JPH07263020A - Alkaline secondary battery - Google Patents

Abstract

PURPOSE:To reduce specific resistance of an electrode board, improve current collecting performance, and prolong the cycle life by using an electrode which is composed of a conductive porous material having pares and in which an electrode active material is carried on the electrode board having specific resistance of a prescribed value. CONSTITUTION:A conductive porous material which has pores and has specific resistance not more than 0.01OMEGA.cm is used as one electrode board, and an electrode active material is carried on this electrode board. Particularly when a conductive porous carbon material is used as the conductive porous material, various pore structures, porosity, pore diameters and bulk density can be selected by a manufacturing method. Since the specific resistance of the electrode board is set not more than 0.01OMEGA.cm, electric conductivity is improved, and current collecting performance of the electrode board is improved. Thereby, charging and discharging efficiency can be maintained high, and battery capacity can be sufficiently utilized. Since conditions where an undischarged active material remaining in an electrode without discharging runs out can be restrained, the battery capacity can be maintained high, and the cycle life can be improved.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an alkaline secondary battery.

[0002]

2. Description of the Related Art Since zinc electrodes and iron electrodes have high energy density and are inexpensive, alkaline secondary batteries such as nickel-zinc batteries and nickel-iron batteries have been studied as power sources for electric vehicles. As the electrode base material of these zinc electrodes and iron electrodes, metal punching metal is typically used.
Expanded metal or metal fiber cloth is used.

[0003]

When the electrode substrate of the secondary battery as described above is used, there are problems that the charge and discharge efficiency is low, the battery capacity cannot be fully utilized, and the cycle life is particularly short. Therefore, it is an object of the present invention to provide an electrode substrate for a secondary battery, which has a low specific resistance of the electrode substrate, an excellent current collecting property, and a good cycle life, and solves the above-mentioned problems.

[0004]

According to the present invention, the above object is to provide an electrode active material on an electrode substrate made of a conductive porous material having pores and having a specific resistance of 0.01 Ω · cm or less. This is achieved by an alkaline secondary battery characterized by using an electrode which is supported. The alkaline secondary battery refers to a secondary battery using an alkaline aqueous solution (typically an aqueous solution of potassium hydroxide) as an electrolyte, and is classified as a lead storage battery using an acidic aqueous solution. Typical alkaline secondary batteries include nickel-cadmium storage batteries, nickel-iron storage batteries, nickel-zinc storage batteries, silver oxide-zinc storage batteries, and silver oxide-cadmium storage batteries.

According to the present invention, at least one of the electrode substrates of this alkaline secondary battery has pores and has a resistance of 0.01 Ω.
A conductive perforated material having a specific resistance of not more than cm, more preferably not more than 0.003 Ω · cm is used, and an electrode active material is supported on this electrode substrate. Resistivity is 0.01Ω ・ cm
By the following, the cycle life of the secondary battery is extended. In particular, when a conductive porous carbon material is used as the conductive porous material, various pore structures, porosities, pore diameters, and bulk densities can be selected according to the manufacturing method. It is also possible to use a carbon-carbon composite material, so-called C / C composite. In addition, pyrolytic carbon may be formed on the surface of the constituent material of the conductive porous carbon material. More specifically, for example, a substrate component made of an organic material (carbon precursor such as polyacrylonitrile, rayon, pitch)
After molding the raw material composition in which the matrix and the matrix are mixed, carbonization (usually 500 to 1500 ° C.) and graphitization (usually 1500 to 3000 ° C.) are performed in a non-oxidizing atmosphere,
The specific resistance can be 0.01 Ω · cm or less.

As a raw material of the base component, an organic substance containing α-cellulose as a main component can be used, and this organic substance is a filler component for making a sheet material by making paper.
In addition to normal pulp, rayon pulp containing α-cellulose as a main component can also be used. The form of these pulps is preferably fibrous in order to obtain an electrode substrate having a pore structure. As the matrix, a thermosetting resin having a charcoal ratio of 40% or more is preferable from the strength of the electrode substrate after preparation, and as a thermosetting resin having a charcoal ratio of 40% or more, phenol resin, furan resin, polyimide resin, etc. Can be used.

