JPS6345753A - Negative active material for battery - Google Patents

Abstract

PURPOSE:To increase discharge performance of a battery by mixing solid mercury alloy containing at least one element selected from a group of lead, indium, thallium, cadmium, and bismuth, with nonamalgamated zinc powder or nonamalgamated zinc alloy powder. CONSTITUTION:Solid mercury alloy powder obtained by alloying at least one element selected from a group of lead, indium, thallium, cadmium, and bismuth with mercury by applying mechanical vibration or stirring in a dry process at normal temperature is mixed with nonamalgamated zinc powder or nonamalgamated zinc alloy powder in a specified ratio. Even if this mixture has the same mercury content as zinc alloy powder amalgamated in a wet process or in melting process, hydrogen evolution is remarkably retarded, and discharge performance is retained in a high level as a negative active material for a battery. The ratio of mercury to alloying ingredient is preferable to limit to about 50wt.% in terms of operation. However, when indium alone is used as the alloying ingredient, 60wt.% or more indium can be used. By this process, hydrogen gas evolution is remarkably retarded and discharge performance is retained in a high level.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a negative electrode active material for batteries, and more particularly, the present invention relates to a negative electrode active material for batteries, which has a reduced mercury content, suppresses hydrogen gas generation,
Moreover, it has been devised to maintain the discharge performance of the battery at a high level.

BACKGROUND TECHNOLOGY In alkaline batteries using zinc as a negative electrode active material, a strong alkaline electrolyte such as an aqueous potassium hydroxide solution is used, so the battery must be sealed tightly. 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 corrosion of zinc, which is an active material for the negative electrode, and to reduce the generation of hydrogen gas inside the battery. is carried out exclusively. For this reason, the negative electrode active materials of alkaline batteries commercially available today are
Zinc powder containing a large amount of mercury (about 10% by weight) (hereinafter referred to as high-density zinc powder) is used for negative electrode activation. There are strong expectations for the development of batteries using this material.

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 are zinc alloy powders made by adding lead, indium, etc. to zinc. By using these zinc alloy powders, the amount of mercury can be reduced and hydrogen gas generation inside the battery can be suppressed to a level equal to or greater than that of conventional highly arborized zinc powders, but this is still not sufficient.

In addition, the process of making zinc powder for batteries usually involves ■
Either the method of classifying the atomized powder of molten zinc and wet freezing, or the method of classifying the atomized powder of molten zinc is adopted, but the method of ■ involves wet freezing and drying. When zinc oxide (Z
On the other hand, method (2) pollutes the environment due to mercury volatilization from melted frozen zinc. In addition, there is a problem that the effect of suppressing hydrogen gas generation relative to the amount of mercury added tends to be inferior to that of method (2). Although the conventional method of freezing zinc powder has the above-mentioned problems, the present situation is that suitable methods other than these have hardly been studied.

Under these circumstances, some of the inventors of the present invention have previously proposed a mixture of non-oxidized zinc powder and frozen zinc powder as a negative electrode active material for batteries (Japanese Patent Application No. 60-1466
No. 22).

However, the frozen zinc powder used here is
Since it was obtained by the method described above, it still has the above-mentioned problem of ZnO production.

In addition, according to the above-mentioned wet freezing method, the reaction between mercury and zinc is slow, so in the proposed method, the mercury content of the frozen zinc powder is within a range of 3 to 15% by weight, which is easy to operate. The mixing ratio of glazed zinc powder to non-viscous zinc powder increases to 15:1 to 1:1, and the influence of ZnO becomes even greater, causing the problem of secondary gas generation due to ZnO. be.

<Object of the Invention> The present invention was made in view of the above-mentioned circumstances, and provides a negative electrode active for batteries that has a low mercury content, suppresses hydrogen gas generation, and can maintain high discharge performance of the battery. The purpose is to provide the substance.

Means for Achieving the Object> As a result of intensive research to achieve the above object, the present inventors have discovered that one or more elements selected from the group consisting of indium, thallium, cadmium, and bismuth. A mixture of a specific amount of solid mercury alloy powder obtained by freezing mercury by applying mechanical vibration or stirring at room temperature, and a non-visculating zinc powder or a non-visculating zinc alloy powder is a mixture. , it becomes a negative electrode active material for batteries that can significantly suppress the amount of hydrogen gas generated and maintain a high level of discharge performance even if the mercury content is equivalent to that of conventional wet or melted zinc alloy powder. I found out that. In addition to the above-mentioned mechanical freezing method, the solid mercury alloy powder can also be obtained by mixing mercury and the above-mentioned alloy components, heating the mixture to its melting temperature, and alloying it in a molten or semi-molten state. It was confirmed. The structure of the present invention based on this knowledge is based on a solid mercury alloy powder containing one or more elements selected from the group consisting of lead, indium, thallium, cadmium, and bismuth, and a non-grading zinc powder or a non-grading zinc powder. It is characterized by being mixed with zinc alloy powder.

