JPS6290851A - Zinc alkaline cell - Google Patents

Abstract

PURPOSE:To obtain an overall efficiency of excellent discharge, preservation, and antileakage properties and the like with little environmental pollution, by applying a zinc alloy containing Zn as the main component, and specific ratio of In, Mg, Ca, and Te as a negative electrode. CONSTITUTION:For a negative electrode 2 of a zinc alkaline type cell, a zinc alloy containing Zn as the main component, 0.005-0.5wt% of In, 0.005-0.2wt% of Mg, and 0.01-0.5wt% of at least either Ca or Te is used as an active substance. Mg fanctions to smooth the surface of the zinc alloy powder and reduce the surface area. Although Mg is more easily corroded than Zn, In is compounded with Mg to negate the bad influence of Mg. Moreover, by adding Ca or Te to Zn added with In and Mg, the anticorrosion of the alloy can be remarkably improved. In such a composition, an anticorrosive zinc anode with a low mercurating rate is realized, and a zinc alkaline cell of excellent discharge and preservative properties with little environmental pollution 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,
This invention relates to improvements in negative electrodes for zinc-alkaline batteries using mercury dioxygen oxide, nickel hydroxide, and the like.

A common problem with conventional zinc-alkaline batteries is corrosion due to electrolysis of the negative electrode zinc during storage;

Conventionally, 5 to 10 weight is added to zinc? . It has been adopted as an industrial method to suppress corrosion by adding a certain amount of mercury to a level that poses 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, it has been proposed to improve corrosion resistance and reduce the hydration rate by using an alloy powder in which lead, cadmium, indium, gallium, etc. are added to zinc. 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 and lead, or a combination of indium and lead with gallium added thereto, and a zinc alloy with gallium and lead added. Until now, promising threads have been proposed.

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

In addition, with the aim of mainly improving manganese dry batteries, there has been a proposal to use zinc or a zinc alloy with indium added to the zinc alloy for the negative electrode, which has a significant anti-corrosion effect (Japanese Patent Publication No. 3204/1983).

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, A1. Although it is described including cases in which 1 or 2 m or more of Ag, Mg, Si, Ni, Mn, etc. are included as impurities or additives, other than the effectiveness when indium and lead are used together as additive elements, It is not clear whether each of the miscellaneous elements mentioned above is added as an impurity or as an effective element, and it is not even clear whether the elements are 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 water ratio without deteriorating the corrosion resistance and discharge performance of negative electrode zinc, and improves discharge performance, storage stability, and 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, indium Q, 005 to 0.5% by weight, magnesium 0°005 to 0.2MM%, and at least one of calcium and tellurium. It is characterized by using a zinc alloy containing 0.01 to 0.5% by weight.

Action The mechanism of action of the anticorrosion effect of the addition of each element and the combined effect of these elements is unclear, but it is inferred as follows.

Mg has the effect of reducing surface irregularities and smoothing the surface of the zinc alloy powder, which is pulverized by spraying molten zinc alloy, thereby reducing the surface area.

However, since Mg is electrochemically more base than zinc, it is more likely to corrode than zinc, and adding it alone has little effect.
Adding too much will actually have the opposite effect.

In addition, In has been known as an additive element with a large anticorrosion effect, and it increases the hydrogen overvoltage of sub-T1) alloys, and
Because it is easily compatible with mercury, it is effective in making the surface condition uniform by hydration, and by combining Mg and In, Mg
This is because the negative effects of g are canceled out, and the combined effect of Mg and In, that is, the effect of reducing the specific surface area and the effect of increasing the hydrogen overvoltage, is improved, thereby improving corrosion resistance.

Furthermore, Ca is added to the zinc to which In and Mg are added.

7. Does adding Te further improve the corrosion resistance of the alloy? This is because Ca and Te have a low affinity for mercury and prevent Hg from diffusing into the zinc alloy powder. think.

As mentioned above, by adding predetermined amounts of In, Mg, Ca, and Te to zinc in combination, the corrosion resistance of the zinc alloy used for the negative electrode is significantly improved. As a result, a corrosion-resistant zinc negative electrode with a low hydration rate was realized, and a low-pollution alkaline battery with excellent discharge performance and storage performance was created.

