JPH11288729A - Solid electrolytic fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fracture of solid electrolytes caused by thermal stress, and to drive safely. SOLUTION: This fuel cell is constituted by alternately laminating cells where anodes 1 and cathodes 3 are formed on both sides of solid electrolytes 2, and separators 4A made of a NiCr heat resisting alloy. Oxidizing agent gas passage grooves 6A are formed by arranging and laminating gas passage groove forming members 7 having a thermal expansion coefficient smaller than that of the separators 4A and close to that of the solid electrolytes 2, and made of squared materials of LaMnO3 , between the cathodes 3 and the separators 4A.

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 which uses a solid electrolyte and converts Gibbs free energy into electric energy by an electrochemical reaction.

[0002]

2. Description of the Related Art A solid electrolyte fuel cell using a solid electrolyte such as zirconia has a high operating temperature of about 1000 ° C., and thus has a high power generation efficiency and requires no catalyst. It has the advantage that simplification can be expected. Furthermore, since the electrolyte is solid, it is easy to handle and has excellent long-term stability, and is expected to be used as a power generation system in the future.

FIG. 5 is a sectional view of a main part showing an example of a basic configuration of a conventional solid oxide fuel cell. This configuration is a so-called flat plate type configuration, in which a plate-like cell formed by disposing an anode 1 and a cathode 3 on both surfaces of a solid electrolyte 2 and a separator 4 are alternately stacked and fastened from both ends. A fuel gas flow groove 5 is provided on the main surface of the separator 4 facing the anode 1, and an oxidizing gas flow groove 6 is provided on the other main surface of the separator 4 facing the cathode 3. .

In this configuration, when a fuel gas containing hydrogen and an oxidizing gas are supplied from the outside, the fuel gas flowing through the fuel gas flow groove 5 diffuses inside the anode 1 and reaches the solid electrolyte 2. . On the other hand, the oxidizing gas flowing through the oxidizing gas flow groove 6 is reduced at the cathode 3 to become oxide ions, moves inside the solid electrolyte 2, and at the interface between the solid electrolyte 2 and the anode 1, fuel gas An electrochemical reaction occurs with the hydrogen inside to produce water, and at the same time, electric energy is extracted to the outside.

[0005]

In the flat solid electrolyte fuel cell as described above, the separator 4 is usually made of a heat-resistant NiCr-based alloy. In the region, the thermal expansion coefficient of the NiCr heat-resistant alloy is approximately 16 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of YSZ used as the solid electrolyte 2 is 10.5 × 10
It is considerably larger than ^-6 / ° C. For this reason, when a fuel cell formed by alternately laminating cells formed by disposing anodes 1 and cathodes 3 on both surfaces of a solid electrolyte 2 and separators 4 and tightening from both ends to the operating temperature, the solid electrolyte 2 Due to the difference in thermal expansion between the solid electrolyte 2 and the separator 4, a tensile stress is applied to the solid electrolyte 2 and a compressive stress is applied to the separator 4, which causes a problem that the solid electrolyte 2 having poor strength is cracked.

Further, since the NiCr-based heat-resistant alloy is not easily processed, the processing of the separator 4 having the fuel gas flow grooves 5 and the oxidizing gas flow grooves 6 is costly and extremely expensive. there were. The present invention has been made in view of the problems of the prior art as described above, and an object of the present invention is to operate safely without causing damage to the solid electrolyte even when the temperature is raised to the operating temperature, and to provide a separator. An object of the present invention is to provide a solid oxide fuel cell which can be easily processed at a low cost.

[0007]

In order to achieve the above object, the present invention provides a flat cell having an anode and a cathode on both surfaces of a solid electrolyte and a separator made of a gas impermeable material. In a solid oxide fuel cell configured by stacking alternately, between the cell and the separator, a conductive material or a non-conductive material having a surface provided with conductivity, and a temperature range from room temperature to an operating temperature. A gas flow path constituent member formed of a material having a thermal expansion coefficient smaller than that of the separator and smaller than or equal to the thermal expansion coefficient of the solid electrolyte is provided. For example, (1) the cell cathode side and the separator the gas flow path constituting member is formed by, for example, LaMnO ₃ or LaCrO ₃ of such electrically conductive ceramic, or a heat resistant metal conductive ceramic of the same type was coated on the surface disposed between the And the.

