JP4807606B2 - STACK FOR SOLID ELECTROLYTE FUEL CELL AND SOLID ELECTROLYTE FUEL CELL - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid electrolyte fuel cell (SOFC) that uses a solid electrolyte and obtains electric energy by an electrochemical reaction, and more specifically, a fuel cell including a single cell in which a solid electrolyte is sandwiched between electrode layers. The present invention relates to a stack and a solid oxide fuel cell.
[0002]
[Prior art]
In recent years, fuel cells have been attracting attention as clean energy sources that are capable of high energy conversion and are friendly to the global environment, and their application as power sources for automobiles is being studied.
Solid oxide fuel cells (hereinafter abbreviated as “SOFC”) are attracting attention as highly efficient fuel cells.
However, since the electromotive force of a single fuel cell is as low as about 1 V, it is necessary to form a stack by connecting a plurality of single cells in series in order to increase the voltage, so the stacking method is important.
Also, when considering application as a power source for automobiles, it is necessary to increase the output, and one of the technologies for increasing the output of SOFC is to reduce the thickness of the solid electrolyte and electrode. The structure disclosed in Japanese Patent Application Laid-Open No. 8-64216 or the like has an insufficient current collecting function and requires a wiring structure for smoothly extracting current.
[0003]
[Problems to be solved by the invention]
In the conventional fuel cell stack as described above, since the electrode portion also serves as a current collecting function, when the electrode is thinned, the cross-sectional area of the conductive path is reduced and the electric resistance is increased.
Further, if a separator or an interconnector is disposed between the cell elements in order to improve the current collecting function, the proportion of the non-power generation elements in the fuel cell stack increases, and the output density decreases.
Furthermore, since the conventional interconnector is exposed to both an oxidizing gas atmosphere and a reducing gas atmosphere at a high temperature, high durability is required and usable materials are limited.
Furthermore, in order to increase the voltage, it is necessary to connect single cells in series. However, in a flat stack without a gas separator, it is very difficult to connect each single cell in series inside the stack. There is a problem related to complicated wiring structure and an increase in the number of components because serial connection must be performed outside.
[0004]
Accordingly, the present invention has been made in view of such problems of the conventional technology, and the object of the present invention is to achieve a highly reliable fuel cell stack and solid electrolyte that can be reduced in size and output. The purpose is to provide type fuel cells.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by arranging the conductive material responsible for current collection in a predetermined shape, and the present invention has been completed. It was.
[0006]
The invention described in claim 1 is a fuel cell in which a solid electrolyte layer is sandwiched between an air electrode layer and a fuel electrode layer to be electrically and mechanically joined, and an electrochemical reaction field is formed at the interface of the solid electrolyte layer. A fuel cell plate in which a single cell is disposed in a plurality of grooves or holes provided in a conductive substrate or an insulating substrate, and the groove or hole exists in the extending direction of each of the fuel cell plate Two or more conductive materials for conducting the current collected from the reaction field to the outside are joined in a two-dimensional and continuous manner, and each of these fuel cell cell plates, The air electrode layer, the fuel electrode layer, and the solid electrolyte layer are two-dimensionally connected and integrated in substantially the same direction as the stacking direction.
[0007]
In the invention described in claim 2, the electron conductivity of the conductive material described in claim 1 is equal to or higher than the electron conductivity of the material forming the air electrode layer and the fuel electrode layer.
[0008]
According to a third aspect of the present invention, the conductive material according to the first or second aspect of the invention is a lanthanum-strontium-manganese composite oxide, a lanthanum-strontium-cobalt composite oxide, lanthanum chromite, silver, nickel, copper, platinum And an alloy comprising at least one selected from the group consisting of iron and / or stainless steel.
[0009]
The invention according to claim 4 is a portion where the groove or hole of each fuel cell plate according to any one of claims 1 to 3 does not exist, and is a part of the upper surface of the cell plate for fuel cell. The conductive material for conducting the current collected from the reaction field to the outside from the part to the part of the lower surface is penetrated to the outside, and the conductive materials penetrated to the fuel cell plate are connected in series with each other, In addition, the air electrode layer, the fuel electrode layer, and the solid electrolyte layer are two-dimensionally connected and integrated in substantially the same direction as the stacking direction.
