JP2013122862A - Cylindrical alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline storage battery with reduced internal resistance and an excellent high-rate discharge characteristic and cycle life characteristic by focusing the adhesion and space between the inner peripheral wall of its outer packaging can and its group of electrodes.SOLUTION: A cylindrical alkaline storage battery comprises: a cylindrical outer packaging can with a bottom and its upper end being opened; and a group of electrodes being wound in a spiral shape and inserted into the outer packaging can, the group of electrodes being formed with a belt-shaped positive and negative electrode interposing a separator and the negative electrode being positioned at the outermost periphery. The cylindrical alkaline storage battery has a current collection structure in which the outer peripheral part being formed by the negative electrode is contacting the inner peripheral wall of the outer packaging can, and also has a current collection structure in which a positive electrode lead from the positive electrode is connected to a conductive lid plate disposed inside the opening of the outer packaging can. Also, a conductive coating film is coated on the inner peripheral wall of the outer packaging can, and alkaline electrolyte is being filled after the group of electrodes are inserted into the outer packaging can whose diameter to be reduced.

Description

  The present invention relates to a cylindrical alkaline storage battery, and particularly to a battery having an electrode group and an outer can.

  As an alkaline storage battery, a nickel cadmium storage battery, a nickel hydride storage battery, etc. can be mention | raise | lifted according to the kind of active material contained, for example. These alkaline storage batteries include a cylindrical battery in which a spiral electrode group in which a negative electrode plate and a positive electrode plate are wound with a separator interposed therebetween is housed in a cylindrical outer can. A current collecting structure in which the outermost peripheral portion made of the negative electrode is in contact with the inner peripheral wall of the outer can and a structure having a current collecting structure in which the positive electrode lead from the positive electrode is connected to a conductive cover plate disposed in the opening of the outer can. Have.

  Since this type of cylindrical alkaline storage battery is suitable for a wide range of applications, various technological developments have been made to improve various performances.

  For example, a method for manufacturing a battery can having a shape capable of increasing the contact area between an outer can, an inner surface of a side peripheral wall, and an active material has been proposed (see Patent Document 1).

For the purpose of improving the electrolyte solution retention of the separator for the purpose of improving the cycle life, for example, a positive electrode, a negative electrode containing a hydrogen storage alloy, a separator interposed between the positive electrode and the negative electrode, an alkaline electrolyte, The separator is made of a synthetic resin fiber nonwoven fabric, and the compression rate when subjected to a pressure of 10 kgf / cm ² is 40% or less with respect to the thickness before the pressure, and in the compressed state. A cylindrical alkaline storage battery having a thickness of 0.10 mm or more is disclosed (see Patent Document 2).

  For the same purpose, an electrode group having a structure in which a separator is interposed between a positive electrode and a negative electrode is provided. This separator includes 30% by volume or more of syndiotactic polypropylene fibers and is defined in JIS P-8117-1980. Disclosed is a configuration in which the air permeability measured by the Gurley method is 0.5 sec / 100 cc to 10 sec / 100 cc (see Patent Document 3).

JP 2002-15712 A JP 2000-195486 A JP 2000-268800 A

  In the conventional technique which attempts to increase the contact area between the outer can represented by Patent Document 1 and the inner surface of the side peripheral wall and the active material, the high-rate discharge characteristics are improved, but there is a problem in improving the cycle life characteristics.

  On the other hand, the conventional techniques for improving the liquid retention of the separator for improving the cycle life represented by Patent Documents 2 and 3 have a problem in improving the high-rate discharge characteristics because the internal resistance cannot be lowered.

  As described above, in the conventional technique, it is difficult to achieve both high rate discharge characteristics and cycle life characteristics.

  Therefore, the present invention solves the above-described conventional problems, focusing on the adhesion between the outer peripheral wall of the outer can and the electrode group and its space, lowering the internal resistance, and being excellent in high-rate discharge characteristics and cycle life characteristics. An object is to provide an alkaline storage battery.

  In order to achieve the above-described object, in the invention of claim 1, an electrode group formed by winding a strip-shaped negative electrode and a positive electrode in a spiral shape so that the negative electrode is positioned on the outermost periphery through a separator, Inserted into a cylindrical outer can having a bottomed cylindrical shape with an upper end having an inner diameter larger than the maximum diameter, and then injecting an alkaline electrolyte, and further reducing the diameter of the outer can in the cylindrical alkaline storage battery, The outermost peripheral part of the negative electrode has a current collecting structure in contact with the inner peripheral wall of the outer can, and the outer can has a conductive coating applied to the inner peripheral wall.

