JP7315381B2 - alkaline battery - Google Patents

Description

The present invention relates to alkaline batteries, and more particularly to alkaline batteries containing gelled zinc anodes.

In recent years, electronic devices such as digital cameras and video cameras are becoming more sophisticated and smaller, and there is a growing demand for improved performance of alkaline batteries used as power sources for such electronic devices, especially high-load discharge performance.

In alkaline batteries, the following gelled zinc negative electrode is often used as the negative electrode. This gelled zinc negative electrode is manufactured, for example, as follows.

First, molten zinc alloy is sprayed in air to prepare zinc alloy particles, and the obtained zinc alloy particles are collected to obtain zinc alloy powder. Furthermore, a gel electrolyte prepared by mixing an alkaline electrolyte and a gelling agent such as sodium polyacrylate is prepared. Then, the above-described zinc alloy powder is put into the above-described gel electrolyte and mixed. As a result, a gelled zinc negative electrode in which the zinc alloy powder is dispersed in the gelled electrolyte is obtained.

In an alkaline battery containing this gelled zinc negative electrode, a coating of zinc oxide having a high electric resistance value is formed on the zinc surface as discharge progresses. Therefore, alkaline batteries cannot maintain good electrical conductivity, and it is difficult to improve high-load discharge performance. Furthermore, since the surface of the zinc alloy is blocked by the zinc oxide film, the zinc alloy cannot come into contact with the electrolyte, inhibiting the diffusion of zinc ions and increasing the polarization. Ultimately, there is the problem that discharge becomes impossible, and the life of the battery ends prematurely.

By the way, before alkaline batteries were put into practical use, when manganese dry batteries were the mainstream dry batteries, studies were made to improve the high-load discharge performance of ammonium chloride type manganese dry batteries using ammonium chloride (NH ₄ Cl) as the electrolyte, and as a result, zinc chloride type manganese dry batteries using zinc chloride (ZnCl ₂ ) as the electrolyte were developed (see Non-Patent Document 1, etc.).

Here, the ammonium chloride type manganese dry battery and the zinc chloride type manganese dry battery will be specifically described.

First, the discharge reaction of the ammonium chloride type manganese dry battery is as follows.
Zinc (Zn) in the negative electrode dissolves to become zinc ions (Zn ²⁺ ). Manganese dioxide (MnO ₂ ) of the positive electrode reacts with hydrogen ions (H ⁺ ) in an aqueous solution of ammonium chloride (NH ₄ Cl) to become manganese oxyhydroxide (MnOOH) and produce ammonia (NH ₃ ). As the battery reaction continues, ammonia (NH ₃ ) generated at the positive electrode reacts with zinc ions (Zn ²⁺ ) dissolved from the negative electrode to form and precipitate Zn(NH ₃ ) ₂ Cl ₂ , a salt of zinc and ammonium. A crystallized precipitate of Zn(NH ₃ ) ₂ Cl ₂ begins to form on the side of the positive electrode mixture facing the zinc can. When this precipitate forms, it hinders the diffusion of zinc ions (Zn ²⁺ ) that have dissolved from the negative electrode, and the concentration of zinc ions (Zn ²⁺ ) near the zinc can increases, further advancing the precipitation of the product. Such a phenomenon becomes more conspicuous when high-load discharge is performed. In other words, when the precipitation of Zn(NH ₃ ) ₂ Cl ₂ as a reaction product increases at the interface between the positive electrode mixture and the zinc can, there arises a problem that the polarization increases and the discharge operating voltage decreases.

On the other hand, the discharge product of the zinc chloride manganese dry battery is _ZnCl2.4Zn (OH) ₂ . The discharge reaction of the positive electrode is the same as in the ammonium chloride type manganese dry battery, and MnOOH is produced. Zn ²⁺ dissolved at the negative electrode reacts with OH ⁻ ions and Cl ⁻ ions to form ZnCl ₂ 4Zn(OH) ₂ . Even if ZnCl ₂ 4 Zn(OH) ₂ precipitates on the surface of the mixture, unlike Zn(NH ₃ ) ₂ Cl ₂ , which is a reaction product that strongly grows crystals in the ammonium chloride electrolyte, Zn ^{2+ ions do not hinder the diffusion of Zn 2+} ions into the mixture. Therefore, since zinc ions are diffused into the positive electrode material mixture and precipitated, a sharp increase in polarization unlike the ammonium chloride electrolytic solution does not occur even during high-load discharge.

