JPH1140171A - Air-zinc cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance discharge characteristics by improving a water repellent layer of an air-zinc cell. SOLUTION: In this cell, a water repellent layer 4, which is one element that makes a positive electrode assembly for an air-zinc cell, comprises one or more pieces of PTFE(polytetrafluoroethylene) films, at least one of them is pasted to a positive electrode catalyst layer 5 to make an integrated structure, and a thickness of this integrated PTFE film is 170 μm-600 μm. By setting the thickness of the PTFE film in this range, the PTFE film will not be easily peeled off from the positive catalyst layer, and shortening of a battery life time can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc-air battery using oxygen in the atmosphere as a positive electrode active material, and more particularly, to a zinc-air battery having an improved water-repellent layer used as one component of the zinc-air battery. About.

[0002]

2. Description of the Related Art A zinc-air battery uses oxygen in the air as a positive electrode active substance, zinc as a negative electrode active substance, and an alkaline aqueous solution as an electrolytic solution. A button type cell phone is mainly used for hearing aids and pagers. Have been.

One example of these zinc-air batteries is shown in FIG. In the drawing, reference numeral 1 denotes a positive electrode current collector having an air hole 2. Numeral 3 is a diffusion layer for the purpose of diffusing air taken in from the air holes 2 in this layer and uniformly supplying the air to the catalyst layer. 4 is a water-repellent layer, 5
Denotes a positive electrode catalyst layer, and 6 denotes a separator, and these constitute a positive electrode assembly. Reference numeral 8 denotes a negative electrode active material layer, 9 denotes a negative electrode current collecting container, 10 denotes an insulating gasket, and 11 denotes a seal tape.

As described above, a zinc-air battery has a water-repellent layer in a positive electrode assembly, and generally uses one or more PTFE membranes (polytetrafluoroethylene) as a material thereof. . Usually, at least one of the PTFE membranes is used integrally with the positive electrode catalyst layer.

[0005]

However, when the catalyst layer in which the PTFE membrane is integrated is punched into a predetermined size in order to be arranged in the battery, the PTFE membrane and the cathode catalyst layer are cut at the end of the cut end. Had the problem of peeling off.

[0006] When the two materials are peeled off and incorporated into a battery, the electrolyte is accumulated between the two materials and oxygen is not sufficiently supplied to the positive electrode catalyst layer. There is a problem that the discharge characteristics cannot be secured.
The present invention has been made in view of the above problems, and has as its object to improve the discharge characteristics of a zinc-air battery by improving the water-repellent layer.

[0007]

In other words, the present invention uses oxygen in the air as a positive electrode active substance, zinc as a negative electrode active substance, an alkaline aqueous solution as an electrolytic solution, and a positive electrode in which a positive electrode catalyst layer and a water repellent are sequentially arranged from a negative electrode facing surface. In a zinc-air battery having at least two layers, the water-repellent layer is composed of one or more PTFE membranes, and at least one of the layers is bonded to and integrated with the positive electrode catalyst layer. The thickness of the PTFE film to be formed is 170 μm to 600 μm.

As a result of various studies on the PTFE membrane integrated with the positive electrode catalyst layer, the use of the PTFE membrane having a thickness within the above range completely eliminates peeling, and as a result,
It was found that the discharge characteristics could be improved. That is, when the PTFE film is below the above range, the PTFE film is easily peeled off from the positive electrode catalyst layer, and when it is above the above range, it is difficult to integrate with the positive electrode catalyst layer.

[0009]

Embodiments of the present invention will be described below. (Example) An example battery of the present invention was manufactured using PR44 (diameter 11 mm, total height 5.4 mm) as a typical zinc-air battery. FIG. 1 shows a cross-sectional view thereof.

In FIG. 1, reference numeral 1 denotes a positive electrode current collector having an air hole 2. Numeral 3 is a diffusion layer for the purpose of diffusing air taken in from the air holes 2 in this layer and uniformly supplying the air to the catalyst layer. 4 is a water repellent layer, 5 is a positive electrode catalyst layer, 6
Are separators, and these constitute a positive electrode assembly. Reference numeral 8 denotes a negative electrode active material layer, 9 denotes a negative electrode current collecting container, 10 denotes an insulating gasket, and 11 denotes a seal tape.

As shown in Table 1, 17 water-repellent layers 4
0 μm, 200 μm, 300 μm, 450 μm, 600
PTFE films of various thicknesses of μm were used and integrated with the positive electrode catalyst layer. The integration was performed by pressing both materials under pressure of about 2 tons using a rubber roller.

Comparative Example As a comparative example, as shown in Table 1, a water-repellent film was formed using a PTFE film having a size of less than 170 μm and a PTFE film having a size of more than 600 μm. did. Note that the thickness of the conventional PTFE film is 100 μm.

With respect to each of the zinc-air batteries of the above Examples and Comparative Examples, the rate of occurrence of peeling of the water-repellent film and the life of the batteries were examined. The occurrence rate of peeling was determined by counting the number of peeled edges at the end of the above material punched into a predetermined shape. In addition, regarding the life of the battery, a battery constituted using each water-repellent film was subjected to 620Ω discharge, and a battery whose discharge characteristic was less than 80% of the theoretical capacity was counted as a short life. Discharge environment is 20 ℃ 60% R
H. Table 1 shows the results.

[0014]

[Table 1]

From the results shown in Table 1, it is found that 170 μm or more and 600
It can be seen that the zinc-air battery using the PTFE film having a thickness of not more than μm has no peeling and no short life. On the other hand, in the comparative example, when the thickness of the PTFE film was less than the range of the present invention, peeling occurred, and it can be seen that the rate of occurrence of single life was high. In addition, when it exceeds the range of the present invention, it cannot be integrated into the positive electrode catalyst layer.

[0016] As shown in Comparative Example 2, although the PTFE membrane that is normally used also has a short life, in actual production, 100% inspection is performed. No short life will occur.

[0017]

As described above, the zinc-air battery of the present invention does not have a short life and can obtain sufficient discharge characteristics.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an air battery according to an embodiment of the present invention.

[Explanation of symbols]

1: positive electrode current collector container (outer can), 2: air hole, 3:
Diffusion layer, 4 ... water repellent layer, 5 ... positive electrode catalyst layer, 6 ... separator, 7 ... positive electrode assembly, 8 ... negative electrode active material layer, 9 ... negative electrode current collector container, 10 ... insulating gasket, 11 ... seal tape.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masao Kawaguchi 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation

Claims (1)

[Claims] 1. An air zinc having at least two layers of a positive electrode catalyst layer and a water-repellent layer in order from a negative electrode facing surface, using oxygen in the air as a positive electrode active substance, zinc as an negative electrode active substance, and an alkaline aqueous solution as an electrolytic solution. In the battery, the water-repellent layer is composed of one or more PTFE films, and
Has a structure in which the sheets are bonded to and integrated with the positive electrode catalyst layer, and the thickness of the integrated PTFE film is 170 μm or more.
A zinc-air battery having a thickness of 600 μm.