (meth) acrylic resin can be exemplified.
　活物質層には、結着剤が活物質層全体の質量に対して、０．１～１５質量％で含まれるのが好ましく、０．３～１０質量％で含まれるのがより好ましく、０．５～７質量％で含まれるのがさらに好ましい。結着剤が少なすぎると電極の成形性が低下し、また、結着剤が多すぎると電極のエネルギー密度が低くなるためである。 The active material layer preferably contains the binder in an amount of 0.1 to 15% by mass, more preferably 0.3 to 10% by mass, based on the mass of the entire active material layer. More preferably, it is contained at 0.5 to 7% by mass. This is because if the amount of the binder is too small, the moldability of the electrode decreases, and if the amount of the binder is too large, the energy density of the electrode decreases.
　導電助剤は、電極の導電性を高めるために添加される。そのため、導電助剤は、電極の導電性が不足する場合に任意に加えればよく、電極の導電性が十分に優れている場合には加えなくても良い。具体的な導電助剤としては、コバルト、ニッケル、銅などの金属、コバルト酸化物などの金属酸化物、及びコバルト水酸化物などの金属水酸化物、カーボンブラック、黒鉛、炭素繊維などの炭素材料が例示される。 The conductive additive is added to increase the conductivity of the electrode. Therefore, the conductive assistant may be arbitrarily added when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent. Specific conductive assistants include metals such as cobalt, nickel and copper, metal oxides such as cobalt oxide, metal hydroxides such as cobalt hydroxide, and carbon materials such as carbon black, graphite and carbon fiber. Is exemplified.
　活物質層には、導電助剤が活物質層全体の質量に対して、０．１～２０質量％で含まれるのが好ましい。正極活物質層には、導電助剤が正極活物質層全体の質量に対して、１～１５質量％で含まれるのが好ましく、３～１２質量％で含まれるのがより好ましく、５～１０質量％で含まれるのがさらに好ましい。負極活物質層には、導電助剤が負極活物質層全体の質量に対して、０．１～５質量％で含まれるのが好ましく、０．２～３質量％で含まれるのがより好ましく、０．３～１質量％で含まれるのがさらに好ましい。導電助剤が少なすぎると効率のよい導電パスを形成できず、また、導電助剤が多すぎると活物質層の成形性が悪くなるとともに電極のエネルギー密度が低くなるためである。 The active material layer preferably contains the conductive additive in an amount of 0.1 to 20% by mass based on the total mass of the active material layer. The positive electrode active material layer preferably contains the conductive additive in an amount of 1 to 15% by mass, more preferably 3 to 12% by mass, and more preferably 5 to 10% by mass, based on the total mass of the positive electrode active material layer. More preferably, it is contained by mass%. The negative electrode active material layer preferably contains the conductive auxiliary in an amount of 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, based on the total mass of the negative electrode active material layer. , 0.3 to 1% by mass. If the amount of the conductive auxiliary agent is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary agent is too large, the moldability of the active material layer deteriorates and the energy density of the electrode decreases.
　本発明の負極は、本発明の負極活物質を具備する。本発明の負極は、集電体と集電体の表面に形成された負極活物質層とを含む。
　負極活物質層は、本発明の負極活物質を含み、必要に応じて負極添加剤、結着剤及び導電助剤を含む。結着剤及び導電助剤については上述したとおりである。 The negative electrode of the present invention includes the negative electrode active material of the present invention. The negative electrode of the present invention includes a current collector and a negative electrode active material layer formed on a surface of the current collector.
The negative electrode active material layer contains the negative electrode active material of the present invention, and optionally contains a negative electrode additive, a binder, and a conductive auxiliary. The binder and the conductive assistant are as described above.
　負極活物質層には、負極活物質が負極活物質層全体の質量に対して、８５～９９質量％で含まれるのが好ましく、９０～９８質量％で含まれるのがより好ましい。 The negative electrode active material layer preferably contains the negative electrode active material in an amount of 85 to 99% by mass, more preferably 90 to 98% by mass, based on the mass of the entire negative electrode active material layer.
　負極添加剤は、ニッケル金属水素化物電池の電池特性を向上させるために負極に添加されるものである。負極添加剤としては、ニッケル金属水素化物電池の負極添加剤として用いられるものであれば限定されない。具体的な負極添加剤として、ＣｅＦ３及びＹＦ３などの希土類元素のフッ化物、Ｂｉ２Ｏ３及びＢｉＦ３などのビスマス化合物、Ｉｎ２Ｏ３及びＩｎＦ３などのインジウム化合物、並びに、正極添加剤として例示した化合物を挙げることができる。 The negative electrode additive is added to the negative electrode in order to improve the battery characteristics of the nickel metal hydride battery. The negative electrode additive is not limited as long as it is used as a negative electrode additive of a nickel metal hydride battery. As specific negative electrode additives, fluorides of rare earth elements such as CeF 3 and YF 3 , bismuth compounds such as Bi 2 O 3 and BiF 3 , indium compounds such as In 2 O 3 and InF 3 , and positive electrode additives And the compounds exemplified above.
　負極活物質層には、負極添加剤が負極活物質層全体の質量に対して、０．１～１０質量％で含まれるのが好ましく、０．５～５質量％で含まれるのがより好ましい。 The negative electrode active material layer preferably contains the negative electrode additive in an amount of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total mass of the negative electrode active material layer. .
　集電体の表面に活物質層を形成させるには、ロールコート法、ダイコート法、ディップコート法、ドクターブレード法、スプレーコート法、カーテンコート法などの従来から公知の方法を用いて、集電体の表面に活物質を塗布すればよい。具体的には、活物質、溶剤、並びに必要に応じて結着剤、導電助剤及び添加剤を混合してスラリーにしてから、当該スラリーを集電体の表面に塗布後、乾燥する。溶剤としては、Ｎ－メチル－２－ピロリドン、メタノール、メチルイソブチルケトン、水を例示できる。電極密度を高めるべく、乾燥後のものを圧縮しても良い。 In order to form an active material layer on the surface of the current collector, the current is collected using a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method. The active material may be applied to the surface of the body. Specifically, an active material, a solvent, and, if necessary, a binder, a conductive auxiliary agent, and an additive are mixed to form a slurry, and the slurry is applied to the surface of the current collector and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The dried product may be compressed to increase the electrode density.
　具体的には、本発明のニッケル金属水素化物電池は、電解液とセパレータも具備する。 Specifically, the nickel metal hydride battery of the present invention also includes an electrolyte and a separator.
　電解液はアルカリ金属の水酸化物が溶解した水溶液である。アルカリ金属の水酸化物としては、水酸化リチウム、水酸化ナトリウム、水酸化カリウムを例示できる。電解液には、１種類のアルカリ金属の水酸化物を含んでいてもよいし、複数種類のアルカリ金属の水酸化物を含んでいてもよい。特に、水酸化リチウム、水酸化ナトリウム及び水酸化カリウムの３種類のアルカリ金属の水酸化物を含んでいるものが好ましい。
　電解液における、アルカリ金属の水酸化物の濃度としては、２～１０ｍｏｌ／Ｌが好ましく、３～９ｍｏｌ／Ｌがより好ましく、４～８ｍｏｌ／Ｌがさらに好ましい。 The electrolytic solution is an aqueous solution in which an alkali metal hydroxide is dissolved. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. The electrolytic solution may contain one kind of alkali metal hydroxide, or may contain plural kinds of alkali metal hydroxides. Particularly, those containing three kinds of alkali metal hydroxides of lithium hydroxide, sodium hydroxide and potassium hydroxide are preferable.
The concentration of the alkali metal hydroxide in the electrolyte is preferably 2 to 10 mol / L, more preferably 3 to 9 mol / L, and still more preferably 4 to 8 mol / L.
　電解液には、ニッケル金属水素化物電池用電解液に採用される公知の添加剤が添加されていてもよい。添加剤として、塩化リチウム、塩化ナトリウムなどのアルカリ金属ハロゲン化物、タングステン酸ナトリウムなどのタングステン酸アルカリ金属塩を例示できる。 (4) The electrolyte may contain a known additive employed in the electrolyte for nickel metal hydride batteries. Examples of the additive include alkali metal halides such as lithium chloride and sodium chloride, and alkali metal tungstates such as sodium tungstate.
　特に、アルカリ金属の水酸化物とアルカリ金属ハロゲン化物とを含む水溶液からなる電解液が好ましい。アルカリ金属ハロゲン化物の存在が好ましい理由は、以下のとおりである。 Particularly, an electrolytic solution composed of an aqueous solution containing an alkali metal hydroxide and an alkali metal halide is preferable. The reason why the presence of an alkali metal halide is preferable is as follows.
　アルカリ金属ハロゲン化物は、電解液中で、アルカリ金属カチオンとハロゲンアニオンに電離して存在すると考えられる。そして、マイナスの電荷を有するハロゲンアニオンが正極に電気的に吸着することで、正極はハロゲンアニオンで被覆された状態となる。ハロゲンアニオンで被覆された正極においては、正極本体に対する水分子の直接接触が抑制されるため、正極における酸素発生が抑制されると考えられる。 It is considered that the alkali metal halide is ionized into the alkali metal cation and the halogen anion in the electrolytic solution. Then, the negatively charged halogen anion is electrically adsorbed to the positive electrode, so that the positive electrode is coated with the halogen anion. In the positive electrode coated with the halogen anion, direct contact of water molecules with the positive electrode body is suppressed, so that it is considered that generation of oxygen in the positive electrode is suppressed.
　また、アルカリ金属カチオンは、電解液中で、電解液中の水分子と配位した状態となると考えられる。ここで、水分子はアルカリ金属カチオンと強く配位した状態となることで耐酸化性が向上して、その酸素発生電位が高くなることも期待できる。 ア ル カ リ Also, it is considered that the alkali metal cation is coordinated with water molecules in the electrolytic solution in the electrolytic solution. Here, it can be expected that the water molecule is in a state of being strongly coordinated with the alkali metal cation, thereby improving the oxidation resistance and increasing the oxygen generation potential.
　アルカリ金属カチオンのうちイオン半径が小さいものほど、水分子と配位しやすいといえる。アルカリ金属カチオンのイオン半径は、Ｌｉ+＜Ｎａ+＜Ｋ+＜Ｒｂ+＜Ｃｓ+＜Ｆｒ+の順であることが知られている。したがって、アルカリ金属ハロゲン化物としては、リチウムハロゲン化物が最も好ましく、ナトリウムハロゲン化物が次に好ましく、カリウムハロゲン化物がその次に好ましいといえる。 It can be said that the smaller the ionic radius of the alkali metal cation, the easier it is to coordinate with water molecules. It is known that the ionic radius of the alkali metal cation is in the order of Li + <Na + <K + <Rb + <Cs + <Fr + . Therefore, as the alkali metal halide, lithium halide is most preferred, sodium halide is most preferred, and potassium halide is second most preferred.
