JPH0719601B2 - Zinc alloy for alkaline zinc battery, method for producing the same, and alkaline zinc battery using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a battery using zinc as a main active material of a negative electrode and an alkaline aqueous solution as an electrolytic solution, and suppressing an increase in battery internal pressure due to hydrogen gas generated in the battery. The present invention provides a zinc battery having excellent storability.

2. Description of the Related Art Conventionally, in this type of alkaline zinc battery, hydrogen gas is generated due to self-depletion or corrosion of zinc during storage of the battery or after partial discharge.
We have added about 1.5% by weight of mercury to alloys containing aluminum and lead to form an amalgam, which has suppressed the rise in battery internal pressure. As a result, the internal pressure of the battery is prevented from rising during storage, the storability is secured, and the battery is widely used as a practical battery with little deterioration in battery performance.

However, as social needs for low pollution have increased in recent years, the amount of mercury used must be further reduced, and the above-mentioned practical performance must be secured without using mercury. Has been done since. However, even if it is possible to reduce the amount of mercury to some extent, there is currently no means that enables an essential solution, and it is not possible to secure sufficient corrosion resistance of the negative electrode zinc without using mercury. It is considered extremely difficult.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By reducing the amount of mercury added to a zinc alloy containing indium, aluminum, and lead to zinc to less than 1.5% by weight, it is possible to achieve an extremely low level of unremoved zinc or 0.04% by weight (400 ppm). When a battery is constructed using zinc fluoride, hydrogen generation due to the corrosion reaction of zinc increases during storage of the battery or after the battery is partially discharged, and the internal pressure of the battery increases significantly. It is considered that the cause of the increase in hydrogen generation is originally that mercury has an action of increasing the hydrogen overvoltage on the zinc surface and suppressing the corrosion reaction, but the absolute amount of mercury is reduced to the limit. When such a significant increase in internal pressure occurs in the battery, there is a problem in that the electrolyte leaks, the storage property of the battery is significantly impaired, and practical performance cannot be ensured.

The present invention solves such a problem. Hydrogen gas generated during storage of a battery using an unreduced or extremely low-reduced zinc alloy, or after partial discharge is used as a low-reduced zinc alloy for indium, It is an object of the present invention to provide a battery having good storage properties, which is suppressed by coating with a low boiling point alloy containing gallium or further coating with a fluorine-based surfactant.

Means for Solving the Problem In order to solve this problem, the present invention provides an unreduced or negative mercury as a main active material of a negative electrode, in an alkaline zinc battery having a low-reduction zinc alloy up to 400 ppm of mercury, wherein the low-reduction zinc is used. The alloy is coated with a low boiling point alloy containing gallium or indium, or is further coated with a low boiling point alloy and a fluorine-based surfactant. The coating is performed by adding a low boiling zinc alloy containing low-grade zinc alloy and gallium and indium in an aqueous solution of an alkali metal hydroxide and stirring the mixture to coat the zinc alloy, or by dry-mixing both. To coat. The content of the fluorine-based surfactant here is preferably 0.01 to 1% by weight with respect to the zinc alloy.

Action With this configuration, it is possible to reduce the hydrogen gas generated by the effect of the low boiling point alloy containing gallium and indium coated on the surface of the zinc alloy or the fluorine-based surfactant, and as a result, the leakage resistance of the battery is improved. improves.

The action mechanism of the low boiling point alloy or the fluorine-based surfactant used in the present invention is unclear, but it is presumed as follows.

When zinc is discharged in an alkaline electrolyte, the surface of the particles becomes rough due to elution of zincate ions from zinc particles and elution of zinc fine particles (solid state). In addition, the eluted zinc particles are
Increases the electrical conductivity of zinc oxide formed by discharge. This phenomenon is considered to be one of the causes of promoting the corrosion reaction of zinc. By coating the zinc particles with a low boiling point alloy (liquid state) containing gallium and indium, the surface becomes liquid and the surface of the zinc particles is prevented from being roughened, and the elution of solid zinc fine particles can be suppressed. . Further, since this low boiling point alloy contains indium, the hydrogen overvoltage on the surface of zinc can be improved and the corrosion reaction of zinc can be suppressed. On the other hand, the corrosion reaction of zinc in an alkaline electrolyte is chemically represented by the following equation.

