JP2013120743A - Flat alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat alkaline battery which has a high capacity, and is excellent in productivity.SOLUTION: The flat alkaline battery comprises a positive electrode composed of a compact of a positive electrode mixture containing at least manganese dioxide, a negative electrode including zinc or zinc alloy particles, a separator, and an alkaline electrolyte, which are all encased in a battery container including an exterior can, an aperture-sealing plate and a resin gasket. The specific surface area of the manganese dioxide contained in the positive electrode mixture is 15-30 m/g. It is preferable that the positive electrode mixture contains silver oxide and/or silver-nickel complex oxide. Also, it is preferable for the flat alkaline battery that the positive electrode mixture compact has an outer peripheral part disposed between an inner surface of the exterior can and the resin gasket.

Description

  The present invention relates to a flat alkaline battery having a high capacity and excellent productivity.

  In recent years, flat-type alkaline batteries such as buttons and coins have been widely used as power sources for electronic devices such as electronic toys. On the other hand, it is also demanded to reduce the manufacturing cost of the battery and increase the productivity.

  As a positive electrode active material of a flat alkaline battery, manganese dioxide and silver oxide are known. Since manganese dioxide is less expensive than silver oxide, it can be used as a positive electrode active material to reduce the manufacturing cost of a flat alkaline battery. On the other hand, manganese dioxide has a smaller capacity per volume than silver oxide. Therefore, in the flat alkaline battery using manganese dioxide as the positive electrode active material, development of a technique for increasing the capacity is required.

  By the way, in the alkaline battery, improvement of its characteristics is also performed by changing the structure of manganese dioxide used for the positive electrode active material. For example, Patent Document 1 proposes an alkaline battery with improved load characteristics by using manganese dioxide having a larger specific surface area than usual as a positive electrode active material. However, it is not easy to increase the capacity of the flat alkaline battery by applying the technique disclosed in Patent Document 1.

JP 2005-322613 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a flat alkaline battery having a high capacity and excellent productivity.

The flat alkaline battery of the present invention that has achieved the above object comprises a positive electrode comprising a molded body of a positive electrode mixture containing at least manganese dioxide, a negative electrode containing zinc particles or zinc alloy particles, a separator, and an alkaline electrolyte. A flat alkaline battery accommodated in a battery container comprising an outer can, a sealing plate and a resin gasket, wherein the specific surface area of manganese dioxide contained in the positive electrode mixture is 15 to 30 m ² / g. It is characterized by.

  In the battery industry, a flat battery with a diameter larger than the height is called a coin-type battery or a button-type battery, but there is a clear gap between the coin-type battery and the button-type battery. There is no difference, and the flat alkaline battery of the present invention includes both coin-type batteries and button-type batteries.

  According to the present invention, a flat alkaline battery having a high capacity and excellent productivity can be provided.

It is a side view which shows typically an example of the flat alkaline battery of this invention. It is principal part sectional drawing of the flat alkaline battery shown in FIG. It is principal part sectional drawing which shows typically the other example of the flat alkaline battery of this invention.

  The positive electrode according to the flat alkaline battery of the present invention is composed of a molded body of a positive electrode mixture, and the positive electrode mixture contains manganese dioxide as a positive electrode active material.

In the present invention, manganese dioxide having a specific surface area of 30 m ² / g or less is used as the manganese dioxide related to the positive electrode mixture. Manganese dioxide used as a positive electrode active material of an alkaline battery usually has a specific surface area of 35 m ² / g, for example, as used in the comparative example (paragraph [0061] Table 1) of Patent Document 1. The degree and the larger. In the flat alkaline battery of the present invention, a battery having a specific surface area smaller than that of manganese dioxide employed in ordinary alkaline batteries is used to increase the capacity per volume of the molded body of the positive electrode mixture, thereby increasing the capacity. I am trying.

However, if the specific surface area of manganese dioxide related to the positive electrode mixture is too small, the reaction area in the manganese dioxide particles decreases, and the reactivity decreases. Therefore, the specific surface area of manganese dioxide according to the positive electrode mixture in the present invention is 15 m ² / g or more, and preferably 25 m ² / g or more.

