JP2005222880A - Sheet-like zinc electrode and alkaline battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet-like zinc electrode capable of constituting an alkaline battery enhancing high rate discharge characteristics and to provide the alkaline battery enhancing the high rate discharge characteristics by using the sheet-like zinc electrode. <P>SOLUTION: When the sheet-like zinc electrode 50 is constituted by holding a zinc-containing mix 52 in a support 51, the composition of the zinc-containing mix is specified so that at least zinc powder and at least one binder selected from the group comprising polystyrene, a polystyrene family copolymer, and a maleic acid family copolymer are contained, the mass ratio of the whole binder component containing the above binder is made 0.1-4% of the zinc powder, the porosity of the zinc-containing mix is made 40-75%, and the alkaline battery is constituted by using the sheet-like zic electrode as a negative electrode. As a thickening agent, carboxymethylcellulose is preferable, and as the binder, styrene-butadiene rubber is preferable. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to a sheet-like zinc electrode and an alkaline battery using it as a negative electrode.

  An alkaline battery using zinc as a negative electrode active material is used as a power source for various electronic devices, and various characteristics are required depending on its use. In particular, in digital cameras that have become popular in recent years, in order to increase the number of images that can be taken as much as possible, it is necessary to increase the capacity of the battery and further improve the load characteristics such as the large current discharge characteristics. Battery design is under consideration.

  In order to increase the capacity of the battery, it is necessary to increase the filling amount of the active material. However, if the active material is not effectively used for discharging, it will not lead to an increase in capacity. Higher capacity cannot be achieved only by increasing the capacity.

  Moreover, to improve the load characteristics, it is necessary to increase the reaction area of the active material and improve the conductivity, but as the reaction area of the active material increases, gas generation due to reaction with the electrolyte tends to occur. Therefore, in the negative electrode, it is generally performed that an additive element capable of suppressing gas generation is contained in zinc which is a negative electrode active material.

As means for increasing the reaction area of the active material, a method of winding a sheet-like zinc electrode to produce a wound body is known. As this sheet-like zinc electrode, a paste made of zinc powder and a binder is applied to a punching metal or an expanded metal and dried, or a sheet made of zinc powder and polytetrafluoroethylene and a punching metal are used. Examples of such materials include pasted ones, zinc plates, and zinc expanded metal or punched metal.
JP-A-56-103866 JP 58-25081 A JP-A-8-227721 JP-A-8-241721

  However, the zinc plate or zinc-punched metal or expanded metal itself is an active material, and the discharge reaction involves dissolution and precipitation of zinc, and the zinc disappears as the discharge progresses. There was a problem that the utilization rate decreased due to disappearance and the large current discharge characteristics deteriorated. Furthermore, zinc plates and zinc punched metal or expanded metal have almost no porosity of zinc itself, so the electrolyte permeability and retention characteristics are poor, which also reduces the utilization rate. It causes a decrease in large current discharge characteristics.

  In addition, a sheet-like zinc electrode made of a rolled sheet of zinc powder and polytetrafluoroethylene and a copper punching metal has a zinc layer porosity of 10 to 30%, so that the electrolyte can penetrate and retain. However, the utilization factor of a sheet-like zinc electrode falls. Therefore, if the pressure bonding is weakened to increase the porosity to 30% or more, there has been a problem that the rolled sheet of zinc powder and polytetrafluoroethylene falls off from the punching metal of the base material or peels off. In particular, when a binder such as polytetrafluoroethylene that is bound in a fibrous form is used, such a problem is likely to occur, and the yield is deteriorated.

  The present invention solves the problems of the conventional sheet-like zinc electrode as described above and the alkaline battery using the same as the negative electrode, and provides a sheet-like zinc electrode capable of constituting an alkaline battery having excellent large current discharge characteristics. It is another object of the present invention to provide an alkaline battery having excellent high-current discharge characteristics.

  In the present invention, when a sheet-like zinc electrode is formed by holding a zinc-containing mixture on a support, the composition of the zinc-containing mixture is at least composed of zinc powder, polystyrene, styrene-based copolymer, and maleic acid. And at least one binder selected from a copolymer, and the mass ratio of the whole binder component including the binder in the zinc-containing mixture is 0.1 to 4 with respect to the zinc powder. %, And the porosity of the zinc-containing mixture is 40 to 75%.

  ADVANTAGE OF THE INVENTION According to this invention, the sheet-like zinc electrode which can comprise the alkaline battery excellent in the large current discharge characteristic can be provided, and the large current discharge characteristic is excellent using the sheet-like zinc electrode for the negative electrode. An alkaline battery can be provided.