  In this configuration, the conductive coating is applied to the inner peripheral wall of the outer can and inserted into the outer can having an inner diameter larger than the maximum diameter of the electrode group. The adhesion of the negative electrode is improved and the contact resistance is reduced. Moreover, the space formed between the outer peripheral wall of the outer can and the negative electrode is reduced, the alkaline electrolyte present in the space is also reduced, and the alkaline electrolyte retained in the separator is increased. As a result, the cycle life is improved.

  In the second aspect of the invention, the conductive coating film is composed of graphite and carbon black, and the graphite content is 55 wt% to 80 wt%, and the carbon black content is 20 wt% to 45 wt%.

  In the configuration described above, the use of graphite and carbon black for the conductive coating further reduces the presence of alkaline electrolyte in the space formed between the inner peripheral wall of the outer can and the negative electrode due to the water repellent effect of graphite. As a result, the electrolyte solution retained in the separator increases. Also, by using carbon black with a large specific surface area, the surface roughness of the conductive coating increases, and the contact between the inner peripheral wall of the outer can and the negative electrode changes from point contact to surface contact, and an ideal current collection effect is exhibited. The

  In the invention of claim 3, the outermost peripheral portion of the negative electrode is thinner than the inner peripheral portion, and the end thickness of the outermost peripheral portion of the negative electrode is in the range of 0.10 mm to 0.35 mm. Yes.

  In the above configuration, the space formed between the outer peripheral wall of the outer can and the negative electrode is reduced, the adhesion between the outer peripheral wall of the outer can and the negative electrode is improved, and the contact resistance is reduced. In addition, the alkaline electrolyte present in the space is reduced, and the alkaline electrolyte retained in the separator is further increased.

  In the invention of claim 4, the separator is a polyolefin nonwoven fabric imparted with hydrophilicity by sulfuric acid treatment, and a polyolefin nonwoven fabric imparted hydrophilicity by fluorine treatment, surfactant treatment or plasma treatment, and The combined ratio of the separator to which hydrophilicity is imparted by other than the sulfuric acid treatment is 35 wt% or more and 75 wt% of the whole separator.

  In the configuration described above, the outer peripheral wall of the outer can can be obtained by using a combination of fluorine treatment, surfactant treatment, or plasma treatment that has higher hydrophilicity than a separator that has been rendered hydrophilic by sulfuric acid treatment. By reducing the space formed between the negative electrode and the negative electrode, the excess alkaline electrolyte can be reliably held in the separator.

  The present invention is a structure in which the outermost peripheral negative electrode constituting the electrode group in the cylindrical alkaline storage battery is in contact with the inner peripheral wall of the outer can, and after inserting the electrode group into the outer can coated with the conductive coating film, By reducing the diameter of the outer can and improving the adhesion between the inner peripheral wall of the outer can and the negative electrode of the outermost peripheral portion constituting the electrode group, an alkaline storage battery having a low internal resistance of the battery can be provided. Moreover, the space formed between the outer peripheral wall of the outer can and the negative electrode is reduced, the alkaline electrolyte present in the space is also reduced, and the alkaline electrolyte retained in the separator is increased. As a result, the cycle life is improved.

1 is a partially cutaway perspective view of a cylindrical nickel-metal hydride storage battery according to an embodiment of the present invention. 1 is a cross-sectional view of a cylindrical nickel-metal hydride storage battery according to an embodiment of the present invention. The longitudinal cross-sectional view of the diameter-reduction mold which concerns on one Embodiment of this invention

Hereinafter, a cylindrical nickel-metal hydride storage battery according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the cylindrical nickel-metal hydride storage battery includes an outer can 1 having a bottomed cylindrical shape with an open upper end, and the outer can 1 has conductivity and functions as a negative electrode terminal. A conductive coating film 21 is formed on the inner peripheral wall of the outer can. In the opening of the outer can 1, a conductive cover plate 3 is disposed via a ring-shaped insulating packing 2, and the insulating packing 2 and the cover plate 3 are fixed in the opening by caulking the opening edge. Yes. The outer can is provided with a groove 4 to securely fix the insulating packing to the outer can. In addition, a sealing agent such as blown asphalt, polybutene, polyamide, or the like is disposed between the opening edge of the caulked outer can 1 and the insulating packing 2 as a single substance or a mixture for the purpose of improving sealing performance ( Not shown).

