JPH0754704B2 - Zinc alloy powder for alkaline battery and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc alloy powder for alkaline batteries and a method for producing the same, and more specifically, it suppresses the generation of hydrogen gas by containing iron in an amount of 1 ppm or less and containing a specific additive element. However, the present invention relates to a zinc alloy powder for a seamless alkaline battery having improved leakage resistance and a method for producing the same.

[0002]

2. Description of the Related Art Mercury in zinc fluoride powder used as a negative electrode active material for alkaline batteries suppresses generation of hydrogen gas due to corrosion of zinc and prevents leakage of the battery due to this. It was considered to be an essential component for the negative electrode active material of alkaline batteries.

However, there is a demand for reduction of mercury from the viewpoint of environmental measures. Therefore, by adding lead, aluminum, bismuth, indium, etc. to zinc as additive elements, the content of mercury is reduced from 10% by weight. Even if the amount was drastically reduced to about 1% by weight, it became possible to suppress the generation of hydrogen gas.

[0004] However, as a further social demand, it has been recently demanded that the content of mercury in the negative electrode active material be 0% by weight, in other words, it should be constant. As described above, the situation is significantly different when the negative electrode active material is made unconstrained, and it is difficult to suppress the hydrogen gas generation amount to a predetermined level even if the above-mentioned additional elements are added. That is, conventionally, a zinc alloy powder as a negative electrode active material to which various additive elements are added has been proposed (for example, Japanese Patent Publication No. 2-2298).
No. 4, JP-A-61-153950), these can achieve the desired suppression of hydrogen gas generation even when the mercury content is 1% by weight or less, but they could not be realized by the unconstrained. .

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

However, in the zinc alloy powder having a mercury content of 0% by weight, the content of impurities is 10 p as described above.
The effect of suppressing the generation of the desired hydrogen gas could not be obtained even if the content was reduced to about pm and an additive element such as lead was contained.

[0007] As described above, making the negative electrode active material unconstrained is accompanied by fundamentally different difficulty from that in the case of lowering the mercury content of 0.6 to 1% by weight. No alkaline battery has been obtained in which the zinc alloy powder of No. 1 is used as the negative electrode active material to suppress the generation of hydrogen gas, and thus to improve the leakage resistance.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. In the unconstrained state, the generation of hydrogen gas can be significantly suppressed and the discharge performance can be brought to a practical level. An object is to provide a zinc alloy powder for alkaline batteries that can be retained and a method for producing the same, and an ultimate object is to improve the leakage resistance of a mercury-free alkaline battery.

[0009]

Means for Solving the Problems The inventors of the present invention have earnestly studied in accordance with this object, and as a result, use zinc having a very small content of iron as an impurity, and by adding a specific additive element thereto, The inventors have found that the above objects can be achieved by the synergistic effect of the two, and have reached the present invention.

That is, the zinc alloy powder for a non-alkaline alkaline battery of the present invention has the following (1) to (6): (1) 0.01 to 0.5% by weight of bismuth and 0.01 to 0.
5% by weight, 0.01 to 0.5% by weight of lead, 0.01 to 0.5% by weight of (2) bismuth, and 0.01 to 0.5% of indium.
0.5% by weight, 0.005 to 0.5% by weight of calcium, 0.01 to 0.5% by weight of (3) lead, and at least one selected from bismuth, aluminum, and calcium in a total of 0 to 1. 0% by weight, and (4) calcium to 0.
005-0.5 wt%, bismuth 0.01-0.5 wt% and aluminum 0-0.5 wt%, (5) lead 0.01-0.5 wt%, indium 0.01 ~
0.5% by weight, 0.01 to 0.5% by weight of calcium, 0 to 0.5% by weight of aluminum, and (6) lead of 0.
01-0.5% by weight, 0.01-0.5% by weight of indium, less than 0.01% by weight of calcium and 0.01-0.5% by weight of aluminum, and the balance iron. Is contained in an amount of 1 ppm or less.