　また、正極に吸着したハロゲンアニオンが酸化されて、ハロゲン単体となることは好ましくない。ハロゲンアニオンの耐酸化性は、Ｆ-＞Ｃｌ-＞Ｂｒ-＞Ｉ-の順であることが知られている。したがって、耐酸化性の観点からは、アルカリ金属ハロゲン化物としては、アルカリ金属フッ化物が最も好ましく、アルカリ金属塩化物が次に好ましく、アルカリ金属臭化物がその次に好ましいといえる。 Further, it is not preferable that the halogen anion adsorbed on the positive electrode is oxidized to become a simple halogen. Oxidation resistance of the halogen anions, F -> Cl -> Br -> I - are known to be in the order of. Therefore, from the viewpoint of oxidation resistance, the alkali metal halide is most preferably an alkali metal fluoride, the alkali metal chloride is more preferred, and the alkali metal bromide is the second most preferred.
　アルカリ金属ハロゲン化物として、ＬｉＦ、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、ＮａＦ、ＮａＣｌ、ＮａＢｒ、ＮａＩ、ＫＦ、ＫＣｌ、ＫＢｒ及びＫＩを例示できる。水分子との配位性、及び、耐酸化性の観点からみて、アルカリ金属ハロゲン化物として、ＬｉＦ、ＬｉＣｌ、ＮａＦ、ＮａＣｌが好ましいといえる。溶解度の観点を加えると、アルカリ金属ハロゲン化物として、ＬｉＣｌ及びＮａＣｌが好ましいといえる。 Examples of the alkali metal halide include LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr and KI. From the viewpoint of coordination with water molecules and oxidation resistance, LiF, LiCl, NaF, and NaCl are preferable as the alkali metal halide. From the viewpoint of solubility, it can be said that LiCl and NaCl are preferable as alkali metal halides.
　電解液には、１種類のアルカリ金属ハロゲン化物を用いてもよいし、複数種類のアルカリ金属ハロゲン化物を用いてもよい。電解液における、アルカリ金属ハロゲン化物の濃度としては、０．０１～１ｍｏｌ／Ｌが好ましく、０．０３～０．５ｍｏｌ／Ｌがより好ましく、０．０５～０．３ｍｏｌ／Ｌがさらに好ましく、０．０５～０．１ｍｏｌ／Ｌが特に好ましい。 (4) One kind of alkali metal halide or a plurality of kinds of alkali metal halides may be used for the electrolytic solution. The concentration of the alkali metal halide in the electrolyte is preferably 0.01 to 1 mol / L, more preferably 0.03 to 0.5 mol / L, still more preferably 0.05 to 0.3 mol / L. 0.05 to 0.1 mol / L is particularly preferred.
　セパレータは、正極と負極とを隔離して、両極の接触による短絡を防止しつつ、電解液の貯留空間及び通路を提供するものである。セパレータとしては、公知のものを採用すればよく、ポリテトラフルオロエチレン、ポリプロピレン、ポリエチレン、ポリイミド、ポリアミド、ポリアラミド（Ａｒｏｍａｔｉｃ　ｐｏｌｙａｍｉｄｅ）、ポリエステル、ポリアクリロニトリル等の合成樹脂、セルロース、アミロース等の多糖類、フィブロイン、ケラチン、リグニン、スベリン等の天然高分子、セラミックスなどの電気絶縁性材料を１種若しくは複数用いた多孔体、不織布、織布などを挙げることができる。また、セパレータは多層構造としてもよい。 (4) The separator separates the positive electrode and the negative electrode, and provides a storage space and a passage for the electrolyte while preventing a short circuit due to contact between the two electrodes. Known separators may be used as the separator, and synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic @ polyamide), polyester, and polyacrylonitrile; polysaccharides such as cellulose and amylose; and fibroin. , Natural polymers such as keratin, lignin and suberin, and porous bodies, non-woven fabrics and woven fabrics using one or more electrically insulating materials such as ceramics. Further, the separator may have a multilayer structure.
　セパレータは、表面に親水化処理が施されていることが好ましい。親水化処理としては、スルホン化処理、コロナ処理、フッ素ガス処理、プラズマ処理を例示できる。 The surface of the separator is preferably subjected to a hydrophilic treatment. Examples of the hydrophilization treatment include a sulfonation treatment, a corona treatment, a fluorine gas treatment, and a plasma treatment.
　本発明のニッケル金属水素化物電池の具体的な製造方法の一態様について述べる。
　正極と負極とでセパレータを挟持して電極体とする。正極の集電体及び負極の集電体から外部に通ずる正極端子及び負極端子までを、集電用リード等を用いて接続した後に、電極体に電解液を加えてニッケル金属水素化物電池とする。 One embodiment of a specific method for manufacturing the nickel metal hydride battery of the present invention will be described.
A separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. After connecting from the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collecting lead or the like, an electrolytic solution is added to the electrode body to obtain a nickel metal hydride battery. .
　本発明のニッケル金属水素化物電池の形状は特に限定されるものでなく、角型、円筒型、コイン型、ラミネート型等、種々の形状を採用することができる。 形状 The shape of the nickel metal hydride battery of the present invention is not particularly limited, and various shapes such as a prismatic shape, a cylindrical shape, a coin shape, and a laminate shape can be adopted.
　本発明のニッケル金属水素化物電池は、車両に搭載してもよい。車両は、その動力源の全部あるいは一部にニッケル金属水素化物電池による電気エネルギーを使用している車両であればよく、例えば、電気車両、ハイブリッド車両などであるとよい。車両にニッケル金属水素化物電池を搭載する場合には、ニッケル金属水素化物電池を複数直列に接続して組電池とするとよい。ニッケル金属水素化物電池を搭載する機器としては、車両以外にも、パーソナルコンピュータ、携帯通信機器など、電池で駆動される各種の家電製品、オフィス機器、産業機器などが挙げられる。さらに、本発明のニッケル金属水素化物電池は、風力発電、太陽光発電、水力発電その他電力系統の蓄電装置及び電力平滑化装置、船舶等の動力及び／又は補機類の電力供給源、航空機、宇宙船等の動力及び／又は補機類の電力供給源、電気を動力源に用いない車両の補助用電源、移動式の家庭用ロボットの電源、システムバックアップ用電源、無停電電源装置の電源、電動車両用充電ステーションなどにおいて充電に必要な電力を一時蓄える蓄電装置に用いてもよい。 ニ ッ ケ ル The nickel metal hydride battery of the present invention may be mounted on a vehicle. The vehicle may be any vehicle that uses electric energy from a nickel metal hydride battery for all or a part of its power source, such as an electric vehicle or a hybrid vehicle. When a nickel metal hydride battery is mounted on a vehicle, a plurality of nickel metal hydride batteries may be connected in series to form an assembled battery. Examples of devices on which the nickel metal hydride battery is mounted include various types of battery-driven home appliances, office devices, industrial devices, and the like, such as personal computers and portable communication devices, in addition to vehicles. Further, the nickel metal hydride battery of the present invention is a power storage device and a power smoothing device for wind power generation, solar power generation, hydroelectric power generation and other power systems, power sources for ships and the like and / or power supply sources for auxiliary equipment, aircraft, Power supply for spacecraft and other power supplies and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, The present invention may be applied to a power storage device that temporarily stores electric power required for charging at a charging station for an electric vehicle or the like.
　以上、本発明の実施形態を説明したが、本発明は、上記実施形態に限定されるものではない。本発明の要旨を逸脱しない範囲において、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。 Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The present invention can be implemented in various forms with modifications, improvements, and the like that can be made by those skilled in the art without departing from the gist of the present invention.
　以下に、実施例及び比較例などを示し、本発明をより具体的に説明する。なお、本発明は、これらの実施例によって限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. Note that the present invention is not limited by these examples.
　（実施例１）
　（正極活物質の製造）
　ニッケル、コバルト及び亜鉛のモル比が９４．５：４．５：１．１になるように硫酸ニッケル、硫酸コバルト及び硫酸亜鉛を秤量し、これらを、アンモニウムイオンを含む水酸化ナトリウム水溶液に加えて、混合水溶液を調製した。撹拌下の混合水溶液に、水酸化ナトリウム水溶液を徐々に添加して、混合水溶液のｐＨを１３～１４とした。それにより、水酸化ニッケルを主体とし、コバルト及び亜鉛を固溶した前駆体粒子を製造した。得られた前駆体粒子（正極活物質本体）を水で洗浄した後、乾燥した。 (Example 1)
(Manufacture of positive electrode active material)
Nickel sulfate, cobalt sulfate, and zinc sulfate were weighed so that the molar ratio of nickel, cobalt, and zinc became 94.5: 4.5: 1.1, and these were added to an aqueous solution of sodium hydroxide containing ammonium ions. , To prepare a mixed aqueous solution. An aqueous sodium hydroxide solution was gradually added to the mixed aqueous solution under stirring to adjust the pH of the mixed aqueous solution to 13 to 14. Thus, precursor particles containing nickel hydroxide as a main component and solid solution of cobalt and zinc were produced. The obtained precursor particles (positive electrode active material body) were washed with water and then dried.
　Ｐ－１）工程
　得られた前駆体粒子をアンモニア水溶液中に投入して懸濁液とした。懸濁液のｐＨを９～１０に維持しながら、硫酸コバルト水溶液を懸濁液に添加した。それにより、前駆体粒子の表面に水酸化コバルトが析出することで、水酸化コバルトの層を備えた粒子を得た。 Step P-1) The obtained precursor particles were put into an aqueous ammonia solution to form a suspension. An aqueous solution of cobalt sulfate was added to the suspension while maintaining the pH of the suspension at 9-10. As a result, cobalt hydroxide was deposited on the surface of the precursor particles to obtain particles having a layer of cobalt hydroxide.
　Ｐ－２）工程
　前段落で得られた水酸化コバルトの層を備えた粒子を、酸素を含む高温空気中に対流させつつ、水酸化ナトリウム水溶液及び水酸化リチウム水溶液を噴霧して、加熱処理を施した。これにより、前記粒子の表面の水酸化コバルトが、導電性の高いオキシ水酸化コバルトとなるとともに、オキシ水酸化コバルトの層中にナトリウム及びリチウムが取り込まれ、ナトリウム及びリチウムを含有したオキシ水酸化コバルト層が形成される。
　その後、オキシ水酸化コバルト層を備えた粒子を濾取し、水洗いしたのち、６０℃で乾燥させた。このようにして、ナトリウム及びリチウムを含有するオキシ水酸化コバルト層で被覆された、実施例１の正極活物質を製造した。 Step P-2) The particles having the layer of cobalt hydroxide obtained in the preceding paragraph are sprayed with an aqueous solution of sodium hydroxide and an aqueous solution of lithium hydroxide while being convected in high-temperature air containing oxygen. gave. Thereby, the cobalt hydroxide on the surface of the particles becomes cobalt oxyhydroxide having high conductivity, and sodium and lithium are taken into the layer of cobalt oxyhydroxide, and the cobalt oxyhydroxide containing sodium and lithium is contained. A layer is formed.