  After caulking the opening edge, the body portion and the caulking portion of the outer can are reduced in diameter, and the groove 4 is crimped. The outer peripheral surface of the outer can 1 is covered with an outer label 5 for ensuring insulation. Further, a donut-shaped insulating member 6 is disposed between the caulking portion and the exterior label 5 so as to cover the cover plate 3.

  The cover plate 3 has a gas vent hole 7 in the center, and a rubber valve element 8 is disposed on the outer surface of the cover plate 3 so as to close the gas vent hole 7. Further, a cap-like positive electrode terminal 9 covering the valve body 8 is fixed on the outer surface of the lid plate 3, and the positive electrode terminal 9 presses the valve body 8 against the lid plate 3. Therefore, at the normal time, the outer can 1 is airtightly closed by the cover plate 3 together with the insulating packing 2 and the valve body 8. On the other hand, when gas is generated in the outer can 1 and its internal pressure increases, the valve body 8 is compressed, and the gas is released from the outer can 1 through the gas vent hole 7. That is, the cover plate 3, the valve body 8, and the positive electrode terminal 9 form a safety valve.

  A substantially cylindrical electrode group 10 is accommodated in the outer can 1 together with an alkaline electrolyte (not shown), and the outermost peripheral portion of the electrode group 10 is in direct contact with the inner peripheral wall of the outer can 1. Although detailed conditions will be described later, a conductive coating film is formed on the inner peripheral wall of the outer can, and the electrode group 10 can be smoothly accommodated in the outer can and the internal volume filled with the active material can be ensured. Therefore, the inner diameter of the outer can is larger than the maximum diameter of the electrode group 10.

  The electrode group 10 includes a positive electrode 11, a negative electrode 12, and a separator 13. Examples of the alkaline electrolyte include a sodium hydroxide aqueous solution, a lithium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and an aqueous solution obtained by mixing two or more of these. Etc.

Further, in the outer can, a positive electrode lead 14 is disposed between one end of the electrode group 10 and the lid plate 3,
Both ends of the positive electrode lead 14 are connected to the positive electrode 11 and the lid plate 3. Therefore, the positive electrode terminal 9 and the positive electrode 11 are electrically connected via the positive electrode lead 14 and the cover plate 3. An insulating member 15 with a circular slit is disposed between the cover plate 3 and the electrode group 10, and the positive electrode lead 14 extends through a slit provided in the insulating member 15 with a circular slit. A circular insulating member 16 is also disposed between the electrode group 10 and the bottom of the outer can 1.

  Referring to FIG. 2, in the electrode group 10, the positive electrode 11 and the negative electrode 12 are alternately overlapped when viewed in the radial direction of the electrode group 10 with the separator 13 interposed therebetween. More specifically, each of the electrode groups 10 includes a strip-like positive electrode 11, a negative electrode 12, and a separator 13, and the positive electrode 11 and the negative electrode 12 are spirally formed using a core from one end of the separator 11. It is formed by winding. Therefore, the end portions of the innermost peripheral portion of the positive electrode 11 and the negative electrode 12, the inner end portion 17 of the positive electrode, and the inner end portion 18 of the negative electrode are positioned on the center side of the electrode group 10, while the end portions of the outermost peripheral portion of the positive electrode 11 and the negative electrode 12 The positive electrode outer end 19 and the negative electrode outer end 20 are positioned on the outer peripheral side of the electrode group 10. The negative electrode 12 is longer than the positive electrode 11 and extends spirally from the inner side of the positive electrode inner end 17 to the outer side of the positive electrode outer end 19, and sandwiches the positive electrode 11 from both sides across the entire longitudinal direction via the separator 13. Yes. The separator 13 is not wound around the outermost peripheral portion of the electrode group 10, and the outermost peripheral portion of the electrode group 10 is a negative electrode. In the outermost peripheral part of the electrode group 10, the negative electrode 12 and the outer can 1 are electrically connected to each other, and the negative electrode outer end 20 is sufficient for the negative electrode 12 to cover the outside of the positive electrode outer end 19 through the separator 13. It is located in the vicinity of the positive electrode outer end 19, separated by a length.