In the present invention, the iron content is 1 ppm.
It must be: When the iron content exceeds 1 ppm, the effect of suppressing the generation of hydrogen gas is small. The iron content of 1 ppm or less as used herein means ICP which is a usual analytical means without using a separation operation of zinc and iron.
Or below the analytical limit value when the atomic absorption method is used. Conventionally, such zinc or zinc alloy powder having a low iron content has not been used as a negative electrode active material, and no such report has been known. High-purity zinc metal can be made for special purposes, for example, for semiconductors using a method such as the zone melting method,
It is also expensive in price and cannot be used as a raw material for dry batteries. Moreover, the example used as an alloy powder is not found either. Among the zinc ingots obtained as industrial products, the highest purity rectified zinc has an iron concentration of 20 ppm or less according to Japanese Industrial Standards, and even if the impurity level is particularly low, the iron concentration is generally low. 2 pp
It is m or more. In addition, electric zinc is at the same level.

The present invention also contains a component selected from the above (1) to (6). If the content of each component element deviates from the above range, there arises a problem that the desired effect of suppressing the generation of hydrogen gas cannot be obtained or that practical discharge performance cannot be maintained. Even if the additive elements other than the above components, such as aluminum, bismuth, and calcium contained in the zinc alloy powder conventionally used as the negative electrode active material, are contained alone, the above-described effects of the present invention cannot be obtained.

Next, the manufacturing method of the present invention will be described. In the present invention, zinc having an iron content of 1 ppm or less is used. Examples of such zinc having a low iron content include zinc ingot obtained from zinc deposited by electrolysis and zinc produced by distillation. Conventionally, a zinc ingot obtained by melting deposited zinc with a flux such as ammonium chloride and casting it in a mold has been used as a zinc raw material for a negative electrode active material. In such a zinc ingot, the iron content cannot be 1 ppm or less. The reason is that the dross part floating in the melting step of zinc is removed, but zinc partially recovered in the removal step is returned to the melting part. This is because the iron content from the separator is usually mixed in this dross removal step. In addition, contamination of iron from the melt pump, mold, and environment is expected.

In the molten zinc having a low iron content, each of the additive elements shown in the above (1) to (6) is dissolved so as to have a content within a predetermined range. Then, next, it is pulverized by an atomizing method and further sieved to obtain a zinc alloy powder. The content of iron in the melting and atomizing atmosphere at this time is preferably 0.009 mg / m ³ or less from the viewpoint of further improving the effect of suppressing hydrogen gas generation. It is also desirable to magnetically sort the obtained zinc alloy powder from the same viewpoint.

A flow sheet showing the difference between the conventional method and the method for producing the zinc alloy powder of the present invention is shown in FIG. The iron content in the zinc alloy powder thus obtained is 1 ppm or less as described above, and the zinc alloy powder has an allowable upper limit of leakage resistance of about 300 μl / da.
It is possible to suppress the generation of hydrogen gas below y · cell (AA type).

Conventionally, the mechanism of hydrogen gas generation due to corrosion of zinc is clarified by actually going into the gas generation site only by discussing the relationship of the crystal structure by macroscopically measuring and estimating the gas amount. I've never been there. The inventors of the present application, who thought that this might be the reason why the various applied technologies could not be put to practical use with respect to a mercury-free battery, did not perform zinc observation by careful microscopic observation of the gas generation site and EPMA analysis. It has been found that, when fine particles of iron or its oxides, alloys, etc. as unavoidable impurities contained in the powder are present between zinc particles and / or on the surface, the fine particles serve as a source of hydrogen gas generation.

That is, the zinc powder was immersed in an aqueous potassium hydroxide solution similar to the electrolytic solution of an alkaline battery, and it was observed with an optical microscope that there were specific sites where gas was continuously generated. Next, the state of gas generation was similarly observed using relatively large particles, thin rod-shaped or plate-shaped zinc. And
It was confirmed that there was a place where gas was generated from the same place for a long time, and a mark was attached to the place where continuous gas was generated using a sharp instrument. Next, the zinc was subjected to compositional analysis by EMPA.

