JPH0133025B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in the manufacturing method of air electrodes used in air batteries, and is aimed at improving the storage performance of air batteries. Conventional air electrodes are manufactured by mixing powdered carbon powder with a water-repellent binder such as polytetrafluoroethylene (PTFE) powder, and then press-molding the mixture onto a conductive material such as nickel net into a thin plate shape. was. The above-mentioned conventional air electrode has a disadvantage that the activity of the surface of the carbon powder deteriorates during long-term storage, resulting in a decrease in oxygen reduction ability and a deterioration in the storage performance of the battery. In order to improve this, catalysts such as silver, palladium, and platinum were added and mixed to maintain the oxygen reduction ability, but the amount added was large and expensive. It is an object of the present invention to obtain an air battery that is inexpensive and has good characteristics in long-term storage and long-term discharge with a weak current, using an air electrode in which cobalt phthalocyanine having a sulfonic group and a sulfonic acid derivative of the present invention is coexisting. This is what I did. The air electrode 3 of the present invention uses a powdery carbon powder with a surface area of about 800 m ² /g obtained by a gas adsorption method, and is made of a cobalt phthalocyanine derivative having a hydrophilic sulfon group and a sulfonic acid derivative as shown in the following formula. Dissolve 2g in 200c.c. of water and add 10g of carbon powder to this solution.
After thoroughly soaking, remove moisture by straining,
Stainless steel is produced by drying under reduced pressure at 100℃ to evaporate moisture, heat-treating the cobalt phthalocyanine sulfonic acid derivative and carbon powder in an electric furnace, and treating it with an emulsion of PTFE, a water-repellent binder. They are held together from both sides by nets to form air electrodes. Especially 350℃~1000℃
It is thought that the carbon powder that was heat-treated between 2 and 3 times showed excellent oxygen reduction ability, and that the heat treatment changes the cobalt phthalocyanine in the catalyst into a highly conjugated bond, making the carbon powder stable and lasting. However, at temperatures below 350°C, the co-yoke does not proceed, so much effect is not observed, and at temperatures above 1000°C, cobalt phthalocyanine sublimes significantly due to heat, so the expected effect cannot be obtained. It should be noted that when the heat treatment was carried out in an inert gas such as nitrogen or argon, a reducing gas such as hydrogen, or in a vacuum, the weight loss due to oxidation was less and the effect was better. The electric electrode of the present invention uses cobalt phthalocyanine having a sulfonic group and a sulfonic acid derivative as shown in the following formula. In addition, in the air electrode of the present invention, the surface of the carbon powder is treated to be water-repellent, and the electrolyte is given viscosity, so that an extremely thin layer of the electrolyte is formed on the surface of the carbon powder through wetting due to penetrating force and surface tension, and oxygen Since it maintains a high reducing ability and can secure a wide discharge area, it can provide high performance when used in air batteries. Furthermore, it is also possible to regulate the voltage by allowing the cobalt phthalocyanine to coexist with a substance having a more noble potential than oxygen, such as manganese dioxide, nickel oxyhydroxide, silver oxide, etc., so that the air electrode can operate normally. was confirmed. A button-type air cell using an air electrode according to an embodiment of the present invention will be explained based on the drawings. 1 is a positive electrode can that also serves as a positive electrode terminal, and is provided with an air supply hole 2 at the bottom; 3 is an air electrode of the present invention; in contact with the bottom of the positive electrode can 1 is a conductive porous reinforcement 4 such as a stainless steel net. Both sides are reinforced, and the periphery is pressed and fixed with a gasket 5. 6 is viscosity 10000
The electrolyte retaining layer is impregnated with centipoise caustic alkaline gel electrolyte, is a nonwoven fabric or porous material with excellent retention and liquid resistance, and is interposed between the negative electrode 7 and the air electrode 3. . 8 is a load can that also serves as a load terminal, and is connected to the positive electrode can 1 through the gasket 5.
The battery is sealed by bending the opening. A liquid-absorbing paper 9 is interposed inside the air supply hole 2 to prevent the electrolyte from leaking, and absorbs leaking electrolyte.An air electrode is placed outside the air supply hole 2 due to the influence of carbon dioxide gas during storage. A sealing material 10 is attached to prevent air from entering so as to prevent the parts from deteriorating. Next, cobalt phthalocyanine having a sulfonic group and a sulfonic acid derivative according to the present invention and An air electrode made of carbon powder and a diameter of 11.5 mm using a caustic potash electrolyte with a viscosity of 10,000 centipoise.
Thirty pieces each of the button-type air battery of the present invention [A] with a height of 5.2 mm and the conventional product of the same type air battery [B] using a conventional air electrode made of carbon powder,
Store at 25℃, 10 each for 6 months and 12 months,
Table 1 shows the retention rate of discharge capacity with respect to the initial stage after discharging at a constant current of 1.5 mA and setting the product [A] of the present invention as 100.

[Table] Table 2 also shows the results of calculating the capacitance efficiency of the air electrode from the zinc utilization efficiency after long-term discharge with a weak current of 0.1 mA.

[Table] Table 1 shows that the air battery using the air electrode of the present invention has excellent storage performance, and Table 2 shows that it can withstand long-term discharge with a weak current. As described above, an air electrode manufactured from cobalt phthalocyanine having a sulfonic group and a derivative of sulfonic acid and carbon powder provides an air battery that is inexpensive and has good characteristics in long-term storage and long-term discharge with weak current. be able to.

[Brief explanation of drawings]

The figure is a sectional view of an air cell using an air electrode according to an embodiment of the present invention. 1... Positive electrode can, 2... Air supply hole, 3... Air electrode.

Claims (1)

[Claims] 1. A mixture of cobalt phthalocyanine having both a sulfonic group and a sulfonic acid derivative and carbon powder mixed in water is overdried, heated in a non-oxidizing atmosphere, and then polytetrafluoroethylene is added. A method for manufacturing an air electrode, characterized by: