JP2003068372A - Air-zinc battery and manufacturing method of oxygen electrode of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the life of an air-zinc battery when discharged at a high temperature. SOLUTION: Related to an air-zinc battery, with oxygen as the positive-pole active material and zinc as negative-pole active material, an electrode layer 14 which reduces the positive-pole oxygen at least comprises a catalyst layer 6 which adsorbs and reduces oxygen and a water-repellent layer 8 which is press-fitted to the catalyst layer. The material whose Gurley value is 50-500 seconds is used as the water-repellent layer 8 press-fitted to the catalyst layer 6 to form an electrode layer. Thus, the electrolyte is prevented from accumulating between the catalyst layer and the water-repellent layer, to extend its life shortened by discharging at a high temperature.

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, and more particularly, to a zinc-air battery which has a positive electrode layer improved so as to be stably discharged even under high temperature and high humidity and to prevent a short life. Regarding

[0002]

2. Description of the Related Art Since zinc-air batteries have a large capacity per unit volume, they have been conventionally used for hearing aids and pagers. In recent years, to further expand the applications,
We are examining compatibility with various devices, but one of the characteristics of zinc-air batteries is that the battery characteristics are easily affected by the operating environment.

Here, the environment of use is roughly classified into low temperature or high temperature, low humidity or high humidity. That is, it can be divided into low temperature low humidity, low temperature high humidity, high temperature low humidity, high temperature high humidity,
Generally, the low temperature region and the low humidity region can be adapted by designing a high electrolyte solution concentration or further increasing the electrolyte solution amount.

Further, in the case of a light load application, the amount of oxygen flowing into the battery can be reduced by reducing or reducing the air holes, thereby reducing the influence of humidity.

However, when designed for heavy loads,
The environment of use, especially the influence of humidity, was so great that it was difficult to use in equipment where the environment of use changes greatly during use. After all, in this case, there was no choice but to reduce the amount of zinc in the negative electrode, and forcibly adding zinc caused liquid leakage during discharge or over discharge.

As described above, various measures have been taken depending on the situation, but even in the high temperature region, these measures could not suppress the defects. That is, in the discharge in the high temperature region, the electrolyte solution in the positive electrode catalyst layer permeates quickly, and the operating voltage suddenly drops during the discharge, resulting in a short life.

When the battery that caused the short life is disassembled and investigated, an electrolytic solution accumulates between the positive electrode catalyst layer and the water repellent layer, and this electrolytic solution inhibits the supply of oxygen, resulting in a so-called suffocation state. It can be seen that the operating voltage has dropped.

Generally, the phenomenon of the accumulation of the electrolytic solution occurs when the bonding strength between the water-repellent microporous membrane used for the water-repellent layer and the mixture sheet prepared as the catalyst layer is low. Therefore, as a countermeasure against this, it has been proposed to simply improve the pressure bonding strength of the same material. However, if the pressure bonding strength is simply increased, the supply of oxygen to the positive electrode catalyst layer is hindered, sufficient polarization characteristics as an air oxygen reduction electrode cannot be obtained, and the variation in the Gurley value of the electrode also becomes large, resulting in It was found that a reliable zinc-air battery could not be obtained.

Further, as a countermeasure against this, there has been proposed a manufacturing method in which a solvent such as alcohol is impregnated in advance in a water-repellent microporous membrane which is a water-repellent layer, and the catalyst layer (mixture sheet) is bonded as it is. However, in this case, the impregnated solvent cannot be completely removed in the subsequent steps, so that when the battery is overdischarged, liquid leakage may occur from the air holes.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above situation, and an object thereof is to prevent the occurrence of a short life in discharge in a high temperature region in an air zinc battery.

[0011]

That is, according to the present invention, oxygen is used as a positive electrode acting substance and zinc is used as a negative electrode acting substance, and the electrode layer for reducing the positive electrode oxygen is at least a catalyst layer for adsorbing and reducing oxygen, and In a zinc-air battery having a water-repellent layer pressure-bonded to a catalyst layer, the water-repellent layer has a Gurley value of 50 to 50.
The present invention relates to a zinc-air battery, which is formed by press-bonding a material of 0 second to the catalyst layer.

Further, in the present invention, a metal positive electrode current collector is pressure-filled with an oxygen reduction catalyst sheet to form a catalyst layer, and a water repellent layer is obtained by pressure-bonding a material having a Gurley value of 50 to 500 seconds on one surface thereof. And a method for manufacturing an oxygen electrode of a zinc-air battery.

As described above, in the present invention, a material having a Gurley value of 50 to 500 seconds is used as the water-repellent layer, and the catalyst layer is pressure-bonded to the water-repellent layer. Can be eliminated.

