JPS60158552A - Manufacture of paste type cadmium anode - Google Patents

Abstract

PURPOSE:To increase oxygen gas absorbing ability by forming a large number of cracks by heating on the surface of plate prepared by filling paste containing alkali resistant fibers in a core. CONSTITUTION:Paste is prepared in such a way that alkali resistant fibers are dispersed in cadmium oxide powder and they are kneaded with viscous solution prepared by dissolving, for example, polyvinyl alcohol in water and ehtylene glycol. The paste is spreaded on a nickel plated steel porous plate. The coated plate is passed through a slit to adjust thickness and quickly dried to form cracks on its surface. By forming cracks on the plate, effective surface area is increased, and oxygen absorbing ability is improved. Since alkali resistant fibers serves as reinforcing agent, coming off of the active material is prevented during handling.

Description

Detailed Description of the Invention The present invention provides improvements in the oxygen gas absorption performance of paste-type cadmium cathodes used in sealed nickel-cadmium storage batteries.
It is related to.

Conventional cadmium cathodes for sealed nickel-type cadmium storage batteries have been put into practical use, such as sintered type, paste type, pressed type, and electrodeposition type. Paste-type electrodes are made mainly of cadmium oxide powder, cadmium hydroxide powder, or a mixture thereof, with reinforcing agents such as fibers, and conductive powder added to water or an organic solvent such as polyvinyl alcohol or polytetrafluoroethylene. It is made by kneading a liquid with a binder dissolved or dispersed therein to form a paste, which is then applied onto a core material such as a perforated plate made of nickel plated iron and dried. The manufacturing method is simple, and unlike the sintering method, there is no need to use a large amount of expensive nickel powder, so it is widely used as an inexpensive electrode with stable characteristics. However, the conventional paste type cadmium electrode is different from the sintered type (
However, the oxygen gas absorption performance of the paste type cathode is inferior, and improvements need to be made in terms of the type and amount of binder, the porosity and pore size distribution of the electrode, and the amount of battery electrolyte. It has been done. In addition, in recent years, there have been many applications that require rapid charging of about 1 hour, and this is due to the slow absorption rate of oxygen and gas, so it is necessary to do something to reduce the current during overcharging to about 0.5 RA or less. It was necessary to detect and control the charging state using the following method.

In view of the above point 1, the present invention improves the carbon self-oxygen gas absorption performance of the paste type cathode, prevents the safety valve from operating even if overcharged with a current of about 1 orb A, and allows rapid charging in about 1 hour. This made it possible.

In the present invention, a large number of fine racks are placed on the surface of the electrode plate during drying to increase the effective surface area of the cathode and improve the oxygen gas absorption performance. In order to maintain elasticity (as a fall-off prevention agent), alkali-resistant fibers such as synthetic fibers such as polyamide and acrylic fibers and metal fibers are added.

Next, one embodiment of the present invention will be described.

Cadmium oxide (particle size 0. fl 5 II) l
After #I acrylic fiber (length 1 mm) 20F was well dispersed, polyvinyl alcohol 23y was dissolved in water ssmn and ethylene glycol 34omi to form a viscous liquid and kneaded to form a paste. This paste-like material was applied to a nickel-plated porous piece of iron and shaped by passing it through a slit.

The subsequent drying was carried out rapidly so that cracks were likely to occur. That is, 120" hot air was applied to the electrode plate at a perpendicular 1ζ wind speed of about 10 m/- to dry it in about 6 minutes.

The electrode plate was 0.7 mm after drying. The electrode plate produced in this way has many cracks with a width of about 0.1 mm, but since they contain alkali-resistant fibers or reinforcing agents,
It did not fall off due to subsequent handling. This electrode was chemically formed using a conventional method and combined with a sintered nickel oxide electrode and a polyamide separator to form a wound battery. The battery is KR-3C type.

A 30% KOH aqueous solution was used as the battery electrolyte.

The figure shows the change in battery internal pressure when rapidly charging at 1.2 A at an ambient temperature of 1 [20° C.]. A is the change in battery internal pressure of a battery using a normal electrode with no cracks, and B is a change in battery internal pressure of a battery using the electrode shown in the example of the present invention. P is the safety valve operating pressure of the battery. As described above, there is no margin for changes in the battery internal pressure A in a normal battery relative to the safety valve operating pressure P, and when the ambient temperature f becomes low, gas leaks outside the battery, resulting in a significant shortening of the battery life. In contrast to this, the battery internal pressure B of the battery according to the present invention
is at most about 1/3 of the safety valve operating pressure P, which is 1.2
It was found that there was no gas leakage when charging at around A (equivalent to ICmA). Furthermore, there was no difference in discharge characteristics between the two.

In this way, it was found that the rise in battery internal pressure could be suppressed, but this is thought to be due to the fact that the surface area of the cathode plate ζ was cracked, which increased the effective surface area and increased the oxygen gas absorption capacity. It will be done.

As mentioned above, the present invention has great industrial value, such as improving the oxygen gas absorption performance of a paste-type cadmium cathode and maintaining the peeling strength of the electrode plate paste.

[Brief explanation of drawings]

The drawing is a comparison diagram of battery internal pressure between a conventional battery and a battery according to the present invention. Patent applicant charging time −

Claims (1)

[Claims] A method for producing a paste-type cadmium cathode, characterized in that a paste-like substance added with alkali-resistant fibers is poured into a core material, and cracks are generated on the surface of the electrode plate when the electrode plate is dried.