JPS58115762A - Manufacture of negative electrode plate for sealed nickel-cadmium storage battery - Google Patents

Abstract

PURPOSE:To facilitage sealing of a storage battery by increasing the oxygen-gas absorbing ability of the negative electrode plate by subjecting the negative electrode plate, which is packed wih an active material made of cadmium, to electrolytic oxidation carried out in an aqueous solution containing salts. CONSTITUTION:An electrolytic oxidation is carried out in an aqueous ammonium-acetate solution by using a nickel dummy plate as a cathode, and using as an anode a negative electrode plate, which is prepared by packing a sintered plate with an active material made of cadmium. Next, the negative electrode plate is washed with water before dried, and subjected to formation treatment carried out in an aqueous NaOH solution. After that, thus obtained electrode plate is used as a negative electrode plate, and combined with a positive electrode plate, which supports an active material made of nickel hydroxide, so as to constitute a nickel cadmium storage battery. As a result, the oxygen-gas absorbing ability of the negative electrode plate, which is represented by weight reduction caused during the overcharge cycle life test of the storage battery, can be widely increased. Consequently, the high sealing performance of the battery is secured, and a stable characteristic with a small variation can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to reducing the
M' on a method for manufacturing a cathode plate for a sealed nickel-cadmium storage battery, which is sealed by absorbing elementary gas at the cathode.
ru.

In general, sealed nickel-cadmium storage batteries differ from lead-acid batteries in that they can be completely sealed and can be rapidly charged and discharged. Conventionally, even with quick charging and δ, it would light up in about 4 hours;
However, with recent advances in technology, this time has been shortened to the point where charging can be completed in about an hour. In order to shorten the charging time in this way, it is necessary to charge with a large current, but the capacity of the cathode plate is smaller than that of the negative plate, so that charging is completed before the cathode plate. If you charge with a large current, a large amount of oxygen will be generated from the @ electrode plate at the end of charging, and this oxygen will react and be absorbed by the cathode plate, so the cathode will no longer be photoelectrically charged (hydrogen will not be generated either). Therefore, the internal pressure of the battery remains constant, making it possible to completely seal the battery.

However, as the charging current increases, the amount of oxygen gas generated increases, reducing the oxygen gas absorption capacity of the cathode plate by 1.
When the safety valve rotates, the internal pressure increases, and when the safety valve is activated, the electrolyte is electrolyzed and the generated sludge gas and hydrogen gas escape to the outside, which can cause the electrolyte to decrease quickly and cause the battery to deteriorate. This will happen.

Therefore, in order to shorten the charging time, a cathode plate with extremely good oxygen gas absorption is required.

Factors related to the oxygen gas absorption ability of the cathode plate are the surface condition and internal structure of the cathode plate. In particular, the surface condition is important, and many small pores must exist.

Generally, cathode plates are manufactured by repeating the process of immersing a porous sintered nickel plate in a cadmium nitrate solution, electrolytically reducing it in an alkaline solution, washing with water, and drying it three to six times. As metal cadmium, its oxides, and hydroxides adhere to the surface of the electrode plate as it is repeated, 7 methods for removing this include mechanical removal using a brush and immersion in an acid solution. The method of dissolving is mainly adopted, but although the former method can remove quite large deposits on the surface, the deposits in the micropores involved in gas diffusion remain, so it is difficult to remove them. On the other hand, by controlling the acid concentration and immersion time, the latter can simultaneously remove large deposits on the surface and deposits in the micropores.
It is possible to improve the oxygen gas absorption ability, but if the acid concentration is too high or the immersion time is too long, not only the surface adhesion but also the necessary active material will be dissolved. The amount of substance decreases and has a negative impact on life performance. In the opposite case, surface adhesion remains and reduces the oxygen gas absorption ability. As described above, the acid immersion method has the disadvantage that it is extremely difficult to control the conditions.

The present invention aims to eliminate such drawbacks, and aims to facilitate the sealing of a nickel-cadmium storage battery and to stabilize its life characteristics.

The present invention has been made to achieve the above-mentioned object, and the cathode plate is electrolytically oxidized in an aqueous solution containing salts to form an interface with the millet liquid. By selectively removing a certain amount of deposits mainly consisting of cadmium on the surface of the negative electrode plate, the negative electrode plate retains a certain amount of active material, and the contact area with oxygen gas on the negative electrode plate is increased. This is a method of manufacturing a cover plate that makes it easy to seal the battery.

An embodiment of the present invention will be described.

Length 2500. A sintered plate with a width of $3 sm, with a cathode plate impregnated with about 1°f of active material as an anode and a nickel dummy plate as a shade tree, is 1mof! l in aqueous ammonium acetate solution of //
d m" Electrolytic oxidation was carried out between Iw and # with a current of 6 A at a roaring rate. The cathode plate was then washed with water and dried, and a chemical conversion treatment was performed in a 20% NaOH aqueous solution. The thus obtained electrode plate was used as a cathode plate. In addition, a nickel-cadmium storage battery was created by combining an anode plate holding an active material made of nickel hydroxide.

Weight loss during an overcharge cycle life test of a nickel-cadmium storage battery equipped with a cathode plate made in this way (this weight loss is caused by incomplete absorption of oxygen gas at the negative electrode, which increases the internal pressure of the battery and seals the battery). This occurs because the gas generated by electrolysis of water is released to the outside.
This is a guide to the gas absorption capacity of the cathode plate. ) are shown in the drawing. As shown, in the test pattern of charging L5A for 70 minutes and leaving it for 110 minutes, the battery was 11% lower than the conventional untreated battery.
/10, and it was found that there was no variation in weight loss caused by the acid treatment method.

As described above, according to the present invention, it is possible to dramatically increase the absorption of oxygen gas in the cathode plate of a nickel-cadmium storage battery, and as a result, it is possible to ensure high sealing of the battery, which allows charging to be carried out even more efficiently than at present. Since the process can be carried out using electric current and the amount of processing can be adjusted arbitrarily, it is possible to obtain a battery with stable characteristics with little variation.

[Brief explanation of the drawing]

The drawing is a characteristic diagram comparing the oxygen gas absorption ability of a conventional nickel-cadmium storage battery and a nickel-cadmium storage battery using the cathode plate according to the present invention. patent applicant

Claims (1)

[Claims] A method for producing a cathode plate for a sealed nickel-cadmium storage battery, which comprises electrolytically oxidizing a cathode plate impregnated with an active material made of cadmium in an aqueous S solution containing salts.