JPS6250946B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to fuel cells, particularly fuel cells for electric power.

[Conventional technology]

Fuel cells, which produce electrical energy from fuel and oxidizer, are a long-known technology.
A fuel cell consists of a fuel electrode, an oxidizer electrode spaced apart from the fuel electrode, an electrolyte placed between these electrodes in contact with them, a separator that also serves as a current collector, and a fuel electrode, an oxidizer electrode and a separator. The basic structure is a gas passage for fuel gas and oxidant gas formed between the two. The electrolyte may be a solid, a spacing paste, a free-flowing liquid, or a liquid held within a matrix. Among these, fuel cells using electrolytes supported in a matrix are suitable for many applications.

However, in order for a fuel cell using an aqueous electrolyte held within such a matrix to operate under optimal conditions, the matrix must have certain properties. For example, the matrix must be hydrophilic, it must be continuous to prevent cross-over and mixing of gases within the fuel cell, it must be free of pinholes or cracks, and it is typically less than 1 mm. However, in order to reduce the internal resistance, it must be as thin as possible, and the matrix must be in close contact with the catalyst layer. Furthermore, in order to make the current distribution uniform, it is desirable that the matrix thickness be uniform and the size of the matrix pores be uniform, and the matrix material must be thermally and chemically stable and economical. Must be. If a matrix having such properties is impregnated with an electrolyte and combined with electrodes to assemble a battery, stable performance can be expected over a long period of time.

However, the matrix and electrodes are porous, and fuel gas and oxidant gas are constantly flowing through the electrode matrix, resulting in electrolyte loss through evaporation and deterioration of cell performance during long-term operation. Ta.

To eliminate this problem, the matrix can be impregnated with electrolyte from the gas path of the separator through holes drilled in the electrode base material, or the cell can be made vertical and the electrolyte passageway and upper electrolyte reservoir provided at the top of the cell can be impregnated into the matrix. A method has been proposed in which a matrix is impregnated with an electrolyte through a matrix.

[Problem that the invention seeks to solve]

Of the above proposals, the former method has the drawback that the electrolyte adheres to the electrode base material during electrolyte impregnation, which impedes gas diffusion and reduces battery output. Since impregnation is carried out from an electrolyte reservoir, there is a drawback that impregnation time is required in the case of large electrodes.

The present invention eliminates these problems and provides a fuel cell in which an electrolyte supply path for supplying electrolyte to the matrix from outside the cell can be easily configured and stable cell output can be obtained. The purpose is to make it possible.

[Means for solving problems]

The configuration of the present invention, which was adopted to solve the above-mentioned problems, is to arrange a matrix that holds an electrolyte between a pair of electrodes, a fuel electrode and an oxidizer electrode, and apply fuel to the fuel electrode and the oxidizer electrode, respectively. In a fuel cell formed by stacking unit cells in which gas and oxidant gas flow paths are interposed via a separator, an electrolyte communication hole located in the electrode is provided on at least one side of a pair of electrodes of the separator. A groove-shaped electrolyte supply path is provided that communicates with the matrix through the electrode, and this electrolyte supply path communicates with an electrolyte path that communicates the electrode, matrix, and separator through an electrolyte reservoir provided in an adjacent electrode, thereby providing electrolyte communication. It is characterized in that a water-repellent layer is provided on the hole and the surface of the electrolyte supply channel that is in contact with the electrode.

[Effect]

The present invention provides a groove-shaped electrolyte supply channel provided in a separator in contact with a fuel electrode and an oxidizer electrode, an electrolyte communication hole that communicates this electrolyte supply channel with a matrix, and an electrolyte supply channel provided in the electrode or separator. It has a passage that communicates the separator, fuel electrode, matrix, and oxidizer electrode through an electrolyte reservoir, and by making it possible to supply electrolyte to the matrix, changes in the amount of electrolyte in the matrix due to moisture absorption and evaporation can be prevented. It is made possible to absorb and retain a certain amount of electrolyte within the matrix.

〔Example〕

Examples will be described below.

Figures 1 to 5 relate to a phosphoric acid fuel cell that uses hydrogen-rich gas as a fuel, oxygen in the air as an oxidizer, and phosphoric acid as an electrolyte, and the same parts are given the same reference numerals. .

