JPH04289661A - Zinc alloy powder for alkaline battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide zinc alloy powder for an alkaline battery and its manufacture, capable of sharply restraining hydrogen gas generation and also of retaining discharge performance in a practical level in a non-mercuriged condition. CONSTITUTION:Zinc alloy powder for an alkaline battery and its manufacture have a feature of containing a iron of 5ppm and less and components selected from the following (1) or (2); (1): bismuth of 0.01-0.5wt.%, indium of 0.01-0.5wt.%, and at least one kind of total 0.05-0.1wt.% selected from magnesium, zirconium, lithium, lanthanum, barium, silicon, boron, and tantalum; (2): aluminum of 0.01-0.5wt.%, indium of 0.01-0.5wt.%, and at least one kind of total 0.005-0.1wt.% selected from magnesium, zirconium, lithium, lanthanum, barium, silicon, boron, and tantalum.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a zinc alloy powder for alkaline batteries and a method for producing the same. Specifically, the iron content is 1 ppm or less, and hydrogen gas generation is suppressed by containing specific additive elements. The present invention also relates to a zinc alloy powder for alkaline batteries that improves the leakage resistance of batteries, and a method for producing the same.

0002

[Prior Art] Mercury in the zinc oxide powder used as the negative electrode active material of alkaline batteries is used to suppress the generation of hydrogen gas due to corrosion of zinc and to prevent battery leakage caused by this. , was considered an essential component of the negative electrode active material of alkaline batteries.

[0003] However, there is a need to reduce mercury from the perspective of environmental measures, and for this reason, by adding lead, aluminum, bismuth, indium, etc. to zinc as additive elements, the mercury content can be reduced from 10% by weight. Even if the content was significantly reduced to around 1% by weight, it became possible to suppress the generation of hydrogen gas.

However, as a further social demand, in recent years there has been a demand for reducing the mercury content in the negative electrode active material to 0% by weight, in other words, to make it zero. As described above, when the negative electrode active material is made non-reactive, the situation is significantly different, and even if the above-mentioned additive elements are added, it is difficult to suppress the amount of hydrogen gas generated to a predetermined level. That is, although zinc alloy powders containing various additive elements have been proposed as negative electrode active materials (for example, Japanese Patent Publication No. 2-2298
4, JP-A No. 61-153950), these can achieve the desired suppression of hydrogen gas generation even if the mercury content is 1% by weight or less, but this could not be achieved with no hydrogenation. .

On the other hand, attempts have been made to suppress the generation of hydrogen gas and improve discharge performance by reducing the content of impurities in zinc.
Publication No. 123653 describes the reduction of impurities such as iron and chromium, and Table 1 on page 4 of the same publication states that it contains certain amounts of lead, indium, and aluminum, and 1% by weight of mercury. In the negative electrode active material using the contained zinc chloride alloy powder, by reducing the iron content to about 10 ppm, the discharge performance is improved while suppressing the generation of hydrogen gas.

However, in zinc alloy powder with a mercury content of 0% by weight, the impurity content is reduced to 10p as described above.
Even if the hydrogen content was reduced to about pm and additional elements such as lead were contained, the desired effect of suppressing the generation of hydrogen gas could not be obtained.

[0007] As described above, making the negative electrode active material non-permeable involves fundamentally different difficulties than making the mercury content as low as 0.6 to 1% by weight. An alkaline battery that uses zinc alloy powder as a negative electrode active material, suppresses hydrogen gas generation, and improves leakage resistance has not yet been obtained.

[0008]

[Problems to be Solved by the Invention] The present invention has been made to solve the problems of the prior art, and it significantly suppresses the generation of hydrogen gas in non-operating mode, and also brings the discharge performance to a practical level. The purpose of the present invention is to provide a zinc alloy powder for alkaline batteries that can be retained and a method for producing the same, and the ultimate purpose is to improve the leakage resistance of mercury-free alkaline batteries.

[0009]

[Means for Solving the Problem] As a result of intensive research in line with this purpose, the present inventors have found that by using zinc, which has an extremely low content of iron as an impurity, and adding specific additive elements to it, The inventors have discovered that the above object can be achieved through the synergistic effect of the two, and have arrived at the present invention.

That is, the zinc alloy powder for alkaline batteries of the present invention contains 5 ppm or less of iron and the following (1) or (2): (1) 0.01 to 0.5 wt% of bismuth and 0.01 to 0.5 wt% of indium. 0.01 to 0.5% by weight and at least one selected from magnesium, zirconium, lithium, lanthanum, barium, silicon, boron, and tantalum in total of 0.0%
05-0.1% by weight, (2) 0.01-0.5% by weight of aluminum, 0.01-0.5% by weight of indium, and magnesium, zirconium, lithium, lanthanum, barium, silicon,
A total of 0 of at least one selected from boron and tantalum
．． 0.005 to 0.1% by weight.

