JPS6340024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for impregnating a matrix of a fuel cell with an electrolyte, which has a matrix impregnated with a highly hygroscopic electrolyte.

(Prior Art) In general, in this type of fuel cell, an electrolyte compartment is formed by faces of a fuel electrode and an oxidizer electrode facing each other, and a fuel electrode and an oxidizer electrode on the opposite side from the electrolyte compartment are formed with an electrolyte compartment. A gas compartment is formed in each case. The electrolyte compartment is filled with a matrix of non-electronically conductive, porous material which is impregnated with an electrolyte such as phosphoric or sulfuric acid. Additionally, a groove is provided at the end of the electrolyte compartment, and the groove is filled with an electrolyte reservoir made of a porous material. To impregnate the matrix with electrolyte, the fuel cell is vertically, horizontally, or slightly tilted, and a predetermined concentration of electrolyte is supplied to the matrix through an electrolyte reservoir.

(Problems to be Solved by the Invention) However, after this impregnation, when the fuel cell is operated at a predetermined temperature, the electrolytic solution increases in volume due to thermal expansion. For example, when operating at 190 degrees C,
Compared to the volume of the electrolyte at room temperature of 15 degrees Celsius before operation, the volume increases by about 10%. Furthermore, when the battery is out of operation, the electrolytic solution absorbs moisture from the atmosphere, decreasing its concentration and increasing its volume.
For example, phosphoric acid with a concentration of 100% at a temperature of 190 degrees Celsius is
When left in the atmosphere at 40 degrees Celsius and 80% humidity, the volume of phosphoric acid increases by about three times and the concentration decreases to about 42%. When impregnating the electrolyte into the matrix, if the porous electrolyte reservoir and the pores in the matrix are to be completely impregnated with the electrolyte, it is important to avoid atmospheric pressure due to thermal expansion of the electrolyte during operation or due to outage. The electrolyte that increases due to the absorption of humidity reaches the gas side layer via the catalyst layer of the electrode, and the electrode surface becomes wet with the electrolyte, inhibiting the diffusion of the reaction gas and causing a decrease in the electrode characteristics. There's a problem. In extreme cases, the disadvantage is that the electrolyte leaks into the gas compartment, blocking the gas passage and impeding the flow of the reaction gas.

In view of the above-mentioned points, the present invention provides a method for impregnating an electrolyte into a fuel cell matrix, which eliminates the drawbacks of the prior art and maintains high performance cell characteristics even when the fuel cell is in operation or out of operation for a long period of time. The purpose is to provide.

SUMMARY OF THE INVENTION According to the invention, this object is achieved by impregnating the electrolyte reservoir and the matrix with a low concentration electrolyte and supplying a dry gas having the operating temperature of the fuel cell to the gas compartment. This is achieved by

(Function) With this method, this low concentration electrolyte is concentrated to a predetermined concentration, and its characteristics are maintained at high performance even when the fuel cell is in operation for a long period of time, which is the intended purpose, or when the operation is stopped. Ru.

(Embodiment) According to the present invention, the matrix is arranged such that the electrolyte at the operating temperature moves from the electrolyte reservoir to the matrix, completely filling the matrix, and leaving almost no electrolyte in the electrolyte reservoir. It is preferable to have a larger electrolyte retention capacity than the electrolyte reservoir.

Further, in accordance with one embodiment of the present invention, the electrolyte retention capacity may be such that the water repellency of the matrix is less than that of the electrolyte reservoir.

Furthermore, in accordance with another embodiment of the present invention, it is desired that the electrolyte holding power be such that the particle size of the matrix is smaller than that of the electrolyte reservoir.

Next, one embodiment of the present invention will be described in detail based on the drawings.