Anode reaction ^{Zn + 40H - = Zn (OH} ) 2- + 2e - cathodic reaction ^{_{2H 2 O + 2e - = 20H}} - + H 2 When the fluorine-containing surfactant to form adsorbed film on anode zinc surface hydroxyl ions that cause the anode reaction Is prevented from approaching the zinc negative electrode, and water molecules necessary for the cathode reaction cannot exist near the surface of the zinc negative electrode, and corrosion of zinc is suppressed.

As described above, by using the constitution of the present invention, the coating film of a low boiling point alloy containing gallium and indium, and the anticorrosive effect of the fluorine-based surfactant reduce the increase in the internal pressure of the battery after storage and after partial discharge, which is good. It is possible to provide an alkaline battery having excellent storability.

Example (Example 1) A method for producing a zinc alloy powder (hereinafter, referred to as a surface-coated zinc alloy) in which the surface of a smoothed zinc alloy particle is coated with a low boiling point alloy containing indium and gallium, and the zinc alloy powder is used. An example in which a gel zinc negative electrode is applied to an alkaline manganese battery will be described.

FIG. 1 is a sectional view showing a particle model of the surface-coated zinc alloy powder obtained in this example. In FIG. 1, 1 is a zinc alloy, and 2 is a coating of a low boiling point alloy containing indium and gallium.

The surface-coated zinc alloy in this example was prepared as follows. 2 kg of unrestricted zinc alloy (in this example, one containing 500 ppm of indium, lead, and aluminum was used) was put into a 5 wt% potassium hydroxide aqueous solution 1, and then an appropriate amount of indium and gallium alloy was added. And stir. After stirring in an alkaline aqueous solution for about 1 hour, it is filtered and washed 10 times or more with distilled water. After washing with distilled water, remove water with acetone and dry at 60 ° C. The surface-coated zinc alloy was obtained by the above steps. In order to confirm that this alloy has a high concentration of indium and gallium on the surface as shown in FIG. 1,
A simple quantitative analysis of the alloy surface was performed. The results obtained are shown in Table 1.
It was shown to. The analytical value is the ratio of the elements present up to a depth of about 1 μm from the powder surface. The instruments used in the simple quantitative analysis were Akashi DS130 and EDAX (energy dispersion method).

Material No. 1 is a non-coated zinc alloy before coating, No. 2, No. 3 and No. 4 are gallium and indium alloys, respectively.
2, 0.5 and 1.5 wt% coated alloy. As is clear from this analysis result, in the surface coating alloy, the ratio of gallium and indium in the surface is higher than the ratio of gallium and indium to the total amount input for coating.
In other words, it was found that the alloy obtained by the above method was not the low boiling point alloy all diffused inside zinc but the surface coating alloy as shown in FIG. Also, instead of coating in an alkaline aqueous solution,
The same result was obtained as a result of performing a simple quantitative analysis on the surface-coated alloy coated dry.

FIG. 2 shows the alkaline manganese battery LR6 used in this example.
3 is a structural cross-sectional view of FIG. In FIG. 2, 3 is a positive electrode mixture, 4
Is a gel negative electrode using surface-coated alloy powder, 5 is a separator,
Reference numeral 6 is a current collector of the gel negative electrode. Reference numeral 7 is a positive electrode cap, 8 is a metal case, 9 is a battery outer can, 10 is a polyethylene resin sealing body, and 11 is a bottom plate. The gel negative electrode was prepared as follows. First, 40 wt% potassium hydroxide solution (Zn
(Including O), 3% by weight of sodium polyacrylate and 1% by weight of carboxymethyl cellulose are added to gel.
After that, a surface coating alloy powder having a weight ratio twice that of the gel electrolyte was added and mixed. In the alkaline manganese battery using the gel negative electrode prepared as described above, the corrosion inhibition effect was examined. The experimental method is to prototype the alkaline manganese battery shown in Fig. 2 and discharge 15% of the theoretical capacity at 1 / A.
After that, disassemble the battery and collect 2 g of the gel negative electrode for 10 days.
The amount of hydrogen gas generated under the temperature of 60 ° C was measured. As a comparison, Table 2 shows the measurement results of the hydrogen gas generation amount in the case of only the alloy. The amount of hydrogen gas generated was shown as an index with 100 when the uncoated zinc alloy was not coated. In Table 2, the zinc alloy coated is mercury
As for the case of 400 ppm, the results of the same experiment as in the case of unblended are shown. As for the gas generation index, for those containing mercury, 400 ppm of mercury was included, and the index was set to 100 when nothing was coated.

