JPH1064555A - Button type zinc air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop the penetration of an electrolyte between a catalyst layer and a water repellent film by inserting an electrolyte absorber into between the catalyst layer and the water repellent layer forming an air electrode in a button type zinc air battery. SOLUTION: In a button type zinc air battery, an electrolyte absorber 12 is inserted into between a catalyst layer 6 and a water repellent film 7 forming an air electrode 5, and the penetration of an electrolyte between the catalyst layer 6 and the water repellent film 7 is suppressed. As the electrolyte absorber 12, at least one of crosslinked polyacrylic acid, crosslinked polyacrylate, isobutylene - maleic anhydride copolymer, and a salt of this copolymer is used. An electrolyte 2 penetrated from a negative electrode side is absorbed in the electrolyte absorber 12, a space capable of penetrating air is ensured between the catalyst layer 6 and the water repellent film 7, and the button type zinc air battery capable of conducting high rate discharge is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of supplying air to an air electrode in a button-type zinc-air battery.

[0002]

2. Description of the Related Art A button-type zinc-air battery is a battery developed as an alternative power supply to a mercury battery. It uses oxygen instead of mercury oxide for the positive electrode, is low in mercury, is environmentally friendly, and has excellent electric capacity and light weight. Due to its features, the demand for power supplies for hearing aids and pagers is rapidly growing, and further growth is expected in the future due to the miniaturization and portableness of electronic devices.

A zinc-air battery is a battery using oxygen in the air as a positive electrode active material and zinc as a negative electrode active material.
A conventional button-type zinc-air battery will be described with reference to FIG.

In FIG. 7, 21 is a negative electrode case, 22 is a negative electrode made of zinc and an alkaline electrolyte, 23 is a ring-shaped insulating gasket, 24 is a separator, 25 is an air electrode,
It is composed of a collector metal, a catalyst layer 26, and a water-repellent film 27. The water-repellent film 27 is for supplying oxygen to the air electrode 25 and preventing the electrolyte from leaking outside the battery. . 2
Reference numeral 8 denotes an air diffusion paper for uniformly diffusing air, 29 denotes a positive electrode case, and a concave portion for accommodating the air diffusion paper 28 is formed on the bottom surface thereof so that the air diffusion paper 28 is compressed so that the air diffusion function does not deteriorate. ing. Reference numeral 30 denotes an air hole provided on the bottom surface of the positive electrode case 29, and 31 denotes a seal paper for sealing the air hole 30.

[0005] A conventional button-type zinc-air battery is provided with a positive electrode case 29 to prevent the electrolyte solution inside the battery from leaking.
Is sealed by mechanically caulking inward through an insulating gasket 23 to seal the opening. At the time of the sealing, a mechanical load is applied to the bottom surface of the insulating gasket 23, and as a result, a force is exerted on the air electrode 25 and the separator 24 to protrude toward the negative electrode 22. Therefore, during storage and discharge of the battery, the electrolyte penetrates between the catalyst layer 26 and the water-repellent film 27 constituting the air electrode 25,
There is a problem that supply of air to the air electrode 25 is obstructed and large-current discharge becomes impossible, and a reduction in discharge sustaining voltage is observed.

As means for solving this problem, the following proposals have been conventionally made.

One of the proposals is to dispose a compressible expansion body such as a porous synthetic plastic in a negative electrode to prevent the air electrode from protruding to the negative electrode side by a sealing (for example, US Pat. No. 4,054,726).

Another one is to arrange an air electrode layer with a reduced amount of water repellent binder on the negative electrode side and an air electrode layer with an increased amount of water repellent binder on the air hole side. (See, for example, Japanese Patent Publication No. 5-19263).

[0009]

The button-type zinc-air batteries proposed in the prior art have the following problems.

In the former proposal, the amount of the active material that can be filled in the negative electrode is reduced by the volume of an expanded body such as a porous plastic, and the electric capacity is reduced. In the latter proposal, the water-repellent binder is used. When two layers of air electrodes having different amounts are formed and integrated, the thickness of the air electrode increases, and as a result,
Since the amount of the negative electrode decreases, the amount of the negative electrode active material decreases, and the electric capacity decreases as in the former case.

[0011]

In order to solve the above-mentioned problems, a button-type zinc-air battery according to the present invention comprises an electrolytic cell formed between a catalyst layer forming an air electrode and a water-repellent film or on the catalyst layer itself. An electrolyte absorber is disposed at least on the catalyst layer by disposing a liquid absorber. Then, the electrolyte penetrated from the negative electrode side is absorbed by the electrolyte absorber by the electrolyte absorber thus arranged, and a space through which air is transmitted between the catalyst layer and the water-repellent film is secured, so that the capacity is increased. Thus, a button-type zinc-air battery capable of high-load discharge can be obtained without causing deterioration of the battery.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an electrolyte absorber is disposed on a catalyst layer forming an air electrode.

In order to dispose the electrolyte absorber in the catalyst layer, it is effective to insert the electrolyte absorber between the catalyst layer and the water-repellent film or to add the electrolyte absorber to the catalyst layer. It is.

[0014] In addition, when the electrolyte is inserted between the catalyst layer and the water-repellent film, the electrolyte absorber may be a crosslinked polyacrylic acid, a salt of a crosslinked polyacrylic acid, a copolymer of isobutylene-maleic anhydride, At least one selected from the group of salts of this copolymer is preferred.

Further, as the electrolyte solution absorbent to be added to the catalyst layer, at least one selected from the group consisting of a copolymer of crosslinked polyacrylic acid and salts of this copolymer is preferable.

