JPS60146456A - Zinc alkaline battery - Google Patents

Abstract

PURPOSE:To obtain a high-capacity zinc alkaline battery containing only a small amount of mercury by using as the negative active material a powder prepared by amalgamating an alloy principally composed of zinc and containing Ga and Tl. CONSTITUTION:A powder prepared by amalgamating an alloy (Zn-Ga-Tl) powder principally composed of Zn and containing Ga and Tl, is used as an active material for a negative electrode 5. It is preferable that the above powder be prepared by performing amalgamation by a wet method by dropping Hg into KOH solution of 30% concentration containing the alloy powder while stirring it to coat the surfaces of the alloy particles with Hg, followed by washing the amalgamated powder with water before drying the powder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a zinc anode for a lll'i lead-alkaline battery oriented towards low mercury.

Structure of conventional example and its problems Conventionally, frozen zinc powder has been used as the negative electrode active material of alkaline batteries, for example, alkaline batteries that use silver oxide, manganese dioxide, mercury oxide, etc. in the electrode. Compared to Leclanchier batteries that use a neutral electrolyte, this zinc-alkaline battery suffers from severe corrosion and dissolution of the zinc powder by the electrolyte, resulting in the generation of hydrogen gas and a basic problem that causes significant self-depletion. There was a problem.

As a measure to prevent this, it is necessary to maintain the hydrogen overvoltage of the lead 11 powder at a high level, and icing treatment with mercury (Hq) is generally performed.

However, even if the surface of the instant lead powder is coated with H (J) in i), if storage continues for 14 periods, the Hg on the surface of the zinc powder
diffuses into the grain boundaries of zinc and moves into the grain interior. Therefore, the Hq concentration initially on the particle surface gradually decreases, the hydrogen overvoltage on the surface decreases, and self-depletion progresses with the generation of hydrogen gas.

This patented phenomenon promotes high-temperature storage in the case of 4+ digits. In order to suppress this phenomenon, conventionally, a large amount of Hg was coated and retained on the surface of the zinc powder in advance.

However, this leads to a decrease in the amount of active material of zinc itself,
There was a drawback that the actual discharge capacity decreased. Therefore, it is desirable to limit the amount of Hq added to the zinc powder as much as possible.

This is because, in addition to increasing the actual discharge capacity, when discarding a discharged battery, there is a risk that the Hg in the battery will contaminate the environment and cause pollution problems. Many proposals have been made to reduce the freezing rate of zinc powder.

For example, as shown in JP-A-48-7733, after In or In compound is dissolved in HCl in advance,
A manufacturing method has been proposed in which the zinc particles are diluted with water and the zinc particles are treated with this solution to form an In alloy on the particle surface.

In addition, as shown in Jpn. Pat.
Alloys have also been proposed.

In this way, In is attached to the surface of Zn,
An alloy of n-In is already known. These effects of adding In are aimed at increasing the hydrogen overvoltage in an alkali. However, with the addition of In, the effect of raising the hydrogen overvoltage of l: is smaller than that of Hq, and the diffusion movement of Hg to the grain boundaries of zinc is sufficiently inhibited.
1) The object of the invention is to provide a zinc-alkaline battery with a high capacity and low mercury, which eliminates the drawbacks of the above-mentioned conventional examples.

Structure of the Invention The present invention has Zn as a main component and Ga as an alloying element.
and TI to form an alloy (Zn-Ga-T l
) is used by freezing the powder, preferably fki! According to the formula method, Hq was added dropwise to the powder while stirring in KOH at a concentration of 30%, and the powder surface was treated with Hq.
After coating, it was washed with water and dried.

Description of Examples Based on a Zn ingot with a purity of 99.99%, G
○ and l for a and TI respectively! wt% added Zn −, G
Make a ternary alloy of a-T I. The alloy trial production conditions at this time were as follows: Using a graphite crucible, a Zn ingot was previously heated and melted in an electric furnace at about 600°C in an inert atmosphere to create a molten metal, and the molten metal was mixed with Ga and T as additive elements. / for each 0.
After adding 2 wt% and thoroughly stirring to obtain a uniform composition, a ternary alloy powder with a mesh of j'150 to 150 is produced by a spraying method.

