JP2013182843A - Flat alkaline battery and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat alkaline battery which has heavy and light load discharge characteristics, and achieves good productivity and a method of manufacturing the battery.SOLUTION: The flat alkaline battery of the invention comprises: a positive electrode composed of a compact of a positive electrode mixture; a negative electrode including zinc or zinc alloy particles; a separator; and an alkaline electrolyte, which are encased in a battery container including an exterior can, an aperture-sealing plate and a resin gasket. The positive electrode mixture contains a complex including manganese dioxide, graphite and alkali metal hydroxide, and a silver-nickel complex oxide, provided that the content of the graphite is 5-10 mass%. The flat alkaline battery can be manufactured by a method of manufacturing a flat alkaline battery according to the invention, which comprises the steps of: pressing a mixture of manganese dioxide, graphite and aqueous solution of alkali metal hydroxide into a sheet-like material; pulverizing the sheet-like material to form a complex; mixing the complex with silver-nickel complex oxide to prepare a positive electrode mixture; and compacting the positive electrode mixture.

Description

  The present invention relates to a flat alkaline battery excellent in heavy load discharge characteristics, light load discharge characteristics and productivity, and a method for manufacturing the same.

  In recent years, flat alkaline batteries such as button-shaped and coin-shaped batteries have been used for a wide range of applications, including power supplies for electronic devices such as electronic toys. For example, discharge with a large current is required in a short period of time. Application to a use that requires heavy load discharge is also being studied.

  In an alkaline battery, a positive electrode active material such as manganese dioxide, a conductive material such as graphite, and a positive electrode mixture containing a binder are generally used for the positive electrode. It is known that, for example, the content of the conductive auxiliary in the positive electrode mixture may be increased in order to increase the resistance.

  However, graphite and the like used as a conductive aid are bulky compared to manganese dioxide and the like, and increasing the content of the conductive aid in the positive electrode mixture greatly reduces the fluidity of the positive electrode mixture. . In order to industrially produce a molded product of a positive electrode mixture of a flat alkaline battery, a process of continuously introducing a powdered positive electrode mixture into a molding machine using a hopper or the like, Since the fluidity of the positive electrode mixture is lowered due to the continuous formation, it is impossible to continuously produce a molded body of the positive electrode mixture, and the productivity of the flat alkaline battery is greatly impaired.

  In addition, as described above, graphite and the like are bulky compared to manganese dioxide and the like, and therefore, when the content of the conductive additive in the positive electrode mixture is increased, a large volume of the positive electrode mixture is used as the conductive auxiliary agent. Therefore, it becomes necessary to greatly reduce the amount of the positive electrode active material in the positive electrode mixture, and there is a problem that the capacity of the battery is impaired. For example, in the case of a cylindrical alkaline battery in which a cylindrical positive electrode mixture molded body is used and the battery volume is relatively large, the content of the positive electrode active material in the positive electrode mixture is greatly reduced. It is also possible to increase the content of the conductive auxiliary without any problem. On the other hand, a flat alkaline battery generally has a shape that is very small and has no capacity in the battery, and the shape of the molded body of the positive electrode mixture is usually a pellet. For this reason, the above-mentioned problem due to an increase in the content of the conductive additive in the positive electrode mixture can be prominent.

  Under such circumstances, there is also a proposal to try to avoid the above problems by using silver-nickel composite oxide (silver nickelite) instead of carbon material such as graphite as the conductive additive of the positive electrode mixture. (Patent Document 1).

JP-A-8-171903

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a flat alkaline battery excellent in heavy load discharge characteristics, light load discharge characteristics and productivity, and a method for manufacturing the same. .

  The flat alkaline battery of the present invention that has achieved the above object comprises a positive electrode made of a positive electrode mixture, a negative electrode containing zinc particles or zinc alloy particles, a separator and an alkaline electrolyte, an outer can, a sealing plate, A flat alkaline battery housed in a battery container made of a resin gasket, wherein the positive electrode mixture comprises a composite containing manganese dioxide, graphite and an alkali metal hydroxide, and a silver-nickel composite oxide. The graphite content is 5 to 10% by mass.