FIG. 1 is a partial sectional view of one embodiment, and FIGS. 2 and 3 are plan views of different main parts. In these figures, 1 is a matrix, and a kneaded product of silicon carbide and polytetrafluoroethylene, a phenolic resin, or the like is used. 2 is a fuel electrode made of a fuel electrode base material 2a and a fuel electrode catalyst layer 2b; 3 is an oxidizer electrode made of an oxidizer electrode base material 3a and an oxidant electrode catalyst layer 3b; 4 is a fuel electrode gas path; 5 is an oxidizer The electrode gas path 6 is a separator. A required number of unit cells each having a matrix 1 disposed between a fuel electrode 2 and an oxidizer electrode 3 are stacked with separators interposed therebetween. 72 is an electrolyte supply groove, 82 is an electrolyte reservoir, 92 is an electrolyte communication hole, 10
11 is an electrolyte passage provided at the edge of the stacked battery so as to communicate the electrode, matrix and separator, and 11 is a seal. That is, the separator 6 is provided with an electrolyte supply groove 72 and an electrolyte passage 10, as shown in FIG. 2, and the fuel electrode 4 is provided with an electrolyte passage 10, as shown in FIG.
An electrolyte reservoir 82 communicating with the electrolyte passage 10 and an electrolyte communication hole 92 communicating the electrolyte between the electrolyte supply groove 72 and the matrix 1 are provided.

In a fuel cell having such a configuration, when an electrolyte is supplied, the electrolyte passage 10 is filled with the electrolyte and the electrolyte reservoir 82 of each cell is overflowed. The filled electrolyte enters the electrolyte supply groove 72 through the lower hole 82a and is supplied to the matrix 1 through the electrolyte communication hole 92. In this case, in order to prevent the electrolyte from wetting the fuel electrode base material 2a, the fuel electrode base material 2a is coated with, for example, polytetrafluoroethylene to make it water repellent. Furthermore, when the electrolyte enters the fuel electrode base material 2a due to the electrolyte supply pressure, the number of stacked cells serving as the electrolyte supply unit may be reduced to lower the electrolyte supply pressure. After filling the electrolyte supply groove 72 with the electrolyte, the electrolyte is removed from the electrolyte passage 10 to prevent a liquid short circuit caused by the electrolyte. At this time, electrolyte is also removed from the electrolyte reservoir 82, but this does not affect performance.

In the fuel cell configured as above,
When the amount of electrolyte in the matrix 1 increases due to moisture absorption, the excess amount passes through the electrolyte communication hole 92 and overflows into the electrolyte supply groove 72, and further flows into the electrolyte reservoir 82.
It is overflowing and stored. Further, when the electrolyte in the matrix 1 becomes insufficient due to evaporation, the insufficient amount is replenished from the electrolyte supply groove 72 through the electrolyte communication hole 92.

Therefore, the amount of electrolyte in the matrix 1 is always kept constant, stabilizing the battery performance, and storing surplus electrolyte during moisture absorption, so that the amount of electrolyte in the fuel electrode catalyst layer 2b and the oxidizer electrode catalyst is kept constant. layer 3
(b) will not be excessively wetted, and the electrode performance will be stabilized. Furthermore, when the electrolyte in the electrolyte supply groove 72 decreases, the electrolyte can be replenished through the electrolyte passage 10, so that there is no reduction in battery performance due to electrolyte shortage. Moreover, the electrolyte communication hole 9
2 can be determined depending on the electrolyte absorption capacity of the matrix 1, so that the electrolyte can penetrate into the matrix 1 at a sufficient rate.
Further, since the electrolyte supply groove 72 is provided to limit the electrolyte supply path, the electrode base material is not wetted during electrolyte supply, and gas diffusion is not hindered.

FIG. 4 shows a partial sectional view of another embodiment. In this embodiment, the first point is that the electrolyte reservoir 82, the electrolyte supply groove 72, and the electrolyte communication hole 92 are filled with fibers 12. This is different from the embodiment shown in the figure. The fibers 12 have the effect of improving the electrolyte impregnation rate and making the electrolyte distribution uniform due to their capillary force.

