JPS60140656A - Production of cadmium negative electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To eliminate the chemical conversion process and simplify the production process by coating a conductive, porous plate with a slurry-like active material kneaded with nickel powder, cadmium oxide, and metallic cadmium powder obtained by reducing cadmium oxide powder in the reducing atmosphere using an adhesive solution then drying it. CONSTITUTION:Cadmium oxide powder of 0.5-1mu is heated in a hydrogen stream to obtain metallic cadmium by reducing cadmium oxide. A mixture of metallic cadmium thus obtained, cadmium oxide, and nickel powder at a ratio of 2:7:1 is kneaded with an organic, adhesive solution, then a nickel-plated porous iron plate is coated with it and is dried to obtain an electrode plate. The electrode plate thus obtained does not contain impurities such as zinc sulfate as before, and metallic cadmium grains existing in an active material are fine, thereby the electrode plate has advantages that it is excellent in the charging/ discharging characteristics and also the capacity reduction while left as it is little.

Description

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

Conventionally, typical methods for manufacturing cadmium cathode plates for alkaline storage batteries include the following. The first method is currently the most widely used, and uses a thin perforated iron plate with nickel plating, a net, or a net as an active material holder that also serves as a current collector. Ru → wo Sat-/Me hand J
A slurry kneaded with an aqueous binder solution such as Shishichi Rouleau 7 is applied, dried, and then sintered in a hydrogen stream at a temperature of, for example, about 900° C. to obtain a porous substrate having a porosity of 70 to 8,596. After that, this substrate is impregnated with a highly concentrated cadmium nitrate solution, dried, electrolyzed in a caustic alkaline solution kept at a high temperature, washed with water, dried, or simply immersed in a caustic alkaline solution, washed with water, and dried. It is called the "sintering method." These manufacturing methods require a complicated active material filling process and require repeated filling, resulting in relatively expensive electrode plates.

The second 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." In this manufacturing method, the mechanical strength of the active material is weaker than that of a sintered electrode plate in which the active material is firmly held in a nickel sintered porous body, and the active material peels off from the core material during the assembly process etc. It has the disadvantage of being easy to do.

On the other hand, in alkaline storage batteries that use cadmium as the cathode active material, the capacity of the cathode plate is 20 to 30% greater than the capacity of the anode plate.
Battery capacity is dominated by the anode plate. This is because the cathode plate is more susceptible to deep charging and discharging, and the capacity decreases to a greater degree as the charging and discharging cycles progress. For these reasons,
The state of the electrode plate at the time of assembly is usually that the anode plate is in a fully discharged state,
The cathode plate is charged to about 20 to 30% of the battery capacity. This is also the case with paste-type cathode plates, where a paste consisting mainly of cadmium oxide is applied to the core material, dried and then chemically converted in a caustic alkaline solution to reduce some of the cadmium oxide to metallic cadmium. After it is completely reduced to metallic cadmium, it is discharged, leaving some metallic cadmium, and is then incorporated into a battery.

Furthermore, the chemically formed electrode plates require one culm of washing and drying, so if the process from applying the paste to assembly was carried out in a continuous line, the production equipment line would be extremely long, which would be impractical. .

From this point of view, it has been proposed to use metal cadmium as a part of the starting material in order to eliminate the above-mentioned chemical conversion process of paste-type electrode plates and simplify the alkaline storage battery manufacturing process.

What about this metal cadmium? 8 For reasons such as activity within the pond, it is desirable that the powder be as fine as possible. As a method for obtaining such fine metal cadmium, a method has been proposed in which metal cadmium is precipitated by adding zinc powder to a cadmium sulfate aqueous solution, but zinc sulfate remains in the cadmium obtained in this way. Therefore, it has disadvantages such as requiring a long time of washing with water.

The present invention aims to obtain fine metallic cadmium containing no impurities by directly reducing cadmium oxide powder.

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

Cadmium oxide powder of 05 to 1 μm was heated to about 29 μm in a hydrogen stream.
The mixture is heated to 0° C. to reduce cadmium oxide and obtain metal cadmium. The thus obtained mixture of 2:1 of metal cadmium, cadmium oxide, and nickel powder was kneaded with an organic adhesive solution, and then applied and dried on a nickel-coated iron porous plate to obtain the desired electrode plate.

The electrode plates obtained in this way do not contain impurities such as zinc sulfate unlike conventional ones, and the metal cadmium particles present in the active material are also fine, so they not only have excellent charge and discharge characteristics, but also have a high capacity when left unused. It has advantages such as less deterioration.

patent applicant

Claims (1)

[Claims] A slurry active material obtained by kneading metallic cadmium powder obtained by reducing cadmium oxide powder in a reducing atmosphere, cadmium oxide and nickel powder with an adhesive solution is applied to a conductive porous plate and dried. A method for producing a cadmium cathode plate for an alkaline storage battery, characterized by: