JPH04368776A - Zinc-alloy powder for alkaline battery, and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the corrosion-resistance and battery-characteristic of zinc-alloy powder for an alkaline battery by using as the anodic active-material of the battery the zinc-alloy powder obtained through the process of alloying a specific alloy-element with zinc, then forming the resultant alloy in powdered grains and substituting indium oxide for the surface of each of the grains in a solution of potassium hydroxide. CONSTITUTION:An alloy element obtained through the process of using as its ingredients aluminium, gallium, indium, magnesium, calcium and 0.0001 to 5.0wt% of lead respectively and then alloying them with one another is alloyed with zinc, and then the resultant zinc alloy is formed in specific powder through an atomizing process. Then the zinc-alloy powder is soaked in an aqueous solution of potassium hydroxide containing indium oxide and gallium oxide, so that both of indium oxide and gallium oxide may be substituted for the surface of the powder. The hydrogen- overvoltage of the resultant powder can thus be heightened while the powder can be smoothed at its surface to improve its corrosion-resistance. When the powder is used as the anodic active-material 4 of an alkaline battery, the quantity of hydrogen gas generated can be reduced so as to produce the effect of preventing deterioration in the battery-characteristic of the powder.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a zinc alloy powder for use in alkaline batteries with improved properties and a method for producing the same, and in particular to a method of replacing the surface of the zinc alloy powder with either or both of indium oxide and gallium oxide. The present invention relates to a zinc alloy powder for alkaline batteries, which is characterized by a small amount of gas generation and improved battery performance at low temperatures, and a method for producing the same.

0002

BACKGROUND OF THE INVENTION Zinc or zinc alloys have heretofore been preferably used as negative electrode active materials for batteries such as alkaline dry batteries because of their high hydrogen overvoltage and relatively low cost. However, when only zinc is used as the negative electrode active material, there is a problem in that it is difficult to sufficiently suppress hydrogen gas generated in large quantities during battery use, and electrolyte leakage occurs.

[0003] One effective method for suppressing hydrogen gas generation that has been widely used in recent years to solve the above-mentioned problems is to convert zinc into hydrogen. However, since this method uses a considerable amount of mercury, environmental pollution when disposing of waste dry batteries has become a serious problem. Therefore, there is a need for the development of a zinc alloy that can achieve the desired effect with as low or no stress as possible.
As disclosed in ``Zinc Alloy for Batteries and Method for Producing the Same'', we have achieved some results in the development of zinc alloys that can achieve desired effects with low or no stress.

0004

[Problems to be Solved by the Invention] As mentioned above, from the perspective of preventing environmental pollution, it is desired to develop a zinc alloy that has lower or no stress and has the effect of suppressing gas generation. As indicated in the above-mentioned publication by the present inventors, it is considered that it is not effective for the purpose of suppressing hydrogen gas generation unless the amount of mercury added during oxidation is 0.3% by weight or more. Ta.

[0005] Therefore, the present invention provides a zinc alloy powder for alkaline batteries, which can significantly suppress the amount of hydrogen gas generated compared to conventional non-oxidized zinc alloy powders, and improve battery characteristics at low temperatures, and its production. The purpose is to provide law.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have conducted extensive research and have determined that the surface of zinc alloy powder used as a negative electrode active material for alkaline batteries can be made of either indium oxide or gallium oxide. It has been discovered that by substituting one or both of the two, the amount of hydrogen gas generated can be significantly suppressed even in the case of zinc alloy powder with low or no flux, and furthermore, the deterioration of discharge performance at low temperatures can be prevented. The present invention was achieved.

That is, the present invention provides aluminum, gallium, indium, thallium, magnesium, calcium, strontium, tin, lead, bismuth, cadmium,
At least one metal selected from the group consisting of silver, tellurium, copper, nickel, barium, and germanium is added to 0.
Zinc alloy powder containing 0001 to 5.0% by weight, the remainder consisting of zinc and unavoidable impurities, characterized in that the surface of the powder is substituted with either or both of indium oxide and gallium oxide. Zinc alloy powder for alkaline batteries; and alloying elements consisting of aluminum, gallium, indium, thallium, magnesium, calcium, strontium, tin, lead, bismuth, cadmium, silver, tellurium, copper, nickel, barium and germanium. Using 0.0001 to 5.0% by weight of at least one metal selected from the group, this metal, zinc and unavoidable impurities were mixed and melted to form an alloy, and this alloy was formed into a powder by a spraying method. rear,
The zinc alloy powder is immersed in a potassium hydroxide aqueous solution containing one or both of indium oxide and gallium oxide, and the surface of the powder is replaced with one or both of indium oxide and gallium oxide. The present invention provides a method for producing a characteristic zinc alloy powder for alkaline batteries.

[0008]

[Operation] According to the present invention, alloying elements are mixed and melted with zinc and unavoidable impurities to form an alloy, formed into powder by a spraying method, and the surface of the zinc alloy powder particles is coated with indium oxide in an aqueous solution of potassium hydroxide. and/or substituted with gallium oxide.

Indium and gallium have the effect of increasing the hydrogen overvoltage and smoothing the surface of the alloy powder to improve corrosion resistance. In the grain boundaries of the alloy powder obtained by the above spraying method (indium and/or gallium added to molten zinc), indium and/or gallium, which have the above-mentioned effects, are present, suppressing intergranular corrosion. However, by further substituting the surface of the zinc alloy powder with indium and/or gallium as in the present invention, corrosion from the grain boundaries is further suppressed, and as a result, the amount of hydrogen gas generated is significantly reduced. It reduces it. Furthermore, since indium and gallium are also low melting point metals, their presence on the powder surface has the effect of preventing deterioration of battery characteristics at low temperatures.