The configuration of the present invention will be explained in more detail below.

The solid mercury alloy powder used in the present invention is a solid alloy product obtained by reacting liquid mercury with one or more elements selected from the group consisting of indium, thallium, cadmium, and bismuth at a predetermined ratio. and
To explain in detail, liquid mercury and one or more elements selected from the group consisting of lead, indium, thallium, cadmium, and bismuth are placed in a nonmetallic airtight container in a predetermined ratio, and then subjected to severe mechanical processing under dry conditions at room temperature. Either react the mercury with the alloy component by applying physical vibration or stirring, or place the alloy component and liquid mercury in a ceramic crucible, heat it to melt or semi-melt it at a low temperature, cool it, and then crush it. This is obtained by

Here, as a device for applying mechanical vibration or stirring, a vibrator, a high-speed rotating mixer, etc. can be used. The time required for this reaction cannot be specified as it varies depending on the type of apparatus or its operating conditions, but it may be carried out until both reactions are completed and liquid mercury is no longer observed. for example,
When water filOg and 10 g of lead powder were reacted using a small high-speed vibration mixer, the reaction was completed in about 5 minutes. Incidentally, since the reaction product obtained by such mechanical vibration or stirring is in the form of a powder, there is no particular need for pulverization or the like.

In addition, when obtaining a solid mercury alloy powder by heat melting or semi-melting, as can be seen from the alloy phase diagram, especially when lead, indium, etc. are selected as alloy components, the melting temperature is higher than that of mercury-zinc. This is significantly lower than in the case of mercury (see Examples below), the volatilization of mercury into the environment can be suppressed to a minimum, and the dissolution operation is also facilitated.

When obtaining the solid mercury alloy powder of the present invention in this way, any ratio may be used as long as the reaction product becomes a solid, but the ratio of mercury to alloy components is approximately the same as water@
Operationally, it is preferable that SO is around 50% by weight and the alloy component is around 50% by weight. However, if indium is used alone as an alloying component, the product will be liquid at room temperature at a ratio of 1:1, so in this case, indium will be used at 60%. It is necessary to set the amount of ij to % or more.

By mixing an appropriate amount of non-transforming zinc powder or non-transforming zinc alloy powder into the solid mercury alloy powder obtained as described above, a battery with an extremely excellent hydrogen gas generation suppressing effect and good discharge performance can be produced. Even if the average mercury content of the negative aIi active material for batteries is 3% by weight or less, the intended purpose can be sufficiently achieved, and it can be obtained from 0.1 to 1% by weight. Even at a small amount of 5% by weight, hydrogen gas generation is suppressed to an extremely low level.

In addition, in the present invention, as shown in the examples below, alloy components that are present in zinc and increase the hydrogen overvoltage of zinc,
For example, it has been confirmed that a non-toxic zinc alloy powder containing lead, indium, thallium, gallium, etc. may be used, and in this case, the effect of the present invention is further improved by increasing the hydrogen overvoltage.

Effects> Although the effects of the present invention have not been fully elucidated, they can be estimated as follows.

■ In an alkaline electrolyte, the mercury in the mercury-zinc alloy powder transfers to the non-transformed zinc powder or non-transformed zinc alloy powder, forming a highly concentrated mercury-containing layer on its surface, which causes hydrogen gas generation. @do.

■ Hydrogen gas generation can be reduced because ZnO is not produced due to the wet freezing process.

■ When non-irradiated zinc alloy powder is used, hydrogen gas generation is suppressed synergistically by working with the hydrogen overvoltage improving effect of its additive components.

EXAMPLES The present invention will be further specifically described below based on Examples and Comparative Examples.

Example 1 50 g of water and 50 g of lead powder were vigorously mixed and stirred for about 15 minutes in a thick-walled glass container to obtain solid mercury-lead alloy powder having the composition shown in Table 1. . Next, this powder and non-oxidized zinc powder were mixed at a weight ratio of 1:49, so that the average mercury content was 1. A mixed powder containing O3i amount % was obtained.

The particle size of this mixed powder was 48 to 150 mesh. Note that this particle size is the same in the following examples and comparative examples.

A hydrogen gas generation test was conducted using this mixed zinc alloy powder, and the results are shown in Table 1.

The hydrogen gas generation test was conducted using 5 ml of a potassium hydroxide aqueous solution with a concentration of 40% by weight saturated with zinc oxide as the electrolytic solution, and 10 g of mixed zinc alloy powder at 45°C.
The amount of gas generated (rrt'/g) for 50 days was measured.

