JPS5956364A - Manufacture of electrolyte matrix for fuel cell - Google Patents

Abstract

PURPOSE:To provide an electrolyte matrix having increased holding ability of electrolyte without decreasing its mechanical strength, and high reliability by mixing a binder obtained by covering water repellent resin with an inactive inorganic compound, and an insulating inactive inorganic compound having larger particle size than above inorganic compound. CONSTITUTION:A binder obtained by covering a water repellent resin 11 with an inactive inorganic compound 9, and an insulating inactive inorganic compound 10 having larger particle size than above inorganic compound are mixed and they are molded, then dried and sintered. The water repellent resin 11 is fibrous fluorine resin. Mean particle size of insulating inactive inorganic compounds 10 is preferable to make 1-10mum and that of inactive inorganic compounds is desirable to make 1mum or less. Carbon, silicon carbide, silicone nitride, or zirconium oxide is used as the compound 9, and silicon carbide or silicon nitride is used as the compound 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a highly hydrophilic electrolyte matrix for fuel cells.

A conventional fuel cell of this type is shown in FIG. In the figure, (1) is a gas separation plate having a fuel flow path (2) on one side and an oxidizer flow path (3) on the other side. (4) is a fuel electrode, (5) is an electrolyte matrix,
(6) is an oxidizing agent electrode, (7) is a catalyst layer, and (8) is a gasket that prevents leakage of electrolyte and the like.

Next, the operation will be explained. The fuel and oxidant supplied to the fuel flow path (2) and the oxidizer flow path (31) are ionized at the fuel electrode (4) and the oxidizer electrode (6), respectively,
Both ions react to form a compound.

When the fuel is hydrogen and the oxidizer is oxygen, water is produced and a current is generated between both electrodes [41, +61. Electrolytic tube
-IJ Lux 5) holds an ion-conductive electrolyte and has the role of moving ions generated at the fuel electrode (4) or oxidizer electrode +61 to the other electrode. If the OH- ion is an acid, H
The reaction progresses as the ions move. Now, various materials are used for this matrix (51) depending on the operating temperature of the battery and the type of electrolyte, but for example, in the case of a phosphoric acid fuel cell that operates at 190°C, the A material in which an inert compound such as silicon carbide is fixed with polytetrafluoroethylene is used.

Conventional fuel cells are constructed as described above, and since the polytetrafluoroethylene, which is the binder in the electrolyte matrix, exhibits water repellency, too much binder reduces the electrolyte retention, and too little binder reduces the electrolyte retention. This had the disadvantage that the strength of the electrolyte matrix was reduced.

This invention was made in order to eliminate the drawbacks of the conventional products as described above.
The hydrophilicity of the above-mentioned fixing agent is improved by mixing the fixing agent coated with Compound I) and an electrically insulating inert inorganic compound (Compound ■) whose particle size is larger than that of Compound 1, molding the mixture, and then heating and baking it. The purpose of the present invention is to provide a method for producing a highly reliable electrolyte matrix for fuel cells, which can increase the electrolyte retention capacity and increase the electrolyte retention strength without impairing the strength of the electrolyte matrix.

An embodiment of the present invention will be described below with reference to the drawings. Second
The figure is a schematic diagram showing an outline of a cross section of an electrolyte matrix. In the figure, +91 is an inert inorganic compound (compound ■
), α[ is an electrically insulating inert inorganic compound (compound ■) having a larger particle size than compound ■(9). Compound I (9
1 covers the surface of the fibrous water-repellent resin to form a hydrophilic adhesive. The manufacturing method is shown below.

Example 1 PTF'E is made into fibers by kneading a dispersion of polytetrafluoroethylene (hereinafter abbreviated as PTFE), which is a water-repellent resin (11), and water. Silicon nitride, which is an inert inorganic compound (compound I) +91 and has an average particle size of 0.1 μm, is dispersed in water together with a surfactant and the like. After mixing the fiberized PTFE dispersion and the silicon nitride dispersion, by adding a depositing agent, etc., fiberized PTFE can be prepared.
Deposit silicon nitride on the surface of the FE. The resulting paste was mixed with an inert inorganic compound (compound n) ao+ and α-type silicon carbide with an average particle size of 51 tm, and after forming into a sheet,
Bake at 00-350°C. The resulting electrolyte matrix +51 was heated to approximately 150°C prior to battery assembly.
Impregnate with 8% phosphoric acid.