  Examples of the material of the separator 13 include polyamide fiber nonwoven fabrics, and polyolefin fiber nonwoven fabrics such as polyethylene and polypropylene that are provided with hydrophilic functional groups.

  The positive electrode 11 has a strip-shaped conductive positive electrode core (not shown), and a positive electrode mixture is held in the core. Examples of the positive electrode core include a foamed nickel base material having a porous structure. In the case of a foamed nickel base material, the positive electrode mixture is held in the communication hole of the foamed nickel base material.

  The positive electrode mixture includes, for example, a positive electrode active material, an additive, and a binder. The positive electrode active material is not particularly limited, and examples thereof include nickel hydroxide particles or nickel hydroxide particles in which cobalt, zinc, cadmium or the like is dissolved. Examples of the additive include a conductive agent made of a cobalt compound, and examples of the binder include a hydrophilic or hydrophobic polymer.

  The negative electrode 12 has a conductive negative electrode core having a strip shape, and a negative electrode mixture is held in the negative electrode core. The negative electrode core is made of a sheet-like metal material having a plurality of through-holes (not shown) in the thickness direction, and examples thereof include a punching metal, a metal powder sintered body substrate, an expanded metal, and Nickel net etc. can be mentioned. In particular, a punched metal or a metal powder sintered body substrate that is sintered after molding metal powder is suitable for the negative electrode core.

Since the negative electrode mixture is a nickel-metal hydride storage battery, it is a hydrogen storage alloy particle capable of occluding and releasing hydrogen as the negative electrode active material. If necessary, addition of a conductive agent, a thickener, a binder, etc. Contains agents. In the present specification, the hydrogen storage alloy is also referred to as a negative electrode active material for convenience of explanation. Further, the hydrogen storage alloy particles may be any particles as long as they can store hydrogen generated electrochemically in an alkaline electrolyte during charging and can easily release the stored hydrogen during discharge. Such a hydrogen storage alloy is not particularly limited. For example, AB ₅ type such as LaNi ₅ or MmNi ₅ (Mm is Misch metal), or AB ₃ type such as rare earth-magnesium-nickel hydrogen storage alloy. The one of the system is mentioned.

  The conductive agent is not particularly limited except that it is a material having electron conductivity, and various electron conductive materials can be used. Specifically, for example, graphite such as natural graphite (such as flake graphite), artificial graphite, and expanded graphite, for example, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black Examples thereof include conductive fibers such as carbon fibers and metal fibers, metal powders such as copper powder, and organic conductive materials such as polyphenylene derivatives, among others, artificial graphite and ketjen black Carbon fiber is preferred. The electron conductive materials exemplified above may be used alone or in combination of two or more. Moreover, you may use the electron conductive material of the said example coat | covered on the surface of a negative electrode active material.

  The thickener imparts viscosity to the negative electrode mixture paste when the negative electrode active material is produced using the negative electrode mixture paste. For example, when water is used as a dispersion medium for the negative electrode mixture paste, carboxymethyl cellulose (CMC) and its modified body, polyvinyl alcohol, methyl cellulose, polyethylene oxide, polyacrylic acid, polyacrylate, etc. are used as a thickener. Can be used.

The binder serves to bind the hydrogen storage alloy powder or the conductive agent to the current collector. The binder may be either a thermoplastic resin or a thermosetting resin. Specific examples of the binder include, for example, styrene-butadiene copolymer rubber (SBR), for example, polyolefin such as polyethylene and polypropylene, for example, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer Polymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoro Ethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexaful Fluoropolymers such as propylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene -Methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, Na ⁺ ion cross-linked product of these ethylene- (meth) acrylic acid copolymers, and the like. These may be used alone or in combination of two or more.

  The solid content of the conductive coating film 21 formed on the inner peripheral wall of the outer can described above is formed of a mixture of graphite and carbon black. As a binder, the compound which has vinyl groups, such as polyvinyl chloride and polyvinyl butyral, is preferable, may be used independently and may be used in mixture of 2 or more types. From the viewpoints of adhesion to the inner peripheral wall of the outer can and electrical conductivity, 10 wt% to 20 wt% of polyvinyl butyral and 90 wt% to 80 wt% of solid content are the most preferable blending ratio. Further, methyl ethyl ketone, cyclohexanone, water and the like are preferable as the solvent, and two or more kinds of solvents may be mixed and used. From the environmental aspect, water is more preferable.

