JPS61140065A - Zinc alloy battery - Google Patents

Abstract

PURPOSE:To reduce the hardening rate of negative pole zinc and to obtain a low pollution zinc alkali battery by employing zinc alloy containing Ni and Pb within proper content for the negative pole. CONSTITUTION:Zinc alloy containing 0.01-0.5wt% of nickel and 0.01-0.5wt% of lead is employed for the negative pole of zinc alloy battery. When adding both Ni and Pb to negative pole zonc, remarkable corrosion-proof effect is achieved when compared with the case where said element is added independently. It is presumed that the concentration of mercury in zinc alloy surface layer is maintained sufficiently high by containing both elements in zinc alloy to form zinc alloy surface having high hydrogen overvoltage through hardening with small amount of mercury. Remarkable complex effect is recognized only when the content of said element 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 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 using frozen zinc powder, which is made by adding 6 to 10% by weight of mercury to zinc, and to suppress corrosion to the extent that there is no practical problem. . However, in recent years, there has been an increasing social need to 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 to improve corrosion resistance and reduce the rate of icing using an alloy powder to which indium, gallium, etc. are added. These corrosion-inhibiting effects are not only due to the single additive element, but also due to the combined effect of multiple additive elements. It has been proposed as a promising system.

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

In addition, with the aim of improving manganese dry batteries, it has been proposed that using zinc or a zinc alloy with indium added to the zinc alloy for the negative electrode has a great anti-corrosion effect (
Special Publication No. 33-3204).

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

Bi, Sb, Al, Ag, Mg, St
, Ni, Mn, etc. as impurities or additives, including the case where one or more types are included, but there is no explanation other than the effectiveness when indium and lead are used together as additive elements, and it does not indicate which element. It is not even clear whether it is effective for corrosion prevention.
There is no description of appropriate amounts other than indium and lead plates.

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 freezing rate without deteriorating the corrosion resistance and discharge performance of negative electrode zinc, and improves discharge performance, storage performance, and storage performance 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 powder, etc. as the main components in the electrolyte, zinc as the negative electrode active material, and manganese dioxide, silver oxide, mercury oxide, etc. as the positive electrode active material. Nickel (N
i) 10.01~Q5% by weight, lead (pb)
, o1 to o, s in weight percent.

The present invention provides that among the additive elements in the conventional zinc alloy,
Focusing on the fact that NL is a low-cost, non-polluting element with no concerns about environmental pollution, we conducted an experiment to examine the effect of adding Ni, and found that although zinc alloys with Nt added alone have poor corrosion resistance,
This work was completed based on the discovery that when Ni and PB are added at the same time, a remarkable synergistic anticorrosion effect can be obtained compared to when both elements are added alone.

Although the mechanism of action 1 is unclear due to the anticorrosive effect of adding Ni or Pb alone, and the combined effect of Ni and Pb, it is inferred as follows. First, zinc (
Compared to Zn), the solubility of Ni is low, but the cooling rate when powdered by the injection method is very high, approximately 102°C/sec.
Since it is on the order of c, there is a possibility that it will form a solution with zinc at an appropriate content (0.01 to 0.5% by weight) in the examples described later. Therefore, when a zinc alloy is frozen from the surface, Ni, which originally has a low affinity for mercury, suppresses the diffusion of mercury into the crystal and contributes to maintaining a high concentration of mercury on the surface of the zinc alloy. It is possible that In addition, PB tends to segregate near the grain boundaries of zinc alloys, and contributes to maintaining a high mercury concentration on the surface by suppressing the diffusion of mercury in the zinc alloy that has hydrated from the surface into the interior through the grain boundaries. It seems to be. However, adding these elements alone is insufficient to effectively suppress the diffusion of mercury in the surface layer of the hydrated zinc alloy into the interior. This is because it only has the effect of suppressing either diffusion into crystal grains or diffusion through grain boundaries. In the present invention, by including both of the above elements in the zinc alloy, the above-mentioned mercury diffusion suppressing effects of both elements are combined, and the mercury concentration in the surface layer of the zinc alloy is maintained sufficiently high. It is presumed that hydration with mercury was able to form a zinc alloy surface with a large hydrogen overpotential. As described above, the present invention has experimentally investigated the combination of additive elements and their contents in the zinc alloy used in the negative electrode, and has succeeded in creating a zinc negative electrode with a low bushing rate that has both discharge performance and corrosion resistance, and has achieved low pollution. This provided an effective means for realizing zinc-alkaline batteries.

Hereinafter, it will be explained in detail using examples.

Examples Various zinc alloys were prepared by adding various elements as shown in the table later to zinc ingots with a purity of 99.997% or more.
Melt at 00°C and inject with compressed air to powder, 6
The particles were sieved to a particle size range of 0 to 160 mesh. Next, the above powder was put into a 10% by weight aqueous solution of caustic potash, and a predetermined amount of mercury was added dropwise while stirring to hydrate it. Thereafter, it was washed with water, substituted with acetone, and dried to produce a frozen zinc alloy powder. Furthermore, glazed 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 frozen 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 in which a 40% by weight aqueous solution of caustic potassium is 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, e is a positive electrode ring made of nickel-plated iron, and T is stainless steel. The positive electrode can is made of steel, and the inside and outside surfaces are nickel plated. 8 is a polypropylene gasket,
By bending the positive electrode can, it is compressed between the positive electrode can and the sealing plate. The prototype battery has a diameter of 11.6 cm and a height of 5.4 cm, and the weight of the hydrated powder of the negative electrode is 193 cm.
The amount of mercury added (icing 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 at 60°C for one month. Discharge performance is 20℃
It is expressed as the discharge duration when discharge is performed at 510Ω with a final voltage of 0.9V.

As seen in this table, when comparative examples (1 to 3) are compared with each other, it is found that when a single element is added (2, 3), compared to the case (1) where no added element is added, the The discharge performance was improved to some extent, and some improvement was also observed in changes in the total height of the battery, which can directly evaluate the corrosion of the negative electrode zinc and the amount of hydrogen gas generated.

However, these improvement effects are insufficient for practical use.
Improvement effects were obtained only when Ni and PB were combined and contained in appropriate amounts (5, 6, 7, 10, 11).
A significant combined effect was observed.

Therefore, when expressing the content of additional elements in a suitable zinc alloy composition in weight percent, 0.01≦Ni≦0.61. O, o1≦p
b≦0.5ch.

On the other hand, if there is an excess or deficiency in the added element (4, S.

9.12) was not much different from the good Comparative Example (3), or even inferior in some cases, and a remarkable composite effect was observed only within the above-mentioned appropriate content range.

Therefore, by using a zinc alloy containing Ni and PB 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 permissible amount of hydrogen gas generated is relatively large. Therefore, when the present invention is applied to such a battery, it can be carried out with a lower rate of hydrogenation, and in some cases, with the battery being anhydrous.

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

[Brief explanation of drawings]

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,
5...Silver oxide positive electrode.

Claims (1)

[Claims] Nickel 0.01-0.5% by weight, lead 0.01-0
．． A zinc alkaline battery using a zinc alloy containing 5% by weight as a negative electrode active material.