Therefore, in order to improve the high-load discharge performance, we investigated whether the above-described technique could be applied to alkaline batteries.

Written by Kazumasa Yoshida, National Museum of Nature and Science, Industrial Technology History Data Information Center ed. "Technology Systematization Survey Report Vol.

However, when zinc chloride (ZnCl ₂ ) is applied to an alkaline battery, there is a problem that the positive electrode can is corroded and the gas pressure inside the positive electrode can increases, leading to leakage.

Therefore, there is a demand for the development of an alkaline battery capable of suppressing corrosion of the positive electrode can, suppressing an increase in gas pressure in the positive electrode can, and improving discharge performance under high load.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an alkaline battery which is excellent in high-load discharge performance.

In order to achieve the above object, the alkaline battery of the present invention includes a positive electrode can also serving as a positive electrode terminal, a positive electrode in contact with the inner surface of the positive electrode can, a separator disposed inside the positive electrode and in contact with the positive electrode and holding an alkaline electrolyte, and a negative electrode disposed inside the separator and in contact with the separator, wherein the negative electrode is a gelled zinc negative electrode containing a gelled zinc negative electrode mixture, and the gelled zinc negative electrode mixture contains chloride. characterized by

Moreover, it is preferable that the chloride is potassium chloride.

Moreover, it is preferable that the chloride is contained in an amount of 7.4% by weight or more with respect to the weight of the gelled zinc anode mixture.

本発明のアルカリ電池は、正極端子を兼ねる正極缶と、前記正極缶の内面と接する正極と、前記正極よりも内側に配設され且つ前記正極と接しており、アルカリ電解液を保持しているセパレータと、前記セパレータよりも内側に配設され且つ前記セパレータと接している負極とを備えており、前記負極は、ゲル状亜鉛負極合剤を含むゲル状亜鉛負極であり、前記ゲル状亜鉛負極合剤は、塩化物を含んでいることから、放電の際の生成物としてＺｎＯの代わりにＺｎＣｌ _２・４Ｚｎ（ＯＨ） _２が生じるので、負極の導電性を良好な状態に維持できる。 Therefore, according to the present invention, it is possible to provide an alkaline battery with excellent high-load discharge performance.

1 is a cross-sectional view showing an alkaline battery according to an embodiment of the invention; FIG.

An alkaline battery 1 (hereinafter referred to as battery 1) according to an embodiment of the present invention will be described below with reference to the drawings. The battery 1 to which the present invention is applied is, for example, a JIS standard LR6 type (AA or AA type) alkaline manganese battery as shown in FIG.

As shown in FIG. 1, the battery 1 includes a bottomed cylindrical battery can (hereinafter referred to as a positive electrode can 11) whose upper end is open. The positive electrode can 11 is made of metal and has electrical conductivity. A convex positive terminal portion 12 protruding outward is integrally formed on the bottom wall of the positive electrode can 11 , and this positive electrode terminal portion 12 functions as a positive electrode terminal of the battery 1 .

A sealing member 16 is fixed to the opening 14 of the positive electrode can 11 . The sealing body 16 includes a negative electrode cap 32 that serves as a negative terminal, a negative electrode current collector 31 fixed to the center of the negative electrode cap 32 , and a sealing gasket 35 combined with the negative electrode cap 32 . The sealant 16 is fixed to the opening 14 of the positive electrode can 11 by abutting the sealing gasket 35 on the inner side of the opening 14 of the positive electrode can 11 and crimping the opening rim 18 of the positive electrode can 11 in this state. That is, the sealing member 16 hermetically closes the opening 14 of the positive electrode can 11 .