[0010]
The invention according to claim 5 is provided with an insulating portion in the single cell for fuel cell or the conductive material according to any one of claims 1 to 4, and includes one or a plurality of single cells and the air electrode layer side, and A current collecting section for collecting current on the fuel electrode layer side is formed.
[0011]
In the invention described in claim 6, the average area Sc of the cross section of the current collector described in claim 5 is larger than the average area Sr of the cross section of the reaction field.
[0012]
In the invention according to claim 7, the average area Sc of the cross section of the current collector described in claim 6 and the average area Sr of the cross section of the reaction field satisfy the relationship of Sc / Sr ≧ 10. .
The invention according to claim 8 uses the solid oxide fuel cell stack according to any one of claims 1 to 7 as a power generation element.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the single cell and the cell plate for the solid oxide fuel cell of the present invention will be described in detail. In the present specification, “%” indicates a mass percentage unless otherwise specified.
For convenience of explanation, one surface of each layer such as a single cell or an electrode layer is described as “upper surface, front surface” and the other surface is described as “lower surface, back surface”, etc., but these are equivalent elements and are mutually replaced. It goes without saying that such a configuration is also included in the scope of the present invention. Furthermore, the cell plate is a practical product form for promoting the integration of single cells and increasing the output of the resulting fuel cell.
[0014]
As described above, the unit cell of the present invention is formed by sandwiching a solid electrolyte layer between an air electrode layer and a fuel electrode layer, and arranging this on a substrate.
Here, the substrate is not particularly limited to a silicon (Si) substrate, and any of a conductive substrate and an insulating substrate can be employed. For example, a glass substrate or a metal substrate can be used. Thereby, the cost concerning a board | substrate can be reduced. However, it is particularly desirable to use a Si substrate or a metal substrate.
Moreover, the said clamping body (laminated body of an air electrode layer, a solid electrolyte layer, and a fuel electrode layer) is arrange | positioned in the groove | channel or hole provided in the board | substrate. Thus, the electrode current collector is formed without effectively reducing the output density by effectively using the dead space in the single cell. In addition, since the electrode current collector does not contact the source gas (oxidizing gas and fuel gas), a material having low gas durability can be used. Furthermore, the reaction field (power generation unit) formed by the contact of the raw material gas is fixed in a desired form. Such grooves and holes can be formed in various shapes in consideration of the output of the fuel cell, the raw material gas flow path, and the like, and the depths of the grooves and holes are not particularly limited.
[0015]
Moreover, as a constituent material of the air electrode layer and the fuel electrode layer, for example, nickel (Ni), copper (Cu), and their cermets can be used as the fuel electrode layer, and as the air electrode layer, LSM, LSC and Pt or the like can be used.
[0016]
Further, the solid electrolyte layer is necessary for developing a power generation function, and is a conventionally known material having oxygen ion conductivity, such as neodymium oxide (Nd ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ). Stabilized zirconia in which yttria (Y ₂ O ₃ ) and gadolinium oxide (Gd ₂ O ₃ ) are dissolved, ceria (CeO ₂ ) -based solid solution, bismuth oxide, LaGaO _{3 and the} like can be used. It is not limited to.
[0017]
The unit cell of the present invention is characterized in that the air electrode layer and the fuel electrode layer are electrically and mechanically joined to the solid electrolyte layer to form an electrochemical reaction field at the interface of the solid electrolyte layer. In addition, a conductive material capable of collecting current from the reaction field and conducting current to the outside is inserted into a portion of the substrate in the extending direction and where the groove or hole does not exist.
Thus, the direct current resistance when the stack is formed can be reduced, and single cells can be connected in series in the stack. Further, since the conductive material is not exposed to gas, even a material having low durability can be used. Furthermore, mechanical strength can be improved by using a strong material as the conductive material.
[0018]
Examples of the conductive material include lanthanum-strontium-manganese (La-Sr-Mn) composite oxide, lanthanum-strontium-cobalt (La-Sr-Co) composite oxide, lanthanum chromite, silver (Ag), nickel (Ni), copper (Cu), platinum (Pt) or iron (Fe), and alloys comprising metals according to any combination thereof, and / or stainless steel can be used. In this way, by selecting a material that can alleviate the difference in thermal expansion coefficient of other portions, it is possible to alleviate the heat shock when the stack is formed, and to raise the temperature of the fuel cell stack at high speed. In addition, an electrode layer current collector having a high current collecting function and stable even at high temperatures can be formed.
