JP5061582B2 - battery - Google Patents

Description

  The present invention relates to a battery using an electrode plate in which a porous metal substrate is filled with an active material, and more particularly to improvement in productivity and improvement in reliability.

  In recent years, there has been a rapid increase in the number of electric devices that are required to be small and light, such as mobile electronic devices such as mobile computers and digital cameras. As a power source for these devices, a sealed alkaline storage battery using a positive electrode (= hereinafter referred to as a non-sintered nickel electrode plate) in which a porous metal is filled with an active material mainly composed of nickel hydroxide is used. The energy per unit volume and unit mass is higher than that of a nickel cadmium storage battery or a lead storage battery using a sintered nickel electrode plate. Of these, nickel-metal hydride storage batteries using an electrode made of a hydrogen storage alloy for the negative electrode are widely used as a power source that is particularly clean for the environment and as a power source for the electric equipment, such as hybrid electric vehicles (HEV) and conventional nickel cadmium. Applications have also begun in fields that require high output characteristics and long life characteristics, such as power tools such as power tools and toys that use batteries.

  The non-sintered nickel electrode plate is formed by filling an alkali-resistant metal porous body with an active material mainly composed of nickel hydroxide, a conductive agent precursor mainly composed of cobalt and a binder, and then compression molding. It is manufactured by cutting to a predetermined dimension. The coating material is filled with a powder of the material made into a paste with an aqueous solution in which a thickener is dissolved, and the metal porous body is immersed in the paste, or the paste is applied to the metal porous body. To do. Here, the active material or the active material mainly composed of nickel hydroxide refers to a hydroxide and an oxide mainly composed of nickel and containing cobalt and zinc. Since the non-sintered nickel electrode plate can be manufactured by such a method, there are advantages that a large amount of active material can be filled and the process is simplified and the productivity is high as compared with the sintered nickel electrode plate.

  However, the non-sintered nickel electrode plate has a problem that the positive electrode powder held on the end surface of the electrode plate is dropped and the end portion of the metal porous body is exposed. The exposed end portion of the porous metal body has extremely low strength because it does not hold powder, and therefore, burrs are formed by a slight external force applied to this portion. For example, in the step of winding the positive electrode plate and the negative electrode plate through the separator, the end face of the electrode plate is rubbed against a guide rail provided on a table for conveying the positive electrode plate toward the winding center, and the positive electrode powder is rubbed. Then, the end of the metal porous body is burred in the direction perpendicular to the electrode surface. This burr causes a short circuit by breaking through the separator when winding the positive electrode plate and the negative electrode plate through the separator. Here, the positive electrode powder refers to a mixture of the active material mainly composed of nickel hydroxide, a conductive agent precursor mainly composed of cobalt, a rare earth compound, a binder, and the like. A rare earth hydroxide or oxide is used as the rare earth compound.

  Further, the burr generated at the end portion of the porous metal body bites into the separator and shortens the distance between the electrodes even if it does not break through the separator to cause a short circuit, and thus causes the following problems. That is, a battery with a short inter-electrode distance has a problem of short-circuiting when the positive electrode expands due to charge / discharge. Furthermore, in batteries with a shorter distance between the electrodes, cobalt in the positive electrode and negative electrode and manganese contained in the hydrogen storage alloy of the negative electrode elute and precipitate in the separator, and have some conductivity. However, there is a problem that a short-circuit occurs due to contact with the burr that bites into the separator.

  Conventionally, the following methods have been applied to solve the above-described problems.

  In Patent Document 1, as a method for preventing the metal burr from penetrating the separator, “the peripheral edge of the positive electrode and / or the peripheral edge of the negative electrode is covered with an alkali-resistant heat-fusible resin including its cut end face. (Patent Document 1, paragraph [0004]) has been proposed. However, even when the electrode plate periphery is covered with an alkali-resistant heat-fusible resin as in Patent Document 1, the problem of short circuit due to burrs at the end of the metal porous body is hardly improved. This is because the coated alkali-resistant heat-sealable resin does not have sufficient slidability and easily falls off the surface of the electrode plate. For example, when winding the positive electrode plate and the negative electrode plate coated with the outer periphery of the electrode plate with a heat-fusible resin through a separator, if the coated part is rubbed against a guide rail or the like, the heat-adhesive resin is at an early stage. It falls off and the positive electrode powder is exposed. The exposed positive electrode powder is also rubbed off by the guide rail, and as a result, burrs are generated at the end portion of the exposed metal porous body. Further, as another problem, when the peripheral edge portion of the electrode is covered with the heat-welding resin as in Patent Document 1, including the cut end face, the covered portion of the electrode becomes difficult to react, so that the discharge performance is reduced. There was also.

  In Patent Document 2, as a method for preventing the positive electrode powder from falling off the electrode plate, “an active material paste formed by kneading nickel hydroxide, water, a thickener, and a binder is applied to the conductive substrate. A nickel positive electrode plate ”(Patent Document 2, Claim 1) characterized in that it is filled and a binder is applied to the surface thereof is proposed as an example of a binder applied to the surface. Polytetrafluoroethylene powder is mentioned. However, even when polytetrafluoroethylene powder is applied to the electrode plate surface as in Patent Document 2, the problem that burrs occur at the end of the metal porous body has been hardly improved. This is because polytetrafluoroethylene powder does not have sufficient adhesion to the electrode plate, so that it easily falls off the surface of the electrode plate when handling the electrode plate. For example, when a positive electrode plate and a negative electrode plate coated with polytetrafluoroethylene powder are wound through a separator, if the coated portion is rubbed against a guide rail or the like, the polytetrafluoroethylene powder falls off at an early stage. The positive electrode powder is exposed. The exposed positive electrode powder is also rubbed off by the guide rail, and as a result, burrs are generated at the end portion of the exposed metal porous body.