Conventionally, the water-repellent layer has a Gurley value of 1500 to 20.
A material of 00 seconds was used, which was pressed onto the catalyst layer. In that case, as described above, a short life occurs due to discharge at high temperature, and when the battery is disassembled and investigated, an electrolyte solution accumulates between the water repellent layer and the catalyst layer, which causes the short life. I knew it was. In the present invention, focusing on this point, by using a material having a Gurley value in the above range as the water-repellent layer and press-bonding the material to the catalyst layer to form an oxygen electrode, the above-mentioned problems could be solved. .

The Gurley value in the above is a numerical value indicating the air permeability in accordance with JIS 8117, and specifies the time (seconds) during which 100 ml of air passes through an area of 645 mm ² of a test object such as paper. It is measured and calculated using a device. The higher the value, the lower the air permeability.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. PR44P (diameter 11 mm, total height 4.5 mm) was used as a typical air zinc battery. The sectional view is shown in FIG.

As shown in FIG. 1, this battery has an oxygen reduction electrode 14 for taking in oxygen in the atmosphere as a positive electrode, and a gel housed in a negative electrode case 11 which also serves as a current collector and a sealing member as a negative electrode. A button type air zinc battery having a negative electrode 10 (a mixture of an aqueous solution of potassium hydroxide as an electrolyte and zinc powder). The gel negative electrode 10 contains 30 as an electrolytic solution.
Grain size 1 containing 1% mercury and 500 ppm lead as an alloy as zinc using an aqueous solution of potassium hydroxide in weight%
Using zinc phosphide powder of 0 to 300 μm, the weight ratio of the electrolyte solution to the zinc powder is 250 g of the electrolyte solution to 1 kg of the zinc powder,
These are mixed with polyacrylic acid (gelling agent).

On the other hand, the positive electrode side will be described. A positive electrode case 1 having an air hole 2 on the bottom surface and PTFE inside the positive electrode case 1.
A water-repellent film 4 made of a film, an oxygen reduction electrode 14, and a separator 7 are placed. The oxygen reduction electrode 14 is activated carbon,
A positive electrode catalyst layer 6 formed by forming a positive electrode catalyst powder composed of manganese oxide, a conductive material and PTFE powder into a sheet shape is pressure-bonded and integrated into a nickel-plated positive electrode current collector 5 made of a stainless steel net, and then repelled. The water repellent layer 8 is formed by pressure-bonding a PTFE film different from the water film 4. Three
Is a diffusion paper, and is placed inside the positive electrode case 1 so as to cover the air holes 2. Reference numeral 13 is a seal tape.

Example 1 The positive electrode catalyst layer 6 is the positive electrode current collector 5
In the sheet molded body which has been pressure-bonded with, a microporous film made of PTFE having a Gurley value of 500 seconds is used as the water-repellent layer 8 so that the Gurley value of the oxygen reduction electrode 14 after pressure bonding is 10,000 seconds.
It mechanically crimped using a metal roller. Using the oxygen reduction electrode, the zinc-air battery shown in FIG. 1 was produced.

(Example 2) Gurley value of 10 as the water-repellent layer 8
Using a PTFE microporous membrane for 0 seconds, the oxygen reduction electrode 14 was mechanically pressure-bonded using a metal roller so that the Gurley value of the oxygen reduction electrode 14 after the pressure bonding was 10,000 seconds. The zinc-air battery of FIG. 1 was produced in the same manner as in Example 1 except for the above.

(Embodiment 3) The water repellent layer 8 has a Gurley value of 50.
Second, a microporous membrane made of PTFE was mechanically pressure-bonded using a metal roller so that the Gurley value of the oxygen reduction electrode 14 after pressure-bonding was 10,000 seconds. The zinc-air battery of FIG. 1 was produced in the same manner as in Example 1 except for the above.

(Conventional example) A microporous film made of PTFE having a Gurley value of 2000 seconds is used as the water-repellent layer 8 and a metal roller is used so that the Gurley value of the oxygen reduction electrode 14 after pressure bonding is 10,000 seconds. Crimped The zinc-air battery of FIG. 1 was produced in the same manner as in Example 1 except for the above.

(Comparative Example 1) The water-repellent layer 8 has a Gurley value of 1000.
Second, a microporous membrane made of PTFE was mechanically pressure-bonded using a metal roller so that the Gurley value of the oxygen reduction electrode 14 after pressure-bonding was 10,000 seconds. The zinc-air battery of FIG. 1 was produced in the same manner as in Example 1 except for the above.

(Comparative Example 2) The water repellent layer 8 has a Gurley value of 10
Second, a microporous membrane made of PTFE was mechanically pressure-bonded using a metal roller so that the Gurley value of the oxygen reduction electrode 14 after pressure-bonding was 10,000 seconds. The zinc-air battery of FIG. 1 was produced in the same manner as in Example 1 except for the above.

