JPS5979976A - Manufacturing method of sintered substrate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To prevent a nickel sintered body from being eroded in an acid solution by spraying the high temperature gas containing oxygen on the nickel sintered substrate and forming an acid-proof nickel oxide layer on the surface of the sintered body. CONSTITUTION:The mixed gas composed of oxygen and nitrogen (volume ratio 1 to 1) heated at approximately 600 deg.C was sprayed on a sintered substrate (porosity 80%) obtained by sintering carbonyl nickel powder in a normal way at a flow rate of 4 to 5m for approximately one minute. By spraying the gas, a nickel oxide layer could uniformly be formed both on the surface and at the inside of the sintered substrate and acid resistance could be improved. A nickel cadmium storage battery was obtained by fabricating a nickel positive plate and a cadmium megative plate in a known method using this sintered substrate. After this battery is charged at one-hour rate, characteristics were checked by discharging it at one-hour rate. As a result, a battery 1 by this invention that had the surface of the sintered body oxidized had high discharge capacity and excellent characteristics as compared with a battery 2 that did not have the surface of the sintered body oxidized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a sintered body of nickel powder for use in alkaline batteries, particularly nickel cadmium storage batteries.

Conventionally, sintered substrates for alkaline storage batteries are produced by coating a porous metal plate with a slurry consisting of a binder solution such as methylcellulose or carboxymethylcellulose and a sintering metal powder such as carbonyl nickel or iron, and then reducing it with hydrogen. The sintered substrates thus obtained, especially the nickel sintered substrates, which were produced by sintering in an atmosphere, exhibit extremely high reactivity in acidic atmospheres. To manufacture electrodes for nickel-cadmium storage batteries, a method is generally adopted in which the nickel sintered body is immersed in a nickel nitrate solution for the positive electrode and in a cadmium nitrate solution for the negative electrode, and electrolytically reduced to fill the active material. This method had the disadvantage that the nickel sintered body eroded and became brittle because the nickel nitrate and cadmium nitrate solutions were acidic.

In view of the above points, the present invention aims to prevent nickel sintered bodies from being eroded in these acidic solutions.

In order to achieve the above object, the present invention sprays a high-temperature gas containing oxygen onto a nickel sintered substrate to form an acid-resistant Nisokel oxide layer on the surface of the sintered body.

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

Approximately 6.0 MCII: A heated mixed gas of oxygen and nitrogen (volume ratio 1:1) is applied to a sintered substrate (porosity 80%) made by sintering carbonyl nickel powder in a conventional manner at a flow rate of 4 to 5 m/sec. I sprayed it for about 1 minute.

By spraying, a layer of nickel oxide could be uniformly formed not only on the surface of the sintered substrate but also inside the sintered substrate, thereby improving acid resistance. Using this sintered substrate, a nickel anode plate and a cadmium cathode plate were fabricated by a known method to obtain a nickel-cadmium storage battery.

This battery was charged at a 1 hour rate and then similarly discharged at a 1 hour rate to examine its characteristics. The results are shown in the drawing.

Sample No. 1 has the surface of the sintered body oxidized, and sample No. 2 has the surface of the shingled body not oxidized. The sintered body whose surface was oxidized had a larger discharge capacity and better characteristics than the sintered body whose surface was not oxidized.

As described above, according to the present invention, it is possible to prevent the nickel sintered body from becoming brittle, and the battery characteristics can be improved, so that the present invention has great industrial value.

[Brief explanation of the drawing]

The drawing is a characteristic diagram of the alkaline storage battery according to the present invention, which was charged at a 1-hour rate and then discharged at a 1-hour rate.

Claims (1)

[Claims] A method for manufacturing a sintered substrate for an alkaline battery, which forms an oxidized layer on the sintered body by spraying high temperature gas containing oxygen onto the surface of the sintered body of porous sintered metal.