  Further, the method for producing a flat alkaline battery of the present invention comprises a positive electrode made of a positive electrode mixture, a negative electrode containing zinc particles or zinc alloy particles, a separator, and an alkaline electrolyte, an outer can, a sealing plate, and a resin product. A method for producing a flat alkaline battery accommodated in a battery container comprising a gasket, wherein a mixture of manganese dioxide, graphite and an aqueous solution of an alkali metal hydroxide having a concentration of 45% by mass or more is pressed. A sheet-like material, and pulverizing the sheet-like material to form a composite containing manganese dioxide, graphite, and an alkali metal hydroxide; and mixing the composite and the silver-nickel composite oxide And a step of preparing a positive electrode mixture having a graphite content of 5 to 10% by mass and a step of forming the positive electrode mixture to form a formed body of the positive electrode mixture. .

  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.

  ADVANTAGE OF THE INVENTION According to this invention, the flat alkaline battery excellent in the heavy load discharge characteristic, the light load discharge characteristic, and productivity, and its manufacturing method can be provided.

It is a side view which represents 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 represents typically the other example of the flat alkaline battery of this invention.

  The flat alkaline battery of the present invention contains a composite containing manganese dioxide, graphite and an alkali metal hydroxide (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.) and a silver-nickel composite oxide. It has the molded object formed with the positive mix which does.

  As described above, if the graphite content in the positive electrode mixture is increased in order to increase the heavy load discharge characteristics of the flat alkaline battery, the fluidity of the positive electrode mixture is lowered and the continuous production of the molded body of the positive electrode mixture is possible. This makes it difficult to cause a reduction in the productivity of the molded body, and hence the productivity of the flat alkaline battery.

  Therefore, in the present invention, a molded body of a positive electrode mixture formed using a composite containing manganese dioxide, graphite, and an alkali metal hydroxide is used. Since the positive electrode mixture containing the composite can maintain high fluidity even if the graphite content is increased, for example, a powdered positive electrode mixture is continuously formed by using a hopper. Therefore, it is possible to increase the productivity of the molded body of the positive electrode mixture, and thus the productivity of the flat alkaline battery.

  Further, by using a composite containing manganese dioxide, graphite, and an alkali metal hydroxide, it becomes possible to increase the dispersibility of graphite in the molded body of the positive electrode mixture, and further, forming the positive electrode mixture. Since the body contains an alkali metal hydroxide inside the battery, the amount of alkaline electrolyte retained in the positive electrode mixture molded body is increased. Heavy load discharge characteristics can be enhanced while maintaining high discharge characteristics. And since the molded object of the positive mix which concerns on this invention is formed by the positive mix containing the silver-nickel composite oxide which can function as a conductive support agent with the said composite, this silver-nickel composite The heavy load discharge characteristics of the flat alkaline battery are also improved by the action of the oxide.

  In the flat alkaline battery of the present invention, these heavy load discharge characteristics improving action by the respective components of the positive electrode mixture functions in combination to ensure excellent heavy load discharge characteristics and light load discharge characteristics. it can.

  Further, the alkali metal hydroxide contained in the molded product of the positive electrode mixture according to the present invention has an effect of increasing the strength of the composite, and further, it is considered that crystal growth occurs inside the molded product. The strength of the increases. In addition, the silver-nickel composite oxide contained in the molded body of the positive electrode mixture according to the present invention also has an effect of increasing the strength of the molded body. Therefore, since the molded product of the positive electrode mixture according to the present invention has high productivity, the productivity of the flat alkaline battery of the present invention is improved also by these actions.

  In the positive electrode mixture according to the flat alkaline battery of the present invention, the graphite content is 5% by mass or more from the viewpoint of enhancing the heavy load discharge characteristics of the battery. As described above, since graphite is bulky, for example, to obtain a molded body of a positive electrode mixture having the same size as that used in conventional flat alkaline batteries, while having such a high content. Is difficult, and it is necessary to greatly reduce the amount of manganese dioxide contained in the molded body of the positive electrode mixture, which may cause a decrease in capacity. However, in the flat alkaline battery of the present invention, since graphite is once combined with manganese dioxide or the like and then used for forming a molded body of the positive electrode mixture, graphite is reduced while suppressing the weight loss of manganese dioxide as much as possible. Even with such a high content, an increase in the size of the molded body of the positive electrode mixture can be suppressed. Therefore, in the flat alkaline battery of the present invention, the content of graphite in the positive electrode mixture is increased as described above to improve the heavy load discharge characteristics and suppress the decrease in light load discharge characteristics (capacity decrease). It is possible.