  The specific surface area of manganese dioxide as used in the present specification is a specific surface area of the surface of manganese dioxide and fine pores, as measured and calculated using the BET equation, which is a theoretical formula for multi-layer adsorption. Specifically, it is a value obtained as a BET specific surface area using a specific surface area measuring device (“Macsorb HM model-1201” manufactured by Mounttech) by a nitrogen adsorption method.

  Manganese dioxide having the specific surface area can be produced, for example, by adjusting electrolysis conditions (such as current value) when synthesizing manganese dioxide by an electrolytic method.

  The content of the manganese dioxide in the positive electrode mixture is preferably 40% by mass or more, and more preferably 45% by mass or more, from the viewpoint of increasing the battery capacity and improving the productivity. As described later, the positive electrode mixture preferably contains a conductive additive, silver oxide, silver-nickel composite oxide, etc. If the amount of the manganese dioxide in the positive electrode mixture is too large, The amount of components other than manganese dioxide decreases, and there is a possibility that the effects of using these cannot be sufficiently ensured. Therefore, the content of the manganese dioxide in the positive electrode mixture is preferably 97% by mass or less, and more preferably 95% by mass or less.

  The positive electrode mixture of the positive electrode according to the present invention preferably contains silver oxide (eg, silver oxide, silver oxide). Similarly to manganese dioxide, silver oxide functions as a positive electrode active material and also functions as a molding agent for a molded body of a positive electrode mixture. Therefore, when the positive electrode mixture contains silver oxide, the shape of the molded body of the positive electrode mixture can be maintained well without using a resin binder described later. May not be contained.

  The silver oxide used for the positive electrode mixture may be, for example, a fine powder having a diameter of 0.1 to 5 μm that is normally distributed. Granules obtained by granulating such fine powder of silver oxide The shape is more preferable. When granular silver oxide is used, the resistance is lower than when it is used in the form of fine powder, so that the load characteristics of the flat alkaline battery can be further improved.

The particle size of the granular silver oxide is preferably 50 μm or more, more preferably 75 μm or more, more preferably 500 μm or less, and even more preferably 300 μm or less. Furthermore, the bulk density of the granular silver oxide is preferably 1.5 g / cm ³ or more, more preferably 1.8 g / cm ³ or more, and preferably 3.5 g / cm ³ or less. More preferably, it is 2.6 g / cm ³ or less. Silver oxide in such a form has better fluidity than powdered ones, improves weighing and formability, lowers resistance and improves reactivity, and thus has better load characteristics. In addition, the individual characteristics of the manufactured positive electrode (and thus the flat alkaline battery) are stabilized. The particle size of granular silver oxide as used herein is determined by measuring the number of particles n and the diameter d of each particle by scattering of laser light using a microtrack particle size distribution meter “9320-X100” manufactured by Honeywell. The calculated number average particle diameter. Further, the bulk density of granular silver oxide referred to in the present specification is determined using a bulk density measuring device by placing a predetermined amount of granular silver oxide in a container in accordance with the bulk density measuring method specified in JIS R 1628. Value.

  In the case where silver oxide is contained in the positive electrode mixture, the content of silver oxide in the positive electrode mixture is preferably 2% by mass or more from the viewpoint of ensuring the above-mentioned effects better by its use. More preferably. However, as described above, silver oxide is more expensive than manganese dioxide. Therefore, if the amount of silver oxide in the positive electrode mixture is excessively increased, the effect of improving battery productivity by using the manganese dioxide is reduced. There is a fear. Therefore, the content of silver oxide in the positive electrode mixture is preferably 45% by mass or less, and more preferably 40% by mass or less.

  Moreover, it is also preferable that the positive electrode mixture of the positive electrode according to the present invention contains a silver-nickel composite oxide. The silver-nickel composite oxide also functions as a molding agent for the molded product of the positive electrode mixture, like silver oxide. Therefore, when the positive electrode mixture contains a silver-nickel composite oxide, the shape of the molded body of the positive electrode mixture can be favorably maintained without using a resin binder described later. May not contain a resin binder.