Further, in Patent Document 3, as another method of preventing the positive electrode powder from falling off, “fluorine rubber or olefin latex binder is applied and dried on the end of the core material coated with the active material” (Patent Document 3). 3. Claim 1) A method has been proposed. Even when fluororubber or olefin-based latex binder is applied to the end of the electrode plate as in Patent Document 3, the problem that burrs occur at the end of the metal porous body has not been sufficiently improved. This is because, in Patent Document 3, no resin is applied to the end face of the electrode plate, and even if it is applied, fluororubber or olefin-based latex binder has high adhesiveness, so that sliding is applied to the portion where these are applied. This is because the property is not sufficient, and it easily falls off the surface of the electrode plate when rubbed with an external member. For example, when winding a positive electrode plate and a negative electrode plate coated with fluororubber or olefinic latex binder on the end through a separator, if the coated part is rubbed against a guide rail or the like, fluororubber or olefinic The latex-like binder falls off at an early stage to expose the positive electrode powder. The exposed positive electrode powder is also rubbed off by the guide rail, and as a result, burrs are generated at the end portion of the exposed metal porous body.
JP 05-190200 A JP 09-161794 A JP-A-2004-179119

  As described above, a battery using an electrode manufactured by a method of filling an active material into a porous metal body like a conventional alkaline storage battery using a non-sintered nickel electrode plate has insufficient short-circuit resistance, For this reason, there has been a problem that a short circuit occurs during manufacturing, or a short circuit or a fine short circuit occurs when the charge / discharge cycle is repeated. And in the assembled battery comprised using such a battery, since a short circuit was accelerated, there existed a problem that cycle life performance was short. This fine short circuit is caused by expansion and contraction of the electrode during overcharge and overdischarge. Overcharge and overdischarge are caused by variations in capacity and charge / discharge characteristics between individual batteries.

  Therefore, the problem to be solved by the present invention is to improve the short circuit resistance of the battery by securing the distance between the positive and negative electrodes, to suppress the output decrease after repeated cycles, and to reduce the life performance of the assembled battery. It is to suppress.

  As a result of intensive studies, the present inventors have found that the burr generated in the positive electrode plate accounts for most of the causes of the above-mentioned problems, and adopting the following means to make the positive electrode plate have a specific configuration. It has been found that a battery having both excellent short circuit resistance and excellent discharge performance can be realized.

  That is, the present invention includes a pole group in which a strip-shaped positive electrode plate and a negative electrode plate are wound via a separator, and at least one of the two electrode plates is obtained by filling a metal porous body with an active material. The battery is characterized in that the at least one electrode plate is coated with a mixture containing polytetrafluoroethylene and fluororubber on the surface of the end portion on the long side.

  In the battery of the present invention, the content of fluororubber in the mixture containing polytetrafluoroethylene and fluororubber is 10% or more and 30% or less with respect to the total weight of polytetrafluoroethylene and fluororubber. preferable.

In the battery of the present invention, the amount of polytetrafluoroethylene applied is preferably 0.4 mg or more per 1 cm ² of application area.

  In the battery of the present invention, the battery is a nickel metal hydride storage battery, the positive electrode plate is a porous metal filled with an active material mainly composed of nickel hydroxide, and the end on the long side of the positive electrode plate It is preferable that a mixture containing polytetrafluoroethylene and fluororubber is applied to the surface.

  According to the present invention, it is possible to greatly reduce the occurrence of short-circuit failure during battery assembly without significantly degrading the output performance of the battery, and to greatly reduce the occurrence rate of short-circuit of the battery even when the cycle has elapsed.

  In addition, by configuring the assembled battery using the battery of the present invention, the battery is accelerated by the battery capacity variation unique to the assembled battery, the overcharge that occurs due to the variation in the characteristics of charge and discharge, and the expansion and contraction of the electrode due to overdischarge. Since a short circuit can be suppressed and durability can be improved, an assembled battery having extremely excellent cycle life performance can be obtained.

  In a battery comprising a pole group in which a strip-like positive electrode plate and a negative electrode plate are wound via a separator, at least one of the two electrode plates is a metal porous body filled with an active material, By applying a mixture containing polytetrafluoroethylene and fluororubber to the surface of the end on the long side of at least one electrode plate, the powder of active material or the like held on the end of the electrode plate It is possible to reliably prevent the dropout. The falling off of the powder such as the active material at the end is the first stage of the generation of burrs. By suppressing this, the end of the metal porous body is not exposed, and therefore no burrs are formed. Therefore, in the battery of the present invention, a sufficient distance between the positive and negative electrodes is ensured, and as a result, excellent short circuit resistance is obtained. Moreover, since the battery of the present invention has excellent short-circuit resistance after the cycle life, the reliability is extremely high.

  In the battery of the present invention, the polytetrafluoroethylene in the mixture containing polytetrafluoroethylene and fluororubber has the effect of greatly improving the slipperiness between the surface of the electrode plate and other members. Therefore, the electrode plate on which the mixture is applied to the surface of the end portion can prevent the powder of the active material from falling off even when the electrode plate is rubbed against an external member such as a guide rail. The reason why the slipperiness is greatly improved is that the contact between the polytetrafluoroethylene applied to the surface of the electrode plate and an external member such as a guide rail is a point contact or a contact in an extremely small area. As a result, the frictional resistance is at a low level. The contact is point contact or contact in an extremely small area because polytetrafluoroethylene is present in the form of particles or fibers.

  In the battery of the present invention, the fluororubber in the mixture containing polytetrafluoroethylene and fluororubber has an effect of preventing the polytetrafluoroethylene in the mixture from falling off the electrode plate. When fluororubber is not used, polytetrafluoroethylene has a problem that it is easy to drop off from the electrode plate because it does not have sufficient binding properties with the electrode plate. For example, when a positive electrode plate and a negative electrode plate coated with polytetrafluoroethylene alone on the surface of the end portion are wound through a separator, if the coated portion is rubbed against a guide rail, the polytetrafluoroethylene particles fall off As a result, the positive electrode powder is exposed. When dropping occurs, the effect of improving the slipperiness by the polytetrafluoroethylene particles as described above cannot be obtained. That is, the effect of increasing the slidability of the surface of the electrode plate by polytetrafluoroethylene is obtained by using a mixture of fluororubber. The fluororubber used in the present invention is preferably one that is difficult to be decomposed at the positive electrode potential. For example, vinylidene fluoride (FKM), polytetrafluoroethylenepropylene (FEPM), tetrafluoroethylene-purple fluorovinyl ether System (FFKM) and the like. Among these, vinylidene fluoride rubber is preferable because it is easily available and inexpensive.

  Since the present invention solves the problem by ensuring a sufficient distance between the positive and negative electrodes, it can be applied even to a storage battery, and further, a discharge reaction or charge / discharge reaction system Even if it is a battery and storage battery from which it differs, it is applicable. For example, the present invention can be applied to an alkaline storage battery, a lead storage battery, and a storage battery using a nonaqueous electrolyte. In particular, it is preferable to apply to a nickel-metal hydride storage battery using a non-sintered nickel electrode plate as a positive electrode because of its high energy density, long life, and high high rate discharge performance.