  However, if the amount of graphite in the positive electrode mixture is too large, for example, the content of manganese dioxide, which is the positive electrode active material, decreases, which may cause a reduction in battery capacity. Therefore, the content of graphite in the positive electrode mixture is 10% by mass or less.

  In the flat alkaline battery of the present invention, graphite is contained in the positive electrode mixture by a composite formed together with manganese dioxide or an alkali metal hydroxide.

  Further, in the positive electrode mixture according to the flat alkaline battery of the present invention, as described above, the silver-nickel composite oxide increases the conductivity of the molded body of the positive electrode mixture as a conductive additive, and the heavy load discharge characteristics of the battery This contributes to improvement, and also contributes to the improvement of the strength of the positive electrode material mixture. Furthermore, 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 produced reaction precipitate is separated from the reaction solution, and the collected reaction precipitate is washed with water, dried, pulverized as necessary, etc., and the silver-nickel composite oxidation represented by the above general formula. Get things.

  In the positive electrode mixture according to the flat alkaline battery of the present invention, the content of the silver-nickel composite oxide is preferably 3.0% by mass or more from the viewpoint of ensuring the above-described effect by its use. It is more preferable that it is 4.0 mass% or more. However, if the amount of the silver-nickel composite oxide in the positive electrode mixture is too large, the cost of the battery is increased, so that the productivity improvement effect 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.

  The composite constituting the positive electrode mixture according to the flat alkaline battery of the present invention is prepared by mixing, for example, manganese dioxide, graphite, and an aqueous solution of an alkali metal hydroxide, and pressing the mixture to obtain a sheet. It can be obtained by pulverizing the sheet.

  It is preferable to use an alkali metal hydroxide aqueous solution having a concentration of 45% by mass or more of the alkali metal hydroxide used for preparing the composite. By using such a high-concentration alkali metal hydroxide aqueous solution, the binding property of each component at the time of forming the composite is improved, and a composite with higher strength can be formed. In addition, if the composite is prepared using an alkali metal hydroxide aqueous solution having a high concentration as described above, the retention of the alkaline electrolyte in the molded body of the positive electrode mixture can be further improved, so that heavy load discharge A flat alkaline battery having better characteristics can be formed.

  More preferably, the alkali metal hydroxide aqueous solution used in the preparation of the composite is a potassium hydroxide aqueous solution. Therefore, the alkali metal hydroxide contained in the composite is more preferably potassium hydroxide.

  In the case of an aqueous solution of an alkali metal hydroxide, for example, potassium hydroxide, the saturation concentration at room temperature is about 50% by mass. Therefore, when an aqueous solution having a higher concentration is used, It is desirable to perform temperature control during production. Usually, preparation of an aqueous solution of a high concentration alkali metal hydroxide is carried out under heated conditions in order to enhance solubility, but a high concentration aqueous solution exceeding the saturation concentration at room temperature is prepared and used. When the composite is produced by using the composite, it is preferable that the components of the composite are mixed under temperature conditions where the aqueous solution does not reach a saturated concentration. Specifically, the preparation of an aqueous solution of an alkali metal hydroxide and the mixing of the components of the composite using the same are preferably performed at 35 ° C. or higher, and are also performed at 70 ° C. or lower. It is preferable.

  However, if the concentration of the alkali metal hydroxide in the aqueous solution of the alkali metal hydroxide is too high, it becomes difficult to sufficiently dissolve even if the temperature is raised as described above. Therefore, the concentration of the alkali metal hydroxide in the aqueous solution of the alkali metal hydroxide is preferably 65% by mass or less.

  In addition, the aqueous solution of the alkali metal hydroxide used for preparation of the composite can have the same components as the alkaline electrolyte of the flat alkaline battery. Specifically, for example, an aqueous solution of an alkali metal hydroxide used for producing the composite may contain zinc oxide or the like.

