JPS61140063A - Zinc alkali 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 proper content of Ni and Tl for the negative pole. CONSTITUTION:Zinc alloy containing 0.01-0.5wt% of nickel and 0.01-0.5wt% of thallium is employed for the negative pole of zinc alkali battery. When adding both Ni and Tl to negative pole zinc, considerable 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 Tl while Ni will contribute considerably to suppress dispersion of mercury into the particles and the corrosion resistance is improved considerably through formation of zinc alloy surface having high hydrogen overvoltage. Remarkable complex effect is recognized only when the content of Ni and Tl in zinc alloy composition is within said range. Consequently, a zinc negative electrode 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 frozen zinc 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 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.

Although all of these can be expected to have a certain degree of corrosion resistance and a certain degree of reduction in icing rate, it is necessary to search for an alloy system with even better corrosion resistance.

In addition, with the aim of improving manganese dry batteries, there is a proposal by Wang 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, Or, Pb, Ca, Hg, and B are used as elements in the zinc alloy.
i, Sb.

The description includes cases in which one or more of Al, Ag, M(, Si, Ni, Mn, etc.) are used as impurities or additives, but when indium and lead are used together as additive elements. Other than the effectiveness of corrosion prevention, there is no clear distinction as to whether each of the miscellaneous elements listed above is added as an impurity or as an effective element, and it is not even clear which elements are effective for corrosion prevention. There is no description of the 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 hydration rate without deteriorating the corrosion resistance and discharge performance of negative electrode zinc, and improves discharge performance, storage stability, and low pollution.
The aim is to provide a complete range of zinc alkaline earth products 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 for the electrolyte, zinc for the negative electrode active material, and manganese dioxide, silver oxide, mercury oxide, etc. for the positive electrode active material. Nickel (N
i) 0.01 to 0.5% by weight, thallium (Tl) f
It is characterized by using a zinc alloy containing 1 to 01% by weight of o and o.

The present invention focused on the fact that among the additive elements in the conventional zinc alloy, Ni is a low-cost and non-polluting element that does not cause environmental pollution, and conducted experiments on the effect of adding Ni. Zinc alloy added alone has poor corrosion protection, but
This work was completed based on the discovery that when Ni and Tg are added at the same time, a more significant synergistic anticorrosive effect can be obtained than when both elements are added alone.

The mechanism of action regarding the anticorrosive effect of Ni or T/Q added alone, and the combined effect of Ni and Ta is unclear, but is presumed to be as follows.

First, the solubility of Ni is lower than that of zinc (Zn), but the cooling rate when powdering it by injection method is approximately 102°C/SeC.
Since it is very large, on the order of
! ″′@4“t, t”’6ET*@’eiJ”66.6
°1・87・1Ni, which has a low affinity for mercury, suppresses the diffusion of mercury into the crystal, reducing the amount of mercury a on the surface of the zinc alloy.
They are expected to play a role in maintaining high standards. 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, Ta is naturally compatible with mercury,
Although it is effective in making the surface of the zinc alloy uniform by graining, it is considered to be insufficient in preventing the diffusion of mercury into the interior of the particles.

In the present invention, it is considered that the above-mentioned inadequacies in the effects of both elements are fully compensated for, and a combined effect is obtained by taking advantage of the strengths of each element. In other words, the compatibility of the zinc alloy surface with mercury is improved by the addition of 4, and Ni is strongly involved in inhibiting the diffusion of mercury into the interior of the particles, resulting in the formation of a zinc alloy surface with a large hydrogen overvoltage. It is estimated that corrosion resistance has been significantly improved. 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 freezing rate that has both discharge performance and corrosion resistance. .

Hereinafter, it will be explained in detail using examples.

Examples Various types of zinc alloys were prepared by adding various elements as shown in the table later to zinc ingots with an N degree of 99.997% or more.
o It was melted in O'C, pulverized by spraying with compressed air, and sieved to a particle size range of S○ 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.

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 coated with a copper plate 1'. 2 is a zinc negative electrode prepared by gelling an electrolytic solution of a 40 weight range aqueous solution of caustic potassium saturated with zinc oxide with carboxymethylcellulose, and dispersing frozen powder in this gel. 3 is a cellulose-based liquid retaining material, 4 is a porous polypropylene separator, 6 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 plated with nickel, and 7 is a positive electrode can made of stainless steel, the inner and outer surfaces of which are plated with nickel. A polypropylene gasket 8 is compressed between the positive electrode can and the sealing plate by bending the positive electrode can. The prototype battery had a diameter of 11.6 mm, a height of 6.4 mm, and the weight of the negative electrode ice powder was unified to 1,931,111 g, and the amount of mercury added (freezing rate) was the same as that of the zinc alloy powder. All had 3 weight widths. 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°C
It is expressed as the discharge duration when discharged at 610Ω with a final voltage of 0.9V.

Margin below As can be seen in this table, when comparing comparative examples (1 to 3) 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 case (2, 3) after storage The discharge performance of the battery 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 :T5 are combined and contained in an appropriate amount (
An improvement effect was obtained only in cases 5, 6, 7, 10, and 11), and a remarkable combined effect was observed.

Therefore, if the content of additional elements in a suitable zinc alloy composition is expressed in weight range, it is 0. Q1≦Ni≦0.5%, 0.01
≦'re≦0.5%.

On the other hand, if there is an excess or deficiency in the added elements ("+8+9.1
2) is not much different from the good comparative example (3), or may even be 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 N1 and Te 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 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 large. When the present invention is applied to such a battery, it can be carried out with a lower rate of dehydration, and in some cases without ice.

Effects of the Invention As described above, the present invention can reduce the freezing 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, 6
...Silver oxide positive electrode.

Claims (1)

[Claims] 0.01-0.5% by weight of nickel, 0.0% of thallium
A zinc alkaline battery using a zinc alloy containing 1 to 0.5% by weight as a negative electrode active material.