JPS58112261A - Electrolyte matrix for fuel cell - Google Patents

Abstract

PURPOSE:To increase the output and enhance the reliability of an electrolyte matrix for a fuel cell by making the electrolyte matrix to have a three-layered structure consisting of an electronic insulating film highly transmitting electrolyte, and electrolyte-holding layers which are made in close contact with the surfaces of said electronic insulating film. CONSTITUTION:An electrolyte matrix 1 is constituted of an electronic insulating film 2 and electrolyte-holding layers 3a and 3b which are made in close contact with the surfaces of the film 1. Electrodes 5a and 5b are pressongly provided over the surfaces of the matrix 1, with catalyst layers 4a and 4b provided between the matrix 1 and the electrodes 5a and 5b. The electrodes 5a and 5b are made of a porous graphite-fiber paper, and catalyst layers 4a and 4b are provided on the electrolyte-matrix-1-side surfaces of the electrodes 5a and 5b by application. As the above electronic insulating film, a nonwoven fabric of a phenol resin, a nonwoven fabric of fibrous silicon carbode or the like is employed. As the above electrolyte-holding layer, in a battery containing phosphoric acid as electrolyte, a member prepared by impregnating a powder of silicon carbide, zirconia or the like with concentrated phosphoric acid, or a member prepared by kneading both concentrated phosphoric acid and polytetrafluoroethylene into silicon carbide powder is employed.

Description

[Detailed description of the invention] Technical field of invention The present invention relates to an electrolyte matrix and a matrix for fuel cells.

TECHNICAL BACKGROUND OF THE INVENTION Fuel cells that obtain DC power by reacting a gas that is easily oxidized, such as hydrogen, with a gas that has oxidizing power, such as oxygen, through an electrochemical reaction process are widely known. This fuel cell usually consists of a pair of gas diffusion electrodes, in which an electrolyte such as a phosphoric acid solution is placed between the IJ wax electrodes, and a load is connected between both electrodes, while hydrogen is applied to the outer surface of one of the electrodes. DC power is supplied to the load by contacting the 51f gas containing oxygen and contacting the outer surface of the other electrode with a gas containing oxygen. Note that a catalyst such as platinum is usually added to the gas diffusion electrode in order to facilitate the reaction. Further, when used as a practical power generation device, a method is adopted in which a plurality of the above-mentioned fuel cells are connected in series.

By the way, the characteristics of such a fuel cell are greatly influenced by the matrix or the matrix impregnated with the electrolyte. In other words, in order to operate the fuel cell stably, the electrolyte matrix and the matrix must (1) be chemically and thermally stable under the operating conditions of the fuel cell, (2) be well impregnated with electrolyte, and be of good quality. The following characteristics are required: (3) high hydrogen ion conductivity, (4) being an insulator, and (5) being thin overall.

For this reason, conventional fuel cells use electrolyte matrices with a single layer structure designed to meet the above-mentioned requirements as much as possible.

Problems with the Background Art Conventional electrolyte matrices for fuel cells have a single-layer structure as described above, and such a structure cannot essentially satisfy all of the above-mentioned demands. There was an unavoidable problem in that the reliability of the fuel cell and the output decreased. In other words, the only way to reduce ionic resistance and increase output is to reduce the thickness of the electrolyte matrix, and if the electrolyte matrix is made thinner than this, the probability of internal short circuits will increase. Therefore, in order to prevent internal short circuits, the electrolyte matrix must be made thicker to some extent, which inevitably results in a decrease in output, and in the end, it is extremely difficult to satisfy the above requirements. .

OBJECTS OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to provide an electrolyte matrix for fuel cells that can contribute to increased output and improved reliability. There is a particular thing.

Summary of the Invention The electrolyte matrix according to the present invention is characterized by having a three-layer structure consisting of an electronic insulating thin film with high electrolyte permeability and an electrolyte holding layer provided closely on both sides of the electronic insulating thin film. There is.

