JPH05151962A - Positive electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To provide a positive electrode plate for alkaline storage battery with high energy density and good lifetime characteristic by lessening the adding amount of cobalt compound. CONSTITUTION:A compound layer 4 containing cobalt compound re-educed in the from of cobalt oxy-hydroxide is provided over the surface of an active material 3 to form an active material layer 2. A hydrophilic organic substance film 6 is formed over the surface of this active material layer 2. This permits lessning the adding amount of cobalt compound because the hydrophilic organic substance film 6 prevents the dissolved cobalt ions from dispersing.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an anode plate for an alkaline storage battery.

[0002]

2. Description of the Related Art An anode plate for an alkaline storage battery is constructed by holding an anode active material such as nickel on a current collector. Generally, an anode plate for an alkaline storage battery is classified into a sintered type anode plate and a paste type anode plate depending on the constitution of the current collector and the mode of the active material. In order to manufacture a sintered anode plate, first, a slurry prepared by kneading an aqueous binder solution such as methyl cellulose or carboxymethyl cellulose and a sintering powder such as carbonyl nickel powder is applied to a perforated plate such as iron plated with nickel. Then, dry and sinter to make a current collector (sintered substrate).
Next, the impregnation step of immersing the sintered substrate in an acidic solution containing nickel nitrate as a main component and then further immersing it in an aqueous solution of sodium hydroxide etc. is repeated several times to obtain an active material containing nickel hydroxide as a main component. The material is manufactured by filling a sintered substrate. The paste type anode plate is manufactured by directly filling a nickel hydroxide powder bound with an organic paste such as polyvinyl alcohol into a current collector (three-dimensional mesh structure or the like) such as foamed nickel. In the former type of sintered anode plate, it is difficult to densely fill the active material because the impregnation process must be repeated.
The energy density of the anode plate cannot be made sufficiently high. On the other hand, the latter paste-type anode plate can increase the packing density per volume of the active material, but has larger pores in the matrix of the three-dimensional mesh structure, which is a current collector, than the sintering-type anode plate. Therefore, the current collecting effect is deteriorated, the utilization factor of the active material is lowered, and the energy density cannot always be sufficiently increased. Thus, neither the sintered type anode plate nor the paste type anode plate can sufficiently increase the energy density. Therefore, various techniques for increasing the energy density of the anode plate for an alkaline storage battery have been studied conventionally.

As a technique for increasing the utilization rate of the active material of the sintered type anode plate, for example, a layer containing a cobalt compound such as cobalt hydroxide reprecipitated as cobalt oxyhydroxide on the surface of the active material is formed. Japanese Patent Application Laid-Open No. 59-163753 discloses a technique for increasing the utilization rate of the active material during discharge. In an anode plate in which a cobalt compound such as cobalt hydroxide is added to the surface of an active material, when the cobalt compound is placed in an electrolytic solution to assemble a battery, the cobalt compound dissolves into a dissolved species [hydrooxocobalt (II) ion ( HCoO
₂ ^-)] as dissolved in the electrolyte. When the battery is first charged, HCoO ₂ ⁻ is re-precipitated on the surface of the active material as highly conductive cobalt oxyhydroxide, and the conductivity of the surface of the active material of the anode plate is improved. Further, as a technique for increasing the utilization rate of the active material of the paste type anode plate, there is disclosed in Japanese Patent Laid-Open No. Sho 62-62.
No. 256367, a paste containing a powder of a cobalt compound such as cobalt hydroxide or cobalt oxide or a powder of metallic cobalt added to a powder of nickel hydroxide as an active material is used to activate an anode plate at the time of discharging. Techniques for increasing the utilization rate of substances are disclosed. In addition, 3-2
Japanese Unexamined Patent Publication No. 0860 discloses a technique in which a layer composed of nickel, cobalt, cadmium and a compound of these metals is formed on the surface of an active material to obtain an anode plate having a high discharge capacity.

[0004]

However, in the conventional anode plate, most of HCoO ₂ ⁻ dissolved in the electrolytic solution is diffused into the electrolytic solution without being reprecipitated on the surface of the active material.
By adding a relatively large amount of cobalt compound to the active material layer, HC
The necessary amount of redeposition of oO ₂ ^{− on} the surface of the active material was secured. For example, in a sintered anode plate, at least 0.5 wt% or more, preferably 2 to 4 wt% of a cobalt compound was added to the active material. Further, in the paste type anode plate, 5 to 30 wt% of the cobalt compound was added to the active material. If the addition amount of the cobalt compound is increased, the filling amount of the nickel hydroxide as the active material is relatively decreased, so that the capacity is lowered and the anode plate is sufficiently charged even though the cobalt compound is added. The energy density could not be increased.

An object of the present invention is to provide an anode plate used in an alkaline storage battery having high energy density and good life characteristics.