The figure shows a schematic configuration diagram of an embodiment of the present invention. In the figure, a fuel cell 1 forms an electrolyte compartment 5 by the facing surfaces of a fuel electrode 2 and an oxidizer electrode 3. As shown in FIG. The electrolyte compartment 5 is filled with a matrix 4 which is a porous material having non-electronic conductivity.
The pores of this matrix 4 are impregnated with an electrolytic solution such as phosphoric acid or sulfuric acid. Each electrode 2, 3 consists of an electrode base material 6, 7 and a catalyst layer 8, 9. The electrode base materials 6 and 7 are electrode support members, and the catalyst layers 8 and 9 are provided on the electrode base materials 6 and 7 in a layered manner. The separator plates 12 and 13 are in contact with a part of the electrode base materials 6 and 7,
On the opposite side of the electrodes 2, 3 from the electrolyte compartment 5, gas compartments 10, 11 are formed to prevent current collection and mixing of the reaction gases. The separator plates 12 and 13 are provided with grooves 18 to 21 connected to the ends of the electrolyte compartment 5, and the grooves 18 to 21 are penetrated from side to side and have holes 14 communicating with the matrix 4, 15, 16, and 17 are provided. Grooves 18 to 21 are filled with a porous material to constitute an electrolyte reservoir 22. The matrix 4, the electrolyte reservoir 22, and the electrodes 2 and 3 are made of a porous material in which carbon compound particles are bound together with a binder such as tetrafluoroethylene. This tetrafluoroethylene has water repellent properties, and by slightly changing its amount, the matrix 4, electrolyte reservoir 22, electrodes 2, 3
Increase the particle size in the order of matrix 4,
By selecting a larger electrolyte reservoir 22 and then electrodes 2 and 3 in this order, the electrolyte holding force can be made smaller in the order of the matrix 4, the electrolyte reservoir 22, and the electrodes 2 and 3. Note that when the electrolytic solution absorbs moisture in the atmosphere and increases in volume due to suspension of operation of the fuel cell 1, the electrolytic solution reservoir 22 has a sufficient volume to accommodate the increased electrolytic solution. for example,
The electrolytic solution reservoir 22 has a volume approximately twice as large as the electrolytic solution holding volume impregnated into the matrix 4 and the catalyst layers 8 and 9 of the electrodes 2 and 3.

The electrolytic solution impregnated into the fuel cell 1 configured in this way is diluted to a predetermined concentration, and the electrolytic solution is diluted to a predetermined concentration.
The electrolyte reservoir 22 and the pores of the matrix 4 are impregnated through the electrolyte impregnation holes 14 to 17 of 2 and 13. Thereafter, the water in this diluted electrolyte is evaporated at the operating temperature of the fuel cell 1.
As the electrolytic solution is concentrated to a predetermined concentration, the electrolytic solution impregnated in the electrolytic solution reservoir 22 moves from the electrolytic solution reservoir 22 to the matrix 4 due to the difference in electrolytic solution holding power, and the pores of the matrix 4 are completely filled with the predetermined concentration. The electrolyte reservoir 22 is filled with a concentrated electrolyte, but at the operating temperature of the battery 1 this electrolyte is hardly retained in the electrolyte reservoir 22 . For example, at an operating temperature of 190 degrees Celsius of the fuel cell 1, in order to retain 100% phosphoric acid in the matrix 4, approximately 33.3%
After impregnating the electrolyte reservoir 22 and the pores of the matrix 4 with a low concentration of phosphoric acid, dry air or nitrogen at 190 degrees Celsius is introduced into the gas compartments 10 and 1.
1, evaporate the water in the diluted phosphoric acid, and
% concentration of phosphoric acid. By the way, the water vapor pressure of about 33.3% phosphoric acid is about 14.8 mm of mercury. Since this water vapor pressure is approximately equal to the saturated water vapor pressure in the atmosphere at room temperature, this phosphoric acid is transferred to the electrolyte reservoir 2.
When impregnating phosphoric acid 2 and matrix 4, it is possible to prevent the phosphoric acid concentration from changing due to absorption of moisture from the atmosphere.

(Effects of the Invention) As explained above, according to the present invention, the electrolytic solution impregnated into the matrix is a low-concentration electrolytic solution that is impregnated into the electrolytic solution reservoir and the pores of the matrix, and then the electrolytic solution is impregnated into the electrolytic solution reservoir and the pores of the matrix, and then the electrolytic solution is impregnated into the electrolytic solution reservoir and the pores of the matrix. The desired purpose can be achieved by supplying dry air or nitrogen to the compartment to remove water from the electrolyte and concentrate it to a predetermined concentration, while also moving the electrolyte from the electrolyte reservoir into the matrix. If the material and particle size are selected accordingly, the electrolyte reservoir retains almost no electrolyte at operating temperatures, so the cell properties can be maintained even during long-term operation or out-of-operation of the fuel cell. It has the effect of maintaining performance.

[Brief explanation of the drawing]

The figure is a schematic configuration diagram of an embodiment of the present invention. 1: Fuel cell, 4: Matrix, 5: Electrolyte compartment, 10, 11: Gas compartment, 18, 19,
20, 21: Groove, 22: Electrolyte reservoir.

Claims (1)

[Claims] 1. A method for impregnating a matrix of a fuel cell with an electrolyte, comprising a gas compartment through which a reactive gas flows, a matrix impregnated with a hygroscopic electrolyte, and an electrolyte reservoir, wherein the matrix and the electrolyte reservoir are impregnated with a low concentration. A method for impregnating a matrix of a fuel cell with an electrolyte, characterized in that a dry gas having an operating temperature of the fuel cell is supplied to the gas compartment.