Here, the negative electrode cap 32 includes a disk-shaped top wall 34, a peripheral wall 36 extending from the peripheral edge of the top wall 34 toward the inside of the battery 1, and a flange portion 38 formed by folding the tip of the peripheral wall 36. A gas vent hole 40 is provided at a predetermined position near the boundary with the flange portion 38 in the peripheral wall 36 .

The negative electrode current collector 31 is a rod-shaped member made of metal, and has a columnar body portion 42, a head portion 44 located on the base end side of the body portion 42 and having a larger diameter than the body portion 42, and a tapered portion 46 located on the tip side of the body portion 42 and tapered from the body portion 42. The head portion 44 of the negative electrode current collector 31 is welded to the inner surface of the top wall 34 of the negative electrode cap 32 . For example, brass is used as the material of the negative electrode current collector 31 . This negative electrode current collector 31 is inserted into a gelled zinc negative electrode 24 as the negative electrode 2 to be described later, and electrically connects the negative electrode 2 (gelled zinc negative electrode 24) and a negative electrode terminal (negative electrode cap 32).

The sealing gasket 35 has a cylindrical central cylindrical body 48 and an annular collar portion 50 extending from the periphery of the central cylindrical body 48 . The sealing gasket 35 is made of an insulating resin material such as polyamide resin. The body portion 42 of the negative electrode current collector 31 is fitted into the central through hole 52 of the central cylindrical body 48 . Airtightness is maintained between the main body portion 42 of the negative electrode current collector 31 and the central through hole 52 of the central cylindrical body 48 . As shown in FIG. 1, the outer peripheral edge of the flange 50 is folded back so as to be interposed between the opening 14 of the positive electrode can 11 and the flange 38 of the negative electrode cap 32, forming an annular outer peripheral wall 54. The outer peripheral wall 54 of the flange 50 hermetically closes the opening 14 of the positive electrode can 11 and electrically insulates between the positive electrode can 11 and the negative electrode cap 32 . A thin portion 56 is provided between the central cylindrical body 48 and the outer peripheral wall 54 in the collar portion 50 . This thin portion 56 is broken when gas is abnormally generated in the positive electrode can 11 and the pressure inside the positive electrode can 11 rises. As a result, the abnormally generated gas is discharged to the outside of the positive electrode can 11, preventing the battery 1 from exploding. That is, the sealing gasket 35 also functions as a safety valve for the battery 1 .

Inside the cathode can 11 , a plurality of hollow cylindrical cathode mixtures 21 are accommodated so as to be in contact with the inner peripheral surface of the cathode can 11 .

Here, a conductive film is formed on the inner wall of the positive electrode can 11 for the purpose of promoting electrical connection between the positive electrode mixture 21 and the positive electrode can 11 . This conductive film is obtained by applying a mixture of graphite dispersed in an appropriate solvent to the inner wall of the positive electrode can 11 and drying it.

The positive electrode mixture 21 is manufactured, for example, as follows.
First, particles of manganese dioxide as a positive electrode active material, particles of graphite as a conductive material, an alkaline electrolyte, a binder and, if necessary, a positive electrode additive are prepared and mixed to obtain a mixture. Next, the obtained mixture is processed through processes such as rolling, pulverization, granulation, and classification, and then the powder of the obtained mixture is compressed into a hollow cylindrical shape to produce the positive electrode mixture 21. In the molded positive electrode material mixture 21, the positive electrode active material particles and the conductive material particles are bound to each other, and the alkaline electrolyte exists at the grain boundaries between the particles.

A plurality of cylindrical positive electrode mixtures 21 are manufactured, and these positive electrode mixtures 21 are stacked in a direction along the cylindrical axis of the positive electrode can 11 so as to be coaxial with the cylindrical axis of the positive electrode can 11 and are press-fitted into the positive electrode can 11. In the battery 1 of the present embodiment, as shown in FIG. 1, three positive electrode mixtures 21 are press-fitted into the positive electrode can 11, and these three positive electrode mixtures 21 cooperate to form the positive electrode 3.

