JP2654502B2 - Solid electrolyte fuel cell with mechanical seal structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolyte fuel cell having a mechanical seal structure which does not require a sealant.

[0002]

2. Description of the Related Art Recently, fuel cells that directly convert chemical energy inherent in fuel into electric energy using oxygen and hydrogen as an oxidant and a fuel, respectively, have been used to save resources.
It is receiving attention from the viewpoint of environmental protection.

[0003] A solid electrolyte fuel cell using zirconia doped with yttria or the like as an electrolyte layer and using a lanthanum chromite-based oxide or the like as a separator has a high operating temperature, high power generation efficiency, and comprehensive use of high-temperature waste heat. Due to its high efficiency, research and development is progressing.

FIG. 9 is a sectional view of a conventional solid oxide fuel cell. In this solid electrolyte fuel cell, a flat cell 13 in which a fuel electrode 15 and an air electrode 16 are arranged so as to sandwich a solid electrolyte layer 14 and an adjacent cell 13 are electrically connected in series and each cell 13 is configured as a multi-layer stack by alternately stacking separators 10 for distributing fuel gas and oxidizing gas.

[0005] The internal manifold type solid electrolyte fuel cell has an integral structure in which the separator 10 has functions of supply / discharge, distribution, and electrical connection of oxidant and fuel gas. Therefore, a gas supply / exhaust hole is formed in the side of the separator, gas is supplied / exhausted from the hole to the electrode surface of the unit cell 13, and gas is evenly distributed to every corner of the electrode surface. In order to connect the adjacent batteries 13 in series, a groove 10c is formed on the electrode surface. On the other hand, gas supply / exhaust holes (not shown) are formed in portions of the solid electrolyte layer 14 of the unit cell where no electrodes are provided, and these holes are connected in the process of stacking the batteries 13 to form a gas passage inside the stack. Has formed.

When the fuel and the oxidizing gas are mixed inside the stack, not only the efficiency of the fuel cell is reduced, but also the fuel is burned by the mixing to locally increase the temperature, and the thermal stress distribution becomes non-uniform. Shorten life.

[0007]

Conventionally, there is a method of sandwiching a sealant 12 on a seal surface between a unit cell and a separator in order to prevent fuel and oxidant gas from being mixed in a stack. This sealant 12 has the disadvantage that no suitable material can be found. In addition, there is a method of using a ceramic adhesive as a sealant, but when completely adhered with a ceramic adhesive, a distortion occurs in an adhesive portion due to a difference in thermal expansion of each constituent material,
In addition to cracking the solid electrolyte layer of the unit cell, deterioration of the adhesive during a plurality of thermal cycles causes gas leakage. Further, there is a method using silica-based glass as a sealant. However, a silica component in the sealant evaporates during long-term operation, and adheres and deposits on a low-temperature portion. As a result, deterioration of the electrode is caused, and there is a problem in long-term operation.

The present invention has been made in view of the above points, and completely seals between a unit cell and a separator by a mechanical sealing method without using a sealant at all, and operates stably for a long period of time. It is an object of the present invention to provide a solid electrolyte fuel cell that can be used.

[0009]

Means for Solving the Problems To solve the above problems, the present invention electrically connects a flat cell having a fuel electrode and an air electrode with a solid electrolyte layer interposed therebetween and an adjacent cell. In a solid electrolyte fuel cell configured by alternately stacking separators connected in series and distributing fuel gas and oxidizing gas to each unit cell, the surface of the separator facing the fuel electrode side of the unit cell Part that does not touch the electrode
No electrode on the fuel electrode side surface of the solid electrolyte layer of the unit cell
A spacer interposed in an airtight state between the portion and a heat-resistant metal interposed in an elastically compressed state between the surface of the separator facing the fuel electrode side of the unit cell and the fuel electrode of the unit cell. By providing a mesh or felt, airtightness on the fuel electrode side is ensured, and the spacer is used.
And presses the solid electrolyte layer of the unit cell to remove the solid electrolyte layer.
Direct surface contact with the air electrode side separator surface while bending
By, characterized by the this <br/> to ensure airtightness of the air electrode side at the same time.

