JPS61140062A - Zinc alkali battery - Google Patents

Abstract

PURPOSE:To reduce the hardening rate of negative pole zinc thus to obtain a zinc alkali battery of low pollution by employing zinc alloy containing proper content of Ni and In for the negative pole. CONSTITUTION:Zinc alloy containing 0.01-0.5wt% of nickel and 0.01-0.5wt% of indium is employed for the negative pole of zinc alkali battery. When adding Ni and In simultaneously to the negative pole zinc, considerable corrosion-proof effect is achieved when compared with the case where said element is employed independently. It is presumed that the affinity with mercury on the surface of zinc alloy is improved through addition of In while Ni will contribute to suppress dispersion of mercury into the particle thus to form a zinc alloy surface having high hydrogen overvoltage and to improve the corrosion resistance considerably. Remarkable complex effect is recognized only when the content of Ni and In is within said range. Consequently, a zinc negative pole having low hardening rate while provided with excellent 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 using zinc hydrate powder, which is made by adding 5 to 10% by weight of mercury to zinc, and to suppress corrosion to a level that causes no practical problems. . 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 hydration rate by 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 some degree of corrosion resistance.

Although it is expected that the hydration rate will be reduced to some extent, even more
It is necessary to search for alloy systems with good corrosion resistance.

Furthermore, with the aim of mainly improving manganese dry batteries, there has been a proposal that using zinc or a zinc alloy in which indium is added to a zinc alloy for the negative electrode is highly effective in preventing corrosion (Japanese Patent Publication No. 33-3204).

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

Bi, Sb, Mu1. Mug, Mg, Si, Ni,
The description includes the case where one or two or more of Mn etc. are included as impurities or additives, but other than the effectiveness of using indium and lead together as additive elements, There is no clear distinction as to whether it is added as an impurity or as an effective element, and it is not even clear which elements are effective for corrosion prevention, and there is no mention of the appropriate amount of addition other than indium and lead.

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 to Solve the Problems The present invention uses an alkaline aqueous solution containing caustic potash, caustic soda, etc. as its main components as an electrolyte, zinc as a negative electrode active material, and manganese dioxide, silver oxide, mercury oxide, or mercury oxide as a positive electrode active material. Nickel (N
A zinc alloy containing 0.01 to 0.5% by weight of i) and 0.01 to 0.5% by weight of indium (In) is used.

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 with Ni added alone have poor corrosion resistance, but N
This work was completed based on the discovery that when i and In are added at the same time, a remarkable synergistic anticorrosive effect can be obtained compared to when both elements are added alone.

Effect: Anticorrosion effect due to the addition of Ni or In alone,
and effects on the combined effect of Ni and In.
Although the mechanism is unclear, it is presumed to be first-order.

First, although the solubility of Ni is low in zinc (Zn),
Cooling rate when powdering by injection method is approximately 102'C/se
Since it is very large, on the order of a, there is a possibility that it will be dissolved with zinc at the appropriate content (001 to 0.5% by weight) in the examples described below. Therefore, it can be expected that the element Ni, which has a low affinity for mercury, plays a role in suppressing the diffusion of mercury into the crystal and maintaining a high mercury concentration on the surface of the zinc alloy.

On the other hand, there is also a concern that it may actually worsen the adhesion of mercury to the surface of the zinc alloy. In addition, although In is inherently compatible with mercury and is effective in making the surface of zinc alloy uniform by icing, it is considered 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
Improved by adding N to suppress the diffusion of mercury inside one particle.
It is presumed that corrosion resistance was significantly improved by forming a zinc alloy surface with a large hydrogen overvoltage due to the strong involvement of i. As described above, the present invention experimentally investigated the combination of additive elements and their contents in the zinc alloy used for the negative electrode, and realized a zinc negative electrode with a low water conversion rate that combines discharge performance and corrosion resistance. be.

A detailed explanation will be given below based on examples.

Examples Various zinc alloys were prepared by adding various elements as shown in the table below to zinc ingots with a purity of 99.997% or more.
Melt it at 00°C and inject it with compressed air to powder it,
It was sieved to a particle size range of 50-150 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, replaced with μ 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.

Using these hydrated powders, the button-shaped silver oxide battery shown in the figure was manufactured. 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 in which an electrolyte containing a 40% by weight aqueous solution of caustic potassium saturated with zinc oxide is gelled with carboxymethylcerolose, and hydrated powder is dispersed 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 nickel-plated iron, and T is stainless steel. The positive electrode can is made of aluminum, and the inside and outside surfaces are nickel plated. 8
is a polypropylene gas get that is compressed between the positive electrode can and the sealing plate by bending the positive electrode can. The prototype battery had a diameter of 11.6mm and a height of 54mm, the weight of the hydrated powder of the negative electrode was unified to 193mg, and the amount of mercury added (hydration rate) was the same as that of the zinc alloy powder. It was bound at 3% by weight. Composition of the zinc alloy of the prototype battery and 1 at 60'C
The following table shows the changes in discharge performance and total battery height after storage for one month. The discharge performance is 0.5 at 510Ω at 20'C.
It is expressed as the discharge duration when discharge is performed with a final voltage of 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.
When Ni and In are combined and contained in appropriate amounts (5
, 6, 7, 10, 11), and a remarkable combined effect was observed.

Therefore, the content of additional elements in a suitable zinc alloy composition expressed in weight percent is 0.01≦Ni≦0.6%.

0.01≦In 50.5%.

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

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

Therefore, by using a zinc alloy containing Ni and In within 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 example, a battery using a frozen zinc 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 small. If the present invention is applied to such a battery because it is large.

Furthermore, it can be carried out with low water content or without ice in some cases.

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...Ashibuchi arsenic positive electrode.

Claims (1)

[Claims] 0.01 to 0.6% by weight of nickel and 0.6% by weight of indium.
A zinc alkaline battery using a zinc alloy containing 01 to 0.5% by weight as a negative electrode active material.