JPH0963573A - Manufacture of hydrogen storage alloy electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing process of a hydrogen storage alloy electrode with high initial activation characteristics and high internal conductivity. SOLUTION: Oxide of misch metal attached onto the surface nickel layer of hydrogen storage alloy powder, having a property easily soluble to a acid or an alkali is removed by acid treatment or alkali treatment. A nickel oxide film or a nickel hydroxide film, which was not yet sufficiently removed by the acid treatment or the alkali treatment on the surface of a nickel rich layer is removed by reduction treatment. The reactivity and conductivity of the hydrogen storage alloy powder are enhanced, and the initial activation characteristics and the conductivity of a hydrogen storage alloy electrode are enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hydrogen storage alloy electrode, and more particularly to improving the initial activation characteristics thereof.

[0002]

2. Description of the Related Art Conventionally, in a method for producing a hydrogen storage alloy electrode in which a paste formed by mixing hydrogen storage alloy powder with a binder is applied to a metal current collector, the hydrogen storage alloy powder is plated with nickel. It has been proposed to improve the initial activation characteristics, the cycle life, the internal conductivity, etc. of the hydrogen storage alloy electrode by applying copper plating or copper plating.

Prior to mixing with the binder, miscible metal such as La that is easily oxidized and its oxide protruding on the surface of the hydrogen storage alloy powder and its oxide are removed by acid treatment or alkali treatment to remove the hydrogen storage alloy powder. It has also been proposed to form a nickel-rich layer on the surface portion of the above to obtain the same effect as the above nickel plating. For example, JP-A-3-152868 proposes to treat the hydrogen-absorbing alloy powder with an acidic aqueous solution before mixing with a binder, and then with an alkaline aqueous solution to improve the initial activation characteristics. No. 101821 proposes treating a hydrogen storage alloy powder with a high temperature alkaline aqueous solution before mixing with a binder to improve initial activation characteristics, and JP-A-5-13077 discloses treating with a high temperature alkaline aqueous solution. It is proposed that the hydrogen storage alloy electrode formed by using the above hydrogen storage alloy powder is treated again with a high temperature alkaline aqueous solution to improve the initial activation characteristics.

[0004]

However, although the above-mentioned acid treatment or alkali treatment removes the oxide of the misch metal formed on the surface of the hydrogen storage alloy powder, the oxide film on the surface of the nickel rich layer (nickel) is removed. However, there was a problem that the hydrogen hydroxide film could not be removed sufficiently and the initial activation characteristics and internal conductivity of the hydrogen storage alloy electrode were deteriorated.

The present invention has been made in view of the above point of view, and it is an object to be solved to provide a method for producing a hydrogen storage alloy electrode having improved initial activation characteristics and internal conductivity.

[0006]

[Means for Solving the Problems and Effects of the Invention] The first constitution of the present invention is to use hydrogen storage alloy powder, which has been treated with at least one of acid and alkali, washed with water and dried, as a thickener or a binder. In the method for producing a hydrogen storage alloy electrode, which is formed by depositing a mixed paste on a metal current collector, after washing with water and drying, after reducing the hydrogen storage alloy powder, the thickener or binder A method for producing a hydrogen storage alloy electrode, which comprises mixing with a binder.

According to this structure, the misch metal oxide having a property of being easily oxidized or dissolved in alkali and protruding from the surface nickel layer of the hydrogen storage alloy powder can be removed after the acid treatment or the alkali treatment. it can. Further, the subsequent reduction treatment can remove the nickel oxide film and the nickel hydroxide film on the surface of the nickel-rich layer, which could not be sufficiently removed by these acid treatment or alkali treatment. Therefore, the reactivity and conductivity of the hydrogen storage alloy powder are improved, and the initial activation characteristics and conductivity of the hydrogen storage alloy electrode can be improved.

In an example of a conventional hydrogen storage secondary battery, one charge / discharge cycle is completed in 10 hours, and if the number of cycles required for initial activation is 7, the time required for initial activation ( The time required to achieve a capacity of about 95% of the maximum capacity) is 70 hours, and the power required for it cannot be ignored. Improving the initial activation characteristics will improve productivity and manufacturing facility utilization rate. It has important meaning.

A second structure of the present invention is a metal current collector comprising a paste formed by mixing hydrogen-absorbing alloy powder, which has been treated with at least one of acid and alkali, washed with water and dried, with a thickener or a binder. In the method for producing a hydrogen storage alloy electrode formed by depositing on a body, the hydrogen storage alloy electrode, wherein the hydrogen storage alloy electrode formed by depositing the paste on the metal current collector is subjected to reduction treatment. It is a manufacturing method of an electrode.
According to the present invention, since the hydrogen storage alloy electrode is subjected to the reduction treatment, it is possible to reduce the nickel oxide film formed on the surface of the hydrogen storage alloy powder before forming the electrode after the reduction treatment in the first configuration. Therefore, the effect can be further improved.

