JP2006202678A - Positive pole active substance and its manufacturing method and nonaqueous electrolyte battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery with excellent battery performance under a high-temperature environment. <P>SOLUTION: Fluorination treatment is given to a material expressed by: Li<SB>x</SB>Ni<SB>a</SB>Mn<SB>b</SB>Co<SB>c</SB>O<SB>z</SB>(0<x≤1.3, 0<a<1, 0<b<0.6, 0<c<1, a+b+c=1, 1.7≤z≤2.3) to impart a fluoride on the surface of a positive pole active substance, whereby battery performance is improved at a high-temperature environment. Further, the fluoride is imparted only on the surface of positive pole active substance particles, and not inside the particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a positive electrode active material and a method for producing the same. Moreover, it is related with the nonaqueous electrolyte battery using the same.

  In recent years, attention has been focused on non-aqueous electrolyte batteries that can obtain high energy density as power supplies for electronic devices, power storage power supplies, and electric vehicle power supplies that are becoming higher performance and smaller.

The non-aqueous electrolyte batteries currently on the market are mainly LiCoO ₂ for the positive electrode, the carbonaceous material that absorbs and releases lithium ions for the negative electrode, and the electrolyte such as lithium hexafluorophosphate (LiPF ₆ ) for the electrolyte is ethylene carbonate. Those dissolved in a non-aqueous solvent as a constituent are used.

In addition to LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _{4 and the} like have been studied as positive electrode active materials. In recent years, a material having an α-NaFeO ₂ type layered structure and a composition represented by LiNi _a Mn _b Co _c O ₂ (a + b + c = 1) has been studied.

  One of the performances required for such a nonaqueous electrolyte battery is charge / discharge cycle performance under a high temperature environment. That is, portable devices are often used in a high temperature environment. In addition, power storage power supplies, electric vehicle power supplies, etc. are particularly problematic not only in terms of the environmental temperature of use but also in the storage of heat due to the increase in size of the battery. There has been a strong demand for a non-aqueous electrolyte battery having a small discharge rate and a small decrease in discharge capacity even after repeated charge and discharge in a high temperature environment. As one of the mechanisms in which self-discharge occurs in a high temperature environment and the mechanism in which the discharge capacity decreases when repeated charge and discharge is performed in a high temperature environment, the surface film formed on the surface of the electrode active material in a high temperature environment is It is presumed that the resistance is higher than that of the surface film formed in a room temperature environment. However, it has been difficult to improve the charge / discharge cycle performance under a high temperature environment and the self-discharge performance under a high temperature environment only by suppressing the surface film formation.

On the other hand, a technique for improving various battery characteristics by incorporating fluorine into the positive electrode active material has been studied. For example, Patent Document 1 discloses a technique of fluorinating LiCoO ₂ using NF ₃ gas to increase the voltage and energy density. According to the study by the present inventors, LiCoO ₂ When the fluorination treatment was performed, the capacity was greatly reduced, and the battery performance in a high temperature environment deteriorated.

In Patent Document 2, LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ and lithium carbonate are mixed and a battery is assembled using an electrolytic solution containing 20 to 200 ppm of hydrogen fluoride. A method for producing a lithium secondary battery including a step of reacting hydrogen fluoride in a liquid is described. However, this method cannot sufficiently improve the charge / discharge cycle performance under a high temperature environment and the self-discharge performance under a high temperature environment.

Patent Document 3 discloses a technique for obtaining a positive electrode active material containing 420 ppm or 1200 ppm of fluorine by mixing LiF with a raw material and baking it when synthesizing a positive electrode active material. And the effect by which the chemical reactivity of the electrolyte solution and positive electrode active material in 200-300 degreeC is suppressed is shown. However, according to the study by the present inventors, even when this method is applied to positive electrode materials having various elemental compositions, the charge / discharge cycle performance under a high temperature environment and the self-discharge performance under a high temperature environment There was a tendency that it was not improved and decreased. Also, the discharge capacity of the active material itself tended to decrease. The cause of this is not necessarily clear, but it is presumed that the content of fluorine becomes excessive, fluorine exists inside the active material, LiF may remain, and the like. It was.
Japanese Patent No. 3340515 JP 2004-95188 A JP 2004-296098 A International Publication No. 02/086993 Pamphlet

  This invention is made | formed in view of the said problem, The objective is to provide the nonaqueous electrolyte battery excellent in the cycling performance in high temperature, and the high temperature storage performance.