Hereinafter, this will be explained in detail using examples.

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 about 500°C, and powdered by spraying with compressed air. 150
It was sieved into a mesh particle size range. Next, the above powder was put into a 10% by weight aqueous solution of caustic potash, and while stirring, a predetermined amount of mercury was added dropwise to hydrate it. Then wash with water,
The mixture was replaced with acetone and dried to produce zinc hydrate alloy powder.

Further, zinc hydride powder or zinc hydrate alloy powder 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, 1 is a sealing plate made of stainless steel, and its inner surface is plated with steel 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 hydrated 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. This is a positive electrode can made of nickel, and the inside and outside surfaces are nickel plated (not shown). 8
is a polypropylene gasket 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 11.6 mm and a height of 5.4 mm, the weight of the hydrated powder of the negative electrode was unified to 193 mg, and the amount of mercury added (hydration rate) was 2% to the zinc alloy powder.
It was expressed as weight%.

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. The discharge performance was expressed as the discharge duration when discharging at 510Ω at 20° C. with a final voltage of 0.9V.

Further, after being left at a temperature of 60° C. and a humidity of 90% for one month, the state of leakage was visually determined, and the number of batteries leaking was also indicated.

Regarding changes in the total battery height in this table, it is normal for the total battery height to decrease during the period after the battery is sealed until the stress relationship between each battery component stabilizes over time. . However, in a battery where a large amount of hydrogen gas is generated due to corrosion of the zinc negative electrode, there is a strong tendency to increase the total battery height due to an increase in battery internal pressure that counteracts the above-described force for decreasing the total battery height. Therefore, the corrosion resistance of the zinc negative electrode can be evaluated by the increase or decrease in the total height of the battery due to storage. 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 zinc is depleted due to corrosion.
The discharge performance deteriorates significantly 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.

Now, in the table, No. listed as a comparative example of the present invention,
When an additive element is added alone among 1 to 6 (No, l
, 2, 3.4), when two elements are added (N
o, 5.6>, the corrosion resistance and discharge performance of the zinc negative electrode are somewhat improved.

However, the examples of the present invention (NO98, 9,
12, 13, 14, 1? , 18.19.20.23.
In the case of 24°26, 27), the corrosion resistance and discharge performance are even better than those of the comparative example, and the combined effect of the added elements is clearly exhibited. - Even if crab elements coexist, there is an excess or deficiency in the content (No, 7.10.11゜1
5, 16, 21, 22, 25) are not much different from the comparative example, and the combined effect is poor.

As mentioned above, the present invention achieves low water content by using a zinc alloy in which In, Mg, Ca, and Te coexist in an appropriate combination, for example, in an appropriate content as shown in (No, 26.27>) for the negative electrode. The content of each element is 0.5% by weight for In and 0.005% by weight for Mg.
~0.2% by weight, the sum of one or two of Ca and Te, or 0.2% by weight. A suitable range is OI to 0.5% by weight.

As described above, the present invention has discovered that the corrosion resistance of zinc alloys used for negative electrodes can be 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-alkali material with low pollution and excellent practical performance. This is the realization of a battery. In addition, in the examples, a battery using a zinc carbide negative electrode was explained, but in an open air battery or a sealed zinc alkaline battery equipped with a hydrogen absorption mechanism,
Since the permissible amount of hydrogen gas to be generated is relatively large, when the present invention is applied to such a case, it is possible to carry out the process with a lower tree reduction ratio, and in some cases, with anhydrous state.

Effects of the Invention As described above, the present invention can reduce the spring ratio 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 2- Zinc negative electrode 4--Ichimaru/l router 5- #Saigin JT+Usagi

Claims (1)

[Claims] A zinc alloy containing 0.005 to 0.5% by weight of indium, 0.005 to 0.2% by weight of magnesium, and 0.01 to 0.5% by weight of at least one of calcium and tellurium is used as the negative electrode active material. Zinc alkaline battery used.