JPS6310867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fuel cells, and more particularly to the supply of electrolyte from an electrolyte reservoir to a wet seal section and the replenishment channel of electrolyte from a wet seal section to a reaction section.

FIG. 1 is a cross-sectional view showing the main parts of a conventional fuel cell. Reference numeral 1 denotes a gas separation plate, and a fuel flow path 2 is provided on one side and an oxidizer flow path 3 is provided on the other side. 4 is a fuel electrode, 5 is an electrolyte matrix, 6 is an oxidizer electrode,
4a, 5a, 6a are the parts where the battery reaction occurred, 4
b, 5b, and 6b are respective seal portions that are treated to be air-impermeable and to be impermeable to electrolytes such as phosphoric acid.

The operation of a conventional fuel cell will be explained. Hydrogen in the fuel gas supplied from the fuel flow path 2 is ionized in the fuel electrode reaction section 4a and separated into hydrogen ions and electrons, and the hydrogen ions move through the phosphoric acid electrolyte in the electrolyte matrix reaction section 5a. At the oxidizing agent electrode reaction portion 6a, the oxidizing agent (oxygen in the air) supplied from the oxidizing agent channel 3 is combined with the oxidizing agent (oxygen in the air) to become water vapor. Electrons generated in the fuel electrode reaction portion 4a are extracted to the outside and used as electric power. In this operation, an airtight structure is required because it is undesirable for the fuel gas and oxidant to leak from the peripheral portion of the electrode to the outside of the cell from the viewpoint of reaction and safety. The phosphoric acid impregnated in the electrolyte matrix also
Leakage to the outside is unfavorable in terms of reaction.For these reasons, in conventional batteries, the peripheral edges (sealed portions) 4b and 6b of the electrodes and the peripheral edge (sealed portion) 5b of the electrolyte matrix are treated with a filler. It was made air-impermeable or impermeable. Alternatively, the peripheral edge 4 of the electrode and electrolyte matrix
Gaskets were placed on b, 5b, and 6b for more aggressive sealing.

Since conventional fuel cells are constructed as described above, it is important to ensure the reliability of the treatment of the electrodes and the peripheral edges 4b, 5b, 6b of the electrolyte matrix. The electrolyte matrix 5 is also a porous membrane with a thickness of about 0.1 to 1 mm and made of fine powder such as silicon carbide and polytetrafluoroethylene. It is difficult to achieve air-impermeability and impermeability treatment with materials, and sufficient reliability has not been obtained.In addition, when sealing is performed with a packing, the thickness of the electrodes 4, 6 and electrolyte matrix 5 and the packing must be adjusted. Although it is necessary to make adjustments, it is extremely difficult to adjust the dimensions of both.

This invention was made to eliminate the above-mentioned drawbacks of the conventional method, and includes providing an electrolyte reservoir in the facing portion of the electrode and the gas separation plate, which communicates with the peripheral edge of the electrode and the electrolyte matrix. The central part of the electrode and the electrolyte matrix is made hydrophilic from the reservoir, and the peripheral edge of the electrode and the electrolyte matrix is made hydrophilic from the central part, and the electrolyte is transferred from the reservoir to the peripheral edge, that is, the sealing part. By supplying the electrolyte with the highest priority, wet sealing is ensured, and when the peripheral edge portion is filled with electrolyte, the electrolyte is smoothly replenished from the reservoir to the central portion.

Embodiments of the invention will be described below with reference to the drawings.
FIG. 2 is a cross-sectional view of the main parts of the fuel cell of the present invention, and 4 and 6 are a fuel electrode and an oxidizer electrode, respectively, which are porous membranes made of carbon paper coated with a catalyst having an average particle size of several μm. 4c is the peripheral edge of the fuel electrode;
The periphery of the fuel electrode substrate is filled with fine silicon carbide (SiC) particles with an average particle size of about 1 μm. Reference numeral 5 denotes an electrolyte matrix laminated on the electrode, which is a porous film made of powder such as silicon carbide and polytetrafluoroethylene with an average particle size of several μm, and the peripheral edge 5c of the electrolyte matrix has an average particle size of several μm.
Filled with fine silicon carbide particles of about 1 μm. Reference numeral 7 denotes the peripheral end portion of the oxidizer electrode 6, which is composed of a sealing gasket, but may have the same structure as the peripheral end portion 4c of the fuel electrode. Reference numeral 8 denotes a gas separation plate 1 facing the peripheral edge portion 4c of the fuel electrode.
An electrolyte reservoir formed in the section communicates with the peripheral edge 4c so that the stored electrolyte can be supplied to the peripheral edge 4c.
Reservoir 8 is filled with carbon fiber,
The average spatial width is about several tens of μm. reservoir 8,
Peripheral edges 4c, 5c of electrodes and electrolyte matrix
In this order, the space width or particle diameter is gradually made smaller, and the hydrophilicity based on the capillary phenomenon is gradually strengthened.

Therefore, when the reservoir 8 is impregnated and filled with an electrolyte, for example, phosphoric acid, the phosphoric acid is constantly supplied to the more hydrophilic peripheral edges 4c, 5c and wets the peripheral edges 4c, 5c, thereby ensuring a wet seal. . When the peripheral edges 4c, 5c are sufficiently impregnated with phosphoric acid, the reactive parts 4a, 6a, 5a have weaker hydrophilicity than the peripheral edges 4c, 5c, but have stronger hydrophilicity than the reservoir 8, so the reactive parts 4a,
Phosphoric acid is supplied to 6a, 5a via peripheral edges 4c, 5c. The phosphoric acid in the reaction parts 4a, 6a, and 5a gradually disappears during battery operation, resulting in a decrease in battery characteristics and a crossover phenomenon in which the fuel gas and oxidizer react directly and the battery becomes inoperable. In order to prevent this, it is necessary to replenish phosphoric acid continuously or periodically. The reservoir of the above embodiment has this replenishment function.

Note that phosphoric acid may be replenished to the reservoir from a phosphoric acid reservoir (not shown) outside the battery that communicates with the reservoir. Further, the reservoir may be installed on the ribbed electrode in addition to the gas separation plate.

As described above, the present invention provides an electrolyte reservoir that communicates with the peripheral edges of the electrode and the electrolyte matrix at the facing portion of the electrode and the gas separation plate, and also makes the center portion of the electrode and the electrolyte matrix hydrophilic from the reservoir. When the reservoir is filled with electrolyte, reservoir a, the center part b of the electrode and electrolyte matrix, and the electrode and electrolyte matrix are The electrolyte is supplied first to the most hydrophilic peripheral edge c of the peripheral edges c, thereby ensuring wet sealing and increasing reliability, and then the peripheral edge c is filled with electrolyte. When the central portion b is less hydrophilic than the peripheral edge c, but more hydrophilic than the reservoir a, the electrolyte is replenished more smoothly than the reservoir a.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of a conventional fuel cell, and FIG. 2 is a sectional view showing the main parts of the fuel cell of the present invention. In the figure, 1 is a gas separation plate, 14 is a fuel electrode, 5 is an electrolyte matrix, 6 is an oxidizer electrode, 4a, 5
4c and 5c are the fuel electrodes and the peripheral edge of the electrolyte matrix, and 8 is the reservoir. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a fuel cell having a fuel electrode, an electrolyte matrix, an oxidizer electrode, and a gas separation plate, an electrolyte reservoir is provided in a portion facing the electrode and the gas separation plate, the electrolyte reservoir communicating with the peripheral edge of the electrode and the electrolyte matrix; . A fuel cell characterized in that a central portion of the electrode and the electrolyte matrix is made more hydrophilic than the reservoir, and a peripheral edge portion of the electrode and the electrolyte matrix is made more hydrophilic than the central portion.