As shown in FIG. 1, a bottomed cylindrical separator 22 is provided on the inner peripheral side of the laminated positive electrode mixture 21 . The separator 22 electrically isolates the positive electrode mixture 21 described above from the gelled zinc negative electrode mixture 23 described later, and also functions to retain an alkaline electrolyte. This separator 22 is made of a material that is excellent in electrical insulation, liquid retention and alkali resistance. Such a separator 22 is not particularly limited, but it is preferable to use, for example, a separator used in general alkaline batteries. Here, specifically, it is preferable to use a separator made of cellulose fiber and polyvinyl alcohol fiber.

As shown in FIG. 1, the center space 58 of the separator 22 is filled with a gelled zinc negative electrode mixture 23 as a negative electrode mixture. That is, in the battery 1 , the gelled zinc negative electrode mixture 23 forms the gelled zinc negative electrode 24 as the negative electrode 2 .

The gelled zinc negative electrode mixture 23 described above contains a zinc alloy as a negative electrode active material, a chloride, an alkaline electrolyte, and a gelling agent. This gelled zinc anode mixture 23 is formed by adding and mixing zinc alloy powder and chloride to a gelled electrolyte prepared by mixing a gelling agent and an alkaline electrolyte.

Here, the gelling agent is not particularly limited, and for example, polyacrylic acid or sodium polyacrylate is used. Also, the alkaline electrolyte is not particularly limited, and for example, a KOH aqueous solution or an alkaline aqueous solution obtained by adding ZnO to a KOH aqueous solution is used.

As for the zinc alloy, it is preferable to employ a zinc alloy that is used as a negative electrode active material for alkaline batteries. Here, a procedure for preparing zinc alloy powder, which is an aggregate of zinc alloy particles, will be described. First, metal raw materials are weighed and mixed so as to obtain a zinc alloy having a predetermined composition, and the mixture is melted in, for example, an induction melting furnace. A gas atomization method or a centrifugal atomization method is applied to the obtained molten metal to produce zinc alloy particles. Then, the obtained zinc alloy particles are collected and classified to obtain zinc alloy powder having a desired particle size. At this time, it is preferable to use, in addition to zinc, bismuth, aluminum, indium, or the like as raw materials constituting the zinc alloy.

Here, it is preferable to employ a zinc alloy containing 0.005 to 0.02% by mass of bismuth, 0.0035 to 0.015% by mass of aluminum, and 0.01 to 0.06% by mass of indium. A zinc alloy with this composition has the effect of suppressing the generation of hydrogen gas. Indium and bismuth also improve the discharge performance of the battery. When such a zinc alloy containing bismuth, aluminum and indium is used as the negative electrode active material, the self-dissolution rate of the zinc alloy in the alkaline electrolyte becomes a moderate value, the generation of hydrogen gas is also suppressed, and it is effective in preventing leakage from the inside of the battery.

The gelled zinc anode mixture 23 of the present invention is characterized by adding a chloride. The chloride is not particularly limited, and for example, it is preferable to use a chloride that is a compound of chlorine and an element that is more positive than chlorine. Such chlorides include, for example, MCl _x (where M represents any element of Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba, and x represents a number of 1 or 2). More preferably, potassium chloride (KCl) is used.

The role played by this chloride is as a source of chloride ions (Cl ⁻ ). Specifically, the presence of chlorine ions (Cl ⁻ ) produces ZnCl ₂ .4Zn(OH) ₂ as a discharge product, thereby suppressing the increase in polarization of the battery 1 .

The chemical reaction at the negative electrode of a typical alkaline battery is represented by the following formula (I).
Zn+2OH ⁻ →ZnO+H ₂ O+e ⁻ (I)

In the negative electrode of an alkaline battery, a zinc oxide film having a high electric resistance value is formed on the zinc surface by a discharge reaction, and the surface of the zinc alloy is clogged with this zinc oxide film. As a result, discharging becomes impossible, and the life of the battery ends prematurely.

