JP4192481B2 - Flat plate type solid oxide fuel cell and its manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat plate solid oxide fuel cell and a method for manufacturing the same.
[0002]
[Prior art]
A flat plate type solid oxide fuel cell has a structure in which a cell composed of three layers of an air electrode, an electrolyte, and a fuel electrode and a separator for electrically connecting the cells are sequentially stacked. The separator is provided with a gas flow path for flowing an oxidant on the air electrode side of the cell and a fuel gas on the fuel electrode side. The size of the cell is generally proposed to be about 5 cm × 5 cm to 10 cm × 10 cm, and as the shape of the separator, an orthogonal groove or a dimple shape is proposed. Yes. Oxidizing agent at a high temperature of about 1000 ° C. The material of the conventional separators, conductive oxide such as chemically stable LaSrCrO ₃ in an atmosphere of both the fuel gas have been proposed. However, metal separators have been proposed for reasons such as poor workability and high cost, but when used for a long time in the above atmosphere, an oxide film is formed on the surface, and the contact resistance between the cell / separator is low. There was a problem of increasing. On the other hand, Japanese Patent Application Laid-Open No. 8-203544 proposes a method for manufacturing a separator for a solid oxide fuel cell in which a conductive oxide layer is formed on the entire surface of a metal as a base material using a thermal spraying method. JP-A-8-273683 proposes a heat treatment method after coating by a thermal spraying method.
[0003]
[Problems to be solved by the invention]
The conductive oxide layer on the surface of the metal base described above is formed on the entire surface area of the metal substrate as shown in FIG. 1, but with the change in temperature at the start and stop of the fuel cell, Peeling due to thermal stress due to difference in thermal expansion coefficient is likely to occur. Moreover, since the conductive oxide layer is formed by a thermal spraying method and does not have high adhesion to the substrate, peeling due to the thermal stress is likely to occur. As a result, there is a problem that the contact resistance between the cell and the separator increases and the power generation performance decreases. In addition, the thermal spraying process requires a high temperature process, which is a problem of energy consumption and high cost. If the heat treatment is performed after the film formation by the thermal spraying method disclosed in Japanese Patent Laid-Open No. 8-273683, the cost is further increased.
[0004]
The present invention has been made to solve the above problems, and provides a separator having excellent durability and a method for producing the same.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a first invention is a flat solid having a structure in which a cell composed of three layers of a fuel electrode, an electrolyte, and an air electrode and a separator for electrically connecting the cells are sequentially laminated. In the oxide fuel cell, the separator supports the cell and has a three-dimensional metal substrate having a plurality of projections that form a ventilation space between the cell and the surface of the metal substrate formed by an aerosol deposition method. A flat solid oxide fuel cell comprising: a conductive oxide layer, wherein electrons are transferred between the cell and the metal substrate through the conductive oxide layer. To do. In this case, the conductive oxide refers to oxide ceramics having a conductivity of 1 S · cm ⁻¹ or more at a temperature of 700 to 1000 ° C. In addition, the aerosol deposition method is a method in which an aerosol in which fine particles are dispersed in a gas is sprayed and collided toward the surface of the substrate, and a structure layer made of a constituent material of the fine particles is formed on the substrate surface without firing. Say how.
[0006]
In the contact between the conductive oxide layer and the cell, they may be brought into direct contact with each other, or on the side in contact with the fuel electrode of the cell for the purpose of preventing contact failure due to deformation of the cell or metal substrate. Ni felt or the like may be interposed between the conductive oxide layer and the cell, and conductive oxide powder such as lanthanum cobaltite may be interposed on the side of the cell that contacts the air electrode. Further, in the cell, a catalyst layer material for reducing the activation overvoltage may be interposed at the interface between the electrode and the electrolyte, or the catalyst layer material and the electrode material may have a compositionally and microstructured inclined structure. .
[0007]
According to the present invention, since the conductive oxide layer is formed on the surface of the metal substrate by the aerosol deposition method, the coefficient of thermal expansion of the conductive oxide layer and the metal substrate accompanying the temperature change at the start and stop of the fuel cell It is possible to provide a flat-plate solid oxide fuel cell that suppresses peeling of the conductive oxide layer due to thermal stress due to the difference between the two and has excellent durability.