From the viewpoints of preventing the electrode active material from falling off, preventing the aggregation of active material particles, and improving the electrical conductivity, microfibrillated pulp or graphite particles are mixed in the papermaking process in order to increase the surface area of the electrode substrate. Carbonization in a non-oxidizing atmosphere,
It is also possible to obtain an electrode substrate having a specific resistance of 0.01 Ω · cm or less by performing graphitization treatment. Also, carbon-carbon composite material,
In the case of an electrode substrate composed of a so-called C / C composite, as the base component, fibers or carbon fibers made of a graphitizable organic substance, powders or carbon powders made of a graphitizable organic substance, graphite Using a composition selected from at least one of carbonized carbon fiber, graphitized carbon powder, and a molded body with a matrix,
Graphitized in a non-oxidizing atmosphere to give a resistivity of 0.01Ω
-It is also possible to obtain an electrode substrate having a size of cm or less.

The carbon-carbon composite material is composed of a carbon precursor, carbon fibers, and carbon powder particles as a constituent material, and is molded by using a carbonizable or graphitizable binder called a matrix,
It is a composite material obtained by firing and carbonization. As the matrix, a thermosetting resin such as a phenol resin, a thermoplastic resin such as polyacrylonitrile or pitch, a reinforcing material such as carbon black or natural graphite, or a pyrolytic carbon obtained by a CVD method is used. It is also possible to obtain an electrode substrate having a specific resistance of 0.01 Ω · cm or less by graphitizing an activated carbon fiber aggregated body containing activated carbon fibers as a main component. In order to further reduce the specific resistance and improve the conductivity, the activated carbon fiber preferably has a curled shape in which the fibers are easily entangled with each other. Further, when the activated carbon fiber composed of a graphitic carbon-based pitch system is used as the activated carbon fiber, an electrode substrate having a specific resistance of 0.01 Ω · cm or less can be obtained by the graphitization treatment at about 2000 ° C. .

Further, as the base component of the carbon-carbon composite material,
If hollow fibers are used, an electrode substrate having a specific resistance of 0.01 Ω · cm or less may be obtained. It becomes possible to support the electrode active material inside the fiber, which is effective in reducing the weight of the battery. Alternatively, an electrode substrate having a specific resistance of 0.01 Ω · cm or less may be obtained by forming pyrolytic carbon on the surface of the conductive porous carbon material by the CVD method.

It is desirable to control and select the pore size of the electrode substrate in order to prevent the active material carried inside from falling off, preventing aggregation, etc. The pore size is selected according to the particle size of the active material,
Generally, the particle size is 100 μm or more, and more preferably 1 μm
Those having a pore size of m or more and 50 μm or more are used. The increased porosity allows more active material to be supported, which increases the energy density of the battery. However, like the pore size, the porosity is selected from the dropout and aggregation prevention of the active material, and preferably, the porosity is 40% or more and 95% or less.

The electrode active material is not particularly limited, but typically nickel hydroxide, cadmium hydroxide, zinc hydroxide, iron hydroxide, zinc oxide, silver oxide or the like can be used. To support the electrode active material on the electrode substrate, the electrode active material is made into a paste and applied to the electrode substrate,
The raw material solution of the electrode active material can be impregnated into the electrode substrate and subjected to electrolysis, thermal decomposition treatment or the like.

The active material is preferably atomized as much as possible in order to increase the reaction area and capacity, and is selected in the pore size of the substrate, the manufacturing method and the like. The present invention, in one preferred embodiment, uses a zinc electrode. As this zinc electrode, an electrode substrate having the specific resistance of 0.01 Ω · cm or less is used, and an electrode active material is directly carried in the pores of the electrode substrate. With this configuration, it is not necessary to add a conductive material such as metal particles to the electrode active material in order to obtain current collecting properties.

Further, the zinc electrode may be composed of a zinc composite oxide in which zinc oxide, which is an electrode active material, is replaced with an element having a hydrogen overvoltage larger than zinc and a redox potential higher than that of zinc. At least one of indium, thallium, tin, lead, and bismuth is an element having a hydrogen overvoltage larger than that of zinc substituting zinc of zinc oxide and having a noble oxidation-reduction potential.
Elements containing seeds are optimal.