  When the liquid mixture in which the solid content and the binder are dispersed in the solvent is sprayed and applied to the outer can rotated at high speed, and dried to remove the solvent, the inner peripheral wall of the outer can has a thickness of 2 to 10 μm. A coating film 21 is formed. The coating film formation range of the outer peripheral wall of the outer can is a range of 5.50 mm or less (including the bottom surface of the outer can) from the opening edge of the outer can 1.

  Next, the diameter reduction after caulking the opening edge of the outer can 1 will be described.

  After the caulking process described above, the body portion 31 and the caulking portion 32 of the outer can 1 are reduced in diameter by passing the outer can 1 through the circular cast body 30 shown in FIG. By inserting into the circular casting 30 from the negative terminal direction of the battery and reducing the diameter, stress on the insulating packing is relieved. After the diameter reduction processing, the pressure bonding of the groove, the donut-shaped insulating member 6 is arranged on the upper part of the caulking portion, and the exterior label 5 is covered.

  Next, the blending ratio of graphite and carbon black in the conductive coating film 21 will be described in detail. The compounding ratio is most preferably 55 wt% to 80 wt% of graphite and 35 wt% to 20 wt% of carbon black. The effect of reducing the presence of alkaline electrolyte in the space formed between the inner peripheral wall of the outer can and the negative electrode due to the water repellent effect of graphite, and the use of carbon black with a large specific surface area enables the coating film surface roughness This is because the current collection effect that the contact resistance between the inner peripheral wall of the outer can and the negative electrode is reduced is maximized.

  Next, the negative electrode 12 constituting the electrode group 10 will be described in detail. After inserting the electrode group 10 into the outer can 1, a space 22 composed of the outer peripheral inner wall, the outermost negative electrode outer end 20, the separator located outside the negative electrode outer end 20 and the inner peripheral negative electrode is generated. . When the volume of the space 22 is smaller, the internal resistance of the battery can be lowered by improving the adhesion between the inner peripheral wall of the outer can and the negative electrode 12 at the outermost periphery, which is an effect of the present invention. Further, the space 22 formed between the inner wall of the outer can and the negative electrode 12 is reduced, and the effect of reducing the alkaline electrolyte present in the space 22 is further exhibited.

  As a method of reducing the space 22, when the electrode group 10 is configured and the negative electrode 12 positioned at the outermost peripheral portion is manufactured, the thickness of the portion positioned at the outermost peripheral portion is made thinner than the portion positioned at the inner peripheral portion. Or after applying a negative electrode mixture to punching metal, the method of shaving the thickness of the part located in an outermost peripheral part thinner than the part located in an inner peripheral part, etc. are mentioned. The thickness of the outermost negative electrode outer end 20 may be in the range of 0.10 mm to 0.35 mm.

Next, the separator 13 will be described in detail. Before that, the self-discharge of the alkaline storage battery will be described. Alkaline storage batteries undergo self-discharge during storage. This is because nitrate ions (NO ₃ ⁻ ) remaining in the positive electrode elute into the electrolyte after the assembly of the battery, and this is reduced at the negative electrode and nitrite ions (NO _2). ^-) or become ammonium ions _(NH ^{4 +)} nitrogen-based impurities such as nitrate ion (NO ₃ is oxidized at the positive electrode again ^- a). It is considered that the so-called shuttle reaction is caused between the positive electrode and the negative electrode. Polyamide nonwoven fabrics that have been used in nickel cadmium storage batteries have been gradually decomposed in alkaline electrolyte to produce ammonia, which is oxidized to nitrate ions at the positive electrode and self-discharged due to the shuttle effect that is reduced at the negative electrode. It was a big one. As an alternative, polyolefin nonwoven fabrics have been used.

  Since this type of polyolefin-based nonwoven fabric is inferior in hydrophilicity with an alkaline electrolyte, it is necessary to perform hydrophilic treatment to improve hydrophilicity. Therefore, in order to improve the hydrophilicity with the alkaline electrolyte of the separator made of polyolefin nonwoven fabric, the polyolefin nonwoven fabric is subjected to various hydrophilic treatments such as sulfuric acid treatment, fluorine treatment, surfactant treatment, plasma treatment, It came to be used as the separator 13 excellent in hydrophilicity.