Thereafter, the particles provided with the cobalt oxyhydroxide layer were collected by filtration, washed with water, and dried at 60 ° C. Thus, the positive electrode active material of Example 1 covered with the cobalt oxyhydroxide layer containing sodium and lithium was produced.
　（負極活物質の製造）
　希土類－Ｍｇ－Ｎｉ系の水素吸蔵合金として、（Ｌａ，Ｓｍ，Ｍｇ，Ｚｒ）１．０（Ｎｉ，Ａｌ）３．６で表されるＡ２Ｂ７型水素吸蔵合金を準備した。当該Ａ２Ｂ７型水素吸蔵合金において、Ｎｉ含量は６２質量％であった。 (Production of negative electrode active material)
An A 2 B 7 type hydrogen storage alloy represented by (La, Sm, Mg, Zr) 1.0 (Ni, Al) 3.6 was prepared as a rare earth-Mg—Ni hydrogen storage alloy. In the A 2 B 7 type hydrogen storage alloy, the Ni content was 62% by mass.
　（負極活物質の細粉砕工程）
　蒸留水に、水素吸蔵合金の粗粉末、及び、ポリビニルアルコールを、水素吸蔵合金の濃度が１０質量％となるように配合して、混合機で混合して混合物とした。なお、ポリビニルアルコールの含有量は、水素吸蔵合金に対して０．５質量％であった。この混合物を大気中でビーズミルに移し、当該ビーズミル中で混合した後に、ビーズミルから排出した。ビーズミルのビーズとしてはジルコニア製のものを用いた。
　ビーズミルから排出された混合物は、循環用配管を経由して混合機に輸送された後に、再度ビーズミルに戻された。つまり、水素吸蔵合金及び水はビーズミルと混合機との間を循環し、水素吸蔵合金はビーズミルで繰り返し粉砕された。
　以上の工程により得られた粉砕生成物を濾取して、水素吸蔵合金粉末と少量の水とを含む実施例１の粉砕濾過生成物を得た。実施例１の粉砕濾過生成物を以下のアルカリ処理工程に供した。
　なお、実施例１の粉砕濾過生成物における水素吸蔵合金粉末の平均粒子径（Ｄ５０）は、７μｍであった。 (Fine crushing process of negative electrode active material)
A coarse powder of the hydrogen storage alloy and polyvinyl alcohol were mixed with distilled water so that the concentration of the hydrogen storage alloy was 10% by mass, and mixed with a mixer to form a mixture. The content of polyvinyl alcohol was 0.5% by mass with respect to the hydrogen storage alloy. The mixture was transferred to a bead mill in the atmosphere, mixed in the bead mill, and then discharged from the bead mill. The beads used in the bead mill were made of zirconia.
The mixture discharged from the bead mill was transported to the mixer via a circulation pipe, and then returned to the bead mill again. That is, the hydrogen storage alloy and water circulated between the bead mill and the mixer, and the hydrogen storage alloy was repeatedly pulverized by the bead mill.
The pulverized product obtained in the above steps was collected by filtration to obtain a pulverized filtered product of Example 1 containing the hydrogen storage alloy powder and a small amount of water. The crushed and filtered product of Example 1 was subjected to the following alkali treatment step.
The average particle size (D 50 ) of the hydrogen storage alloy powder in the pulverized filtration product of Example 1 was 7 μm.
　（負極活物質のアルカリ処理工程：Ｎ－１）工程）
　ａ）工程
　第１アルカリ水溶液として、水酸化ナトリウムを４０質量％で含有する水酸化ナトリウム水溶液を準備した。撹拌条件下、第１アルカリ水溶液５０質量部に、実施例１の粉砕濾過生成物５０質量部を加えて懸濁液とした。この懸濁液を９０℃に加熱して１時間保持し、その後、室温に冷却した。 (Alkali treatment step of negative electrode active material: step N-1)
a) Step As an aqueous first alkali solution, an aqueous sodium hydroxide solution containing 40% by mass of sodium hydroxide was prepared. Under stirring conditions, 50 parts by mass of the pulverized and filtered product of Example 1 was added to 50 parts by mass of the first alkaline aqueous solution to form a suspension. The suspension was heated to 90 ° C. and held for 1 hour, then cooled to room temperature.
　ｂ）工程
　第２アルカリ水溶液として、水酸化ナトリウムを０．４質量％で含有する水酸化ナトリウム水溶液を準備した。ａ）工程終了後の懸濁液を吸引濾過して、第１アルカリ水溶液から水素吸蔵合金を分離した。吸引濾過を継続した状態で、水素吸蔵合金の上から第２アルカリ水溶液５０質量部を注ぎ、水素吸蔵合金を洗浄した 。 b) Step As an aqueous second alkali solution, an aqueous sodium hydroxide solution containing 0.4% by mass of sodium hydroxide was prepared. a) The suspension after completion of the step was subjected to suction filtration to separate the hydrogen storage alloy from the first aqueous alkali solution. While suction filtration was continued, 50 parts by mass of a second alkaline aqueous solution was poured over the hydrogen storage alloy to wash the hydrogen storage alloy.
　Ｎ－２）工程
　ｂ）工程の吸引濾過を継続した状態で、水素吸蔵合金の上から水３００質量部を注ぎ、水素吸蔵合金を水洗した。 N-2) Step While the suction filtration in the step b) was continued, 300 parts by mass of water was poured from above the hydrogen storage alloy, and the hydrogen storage alloy was washed with water.
　前段落で得た濾過物全量に、５質量％の過酸化水素水を５０質量部加えて２０分間撹拌した。その後に吸引濾過を行い、水素吸蔵合金の上から水３００質量部を注ぎ、水素吸蔵合金を水洗した。この濾過後の水素吸蔵合金を実施例１の負極活物質とした。 (5) To the total amount of the filtrate obtained in the previous paragraph, 50 parts by mass of a 5% by mass aqueous hydrogen peroxide solution was added, followed by stirring for 20 minutes. Thereafter, suction filtration was performed, 300 parts by mass of water was poured from above the hydrogen storage alloy, and the hydrogen storage alloy was washed with water. The filtered hydrogen storage alloy was used as the negative electrode active material of Example 1.
　（電池製造工程）
　以下のとおり、実施例１のニッケル金属水素化物電池を製造した。 (Battery manufacturing process)
A nickel metal hydride battery of Example 1 was manufactured as follows.
　実施例１の正極活物質を９４．３質量部、導電助剤としてコバルト粉末を１質量部、結着剤としてアクリル系樹脂エマルションを固形分として３．５質量部、結着剤としてカルボキシメチルセルロースを０．７質量部、正極添加剤としてＹ２Ｏ３を０．５質量部、及び、適量のイオン交換水を混合して、スラリーを製造した。正極用集電体として厚み２０μｍのニッケル箔を準備した。このニッケル箔の表面に、上記スラリーを膜状に塗布した。スラリーが塗布されたニッケル箔を乾燥して水を除去し、その後、ニッケル箔をプレスして、集電体上に正極活物質層が形成された正極を製造した。
　当該正極の集電体上に存在する正極活物質層の量は２８ｍｇ／ｃｍ２であり、正極活物質層の密度は、２．９ｇ／ｃｍ３であった。 94.3 parts by mass of the positive electrode active material of Example 1, 1 part by mass of cobalt powder as a conductive additive, 3.5 parts by mass of an acrylic resin emulsion as a binder, 3.5 parts by mass as a binder, and carboxymethyl cellulose as a binder. 0.7 parts by mass, 0.5 parts by mass of Y 2 O 3 as a positive electrode additive, and an appropriate amount of ion-exchanged water were mixed to prepare a slurry. A nickel foil having a thickness of 20 μm was prepared as a positive electrode current collector. The slurry was applied in the form of a film to the surface of the nickel foil. The nickel foil coated with the slurry was dried to remove water, and then the nickel foil was pressed to produce a positive electrode having a positive electrode active material layer formed on a current collector.
The amount of the positive electrode active material layer present on the current collector of the positive electrode was 28 mg / cm 2 , and the density of the positive electrode active material layer was 2.9 g / cm 3 .
　実施例１の負極活物質を９７．８質量部、結着剤としてアクリル系樹脂エマルションを固形分として１．５質量部、結着剤としてカルボキシメチルセルロースを０．７質量部、及び、適量のイオン交換水を混合して、スラリーを製造した。負極用集電体として厚み２０μｍのニッケル箔を準備した。このニッケル箔の表面に、上記スラリーを膜状に塗布した。スラリーが塗布されたニッケル箔を乾燥して水を除去し、その後、ニッケル箔をプレスして、集電体上に負極活物質層が形成された負極を製造した。 97.8 parts by mass of the negative electrode active material of Example 1, 1.5 parts by mass of an acrylic resin emulsion as a solid content as a binder, 0.7 parts by mass of carboxymethyl cellulose as a binder, and an appropriate amount of ions Exchanged water was mixed to produce a slurry. A nickel foil having a thickness of 20 μm was prepared as a negative electrode current collector. The slurry was applied in the form of a film to the surface of the nickel foil. The nickel foil coated with the slurry was dried to remove water, and then the nickel foil was pressed to produce a negative electrode in which a negative electrode active material layer was formed on a current collector.
　電解液として、水酸化カリウムの濃度が５．４ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．８ｍｏｌ／Ｌであり、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌであり、塩化リチウムの濃度が０．０５ｍｏｌ／Ｌである水溶液を準備した。 As the electrolytic solution, the concentration of potassium hydroxide is 5.4 mol / L, the concentration of sodium hydroxide is 0.8 mol / L, the concentration of lithium hydroxide is 0.5 mol / L, and the concentration of lithium chloride is Was prepared at 0.05 mol / L.
　セパレータとして、スルホン化処理が施された厚さ１０４μｍのポリオレフィン繊維製不織布を準備した。 (4) A non-woven fabric made of sulfonated polyolefin fiber and having a thickness of 104 μm was prepared as a separator.
　正極と負極とでセパレータを挟持し、極板群とした。樹脂製の筐体に、極板群を配置して、さらに上記電解液を注入し、筐体を密閉することで、実施例１のニッケル金属水素化物電池を製造した。 セ パ レ ー タ A separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. The nickel metal hydride battery of Example 1 was manufactured by disposing the electrode group in a resin housing, further injecting the above-mentioned electrolyte solution, and sealing the housing.
　（実施例２）
　Ｐ－１）工程における硫酸コバルト水溶液の添加量と、Ｐ－２）工程における水酸化ナトリウム水溶液の噴霧量を、若干変化させたこと以外は、概ね実施例１と同様の方法で、実施例２の正極活物質を製造した。
　実施例２の正極活物質を用いたこと以外は、実施例１と同様の方法で、実施例２のニッケル金属水素化物電池を製造した。 (Example 2)
Example 2 was carried out in substantially the same manner as in Example 1 except that the amount of the aqueous solution of cobalt sulfate added in the step P-1) and the spray amount of the aqueous solution of sodium hydroxide in the step P-2) were slightly changed. Was produced.
