JPS5929374A - Manufacture of cadmium electrode for alkaline battery - Google Patents

Abstract

PURPOSE:To secure a sufficient amount of an active material by carrying out immersion only few times by filling the holes of a porous conductive base plate with saturated steam, then immersing the base plate in aqueous cadmium-nitrate solution having a temperature below the saturation temperature. CONSTITUTION:A base plate with 75-80% porosity is prepared from a perforated nickel-plated steel plate used as a core material by fixing carbonyl nickel to the perforated plate before sintering is performed. After the holes of the base plate are filled with saturated steam with over 100 deg.C temperature, the base plate is immersed in about 5mol/l aqueous cadmium-nitrate solution with 70 deg.C temperature. At this point, since saturated steam existing in the holes condenses, the aqueous solution can be compulsorily incorporated into the holes. After the above immersion, the base plate is held in alkali solution with about 80 deg.C temperature, thereafter being washed with water before dried. The process is repeatedly carried out 4-6 times until a desired amount of the active material is secured. By carrying out the above described method, a sufficient amount of the active material can be obtained by carrying out immersion only few times.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for manufacturing cadmium electrodes for alkaline batteries.

A cadmium cathode plate is manufactured by filling an active material into a conductive porous substrate (hereinafter referred to as "substrate") made by sintering nickel powder, and then chemically forming the active material in an alkaline solution. To fill the active material, the substrate is roughly immersed in a cadmium nitrate aqueous solution and then electrolytically reduced in an alkaline solution to form Cd metal, or it is converted to cd(OH)t without electrolysis2.
There is a way. (The former is called "electrolytic impregnation" and the latter is called "chemical impregnation.") Electrolytic impregnation requires a large amount of current in the process, so it requires a large amount of equipment and maintenance costs. On the other hand, chemical impregnation can simplify the equipment by omitting the energizing equipment, and can reduce equipment and maintenance costs.

Conventionally, as impregnation with cadmium nitrate is repeated, the active material becomes unevenly distributed due to Δ, making it difficult for cadmium nitrate to enter the pores of the substrate. In particular, chemical impregnation has the disadvantage that if the number of impregnations is small, the amount of active material becomes insufficient compared to electrolytic impregnation.

In view of the above points, an object of the present invention is to provide a method for producing a cadmium electrode for alkaline batteries that can secure a sufficient amount of active material with a small number of impregnations.

In the present invention, the pores of a conductive porous substrate are filled with saturated water vapor, and then the substrate is immersed in an aqueous cadmium nitrate solution at a temperature below the saturation temperature.

The present invention is particularly effective in chemical impregnation.

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

First, after using a perforated steel plate as a core material, carbonyl nickel is coated with 411 layers of carbonyl nickel, and the pores of the sintered substrate with a porosity of 75 to 80 inches are filled with saturated water vapor at a temperature of 100°C or higher. The substrate is immersed in an aqueous solution of about 5 mnl/l of cadmium nitrate at a temperature of 70°C. Since saturated water vapor condenses, the aqueous solution can be forcibly taken into the pores.

After immersion, it is kept in an alkaline solution at about 80°C, washed with water, and dried. This process is repeated 4 to 6 times to ensure the amount of active material.

In the drawing, A is the theoretical value of the amount of active material, B is the pores of the substrate containing saturated water vapor of 100°CQJ, and C.
does not contain saturated water vapor.

It can be seen from the drawings that the amount of active material loaded with saturated water vapor is significantly higher than that without. Furthermore, since the filling rate of Cd (OH) 2 is practically required to be 40% or more, it can be seen that the number of impregnation times is only 4 for those containing saturated steam.

), as mentioned above, the present invention is of great industrial value, as even in chemical impregnation, it is possible to obtain a sufficient amount of active material for practical use with a small number of impregnations.

[Brief explanation of drawings]

The drawing is a curve diagram showing the relationship between the number of impregnations and the filling rate of active material in the present invention. Patent applicant Shin-Kobe Electric Co., Ltd.

Claims (1)

[Claims] A method for producing a cadmium electrode for an alkaline battery, which comprises filling the pores of a conductive porous substrate with saturated water vapor and then immersing the substrate in a cadmium nitrate aqueous solution at a temperature below the saturation temperature.