[0008]
In order to achieve the above object, the second invention is a flat solid oxide having a structure in which a cell composed of three layers of a fuel electrode, an electrolyte, and an air electrode and a separator for electrically connecting the cells are sequentially laminated. A solid fuel cell, wherein the separator supports a cell and has a three-dimensional metal substrate having a plurality of protrusions that form a ventilation space between the cell and the metal substrate so as to cover a tip portion of the protrusion. A flat solid oxide comprising a plurality of conductive oxide layers bonded directly to each other, and causing movement of electrons between the cell and the metal substrate through the conductive oxide layer A fuel cell is provided.
[0009]
According to the present invention, since the conductive oxide layer formed on the metal substrate is arranged in a small area in a projecting manner, the conductive oxide layer and the metal substrate are changed in accordance with the temperature change at the start and stop of the fuel cell. It is possible to provide a flat-plate solid oxide fuel cell excellent in durability by suppressing peeling of the conductive oxide layer caused by thermal stress due to a difference in thermal expansion coefficient. The conductive oxide layer covering the protrusion of the metal substrate is preferably applied only to the contact area with the cell, but is not limited thereto, and may be larger than the area of this area in each protrusion. The larger the total contact area with the cell, the better from the viewpoint of reducing the contact resistance, but the smaller the respective area of the conductive oxide layer on the protrusion, the less the film cracking and peeling at the time of temperature change. is there. Therefore, it is convenient to increase the number of protrusions. The area of each conductive oxide layer is uniquely determined from the relationship between the film thickness, the difference in thermal expansion coefficient between the conductive oxide layer and the metal substrate, the adhesion between them, the elastic modulus of the metal substrate, etc. Can not be defined, it is good to adopt the optimal value from these combinations.
[0010]
In order to achieve the above object, the third invention is the flat solid oxide fuel cell according to claim 1 or 2, wherein the conductive oxide layer is in contact with the air electrode of the cell and the fuel electrode. The main component of the conductive oxide layer on the side in contact with the air electrode of the cell is a perovskite oxide containing at least lanthanum and an alkaline earth element, and Provided is a flat plate solid oxide fuel cell characterized in that the main component of the conductive oxide layer on the side in contact with the fuel electrode of the cell is a perovskite oxide containing at least lanthanum and chromium.
[0011]
As the material for the metal substrate, when the operating temperature of the fuel cell is an intermediate temperature range of 800 ° C. or lower, ferritic stainless materials such as SUS430 and its developed material are desirable from the viewpoint of matching thermal expansion coefficients, and the operating temperature is In the case of a high temperature range of 800 ° C. or higher, from the viewpoint of heat resistance, a heat-resistant metal material such as Inconel 600, Hastelloy, or a Ni-based alloy doped with a rare earth element is preferable.
[0012]
According to the present invention, the film resistance of the conductive oxide layer can be lowered by making the main component of the conductive oxide layer on the side in contact with the air electrode of the cell a perovskite oxide containing at least lanthanum. At the same time, when a chromium oxide film is formed at the interface between the metal substrate and the conductive oxide layer, lanthanum and alkaline earth elements in the conductive oxide layer diffuse and dissolve in the chromium oxide film. Since the element is doped with lanthanum chrome oxide, it has conductivity, so that a significant increase in resistance can be suppressed. In addition, the main component of the conductive oxide layer on the side in contact with the fuel electrode of the cell is a perovskite oxide containing at least lanthanum and chromium, so that the film resistance of the conductive oxide layer can be maintained even in a humidified fuel gas atmosphere. When the chromium oxide film is formed at the interface between the metal substrate and the conductive oxide layer, the lanthanum in the conductive oxide layer diffuses and dissolves in the chromium oxide film, and the conductivity becomes low. Since the lanthanum chromium oxide having the above can be formed, a significant increase in resistance can be suppressed.