As a result, the continuous gas generation point is always 0.
It was found that fine particles of mainly 5 to 5 μm containing iron were unevenly distributed. In some cases, chromium, nickel, silver, sulfur, and oxygen were detected as components other than iron. From this, it was found that the gas generation was mainly caused by a very small amount of iron or iron oxide particles being mixed.

As shown in Table 1, various particles having an average particle diameter of 0.1 to several mm are added to zinc powder or a zinc plate to a concentration of about 1 to several ppm, and potassium hydroxide is added. The situation of gas generation was observed in the aqueous solution. The results are shown in Table 1.

[0020]

[Table 1]

From the results shown in Table 1, it was found that particles of iron, iron oxide and stainless steel were the center of gas generation. Thus, it was found that the gas generation source was fine particles, which were also mainly iron-based particles.

Therefore, in the present invention, the content of iron is made extremely small and a specific additive element is contained in a fixed amount. This suppresses the generation of hydrogen gas due to the synergistic effect of the two.

[0023]

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

Examples 1-36 and Comparative Examples 1-7 In a room with an iron content of 0.005 mg / m ^{3 in} the atmosphere, ionized zinc having an iron content of 1 ppm or less was melted at about 500 ° C. Then, a predetermined amount of each element shown in Tables 2 to 3 was added thereto to prepare a molten zinc alloy. In Comparative Example 1, no element was added.

Next, this was directly pulverized in the same atmosphere using high pressure argon gas (jet pressure 5 kg / cm ² ), and the obtained zinc alloy powder was sieved to a particle size of 50 to 150 mesh.

Further, magnetic separation was performed using a magnet to remove free iron powder. The iron contents of the obtained zinc alloy powders were all 1 ppm or less.

Here, in a 40% aqueous potassium hydroxide solution saturated with zinc oxide, carboxymethylcellulose and sodium polyacrylate as gelling agents were added to 1.
About 0% was added to prepare an electrolytic solution.

The above zinc alloy powder was used as the negative electrode active material, and 3.0 g of the zinc alloy powder was mixed with 1.5 g of the electrolytic solution to form a gel, which was directly used as the negative electrode material, and the alkaline manganese battery shown in FIG. Created.

After the alkaline manganese battery was partially discharged by 25%, the amount of hydrogen gas generated due to corrosion of the zinc alloy powder was measured, and the obtained results are shown in Tables 2 and 3.
In addition, 25% partial discharge constitutes a mercury-free alkaline manganese battery, and the discharge time up to 0.9 V is 100%.
In that case, the hydrogen gas generation rate is maximized per 25% partial discharge. Therefore, the discharge condition was 1% for 11 minutes, and 25% partial discharge was performed.

The alkaline manganese battery shown in FIG. 2 has a positive electrode can 1, a positive electrode 2, a negative electrode (gelled zinc alloy powder) 3, a separator 4, a sealing body 5, a negative electrode bottom plate 6, a negative electrode current collector 7,
Cap 8, heat-shrinkable resin tube 9, insulating ring 1
It is composed of 0, 11 and an outer can 12.

Comparative Examples 8 to 29 Starting from a zinc ingot in which electroanalyzed zinc having an iron content of 1 ppm or less was cast as usual as a starting material, and an iron content of about 500 mg / m ^{3 in} an atmosphere of about 500. Melt at ℃,
A predetermined amount of each element shown in Table 3 was added to this to prepare a zinc alloy melt.

Next, this was pulverized in the same atmosphere using high-pressure argon gas (jet pressure 5 kg / cm ² ), and the obtained zinc-zinc alloy powder was sieved to a particle size of 50 to 150 mesh.

The iron content of each of the obtained zinc alloy powders was 3 ppm. It should be noted that no magnetic force selection was performed here.