  The ratio of polytetrafluoroethylene in the mixture containing polytetrafluoroethylene and fluororubber used in the battery of the present invention is preferably 70% or more based on the total weight of polytetrafluoroethylene and fluororubber. By setting the content to 70% or more, the ease of slipping when rubbing against the guide rail is further increased, so that the peeling of the applied mixture and the falling off of the powder such as the active material can be greatly improved.

  The content of fluororubber used in the battery of the present invention is preferably 10% or more and 30% or less with respect to the total weight of polytetrafluoroethylene and fluororubber. By setting the content to 10% or more, the binding property of the polytetrafluoroethylene particles is further increased, and the separation of the particles can be greatly improved. By setting the content to 30% or less, it is possible to suppress the adhesiveness of the portion coated with the mixture containing polytetrafluoroethylene and fluororubber from becoming too high. Problems such as adhesion can be suppressed.

In the battery of the present invention, the amount of polytetrafluoroethylene applied in the applied mixture is preferably 0.4 mg / cm ² or more because the short-circuit resistance performance is reliably improved, and further excellent short-circuit resistance is obtained. Therefore, it is preferably 0.8 mg / cm ² or more.

  In the battery of the present invention, the effect of the present invention can be obtained if the end of the electrode plate to which the mixture containing polytetrafluoroethylene particles and fluororubber is applied includes at least the end face. If a side surface portion having a height of 5 mm or more is included, extremely excellent short-circuit resistance can be obtained. The end portion and the end surface included in the end portion are preferably those on the long side sandwiched between the counter electrodes during winding. In the case of a positive electrode plate of a non-sintered nickel electrode plate, the end of the positive electrode plate that is sandwiched by the negative electrode plate breaks through the separator when a small amount of burrs occur during winding It is because there is a fear of reaching.

  In the battery of the present invention, a dispersion of polytetrafluoroethylene particles having a concentration of 20% or more and 60% or less is applied as a method of applying a mixture containing polytetrafluoroethylene and fluororubber to the surface of the end portion of the electrode plate. Is preferably used because it can be easily applied. If the concentration is less than 20%, it is difficult to apply a certain amount in order to maintain short circuit resistance, which is not preferable. If the concentration exceeds 60%, the amount to be applied becomes too large. Therefore, it is preferable to use a solution having a concentration of 20% or more and 60% or less. In addition, it is preferable to use a fluororubber-containing dispersion having a concentration of 10% to 35%, because the fluororubber can be easily applied. If the concentration is less than 10%, it is difficult to apply a certain amount in order to maintain short circuit resistance, which is not preferable. If the concentration is too high, the amount applied will be too large, and it is preferable to use a solution with a concentration of 10% to 35%.

  The method of applying the dispersion to the electrode plate can be applied by bringing a brush or sponge immersed in the dispersion into contact with each other or by immersing the electrode plate in a liquid surface. However, it is more preferable to transfer the coating roll to the electrode and apply it, since the determination is easy to control.

  In the battery of the present invention, when a mixture containing polytetrafluoroethylene and fluororubber is applied and dried, and the polytetrafluoroethylene particles are made fibrous by rubbing the applied portion, the powder retainability is improved. It is preferable because it improves dramatically.

  In the battery of the present invention, excellent high rate discharge characteristics can be obtained by using polytetrafluoroethylene in a particulate or fibrous state.

When the present invention is applied to a nickel-metal hydride storage battery, the positive electrode active material is a mixture of nickel hydroxide with zinc hydroxide and cobalt hydroxide, and obtained by uniformly dispersing them by a coprecipitation method. The use of nickel hydroxide composite hydroxide is preferred. For additives other than nickel hydroxide composite oxide, cobalt hydroxide, cobalt oxide or the like is used as a conductive modifier. A part of the nickel oxide composite oxide that is oxidized using oxygen or oxygen-containing gas, or a chemical such as K ₂ S ₂ O ₈ or hypochlorous acid can be used. Further, as an additive, an oxide or hydroxide of rare earth elements such as Y and Yb can be used as a substance for improving oxygen overvoltage.

When the present invention is applied to a nickel-metal hydride storage battery, as the negative electrode active material, the hydrogen storage alloy that is the main constituent element is an alloy that is capable of storing hydrogen and is generally referred to as an AB ₂ or AB ₅ system. There are no particular restrictions on the composition. Particularly preferably, an alloy in which a part of Ni of MmNi ₅ (Mm is a mixture of rare earth elements) of an AB type ₅ alloy is replaced with Co, Mn, Al, Cu, etc. has excellent charge / discharge cycle life characteristics and high discharge. It is preferable because it has a capacity. In addition to yttrium, ytterbium and erbium, gadolinium and cerium oxides and hydroxides may be added as anticorrosive additives, or these elements may be preliminarily contained in the hydrogen storage alloy as metals.

  When the present invention is applied to a nickel metal hydride storage battery, it is desirable that the positive electrode active material powder and the negative electrode material powder have an average particle size of 50 μm or less. In particular, the hydrogen storage alloy powder, which is a negative electrode active material, should have a small particle size of 40 μm or less for the purpose of improving the high output characteristics of the sealed nickel-metal hydride storage battery. It is desirable that the particle size not be less than 20 μm. When a layer having a large Ni content is arranged in the surface layer and the inside of the alloy between 50 nm and 400 nm in the hydrogen storage alloy, an excellent high rate discharge performance can be obtained even with a large particle size, so the average particle size is 30 μm to 50 μm. Is more preferable.

  Various pulverizers and classifiers are used to obtain the powder in a predetermined shape. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air flow type jet mill, or the like is used. At the time of pulverization, wet pulverization may be used using water or an aqueous solution of an alkali metal hydroxide. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used. Both dry and wet methods are used as necessary.

  In the positive electrode plate and the negative electrode plate used in the present invention, a conductive agent, a binder, a thickener, a filler, and the like may be contained as other components in addition to the active material that is a main component.

  The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect battery performance. Usually, natural graphite such as scaly graphite, scaly graphite, earthy graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber, vapor grown carbon, metal (copper, nickel, gold, etc.) Conductive materials such as powder and metal fibers can be included as one kind or a mixture thereof. Among these conductive agents, acetylene black is desirable from the viewpoints of electron conductivity and coatability. The addition amount of the conductive agent is preferably 0.1% by weight to 10% by weight with respect to the total weight of the positive electrode or the negative electrode. In particular, it is desirable to use acetylene black by pulverizing into ultrafine particles of 0.1 to 0.5 μm because the required carbon amount can be reduced. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, a powder mixer such as a V-type mixer, an S-type mixer, a grinder, a ball mill, or a planetary ball mill can be used in a dry or wet manner.