[0013]
In order to achieve the above object, a fourth invention is the flat solid oxide fuel cell according to claim 3, wherein the conductive oxide layer is in contact with the air electrode and the fuel electrode. Lanthanum manganite doped with alkaline earth element as a main component of the conductive oxide layer on the side in contact with the air electrode of the cell, and lanthanum doped with alkaline earth element Cobaltite, lanthanum cobaltite doped with alkaline earth elements and Fe, lanthanum chromite doped with alkaline earth elements, or a mixture thereof, and the conductive oxide layer on the side in contact with the fuel electrode of the cell Provided is a flat solid oxide fuel cell characterized by being a lanthanum chromite doped with an alkaline earth element.
[0014]
According to the present invention, the main component of the conductive oxide layer on the side in contact with the air electrode of the cell is lanthanum manganite doped with alkaline earth element, lanthanum cobaltite doped with alkaline earth element, alkaline earth The film resistance of the conductive oxide layer can be reduced by using a lanthanum cobaltite doped with an elemental element and Fe, lanthanum chromite doped with an alkaline earth element, or a mixture thereof, and a metal substrate. When a chromium oxide film is formed at the interface between the lanthanum and the conductive oxide layer, the lanthanum and the alkaline earth element in the conductive oxide layer are diffused and dissolved in the chromium oxide film, and the ant potassium earth element is doped. Since the lanthanum chrome oxide has conductivity, a significant increase in resistance can be suppressed. In addition, the conductive oxide layer on the side in contact with the fuel electrode of the cell is made of lanthanum chromite doped with an alkaline earth element, thereby reducing the membrane resistance of the conductive oxide layer even in a humidified fuel gas atmosphere. In the case where a chromium oxide film is formed at the interface between the metal substrate and the conductive oxide layer, the lanthanum chromium in the conductive oxide layer diffuses and dissolves in the chromium oxide film and has conductivity. Since an oxide can be formed, a significant increase in resistance can be suppressed.
[0015]
A fifth invention for achieving the above object is the flat solid oxide fuel cell according to any one of claims 1 to 4, wherein the thickness of the conductive oxide layer is not less than 1 μm and not more than 30 μm. A flat plate solid oxide fuel cell is provided.
[0016]
According to the present invention, it is possible to provide a flat solid oxide fuel cell with higher durability by setting the thickness of the conductive oxide layer to 1 μm or more and 30 μm or less. The reason why the thickness of the conductive oxide layer is 1 μm or more and 30 μm or less is that when the thickness is 1 μm or more, the effect of suppressing the formation of an oxide film with high electrical resistance on the surface of the metal substrate is increased, and the thickness is 30 μm. This is because the effect of suppressing the peeling of the conductive oxide layer due to the thermal stress accompanying the temperature change at the start and stop of the fuel cell is enhanced by the following.
[0017]
A sixth invention for achieving the above object is the flat solid oxide fuel cell according to any one of claims 1 to 4, wherein the thickness of the conductive oxide layer is 5 μm or more and 20 μm or less. A flat plate solid oxide fuel cell is provided.
[0018]
According to the present invention, it is possible to provide a flat solid oxide fuel cell with higher durability by setting the thickness of the conductive oxide layer to 5 μm or more and 20 μm or less. The reason why the thickness of the conductive oxide layer is 5 μm or more and 20 μm or less is that when the thickness is 5 μm or more, the effect of suppressing the formation of an oxide film having a high electrical resistance on the metal substrate surface is further increased. This is because when the thickness is 20 μm or less, the effect of suppressing the peeling of the conductive oxide layer due to the thermal stress accompanying the temperature change when the fuel cell is started or stopped is further enhanced.
[0019]
7. A flat solid oxide fuel according to claim 2, wherein the conductive oxide layer is formed on the surface of the metal substrate by an aerosol deposition method. Provide batteries.
[0020]
According to the present invention, since the conductive oxide layer is formed on the surface of the metal substrate by the aerosol deposition method, the conductive oxide layer is caused by the thermal stress accompanying the temperature change at the start and stop of the fuel cell. It is possible to provide a flat plate solid oxide fuel cell that suppresses peeling and has excellent durability.
[0021]
Further, in the present invention, at least the above-mentioned three-dimensional metal substrate having a plurality of protrusions that support a cell and form a ventilation space between the aerosol in which conductive oxide fine particles are dispersed in a gas. A plurality of conductive oxide layers made of constituent materials of the conductive oxide fine particles are formed at least on the tip portion of the projection without being fired and collided toward the tip portion of the projection. A flat-plate solid oxide fuel cell comprising: a step of producing a separator comprising the metal substrate and the conductive oxide layer; and a step of sequentially laminating the separator and a cell comprising a fuel electrode, an electrolyte, and an air electrode. A manufacturing method of is provided.