  There is no restriction | limiting in particular about the mixing method of each structural component which concerns on preparation of the said composite body, For example, a well-known batch type mixer (kneader) etc. can be used. Moreover, there is no restriction | limiting in particular also about the method of pressing the mixture of each structural component, and making it into a sheet-like thing, For example, a roll press machine etc. can be used.

  It is preferable to classify the pulverized product of the sheet-like material, thereby obtaining a composite having a desired particle size distribution.

  In the composite, the graphite content is preferably 6% by mass or more, and is preferably 8.5% by mass or less. By setting the graphite content in the composite to the above values, it becomes easy to adjust the graphite content in the positive electrode mixture to the above values.

  In addition, in the preparation of the composite, the amount of alkali metal hydroxide aqueous solution added to all materials used for composite preparation (manganese dioxide, graphite and alkali metal hydroxide aqueous solutions, and more The amount of the alkali metal hydroxide aqueous solution added at the time of producing the composite is the same in the following), and is preferably 3% by mass or more. The binding property of the body can be further increased. However, if the amount of the alkali metal hydroxide aqueous solution used in the preparation of the composite is too large, the amount of water in all the materials used for the preparation of the composite increases, making it difficult to manufacture the composite. There is a risk of becoming. Therefore, in the production of the composite, the amount of the alkali metal hydroxide aqueous solution added is preferably 12% by mass or less based on the total material used for the production of the composite.

  The composite may contain a binder as necessary. Specific examples of the binder include carboxymethyl cellulose, methyl cellulose, polyacrylate, polytetrafluoroethylene (PTFE), polyethylene, and the like. The binder content in the composite is preferably, for example, 0.1 to 4% by mass.

  In addition, it is preferable that content of the manganese dioxide in the said composite is 30-95 mass%.

  The composite can be mixed with a silver-nickel composite oxide to prepare a positive electrode mixture, which can be pressure-molded according to a conventional method to produce a molded body of the positive electrode mixture.

  The negative electrode according to the flat alkaline battery of the present invention contains zinc particles or zinc alloy particles (hereinafter sometimes collectively referred to as “zinc-based particles”), and zinc in these particles is an active material. Acts as 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.

  The alkaline electrolyte for the flat alkaline battery of the present invention includes an alkali metal hydroxide (sodium hydroxide, potassium hydroxide, lithium hydroxide) similar to that used for producing the composite according to the positive electrode mixture. Etc.) is used. The alkaline electrolyte is also preferably an aqueous solution of potassium hydroxide, similar to the one used for producing the composite.

  The concentration of the alkaline electrolyte is, for example, in the case of an aqueous solution of potassium hydroxide, potassium hydroxide 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. It is desirable that the electrolytic solution with excellent conductivity can be obtained by adjusting the concentration of the aqueous solution to such a value.

  In addition to the above-described components, various known additives may be added to the alkaline electrolyte as necessary within the 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 formed of a positive electrode mixture containing a composite containing manganese dioxide, graphite, and an alkali metal hydroxide, and a silver-nickel composite oxide. 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.

  Since the flat alkaline battery of the present invention is excellent in heavy load discharge characteristics, for example, it is suitable for applications requiring discharge with a large current in a short time, and conventionally known flat alkaline batteries The present invention can be applied to the same application as a battery (a flat battery 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
<Preparation of positive electrode>
89.06: 5.24 of electrolytic manganese dioxide, graphite, PTFE powder, and aqueous potassium hydroxide solution (aqueous solution having a potassium hydroxide concentration of 56% by mass and further containing 2.9% by mass of zinc oxide). : 0.2: 5.5 (mass ratio) mixture and press treatment were performed using an open roll. The obtained sheet was pulverized with a roll crusher to obtain a composite containing manganese dioxide, graphite, PTFE, and potassium hydroxide.

The composite: 95.5% by mass and a silver-nickel composite oxide (expressed as Ag _X Ni _{Y 2} O ₂ , X / Y = 1): 4.5% by mass were mixed with a positive electrode mixture ( The graphite content in the positive electrode mixture is 5 mass%), and this positive electrode mixture is pressure-molded into a disk shape with a packing density of 3.5 g / cm ³ , a diameter of 10.88 mm, and a height of 1.85 mm. Thus, a molded body of the positive electrode mixture was produced.

