JPH0992239A - Button type alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a button type alkaline battery with long storage life performance, high capacity, and high electrolyte leakage resistance by specifying the shape of a negative case and forming a tin plating layer on the inner surface of the negative case. SOLUTION: In a button type alkaline battery using zinc 4 as a negative active material and an alkaline aqueous solution as an electrolyte, a negative case 1 in which the negative active material is mainly housed is formed in the shape of a cup, and a tin plating layer is formed on the inner surface of the negative case 1. In addition, the relation of the inner diameter (a) of the opening part of the negative case 1 and the inner diameter (b) of the central part of the negative case 1 is specified to a<b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved button type alkaline battery using zinc as a negative electrode active material and an alkaline aqueous solution as an electrolytic solution, and more particularly to an improved button type air zinc battery.

[0002]

2. Description of the Related Art Button-type zinc-air batteries are small hearing aids,
Used in small pagers. Compared to other button-shaped batteries of the same size, zinc, which is the negative electrode active material, can be additionally filled, so that the electric capacity is large. In particular, the button-type zinc-air battery used in small hearing aids has an R44 (outer diameter φ11.6 mm x total height φ5.4 mm) that is about 2.1 times more electricity than the mercury battery used for the same purpose. Has capacity.

However, a small hearing aid with a large current consumption is
Even with a button-type zinc-air battery, which has a short battery life of less than one week, improvement in performance has been desired.

A conventional example of a button type zinc-air battery will be described with reference to FIG. Reference numeral 1 denotes a negative electrode case, which is a clad or a plated material having a plurality of metals having copper on the inner surface and nickel on the outer surface. The negative electrode case is pressed into a cup shape having an opening having a U-shaped cross section. The opening having a U-shaped cross section includes a button-type air zinc battery as a means for tightly adhering the extension of the copper layer on the inner surface of the sealing plate to the resin gasket 2 in order to prevent liquid leakage. It is the most commonly used means for button alkaline batteries.

However, as can be seen from FIG. 4, since the material of the negative electrode case 1 is duplicated on the side wall of the battery, there is a drawback that the volume for accommodating the negative electrode zinc 4 is reduced.

Although efforts to reduce the material thickness of the negative electrode case 1, the gasket 2 and the positive electrode case 3 in order to increase the volume for accommodating the negative electrode zinc 4 have been continued from the past,
It is very difficult to process the parts that the material thickness of the negative electrode case 1 and the positive electrode case 3 is 0.1 mm or less and that the gasket 2 is 0.15 mm or less.

In order to solve this problem and secure the capacity of the negative electrode case 1 as large as possible, the method shown in FIG. 5 was considered. FIG. 5 shows a shape in which the opening of the negative electrode case 1 has no folded portion.

The negative electrode case 1 has a battery side wall portion made of a single layer material, and therefore, when compared with the R44 size button type zinc-air battery, the negative electrode case volume is about 10 compared with the battery of FIG.
%To increase.

FIG. 6 is an enlarged view of portion A in FIG. 5, and in FIG. 6, the opening of the negative electrode case which does not have a folded portion in this opening has a cross-section made of three materials, copper 9a, stainless steel 9b, and nickel 9c. It is exposed on the inner surface of the bottom of the L-shaped gasket 2.

When the battery is constructed, a negative electrode case is filled with zinc 4 as a negative electrode active material and an electrolytic solution. Since the surface of particles of zinc 4 is coated with mercury for corrosion protection, the surface of copper 9a is also amalgamated with mercury when the negative electrode case 1 is filled, and the negative electrode zinc 4 and the copper surface 9a have the same potential. .

[0011]

However, the negative electrode case 1
Since the stainless steel 9b and nickel 9c which are not amalgamated are exposed at the end of the battery, when the electrolyte in the battery invades and adheres to it, a potential difference with zinc occurs, and the electrolyte decomposes from the end and hydrogen gas is generated. Generate.

As a result, the internal pressure of the button-type zinc-air battery rises, and the positive electrode case 3 and the air hole 9 opened in the bottom portion.
And the boundary between the negative electrode case 1 and the gasket 2, the positive electrode case 3
The electrolyte is extruded from the boundary between the gasket 2 and the gasket 2 to cause leakage. As a countermeasure against this, an attempt was made to fill the gasket 2 with the resin sealing material 10 between the negative electrode cases 1 to prevent the invasion of the electrolytic solution during battery construction. But it is impossible to prevent it completely. In the initial stage of battery construction, even if the invasion of the electrolytic solution can be prevented, it gradually invades during storage of the battery, and during storage of the battery, some batteries may leak significantly.