It is also effective to use a heating element such as a nickel-chromium alloy as the conductive material. In this case, it can be used as a heat source for starting up a stack or the like by energization.
[0019]
Furthermore, the electronic conductivity of the conductive material is preferably equal to or higher than the electronic conductivity of the material forming the air electrode layer and the fuel electrode layer. Thus, the resistance of each electrode layer current collector is sufficiently reduced, and current collection tends to be smooth. Further, when the cell plate is constructed, the temperature distribution in the cell plate can be made uniform, and the thermal durability of the stack can be improved.
[0020]
In the fuel cell plate according to the present invention, a plurality of the above-described single cells are two-dimensionally and continuously or intermittently provided in a direction substantially perpendicular to the stacking direction of the air electrode layer, the fuel electrode layer, and the solid electrolyte layer. Joined. In this case, it is effective because the balance between the electric resistance and the power generation output can be adjusted by appropriately changing the number of single cells handled by the conductive material.
Here, the case where the cell plate is formed by intermittently joining the single cells means that the cell plate is a cell plate formed by combining single cells having a configuration in which the conductive material is removed from the single cell of the present invention. In other words, a conductive material is provided for every two or more single cell units.
[0021]
Next, the stack for the solid oxide fuel cell of the present invention will be described.
Such a solid oxide fuel cell stack is formed by connecting a plurality of the above-mentioned single cells or cell plates for a fuel cell two-dimensionally in substantially the same direction as the stacking direction of the air electrode layer, fuel electrode layer, and solid electrolyte layer. It is made up of. When such a stack is used as a power generation element, a fuel cell excellent in output characteristics (suitable for an automobile power source) can be obtained.
[0022]
In addition, it is preferable that an insulating part is provided in the single cell or the conductive material for the fuel cell to form a current collecting part for collecting current on one or a plurality of single cells and on the air electrode layer side and the fuel electrode layer side. is there. That is, the reaction field responsible for electrode reaction and the current collector responsible for current transport can be separated for each desired unit, the direct current resistance of the stack can be reduced, and single cells can be easily connected in series.
The said insulation part can be provided so that it may be connected in series. Examples of the insulator constituting the insulating part include alumina, SiN, and glass.
In the solid oxide fuel cell stack of the present invention, it is desirable to insulate each electrode layer from the conductive material.
[0023]
Furthermore, the average area Sc of the cross section of the current collector is preferably larger than the average area Sr of the cross section of the reaction field. Specifically, the average area Sc of the cross section of the current collector and the average area Sr of the cross section of the reaction field satisfy the relationship Sc / Sr ≧ 10, that is, the cross sectional area of the current collector is The cross-sectional area of the reaction field responsible for current collection is preferably 10 times or more. In this case, the resistance of the electrode layer current collector can be made sufficiently small, and current can be collected smoothly.
[0024]
Next, the solid oxide fuel cell of the present invention will be described.
Such a fuel cell is obtained by configuring the above-described solid oxide fuel cell stack as a power generation element. As a result, since the conductive material is formed as a stack, the conductive material can be used as an interconnector (electric conduction path), and the fuel cell can be easily thinned and miniaturized.
[0025]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail with reference to drawings, this invention is not limited to these Examples.
[0026]
In Example 1 and Example 2, a plurality of unit cell plates A and unit cell plates B were laminated to produce a solid oxide fuel cell, and performance evaluation was performed.
[0027]
(Example 1)
1) Fabrication of substrate As a (100) -oriented single crystal silicon substrate (5 inch diameter, thickness 1.0 mm) having a resistivity of 10 to 11 Ωcm mixed with antimony, one whose surface is mirror-polished is used for dicing. -It cut | disconnected in the square shape of 5 cm square so that each edge | side may become a (110) direction with a saw. This square product was immersed in a mixed solution of water: hydrogen peroxide: ammonium hydroxide = 5: 1: 0.05 kept at 90 ° C. for 10 minutes, and then purified with a 5% hydrofluoric acid aqueous solution for 1 minute. It was taken out after being immersed in water for 1 minute, and was then carried into an ultra-high vacuum specification, multi-target sputtering apparatus immediately after drying by nitrogen gas injection. With respect to the film formation surface of the square silicon substrate housed in the substrate holder of the apparatus, the outer edge portion was covered with an Inconel mask so that the peripheral portion was not formed. The film formation area was set to be a 4 cm square portion of the central portion of the square substrate.