Here, when a chloride such as KCl is added to the negative electrode, ZnCl ₂ .4Zn(OH) ₂ is produced as a discharge product due to the action of Cl ⁻ . ZnCl ₂ .4Zn(OH) ₂ is not as high in electrical resistance as ZnO and can maintain good electrical conductivity, which contributes to improving the high-load discharge performance of alkaline batteries. ZnCl ₂ .4Zn(OH) ₂ is less likely to inhibit the diffusion of zinc ions than ZnO, and can suppress an increase in polarization.

Furthermore, by adding KCl only to the negative electrode, corrosion of the positive electrode can 11 can be suppressed. In battery 1 , negative electrode 2 is positioned in the center of battery 1 . That is, a positive electrode mixture 21 is arranged inside the positive electrode can 11, a separator 22 is arranged inside the positive electrode mixture 21, a gelled zinc negative electrode mixture 23 as the negative electrode 2 is arranged inside the separator 22, and KCl is contained in the gelled zinc negative electrode mixture 23. For this reason, ZnCl ₂ .4Zn(OH) ₂ generated by the action of KCl is present in the central negative electrode 2 of the battery 1 . Therefore, there is a gap from the positive electrode can 11, and corrosion of the positive electrode can 11 is suppressed. In addition, KCl is less soluble in water than ZnCl ₂ , so it is difficult to diffuse inside the battery and tends to remain in the negative electrode 2 . Therefore, ZnCl ₂ .4Zn(OH) ₂ as a discharge product generated by the action of Cl ⁻ of KCl is likely to be generated in the central negative electrode 2 of the battery 1 . From this also, it can be said that corrosion of the positive electrode can 11 can be suppressed.

Next, the procedure for assembling the battery 1 will be described.
First, a hollow cylindrical positive electrode mixture 21 is press-fitted into the prepared positive electrode can 11 . After that, the bottomed cylindrical separator 22 is inserted into the hollow portion of the positive electrode mixture 21 . Then, an alkaline electrolyte is supplied into the separator 22 to permeate the separator 22 with the alkaline electrolyte. Here, the alkaline electrolyte with which the separator 22 is impregnated is not particularly limited, and for example, a KOH aqueous solution is used.

Next, the gelatinous zinc anode mixture 23 prepared as described above is injected into the central space portion 58 of the separator 22 . As a result, the central space 58 of the separator 22 is filled with the gelled zinc negative electrode mixture 23 to form the gelled zinc negative electrode 24 .

Next, the negative electrode current collector 31 of the sealing member 16 is inserted into the gelled zinc negative electrode 24 . When the flange portion 50 of the sealing gasket 35 comes into contact with the upper end of the separator 22 and the outer peripheral wall 54 of the sealing gasket 35 reaches the vicinity of the opening 14 of the positive electrode can 11, the insertion of the negative electrode current collector 31 is stopped. At this time, the sealing member 16 is arranged at a predetermined position of the opening 14 of the positive electrode can 11 . In this state, the opening edge 18 of the positive electrode can 11 is crimped. As a result, the opening 14 of the positive electrode can 11 is hermetically closed, and the battery 1 is formed.

The battery 1 has a so-called inside-out structure, in which the battery can (positive electrode can 11) is on the positive electrode side and the sealing member 16 is on the negative electrode side. The positive electrode mixture 21 , the separator 22 and the gelled zinc negative electrode mixture 23 constitute the power generation element 20 of the battery 1 .

[Example]
1. Production of Alkaline Manganese Battery ( Comparative Example 1)

(1) Production of positive electrode mixture 90.80 parts by weight of electrolytic manganese dioxide was mixed with 5.96 parts by weight of graphite, 2.83 parts by weight of an alkaline electrolyte (40% by mass KOH aqueous solution), 0.18 parts by weight of polyacrylic acid, and 0.02 parts by weight of silica. Next, the mixture formed into a mass by rolling was put into a crusher and finely pulverized to obtain a raw material powder. Next, the obtained raw material powder was fed into a granulator to bond the particles constituting the raw material powder to form particles having a certain size or larger. The raw material powder that has undergone such a granulation process is put into a classifier and classified to obtain a raw material powder in which particles of 60 mesh or less are 30% or less. 0.20 parts by weight of calcium stearate was mixed with the classified raw material powder, and calcium stearate was applied to the surface of the particles in the raw material powder. A positive electrode mixture 21 was obtained by compressing such a raw material powder into a cylindrical shape. A plurality of cylindrical positive electrode mixtures 21 were manufactured.

