JPS61131365A - Alkaline battery - Google Patents

Abstract

PURPOSE:To completely eliminate or to extremely reduce the mercury content of a negative electrode zinc side by using globular zinc or globular zinc alloy which is coated and formed with an alloy layer of bismuth or bismuth and mercury as a negative electrode. CONSTITUTION:An alloy layer of bismuth or bismuth and mercury is coated and formed on the surface of globular zinc, in which the shape of zinc particles is approximately a globe, or of globular zinc alloy which uses zinc as a main component and is containing a kind of element or more of iron, cadmium, lead, bismuth, gallium, indium, thallium, tin, magnesium and aluminium to use it as a negative electrode. Whereby, it is possible to increase hydrogen overvoltage and to highly increase the restraining effect of hydrogen gas generation and the preventing effect of corrosion, and even when completely eliminating or extremely reducing mercury, it is possible to obtain the battery performance equivalent to or in excess of the conventional battery performance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to improvements in alkaline batteries using zinc as a negative electrode.

(Prior art) As is well known, in general alkaline batteries such as alkaline manganese batteries, mercury batteries, and silver oxide batteries, the negative electrode is formed by pressure forming, sintering, or gelling granulated zinc. . By using granular zinc, the overall surface area is increased to suppress passivation of the zinc surface as the discharge progresses as much as possible.

In addition, surface conditions such as distortion and cracking resulting from the manufacturing method of zinc particles promote corrosion. To prevent this, mercury is added to granular zinc to form it into an amalgam. Amalgamating the surface of zinc particles has great effects in terms of preventing corrosion of the zinc particles and suppressing hydrogen gas generation due to an increase in hydrogen overvoltage in an alkaline electrolyte. The use of amalgamated granular zinc greatly improved the discharge and storage performance of alkaline batteries.

(Problems to be Solved by the Invention) The technology of amalgamating negative electrode zinc, which has greatly contributed to improving the performance of alkaline batteries, has the inherent problem of using mercury, which is a harmful substance. From the perspective of pollution prevention, it is desirable that the mercury content of batteries be as low as possible. To this end, research is actively being conducted to reduce the mercury content in zinc in the negative electrode (lower the degree of freezing), or to use completely unoxidized zinc in the negative electrode to avoid deteriorating battery performance. .

Currently, countermeasures such as adding metals such as indium, gallium, and lead to zinc have been put into practical use. However, adding metals as described above alone does not provide sufficient corrosion protection or suppressing hydrogen gas generation, and a certain degree of effectiveness has been obtained by using them in combination with mercury.

Even so, it is not enough to significantly reduce the amount of water I1m used compared to the conventional method.

Research is also being conducted to review the particle shape of zinc. For example, as disclosed in JP-A No. 58-21b760, instead of the conventional irregularly shaped granular zinc,
It has been found that when spherical zinc, which has a particle shape that is almost spherical, is used, corrosion resistance is improved and hydrogen gas generation is reduced. However, as mentioned above, even when using spherical zinc,
Sufficient practical performance cannot be achieved unless it is amalgamated with a considerable amount of mercury.

This invention was made in view of the above-mentioned 181 problems of the conventional technology, and its purpose is to significantly reduce the amount of mercury used in the amalgamation of negative electrode zinc, and in some cases even without using mercury at all. Our objective is to provide an alkaline battery that maintains its performance.

(Means for Solving the Problems) Therefore, in the present invention, zinc particles are mainly composed of spherical zinc or zinc having an almost spherical shape, and iron, cadmium, lead,
Bismuth, gallium, indium.

A spherical zinc alloy containing one or more elements of thallium, tin, magnesium, and aluminum, and whose surface is coated with bismuth or an alloyed layer of bismuth and mercury, is used as the negative electrode. there was.

