JPS59177859A - Manufacture of cadmium anode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To provide cadmium anode plate in which active material strongly adheres to core material, for an alkaline storage battery by applying cadmium plating on conductive core material and oxidizing the plating surface, then coating it with paste mainly comprising CdO. CONSTITUTION:Cadmium plating is applied on core material comprising conductive porous thin plate and the surface of the plating layer is oxidized to form CdO, Cd(OH)2 layer. The core material is coated with paste mainly comprising CdO and they are dried and provided with formation. By this process, CdO layer of the core material and a part of CdO of active material are reduced, and the network of metallic Cd is formed. By this network, active material strongly adheres to the core material and coming off of active material is prevented in a battery assembling process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for manufacturing a cadmium cathode plate for an alkaline storage battery.

Conventional methods for manufacturing cathode plates for alkaline storage batteries include the following. The most commonly used method is to use a slurry of nickel powder mixed with an aqueous solution of a binder such as carboxymethyl cellulose on a thin perforated iron plate or net plated with nickel as an active material holder that also serves as a current collector. After coating and drying, it is sintered in a hydrogen stream at a temperature of, for example, about 900° C. to obtain a porous substrate with a porosity of 70 to 85%. Furthermore, this substrate is impregnated with a highly concentrated cadmium nitrate solution, dried, electrolyzed in a caustic alkaline solution kept at high temperature, washed with water, and dried, or simply immersed in a caustic alkaline solution, washed with water, and dried. is the method of
It is called sintering type. However, these manufacturing methods
The process of filling the active material is complicated and requires repeated filling, resulting in a relatively expensive electrode plate.

Another method is to directly apply a paste-like active material containing cadmium oxide as a main component to the core material made of the conductive porous plate or net and dry it, which is more effective than the sintering method. It is very simple and is called the paste method.

The paste-type electrode plate has the disadvantage that the active material is more likely to peel off from the core material during the assembly process, etc., than a sintered-type electrode plate in which the active material is firmly held by the nickel sintered porous body. Ta. In order to prevent the active material from falling off, a method has also been proposed in which a synthetic resin or the like is mixed with a cadmium active material and the active material is bound by heat or pressure. If synthetic resin is mixed in to an extent that minimizes the amount of active material falling off, the amount of active material will be relatively reduced, and the discharge capacity per unit volume of the electrode plate will decrease, so it is not very effective. Not in a good way. Further, although this method improves the strength of the active material itself, it has little effect on improving the adhesion to the core material, especially the perforated plate made of iron coated with nickel, which is the most commonly used material. Next, paste-type electrode plates are usually chemically formed in a caustic alkaline solution to reduce some of the cadmium oxide to metallic cadmium, or after completely reducing the cadmium oxide to metallic cadmium, by discharging some of the gold (
It is treated with Σ group cadmium and incorporated into the battery.
By doing this, a network of metallic cadmium exists inside the active material, so the mechanical strength of the active material itself is improved, but the adhesion between the core material and the active material is hardly improved.)

In view of the above points, the present invention aims to improve the adhesion between the core material and the active material in a paste-type cadmium cathode plate, thereby preventing the active material from peeling off during the assembly process or the like.

In the present invention, the surface of the conductive core material is plated with cadmium, and then the surface of the cadmium layer is oxidized to form a layer of cadmium oxide or cadmium hydroxide on the surface of the core material.

Thereafter, a paste containing cadmium oxide as a main component is applied to the core material using a conventional method and dried to obtain the desired electrode plate. When the electrode plate obtained in this way is chemically formed by the method described above, the cadmium oxide layer on the surface of the core 4 and the metallic cadmium network formed by reducing a part of the cadmium oxide of the active material, The active material is firmly fixed to the base.

EXAMPLE An iron perforated plate having a thickness of 0.08 mm was plated with cadmium in an alkaline plating bath mainly containing a cylindrical complex salt. The thickness of the plating layer was approximately 10 μm. Thereafter, this perforated plate is immersed in a %wt% caustic soda solution and then heated and dried in a flame to form cadmium hydroxide and cadmium oxide layers on the surface of the cadmium plating layer. Immersing the core material in a caustic soda solution facilitates the oxidation of the cadmium plating layer. If this treatment is not performed, only a very thin oxide film will be formed on the surface of the plating layer, which is the purpose of the present invention. However, a core material with excellent adhesion to the active material cannot be obtained.

The thus obtained electrode plate was chemically formed in a caustic alkaline solution, washed with water, and dried. The adhesion between the active material and the core material of this electrode plate and that of electrode plate A manufactured by a conventional method in which chemical formation, water washing, and drying were performed under the same conditions as the above-mentioned method were measured. The measurement was performed by winding the electrode plate around a round bar with a radius of 5 mm, then unwinding it, and measuring the change in weight before and after. The results are shown in the drawings, and the electrode plate B according to the present invention showed almost no drop-off of the active material.

As described above, the present invention has great industrial value as it can improve the adhesion between the core material and the active material and prevent the active material from peeling off.

[Brief explanation of the drawing]

The drawing is a curve diagram showing the results of an adhesion test between an active material and a core material of an electrode plate according to the present invention and an electrode plate according to a conventional method. Patent application 7゛,

Claims (1)

[Claims] After applying cadmium plating to a conductive porous thin plate, the surface of the cadmium plating is oxidized to form a cadmium oxide or cadmium hydroxide layer, and then a paste containing cadmium oxide as the main component is applied. A method for producing a cadmium cathode plate for alkaline storage batteries.