(2) Production of gelled zinc negative electrode mixture Zn, Bi, Al, and In were weighed to prepare a mixture containing these in the following formula (II) by mass ratio.
Zn:Bi:Al:In=99.9:0.012:0.010:0.020 (II)

The resulting mixture was melted in a high-frequency induction melting furnace in an argon gas atmosphere to obtain a molten zinc alloy. Next, the molten metal was poured into a crucible called a tundish, and a high-pressure gas was blown to the molten metal flowing out from a hole provided in the bottom of the crucible to scatter and solidify the molten metal. A zinc alloy powder was thus obtained.

The obtained zinc alloy powder was classified to prepare a zinc alloy powder containing 30% by mass of particles having a particle size of 75 μm or less.

Next, a powder of potassium chloride (KCl) was prepared as a chloride.
Furthermore, polyacrylic acid and crosslinked sodium polyacrylate were prepared as gelling agents, and an alkaline electrolyte in which 2.6% by mass of ZnO was added to an aqueous solution containing 35% by mass of KOH was prepared as an alkaline electrolyte.

Next, the polyacrylic acid, the crosslinked sodium polyacrylate, and the alkaline electrolyte prepared as described above were mixed to prepare a gelled electrolyte, and zinc alloy powder and KCl powder were further mixed into the gelled electrolyte to prepare a gelled zinc anode mixture 23. At this time, the zinc alloy powder was 64.38 parts by weight, the KCl was 3.20 parts by weight, the polyacrylic acid was 0.35 parts by weight, the crosslinked sodium polyacrylate was 0.19 parts by weight, and the alkaline electrolyte was 31.87 parts by weight. Here, the content of KCl is 3.2% by weight with respect to the weight of the gelled zinc anode mixture.

(3) Assembly of Alkaline Manganese Battery Three cylindrical positive electrode mixtures 21 were press-fitted into the positive electrode can 11 for a JIS standard LR6 (AA or AA) alkaline manganese battery. As the positive electrode can 11, a bottomed cylindrical can obtained by pressing a nickel-plated steel plate, having an opening 14 at the upper end and a convex positive electrode terminal portion 12 on the bottom wall was used. The positive electrode mixture is in contact with the inner wall of the positive electrode can 11 , and the positive electrode can 11 and the positive electrode terminal portion 12 are at the same potential as the positive electrode mixture 21 . A conductive film containing graphite is formed on the inner wall of the positive electrode can 11 .

Next, the bottomed cylindrical separator 22 was inserted into the central space 60 formed by the three positive electrode mixtures 21 . The separator 22 was made of cellulose fiber and polyvinyl alcohol fiber, and had a thickness of 0.12 mm (basis weight of 39.0 g/m ² ).

Next, an alkaline electrolyte was supplied to the separator 22 to impregnate the separator 22 with the alkaline electrolyte. The alkaline electrolyte used here was an aqueous solution containing 37% by mass of KOH.

Next, the central space 58 of the separator 22 was filled with the gel zinc anode mixture 23 prepared as described above. A gelled zinc negative electrode 24 was thus formed.

Next, the sealing member 16 was attached to the positive electrode can 11 . At this time, the negative electrode current collector 31 of the sealing body 16 was inserted into the gelled zinc negative electrode 24 , and the sealing body 16 was arranged at a predetermined position of the opening 14 of the positive electrode can 11 . Here, the negative electrode cap 32 of the sealant 16 has the same potential as the gelled zinc negative electrode 24 via the negative electrode current collector 31 . After that, the opening edge 18 of the positive electrode can 11 was caulked, and the opening 14 of the positive electrode can 11 was hermetically closed to assemble the battery 1 .