  As binders, thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyethylene, and polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, and styrene butadiene rubber (SBR) are usually used. Polymers having rubber elasticity such as fluoro rubber can be used as one kind or a mixture of two or more kinds. The addition amount of the binder is preferably 0.1 to 3% by weight with respect to the total weight of the positive electrode or the negative electrode. As said thickener, polysaccharides, such as carboxymethylcellulose and methylcellulose, can be normally used as 1 type, or 2 or more types of mixtures. The addition amount of the thickener is preferably 0.1 to 3% by weight with respect to the total weight of the positive electrode or the negative electrode.

  The filler is not particularly limited as long as it does not adversely affect battery performance. Usually, olefinic polymers such as polypropylene and polyethylene, carbon and the like are used. The addition amount of the filler is preferably 5% by weight or less with respect to the total weight of the positive electrode or the negative electrode.

  The positive electrode plate and the negative electrode plate used in the present invention are obtained by mixing each active material, conductive agent and binder with water, and then impregnating the obtained mixture into a metal porous body or substrate detailed below, or It is suitably produced by applying and drying. About the application method, for example, it is desirable to apply to any thickness and any shape using means such as roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, etc. Is not to be done.

  As the metal porous body of the electrode plate used in the present invention, there is no particular choice as long as it is an electronic conductor that does not adversely affect the constructed battery. For example, nickel or a nickel-plated steel plate can be suitably used, and a two-dimensional device such as a punched steel plate can be used in addition to a foam, a formed fiber group, and a three-dimensional device subjected to uneven processing. The thickness is not particularly limited, but a thickness of 5 to 700 μm is used.

  When the present invention is applied to an alkaline storage battery such as a nickel metal hydride storage battery, it is preferable to use nickel having excellent corrosion resistance and oxidation resistance against alkali, and the shape thereof is a foam having a structure with excellent current collecting properties. Is preferred.

  When the present invention is applied to an alkaline storage battery such as a nickel-metal hydride storage battery, an iron or steel foil or plate that is inexpensive and excellent in electrical conductivity is punched as a negative electrode base, and Ni is used to improve reduction resistance. It is preferable to use a perforated plate that has been plated. The punching hole diameter of the steel sheet is preferably 1.7 mm or less and the opening ratio is 40% or more, and thereby the adhesion between the negative electrode active material and the current collector is excellent even with a small amount of binder. In addition to calcined carbon fiber and conductive polymer, the surface of the current collector nickel should be treated with nickel powder, carbon, platinum, etc. attached for the purpose of improving adhesion, conductivity and oxidation resistance. Can do. The surface of these materials can be oxidized.

  As the separator used in the present invention, a known porous film or nonwoven fabric exhibiting excellent high rate discharge characteristics can be used alone or in combination. Examples of the material constituting the separator include polyolefin resins typified by polyethylene and polypropylene, and nylon. The porosity of the separator is preferably 80% by volume or less from the viewpoint of strength and gas permeability. Further, the porosity is preferably 20% by volume or more from the viewpoint of charge / discharge characteristics. The separator is preferably subjected to a hydrophilic treatment. For example, a hydrophilic group graft polymerization treatment, sulfonation treatment, corona treatment, PVA treatment may be applied to the surface of a polyolefin resin fiber such as polyethylene, or a sheet obtained by mixing fibers that have already undergone these treatments may be used. .

  When the present invention is applied to an alkaline storage battery such as a nickel metal hydride storage battery, as the electrolytic solution, those generally proposed for use in alkaline batteries or the like can be used. Water may be used as a solvent, and the solute may be, but not limited to, potassium, sodium, lithium hydroxide dissolved in a mixture of two or more thereof. Anticorrosives for alloys, overvoltages at the positive electrode, corrosion resistance of the negative electrode, and additives to the electrolyte for improving self-discharge, such as yttrium, ytterbium, erbium, calcium, sulfur, zinc, etc. The compounds can be added alone or in admixture of two or more. The concentration of the electrolyte salt in the electrolyte solution is an aqueous solution containing 5 to 7 mol / l potassium hydroxide and 0.5 to 0.8 mol / l lithium hydroxide in order to reliably obtain a battery having high battery characteristics. Is preferred.

  The electrolyte used in the battery of the present invention is preferably injected after the wound electrode group is stored in the battery case. As the injection method, it is possible to inject at normal pressure, but a vacuum impregnation method, a pressure impregnation method, and a centrifugal impregnation method can also be used.

  When the present invention is applied to an alkaline storage battery such as a nickel metal hydride storage battery, examples of the material for the exterior body of the storage battery include nickel-plated iron, stainless steel, polyolefin resin, and the like, or a composite thereof.

  A nickel-metal hydride storage battery comprising a pole group obtained by winding a strip-like positive electrode plate and a negative electrode plate filled with a metal porous body with an active material mainly composed of nickel hydroxide through a separator, A nickel-metal hydride storage battery having a feature in which a mixture containing polytetrafluoroethylene and fluororubber is applied to one long side end of the surface of the positive electrode plate is taken as an example to illustrate the present invention. I will explain it.

(Preparation of positive electrode plate)
An ammonium complex and an aqueous sodium hydroxide solution were added to an aqueous solution in which nickel sulfate, zinc sulfate and cobalt sulfate were dissolved at a predetermined ratio to form an ammine complex. Caustic soda is further added dropwise with vigorous stirring of the reaction system, and the pH of the reaction system is controlled to 11 to 12, and the spherical high-density nickel hydroxide particles serving as the core layer base material are converted into nickel hydroxide: zinc hydroxide: cobalt hydroxide. = 88.45: 5.12: 1.1.

  The high-density nickel hydroxide particles were put into an alkaline aqueous solution controlled to pH 10-13 with caustic soda. While stirring the solution, an aqueous solution containing cobalt sulfate and ammonia at predetermined concentrations was added dropwise. During this time, an aqueous caustic soda solution was appropriately dropped to maintain the pH of the reaction bath in the range of 11-12. The pH was maintained in the range of 11 to 12 for about 1 hour, and a surface layer made of a mixed hydroxide containing Co was formed on the surface of the nickel hydroxide particles. The ratio of the surface layer of the mixed hydroxide was 4.0 wt% with respect to the core layer mother particles (hereinafter simply referred to as the core layer).

  50 g of nickel hydroxide particles having a surface layer made of the mixed hydroxide was put into a 30 wt% (10N) aqueous caustic soda solution at a temperature of 110 ° C. and sufficiently stirred. Subsequently, an excess of K2S2O8 was added to the equivalent of cobalt hydroxide contained in the surface layer, and it was confirmed that oxygen gas was generated from the particle surface. The active material particles were filtered, washed with water and dried.

