JP3286346B2 - Zinc alkaline battery - 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 alkaline battery, and more particularly, to an improvement of a negative electrode thereof.

[0002]

2. Description of the Related Art As a problem common to conventional zinc alkaline batteries, corrosion of a negative electrode active material by an electrolyte during storage can be cited. As a countermeasure against this problem, zinc oxide containing about 5 to 10% by weight of mercury with respect to zinc is used as a negative electrode active material to increase the hydrogen overvoltage of the negative electrode active material and make the corrosion by the negative electrode active material electrolyte practical. Controls have been performed to the extent that there is no problem.

In recent years, however, due to pollution,
Reducing mercury content in batteries has increased as a social need, and various studies have been made. For example, a zinc alloy containing lead and aluminum in zinc is calcined with an indium-mercury alloy, and a mercurized zinc alloy powder in which the content of mercury is reduced to about 0.6% by weight (Japanese Patent Publication No. 1-41214).
Gazettes) have been used as active materials.

Further, technical improvements have been made, and zinc alloy powder having a mercury content of about 0.15% by weight has been used as a negative electrode active material.

[0005]

In recent years, environmental pollution by mercury has become a problem worldwide, and the development of batteries containing no mercury has been strongly expected. According to the conventional technique, as described above, the mercurization rate is as low as about 0.6% by weight, and even as low as 0.15% by weight. However, since mercury is contained in the negative electrode active material, it is essential. It cannot be said that environmental problems have been solved.

[0006] Considering resource issues in addition to environmental issues, it is desirable to regenerate zinc or the like from used batteries. However, if zinc is accompanied by mercury, measures against mercury in the regeneration step become a problem. An object of the present invention is to solve such a problem, and an object of the present invention is to provide a zinc-alkali battery that does not reduce corrosion resistance and discharge performance even if it is made non-melted.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a zinc alloy powder containing bismuth is coated with indium on a surface thereof and has a bulk specific gravity of 2.30. A negative electrode active material composed of indium-coated zinc alloy powder of about 2.90 g / cc and 62 to 75 w
A gel negative electrode containing a range excluding t% is provided.
And features.

The invention of claim 2 is characterized in that the bismuth content is 0.005 to 0.05% by weight and the indium coating amount is 0.05 to 0.80% by weight.

[0009]

The following effects are obtained by the above-mentioned structure. When bismuth is added to zinc and alloyed,
Bismuth acts to increase the hydrogen overpotential of the zinc powder as the negative electrode active material, and gas generation due to corrosion is suppressed. Further, when indium is added and coated on the surface of the bismuth zinc alloy powder, indium acts on the surface of the zinc alloy to increase the hydrogen overvoltage, so that the effect of adding indium can be exhibited most effectively. Therefore, the corrosion of the negative electrode can be effectively suppressed in combination with the function and effect of the bismuth, and gas generation due to the corrosion can be suppressed to a low level.

Further, in the above configuration, the bulk specific gravity of the bismuth-coated zinc alloy powder obtained by adding and coating indium on the surface of the bismuth zinc alloy powder is limited to 2.30 to 2.90 ^g / _cc. The corrosion resistance of the negative electrode can be improved without lowering the performance. The reason for this has not been fully elucidated, but is considered as follows. That is, indium coated on the surface of the zinc alloy powder changes the shape of the surface of the powder. Here, indium has better conductivity than zinc, and in general, pure metal has better conductivity than alloy. Therefore, the indium coated on the zinc alloy powder comes into contact with each other in the negative electrode to increase the conductivity of the negative electrode. In particular, since the bulk specific gravity of the indium-coated bismuth-zinc alloy powder is limited to 2.30 to 2.90 g / ml, the powder can have a shape that easily contacts each other in the negative electrode, that is, a shape having moderate irregularities. Thereby, it is considered that the conductivity of the negative electrode is further increased and the discharge performance of the battery can be improved. On the other hand, when the bulk specific gravity of the indium-coated zinc alloy powder is less than 2.30 g / ml, the shape of the powder approaches a needle shape and the surface area (reaction surface area) becomes excessive, so that the corrosion resistance is reduced and When the bulk specific gravity of the alloy powder exceeds 2.90 g / ml, it is considered that the shape of the powder approaches a sphere and the surface area (reaction surface area) becomes too small, so that the discharge performance is reduced.

[0011]

[Example 1]

[Preparation of coated zinc alloy powder] A zinc base metal having a purity of 99.995% or more is melted at about 500 ° C, a predetermined amount of bismuth is added, and a bismuth zinc melt containing 0.02% bismuth is formed. Was sprayed with a high-pressure gas and powdered to prepare a bismuth zinc alloy raw powder. When spraying the bismuth zinc melt, the pressure of the high-pressure gas was set to 2 ± 0.2.
Kgf / cm ² was adjusted so that the powder became a powder having a desired bulk specific gravity.

