JPS61181067A - Zinc alkaline cell - Google Patents

Abstract

PURPOSE:To reduce gelation rate of negative electrode zinc thus to achieve low contamination by employing zinc alloy containing specific metal as the negative electrode active substance. CONSTITUTION:Zinc alloy containing 0.01-0.5wt% of indium and 0.005-0.3wt% of strontium is employed as the negative electrode of so-called zinc alkaline cell employing alkaline aqueous solution mainly composed of caustic potash, caustic soda, etc. as the electrolyte, zinc as the negative electrode active sub stance, manganese dioxide, silver oxide, mercury oxide, oxygen, etc. as the positive electrode active substance. Strontium has high affinity with mercury to eliminate crimp on the surface of sprayed zinc powder particle which are normally employed in alkaline cell thus to smooth the surface. But, standard potential of strontium is quite low thereby sufficient corrosion-proof effect is not achieved through addition of only strontium. While, indium has high hydrogen over voltage and affinity with mercury. Consequently, gelation of negative electrode zinc can be reduced resulting in a low contamination zinc alkaline cell.

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 powder, which is made by adding about 5 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 in which alloy powder containing indium, gallium, etc. is added to improve corrosion resistance and reduce the corrosion rate. 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 to reduce the degree of corrosion to some extent, it is necessary to search for an alloy system with even better 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, AI, Ag, 1Vlr, Si,
Although it is described including the case where Ni, Mn, etc. are included as impurities or additives, one or more types are included, but apart from the effectiveness when indium and lead are used together as additive elements, each of the miscellaneous above-mentioned It is not clear whether an element is added as an impurity or an effective element, and it is not even clear which element is effective for corrosion prevention, and the appropriate amount of addition is unknown.

There is no mention of anything other than 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 the discharge performance, storage performance, 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 for the electrolyte, zinc for the negative electrode active material, and manganese dioxide, silver oxide, mercury oxide, etc. for the positive electrode active material. The negative electrode of a so-called zinc-alkaline battery that uses oxygen etc. contains zinc as the main component and 0.01 to 0.5% by weight of indium (In).
It is characterized by using a zinc alloy containing 0.005 to 0.3% by weight of strontium (Sr).

Effects If we speculate about the effects of the additive elements here, strontium has a high affinity for mercury, and also has the effect of eliminating wrinkles and smoothing the surface of the particles of atomized zinc powder normally used for alkaline batteries. Therefore, when the zinc surface is hydrated with metallic mercury, a condition is created in which the hydration can be done uniformly, and the surface area is reduced, which is thought to exhibit an anticorrosion effect. However, the standard potential of strontium is very low, and adding strontium alone does not provide sufficient corrosion protection. On the other hand, indium has a high hydrogen overvoltage,
It has a high affinity for mercury. This indium is believed to eliminate the negative effects of adding strontium to zinc and exhibit a synergistic effect.

The present invention has been made through experimental studies based on the above speculations, and has succeeded in significantly improving the corrosion resistance of the zinc alloy used in the negative electrode and reducing the wood reduction rate. Hereinafter, the present invention will be described in detail in Examples of the present invention, which provide a battery.

Examples Various zinc alloys were prepared by adding the various elements shown in the following table to zinc ingot with a purity of 99.997%, melted at 500°C in a ladle, and powdered by spraying with compressed air. ~15
The particles were sieved to a particle size range of 0 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 acetone, and dried to produce a zinc hydrate alloy powder.

Furthermore, hydrated zinc powder or zinc hydrated alloy powder other than the examples of the present invention were also prepared in the same manner as comparative examples.

゛Using these hydrated powders, we manufactured the button-shaped silver oxide battery shown in the figure. In the figure, ■ is a sealing plate made of stainless steel, and the inner surface of the plate is plated with copper plate 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 carboxymethylcellulose, and dispersing zinc hydrate alloy powder in this gel. 3 is a cellulose-based liquid retaining material, 4 is a separator made of porous polypropylene, 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 7 is stainless steel. The positive electrode can is made of steel, and its inner and outer 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 11.6 nm+ and a height of 5.4-tm.
, the weight of the hydrated powder of the negative electrode was unified to 193 mg,
The amount of mercury added (hydration 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. Note that the discharge performance was expressed as the discharge duration when discharge was performed at 20° C. at 510Ω with a final voltage of 0.9V.

In this table, changes in the total height of the battery are determined by the stress relationship between each battery component over time after the battery is sealed (the total height of the battery usually decreases during the period until it stabilizes). However, in batteries where a large amount of hydrogen gas is generated due to corrosion of the zinc negative electrode, there is a strong tendency for the total battery height to increase due to an increase in battery internal pressure that counters the above-mentioned force for decreasing the total battery height. The corrosion resistance of the zinc negative electrode can be evaluated by the increase or decrease in the corrosion resistance.In addition, in batteries with insufficient corrosion resistance, the total height of the battery increases, the leakage resistance deteriorates due to an increase in battery internal pressure, and the zinc is consumed due to corrosion. ,
The discharge performance is significantly deteriorated due to the formation of an oxide film on the zinc surface and the inhibition of the discharge reaction due to the presence of hydrogen gas, and the discharge duration also largely depends on the corrosion resistance of the zinc negative electrode.

In the table, when strontium is added alone (N
In case o, 3), the characteristics are worse than in the case of no addition (No, 1), and in the case of adding indium alone (No, 2), the characteristics are slightly improved compared to the case of no addition. However, in the example of the present invention in which strontium and indium coexist in appropriate contents (No. 5.6.7.l O,l 1
．． ), the corrosion resistance and discharge performance are even better than those of the comparative example, and the combined effects of the added elements are remarkable. On the other hand, even when additive elements are present, there is no significant difference from the comparative example when there is excess or deficiency in the content (No, 4.8, 9.12).
The combined effect is poor. As mentioned above, by using a zinc alloy containing strontium and indium together in an appropriate content for the negative electrode, we succeeded in reducing the bushing rate, and the indium content is 0.01 to 0.5% by weight. %, and strontium is suitably 0.005 to 0 to 3% by weight.

As described above, the present invention has discovered that the corrosion resistance of the zinc alloy used for the negative electrode is improved due to the synergistic effect of the combination of the above-mentioned additive elements, and has determined the appropriate content to create a zinc-alkaline alloy with low pollution and excellent practical performance. This is the realization of a battery. In addition, in the examples, a battery using a zinc hydrate negative electrode was explained, but in an open air battery or a sealed zinc alkaline battery equipped with a hydrogen absorption mechanism,
Since the allowable amount of hydrogen gas to be generated is relatively large, when the present invention is applied to such a case, the hydrogen gas can be further reduced in rate, and in some cases, it can be carried out without 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. Name of agent: Patent attorney Toshio Nakao and 1 other person

Claims (1)

[Claims] A zinc alkaline battery using a zinc alloy containing 0.01 to 0.5% by weight of indium and 0.005 to 0.3% by weight of strontium as a negative electrode active material.