A third structure of the present invention is the above first and second embodiments.
Further, in the above-mentioned constitution, after being treated with at least one of acid and alkali, washed and dried, hydrogen-absorbing alloy powder is mixed with a thickener or a binder to form a paste on a metal current collector. In the method for producing a hydrogen storage alloy electrode, which is washed with water, dried, after reduction treatment of the hydrogen storage alloy powder, while mixing with the thickener or binder,
The hydrogen storage alloy electrode formed by applying the paste to the metal current collector is reduced. According to the present invention, since the reduction treatment is performed twice, the above-mentioned effects can be further improved.

A fourth structure of the present invention is the above first to third structures.
In any one of the above configurations, the reduction treatment is further performed using hydrogen peroxide solution. The hydrogen peroxide solution does not need to be washed with a large amount of washing water after the acid treatment or alkali treatment described above, and is simple in process. A fifth configuration of the present invention is characterized in that, in any one of the first to third configurations, the reduction treatment is further performed using high temperature hydrogen gas. Hot hydrogen gas is simple as it does not require subsequent water washing such as the acid and alkali treatments described above.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described based on the following examples.

[0013]

EXAMPLES Examples of the method for manufacturing a hydrogen storage alloy electrode according to the present invention will be described below. (Example 1) composition MmNi _3.6 Co _0.75 Al _0.3 Mn
Hydrogen storage alloy powder of _0.35 (La / Mm = 0.6) was mechanically crushed to 150 mesh or less, and hydrogen storage alloy powder was immersed in 6NKOH aqueous solution at 80 ° C. for 24 hours to alkali-etch the alloy surface. After washing with water and drying (in air), CMC (carboxymethyl cellulose) 2wt
% Aqueous solution to the alloy weight of 20 wt% and stirred,
A paste was formed.

Next, this paste was filled in a foamed nickel current collector (10 cm × 10 cm, 550 g / m ² ) and
Dry at 0-80 ℃ and roll press to a thickness of 0.6m
It was set to m. Next, this electrode was immersed in 30 wt% hydrogen peroxide water for 3 hours, then washed with water and dried. The obtained hydrogen storage alloy electrode was sandwiched between a pair of sintered nickel electrodes via a separator and immersed in a 6NKOH aqueous solution to prepare 10 negative electrode regulated batteries (example products), and then the negative electrode theoretical capacity was set. As a reference, charge at 0.1C for 10.5 hours, then
A charge / discharge cycle of discharging to 0.8 V at 0.1 C was performed for the activation treatment. Further, as comparative examples, 10 comparative example products were produced in the same manufacturing steps as those of the above-described example products, except that only immersion in hydrogen peroxide solution was omitted. The measurement results of the number of charge / discharge cycles and the capacity utilization rate (ratio of the actual capacity to the negative electrode theoretical capacity) at this time are shown in FIG. In FIG. 1, the average value of the example product is shown by a white circle, and the average value of the comparative example product is shown by a black circle. It can be seen from FIG. 1 that the initial activation characteristics can be remarkably improved by the reduction treatment. (Example 2) Next, three hydrogen-absorbing alloy electrodes produced in Example 1 were sandwiched between four sintered nickel electrodes via separators to form 10 prismatic sealed batteries as Example products. , 0.1 C based on the theoretical capacity of the positive electrode (100% of the theoretical capacity of the negative electrode) for 10.5 hours, and then 0.1
A charging / discharging cycle of discharging to 1.0 V at C was performed for the activation treatment. With the same structure, only 10 hydrogen-absorbing alloy electrodes were manufactured, and the internal pressures of the batteries were measured at the end of charging. FIG. 2 shows the average value (white circle) of the battery internal pressure of each Example product and the average value (black circle) of the battery internal pressure of each Comparative Example product. It can be seen from FIG. 2 that the internal pressure of the battery can be significantly reduced by the reduction treatment.