(Example 1 )
A gelatinous zinc anode mixture 23 was prepared by adding 7.40 parts by weight of KCl. At this time, the zinc alloy powder was 61.59 parts by weight, the polyacrylic acid was 0.34 parts by weight, the crosslinked sodium polyacrylate was 0.18 parts by weight, and the alkaline electrolyte was 30.49 parts by weight. Battery 1 was assembled in the same manner as in Comparative Example 1. Here, the content of KCl is 7.4% by weight with respect to the weight of the gelled zinc anode mixture.

(Comparative example 2 )
A gel zinc anode mixture 23 was prepared without adding KCl. At this time, the zinc alloy powder was 66.51 parts by weight, the polyacrylic acid was 0.37 parts by weight, the crosslinked sodium polyacrylate was 0.20 parts by weight, and the alkaline electrolyte was 32.92 parts by weight. Battery 1 was assembled in the same manner as in Comparative Example 1. Here, the content of KCl is 0% by weight with respect to the weight of the gelled zinc anode mixture.

2. Evaluation of alkaline manganese batteries (1) Internal resistance
For each battery of Comparative Example 1, Example 1 , and Comparative Example 2 , the internal resistance R was determined based on the following formula (III).
R=(EE _i )/I (III)

Here, E represents the open circuit voltage, E _i represents the closed circuit voltage when a current of 1 A is applied for 0.1 seconds, and I represents a current of 1 A. That is, for each battery, the open circuit voltage and the closed circuit voltage when a current of 1 A was applied for 0.1 second were measured, and the internal resistance R was obtained from the measured values. Taking the value of the internal resistance R of Comparative Example 2 as 100, the ratio between the internal resistance R of each battery and the internal resistance R of Comparative Example 2 was determined.

(2) Discharge capacity
Each battery of Comparative Example 1, Example 1 , and Comparative Example 2 was subjected to 250 mA intermittent discharge, 750 mA intermittent discharge, and 1500 mW pulse discharge, and the discharge capacity was measured during each discharge.

Here, the conditions for each discharge are shown below.
In the 250 mA intermittent discharge, a cycle of discharging at 250 mA for 1 hour and resting for 23 hours was performed once, and the discharge capacity was measured until reaching the final voltage (0.90 V) to obtain the discharge capacity. Taking the value of the discharge capacity of Comparative Example 2 as 100, the ratio between the discharge capacity of each battery and the discharge capacity of Comparative Example 2 was determined.

In the 750 mA intermittent discharge, a cycle of discharging at 750 mA for 2 minutes, then resting for 58 minutes was repeated eight times, and then resting for 16 hours, and the discharge capacity was measured until the final voltage (1.10 V) was reached to obtain the discharge capacity. Taking the value of the discharge capacity of Comparative Example 2 as 100, the ratio between the discharge capacity of each battery and the discharge capacity of Comparative Example 2 was determined.

In the 1500 mW pulse discharge, a cycle of discharging at 1500 mW for 2 seconds and then discharging at 650 mW for 28 seconds was repeated 10 times and then rested for 55 minutes. Taking the value of the discharge capacity of Comparative Example 2 as 100, the ratio between the discharge capacity of each battery and the discharge capacity of Comparative Example 2 was determined.

(3) Amount of gas in battery
Each battery of Comparative Example 1, Example 1 , and Comparative Example 2 was stored at room temperature (25° C.) for 3 months, and then the amount of gas in the battery was measured. The results are shown in Table 1 as the amount of gas in the battery. The smaller the amount of gas in the battery, the less the corrosion of the positive electrode can 11 progresses, indicating that the corrosion of the positive electrode can 11 is suppressed.

