JPS61140067A - Zinc alkali battery - Google Patents

Abstract

PURPOSE:To obtain a low pollution alkali battery by employing zinc alloy containing Ni and Ag within proper content for the negative pole thereby reducing the hardening rate of negative pole alloy. CONSTITUTION:Zinc alloy containing 0.01-0.5wt% of nickel and 0.01-0.5wt% of silver is employed for the negative pole of zinc alkali battery. When adding Ni and Ag to negative pole zinc, remarkable corrosion-proof effect is achieved when compared with the case where said element is added independently. It is presumed that the affinity with mercury on the surface of zinc alloy is improved through addition of Ag while Ni will contribute to suppress dispersion of mercury into the particle to improve the corrosion resistance considerably through formation of zinc alloy surface having high hydrogen overvoltage. Remarkable complex effect is recognized only when the content of Ne and Ag in zinc alloy composition is within said range. Consequently, a zinc negative pole having low hardening rate while provided with discharge performance and corrosion resistance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses zinc as a negative electrode active material, an alkaline aqueous solution as an electrolyte, and manganese dioxide, silver oxide, or silver oxide as a positive electrode active material.
This invention relates to improvements in negative electrodes for zinc-alkaline batteries using mercury oxide, oxygen, nickel hydroxide, etc.

A common problem with conventional zinc-alkaline batteries is corrosion of the negative electrode zinc by the electrolyte during storage.

Conventionally, it has been adopted as an industrial method to increase the hydrogen overvoltage by adding around 5 to 10 parts of mercury to the zinc powder all over the zinc powder, thereby suppressing corrosion to the extent that there is no practical problem. . However, in recent years, there has been an increasing social need to completely reduce the amount of mercury contained in batteries in order to reduce pollution, and various studies have been conducted. For example, lead and cadmium in zinc.

A method has been proposed in which the corrosion resistance is completely improved by using an alloy powder to which iridium, gallium, etc. are added, and the corrosion rate is reduced. These corrosion-inhibiting effects are not only due to the single additive element, but also due to the combined effect of multiple additive elements, such as indium, lead, or gallium? In the past, zinc alloys with added gallium and lead have been proposed as promising systems.

Although all of these can be expected to have a certain degree of corrosion resistance and to reduce the degree of corrosion to some extent, it is necessary to search for an alloy system with even better corrosion resistance.

Also, mainly improvements to manganese dry batteries? To this end, there is a proposal that using zinc or a zinc alloy in which indium is completely added to the zinc alloy for the negative electrode has a large anticorrosion effect (Japanese Patent Publication No. 3204/1983).

Problems to be Solved by the Invention Among the above proposals, in addition to indium, Fe, Cd, Or, Pb, Ca, and Hg are used as elements in the zinc alloy.

Bi, Sb, Mu1. Mq+ “J s S11” +
"4$'l" is described including the case where one or more types of impurities or additives are included, but apart from the effectiveness when indium and lead are used together as additive elements, the above miscellaneous It is not clearly stated whether each element is included as a total impurity or added as an effective element, and it is not even clear which elements are effective for corrosion prevention, and the appropriate amount to add is indium.

There is no description other than the lead plate.

It remains a challenge for the future to study the effects of the combination of these elements in zinc-alkaline batteries and to find an effective alloy composition.

The present invention reduces the oxidation rate without deteriorating the corrosion resistance and discharge performance of negative electrode zinc, and improves the discharge performance, storability, and storability with low pollution.
The purpose is to provide a zinc-alkaline battery with excellent overall performance such as leakage resistance.

Means for Solving the Problems The present invention uses an alkaline aqueous solution containing caustic potash, caustic soda, etc. as the main components in the electrolyte, zinc as the negative electrode active material, and manganese dichloride, silver oxide, and oxide as the positive electrode active material. Nickel (N
i) Total 0.01-0.5% by weight, silver (muq)'to, 0
It is characterized by using zinc alloy gold containing 1 to 0.5% by weight.

The present invention provides that among the additive elements in the conventional zinc alloy,
Focusing on the fact that Ni is an inexpensive and non-polluting element that does not cause environmental pollution, we conducted an experiment to determine the effect of Ni addition.
Zinc alloys containing Ni f alone have poor corrosion protection, but
This work was completed based on the discovery that when Ni and Muqt are added at the same time, a remarkable synergistic anticorrosion effect can be obtained compared to when both elements are added alone.

Corrosion prevention effect by adding Ni or target alone, E″゛8″°′″o'4114#'Ih*IcQ"101-1
1. Although it is unclear, it can be inferred as follows. First, although the solubility of Ni is low compared to zinc (Zn), the cooling rate during powderization by the injection method is very high, on the order of approximately 102°C/see, so it is not suitable for use in the examples described below. If the content is low (0.01 to 0.5% by weight), there is a possibility that it will form a solution with zinc. Therefore, it is expected that Ni, which originally has a low affinity for mercury, will suppress the diffusion of mercury into the crystal and play the role of maintaining a high mercury concentration on the surface of the zinc alloy. On the other hand, there is also a concern that the adhesion of mercury to the surface of the zinc alloy may become worse. In addition, muq is naturally compatible with mercury and is effective in making the surface of zinc alloy homogeneous by making it sticky, but it is thought to be insufficient in preventing mercury from diffusing into the interior of the particles. .

