JPH05166523A - Flat solid oxide fuel cell - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a flat plate solid oxide fuel cell in which a separator and a unit cell can be stacked in a gas-tight manner without using a seal. [Structure] A gently curved surface was formed on a separator that presses the periphery of the solid electrolyte layer, and a cushion material was inserted between the fuel electrode and the separator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate solid oxide fuel cell, and more particularly to a flat plate solid oxide fuel cell having a sealless structure.

[0002]

2. Description of the Related Art Recently, a fuel cell, which uses oxygen and hydrogen as an oxidant and a fuel, directly converts the chemical energy originally possessed by the fuel into electric energy, has been attracting attention from the viewpoint of resource saving and environmental protection. In particular, since the solid oxide fuel cell has a high operating temperature of 800 to 1000 ° C, it has a higher power generation efficiency in principle than the phosphoric acid type and molten carbonate type fuel cells and can effectively use the exhaust heat. Since all the constituent materials are solid and have many advantages such as easy handling, research and development have been advanced.

A flat plate solid oxide fuel cell is constructed by alternately stacking flat plate cells and separators with packing or sealing material interposed therebetween (hereinafter referred to as a stack) and tightening them. A unit cell has a flat solid electrolyte layer sandwiched between, for example, an air electrode on the front surface and a fuel electrode on the back surface.By passing an oxidant gas and a fuel gas on the respective surfaces of these electrodes, an electrode between the electrodes is formed. An electromotive force can be generated. Since the operating temperature of the stack reaches about 1000 ° C., the material of the unit cell and the separator is required to have chemical stability and mechanical strength.

It is necessary to seal the separator and the unit cell so that the fuel gas and the oxidant gas do not leak or mix inside the stack. If the fuel gas and the oxidant gas are mixed, not only the efficiency of the fuel cell is lowered but also the mixture is burned to cause a local temperature rise of the point cell, resulting in non-uniform thermal stress distribution and Shorten the life. Therefore, the packings and seals described above are used to prevent gas leakage and mixing in the stack.

Further, according to the conventional stack structure, since the contact surface between the separator and the unit cell, that is, the joint surface is a flat surface, the peripheral edge of the solid electrolyte layer is sandwiched between the separators. In the laminating step, the solid electrolyte layer sandwiched between the flat surfaces of both separators may be pulled and damaged during tightening, and there is a problem that both gases leak and mix from this portion.

[0006]

[Problems to be Solved by the Invention] Conventionally, no promising material to be used for packing has been found, and no practical sealing material has been found. Particularly, a material suitable for each material of the stack is found from the viewpoint of chemical stability. Is difficult.

The present invention has been made in view of the above points, and an object of the present invention is to provide a flat plate solid oxide fuel cell having a sealless structure which does not require sealing.

[0008]

In order to solve the above-mentioned problems, the present invention relates to a plate-shaped unit cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer, and the unit cell is electrically connected in series. In a flat plate solid oxide fuel cell constituted by alternately stacking separators for connecting the fuel gas to the fuel electrode and the oxidant gas to the air electrode, the separator for sandwiching the solid electrolyte layer is loose. Form a unique situation,
It is characterized in that the unit cell is sandwiched between the upper and lower separators, the peripheral edge of the solid electrolyte layer of the unit cell is sandwiched, and a conductive cushion material is inserted between the fuel electrode and the separator.

[0009]

As described above, since the gradual phase is formed on the separator and the cushioning material is inserted between the separator and the fuel electrode, the solid electrolyte layer can be pulled elastically well in the process of stacking and tightening the stack. There was no breakage, and the tightness between the tightened separators and between the separator and the solid electrolyte layer was improved, and no seal was required.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a flat plate solid oxide fuel cell of the present invention, FIG. 2 is a sectional view taken along the line II--II of FIG. 1, and FIG.
III-III line sectional view of FIG. 4, FIG. 4 is a IV-IV line sectional view of FIG.

The flat plate solid oxide fuel cell (stack) of the present invention comprises a flat plate single cell in which a fuel electrode 3 and an air electrode 4 are arranged so as to sandwich a solid electrolyte layer 2, and the single cell is connected in series. It is configured by alternately stacking separators 1 for distributing the fuel gas to the fuel electrode and distributing the oxidant gas to the air electrode.

FIGS. 2, 3 and 4 show one unit cell stacked between two separators 1, 1.
The individual separators 1 and 1 are shown separated from each other with a slight gap as shown in the drawing. This is for the purpose of making the description of the present invention easy to understand, and it is naturally crimped during the operation of the stack.

