JPH0365618B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to improvement of the negative electrode of a zinc-alkaline battery using zinc as the negative electrode active material, an alkaline aqueous solution as the electrolyte, and manganese dioxide, silver oxide, mercury oxide, oxygen, nickel hydroxide, etc. as the positive electrode active material. It is something. Prior Art A common problem with zinc-alkaline batteries is corrosion of the negative electrode zinc by electrolyte during storage. Conventionally, an industrial method has been used to increase the hydrogen overvoltage by using zinc chloride powder containing 5 to 10% by weight of mercury to suppress corrosion to a level that poses no practical problems. . However, in recent years,
In order to reduce pollution, there is a growing social need to reduce the amount of mercury contained in batteries, and various studies are being conducted. For example, a method has been proposed in which an alloy powder in which lead, cadmium, indium, etc. are added to zinc is used to improve corrosion resistance and reduce the degree of corrosion. 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. In addition, we mainly aim to improve manganese dry batteries.
It has been proposed that the use of zinc or a zinc alloy prepared by adding indium to a zinc alloy for the negative electrode has a great anticorrosive effect (Japanese Patent Publication No. 33-3204). Problems to be solved by the invention Among the above proposals, as an element in zinc alloy,
In addition to indium, Fe, Cd, Cr, Pb, Ca, Hg,
The description includes cases in which one or more of Bi, Sb, Al, Ag, Mg, Si, Ni, Mn, etc. are included 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 aims to provide a zinc-alkaline battery with low pollution and excellent overall performance such as discharge performance, storage performance, and leakage resistance, by reducing the corrosion resistance and discharge performance of the negative electrode zinc. purpose. Means for Solving the Problems The present invention uses an aqueous alkaline solution containing caustic potash, caustic soda, etc. as the main components in the electrolyte, zinc as the negative electrode active material, manganese dioxide, silver oxide, mercury oxide, etc. as the positive electrode active material, The negative electrode of a so-called zinc-alkaline battery that uses oxygen etc. is made mainly of zinc, with 0.01 to 0.5% by weight of nickel (Ni) and indium (In).
It is characterized by using a zinc alloy containing 0.01 to 0.5% by weight and 0.01 to 0.5% by weight of thallium (Tl). In the present invention, among the additive elements or impurities in the conventional zinc alloy, experiments were conducted focusing on Ni, for which the effects of addition were not known. , found that the combined effect with Tl was extremely significant,
This study determined the effective zinc alloy composition for reducing the rate of reduction of zinc negative electrodes. Effect The mechanism of action regarding the anticorrosion effect of adding Ni, In, or Tl alone, and the combined effect of these elements is unclear, but it is inferred as follows. First, although the solubility of Ni in zinc is small, the cooling rate during powderization by the injection method is extremely high, on the order of 10 ³ °C/sec. %), there is a possibility that Ni may become solution with zinc in zinc alloy powder. Therefore, when a zinc alloy is oxidized from the surface, Ni, which has a low affinity for mercury, is expected to suppress the diffusion of mercury into the crystal and contribute to maintaining a high mercury concentration on the surface of the zinc alloy. Ru. On the other hand, there is a concern that the adhesion of mercury to the surface of the zinc alloy may become worse, and adding Ni alone will not provide a significant anticorrosion effect. In addition, In and Tl increase the hydrogen overvoltage of zinc alloys and are easily compatible with mercury, so they are effective in making the surface condition of zinc alloys uniform through oxidation, and they also improve the surface and grain boundaries of zinc alloys. It is also expected to play a role in fixing mercury. Furthermore, it is known that the effects of In and Tl as the above-mentioned anticorrosion additive elements are greater when In and Tl are added simultaneously than when added alone. The present invention uses a small amount of mercury to maximize the mercury concentration on the surface of the zinc alloy to obtain a zinc negative electrode with better corrosion resistance and a lower rate of corrosion. This combines the fixation of mercury on the zinc alloy surface and grain boundaries due to the coexistence of In. 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 lowering the rate of oxidation. It provides alkaline batteries. Example: Various zinc alloys were created by adding various elements shown in the following table to zinc ingot with a purity of 99.997% or more.
It was melted at 500°C, pulverized by blasting with compressed air, and sieved to a particle size range of 50-150 mesh. Next, the powder was put into a 10% by weight aqueous solution of caustic potash, and a predetermined amount of mercury was added dropwise to the solution while stirring. Thereafter, it was washed with water, substituted with acetone, and dried to produce a zinc chloride alloy powder. Further, zinc chloride powder or zinc chloride alloy powder other than the examples of the present invention were also prepared in the same manner as comparative examples. The button-shaped silver oxide battery shown in the figure was manufactured using these oxidized powders. In the figure, reference numeral 1 denotes a sealing plate made of stainless steel, the inner surface of which is plated with copper 1'. 2 is a zinc negative electrode prepared by gelling an electrolytic solution of a 40% by weight aqueous solution of caustic potassium saturated with zinc oxide with carboxymethyl cellulose, and dispersing zinc oxide 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 made of stainless steel. With the positive electrode can,
Its inner and outer surfaces are decorated with nickel metal.
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 mm and a height of 5.4 mm.
The weight of the oxidized powder of the negative electrode was unified to 193 mg, and the amount of mercury added (the oxidized ratio) 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 changes in discharge performance and total battery height after storage at 60°C for one month. The discharge performance is 510Ω at 20℃.
It is expressed as the discharge duration when discharge is performed with a final voltage of 0.9V.