An aerosol deposition method for forming a thick film (layer) of a brittle material such as an oxide on a substrate, which is the above-described manufacturing method, will be described. In the aerosol deposition method, an aerosol in which fine particles of mainly brittle materials such as ceramics are dispersed in a gas is directed to a substrate made of a metal material in a relatively low temperature environment such as room temperature. This is a technique in which a thick ceramic film is formed on a substrate without firing by spraying through a nozzle for injection at a speed of 5 mm. It is characterized in that a high-strength structure similar to a fired body, in which crystals are joined together, can be formed instead of powder. Compared with a technique such as thermal spraying, a dense and high-hardness thick film can be formed. When a ductile material such as a metal is used for a substrate, an anchor portion in which a brittle material bites into the substrate is formed by the impact of collision of fine particles, and thus has a feature of excellent adhesion strength. Further, it is easy to form a thick film (layer) in a spot manner by making the nozzle an arbitrary shape.
By using this method to produce a separator for a solid oxide fuel cell, a separator having excellent electrical conductivity due to good adhesion between the conductive oxide layer and the metal substrate and high density. It is possible to produce a flat solid oxide fuel cell having excellent durability and good power generation performance.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
2 to 4 are diagrams showing a separator for a solid oxide fuel cell. FIG. 6 shows a schematic diagram of a production apparatus 20 (aerosol deposition apparatus) used for realizing this embodiment.
The fuel cell separator 1 includes a SUS430 substrate 10 and a LaSrFeCoO ₃ layer 11. In the production apparatus 20, a nitrogen gas cylinder 201 is connected to an aerosol generator 203 containing LaSrFeCoO ₃ fine particles having a particle diameter of 0.5 μm via a gas transport pipe 202, and installed in a formation chamber 205 via an aerosol transport pipe 204. Connected to the nozzle 206 having an aerosol injection port. A SUS430 substrate 10 installed on the XY stage 207 is disposed at the tip of the nozzle 206. The formation chamber 205 is connected to a vacuum pump 208.
[0023]
A procedure for manufacturing the fuel cell separator 1 using the manufacturing apparatus 20 having the above configuration will be described below. The nitrogen gas cylinder 201 is opened, and nitrogen gas is introduced into the aerosol generator 203 through the transport pipe 202 to generate an aerosol containing LaSrFeCoO ₃ fine particles. The aerosol is sent to the nozzle 206 through the transport pipe 204 and ejected at a high speed from the opening of the nozzle 206. At this time, the inside of the forming chamber 205 is placed in a reduced pressure environment of several kPa by the operation of the vacuum pump 208.
[0024]
LaSrFeCoO ₃ fine particles collide with the SUS430 substrate 10 disposed at the tip of the opening of the nozzle 206 at a high speed, the particles are deformed and crushed by the kinetic energy, and a part bites into the SUS430 substrate 10 to form an anchor layer. Part of the particles are joined together, and this is repeated to form a dense LaSrFeCoO ₃ layer on the SUS430 substrate 10. The SUS430 substrate 10 is swung by the XY stage 207, and the LaSrFeCoO ₃ layer is formed in a desired area, and the LaSrFeCoO ₃ layer 11 having a film thickness of 15 μm is obtained on the SUS430 substrate 10. All these processes can be performed at room temperature.
[0025]
In the separator 1 thus obtained, the SUS430 substrate 10 and the LaSrFeCoO ₃ layer 11 are firmly bonded, and since the separator 1 is formed at room temperature, the residual stress of the LaSrFeCoO ₃ layer is small, and the Cr ₂ O layer is formed on the surface of the SUS430 substrate. An oxide film such as _three films is not formed. The surface after the formation has a surface roughness of Ra = 0.18 μm, but this surface may be polished or used as it is in consideration of the electrical connection with the cell electrode in the subsequent process. Is also suitable.