  In other words, when zinc is an active material, zinc oxide having poor conductivity is generated on the surface of the metallic zinc when discharged, so that the conductivity between particles is reduced, and reaction resistance is particularly high in large current discharge. Therefore, current collection can be always obtained in the process of the discharge reaction progressing, and sufficient current collection can be obtained even in a large current discharge. Further, the composition of the zinc-containing mixture includes at least zinc powder and at least one binder selected from polystyrene, a styrene-based copolymer and a maleic acid-based copolymer, Necessary for the paste containing the zinc-containing mixture (zinc-containing mixture paste) by making the mass ratio of the whole binder component including the binder 0.1 to 4% with respect to the zinc powder. The viscosity of the zinc-containing mixture in the battery is set to 40 to 75% while suppressing the inhibition of the discharge reaction by the binder component such as a thickener and a binder while ensuring a high viscosity and binding property. As a result, the decrease in the filling amount is suppressed while ensuring the necessary permeability and retention of the electrolyte solution, and in combination with the use of the support, an alkaline battery with excellent large current discharge characteristics is constructed. To do It is possible to provide a sheet-like zinc electrode can.

  In the present invention, the zinc constituting the zinc-containing mixture needs to be anhydrous silver, but besides pure zinc, zinc contains at least one element such as indium, bismuth, and aluminum. It may be a thing. The contents of these elements at that time are 0.01 to 0.07 mass% for indium, 0.007 to 0.07 mass% for bismuth, and 0.001 to 0.007 mass% for aluminum. Preferably there is. In addition, as the particle size of zinc, it is preferable to use one having an average particle size of 20 to 75 μm because the preparation of the zinc-containing mixture paste is easy and the characteristics of the electrode are good. .

  In the present invention, at least one selected from polystyrene, a styrene copolymer, and a maleic acid copolymer is used as a binder. These binders exhibit excellent binding properties without applying a treatment such as rolling after the zinc-containing mixture paste is applied to the support and dried, but may contain other binders. In order to adjust the viscosity of the zinc-containing mixture paste, a thickener may be added. In many cases, the binder itself has a thickening action or the thickening agent has a binding action, and it is difficult to clearly distinguish the binder from the thickening agent. And expressed as “binding component”.

  In the styrene copolymer used as the binder, the monomer constituting the monomer unit other than the styrene unit is an olefin represented by ethylene, an ethylenically unsaturated monomer such as an unsaturated carboxylic acid represented by acrylic acid, or butadiene. Dienes typified by can be selected and adopted as appropriate.

  Examples of the olefin include propylene, ethylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene and 3-ethyl. Examples thereof include -1-pentene and 1-octene.

  Examples of the ethylenically unsaturated monomer other than the olefin include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and octyl. Methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, acrylonitrile, methacrylonitrile, vinyl acetate, acrylamide, methacrylamide, N-methylacrylamide, N, N′-dimethylacrylamide, N-isopropylacrylamide , Vinylpyrrolidone, itaconic acid, 2-acrylamido-2-methyl-propa Sulfonic acid, 2-acrylamidoethanesulfonic acid, 2-methacrylamide amidoethanesulfonic acid, 3-methacrylamidopropanesulfonic acid, methyl acrylate sulfonic acid, methyl methacrylate sulfonic acid, acrylic acid-2-ethylsulfonic acid, methacrylic acid 2-ethylsulfonic acid, acrylic acid-3-propylsulfonic acid, methacrylic acid-3-propylsulfonic acid, acrylic acid-2-methyl-3-propylsulfonic acid, methacrylic acid-2-methyl-3-propylsulfonic acid, Acrylic acid-1′1-dimethyl-2-ethylsulfonic acid, methacrylic acid-1′1-dimethyl-2-ethylsulfonic acid or salts thereof, methyl vinyl ketone, ethyl vinyl ketone, methyl vinyl ether, ethyl vinyl ether, fluorine-containing Ethylene, vinyl allylbenzene Zen, etc. N- vinylacetamide and the like.

  Moreover, as a monomer unit other than maleic acid in the maleic acid copolymer, a styrene unit can be selected in addition to the monomer unit.

  The styrene unit may be a styrene derivative. As the maleic acid component for obtaining a maleic acid copolymer, maleic acid or an anhydride thereof or a salt thereof is used. Examples thereof include sodium salt, potassium salt, calcium salt and ammonium salt of maleic acid.

  In the present invention, the binder is particularly preferably a styrene butadiene rubber, a styrene maleic acid copolymer, or a styrene acrylic acid copolymer. When these binders are used, an excellent binding effect can be obtained with a small amount of addition.

  Examples of the thickener include celluloses such as methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose, natural polysaccharides such as welan gum, polyacrylamide, polyvinyl pyrrolidone, polyethylene oxide, and poly-N-vinylacetamide. Polyacrylic acid and the like can be used, but carboxymethyl cellulose is particularly hydrophilic and has good affinity with the electrolyte, and the presence of carboxymethyl cellulose around the zinc particles allows the electrolyte to surround the zinc particles. This is particularly preferable in the present invention because the retention of the metal is improved and the discharge reaction proceeds smoothly.