In the button-type zinc-air battery constructed as described above, the electrolyte that has permeated from the negative electrode side during storage and discharge is applied to the inside of the catalyst layer itself or between the catalyst layer and the water-repellent film. The electrolyte absorber is absorbed by the disposed electrolyte absorber, and the electrolyte absorber swells. As a result, there is no electrolyte reservoir formed between the catalyst layer and the water-repellent film, and there is a gap through which air can pass. High load discharge is ensured and capacity is not reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

1 and 2, reference numeral 1 denotes a negative electrode case, 2 denotes a negative electrode made of zinc and an alkaline electrolyte, 3 denotes a ring-shaped insulating gasket, 4 denotes a separator, 5 denotes a current collector metal, a catalyst layer 6, and water repellency. Air electrode composed of membrane 7, 8
Is an air diffusion paper for uniformly diffusing air, 9 is a positive electrode case, and the air diffusion paper 8 is accommodated in a concave portion formed on the inner surface with the bottom surface protruding outward. Reference numeral 10 denotes an air hole formed on the bottom surface of the positive electrode case 9, and reference numeral 11 denotes a seal paper for sealing the air hole 10 when not in use. Further, the water repellent film 7 prevents supply of oxygen to the catalyst layer 6 and leakage of the electrolytic solution to the outside of the battery. In FIG. 1, reference numeral 12 denotes an electrolyte absorber disposed between the catalyst layer 6 and the water-repellent film 7. In FIG. 2, the electrolyte absorber 12 is added to the catalyst layer 6.

(Example 1) As the electrolyte absorber 12,
A cross-linked polyacrylic acid, isobutylene-maleic anhydride copolymer is used, disposed between the catalyst layer 6 and the water-repellent film 7, and PR
A button-type zinc-air battery A having a size of 2330 (diameter: 23.1 mm, height: 3.0 mm) was prepared (see FIG. 1), and a discharge test was performed under the following conditions. For comparison, a button-type zinc-air battery B in which no electrolytic solution absorber is provided between the catalyst layer 6 and the water-repellent film 7 was used as a conventional example. The discharge conditions were: load: 82Ω, 6
At 2 Ω and at a temperature of 20 ° C., the results of the discharge test are shown in FIGS.
As shown in FIG.

As is clear from FIGS. 3 and 4, in the conventional battery B, under both loads (82Ω and 62Ω), the electrolyte penetrates between the catalyst layer and the water-repellent film to diffuse air. In contrast, in the battery A of the embodiment, the action of the electrolyte absorber 12 makes it difficult for the diffusion of air to be inhibited by the accumulation of the electrolyte, and the load 6
Although a slight voltage drop at the end of discharge was observed in the 2Ω discharge (see FIG. 4), the discharge with a load of 82Ω discharged at a stable voltage until the end (see FIG. 3).

(Embodiment 2) The air electrode of a zinc-air battery is generally made of a catalyst and polytetrafluoroethylene (PTFE).
And kneaded with water and filled in a current collector, and then water and PTF
In order to remove the surfactant slightly contained in E, 2
It is formed by drying at about 00 ° C. Therefore, the electrolyte absorber added to the catalyst layer 6 is required to have a heat resistance of 200 ° C. or higher.

For this reason, in this embodiment, an isobutylene-maleic anhydride copolymer was added to the catalyst layer 6 as an electrolyte absorber having high heat resistance, to produce a PR2330 button-type zinc-air battery (see FIG. 2). A discharge test was performed under the same conditions as in Example 1, and the results are as shown in FIGS.

As is clear from FIGS. 5 and 6, the discharge is stable, and even the discharge with a load of 62Ω is discharged at a stable voltage until the end.

Further, when both the first and second embodiments are combined, and the electrolyte absorber is inserted between the catalyst layer to which the electrolyte absorber is added and the water-repellent film, The same effect as in the case was confirmed.

It has also been confirmed that the same effect can be obtained with the sodium salt and potassium salt of the isobutylene-maleic anhydride copolymer used in this example as the electrolyte absorber.

[0026]

The present invention is embodied in the form described above, and can inhibit the diffusion inhibition of air generated by the permeation of the electrolyte between the catalyst layer and the water-repellent film. A button-type zinc-air battery excellent in large current discharge can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main part of a button-type zinc-air battery according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view showing a main part of a button-type zinc-air battery according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a discharge curve of an 82Ω load in Example 1.

FIG. 4 is a diagram showing a discharge curve of a 62Ω load in Example 1.

FIG. 5 is a diagram showing a discharge curve of an 82Ω load in Example 2.

FIG. 6 is a diagram showing a discharge curve of a 62Ω load in Example 2.

FIG. 7 is a cross-sectional view showing a main part of a conventional button-type zinc-air battery.

[Explanation of symbols]

 Reference Signs List 5 air electrode 6 catalyst layer 7 water repellent film 12 electrolyte absorber

Continued on the front page.

Claims (5)

[Claims] 1. A button-type zinc-air battery in which an electrolyte absorber is disposed on a catalyst layer forming an air electrode. 2. The button-type zinc-air battery according to claim 1, wherein an electrolyte absorber is inserted between the catalyst layer forming the air electrode and the water-repellent film. 3. The button-type zinc-air battery according to claim 1, wherein an electrolyte absorber is added to the catalyst layer forming the air electrode. 4. The electrolyte absorbing material is at least one selected from the group consisting of cross-linked polyacrylic acid, salts of cross-linked polyacrylic acid, copolymers of isobutylene-maleic anhydride, and salts of the copolymer. 3. A button-type zinc-air battery according to claim 2. 5. The button-type zinc-air battery according to claim 3, wherein the electrolyte absorber is at least one selected from the group consisting of a copolymer of isobutylene-maleic anhydride and salts of the copolymer.