[0006]

According to the invention of claim 1, an alkaline storage battery anode is provided with an active material layer in which a compound layer containing a cobalt compound re-deposited as cobalt oxyhydroxide is formed on the surface of the active material. A hydrophilic organic film is formed on the surface of the active material layer for the plate.

According to a second aspect of the invention, the compound layer of the alkaline storage battery anode plate of the first aspect contains cadmium hydroxide.

[0008]

When a hydrophilic organic film is formed on the surface of the active material layer as in the first aspect of the invention, the cobalt compound is converted into HC.
Even if dissolved in the electrolytic solution as oO ₂ ⁻ , it is possible to prevent HCoO ₂ ^{− from} being dissipated to the outside of the anode plate due to the hydrophilic organic film. Therefore, a relatively large amount of cobalt oxyhydroxide can be re-precipitated on the surface of the active material during the initial charging of the battery. Therefore, the necessary and sufficient cobalt oxyhydroxide layer can be formed with a small amount of the cobalt compound added, and the amount of the active material can be increased by the amount of the cobalt compound added. Therefore, the packing density of the active material can be increased and the energy density of the anode plate can be increased. If the hydrophilic organic film is formed on the surface of the active material layer at least until the first charging after the battery is formed, it fulfills its function, but even after the initial charging, the surface of the active material layer is fulfilled. If the hydrophilic organic substance coating is formed on the surface of the active material, it has a function of suppressing the dropout of cobalt oxyhydroxide re-precipitated on the surface of the active material.

When the compound layer contains cadmium hydroxide as in the invention of claim 2, dissolution of the cobalt compound in the electrolytic solution is promoted, so that the cobalt oxyhydroxide is re-applied to the surface of the active material. The amount of precipitation increases, and the energy density of the anode plate can be increased. Further, when the compound layer contains cadmium hydroxide, it is possible to prevent the active material from falling off due to the swelling of the anode plate.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is an enlarged schematic view showing a surface portion of an embodiment in which the present invention is applied to a sintered nickel anode plate. In FIG. 1, reference numeral 1 denotes a sintered base that constitutes a current collector, and this sintered base 1 is formed by sintering nickel powder. 2 is an active material layer, and this active material layer 2
Is formed by forming a compound layer 4 containing a cobalt compound as a main component on the surface of an active material 3 containing nickel hydroxide as a main component. In the anode plate of this embodiment, the compound layer 4 is formed of a material obtained by adding cadmium hydroxide to a cobalt compound such as cobalt oxide or cobalt hydroxide which is redeposited on the surface of the active material 3 as cobalt oxyhydroxide. There is. The compound layer 4 is formed so as to cover the surface of the active material 3 and the exposed surface of the sintered substrate 1.
Thereby, the adhesion between the active material 3 and the sintered body 1 is improved.
Reference numeral 5 denotes a porous portion formed in the active material layer 2, and the electrolytic solution penetrates into the porous portion 5 to charge and discharge the battery.
Reference numeral 6 denotes a hydrophilic organic substance coating film having alkali resistance formed on the surface of the active material layer 2. In this embodiment, the hydrophilic organic substance coating film 6 is formed of polyvinyl alcohol (PVA). The hydrophilic organic substance coating 6 is permeable to the electrolytic solution but is HC
oO ₂ ^- is as long as it does not easily transparent, PVA
Alternatively, the coating 6 may be formed of a cellulose derivative such as carboxymethyl cellulose or methyl cellulose.

When the anode plate of this embodiment is placed in the electrolytic solution for assembling a battery or for chemical conversion treatment, the electrolytic solution enters the porous portion 5 of the anode plate and the cobalt oxide or the water of the compound layer 4 is added. Cobalt oxide is eluted in the electrolytic solution in the porous portion 5. The eluted HCoO ₂ ^- is a hydrophilic organic film 6
Most of it is not released from the area surrounded by and is deposited on the surface of the active material 3 as cobalt oxyhydroxide during the first charge of the battery. Cobalt oxyhydroxide is the active material 3
The hydrophilic organic film 6 prevents the cobalt oxyhydroxide from falling off even after being deposited.

Next, a method of manufacturing the anode plate for alkaline storage batteries of this embodiment will be described. First, the sintered substrate 1 made of nickel having a porosity of 85% was dipped in a solution containing nickel nitrate 6 mol / l (temperature 50 ° C.) for 15 minutes, and then at 70 ° C.
For 20 minutes, and then, dipping in a 20% aqueous solution of potassium hydroxide, and then removing excess alkali by washing with water and drying the same, which is repeated 4 to 5 times. Was filled. Next, the sintered substrate 1 filled with the active material 3 is immersed in an aqueous solution of cadmium nitrate and cobalt nitrate (temperature: 50 ° C.) for 20 minutes, and after this immersion, dried at 90 ° C. for 20 minutes, and then 20% potassium hydroxide. It was further immersed in the aqueous solution for 20 minutes. Then, after removing excess alkali by washing with water, it was dried to form the compound layer 4 on the surface of the active material 3 to form the active material layer 2. Next, the sintered substrate 1 on which the active material layer 2 is formed is immersed in an aqueous solution of polyvinyl alcohol having a predetermined concentration and then dried to form a hydrophilic organic film 6 on the surface of the active material layer 2 for an unformed alkaline storage battery. A nickel anode plate was manufactured.