(Function) By coating the surface of spherical zinc or a spherical zinc alloy containing the aforementioned trace elements with a layer of bismuth or an alloyed layer of bismuth and mercury, hydrogen overvoltage is increased, hydrogen gas generation is inhibited, and corrosion prevention is achieved. has dramatically increased, and even if mercury is completely eliminated or mercury is reduced to a very low level, battery performance equivalent to or better than conventional batteries can be obtained.

(Example) An example of the present invention will be described together with a manufacturing method thereof. Bismuth is coated on the surface of a spherical zinc particle having a substantially spherical particle shape or a spherical zinc alloy containing the above-mentioned trace element by the following procedure.

First, add 1.09 metal bis7s to 3-dilute nitric acid (HNO3).
) and diluted with a large amount of water to obtain bissubnitrate vs [Bi (OH)2 NO3, Bi (OH) (N
03)2, etc.] to make a sol-like solution. 979 to this solution
Add and mix the above spherical zinc or spherical zinc alloy,
Uniform bismuth coating by substitution reaction of zinc and bismuth
Get layers. The spherical zinc produced in this way is the first example, and the spherical zinc alloy (containing 0.05% lead) is the second example.

3 g of mercury is added to the spherical zinc 2 spherical zinc alloy having the bismuth coating layer of the first and second embodiments described above, and the surface is amalgamated by a conventional treatment method. As a result, the surface has zinc-
A bismuth-mercury alloy layer is applied. A third example of spherical zinc with a freezing degree of 3% made in this way,
A fourth example is a spherical zinc alloy (containing 0.05% lead).

Spherical zinc or spherical zinc alloy coated with bismuth or an alloyed layer of bismuth and mercury of the above four examples, and spherical zinc with an unoxidized degree of 5% (referred to as Comparative Example A),
The following comparative tests were conducted on six types of powderless spherical zinc (referred to as Comparative Example B).

61! Each of the above powders was immersed in an alkaline electrolyte (a 40% solution of potassium hydroxide saturated with zinc hydride).
C. for 15 days, and the amount of hydrogen gas generated on the 15th day was measured. The results are as follows.

・First embodiment---0,oo511i2/a-
day・2nd example...0.004mG/
! It・day・3rd example・・・・・・0.002
-/Q・day・4th example...0.001
+nQ/i)・day・Comparative example A・−・−0,005
m2/+J -daV・Comparative example B...0.0
3 mQ/g ・dayAs is clear from this result,
The hydrogen gas generating layer of spherical zinc and spherical zinc alloy coated with bismuth without ice according to the first and second embodiments of the present invention is a comparative example A with a 5% ice layer, which is conventionally used in practical use. It is about the same.

In addition, the third method of the present invention, which has a 3% frozen layer and a significantly reduced amount of mercury,
In the case of Example and Fourth Example, the amount of hydrogen gas generated was reduced to less than half that of Comparative Example A.

If an alkaline battery is constructed using a spherical zinc coated with bismuth or an alloyed layer of bismuth and mercury as shown in the examples, or a spherical zinc alloy containing a very young additive element, its storage performance will be the same as that of conventional batteries. It will improve to the same degree or roughly.

Moreover, the amount of mercury can be significantly reduced or even eliminated altogether.

Although the above description does not mention the positive electrode, the present invention is applicable to various alkaline batteries regardless of what material is used for the positive electrode.

(Effects of the Invention) As explained in detail above, in the alkaline battery according to the present invention, even if the mercury content on the negative electrode zinc side is completely eliminated or is significantly reduced compared to the conventional one, the discharge performance and storage The performance will be equivalent to or better than conventional batteries using zinc with a low ice layer.

Claims (1)

[Claims] (1) Spherical zinc whose zinc particle shape is almost spherical or spherical zinc whose main component is zinc and which contains one or more elements of iron, cadmium, lead, bismuth, gallium, indium, thallium, tin, magnesium, and aluminum. An alkaline battery characterized in that a spherical zinc alloy or a spherical zinc alloy whose surface is coated with bismuth or an alloyed layer of bismuth and mercury is used as a negative electrode.