The zinc electrode can be manufactured by supporting a zinc compound in the pores and then by supporting zinc oxide in the pores by thermal decomposition. In addition, a mixed composition of a zinc compound and a compound of an element having a hydrogen overvoltage larger than that of zinc and a redox potential higher than that of zinc is supported in the pores, and an active material containing zinc oxide as a main component is pyrolyzed. The substance is carried in the pores.

Thus, according to the present invention, as a preferred embodiment, a zinc electrode made of a zinc composite oxide in which zinc of zinc oxide is replaced by an element having a hydrogen overvoltage larger than that of zinc and a redox potential of noble is used. As a nickel-zinc secondary battery and a zinc electrode, a mixed composition of a zinc compound and a compound of an element having a hydrogen overvoltage larger than that of zinc and a redox potential higher than that of zinc is carried in an electrode substrate hole. Then
An alkaline secondary battery in which an active material containing zinc oxide as a main component is carried in the pores by thermal decomposition is provided.

According to the present invention, in one preferred embodiment, this zinc electrode and a nickel electrode as a counter electrode are used,
And an aqueous solution of potassium hydroxide (eg, 30 as an electrolyte)
A nickel-zinc battery using a (wt% solution) is provided. As the nickel electrode, for example, a substrate made of sponge-like nickel metal, paste-like nickel hydroxide filled in the substrate, supported, and rolled can be used.

[0017]

According to the present invention, the specific resistance of the electrode substrate is 0.01
When it is Ω · cm or less, the conductivity is improved and the current collecting property of the electrode substrate is improved. Thereby, the charge / discharge efficiency can be maintained high and the capacity of the battery can be fully utilized. Further, since the charge / discharge efficiency can be maintained at a high level, the undischarged active material remaining in the electrode without being discharged is eliminated, and the current is concentrated on the undischarged active material during the charge / discharge process, especially during charging, resulting in aggregation or grain growth. Since the reduction of the active material surface area due to the generation, that is, the reduction of the battery reaction area, is also suppressed, the battery capacity can be kept high and the cycle life is improved.

[0018]

【Example】

Example 1 As a base component composed of an organic substance, α-cellulose was 90%.
% Or more of rayon pulp at 80% by weight, a raw material composition obtained by mixing 19% by weight of a papermaking binder as a matrix and 1% by weight of vinylon binder was uniformly dispersed in water, and a wet sheet material was obtained using a papermaking machine. .

After the wet sheet material is dried, the dried sheet material is impregnated with a phenol resin having a residual carbon rate of 45% by a resin impregnating device and semi-cured. Subsequently, the phenol resin-impregnated sheet material is cut into a predetermined size, 10 to 20 sheets are laminated, compression-molded by a pressure machine and cured. This compression molded body is sandwiched between graphite plates and subjected to calcination carbonization treatment at 1800 ° C. in an electric furnace. Next, this carbon material was graphitized at 3000 ° C. in a graphitizing furnace to obtain an electrode substrate (hereinafter referred to as a substrate) made of a conductive porous carbon material.

In the above production method, the fiber diameter of the base component,
Substrates (Sample Nos. AH) in which the porosity, the pore diameter, and the bulk density were controlled by changing the composition were prepared. Table 1 shows 18
Table 2 shows the characteristic values of the substrate after carbonization at 00 ° C.
The characteristic values of the substrate after graphitization at 00 ° C. are shown. The specific resistance was measured by a potential drop method (JIS R7202), and the bulk density, the porosity, and the average pore diameter were measured by a porosimeter by a mercury injection method.

[0021]

[Table 1]

[0022]

[Table 2]

Sample No. 60 ~ 70 substrates E to H
A zinc electrode was prepared by adjusting the size to × 2 ^t and using the following manufacturing method. The substrate was previously subjected to ultrasonic cleaning in acetone for 10 minutes or more, and after cleaning, dried at 110 ° C. A zinc nitrate solution (50 wt%) was used as a zinc compound as a raw material of the electrode active material.
The substrate is placed in a zinc nitrate solution, and deaeration (at 1000 Pa for 30 minutes or more) is performed using a vacuum container to support zinc nitrate in the substrate pores. Next, the substrate supporting zinc nitrate is dried at 130 ° C. for 30 minutes or more to remove water and water of crystallization of zinc nitrate, and then thermally decomposed in air at 250 to 600 ° C. to remove zinc oxide into the pores of the substrate. Zinc electrodes (Sample Nos. 1 to 4) were obtained by carrying. The amount of zinc oxide supported was 3 g for each zinc electrode.

