JPH0685324B2 - Zinc alkaline battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to zinc as a negative electrode active material, an alkaline electrolyte as an electrolytic solution, and manganese dioxide, silver oxide as a positive electrode active material.
In a zinc-alkaline battery using mercury oxide, oxygen, nickel hydroxide, etc., it particularly relates to improvement of the negative electrode.

2. Description of the Related Art Conventionally, a common problem of this type of zinc alkaline battery is corrosion of the negative electrode zinc during storage by an electrolytic solution. It has been used as an industrial method for a long time to increase the hydrogen overvoltage by using zinc fluoride powder in which 5 to 10% by weight of mercury is added to zinc and suppress corrosion to the extent that there is no practical problem. There is.

However, in recent years, to reduce pollution, reduction of mercury contained in a battery has been increasing as a social need, and various studies have been made. For example, a method has been proposed in which alloy powder added with zinc, cadmium, indium, gallium, or the like is used to improve the corrosion resistance and reduce the conversion rate.
In addition to the effect of the additional element alone, these corrosion inhibition effects have a large composite effect of a plurality of additional elements, and indium and lead or zinc alloys in which gallium is added to these elements have been proposed as promising systems.

Further, a zinc alloy in which gallium and silver are added to lead and cadmium (JP-A-61780780), a zinc alloy in which aluminum is added to gallium and thallium (JP-A-61-78061),
Zinc alloy in which one or more kinds of silver, gallium, thallium, and cadmium are added to aluminum and lead (Japanese Patent Laid-Open No. Sho 61-61).
-78059) etc.

Problems to be Solved by the Invention The zinc alloys according to such a proposal can be expected to have corrosion resistance to some extent, and the reduction rate can be reduced to some extent.
The effect of the combination of these elements is not sufficient at present, and it is a future subject to elucidate the alloy composition by an effective combination.

The present invention solves such a problem, and reduces deterioration rate without deteriorating the corrosion resistance of the negative electrode zinc, and has low pollution and excellent overall performance such as discharge performance, storage performance and liquid leakage resistance. In order to provide the zinc negative electrode with the characteristics, the purpose is to select an additive element and appropriately combine the contents.

Means for Solving the Problems In order to solve this problem, the present invention provides 0.01 to 0.5% by weight of one or more of lead, cadmium and gallium, 0.01 to 0.2% by weight of aluminum, and at least one of barium and strontium. By using a zinc alloy containing 0.01 to 0.2% by weight as a negative electrode active material, reduction of mercury in a zinc alkaline battery is realized.

Action The action mechanism of each additive element according to the present invention is not clear,
The synergistic effect of anticorrosion is presumed as follows.

First, lead, cadmium, and gallium increase the hydrogen overvoltage. In particular, gallium has a very high hydrogen overvoltage, and since it is a liquid at around room temperature, it seems to have an effect similar to that of mercury. Also, lead and cadmium are segregated near the grain boundaries of the zinc alloy and are cheap, and when the zinc alloy is screened from the surface, mercury in the surface layer is suppressed from diffusing into the zinc alloy through the grain boundaries, It is considered to contribute to maintaining a high mercury concentration.

Zinc used in alkaline batteries is in the state of so-called atomized zinc powder, which is zinc powder produced by spray-solidifying molten zinc with compressed air or the like. The addition of aluminum affects the particle shape of the atomized zinc powder, and has the effect of making the particles spherical and smoothing the surface thereof. The spheroidizing of the particles and the smoothing of the surface thereof can reduce the surface area where the zinc powder is brought into contact with the electrolytic solution to cause a corrosion reaction, thereby increasing the corrosion resistance.

When strontium or barium is added at the same time as aluminum, it has the effect of further sphericalizing the shape of the above atomized zinc powder, smoothing the surface, and corrosion resistance,
It can be further improved.

It was confirmed by basic corrosion resistance experiments that the above-mentioned additional elements have little effect on corrosion resistance when added alone, or the opposite effect. It is considered that the combined addition reduces synergistic effects by reducing adverse effects on the corrosion resistance of each additive alloy, for example, the influence of a base potential on the electrochemistry of aluminum, strontium, and barium.

The present invention experimentally examines the combination of additive elements in a zinc alloy and the content thereof, and realizes a low-pollution and highly practical zinc alkaline battery that has both a sufficient reduction rate and sufficient corrosion resistance and discharge performance. It is a completed effective means. Less than,
This will be described in detail with reference to examples.

Example Various zinc alloys were prepared by adding various elements to a zinc ingot having a purity of 99.997% or more, as shown in the table below, and were melted at about 500 ° C. and sprayed with compressed air to be powdered. It was sieved to a particle size range of 150 mesh. Then, the above powder was put into a 10% by weight aqueous solution of caustic potash, and a predetermined amount of mercury was dropped to the solution while stirring to make it selective. Then, it was washed with water, replaced with acetone and dried to prepare a zinc hydride alloy powder. Further, zinc fluorinated alloy powders other than the examples of the present invention were prepared by the same method as comparative examples.