Further, the present invention is characterized in that the spacer is made of partially stabilized zirconia.

Further, the present invention is characterized in that the spacer is made of a heat-resistant metal.

[0012]

The zirconia spacer is interposed between the peripheral edge of the surface of the separator facing the fuel electrode side of the unit cell and the peripheral edge of the solid electrolyte layer of the unit cell in a sealed state. The separator, the electrolyte layer and the spacer of the unit cell between them, are kept in sealing by surface contact with each other, so that gas leakage and mixing can be prevented. Since a mesh or felt of a heat-resistant metal is interposed in a resiliently compressed state between the surface of the separator facing the fuel electrode side of the unit cell and the fuel electrode of the unit cell, the upper separator and the fuel electrode are meshed. Alternatively, the separator and the air electrode are elastically pressurized from the fuel electrode side on the back surface and come into direct contact with each other to be in a good conduction state.

At this time, both electrodes of the unit cell, the solid electrolyte layer,
The separator and the spacer are always pressed against each other even if there is an error in the accuracy of the thickness of the separator and the spacer because the elastic mesh is interposed.

[0014]

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

FIG. 8 is a sectional view of a solid electrolyte fuel cell having a mechanical seal structure according to the present invention.

In the solid electrolyte fuel cell of the present invention, a flat cell 3 in which a fuel electrode 5 and an air electrode 6 are arranged so as to sandwich a solid electrolyte layer 4 and an adjacent cell 3 are electrically connected in series. The separators 1 for distributing the fuel gas and the oxidizing gas are alternately stacked on each unit cell.

FIG. 1 is a plan view of the separator 1, and FIG.
1. FIG. 3 is a sectional view taken along line III-III of FIG.

The separator 1 is a plate-shaped sintered body obtained by press-molding strontium dopantran chromite and firing in air. Gas supply / exhaust holes 1a are formed in four corners, and grooves 1c are formed in the electrode surfaces to evenly distribute the gas to all corners of the electrode surface of the unit cell 3. Protrusions 1b are provided between the grooves 1c to connect adjacent cells 3 in series. As can be seen from FIG.
c communicates with two left and right diagonal supply / exhaust holes 1a, and a groove 1c on the back surface communicates with two other left / right diagonal supply / exhaust holes 1a. The peripheral edge 1d of the front and back surfaces of the separator 1 is the spacer 2 or the solid electrolyte layer 4 of the unit cell 3.
This is the side to overlap with.

FIG. 4 is a plan view of the spacer 2, and FIG. 5 is a sectional view taken along line VV of FIG.

The spacer 2 is made of partially stabilized zirconia or a refractory metal and has a thickness of 300 microns. A substantially square hole 2e is formed in the center and 4
A gas supply / exhaust hole 2a is opened at a corner. The hole 2e is wider than the area of each of the electrodes 5 and 6 of the unit cell 3, and the hole 2a has the same size and arrangement as the supply / exhaust hole 1a of the separator 1. A peripheral portion 2 d on the front and back surfaces of the spacer 2 is a sealing surface for overlapping with the separator 1 or the solid electrolyte layer 4 of the unit cell 3.

FIG. 6 is a plan view of the cell 3, and FIG. 7 is a line of FIG.
It is a VII-VII sectional view.

The unit cell 3 is formed by coating Ni / YSZ cermet as the fuel electrode 5 and (La, Sr) MnO ₃ as the air electrode 6 by screen printing so as to sandwich the solid electrolyte layer 4. The solid electrolyte layer 4 is made of a zirconia sintered body (YSZ) doped with yttria or the like. Gas supply / exhaust holes 3 a are formed at four corners of the solid electrolyte layer 4. This gas supply / exhaust hole 3a is
And the size and arrangement of the air supply / exhaust holes 1a. In addition, a peripheral portion 3 d of the front surface and the back surface of the solid electrolyte layer 4 is a surface for overlapping with the separator 1 or the spacer 2.

A mesh or felt 7 made of a heat-resistant metal such as nickel shown in FIG. 8, having electron conductivity and elasticity under a reducing atmosphere, and having a size covering the entire surface of the fuel electrode 5 of the cell 3 is used. It is elastically interposed between the separator and the fuel electrode.

