JPS60105169A - Zinc anode material for alkaline dry battery - Google Patents

Abstract

PURPOSE:To obtain material having improved corrosion resistance regardless of decreased mercury content by dispersing zinc powder in alkaline solution and gradually adding liquid amalgam effective to increase hydrogen overvoltage to amalgamate zinc powder. CONSTITUTION:Zinc powder is dispersed in alkaline solution such as potassium hydroxide, Liquid amalgam containing 3wt% or less of Hg and about 0.01- 3wt% of at least Bi, Pb, Cd, and Tl against Zinc to be amalgamated is prepared. The liquid amalgam is gradually added to dispersed zinc powder to amalgamate zinc powder. Since these elements such as Bi, Pb, Cd, and Tl increase hydrogen overvoltage of zinc and are easy to be amalgamated, they can be used as liquid amalgam. Therefore, zinc powder is easily amalgamated and uniformly covered with these elements.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a cathode material for alkaline dry batteries using unformed zinc powder.

(b) Preliminary technology It is known that the zinc cathode of an alkaline dry cell self-discharges during storage of the dry cell, and hydrogen is generated in the alkaline solution according to the following equation.

Z n + H20 + - Z nO + H2↑ Z n + 2H20 + Z n (OH)2 +H2 It has become. however,
When a predetermined amount of hydrogen gas is generated, the pressure inside the dry cell increases to J: s, and the alkaline solution leaks to the outside.
This will seriously reduce the commercial value of dry batteries.

For this reason, the zinc cathode of conventional alkaline batteries.

111 (
Lead powder containing more than 3% by weight of mercury is often used, or a metal or a compound thereof that increases the hydrogen overvoltage after freezing is added.

However, because this conventional method uses a large amount of mercury,
Since it is disadvantageous in terms of cost and pollution prevention, it is desired to reduce the amount of mercury, as well as the formulation of cheaper additives and good coating electrodeposition on zinc dust. .

(C) Disclosure of the Invention The present invention solves the conventional demands such as the following.

That is, when producing powdered zinc powder for alkaline dry IF ponds, the present invention first stirs and suspends zinc powder in an alkaline solution, and then adds mercury as a main component to this solution, which is effective for increasing hydrogen overvoltage. Furthermore, mercury and bismuth, lead, and mium, which are extremely easy to amalgamate.

Add one or more types of thallium 4Ji! This relates to a cathode material in which powdered zinc is frozen by gradually adding liquid amalgam.

In this case, one or more selected from hismuth, lead, cadmium, and thallium. The content of j, lil is river (0.01-3.Owt% range is k(preferably, 0
．． Is the effect ti below 01%? <, 3.0% or more1. Then it becomes saturated. Further, according to this range, the desired effect can be sufficiently achieved with mercury +11 of 3 wt% or less based on the weight of the zinc powder.

The wooden lead powder produced in this way is
Mixing contact between each component on the surface layer is sufficiently carried out, corrosion resistance in alkaline liquid is excellent, and the amount of mercury for freezing can be reduced.

(D) Example a) For comparison, 250 g of zinc powder (purity 99.8% or higher, 100 menschunder) was first added to one cup of 10% caustic potassium solution, and the mixture was stirred at a temperature of IBso℃. Sample a was prepared using a conventional method in which metallic mercury was gradually dropped to a concentration of 4 wt % mercury.

b) Next, while stirring and suspending 250 g of the zinc powder in the above -.1-potassium solution at a temperature of 70°C, add mercury in proportion to the amount of zinc powder (add 11 at a time and simultaneously feed 4 of this zinc powder). −
A sample according to the present invention to which a lead-based liquid alloy was added was obtained. ”
For addition of the static alloy mentioned above, mercury is 2wt relative to the weight of zinc powder.
%, lead is 11000 pp.

c) Another sample C of the present invention was prepared by adding a liquid amalgam containing 2 wt % mercury and 11,000 ppp of hismuth in the same manner as in section h b).

d) Also, 1wt of mercury with the same hand 11" as in 1-b)
A test sample 0'[d according to the present invention was prepared in which a liquid amalgam containing 2,500 ppm of bismuth was added.

e) In addition, a sample e according to the present invention was prepared in which a liquid amalgam containing 2000 ppm of bismuth and 2 wt% of mercury was added in the same order as in b) above.

f) Furthermore, in the same way as in b] above, 3 wt% of mercury was added in 11
, cadmium 400PplIl, thallium 400ppm
A sample f according to the present invention was prepared in which a liquid mercury-metallium amalgam containing 1 mmium thallium was added.

For each sample, stop stirring after the freezing process is completed.
-It! It! Jliil was sedated and then washed with water.

It is a powder obtained by drying.

Next, samples a to f of L-terminated 'IIξ lead powder were heated at a temperature of 6
It was immersed in a 40% caustic potash solution at 0°C to determine hydrogen evolution IN. The results are shown in the graph in the attached drawing.

As is clear from this graph, compared to conventional method a, the cathode materials b to f of the present invention show that mercury at least generates hydrogen (≠ or decreases).

(E) Effects of the Invention The cathode material for alkaline dry batteries according to the present invention includes hismuth, lead, cadmina l1. Contains one or more selected from thallium. These metals easily amalgamate with mercury and can be used as oily amalgam. Zinc dust also easily amalgamates with mercury, so the surface of the zinc dust is sufficiently coated. , corrosion resistance +1 even if the amount of mercury used is reduced compared to conventional products.
It is highly economical and easy to manufacture.

[Brief explanation of drawings]

The figure shows the cathode material according to the present invention (samples b-f) and the conventional VA8
It is a comparative graph showing the degree of hydrogen scum generation when material i (sample a) is immersed in an alkaline solution.

Claims (1)

[Claims] (+) Lnr lead powder is stirred in an alkaline solution PJ%, and liquid amalgam containing at least one of bismuth, lead, cadmium, and thallium is added thereto. Zinc cathode material for alkaline batteries. (2) Mercury is 3 rP, 4i% or less based on the weight of zinc powder,
In addition, the content of one or more selected from hismuth, lead, cadmium, and thallium is 0. Zinc cathode material for alkaline dry batteries according to claim 1, which has a market weight of O1 to 3%.