In order to solve the above-mentioned problems, the present inventors have conducted fluorination treatment by selecting a lithium transition metal compound having an α-NaFeO ₂ type layered structure and having a specific element composition range as a result of intensive studies. Surprisingly, the present inventors have found that the battery performance under a high temperature environment, which tends to be deteriorated by the conventional technology, is improved, and thus the present invention has been achieved. That is, the technical configuration and operational effects of the present invention are as follows. However, the action mechanism includes estimation, and its correctness does not limit the present invention.

One aspect of the present invention has an α-NaFeO ₂ type layered structure, and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0.6, This is a method for producing a positive electrode active material in which a material represented by 0 <c <1, a + b + c = 1, 1.7 ≦ z ≦ 2.3) is subjected to fluorination treatment.

  Further, the present invention is the above-described method for producing a positive electrode active material, characterized in that a fluorination treatment is performed so that a fluorine compound is present on the particle surface of the positive electrode active material.

  Further, the present invention is the above-described method for producing a positive electrode active material, characterized by subjecting the positive electrode active material particles to a fluorination treatment so that no fluorine compound is present at the center.

  Moreover, this invention is a positive electrode active material manufactured by the manufacturing method of the said positive electrode active material.

  Moreover, this invention is a nonaqueous electrolyte battery using the said positive electrode active material.

According to such a configuration, a positive electrode active material that can be a nonaqueous electrolyte battery excellent in battery performance under a high temperature environment, a method for producing the same, and a nonaqueous electrolyte battery excellent in battery performance under a high temperature environment Can provide.
With the configuration of the present invention, battery performance under a high temperature environment, specifically, charge / discharge cycle performance under a high temperature environment and self-discharge performance under a high temperature environment can be improved. Although it cannot be said that the mechanism of action has been sufficiently analyzed, by performing fluorination treatment on a lithium transition metal compound having a specific elemental composition, only an appropriate degree is applied to the surface of the active material particles. Fluorination can be performed, and the degree thereof is sufficient as compared with the method of containing HF in the electrolytic solution, and the content of fluorine is compared with the method of containing LiF in the raw material before synthesis of the positive electrode active material. The amount is not excessive, and it is presumed that the fluorine content can be prevented from reaching the inside of the active material particles. The degree of this action is presumed to be closely related to the elemental composition of the lithium transition metal compound, particularly the Mn content.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte battery excellent in the battery performance in a high temperature environment can be provided.

  The present invention is described in detail below, but the present invention is not limited to these descriptions.

It has an α-NaFeO ₂ type layered structure, and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0.6, 0 <c <1, The material represented by a + b + c = 1, 1.7 ≦ z ≦ 2.3) can be synthesized, for example, by the method described in detail in Patent Document 4, and the ratio of the metal oxide used as a raw material is adjusted. Thus, the elemental composition ratio can be arbitrarily adjusted. The composition of _{Li x Ni a Mn b Co c} O z used in the present invention include, among others coefficients a and b of the ratio substantially 1: preferably those which 1, considering the errors in the process | a- b | ≦ 0.03. The composition of this material has been described above as a + b + c = 1 for convenience, but may contain elements other than Ni, Mn, and Co. As such an element, an element that can be substituted for Mn present in the crystal lattice of this material is preferable. Specifically, Be, B, V, C, Si, P, Sc, Cu, Zn, Ga, Ge , As, Se, Sr, Mo, Pd, Ag, Cd, In, Sn, Sb, Te, Ba, Ta, W. Examples include, but are not limited to, Pb, Bi, Fe, Cr, Ni, Ti, Zr, Nb, Y, Al, Na, K, Mg, Ca, Cs, La, Ce, Nd, Sm, Eu, and Tb. Is not to be done. These may be used alone or in combination of two or more. Among these, it is more preferable to use any of V, Al, Mg, Cr, Ti, In, and Sn because an effect of improving the high rate discharge performance can be obtained. The content of these elements is preferably 0.1 or less.

