JPS5942949B2 - nickel electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in nickel electrodes used in nickel-cadmium, nickel-zinc storage batteries, etc., and its purpose is to provide electrodes that are low in cost and have practically desirable properties.

Conventional nickel electrodes are made of sintered nickel powder with a porosity of 7.
The active material was produced by using a 5-85% substrate, immersing it in a nickel nitrate solution with an adjusted concentration, and then thermally decomposing it. The electrode obtained by this method has good performance, is resistant to high rate discharge, and has a long life. However, the above sintered nickel electrode had the disadvantage of high cost. The reason for this is that in order to obtain the substrate, sintering is performed in a high-temperature reducing atmosphere, and the process of filling the active material is repeated many times, resulting in high equipment costs, utility costs, and personnel costs. Recently, in order to obtain a low-cost nickel electrode while maintaining the advantages of sintered electrodes as much as possible, active materials, conductive materials, synthetic resin binders, etc.
Mix appropriate amounts of each to make a paste, apply it to a current collector made of nickel punching metal, dry it, and heat it at the same time as pressurizing it, or heat it at an appropriate temperature after pressure molding to make an electrode plate. Attention has been paid. Among these, those using polystyrene as a binder are known to have good alkali resistance and cycle life. For example, weigh out 70% by weight of nickel hydroxide, 15% by weight of scale graphite, 10% by weight of polystyrene powder, and 5% by weight of cobalt oxide, add an appropriate amount of water, mix well, make a paste, and then nickel punch. It was applied to both sides of a metal current collector, dried, pressure-molded, and further heated to 150°C to obtain a nickel electrode.

This electrode plate has an excellent recycling life as mentioned above, but the drawback is that the obtained electrode plate lacks flexibility, and when used in a spiral shape, the active material often falls off due to cracks. It was hot. As stated above, the purpose of the present invention is to improve a nickel electrode obtained by press-molding a mixture mainly consisting of an active material, a conductive material, and a binder into a current collector, and is available at a low cost. The objective is to provide a practical electrode that does not fall off.

Embodiments of the present invention will be described with reference to drawings of a cylindrical nickel-cadmium storage battery.

The figure is a longitudinal sectional view showing an outline of the overall configuration. 1 is a negative electrode plate, which is a paste-type electrode plate in which a mixture mainly composed of cadmium oxide is applied to a nickel current collector, dried, and then pressed; 2 is a separator, which is made of polyamide nonwoven fabric, and is interposed between negative electrode 1 and positive electrode 3. The structure is such that it protrudes 1 to 3 mm from the ends of the positive and negative electrode plates.

3 is the positive electrode of the present invention, in which a mixture mainly consisting of a live substance, a conductive material, and a binder is applied to both sides of a nickel punched metal current collector, dried, and then pressure-molded and heat-treated, which is different from the conventional one. The key point is that ethylene monovinyl acetate copolymer resin powder or styrene-butadiene latex is used in combination with polystyrene as a binder.

4 is a lead of the positive electrode plate 3, which is protected by an insulating tube, and is electrically connected to a sealing plate 5 by spot welding, so that the sealing plate 5 becomes a positive terminal.

Reference numeral 6 denotes a negative electrode lead, and by spot welding its end to the inner surface of the outer can 1, the outer can T becomes a negative electrode terminal.

8 is a lower insulating plate, and 9 is an upper insulating plate, each having a hole through which the positive electrode lead 4 passes.

Note that a 7N aqueous potassium hydroxide solution was used as the electrolyte. Although the battery configuration is as described above, the feature of the present invention is the binder, which is a mixture mainly consisting of an active material, a conductive material, and a binder for the positive electrode mixture. explain. Weigh out nickel hydroxide, graphite scales, binder, and cobalt oxide so that the solid content weight ratio is as shown in Table 1, add an appropriate amount of water, and mix thoroughly to form a positive electrode mixture paste. get. Apply this paste to both sides of the core material of nickel punching metal with a thickness of 0.1771771, and dry it at about 80°C for 30 to 60 minutes.
%. Add this to 140 more
A nickel electrode is obtained by heat treatment at ~180°C for 60 minutes.
Using the thus obtained electrode of the present invention, a cylindrical battery was prototyped with the configuration described above.

Table 2 shows the yield, cycle life, and price ratio of the nickel electrode in comparison with the sintering method and the conventional pressurizing method using only polystyrene as a binder. The disadvantages of conventional
The cost of sintering is high, and electrodes obtained by pressure-molding the active material, conductive material, and other materials using polystyrene as a binder have excellent cycle life, but lack flexibility and are difficult to assemble. During the swirling process during the process, the active material may break or fall off due to severe cracking, resulting in poor yield. The present invention makes it possible to provide an electrode at low cost and with good yield.

That is, as shown in Table 2, the cost is about X compared to the conventional sintering method. Although it is not as long as the sintered type in terms of lifespan, ethylene monovinyl acetate copolymer or ethylene-vinyl acetate
By appropriately selecting the amount of the butadiene copolymer added, the yield can be improved significantly while being comparable to the case where only polystyrene is used. The reason for the improvement in yield is thought to be that the ethylene monovinyl acetate copolymer and the styrene-butadiene copolymer are highly flexible, providing flexibility that polystyrene alone lacks. However, if the amount of ethylene monovinyl acetate copolymer resin or styrene-butadiene copolymer added is too large, the life will deteriorate, so the amount must be regulated. Furthermore, judging from the yield and cycle life in Table 2, the appropriate ratio in the case of polystyrene lyethylene monovinyl acetate copolymer is 6:
The ratio is in the range of 4 to 4:6, and in the case of polystyrene-restyrene-butadiene copolymer, it is in the range of 9:1 to 7:3. The ethylene monovinyl acetate copolymer resin used in the present invention has a vinyl acetate content of 4.5 to 14% by weight, and the styrene-butadiene copolymer has a butadiene content of 40 to 70% by weight to achieve similar effects. It was hot.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view of a Nickel-cadmium storage battery showing an embodiment of the present invention. 1... Negative electrode, 2... Separator, 3...
...Positive electrode.

Claims (1)

[Scope of Claims] 1. An electrode mainly composed of an active material made of a nickel compound, a conductive material, and a binder, the binder being made of an ethylene-vinyl acetate copolymer and a styrene-butadiene copolymer. A nickel electrode characterized by the combination of one type selected from the group and polystyrene. 2. The nickel electrode according to claim 1, wherein the weight ratio of polystyrene and ethylene-vinyl acetate copolymer as a binder is 6:4 to 4:6. 3. The nickel electrode according to claim 1, wherein the weight ratio of polystyrene and styrene-butadiene copolymer as the binder is 9:1 to 7:3.