(4) Discussion As shown in Table 1, in Comparative Example 1 and Example 1 , in which the gelled zinc negative electrode mixture contains KCl as a chloride, compared to Comparative Example 2 in which the gelled zinc negative electrode mixture does not contain chloride, it can be seen that the internal resistance value is lower and the discharge capacity is improved. In other words, it can be said that the batteries of Comparative Example 1 and Example 1 have significantly improved conductivity and improved high-load discharge performance. Further, as shown in Table 1, it can be seen that as the amount of KCl added increases, the internal resistance decreases and the discharge capacity increases. Moreover, it can be seen that the increase in the discharge capacity is more remarkable in high-load discharge. This is believed to be due to the fact that the inclusion of chloride in the gelled zinc negative electrode mixture suppresses the formation of ZnO, which has a high electrical resistance value, on the surface of the zinc alloy during the discharge reaction, and instead, the formation of ZnCl ₂ 4Zn(OH) ₂ , which is superior in conductivity to ZnO.

Furthermore, in Comparative Example 1 and Example 1 containing KCl, the amount of gas in the battery was 0.65 mL in Comparative Example 1 and 0.30 mL in Example 1 , and was 1 mL or less. This is equal to or lower than Comparative Example 2 containing no KCl, in which the amount of gas in the battery is 0.55 mL. From this, even if KCl was contained in the negative electrode, it can be said that the positive electrode can was hardly corroded, because the gas produced when the positive electrode can was corroded was not generated much. This is probably because even if KCl is contained in the negative electrode, the corrosive ^Cl.sup.- which is a discharge product stays in the negative electrode and does not reach the positive electrode can. Therefore, even if KCl is added, corrosion of the positive electrode can is considered to be almost negligible.

The present invention is not limited to the above-described embodiments and examples, and various modifications are possible. For example, although alkaline manganese batteries have been described in the above embodiments and examples, the present invention can be applied not only to alkaline batteries using manganese as a positive electrode active material, but also to alkaline batteries using a nickel oxyhydroxide compound as a positive electrode active material.

<Aspect of the present invention>
A first aspect of the present invention is an alkaline battery comprising: a positive electrode can also serving as a positive electrode terminal; a positive electrode in contact with the inner surface of the positive electrode can; a separator disposed inside the positive electrode and in contact with the positive electrode and holding an alkaline electrolyte;

According to this first aspect, since the gelled zinc negative electrode mixture contains chloride, ZnCl ₂ 4Zn(OH) ₂ is generated instead of ZnO as a product during discharge, so that the conductivity of the negative electrode can be maintained in a good state, and the high-load discharge performance of the alkaline battery can be enhanced.

A second aspect of the present invention is the alkaline battery according to the first aspect of the present invention, wherein the chloride is potassium chloride.

According to the second aspect, potassium chloride has a relatively low solubility in water and stays in the negative electrode, so that ZnCl ₂ 4Zn(OH) _2, which is a product during discharge, is likely to be generated in the negative electrode and can be suppressed from corroding the positive electrode can.

A third aspect of the present invention is the alkaline battery according to the first or second aspect of the present invention, wherein the chloride is contained in an amount of 7.4% by weight or more with respect to the weight of the gelled zinc anode mixture.

According to the third aspect, the internal resistance of the battery can be reduced and the discharge capacity can be increased, and the effect can be exhibited particularly by increasing the discharge capacity under high load.

1 alkaline battery (battery)
2 negative electrode 3 positive electrode 11 positive electrode can 12 positive electrode terminal part 14 opening 16 sealing body 20 power generation element 21 positive electrode mixture 22 separator 23 gelled zinc negative electrode mixture 24 gelled zinc negative electrode 31 negative electrode current collector 32 negative electrode cap 35 sealing gasket

Claims (1)

A positive electrode can also serving as a positive electrode terminal, a positive electrode in contact with the inner surface of the positive electrode can, a separator disposed inside the positive electrode and in contact with the positive electrode and holding an alkaline electrolyte, and a negative electrode disposed inside the separator and in contact with the separator,
The negative electrode is a gelled zinc negative electrode containing a gelled zinc negative electrode mixture,
The gelled zinc anode mixture contains a chloride ,
the chloride is potassium chloride,
The alkaline battery, wherein the potassium chloride is contained in an amount of 7.4% by weight or more with respect to the weight of the gelled zinc negative electrode mixture .

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