JPS60158554A - Alkaline battery - Google Patents

Abstract

PURPOSE:To reduce the amount of mercury to be added to zinc by using zinc- thallium-mercury alloy and alkaline electrolyte prepared by dissolving a specified amount of zinc oxide. CONSTITUTION:A zinc-thallium-mercury alloy anode and alkaline electrolyte containing 1-7% zinc oxide are used. For example, monothallium nitrate is dissolved in water, then zinc powder is added in the solution and stirred. The solution is filtered out and zinc-thallium alloy obtained are dried at 70 deg.C. The zinc- thallium alloy is added into potassium hydroxide solution, then mercury is added to it, and they are stirred and filtered and washed until the pH of the filtrate becomes about 7. The alloy powder is dried under reduced pressure at 40 deg.C. Zinc-thallium-mercury alloy powder having a amalgamation ratio of 0.5% is obtained.

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.

(b) Conventional technology In this type of battery, when zinc as a cathode active material is present in an alkaline electrolyte, it dissolves with hydrogen generation, which leads to self-discharge of the cathode and deteriorates storage performance. There is an inconvenience that as the internal pressure of the battery decreases, the internal pressure of the battery increases, causing a leakage phenomenon.

In order to prevent such inconveniences, C: hydrated zinc powder is generally used as the 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 service 133-1973
No. 86 Publication I: According to 1, the amount of added mercury is usually 1d8 to 15
%, but if a corrosion inhibitor is added, the amount of mercury added can be reduced to 5%.
There is a disclosure that it is possible to reduce the amount to % or less (3 to 5% as a specific example).

Q. Purpose of the Invention The purpose of the present invention is to investigate additives to frozen zinc, and to drastically reduce the amount of mercury added by taking into account the dependence of the zinc oxide concentration in the alkaline electrolyte. There is.

4. Structure of the Invention The present invention resides in an alkaline battery comprising an anode, a cathode containing a zinc-thallium-mercury alloy as an active material, and an alkaline electrolyte in which 1 to 7% of zinc oxide is dissolved.

Example: After adding 5.0 y of thallium nitrate to 500 ml of water and stirring to dissolve it, 500 ff of zinc powder was added and stirred well for 10 minutes, and then the solution was passed through the mouth to obtain a zinc-thallium alloy. Powder = l (dry at 70″C.

After drying, this zinc-thallium alloy powder'f 500 m
Add 2.5y of mercury to a 20% by weight aqueous potassium hydroxide solution of e, stir well for 30 minutes, pass through the solution, and then wash with water until the pH of the passthrough becomes approximately 7. . After that, it was dried under vacuum at 40°C and used as a zinc-thallium-mercury alloy powder (with a hydrogenation rate of 0.5%) as a cathode active material.
).

In addition, after raising the temperature of a 40% by weight aqueous potassium hydroxide solution to 80°C, zinc oxide was added to the solution to give a concentration of 1%, 5%, and 7% g, and dissolved to form the alkali of the present invention. Obtain electrolyte.

On the other hand, for comparison, the conventionally used zinc hydrate (freezing rate: 1.5%, 6.0%, lO%) and the alkali solution containing zinc oxide t-saturated in a 40% by weight potassium hydroxide aqueous solution. All electrolytes were prepared.

Table 1 shows that certain amounts of zinc-thallium-mercury alloy powder and frozen zinc powder were taken out and immersed in various alkaline electrolytes having different total zinc oxide concentrations.

This is a comparison of the amount of gas generated when the samples were left at a temperature of 45°C for 6 days.

Table 2 shows a cathode made of zinc-thallium-mercury alloy powder or frozen zinc powder as an active material, an anode made of manganese dioxide as an active material, and an alkali made of various potassium hydroxide aqueous solutions with different concentrations of zinc oxide. 100 alkaline batteries were made using each of the ``Tunkai solution'' and warmed up. t6D℃
, shows the results of examining the number of leaks after 6 months of being left at 90% humidity.

As is clear from Tables 1 and 2 (Table 1, Table 2), the higher the freezing rate of frozen zinc, the less gas it generates, and the more the leakage phenomenon occurs. It can be seen that the amount of gas generated and the leakage phenomenon are also affected by the concentration of zinc oxide in the electrolyte.

Now, as in the battery of the present invention, zinc-thallium-mercury alloy powder is used as the cathode active material, and the zinc oxide concentration is 1 to 7%.
When using an alkaline electrolyte, the amount of mercury added is 0.
．． Even if it is 5%, the amount of gas generated can be suppressed compared to the case where conventional long-lived zinc (freezing rate: 7.0%) is used as the cathode active material.

(f) Effects of the invention As mentioned above, by using a zinc-thallium-mercury alloy as a cathode active material and using an alkaline electrolyte in which 1 to 7% of zinc oxide is dissolved, the ice that was conventionally used as a cathode active material is reduced. It is possible to obtain the same or better battery performance by using only a very small amount of mercury in the mercury addition port, and its industrial value is extremely large.

Applicant: Sanyo Electric Co., Ltd. Agent: Patent attorney Shizuo Sano

Claims (1)

[Claims] (2) An alkaline battery comprising an anode, a cathode made entirely of a zinc-thallium-mercury alloy active material, and an alkaline electrolyte in which zinc oxide't-1 to 7% is dissolved.