Therefore, the method shown in the sectional view of FIG. 4 was devised. The negative electrode case 1 is formed into a cup shape, the opening has a folded portion having a U-shaped cross section, and the negative electrode case 1 is press-molded so that the inner diameter b of the central portion is larger than the inner diameter a of the opening. A button type alkaline battery, especially a button type zinc-air battery.

Since the negative electrode case 1 is press-molded with a metal mold, impurities such as press oil and metal powder adhere to the inner surface of the negative electrode case 1. After the press molding, the negative electrode case 1 is washed with a solvent such as trichloroethylene, but since the inner central portion of the negative electrode case 1 is larger than the opening portion, impurities attached to the copper surface of the inner central portion cannot be completely removed. Fine dissimilar metals such as iron and nickel have a potential difference with the negative electrode zinc during battery storage,
It decomposes the alkaline electrolyte inside the battery to generate hydrogen gas. Hydrogen gas deteriorates the battery discharge performance, and also causes the electrolyte solution to be pushed out from the air holes opened in the positive electrode case of the zinc-air battery, resulting in a significant deterioration in quality.

[0015]

In order to achieve this object, the shape of the present invention is formed in a cup shape, the opening portion has a folded portion having a U-shaped cross section, and the opening portion has a central portion with respect to the inner diameter a. A negative electrode case 1 is press-molded to have a large inner diameter b, and the inner surface of the negative electrode case 1 is plated with electroless tin to employ the negative electrode case 1 to form a button-type zinc-air battery.

[0016]

By adopting this structure, the internal volume of the negative electrode case is approximately 8 in the R44 size compared to the negative electrode case 1 in FIG.
% The volume becomes large, and iron adhered to the inner surface of the negative electrode case,
Fine dissimilar metals such as nickel are hidden by the tin-plated layer, and there is no potential difference with the negative electrode zinc during battery construction, which suppresses battery deterioration during battery storage, and has excellent leakage resistance that does not leak from the air holes. The performance can be obtained.

[0017]

Embodiments of the present invention will be described below.

The negative electrode case is press-molded by a conventional method as shown in FIG. Next, in the step shown in FIG. 3, the negative electrode case 7 is fixed at its outer peripheral portion with a mold 12, and the negative electrode case 1 is remolded with a press mold 11 sandwiching 13 parts of an elastic resin such as urethane rubber. Upper and lower press dies 1
The elastic body 13 sandwiched by 1 receives the outward shape at the time of pressurization to obtain the target negative electrode case 1. 14 is a spring. After the pressing is completed, the elastic body 13 has the same diameter as the press die 11 and can be taken out from the negative electrode case 1.

The pressed negative electrode case 1 is degreased with trichlorethylene and then washed with an alkaline detergent. Next, tin plating is performed by an electroless method. Although tin plating can be performed by the electrolytic method, in the case of the electroless method, tin does not adhere to the nickel layer on the outer surface of the negative electrode case 1 clad material, and only the copper surface is selectively plated. It

By electroless plating, it is possible to relatively uniformly plate a deep scratch or a deep recess on the copper surface, and cover and hide with tin. However, in the case of electrolytic plating, the impurities adhering to and exposed on the surface can be hidden, but the impurities that have penetrated deeply cannot be plated, and the suppression of hydrogen gas generation is insufficient.

The electroless tin plating is an aqueous solution containing 2% by weight of stannous chloride, 5% by weight of tartaric acid and 5% by weight of thiourea, and the negative electrode case 1 is placed in a plating solution in a plating tank. The inside of the plating tank is heated to 30 to 40 ° C. and rotated.

The copper layer on the inner surface of the negative electrode case 1 is 0.01 to
0.5 μm tin is electroless plated. By examining various components of the plating solution, it is possible to perform tin plating of 0.5 μm or more, but the negative electrode case 1 with the desired performance is 0.0
1 to 0.5 μm is sufficient, preferably 0.01 to
0.3 μm.

FIG. 1 is a cross-sectional view of the button type zinc-air battery of the present invention, and the construction method will be described. Reference numeral 3 is a positive electrode case having an air hole 9 at the bottom. The diffusion paper 8 is for the purpose of sufficiently diffusing oxygen in the air into the air electrode 5, is porous, and generally uses a nonwoven fabric mainly composed of a cellulosic material. It is placed in the recess of the positive electrode case 3.