  The silver-nickel composite oxide has a function of absorbing hydrogen gas. For example, as will be described later, it is preferable to use anhydrous silver type zinc particles and the like used as the negative electrode of the flat alkaline battery from the viewpoint of reducing environmental load, but anhydrous silver type zinc particles and the like In the battery using the battery, hydrogen gas is likely to be generated inside, which may cause the battery to swell. However, in a flat alkaline battery having a positive electrode mixture molded body containing a silver-nickel composite oxide, even when anhydrous silver type zinc particles or the like are used, the hydrogen gas generated inside is silver-nickel composite oxide. Since the matter absorbs, the occurrence of battery swelling due to the hydrogen gas can be well suppressed.

Examples of the silver-nickel composite oxide include those represented by AgNiO ₂ and the general formula Ag _X Ni _Y O ₂ , wherein X / Y is greater than 1 and 1.9 or less. Among these, those represented by the general formula Ag _X Ni _Y O ₂ and having X / Y greater than 1 and 1.9 or less are more preferable. In the silver-nickel composite oxide represented by the above general formula, Ag is excessively incorporated in the crystal than AgNiO ₂ which is widely used as the silver-nickel composite oxide. Therefore, the conductivity and moldability of the positive electrode can be improved as compared with the case of using AgNiO ₂ .

The silver-nickel composite oxide represented by the general formula Ag _X Ni _Y O ₂ and having X / Y greater than 1 and 1.9 or less, for example, oxidizes Ag salt of inorganic acid and Ni salt of inorganic acid. It can manufacture by making it react in basic alkaline aqueous solution.

  Specifically, for example, an Ag salt of an inorganic acid and an Ni salt of an inorganic acid are neutralized with an alkali metal hydroxide in water, and before the neutralization reaction, during the neutralization reaction, or the neutralization reaction After the reaction, an oxidizing agent is added to the reaction solution to carry out an oxidation treatment. It is preferable to add the oxidizing agent a plurality of times before, during or after the neutralization reaction.

Examples of the inorganic acid Ag salt include silver hydrochloride, silver nitrate, silver sulfate, and silver phosphate. Examples of Ni salts of inorganic acids include nickel hydrochloride, nickel nitrate, nickel sulfate, and nickel phosphate. Further, examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Examples of the oxidizing agent include KMnO ₄ , K ₂ S ₂ O ₈ , NaOCl, Na ₂ S ₂ O ₈ , H ₂ O ₂ , and ozone.

  In the neutralization reaction, it is preferable to increase the alkalinity in the reaction solution. For example, the molar amount of Ag in the Ag salt of the inorganic acid and the molar amount of Ni in the Ni salt of the inorganic acid. The molar amount of the alkali metal hydroxide is preferably about 5 times the total amount. In addition, the amount of the oxidizing agent used is preferably equal to or greater than the oxidation, that is, the valence change of the metal ion, and more preferably about twice the equivalent.

  The temperature during the neutralization reaction and oxidation treatment is preferably, for example, between room temperature and 100 ° C. (more preferably 30 to 50 ° C.). The neutralization reaction and the oxidation treatment are preferably performed while stirring the reaction solution.

  After the oxidation treatment, the generated reaction precipitate is separated from the reaction solution, and the collected reaction precipitate is washed with water, dried, crushed as necessary, etc., and the silver-nickel composite represented by the above general formula Obtain an oxide.

  When the silver-nickel composite oxide is contained in the positive electrode mixture, the content of the silver-nickel composite oxide in the positive electrode mixture is 2% by mass or more from the viewpoint of ensuring the above-described effects better. It is preferable that the content is 3% by mass or more. However, if the amount of the silver-nickel composite oxide in the positive electrode mixture is too large, the effect of increasing the battery capacity by using the manganese dioxide may be reduced. Therefore, the content of the silver-nickel composite oxide in the positive electrode mixture is preferably 5% by mass or less, and more preferably 4.5% by mass or less.

  In addition, the positive electrode mixture of the positive electrode according to the present invention preferably contains a conductive additive. Examples of the conductive aid include carbonaceous materials such as carbon black, graphite, and graphite.

  The content of the conductive additive in the positive electrode mixture is preferably 1% by mass or more. In addition, by increasing the amount of the conductive assistant in the positive electrode mixture as described above, the conductivity in the positive electrode (positive electrode mixture molded body) can be improved, and the load characteristics of the battery can be further improved. Therefore, the content of the conductive additive in the positive electrode mixture is more preferably 3% by mass or more, and further preferably 4% by mass or more. However, for example, when a carbonaceous material is used as the conductive assistant, its bulk density is small. Therefore, if these are added in a large amount to the positive electrode mixture, it becomes difficult to increase the filling amount of the positive electrode active material. Therefore, the content of the conductive additive in the positive electrode mixture is preferably 7% by mass or less, and more preferably 6% by mass or less.