A nickel metal hydride battery of Example 2 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Example 2 was used.
　（実施例３）
　Ｐ－１）工程における硫酸コバルト水溶液の添加量と、Ｐ－２）工程における水酸化ナトリウム水溶液及び水酸化リチウム水溶液の噴霧量を、若干変化させたこと以外は、概ね実施例１と同様の方法で、実施例３の正極活物質を製造した。
　実施例３の正極活物質を用いたこと以外は、実施例１と同様の方法で、実施例３のニッケル金属水素化物電池を製造した。 (Example 3)
A method similar to that of Example 1 except that the amount of the aqueous solution of cobalt sulfate added in the step P-1) and the amount of the aqueous sodium hydroxide solution and the aqueous solution of lithium hydroxide in the step P-2) were slightly changed. Thus, the positive electrode active material of Example 3 was manufactured.
A nickel metal hydride battery of Example 3 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Example 3 was used.
　（実施例４）
　正極活物質本体の製造においてニッケル、コバルト及び亜鉛のモル比を若干変化させ、かつ、Ｐ－１）工程における硫酸コバルト水溶液の添加量と、Ｐ－２）工程における水酸化ナトリウム水溶液の噴霧量を、若干変化させたこと以外は、概ね実施例１と同様の方法で、実施例４の正極活物質を製造した。
　実施例４の正極活物質を用いたこと以外は、実施例１と同様の方法で、実施例４のニッケル金属水素化物電池を製造した。 (Example 4)
In the production of the positive electrode active material main body, the molar ratio of nickel, cobalt and zinc was slightly changed, and the addition amount of the aqueous solution of cobalt sulfate in the step P-1) and the spray amount of the aqueous sodium hydroxide solution in the step P-2) were changed. A positive electrode active material of Example 4 was manufactured in substantially the same manner as in Example 1, except for a slight change.
A nickel metal hydride battery of Example 4 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Example 4 was used.
　（実施例５）
　負極活物質の製造において、Ｎ－１）工程及びＮ－２）工程を行わなかったこと以外は、概ね実施例１と同様の方法で、実施例５の負極活物質を製造した。
　実施例５の負極活物質を用いたこと以外は、実施例１と同様の方法で、実施例５のニッケル金属水素化物電池を製造した。
　なお、実施例５の負極活物質は、Ｎ－２）工程における過酸化水素での酸化が実施されていないものの、大気に接触したため、一定程度酸化されている。 (Example 5)
In the production of the negative electrode active material, the negative electrode active material of Example 5 was produced in substantially the same manner as in Example 1, except that the steps N-1) and N-2) were not performed.
A nickel metal hydride battery of Example 5 was manufactured in the same manner as in Example 1, except that the negative electrode active material of Example 5 was used.
Note that the negative electrode active material of Example 5 was not oxidized with hydrogen peroxide in the step N-2), but was oxidized to a certain extent because it was in contact with the atmosphere.
　（実施例６）
　負極活物質の製造において、粉砕条件を緩和したこと、及び、Ｎ－２）工程における過酸化水素での酸化を行わなかったこと以外は、概ね実施例１と同様の方法で、実施例６の負極活物質を製造した。
　実施例６の負極活物質を用いたこと以外は、実施例１と同様の方法で、実施例６のニッケル金属水素化物電池を製造した。
　実施例６の水素吸蔵合金粉末の平均粒子径（Ｄ５０）は、１５μｍであった。
　また、実施例６の負極活物質は、Ｎ－２）工程における過酸化水素での酸化が実施されていないものの、Ｎ－１）工程におけるｂ）工程などで大気に接触したため、一定程度酸化されている。 (Example 6)
In the production of the negative electrode active material, the method of Example 6 was repeated in substantially the same manner as in Example 1, except that the grinding conditions were relaxed and that oxidation with hydrogen peroxide was not performed in the step N-2). A negative electrode active material was manufactured.
A nickel metal hydride battery of Example 6 was manufactured in the same manner as in Example 1, except that the negative electrode active material of Example 6 was used.
The average particle size (D 50 ) of the hydrogen storage alloy powder of Example 6 was 15 μm.
Further, although the negative electrode active material of Example 6 was not oxidized with hydrogen peroxide in Step N-2), it was oxidized to a certain extent because it came into contact with the atmosphere in Step b) in Step N-1). ing.
　（実施例７）
　正極活物質本体の製造におけるＰ－２）工程において、水酸化リチウム水溶液の噴霧を行わなかったこと以外は、概ね実施例１と同様の方法で、実施例７の正極活物質を製造した。
　実施例７の正極活物質を用いたこと以外は、実施例１と同様の方法で、実施例７のニッケル金属水素化物電池を製造した。 (Example 7)
The positive electrode active material of Example 7 was produced in substantially the same manner as in Example 1 except that the aqueous lithium hydroxide solution was not sprayed in the step P-2) in the production of the positive electrode active material body.
A nickel metal hydride battery of Example 7 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Example 7 was used.
　（実施例８）
　負極活物質の製造におけるＮ－１）工程のａ）工程において、懸濁液を９０℃に加熱して３時間保持したこと以外は、概ね実施例１と同様の方法で、実施例８の負極活物質を製造した。
　実施例８の水素吸蔵合金粉末の平均粒子径（Ｄ５０）は、９μｍであった。
　また、電解液として、水酸化カリウムの濃度が５．４ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．８ｍｏｌ／Ｌであり、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌであり、タングステン酸ナトリウムの濃度が０．０１ｍｏｌ／Ｌである水溶液を準備した。
　実施例８の負極活物質、及び、上記の電解液を用いたこと以外は、実施例７と同様の方法で、実施例８のニッケル金属水素化物電池を製造した。 (Example 8)
In the step a) of the step N-1) in the production of the negative electrode active material, except that the suspension was heated to 90 ° C. and held for 3 hours, the negative electrode of the example 8 was produced in substantially the same manner as in the example 1. An active material was manufactured.
The average particle diameter (D 50 ) of the hydrogen storage alloy powder of Example 8 was 9 μm.
As the electrolyte, the concentration of potassium hydroxide is 5.4 mol / L, the concentration of sodium hydroxide is 0.8 mol / L, the concentration of lithium hydroxide is 0.5 mol / L, and tungstic acid is used. An aqueous solution having a sodium concentration of 0.01 mol / L was prepared.
A nickel metal hydride battery of Example 8 was manufactured in the same manner as in Example 7, except that the negative electrode active material of Example 8 and the above-mentioned electrolyte solution were used.
　（比較例１）
　正極活物質本体の製造においてニッケル、コバルト及び亜鉛のモル比を若干変化させ、かつ、Ｐ－２）工程において、水酸化ナトリウム水溶液及び水酸化リチウム水溶液の噴霧を行わなかったこと以外は、概ね実施例１と同様の方法で、比較例１の正極活物質を製造した。
　比較例１の正極活物質を用いたこと以外は、実施例１と同様の方法で、比較例１のニッケル金属水素化物電池を製造した。 (Comparative Example 1)
Except that the molar ratio of nickel, cobalt and zinc was slightly changed in the production of the positive electrode active material body, and that the aqueous sodium hydroxide solution and the aqueous lithium hydroxide solution were not sprayed in the step P-2). A positive electrode active material of Comparative Example 1 was produced in the same manner as in Example 1.
A nickel metal hydride battery of Comparative Example 1 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Comparative Example 1 was used.
　（比較例２）
　負極活物質の製造において、粉砕条件を緩和したこと、並びに、Ｎ－１）工程及びＮ－２）工程を行わなかったこと以外は、概ね実施例１と同様の方法で、比較例２の負極活物質を製造した。
　比較例２の負極活物質を用いたこと以外は、実施例１と同様の方法で、比較例２のニッケル金属水素化物電池を製造した。
　比較例２の水素吸蔵合金粉末の平均粒子径（Ｄ５０）は、１５μｍであった。 (Comparative Example 2)
In the production of the negative electrode active material, the negative electrode of Comparative Example 2 was produced in substantially the same manner as in Example 1 except that the grinding conditions were relaxed and the steps N-1) and N-2) were not performed. An active material was manufactured.
A nickel metal hydride battery of Comparative Example 2 was manufactured in the same manner as in Example 1, except that the negative electrode active material of Comparative Example 2 was used.
The average particle diameter (D 50 ) of the hydrogen storage alloy powder of Comparative Example 2 was 15 μm.
　（比較例３）
　正極活物質本体の製造におけるＰ－２）工程において、水酸化リチウム水溶液の噴霧を行わなかったこと以外は、概ね実施例１と同様の方法で、比較例３の正極活物質を製造した。なお、比較例３の正極活物質は本発明の正極活物質の一態様であるが、表記による混乱を避けるため、便宜上、「比較例３の正極活物質」と記述する。
　比較例３の正極活物質及び比較例２の負極活物質を用いたこと以外は、実施例１と同様の方法で、比較例３のニッケル金属水素化物電池を製造した。 (Comparative Example 3)
The positive electrode active material of Comparative Example 3 was manufactured in substantially the same manner as in Example 1 except that the aqueous lithium hydroxide solution was not sprayed in the step P-2) in the manufacture of the positive electrode active material body. Note that the positive electrode active material of Comparative Example 3 is one embodiment of the positive electrode active material of the present invention, but is referred to as “the positive electrode active material of Comparative Example 3” for convenience to avoid confusion.
A nickel metal hydride battery of Comparative Example 3 was manufactured in the same manner as in Example 1, except that the positive electrode active material of Comparative Example 3 and the negative electrode active material of Comparative Example 2 were used.
　実施例１～実施例７、比較例１～３のニッケル金属水素化物電池の一覧を表１に示す。　 Table 1 shows a list of nickel metal hydride batteries of Examples 1 to 7 and Comparative Examples 1 to 3.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　（評価例１：正極活物質の物性）
　実施例１～実施例４、実施例７、比較例１、比較例３の正極活物質につき、リチウム及びナトリウム含有量の分析、平均粒子径の測定、ＢＥＴ比表面積の測定、コバルトの価数の測定、及び、抵抗率の測定を行った。 (Evaluation Example 1: Physical Properties of Positive Electrode Active Material)
For the positive electrode active materials of Examples 1 to 4, Example 7, Comparative Example 1 and Comparative Example 3, analysis of lithium and sodium contents, measurement of average particle diameter, measurement of BET specific surface area, measurement of valence of cobalt The measurement and the measurement of the resistivity were performed.
　リチウム及びナトリウム含有量の分析を、各正極活物質を溶解した溶液を用いた原子吸光法で行ったところ、実施例１～実施例４の正極活物質におけるリチウム含有量は概ね０．１質量％程度であり、ナトリウム含有量は概ね０．２～０．６質量％程度であった。
　実施例７、比較例１及び比較例３の正極活物質からはリチウムが検出されなかった。比較例１の正極活物質からは若干量のナトリウムが検出された。また、実施例７及び比較例３の正極活物質におけるナトリウム含有量は、実施例１～実施例４の正極活物質と同程度であった。 The lithium and sodium contents were analyzed by atomic absorption spectrometry using a solution in which each positive electrode active material was dissolved. As a result, the lithium content in the positive electrode active materials of Examples 1 to 4 was approximately 0.1% by mass. And the sodium content was about 0.2 to 0.6% by mass.