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

[0035]

[Table 2]

[0036]

[Table 3]

As shown in Tables 2 and 3, Examples 1 to 1 having an iron content of 1 ppm or less and having a specific composition
The zinc alloy powders of No. 36 are all about 300 μl / day · cell where the hydrogen gas generation amount is the upper limit of the leakage resistance.
(AAA type) or less. On the other hand, in the zinc alloy powders of Comparative Examples 1 to 7, the composition deviates from the range defined by the present invention even though the iron content is 1 ppm or less. Is not recognized. Furthermore, the zinc alloy powders of Comparative Examples 8 to 29 have an iron content of 3
Since it is ppm, the effect of suppressing the generation of hydrogen gas is not recognized regardless of whether the composition falls within the range specified in the present invention.

With respect to the zinc alloy powders of this example and the comparative example, the relationship between the content of each element and the content of iron and the hydrogen gas generation amount was plotted, and the results are shown in FIGS. In each figure, the circled numbers represent the example numbers, and the squared numbers represent the comparative example numbers.

As is clear from this result, the hydrogen gas generation amount of each example is greatly reduced as compared with each comparative example.

Examples 37 to 40 Zinc alloy powders were obtained with the same composition and conditions as in Example 12 except that the magnetic force selection was not carried out (Example 3).
7). In addition, the content of iron is 5 in the melting and atomizing atmosphere.
A zinc alloy powder was obtained under the same composition and conditions as in Example 12 except that the treatment was performed in an atmosphere of mg / m ³ (Example 38).

Similarly, a zinc alloy powder was obtained under the same composition and conditions as in Example 27 except that the magnetic force selection was not carried out (Example 39). Further, a zinc alloy powder was obtained with the same composition and conditions as in Example 27 except that the melting and atomizing atmosphere was performed in an atmosphere having an iron content of 5 mg / m ³ (Example 40).

The iron contents of the zinc alloy powders thus obtained were all 1 ppm or less. Using this zinc alloy powder, an alkaline battery shown in FIG. 2 was prepared in the same manner as in Example 1, 25% partial discharge was performed, and the hydrogen gas generation amount was measured. The results are shown in Table 4.

[0043]

[Table 4]

As can be seen from Table 4, Examples 37 to 3
8 has almost the same results as in Example 12, and Examples 39 to
For 40, almost the same results as in Example 27 were obtained.

EXPERIMENTAL EXAMPLE The zinc alloy powders of Example 2 and Comparative Example 11 were screened so as to contain 1% by weight and 10% by weight of mercury to obtain a zinc halide alloy powder.

Using this zinc hydride alloy powder, an alkaline battery shown in FIG. 1 was prepared in the same manner as in Example 1, 25% partial discharge was performed, and the amount of hydrogen gas generated was measured. The results are plotted together with the values of Example 2 and Comparative Example 11 and are shown in FIG.
Shown in.

As shown in FIG. 14, when the iron content is 3 ppm, the mercury content is less than the upper limit of the liquid leakage resistance at 1 wt% or more, whereas the iron content is 1p
Below pm, the allowable upper limit of the liquid leakage resistance is lower than that of the presence or absence of mercury.

Further, similar tests were conducted on the zinc alloy powders of Example 12 and Comparative Example 16, but almost the same results were obtained.

[0049]

As described above, the iron content is 1 pp.
By dissolving zinc of m or less and a specific additive element in a molten metal and directly atomizing the molten metal, the iron content is 1
A zinc alloy powder for alkaline batteries having a ppm or less is obtained.

This zinc alloy powder can be used as a negative electrode active material of an alkaline battery in spite of being unconstrained.
The generation of hydrogen gas can be significantly suppressed, and the discharge performance can be maintained at a practical level. Further, since it does not contain mercury, an alkaline battery using this zinc alloy powder as a negative electrode active material meets social needs.

[Brief description of drawings]

FIG. 1 is a flow sheet showing a conventional method and a method for producing a zinc alloy powder of the present invention.

FIG. 2 shows a side sectional view of an alkaline manganese battery according to the present invention.

3 to 13 are graphs showing the relationship between the content of each element and the content of iron and the amount of hydrogen gas generated in the zinc alloy powders in Examples and Comparative Examples.

