JPH0622117B2 - Zinc alkaline battery - Google Patents

Description

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

2. Description of the Related Art A common problem with zinc alkaline batteries is corrosion of the negative electrode zinc during storage by the electrolytic solution. Heretofore, it has been adopted as an industrial method to increase hydrogen overvoltage by using zinc fluoride powder obtained by adding about 5 to 10% by weight of mercury to zinc to suppress corrosion to such an extent that there is no practical problem. .
However, in recent years, reducing the amount of mercury contained in a battery has become a social need to reduce pollution, and various studies have been made. For example, a method has been proposed in which an alloy powder obtained by adding lead, cadmium, indium, gallium, or the like to zinc is used to improve the corrosion resistance and reduce the conversion rate. In addition to the effect of a single additive element, these corrosion inhibition effects have a large composite effect of multiple additive elements. Indium and lead, or those in which gallium is further added, and zinc alloys in which gallium and lead are added, etc. Conventionally, it has been proposed as a promising system.

All of these can be expected to have a certain degree of corrosion resistance, and although it is possible to expect a reduction in the degree of conversion to a certain extent, it is necessary to search for alloy systems with even better corrosion resistance.

In addition, there is a proposal that using a zinc alloy obtained by adding indium to zinc or a zinc alloy for the negative electrode has a great effect on the anticorrosion mainly for the purpose of improving the manganese dry battery.
(Japanese Examined Patent Publication No. 33-3204).

Problems to be Solved by the Invention In the above proposals, in addition to indium, Fe, Cd, Cr, Pb, Ca, Hg, Bi, Sb, Al, Ag and M are used as elements in the zinc alloy.
Although it is described to include one or two or more of g, Si, Ni, Mn, etc. as impurities or additives, in addition to the effect of using indium and lead as additive elements, the above The classification of whether each miscellaneous element of is included as an impurity or added as an effective element is not specified,
It is not known even which element is effective for anticorrosion, and there is no description other than indium and lead regarding the appropriate addition amount.

It is still a future subject to investigate the effect of the combination of these elements, and further to investigate this in a zinc alkaline battery to obtain an effective alloy composition.

INDUSTRIAL APPLICABILITY The present invention reduces the corrosion rate of the negative electrode zinc without degrading the discharge performance, the discharge performance, the storability, and the low pollution.
It is an object of the present invention to provide a zinc-alkaline battery having excellent overall performance such as leakage resistance.

Means for Solving the Problems The present invention is directed to an electrolytic solution containing an alkaline aqueous solution containing caustic potash, caustic soda, etc. as a main component, zinc as a negative electrode active material, and manganese dioxide, silver oxide, mercury oxide as a positive electrode active material. A negative electrode of a so-called zinc alkaline battery using oxygen or the like contains zinc as a main component, 0.01 to 0.5% by weight of nickel (Ni), 0.01 to 0.5% by weight of lead (Pb), and cadmium (Cd). ) From 0.01 to
A zinc alloy containing 0.5% by weight is used.

The present invention, among the additional elements or impurities in the above-mentioned conventional zinc alloy, paying attention to the fact that Ni is a non-polluting element that is inexpensive and does not cause environmental pollution, and conducts experiments on the effect of adding Ni. The zinc alloy with Ni added alone has poor anticorrosion property, but when Ni, Pb, and Cd are coexistent, the combined corrosion protection is more remarkable than when 1 or 2 of the above elements are added. It was completed by finding out the effects.

Action The mechanism of action for the anti-corrosion effect by the addition of Ni, Pb, or Cd alone and the combined effect of these elements is unclear, but it is presumed as follows.

First, the solubility of Ni in zinc is small, but the cooling rate when powdered by the injection method is very high on the order of 10 ³ ° C / sec. Therefore, a zinc alloy with an appropriate content in the examples described later is used. In powder, Ni may be solutionized with zinc. Therefore, when the zinc alloy is screened from the surface, it is considered that Ni, which has a low affinity for mercury, suppresses the diffusion of mercury into the crystal and contributes to maintain a high mercury concentration on the surface of the zinc alloy. Further, Pb and Cd tend to segregate near the grain boundaries of the zinc alloy, and suppress the diffusion of mercury in the surface layer of the zinc hydride alloy into the interior through the grain boundaries to maintain a high surface mercury concentration. It seems to contribute. It is considered that this effect has some combined action, which is larger when Pb or Cd is added together than when Pb or Cd is added alone. The present invention more effectively suppresses the inward diffusion of mercury in the surface layer of the zinc alloy, which is selected by the combined effect of the above three elements, and reliably maintains the surface mercury concentration to maintain the hydrogen voltage for a long time. The corrosion resistance of the negative electrode zinc is remarkably improved by keeping the same for a long time. That is,
Experiments were carried out in anticipation of the anticorrosion effect by combining the effect of suppressing the diffusion of mercury into the crystal grains by Ni and the effect of suppressing the grain boundary diffusion by the coexistence of Pb and Cd. By using the coexisting zinc alloy, the zinc negative electrode was successfully reduced in the rate of reduction, and it provided an effective means for realizing a low-pollution zinc alkaline battery.