  Moreover, as a support body, metal foil, a punching metal, an expanded metal, a metal foam etc. can be used, for example, The metal porous body of the following structure is especially preferable as a support body. That is, as the support for the sheet-like zinc electrode of the present invention, a large number of independent openings 8 formed by pressing the flat metal plate 2 as shown in FIGS. The metal porous body 1 has a large number of protrusions 3 formed so as to protrude alternately on the front and back of the metal plate 2. Each protrusion 3 is formed in a truncated pyramid shape in which the area of the upper base 5 (protruding portion) is narrower than the area of the lower base 6. In the upper base 5 of each protrusion 3, a polygonal opening 8 is formed in plan view having an opening 10 punched out from the upper base 5 toward the lower base 6. Then, when the distance dimension in the vertical direction between the upper base 5 on the front surface side and the upper base 5 on the back surface side, that is, the thickness dimension of the metal porous body 2 is d, and the height dimension of the punched portion is e, The dimensions of each part are set so that 0.3 <e / d <0.9 holds. Here, the “polygonal opening 8 in plan view” is a concept including a substantially polygonal opening in which a part of a corner is rounded, and includes a polygonal shape as a whole. .

  That is, as shown in FIG. 1, the metal porous body is embossed so that the protrusions 3 are opposite to each other on the front and back surfaces, and the opening 8 has an opening 10 in the center of the protrusion 3 on the front and back sides. It has a high space ratio. Therefore, when this porous metal body 1 is used as a support for a sheet-like zinc electrode, a large amount of zinc-containing mixture paste can be applied and filled, which contributes to an increase in battery capacity. it can. Moreover, since the current collecting ability can be improved, the utilization factor of zinc as an active material can be improved.

  In addition, as shown in FIGS. 1 to 2, the porous metal body 1 has a truncated pyramid-shaped projection 3 with an upper base 5 (projecting portion, that is, a projecting end surface of the projection) having a smaller area than the lower bottom 6. Therefore, a zinc-containing mixture paste (hereinafter also simply referred to as “paste”) can easily enter the protrusions 3 and the paste filling rate during application can be improved. Since the upper bottom side opening 8 provided in each projection 3 has a polygonal shape (for example, the upper bottom side opening 8 has a quadrangular shape), the upper bottom side opening 8 is widened so that the filling amount and the filling property of the paste can be increased. Can be improved. In FIG. 1, x indicates the length that the upper base 5 (see FIG. 2) occupies in the horizontal direction in FIG. 1, and y indicates the length that the lower base 6 (see FIG. 2) occupies in the horizontal direction in FIG. Show. The openings 8 of the metal porous body 1 shown in FIGS. 1 to 2 are a rectangular pyramid-shaped small concave portion 9 formed in the central portion of the upper base 5 and a lower portion in the central portion of the small concave portion 9. This refers to a portion composed of a cross shuriken-shaped opening 10 punched out toward the bottom 6.

  Further, in the metal porous body 1, since the punching burr 7 is produced from the upper base 5 toward the lower base 6, it is possible to prevent the formation of sharp metal protrusions on the surface of the metal porous body 1. It is possible to avoid the problem that the metal porous body 1 breaks or cannot be uniformly applied by being caught on the doctor blade during continuous application of the paste. And, regarding the thickness dimension (d) of the porous metal body 1 and the height dimension (e) of the punched portion, e / d is preferably 0.3 to 0.9. This is because if the e / d is set as such, the punching burr 7 formed from the upper base 5 to the lower base 6 of the projection 3 is not lowered on the lower base 6 side without reducing the current collection efficiency. It is because it can prevent protruding from the outermost surface.

  As shown below, the porous metal body 1 having the above-described three-dimensional structure has a vertical surface and a plurality of convex portions and concave portions alternately arranged vertically and horizontally on the surface rotating in the opposite direction. It can be manufactured by passing a metal plate through the gap between the pair of embossing rolls. Hereinafter, the surface shape of the embossing roll will be described with reference to FIG. Each convex portion 14 of the pair of embossing rolls 12a and 12b is formed to project downward in a quadrangular pyramid shape, and in the center of the projecting portion 20, a quadrangular pyramid minute concave portion 17 is formed. Yes. Each of the recesses 15 is formed in a shape of a quadrangular pyramid that spreads upward, and in the center of the depression 21 is a cross shuriken shape having four apexes facing the corners of the recess 15 in plan view. The minute convex part 18 which exhibits is projected and formed. The ridge portion connecting each vertex of the minute convex portion 18 and the central projecting vertex portion is formed in a cutting edge shape. The convex and concave portions 14 and 15 have a square shape having a vertical and horizontal dimension of 1 mm × 1 mm in plan view. The minute uneven portions 17 and 18 have a square shape of 0.4 mm × 0.4 mm. Here, the height dimension of the convex part 14 and the depth dimension of the concave part 15 are 0.4 mm, the height dimension of the micro convex part 18 and the depth dimension of the micro concave part 17 are 0.35 mm.