【table】

[Table] Regarding changes in total battery height in this table,
After the battery is sealed, the total height of the battery typically decreases during the period until the stress relationship between the battery components becomes stable 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 based on the change in total battery height due to storage. In addition, batteries with insufficient corrosion resistance will not only increase the total height of the battery, but also deteriorate leakage resistance due to an increase in battery internal pressure, as well as depletion of zinc due to corrosion, formation of an oxide film on the surface of zinc, and the presence of hydrogen gas. The discharge performance is significantly deteriorated due to inhibition of the discharge reaction by the zinc negative electrode, and the discharge duration also largely depends on the corrosion resistance of the zinc negative electrode. In the table, No. 1 listed as a comparative example of the present invention
- 6, zinc alloys with two elements added (Nos. 4, 5, 6) contain more zinc than when using zinc alloys with only one additive element added (Nos. 1, 2, 3). Both the corrosion resistance and discharge performance of the negative electrode have been improved to some extent.
However, Examples of the present invention (Nos. 8, 9, 10, 13,
In the case of Nos. 14, 17, and 18), the corrosion resistance and discharge performance are even better than those of the comparative examples, and the combined effects of the added elements are clearly exhibited. On the other hand, even when the above three elements coexist, there is an excess or deficiency in their content (No.
7, 11, 12, 15, 16, 19) are not significantly different from the comparative examples,
The combined effect is poor. As mentioned above, the present invention has succeeded in reducing the reduction rate by using a zinc alloy in which the above three elements coexist in appropriate contents in the negative electrode, and the content of each element is 0.01≦Ni≦0.5. Weight%, 0.01
It is appropriate that ≦In≦0.5% by weight and 0.01≦Tl≦0.5% 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 due to the synergistic effect of the combination of the above-mentioned additive elements, and by determining the appropriate content, we have developed a zinc-alkaline battery with low pollution and excellent practical performance. This has been realized. In addition, in the examples, a battery using a zinc chloride 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 small. Therefore, when applying the present invention to such cases, it is possible to further reduce the rate of change, or in some cases, it may be carried out without changing the rate of change. Effects of the Invention As described above, the present invention is extremely effective in reducing the oxidation rate of negative electrode zinc and obtaining a low-pollution zinc-alkaline battery.

[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.

Claims (1)

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