The method for producing the PTFE microporous membrane in each of the above examples will be described below. As a method for producing a porous PTFE membrane, there have been conventionally the following methods.
A process comprising the steps of mixing a fine powder of PTFE and a filler and molding it into a film, removing the filler and opening pores, stretching the film and controlling the air permeability thereof. Was the way. In the present invention, the PTFE films used for the water repellent film 4 and the water repellent layer 8 were produced by the biaxial stretching method. The Gurley value was controlled by the amount of stretching, which is a method in which a large number of micropores are generated by mechanically stretching the PTFE film formed into a sheet in advance. Generally, when the Gurley value becomes smaller, the PTF
The mechanical strength of the E film decreases. The stretching speed was adjusted to avoid the breakage of the film caused by this.

100 batteries of each of the above-mentioned examples, conventional examples, and comparative examples were produced, and 50 of them were each subjected to a temperature of 2
It was discharged at 62Ω in an environment of 0 ° C and a humidity of 60%, and the duration until the final voltage was 1.0 V was examined. The number of batteries certified as having a short life was confirmed, assuming that the duration was 20 hours or less as a short life. Next, the remaining 50 batteries were similarly tested at a temperature of 45 ° C. DRY to confirm the number of short-life batteries. The results are shown in Table 1.

[0027]

[Table 1]

From the results shown in Table 1, all batteries were
Although the short life does not occur at a humidity of 60%, 10 short lives occur in the conventional example under the condition of 45 ° C. DRY. Further, the comparative example 1 has a short life of 3, and the comparative example 2 has a short life of 10. On the other hand, it was confirmed that in Examples 1 to 3, no short life occurred.

When the battery having a short life was disassembled, in the conventional example and the comparative example 1, an electrolytic solution accumulation was confirmed between the water repellent layer 8 and the catalyst layer 6. It is considered that this is because the electrolytic solution rapidly permeated due to the discharge at a high temperature, and the electrolytic solution accumulated in front of the water-repellent layer 8. On the other hand, in Comparative Example 2, an electrolytic solution accumulation was confirmed between the water repellent layer 8 and the water repellent film 4. It is considered that the cause of the short life is the same, but the place where the electrolytic solution accumulates was different.

Although the reason for this is not clear, in Comparative Example 2, the PTFE film used for the water repellent layer 8 has a small Gurley value, so that the film density is low and the mechanical strength is weak. It was necessary to increase the pressure when mechanically pressure-bonding this to the catalyst sheet molded body. As a result, it is considered that the PTFE film was excessively stretched, the numerous micropores existing in the PTFE film became large, and the electrolyte solution flowed out from there during discharge, resulting in a short life.

[0031]

As described above, the zinc-air battery of the present invention discharges stably even in a high temperature environment, and does not have a short life as in the prior art.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a zinc-air battery that is an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive electrode case, 2 ... Air hole, 3 ... Diffusion paper, 4 ... Water repellent film, 5 ... Current collector, 6 ... Positive electrode catalyst layer, 7 ... Separator, 8
... Water repellent layer, 10 ... Gel negative electrode, 11 ... Negative electrode case, 12 ...
Gasket, 13 ... Seal tape, 14 ... Oxygen reduction electrode.

Claims (5)

[Claims] 1. An electrode layer for reducing positive electrode oxygen, comprising oxygen as a positive electrode acting substance and zinc as a negative electrode acting substance, and at least:
In an air zinc battery having a catalyst layer that adsorbs and reduces oxygen, and a water repellent layer pressure-bonded to the catalyst layer, the water-repellent layer is obtained by pressure-bonding a material having a Gurley value of 50 to 500 seconds to the catalyst layer. An air zinc battery characterized by being formed. 2. The zinc-air battery according to claim 1, wherein the material having a Gurley value of 50 to 500 seconds is polytetrafluoroethylene. 3. The zinc-air battery according to claim 1, wherein the water-repellent layer and the catalyst layer are bonded together by mechanical pressure bonding. 4. A positive electrode current collector made of metal is pressure-bonded with an oxygen reduction catalyst sheet to form a catalyst layer, and a material having a Gurley value of 50 to 500 seconds is pressure-bonded to one surface thereof to form a water repellent layer. A method for manufacturing an oxygen electrode of a zinc-air battery, comprising: 5. The method according to claim 4, wherein a material having a Gurley value of 50 to 500 seconds is pressure-bonded to the catalyst layer with a metal roller, and the pressure is adjusted so that the oxygen electrode after the pressure has a Gurley value of 10,000 seconds. Method for manufacturing oxygen electrode of zinc-air battery.