In this case, it is also possible to create a quaternary alloy of Zn-Ga-Tl-Hg by mixing Ga, TI, and Hq in the necessary molten Zn, and then turn this into powder by a spraying method. .

Using the Zn alloy powder made in this way, we will evaluate the method of measuring and evaluating the amount of gas generated without stirring, and we will apply it to a button-type battery and confirm its effectiveness.

First, the amount of gas generated was measured using Zn powder 10. ZnO
The sample was placed in 1 volume of KOH electrolyte with a concentration of 40 parts dissolved therein and left at 46°C for 3 months, and the total amount of gas generated was investigated.

10,000, battery evaluation is button type silver oxide battery TIS nominal
I made a prototype of 5R44 type and achieved 500 at 20'C! -) Discharge duration during continuous discharge p+r4 solid 1゜In the figures for explaining embodiments of the present invention with reference to the drawings, 1 is iE 4'?, which also serves as a positive terminal. 2 is a positive electrode mixture formed by mixing and molding silver oxide, M n 02, and graphite; 3 is a separator made of a microporous synthetic resin film that is in close contact with the positive electrode; 4 is an electrolyte holding shrine made of a synthetic nonwoven fabric. , 6 is a gel-like negative electrode body made of a mixture of frozen zinc powder, synthetic glue, and Alka J IJ electrolyte.

6 is a negative electrode can which also serves as a negative electrode terminal. Reference numeral 7 denotes an insulating backing made of synthetic resin, which is made by bending the eye end of the positive electrode can inward to tighten the entire battery and seal the opening.

Effects of the Invention Regarding the effects of the present invention, compared with the conventional example, the amount of gas generated and the discharge time shown in the following table are as follows.
The material tl' subjected to the aging treatment had properties equivalent to those of the conventionally applied zinc powder "C" with a freezing rate of 10. In addition, in DJ of the Zn-I-1g system with a conversion rate of 1, Hq7' on the powder surface is small, and during storage, Hq diffuses into the grain boundaries of 110 lead. Bq slippage is reduced, hydrogen overvoltage is reduced, and gas generation is promoted.

In addition, the "B" of the Zn-ln-Hg system has 1% Hq, but since In is added, B does not reach the Zn grain boundaries.
The diffusion movement of q is suppressed, and Hq on the surface of the zinc powder remains relatively uniform even after high-temperature storage, and this effect is evident to some extent. Note that the addition of In alone may not be able to completely suppress the diffusion and movement of Hg, and self-depletion may proceed.

rA of the present invention has an excellent effect of stably retaining H (J) on the surface of 1111 lead powder after icing treatment by simultaneously adding Ga and Td as effective additive elements and alloying them. It can be seen that

This alloy is stable in alkaline electrolytes, making it possible to minimize Hq, which is about the same as that of conventional frozen zinc. It is possible to provide

In the above embodiments, a button-type silver oxide battery was explained as an example, but Alka IJ-N, 1, which uses zinc as the negative electrode active material,
This can be widely applied to ljL.

In addition, Ga and Tl are each used as effective additive elements of the present invention.
．． The case where 2% was added was explained, but even if the amount was more than 2%, it was not very effective for improving the battery characteristics.

[Brief explanation of the drawing]

The figure is a half-sectional view of a button-type silver oxide battery in an example of the present invention. 1...Positive electrode can, 2...Positive electrode mixture, 3.
・Separator, 4... Electrolyte holding material, 6...
・Gel zinc 9 poles, 6...Negative terminal, 7...
Gasket, 8... Positive electrode current collection ring.

Claims (2)

[Claims] (1) Zinc is the main component, with Ga and Tt as effective additive elements.
11. A 11-top lead alkaline battery characterized in that an alloy to which is added is hydrated and used as a negative electrode active material. (2) An ili lead-alkaline battery according to claim 1, in which alloy powder is subjected to freezing treatment using I-Iq by a wet method.