[0026]
FIG. 5 is a cross-sectional view of the fuel cell stack 3 using the separator 1 and laminated with a flat plate cell. The separator 1 and the flat plate type cell on the anode side is bonded via an electrically conductive felt such as Ni felt, the cathode side may be bonded via a conductive oxide powder such as LaSrFeCoO ₃ powder.
[0027]
【The invention's effect】
As described above, according to the present invention, since the conductive oxide layer is formed on the surface of the metal substrate by the aerosol deposition method, the conductive oxide layer and the metal accompanying the temperature change at the start and stop of the fuel cell are used. It is possible to provide a flat solid oxide fuel cell that is excellent in durability by suppressing peeling of the conductive oxide layer caused by thermal stress due to the difference in thermal expansion coefficient of the substrate.
In addition, since the conductive oxide layer formed on the metal substrate is arranged in a small area in a protruding manner, the thermal expansion coefficient of the conductive oxide layer and the metal substrate due to the temperature change at the start and stop of the fuel cell It is possible to provide a flat-plate solid oxide fuel cell that suppresses peeling of the conductive oxide layer due to thermal stress due to the difference and has excellent durability.
Furthermore, by making a separator for a solid oxide fuel cell using the aerosol deposition method, the adhesion between the conductive oxide layer and the metal substrate is good and the structure is electrically conductive due to its high density. Therefore, it is possible to produce a flat plate solid oxide fuel cell having excellent durability and excellent power generation performance.
[Brief description of the drawings]
1 is a sectional view of a conventional separator. FIG. 2 is a perspective view of a separator according to the present invention. FIG. 3 is a perspective view of a separator according to the present invention. FIG. 4 is a perspective view of a separator according to the present invention. FIG. 6 is a perspective view of a cell stack according to the present invention. FIG. 6 is a diagram showing an example of a separator manufacturing apparatus according to the present invention.
10: Substrate 20: Fabrication device (aerosol deposition device)

Claims (6)

In a flat solid oxide fuel cell having a structure in which a cell composed of three layers of a fuel electrode, an electrolyte, and an air electrode and a separator for electrically connecting the cells are sequentially laminated, the separator is A solid metal substrate having a plurality of protrusions for supporting a cell and forming a ventilation space between the cell and a conductive oxide layer formed on the surface of the metal substrate by an aerosol deposition method. And a movement of electrons between the cell and the metal substrate is caused through the conductive oxide layer. The conductive oxide layer is provided on both sides of the cell in contact with the air electrode and the fuel electrode, and the main component of the conductive oxide layer on the cell in contact with the air electrode is It is a perovskite oxide containing at least lanthanum and an alkaline earth element, and the main component of the conductive oxide layer on the side in contact with the fuel electrode of the cell is a perovskite oxide containing at least lanthanum and chromium. The flat plate type solid oxide fuel cell according to claim 1. The main component of the conductive oxide layer in contact with the air electrode of the cell is lanthanum manganite doped with alkaline earth element, lanthanum cobaltite doped with alkaline earth element, alkaline earth element and Fe. One selected from the group of doped lanthanum cobaltite, lanthanum chromite doped with alkaline earth elements, or a mixture selected from these groups, the conductivity on the side in contact with the anode of the cell 3. The flat plate solid oxide fuel cell according to claim 1, wherein the oxide layer is lanthanum chromite doped with an alkaline earth element. The thickness of the said conductive oxide layer is 1 micrometer or more and 30 micrometers or less, The flat type solid oxide fuel cell as described in any one of Claims 1-3 characterized by the above-mentioned. 5. The flat solid oxide fuel cell according to claim 1, wherein the conductive oxide layer has a thickness of 5 μm to 20 μm. An aerosol, in which conductive oxide fine particles are dispersed in a gas, is applied to at least the tip portion of the three-dimensional metal substrate having a plurality of protrusions that support the cell and form a ventilation space with the cell. A plurality of conductive oxide layers made of constituent materials of the conductive oxide fine particles are formed on at least a tip portion of the projection without being fired and collided toward the metal substrate, and the metal substrate, A method for producing a flat plate solid oxide fuel cell comprising a step of producing a separator comprising the conductive oxide layer, and a step of sequentially laminating the separator and a cell comprising three layers of a fuel electrode, an electrolyte and an air electrode.

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