  In addition, the positive electrode mixture of the positive electrode according to the present invention may contain a resin binder from the viewpoint of maintaining the shape of the molded body. Specific examples of the resin binder include polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, and the like.

  When using a resin binder for the positive electrode mixture, the content of the resin binder in the positive electrode mixture is preferably 2 to 7% by mass, for example.

  As described above, when the positive electrode mixture contains silver oxide or silver-nickel composite oxide, the positive electrode mixture may contain a resin binder, but silver oxide or silver-nickel composite oxide However, since it functions as a molding agent for the molded body, the positive electrode mixture may not contain a resin binder. The positive electrode mixture of the positive electrode according to the present invention more preferably contains both silver oxide and silver-nickel composite oxide.

The density of the molded body of the positive electrode mixture is preferably 3.2 g / cm ³ or more, and more preferably 3.3 g / cm ³ or more. By setting the density of the molded body of the positive electrode mixture as described above, the capacity of the battery can be increased by filling the positive electrode active material more. However, as the density of the molded body of the positive electrode mixture increases, the voids in the molded body of the positive electrode mixture may decrease and the alkaline electrolyte may not easily permeate, which may reduce the effect of increasing the battery capacity. In addition, since the molded body of the positive electrode mixture having a high density becomes difficult to mold itself, the density of the molded body of the positive electrode mixture is preferably 7.0 g / cm ³ or less, and 6.0 g / cm More preferably, it is not more than cm ³ .

  The density of the molded body of the positive electrode mixture is determined from the area of the molded body of the positive electrode mixture calculated using a projector and the thickness of the molded body of the positive electrode mixture measured using a micrometer. The volume of the molded body is calculated, and the volume is obtained using this volume and the mass of the molded body of the positive electrode mixture that has been separately measured. In the case of a molded body of a positive electrode mixture in a flat alkaline battery, the positive electrode mixture molded body is taken out from the battery, and if necessary, the alkaline electrolyte component is removed through a process such as washing and drying. The mass of the mixture compact is measured, and the density is determined by the above method.

  The positive electrode can be produced by pressure-molding a positive electrode mixture prepared by mixing the manganese dioxide, which is a positive electrode active material, and the above-described components used as necessary, according to a conventional method.

  In this case, it is more preferable to employ the following manufacturing method. First, the manganese dioxide and the components used as necessary are dry-mixed to prepare a positive electrode mixture, which is pressure-molded according to a conventional method. Next, the obtained molded body is crushed to form a flake or the like, which is further pressure-molded according to a conventional method to obtain a positive electrode. According to such a manufacturing method, the dispersion of the conductive additive in the molded body of the positive electrode mixture can be improved, and a molded body of the high-density positive electrode mixture as described above can be obtained.

  The negative electrode according to the present invention contains zinc particles or zinc alloy particles (hereinafter sometimes collectively referred to as “zinc-based particles”), and zinc in these particles acts as an active material. As an alloy component of the zinc alloy particles, for example, mercury (for example, the content is 1 to 5 mass%), indium (for example, the content is 50 to 500 mass ppm), bismuth (for example, the content is 50 to 500 mass). ppm) and the like (the balance being zinc and inevitable impurities). The zinc-based particles possessed by the negative electrode may be one type alone or two or more types.

  Examples of the zinc-based particles include particles in which the ratio of powder having a particle size of 100 to 200 μm is 50% by volume or more, more preferably 90% by volume or more, in all powders. The volume ratio of the powder having a particle diameter of 100 to 200 μm in the powder of zinc or the like here is measured by the same measuring method and measuring apparatus as the above-mentioned “granular silver oxide” particle diameter measuring method.

