JPH04121961A - Zinc alloy for zinc alkaline battery and its manufacture and zinc alkaline battery using it - Google Patents

Abstract

PURPOSE:To obtain a secondary battery with has an excellent storage quality and also has an excellent cycle life by equipping as anode active substance a non-amalgamated zinc alloy whose surface is covered with an indium layer and a low melting point alloy layer containing gallium on the outside. CONSTITUTION:A non-amalgamated zinc alloy containing bismuth and calcium is charged into a potassium hydroxide solution dispersed with indium hydroxide, and indium is electrically deposited while being agitated. Afterwards, the alloy is heated to 70 deg.C and agitated by adding an appropriate quantity of metal gallium. After 10 minute agitation in an alkaline solution, more than 10 times filtering cleaning is performed by using distilled water. After cleaning by means of distilled water, water is removed by means of acetone, and dried at 60 deg.C. A zinc alkaline batter is produced by using the gellike zinc anode 4 at which the surface covered non-amalgamated zinc alloy thus obtained and a surface active agent having a polyethylene oxide base are mixed and dispersed into a gellike alkaline electrolytic liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a battery that uses zinc as a negative electrode material and an aqueous alkaline solution as an electrolyte. In particular, to provide a zinc-alkaline battery that suppresses the rise in battery internal pressure due to hydrogen gas generated within the battery and has excellent storage properties, and to suppress the precipitation of zinc dendrites during charging and discharging to improve the charge-discharge cycle life. The present invention provides an excellent alkaline zinc secondary battery.

Conventional technology This type of zinc-alkaline battery has traditionally been made mainly of zinc, with indium, aluminum, Amalgamation has been achieved by adding about 15% by weight of mercury to alloys containing lead to suppress increases in battery internal pressure. This prevents the internal pressure of the battery from increasing during storage and ensures storage stability, making it popular as a practical battery with little deterioration in battery performance.

However, as social needs for lower pollution have increased in recent years, it is necessary to further reduce the amount of mercury used, and even to achieve the above practical performance without using mercury at all. This has been done for a long time. However, even if it is possible to reduce the amount of mercury to some extent, the current situation is that there is no means that can provide a fundamental solution, and it is extremely difficult to ensure sufficient corrosion resistance of negative electrode zinc without using mercury. It is considered.

Zinc-alkaline secondary batteries were put into practical use early on due to their high energy density, but they had the problem of poor reversibility during charging and discharging of the zinc negative electrode and short charge-discharge cycle life.

In order to solve these problems, attempts are being made to combine various technologies such as adding additives to electrodes, optimizing the amount of electrolyte, and battery structure. Among these techniques, it is known that adding mercury to metal zinc particles can suppress the precipitation of dendrites on the surface of the zinc electrode and improve the charge/discharge cycle life.

However, the above performance must be achieved without using mercury.

We have proposed coating the zinc alloy surface with a low melting point alloy containing indium and gallium in order to ensure the above-mentioned corrosion resistance and charge/discharge cycle life.

Problems to be Solved by the Invention When a battery is constructed using non-oxidized zinc, hydrogen generation due to the corrosion reaction of the zinc is promoted during battery storage or after partially discharging the battery, resulting in a significant increase in battery internal pressure. Can be seen. The reason for promoting hydrogen generation is thought to be due to the elimination of mercury, which originally has the effect of increasing the hydrogen overvoltage on the zinc surface and inhibiting corrosion reactions. If such a significant increase in internal pressure occurs within the battery, there is a problem in that the electrolyte leaks, greatly impairing the battery's storability and making it impossible to ensure practical performance.

Furthermore, in sealing a zinc-alkaline secondary battery, it is necessary for oxygen gas generated from the positive electrode during overcharging to reach the negative electrode through a separator and to be absorbed by the negative electrode. In order to cause gas absorption to occur on the surface of the negative electrode plate, it is necessary to expose as much of the surface of the negative electrode to the gas phase as possible, and for this purpose a liquid-regulated type with less free electrolyte must be used. On the other hand, if the electric group formation is reduced, it becomes difficult to retain the zincate ions generated during discharge near the negative electrode, and mercury, which is thought to play a role in making the reaction uniform, disappears, resulting in zinc dendrites. This leads to a reduction in cycle life due to crystal precipitation.

In order to solve these problems, we tried coating the zinc alloy surface with a low melting point alloy containing indium and gallium, and although the results were improved, there were manufacturing variations when processing large quantities of the alloy. The problem is that it is large and takes time to process. Further, there is a demand for further improvement in cycle life of secondary batteries.