  For the negative electrode, 160 mg of mercury-free zinc particles having a ratio of particles that can pass through a 60-mesh sieve having an average particle diameter of 100% by mass and 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 11.25 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 11 mm and a thickness of 5.2 mm was produced.

Example 2
The ratio of electrolytic manganese dioxide, graphite, PTFE powder, and aqueous potassium hydroxide solution (same as that used in Example 1) was 87.29: 7.01: 0.2: 5.5 (mass). The composite containing manganese dioxide, graphite, PTFE, and potassium hydroxide was obtained in the same manner as in Example 1 except that the ratio was changed to (Ratio).

  Except for using the above composite, a molded product of the positive electrode mixture was produced in the same manner as in Example 1 (the graphite content in the positive electrode mixture was 6.7% by mass). A flat alkaline battery was produced in the same manner as in Example 1 except that was used.

Example 3
The ratio of electrolytic manganese dioxide, graphite, PTFE powder, and aqueous potassium hydroxide solution (same as that used in Example 1) was 83.83: 10.47: 0.2: 5.5 (mass). The composite containing manganese dioxide, graphite, PTFE, and potassium hydroxide was obtained in the same manner as in Example 1 except that the ratio was changed to (Ratio).

  A positive electrode mixture molded body was produced in the same manner as in Example 1 except that the composite was used (the graphite content in the positive electrode mixture was 10% by mass), and this positive electrode mixture molded body was used. A flat alkaline battery was produced in the same manner as in Example 1 except that.

Comparative Example 1
The ratio of electrolytic manganese dioxide, graphite, PTFE powder, and aqueous potassium hydroxide solution (same as that used in Example 1) was 91.16: 3.14: 0.2: 5.5 (mass). The composite containing manganese dioxide, graphite, PTFE, and potassium hydroxide was obtained in the same manner as in Example 1 except that the ratio was changed to (Ratio).

  Except that the composite was used, a positive electrode mixture molded body was prepared in the same manner as in Example 1 (the graphite content in the positive electrode mixture was 3% by mass), and this positive electrode mixture molded body was used. A flat alkaline battery was produced in the same manner as in Example 1 except that.

Comparative Example 2
The ratio of electrolytic manganese dioxide, graphite, PTFE powder, and aqueous potassium hydroxide solution (same as that used in Example 1) was 81.74: 12.56: 0.2: 5.5 (mass). The composite containing manganese dioxide, graphite, PTFE, and potassium hydroxide was obtained in the same manner as in Example 1 except that the ratio was changed to (Ratio).

  A positive electrode mixture molded body was produced in the same manner as in Example 1 except that the above composite was used (the graphite content in the positive electrode mixture was 12% by mass), and this positive electrode mixture molded body was used. A flat alkaline battery was produced in the same manner as in Example 1 except that.

Comparative Example 3
The ratio of electrolytic manganese dioxide, graphite, PTFE powder, and aqueous potassium hydroxide solution (same as that used in Example 1) was 78.6: 15.7: 0.2: 5.5 (mass). The composite containing manganese dioxide, graphite, PTFE, and potassium hydroxide was obtained in the same manner as in Example 1 except that the ratio was changed to (Ratio).

  A positive electrode mixture molded body was produced in the same manner as in Example 1 except that the composite was used (the graphite content in the positive electrode mixture was 15% by mass), and this positive electrode mixture molded body was used. A flat alkaline battery was produced in the same manner as in Example 1 except that.

  About each battery of an Example and a comparative example, the following heavy load discharge characteristic evaluation and light load discharge characteristic evaluation were performed. These results are shown in Table 1.

<Heavy load discharge characteristics evaluation>
For each battery of the example and the comparative example, continuous discharge was performed with a resistance value of 10Ω and a final voltage of 0.8 V, and the time during which discharge could be continued was measured.

<Light load discharge characteristics evaluation>
About each battery of Example and Comparative Example (battery different from that subjected to heavy load discharge characteristics evaluation), discharge was performed with a resistance value of 6.8 kΩ and a final voltage of 1.2 V, and a discharge capacity was obtained.