No lithium was detected from the positive electrode active materials of Example 7, Comparative Examples 1 and 3. Some amount of sodium was detected from the positive electrode active material of Comparative Example 1. Further, the sodium contents in the positive electrode active materials of Example 7 and Comparative Example 3 were almost the same as those of the positive electrode active materials of Examples 1 to 4.
　平均粒子径（Ｄ５０）の測定は、一般的なレーザー回折式粒度分布測定装置を用いて行った。ＢＥＴ比表面積の測定は、一般的なＢＥＴ比表面積測定装置を用いて行った。コバルトの価数の測定は、ヨードメトリー法で行った。抵抗率の測定は、粉体抵抗率測定システム（株式会社三菱アナリテック）を用いて、正極活物質の粉末２．０gに対して、２５℃、相対湿度４０～５０％の条件下、２０ｋＮの荷重をかけた上で測定した。
　以上の結果を表２に示す。　 The average particle diameter (D 50 ) was measured using a general laser diffraction type particle size distribution analyzer. The measurement of the BET specific surface area was performed using a general BET specific surface area measuring device. The valence of cobalt was measured by an iodometry method. The resistivity was measured using a powder resistivity measuring system (Mitsubishi Analytech Co., Ltd.) at 20 kN under the conditions of 25 ° C. and a relative humidity of 40 to 50% for 2.0 g of the powder of the positive electrode active material. The measurement was performed after applying a load.
Table 2 shows the above results.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２から、アルカリ金属、特にリチウムの存在に因り、正極活物質のコバルトの価数が高くなり、かつ、正極活物質の抵抗率が低くなることがわかる。
　また、ナトリウム含有量が実施例１～実施例４の正極活物質と同程度である実施例７及び比較例３の正極活物質は、比較例１の正極活物質よりも好適な物性値を示したものの、ナトリウムと共にリチウムを含有する実施例１～実施例４の正極活物質の物性値には及ばなかった。 Table 2 shows that the valence of cobalt of the positive electrode active material increases and the resistivity of the positive electrode active material decreases due to the presence of the alkali metal, particularly lithium.
Further, the positive electrode active materials of Example 7 and Comparative Example 3 having the same sodium content as the positive electrode active materials of Examples 1 to 4 exhibited more preferable physical property values than the positive electrode active material of Comparative Example 1. However, it did not reach the physical properties of the positive electrode active materials of Examples 1 to 4 containing lithium together with sodium.
　（評価例２：負極活物質の物性）
　実施例１、実施例５、実施例６、実施例８、比較例２の負極活物質につき、酸素濃度の測定、ＢＥＴ比表面積の測定、及び、飽和磁化の測定を行った。
　酸素濃度の測定は、酸素・窒素・水素分析装置（不活性ガス溶融法）を用いて行った。ＢＥＴ比表面積の測定は、一般的なＢＥＴ比表面積測定装置を用いて行った。飽和磁化の測定は、振動試料型磁力計（Ｖｉｂｒａｔｉｎｇ　Ｓａｍｐｌｅ　Ｍａｇｎｅｔｏｍｅｔｅｒ）を用いて行った。
　以上の結果を表３に示す。　 (Evaluation Example 2: Physical Properties of Negative Electrode Active Material)
For the negative electrode active materials of Example 1, Example 5, Example 6, Example 8, and Comparative Example 2, measurement of oxygen concentration, measurement of BET specific surface area, and measurement of saturation magnetization were performed.
The oxygen concentration was measured using an oxygen / nitrogen / hydrogen analyzer (inert gas melting method). The measurement of the BET specific surface area was performed using a general BET specific surface area measuring device. The measurement of the saturation magnetization was performed using a vibrating sample magnetometer.
Table 3 shows the above results.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　（評価例３）
　ＳＯＣ（Ｓｔａｔｅ　ｏｆ　Ｃｈａｒｇｅ）６０％に調整した実施例１～実施例８、比較例１～比較例３のニッケル金属水素化物電池について、２５℃の条件下、１Ｃレートで５秒間放電させた。放電前後の電圧変化量及び放電時の電流値から、オームの法則に基づき、放電抵抗を算出した。結果を表４に示す。　 (Evaluation example 3)
The nickel metal hydride batteries of Examples 1 to 8 and Comparative Examples 1 to 3 adjusted to an SOC (State of Charge) of 60% were discharged at 25 ° C. at a rate of 1 C for 5 seconds. The discharge resistance was calculated based on Ohm's law from the amount of voltage change before and after discharge and the current value during discharge. Table 4 shows the results.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　表４の結果から、リチウム又はナトリウムがドープされた正極活物質と酸素濃度が高い負極活物質の両者を備える実施例１～実施例８のニッケル金属水素化物電池においては、放電抵抗が低いことがわかる。また、実施例１～実施例４の放電抵抗の値と、実施例５及び実施例６の放電抵抗の値と、比較例２の放電抵抗の値、並びに、実施例７及び実施例８の放電抵抗の値から、負極活物質の酸素濃度が高いほど、放電抵抗の値が小さくなることがわかる。 Table 4 shows that the nickel metal hydride batteries of Examples 1 to 8 including both the lithium or sodium doped positive electrode active material and the high oxygen concentration negative electrode active material have low discharge resistance. Understand. Further, the values of the discharge resistors of Examples 1 to 4, the values of the discharge resistors of Examples 5 and 6, the values of the discharge resistors of Comparative Example 2, and the values of the discharge resistors of Examples 7 and 8 were used. From the value of the resistance, it is found that the higher the oxygen concentration of the negative electrode active material, the smaller the value of the discharge resistance.
　（評価例４）
　実施例１及び比較例１のニッケル金属水素化物電池に対して、５０℃の条件下、１ＣでＳＯＣ２０％からＳＯＣ６０％まで充電させた後に１ＣでＳＯＣ６０％からＳＯＣ２０％まで放電させるとの充放電サイクルを、３５０回繰り返した。
　充放電サイクルを３５０回繰り返した後の実施例１及び比較例１のニッケル金属水素化物電池について、評価例３と同様の方法で、放電抵抗を測定した。そして、評価例３の放電抵抗に対する、充放電サイクルを３５０回繰り返した後の放電抵抗の増加率を算出した。
　また、初回充放電サイクル時の放電容量に対する、３５０回充放電サイクル時の放電容量の割合を、容量維持率として算出した。
　以上の結果を、表５に示す。なお、実施例１及び比較例１のニッケル金属水素化物電池は、いずれも実施例１の負極活物質を具備している。　 (Evaluation example 4)
Charge / discharge cycle of charging the nickel metal hydride batteries of Example 1 and Comparative Example 1 at 50 ° C. from 1% SOC to 60% SOC at 1C and then discharging from 60% SOC to 20% SOC at 1C. Was repeated 350 times.
With respect to the nickel metal hydride batteries of Example 1 and Comparative Example 1 after repeating the charge / discharge cycle 350 times, the discharge resistance was measured in the same manner as in Evaluation Example 3. Then, with respect to the discharge resistance of Evaluation Example 3, the rate of increase in the discharge resistance after 350 charge / discharge cycles were repeated was calculated.
In addition, the ratio of the discharge capacity during the 350th charge / discharge cycle to the discharge capacity during the first charge / discharge cycle was calculated as the capacity retention ratio.
Table 5 shows the above results. The nickel metal hydride batteries of Example 1 and Comparative Example 1 each include the negative electrode active material of Example 1.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
　表５の結果から、抵抗の点でみても、容量維持率の点でみても、実施例１のニッケル金属水素化物電池が優れているといえる。本発明のニッケル金属水素化物電池が電池特性に優れることが裏付けられたといえる。 結果 From the results in Table 5, it can be said that the nickel metal hydride battery of Example 1 is excellent both in terms of resistance and capacity retention. It can be said that the nickel metal hydride battery of the present invention has excellent battery characteristics.
　（参考例１）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＬｉＣｌを溶解させて、ＬｉＣｌを０．０５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例１の電解液とした。 (Reference Example 1)
LiCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing LiCl at 0.05 mol / L. The aqueous solution produced as described above was used as the electrolyte of Reference Example 1.
　（参考例２）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＬｉＣｌを溶解させて、ＬｉＣｌを０．２ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例２の電解液とした。 (Reference Example 2)
LiCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing 0.2 mol / L of LiCl. The aqueous solution produced as described above was used as the electrolyte of Reference Example 2.
　（参考例３）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＬｉＣｌを溶解させて、ＬｉＣｌを０．５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例３の電解液とした。 (Reference Example 3)
LiCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing 0.5 mol / L of LiCl. The aqueous solution produced as described above was used as the electrolyte of Reference Example 3.
　（参考例４）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＫＣｌを溶解させて、ＫＣｌを０．０５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例４の電解液とした。 (Reference Example 4)
KCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing 0.05 mol / L of KCl. The aqueous solution produced as described above was used as the electrolyte of Reference Example 4.
　（参考例５）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＫＣｌを溶解させて、ＫＣｌを０．５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例５の電解液とした。 (Reference Example 5)
KCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing KCl at 0.5 mol / L. The aqueous solution produced as described above was used as the electrolyte of Reference Example 5.
　（参考比較例１）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液を、参考比較例１の電解液とした。 (Reference Comparative Example 1)
An aqueous solution in which the concentration of potassium hydroxide was 5.5 mol / L, the concentration of sodium hydroxide was 0.5 mol / L, and the concentration of lithium hydroxide was 0.5 mol / L was obtained as Reference Comparative Example 1. Electrolyte solution.
　（参考評価例１）
　参考例１～参考例５の電解液を、２５℃、０℃又は－４０℃条件下に２０時間保管し、その性状を観察した。結果を表６に示す。　 (Reference evaluation example 1)
The electrolyte solutions of Reference Examples 1 to 5 were stored at 25 ° C., 0 ° C., or −40 ° C. for 20 hours, and the properties were observed. Table 6 shows the results.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　参考例の電解液は、いずれの温度条件下においても、塩の析出や水溶液の凝固は観察されず、良好な液体状態を維持することが確認された。 電解 Under any temperature conditions, no precipitation of salt and no solidification of the aqueous solution were observed, and it was confirmed that the electrolyte solution of the reference example maintained a good liquid state.
　（参考例１－ｈalf）
　以下のとおり、参考例１の電解液を具備する参考例１－ｈalfのハーフセルを製造した。 (Reference Example 1-h alf)
As follows, to produce a half cell of Reference Example 1-h alf comprising the electrolytic solution of Example 1.