Next, in order to investigate the discharge capacity of a battery using the anode plate for an alkaline storage battery of this embodiment, various anode plates a ...
m manufactured by using these anode plates.
The test was performed by making M (see Table 1). For the anode plates a to i, the compounding weight ratios of the cobalt compound and the cadmium compound that compose the compound layer 4 and the concentration (%) of the polyvinyl alcohol aqueous solution used to form the hydrophilic organic substance coating film 6 are used.
The anode plates according to the examples of the present invention are different in the composition ratio of cobalt and cadmium and the weight% of the hydrophilic organic film with respect to the active material, which are manufactured by changing the above. Anode plates j and k are conventional anode plates having no hydrophilic organic coating. The anode plates 1 and m are comparative anode plates having a hydrophilic organic coating but not having a compound layer containing a cobalt compound. The anode plates a to m have the same structure except for the structure of the compound layer and the hydrophilic organic film and the amount of active material. The battery manufactured using each of the anode plates a to m is an AA type nickel-cadmium battery combined with a sintered cadmium cathode.
Each battery was charged at 600 mA for 1.5 hours and then repeatedly discharged and charged at 600 mA to a voltage of 1 V, and 1 C discharge capacity at the end of the first cycle and the 300th cycle of each battery was measured. The measurement results are as shown in Table 1 below.
In Table 1, the Co content% means the weight% of cobalt in the cobalt compound with respect to the active material, and the organic substance coating amount% means the weight% of the hydrophilic organic substance coating with respect to the active material.

[0015]

[Table 1] From the measurement results, the batteries A to I using the anode plates a to i of the present example are the same as those of the comparative examples not including the conventional anode plates j and k having no hydrophilic organic film and the compound layer containing the cobalt compound. It can be seen that the active material utilization rate is higher and the 1C discharge capacity is higher than the batteries J to M using the anode plates 1 and m. Further, the batteries B and C using the anode plates b and c of this example containing a smaller amount of cobalt compound in the compound layer than the conventional anode plate j are the same as the conventional anode plate j having no hydrophilic organic film. From the battery J used, it can be seen that the 1C discharge capacity at the end of 300 cycles of charging and discharging is higher and the life characteristics are improved. This means that the cobalt oxyhydroxide re-precipitated on the surface of the active material is dissipated outside the anode plate by the hydrophilic organic film 6
Is suppressed. Further, in the battery G in which the compound layer is formed only of the cobalt compound and the anode plate g containing no cadmium compound is used, the initial discharge capacity is high, but the discharge capacity decreases when charging and discharging are repeated. From this, when the cadmium compound is added to the active material, the discharge capacity is less likely to decrease even after repeated charge and discharge,
It can be seen that the function of the hydrophilic organic substance coating can be improved.

(Embodiment 2) FIG. 2 is an enlarged schematic view of a surface portion of an embodiment in which the present invention is applied to a paste type nickel anode plate. In FIG. 2, reference numeral 10 denotes a three-dimensional mesh structure that constitutes a current collector, and this three-dimensional mesh structure 10 is composed of a foam metal porous body made of nickel. 20 is an active material layer, and this active material layer 20 is the three-dimensional network structure 1
The compound layer 40 is formed on the surface of the active material 30 filled in 0. The active material 30 is composed of powder containing nickel hydroxide as a main component. In the anode plate of this embodiment, the compound layer 40 is formed of cobalt oxide re-deposited on the surface of the active material 30 as cobalt oxyhydroxide or a material obtained by adding cadmium hydroxide to a cobalt compound of cobalt hydroxide. There is. Reference numeral 50 denotes a porous portion formed in the active material layer 20, and the electrolytic solution penetrates into the porous portion 50 to charge and discharge the battery. Reference numeral 60 denotes a hydrophilic organic film having alkali resistance formed on the surface of the active material layer 20. Also in this embodiment, the hydrophilic organic film 60 is formed of polyvinyl alcohol (PVA).

Also in this embodiment, as in the anode plate of Embodiment 1, the hydrophilic organic coating 60 prevents the dissipation of cobalt ions. Therefore, most of the cobalt ions are deposited on the active material 30 as cobalt oxyhydroxide when the battery is first charged.

