JPS607060A - Manufacture of positive plate for nickel cadmium storage battery - Google Patents

Abstract

PURPOSE:To obtain a positive plate for a nickel cadmium storage battery containing a reduced amount of nitrate radicals by impregnating a sintered nickel base plate with nickel nitrate, then immersing the impregnated plate in an aqueous solution of potassium hydroxide or the like. CONSTITUTION:After a porous sintered nickel base plate is impregnated with nickel nitrate, the impregnated plate is subjected to catholysis in aqueous sodium-hydroxide solution to convert nickel nitrate into nickel hydroxide thereby causing nitrate ions to be discharged outside the sintered base plate. After that, the base plate is immersed in either sodium hydroxide or aqueous sodium- hydroxide solution at ordinary temperature or above so as to cause nitrate radicals contained in the positive plate to be exhausted outside. According to such a method as mentioned above, the content of nitrate radicals in the positive plate for a nickel cadmium storage battery is greatly decreased, thereby improving the self discharge performance of the battery.

Description

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

Conventionally, the manufacturing method for anode plates for nickel-cadmium storage batteries is as follows:
A slurry made by mixing a binder with nickel powder is applied to a nickel core material or a nickel-plated core material to an iron plate, and sintered in a reducing gas atmosphere furnace at 700 to 900°C. Make a sintered substrate. Next, the substrate is filled with an active material mainly composed of nickel hydroxide.

Filling with this active material involves immersing the sintered substrate in an aqueous solution of nickel nitrate heated to 80 to 90°C, and then removing the nitrate radicals of the nickel nitrate impregnated into the sintered substrate. The sintered substrate is subjected to negative electrolysis in an aqueous solution of sodium hydroxide, and the nitrate radicals in the sintered substrate are released to the outside of the sintered substrate. At this time, the ratio of nitrate radicals released to the outside of the sintered substrate by negative electrolysis is about 80 to 9,596 of the impregnated nitrate radicals.

To fill the pores of a sintered substrate with a specified amount of active material,
It is necessary to repeat this impregnation and electrolysis 5 to 6 times, and each time the impregnation is repeated, nitrate radicals are accumulated in the sintered substrate, eventually reaching a concentration of 2.000 ppm to 10,000 ppm. The electrode plate obtained in this way is charged and discharged in the next step of chemical formation, and its concentration is increased from 800 to 1.0.
00ppm. However, 800-1.
Anode plates containing OOOppm nitrate radicals have extremely poor self-discharge while the battery is left, and when left at 40°C for 7 days, the remaining capacity is approximately 50 to 65% of the initial capacity. was.

The present invention obviates the above-mentioned drawbacks, and embodiments thereof will be described below.

Negative electrolysis. After repeating this impregnation and electrolysis several times, 1
By immersing the anode plate in an aqueous solution of 0 to 40% potassium hydroxide or sodium hydroxide for 30 minutes to 1 hour, the nitrate radicals inside the anode plate are discharged to the outside.

The figure shows the change in the concentration of nitrate groups in the anode plate after chemical formation when the temperature of the dipping solution of sodium hydroxide of 2096 is changed.
The concentration of nitrate radicals in the anode plate immersed in a 20°C immersion solution after chemical formation was s
o o ppm, and the anode plate immersed in a 100° C. immersion solution after chemical formation has a significantly lower amount of 400 pl)m.

Also, the temperature of the immersion liquid is preferably between room temperature and 100°C.
In particular, if the temperature is 100°C, the amount of nitrate radicals removed will be large.

In this way, the concentration of nitrate groups in the anode plate after conventional chemical formation is 8.
00-1.000 ppm, compared to 1, that of the anode plate according to the present invention is significantly lower.

In addition, a battery assembled using the anode plate according to the present invention was heated at 40°C.
, after leaving it for 7 days, the initial capacity was 70-8096.
The remaining capacity of conventional batteries (50 to 6 of the initial capacity)
5% remaining capacity), it can be seen that self-discharge while the battery is left is extremely small.

As described above, according to the present invention, the content of nitrate radicals in the anode plate is significantly reduced, and the self-discharge performance of the battery is significantly improved compared to conventional products. It is a big thing.

[Brief explanation of the drawing]

The drawing is a characteristic curve of the concentration change of nitrate radicals in the anode plate after chemical formation with respect to the temperature change of the immersion liquid according to an embodiment of the present invention.

Claims (1)

[Claims] Nickel characterized by impregnating nickel nitrate into the pores of a sintered nickel substrate to convert the nickel nitrate into nickel hydroxide, and then immersing it in an aqueous solution of potassium hydroxide or sodium hydroxide at a temperature above room temperature. A method for manufacturing anode plates for cadmium storage batteries.