JPS58121561A - Manufacture of gas diffusion electrode for battery - Google Patents

Abstract

PURPOSE:To form a catalyst layer having uniform thickness by placing catalyst powder and polytetrafluorohtylene aqueous suspension in a press mold and pressing them with a press. CONSTITUTION:A lower punch 2 is put in a bottom of a die 1 having an inner diameter of 30cm, and a catalyst slurry comprising 3pts.wt. platinum black powder having a particle size of about 10mum and 5pts.wt. polytetrafluoroethylene aqueous suspension (20%) is poured thereon. Then an upper punch 4 is placed inside the die 1. This press mold is pressed at a pressure of 200kg/cm<2> with a press. A cake obtained is heated at 300 deg.C to form a gas diffusion electrode. When a large electrode is manufactured, a metallic net 6 (about 100 mesh) is used as a reinforcing material and a current collector. The scattering in thickness of an electrode is 0.01mm. or less, and is better than that of 0.02mm. of a conventional electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a gas diffusion electrode in which a catalyst layer of uniform thickness is provided by pressing slurry-like raw materials.

Conventionally, polyester fibers are placed on porous substrates as electrodes for fuel cells, etc.
K, which manufactures a gas diffusion chain equipped with a catalyst layer using ethylene chloride as a binder, uses a method of applying a mixture of catalyst powder and a binder onto a porous substrate with a trowel or by blow-sewing it. Ta. However, with this method, not only does it require considerable skill to form a layer on a porous substrate, but also there is considerable variation in the thickness of the catalyst layer, especially in the thickness of the catalyst layer. Is it a serious drawback? [
It was +. A single variation can cause a fire during battery work.1
It was a long time ago, and I was in Chiro's first row. Also, Sho Kosho 38
-963 MF', a mixture of carbon powder and polytrifluorochloride ethylene is made into a thin film in advance,
A method has been proposed in which the film is crimped onto a conductor of 1-quality material, but in this method, the film is rolled onto a thin film. It has six drawbacks. In addition to these methods, a method has been proposed in which a slurry of a mixture of catalyst powder and polytetrafluoroethylene aqueous suspension is deposited on a porous substrate by a vacuum filtration method to create a cake cake, and then pressurized. has been done.

However, even when this method is used, although the webbing is almost uniform near the center, cracks tend to appear on the periphery.

Moreover, steps such as making the cake, pressing it, and cutting it into a desired shape are required, which poses a problem from the viewpoint of industrial productivity.

The present invention aims to eliminate the upper Ne defect, and its main feature is a method in which a catalyst powder and a polytetrafluoroethylene water suspension are placed in a press mold and pressurized by a press. → - Wow, if such a method is adopted, a catalyst layer having a uniform thickness can be formed without any skill required. Furthermore, the number of steps required for this process is kept to a minimum, which is very advantageous for industrial productivity.

Examples of the present invention will be shown below.

FIG. 1 shows a press mold. Put the matching male mold 2 into the bottom of the female mold 1 with an inner diameter of 30 mm, and add 3 parts of platinum black powder with a particle size of about 10 μm as a catalyst and a polytetrafluoroethylene water M suspension (20%) 5 Pour 3 parts of the mixed slurry. Furthermore, another male mold 4 is placed into the female mold 1 from above. Place the pressed mold filled with strained silk into a press machine, and
[] Press OK. 3 cakes obtained in this way
The gas diffusion electrode of the present invention can be obtained by heat treatment at 00°C. In this case, to make a large electrode for the funeral, pour the slurry into the male mold placed inside the female mold with a metal mesh (about 100 mesh) placed as a reinforcing material and current collector. FIG. 2 shows a gas dispersion electrode obtained by using the same manufacturing method as in the fabrication example.

The variation in the thickness of the electrodeposition obtained by the present invention is 0.0
It is less than 1 m1, which is longer than the best value of 0.02 m obtained conventionally. Moreover, in the case of the conventional manufacturing method, the thickness of the periphery is different from that of the center, so the variation was evaluated only in the I'X in the middle and around the edges. The exposed gas diffusion electrode is uniform over the entire surface and can be built into the mold of the product at the pressing stage without the need for extra cutting around the edges unlike conventional products, making it efficient and efficient in terms of materials. Since then, there has been no need to waste any more.

According to the method of the present invention, the catalyst is □
Manufacturing gas diffusion electrodes by forming layers or applying nitrogen by blowing them previously required a lot of skill, but now even beginners can easily manufacture gas diffusion electrodes, and the thickness of the catalyst layer can be increased. However, it is extremely uniform and there is little variation in the product due to individual differences. Moreover, industrial productivity can be greatly improved, as the number of processes involved in manufacturing is extremely small.

In addition, when producing a mixed cake of catalyst powder and polytetrafluoroethylene, all conventionally known catalysts can be used as the catalyst powder.

[Brief explanation of drawings]

Fig. 1 is a cross section of a press mold showing an example of the method of the present invention, and Fig. 2 is an example of a gas diffusion electrode obtained by the method of the present invention, which includes a wire mesh for reinforcement. 1.Female mold 2.Male mold (lower part) 3.Mixed slurry of electrode material 4.Male mold (upper part) 5.Mold stand 6.Wire mesh and above Figure 2

Claims (1)

[Claims] (1) Mix catalyst powder alone or a mixture with a powder with good electrical conductivity, powder of binder (polytetrafluoroethylene, etc.) and a suitable dispersion medium, and add a dispersant in the form of a solution. 1. A method for manufacturing a gas diffusion electrode for a battery, which method comprises forming a slurry by cold pressing into a desired shape.