It has an α-NaFeO ₂ type layered structure, and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0.6, 0 <c <1, The method of subjecting the material represented by a + b + c = 1, 1.7 ≦ z ≦ 2.3) to fluorination treatment is not particularly limited, but depending on the pyrolysis gas of F ₂ gas or NF ₃ gas There are methods of treating, and using these methods is preferable in that a film mainly composed of a fluorine compound can be formed stably and uniformly only on the surface of the material. In particular, the method using F ₂ gas is more preferable because the activity of F ₂ gas is high, so that processing can be performed at a relatively low temperature in a short time and the manufacturing cost can be suppressed. When the fluorine compound present on the surface of the material is regarded as a film, the film thickness can be arbitrarily controlled by adjusting the processing gas injection pressure, the processing temperature, and the processing time.

Specifically, it has an α-NaFeO ₂ type layered structure, and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0.6, 0 <C <1, a + b + c = 1, 1.7 ≦ z ≦ 2.3) is preferably sealed in a sealed container, degassed, and then injected with fluorine gas and held for a certain period of time. More preferably, the temperature in the sealed container is raised during the holding.

  As the fluorine gas, a mixed gas such as a fluorine / argon mixed gas may be used, or a method of injecting a predetermined amount of pure fluorine gas in a reduced pressure state may be used. As the purity of the fluorine gas to be used, it is preferable that oxygen is not mixed. From this viewpoint, it is preferable to note that a gas in which the oxygen content is reduced as much as possible is used.

The amount of fluorine gas injected is preferably 0.02 × 10 ⁵ Pa or more and 1.0 × 10 ⁵ Pa or less. By setting the injection amount of fluorine gas to 0.02 × 10 ⁵ Pa or more, the degree of fluorination of the material particle surface can be made sufficient, and charge / discharge cycle performance in a high temperature environment and in a high temperature environment The positive electrode active material which can be set as the battery which improved the self-discharge performance in can be provided. The injection amount of fluorine gas is more preferably 0.5 × 10 ⁵ Pa or more, and further preferably 0.1 × 10 ⁵ Pa or more. Moreover, by setting the injection amount of fluorine gas to 1.0 × 10 ⁵ Pa or less, it is possible to reduce the possibility that the degree of fluorination becomes excessive, and thus a non-aqueous electrolyte battery having a sufficient discharge capacity can be obtained. A positive electrode active material can be provided.

  The holding temperature after the fluorine gas injection may be room temperature, but is preferably 75 ° C to 150 ° C. By setting the holding temperature after the fluorine gas injection to a temperature of 75 ° C. to 150 ° C., the fluorination of the material particle surface can be rapidly advanced and completed.

By the above fluorination treatment, it has an α-NaFeO ₂ type layered structure and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0. 6, 0 <c <1, a + b + c = 1, 1.7 ≦ z ≦ 2.3) The fluorine compound is present on the very surface of the particle of the material, and the fluorine compound is present inside the particle of the material. It is possible to produce a positive electrode active material that does not exist.

It has an α-NaFeO ₂ type layered structure, and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0.6, 0 <c < The form of one particle of the material represented by 1, a + b + c = 1, 1.7 ≦ z ≦ 2.3) is in the form of a secondary particle in which a large number of primary particles are aggregated. The “positive electrode active material particles” referred to in the specification of the present application refers to a single particle in the form of a secondary particle in which a large number of the primary particles are aggregated.

    As the organic solvent constituting the nonaqueous electrolyte according to the present invention, an organic solvent generally used for a nonaqueous electrolyte for a nonaqueous electrolyte battery can be used. For example, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate; cyclic esters such as γ-butyrolactone, γ-valerolactone, propiolactone; dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, diphenyl carbonate Chain carbonates such as methyl acetate, chain esters such as methyl acetate and methyl butyrate; Ethers such as tetrahydrofuran or derivatives thereof, 1,3-dioxane, dimethoxyethane, diethoxyethane, methoxyethoxyethane, methyldiglyme; acetonitrile In addition, nitriles such as benzonitrile can be used alone, or a mixture of two or more of these, but is not limited thereto. In addition, a phosphate ester, which is a flame retardant solvent that is generally added to an electrolyte solution for a non-aqueous electrolyte battery, can also be used. For example, trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trifluoroethyl phosphate), triphosphate phosphate (Triperfluoroethyl) and the like are exemplified, but not limited thereto. These may be used alone or in combination of two or more.