In this embodiment, as shown in FIG.
The fuel gas is made to flow in the A direction, and the oxidant gas is made to flow perpendicularly to the B direction. Therefore, on both sides of the separators 1 and 1 facing the fuel electrode 3 and the air electrode 4, respectively, grooves 6 for gas passages are formed.
Are formed in an orthogonal state. Referring to FIG. 2, the fuel gas groove 6 is formed in a direction perpendicular to the paper surface, and the oxidant gas groove is formed in the left-right direction on the paper surface.

On the other hand, the fuel electrode 3 and the air electrode 4 are attached to both sides of the solid electrolyte layer 2 of the unit cell as described above.
These electrodes 3 and 4 are not provided on the entire surface of the solid electrolyte layer 2, and as shown in FIG. 2, the four sides, that is, the peripheral edges are not attached and the solid electrolyte layer 2 is exposed. As shown in FIGS. 3 and 4, this exposure 2a is pressure-contacted between the upper and lower separators 1 and 1, and this pressure-contact prevents gas from leaking from the stack.

According to this embodiment, the facing (left and right in FIG. 3 and FIG. 4) joining surfaces 1a and 1b of the separator 1 are formed into gentle curved surfaces, and the curved surfaces 1a of the upper and lower separators 1 are convex. Curved surface of the lower separator 1 joining surface 1
b is a concave curved surface (FIGS. 3 and 4). Therefore, the exposed portion 2a of the solid electrolyte layer 2 is warped and pinched between the curved surfaces 1a and 1b of the upper and lower separators 1 and 1. The curved surfaces of the upper and lower separators 1 and 1 are convex and concave curved surfaces so as to fit with each other (FIGS. 3 and 4).

Further, according to this embodiment, the conductive cushion material 5 is inserted into the fuel gas chamber formed between the fuel electrode 3 of the unit cell and the separator 1. The cushion material 5 is, for example, a thin metal strip formed into a sponge shape, a mesh shape, or the like, and has conductivity and cushioning characteristics between the separator and the fuel.

The corners of the separator 1 contacting the solid electrolyte layer 3 are slightly rounded so that the exposed portions 2a of the thin solid electrolyte layer 2 are not damaged by the corners of the separator when the stack is assembled. ing.

[0019]

As described above, the present invention is a flat plate solid oxide fuel cell in which the periphery of the solid electrolyte layer of a single cell is sandwiched by separators, and the sandwiching surface of the separator is a gently curved surface, By inserting a conductive cushioning material between the fuel electrode and the separator facing it, it is possible to improve the sealing performance of the fuel cell and prevent gas leakage and mixing, and the cushioning material allows the electrode and the separator to be separated. The excellent effect of improving the performance of the stack is obtained by improving the contact and conduction between and.

Further, during the tightening work for assembling the stack by stacking the separator and the unit cells, the peripheral edge portion of the solid electrolyte layer of the unit cell is sandwiched between the curved surface pressing portions of the separator, so that the separator is tightened in a flat state as in the conventional case. It is possible to prevent the solid electrolyte layer from being damaged due to an unreasonable tensile force.

Further, since the separator structure does not require a seal, a material having a large coefficient of thermal expansion such as metal can be used for the separator, and there is no restriction on the material of the separator.

[Brief description of drawings]

FIG. 1 is a plan view of a flat plate solid oxide fuel cell of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

3 is a sectional view taken along the line III-III in FIG.

4 is a sectional view taken along line IV-IV in FIG.

[Explanation of symbols]

 1 Separator 2 Solid Electrolyte Layer 3 Fuel Electrode 4 Air Electrode 5 Cushion Material 6 Groove

Claims (1)

[Claims] 1. A flat plate-shaped cell in which a fuel electrode and an air electrode are arranged so as to sandwich a solid electrolyte layer, and the cells are electrically connected in series and a fuel gas is oxidized to an air electrode in the fuel electrode. In a plate-shaped solid electrolyte fuel cell configured by alternately stacking separators that distribute the agent gas, a gentle curved surface is formed in the separator that presses the solid electrolyte layer, and a unit cell is sandwiched by upper and lower separators, A flat plate solid oxide fuel cell characterized in that a peripheral edge of a solid electrolyte layer of a unit cell is sandwiched and a conductive cushion material is inserted between a fuel electrode and a separator.