[0011] In the present invention, the iron content is 5 ppm.
It is necessary that the following is true. When the iron content exceeds 5 ppm, the effect of suppressing hydrogen gas generation is small. Conventionally, zinc or zinc alloy powder with a low iron content has not been used as a negative electrode active material, and no such report is known. High-purity zinc ingots can be made for special purposes, such as semiconductors, using methods such as zone melting, but they are expensive and cannot be used as raw materials for dry batteries. do not have. Furthermore, there are no examples of its use as an alloy powder.

[0012] Furthermore, in the present invention, the above (1) or (2)
). If the content of each component element deviates from the above range, problems arise in that the desired effect of suppressing the generation of hydrogen gas cannot be obtained or that practical discharge performance cannot be maintained. Even if additive elements other than these components, such as aluminum, bismuth, calcium, etc. contained in zinc alloy powder conventionally used as a negative electrode active material, are contained alone, the effects of the present invention described above cannot be obtained.

Next, the manufacturing method of the present invention will be explained.

[0014] In the present invention, zinc having an iron content of 5 ppm or less is used. Examples of such zinc with a low iron content include zinc deposited by an electrolytic method and zinc ingots produced by a distillation method. Conventionally, deposited zinc was melted together with a flux such as ammonium chloride, and a zinc ingot, which was cast into a mold, was used as the zinc raw material for the negative electrode active material. In such a zinc ingot, the iron content is 5 ppm.
It cannot be: The reason for this is that the dross that floats during the zinc melting process is removed, but some of the zinc that is recovered during the removal process is returned to the melting zone. This is because in this dross removal step, iron is usually mixed in from the separator. In addition, iron contamination from the molten metal pump, mold, and environment is also expected.

[0015] Each of the additional elements shown in (1) or (2) above is added to this molten zinc having a low iron content so that the content falls within a predetermined range. Then, it is pulverized by an atomization method and further sieved to obtain zinc alloy powder. At this time, it is desirable that the iron content in the melting and atomizing atmosphere be 0.009 mg/m 3 or less from the viewpoint of further improving the effect of suppressing hydrogen gas generation. It is also desirable from the same point of view to magnetically sort the obtained zinc alloy powder.

The iron content in the zinc alloy powder thus obtained is 5 ppm or less, as mentioned above, and this zinc alloy powder has an iron content of about 300 μm, which is the upper limit of leakage resistance.
Hydrogen gas generation can be suppressed to less than 1/day cell (AA type).

[0017]

[Operation] Conventionally, the mechanism of hydrogen gas generation due to corrosion of zinc has only been discussed in relation to the crystal structure based on macroscopic gas volume measurements and speculation, but it has not been possible to actually investigate the gas generation site. There was no. The inventors of the present invention found that the region where gas is continuously generated is a region where a very small amount of iron, stainless steel, and iron oxide are mixed and unevenly distributed. Therefore, in the present invention, the iron content is made extremely small, and a specific additive element is also included in a certain amount. This suppresses the generation of hydrogen gas due to the synergistic effect of both.

[0018]

[Examples] The present invention will be specifically explained below based on Examples and Comparative Examples.

Examples 1 to 28 and Comparative Examples 1 to 12 In a room where the iron content in the atmosphere is 0.005 mg/m3, about 50% of electrolysed zinc having an iron content of 4 ppm is
The zinc alloy was melted at 00°C, and predetermined amounts of each element shown in Tables 1 and 2 were added thereto to create a molten zinc alloy.

[0020] Next, this was directly pulverized in the same atmosphere using high-pressure argon gas (ejection pressure 5 kg/cm2), and the obtained zinc alloy powder was sieved to a particle size of 50 to 150 mesh.

Furthermore, free iron powder was removed by magnetic separation using a magnet. The iron content of the obtained zinc alloy powders was 4 ppm in all cases.

[0022] Here, carboxymethyl cellulose and sodium polyacrylate are added as a gelling agent to a 40% potassium hydroxide aqueous solution saturated with zinc oxide.
An electrolytic solution was prepared by adding about 0%.

Using the zinc alloy powder described above as the negative electrode active material, 3.0 g of this zinc alloy powder was mixed with 1.5 g of electrolyte to form a gel, and the resultant mixture was used as the negative electrode material to form an alkaline manganese battery as shown in FIG. Created.

After partially discharging this alkaline manganese battery by 25%, the amount of hydrogen gas generated due to corrosion of the zinc alloy powder was measured, and the results are shown in Tables 1 and 2. In addition, 25% partial discharge constitutes a mercury-free alkaline manganese battery, and the discharge time up to 0.9V is 100%.
This is because the hydrogen gas generation rate is maximum at around 25% partial discharge, and the discharge conditions of 1Ω and 11 minutes were defined as 25% partial discharge.

The alkaline manganese battery shown in FIG.
, positive electrode 2, negative electrode (gelled zinc alloy powder) 3, separator 4, sealing body 5, negative electrode bottom plate 6, negative electrode current collector 7, cap 8, heat-shrinkable resin tube 9, insulating ring 10,
11, and an outer can 12.

Comparative Examples 13 to 52 Using as a starting material a zinc ingot in which electrolyzed zinc with an iron content of 4 ppm was cast as usual, 5 mg/m
It is melted at about 500℃ in the atmosphere of 3, and
A molten zinc alloy was prepared by adding predetermined amounts of each element shown in 3.