The indium zinc alloy raw powder produced in this manner was sieved and sized to a particle size range of 20 mesh to 325 mesh to obtain a bismuth zinc alloy powder for indium coating. Next, this bismuth zinc alloy powder and a predetermined amount of metal indium were put into a rotating drum filled with nitrogen gas, and the rotating drum was heated to 180 ° C. for 1 hour.
Rotated for hours. By such a treatment, indium is heated to a temperature not lower than the melting point (156.6 ° C.) and is melted. Indium is gradually adhered to and coated on the surface of the zinc alloy powder, thereby producing an indium-coated zinc alloy powder.

When the bulk specific gravity of the zinc alloy powder was measured, it was 2.60 (g / ml). The indium coating method is referred to as a rotating drum method. Also,
The sieving and sizing are performed using a JIS standard sieve, and the bulk specific gravity is determined according to Japanese Industrial Standards “Test method for apparent density of metal powder” (Z2504-1
979). [Production of Battery] Using the indium-coated zinc alloy powder produced above, an LR6 type battery shown in FIG. 1 was produced.

In FIG. 1, reference numeral 1 denotes a positive electrode can, in which a positive electrode 5 mainly composed of manganese dioxide, a separator 6, and a negative electrode 7 containing indium-coated zinc alloy powder are arranged. I have. A negative electrode terminal plate 2 is attached to the opening of the positive electrode can 1 via a sealing gasket 3. The negative electrode terminal plate 2 is electrically connected to the negative electrode 7 via a current collector 4. I have.

Here, the negative electrode 7 is formed by gelling an electrolyte solution obtained by saturating zinc oxide in a 40% aqueous solution of potassium hydroxide with polyacrylic acid, and the gel is coated with the coated zinc alloy powder (in the comparative example, Zinc powder or Zinc alloy powder
Were mixed and dispersed. On the other hand, the positive electrode was manufactured by mixing graphite with manganese dioxide and pressing the mixture.

The battery fabricated in this manner is hereinafter referred to as a battery of the present invention (A ₁ ). [Example 2] [Preparation of coated zinc alloy powder] A zinc alloy powder containing 0.02% bismuth was put in an indium sulfate aqueous solution,
By stirring for 0 minute, indium was coated on the surface of the zinc alloy powder. Next, the indium-coated powder was washed with ion-exchange purified water, further washed with acetone, and dried at 45 ° C. for 24 hours. Then, sieving and sizing were performed in the same manner as in Example 1 to prepare an indium-coated zinc alloy powder having a bulk specific gravity value of 2.60 (g / ml). The above indium coating method is referred to as a solution method.

In the above description, an aqueous solution of indium sulfate was used as a solution for coating indium, but the coating method according to the present invention is not limited to this solution, and instead of indium sulfate, indium such as indium chloride may be used. Salts may be used. [Production of Battery] Using the above-mentioned indium-coated zinc alloy powder, an LR6 type battery was produced in the same manner as in Example 1.

The battery fabricated in this manner is hereinafter referred to as a battery of the present invention (A ₂ ). [Comparative Example 1] An LR6 type battery was manufactured in the same manner as in the above Example except that pure zinc powder was used.
The battery fabricated in this manner is hereinafter referred to as Comparative Example Battery (X ₁ ). [Comparative Example 2] An LR type battery was manufactured in the same manner as in the above Example, except that zinc and metal indium were melt-mixed, and an indium alloy manufactured by pulverizing the melt by high-pressure gas atomization was used. did.

The battery thus manufactured is hereinafter referred to as Comparative Example Battery (X ₂ ). [Comparative Example 3] As a conventional product, a mercurized zinc alloy powder (bulk specific gravity of 3.2 to 4. 0.%) to which 0.02% of indium, 0.05% of lead, 0.05% of aluminum and 0.6% of mercury are added. 0
g / ml) to produce the same LR type battery as above.

The battery fabricated in this manner is hereinafter referred to as Comparative Battery (X ₃ ). [Experiment 1] A discharge performance test was performed for each of the batteries prepared above, and the discharge performance of each battery was compared and examined. The discharge performance test was conducted by a method of measuring the duration up to a final voltage of 0.9 V under a discharge condition of 3.9 Ω and a discharge condition of 20 ° C.

The results of these measurements are shown in Table 1 below. Table 1
As is clear from the above, the batteries of the present invention (A ₁ ) and (A ₂ ) have a significantly longer discharge duration than the comparative battery (X ₁ ) using pure zinc powder. Compared to the comparative example (X ₂ ) used, the discharge duration was significantly longer. Furthermore, the batteries (A ₁ ) and (A ₂ ) of the present invention exhibit the same discharge duration as the comparative battery (X ₃ ) using zinc mercuride as a conventional product. The battery of the present invention (A ₁ )
And (A ₂ ) show the same discharge duration, and no difference was observed between the indium coating methods.

[0022]

[Table 1]

[Experiment 2] To examine the effect of the difference in the bulk specific gravity of the coated indium zinc alloy powder on the battery discharge performance and the gas generation suppressing effect, the powder was produced in the same manner as in the above-described embodiment except that the bulk specific gravity was different. Using the various coated indium zinc alloy powders, a discharge test and a gas generation test were performed on the battery manufactured in the same manner as in Example 1.

