JPS6046514B2 - Manufacturing method of battery air electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an air electrode used in a metal-air battery, and particularly aims to provide a manufacturing method suitable for batteries using a neutral electrolyte such as marine electrolyte as the electrolyte. It is.

Conventionally, air electrodes used in metal-air batteries have been manufactured by mixing activated carbon and graphite, impregnating and adsorbing a water repellent made of tetrafluoroethylene resin, and then press-molding the mixture. The reason why activated carbon and graphite are mixed in this way is that activated carbon has excellent activity but low strength, and this is reinforced with graphite, which has high strength. However, activated carbon and graphite differ not only in their activity and strength but also in their ability to adsorb water repellents, and when a mixture of these is impregnated with a water repellent and adsorbed, much of it is adsorbed by graphite and not much by activated carbon. Therefore, when the battery is used, the activated carbon deteriorates quickly, resulting in a shortened lifespan. For this reason, in the past, the amount of water repellent was increased so that the activated carbon could be sufficiently impregnated with and adsorbed, but this made the water repellent stronger and caused problems such as voltage rise. Board properties deteriorate,
This tendency is particularly noticeable when a neutral electrolyte solution such as seawater is used. The present invention has been made in view of the above circumstances, and its purpose is to provide a battery that has excellent electrode plate performance even when a neutral electrolyte is used, and that can maintain the life of the air electrode. A method for manufacturing an air electrode is provided.

That is, in the present invention, a water repellent agent is separately adsorbed onto activated carbon and graphite, and after these are dried, a binder is added to the activated carbon and graphite, the mixture is pulverized, and then this is placed on a substrate and shaped into a desired shape. There is a method of pressure molding.

The method of the present invention will be explained in detail below.

First, activated carbon and graphite are impregnated and adsorbed with a water repellent in which tetrafluoroethylene resin is separately dispersed.

By separately impregnating and adsorbing water repellent in this way,
The water repellent is not adsorbed only on the graphite, but appropriate amounts of the water repellent are adsorbed on each of the graphite and activated carbon. In this case, the amount of water repellent to be impregnated into the activated carbon and graphite is determined by taking into account electrode life time, electrode plate characteristics, adhesion to the substrate, etc. 32 to 7 parts of water, and 100 parts of graphite
It is preferable to use 32 to 50 parts by weight of the water repellent agent.
Next, the activated carbon and graphite impregnated with a water repellent and adsorbed thereon are dried, and then fired.

This drying is carried out, for example, at 120°C for about 3 hours, and the baking is carried out at 300-360°C for about 1 hour. Furthermore, the fired activated carbon and graphite are mixed and crushed with a binder,
This is placed on a substrate 1 shown in FIG. 1 and pressure-molded into a desired shape.

Here, the amount of graphite relative to activated carbon is preferably 80 parts by weight of graphite per 10 parts of activated carbon, and as a binder, for example, polytetrafluoroethylene resin (PTF'E) is used, and the total amount of activated carbon and graphite is Approximately 10 parts by weight per 10 parts by weight is suitable. The substrate 1 is made of a mesh such as zinc wire mesh, copper wire mesh, nickel wire mesh, etc., and the mesh size is preferably about 50 mesh in consideration of the adhesion between activated carbon and graphite. Furthermore, the breath pressure during pressurization is 500k9/C!
It is sufficient if it is equal to or larger than l. As shown in Figure 1, the air electrode thus obtained has a carbon electrode 2 made of activated carbon and graphite on a base 1 made of wire mesh. Because it is adsorbed, it has excellent air electrode characteristics such as voltage rise, and can maintain a long service life. Next, the above-described manufacturing method was specifically carried out to confirm its effectiveness.

Water repellent 1 containing activated carbon 25y and tetrafluoroethylene resin
2y was impregnated and adsorbed, and graphite 25y was impregnated and adsorbed with the water repellent 12y, and after drying at 120°C for 3 hours, they were fired at 300 to 360°C for 1 hour.

Next, this activated carbon and graphite were mixed and pulverized together with 10y of polytetrafluoroethylene resin (PTFE) as binggu, and this was placed on a base made of nickel wire mesh and 500k9/CI
Pressure molding was performed with a press pressure of L. The voltage rise characteristics of the thus obtained air electrode in seawater were investigated using a mercurous chloride electrode (HgCl2, calomel electrode) as a reference electrode. The results are shown in curve a of FIG. In contrast,
Activated carbon 25y and graphite 25y are mixed, water repellent 20y is impregnated and adsorbed into this mixture, and an air electrode is produced in the same manner as in the above example. The voltage rise characteristics were investigated.

The results are shown by curve b in FIG. Note that the method of the present invention is not limited to the above-mentioned embodiments; activated carbon and graphite may be mixed and ground together with a binder, and then granulated with alcohol or the like.

That is, after drying and calcining the activated carbon and graphite that have been impregnated and adsorbed with a water repellent agent, they are mixed and ground with Ba-Inter, and then this mixed powder is sprayed with alcohol, acetone, a cationic surfactant solution, etc. Alternatively, an air electrode is produced by stirring these together with a mixed powder to granulate them, placing the thus obtained granular carbon powder on a substrate, and press-molding it. In this case, when alcohol is used as a granulating agent, for example, mixed powder 201
A ratio of approximately 5 to 20 cc of alcohol to the amount of alcohol is preferred, and a ratio of approximately 15 cc is particularly preferred. When a granulating agent such as alcohol is used in this way, there is no scattering of powder during pressing, and the pressing operation is easy, and pressing can be performed over the entire surface of the base.
It is possible to improve the plate properties such as the life of the plate and the polarization value.

As explained above, according to the present invention, activated carbon and graphite are treated separately to make them water repellent and then mixed together, so that the air electrode has excellent properties and has a long service life. This method is extremely useful as a method for manufacturing air electrodes for metal-air-seawater batteries using a neutral electrolyte such as seawater.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an air electrode according to the method of the present invention, and FIG. 2 is a diagram showing the voltage rise characteristics of a metal-air battery using the same air electrode in comparison with that of a conventional battery. 1...Base, 2...Yoichi Bon pole.

Claims (1)

[Claims] 1. Activated carbon and graphite are separately impregnated and adsorbed with a water repellent, and after drying these, a binder is added to the activated carbon and graphite, mixed and pulverized, and then placed on a substrate and pressurized into the desired shape. A method for manufacturing a battery air electrode, characterized by molding.