The sulfuric acid treatment is performed by treating the nonwoven fabric with an acid containing a sulfuric acid group such as sulfuric acid or fuming sulfuric acid. The functional group resulting from S, such as a sulfone group (—SO ₃ H), is introduced into the nonwoven fabric fiber by the sulfuric acid treatment. The non-woven fabric made of polyolefin treated with sulfuric acid can capture nitrogen-based impurities eluted in the electrolytic solution. The sulfuric acid-treated polyolefin non-woven fabric can provide an alkaline storage battery with excellent storage characteristics.

The fluorine treatment is performed, for example, by treating the nonwoven fabric with a mixed gas obtained by further adding oxygen gas, carbon dioxide gas, sulfur dioxide gas or the like to fluorine gas diluted with an inert gas. By the fluorine gas treatment, hydrophilic groups such as OH, COOH, and SO ₃ H are introduced into the nonwoven fabric fibers.

  In the surfactant treatment, the nonwoven fabric is dipped in a solution in which the surfactant is dissolved and then dried. Examples of the surfactant that can be used include saturated carboxylates such as fatty acid salts, alkyl ethoxy carboxylates, acylated amino acid salts, sulfate ester salts, sulfonates, and the like. In the surfactant treatment, the surfactant is adsorbed on the fibers of the nonwoven fabric, and the hydrophilicity is improved.

  The plasma treatment is performed by converting oxygen gas into plasma to generate oxygen radicals and treating the nonwoven fabric with the oxygen radicals. By the plasma treatment, hydrophilic functional groups such as OH and COOH groups are introduced into the fibers of the nonwoven fabric.

  Compared to sulfuric acid treatment, fluorine treatment, surfactant treatment, and plasma treatment are simpler and do not have the function of trapping nitrogen-based impurities eluted in the electrolyte solution. It has high characteristics. Of these hydrophilization treatments, fluorine treatment is preferred because of the excellent separator properties and long-term stability of the resulting separator.

  Combined use of polyolefin nonwoven fabric subjected to sulfuric acid treatment and fluorine treatment or surfactant treatment or plasma treatment, and the combined proportion of nonwoven fabric imparted with hydrophilicity other than sulfuric acid treatment is in the range of 35 wt% to 75 wt% of the entire nonwoven fabric. If specified, the self-discharge characteristics are not impaired, and the liquid absorption is improved. By reducing the diameter of the outer can, the space formed between the inner peripheral wall of the outer can and the negative electrode is reduced, resulting in excess alkaline electrolysis. The liquid can be reliably held in the separator 13.

  In addition, as for the combined use method of a separator, a different kind separator can be used together by heat welding, and the overlap of the welding part is preferably 8.0 mm or less. Moreover, it can be used together by superimposing a plurality of sheets. The combination ratio can be arbitrarily controlled within the above weight range.

  Hereinafter, although the example and the example of the present invention are given and the composition and effect of the present invention are further explained, the present invention is not limited to these examples. 100 AA-sized cylindrical nickel-metal hydride storage batteries were produced in the following examples and comparative examples. The following evaluation tests were performed on the batteries of the obtained examples and comparative examples.

(1) Measurement of high rate discharge characteristics For each battery of the example and the comparative example, after charging for 1.5 hours at a current value of 1 ItA, the discharge capacity when discharged to a final voltage of 1.0 V at a current value of 3 ItA It was measured. The results are shown in each table, normalized with the result of Comparative Example 1 being 100. In addition, the result of each battery is an average value of 50 pieces.

(2) Measurement of cycle life For each battery of the example and comparative example, after charging for 1.5 hours at a current value of 1 ItA, charging to discharge to a final voltage of 1.0 V at a current value of 1 ItA while measuring the discharge capacity. The discharge cycle was repeated until the discharge capacity became 80% or less of the initial discharge capacity, and the number of cycles was counted. The results are shown in each table, normalized with the result of Comparative Example 1 being 100. In addition, the result of each battery is an average value of 50 pieces.

<Example 1>
Can made from a nickel-plated steel sheet with a thickness of 0.35 mm by press working with an outer diameter of 14.25 mm, a side thickness of 0.13 mm, and a height of 51.40 mm having a predetermined opening and body thickness And the exterior can was produced.