As is clear from Table 2, the zinc alloy coated with the low boiling point alloy containing indium and gallium has an effect of suppressing the generation of hydrogen gas by about half as compared with the uncoated zinc alloy.

(Example 2) A method for producing a zinc alloy powder (surface-coated zinc alloy) in which the surface of a smoothed zinc alloy particle is coated with a low boiling point alloy containing indium and gallium and a fluorine-based surfactant, and the zinc alloy powder An example in which a gelled zinc negative electrode is applied to an alkaline manganese battery will be described.

FIG. 3 is a sectional view showing a particle model of the surface-coated zinc alloy powder obtained in this example. In FIG. 3, 12 is a zinc alloy, 13 is a coating of a low boiling point alloy containing indium and gallium, and 14 is a coating containing a fluorine-based surfactant.

The surface-coated zinc alloy in this example was prepared as follows. 2 kg of unrestricted zinc alloy (in this example, one containing 500 ppm of indium, lead, and aluminum was used) was put into a 5 wt% potassium hydroxide aqueous solution 1, and then an appropriate amount of indium and gallium alloy was added. And stir. After stirring in an alkaline aqueous solution for about 1 hour, it is filtered and washed 10 times or more with distilled water. After washing with distilled water, remove water with acetone and dry at 60 ° C. After that, it is dipped in a solution containing a fluorine-based surfactant to be attached to the surface, and then the solvent is removed to form a film. As the fluorine-based surfactant, one having both a perfluoroalkyl group and a polyethylene group was used. Using the surface coating alloy obtained by the above steps, a gel negative electrode was prepared in the same manner as in Example 1, and the alkaline manganese battery shown in FIG. The method for evaluating the corrosion inhibition effect of the surface-coated zinc alloy was 1 / A as in the method described in Example 1.
After discharging 15% of theoretical capacity, disassemble the battery and set the gel negative electrode
A method of measuring 2 g of hydrogen gas generated at a temperature of 60 ° C. for 10 days was used. The results obtained are shown in Table 3.

In Table 3, the hydrogen generation amount is shown as an index when the hydrogen gas generation amount of the uncoated zinc alloy is 100. As is clear from this table, the surface-coated alloy prepared in this example can provide an alkaline zinc battery excellent in leakage resistance by suppressing hydrogen generation to less than half.

Next, the coating amount of the fluorine-based surfactant was examined.
The experimental method is to cover the zinc alloy by changing the concentration of the fluorine-based surfactant in the solution when the alloy is immersed in the solution containing the fluorine-based surfactant, and examine the hydrogen gas generation amount and discharge performance at that time. did. The alkaline manganese battery shown in Fig. 2 was prototyped, and the hydrogen gas generation was measured by collecting 2g of the gel negative electrode of the battery after 15% discharge at 1 / A, and generating hydrogen gas at a temperature of 60 ° C for 10 days. Measure the quantity. Regarding the discharge performance of the battery, continuous discharge of 10Ω was performed. The coating film formed on the surface of the zinc alloy contains 0.5% by weight of a low boiling point alloy containing indium and gallium, and a specified amount of a fluorine-based surfactant. The obtained results are shown in FIG.