Next, a method for manufacturing the anode plate for an alkaline storage battery of Example 2 will be described. First, the average particle size is 10 to 20
After immersing the nickel hydroxide powder of μm in an aqueous solution (temperature 50 ° C.) in which cadmium nitrate and cobalt nitrate are mixed, it is dried at 90 ° C. for 5 minutes and then immersed in a 20 wt% potassium hydroxide aqueous solution to remove excess alkali. The compound layer 40 (cobalt content: 1.5
A powder of the active material 30 made of nickel hydroxide powder having 9%) formed on the surface was prepared. Next, to 100 g of the powder of the active material 30, 1.2 g of carboxymethyl cellulose as a binder and 30 g of water were added and kneaded to prepare a slurry. Then, the slurry is filled in the three-dimensional network structure 10 made of a foamed metal porous body made of nickel having a porosity of 95%, and then dried to obtain the three-dimensional network structure 10 having the active material layer 20. It was Next, the three-dimensional network structure 10 having the active material layer 20 was immersed in a PVA aqueous solution having a concentration of 1% and then dried to manufacture an anode plate for an alkaline storage battery provided with the hydrophilic organic film 60.

In this embodiment, the nickel hydroxide powder was dipped in an aqueous solution containing a mixture of cadmium nitrate and cobalt nitrate and then dipped in an aqueous potassium hydroxide solution to neutralize the compound layer 40. A slurry is formed by using a mixed powder of nickel powder, cadmium oxide powder, and cobalt oxide powder, and the slurry is filled in the three-dimensional network structure 10 and then immersed in an alkaline solution, and the surface of the nickel hydroxide powder is wetted with water. The compound layer 40 containing cadmium oxide and cobalt hydroxide may be formed by dissolution precipitation.

Next, in order to investigate the discharge capacity of the battery using the anode plate for alkaline storage battery of this embodiment, various anode plates n to q were used.
And batteries N to Q manufactured by using these anode plates.
(See Table 1) was prepared and tested. The anode plate n is the anode plate of this embodiment. The anode plate o is a conventional anode plate in which the compound layer 40 is formed of only a cobalt compound and does not have a hydrophilic organic film. The anode plate p is a conventional anode plate that has a hydrophilic organic film and does not have a compound layer. Anode plate q is a comparative anode plate having a hydrophilic organic film and having a compound layer formed only of a cadmium compound. still,
The anode plates o to q have the same constitution as the anode plate n except for the constitution of the compound layer and the hydrophilic organic substance coating film and the amount of the active material. The battery manufactured using each of the anode plates n to q is an AA type nickel-cadmium battery combined with a sintered cadmium cathode. 60 after charging each battery at 600mA for 1.5 hours
Repeatedly charge and discharge to discharge voltage up to 1V at 0mA,
1C at the end of the 1st cycle and 300th cycle of each battery
The discharge capacity was measured. The measurement results are as shown in Table 2 below.

[0021]

[Table 2] From the measurement results, the battery N using the anode plate n of this example
However, a conventional anode plate o without a hydrophilic organic film, a conventional anode plate p without a compound layer, and an anode plate q of a comparative example in which a compound layer was formed only with a cadmium compound were used. It can be seen that the active material utilization rate and life characteristics are improved as compared with the batteries O to Q.

[0022]

According to the invention of claim 1, since the cobalt oxyhydroxide layer can be formed with a small amount of cobalt added,
The amount of the active material can be increased, and the packing density of the active material can be increased. Therefore, when the anode plate of the present invention is used, the energy density and life performance of the battery can be improved.

According to the second aspect of the invention, since the active material layer contains cadmium hydroxide, the amount of redeposition of cobalt oxyhydroxide on the surface of the active material is increased and the energy density of the anode plate can be increased. .. Further, since the active material can be prevented from falling off due to the swelling of the anode plate, the life performance of the battery can be improved.

[Brief description of drawings]

FIG. 1 is an enlarged schematic view of a surface portion of an example applied to a sintered nickel anode plate.

FIG. 2 is an enlarged schematic view of a surface portion of an example applied to a paste type nickel anode plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sintered substrate, 10 ... Three-dimensional network structure, 2, 20 ... Active material layer, 3, 30 ... Active material, 4, 40 ... Compound layer, 6,
60 ... Hydrophilic organic film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Tsunoda 2-1-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo Shin-Kindo Electric Co., Ltd.

Claims (2)

[Claims] 1. An anode plate for an alkaline storage battery, comprising an active material layer comprising a compound layer containing a cobalt compound redeposited as cobalt oxyhydroxide on the surface of the active material, the active material layer comprising: An anode plate for an alkaline storage battery having a hydrophilic organic film formed on its surface. 2. The anode plate for an alkaline storage battery according to claim 1, wherein the compound layer contains cadmium hydroxide.