FIG. 14 is a graph showing the relationship between the mercury content in the zinc alloy powder and the hydrogen gas generation amount.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Tomiko Yamaguchi 1436-3 Takehara-cho, Takehara-shi, Hiroshima Prefecture Mitsui Mining & Smelting Co., Ltd. In-house (72) Inventor Shuji Tsuchida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. Bismuth in an amount of 0.01 to 0.5% by weight, indium in an amount of 0.01 to 0.5% by weight, and lead in an amount of 0.01 to 0.5% by weight.
A zinc alloy powder for a non-alkaline alkaline battery, characterized by comprising 5% by weight and the balance zinc containing 1 ppm or less of iron as an accompanying impurity. 2. Bismuth of 0.01 to 0.5% by weight, indium of 0.01 to 0.5% by weight, and calcium of 0.
005 to 0.5% by weight, the balance 1
Zinc alloy powder for a non-alkaline alkaline battery, which is characterized by comprising zinc in an amount of ppm or less. 3. Lead in an amount of 0.01 to 0.5% by weight, at least one selected from bismuth, aluminum, and calcium in a total amount of 0 to 1.0% by weight, and the balance containing 1 ppm or less of iron as an accompanying impurity. A zinc alloy powder for a seamless alkaline battery, characterized by comprising zinc. 4. Containing 0.005 to 0.5% by weight of calcium, 0.01 to 0.5% by weight of bismuth, 0 to 0.5% by weight of aluminum, and the balance of 1 ppm or less of iron as an accompanying impurity. Zinc alloy powder for a non-alkaline alkaline battery, characterized by comprising: 5. Lead in an amount of 0.01 to 0.5% by weight, indium in an amount of 0.01 to 0.5% by weight, and calcium in an amount of 0.01 to 0.5% by weight.
0.5% by weight and 0-0.5% by weight of aluminum,
A zinc alloy powder for a non-alkaline alkaline battery, the balance of which is zinc containing 1 ppm or less of iron as an accompanying impurity. 6. 0.01 to 0.5% by weight of lead, 0.01 to 0.5% by weight of indium, less than 0.01% by weight of calcium and 0.01 to 0.5% by weight of aluminum, A zinc alloy powder for a non-alkaline alkaline battery, the balance of which is zinc containing 1 ppm or less of iron as an accompanying impurity. 7. An electroanalyzed zinc containing 1 ppm or less of iron, and (1) to (6) below: (1) 0.01 to 0.5% by weight of bismuth and 0.01 to 0.5% by weight of indium. %, Lead 0.01 to 0.5 wt%, (2) bismuth 0.01 to 0.5 wt%, indium 0.01 to 0.5 wt%, calcium 0.005 to
0.5% by weight, (3) 0.01 to 0.5% by weight of lead and 0 to 1.0% by weight of at least one selected from bismuth, aluminum and calcium, and (4) 0.005 of calcium. ~ 0.5 wt%, 0.01-0.5 wt% bismuth and 0-aluminium
0.5% by weight, (5) 0.01 to 0.5% by weight of lead and 0.
01 to 0.5% by weight, 0.01 to 0.5% by weight of calcium and 0 to 0.5% by weight of aluminum, (6) 0.01 to 0.5% by weight of lead and 0.
01-0.5 wt%, less than 0.01 wt% calcium, and 0.01-0.5 wt% aluminum, the above-mentioned additional elements are dissolved and the molten metal is added. Characterized by direct atomization,
A method for producing a zinc alloy powder for a seamless alkaline battery, containing 1 ppm or less of iron, which is an accompanying impurity. 8. The method for producing a zinc alloy powder for an alkaline battery according to claim 7, wherein the iron content in the melting and atomizing atmosphere is 0.009 mg / m ³ or less. 9. The method for producing a zinc alloy powder for an alkaline battery according to claim 7, wherein the atomized powder obtained is magnetically selected. 10. An alkaline battery using the zinc alloy powder according to claim 1 as a negative electrode active material.