    The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.1 mol / l to 5 mol / l, more preferably 1 mol / l to 2... In order to reliably obtain a non-aqueous electrolyte battery having high battery characteristics. 5 mol / l.

  EXAMPLES Further details of the present invention will be described below with reference to examples, but the present invention is not limited to these descriptions.

It has an α-NaFeO ₂ type layered structure, and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0.6, 0 <c <1, As a material represented by a + b + c = 1, 1.7 ≦ z ≦ 2.3), LiNi _0.42 Mn _0.42 Co _0.16 O ₂ , LiMn _0.33 Ni _0.33 Co _0.34 O ₂ , LiMn _0.25 Ni _0.25 Co _0.5 O ₂ , LiMn _0.16 Materials having compositions of Ni _0.16 Co _0.68 O ₂ and LiMn _0.08 Ni _0.08 Co _0.84 O ₂ were synthesized as follows.

Hereinafter, a method for obtaining a material having a LiMn _0.42 Ni _0.42 Co _0.16 O ₂ composition will be described as an example, but the materials of other compositions should be adjusted in the molar ratio of the transition metal compound used for the preparation of the following raw material solution. Can be arbitrarily synthesized.

  3.5 liters of water was placed in a closed reaction tank. Further, a 32% aqueous sodium hydroxide solution was added so that pH = 11.6. The mixture was stirred at a rotational speed of 1200 rpm using a stirrer equipped with a paddle type stirring blade, and the solution temperature in the reaction vessel was kept at 50 ° C. by an external heater. Further, argon gas was blown into the reaction tank solution to remove dissolved oxygen in the solution. Manganese sulfate pentahydrate (0.738 mol / l), nickel sulfate hexahydrate (0.738 mol / l), cobalt sulfate heptahydrate (0.282 mol / l) and hydrazine monohydrate (0. A raw material solution in which 0101 mol / l) was dissolved was prepared. The raw material solution was continuously added dropwise to the reaction vessel at a flow rate of 3.17 ml / min. In synchronization with this, a 12 mol / l ammonia solution was added dropwise and mixed at a flow rate of 0.22 ml / min. Further, a 32% aqueous sodium hydroxide solution was intermittently added so that the pH of the solution in the reaction tank was constant at 11.4 ± 0.1. Further, the temperature of the solution in the reaction vessel was intermittently controlled with a heater so as to be constant at 50 ° C. In addition, argon gas was blown directly into the liquid so that the inside of the reaction vessel had a reducing atmosphere. Further, the slurry was discharged out of the system using a flow pump so that the amount of the solution was always a constant amount of 3.5 liters. After the elapse of 60 hours from the start of the reaction, a slurry of Ni-Mn-Co composite oxide, which is a reaction crystallized product, was collected for 5 hours. The collected slurry was washed with water, filtered, and dried overnight at 80 ° C. to obtain a dry powder of a Ni—Mn—Co coprecipitation precursor.

The obtained Ni—Mn—Co coprecipitated precursor powder is sieved to less than 75 μm, the lithium hydroxide monohydrate powder is weighed so that Li / (Ni + Mn + Co) = 1.0, and a planetary kneader is used. And mixed. This was filled in an alumina pot and heated to 850 ° C. at a heating rate of 100 ° C./hr under a flow of dry air using an electric furnace, maintained at a temperature of 850 ° C. for 15 hours, and then 100 ° C. / It cooled to 200 degreeC with the cooling rate of hr, and stood to cool after that. The obtained powder was sieved to 75 μm or less to obtain a lithium nickel manganese cobalt composite oxide powder. As a result of X-ray diffraction measurement, the obtained powder confirmed a single phase having a layered rock salt type crystal structure. As a result of ICP emission spectroscopic analysis, the composition of LiMn _0.42 Ni _0.42 Co _0.16 O ₂ was confirmed.