Example Various zinc alloys were prepared by adding various elements shown in the following table to zinc ingot having a purity of 99.997% or more, and the temperature was about 500 ° C.
50 to 1
It was sieved to a particle size range of 50 mesh. Then, 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 effect hydration. Then, it was washed with water, replaced with acetone and dried to prepare a zinc hydride alloy powder.

A button type silver oxide battery shown in the figure was produced using these selected powders. In the figure, 1 is a stainless steel sealing plate, the inner surface of which is plated with copper 1 '. Reference numeral 2 is a zinc negative electrode in which a 40 wt% aqueous solution of caustic potash was used to gel an electrolytic solution saturated with zinc oxide by carboxymethyl cellulose, and a zinc halide alloy powder was dispersed in the gel. 3 is a cellulosic liquid-retaining material, 4 is a separator made of porous polypropylene, 5 is a positive electrode formed by mixing silver oxide with graphite and pressure-molded, 6 is a positive electrode ring made of iron plated with nickel, and 7 is stainless steel The positive electrode can is made of nickel and has nickel plating on the inner and outer surfaces. Reference numeral 8 denotes a polypropylene casquette, which 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 mm and a height of 5.4 mm.
The weight of the negative electrode and the selective powder was unified to 193 mg, and the amount of mercury added (selective rate) was 1% by weight based on the zinc alloy powder.

The following table shows the composition of the zinc alloy of the prototype battery and the change in the total battery height of the discharge performance after storage at 60 ° C. for one month. The discharge performance was expressed by the discharge duration when discharged at 510 Ω at 20 ° C. with a final voltage of 0.9V.

Regarding the change in the total battery height in this table, it is customary that the total battery height decreases after the battery is sealed until the stress relationship between the battery constituent elements stabilizes over time.
However, in a battery in which 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 the internal pressure of the battery, which opposes the above-described force of reducing the total battery height. Therefore, the corrosion resistance of the zinc negative electrode can be evaluated by increasing or decreasing the total height of the battery due to storage. In addition, in the case of batteries with insufficient corrosion resistance, the total height of the battery increases and the leakage resistance deteriorates due to an increase in the internal pressure of the battery.
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 internal presence of hydrogen gas, and the discharge duration also largely depends on the corrosion resistance of the zinc negative electrode.

In the table, among No. 1 to 6 listed as comparative examples of the present invention, two kinds of elements were added more than when the zinc alloy to which the additional element was added alone was used (No. 1, 2, 3). Case (N
The corrosion resistance and the discharge performance of the zinc negative electrode are somewhat improved in o.4, 5, 6). However, the embodiment of the present invention (No. 8, 9, 1) in which the three elements of Ni, pb, and Cd are made to depend on proper contents
In the case of 0, 13, 14, 17, 18), the corrosion resistance and the discharge performance are further improved as compared with the above-mentioned comparative example, and the combined effect of the additional elements is remarkably shown. On the other hand, even if the above three elements are present together, if there is an excess or deficiency in the content (No. 7, 11, 12, 15, 1
6 and 19) are not so different from the comparative examples, and the combined effect is poor. As described above, the present invention succeeds in lowering the rate of reduction by using a zinc alloy in which the above three elements are coexisted in proper contents in the negative electrode, and the content of each element is 0.01 ≦ Ni. ≦ 0.5% by weight, 0.01 ≦ pb ≦ 0.5% by weight, 0.01 ≦ Cd ≦
It is suitable to be 0.5% by weight.

As described above, the present invention is used in the negative electrode due to the synergistic effect of the combination of the above-mentioned additional elements, it was found that the corrosion resistance of the zinc alloy is improved, the appropriate content is determined, low pollution and excellent zinc performance It is an implementation of an alkaline battery. In the examples, the void using the zinc hydride negative electrode was described, but in the case of an open type electric battery or a sealed zinc alkaline battery equipped with a hydrogen absorption mechanism,
Since the hydrogen gas generation allowance is comparatively large, when the present invention is applied in such a case, it can be carried out with a further lowering rate, and in some cases, with no reduction.

Effects of the Invention As described above, the present invention can reduce the conversion rate of negative electrode zinc,
It is extremely effective in obtaining a low-pollution zinc alkaline battery.

[Brief description of drawings]

The figure is a side view in which a button-shaped silver oxide battery used in an example of the present invention is partially sectioned. 2 ... Zinc negative electrode, 4 ... Separator, 5 ... Silver oxide positive electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ryoji Okazaki Ryoji Okazaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 652-15 Takehara-cho, Takehara-shi, Hiroshima Prefecture

Claims (1)

[Claims] 1. Nickel 0.01 to 0.5% by weight, lead 0.01 to 0.5% by weight, and cadmium 0.01 to 0.
A zinc alkaline battery using a zinc alloy containing 5% by weight as a negative electrode active material.