JPH0151026B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electrode plate for a fuel cell, and in particular is formed by carbonizing a carbon material and a binder, and is formed to be capable of holding an electrolyte inside. This invention relates to an electrode plate for fuel cells.

[Background of the invention]

Conventionally, the electrode plates of a fuel cell consist of a pair of electrode plates 1A and 1B, as shown in FIG. . As shown in FIG. 2, the electrode plates 1A and 1B each have a carbon material 4 such as carbon fiber, carbon powder, or carbon particles as their main material, and a binder 5 such as a phenolic resin is mixed therein, and then heated using a heat press or the like. By curing and binding the binder 5,
It is known that a flat plate part 6 and a plurality of protrusions 8 forming gas passages 7 on one side thereof are integrally molded and then carbonized and fired at a high temperature.

When a battery generates power, the electrolyte gradually evaporates and disappears as water vapor generated by the battery's power generation is released to the outside of the battery, shortening the battery life.
As a method of preventing this, a method is generally adopted in which the gap in the electrode plate 1 is used as an electrolyte reservoir, and the electrolyte that is insufficient due to evaporation is replenished to maintain battery life.

The space used as an electrolyte reservoir in such an electrode plate is approximately 20 to 30% of the total space, but in order to constitute this space, it is necessary to reduce the amount of the carbon material 4 or the binder 5. However, when such a gap is provided, the strength of the entire electrode plate is reduced and the electrode plate is difficult to handle.In addition, when the gas flow path 7 is formed by cutting, the protrusion 8 on the side surface of the gas flow path is It has the disadvantage of being easily chipped. Furthermore, if the material is to be molded by a press or the like, as shown in FIG. Easy to refine. As a result, gas diffusion may become insufficient, and the protrusions 8 are porous and have a low density, resulting in high electrical resistance and reduced battery efficiency.

Therefore, in conventional press-based manufacturing of electrode plates, if the electrode plate is made more porous to form an electrolyte reservoir to store the electrolyte that is insufficient due to evaporation loss, the strength decreases, and conversely, the strength decreases. When the electrode plate was raised, there was a problem in that the necessary voids for storing electrolyte within the electrode plate could not be obtained. In order to solve this problem, it has been necessary to perform complicated operations such as filling the recesses of the press mold (corresponding to the protrusions of the electrode plate) with a carbon material in advance and heat pressing.

[Purpose of the invention]

An object of the present invention is to provide an electrode for a fuel cell of this type that has sufficient porosity to store electrolyte that is insufficient due to evaporation during power generation without reducing mechanical strength, and has low electrical resistance. The purpose is to provide a board.

[Summary of the invention]

That is, the present invention is a porous plate obtained by carbonizing a carbon material and a binder, and has a flat plate part and a plurality of protrusions on one side of the plate part for forming a gas flow path. A concave portion is provided on the flat plate portion side corresponding to the protruding portion, and a tip portion of the protruding portion is made into a porous portion having a higher density than the flat plate portion, and an electrode plate main body is provided within the concave portion. The intended purpose is achieved by filling the electrolyte holding material with a larger internal pore than that of the electrolyte holding material.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 4A is a sectional view of an electrode plate according to an embodiment of the present invention.

In this example, carbon fiber is used as the main material,
A recess 10 is provided at the position of the flat plate part 6 corresponding to the protruding part 8 constituting the gas flow path 7, and the area around the bottom of this recess, that is, the tip of the protruding part 8 is made to have a higher density than the flat part 6. Form into. The recess 10 is filled with an electrolyte retaining material containing metal phosphate as a main component.

Such an electrode plate can be manufactured, for example, by a filtration method as follows. First, an aqueous dispersion solution in which carbon fibers are appropriately dispersed is filtered through a filter to form a mat of carbon fibers on the filter. The dried pine is then impregnated with a binder, such as a phenolic resin.

Next, as shown in FIG. 4B, the mat 11 impregnated with a binder is sandwiched between molds A and B, and the heights of the gas flow path, ridges, and recesses are adjusted to predetermined dimensions using a heat press or the like. The binder is cured by applying pressure and heat, and then heated at a high temperature in an inert gas or vacuum to fully carbonize it. It is important to note that when forming these protrusions, as shown in Figure 6, the molding process during heat pressing is done so that the gas outlet and the protrusions have different dimensions. be. In this way, the protruding portion 8 has a higher density than the gas flow path portion 7.

In this way, a porous electrode plate is obtained which has a protrusion forming a gas flow path on one side and a recess for filling an electrolyte holding material on the other side. Next, an electrolyte retaining material in the form of a paste is applied to the electrode recessed surface of the electrode plate using a doctor blade method or the like to fill the recessed part.

After constructing a battery using a porous electrode plate filled with an electrolyte holding material as described above, an electrolyte is injected between both electrodes and the electrolyte is held in the electrolyte holding material. In this way, in the battery, as shown in FIG. 5, during battery power generation, the electrolyte evaporates from the gas flow path 7 in the direction of the arrow, and the electrolyte retaining layer 3 and the recess 10
There is a difference in the amount of electrolyte between the recess 10 and the electrolyte retaining material filling section, and the electrolyte in the recess 10 moves through the catalyst layer 2 to the electrolyte retaining layer in the direction of the arrow.

In addition, since the protrusions 8 are highly dense, the strength of the protrusions 8 is improved, and the electrical resistance of the protrusions 8 is reduced, resulting in improved battery efficiency.

In the present invention, metal phosphate is mentioned as an electrolyte holding material, but it is not limited to this.
It may be of the same quality as the matrix normally used for the electrolyte layer, or it may be of the same quality as the electrolyte plate but with a lower density.

〔Effect of the invention〕

According to the present invention, a recess is provided in a part of the flat plate side of the electrode plate, and this recess can be filled with an electrolyte retaining material, so that the electrolyte can be retained. Since the protrusions are highly dense, the battery is mechanically strong and has low electrical resistance, thus increasing battery efficiency.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the structure of a battery, Figure 2 is an explanatory diagram schematically showing the material composition of a conventional electrode plate, Figure 3 is an explanatory diagram of a conventional electrode plate made by press molding, Figure 4A is a sectional view of an electrode plate showing an example of the present invention, Figure 4B is an explanatory diagram showing a method for manufacturing the electrode plate of Figure 4A, and Figure 5 is a cross-sectional view of the electrode plate of Figure 4A. An explanatory diagram showing the flow of electrolyte in the battery used, and FIG. 6 is a sectional view of an electrode plate showing another example of the present invention. DESCRIPTION OF SYMBOLS 1... Porous electrode plate, 2... Catalyst layer, 3... Electrolyte holding layer, 4... Carbon material, 5... Binder, 6... Flat plate part, 7... Gas flow path, 8... Protrusion Striped portion, 10... recessed portion (electrolyte holding material filling portion).

Claims (1)

[Scope of Claims] 1. A porous plate obtained by carbonizing a carbon material and a binder, which has a flat plate portion and a plurality of protrusions on one side of the plate portion for forming gas flow paths, for use in fuel cells. In the electrode plate, a grooved portion is provided on the flat plate portion side corresponding to the protruding portion, the tip of the protruding portion is made into a porous portion with a higher density than the flat plate portion, and an electrode is provided in the grooved portion. 1. An electrode plate for a fuel cell, characterized in that it is filled with an electrolyte holding material having a larger internal void than the plate body. 2. The electrode plate for a fuel cell according to claim 1, wherein the electrolyte holding material is a particle combination of metal phosphate.