Next, it has an α-NaFeO ₂ type layered structure, and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0.6, 0 <c <1, a + b + c = 1, 1.7 ≦ z ≦ 2.3) The materials having the respective compositions described above were subjected to fluorination treatment by the following procedure. As an example, the case of using LiNi _0.42 Mn _0.42 Co _0.16 O ₂ powder will be described as an example, but the same applies to the procedure of fluorination treatment for materials of other compositions. LiNi _0.42 Mn _0.42 Co _0.16 O ₂ powder was sealed in a nickel sealed container and degassed, and then fluorine gas (purity 99.4-99.7%, manufactured by Daikin Industries, Ltd.) was added at 0.2 × 10 ^5. Injected to a pressure of Pa. Next, the inside of the sealed container was heated to 100 ° C., held for 10 minutes, then returned to room temperature, and air was injected to atmospheric pressure. In this way, LiMn _0.42 Ni _0.42 Co _0.16 O ₂ powder having a fluorine compound on the surface was obtained. As a result of X-ray diffraction measurement, it was confirmed that the obtained powder was a single phase having an α-NaFeO ₂ type layered structure even after the fluorination treatment. As a result of X-ray photoelectron spectroscopy (XPS) measurement, the F _1s peak was present on the surface of the powder, and the size of the peak was gradually reduced by etching. It was confirmed that it exists only on the surface.

  Next, the nonaqueous electrolyte battery produced in this example will be described. FIG. 1 is a cross-sectional view of the nonaqueous electrolyte battery used in this example, and is composed of a pole group 4 including a positive electrode 1, a negative electrode 2 and a separator 3, a nonaqueous electrolyte, and a metal resin composite film 5. The positive electrode 1 is formed by applying a positive electrode mixture 11 on a positive electrode current collector 12. The negative electrode 2 is formed by applying a negative electrode mixture 21 on a negative electrode current collector 22. The nonaqueous electrolyte is impregnated in the pole group 4. The metal resin composite film 5 covers the pole group 4 and is sealed on all four sides by heat welding.

  Next, a method for manufacturing the nonaqueous electrolyte battery manufactured in this example will be described. The positive electrode 1 is a mixture of a positive electrode active material and acetylene black, which is a conductive agent, and further mixed with an N-methyl-2-pyrrolidone solution of polyvinylidene fluoride as a binder, and this mixture is a positive electrode current collector made of an aluminum foil. After apply | coating to the single side | surface of the body 12, it dried and pressed so that the thickness of the positive mix 11 might be set to 0.1 mm. The positive electrode 1 was obtained by the above process.

  In the negative electrode 2, graphite as a negative electrode active material and an N-methyl-2-pyrrolidone solution of polyvinylidene fluoride as a binder were mixed, and this mixture was applied to one surface of a negative electrode current collector 22 made of copper foil. Then, it dried and pressed so that the negative mix 21 thickness might be set to 0.1 mm. The negative electrode 2 was obtained by the above process.

  The pole group 4 was configured by facing the positive electrode mixture 11 and the negative electrode mixture 21, placing the separator 3 therebetween, and laminating the positive electrode 1, the separator 3, and the negative electrode 2 in this order. Next, the electrode group 4 was impregnated with the non-aqueous electrolyte by immersing the electrode group 4 in the non-aqueous electrolyte. Furthermore, the pole group 4 was covered with the metal resin composite film 5, and the four sides were sealed by heat welding. A nonaqueous electrolyte battery was obtained by the above production method.

(Invention battery 1)
1 liter of mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 6: 4 as a non-aqueous electrolyte using LiMn _0.42 Ni _0.42 Co _0.16 O ₂ subjected to fluorination treatment by the above method as a positive electrode active material In addition, a nonaqueous electrolyte battery having a capacity of 10 mAh was prepared using 1 mol of LiPF ₆ dissolved therein, and this battery 1 was obtained.

(Invention battery 2)
Except for using 1 mol of LiClO ₄ dissolved in 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 6: 4 as the non-aqueous electrolyte, the same as the battery 1 of the present invention. Thus, a non-aqueous electrolyte battery having a capacity of 10 mAh was produced and used as the battery 2 of the present invention.