A carboxymethyl cellulose (CMC) aqueous solution was added to the active material particles to form a paste of the active material particles: CMC solute: polytetrafluoroethylene = 99.2: 0.5: 0.3%. An m ² porous nickel body (Nickel Celmet # 8 manufactured by Sumitomo Electric Co., Ltd.) was filled. Then, after drying at 80 ° C., pressing to a predetermined thickness and cutting, a 4 mm wide polypropylene tape is applied so as to wrap the end face of the winding end, and a width of 4 mm and 7.5 mm (inside, uncoated part 1 mm) A strip-shaped nickel positive electrode plate having a length of 1150 mm and a capacity of 6500 mAh (6.5 Ah) was used.

(Application of a mixture containing polytetrafluoroethylene and fluororubber)
A mixture of polytetrafluoroethylene and fluororubber was applied to the lower end of the nickel positive electrode plate by the following procedure. As the fluororubber, vinylidene fluoride rubber (Daiel (TM) latex) was used. A resin dispersion containing polytetrafluoroethylene and vinylidene fluoride rubber at a weight ratio of 90%: 10% is quantitatively applied to a rotating roll having a groove processing with a width of 1 mm and a depth of 1 mm, and the length of the positive electrode plate is applied to the groove. After transferring the resin dispersion to the end portion on the long side by moving the lower end surface on the side side in contact with each other, it is dried at 80 ° C. and then pressed to a predetermined thickness. An electrode plate in which polytetrafluoroethylene and vinylidene fluoride rubber were applied to the electrode surface having a height of 0.5 mm was obtained. The amount of polytetrafluoroethylene applied was 50 mg per meter of positive electrode plate. This application amount is 4 mg / cm ² in terms of weight per 1 cm ² area of the applied part. Conversion can be calculated by dividing the coating weight per meter of the positive electrode plate by the coating area. The application area can be calculated by the following formula. S = H × L × 2 + T × L. In this equation, S is the coating area (unit cm), H is the coating height from the lower end surface of the electrode (0.05 cm in Example 1), L is 100 (unit cm), and T is the electrode thickness (in Example 1). 0.0226 cm). It was confirmed that polytetrafluoroethylene was in the form of particles by dissolving an electrode produced in the same manner with nitric acid and observing it with a microscope and SEM. In addition, since the portion where the mixture of polytetrafluoroethylene and fluororubber is applied looks white, it can be visually distinguished from the portion where the mixture is not applied. The polytetrafluoroethylene in the applied mixture Can be distinguished from polytetrafluoroethylene mixed in a paste filled in a nickel porous body. The polytetrafluoroethylene used in the present invention is preferably particles having an average particle size of 0.2 to 0.3 μm from the viewpoint of ease of application to the surface of the positive electrode plate and slipperiness.
(Preparation of negative electrode plate)
A hydrogen-absorbing alloy powder having a composition of AB ₅ type rare earth-based MmNi _3.6 Co _0.6 Al _0.3 Mn _0.35 having a particle size of 30 μm and a hydrogen-absorbing alloy powder after hydrogen-absorbing treatment is obtained at a specific gravity of 48 ° It was immersed in a weight% aqueous NaOH solution and immersed in an aqueous solution at 100 ° C. for 4 hours. Then, after pressure-separating and isolate | separating a process liquid and an alloy, the pure water was added by the same weight as an alloy weight, and the ultrasonic wave of 28 KHz was applied for 10 minutes. Thereafter, pure water was poured from the lower part of the stirring layer while gently stirring, and the rare earth hydroxide released from the alloy was removed by flowing the waste water. Then, it washed with water until it became PH10 or less, and filtered under pressure. Thereafter, hydrogen desorption was performed by exposure to warm water at 80 ° C. Hot water is filtered under pressure, washed again with water, the alloy is cooled to 25 ° C., 4% hydrogen peroxide is added under stirring with the same amount as the weight of the alloy, hydrogen is desorbed, washed with water, and hydrogen storage alloy for electrodes. Got. The obtained alloy and styrene-butadiene copolymer were mixed at a solid content weight ratio of 99.35: 0.65, dispersed in water to form a paste, and iron was nickel-plated using a blade coater. After being applied to the punched steel sheet, it was dried at 80 ° C. and then pressed to a predetermined thickness to obtain a hydrogen storage alloy negative electrode plate having a width of 47.5 mm and a length of 1175 mm and a capacity of 11000 mAh (11.0 Ah).

(Production of sealed nickel metal hydride electrode group)
The negative electrode plate, a 120 μm-thick polypropylene non-woven separator with a sulfonation treatment, and the positive electrode plate were combined and wound into a roll to form a pole group.

(Short-circuit inspection of sealed nickel-hydrogen electrode group)
A voltage of 400 V was applied to the electrode group for 5 seconds, a battery that passed a current of 0.1 mA or more was discarded as defective, and a battery that did not flow a current of 0.1 mA or more was used as a good product.

(Insulation breakdown inspection of sealed nickel-hydrogen electrode group)
The voltage applied to the electrode group from 400 V to 600 V at a rate of 100 V / 2 seconds was boosted, and the average value of the voltage at which a current of 0.1 mA or more flowed was defined as the dielectric breakdown voltage of the electrode group.

(Production of sealed nickel-metal hydride storage battery)
The end face of the positive electrode metal porous body protruded from one winding end face of the pole group has a thickness of 0.4 mm made of a nickel-plated steel plate, a circular through hole in the center, and 0 in four places (4 slits). A disc-shaped upper current collector plate (positive electrode current collector plate) having a radius of 14.5 mm provided with a 5 mm clog (clamping portion to the electrode) was joined by resistance welding. Resist the 0.4mm-thick disk-shaped lower current collector plate (negative electrode current collector plate) made of a steel plate with nickel plating on the end surface of the negative electrode substrate that protrudes from the other end surface of the wound pole group. Joined by welding. Prepare a bottomed cylindrical battery case made of nickel-plated steel plate, and attach the current collector plate to the electrode plate group, the positive current collector plate is the open end side of the battery case, and the negative current collector plate is It accommodated in the battery case so that it might contact | abut to the bottom of a battery case, and the center part of the negative electrode current collector plate was joined to the wall surface of the battery case by resistance welding. Next, a predetermined amount of an electrolytic solution composed of an aqueous solution containing 6.8N KOH and 0.8N LiOH was injected.