  As is apparent from Table 1, a composite containing a composite containing manganese dioxide, graphite and an alkali metal hydroxide, and a silver-nickel composite oxide, and formed of a positive electrode mixture having an appropriate graphite content. The flat alkaline batteries of Examples 1 to 3 having the formed body have a long discharge duration at the time of heavy load discharge characteristic evaluation and a large discharge capacity at the light load discharge characteristic evaluation. Discharge characteristics are good.

  On the other hand, the battery of Comparative Example 1 having a molded body formed of a positive electrode mixture having a low graphite content has a short discharge duration at the time of heavy load discharge characteristic evaluation and is inferior in heavy load discharge characteristics. Furthermore, the batteries of Comparative Examples 2 and 3 having a molded body formed of a positive electrode mixture having a high graphite content have a low discharge capacity in light load discharge characteristics evaluation and inferior in light load discharge characteristics.

  Moreover, the productivity evaluation test of a flat alkaline battery and the measurement of the amount of alkaline electrolyte absorbed in the molded body of the positive electrode mixture were performed by the following methods. These results are shown in Table 2.

<Productivity evaluation test>
Except that the concentration of the aqueous potassium hydroxide solution was changed to 45% by mass, a composite containing manganese dioxide, graphite, PTFE, and potassium hydroxide was prepared in the same manner as in Example 1, and this composite was used. Were the same as in Example 1 to obtain a molded body (B) of the positive electrode mixture.

  Further, a composite containing manganese dioxide, graphite and PTFE was prepared in the same manner as in Example 1 except that no potassium hydroxide aqueous solution was used, and the same procedure as in Example 1 was performed except that this composite was used. Thus, a molded body (C) of the positive electrode mixture was obtained.

  The same positive electrode mixture molded body (A) used in the flat alkaline battery of Example 1 and the above positive electrode mixture molded bodies (B) and (C) were placed on a base with a hole of φ10 mm. The strength of these compacts was determined by pressing the central part with a φ1 mm rod and measuring the load when the compacts crack.

<Measurement of Alkaline Electrolyte Absorption Amount of Positive Electrode Mixture>
After measuring the mass of each of the molded bodies (A), (B), and (C) of the positive electrode mixture, 1 in the same alkaline electrolyte as that used in the production of the flat alkaline battery in Example 1. The sample was immersed for a while, taken out from the alkaline electrolyte, and the mass was measured. And about each molded object, the mass before immersion was subtracted from the mass after being immersed in alkaline electrolyte, and alkaline electrolyte absorption amount was calculated | required.

  As shown in Table 2, the positive electrode mixture shaped bodies (A) and (B) formed using a composite that also contains an alkali metal hydroxide use a composite that does not contain an alkali metal hydroxide. Compared to the formed body (C), the strength is high. Therefore, in the production of the flat alkaline battery, when using the molded body (A) or (B) of the positive electrode mixture, compared to the case of using the molded body (C), the molded body of the positive electrode mixture Since the generation of defective products due to breakage or the like can be suppressed, battery productivity can be increased. In addition, the molded body (A) of the positive electrode mixture using the composite prepared by using a higher concentration aqueous solution of the alkali metal hydroxide has higher strength than the molded body (B), It can also be seen that the productivity of the battery can be further increased.

  Furthermore, the molded product (A) and (B) of the positive electrode mixture formed using the composite containing the alkali metal hydroxide is formed using the composite not containing the alkali metal hydroxide. Compared to the body (C), the amount of the alkaline electrolyte absorbed is large, and the amount of the alkaline electrolyte retained in the flat alkaline battery is expected to be larger. Guessed.

  Moreover, the flat alkaline batteries of Examples 4 to 8 below were prepared, and their storage characteristics were evaluated.

Example 4
The same composite containing manganese dioxide, graphite, PTFE and potassium hydroxide as prepared in Example 1: 98.9% by mass, and the same silver-nickel composite oxide used in Example 1: 1 Mass% and iron powder: 0.1 mass% are mixed to make a positive electrode mixture (the graphite content in the positive electrode mixture is 5.2 mass%), and the same procedure as in Example 1 except that this is used. Thus, a molded body of the positive electrode mixture was produced. A flat alkaline battery was produced in the same manner as in Example 1 except that this positive electrode mixture molded body was used.

