JPH1154130A - Air electrode for air cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a catalyst layer from collapsing in an air cell, in which the catalyst layer consisting of an oxygen reduction catalyst and a collector body and an air electrode consisting of a gas diffusion layer, are arranged inside a positive electrode case. SOLUTION: By using an air electrode stamping punch 14 possessing a projection step part 15 on an air electrode abutting face, the air electrode is formed into a truncated cone shape with a larger diameter of a collector body larger than a catalyst part, and the truncated cone shape air electrode is used. As the collector body diameter, that is, a bottom part 17 of the air electrode is large, sufficient contact with a positive electrode case can be secured, and on the other hand, application of friction with the positive electrode case inside wall is suppressed in insertion of the air electrode into the positive electrode case as the diameter of a top face 18 in the catalyst part is small, so that electrically stable and highly fluid-leakage-resistant battery, in which the catalyst layer is prevented from collapsing and being clamped and excellent fluid- tightness is provided, can be provided stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air battery in which an air electrode comprising a catalyst layer comprising an oxygen reduction catalyst and a current collector and a gas diffusion layer is disposed inside a positive electrode case.

[0002]

2. Description of the Related Art An air battery has a higher energy density than other primary batteries because it uses a large amount of a negative electrode active material because oxygen in the air outside the battery is used as a positive electrode active material. In addition, since it has features such as low mercury, environmental friendliness, and stable discharge voltage until the end of discharge, there is a great demand for hearing aid power supplies.

FIG. 5 shows the structure of a conventional zinc-air battery. As shown in FIG. 5, the zinc electrode 1 is housed in a sealing plate 2 which is a negative electrode case, seals the positive electrode case 4 via a gasket 3, and a separator 5 is composed of a catalyst-based air electrode 6 and a zinc electrode. Isolate one. Numeral 7 denotes a water-repellent film for supplying oxygen in the air to the inside of the battery and preventing the electrolyte from leaking out of the battery. In contact. The seal paper 10 seals the air hole 8 when the battery is not used, prevents air from entering the battery, and prevents deterioration of the battery.

In the above-described conventional zinc-air battery, the conductivity between the current collector in the air electrode 6 and the positive electrode case 4 depends on the circumferential end face of the circularly punched current collector and the inside of the side wall of the positive electrode case 4. Obtained by contact. Therefore, when the diameter of the air electrode 6 is small, sufficient contact with the positive electrode case 4 cannot be obtained, and the internal resistance of the battery increases, and a discharge abnormality occurs in which the voltage decreases during discharging.

[0005]

In order to prevent this,
In conventional air batteries such as zinc-air batteries, the air electrode was made larger.However, if it was too large, when the air electrode was inserted into the positive electrode case when the battery was constructed, the air electrode formed into a sheet shape was not used. When the catalyst is rubbed against the inner wall of the positive electrode, the circumference of the catalyst portion of the air electrode collapses, and a massive catalyst is formed inside the battery. When a battery is formed in this state, a massive catalyst is interposed between the battery components as a foreign substance, so that a liquid-tight sealing cannot be performed and the liquid leakage resistance is reduced. For this reason, the diameter of punching the cathode from the constituent material of the cathode has to be controlled in a narrow range, and it has been necessary to exchange the punch for the cathode in a relatively short period of time.

Accordingly, the present invention is directed to an air electrode for supplying an air cell which has a low catalyst internal resistance and a low cell internal resistance and has excellent liquid leakage resistance, and an air cell for an air cell which has a small exchange of a punch for punching the air electrode. It is intended to realize a method for manufacturing a cathode.

[0007]

According to the present invention, in order to solve the above-mentioned problems, an air electrode comprising a catalyst layer in which a current collector is unevenly distributed in an oxygen reduction catalyst and a gas diffusion layer is provided inside a positive electrode case. In the air electrode for an air battery to be provided, the air electrode has a shape in which the diameter on the current collector side is larger than the diameter of the catalyst surface on the side opposite to the current collector side.

Therefore, the side surface of the current collector having a large diameter dimension contacts the inner wall surface of the positive electrode case to achieve good conduction, and the side surface of the weak catalyst layer is rubbed against the inner wall surface of the positive electrode case during battery construction. Less, so that the periphery of the catalyst does not fall off.

Further, according to the present invention, an air electrode punch having a protruding step at the tip is used to bend the catalyst layer in which the current collector is unevenly distributed in the oxygen reduction catalyst from the current collector side and to punch out the current collector. This is a method for manufacturing an air electrode for an air battery having a truncated cone shape whose body side diameter is larger than the diameter of the catalyst surface opposite to the current collector side.

Then, at the air electrode according to the method of the present invention,
An air electrode having a diameter on the current collector side larger than the diameter of the catalyst surface opposite to the current collector side can be easily manufactured.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be carried out in the form described in the claims. As described in the claim 1, the catalyst layer and the gas diffusion layer in which the current collector is unevenly distributed in the oxygen reduction catalyst are provided. In the air electrode for an air battery in which the air electrode composed of: is disposed inside the positive electrode case, the air electrode has a truncated cone shape in which the diameter on the current collector side is larger than the diameter of the catalyst surface on the side opposite to the current collector side. Is used, the current collector side having a large diameter contacts the inner wall of the positive electrode case, and the periphery of the catalyst layer where no current collector is present is less rubbed by the inner wall of the positive electrode case during battery construction. Does not fall off.

According to a second aspect of the present invention, a catalyst layer in which a current collector is unevenly distributed in an oxygen reduction catalyst is bent and punched from the current collector side by an air electrode punch having a protruding step at the tip. This makes it possible to easily produce a truncated conical air electrode having a diameter on the current collector side larger than the diameter of the catalyst surface on the side opposite to the current collector side.