A single battery plate was fabricated using the Si substrate.
[0028]
2) Production of single cell plate A The substrate temperature was raised to 700 ° C. using a radiation heater on the silicon substrate, and a nickel oxide film having a film thickness of about 5000 mm was formed by RF sputtering using a metallic nickel target. Grown up.
Next, the substrate temperature is lowered to 600 ° C., and a 10 mol% yttria-added stabilized zirconia (hereinafter referred to as “10YSZ”) sintered body target is used to form a 10 YSZ thin film having a thickness of about 2 μm on the nickel oxide film. Grew.
Next, the substrate temperature was lowered to 500 ° C., and a polycrystalline LSM film having a film thickness of about 3000 mm was grown using a sintered compact target of LSM.
In this way, a nickel oxide film, a 10YSZ film, and a polycrystalline LSM film were sequentially laminated on one side of the silicon substrate.
[0029]
Next, a PSG (phosphosilicate glass) film having a thickness of about 5000 mm is deposited on both surfaces of the substrate by atmospheric pressure CVD, and then the back surface of the silicon substrate (the back surface of the surface on which the 10YSZ film or the like is laminated) The pattern shown in FIG. 1 was transferred by photolithography, and only the transfer portion corresponding to the white portion in FIG. 1 was removed by immersion in a hydrofluoric acid-based etching solution. Here, the reason why the width of the etching pattern is narrow is that the etching stops in the middle of the substrate during anisotropic etching.
After removing the photoresist by ashing, the substrate is immersed in an anisotropic etching solution of hydrazine hydrate kept at about 60 ° C. for about 8 hours, and the silicon substrate is made to correspond to the above pattern as shown in FIG. Etching is performed to make a small opening 2 in the surface of the substrate so that the laminated thin film is partially self-supporting. Moreover, the groove | channel 3 used as an electrode current collection part is simultaneously formed between small openings. This groove does not penetrate the substrate in the thickness direction.
Next, the silicon substrate was dipped in a hydrofluoric acid etching solution to remove the protective PSG film 4.
Subsequently, with respect to the surface where the laminated film is not formed, the substrate temperature is raised to 500 ° C. using a radiation heater, and along the gas flow path by RF sputtering using a sintered nickel metal target. Then, a nickel oxide film having a thickness of about 3000 mm was grown, and then a metal nickel paste was filled in a groove serving as an electrode current collector and dried to produce a unit cell plate A.
The size of each element part is 1.0 mm × 1.0 mm for the opening 2, the distance between the openings 2 is 1.0 mm, and the width of the groove is 0.8 mm at the longest part (the bottom of the triangle when viewed in cross section). The depth of the groove is 0.7 mm.
[0030]
3) Manufacture of single battery plate B With respect to the above silicon substrate, the substrate temperature is raised to 700 ° C. using a radiation heater, and a polycrystalline film having a film thickness of about 5000 mm by RF sputtering using a sintered compact target of LSM. An LSM film was grown.
Next, the substrate temperature was lowered to 600 ° C., and a 10 YSZ thin film having a thickness of about 2 μm was grown on the LSM film by using a sintered body target of 10 mol% yttria-added stabilized zirconia (hereinafter referred to as 10YSZ). .
Next, the substrate temperature was lowered to 500 ° C., and a nickel oxide film having a thickness of about 3000 mm was grown using a metallic nickel target. In this manner, a polycrystalline LSM film, a 10YSZ film, and a nickel oxide film were sequentially laminated on one surface of the silicon substrate.