  The convex and concave portions 14 and 15 and the minute concave and convex portions 17 and 18 of the upper and lower embossing rolls 12a and 12b are arranged so as to be different from each other. That is, the concave portion 15 of the lower roll 12b is located at a position facing the convex portion 14 of the upper roll 12a, and similarly, the lower roll 12b is located at a position facing the minute convex portion 18 of the upper roll 12a. The upper and lower embossing rolls 12a and 12b are arranged so that the minute concave portion 17 is located. As a result, the opposing gap between the upper and lower embossing rolls 12a and 12b has a wave-tooth shape in which the upper and lower convex and concave portions 14 and 15 and the minute concave and convex portions 17 and 18 are engaged.

  When the metal plate is fed into the facing gap between the pair of upper and lower embossing rolls 12a and 12b, the truncated pyramid-shaped projections 3 are alternately projected on the front and back surfaces of the metal plate by the upper and lower convex recesses 14 and 15. Formed by embossing. At the same time, a small pyramid-shaped concave portion 9 is formed in each projection 3, and the central portion of the small concave portion 9 is pierced by a minute convex portion 18 to form a cross shuriken-shaped opening 10. A polygonal opening 8 having an opening 10 punched out from the bottom 5 toward the bottom 6 is formed. The small recess 9 has a petal shape in which four petal-like burrs are expanded.

  FIG. 3 is a photograph of the surface of the metal porous body 1 taken from an oblique direction (magnification 20 times) in order to show the unevenness of the surface of the metal porous body 1 obtained by the above method. The body 1 has a grid pattern in which openings 8 having a large number of fine openings (openings 10) are arranged at a fine pitch. Further, it was confirmed that there were no burrs or sharp protrusions on the surface. 1 and 2 are schematic views showing the protrusions 3 formed on both the front and back surfaces of the metal plate (copper plate) 2 and do not accurately reflect the dimensions of each part. .

  The material of the above-mentioned porous metal support is copper, tin, an alloy of copper and zinc (brass), an alloy of copper and tin, a galvanized copper, a tin plated copper, stainless steel Nickel, nickel-plated iron, etc. can be used, especially copper, tin, copper-zinc alloy, copper-tin alloy, copper-zinc-plated, copper-tin-plated, etc. Is preferred. The standard electrode potential of zinc is a low potential of −1.284 V. When a material having a low hydrogen overvoltage such as nickel or iron is used for the support, gas generation from the support increases, This is because the capacity may be reduced or the internal pressure may be increased to cause liquid leakage. However, when a metal having a relatively high hydrogen overvoltage such as zinc, copper, or tin is used, there is no such risk.

  The sheet-like zinc sheet electrode of the present invention is produced, for example, as follows.

  Prepare zinc-containing mixture paste by dispersing zinc, thickener, binder, etc. as active material in water, and apply, fill and dry the resulting zinc-containing mixture paste on the support. By holding the mixture on the support, a sheet-like zinc electrode is produced.

  In the present invention, the composition of the zinc-containing mixture is expressed in terms of mass ratio: zinc: binding component = 100: 0.1 to 4, that is, the total mass ratio of the binding component is 0.1 However, when the binding component is less than the above, the binding property is inferior, so that the zinc-containing mixture is peeled off from the support or the powder falls off. This causes problems such as reduction and obstruction of the discharge reaction. The ratio of the binder component is preferably 0.3 to 1.5%. Furthermore, the polystyrene, styrene copolymer and maleic acid copolymer used as the binder preferably have a total amount of these binders of 0.05 to 2% with respect to zinc, and 0.3 to 1.5%. It is more preferable. By setting the ratio of these binders within the above range, both sufficient binding properties and discharge characteristics can be achieved. Moreover, a thickener can be used as needed if it is in the said range as a total amount of a binder component.

  The sheet-like zinc electrode of the present invention is produced by applying the zinc-containing mixture paste to a support, filling, drying, cutting to a predetermined size, The porosity of the mixture is 40 to 75% by volume ratio. This is because when the porosity of the zinc-containing mixture is lower than the above range, the electrolytic solution has poor permeability and retention, so that the discharge characteristics are deteriorated, particularly in a large current discharge, and when the porosity is higher than the above range. This is because the filling amount decreases and the amount of thickener and binder decreases, so that the viscosity and binding force required for application to the support are lost. Moreover, in order to make the porosity of a sheet-like zinc electrode into the said range, it is a grade which does not perform the rolling after drying or prepares a paste composition and rolls slightly, and as a porosity, it is 55 to 75%. preferable.

  The sheet-like zinc electrode is used, for example, as a negative electrode of an alkaline battery. When an alkaline battery is produced using the sheet-like zinc electrode, for example, a sheet-like manganese dioxide electrode or a nickel electrode is used as the positive electrode. It is done.

  The sheet-like manganese dioxide electrode is produced, for example, as follows. Prepare a paste consisting of manganese dioxide, graphite, thickener, binder, water, and apply the resulting manganese dioxide-containing mixture paste to a nickel foam, fill it, and dry it. The sheet-like manganese dioxide electrode is produced by holding the body and press-molding in that state to adjust the thickness and the like.

  In preparing an alkaline battery, for example, the above-mentioned sheet-like zinc electrode is wound in a spiral shape together with a counter-like sheet-like manganese dioxide electrode via a separator to form a wound structure electrode body, and a metal can together with the electrolyte It is enclosed in a battery to make a battery.

  Examples of the present invention will be described below. However, the present invention is not limited only to these examples, and can be appropriately changed without departing from the spirit of the present invention.

Example 1
In producing the sheet-like zinc electrode, a porous metal body having the following constitution was used as a support.

  That is, as shown in FIG. 1 and FIG. 2, the metal porous body 1 is formed by pressing a metal plate made of copper and having a thickness of 33 μm. A large number of quadrangular pyramid-shaped projections 3 formed so as to protrude are formed. Then, on both the front and back surfaces of this metal plate, a quadrangular pyramid-shaped projection 3 composed of an upper base 5 and a lower base 6 was formed in a grid pattern. Each protrusion 3 is formed in the shape of a regular quadrangular pyramid in which the area of the upper base 5 (protrusion) is smaller than the area of the lower base 6, and the vertical and horizontal length dimensions of the lower base 6 are 1.0 mm. The vertical and horizontal length dimensions were set to 0.6 mm.

  A square hole (opening) 8 having a punching burr 7 toward the lower bottom 6 and having a square shape of the upper bottom opening is formed in the upper base 5 of each projection 3. Specifically, the opening 8 has a quadrangular pyramid-shaped concave portion 9 that is recessed in the central portion of the upper base 5, and a cross shuriken punched out toward the lower base 6 in the central portion of the small concave portion 9. And the opening 10. The small recess 9 has a petal shape in which the four petal-shaped pieces are expanded. The vertical and horizontal dimensions (a · b) of the opening 8 here, that is, the vertical and horizontal dimensions of the small concave portion 9 are 0.4 mm × 0.4 mm.

The porous metal body 1 used as a support for the sheet-like zinc electrode in Example 1 has a thickness dimension d of 0.37 mm including the protrusions 3 on the front and back surfaces, as shown in FIG. The height dimension e of the punched part defined by the flat part 5 and the lower end part of the burr 7 was 0.2 mm, and e / d was 0.55. Moreover, the unit mass of the metal porous body 1 after protrusion formation was 315 g / m < ² >.

  The zinc-containing mixture paste was prepared as shown below. That is, 100 parts by mass of zinc having a particle size of 75 μm or less prepared by a gas atomization method, 12.5 parts by mass of a 4% carboxymethylcellulose solution, 1.25 parts by mass of a 50% styrene butadiene rubber dispersion, and 14 parts by mass of water are mixed to form zinc. A containing mixture paste was prepared. The zinc used was zinc containing 150 ppm of bismuth, 500 ppm of indium, and 30 ppm of aluminum and having an average particle diameter of 50 μm. In this zinc-containing mixture, the mass ratio of zinc as an active material, carboxymethyl cellulose as a thickener, and styrene butadiene rubber as a binder is zinc: carboxymethyl cellulose: styrene butadiene rubber = 100: 0.5: 0.625. Met.

  This zinc-containing mixture paste was applied to both surfaces of the support and passed through a blade having a spacing of 0.5 mm to form a coated product having a thickness of 0.6 mm. The coated material was dried at 70 ° C. for 1 hour, and then cut into a width of 36 mm and a length of 37 mm to produce a sheet-like zinc electrode having a theoretical capacity of 1200 mAh.

Subsequently, the manganese dioxide sheet electrode was produced as follows. First, 100 parts by mass of electrolytic manganese dioxide, 6 parts by mass of graphite, 5 parts by mass of 4% carboxymethylcellulose solution, 40 parts by mass of water, and 1 part by mass of 60% polytetrafluoroethylene dispersion were mixed to prepare a manganese dioxide-containing mixture paste. Prepared. Next, this manganese dioxide-containing mixture paste was applied and filled into a 400 g / m ² nickel foam having a thickness of 1.25 mm to obtain a coated product. The coated material was dried at 80 ° C. for 1 hour, and then pressure-molded to form a sheet, which was cut into a width of 36 mm and a length of 56 mm to produce a sheet-shaped manganese dioxide electrode having a theoretical capacity of 1140 mAh.

  The sheet-like zinc electrode and the sheet-like manganese dioxide electrode are respectively used as a negative electrode and a positive electrode, and these are wound through a separator made of a polypropylene nonwoven fabric, and the obtained wound electrode body is a bottomed cylindrical battery. After being inserted into the can, an electrolytic solution (32% aqueous potassium hydroxide solution containing 2.3% zinc oxide and 150 ppm indium hydroxide) was injected, and then the opening of the battery can was sealed, as shown in FIG. A AAA alkaline battery having a structure was prepared.

  Here, the battery shown in FIG. 5 will be described. First, from the relationship between the reference numeral and the member name, 31 is a positive electrode, 32 is a negative electrode, 33 is a separator, 34 is an electrode body with a wound structure, 35 is a battery can, 36 is an annular gasket, 37 is a battery lid, 38 is a terminal plate, 39 is a sealing plate, 40 is a metal spring, 41 is a valve body, 42 is a positive electrode lead body, 43 is an insulator, and 44 is an insulator.

  The positive electrode 31 is composed of a sheet-like manganese dioxide electrode having the above-described configuration. In FIG. 7, the nickel foam used as a support for the production is not shown, but is shown as a single one. Further, the negative electrode 32 is composed of a sheet-like zinc electrode having the above-described configuration. In FIG. 7, the metal porous body having a specific structure used as a support for its production is not shown, but is shown as a single one. ing. The separator 33 is made of a polypropylene non-woven fabric as described above. The positive electrode 31 and the negative electrode 32 are overlapped via the separator 33 and are wound in a spiral shape to form a battery can 35 as a wound electrode body 34. And an insulator 44 is disposed on the top thereof. Further, an insulator 43 is disposed at the bottom of the battery can 35 prior to the insertion of the electrode body 34 having the winding structure. Although not shown in FIG. 5, the outermost peripheral portion of the positive electrode 31 contacts the inner wall of the battery can 35, whereby the battery can 35 functions as a positive electrode terminal.

  The annular gasket 36 is made of nylon 66, the battery lid 37 is composed of a terminal plate 38 and a sealing plate 39, and the opening of the battery can 35 is sealed with the battery lid 37 or the like. That is, after inserting the wound electrode body 34, the insulator 43, the insulator 44, etc. into the battery can 35, an annular groove 35a whose bottom protrudes toward the inner peripheral side in the vicinity of the opening end of the battery can 35. The annular gasket 36 and the battery lid 37 are disposed in the opening of the battery can 35 by supporting the lower part of the annular gasket 36 by the inner peripheral side protruding portion of the groove 35a, and the tip of the groove 35a of the battery can 35 is formed. This is tightened inward to seal the opening of the battery can 35. The terminal plate 38 is provided with a gas discharge port 38 a, the sealing plate 39 is provided with a gas detection port 39 a, and a metal spring 40 and a valve body 41 are disposed between the terminal plate 38 and the sealing plate 39. ing. And the outer peripheral part of the sealing board 39 is bend | folded, the outer peripheral part of the terminal board 38 is inserted | pinched, and the terminal board 38 and the sealing board 39 are fixed.

  In this battery, the valve element 41 closes the gas detection port 39a by the pressing force of the metal spring 40 under normal circumstances, so that the inside of the battery is kept sealed, but gas is generated inside the battery. When the internal pressure of the battery rises abnormally, the metal spring 40 contracts to create a gap between the valve body 41 and the gas detection port 39a, and the gas inside the battery is discharged from the gas detection port 39a and the gas discharge port. When the battery internal pressure decreases and the battery internal pressure returns to normal, the metal spring 40 is restored to the original state, and the valve element 41 is restored again by the pressing force. The gas detection port 39a is closed to keep the inside of the battery in a sealed structure.

  The lead body 42 of the negative electrode 32 is made of copper, and although not shown in FIG. 5, one end thereof is spot welded to the winding end portion of the support of the negative electrode 31, and the other end is the sealing plate 39. The terminal plate 38 can function as a negative electrode terminal by contact with the sealing plate 39.

  Here, in the battery of Example 1, the sheet-like zinc electrode used as the negative electrode 32 will be described with reference to FIG. 6. The sheet-like zinc electrode 50 is formed on the support 51 made of the specific metal porous body. It is produced by applying, filling, and drying the containing mixture paste. In FIG. 6, the zinc containing mixture paste is dried and shown as the zinc containing mixture 52. Then, because the electrolyte solution contains indium hydroxide, a zinc alloy coating 53 containing indium is formed on the surface of the support 51 and the surface of the zinc-containing mixture 52. In FIG. 6, the zinc alloy coating 53 containing indium is formed on both the surface of the support 51 and the surface of the zinc-containing mixture 52, but the surface of the support 51 is illustrated. In some cases, the zinc-containing mixture 52 covers and a zinc alloy coating 53 containing indium is formed on the surface of the zinc-containing mixture 52.

Comparative Example 1
A single-size alkaline battery was fabricated in the same manner as in Example 1 except that a sheet-like zinc electrode was formed using a zinc plate and a sheet-like zinc electrode made of the zinc plate was used. The thickness of the sheet-like zinc electrode was 0.3 mm, the porosity of the zinc layer was of course 0%, and the theoretical capacity was 2150 mAh.

Comparative Example 2
The same as in Example 1 except that the mass ratio of zinc and carboxymethyl cellulose as a thickener to styrene butadiene rubber as a binder was changed to zinc: carboxymethyl cellulose: styrene butadiene rubber = 100: 0.02: 0.02. A sheet-like zinc electrode was prepared, and an AAA alkaline battery was prepared in the same manner as in Example 1 except that the sheet-like zinc electrode was used. The thickness of the sheet-like zinc electrode was 0.5 mm, the porosity of the zinc-containing mixture was 62%, and the theoretical capacity was 800 mAh.

Comparative Example 3
A sheet-like zinc electrode was prepared in the same manner as in Example 1 except that the mass ratio of zinc, carboxymethyl cellulose, and styrene butadiene rubber was changed to zinc: carboxymethyl cellulose: styrene butadiene rubber = 100: 2.5: 2.5. A AAA alkaline battery was produced in the same manner as in Example 1 except that the sheet-like zinc electrode was used. The thickness of the sheet-like zinc electrode was 0.6 mm, the porosity of the zinc-containing mixture was 64%, and the theoretical capacity was 1100 mAh.

Comparative Example 4
A sheet-like zinc electrode was prepared in the same manner as in Example 1 except that the blade interval when applying the zinc-containing mixture paste to the support was 1.0 mm, and the electrode thickness was 0.6 mm by performing a rolling process. A AAA alkaline battery was produced in the same manner as in Example 1 except that the sheet-like zinc electrode was used. The porosity of the zinc-containing mixture of this sheet-like zinc electrode was 15%, and the theoretical capacity was 2050 mAh.

Comparative Example 5
As a binder component, a gel-like zinc-containing mixture containing polyacrylic acid and sodium polyacrylate in a mass ratio of 0.5% with respect to zinc was prepared. Next, a commercially available alkaline battery having a so-called inside-out structure is obtained by filling the gap inside the positive electrode formed with a manganese dioxide-containing mixture in a ring shape with the gel mixture through a cup-shaped separator to form a negative electrode. A similar AAA alkaline battery was produced. The theoretical capacity of the negative electrode of this battery was 1280 mAh.

  Table 1 shows the structure of the zinc-containing mixture of the negative electrodes of the batteries of Example 1 and Comparative Examples 1 to 5. In Table 1, “styrene butadiene rubber” is represented by “SBR”, “carboxymethyl cellulose” is represented by “CMC”, and “polyacrylic acid” is represented by “PAA” because of space limitations. “Sodium polyacrylate” is indicated by “PAS”.

  Further, the pulse discharge characteristics and 0.5 A discharge characteristics of the batteries of Example 1 and Comparative Examples 1 to 5 were examined. The results are shown in Table 2. In addition, the measuring method of the said pulse discharge characteristic and 0.5A discharge characteristic is as follows.

Pulse discharge characteristics:
For each of the batteries of Example 1 and Comparative Examples 1 to 5, 10 batteries were prepared, and a 0.350 A pulse current was passed for 10 seconds at an interval of 1 minute, and a 0.350 A pulse current flowed. Measure the pulse discharge time required for the voltage at that time to drop to 1.0 V or less, and determine the average value of the 10 pulses. Load characteristics, particularly large current discharge characteristics, are evaluated based on the pulse discharge characteristics.

0.5A discharge characteristics:
For each of the batteries of Example 1 and Comparative Examples 1 to 5, 10 batteries were prepared separately from those used for the measurement of the pulse discharge characteristics, and the batteries were continuously discharged at a constant current of 0.5 A. The discharge capacity required for the voltage to drop to 1.0 V or less is measured, 10 average values are obtained, and the ratio of the discharge capacity to the theoretical capacity of the negative electrode is obtained as the utilization factor. The load characteristic is evaluated based on the 0.5 A discharge characteristic.

  As shown in Table 2, in Example 1, both the pulse discharge characteristic and the 0.5 A discharge characteristic have higher numerical values indicating characteristics than those of Comparative Examples 1 to 5, and the battery of Example 1 is Compared with the batteries of Comparative Examples 1 to 5, both the pulse discharge characteristics and the 0.5 A discharge characteristics were excellent, and the large current discharge characteristics were excellent.

  On the other hand, the battery of Comparative Example 1 does not use a support, and the zinc plate itself is a sheet-like zinc electrode, so the theoretical capacity is large, but the permeability of the electrolyte is poor and the discharge reaction does not proceed easily. Furthermore, since zinc which is an active material disappears, sufficient current collection cannot be obtained, so that the large current discharge characteristics are poor.

  Further, in the battery of Comparative Example 2, the amount of thickener and binder in the zinc-containing mixture was less than the range specified in the present invention, so that the viscosity was low and powdering occurred, so the filling amount, that is, the theoretical capacity was Both the pulse discharge characteristics and the 0.5 A discharge characteristics were poor.

  In the battery of Comparative Example 3, the amount of the thickener and the binder in the zinc-containing mixture was larger than the range specified in the present invention, so that the discharge reaction was inhibited and the large current discharge characteristics were deteriorated.

  In the battery of Comparative Example 4, since the sheet-like zinc electrode is compressed, the theoretical capacity and the filling capacity are large, but the permeability of the electrolytic solution is inferior and the discharge reaction is difficult to proceed, and the discharge characteristics are the same as in Comparative Example 1. Declined. Moreover, since the battery of Comparative Example 5 does not use the sheet-like zinc electrode as in Example 1 for the negative electrode, all of the pulse discharge characteristics, the discharge capacity, and the utilization rate are inferior to those of the battery of Example 1. In particular, the discharge time in the pulse discharge was only 60% of the battery of Example 1, and the large current discharge characteristics were inferior.

It is a vertical side view which shows the metal porous body used as a support body of a sheet-like zinc electrode in Example 1 of this invention. 2 is an enlarged plan view of a porous metal body used as a support for a sheet-like zinc electrode in Example 1. FIG. In order to show the uneven | corrugated state of the metal porous body used as a support body of a sheet-like zinc electrode in Example 1, it is the photograph which image | photographed the surface of the metal porous body from the diagonal direction (magnification 20 times). The embossing roll used in manufacture of the metal porous body used as a support body of a sheet-like zinc electrode in this invention is shown, (a) is the one part enlarged plan view, (b) is A- of (a). It is A sectional view. 1 is a longitudinal sectional view schematically showing an alkaline battery of Example 1. FIG. 3 is a cross-sectional view schematically showing a main part of a sheet-like zinc electrode used as a negative electrode of an alkaline battery of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal porous body 3 Protrusion 5 Upper base 6 Lower base 8 Opening part 9 Small recessed part 10 Opening 12 Embossing roll 14 Convex part 15 Concave part 17 Small recessed part 18 Minute convex part 31 Positive electrode 32 Negative electrode 33 Separator 50 Sheet-like zinc electrode 51 Support body 52 Zinc-containing mixture 53 Zinc alloy coating containing indium

Claims (8)

A sheet-like zinc electrode having a support containing a zinc-containing mixture, wherein the zinc-containing mixture is selected from at least zinc powder, polystyrene, a styrene copolymer, and a maleic acid copolymer. At least one binder, and the mass ratio of the whole binder component including the binder in the zinc-containing mixture is 0.1 to 4% with respect to the zinc powder, and the zinc A sheet-like zinc electrode having a porosity of 40 to 75% of the contained mixture. The total amount of polystyrene, styrene-based copolymer and maleic acid-based copolymer in the zinc-containing mixture is 0.05 to 2% with respect to the zinc powder. Sheet zinc electrode. The sheet-like zinc electrode according to claim 1 or 2, wherein the zinc-containing mixture contains at least one selected from a styrene butadiene rubber, a styrene maleic acid copolymer and a styrene acrylic acid copolymer as a binder. The sheet-like zinc electrode according to any one of claims 1 to 3, comprising carboxymethylcellulose as the binding component. The support has a plurality of protrusions formed so as to alternately protrude on the front and back of the metal plate, and each protrusion has a truncated pyramid whose area of the upper base (protruding portion) is smaller than that of the lower base The upper bottom of each protrusion is formed with a polygonal opening in a plan view having an opening punched out from the upper bottom toward the lower bottom, and the upper bottom on the surface side. The metal porous body in which 0.3 <e / d <0.9 is established, where d is the distance between the upper surface and the bottom of the back surface in the vertical direction, and e is the height of the punched portion. The sheet-like zinc electrode according to claim 1, comprising: The sheet-like zinc electrode according to any one of claims 1 to 4, wherein the support is any one of a metal foil, a punching metal, an expanded metal, and a metal foam. The sheet-like zinc electrode according to any one of claims 1 to 6, wherein a material of the support is any one of copper, tin, an alloy of copper and zinc, and an alloy of copper and tin. An alkaline battery using the sheet-like zinc electrode according to claim 1 as a negative electrode.

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