(2) Further, the gas flow path constituting member of (1) is incorporated by applying the same kind of conductive ceramic paste on the surface. (3) Further, the gas flow path constituting member disposed between the anode side of the cell and the separator is made of Ni-YSZ cermet, a heat-resistant metal, or a heat-resistant metal coated with Ni.

(4) Further, the gas flow path constituting member of (3) is incorporated by applying a Ni paste on the surface or inserting a Ni felt. (5) Further, the gas flow path constituting member disposed between the anode side of the cell and the separator is made of a non-conductive ceramic pressed and sandwiched by a metal felt such as a Ni felt.

As described above, a gas flow formed between the cell and the separator by a material having conductivity and a thermal expansion coefficient smaller than the thermal expansion coefficient of the separator and equal to or higher than the thermal expansion coefficient of the solid electrolyte. If the passage component is arranged, when the fuel cell is heated to the operating temperature, the amount of thermal expansion of the gas passage component arranged in contact with the solid electrolyte is compared with the amount of thermal expansion of the separator. Since the temperature is kept low, the thermal stress applied to the solid electrolyte is reduced, and the occurrence of cracks is prevented.

In particular, if the above (1) is satisfied, the thermal stress applied to the cathode side of the cell is reduced. Further, according to the above (2), the gas flow path constituting member disposed between the cathode side of the cell and the separator is incorporated while maintaining good conductivity, so that the internal loss is effectively reduced. Is done. In addition, when the above condition (3) is satisfied, the thermal stress applied to the anode side of the cell is reduced. In addition, the above (4)
According to the above, the gas flow path constituting member disposed between the anode side of the cell and the separator is incorporated while maintaining good conductivity, so that the internal loss is effectively reduced.
In addition, according to (5), the thermal stress applied to the anode side of the cell can be extremely small.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to examples. <Embodiment 1> FIG. 1 is a sectional view of a main part showing a basic structure of a first embodiment of a solid oxide fuel cell according to the present invention. This configuration is basically the same as the conventional example shown in FIG.
A cell in which an anode 1 and a cathode 3 are arranged on both surfaces of a solid electrolyte 2 and separators 4A made of a NiCr heat-resistant alloy are alternately stacked. The difference between the present configuration and the configuration of the conventional example lies in the method of forming the oxidizing gas flow groove 6A disposed facing the cathode 3 of the cell. In the conventional example, the oxidizing gas flow groove 6 is formed in the separator 4. On the other hand, in this embodiment, a paste of LaMnO ₃ is applied to the gas flow groove forming member 7 made of a square material of LaMnO ₃ of a conductive ceramic, and an arrangement example is shown in FIG. As described above, the oxidizing gas passage grooves 6A are formed by arranging the cells on the cathode 3 of the cell 10 and laminating them in combination with the separator 4A having the same LaMnO ₃ paste applied on the surface.

In this configuration, the thermal expansion coefficient of the separator 4A made of a NiCr heat-resistant alloy in the temperature range from room temperature to the operating temperature is 16 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the solid electrolyte 2 is 1
In contrast to 0.5 × 10 ⁻⁶ / ° C., the coefficient of thermal expansion of the gas flow groove forming member 7 made of LaMnO ₃ disposed between the cathode 3 of the cell 10 and the separator 4A is 12 × 10 ^−6. / ℃
The thermal expansion coefficient is considerably smaller than the thermal expansion coefficient of the separator 4A, and is close to the thermal expansion coefficient of the solid electrolyte 2. Therefore, when the battery of the present configuration is heated to the operating temperature, the thermal stress due to the difference in thermal expansion applied to the solid electrolyte 2 is greatly reduced as compared with the conventional example, so that the solid electrolyte cracks as seen in the prior art can be obtained. Is no longer a possibility. Further, the gas flow groove forming member 7 is made of a conductive ceramic LaMnO ₃ material, and is further coated with a LaMnO ₃ paste, so that the internal resistance can be suppressed to a very small value and good power generation can be achieved. Characteristics are obtained.