That is, in the electrolyte matrix and the box according to the present invention, the electronic insulation function is shared by the electronic insulation thin film, and the other functions are shared by the electrolyte holding layer. Here, as the electronic insulating thin film, a nonwoven fabric of phenol resin, a nonwoven fabric of fibrous silicon carbide, a nonwoven fabric of mental pentoxide, a nonwoven fabric of zirconium oxide, etc. are used. These nonwoven fabrics have excellent electrolyte permeability and exhibit good electronic insulation function even if they are sufficiently thin. In addition, as the electrolyte holding layer, there are generally known ones, for example,
In the case of using cynic acid as an electrolyte, powders of silicon carbide, tantalum oxide, zirconia, etc. are impregnated with concentrated phosphoric acid, and silicon carbide powder is mixed with silicic acid and 4-litetrafluoroethylene. etc. are used.

Effect of invention J! With the electrolyte matrix and the matrix having the above-mentioned structure, among the properties required for the electrolyte matrix, the electronic insulation function can be shared by the electronic insulation thin film, and the other functions can be shared by the electrolyte holding layer. Unlike the conventional one-layer structure, it is possible to keep the overall thickness sufficiently thin and still satisfy all the characteristics required for electrolyte matrices and boxes. In particular, by making the thickness thinner, it is possible to reduce ionic resistance, which contributes to an increase in output, and to reduce the occurrence of internal short circuits that are likely to occur when the thickness is made thinner. This can be reliably prevented, and as a result, it can contribute to improved reliability.

EMBODIMENT OF THE INVENTION The figure shows an example of a fuel cell incorporating an electrolyte matrix according to an embodiment of the present invention, and this fuel cell is constructed as follows. That is, 1 in the figure is an electrolyte matrix, and this electrolyte matrix consists of an electronic insulating thin film 2, an electrolyte holding layer 3h provided closely on both sides of the electronic insulating thin film 2, The electronic insulating thin film 2 is made of a phenolic resin nonwoven fabric that has excellent electrolyte permeability and excellent electronic insulation function.The electrolyte retaining layers 3a and 3b are It consists of bulk silicon carbide powder with a diameter of 5 microns or less, mixed with a phosphoric acid solution with a concentration of 95 cm or more and a small amount of polytetrafluoroethylene, and then pressure-formed into a sheet. There is.

Electrodes 5&, 5b are press-contacted to both sides of the electrolyte (IJ) via catalyst layers 4a, 4b.

The electrodes 5&, 5b are made of porous graphite fibers, and the catalyst layers 4&, 4b are formed by coating on the surface facing the electrolyte matrix J. and,
On the outer surface of the electrodes 5&, 5b, a highly conductive plate 7a having a plurality of grooves 6a, 6b on the surface in contact with the outer surface, respectively;
7b is pressure-welded.

In the fuel cell configured in this way, the good conductive plate 7a
, Wb are connected as shown by the broken lines in the figure, and in this state, when gas containing hydrogen is allowed to flow through the grooves 6a and gas containing oxygen is allowed to flow through the grooves 6b. ,
Current flows through the load X, and the function as a fuel cell is exhibited. , l = 0.2 vsm (of which, the thickness of the electronic insulating thin film is O, Oa ~ 0.051), there is no problem, it is stable, and it is more stable than the conventional electrolyte matrix and It was confirmed that large output could be obtained.

In addition, although the above-mentioned example is an example in which the present invention is applied to a device using 9-acid as an electrolyte, it is of course applicable to a device using other electrolytes.

[Brief explanation of drawings]

The figure shows an electrolyte matrix according to an embodiment of the present invention. 1 is a sectional view of a main part of a fuel cell incorporating a fuel cell; J... Electrolyte matrix - Applicant's agent: Patent attorney Takehiko Suzue ---”m

Claims (2)

[Claims] (1) It is characterized by being formed in a three-layer structure consisting of an electronic insulating thin film with high electrolyte permeability and an electrolyte holding layer that is provided in close contact with both sides of the electronic insulating thin film and retains electrolyte. Electrolyte matrix for fuel cells. (2) The electronic insulating thin film is a nonwoven fabric of phenolic resin;
2. The electrolyte matrix for a fuel cell according to claim 1, wherein the electrolyte matrix is selected from a nonwoven fabric of fibrous silicon carbide, a nonwoven fabric of tantalum pentoxide, and a nonwoven fabric of zirconium oxide.