It is believed that the present invention compensates for the insufficiency of the effects of both of the above elements and provides a combined effect that takes advantage of the strengths of each element. In other words, the compatibility of the zinc alloy surface with mercury is
N
= is strongly involved, and as a result, it is presumed that corrosion resistance was significantly improved by forming a zinc alloy surface with a large hydrogen overvoltage. As described above, the present invention has experimentally investigated the combination of additive elements and their contents in the zinc alloy used for the negative electrode, and has realized a zinc negative electrode with a low corrosion rate that combines discharge performance and corrosion resistance. .

Hereinafter, this will be explained in detail using examples.

Various zinc alloys were prepared with various elements added to them, melted at about 500'C, pulverized by spraying with compressed air, and sieved to a particle size range of 50 to 150 mesh. Next, the powder was put into a 10% by weight aqueous solution of caustic potash, and a predetermined amount of mercury was added dropwise to the solution while stirring. Thereafter, it was washed with water, substituted with acetone, and dried to produce a zinc chloride alloy powder. Furthermore, zinc alloy powders other than the examples of the present invention were also prepared in the same manner as comparative examples.

The button-shaped silver oxide battery shown in the figure was manufactured using these oxidized powders. In the figure, reference numeral 1 denotes a sealing plate made of stainless steel, the inner surface of which is plated with copper 1'. 2 is a zinc negative electrode prepared by gelling an electrolytic solution of a 40-fold aqueous solution of caustic potassium saturated with zinc oxide with carboxymethyl cellulose, and dispersing gelatinized powder in this gel. 3 is a cellulose-based liquid retaining material, 4 is a porous polypropylene separator, 5 is a positive electrode made of a mixture of silver oxide and graphite and pressure molded;
6 is a positive electrode ring made of iron with nickel plating, and 7 is a positive electrode can made of stainless steel, and the inside and outside surfaces are nickel plated. A polypropylene gasket 8 is compressed between the positive electrode can and the sealing plate by bending the positive electrode can. The prototype battery has a diameter of 11.611IL and a height of 6
．． 4B, and the weight of the negative electrode powder is 1931! Ig
The amount of mercury added (corrosion rate) was 3% by weight based on the zinc alloy powder. The following table shows the composition of the zinc alloy of the prototype battery, and the changes in discharge performance and total battery height after storage for one month at EO'C. The discharge performance is
It is expressed as the discharge duration when discharging at 20°C at 510Ω with a final voltage of 009V.

Margin below. . 7, see, wa, yo,, compared to ka 0, ~3)
1 Comparing with each other, when there is no added element (1
), when a single element is added (2, 3), the discharge performance after storage is somewhat improved, and the total height of one cell can be easily evaluated to evaluate the corrosion of the negative electrode zinc and the amount of hydrogen gas generated. Some improvement effects were also observed in changes.

However, these improvement effects are insufficient for practical use.
When N1 and Muq are combined and contained in appropriate amounts (s
, e, 7, 1o, and 11), and a remarkable combined effect was observed. Therefore, if we express the content of additional elements in a suitable zinc alloy composition as heavy J1%, then 0.01≦N
i≦0.5%, 0.01≦muq≦O, s%.

On the other hand, if there is excess or deficiency in the added elements (4+ 8 + 9.
12) is a good comparison example (not much different from 31,
In some cases, it was even worse, and a remarkable composite effect was observed only within the above-mentioned appropriate content range.

Therefore, by using a zinc alloy containing Ni and Muq in an appropriate content range for the negative electrode, a zinc-alkaline battery with low pollution and excellent practical performance can be obtained.

In addition, in the examples, a battery using a zinc chloride negative electrode was explained, but in an open air battery or a sealed zinc-alkaline battery equipped with a hydrogen absorption mechanism, the hydrogen gas generation capacity is relatively large. , when applying the present invention to such a battery.

Furthermore, it is possible to carry out the process with a low rate of change or, in some cases, with no rate of change.

Effects of the Invention As described above, the present invention can reduce the filtration rate of negative electrode zinc,
It is extremely effective in obtaining low-pollution zinc-alkaline batteries.

[Brief explanation of the drawing]

The figure is a partially sectional side view of a button-shaped silver oxide battery used in an example of the present invention. 2...Zinc negative electrode, 4...Separator,
6...Silver oxide positive electrode.

Claims (1)

[Claims] 0.01-0.5% by weight of nickel, 0.01-0.0% of silver
．． A zinc alkaline battery using a zinc alloy containing 5% by weight as a negative electrode active material.