Further, according to this configuration, it is not necessary to form the oxidant gas passage groove in the separator 4A, so that the processing cost is reduced and the separator 4A can be manufactured at a low cost. In this embodiment, the gas flow groove forming member 7 is made of conductive ceramic LaM.
Although constituted by square material of nO _3, instead of the square timber of LaMnO _3, lower thermal expansion coefficient than the separator 4A, and the use of large FeCr-based heat-resistant alloy of the thermal expansion coefficient of a solid electrolyte 2, LaMnO the surface ₃ The same effect can also be obtained by forming a gas flow groove forming member by coating the material.

<Embodiment 2> FIG. 3 is a sectional view of a main part showing a basic structure of a solid oxide fuel cell according to a second embodiment of the present invention. In the first embodiment, the gas flow groove forming member 7 is arranged on the surface of the cathode 3 of the cell, and the oxidizing gas flow groove 6A is formed.
The feature of the present embodiment lies in the method of forming the fuel gas flow groove formed facing the anode 1 of the cell. That is, in this embodiment,
On the anode 1 of the cell, a surface for preventing steam oxidation 1
A gas flow groove forming member 7A made of a square material of a FeCr-based heat-resistant alloy plated with 0 μm Ni is arranged, and a separator 4 is formed.
By stacking in combination with B, a fuel gas flow groove 5A is formed.

In this configuration, the FeCr-based heat-resistant alloy forming the gas flow groove forming member 7A is smaller than the NiCr-based heat-resistant alloy forming the separator 4B and has a larger thermal expansion coefficient than the solid electrolyte 2. Therefore, as in the first embodiment, the thermal stress due to the difference in thermal expansion applied to the solid electrolyte 2 when the temperature is raised to the operating temperature is reduced, and the solid electrolyte is not likely to crack.

Further, according to this configuration, since it is not necessary to process the fuel gas flow groove in the separator 4B, the processing cost is reduced, and the separator 4B can be manufactured at a low cost. In the above configuration, when the gas flow groove forming member 7A made of a Ni-plated FeCr-based heat-resistant alloy square member is incorporated, Ni
If the paste is applied and incorporated, the contact resistance can be suppressed to a very small value, which is effective in reducing the internal loss. Also, instead of applying the Ni paste, assembling by inserting Ni felt into the contact surface, the contact resistance is suppressed very small and the internal loss is reduced.

The same effect can be obtained by using the Ni / YSZ forming the anode 1 instead of the FeCr heat-resistant alloy and forming the gas flow groove forming member 7A by the square material in the above configuration. Is obtained. <Embodiment 3> FIG. 4 is a schematic view showing a method of forming a fuel gas passage groove according to a third embodiment of the solid oxide fuel cell of the present invention.

As shown in FIG. 4 (a), the fuel gas flow groove of this configuration is made by placing a zirconia square member 21 having a cross section of 2 mm in width and 1 mm in thickness on a Ni felt 22 having a thickness of 1.5 mm. After arranging and further placing the same Ni felt 22 on the upper part, pressure is applied vertically. FIG. 4B shows the state after pressurization. The compressed Ni felt 22 remains on the upper surface and the lower surface of the zirconia square member 21, and the upper and lower portions of the zirconia square member 21 do not have the Ni felt 22. 22 are arranged in contact with each other. Since the Ni felt 22 is porous, the fuel gas can flow therethrough, and the fuel gas flow groove 5B is formed in a portion where the zirconia square member 21 is not provided. Further, since the Ni felt 22 ensures conductivity, the square member 21 does not need to have conductivity, and zirconia can be used as in this example.

With this configuration, the thermal stress generated in the Ni felt 22 due to thermal expansion is very small, and the zirconia used for the square bar 21 is the same type of material as the solid electrolyte. Is extremely small.
Therefore, there is no possibility that the solid electrolyte may be damaged by thermal stress. Also in this configuration, since it is not necessary to process the fuel gas flow grooves in the separator, the processing cost is reduced,
It can be manufactured at low cost.

