JPH0418674B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of the Invention) The present invention relates to a zinc-alkaline battery, and more particularly, lead, indium, and thallium, which have the effect of increasing the hydrogen overvoltage of zinc or suppressing corrosion of zinc in an alkaline electrolyte, when coexisting with zinc. , cadmium, tin, bismuth, gallium, aluminum, silver, tantalum, and one or more alkali metals such as lithium, sodium, potassium, etc., each containing a specific range of a zinc alloy. This invention relates to a zinc-alkaline battery used as a negative electrode active material. (Background of the Invention) In alkaline batteries and the like that use zinc as a negative electrode active material, the batteries must be sealed tightly because a strong alkaline electrolyte such as an aqueous potassium hydroxide solution is used. This sealing of the battery is particularly important when attempting to miniaturize the battery, but it also traps hydrogen gas generated due to corrosion of zinc during battery storage. Therefore, during long-term storage, the gas pressure inside the battery increases, and the more completely the battery is sealed, the greater the risk of explosion. As a countermeasure, research has been conducted to prevent the corrosion of zinc, which is an active material for the negative electrode, and to reduce the generation of hydrogen gas inside the battery.Zinc hydride, which has increased the hydrogen overvoltage of zinc by adding mercury, is used as the active material for the negative electrode. This is done exclusively. For this reason, the negative electrode active materials of alkaline batteries commercially available today contain a large amount of mercury, approximately 5 to 10% by weight, and there is a social need to develop lower mercury or mercury-free batteries. It has become strongly demanded. Therefore, various proposals have been made regarding zinc alloy powders in which various metals are added to zinc in order to reduce the mercury content in batteries. For example, there is a zinc alloy powder made by adding lead to zinc, or a zinc alloy powder made by the present inventors by adding lead and indium to zinc (Japanese Patent Laid-Open No. 181266/1983). but,
Although these zinc alloy powders have a certain degree of gas generation suppressing effect, it is still not sufficient. For example, when a zinc alloy powder made by adding lead and indium to zinc has a low mercury content of about 1% by weight, gas generation is extremely suppressed at the beginning of a gas generation test; There was a tendency for the gas generation rate to gradually increase over a long period of time. As described above, a battery has not yet been obtained in which the zinc alloy powder, which is the negative electrode active material, has a low resistance, reduces the amount of hydrogen gas generated, and maintains the discharge performance, which is the battery performance, at a high level. (Object of the Invention) In view of the current situation, the present invention provides a zinc-alkaline battery using a negative electrode active material that significantly reduces mercury content, suppresses hydrogen gas generation, and maintains discharge performance at a high level. The purpose is to (Background of the invention) As a result of intensive research in line with this purpose, the present inventors found that lead, an element that has the effect of increasing the hydrogen overvoltage of zinc, in a negative electrode active material made of zinc.
By containing one or more selected from indium, thallium, cadmium, tin, bismuth, gallium, aluminum, silver, and tantalum in a specific range, and further containing one or more alkali metals such as lithium in a specific range, these It was discovered that the synergistic effect of the additive elements can significantly reduce the amount of hydrogen gas generated than conventional zinc alloy powders with reduced flux, and it is possible to obtain a zinc-alkaline battery with excellent discharge performance.The present invention reached. (Structure of the Invention) That is, the present invention contains 0.01 to 0.5% by weight of one or more selected from lead, indium, thallium, cadmium, tin, bismuth, gallium, aluminum, silver, and tantalum, and one or more alkali metals.
This is a zinc-alkaline battery characterized by using a zinc chloride alloy consisting of 0.00005 to 1.0% by weight, less than 5.0% by weight of mercury, and the balance being zinc as a negative electrode active material. In the present invention, as mentioned above, a zinc alloy containing elements such as lead and alkali metal elements in a specific range, which have the effect of increasing the hydrogen overvoltage of zinc or suppressing the corrosion of zinc in an alkaline electrolyte, is used. It is used as a negative electrode active material. The mercury content when converted into water is lower than the mercury content of conventional negative electrode active materials, that is, less than 5.0% by weight, but if the mercury content is lowered and low pollution is considered, it is 3.0% by weight. It is as follows. In particular, in the alloy composition of the present invention, the synergistic effect of the combination of the added components is extremely large, and hydrogen gas generation can be suppressed even at a mercury content of around 1.0% by weight or less. The zinc alloy used in the negative electrode active material of the present invention contains one or more selected from lead, indium, cadmium, tin, bismuth, gallium, aluminum, silver, and tantalum in a range of 0.01 to 0.5% by weight. This increases the hydrogen overvoltage of the resulting zinc alloy and exhibits a corrosion inhibiting effect on the zinc alloy.