In addition, using these mixed zinc alloy powders as a negative electrode active material, we prototyped a battery with the same structure as a commercially available alkaline manganese battery, and under discharge conditions of 20°C and a discharge load of 10Ω, the final voltage was 0.9■ The discharge duration was measured.

The results are shown in Table-1.

Examples 2 to 10 Various mercury alloy powders having the compositions shown in Table 1 were prepared in the same manner as in Example 1. Next, these powders and fM powdered zinc powder were mixed at a weight ratio of 1:49 to obtain a mixed powder having an average mercury content of 1.0% by weight.

Using these mixed powders, a hydrogen gas generation test and a battery performance test were conducted in the same manner as in Example 1, and the results are shown in Table 1.

Example 11 Mercury-feeding gold powder having the composition shown in Table 1 was prepared in the same manner as in Example 1. Next, this powder and non-oxidized zinc alloy powder (
(0.05% by weight of lead, 0.02% by weight of indium, and the balance being zinc) were mixed at a weight ratio of 1:499 to obtain a mixed powder with an average mercury content of 0.1% by weight.

Using this, a hydrogen gas generation test and a battery performance test were conducted in the same manner as in Example 1, and the results are shown in Table 1.

Example 12 50 g of mercury and 50 g of lead powder were placed in a quartz crucible,
After being kept at a temperature of 0° C. for about 1 hour, this was slowly cooled to obtain a solid mercury-lead alloy. Next, after pulverizing this,
It was mixed with anodized zinc powder at a weight ratio of 1:49 to obtain a mixed powder with an average mercury content of 1.0% by weight.

Using this, a hydrogen gas generation test and a battery performance test were conducted in the same manner as in Example 1, and the results are shown in Table 1.

Examples 13 to 21 Solid mercury alloy powders having the compositions shown in Table 1 were obtained in the same manner as in Example 12. This and untreated zinc powder were mixed at 1:4.
A mixed powder having an average content of 1.0% by weight was obtained by mixing at a weight ratio of 9.9% by weight.

Using these, a hydrogen gas generation test and a battery performance test were conducted in the same manner as in Example 1, and the results are shown in Table 1.

Example 22 Using mercury-feeding gold powder obtained in the same manner as in Example 12, a 1:1 ratio of non-irradiated zinc alloy powder (lead 0.05% by weight, indium 0.02% by weight, balance zinc) was added to it. They were mixed at a weight ratio of 499 to obtain a mixed powder with an average mercury content of 0.1% by weight.

Using this, a hydrogen gas generation test and a battery performance test were conducted in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 A hydrogen gas generation test and a battery performance test were conducted on frozen zinc powder with a mercury content of 6.0% by weight prepared by the wet freezing method in the same manner as in Example 1, and the results are shown in Table 2. Indicated.

Comparative Example 2 A hydrogen gas generation test and a battery performance test were conducted on frozen zinc powder with a mercury content of 1.0% by weight prepared by the wet freezing method in the same manner as in Examples 1 and 8, and the results are shown in Table 2. It was shown to.

Comparative Example 3 A hydrogen gas generation test and a battery performance test were conducted on frozen zinc powder with a mercury content of 0.1% by weight prepared by the wet freezing method in the same manner as in Example 1, and the results are shown in Table 2. It was shown to.

Table 2 Table 11 As shown in Table 2, Examples 1 to 22 in which a mixture of solid mercury alloy powder and anhydrous zinc powder or anhydrous zinc alloy powder were used as the negative electrode active material were wet-type. Compared to Comparative Examples 1 to 3 using frozen zinc powder, the hydrogen gas generation suppressing effect is excellent and the discharge performance is maintained at a high level.

<Effects of the Invention> As specifically explained above in conjunction with Examples, the negative electrode active material for batteries according to the present invention significantly suppresses hydrogen gas generation even when the mercury content is reduced, and maintains discharge performance at a high level. can be kept. In addition, since the solid mercury alloy powder used in the negative electrode active material for batteries of the present invention can be produced using the energy of mechanical vibration or stirring, it is possible to produce the solid mercury alloy powder using the energy of mechanical vibration or agitation. It is extremely effective in preventing environmental pollution caused by mercury.

Further, even when this solid mercury alloy powder is produced by a melting method, the melting temperature is lower than that of, for example, a mercury-zinc alloy, so alloying is extremely convenient.

Patent applicant Mitsui Kin W4 Mining Co., Ltd. People

Claims (1)

[Scope of Claims] 1) Solid mercury alloy powder containing one or more elements selected from the group consisting of lead, indium, thallium, cadmium, and bismuth, and non-transparent zinc powder or non-transparent zinc alloy. A negative electrode active material for batteries characterized by being made by mixing with powder. 2) The negative electrode active material for a battery according to claim 1, wherein the solid mercury alloy powder is obtained by alloying by mechanical vibration or stirring in a dry atmosphere, or by heat-melting alloying.