Next, a water repellent film 7 of polytetrafluoroethylene (PTFE) having fine pores of 0.1 to 1 μm is punched and placed on the diffusion paper 8 to have a diameter substantially the same as the inner diameter of the positive electrode case 3.

Numeral 5 is an air electrode. A catalyst material such as manganese oxide and activated carbon and a conductive material such as acetylene black are mixed with a dispersion of PTFE and applied to a metal screen serving as a positive electrode current collector and dried. To form.

The air electrode 5 is punched out in the same diameter as the inner diameter of the positive electrode case 3 and placed on the water repellent film 7. Further, 6 is a separator, which is made of an ion-permeable material mainly composed of polypropylene microporous membrane cellulose or the like, and its purpose is to separate the negative electrode zinc 4 and the air electrode 6.

Negative electrode case 1 is fitted with a gasket 2 made of resin such as nylon 66 and having an L-shaped cross section, and filled with negative electrode zinc 4 and an electrolytic solution of an aqueous solution of potassium hydroxide or sodium hydroxide. The contact surface between the gasket 2 and the negative electrode case 1 is filled with a sealing material such as sulfonated polyethylene or butyl rubber to be liquid-tight. Finally, negative electrode case 1 and positive electrode case 3 filled with various battery power generation materials
Are fitted via a gasket 2 and the opening of the positive electrode case 3 is bent inward by a mold to complete a button-type zinc-air battery.

Inventive product A according to the present embodiment and a battery B having the same structure as the inventive product A but having no tin plating on the inner surface of the negative electrode case 1 are R
Dozens of dozens assembled with 44 size zinc air batteries, 620
As the initial and accelerated deterioration test of continuous discharge of Ω, 60 ℃ 20
After storage for a day, discharge was performed and the results shown in Table 1 were obtained.

[0029]

[Table 1]

The liquid was stored for 20 days in an environment of a temperature of 60 ° C. and a humidity of 90%, and liquid leakage due to gas generation from the inside of the battery through the air holes was investigated. The results are shown in (Table 2).

[0031]

[Table 2]

As shown in (Table 1) and (Table 2), by adopting the present invention, it is possible to obtain a button-type zinc-air battery which has excellent leakage resistance and has little electric storage capacity and large electric capacity. it can.

[0033]

As described above, according to the present invention, the opening of the negative electrode case has a folded portion having an L-shaped cross section, and the inner diameter a of the opening of the negative electrode case formed in a cup shape is set to the central portion of the negative electrode case. Using the negative electrode case 1 having an inner diameter b of a <b,
Further, by tin-plating the inner surface, a button-type alkaline battery having excellent storage performance, a large electric capacity, and excellent leakage resistance, particularly a button-type zinc-air battery is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an embodiment of the present invention.

FIG. 2 is an intermediate step of a press for manufacturing the negative electrode case of the present invention.

FIG. 3 is a simplified view of a pressing process showing the production of the negative electrode case of the present invention.

FIG. 4 is an example of a cross-sectional view of a button-type zinc-air battery showing an example of the related art.

FIG. 5 is an example of a sectional view of a button type zinc-air battery showing another example of the related art.

FIG. 6 is an enlarged cross-sectional view of part A of FIG.

[Explanation of symbols]

 1 Negative electrode case 2 Gasket 3 Positive electrode case 4 Zinc 5 Air electrode 6 Separator 7 Water repellent film 8 Diffusion paper 9 Air holes

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Norimasa Takahashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Fumio Oho, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Within

Claims (3)

[Claims] 1. A button type alkaline battery using zinc as a negative electrode active material and an alkaline aqueous solution as an electrolytic solution, wherein a negative electrode case mainly containing the negative electrode active material is formed into a cup shape, and an inner surface thereof is formed. A button type alkaline battery in which a tin-plated layer is present, and the relationship between the inner diameter a of the opening and the inner diameter b of the central portion of the negative electrode case is a <b. 2. The button type alkaline battery according to claim 1, wherein the opening of the negative electrode case has a folded portion having a U-shaped cross section. 3. The button type alkaline battery according to claim 1, wherein the negative electrode case has four layers of nickel, stainless steel, copper and tin from the outer surface.