That is, when the air electrode is manufactured by punching out a catalyst material having a sheet-shaped gas diffusion layer on one side,
At the tip of the punch, a projecting step with a slightly smaller diameter launches the center of the air electrode and punches out in a deflected state, so that the air electrode to be produced is located on the side of the current collector 11 close to the punch as shown in FIG. It has a truncated cone shape whose diameter is larger than the diameter of the portion of the catalyst surface 12 opposite to the current collector 11 side. In addition, 13 in FIG. 1 is a gas diffusion layer.

According to a third aspect of the present invention, the thickness of the air electrode is a, and the height of the protruding step on the surface in contact with the air electrode is h.
In this case, by using a punching punch satisfying 0.02a ≦ h ≦ 0.50a, the manufacturing method described in claim 2 can be easily implemented.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

First, a punch for punching an air electrode was actually manufactured. The produced punch had a diameter of PR536 (diameter 5.8 mm, height 3.6 m) equal to the inner diameter of the bottom of the positive electrode case.
m), the height h of the projection 15 provided at the tip of the punch 14 is 0.01 a with respect to the thickness a of the air electrode as shown in FIG.
3 and a total of 9 types of punches having a flat surface 16 as shown in FIG.
Type. Then, a battery was prepared using the air electrodes punched by the above nine types of punches, and the resistance to leakage from the sealing portion and the air hole was evaluated. In the example shown in FIG. 2, a truncated cone having a top surface 18 slightly smaller in diameter than the bottom portion 17 is formed. In the conventional case shown in FIG. 3, the bottom portion 17 has the same diameter as the top surface and the current is collected as shown in a cross section in FIG. Body 11a, catalyst surface 12
a and each diameter of the gas diffusion layer 13a are the same.

The test for the resistance to liquid leakage from the sealing portion was conducted at 45 ° C. and 92% R.F. H. After storage under high temperature and high humidity conditions, cresol red was sprayed at room temperature to color, and leakage of the alkaline electrolyte from the gap between the positive electrode case and the gasket or the gap between the gasket and the sealing plate was confirmed. . Table 1 shows the results after storage for 4 weeks.

[0018]

[Table 1]

In Table 1, leakage occurs in the conventional example and in a battery using an air electrode punched with a punch having a height h of 0.01 a of the projecting step 15 of 0.01 a. Since the catalyst was observed inside the battery, it was found that the catalyst was effective when the height h of the projection 15 of the punch was 0.02a or more.

On the other hand, the leak resistance test from the air hole is 45.
70% R.C. H. Was discharged at a constant resistance of 3.0 kΩ under the conditions of high temperature and high humidity, and leakage of the electrolyte from the air holes during the discharge and in the overdischarged state was observed. Table 2 shows the number of liquid leaks after overdischarge for 3 weeks.

[0021]

[Table 2]

In a zinc-air battery, the pressure inside the battery after discharge rises due to volume expansion accompanying oxidation of the negative electrode zinc due to discharge, and the electrolyte is pushed out of the battery through the air hole, and leakage from the air hole is caused. May occur. In Table 2,
When the battery using the air electrode punched with a punch having a height h of the protrusion 15 of 1.00 a or more was disassembled and observed, a circular mark was formed on the gas diffusion layer due to the protrusion of the punch, and the liquid leaked from here. The gas diffusion layer was damaged by the pressure at the time of punching the air electrode because of the occurrence of the gas discharge, and could not withstand the pressure increase inside the battery after the discharge.

[0023]

As described above, according to the present invention, the air electrode of the catalyst layer having a truncated cone shape whose current collector side obtained by using a punch having a protruding step at the tip is larger than the diameter of the opposite side is obtained. By using this, it is possible to stably obtain a battery that is electrically stable, prevents collapse and entrapment of the catalyst layer, has excellent liquid tightness, and has high liquid leakage resistance by a simple configuration and a manufacturing method.

[Brief description of the drawings]

FIG. 1 is a diagram showing an air electrode punched by an air electrode punch of the present invention.

FIG. 2 is an enlarged schematic view of a main part of the air electrode punching punch of the present invention.

FIG. 3 is an enlarged schematic view of a main part of a conventional air electrode punching punch.

FIG. 4 is a view showing an air electrode punched by a conventional air electrode punch.

FIG. 5 is a half sectional side view of a conventional zinc-air battery.

[Explanation of symbols]

 11, 11a Current collector 12, 12a Catalyst surface 13, 13a Gas diffusion layer 14 Punch 15 Projection 17 Bottom 18 Top surface

Claims (3)

[Claims] 1. An air electrode for an air battery in which an air electrode composed of a catalyst layer in which a current collector is unevenly distributed in an oxygen reduction catalyst and a gas diffusion layer is disposed inside a positive electrode case, wherein the air electrode is a current collector. An air electrode for an air battery, wherein the diameter of the body side is larger than the diameter of the catalyst surface on the side opposite to the current collector side. 2. An air electrode punch having a protruding step at its tip is used to deflect the catalyst layer in which the current collector is unevenly distributed in the oxygen reduction catalyst from the current collector side and to punch out the catalyst layer, so that the diameter of the current collector side is reduced. A method of manufacturing an air electrode for an air battery, wherein the diameter of the air electrode is larger than the diameter of the catalyst surface opposite to the current collector. 3. When the thickness of the air electrode is a and the height of the protruding step is h, the air electrode is punched using an air electrode punch having a relationship of 0.02a ≦ h ≦ 0.50a. A method for producing an air electrode for an air battery according to claim 2.