  The zinc-based particles used for the negative electrode may have the above-mentioned form, but from the viewpoint of further improving the load characteristics of the battery, for example, among all the particles, those that can pass through a 200 mesh screen. 50% by mass or more, more preferably 75% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. As described above, when the zinc-based particles of the negative electrode are small, the specific surface area of the entire negative electrode can be increased, so that the reaction at the negative electrode can be advanced efficiently, and the load characteristics (particularly heavy load characteristics) of the battery are good. It becomes.

  From the viewpoint of reducing the size of the zinc-based particles possessed by the negative electrode and further improving the reaction efficiency at the negative electrode, the proportion of the zinc-based particles possessed by the negative electrode that can pass through a 330 mesh screen is 30 It is preferably at least 50% by mass, more preferably at least 50% by mass, even more preferably at least 75% by mass, and the proportion of those that can pass through a 440 mesh screen is 20% by mass or more. Preferably, it is 30% by mass or more, and more preferably 50% by mass or more. In addition, since the handleability falls when the size of the zinc-based particle which the negative electrode has is too small, for example, the minimum size of the zinc-based particle which the negative electrode has is desirably about 1 μm.

  The zinc-based particles are more preferably those that do not contain mercury or those that do not contain lead. If it is a battery using such zinc-based particles, for example, when it is used for power supply of an endoscope camera of a type swallowed from the mouth, observed inside the body for a certain period of time, and then discharged out of the body In addition, even when zinc in the battery leaks into the human body, adverse effects on the human body can be minimized, and environmental pollution due to battery disposal can be suppressed.

  The negative electrode includes, for example, a gelling agent (polyacrylic acid soda, carboxymethyl cellulose, etc.) added as necessary in addition to the zinc-based particles, and is configured by adding an alkaline electrolyte thereto. A negative electrode agent (gelled negative electrode) can be applied. The amount of the gelling agent in the negative electrode is preferably 0.5 to 1.5% by mass, for example.

  The negative electrode can also be a non-gelled negative electrode that does not substantially contain the gelling agent as described above (in the case of a non-gelled negative electrode, the alkaline electrolyte present in the vicinity of the zinc-based particles increases). Since it does not matter if it does not stick, “substantially does not contain a gelling agent” means that it may be contained to the extent that it does not affect the viscosity of the alkaline electrolyte). In the case of a gelled negative electrode, an alkaline electrolyte is present together with a gelling agent in the vicinity of the zinc-based particles, but this alkaline electrolyte is thickened by the action of the gelling agent, The movement, and hence the movement of ions in the alkaline electrolyte, is suppressed. For this reason, the reaction rate at the negative electrode is suppressed, which is considered to impede improvement of the heavy load characteristics of the battery. In contrast, the negative electrode is made non-gelled, and the reaction rate at the negative electrode is increased by keeping the ion migration rate in the alkaline electrolyte high without increasing the viscosity of the alkaline electrolyte present in the vicinity of the zinc-based particles. Thus, the heavy load characteristics can be improved.

  In the flat alkaline battery of the present invention, an electrolytic solution composed of an alkaline aqueous solution, that is, an alkaline electrolytic solution is used. As the alkali, alkali metal hydroxides (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.) are preferably used, and potassium hydroxide is particularly preferred. For example, in the case of an aqueous solution of potassium hydroxide, the concentration of the electrolytic solution is 20% by mass or more, more preferably 30% by mass or more, and 40% by mass or less, more preferably 38% by mass or less. Desirably, by adjusting the concentration of the aqueous solution to such a value, an electrolytic solution having excellent conductivity can be obtained.

  In addition to the above-described components, various known additives may be added to the alkaline electrolyte as necessary within a range not impairing the effects of the present invention. For example, zinc oxide may be added in order to prevent corrosion (oxidation) of the zinc-based particles used for the negative electrode.

  The separator in the flat alkaline battery of the present invention is not particularly limited. For example, a nonwoven fabric mainly composed of vinylon and rayon, a vinylon / rayon nonwoven fabric (vinylon / rayon mixed paper), a polyamide nonwoven fabric, a polyolefin / rayon nonwoven fabric, a vinylon paper, Vinylon linter pulp paper, vinylon mercerized pulp paper, or the like can be used. A hydrophilic microporous polyolefin film (microporous polyethylene film, microporous polypropylene film, etc.), cellophane film, and liquid absorbing layer (electrolyte holding layer) such as vinylon / rayon mixed paper were stacked. It is good also as a separator.

  The structure of the flat alkaline battery of the present invention will be described with reference to the drawings. FIG. 1 is a side view schematically showing an example of a flat alkaline battery of the present invention, and FIG. 2 is a cross-sectional view of the main part of FIG.

  The flat alkaline battery shown in FIGS. 1 and 2 is made of an annular resin having a sealing plate 2 having a negative electrode 4 embedded in an opening of an outer can 1 having a positive electrode 3 and a separator 5 embedded therein. The opening end of the outer can 1 is tightened inward through the gasket 6, and the resin gasket 6 contacts the sealing plate 2, thereby sealing the opening of the outer can 1. The inside of the battery has a sealed structure. That is, the flat alkaline battery shown in FIGS. 1 and 2 includes the positive electrode 3, the negative electrode 4, and the separator 5 in the space (sealed space) in the battery container including the outer can 1, the sealing plate 2, and the resin gasket 6. A power generation element is loaded, and an alkaline electrolyte (not shown) is further injected. The outer can 1 also serves as a positive terminal, and the sealing plate 2 also serves as a negative terminal. As described above, the positive electrode 3 is a molded body of a positive electrode mixture containing manganese dioxide, which is an active material, and the above-described components used as necessary. Further, as described above, the negative electrode 4 may be a gelled negative electrode containing zinc-based particles, or the zinc-based particles may be present as particles.

  For the outer can 1, for example, iron plated with nickel or stainless steel can be used.

  As the sealing plate 2, for example, the surface in contact with the negative electrode 4 is made of a copper alloy such as copper or brass, the main body portion is made of stainless steel, and the outer surface side, that is, the surface opposite to the surface in contact with the negative electrode 4. Is preferably composed of nickel. In this sealing plate 2, the surface in contact with the negative electrode 4 is made of copper or a copper alloy in order to suppress formation of a local battery with zinc. It is not essential to be composed of nickel, it may be composed of other materials, and the surface in contact with the negative electrode 4 may not be copper or a copper alloy as long as it does not form a local battery with zinc. As the resin gasket 6, for example, a material made of nylon 66 or the like is recommended.

  The shape of the flat alkaline battery of the present invention in plan view may be a circle or a polygon such as a quadrangle (square or rectangle). In the case of a polygon, the corner may be curved.

  FIG. 3 is a cross-sectional view of a principal part schematically showing another example of the flat alkaline battery of the present invention. The flat alkaline battery of FIG. 3 employs a so-called bottom structure in which the outer peripheral portion of the positive electrode (positive electrode mixture molded body) 3 is disposed between the inner bottom surface of the outer can 1 and the resin gasket 6. .

  The flat alkaline battery shown in FIG. 2 employs a so-called centering structure in which the resin gasket 6 reaches the bottom of the outer can 1. 6 occupied volume is large. In contrast, the flat alkaline battery shown in FIG. 3 employs a bottom structure to increase the filling amount of the positive electrode (filling amount of the positive electrode active material) in the battery, thereby further increasing the capacity. Can be achieved.

  The flat alkaline battery of the present invention can be applied to the same applications as conventionally known flat alkaline batteries (flat batteries using manganese dioxide or silver oxide as a positive electrode active material).

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
65% by mass of manganese dioxide having a BET specific surface area of 26 m ² / g, 33% by mass of granulated primary silver oxide, and 2% by mass of graphite are dry-mixed to form a positive electrode mixture, and 120 mg of this positive electrode mixture is filled. A molded body of the positive electrode mixture was produced by pressure molding into a disk shape having a density of 3.95 g / cm ³ and a diameter of 6.3 mm and a height of 0.98 mm.

  As the negative electrode, 37 mg of mercury-free zinc particles having a ratio of particles that can pass through a 60-mesh sieve having a mass ratio of 100% by mass and an average particle size of 150 μm were used.

