JPH024106B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintered substrate for alkaline batteries, particularly a nickel powder sintered body used for cadmium electrodes used in nickel-cadmium storage batteries (hereinafter referred to as "Ni--Cd 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 sintering metal powder such as carbonyl nickel or iron, and then sintering it in a hydrogen reducing atmosphere. It was manufactured by tying it together. The sintered substrate thus obtained, especially the nickel sintered substrate, exhibits extremely high reactivity in an acidic atmosphere. In order to manufacture a cadmium electrode, a method is generally adopted in which the nickel sintered body is immersed in cadmium nitrate and then electrolytically reduced to fill it with an active material. According to this method, the nickel sintered body was eroded because the cadmium nitrate solution was acidic. This phenomenon is said to be the cause of forming a Cd--Ni alloy in the active material of a cadmium electrode, and in the case of a Ni--Cd battery, it caused a voltage drop during discharge as shown by curve A in the drawing.

An object of the present invention is to improve voltage characteristics during discharge by preventing a nickel sintered body from being eroded in a cadmium nitrate solution during the manufacture of a cadmium electrode.

In order to achieve the above object, the present invention sinters carbonyl nickel powder in a reducing atmosphere (approximately 800°C), cools the substrate to a temperature of 700 to 300°C, and then cools it in air. By forming an acid-resistant nickel oxide layer on the surface of the sintered body, the nickel sintered body is prevented from being corroded in an acidic solution.

Next, examples of the present invention will be described.

Carbonyl nickel powder in a reducing atmosphere (approx.
The sintered substrate sintered at 800°C) was cooled to a temperature of 700 to 300°C, and then left to cool in air. By cooling in air, an acid-resistant nickel oxide layer was formed on the surface of the sintered body. A cadmium electrode was prepared by a known method using an oxidized sintered substrate, and Ni
- Used as a CD battery.

This battery was charged at a rate of 1 hour and then discharged at a rate of 1 hour in the same manner to examine its characteristics. The results are shown in the drawing. In the drawings, curve B uses a substrate with an oxidized sintered body surface, and curve A uses a substrate whose sintered body surface is not oxidized. When a substrate was used that did not oxidize the surface of the sintered body, the discharge curve became two stages and a voltage drop occurred. However, the material B, in which the surface of the sintered body was oxidized, did not suffer from voltage drop due to two-stage discharge and exhibited good discharge characteristics.

As described above, according to the present invention, the characteristics of Ni-Cd batteries can be significantly improved by a simple method of allowing the sintered substrate to cool in the air after sintering the sintered substrate. The value is enormous.

[Brief explanation of drawings]

The drawings are characteristic curve diagrams of batteries using a substrate with an oxidized sintered body surface and a substrate without oxidation, which were charged at a 1-hour rate and then discharged at a 1-hour rate.

[Claims]

1 Nickel powder is sintered to make a nickel porous substrate, the sintering is performed in an inert gas containing a trace amount of oxygen, and the nickel porous substrate contains 0.01% to 3% by weight of nickel oxide. A method for producing a cadmium electrode, comprising: then impregnating cadmium into the nickel porous substrate.