　フッ素樹脂製の容器に参考例１の電解液を注ぎ、さらに作用極、対極及び参照極を配置して、参考例１－ｈalfのハーフセルとした。なお、作用極としてＮｉメッシュを用い、対極としてＰｔ線を用い、参照極として水銀－酸化水銀電極を用いた。 Fluorine resin container was poured an electrolyte solution of Example 1, further working electrode, by placing the counter electrode and a reference electrode, and the half cell of Reference Example 1-h alf. Note that a Ni mesh was used as a working electrode, a Pt line was used as a counter electrode, and a mercury-mercury oxide electrode was used as a reference electrode.
　（参考例２－ｈalf）
　参考例１の電解液に替えて、参考例２の電解液を用いた以外は、参考例１－ｈalfと同様の方法で、参考例２－ｈalfのハーフセルを製造した。 (Reference Example 2-h alf)
Instead of the electrolyte of Example 1, except for using an electrolytic solution of Reference Example 2, in Reference Example 1-h alf a similar manner was prepared the half cell of Reference Example 2-h alf.
　（参考例３－ｈalf）
　参考例１の電解液に替えて、参考例３の電解液を用いた以外は、参考例１－ｈalfと同様の方法で、参考例３－ｈalfのハーフセルを製造した。 (Reference Example 3-h alf)
Instead of the electrolyte of Example 1, except for using an electrolytic solution of Reference Example 3, Reference Example 1-h alf a similar manner was prepared the half cell of Example 3-h alf.
　（参考例４－ｈalf）
　参考例１の電解液に替えて、参考例４の電解液を用いた以外は、参考例１－ｈalfと同様の方法で、参考例４－ｈalfのハーフセルを製造した。 (Reference Example 4-h alf)
Instead of the electrolyte of Example 1, except for using an electrolytic solution of Reference Example 4, Reference Example 1-h alf a similar manner was prepared the half cell of Example 4-h alf.
　（参考例５－ｈalf）
　参考例１の電解液に替えて、参考例５の電解液を用いた以外は、参考例１－ｈalfと同様の方法で、参考例５－ｈalfのハーフセルを製造した。 (Reference Example 5-h alf)
Instead of the electrolyte of Example 1, except for using an electrolytic solution of Reference Example 5, Reference Example 1-h alf a similar manner was prepared the half cell of Example 5-h alf.
　（参考比較例１－ｈalf）
　参考例１の電解液に替えて、参考比較例１の電解液を用いた以外は、参考例１－ｈalfと同様の方法で、参考比較例１－ｈalfのハーフセルを製造した。 (Reference Comparative Example 1-h alf)
Instead of the electrolyte of Example 1, except for using the electrolytic solution of Comparative Reference Example 1, Reference Example 1-h alf a similar manner was prepared the half-cell of Comparative Reference Example 1-h alf.
　（参考評価例Ａ）
　０℃、２５℃、４５℃又は６０℃の条件下、各ハーフセルの作用極に対して１．５Ｖ（ｖｓ．ＳＨＥ）の電圧を負荷した場合の電流値を測定した。なお、測定中、ハーフセル中の電解液には、窒素がバブリングされていた。結果を表７に示す。　 (Reference evaluation example A)
Under a condition of 0 ° C., 25 ° C., 45 ° C., or 60 ° C., a current value when a voltage of 1.5 V (vs. SHE) was applied to the working electrode of each half cell was measured. During the measurement, nitrogen was bubbled through the electrolytic solution in the half cell. Table 7 shows the results.
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
　参考評価例Ａにて測定された電流値は、水の酸化分解に因る酸素発生に伴い生じたものと解される。参考例のすべてのハーフセルは、参考比較例１－ｈalfのハーフセルと比較して、いずれの温度条件下においても、電流値が小さかった。電解液に対するＬｉＣｌ又はＫＣｌの添加が、酸素発生を抑制したといえる。 It is understood that the current value measured in Reference Evaluation Example A was caused by oxygen generation due to oxidative decomposition of water. All half cell of the reference example, as compared to the half-cell of Comparative Reference Example 1-h alf, in any of the temperature conditions, the current value was small. It can be said that the addition of LiCl or KCl to the electrolyte suppressed the generation of oxygen.
　０．０５ＭのＬｉＣｌを含有する参考例１－ｈalfのハーフセルは、０．０５ＭのＫＣｌを含有する参考例４－ｈalfのハーフセルと比較して、いずれの温度条件下においても、電流値が小さかった。同様に、０．５ＭのＬｉＣｌを含有する参考例３－ｈalfのハーフセルは、０．５ＭのＫＣｌを含有する参考例５－ｈalfのハーフセルと比較して、いずれの温度条件下においても、電流値が小さかった。これらの結果から、アルカリ金属ハロゲン化物のアルカリ金属としては、ＫよりもＬｉの方が優れているといえる。
　また、参考例３－ｈalfのハーフセルの電流値は、他のハーフセルの電流値と比較して、著しく小さいことがわかる。 Half cell of Reference Example 1-h alf containing LiCl in 0.05M, compared to half cell of Example 4-h alf containing KCl of 0.05M, in any of the temperature conditions, the current value It was small. Similarly, half cell of Example 3-h alf containing LiCl in 0.5M, compared to half cell of Example 5-h alf containing KCl in 0.5M, in any of the temperature conditions, The current value was small. From these results, it can be said that Li is superior to K as the alkali metal of the alkali metal halide.
The current value of the half cell of Example 3-h alf, compared to the current value of the other half-cell, it can be seen that significantly less.
　（参考例１－Ｆull）
　以下のとおり、参考例１の電解液を具備する参考例１－Ｆullのニッケル金属水素化物電池を製造した。 (Reference Example 1-F ull )
A nickel metal hydride battery of Reference Example 1- Full equipped with the electrolyte of Reference Example 1 was manufactured as follows.
　正極活物質として水酸化ニッケル粉末を８３．３質量部、導電助剤としてコバルト粉末を５質量部、導電助剤としてカーボンブラックを５質量部、結着剤としてアクリル系樹脂エマルション（ジョンクリルＰＤＸ７３４１、ＢＡＳＦ社）を固形分として５質量部、結着剤としてカルボキシメチルセルロースを０．７質量部、正極添加剤としてＹ2Ｏ3を１質量部、及び、適量のイオン交換水を混合して、スラリーを製造した。正極用集電体として厚み１０μｍのニッケル箔を準備した。このニッケル箔の表面に、ドクターブレードを用いて、上記スラリーを膜状に塗布した。スラリーが塗布されたニッケル箔を乾燥して水を除去し、その後、ニッケル箔をプレスし、接合物を得た。得られた接合物を乾燥機で７０℃、１時間加熱乾燥して、集電体上に正極活物質層が形成された正極を製造した。 83.3 parts by mass of nickel hydroxide powder as a positive electrode active material, 5 parts by mass of cobalt powder as a conduction aid, 5 parts by mass of carbon black as a conduction aid, and an acrylic resin emulsion (Joncryl PDX 7341; BASF) as a solid content, 5 parts by mass of carboxymethylcellulose as a binder, 1 part by mass of Y 2 O 3 as a positive electrode additive, and an appropriate amount of ion-exchanged water. Was manufactured. A nickel foil having a thickness of 10 μm was prepared as a positive electrode current collector. The slurry was applied to the surface of the nickel foil in the form of a film using a doctor blade. The nickel foil to which the slurry was applied was dried to remove water, and then the nickel foil was pressed to obtain a bonded product. The obtained bonded article was dried by heating at 70 ° C. for 1 hour using a drier to produce a positive electrode having a positive electrode active material layer formed on a current collector.
　負極活物質として、Ａ2Ｂ7型水素吸蔵合金を９６．９質量部、導電助剤としてカーボンブラックを０．４質量部、結着剤としてアクリル系樹脂エマルション（ジョンクリルＰＤＸ７３４１、ＢＡＳＦ社）を固形分として２質量部、結着剤としてカルボキシメチルセルロースを０．７質量部、及び、適量のイオン交換水を混合して、スラリーを製造した。負極用集電体として厚み１０μｍのニッケル箔を準備した。このニッケル箔の表面に、ドクターブレードを用いて、上記スラリーを膜状に塗布した。スラリーが塗布されたニッケル箔を乾燥して水を除去し、その後、ニッケル箔をプレスし、接合物を得た。得られた接合物を乾燥機で７０℃、１時間加熱乾燥して、集電体上に負極活物質層が形成された負極を製造した。 96.9 parts by mass of an A 2 B 7 type hydrogen storage alloy as a negative electrode active material, 0.4 parts by mass of carbon black as a conductive aid, and an acrylic resin emulsion (Johncryl PDX7341, BASF) as a binder A slurry was prepared by mixing 2 parts by mass as a solid content, 0.7 parts by mass of carboxymethyl cellulose as a binder, and an appropriate amount of ion-exchanged water. A nickel foil having a thickness of 10 μm was prepared as a current collector for the negative electrode. The slurry was applied to the surface of the nickel foil in the form of a film using a doctor blade. The nickel foil to which the slurry was applied was dried to remove water, and then the nickel foil was pressed to obtain a bonded product. The obtained bonded article was dried by heating at 70 ° C. for 1 hour using a drier to produce a negative electrode having a negative electrode active material layer formed on a current collector.
　セパレータとして、スルホン化処理が施された厚さ１２０μｍのポリプロピレン繊維製不織布を準備した。正極と負極とでセパレータを挟持し、極板群とした。樹脂製の筐体に、極板群を配置して、さらに参考例１の電解液を注入し、筐体を密閉することで、参考例１－Ｆullのニッケル金属水素化物電池を製造した。 A 120 μm-thick nonwoven polypropylene fiber nonwoven fabric that had been subjected to a sulfonation treatment was prepared as a separator. A separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. The electrode group was arranged in a resin housing, the electrolyte of Reference Example 1 was further injected, and the housing was sealed to produce a nickel metal hydride battery of Reference Example 1- Full .
　（参考例２－Ｆull）
　参考例１の電解液に替えて、参考例２の電解液を用いた以外は、参考例１－Ｆullと同様の方法で、参考例２－Ｆullのニッケル金属水素化物電池を製造した。 (Reference Example 2-F ull )
A nickel metal hydride battery of Reference Example 2- Full was manufactured in the same manner as in Reference Example 1- Full except that the electrolyte of Reference Example 2 was used instead of the electrolyte of Reference Example 1.
　（参考例３－Ｆull）
　参考例１の電解液に替えて、参考例３の電解液を用いた以外は、参考例１－Ｆullと同様の方法で、参考例３－Ｆullのニッケル金属水素化物電池を製造した。 (Reference Example 3-F ull )
A nickel metal hydride battery of Reference Example 3- Full was manufactured in the same manner as in Reference Example 1- Full , except that the electrolyte of Reference Example 1 was used instead of the electrolyte of Reference Example 1.
　（参考例４－Ｆull）
　参考例１の電解液に替えて、参考例４の電解液を用いた以外は、参考例１－Ｆullと同様の方法で、参考例４－Ｆullのニッケル金属水素化物電池を製造した。 (Reference Example 4-F ull )
A nickel metal hydride battery of Reference Example 4- Full was manufactured in the same manner as in Reference Example 1- Full , except that the electrolyte of Reference Example 4 was used instead of the electrolyte of Reference Example 1.
