JPH0795444B2 - Alkaline battery negative electrode manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a negative electrode of an alkaline battery such as a nickel-cadmium storage battery or a nickel-hydrogen storage battery.

2. Description of the Related Art Lead-acid batteries and alkaline batteries are used as storage batteries for various power sources. Among them, the alkaline storage battery is expected to have high reliability and can be made compact and lightweight. For this reason, the small size has been widely used for various portable devices, and the large size has been widely used as an industry.

In this alkaline storage battery, an air electrode or the like is also taken up as a positive electrode, but in most cases, it is a nickel electrode. The characteristics have been improved from the pocket type to the sintered type, and it has become possible to further seal and expand the applications.

On the other hand, as the negative electrode, zinc, iron, hydrogen, etc. are used in addition to cadmium. At present, the cadmium electrode is mainly used, but a hydrogen electrode using a hydrogen storage alloy is drawing attention.

In the case of negative electrodes, non-sintering type, which is obtained by adding a binder to the negative electrode material and processing it into a sheet, has been studied for the purpose of cost reduction. There is.

Problems to be Solved by the Invention Since both the cadmium electrode in the charged state and the hydrogen electrode using a hydrogen storage alloy are metals, they are relatively excellent in terms of electron conductivity. ing. That is, these negative electrode material powders are made into a paste together with a binder, and the paste is applied to the porous conductive plate for smoothing. In this case, as a binder, polyvinyl alcohol, carboxymethyl cellulose, or a thermoplastic resin such as insulating polyethylene, polyvinyl chloride, or styrene rubber is used.

In addition, alkali-resistant metal or synthetic resin monofilaments are added to maintain the strength, which, on the contrary, has a problem in that the uniformity of the electrode and the complexity of the manufacturing method are brought about.

The present invention solves such a problem, and an object of the present invention is to provide a method for manufacturing a non-sintered electrode having more uniformity from these backgrounds.

Means for Solving the Problems The present invention is a sheet of alkaline battery negative electrode material using a thermoplastic resin as a binder, and then laminated with a porous conductor such as expanded metal, screen, punching metal, the binder Both are pressure-integrated at a temperature equal to or higher than the softening point of.

Action As described above, according to the present invention, since the sheet is first produced only by the paste composed of the negative electrode material powder and the binder, a more uniform sheet can be formed than the conventional method of coating the porous core material, and then the conductive core Since the porous porous body and the sheet are pressed at a temperature equal to or higher than the softening point of the binder, the sheet and the conductive porous body can be easily integrated.

Example An example of the present invention in which cadmium oxide is used for the negative electrode will be described below.

Commercially available cadmium oxide powder 93 parts, nickel powder 5 parts To this, a 3% (by weight) toluene solution of a styrene-butylene copolymer is added so that this resin becomes 2 parts with respect to cadmium hydroxide to form a paste. . A sheet was produced from this paste by a known doctor blade method and dried at 100 ° C. The thickness is 0.3mm.

The thickness between these two sheets is 0.17 mm, the hole diameter is 1.8 mm, and the opening degree is 53.
% Of iron and nickel-plated punching metal plates were stacked and integrated through a roller press machine with embossing heated to 150 ° C. The average thickness was 0.55 mm. After that, the surface of the plate was electrolytically nickel-plated using a Watt bath, immersed in a 0.3% fluorine resin dispersion, and dried at 120 ° C. for 1 hour. The paste-type cadmium electrode thus obtained was 39 mm wide and 370 mm long.
Then, the lead plate was attached by spot welding.
Partial charge is performed to make a cadmium electrode, and this cadmium electrode is set to A.

Next, for comparison, using the same punching metal and paste as in A, the average thickness of 0.55 mm was also obtained by the conventional method of applying the paste on both sides of the punching metal and passing it between the slits.
Then, the cadmium electrode obtained in the same step as A is added as B.

When the calculated capacity was calculated from the weight using 20 electrodes, the maximum value was 5.9Ah in group A and the minimum value was 5.6Ah, while the maximum value was 5.9Ah in group B but the minimum value was 5.2. It was Ah, and it was found that the variation of A was small.

Therefore, for example, when constructing a battery using a nickel positive electrode, if the capacity of the positive electrode is set to 2.8 Ah and the negative electrode having twice the calculated capacity is used as the design reference, the minimum for B is 5.6 Ah.
It is necessary to make the electrode so that the maximum becomes 6.35 Ah when pulled up to h, but in A, the minimum of 5.6 Ah can be guaranteed, so the electrode of the embodiment can be used as it is. The cost can be reduced by that much, and the capacity also increases slightly. In addition, a A2 sealed nickel-cadmium storage battery was constructed by specifically using A and B and using a known long-life sintered nickel electrode as a counter electrode and a hydrophilically treated polypropylene nonwoven fabric separator. As an electrolytic solution, 20 g / 1 of lithium hydroxide was dissolved in a caustic potash aqueous solution having a specific gravity of 1.22 and used.

First, the initial discharge voltage and capacity were compared. When the constant current charge of 130% of the capacity at a rate of 5 hours and constant current discharge of up to 0.9V was performed at 1.0A, the average voltage of both A and B was 1.22V, and the discharge capacity A was 2.8Ah and B was It was 2.6 Ah.

Next, 10 cells were used for each battery, and the life characteristics were compared under the conditions of this charge / discharge. As a result, the discharge capacity is 65% of the initial value.
The number of cycles that deteriorated to 10 was 1,050 to 1,100 cycles for both A and B.

The above is one example of the case where cadmium oxide is used for the negative electrode, but in the present invention, the same result as above can be obtained even when the hydrogen storage alloy is used for the negative electrode.

Effect of the Invention The method for producing an alkaline battery negative electrode of the present invention can provide an excellent method for producing an alkaline battery negative electrode in which the uniformity of the electrode thickness is improved and the variation in capacity is reduced.

Claims (4)

[Claims] 1. An alkaline battery negative electrode material is formed into a sheet using a thermoplastic resin as a binder, a porous conductor film is laminated on the sheet, and the sheet is formed at a temperature equal to or higher than the softening point of the binder. A method for manufacturing an alkaline battery negative electrode in which a conductor film is pressed and integrated. 2. The method for producing an alkaline battery negative electrode according to claim 1, wherein the alkaline battery negative electrode material contains a powder of cadmium oxide or a hydrogen storage alloy as a main component. 3. The method for producing an alkaline battery negative electrode according to claim 1, wherein the binder is styrene rubber. 4. A porous conductor film is laminated on a sheet of a sheet of an alkaline battery negative electrode material using a thermoplastic resin as a binder, and the sheet is electrically conductive with the sheet at a temperature higher than the softening point of the binder. A method for producing an alkaline battery negative electrode in which a body membrane is pressed and integrated to add a fluororesin dispersion.