The discharge performance test was performed in the same manner as in Experiment 1. The gas generation test was performed by storing various batteries at 60 ° C. for 30 days, decomposing the batteries in water, and collecting gas present in the batteries. And the method for determining the capacity. 2 and 3 show the above experimental results. For comparison, the same procedure was carried out for Comparative Example Battery 3 using the above-mentioned mercurized zinc alloy powder.
As a result, the gas generation amount of the comparative example battery (X ₃ ) was 1.20.
(G / ml) and the discharge duration was 5.25 hours.

As is clear from FIGS. 2 and 3, the gas generation amount of the battery using the indium-coated zinc alloy powder changes remarkably around the bulk specific gravity of the indium-coated zinc alloy powder of about 2.30 (g / ml). When the bulk specific gravity was 2.30 (g / ml) or less, the amount of generated gas increased. On the other hand, the discharge duration of these batteries changed around 2.90 (g / ml) and was 2.9.
There was a tendency to decrease at 0 (g / ml). From these results, when an indium-coated zinc alloy powder having a bulk specific gravity of 2.30 to 2.90 (g / ml) was used, a comparative battery using a conventional calomelted zinc alloy powder was used.
It can be seen that a battery capable of suppressing the gas generation amount to the same extent as (X ₃ ) and exhibiting the same discharge performance can be obtained.

[Experiment 3] In order to determine a suitable bismuth content and a suitable indium coating amount for a zinc alloy,
Indium-coated zinc alloy powders having a bulk specific gravity of 2.60 g / ml in which the bismuth content and the indium coating amount were variously changed were prepared, and batteries using these powders were produced, and a gas generation test was performed. The method for preparing the indium-coated zinc alloy powder, the method for preparing the battery, and the gas generation test are all the same as those described above.

The results are shown in FIG. 4 and FIG. FIG. 4 uses a zinc alloy powder having a bismuth content of 0.02%,
FIG. 5 shows the results when the indium coating amount was changed from 0.03 to 1.00%, and FIG. 5 shows that the bismuth content was changed from 0.005 to 0.07%.
% Of various zinc alloys coated with a fixed amount (0.10%) of indium. From FIG. 4, the gas generation amount in the battery is in the range of 0.05 to 0.
It can be seen that there is almost no change in the range of 80%, and it increases remarkably at 0.005% or less and 0.80% or more. From FIG. 5, the bismuth content in the zinc alloy is almost unchanged in the range of 0.005 to 0.05% and 0.005% or less. % And not less than 0.05%. From these results, the amount of bismuth added was 0.
005-0.05%, and the indium addition amount is 0.05-0.
It can be seen that by setting the range to 80%, a battery having both corrosion resistance and discharge performance can be obtained.

In the above embodiment, manganese dioxide was used as the positive electrode active material. However, it is needless to say that the positive electrode active material is not limited to this.
Oxygen, nickel hydroxide and the like can be used.

[0029]

As described above, according to the present invention, there is no use of mercury and excellent corrosion resistance which is practically comparable to that of a conventional zinc-alkali battery using a zinc-aluminized anode. And a zinc alkaline battery having both strong discharge performance. Further, since the zinc alkaline battery according to the present invention does not contain any mercury, it does not cause any mercury pollution even after its battery life has expired, and a conventional battery using a zinc-aluminized anode. As a result, it is possible to easily collect and reuse each component of the battery. As a result, the present invention has extremely important effects in aspects of environmental conservation and resource recycling.

[Brief description of the drawings]

FIG. 1 is a sectional view of a battery used in Examples of the present invention.

FIG. 2 is a graph showing a relationship between a bulk specific gravity of an indium-coated zinc alloy powder and a gas amount in a battery.

FIG. 3 is a graph showing the relationship between bulk specific gravity of indium-coated zinc alloy powder and battery discharge duration.

FIG. 4 is a graph showing a relationship between an indium coating amount of an indium-coated zinc alloy powder and a gas amount in a battery.

FIG. 5 is a graph showing a relationship between a bismuth content of an indium-coated zinc alloy powder and a gas amount in a battery.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Mutsumi Yano 2--18 Keihanhondori, Moriguchi-shi, Sanyo Electric Co., Ltd. (72) Inventor Yasuo Akai 2--18 Keihanhondori, Moriguchi-shi, Sanyo Excel Co., Ltd. (56) References JP-A-4-366549 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/42 B22F 1/02 H01M 4/06

Claims (2)

(57) [Claims] 1. A negative electrode active material comprising an indium-coated zinc alloy powder having a surface area of bismuth-containing zinc alloy powder coated with indium and having a bulk specific gravity of 2.30 to 2.90 g / cc. 62-75
A gel negative electrode containing a range excluding wt% is provided.
A zinc alkaline battery characterized by that: 2. The bismuth content is 0.005 to 0.005.
0.05% by weight, indium coverage 0.05-0.8
The zinc alkaline battery according to claim 1, wherein the content is 0% by weight.