The present invention solves these problems, and is intended to provide a zinc-alkaline battery using a non-oxidizing zinc alloy, in which bismuth,
By forming an indium layer on the surface of a zinc alloy containing calcium, for example, by electroless plating in an alkaline solution, and then coating it with a low melting point alloy containing gallium,
Compared to direct coating with the above-mentioned low melting point alloys containing indium and gallium, it is possible to treat the surface more uniformly, reduce manufacturing variations, shorten the coating time, and eliminate the problems that occur during battery storage. The present invention provides a battery that suppresses hydrogen gas and has good storage properties. Another object of the present invention is to prevent the precipitation of zinc dendrites when used in a secondary battery, and to provide a secondary battery that has a good cycle life.

Means for Solving the Problems In order to solve the above problems, the present invention provides a zinc alkaline battery having a non-grading zinc alloy, in which the surface of the non-grading zinc alloy is placed between an indium layer and the outside thereof. It is coated with a low melting point alloy containing gallium. The zinc alloy of the present invention is produced by electroless plating of indium on the surface by adding a non-reactive zinc alloy to an alkaline solution containing indium and stirring, and then adding a low melting point alloy containing gallium to the alkaline solution. This can be achieved by coating the surface of an indium-plated zinc alloy by adding it to and stirring.

In addition, the non-oxidized zinc alloy contains 0.001 to 0 bismuth.
．． 1wt%, calcium 0.001-0, l wt
% gold is desirable.

When used as a gelled zinc negative electrode, it is desirable to use a gelled zinc negative electrode in which the zinc alloy described above and a surfactant having a polyethylene oxide group are mixed and dispersed.

Effect: Due to the effects of electroless plated indium, low melting point alloy containing gallium coated on the surface, and bismuth and calcium contained in the non-oxidized zinc alloy, this occurs during storage. Hydrogen gas can be suppressed and the leakage resistance of the battery can be improved.

Furthermore, when used in a secondary battery, precipitation of zinc dendrites can be prevented and a battery with good cycle life can be provided.

The effects of the zinc alloy for zinc-alkaline batteries in the present invention are currently unclear, but are presumed as follows.

When zinc is discharged in an alkaline electrolyte, the surface of the particles becomes rough due to the elution of zincate ions from the zinc particles and the elution of fine zinc particles (in solid form). Furthermore, the eluted zinc fine particles increase the conductivity of zinc oxide produced by discharge.

This current state is thought to be one of the causes that promotes the corrosion reaction of zinc, that is, the generation of hydrogen gas. Even in secondary batteries, when charging under such conditions, the surface of the zinc particles is rough, so a uniform precipitation reaction of zinc does not occur, and the charge is concentrated on the protruding parts of the surface of the zinc particles. However, the zinc precipitation reaction occurs only in that area. This is one of the causes of the precipitation of zinc dendrites, resulting in deterioration of cycle life.

By coating zinc particles with a low melting point alloy (liquid state), the surface becomes liquid, preventing roughening of the surface of the zinc particles, and further suppressing elution of fine zinc particles on solid surfaces.

However, if the zinc alloy surface is directly coated with indium and gallium liquid alloy, there will be large variations when processing a large amount of the alloy, and coating will take time. Therefore, if the zinc alloy surface is electrolessly plated with indium in an alkaline solution in advance and then coated with a low melting point alloy containing gallium in an alkaline solution, gallium and indium tend to alloy, so the indium plated uniformly on the zinc surface can be coated with a low melting point alloy containing gallium. Then, gallium is alloyed, and as a result, it becomes possible to form a more uniform liquid alloy layer on the surface in a short time. Also, the reason why bismuth and calcium are added to the zinc alloy is to refine the structure of the zinc alloy and make it easier to plate indium. This is to prevent the liquid alloy from diffusing into the liquid and maintain the liquid alloy layer on the surface for a longer period of time.

On the other hand, the corrosion reaction of zinc in an alkaline electrolyte is chemically expressed by the following equation.

Anodic reaction Z n + 40H-= Zn(OH) 2-+ 2
e Cathode reaction 2H20+2 e-=20H-+H2 When a surfactant with a polyethylene oxide group is adsorbed to the negative electrode zinc surface and forms a film, the approach of hydroxide ions, which are the cause of the anode reaction, to the zinc negative electrode is blocked.
Furthermore, water molecules necessary for the cathode reaction cannot exist near the surface of the zinc negative electrode, and corrosion of zinc is suppressed.