It is well known that the battery internal pressure has a strong negative correlation with the cycle life of the battery, and it is estimated from FIG. 2 that the cycle life of the product of this embodiment can be remarkably improved. (Example 3) An example product prepared in the same process as in example 1 was used except that the surface of the alloy was acid-etched by immersing it in a 1N formic acid aqueous solution at 30 ° C for 24 hours instead of the alkali etching in the above-mentioned example 1. Ten pieces were produced, and then, a charge / discharge cycle was performed for activation treatment, in which the battery was charged at 0.1 C for 10.5 hours based on the theoretical capacity of the negative electrode, and then discharged to 0.8 V at 0.1 C. Further, as comparative examples, 10 comparative example products were produced in the same manufacturing steps as those of the above-described example products, except that only immersion in hydrogen peroxide solution was omitted. FIG. 3 shows the measurement results of the number of charge / discharge cycles and the capacity utilization rate (ratio of the actual capacity to the negative electrode theoretical capacity) at this time. FIG.
In, the average value of the example product is shown by a white circle, and the average value of the comparative example product is shown by a black circle. It can be seen from FIG. 3 that the initial activation characteristics can be remarkably improved by the reduction treatment. (Example 4) Next, three hydrogen-absorbing alloy electrodes produced in Example 3 were sandwiched between four sintered nickel electrodes via separators to form ten prismatic sealed batteries as Example products. , 0.1 C based on the theoretical capacity of the positive electrode (100% of the theoretical capacity of the negative electrode) for 10.5 hours, and then 0.1
A charging / discharging cycle of discharging to 1.0 V at C was performed for the activation treatment. With the same structure, only 10 hydrogen-absorbing alloy electrodes were prepared, which were the hydrogen-absorbing alloy electrodes of Comparative Example 3, and the battery internal pressures at the end of charging were measured. FIG. 4 shows the average value (white circle) of the battery internal pressure of each Example product and the average value (black circle) of the battery internal pressure of each Comparative Example product. It can be seen from FIG. 4 that the internal pressure of the battery can be significantly reduced by the reduction treatment. (Example 5) composition MmNi _3.6 Co _0.75 Al _0.3 Mn
Hydrogen storage alloy powder of _0.35 (La / Mm = 0.6) was mechanically crushed to 150 mesh or less, and hydrogen storage alloy powder was immersed in 6NKOH aqueous solution at 80 ° C. for 24 hours to alkali-etch the alloy surface. It was washed with water and dried (in air). Next, this hydrogen storage alloy powder was immersed in a 30 wt% hydrogen peroxide solution for 3 hours, then washed with water and dried. Next, 20 wt% of CMC 2 wt% aqueous solution with respect to alloy weight
% And stirred to form a paste. Next, this paste was applied to a foamed nickel current collector (10 cm × 10 cm, 55
0 g / m < ² >), dried at 70-80 [deg.] C., and rolled to a thickness of 0.6 mm.

The obtained hydrogen storage alloy electrode was sandwiched between a pair of sintered nickel electrodes via a separator and immersed in a 6NKOH aqueous solution to prepare 10 negative electrode regulated batteries (example products), and then the negative electrode. 1 at 0.1C based on the theoretical capacity
A charging / discharging cycle of charging for 0.5 hour and then discharging to 0.8 V at 0.1 C was performed for the activation treatment. Further, as comparative examples, 10 comparative example products were produced in the same manufacturing steps as those of the above-described example products, except that only immersion in hydrogen peroxide solution was omitted. The measurement results of the number of charge / discharge cycles and the capacity utilization rate (ratio of the actual capacity to the negative electrode theoretical capacity) at this time are shown in FIG. In FIG. 5, the average value of the example product is shown by a white circle, and the average value of the comparative example product is shown by a black circle. It can be seen from FIG. 5 that the initial activation characteristics can be remarkably improved by the reduction treatment. (Example 6) Next, three hydrogen absorbing alloy electrodes prepared in Example 5 were sandwiched between four sintered nickel electrodes via separators, and ten prismatic sealed batteries were constructed as Example products. , 0.1 C based on the theoretical capacity of the positive electrode (100% of the theoretical capacity of the negative electrode) for 10.5 hours, and then 0.1
A charging / discharging cycle of discharging to 1.0 V at C was performed for the activation treatment. With the same structure, only 10 hydrogen-absorbing alloy electrodes were manufactured, and the internal pressures of the batteries were measured at the end of charging. FIG. 6 shows the average value of the battery internal pressure (white circle) of each example product and the average value of the battery internal pressure (black circle) of each comparative example product. It can be seen from FIG. 6 that the reduction process can significantly reduce the internal pressure of the battery. (Example 7) An example product manufactured in the same process as that of Example 5 except that the surface of the alloy was acid-etched by immersing the alloy surface in a 1N formic acid aqueous solution at 30 ° C for 24 hours instead of the alkali etching in Example 5 described above. Ten pieces were produced, and then, a charge / discharge cycle was performed for activation treatment, in which the battery was charged at 0.1 C for 10.5 hours based on the theoretical capacity of the negative electrode, and then discharged to 0.8 V at 0.1 C. Further, as comparative examples, 10 comparative example products were produced in the same manufacturing steps as those of the above-described example products, except that only immersion in hydrogen peroxide solution was omitted. FIG. 7 shows the measurement results of the number of charge / discharge cycles and the capacity utilization rate (ratio of the actual capacity to the negative electrode theoretical capacity) at this time. Figure 7
In, the average value of the example product is shown by a white circle, and the average value of the comparative example product is shown by a black circle. It can be seen from FIG. 7 that the initial activation characteristics can be remarkably improved by the reduction treatment. (Embodiment 8) Next, three hydrogen-absorbing alloy electrodes prepared in Embodiment 7 are sandwiched between four sintered nickel electrodes via separators to form 10 prismatic sealed batteries as embodiment products. , 0.1 C based on the theoretical capacity of the positive electrode (100% of the theoretical capacity of the negative electrode) for 10.5 hours, and then 0.1
A charging / discharging cycle of discharging to 1.0 V at C was performed for the activation treatment. With the same structure, only 10 hydrogen-absorbing alloy electrodes were prepared, which were the hydrogen-absorbing alloy electrodes of Comparative Example 3, and the battery internal pressures at the end of charging were measured. FIG. 8 shows the average value (white circle) of the battery internal pressure of each Example product and the average value (black circle) of the battery internal pressure of each Comparative Example product. It can be seen from FIG. 8 that the internal pressure of the battery can be significantly reduced by the reduction process. (Example 9) Compared to each of Examples 1 to 6 described above, the reduction treatment was carried out in an atmosphere of high-temperature hydrogen gas (preferably 300 to 600 ° C, pressure of 0.1 to 1 MPa) instead of immersion in hydrogen peroxide solution. What was held for 1 hour was prepared. These hydrogen storage alloy electrodes exhibited substantially the same capacity utilization characteristics and battery internal pressure characteristics as the hydrogen storage alloy electrodes of Examples 1 to 5 above. From this fact, it is understood that the reducing agent used for the reduction treatment is not limited to hydrogen peroxide solution.