In Fig. 4, the solid line shows the amount of gas generated, and the broken line shows 10Ω.
The average voltage during continuous discharge is shown. The amount of hydrogen gas generated is shown as an index with 100 in the case of the uncoated zinc alloy without any coating. As is clear from FIG. 4, when the amount of the fluorine-based surfactant is increased (up to around 0.05% by weight), the gas generation amount is suppressed, and beyond that, it hardly changes. On the other hand, it can be seen that the average voltage gradually decreases with an increase in the amount of the surfactant, and sharply decreases after exceeding 1% by weight. Therefore, considering the relationship between these two,
The amount of the fluorinated surfactant is preferably 0.01 to 1% by weight. Similar results were obtained when a zinc alloy containing 400 ppm of mercury was used.

As described above, according to the present invention, in the alkaline zinc battery, by coating the zinc alloy surface with a low boiling point alloy containing indium and gallium, a zinc-free alloy or an extremely low-zinc alloy Even if the above is used, the effect of suppressing the rise in the internal pressure of the battery due to the corrosion of zinc and improving the liquid leakage resistance can be obtained, and it is possible to provide a non-polluting alkaline zinc battery having good storability.

[Brief description of drawings]

1 is a sectional view showing a particle model of surface-coated zinc alloy powder in Example 1 of the present invention, FIG. 2 is a sectional view of an alkaline manganese battery using a surface-coated zinc alloy, and FIG. 3 is a sectional view of the present invention. FIG. 4 is a cross-sectional view showing a particle model of the surface-coated zinc alloy powder in Example 2, and FIG. 4 is a diagram showing the relationship between the coating amount of the fluorine-based surfactant, the hydrogen gas generation index, and the average voltage during discharge. 1 ... Zinc alloy, 2 ... Low boiling point alloy coating containing indium and gallium, 3 ... Positive electrode mixture, 4 ... Gel negative electrode using surface-coated zinc alloy powder, 5 ... Separator, 11 ... Zinc Alloy, 13 ... Low boiling point alloy film containing indium and gallium, 14 ... Film containing fluorine-based surfactant.

Claims (8)

[Claims] 1. An alkaline zinc battery having a non-selective or low-selective zinc alloy up to 400 ppm of mercury as an active material of a negative electrode, wherein the non-selective or low-selective zinc alloy contains gallium and indium. A zinc alloy for alkaline zinc batteries, which is coated with a low boiling point alloy. 2. An alkaline zinc battery characterized in that the surface of an unreduced or low-reduction zinc alloy having a mercury content of up to 400 ppm is coated with a low-boiling-point alloy containing gallium and indium and a fluorine-based surfactant. For zinc alloy. 3. The zinc alloy for an alkaline zinc battery according to claim 2, wherein the total amount of the fluorine-based surfactant deposited is 0.01 to 1% by weight based on the zinc alloy. 4. A non-blunting or low-grading zinc alloy with a mercury content of up to 400 ppm is added to an aqueous solution of an alkali metal hydroxide, and then a low-boiling alloy containing gallium and indium is added and stirred. A method for producing a zinc alloy for an alkaline zinc battery, which comprises coating the zinc alloy with a low boiling point alloy according to 5. A low-boiling alloy containing gallium and indium is added to a non-blunting or low-boiling zinc alloy containing up to 400 ppm of mercury, and the zinc alloy is coated with the low-boiling alloy by dry stirring. A method for producing a zinc alloy for an alkaline zinc battery, comprising: 6. The method according to claim 4, wherein the alkali metal hydroxide is any one selected from the group consisting of potassium hydroxide, sodium hydroxide, lithium hydroxide, rubidium hydroxide and cesium hydroxide. Manufacturing method of zinc alloy for alkaline zinc battery. 7. An alkaline zinc battery characterized by comprising a negative electrode active material in which the surface of a non-selective or low-reduction zinc alloy having a mercury content of up to 400 ppm is coated with a low-boiling point alloy containing gallium and indium. . 8. A negative electrode active material comprising a zinc-free low-alloying alloy containing up to 400 ppm of mercury and a low-boiling-point alloy containing gallium and indium and a fluorosurfactant coated on the surface of the zinc-free alloy. Alkaline zinc battery characterized by