If the content is less than 0.01% by weight, the desired addition effect cannot be obtained, and if it exceeds 0.5% by weight, the self-discharge of the battery will be accelerated, and good results will be obtained in gas generation suppression and discharge performance. do not have. Zinc alloys containing these elements in appropriate amounts have already been put into practical use in actual batteries and have received some praise, but they are still insufficient to meet the recent social needs for low silver. Not enough. Therefore, the present inventors conducted further research and found that by adding a small amount of alkali metal to the alloy composition to which elements such as lead were added, gas generation could be significantly suppressed. It has been found to be effective. The alkali metals (group IA of the periodic table excluding hydrogen) used here include lithium, sodium,
Potassium is preferred because it is easily available, but rubidium and cesium can also be used. The content of this alkali metal is 0.00005~1.0% by weight (0.5~
(10,000 ppm by weight), and practically it is preferably in the range of 0.50 to 0.0001% by weight. If this content is less than 0.00005% by weight,
A sufficient hydrogen gas generation suppression effect cannot be expected, and
Even if it is contained in an amount exceeding 1.0% by weight, no further effect can be obtained. Previous attempts have been made to improve physical properties such as creep resistance by adding a small amount of lithium to zinc. It is not clear from the knowledge so far whether it has a suppressive effect. If we were to force a guess, it would be thought that due to its strong reducing action, the effect of additives that increase hydrogen overvoltage, such as lead and indium, may be maintained over a long period of time. As with the present invention, there has never been an example of adding an alkali metal to a low-fragility zinc alloy for use as a negative electrode active material. As described above, the zinc-alkaline battery of the present invention uses an alkaline aqueous solution mainly composed of caustic potash, caustic soda, etc. as the electrolyte, the above-mentioned zinc alloy or aqueous zinc alloy as the negative electrode active material, and manganese dioxide as the positive electrode active material. , silver oxide, oxygen, etc. (Description of Examples) The present invention will be specifically described below based on Examples and Comparative Examples. Examples 1 to 8 and Comparative Examples 1 to 2 Zinc ingots with a purity of 99.997% or higher were melted at about 500°C, and lead and indium were added to the melt to contain 0.05% by weight each as shown in Table 1. Then, in an argon gas atmosphere, sodium was quickly added and dissolved with stirring so that it contained 0.05% by weight as shown in Table 1. The zinc alloy thus obtained was flowed out from the pores of the crucible at a temperature of 550°C, and atomized using pressurized air (ejection pressure 3 Kg/cm ² ) by a normal atomization method to create a powdered zinc alloy powder. . Next, mercury was added to the above powder in a 10% potassium hydroxide aqueous solution with stirring so that the content was 1.0% by weight, and a hydrochloric acid treatment was carried out to form a hydrochloric zinc alloy powder (Example 1). I got it. In addition, as shown in Table 1, the following compositions (1) 0.10% by weight of lead, 0.04% by weight of thallium, 0.0005% by weight of lithium (Example 2), (2) 0.20% by weight of lead, 0.10% by weight of indium, Gallium 0.10% by weight Sodium 0.002% by weight (Example 3), (3) Indium 0.01% by weight, Thallium 0.005% by weight, Tin 0.05% by weight Potassium 0.05% by weight (Example 4), (4) Indium 0.05% by weight, Cadmium 0.30% by weight, bismuth 0.05% by weight, cesium 0.001% by weight (Example 5), (5) 0.30% by weight indium, 0.20% by weight aluminum, 0.01% by weight lithium (Example 6), (6) 0.05% by weight thallium, 0.05% by weight of silver, 0.01% by weight of lithium (Example 7), (7) 0.005% by weight of cadmium, 0.005% by weight of tantalum, 0.01% by weight of lithium (Example 8), (8) 0.05% by weight of lead (Comparative Example 1) , (9) A zinc alloy consisting of 0.05% by weight of lead and 0.05% by weight of indium (Comparative Example 2) was prepared, and this was powdered in the same manner as above, and subjected to a filtration treatment,
In Examples 2 to 8, zinc alloy powder with a mercury content of 1.0% by weight was used, and in Comparative Examples 1 to 2, a mercury content of 2.0% was used.
% zinc alloy powder was obtained. A hydrogen gas generation test was conducted using the zinc alloy powder thus obtained, and the results are shown in Table 2. In addition, in the gas generation test, the concentration of the electrolyte was
Using 5 ml of 40% by weight potassium hydroxide aqueous solution saturated with zinc oxide, add 10 g of zinc alloy powder.
In addition, the amount of gas generated (ml/g) at 45°C for 50 days was measured. Further, battery performance was evaluated using an alkaline manganese battery shown in FIG. 1 using these zinc alloy powders as a negative electrode active material. The alkaline manganese battery shown in FIG. 1 is composed of a positive electrode can 1, a positive electrode 2, a separator 3, a negative electrode 4 made of zinc alloy powder gelled with carboxymethyl cellulose, a negative electrode current collector 5, a rubber packing 6, and a pressing plate 7. Using this alkaline manganese battery, we measured the discharge duration to a final voltage of 0.9V under discharge conditions of 4Ω discharge load and 20℃.
The measured values of Comparative Example 2 using the conventional negative electrode active material are
It is expressed as an index set to 100. The results are shown in Table 2.