The electrolyte retained in the electrolyte matrix (5) is composed of compound 1. It exists in the gaps between the particles of IIf91 or α[ or in the gaps between the particles of compound 1 ) has improved electrolyte power.

Example 2 In Example 1, an inert inorganic compound (compound 1')
A similar manufacturing process was performed except that +91 silicon nitride was replaced with β-type silicon carbide. In this case as well, it was observed that the electrolyte holding power was improved compared to the conventional electrolyte matrix IJ Lux5).

Next, the average particle size of the insulating inert inorganic compound (compound 1 [) (Iα) is preferably 1 μm to 10 μm.
If it exceeds 1, the ionic conductivity will decrease, which is undesirable.
When it is less than μm, gas bubble pressure (bubb
This is not preferable because the pressure (le pressure) decreases.

The average particle size of the inert inorganic compound (Compound 1) (9) is smaller than Compound U (101), so it is set to 1 μm or less. In this case, the diameter of the fluororesin is 0.1 μm to 0.5 pm, so Compound I
(The average particle size of 91 is preferably about 0.1 μm.

Further, as compound (1) (91, carbon, silicon carbide, silicon nitride, zirconium oxide, or two or more thereof may be used. As compound IIQI, silicon carbide, silicon nitride, or both may be used. As a fluororesin, P
There is TFE or fluorinated ethylene propylene.

In addition, in the second embodiment, no pore-forming substance was added, but a blowing agent such as ammonium carbonate or a pore-forming substance that can be removed by firing or dissolving after molding may be added.

As described above, according to the present invention, a fixing agent in which a water-repellent resin is coated with an inert inorganic compound (compound
By mixing it with an electrically insulating inert inorganic compound (compound ■) that has a larger particle size, molding it, and then heating and baking it, it is possible to increase the hydrophilicity of the above-mentioned fixing agent and increase the electrolyte holding power. This has the effect of providing a highly reliable electrolyte matrix (IJ lux) without impairing the strength of the electrolyte matrix.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a part of a conventional fuel cell, and FIG. 2 is a schematic view showing a cross-sectional outline of an electrolyte matrix according to an embodiment of the present invention. In the figure, (5) is an electrolyte matrix, (9) is an inert inorganic compound (Compound I), the concave area is an electrically insulating inert inorganic compound (Compound ■), and ■ is a water-repellent resin. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Makoto Kuzuno - Figure 1 Procedural Amendment (Voluntary) Commissioner of the Japan Patent Office 1 Indication of case Relationship to patent application No. 57-166281 Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Hitoshi Katayama 4, Agent Address Mitsubishi Electric Corporation 5, 2-2-3 Marunouchi, Chiyoda-ku, Tokyo, Japan Detailed explanation of the invention in the specification subject to amendment Column 6, Contents of the amendment (1) In the 20th line of page 2 of the specification, the term ``electrolyte cylinder'' is corrected to ``electrolyte.'' (2) On page 5, line 17, insert ``retention of'' after ``solute''. (3) On page 6, line 6 of the same page, the words "ionic conductivity" should be replaced with "bubble pressure".
re ) Correct it as J. (4) On page 6, lines 7 and 8, change the word ``bubble pressure J'' to ``
Ion conductivity” is corrected. that's all

Claims (1)

[Scope of Claims] (1) A fixing agent in which a water-repellent resin is coated with an inert inorganic compound (Compound 1) is mixed with an electrically insulating inert inorganic compound (Compound ■) whose particle size is larger than that of Compound I. A method for producing an electrolyte matrix for a fuel cell, which is formed by heating and calcining the matrix. (2) The water-repellent resin is a fibrous fluororesin, the electrolyte material for fuel cells according to claim 1) The method for producing IJ Lux (3) The average particle size of the compound (1) is 1 μm-10 cotton, the average particle size of compound ■ is 1
A method for producing an electrolyte for a fuel cell according to claim 1 or 2, characterized in that the electrolyte material has a particle size of .mu.m or less. (4) The electrolyte for a fuel cell according to any one of claims 1 to 3, wherein the compound I is at least one of carbon, silicon carbide, silicon nitride, and zirconium oxide. Method of manufacturing the matrix. (5) Claim 1, characterized in that the compound (■) is at least one of silicon carbide and silicon nitride.
A method for producing an electrolyte matrix for a fuel cell according to any one of items 1 to 4.