[0031]
Next, a PSG film having a thickness of about 5000 mm is deposited on both surfaces of the substrate by atmospheric pressure CVD, and then the pattern shown in FIG. 1 is applied to the back surface of the silicon substrate (the back surface of the surface on which the 10YSZ film or the like is laminated). Transfer was performed by lithography, and only the transfer portion corresponding to the white portion in the figure was removed by immersion treatment in a hydrofluoric acid-based etching solution. Here, the reason why the width of the etching pattern is narrow is that the etching stops in the middle of the substrate during anisotropic etching. After removing the photoresist by ashing, the substrate is immersed in an anisotropic etching solution of hydrazine hydrate kept at about 60 ° C. for about 8 hours, and the silicon substrate is made to correspond to the above pattern as shown in FIG. Etching is performed to make a small opening 2 in the surface of the substrate so that the laminated thin film is partially self-supporting. Moreover, the groove | channel 3 used as an electrode current collection part is simultaneously formed between small openings. This groove does not penetrate the substrate in the thickness direction. Next, the silicon substrate was dipped in a hydrofluoric acid etching solution to remove the protective PSG film 4.
Subsequently, with respect to the surface where the laminated film is not formed, the substrate temperature is raised to 500 ° C. using a radiation heater, and RF sputtering is performed along the gas flow path using an LSM sintered body target. A polycrystalline LSM film having a thickness of about 3000 mm was grown, and then a metal nickel paste was filled into a groove serving as an electrode current collector and dried to produce a single battery plate B.
The size of each element part is 1.0 mm × 1.0 mm for the opening part, the interval between the opening parts is 1.0 mm, the width of the groove is 0.8 mm at the longest part (the bottom of the triangle when viewed in cross section), the groove The depth of is 0.7 mm.
[0032]
4) Production of solid oxide fuel cell (lamination of each cell plate)
A slurry of the same LSM air electrode material as the electrode material applied to the flat surface of the unit cell plate A produced by the above procedure is applied onto the flat surface electrode of the unit cell plate A, and then A slurry of the same nickel oxide fuel electrode material as the electrode material deposited on the outermost surface of the flat surface of the battery plate is applied on the flat surface electrode of the single cell plate, and as shown in FIG. The battery plates were stacked facing each other.
After laminating them, a single firing was performed at 600 ° C. in a firing furnace to produce a fuel cell.
[0033]
[Performance evaluation]
A fuel cell in which two unit cell plates A and one unit cell plate B are laminated is installed in an electric furnace, heated to 700 ° C., pure oxygen and pure hydrogen are used as source gases, respectively, and AC impedance measurement, power generation A test was conducted.
As a result of the AC impedance measurement, the DC resistance was 0.3Ω when the electrode layer current collector was not formed, whereas the one produced in this example showed a small resistance value of 0.03Ω. .
As a result of the power generation test, the open electromotive force was 1.05 V and the maximum output was 0.8 W / cm ² .
[0034]
(Example 2)
The manufacturing process of this example is shown in FIG. FIG. 3 shows a partial cross-sectional view and a plan view of the cell plate.
Using a high silicate glass of 0.5 mm thickness and 5 cm square as a substrate 11, six openings of 2 mmφ and holes (size) to be an electrode current collector were processed. (A)
Next, a silane coupling material is applied to the surface of the Si substrate as the temporary substrate 12, placed on the upper surface of the substrate 11, and heat treated at 200 ° C. for bonding. (B)
Using an evaporation mask from the lower surface of the substrate, 1 μm of YSZ is formed as an electrolyte layer 13 in an opening with a desired pattern by RF sputtering. (C)
Subsequently, 5 μm of LSM is formed by RF sputtering so that the lower electrode layer 14 is directly bonded to the electrolyte layer from the lower surface of the substrate. (D)
The temporary substrate is peeled off with a hydrofluoric acid-based etching solution. (E)
The groove to be the electrode current collector of the substrate is filled with Ni metal paste and dried to form the electrode current collector 15. (F)
5 μm of YSZ and Ni are formed as the upper electrode layer 16 from the upper surface of the substrate by the two-source sputtering method. (G)
The single battery plate thus produced was designated as single battery plate A.
[0035]
Further, in the above manufacturing process, the unit cell plate in which the lower electrode layer is formed with 5 μm of YSZ and Ni by the two-source sputtering method in the step (d), and the upper electrode layer is formed with LSM of 5 μm by the RF sputtering method in the step (g). Was designated as a unit cell plate B.
[0036]
[Performance evaluation]
In the same manner as in Example 1, the power generation characteristics were evaluated at 500 ° C. using a fuel cell in which two unit cell plates A and one unit cell plate B were laminated. The open end voltage was 0.92 V, and the output was 0.22 W / cm ² .