  A nickel plate with a thickness of 0.4 mm is pressed into the shape of 20 in FIG. 1 and has a radius of 12 mm, a maximum lead height of 3 mm, four protrusions on the top, and four protrusions on the lower collar. Prepared lead. Thereafter, the protrusions on the top of the lead were brought into contact with each other and attached to the inner surface of the lid by spot welding in a direct manner. A rubber valve (exhaust valve) and a cap-shaped terminal were attached to the outer surface of the lid. A ring-shaped gasket was attached to the lid so as to envelop the periphery of the lid. The lid was placed on the electrode plate group so that the projection of the protrusion of the auxiliary lead attached to the lid was in contact with the positive electrode current collector plate, and the open end of the battery case was crimped and hermetically sealed. Thereafter, the total height of the battery was adjusted by compression. Note that the height of the projecting piece is adjusted so that the height between the cover and the positive electrode terminal after adjusting the total height of the battery is such that the pressing force is applied to the projection of the projecting piece of the auxiliary lead and the contact surface of the current collector plate. The angle was adjusted. The lid radius is 14.5 mm. The cap radius is 6.5 mm. The caulking radius of the gasket is 12.5 mm.

  The welding output terminal of the resistance welding machine is brought into contact with the cap 80 (positive electrode terminal) and the bottom surface (negative electrode terminal) of the battery case 60, and the energization conditions are set so that the same energization time is obtained with the same current value in the charging direction and the discharging direction. Set. Specifically, the current value is set to 0.46 kA / Ah (3.0 kA) per 1 Ah capacity of the positive electrode plate (6.5 Ah), the energization time is set to 4.0 msec in the charging direction, and 4.0 msec in the discharging direction, The AC pulse energization was set as one cycle so that two cycles could be energized, an AC pulse consisting of a rectangular wave was energized, and welding was performed to weld the contact point of the bottom of the lead to the upper surface of the upper current collector plate. . At this time, it was confirmed that no gas was generated exceeding the valve opening pressure. Thus, a sealed nickel-metal hydride storage battery as shown in FIG. 1 in which the lid 50 and the positive electrode current collector plate 2 were connected by leads was produced.

  The batteries used in the examples and comparative examples of the present invention all weighed about 176 g.

(Measurement of chemical conversion, internal resistance and power density)
The sealed storage battery is left at ambient temperature of 25 ° C. for 12 hours, charged at 130 mA (0.02 ItA) at 1200 mAh, then charged at 650 mA (0.1 ItA) for 10 hours, and then cut at 1300 mA (0.2 ItA). The battery was discharged to a voltage of 1V. Furthermore, after charging at 650 mA (0.1 ItA) for 16 hours, the battery was discharged at 1300 mA (0.2 ItA) to a cut voltage of 1.0 V, and charging / discharging was performed as 4 cycles for 1 cycle. After the completion of the fourth cycle discharge, the internal resistance was measured using 1 kHz alternating current.

  The power density was measured by using a single battery in a 25 ° C. atmosphere at a discharge temperature of 650 mA (0.1 ItA) at 650 mA (0.1 ItA) for 5 hours, and then flowing 10 seconds at 60 A for 12 seconds. After charging the second-second voltage with a discharge capacity of 6A, after charging the second-second voltage at 90A for 12 seconds, the second-second voltage is set to the second-second voltage of 90A discharge and the discharge capacity is charged with 6A. The 10th second voltage at 120A for 12 seconds was set to the 10th second voltage at 120A discharge, and the electric capacity for discharge was charged at 6A, and then the 10th second voltage at 150A for 12 seconds was discharged to 150A. The voltage at the time of 10 seconds was charged, the electric capacity for the discharge was charged at 6 A, and then the voltage at the 10 seconds when flowing at 180 A for 12 seconds was taken as the voltage at the time of 180 A discharge. Each 10-second voltage was linearly approximated with a current value and a voltage value by the method of least squares. The voltage value at a current value of 0A was E0, and the slope was RDC. Then, the output density in the 25 degreeC battery at the time of 0.8V cut was calculated using following Formula. P = (E0−0.8) ÷ RDC × 0.8 ÷ M. In this equation, P represents the power density (unit: W / kg), and M represents the battery weight (unit: kg).

The resin dispersion applied to the lower end surface of the positive electrode of Example 1 was made of polytetrafluoroethylene and vinylidene fluoride rubber (Daiel (TM) latex) at 80%: 20% by resin content and rotation of the coating roll. Except for the numerical conditions, after obtaining a pole group in the same manner as in Example 1, a short circuit inspection was performed in the same manner as in Example 1, and then a part of the batteries were extracted and a dielectric breakdown voltage inspection was performed. Thereafter, the battery obtained in the same manner as in Example 1 was used as the battery of Example 2. Using this battery, the output density was measured in the same manner as in Example 1. The coating amount of polytetrafluoroethylene was 4 mg / cm ² . This value was calculated by measuring that the coating amount per 1 m of the positive electrode plate was 50 mg from the change in weight before and after coating, and then dividing this measured value by the coating area. Moreover, as a result of dissolving the electrode with nitric acid and observing and confirming with a microscope and SEM, the polytetrafluoroethylene and the vinylidene fluoride rubber coated on the electrode were in the form of particles including a lump.

The resin dispersion applied to the lower end surface of the positive electrode of Example 1 was made polytetrafluoroethylene and vinylidene fluoride rubber (DAIEL (TM) latex) at a resin-containing weight of 70%: 30% and the rotation of the coating roll Except for the numerical conditions, after obtaining a pole group in the same manner as in Example 1, a short circuit inspection was performed in the same manner as in Example 1, and then a part of the batteries were extracted and a dielectric breakdown voltage inspection was performed. Thereafter, the battery obtained in the same manner as in Example 1 was used as the battery of Example 3. Using this battery, the output density was measured in the same manner as in 1. The coating amount of polytetrafluoroethylene was 4 mg / cm ² . In addition, as a result of dissolving the electrode with nitric acid and observing and confirming with a microscope and SEM, the polytetrafluoroethylene and the vinylidene fluoride rubber applied to the electrode were in the form of particles including lumps.