As described above, when the zinc alloy powder for alkaline batteries obtained according to the present invention is used as a negative electrode active material in a battery with low or no gradient, the amount of hydrogen gas generated is extremely small and the battery performance is improved. It was confirmed that the discharge performance, especially at low temperatures, was significantly improved. That is, the zinc alloy powder of the present invention was heated to 40% at 45°C saturated with zinc oxide.
When the amount of hydrogen gas generated was measured by immersing it in a KOH aqueous solution, the amount of hydrogen gas generated was 20 to 35% lower than that of conventional zinc alloy powder obtained by adding indium and gallium to molten zinc during spraying. , was confirmed to be at least 7% or more lower, and it was also confirmed that the discharge performance at low temperatures was improved by 20% or more compared to the above-mentioned conventional zinc alloy powder.

[0011] The present invention will be explained in detail below with reference to Examples. However, the scope of the present invention is not limited by the following examples.

0012

Example 1 First, each set of alloying elements shown in Table 1 was mixed and melted with zinc (and inevitable impurities) to form an alloy, and the alloy was produced as a powder of 48 to 150 mesh by a conventional spraying method. The molten metal contained indium and gallium as shown in the table. Next, a part of the zinc alloy powder of each composition obtained in this way was mixed with In2O3.
and/or immersed in an aqueous potassium hydroxide solution containing Ga2O3 to replace the surface of the powder particles with indium and/or gallium. Next, a part of the zinc alloy powder of each composition whose powder surface has been replaced with indium and/or gallium, and a part of the zinc alloy powder of each composition without substitution are placed in a KOH solution for each sample.
Hydrogenation was carried out by adding 0.04% by weight of mercury.

[0013] Certain amounts of each of the substituted and non-substituted, oxidized and non-oxidized samples of the zinc alloy powders of each composition produced as described above were each saturated with zinc oxide.
The sample was immersed in a 40% KOH solution at 5°C, and the amount of hydrogen gas generated was measured. The results are shown in Table 1. Hydrogen gas generation amount (
μl/g·d) is the amount generated per day per gram of alloy powder.

[0014]

[Table 1]

From these results, even if the zinc alloy powder has the same composition, if indium oxide and/or gallium oxide is substituted on the surface of the zinc powder, the molten zinc will contain indium and/or gallium during spraying. It was found that the amount of hydrogen gas generated was significantly suppressed compared to the case where only the hydrogen gas was used. In other words, even non-gradient zinc alloy powders whose surfaces are replaced with indium oxide and/or gallium oxide generate less hydrogen gas than conventional low-gradable zinc alloy powders, and compared to conventional low-mercury zinc alloy powders. It can be seen that it is possible to manufacture and use mercury-free batteries as a battery replacement.

[0016]

Example 2 A zinc alloy powder having the components shown in Table 2 was used as a negative electrode active material for an alkaline manganese battery shown in FIG. 1, and its battery performance was evaluated. In Figure 1, 1 is a positive electrode can, 2 is a positive electrode active material, and 3
is a separator, 4 is a negative electrode active material, 5 is a negative electrode current collector rod, 6
is a rubber packing and 7 is a cap. The evaluation is at a discharge load of 10Ω and a discharge condition of -10°C, with a final voltage of 0.9.
This was done by measuring the discharge time to V. The measured value was determined by making an alkaline manganese battery using a conventional zinc alloy powder as a negative electrode active material to which indium and/or gallium was added only during spraying, performing the same measurements as above, and setting the measured value as 100. Shown as an index. The results are shown in Table 2.

[0017]

[Table 2]

As can be seen from Table 2, battery performance at low temperatures was improved by substituting the surface of the zinc alloy powder with indium and/or gallium.

[0019]

According to the development of the present invention, by substituting the surface of a zinc alloy powder with low or no resistance with either or both of indium oxide and gallium oxide in an aqueous potassium hydroxide solution, Compared to conventional products, the amount of hydrogen gas generated was significantly suppressed, and battery characteristics at low temperatures were improved. Therefore, by using the zinc alloy powder of the present invention, it is possible to manufacture a practical mercury-free battery, and the problem of environmental pollution caused by mercury can be solved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an alkaline manganese battery using the zinc alloy powder for alkaline batteries of the present invention as a negative electrode active material.

[Explanation of symbols]

１‥‥‥Positive electrode can 2‥‥‥Cathode active material ３‥‥‥Separator 4‥‥‥Negative electrode active material 5‥‥‥Negative electrode current collector rod 6.Rubber packing 7. Cap

Claims (2)

[Claims] [Claim 1] Aluminum, gallium, indium, thallium, magnesium, calcium, strontium, tin, lead, bismuth, cadmium, silver, tellurium, copper,
At least one metal selected from the group consisting of nickel, barium, and germanium in an amount of 0.0001 to 5.0
% by weight, the balance being zinc and unavoidable impurities, for use in alkaline batteries, characterized in that the surface of the powder is substituted with either or both of indium oxide and gallium oxide. Zinc alloy powder. [Claim 2] Alloying elements include aluminum, gallium, indium, thallium, magnesium, calcium, strontium, tin, lead, bismuth, cadmium,
At least one metal selected from the group consisting of silver, tellurium, copper, nickel, barium, and germanium is added to 0.
0001 to 5.0% by weight, this metal is mixed and melted with zinc and unavoidable impurities to form an alloy, and this alloy is formed into a powder by a spraying method, and then the zinc alloy powder is mixed with indium oxide and gallium oxide. Zinc alloy powder for alkaline batteries characterized in that the surface of the powder particles is replaced with either or both of indium oxide and gallium oxide by immersing it in an aqueous potassium hydroxide solution containing either or both of them. Manufacturing method.