[0037]
As mentioned above, although this invention was demonstrated in detail by the Example, this invention is not limited to these, A various deformation | transformation is possible within the range of the summary of this invention.
For example, in the present invention, the shape and the like of the single cell and the cell plate can be arbitrarily selected, and a solid oxide fuel cell according to the target output can be produced.
In addition, the conductive material can penetrate not only in the extending direction of the substrate but also in the stacking direction of the electrode layers, and the desired output control is possible by connecting these conductive materials in combination. A fuel cell can be obtained.
[0038]
【The invention's effect】
As described above, according to the present invention, since the conductive material responsible for current collection is arranged in a predetermined shape, it is possible to reduce the size and increase the output, and the highly reliable solid oxide fuel cell stack and A solid oxide fuel cell can be provided.
Moreover, the direct current resistance when it is set as the stack for solid oxide fuel cells can be reduced, and single cells can be connected in series in the stack for solid oxide fuel cells.
Furthermore, since the conductive material is not exposed to gas, even a low durability material can be used. Furthermore, mechanical strength can be improved by using a strong material as the conductive material.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a substrate.
FIG. 2 is a cross-sectional view showing an example of a fuel cell stack.
FIG. 3 is a plan view and a cross-sectional view showing an example of a cell plate.
FIG. 4 is a cross-sectional view showing an example of a manufacturing process of a cell plate.
[Explanation of symbols]
1 Gas flow path (part that becomes gas flow path)
2 Cell holes (parts that become cell holes)
3 groove (current collector) (part that becomes groove (current collector))
4 Unetched part (protective PSG film)
5 Air electrode 6 Fuel electrode 7 Air electrode reaction part 8 Fuel electrode reaction part 9 Electrolyte 10, 11 Substrate (glass substrate)
12 Temporary substrate 13 Electrolyte layer 14 Lower electrode layer 15 Electrode current collector 16 Upper electrode layer

Claims (8)

A single cell for a fuel cell that sandwiches a solid electrolyte layer between an air electrode layer and a fuel electrode layer and is electrically and mechanically joined to form an electrochemical reaction field at the interface of the solid electrolyte layer is formed as a conductive substrate or A fuel cell plate disposed in a plurality of grooves or holes provided in the insulating substrate;
A plurality of two-dimensionally and continuously conductive materials for conducting the current collected from the reaction field to the outside in the extending direction of each cell plate for each fuel cell and the portion where the groove or hole does not exist. Intruding and joining,
Each of the fuel cell plate is two-dimensionally connected and integrated in substantially the same direction as the air electrode layer, the fuel electrode layer, and the solid electrolyte layer. Stack . 2. The solid oxide fuel cell stack according to claim 1, wherein an electronic conductivity of the conductive material is equal to or higher than an electronic conductivity of a material forming the air electrode layer and the fuel electrode layer . The conductive material includes at least one selected from the group consisting of lanthanum-strontium-manganese composite oxide, lanthanum-strontium-cobalt composite oxide, lanthanum chromite, silver, nickel, copper, platinum and iron. The stack for a solid oxide fuel cell according to claim 1 or 2, comprising an alloy comprising: In each of the fuel cell plate, there is no groove or hole for conducting the current collected from the reaction field from a part of the upper surface to a part of the lower surface of the fuel cell plate to the outside. While penetrating conductive material,
The conductive materials penetrating into the fuel cell plate were connected in series with each other, and two-dimensionally connected and integrated in the same direction as the stacking direction of the air electrode layer, the fuel electrode layer, and the solid electrolyte layer. The stack for a solid oxide fuel cell according to any one of claims 1 to 3 . The insulating unit is provided in the single cell or the conductive material for the fuel cell, and a current collecting unit for collecting current on the air electrode layer side and the fuel electrode layer side is formed for each one or a plurality of single cells. The stack for a solid oxide fuel cell according to any one of the above . The stack for a solid oxide fuel cell according to claim 5, wherein an average area Sc of a cross section of the current collector is larger than an average area Sr of a cross section of the reaction field . The stack for a solid oxide fuel cell according to claim 6, wherein an average area Sc of a cross section of the current collector and an average area Sr of a cross section of the reaction field satisfy a relationship of Sc / Sr ≧ 10 . A solid oxide fuel cell comprising the stack for a solid oxide fuel cell according to claim 1 as a power generation element .

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