[Brief description of drawings]

FIG. 1 is a diagram showing initial activation characteristics of a hydrogen storage alloy electrode of Example 1.

FIG. 2 is a diagram showing battery internal pressure characteristics of a sealed battery using the hydrogen storage alloy electrode of Example 1.

FIG. 3 is a diagram showing initial activation characteristics of a hydrogen storage alloy electrode of Example 3.

FIG. 4 is a diagram showing battery internal pressure characteristics of a sealed battery using the hydrogen storage alloy electrode of Example 3.

5 is a diagram showing initial activation characteristics of the hydrogen storage alloy electrode of Example 5. FIG.

FIG. 6 is a diagram showing battery internal pressure characteristics of a sealed battery using the hydrogen storage alloy electrode of Example 5.

FIG. 7 is a diagram showing initial activation characteristics of a hydrogen storage alloy electrode of Example 7.

FIG. 8 is a diagram showing battery internal pressure characteristics of a sealed battery using the hydrogen storage alloy electrode of Example 7.

Claims (5)

[Claims] 1. A metal current collector is coated with a paste formed by mixing hydrogen storage alloy powder, which has been treated with at least one of acid and alkali, washed with water and dried, with a thickener or a binder. In the method for producing a hydrogen storage alloy electrode, the method for producing a hydrogen storage alloy electrode, comprising: washing with water, drying, reducing the hydrogen storage alloy powder, and then mixing with the thickener or binder. Method. 2. A metal current collector is coated with a paste formed by mixing hydrogen-absorbing alloy powder, which has been treated with at least one of acid and alkali, washed with water and dried, with a thickener or a binder. The method for manufacturing a hydrogen storage alloy electrode according to claim 1, wherein the hydrogen storage alloy electrode formed by applying the paste to the metal current collector is subjected to a reduction treatment. 3. A metal current collector is coated with a paste formed by mixing hydrogen-absorbing alloy powder, which has been treated with at least one of acid and alkali, washed with water and dried, with a thickener or a binder. In the method for producing a hydrogen storage alloy electrode according to the above, after washing with water and drying, after reducing treatment of the hydrogen storage alloy powder, while mixing with the thickener or binder, the paste is coated on the metal current collector. A method of manufacturing a hydrogen storage alloy electrode, which comprises subjecting the hydrogen storage alloy electrode formed by deposition to a reduction treatment. 4. The method for producing a hydrogen storage alloy electrode according to claim 1, wherein the reduction treatment is performed using hydrogen peroxide solution. 5. The method for producing a hydrogen storage alloy electrode according to claim 1, wherein the reduction treatment is performed using high temperature hydrogen gas.