A nickel-zinc secondary battery was constructed by using this zinc negative electrode, a nickel electrode, and a potassium hydroxide solution (30 wt%) saturated with zinc oxide as an electrolyte. The structure of this nickel-zinc secondary battery is shown in FIG. In the figure, 1 is a zinc negative electrode, 2 is a nickel positive electrode, 3 is a separator, 4 is an electrolytic solution, 5 is a liquid retaining paper, and 6 is a case. FIG. 2 shows the active material carried on the electrode substrate. Reference numeral 7 is an electrode substrate, and 8 is an active material.

The charge / discharge cycle life evaluation of this battery is as follows.
Charge at a constant current density of 10 mA / cm ² for 5 hours or when the battery voltage reaches 2.1 V, whichever comes first, and discharge at a constant current density of 10 mA / cm ^2. ,
The process is repeated until the battery voltage reaches 1.0V. The cycle life was defined as the life of the battery when it reached 60% of the initial discharge capacity. Table 3 shows the cycle life of each electrode substrate. This gives a cycle life of 420
It became possible to improve to ~ 500 times.

[0026]

[Table 3]

Example 2 Substrate 5 was obtained in the same manner as in Example 1 except that the base component of Example 1 was 75% by weight of rayon pulp containing 90% or more of α-cellulose and 5% by weight of graphite particles. It was As a result of evaluating the characteristics of this substrate by the measuring method described in Example 1, the specific resistance was 0.003 Ω · cm, the bulk density was 0.74 g / cc, the porosity was 62%, and the pore diameter was 3 μm.

A zinc electrode was prepared using this substrate.
The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 460 times.

Example 3 A long fiber of coal pitch carbon fiber which is a base component is impregnated with a matrix resol phenol resin at atmospheric pressure or negative pressure to obtain a prepreg. This prepreg is two-dimensionally oriented, laminated, and molded to obtain 150
A molded product cured at ℃ is obtained. This molded body was carbonized in a non-oxidizing atmosphere, and finally graphitized at 2000 ° C. to obtain a substrate 6 made of a carbon-carbon composite material. As a result of evaluating the characteristics of this substrate by the measuring method described in Example 1, the specific resistance was 0.003 Ω · cm, the bulk density was 1.29 g / cc, the porosity was 30%, and the pore diameter was 10 μm.

A zinc electrode was prepared using this substrate.
The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 470 times.

Example 4 A zinc electrode was prepared using a graphitized carbon-carbon composite material, CP-20 (manufactured by Nippon Carbon Co., Ltd.) as a substrate 7. As a result of evaluating the characteristics of this substrate by the measuring method described in Example 1, a specific resistance of 0.005 Ω · cm and a bulk density of 0.65 g / c
c, the porosity was 65%, and the pore diameter was 45 μm. A zinc electrode was prepared using this substrate. The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 410 times.

Example 5 Graphitized carbon-carbon composite material, C, as in Example 4
A zinc electrode was prepared using CM-F (manufactured by Nippon Carbon) as the substrate 8. As a result of evaluating the characteristics of this substrate by the measuring method described in Example 1, a specific resistance of 0.007 Ω · cm, a bulk density of 0.88 g / cc, a porosity of 48%, a pore diameter of 11 μm,
Met. A zinc electrode was prepared using this substrate. The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 400 times.

Example 6 Graphitized carbon-carbon composite material, F, as in Example 4
A zinc electrode was prepared using GK-200 (manufactured by Nippon Carbon) as the substrate 9. As a result of evaluating the characteristics of this substrate by the measuring method described in Example 1, a specific resistance of 0.008 Ω · cm,
Bulk density 1.01 g / cc, porosity 48%, pore diameter 52μ
It was m. A zinc electrode was prepared using this substrate. The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 400 times.