Due to the above-described effects, it is possible to provide a battery with excellent leakage resistance or a secondary battery with a good cycle life.

Example: A method for producing zinc alloy powder (hereinafter referred to as surface coating alloy) whose surface is electrolessly plated with indium in an alkaline solution and then coated with a low melting point alloy containing gallium, and using the zinc alloy powder. An example in which a gelled zinc negative electrode is applied to an alkaline manganese battery will be described.

FIG. 1 is a cross-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 containing bismuth and calcium, and 2 is an alloy layer obtained by electrolessly plating indium and then coating with a gallium-containing alloy.

The surface-coated zinc alloy in this example was created as follows. 2 kg of an aqueous zinc alloy containing bismuth and calcium is added to 1 liter of a 5% by weight potassium hydroxide aqueous solution in which indium hydroxide is dispersed, and indium is electrodeposited while stirring. After that, warm it to 70℃,
Add appropriate amount of gallium metal and stir. After stirring in the alkaline aqueous solution for 10 minutes, the mixture is filtered and washed with distilled water at least 10 times. After washing with distilled water, the moisture is removed with acetone, and the mixture is dried at 60°C. A surface-coated zinc alloy was obtained through the steps described above. In order to confirm that this alloy had high concentrations 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.

Table 1 Sample No. 1 is a zinc alloy before treatment, and Sample No. 2 is a treated alloy, in which indium hydroxide and gallium metal are added at 0.1 and 0.2 wt%, respectively, to the zinc alloy. It is clear from this analysis that the concentrations of gallium and indium in the surface coating alloy are higher than the proportion of the total amount added for coating. In other words, it was found that the alloy obtained by the above method was a surface coated alloy as shown in FIG.

Figure 2 shows the alkaline manganese battery used in this example, L
This is a structural cross section of R6. In Fig. 2, 3 is the positive electrode mixture;
4 is a gel negative electrode using a surface-coated alloy powder, 5 is a separator, and 6 is a current collector of the gel negative electrode. 7 is the positive electrode cap, 8
1 is a metal case, 9 is a battery case, 10 is a polyethylene resin sealing body, and 11 is a bottom plate. The gel negative electrode was prepared as follows. First, 3% by weight of sodium polyacrylate and 1% by weight of carboxymethyl cellulose are added to a 40% by weight potassium hydroxide aqueous solution (containing ZnO) to form a gel. If a surfactant is used, it is added at the same time and mixed and dispersed. Thereafter, surface coating alloy powder was added and mixed in an amount twice as much by weight as the gel electrolyte. In an alkaline manganese battery using the gel negative electrode prepared as described above, the corrosion inhibition effect was investigated. The experimental method was to fabricate a prototype alkaline manganese battery as shown in Figure 2, and perform discharge under a constant resistance load of 1Ω for 22 minutes. Thereafter, the battery was disassembled, 2 g of the gel negative electrode was collected, and the amount of hydrogen gas generated was measured at a temperature of 60° C. for 10 days. The results are shown in Table 2. The amount of hydrogen gas generated was expressed as an index, with the case where an uncoated zinc alloy was used as 100. For comparison, a case in which indium and gallium low melting point alloys were directly coated and a case in which a surface-coated zinc alloy of the present invention was used with a surfactant having a polyethylene oxide group were also shown.

Table 2 As is clear from Table 2, the alloy of the present invention suppresses gas generation even when coated for a short time. Note that if the amount of surfactant added is less than 1 oppm, there is no effect;
At 1000pp or more, a decrease in battery voltage was observed, so
A concentration of 10-100 ppm is considered suitable. Regarding the amount of bismuth and calcium contained in the zinc alloy, no effect is observed when the amount is less than 0.001wt%, and if more than 0.1wt% is added, disadvantages are seen in the discharge form. ~0,1w
Up to t% is considered appropriate.

Next, an example in which the surface-coated zinc alloy of the present invention is applied to a cylindrical nickel-zinc storage battery will be described.

FIG. 3 is a structural cross-sectional view of the cylindrical nickel-zinc storage battery used in this example. In FIG. 3, 12 is a paste-type negative electrode plate in which a paste mainly composed of the surface-coated zinc alloy powder and zinc oxide powder obtained in the present invention is applied to copper punching metal, and 13 is a porous sintered nickel substrate. A sintered positive electrode plate whose pores are impregnated with an active material mainly composed of nickel hydroxide, and 14 are a liquid-impregnated material and a separator.