(Invention battery 3)
A non-aqueous electrolyte battery having a capacity of 10 mAh was prepared in the same manner as the battery 1 of the present invention, except that LiMn _0.33 Ni _0.33 Co _0.34 O ₂ fluorinated by the above method was used as the positive electrode active material. Invention battery 3 was obtained.

(Invention Battery 4)
A non-aqueous electrolyte battery having a capacity of 10 mAh was produced in the same manner as the battery 1 of the present invention except that LiMn _0.25 Ni _0.25 Co _0.5 O ₂ subjected to fluorination treatment by the above method was used as the positive electrode active material. Invention battery 4 was obtained.

(Invention battery 5)
A nonaqueous electrolyte battery having a capacity of 10 mAh was prepared in the same manner as the battery 1 of the present invention, except that LiMn _0.16 Ni _0.16 Co _0.68 O ₂ subjected to fluorination treatment by the above method was used as the positive electrode active material. Invention battery 5 was obtained.

(Invention battery 6)
A nonaqueous electrolyte battery having a capacity of 10 mAh was prepared in the same manner as the battery 1 of the present invention except that LiMn _0.08 Ni _0.08 Co _0.84 O ₂ subjected to fluorination treatment by the above method was used as the positive electrode active material. Invention battery 6 was obtained.

(Comparative battery 1)
A non-aqueous electrolyte battery having a capacity of 10 mAh was manufactured and compared using the same raw materials and manufacturing method as in the present invention battery 1 except that LiMn _0.42 Ni _0.42 Co _0.16 O ₂ not subjected to fluorination treatment was used as the positive electrode active material. Battery 1 was obtained.

(Comparison battery 2)
A non-aqueous electrolyte battery having a capacity of 10 mAh was produced in the same manner as the battery 1 of the present invention, except that LiCoO ₂ subjected to fluorination treatment by the above method was used as the positive electrode active material.

(Comparative battery 3)
A non-aqueous electrolyte battery having a capacity of 10 mAh was produced as Comparative Battery 3 in the same manner as the battery 1 of the present invention, except that LiCoO ₂ not subjected to fluorination treatment was used as the positive electrode active material.

(Comparison battery 4)
A non-aqueous electrolyte battery having a capacity of 10 mAh was produced in the same manner as the battery 1 of the present invention except that LiMn _0.5 Ni _0.5 O ₂ subjected to fluorination treatment by the above method was used as the positive electrode active material. It was.

(Comparison battery 5)
A non-aqueous electrolyte battery having a capacity of 10 mAh was produced in the same manner as in the present invention battery 1 except that LiMn _0.5 Ni _0.5 O ₂ not subjected to fluorination treatment was used as the positive electrode active material.

(Comparison battery 6)
A non-aqueous electrolyte battery having a capacity of 10 mAh was produced in the same manner as the battery 2 of the present invention except that LiMn _0.42 Ni _0.42 Co _0.16 O ₂ not subjected to fluorination treatment was used as the positive electrode active material. did.

  In addition, the density | concentration of HF contained in the nonaqueous electrolyte used for the present invention batteries 1 to 6 and the comparative batteries 1 to 5 is 15 ppm. From the nonaqueous electrolyte used for the present invention battery 2 and the comparative battery 6 HF is Not detected.

(First discharge capacity test)
The initial discharge capacities of the inventive batteries 1 to 6 and the comparative batteries 1 to 6 were measured. After charging at a constant current and a constant voltage of 20 mA at a current of 2 mA and a final voltage of 4.2 V, the discharge capacity was measured when a constant current was discharged at a current of 2 mA and a final voltage of 2.7 V at 20 ° C. The capacity.

(High temperature cycle test)
A high temperature cycle test was performed on the batteries 1 to 6 of the present invention and the comparative batteries 1 to 6. The test temperature was 50 ° C., and charging was constant current and constant voltage charging with a current of 2 mA and a final voltage of 4.2 V. The discharge was a constant current discharge at a current of 2 mA and a final voltage of 2.7 V. The discharge capacity after 200 cycles when the discharge capacity at the first cycle was 100% was taken as the capacity after the high temperature cycle.