The resin dispersion applied to the lower end face of the positive electrode of Example 1 was made of polytetrafluoroethylene and vinylidene fluoride rubber (DAIEL (TM) latex) at a resin-containing weight of 60%: 40% and rotation of the coating roll Except for the numerical conditions, after obtaining a pole group in the same manner as in Example 1, a short circuit inspection was performed in the same manner as in Example 1, and then a part of the batteries were extracted and a dielectric breakdown voltage inspection was performed. Thereafter, the battery obtained in the same manner as in Example 1 was used as the battery of Example 4. Using this battery, the output density was measured in the same manner as in 1. The coating amount of polytetrafluoroethylene was 4 mg / cm ² . Moreover, as a result of dissolving the electrode with nitric acid and observing and confirming with a microscope and SEM, the polytetrafluoroethylene and the vinylidene fluoride rubber coated on the electrode were in the form of particles including a lump.
(Comparative Example 1)
Except having used the positive electrode which does not coat resin at the positive electrode lower end surface of Example 1, after obtaining a pole group like Example 1, a short circuit test | inspection is done like Example 1, and one part is after that. The battery was removed and a breakdown voltage test was performed. Thereafter, a battery obtained in the same manner as in Example 1 was designated as Comparative Example Battery 1. Using this battery, the output density was measured in the same manner as in Example 1.
(Comparative Example 2)
After obtaining the electrode group in the same manner as in Example 1 except that the resin dispersion applied to the lower end surface of the positive electrode in Example 1 was a dispersion containing 60% polytetrafluoroethylene, the same as in Example 1 was obtained. Then, a short circuit inspection was performed, and then a part of the batteries were extracted and a dielectric breakdown voltage inspection was performed. Thereafter, a battery obtained in the same manner as in Example 1 was used as a battery of Comparative Example 2. Using this battery, the output density was measured in the same manner as in Example 1. In addition, it was confirmed that polytetrafluoroethylene was in the form of particles by dissolving an electrode prepared in the same manner with nitric acid and observing it with a microscope and SEM.
(Comparative Example 3)
After obtaining a pole group in the same manner as in Example 1 except that the resin dispersion applied to the lower end surface of the positive electrode in Example 1 was a dispersion containing 25% of vinylidene fluoride rubber, Example 1 and In the same manner, a short circuit inspection was performed, and then a part of the batteries were extracted and a dielectric breakdown voltage inspection was performed. Thereafter, a battery obtained in the same manner as in Example 1 was used as a battery of Comparative Example 3. Using this battery, the output density was measured in the same manner as in Example 1.
(Reference Example 1)
The resin dispersion applied to the lower end surface of the positive electrode in Example 1 was made polytetrafluoroethylene and styrene butadiene copolymer rubber (hereinafter abbreviated as SBR) at a resin-containing weight of 70%: 30%, and the rotation speed condition of the coating roll Except for the above, after obtaining a pole group in the same manner as in Example 1, a short circuit inspection was performed in the same manner as in Example 1, and then a part of the batteries were taken out and a dielectric breakdown voltage inspection was performed. Thereafter, the battery obtained in the same manner as in Example 1 was used as the battery of Reference Example 1. Using this battery, the output density was measured in the same manner as in Example 1. In addition, it was confirmed that polytetrafluoroethylene was in the form of particles by dissolving an electrode prepared in the same manner with nitric acid and observing it with a microscope and SEM.

  Table 1 shows the breakdown voltage and the output density of the battery as a result of the short circuit inspection of the pole groups of Examples 1 to 4, Reference Example 1 and Comparative Examples 1 to 3. The number of short-circuit inspections was 50.

  From Table 1, it can be seen that the number of defects and the breakdown voltage in the short-circuit inspection during the assembly of the batteries of Examples 1 to 4 are significantly improved as compared with the battery of Comparative Example 1. This means that by applying a mixture containing polytetrafluoroethylene and fluororubber to the lower end portion of the positive electrode plate, the distance between the positive and negative electrodes is ensured and the short circuit resistance is improved. .

  Furthermore, it can be seen from Table 1 that the number of defects and the breakdown voltage of the batteries of Examples 1 to 4 are significantly improved as compared with the batteries of Comparative Examples 2 and 3. This means that the dielectric breakdown voltage is improved and the short-circuit-proof performance is improved when polytetrafluoroethylene or a fluororesin is used alone rather than being applied alone. This is because the slipperiness imparted by the polytetrafluoroethylene is maintained throughout the battery assembly process by preventing the falling of the polytetrafluoroethylene particles due to the stickiness of the fluorinated rubber, and as a result, the electrode This is due to the fact that the burr standing is further suppressed. From Table 1, it can be seen that the battery of Comparative Example 3 has a higher defect rate at the time of the short circuit inspection than that of Comparative Example 1. This is due to the fact that the positive electrode powder was peeled off from the metal porous body and the metal porous body was exposed as a result of the FKM sticking to the guide rail or separator when the positive electrode plate and the negative electrode plate were wound through the separator. To do.

  Moreover, it can be seen from Table 1 that the output densities of the batteries of Examples 1 to 3 are the same as the output density of Comparative Example 1. This means that by applying polytetrafluoroethylene in the form of particles, a short-circuit preventing effect at the time of assembly was obtained without lowering the output. In addition, when polytetrafluoroethylene was less than 70% and fluororubber was more than 30%, the fall of the output considered to be attributed to the fall of the porosity of the resin by fluororubber was confirmed.

  A battery having excellent short-circuit-proof performance, such as the batteries of Examples 1 to 4, is also excellent in that the short-circuit occurrence rate of the battery is greatly reduced even during the cycle. This is demonstrated from the following results obtained by measuring the number of charge / discharge cycles until the capacity drops to 80% of the initial value when the batteries of Examples and Comparative Examples are repeatedly charged and discharged at 45 ° C. That is, the number of cycles of the batteries of Examples 1 to 4 and Comparative Examples 1 and 2 were both 1200 times or more, but after leaving the discharged battery after reaching the end of its life for one week. When the cell voltage was measured, it was confirmed that only the batteries of Comparative Examples 1 and 2 were lowered to below 0.8V. This is presumably because the positive and negative electrodes do not have a sufficient distance between the electrode plates, so that a short circuit occurs due to the expansion of the electrodes due to charge and discharge, and the voltage decreases.

  A battery having excellent short-circuit resistance, such as the batteries of Examples 1 to 4, has an effect of improving the cycle life characteristics of the assembled battery when used as a battery constituting the assembled battery. This effect is obtained when the assembled battery in which six batteries of Example 3 are connected in series and the assembled battery in which six batteries of Comparative Example 1 are connected in series is repeatedly charged and discharged at 45 ° C., and the initial capacity is 80%. It is clear from the following results of measuring the number of charge / discharge cycles until the value drops. That is, the number of cycles of the assembled battery using Example 3 was 1200, while the number of assembled batteries using the battery of Comparative Example 1 was 750. Although this is not necessarily clear, it is considered that the slightly short-circuit that occurred slightly caused variations in battery capacity, and the battery with a small battery capacity was overdischarged, so that the capacity was extremely reduced.