In this configuration, zirconia is used as the square member 21 forming the fuel gas flow groove 5B. However, the material is not limited to zirconia, and the thermal expansion coefficient is taken into consideration so as to reduce thermal stress. You just need to select it. Also,
In this configuration, the Ni felt 22 is used, but another metal felt may be used.

[0022]

As described above, according to the present invention, a flat unit cell having an anode and a cathode disposed on both surfaces of a solid electrolyte and a separator made of a gas impermeable material are alternately laminated. In the solid oxide fuel cell to be
A solid electrolyte between the unit cell and the separator, which is a conductive material or a non-conductive material having conductivity imparted to its surface, and whose thermal expansion coefficient in the temperature range from room temperature to the operating temperature is smaller than that of the separator. Since the gas flow path component made of a material equal to or more than the thermal expansion coefficient of the solid electrolyte is arranged, the thermal stress generated between the solid electrolyte and the separator is reduced, and the solid electrolyte can be safely Thus, a solid oxide fuel cell that can be operated in a short time was obtained.

In addition, since the number of processing steps for forming the reaction gas flow groove to the separator is reduced, a solid oxide fuel cell can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a basic configuration of a first embodiment of a solid oxide fuel cell according to the present invention;

FIG. 2 is a perspective view showing an arrangement example of a gas flow groove forming member 7 of the first embodiment.

FIG. 3 is a sectional view of a main part showing a basic configuration of a second embodiment of the solid oxide fuel cell according to the present invention;

FIG. 4 is a schematic view showing a method for forming a fuel gas flow groove according to a third embodiment of the solid oxide fuel cell of the present invention.

FIG. 5 is a cross-sectional view of a main part showing a basic configuration example of a conventional solid oxide fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode 2 Solid electrolyte 3 Cathode 4A Separator 4B Separator 5 Fuel gas flow groove 5A Fuel gas flow groove 5B Fuel gas flow groove 6 Oxidant gas flow groove 6A Oxidant gas flow groove 7 Gas flow groove forming member 7A Gas flow groove forming member 10 Cell 21 Square member 22 Ni felt

Claims (9)

[Claims] 1. A solid oxide fuel cell comprising a solid electrolyte and a flat cell having an anode and a cathode disposed on both surfaces thereof and a separator made of a gas-impermeable material, which are alternately stacked. Between a conductive material or a non-conductive material having conductivity imparted to its surface, and a coefficient of thermal expansion in a temperature range from room temperature to an operating temperature is smaller than a coefficient of thermal expansion of the separator; 1. A solid oxide fuel cell comprising a gas flow path component formed of a material equivalent to or higher than that of the solid electrolyte fuel cell. 2. The gas flow path constituting member disposed between a cathode side of a cell and a separator comprises a conductive ceramic,
2. The solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell is formed of a heat-resistant metal having a surface coated with a conductive ceramic. 3. 3. The solid oxide fuel cell according to claim 2, wherein said gas flow path constituting member is incorporated by applying a conductive ceramic paste to a surface thereof. 4. The conductive ceramic is LaMnO ₃ or L
solid oxide fuel cell according to claim 2, 3 or 4, characterized in that a Acro _3. 5. The solid electrolyte type according to claim 1, wherein the gas flow path constituting member disposed between the anode side of the cell and the separator is formed of Ni-YSZ cermet. Fuel cell. 6. The gas flow path constituting member disposed between the anode side of the cell and the separator is made of a heat-resistant metal or N 2
2. The solid oxide fuel cell according to claim 1, wherein the solid electrolyte fuel cell is formed of a heat-resistant metal covering i. 7. The solid electrolyte type according to claim 5, wherein the gas flow path constituting member is incorporated by applying a Ni paste on the surface or inserting a Ni felt. Fuel cell. 8. The gas flow path member disposed between the anode side of the cell and the separator is made of a non-conductive ceramic pressed and sandwiched between metal felt layers. Item 2. The solid oxide fuel cell according to Item 1. 9. The solid oxide fuel cell according to claim 8, wherein said metal felt is Ni felt.