  Next, a liquid mixture in which graphite and carbon black were dispersed in an organic solvent polyvinyl butyral as a conductive coating film was prepared. The mixing weight ratio of graphite and carbon black was 70:30, and the mixing weight ratio of the solid content and the organic solvent was 15:85. The liquid conductive material was sprayed and applied to an outer can rotated at high speed, and dried at 170 ° C. for 10 seconds to form a conductive coating film having a thickness of 6 μm on the inner peripheral wall of the outer can. The coating film formation range of the outer peripheral wall of the outer can was the entire inner peripheral wall (including the outer can bottom) including 5.50 mm or less from the opening edge of the outer can.

  For the positive electrode, a paste containing nickel hydroxide particles, cobalt oxide particles and a binder was prepared. After filling this paste with respect to the foamed nickel base material, it was dried and then subjected to rolling / cutting to produce a positive electrode.

For the negative electrode, an ingot of a hydrogen storage alloy of AB5 type having a composition of Mm _1.0 Ni _4.0 Co _0.4 Mn _0.3 Al _0.3 (where Mm represents Misch metal) is mechanically formed. And sieved to obtain hydrogen storage alloy particles. A slurry was prepared by mixing the hydrogen storage alloy particles, polytetrafluoroethylene, sodium polyacrylate and carboxymethyl cellulose as a binder, carbon black as a conductive agent, and water. After applying this slurry to the punching metal, it was dried and then subjected to rolling / cutting to produce a negative electrode.

  The obtained negative electrode and positive electrode were wound by thermally welding two polyamide separators having a thickness of 0.12 mm and subjected to sulfuric acid treatment to produce an electrode group. The outer diameter of the electrode group was 13.70 mm, the outermost end thickness of the negative electrode was 0.35 mm, and the inner thickness other than the outermost periphery was 0.45 mm.

  The alkaline electrolyte was adjusted with ion-exchanged water to have a concentration of 4.40 mol / l sodium hydroxide and 1.10 mol / l potassium hydroxide, and 2.38 g was injected and impregnated under reduced pressure.

  After attaching the cover plate with a safety valve and caulking the opening edge of the outer can, the body part of the outer can is reduced in diameter to 14.00, the grooving part is crimped, and the cover with all valves is attached. A cylindrical nickel-metal hydride storage battery was prepared by attaching.

<Comparative Example 1>
The outer diameter of the outer can was set to 14.00 mm at the time of can making and after caulking the opening edge, the same as in Example 1 except that the diameter was not reduced and the conductive material was not applied to the inner peripheral wall of the outer can. A battery was produced by the method.

<Comparative example 2>
A battery was produced in the same manner as in Example 1 except that the conductive material was not applied to the inner peripheral wall of the outer can.

<Comparative Example 3>
A battery was fabricated in the same manner as in Example 1 except that the outer diameter of the outer can was 14.00 mm at the time of can making, the opening edge was caulked, and then the diameter was not reduced.

  As shown in Table 1, the high rate discharge characteristics and the cycle life were evaluated. As a result, compared with Comparative Example 1, the high rate discharge characteristics were the same for Comparative Example 2, and the cycle life was improved. Regarding Comparative Example 3, the high rate discharge characteristics were improved and the cycle life was equivalent. On the other hand, in Example 1, both the high rate discharge characteristics and the cycle life were improved. In Example 1 of the present invention, improvement in both high rate discharge characteristics and cycle life was recognized due to the synergistic effect of applying a conductive material to the inner peripheral wall of the outer can and reducing the diameter of the outer can.

  Next, the weight ratio of the conductive coating film solids was examined.

<Example 2>
A battery was fabricated in the same manner as in Example 1 except that the weight ratio of graphite to carbon black was 55:45.

<Example 3>
A battery was fabricated in the same manner as in Example 1 except that the weight ratio of graphite to carbon black was 80:20.

  As shown in Table 2, as compared with Example 1, improvement in either the high rate discharge characteristics or the cycle life was recognized. This is because, when the weight ratio of graphite to carbon black is in the range of 55 to 80 wt% graphite and 45 to 20 wt% carbon black, the contact resistance between the outer peripheral wall of the outer can and the negative electrode is reduced, and between the inner peripheral wall of the outer can and the negative electrode. This is considered to be the optimum range in which the effect of reducing the presence of the alkaline electrolyte in the formed space can be exhibited at the same time.

  Next, the thickness of the outermost end of the negative electrode was examined.