  Further, from Table 1, when Example 3 and Reference Example 1 were compared, it was confirmed that even when SBR was used in place of the fluorinated rubber, the short-circuit prevention effect could be enhanced, but the battery output decreased. Although this is not necessarily clear, it is considered that SBR was decomposed by charging / discharging of the battery and melted into the electrolytic solution to reduce the ionic conductivity of the electrolytic solution. In addition, when the battery of Example was cycle charged and discharged at 45 ° C., the battery of Example 3 could be charged and discharged 1200 times until the capacity was reduced to 80% of the initial capacity. Only charging / discharging was possible. This is considered to be because SBR was decomposed by charging / discharging of the battery and pressed the charge reserve capacity of the negative electrode.

  Moreover, it confirmed that a dielectric breakdown voltage improved by making a polytetrafluoroethylene fibrous. This is because the positive electrode powder is covered with a fibrous net to prevent the falling off by making the resin into a fibrous form, and the sliding of the electrode end surface has been improved, so that the burr standing when handling the electrode is further suppressed. It is thought that. Here, as a method of making the polytetrafluoroethylene particles into fibers, the polytetrafluoroethylene resin becomes colorless after applying a mixture of the polytetrafluoroethylene particles and the fluorinated rubber to the lower end of the positive electrode plate. A method of rubbing the coated part with a nickel rod was used.

A battery was also manufactured when the amount of polytetrafluoroethylene applied to the lower end portion of the positive electrode plate was 0.4 mg / cm ² , 0.8 mg / cm ² and 2.4 mg / cm ^2, and other conditions Conducted the short circuit inspection and the breakdown voltage measurement in the same manner as in Example 1. As a result of the short circuit inspection, it was found that the defective product rate was reduced when the polytetrafluoroethylene coating amount was 0.4 mg / cm ² or more. According to the mechanism by which the effect of the present application can be obtained, the short circuit resistance can be improved regardless of the coating amount, but the short circuit resistance can be achieved by setting the coating amount to 0.4 mg / cm ² or more. It means that an improvement in performance can be reliably achieved. Further, as a result of the short circuit inspection, it was found that the application rate is preferably 0.8 mg / cm ² or more because the defect rate can be dramatically improved. Furthermore, as a result of the measurement of the breakdown voltage, it was found that the coating amount is preferably 4 mg / cm ² or more because the breakdown voltage is dramatically improved. The above effect is that a certain insulating layer is formed by the arrangement of polytetrafluoroethylene so dense that a sufficient sliding property can be secured at a coating amount of 0.4 mg / cm ² , and a short-circuit preventing effect is exhibited. The density of polytetrafluoroethylene is further increased at 0.8 mg / cm ² and a sufficient insulating layer can be secured, and a denser insulating layer can be secured at 4 mg / cm ² or more. The upper limit of the amount of polytetrafluoroethylene applied is not particularly limited, but is preferably within a range where a desired active material filling amount can be obtained from the viewpoint of battery capacity design. The polytetrafluoroethylene coating amount was changed by adjusting the number of revolutions of the coating roll, and the other manufacturing steps were the same as in Example 1. Moreover, the effect when the coating amount range described above was specified was also observed in experiments in which the blending ratio of polytetrafluoroethylene and vinylidene fluoride rubber was the same as that of Examples 2-4.

  In addition, when the part where the mixture of polytetrafluoroethylene and vinylidene fluoride rubber is applied is only the lower end surface of the positive electrode, the battery is manufactured even when the height is 1 mm from the lower end surface and the height is 1.5 mm. The other conditions were the same as in Example 1, and the short circuit inspection and the breakdown voltage were measured. As a result, it was found that the effect of the present invention can be obtained as long as it is applied to at least the lower end surface, and the defect rate and the dielectric breakdown voltage do not change even when the applied portion is widened. For this reason, when using a rotating roll as an application | coating method, it turned out that application | coating height can be set to 0.5 mm or more. The particulate polytetrafluoroethylene layer was porous, so the output was not affected. The coating height was changed by adjusting the depth of the groove processed in the rotating roll used for coating, and the other manufacturing steps were the same as in Example 1. In addition, application | coating only to a lower end surface was performed using the brush.

  In addition, a battery was manufactured when the content of polytetrafluoroethylene in the paste filled in the nickel porous body was 0%. Other conditions were the same as those in Examples 1 to 4, and short-circuit inspection was performed. As a result, it was found that when the electrode did not contain polytetrafluoroethylene, the number of defects tended to increase by about 2 during short circuit inspection. This seems to be because when polytetrafluoroethylene is contained, the electrode is flexible and does not crack when entrained. For this reason, in the battery of this invention, what contains the polytetrafluoroethylene in the inside of an electrode is good, and the content is 0.3% or more with a polytetrafluoroethylene resin.

  Moreover, although what stuck the tape to the end surface of the winding end part of a positive electrode plate was used, when the tape of the positive electrode winding end part of Example 1 was not affixed, the defect at the time of winding 2 generate | occur | produced 2 pieces. . In addition, when the resin dispersion applied to the lower end surface is applied to the end face of the positive electrode winding end portion of Example 1 instead of the tape, the defect at the time of winding is 0 out of 50, and the case where the tape is applied It turned out that the effect of the same level is acquired. Therefore, it is preferable that a mixture containing polytetrafluoroethylene and fluororubber is applied to the end surface on the short side of the positive electrode plate used in the battery of the present invention.

The figure which shows the structure of the battery of the Example of this invention.

Claims (3)

  A pole group in which a strip-shaped positive electrode plate and a negative electrode plate are wound via a separator, and at least one of the two electrode plates is a metal porous body filled with an active material, and the at least one electrode In the electrode plate, a mixture containing polytetrafluoroethylene and fluororubber is applied to the surface of the end portion on the long side, and the content ratio of fluororubber in the mixture containing polytetrafluoroethylene and fluororubber is The battery is characterized by being 10% or more and 30% or less with respect to the total weight of polytetrafluoroethylene and fluororubber. The battery according to claim 1, wherein the amount of polytetrafluoroethylene applied is 0.4 mg or more per 1 cm ² of application area. The battery is a nickel metal hydride storage battery, the positive electrode plate is a porous metal filled with an active material mainly composed of nickel hydroxide, and the surface of the end on the long side of the positive electrode plate is polytetrafluoro the battery according to any one of claims 1 to 2 mixture comprising ethylene and fluoro rubber is characterized in that it is coated.

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