Example 5
The same composite containing manganese dioxide, graphite, PTFE and potassium hydroxide as prepared in Example 1: 96.9% by mass and the same silver-nickel composite oxide used in Example 1: 3 Mass% and iron powder: 0.1 mass% are mixed to make a positive electrode mixture (the graphite content in the positive electrode mixture is 5.1 mass%), and the same procedure as in Example 1 except that this is used. Thus, a molded body of the positive electrode mixture was produced. A flat alkaline battery was produced in the same manner as in Example 1 except that this positive electrode mixture molded body was used.

Example 6
The same composite containing manganese dioxide, graphite, PTFE and potassium hydroxide as prepared in Example 1: 95.9% by mass, and the same silver-nickel composite oxide used in Example 1: 4 Mass% and iron powder: 0.1 mass% were mixed to make a positive electrode mixture (the graphite content in the positive electrode mixture was 5.0 mass%), and the same procedure as in Example 1 except that this was used. Thus, a molded body of the positive electrode mixture was produced. A flat alkaline battery was produced in the same manner as in Example 1 except that this positive electrode mixture molded body was used.

  Each flat alkaline battery of Examples 4 to 6 was stored for 1 month in an environment of 20 ° C., and then the amount of increase in the thickness of each battery (the height from the outer surface of the outer can to the outer surface of the sealing plate) was measured. did. These results are shown in Table 3.

  The iron powder blended in the positive electrode mixture according to the batteries of Examples 4 to 6 is for accelerating the generation of hydrogen gas in the battery. As shown in Table 3, silver-nickel in the positive electrode mixture In the batteries of Examples 5 and 6 in which the compact oxide was used from the viewpoint of suppressing the generation of hydrogen gas in the battery, the composite oxide content of Example 4 in which the compact was inappropriate. Compared with the battery, the swelling of the battery after storage is suppressed, and the hydrogen gas generated in the battery is absorbed by the silver-nickel composite oxide, so that the increase in the amount of gas in the battery is suppressed. Conceivable.

  Moreover, the molded body of the positive electrode mixture used in the batteries of Examples 5 and 6 is more than the molded body according to the battery of Example 4 using the positive electrode mixture having a lower silver-nickel composite oxide content. Also, the moldability was good.

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

Claims (4)

A flat alkali in which a positive electrode composed of a molded body of a positive electrode mixture, a negative electrode containing zinc particles or zinc alloy particles, a separator and an alkaline electrolyte are contained in a battery container composed of an outer can, a sealing plate and a resin gasket. A battery,
The positive electrode mixture contains a composite containing manganese dioxide, graphite, and an alkali metal hydroxide, and a silver-nickel composite oxide, and the graphite content is 5 to 10% by mass. A flat alkaline battery characterized by   A composite containing manganese dioxide, graphite, and alkali metal hydroxide is obtained by pressing a mixture of manganese dioxide, graphite, and an aqueous solution of alkali metal hydroxide having a concentration of 45% by mass or more into a sheet-like material. The flat alkaline battery according to claim 1, which is obtained by pulverizing the sheet-like material.   3. The flat alkaline battery according to claim 1, 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. A flat alkali in which a positive electrode composed of a molded body of a positive electrode mixture, a negative electrode containing zinc particles or zinc alloy particles, a separator and an alkaline electrolyte are contained in a battery container composed of an outer can, a sealing plate and a resin gasket. A battery manufacturing method comprising:
A mixture of manganese dioxide, graphite, and an aqueous solution of an alkali metal hydroxide having a concentration of 45% by mass or more is pressed into a sheet, and the sheet is pulverized to obtain manganese dioxide, graphite, and alkali metal. Forming a composite comprising a hydroxide of
Mixing the composite and the silver-nickel composite oxide to prepare a positive electrode mixture having a graphite content of 5 to 10% by mass;
And a step of forming the positive electrode mixture to form a molded body of the positive electrode mixture.