　（参考比較例１－Ｆull）
　参考例１の電解液に替えて、参考比較例１の電解液を用いた以外は、参考例１－Ｆullと同様の方法で、参考比較例１－Ｆullのニッケル金属水素化物電池を製造した。 (Reference Comparative Example 1-F ull )
The nickel metal hydride battery of Reference Comparative Example 1- Full was manufactured in the same manner as in Reference Example 1- Full except that the electrolytic solution of Reference Comparative Example 1 was used instead of the electrolytic solution of Reference Example 1. did.
　（参考評価例Ｉ：充電効率）
　参考例１－Ｆullのニッケル金属水素化物電池について、温度２５℃の条件下、０．１Ｃレートで１．５Ｖまで充電を行った後に、０．１Ｃレートで０．８Ｖまで放電を行った。参考例２－Ｆull～参考例４－Ｆull及び参考比較例１－Ｆullのニッケル金属水素化物電池に対しても、同様の充放電を行った。そして、以下の式を用いて、各ニッケル金属水素化物電池の充放電効率を算出した。結果を表８に示す。
　充放電効率（％）＝１００×（放電容量）／（充電容量）　 (Reference evaluation example I: charging efficiency)
REFERENCE EXAMPLE 1 A Full metal nickel hydride battery was charged at a rate of 0.1 C to 1.5 V at a temperature of 25 ° C., and then discharged to 0.8 V at a rate of 0.1 C. The same charging / discharging was performed on the nickel metal hydride batteries of Reference Example 2-F ull to Reference Example 4-F ull and Reference Comparative Example 1-F ull . Then, the charge / discharge efficiency of each nickel metal hydride battery was calculated using the following equation. Table 8 shows the results.
Charge / discharge efficiency (%) = 100 × (discharge capacity) / (charge capacity)
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
　参考比較例１－Ｆullのニッケル金属水素化物電池と比較して、参考例のニッケル金属水素化物電池の充放電効率が優れていることがわかる。電解液に対するＬｉＣｌとＫＣｌの添加が、ニッケル金属水素化物電池の充放電効率を改良したといえる。 It can be seen that the charge and discharge efficiency of the nickel metal hydride battery of Reference Example is superior to that of Reference Comparative Example 1- Full of the nickel metal hydride battery. It can be said that the addition of LiCl and KCl to the electrolyte improved the charge / discharge efficiency of the nickel metal hydride battery.
　（参考例６）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＬｉＣｌを溶解させて、ＬｉＣｌを０．０５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例６の電解液とした。
　フッ素樹脂製の容器に参考例６の電解液を注ぎ、さらに作用極、対極及び参照極を配置して、参考例６のハーフセルとした。なお、作用極としてＮｉメッシュを用い、対極としてＰｔ線を用い、参照極として水銀－酸化水銀電極を用いた。 (Reference Example 6)
LiCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing LiCl at 0.05 mol / L. The aqueous solution produced as described above was used as the electrolyte solution of Reference Example 6.
The electrolyte solution of Reference Example 6 was poured into a container made of a fluororesin, and a working electrode, a counter electrode and a reference electrode were further arranged to obtain a half cell of Reference Example 6. Note that a Ni mesh was used as a working electrode, a Pt line was used as a counter electrode, and a mercury-mercury oxide electrode was used as a reference electrode.
　（参考例７）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＮａＣｌを溶解させて、ＮａＣｌを０．０５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例７の電解液とした。
　以下、参考例６と同様の方法で、参考例７のハーフセルを製造した。 (Reference Example 7)
NaCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing 0.05 mol / L of NaCl was produced. The aqueous solution produced as described above was used as the electrolyte of Reference Example 7.
Hereinafter, the half cell of Reference Example 7 was manufactured in the same manner as in Reference Example 6.
　（参考例８）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＫＣｌを溶解させて、ＫＣｌを０．０５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例８の電解液とした。
　以下、参考例６と同様の方法で、参考例８のハーフセルを製造した。 (Reference Example 8)
KCl is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing 0.05 mol / L of KCl. The aqueous solution produced as described above was used as the electrolyte of Reference Example 8.
Hereinafter, the half cell of Reference Example 8 was manufactured in the same manner as in Reference Example 6.
　（参考例９）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＫＦを溶解させて、ＫＦを０．０５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例９の電解液とした。
　以下、参考例６と同様の方法で、参考例９のハーフセルを製造した。 (Reference Example 9)
KF is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. , KF at 0.05 mol / L. The aqueous solution produced as described above was used as the electrolyte solution of Reference Example 9.
Hereinafter, the half cell of Reference Example 9 was manufactured in the same manner as in Reference Example 6.
　（参考例１０）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液にＫＢｒを溶解させて、ＫＢｒを０．０５ｍｏｌ／Ｌで含有する水溶液を製造した。上述のとおり製造された水溶液を、参考例１０の電解液とした。
　以下、参考例６と同様の方法で、参考例１０のハーフセルを製造した。 (Reference Example 10)
KBr is dissolved in an aqueous solution in which the concentration of potassium hydroxide is 5.5 mol / L, the concentration of sodium hydroxide is 0.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L. And an aqueous solution containing KBr at 0.05 mol / L. The aqueous solution produced as described above was used as the electrolyte of Reference Example 10.
Hereinafter, the half cell of Reference Example 10 was manufactured in the same manner as in Reference Example 6.
　（参考比較例２）
　水酸化カリウムの濃度が５．５ｍｏｌ／Ｌであり、水酸化ナトリウムの濃度が０．５ｍｏｌ／Ｌであり、かつ、水酸化リチウムの濃度が０．５ｍｏｌ／Ｌである水溶液を、参考比較例２の電解液とした。
　以下、参考例６と同様の方法で、参考比較例２のハーフセルを製造した。 (Reference Comparative Example 2)
An aqueous solution in which the concentration of potassium hydroxide was 5.5 mol / L, the concentration of sodium hydroxide was 0.5 mol / L, and the concentration of lithium hydroxide was 0.5 mol / L was obtained as Reference Comparative Example 2. Electrolyte solution.
Hereinafter, the half cell of Reference Comparative Example 2 was manufactured in the same manner as in Reference Example 6.
　（参考評価例Ｂ）
　２５℃の条件下、各ハーフセルの作用極に対して１．５Ｖ（ｖｓ．ＳＨＥ）の電圧を負荷した場合の電流値を測定した。なお、測定中、ハーフセル中の電解液には、窒素がバブリングされていた。結果を表９に示す。　 (Reference evaluation example B)
Under a condition of 25 ° C., a current value was measured when a voltage of 1.5 V (vs. SHE) was applied to the working electrode of each half cell. During the measurement, nitrogen was bubbled through the electrolytic solution in the half cell. Table 9 shows the results.
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
　参考例６～参考例１０のハーフセルのすべての電流値は、参考比較例２のハーフセルの電流値よりも小さかった。各種のアルカリ金属ハロゲン化物に酸素発生抑制効果があることがわかる。
　また、参考例６～参考例８の結果から、アルカリ金属ハロゲン化物のうちリチウムハロゲン化物が最も酸素発生抑制効果に優れており、次にナトリウムハロゲン化物、その次にカリウムハロゲン化物であるといえる。さらに、参考例８～参考例１０の結果から、アルカリ金属ハロゲン化物のうちアルカリ金属塩化物が最も酸素発生抑制効果に優れており、次にアルカリ金属臭化物、その次にアルカリ金属フッ化物であるといえる。総合的にみると、アルカリ金属ハロゲン化物としては、ＬｉＣｌが最も酸素発生抑制効果に優れているといえる。 All the current values of the half cells of Reference Examples 6 to 10 were smaller than the current values of the half cells of Reference Comparative Example 2. It can be seen that various alkali metal halides have an oxygen generation suppressing effect.
Further, from the results of Reference Examples 6 to 8, it can be said that among the alkali metal halides, lithium halide is the most excellent in suppressing the generation of oxygen, followed by sodium halide and then potassium halide. Furthermore, from the results of Reference Examples 8 to 10, among the alkali metal halides, the alkali metal chloride is most excellent in suppressing the generation of oxygen, followed by the alkali metal bromide and then the alkali metal fluoride. I can say. Comprehensively, it can be said that as an alkali metal halide, LiCl is the most effective in suppressing the generation of oxygen.
　（応用例１）
　電極の厚み側から観察した、応用例１の双極型ニッケル金属水素化物電池の模式断面図を、図１に示す。 (Application Example 1)
FIG. 1 shows a schematic cross-sectional view of the bipolar nickel metal hydride battery of Application Example 1, observed from the thickness side of the electrode.
　応用例１の双極型ニッケル金属水素化物電池１は、
　集電箔２０の一面に正極活物質層２１が形成された正極２と、
　集電箔３０の一面に負極活物質層３１が形成された負極３と、
　集電箔４０の一面に正極活物質層４１が形成され、他面に負極活物質層４２が形成された双極型電極４と、
　親水化処理が施されたポリオレフィン製のセパレータ５と、を具備する。 The bipolar nickel metal hydride battery 1 of the application example 1 is:
A positive electrode 2 in which a positive electrode active material layer 21 is formed on one surface of a current collector foil 20;
A negative electrode 3 in which a negative electrode active material layer 31 is formed on one surface of a current collector foil 30;
A bipolar electrode 4 having a positive electrode active material layer 41 formed on one surface of a current collector foil 40 and a negative electrode active material layer 42 formed on the other surface;
And a polyolefin separator 5 that has been subjected to a hydrophilic treatment.
　正極２の集電箔２０は、ニッケル製であって、厚み２０μｍの矩形の箔である。集電箔２０の上面には、本発明の正極活物質、導電助剤、結着剤及び添加剤を含む正極活物質層２１が形成されている。そして、集電箔２０の周縁は、合成樹脂製の外枠７で固定されており、そして、外枠７の内側には、フッ素含有樹脂製のシール部６が配置されている。シール部６は、集電箔２０の上面と下面に結着されている。 (4) The current collector foil 20 of the positive electrode 2 is made of nickel and is a rectangular foil having a thickness of 20 μm. On the upper surface of the current collector foil 20, a positive electrode active material layer 21 including the positive electrode active material of the present invention, a conductive auxiliary agent, a binder, and an additive is formed. The peripheral edge of the current collector foil 20 is fixed by an outer frame 7 made of synthetic resin, and a seal portion 6 made of a fluorine-containing resin is arranged inside the outer frame 7. The seal portion 6 is bound to the upper and lower surfaces of the current collector foil 20.
　正極２の正極活物質層２１の上面には、セパレータ５が配置されている。セパレータ５には、電解液が含浸されている。セパレータ５の面は、接する正極活物質層２１の面よりも面積が大きい。 セ パ レ ー タ The separator 5 is arranged on the upper surface of the positive electrode active material layer 21 of the positive electrode 2. The separator 5 is impregnated with an electrolytic solution. The area of the surface of the separator 5 is larger than the area of the surface of the positive electrode active material layer 21 that is in contact.