  As the alkaline electrolyte, a 36% by mass potassium hydroxide aqueous solution in which 5% by mass of zinc oxide was dissolved was used. Moreover, the positive electrode can was produced using SUS319J1 (chromium content 23 mass%). Furthermore, the negative electrode terminal plate was produced using a copper-stainless steel-nickel clad plate. Furthermore, “YG9132” from Yuasa Membrane System Co., Ltd. was used as the separator. This separator is formed by laminating a cellophane film having a thickness of 20 μm and a graft film having a thickness of 30 μm. The graft film has a structure in which a polyethylene main chain is graft copolymerized with acrylic acid. It is composed of a polymer. Further, a vinylon-rayon mixed paper having a thickness of 200 μm was used as the electrolytic solution holding layer. The separator and the electrolyte solution holding layer were used by punching into a circle having a diameter of 6.30 mm.

  Using the molded body of the positive electrode mixture, the negative electrode, the alkaline electrolyte, the outer can, the sealing plate, the separator and the electrolytic solution holding layer, and further using the annular gasket made of nylon 66, the structure shown in FIG. A flat alkaline battery having a thickness of 6.8 mm and a thickness of 2.6 mm was produced.

Example 2
65% by mass of manganese dioxide, 29% by mass of granulated primary silver oxide, 4% by mass of silver-nickel composite oxide (AgNiO ₂ ), and 2% by mass of graphite were dry-mixed to form a positive electrode mixture. A molded body of the positive electrode mixture was produced by pressure-molding 120 mg of the mixture into a disk shape having a packing density of 3.88 g / cm ³ , a diameter of 6.3 mm, and a height of 0.99 mm.

  Then, a flat alkaline battery was produced in the same manner as in Example 1 except that the positive electrode mixture formed body was used.

Comparative Example 1
A molded product of the positive electrode mixture was produced in the same manner as in Example 1 except that the manganese dioxide used for the positive electrode mixture was changed to one having a BET specific surface area of 35 m ² / g. A flat alkaline battery was produced in the same manner as in Example 1 except that was used.

Comparative Example 2
A molded product of the positive electrode mixture was produced in the same manner as in Example 1 except that the manganese dioxide used for the positive electrode mixture was changed to one having a BET specific surface area of 13 m ² / g. A flat alkaline battery was produced in the same manner as in Example 1 except that was used.

  For each of the 10 flat alkaline batteries of Examples 1 and 2 and Comparative Examples 1 and 2, the discharge capacity was measured by discharging at 20 ° C. with a resistance value of 15 kΩ and a final voltage of 1.2 V. And in each Example and the comparative example, the average value of the discharge capacity in 10 batteries was calculated.

  These results are shown in Table 1. In Table 1, the minimum value and the maximum value of the discharge capacity in 10 batteries of each example and comparative example are also shown.

  As shown in Table 1, the flat alkaline batteries of Examples 1 and 2 having a molded body formed of a positive electrode mixture containing manganese dioxide having an appropriate specific surface area are positive electrodes containing manganese dioxide having an inappropriate specific surface area. Compared with the batteries of Comparative Examples 1 and 2 having a molded body formed of a mixture, the discharge capacity is high.

  In addition, the battery of Example 1 can achieve the high capacity as described above while reducing the amount of expensive silver oxide used, has a low production cost, and has high productivity.

DESCRIPTION OF SYMBOLS 1 Exterior can 2 Sealing plate 3 Positive electrode (molded body of positive electrode mixture)
4 Negative electrode 5 Separator

Claims (6)

A positive electrode made of a molded product of a positive electrode mixture containing at least manganese dioxide, a negative electrode containing zinc particles or zinc alloy particles, a separator, and an alkaline electrolyte are accommodated in a battery container made of an outer can, a sealing plate, and a resin gasket. A flat alkaline battery,
The flat alkaline battery, wherein the specific surface area of manganese dioxide contained in the positive electrode mixture is 15 to 30 m ² / g.   The flat alkaline battery according to claim 1, wherein the content of manganese dioxide in the positive electrode mixture is 40% by mass or more.   The flat alkaline battery according to claim 1 or 2, wherein the positive electrode mixture further contains silver oxide.   The flat alkaline battery according to claim 1, wherein the positive electrode mixture further contains a silver-nickel composite oxide. The flat alkaline battery according to any one of claims 1 to 4, wherein the density of the molded body of the positive electrode mixture is 3.2 to 7.0 g / cm ³ . The flat alkaline battery according to any one of claims 1 to 5, wherein an outer peripheral portion of a molded body of the positive electrode mixture is disposed between the inner inner surface of the outer can and the resin gasket.

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