The above components are assembled into a multilayer stack as shown in the sectional view of FIG. 8 to constitute a solid oxide fuel cell of the present invention. (1) Upper separator 1 facing fuel electrode 5 of cell 3
A spacer 2 is sandwiched and pressed in a surface contact state between a peripheral portion 1d of the lower surface of the solid electrolyte layer 4 and an upper peripheral portion 3d of the solid electrolyte layer 4 of the unit cell 3. At the same time, the lower peripheral edge 3d of the solid electrolyte layer 4 and the upper peripheral edge 1d of the lower separator 1 are pressed in direct surface contact. (2) The mesh or felt 7 is elastically compressed between the upper surface of the fuel electrode 5 of the unit cell 3 and the lower surface of the upper separator 1 facing the fuel electrode 5 of the unit cell 3.

Each gas is supplied to the solid electrolyte fuel cell constructed as described above from a gas supply hole at a peripheral portion thereof.
Electric power is generated by flowing over the surfaces of both electrodes of the unit cell 3 and discharging the gas through gas exhaust holes at the peripheral edge. Test results,
A good result with an open circuit voltage of 1.07 volts was obtained.

[0026]

As described above, according to the present invention, a mechanical seal is used without using any sealant between the separator, the unit cell, the spacer and the metal mesh, which are the components of the solid oxide fuel cell. did. A metal mesh is placed on the fuel electrode of a unit cell, a spacer made of a thin plate of ceramics or heat-resistant metal is placed around it, and the spacers are stacked with a weight applied via an upper separator. While ensuring the airtightness of the electrode side, at the same time, the electrolyte of the cell on the air electrode side and the separator are pressed, whereby the airtightness of the air electrode side is also simultaneously secured by surface contact, and the fuel electrode of the cell The separator has an excellent effect of being elastically pressed through the metal mesh to maintain good electrical contact.
Therefore, the solid electrolyte fuel cell of the present invention has improved durability for a long time, is resistant to thermal cycling, and has improved reproducibility and yield. In addition, since it is a mechanical seal, there is no need to consider the difference in thermal expansion between materials, and the range of material selection is expanded.

[Brief description of the drawings]

FIG. 1 is a plan view of a separator used in a solid oxide fuel cell of the present invention.

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

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 is a plan view of a spacer used in the solid oxide fuel cell of the present invention.

FIG. 5 is a sectional view taken along line VV of FIG. 4;

FIG. 6 is a plan view of a unit cell used for the solid oxide fuel cell of the present invention.

FIG. 7 is a sectional view taken along line VII-VII of FIG. 6;

FIG. 8 is a sectional view of a solid oxide fuel cell according to the present invention.

FIG. 9 is a cross-sectional view of a conventional solid oxide fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Separator 2 Spacer 3 Cell 4 Solid electrolyte layer 5 Fuel electrode 6 Air electrode 7 Mesh

Claims (3)

(57) [Claims] 1. A flat cell having a fuel electrode and an air electrode disposed so as to sandwich a solid electrolyte layer, an adjacent cell being electrically connected in series, and a fuel gas and an oxidant being connected to each cell. In a solid electrolyte fuel cell configured by alternately stacking separators for distributing gas, a portion of the separator surface facing the fuel electrode side of the unit cell that is not in contact with an electrode and a solid electrolyte layer of the unit cell Of the electrode on the fuel electrode side surface
A spacer interposed airtight between have partial, refractory metal interposed resiliently compressed state between the unit cells facing the fuel electrode side surface and the unit cell of the fuel electrode of the separator By having a mesh or felt of
In addition to ensuring airtightness on the fuel electrode side ,
Pressing the solid electrolyte layer of the unit cell using the solid electrolyte layer
Direct contact with the separator surface on the air electrode side while bending
A solid electrolyte fuel cell having a mechanical seal structure characterized by simultaneously ensuring airtightness on the air electrode side . 2. The solid electrolyte fuel cell according to claim 1, wherein the spacer is made of partially stabilized zirconia. 3. The solid electrolyte fuel cell according to claim 1, wherein the spacer is made of a heat-resistant metal.