15 is a metal case, 16 is a + lead plate, 17 is a lead plate, 18 is an insulating tube, 19 is a bottom insulating plate, 20 is a sealing plate, 21 is a cap, 22 is a safety valve, and 23 is a gasket.

A charge/discharge cycle test was conducted on a battery prototyped with the above configuration. In Figure 4, 0. IC for a certain period of time (1
The number of charge/discharge cycles and the change in discharge capacity when charged (for 3 hours) and discharged with an IC are shown. In Figure 4, (a
) is a cycle characteristic curve when the surface-coated zinc alloy powder according to the present invention is used.

This uses Sample No. 2 in Table 1 above. (b) uses sample No. 1. (C
) uses a zinc alloy directly coated with a low boiling point alloy containing indium and gallium. As is clear from FIG. 4, it can be seen that the surface-coated zinc alloy according to the present invention has an improved cycle life compared to other alloys.

Effects of the Invention As described above, according to the present invention, in a zinc alkaline battery, the surface of a zinc alloy containing bismuth and calcium is covered with an indium layer, and the outside thereof is further coated with a low melting point alloy containing gallium. In addition to suppressing hydrogen gas generation and improving leakage resistance during battery storage, when used as a secondary battery, it suppresses the precipitation of zinc dendrites and provides a secondary battery with a good cycle life. can.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a particle model of surface-coated zinc alloy powder in an example of the present invention, FIG. 2 is a cross-sectional view of an alkaline manganese battery using surface-coated zinc alloy, and FIG. FIG. 4, a cross-sectional view of a nickel-zinc storage battery using a coated zinc alloy, is a diagram showing the relationship between the number of charge/discharge cycles and the amount of discharged electricity. 1... Zinc alloy containing bismuth and calcium, 2... Alloy layer obtained by electrolessly plating indium and then coating with gallium metal, 3.
... Positive electrode mixture, 4 ... Gel negative electrode using surface-coated zinc alloy powder, 5 ... Separator, 12 ... Negative electrode plate, 13 ... Positive electrode plate, 14 ... Liquid-containing agent and separator. Name of agent: Patent attorney Haru Akira Koebi and two others.

Claims (10)

[Claims] (1) A zinc alloy for use in zinc-alkaline batteries, which is a non-grading zinc alloy, the surface of which is coated with an indium layer and an outer layer of a low melting point alloy containing gallium. (2) The non-irradiated zinc alloy contains bismuth from 0.001 to
0.1wt%, calcium 0.001-0.1wt%
A zinc alloy for zinc-alkaline batteries according to claim 1. (3) After electroless plating of indium on the surface by adding a non-reactive zinc alloy to an alkaline solution containing indium and stirring, a low melting point alloy containing gallium is added to the alkaline solution. A method for producing a zinc alloy for a zinc-alkaline battery, which comprises coating the surface of the indium-plated zinc alloy with the low melting point alloy containing gallium by stirring. (4) A zinc-alkaline battery comprising, as a negative electrode active material, a non-reactive zinc alloy whose surface is electrolessly plated with indium in an alkaline solution and then coated with a low melting point alloy containing gallium. (5) The non-ironized zinc alloy contains bismuth from 0.001 to
0.1wt%, calcium 0.001-0.1wt%
A zinc-alkaline battery according to claim 4 containing the zinc-alkaline battery. (6) Zinc-alkaline secondary, characterized in that it has a non-reactive zinc alloy whose surface is electrolessly plated with indium in an alkaline solution and then coated with a low melting point alloy containing gallium as a negative electrode active material. battery. (7) The non-ironized zinc alloy contains bismuth from 0.001 to 0.001.
0.1wt%, calcium 0.001-0.1wt%
A zinc-alkaline secondary battery according to claim 6. (8) After electrolessly plating indium on the surface in an alkaline solution, the surface is coated with a low melting point alloy containing gallium, and a surfactant with a polyethylene oxide group is mixed into a gel-like alkaline electrolyte. A zinc-alkaline battery with a gelled zinc negative electrode mixed and dispersed in. (9) The non-ironized zinc alloy contains bismuth from 0.001 to 0.001.
0.1wt%, calcium 0.001-0.1wt%
A zinc-alkaline battery according to claim 8 containing the zinc-alkaline battery. (10) The surfactant having a polyethylene oxide group should be added in an amount of 10 to 100% relative to the gelled alkaline electrolyte.
The zinc-alkaline battery according to claim 8, wherein the zinc-alkaline battery has a concentration of 0 ppm.