　正極２の正極活物質層２１の上面に配置されたセパレータ５の上面には、負極活物質層４２が対面する方向で双極型電極４が配置されている。 (4) The bipolar electrode 4 is disposed on the upper surface of the separator 5 disposed on the upper surface of the positive electrode active material layer 21 of the positive electrode 2 in the direction in which the negative electrode active material layer 42 faces.
　双極型電極４は、集電箔４０の上面に正極活物質層４１が形成され、下面に負極活物質層４２が形成されている。集電箔４０は正極２の集電箔２０と同様のものであり、正極活物質層４１も正極２の正極活物質層２１と同様のものである。双極型電極４の負極活物質層４２には、本発明の負極活物質及び結着剤が含有されている。 In the bipolar electrode 4, the positive electrode active material layer 41 is formed on the upper surface of the current collector foil 40, and the negative electrode active material layer 42 is formed on the lower surface. The current collector foil 40 is the same as the current collector foil 20 of the positive electrode 2, and the positive electrode active material layer 41 is also the same as the positive electrode active material layer 21 of the positive electrode 2. The negative electrode active material layer 42 of the bipolar electrode 4 contains the negative electrode active material of the present invention and a binder.
　集電箔４０の周縁は、合成樹脂製の外枠７で固定されており、そして、外枠７の内側には、フッ素含有樹脂製のシール部６が配置されている。シール部６は集電箔４０の上面と下面に結着されており、集電箔４０の上面のシール部６はさらに上側の他の双極型電極４の集電箔４０の下面にも結着され、また、集電箔４０の下面のシール部６は正極２の集電箔２０の上面にも結着されている。すなわち、シール部６により、正極活物質層２１、セパレータ５、電解液、及び負極活物質層４２は、密閉状態にある。 周 The periphery of the current collecting foil 40 is fixed by an outer frame 7 made of synthetic resin, and a seal portion 6 made of a fluorine-containing resin is arranged inside the outer frame 7. The sealing portion 6 is bonded to the upper and lower surfaces of the current collecting foil 40, and the sealing portion 6 on the upper surface of the current collecting foil 40 is further bonded to the lower surface of the current collecting foil 40 of the other bipolar electrode 4 above. The sealing portion 6 on the lower surface of the current collector foil 40 is also bonded to the upper surface of the current collector foil 20 of the positive electrode 2. That is, the positive electrode active material layer 21, the separator 5, the electrolytic solution, and the negative electrode active material layer 42 are in a sealed state by the seal portion 6.
　正極２にセパレータ５を介して積層された双極型電極４の上面には、セパレータ５を介して双極型電極４が複数積層されている。
　最上部の双極型電極４の正極活物質層４１の上面には、セパレータ５が配置され、そのセパレータ５の上面には、負極活物質層３１が対面する方向で負極３が配置されている。 On the upper surface of the bipolar electrode 4 laminated on the positive electrode 2 via the separator 5, a plurality of bipolar electrodes 4 are laminated via the separator 5.
The separator 5 is disposed on the upper surface of the positive electrode active material layer 41 of the uppermost bipolar electrode 4, and the negative electrode 3 is disposed on the upper surface of the separator 5 in the direction in which the negative electrode active material layer 31 faces.
　負極３は、集電箔３０の下面に負極活物質層３１が形成されている。集電箔３０は正極２の集電箔２０及び双極型電極４の集電箔４０と同様のものであり、負極活物質層３１も双極型電極４の負極活物質層４２と同様のものである。そして、集電箔３０の周縁は、合成樹脂製の外枠７で固定されており、そして、外枠７の内側には、フッ素含有樹脂製のシール部６が配置されている。シール部６は集電箔３０の上面と下面に結着されており、集電箔３０の下面のシール部６は双極型電極４の集電箔４０の上面にも結着されている。 In the negative electrode 3, the negative electrode active material layer 31 is formed on the lower surface of the current collector foil 30. The current collector foil 30 is the same as the current collector foil 20 of the positive electrode 2 and the current collector foil 40 of the bipolar electrode 4, and the negative electrode active material layer 31 is the same as the negative electrode active material layer 42 of the bipolar electrode 4. is there. The peripheral edge of the current collector foil 30 is fixed by an outer frame 7 made of a synthetic resin, and a seal portion 6 made of a fluorine-containing resin is arranged inside the outer frame 7. The sealing portion 6 is bonded to the upper surface and the lower surface of the current collecting foil 30, and the sealing portion 6 on the lower surface of the current collecting foil 30 is also bonded to the upper surface of the current collecting foil 40 of the bipolar electrode 4.
　正極２、双極型電極４、負極３及びセパレータ５で構成される電池モジュールの厚み方向の上下には、冷却部８がそれぞれ配置されている。冷却部８はアルミニウム製の矩形板であって、空冷可能な貫通孔８０が複数設けられている。 {Circle around (2)} Cooling units 8 are arranged above and below the thickness of the battery module including the positive electrode 2, the bipolar electrode 4, the negative electrode 3 and the separator 5. The cooling unit 8 is a rectangular plate made of aluminum, and is provided with a plurality of through holes 80 capable of air cooling.
　冷却部８の外側には、外部と電気を通電するモジュール正極２２及びモジュール負極３２がそれぞれ配置されている。モジュール正極２２及びモジュール負極３２は、金属製の矩形板である。
　そして、モジュール正極２２及びモジュール負極３２の外側には、拘束具９がそれぞれ配置されている。拘束具９は合成樹脂製の矩形板である。２つの拘束具９は、図示しない複数のボルト及びナットで締結されており、電極の厚み方向に電池モジュールを加圧して拘束している。２つの拘束具９による加圧によって、セパレータ５は圧縮されている。 A module positive electrode 22 and a module negative electrode 32 for supplying electricity to the outside are arranged outside the cooling unit 8. The module positive electrode 22 and the module negative electrode 32 are rectangular plates made of metal.
The restraining tools 9 are arranged outside the module positive electrode 22 and the module negative electrode 32, respectively. The restraint 9 is a rectangular plate made of synthetic resin. The two restraints 9 are fastened with a plurality of bolts and nuts (not shown), and press and restrain the battery module in the thickness direction of the electrodes. The separator 5 is compressed by pressurization by the two restraints 9.
　１　双極型ニッケル金属水素化物電池
　２　正極
　３　負極
　４　双極型電極
　５　セパレータ
　６　シール部
　７　外枠
　８　冷却部
　９　拘束具
　２０　集電箔（正極集電箔）
　２１　正極活物質層
　２２　モジュール正極
　３０　集電箔（負極集電箔）
　３１　負極活物質層
　３２　モジュール負極
　４０　集電箔（双極型電極集電箔）
　４１　正極活物質層
　４２　負極活物質層
　８０　貫通孔 DESCRIPTION OF SYMBOLS 1 Bipolar nickel metal hydride battery 2 Positive electrode 3 Negative electrode 4 Bipolar electrode 5 Separator 6 Seal part 7 Outer frame 8 Cooling part 9 Restraint device 20 Current collector foil (positive electrode current collector foil)
21 positive electrode active material layer 22 module positive electrode 30 current collector foil (negative electrode current collector foil)
31 negative electrode active material layer 32 module negative electrode 40 current collector foil (bipolar electrode current collector foil)
41 Positive electrode active material layer 42 Negative electrode active material layer 80 Through hole

Claims (5)

  1. 　リチウム又はナトリウムを含有するオキシ水酸化コバルト層で被覆された正極活物質と、
    　充放電前における酸素濃度が１０００ｐｐｍ以上の負極活物質と、
    　を備えることを特徴とするニッケル金属水素化物電池。     A cathode active material coated with a cobalt oxyhydroxide layer containing lithium or sodium,
    A negative electrode active material having an oxygen concentration of 1000 ppm or more before charge and discharge,
    A nickel metal hydride battery comprising:
  2. 　前記負極活物質が、希土類元素、Ｍｇ及びＮｉを含有するＡ２Ｂ７型の水素吸蔵合金を含有する、請求項１に記載のニッケル金属水素化物電池。 The negative electrode active material, a rare earth element, containing A 2 B 7 type hydrogen storage alloy containing Mg and Ni, the nickel metal hydride battery according to claim 1.
  3. 　請求項１又は２に記載のニッケル金属水素化物電池の製造方法であって、
    　下記Ｐ－１）工程及びＰ－２）工程を有する、リチウム又はナトリウムを含有するオキシ水酸化コバルト層で被覆された正極活物質の製造工程を含む、製造方法。
    　Ｐ－１）正極活物質の表面に水酸化コバルト層を形成させる工程
    　Ｐ－２）前記水酸化コバルト層が形成された正極活物質を加熱して、前記水酸化コバルト層をオキシ水酸化コバルト層に変換する工程であって、さらに、前記水酸化コバルト層又は前記オキシ水酸化コバルト層にリチウム又はナトリウムをドープする工程     It is a manufacturing method of the nickel metal hydride battery of Claim 1 or 2, Comprising:
    A method for producing a positive electrode active material coated with a lithium or sodium-containing cobalt oxyhydroxide layer, comprising the following steps P-1) and P-2).
    P-1) A step of forming a cobalt hydroxide layer on the surface of the positive electrode active material P-2) The positive electrode active material on which the cobalt hydroxide layer is formed is heated to convert the cobalt hydroxide layer to a cobalt oxyhydroxide layer And doping the cobalt hydroxide layer or the cobalt oxyhydroxide layer with lithium or sodium.
  4. 　前記Ｐ－２）工程において、水酸化リチウム水溶液又は水酸化ナトリウム水溶液を噴霧することでリチウム又はナトリウムをドープする、請求項３に記載の製造方法。 4. The production method according to claim 3, wherein in the step P-2), lithium or sodium is doped by spraying an aqueous solution of lithium hydroxide or an aqueous solution of sodium hydroxide.
  5. 　請求項１又は２に記載のニッケル金属水素化物電池の製造方法であって、
    　下記Ｎ－１）工程及びＮ－２）工程を有する、酸素濃度が１０００ｐｐｍ以上の負極活物質の製造工程を有する、製造方法。
    　Ｎ－１）水素吸蔵合金をアルカリ水溶液で処理する工程
    　Ｎ－２）前記Ｎ－１）工程後の水素吸蔵合金の表面を酸化する工程     It is a manufacturing method of the nickel metal hydride battery of Claim 1 or 2, Comprising:
    A method for producing a negative electrode active material having an oxygen concentration of 1000 ppm or more, comprising the following steps N-1) and N-2).
    N-1) Step of treating the hydrogen storage alloy with an alkaline aqueous solution N-2) Step of oxidizing the surface of the hydrogen storage alloy after the above N-1) step
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JPH08203512A (en) * 1995-01-31 1996-08-09 Toshiba Battery Co Ltd Manufacture of alkaline secondary battery
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