<Example 4>
The thickness of the outermost end of the negative electrode was 0.23 mm. This negative electrode was produced by reducing the thickness of the outermost peripheral part of the punching metal holding the negative electrode and increasing the aperture ratio. Otherwise, a battery was fabricated in the same manner as in Example 1.

<Example 5>
The thickness of the outermost end of the negative electrode was 0.10 mm. This negative electrode was produced by making the thickness of the outermost peripheral portion of the punching metal on which the negative electrode is held thinner than in Example 4 and further increasing the aperture ratio. Otherwise, a battery was fabricated in the same manner as in Example 1.

  As shown in Table 3, compared with Example 1, improvements in both high rate discharge characteristics and cycle life characteristics were observed. This is because the contact resistance between the outer peripheral wall of the outer can and the negative electrode is reduced and the space formed between the inner peripheral wall of the outer can and the negative electrode in the range where the thickness of the negative electrode end is 0.10 to 0.35 mm. This is considered to be the optimum range in which the effect of reducing the presence of the alkaline electrolyte is developed at the same time.

  Next, the separator was examined.

<Example 6>
65% by weight of the separator treated with sulfuric acid and 35% by weight of the separator treated with fluorine were thermally welded to produce separators with different hydrophilic treatments. Otherwise, a battery was fabricated in the same manner as in Example 1.

<Example 7>
25% by weight of the separator treated with sulfuric acid and 75% of the separator treated with fluorine were heat-welded to produce separators with different hydrophilic treatments. Otherwise, a battery was fabricated in the same manner as in Example 1.

  As shown in Table 4, compared with Example 1, improvement in both high rate discharge characteristics and cycle life characteristics was observed. This improves the liquid absorbency of the separator by using a separator subjected to fluorine treatment. This is because the outer can is reduced in diameter, and the space formed between the inner peripheral wall of the outer can and the negative electrode is reduced, so that the excess alkaline electrolyte can be reliably held in the separator.

  In addition, although the nickel hydride storage battery was demonstrated in the above-mentioned Example, it can also be used with a nickel cadmium storage battery, and various variable are possible.

  The present invention is useful for alkaline storage batteries having a high rate discharge and a long cycle life.

DESCRIPTION OF SYMBOLS 1 Exterior can 2 Insulation packing 3 Cover plate 4 Groove 5 Exterior label 6 Donut-shaped insulating member 7 Degassing hole 8 Valve body 9 Positive electrode terminal 10 Electrode group 11 Positive electrode 12 Negative electrode 13 Separator 14 Positive electrode lead 15 Insulating member 16 with slit 16 Insulating member 17 Positive electrode inner end 18 Negative electrode inner end 19 Positive electrode outer end 20 Negative electrode outer end 21 Conductive coating film 22 Space

Claims (4)

  A bottomed cylinder in which an electrode group formed by winding a strip-shaped negative electrode and a positive electrode in a spiral shape so that the negative electrode is positioned on the outermost periphery through a separator has an open upper end having an inner diameter larger than the maximum diameter of the electrode group In a cylindrical alkaline storage battery that is inserted into a cylindrical outer can having a shape, then injected with an alkaline electrolyte, and the outer can is reduced in diameter, the outermost peripheral portion of the negative electrode is in contact with the inner peripheral wall of the outer can. A cylindrical alkaline storage battery comprising an electrical structure, wherein the outer can has an inner peripheral wall coated with a conductive coating film.   2. The cylindrical alkaline storage battery according to claim 1, wherein the conductive coating film is composed of graphite and carbon black, the amount of graphite is 55 wt% or more and 80 wt% or less, and the amount of carbon black is 20 wt% or more and 45 wt% or less.   The outermost peripheral portion of the negative electrode is thinner than the inner peripheral portion, and the end thickness of the outermost peripheral portion of the negative electrode is in a range of 0.10 mm to 0.35 mm. The cylindrical alkaline storage battery described.   The separator is a combination of a polyolefin nonwoven fabric provided with hydrophilicity by sulfuric acid treatment and a polyolefin nonwoven fabric provided with hydrophilicity by fluorine treatment or surfactant treatment or plasma treatment. The cylindrical alkaline storage battery according to any one of claims 1 to 3, wherein the combined ratio of the separator imparted with hydrophilicity other than the sulfuric acid treatment is 35 wt% or more and 75 wt% of the entire separator.