A cylindrical alkaline manganese battery shown in the figure was manufactured using these selected powders. In the figure, 1 is a nickel-plated positive electrode case in which positive electrode is made by mixing manganese dioxide with graphite, pressure-molded 2, separator made of polypropylene non-woven fabric 3, cellulose bottom plate 4, carboxymethyl cellulose gel A gelled negative electrode 5 in which various zinc fluoride alloys are dispersed in an electrolytic solution of an aqueous potassium hydroxide solution is housed. Reference numeral 6 denotes a polypropylene sealing plate that seals the opening of the case 1, and a brass negative electrode current collector 7 is fixed to the center thereof. 8 is a negative terminal plate, 9 is a positive terminal plate,
10, 11 are insulating rings, 12 is a heat-shrinkable resin tube, and 13 is a metal outer can.

The prototype battery was an AA alkaline manganese battery. The weight of the zinc hydride alloy powder used for the negative electrode was unified to 2.80 g, and the amount of mercury added (rate of hydration) was 2% by weight based on the zinc alloy. . The prototype battery was stored at 60 ° C. for 1 month and then evaluated at 20 ° C. for continuous discharge performance under a load of 1 Ω and leakage resistance. The following table shows the breakdown of the zinc alloy for the negative electrode and the test results.

In the case of batteries with insufficient corrosion resistance, the leakage resistance deteriorates due to an increase in the battery internal pressure, and the discharge performance is significantly reduced due to the consumption of zinc due to corrosion, the formation of an oxide film on the zinc surface, and the inhibition of the discharge reaction due to the internal pressure of hydrogen gas. As a result, the discharge duration is largely dependent on the corrosion resistance of the zinc negative electrode.

In the above table, Nos. 1 to 7 listed as comparative examples of the present invention
Corrosion resistance of zinc negative electrode when two elements are added (No5,6,7) and three elements are added more than when added alone (No1,2,3,4) The discharge performance has been somewhat improved. However, examples of the present invention (No 9, 10, 11, 12, 15, 15, 16, 17, 20, 21, 22 in which Pb, Cd, Ca, Al, Ba, Sr are present together in an appropriate combination in an appropriate content , 25,26,27,28,3
In the case of 1,32,33,34,37,38,39,41,42,43), the corrosion resistance and the discharge performance are further improved as compared with the comparative example, and the combined effect of the additional elements is remarkably exhibited. On the other hand, even if the three elements are coexistent, if there is an excess or deficiency in the content (No8, 13, 14, 18, 18, 19, 2)
3,24,29,30,35,36,40) is not so different from the comparative example and the combined effect is poor.

As described above, the present invention is a combination of Pb, Cd, Ga, Al, Ba, Sr appropriately, by using a zinc alloy coexistent with an appropriate content as shown in the example to the negative electrode to achieve a low conversion rate. The total content of additive elements is 0.01 to 0.5 wt% for Pb, Cd, and Ga, 0.01 to 0.5 wt% for Al, and 0.01 to 0.5 wt% for Ba and S.
It is suitable that the total amount of at least one of r is 0.01 to 0.2% by weight.

As described above, the present invention has found that the corrosion resistance of the zinc alloy used for the negative electrode is improved by the synergistic effect of the combination of the above-mentioned additional elements, and by determining an appropriate content, a zinc alkaline battery with low pollution and excellent practicability Is realized. In the examples, the battery using the zinc hydride negative electrode was described, but in the open type air battery and the sealed zinc alkaline battery equipped with the hydrogen absorption mechanism, the allowable generation amount of hydrogen gas is relatively large. Therefore, when the present invention is applied to such a case, it can be carried out with a further lowering rate, and depending on the case, with no reduction.

EFFECTS OF THE INVENTION As described above, according to the present invention, the conversion rate of negative electrode zinc can be reduced, and it is extremely effective in obtaining a low-pollution zinc alkaline battery.

[Brief description of drawings]

The figure is a half cross-sectional view of an alkaline manganese battery used in Examples of the present invention. 2 ... Positive electrode, 3 ... Separator, 5 ... Zinc negative electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ryoji Okazaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Megumi City, Hiroshima Prefecture Takehara City, Takehara Town 652-15 (72) Inventor Nobuyoshi Kasahara 1531-45 Takehara Town, Takehara City, Hiroshima Prefecture

Claims (1)

[Claims] 1. At least one of lead, cadmium, and gallium is 0.01 to 0.5% by weight, and aluminum is 0.01 to 0.2% by weight.
0.01 to 0 of at least one of barium and strontium.
A zinc alkaline battery using a zinc alloy containing 2% by weight as a negative electrode active material.