Example 7 Activated carbon fiber was obtained by subjecting a carbon fiber having a curled shape (made by Dona Carbo S Donac) made of coal pitch as a raw material to activation treatment. The activation treatment was performed with a specific surface area of 500 m ² / g or less in consideration of moldability and substrate strength. The substrate 10 was obtained by subjecting a molded body of the activated carbon fiber felt and the matrix to graphitization at 2000 ° C. As a result of evaluating the characteristics of this substrate by the measuring method described in Example 1, a specific resistance of 0.007 Ω · cm and a bulk density of 0.43 g / c
c, porosity 65%, pore diameter 47 μm. A zinc electrode was prepared using this substrate. The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 400 times.

Example 8 As the carbon fiber of the substrate component in Example 3, long fibers of carbon fiber spun from coal pitch were treated at a treatment temperature of 500 to 7
A hollow carbon fiber was used, which was infusibilized at 00 ° C. in an air / chlorine mixed gas atmosphere and had pores formed in the center of the fiber. The hollow carbon fiber had an outer diameter of 13 μm and an inner diameter of 7 μm. Then, using this hollow carbon fiber, a graphitization treatment was carried out by the same manufacturing method as in Example 3 to obtain a substrate 11 made of a carbon-carbon composite material.

The characteristics of this substrate were evaluated by the measuring method described in Example 1. As a result, the specific resistance was 0.006 Ω · cm, the bulk density was 0.83 g / cc, the porosity was 48%, and the average pore diameter was 8 μm. It was A zinc electrode was prepared using this substrate. The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 410 times.

Example 9 A molded product having a matrix of a curl-shaped carbon fiber felt (manufactured by DonaCarbo S Donac) and a phenolic resin, which is made from coal pitch as a raw material, is graphitized at 2000 ° C. to obtain a substrate. It was Further, a substrate 12 was obtained in which specific resistance was reduced by applying pyrolytic carbon as a matrix to the surface of the substrate by a CVD method using methane as a raw material.

As a result of evaluating the characteristics of the substrate 12 by the measuring method described in Example 1, the specific resistance was 0.003 Ω · cm, the bulk density was 0.56 g / cc, the porosity was 62%, and the pore diameter was 45 μm. . A zinc electrode was prepared using the substrate 12. The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 460 times.

Example 10 Graphitized carbon-carbon composite material of Example 5, CCM-F
(Manufactured by Nippon Carbon Co., Ltd.) and using the same CVD as in Example 9.
By the method, pyrolytic carbon was applied to the surface of the substrate as a matrix to obtain a substrate 13 having a reduced specific resistance. Board 13
As a result of evaluating the characteristics by the measuring method described in Example 1, the specific resistance was 0.003 Ω · cm, the bulk density was 0.97 g / cc, the porosity was 42%, and the pore diameter was 10 μm.

A zinc electrode was prepared using the substrate 13.
The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 460 times.

Example 11 Using the substrate 3 of Example 1, a mixed solution of zinc nitrate and indium nitrate was used as a raw material for an electrode active material, and the composition was 96 atm% zinc and 4 atm% indium. A zinc electrode supporting a zinc composite oxide on a substrate was obtained by the same method. Hereinafter, the battery configuration and cycle life are shown in Example 1.
I went the same way. As a result, the cycle life was 700 times, which is a significant improvement over the conventional example.

Example 12 In Example 11, a mixed solution of zinc nitrate, indium nitrate, and thallium (I) nitrate was used as a raw material for the electrode active material, and the composition was 96 atm% zinc, 2 atm% indium, and 2 atm% thallium. A zinc electrode having a zinc composite oxide supported on a substrate was obtained in the same manner as in Example 1.

Hereinafter, the battery configuration and cycle life are shown in Example 1.
I went the same way. As a result, the cycle life was 900 times, which is a significant improvement over the conventional example.