(High temperature storage test)
A high temperature storage test was performed on the batteries 1 to 6 of the present invention and the comparative batteries 1 to 6. A battery whose initial capacity has been confirmed under the same conditions as in the initial discharge capacity test described above is charged under the conditions described above, stored at an environmental temperature of 60 ° C. for 30 days, and the discharge capacity after storage under the conditions described above is measured. The self-discharge rate was obtained. The self-discharge rate was calculated by (Equation 1).

The results of the initial discharge capacity test, the high-temperature cycle test, and the high-temperature storage test are shown in Table 1, and the battery performance when LiPF ₆ is used as the electrolyte salt is the coefficient c in the general formula Li _x Ni _a Mn _b Co _c O _z 2 to 4 are shown on the horizontal axis.

Comparing the comparative battery 2 and the comparative battery 3, when LiCoO ₂ is used as the positive electrode active material, the initial discharge capacity, the high temperature charge / discharge cycle performance, and the high temperature storage are obtained when the positive electrode active material is subjected to fluorination treatment. It can be seen that the post self-discharge rate deteriorates on the contrary.

Similarly, when the comparative battery 4 and the comparative battery 5 are compared, even when LiMn _0.5 Ni _0.5 O ₂ is used as the positive electrode active material, if the positive electrode active material is fluorinated, the initial discharge capacity, the high temperature It can be seen that both the charge / discharge cycle performance and the self-discharge rate after high-temperature storage deteriorate.

However, when the present invention battery 1 and the comparative battery 1 are compared, when LiMn _0.42 Ni _0.42 Co _0.16 O ₂ is used as the positive electrode active material, the initial discharge capacity is obtained when the positive electrode active material is fluorinated. Significantly improves the high-temperature charge / discharge cycle performance while maintaining the same performance as when using a positive electrode active material that is not fluorinated, and can significantly reduce the self-discharge rate after high-temperature storage Was recognized.

When the present invention battery 2 and the comparative battery 6 are compared, when LiClO ₄ which is an inorganic salt containing no fluorine is used as an electrolyte salt, LiMn _0.42 Ni _0.42 Co _0.16 O ₂ is used as a positive electrode active material. Improved the high-temperature charge / discharge cycle performance and significantly reduced the self-discharge amount by using a positive electrode active material that had been subjected to fluorine treatment.

From FIGS. 2 to 4 in which the results of the present invention batteries 1 to 3 and comparative batteries 1 to 5 are plotted, only when the value of c in the general formula LiNi _a Mn _b Co _c O ₂ is 0 <c <1, It can be seen that performing the fluorination treatment on the positive electrode active material has significant effects on the various characteristics of the battery.

It is sectional drawing of the nonaqueous electrolyte battery of this invention. It is a figure which shows the initial discharge capacity of this invention battery and a comparison battery. It is a figure which shows the high temperature charging / discharging cycle performance of this invention battery and a comparison battery. It is a figure which shows the self-discharge rate after high temperature preservation | save of this invention battery and a comparison battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 11 Positive electrode mixture 12 Positive electrode collector 2 Negative electrode 21 Negative electrode mixture 22 Negative electrode collector 3 Separator 4 Electrode group 5 Metal resin composite film

Claims (5)

It has an α-NaFeO ₂ type layered structure, and Li _x Ni _a Mn _b Co _c O _z (0 <x ≦ 1.3, 0 <a <1, 0 <b <0.6, 0 <c <1, The manufacturing method of the positive electrode active material which fluorinates the material represented by a + b + c = 1, 1.7 <= z <= 2.3). The method for producing a positive electrode active material according to claim 1, wherein the fluorination treatment is performed so that a fluorine compound is present on the particle surface of the positive electrode active material. The method for producing a positive electrode active material according to claim 1 or 2, wherein a fluorination treatment is performed so that a fluorine compound does not exist at the center of the positive electrode active material particles. The positive electrode active material manufactured by the manufacturing method of the positive electrode active material in any one of Claims 1-3. A nonaqueous electrolyte battery using the positive electrode active material according to claim 4.

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