【table】

[Table] As shown in Table 2, zinc contains a specific amount of one or more selected from lead, indium, thallium, cadmium, tin, bismuth, gallium, aluminum, silver, and tantalum, and a specific amount of alkali metal. Examples 1 to 8 in which a zinc chloride alloy powder containing lead was used as a negative electrode active material, Comparative Example 1 in which a zinc chloride alloy powder containing zinc and lead was used as a negative electrode active material, and Comparative Example 1 in which a zinc chloride alloy powder containing lead and indium was added to zinc were used as a negative electrode active material. Compared to Comparative Example 2 in which the added zinc alloy powder was used as the negative electrode active material, the amount of hydrogenation was 1.0%, which was half, but the hydrogen gas generation suppressing effect was extremely large and the discharge performance was excellent. I know that there is. (Effects of the Invention) As explained above, the zinc alloy of the present invention, which contains a component that increases hydrogen overvoltage such as lead in a specific range, and also contains an alkali metal in a specific range, is made into a starch and used as a negative electrode active material. Zinc-alkaline batteries can improve battery performance while significantly suppressing the hydrogen gas generation rate, and also have a low mercury content. Therefore, it is in line with social needs. Therefore, the zinc-alkaline battery of the present invention can be used in a wide range of applications.

[Brief explanation of drawings]

FIG. 1 shows a sectional view of an alkaline manganese battery according to the present invention. 1: positive electrode can, 2: positive electrode, 3: separator,
4: Negative electrode, 5: Negative electrode current collector, 6: Rubber packing,
7: Pressing board.

Claims (1)

[Claims] 1. 0.01 to 0.5% by weight of one or more selected from lead, indium, thallium, cadmium, tin, bismuth, gallium, aluminum, silver, and tantalum;
0.00005 to 1.0% by weight of one or more alkali metals,
A zinc-alkaline battery characterized by using a zinc chloride alloy containing less than 0.5% by weight of mercury and the balance being zinc as a negative electrode active material. 2. The zinc-alkaline battery according to claim 1, wherein the alkali metal is lithium, sodium, potassium, rubidium, or cesium.