Example 13 Using the substrate 6 of Example 3, a mixed solution of zinc nitrate and indium nitrate was used as a raw material of an electrode active material, and the composition was 96 atm% zinc and 4 atm% indium, and Example 1 was used.
A zinc electrode having a zinc composite oxide supported on a substrate was obtained by the same method as described in (1). Hereinafter, the battery configuration and cycle life were the same as in Example 1. As a result, the cycle life is 650 times,
Significantly improved compared to the conventional example.

Example 14 In Example 13, a mixed solution of zinc nitrate, indium nitrate and thallium (I) nitrate was used as the electrode active material material, and the composition was 96 atm% zinc, 2 atm% indium and 2 atm% thallium. A zinc electrode having a zinc composite oxide supported on a substrate was obtained in the same manner as in Example 1.

Hereinafter, the battery configuration and cycle life are shown in Example 1.
I went the same way. As a result, the cycle life was 850 times, which is a significant improvement over the conventional example.

Comparative Example 1 75% by weight of zinc oxide and 15% of zinc metal were used as the electrode active material.
% By weight, and 5% by weight of indium oxide and 5% by weight of indium metal as additives, and after adding a fluororesin,
Water was added and kneaded to obtain a paste-like electrode active material. The paste electrode active material was applied to both surfaces of a copper punching metal electrode substrate 14 having a thickness of 1 mm and a porosity of 50% to prepare a zinc electrode. Then, the battery configuration and cycle life were the same as in Example 1. The specific resistance of the electrode substrate 18 is 0.0
It was 77 Ω · cm. As a result, the cycle life is 300
It was once.

Comparative Example 2 A zinc electrode was prepared by using the electrode substrate D after carbonization at 1800 ° C. of Example 1 as the electrode substrate 15. The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. The specific resistance of the electrode substrate 19 was 0.022 Ω · cm. As a result, the cycle life was 280 times.

Comparative Example 3 A fuel cell electrode substrate (KES-400 manufactured by Kureha Chemical Co., Ltd.) using a pitch-based carbon fiber was used as the electrode substrate. The characteristics of this substrate 16 were evaluated by the measuring method described in Example 1, and as a result, the specific resistance was 0.025 Ω · cm and the bulk density was 0.53 g / c.
c, porosity 56%, pore diameter 38 μm.

A zinc electrode was prepared using this substrate.
The zinc electrode preparation method, battery configuration, and cycle life were the same as in Example 1. As a result, the cycle life was 270 times.

[0051]

[Table 4]

[0052]

EFFECT OF THE INVENTION The electrode substrate of the present invention has a sufficiently low specific resistance and excellent conductivity, so that the electrode active material can be fully utilized and the charge / discharge efficiency can be kept high. The cycle life of the secondary battery is extended.
In particular, since the zinc electrode of the present invention has a sufficiently low specific resistance and excellent conductivity, it becomes possible to fully utilize the electrode active material, and it is possible to maintain high charge / discharge efficiency. Cycle life is extended.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a nickel-zinc secondary battery of an example.

FIG. 2 shows an active material supported on an electrode substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Negative electrode 2 ... Positive electrode 3 ... Separator 4 ... Electrolyte solution 5 ... Liquid retaining paper 6 ... Case 7 ... Electrode substrate 8 ... Active material

Claims (5)

[Claims] 1. An alkali characterized by using an electrode made of a conductive porous material having pores and having an electrode active material supported on an electrode substrate having a specific resistance of 0.01 Ω · cm or less. Secondary battery. 2. The alkaline secondary battery according to claim 1, wherein the electrode substrate is made of a porous graphitized material. 3. The alkaline secondary battery according to claim 1, which is a nickel-zinc secondary battery using a zinc electrode in which the electrode active material is mainly zinc oxide. 4. A nickel-zinc secondary battery using a zinc electrode made of a zinc composite oxide in which zinc of zinc oxide is replaced with an element having a hydrogen overvoltage higher than zinc and a redox potential higher than that of zinc. The alkaline secondary battery according to claim 3. 5. As the zinc electrode, a mixed composition of a zinc compound and a compound of an element having a hydrogen overvoltage higher than zinc and a redox potential higher than that of zinc is carried in the electrode substrate pores, The alkaline secondary battery according to claim 3 or 4, wherein an active material containing zinc oxide as a main component is supported in the pores by thermal decomposition.