The fibers 12 used here include silicon carbide fibers, carbon fibers, glass fibers, phenol resin fibers, and the like. Also, instead of fibers, other hydrophilic materials, such as silicon carbide powder, carbon powder, can be used as a binder, such as
It is also possible to use one bound with polytetrafluoroethylene or polyimide, and the same effect can be obtained. Furthermore, for example, a porous sheet such as a carbon sheet or a silicon carbide sintered body may be used. Further, the same material as the matrix material may be used, but in this case, between the matrix 1, the electrolyte communication hole 92, the electrolyte supply groove 72, and the small holes of the material used in the electrolyte reservoir 82, It is desirable that the small pores of the material used in the matrix 1 be minimized, and that the electrolyte communication holes 92, electrolyte supply grooves 72, and electrolyte reservoirs 82 become larger in this order. That is, by doing this, if a difference is created in the capillary forces, the amount of electrolyte in the matrix 1 will be kept more stable due to this difference in capillary forces. Further, the fibers 12 of the electrolyte reservoir 82 and the electrolyte supply groove 72 can be omitted if the capillary force is within the above-mentioned range.

FIG. 5 shows a partial cross-sectional view of another embodiment. This embodiment differs from the embodiment of FIG. This is the point provided in the section. With such a configuration, the electrolyte replenishment rate can be increased, and
At the time of initial filling, if the electrolyte is supplied from one electrolyte passage 10a and allowed to overflow from the other electrolyte passage 10b, electrolyte filling can be performed reliably.

In the above embodiments, the electrolyte supply groove was provided on the fuel electrode side of the separator, but it may also be provided on the oxidizer side, and furthermore, it may be provided on both the fuel electrode side and the oxidizer electrode side. Good too.

〔Effect of the invention〕

As described above, the present invention makes it possible to easily configure an electrolyte supply path for supplying electrolyte to a matrix from outside the cell, and to provide a fuel cell that can obtain stable cell output. , which has great industrial effects.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of one embodiment of the fuel cell of the present invention, FIGS. 2 and 3 are plan views of different main parts from FIG. 1, and FIGS. FIG. 1...Matrix, 2...Fuel electrode, 2a...
Fuel electrode base material, 2b... Fuel electrode catalyst layer, 3... Oxidizer electrode, 3a... Oxidizer electrode base material, 3b... Oxidizer electrode catalyst layer, 4... Gas path for fuel electrode, 5... Oxidizer electrode gas path, 6... Separator, 72... Electrolyte supply groove, 82... Electrolyte reservoir, 92... Electrolyte communication hole, 10... Electrolyte passage, 11... Seal, 12
……fiber.

Claims (1)

[Claims] 1. A matrix holding an electrolyte is provided between a pair of electrodes, a fuel electrode and an oxidizer electrode, and flow paths for fuel gas and oxidant gas are provided in the fuel electrode and the oxidizer electrode, respectively. In a fuel cell formed by stacking unit cells with a separator in between, at least one side of the pair of electrodes of the separator communicates with the matrix through an electrolyte communication hole located in the electrode. A groove-shaped electrolyte supply path is provided, and the electrolyte supply path communicates with an electrolyte passage communicating the electrode, the matrix, and the separator via an electrolyte reservoir provided in the adjacent electrode, and the electrolyte communication A fuel cell characterized in that a water-repellent layer is provided on the hole and the surface of the electrolyte supply path that contacts the electrode. 2. Claim 1, wherein the groove of the electrolyte supply channel is filled with any one of hydrophilic fibers, a kneaded mixture of hydrophilic powder and a binder, a porous sheet, and a matrix material. The fuel cell described. 3. The fuel cell according to claim 1 or 2, wherein the electrolyte communication hole is filled with either a hydrophilic material or a matrix material. 4. The fuel cell according to claim 3, wherein the hydrophilic material is a kneaded mixture of hydrophilic material powder and a binder. 5. The fuel cell according to any one of claims 1 to 4, wherein the electrolyte reservoir is filled with a hydrophilic material. 6. The fuel cell according to claim 5, wherein the hydrophilic material is a mixture of hydrophilic powder and adhesive. 7. The fuel cell according to any one of claims 1 to 4, wherein the electrolyte reservoir is filled with either a porous sheet or a matrix material. 8. The electrolyte holding power of the matrix, the electrolyte communication hole, the electrolyte supply path, and the electrolyte reservoir is
8. The fuel cell according to any one of claims 1 to 7, wherein the matrix is the largest, and the electrolyte communication holes, the electrolyte supply path, and the electrolyte reservoir become smaller in this order.