Next, this was pulverized using high pressure argon gas (injection pressure 5 kg/cm2) in the same atmosphere, and the obtained zinc-zinc alloy powder was sieved to a particle size of 50 to 150 mesh.

The iron content of the zinc alloy powders obtained was 20 ppm. Note that magnetic selection was not performed here.

Using this zinc alloy powder, an alkaline battery shown in FIG. 1 was prepared in the same manner as in Example 1, a 25% partial discharge was performed, and the amount of hydrogen gas generated was measured. The results are shown in Table 2~
Shown in 3.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033] As shown in Tables 1 to 3, Examples 1 to 3 had an iron content of 5 ppm or less and had a specific composition.
All 28 zinc alloy powders have a hydrogen gas generation rate of approximately 300 μl/day/cell, which is the upper limit of leakage resistance.
(AA type) or less. On the other hand, although the zinc alloy powders of Comparative Examples 1 to 12 have an iron content of 5 ppm or less, their compositions deviate from the range specified by the present invention, so they are effective in suppressing hydrogen gas generation. is not recognized. Furthermore, since the zinc alloy powders of Comparative Examples 13 to 52 have an iron content of 20 ppm, the effect of suppressing hydrogen gas generation is recognized regardless of whether the composition falls within the range specified by the present invention. I can't do it.

Experimental Examples The zinc alloy powders of Example 2 and Comparative Example 15 were atomized to contain 1% by weight and 10% by weight of mercury, respectively, to obtain azinc alloy powders.

Using this zinc oxide alloy powder, an alkaline battery shown in FIG. 1 was prepared in the same manner as in Example 1, and a 25% partial discharge was performed to measure the amount of hydrogen gas generated. The results are plotted together with the values of Example 2 and Comparative Example 15 and are shown in FIG.

As shown in FIG. 2, when the iron content is 20 ppm, mercury content of 1% by weight or more is below the allowable upper limit of leakage resistance, while iron content is 20 ppm. 4p
pm is below the permissible upper limit for leakage resistance, regardless of the presence or absence of mercury.

[0037]

[Effect of the invention] As explained above, the iron content is 5pp.
By dissolving less than m of zinc and specific additive elements in a molten metal and directly atomizing the molten metal, the iron content can be reduced to 5.
A zinc alloy powder for alkaline batteries having a concentration of ppm or less can be obtained.

Although this zinc alloy powder is non-oxidizing, it can be used as a negative electrode active material for alkaline batteries.
Hydrogen gas generation can be significantly suppressed, and discharge performance can be maintained at a practical level. Furthermore, since it does not contain mercury, alkaline batteries using this zinc alloy powder as a negative electrode active material meet social needs.

[Brief explanation of the drawing]

FIG. 1 shows a side sectional view of an alkaline manganese battery according to the present invention.

FIG. 2 is a graph showing the relationship between the mercury content in zinc alloy powder and the amount of hydrogen gas generated.

[Explanation of symbols]

1　Positive electrode can 2 Positive electrode 3 Negative electrode 4 Separator 5 Sealing body 6 Negative electrode bottom plate 7 Negative electrode assembly 8 Cap 9 Heat-shrinkable resin tube 10, 11 Insulation ring 12 Exterior can

Claims (5)

[Claims] [Claim 1] Iron: 5 ppm or less, bismuth: 0.0
1 to 0.5% by weight, 0.01 to 0.5% by weight of indium, and a total of 0.005 to 0.1 of at least one selected from magnesium, zirconium, lithium, lanthanum, barium, silicon, boron, and tantalum. Zinc alloy powder for alkaline batteries characterized by containing % by weight. [Claim 2] Iron: 5 ppm or less, aluminum: 0
．． 01-0.5% by weight, 0.01-0.5% indium
wt% and magnesium, zirconium, lithium,
A total of 0.005 to 0.1% by weight of at least one selected from lanthanum, barium, silicon, boron, and tantalum.
Zinc alloy powder for alkaline batteries characterized by containing. [Claim 3] Zinc having an iron content of 5 ppm or less;
The following (1) or (2): (1) 0.01 to 0.5% by weight of bismuth, 0.01 to 0.5% by weight of indium, and magnesium, zirconium, lithium, lanthanum, barium, silicon, boron, A total of 0.0 of at least one selected from tantalum
05-0.1% by weight, (2) 0.01-0.5% by weight of aluminum, 0.01-0.5% by weight of indium, and magnesium, zirconium, lithium, lanthanum, barium, silicon,
A total of 0 of at least one selected from boron and tantalum
．． An alkali having an iron content of 5 ppm or less, characterized in that the above additive elements are dissolved in a molten metal to a content ratio of 0.005 to 0.1% by weight, and the molten metal is directly atomized. A method for producing zinc alloy powder for batteries. 4. The method for producing zinc alloy powder for alkaline batteries according to claim 3, wherein the iron content in the melting and atomizing atmosphere is 0.009 mg/m 3 or less. 5. The method for producing zinc alloy powder for alkaline batteries according to claim 3 or 4, wherein the obtained atomized powder is magnetically sorted.