JPS59121784A - Manufacture of cadmium electrode - Google Patents

Abstract

PURPOSE:To prevent ionization if nickel metal during later manufacturing process, by forming a thin anti-oxidation nickel layer on the surface of sintered nickel metal. CONSTITUTION:A nickel substrate is sintered in inert gas environment containing micro amount of oxygen such that the amount of nickel oxide after sintering will be higher than 0.01% but lower than 3%. For example, it is held for 5min at 920 deg.C in nitrogen flow containing 0.1% of oxygen to produce a sintered nickel substrate oxidized in the range of 0.01-3%. Consequently in a substrate having nickel oxidized surface, deterioration of impregnation of active substance or emblittlement is not so high while corrosion during manufacturing process is prevented by anti-oxidation film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing sintered cadmium electrodes used in nickel-cadmium batteries and the like.

Conventionally, sintered nickel substrates such as nickel, cadmium, etc.
It has been sintered at °C. This is because nickel becomes brittle when oxidized and the amount of cadmium impregnated decreases. Furthermore, sintered cadmium electrodes can be charged and discharged with large currents, are expensive to use, and have a long lifespan, but they are expensive and have the disadvantage of causing a potential drop (memory effect). are doing.

In view of the above point lc, the present invention is intended to reduce and eliminate the memory effect of the sintered cadmium electrode.

Research on the memory effect of sintered cadmium electrodes has been gaining momentum in recent years.

It is generally accepted that the main cause of the memory effect is the formation of an alloy between nickel and cadmium.

It was found that the rate of direct formation from sintered nickel metal is slow, but the rate of alloy formation is faster when sintered nickel metal is 1ζ ionized during the manufacturing process. Ionization (oxidation) during the manufacturing process of sintered nickel metal occurs during immersion in an impregnating solution containing active material raw materials such as cadmium nitrate, and after leaving it (removing the impregnating solution attached to the surface). I understand. In particular, it became clear that when nitrates were used, the effect of ζ was severe when the temperature was raised. The object of the present invention is to form a thin oxidation-resistant nickel oxide layer on the surface of sintered nickel metal to prevent ionization of the nickel metal during subsequent manufacturing steps.

The present invention produces a sintered nickel substrate oxidized to a concentration of 0.01% to 3% by sintering nickel powder in a weak oxidizing atmosphere. The reduced amount of active material impregnated and the embrittlement of the substrate are not so large (and corrosion during the manufacturing process is prevented due to the formation of an oxidation-resistant film).

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

The liquid slurry of nickel powder used for sintering is carbonyl nickel powder (INCO #255 type).
A mixture kneaded with an aqueous MC solution was used. This slurry liquid was molded through a slit and dried to form a thin plate with a thickness of 090. As a core material for molding, a perforated plate (approximately 0.09 m++n) of iron plated with nickel was used. The product thus produced was sintered by keeping it at 920° C. for 5 minutes in a nitrogen stream (containing 0.1% oxygen). The sintered nickel substrate made in this way contains 1 nickel oxide.
It contained 5%.

The porosity was 82%, the same as that similarly sintered in a hydrogen stream. Using this sintered nickel substrate, a battery was assembled by impregnating it with cadmium using a conventional chemical impregnation method. The amount of impregnation was determined in order to compare the size of the conventional memory effect.
After charging at 0.2 CmA at 5° C. for 10 days, it was disassembled, the cadmium electrode was taken out, and discharged in a 30% KOH aqueous solution using a nickel dummy plate as a partner device. Figure 1 shows the terminal voltage at that time. The discharge current is 0.2CmA (
0.24A). As shown in FIG. 1, in the cadmium electrode A according to the present invention, no potential drop (memory effect) accompanying zero alloy formation was observed. B is a conventional cadmium electrode.

FIG. 2C shows the relationship between the nickel oxide content, the memory electricity iE, and the active material impregnation amount N when the same operation as in the above example was performed with different oxygen concentrations. (KR-C for the test
The effect of reducing the memory electricity amount E (using a type battery) can be seen even with a nickel oxide content of about 0.01%. In particular, at 1% or more, the memory electricity iiE becomes zero. However, when the thickness was 3 or more, a decrease in the amount N of active material impregnated was observed. In this way, by using a sintered nickel substrate containing 01% to 3% nickel oxide, it was possible to suppress the memory effect without reducing the amount N of active material impregnated.

Memory effects occur when left unused for long periods of time or trickle charging.

It appears in cycle service applications where deep discharge is not performed, and significantly reduces battery capacity. In particular, high temperatures can have a very large effect on battery characteristics, such as causing deterioration in a relatively short period of time.By implementing the present invention, these drawbacks could be eliminated.

As described above, according to the present invention, an oxidation-resistant coating is formed on the substrate, thereby preventing corrosion during the manufacturing process, which has great industrial value.

[Brief explanation of the drawing]

Figure 1 shows the temperature at 45°C in one embodiment of the present invention. = 5- A curve diagram showing the results of a cadmium electrode single plate discharge test after 0.2 CmA overcharging JO days. Figure 2 shows the relationship between the nickel oxide content in the sintered body and the amount of memory electricity and active material impregnated. FIG. patent applicant

Claims (1)

[Claims] The amount of nickel oxide after sintering the sintered nickel substrate is 0.
1. A method for producing a cadmium electrode, characterized in that the process is carried out in an inert gas atmosphere containing a trace amount of oxygen of 0.1% or more and 3% or less.