JPS61181071A - Alkaline cell - Google Patents

Abstract

PURPOSE:To reduce the adding amount of mercury by employing zinc-cadmium- mercury alloy as active substance in the negative electrode. CONSTITUTION:Cadmium chloride 40g is added into water 500ml then agitated and dissolved thereafter, zinc powder 500g is added and agitated for 10min. Then upper clean liquid is removed and washed with 500ml water thereafter potassium hydroxide aqueous solution of 20wt% concentration is added while furthermore mercury 2.5g is added and agitated for 30min. Thereafter, it is washed with water until pH of the cleaning water will be about 7 and dried under the temperature of 60 deg.C to produce zinc-cadmium-mercury alloy. Cadmium adsorbed to the surface of zinc will increase the hydrogen over voltage of zinc to suppress production of hydrogen gas while the gelation will contribute for the combined effect of cadmium and mercury thus to reduce production of hydrogen gas considerably, resulting in reduction of adding amount of mercury without increasing production of hydrogen gas.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an alkaline battery using zinc as a cathode active material.

C port 1 Conventional technology In this type of battery, when zinc as a cathode active material is present in an alkaline electrolyte, it dissolves with the generation of hydrogen, which leads to self-discharge of the cathode, deteriorating storage performance and damaging the inside of the battery. There is a disadvantage that the increase in pressure causes liquid leakage.

Therefore, in order to prevent such disadvantages, frozen zinc powder is generally used as a cathode active material. However, since mercury is an extremely harmful substance to the human body, the use of mercury in batteries has become a major social problem.

Therefore, proposals have been made to add various additives for the purpose of reducing the amount of mercury added. For example, the special public official court 1333-1973.
According to Publication No. 86, the amount of mercury added is usually 8 to 15%.
If a corrosion inhibitor is added, the addition of mercury can be reduced to 5%.
There is a disclosure that it is possible to reduce the amount below (3 to 5% as an example).

(c) Problems to be Solved by the Invention It is an object of the present invention to further reduce the amount of mercury added without increasing the amount of hydrogen gas generated.

B) Means for Solving the Problems The present invention is characterized in that a zinc-cadmium-mercury alloy is used as the active material of the cathode.

(E) Function According to the cathode active material made of a zinc-cadmium-mercury alloy, even if the amount of mercury added, that is, the permanent rot is extremely low at 0.5%, the hydrated zinc with a hydration rate of ZO% can be reduced. The amount of hydrogen gas generated is reduced compared to the case of

(f) Example Examples of the present invention will be described in detail below.

After adding 40 f of cadmium chloride to 500 d of water and stirring and dissolving it, 500 yt of zinc powder was added and stirred well for 10 minutes. Then, discard the supernatant liquid and wash with 500 d of water.
Potassium hydroxide aqueous solution 500rId with a concentration of 20% by weight
! Add 2.52 ml of mercury to the nail and stir for 30 minutes.

After that, wash with water until the pH of the washing water becomes about 7.
C. to obtain a zinc-cadmium-mercury alloy. still,
The freezing rate of this alloy is 0.5%.

On the other hand, for comparison, the conventionally used frozen zinc (
The freezing rate was 5.0% and 10%).

The following table shows that fixed amounts of curved lead-cadmium-mercury alloy powder and frozen zinc powder according to the present invention were taken out and immersed in a potassium hydroxide aqueous solution with a n* concentration of 40% by weight at a temperature of 45°C.
This is a comparison of the amount of gas generated when left for days.

As is clear from the above table, although the zinc-cadmium-mercury alloy powder used in the battery of the present invention has a low freezing rate, the amount of gas generated is very small. To consider the reason for this, 1) In the case of the cathode active material used in the present invention's Kameike, the hydrogen overvoltage of zinc is increased due to cadmium adsorbed on the zinc surface, suppressing hydrogen gas generation and further freezing. Therefore, it is thought that the synergistic effect between cadmium and mercury contributed greatly, and the amount of hydrogen gas generated was significantly reduced.

(G1. Effects of the invention As mentioned above, zinc is used as a cathode active material for alkaline batteries.
By using a cadmium-mercury alloy, it is possible to reduce the amount of mercury added without increasing the amount of hydrogen gas generated.

Its industrial value is extremely large.

Claims (1)

[Claims] (1) An alkaline battery comprising an anode, a cathode using a zinc-cadmium-mercury alloy as an active material, and an alkaline electrolyte.