JP2007157567A - Solid electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolyte fuel cell attaining good insulation property and a function basing on a current collector made of a porous material, in case a part becoming heteropolar side against the current collector exists. <P>SOLUTION: The solid electrolyte fuel cell has a heteropolar side cell supporting part 5 supporting a part of a unit cell 1, an insulation layer 6 insulating the cell supporting part 5 from the cathode side current collector 4, and a protection layer 7 covering current collector side face of the insulation layer 6. A load at lamination is made uniform and sufficient gas diffusion/supply function to the unit cell 1 is realized, and good insulation property and a function basing on a current collector made of porous material are attained by preventing short-circuit between the cathode side current collector and the cell supporting part 5, by the insulation layer 6 and the protection layer 7, and by arranging the cathode side current collector 4 on almost whole part of the unit cell 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell that uses a solid electrolyte and obtains electric energy by an electrochemical reaction.

  In general, a solid oxide fuel cell comprises a single cell that is a power generation element by sandwiching an electrolyte layer between a fuel electrode layer and an air electrode layer, and this single cell and separator plates that form a gas flow path are alternately stacked. It has the structure. Further, as a conventional solid oxide fuel cell, a current collector made of a conductive porous material such as Ni felt is interposed between a single cell and a separator plate, and a gas flow path is formed by this current collector. (Patent Document 1).

In the solid oxide fuel cell as described above, the felt-shaped current collector using metal fibers not only has air permeability as a gas flow path, but also has cushioning properties in the thickness direction of the layer. There is an advantage that the contact with the single cell or the separator plate can be made uniform, the contact area can be expanded and long-term stability can be realized, and the manufacturing is easy and the weight is low.
JP 2003-86204 A

  By the way, the solid oxide fuel cells as described above have been researched and developed to have various structures in order to improve performance. At this time, not only the power generation function is enhanced, but also the size and weight reduction and the low heat capacity are achieved. It is important to reduce the thickness in order to realize a reduction in thickness, and since the deformation tends to occur due to the pressure and heat at the time of lamination as the thickness decreases, the sealing property between the fuel gas and the oxidizing gas and the gap between the electrodes It is also very important to ensure sufficient insulation.

  Under these circumstances, in recent years, solid oxide fuel cells have formed a closed space serving as a flow path for fuel gas (or oxidizing gas) on one surface side of a single cell by a separator plate, and outside the separator plate. A gas cell having improved gas sealing performance by flowing an oxidizing gas (or fuel gas) on the other surface side of a single cell has been developed. In such a structure, a single cell is formed outside the separator plate. There may be a portion on the opposite side of the current collector between the other surface of the cell and the current collector made of the porous material.

  Therefore, an insulating layer is provided between the current collector and the different-polarity side portion. However, in order to reduce the weight and thickness of the fuel cell, it is desirable to make the insulating layer as thin as possible. When a felt-like current collector using metal fibers is used in a structure having a simple insulating layer, when the fuel cells are stacked in multiple stages, the metal fibers penetrate the insulating layer and There is a problem that there is a risk of short circuit.

  Further, in order to prevent the above short circuit, if the current collector is disposed so as to avoid the different polarity side portion, the uniformity of the load when the fuel cells are stacked is impaired, and the current collector is disposed outside the separator plate. There is a problem in that the oxidizing gas easily flows in a portion where there is no gas, which results in an insufficient gas supply amount to the single cell, and it has been a problem to solve these problems.

  The present invention has been made paying attention to the above-described conventional problems, and there is a portion on the side opposite to the current collector between the current collector made of the single cell and the porous material. In this case, an object of the present invention is to provide a solid oxide fuel cell capable of achieving both good insulation and a function of a current collector made of a porous material.

  The solid oxide fuel cell of the present invention has a structure in which a current collector made of a conductive porous material such as felt made of metal fibers is interposed between a single cell as a power generation element and a separator plate. And, between the single cell and the current collector, a cell support part that supports a part of the single cell, an insulating layer that insulates between the cell support part and the current collector, and a surface of the insulating layer on the current collector side It has a configuration including a protective layer made of metal or ceramic to cover, and the above configuration is a means for solving the conventional problems.

  Further, the above solid oxide fuel cell can be stacked in multiple stages to constitute a fuel cell stack structure. In this case, a single cell, a current collector disposed on one surface of the single cell, and a separator plate covering the current collector constitute a cell unit, and the cell unit and the other surface of the single cell are disposed. By alternately laminating the interlayer current collector, a structure in which the interlayer current collector is interposed between the single cell of the cell unit and the separator plate of the cell unit adjacent thereto is provided. An insulator is also provided between the interlayer current collector and the separator plate.

  In the fuel cell stack structure described above, the separator support plate is integrally provided with a cell support portion that supports a part of the other surface of the single cell. At this time, since the separator plate including the cell support portion is a constituent part on one electrode side, whereas the interlayer current collector is a constituent part on the other electrode side, the other surface of the single cell and the interlayer Between the current collectors, there is a state in which a cell support portion serving as a different polarity side portion is interposed with respect to the interlayer current collector.

  Therefore, in the fuel cell stack structure described above, an insulating layer that insulates between the cell support and the current collector between the cell support and the interlayer current collector, and a surface of the insulating layer on the side of the current collector. A covering protective layer will be provided.

  According to the solid oxide fuel cell of the present invention, the insulating layer and the protective layer are provided when there is a portion on the side opposite to the current collector between the current collector made of the single cell and the porous material. Can prevent a short circuit between the current collector and the different-polarity side portion, and by disposing a current collector made of a porous material over almost the entire surface of a single cell, A uniform gas load and a sufficient gas diffusion supply function for a single cell can be realized, and both a good insulation and a function of a current collector made of a porous material can be achieved.

  As shown in FIG. 1, the solid oxide fuel cell of the present invention includes a single cell 1 that is a power generation element, and an anode-side collector disposed on one surface (upper surface that is a fuel electrode) of the single cell 1. The electric unit 2 and the separator plate 3 covering the anode side current collector 2 constitute a cell unit CU. FIG. 1 is a cross-sectional explanatory view in which one side of the solid oxide fuel cell is omitted and disassembled, and the right side of the figure is the battery center side.

  The solid oxide fuel cell includes a cell unit CU and a cathode side current collector (interlayer current collector) 4 disposed on the other surface (the lower surface which is an air electrode) of the single cell 1 as a set. And the cathode side current collector 4 are alternately laminated to form a fuel cell stack structure. At this time, an insulator (not shown) is interposed between the cathode-side current collector 4 and the separator plate 3 of another cell unit CU adjacent thereto.

  The single cell 1 has a known structure in which an electrolyte layer is sandwiched between a fuel electrode layer and an air electrode layer. The current collectors 2 and 4 on the anode side and the cathode side are made of a porous material in which, for example, conductive metal fibers are formed in a felt shape, and have spring properties in the thickness direction. Due to this spring property, uniform contact with the single cell 1 and the separator plate 3 can be maintained over a long period of time in the laminated state.

  The separator plate 3 is made of metal and covers a main body 3A that covers one surface of the single cell 1 (the surface on the fuel electrode side) and a part of the other surface (surface on the air electrode side) of the single cell 1. A cell plate 3B to be supported is provided, and the outer peripheral ends of the main body 3A and the cell plate 3B are hermetically joined together by welding or the like, and a fuel gas circulation space is formed inside the cell plate 3B. An anode-side current collector 2 is accommodated.

  Here, the illustrated separator plate 3 has a donut shape, and when the donut-shaped single cells 1 are arranged concentrically as shown in FIG. 2, or a plurality of circular plates as shown in FIG. The single cells 1 may be arranged at a predetermined interval in the circumferential direction.

  For this reason, the cell plate 3B is provided with a cell support portion 5 that supports the inner peripheral edge and the outer peripheral edge of the other surface of the single cell 1 as a configuration divided into an inner side and an outer side as shown in FIG. As shown in FIG. 3, there is a cell support portion 5 that supports the outer peripheral edge of the other surface of each unit cell 1, and in any case, the surface of the unit cell 1 on the air electrode side is exposed. I support it.

  In the above configuration, in the solid oxide fuel cell, a cathode-side current collector (interlayer) made of a porous material is provided between the single cell 1 constituting the cell unit CU and the separator plate 3 constituting another cell unit CU. Current collector 4, and a cell support 5, which is on the side opposite to the cathode side current collector 4, is interposed between the single cell 1 and the cathode side current collector 4. .

  Therefore, in the solid oxide fuel cell, the insulating layer 6 that insulates between the cell support 5 and the cathode-side current collector 4 between the single cell 1 and the cathode-side current collector 4, and the current collector of the insulating layer 6 A protective layer 7 is provided to cover the body side surface.

  As a result, in the solid oxide fuel cell, since the protective layer 7 is provided even if the insulating layer 6 is made extremely thin as one of the means for reducing the size and weight and reducing the heat capacity, the cathode-side current collector 4 is provided. The constituent metal fiber does not penetrate through the insulating layer 6, and the insulating layer 6 and the protective layer 7 can prevent a short circuit between the cathode-side current collector 4 and the cell support portion 5, which is a different polarity side portion. .

  Further, as described above, the solid oxide fuel cells are stacked in multiple stages to form a fuel cell stack structure. In an actual fuel cell system, the fuel cell stack structure is housed in a container, and the inside of the separator plate 3 By supplying the fuel gas to the container and supplying the oxidizing gas (air) into the container, an electrochemical reaction is generated in the single cell 1 to obtain electric energy. At this time, the insulating layer 6 described above is obtained. Further, by providing the protective layer 7, it is possible to realize a sufficient gas diffusion supply function for the single cell 1 and a uniform load during stacking.

  In other words, in order to prevent a short circuit between the cathode-side current collector 4 and the cell support portion 5 that is the portion on the opposite pole side, the cathode-side current collector 4 can be disposed so as to avoid the cell support portion 5. In this case, as described above, when the fuel cell stack structure is accommodated in the container and the oxidizing gas is allowed to flow through the container, the flow of the oxidizing gas concentrates on the portion where the cathode current collector 4 is not present. Further, the supply of the oxidizing gas to the single cell 1 becomes insufficient, and the load at the time of stacking becomes nonuniform.

  On the other hand, in the solid oxide fuel cell, the short circuit between the cathode current collector 4 and the cell support 5 is prevented by the insulating layer 6 and the protective layer 7, and therefore depends on the cell support 5. Without disposing the cathode-side current collector 4 over the entire surface of the single cell 1, a sufficient gas diffusion supply function for the single cell 1 can be obtained, and the load when the layers are stacked can be made uniform. Can be realized.

  In the above configuration, the insulating layer 6 can be formed of an insulating film formed in advance in a sheet shape or an insulating film in which at least one of the cell support portion 5 and the protective layer 7 is coated with an insulating material, for example, 100 μm or less. Sufficient insulation can be obtained with a thickness of the order.

  In particular, in a fuel cell using a solid oxide for the electrolyte layer constituting the single cell 1, the operating temperature reaches about 600 ° C., and therefore the insulating layer 6 is made of a heat-resistant material that can withstand a high operating temperature. It is desirable to use, specifically, a ceramic material is used. The ceramic insulating layer 6 can be formed by a PVD method such as sputtering when an insulating film is formed by coating the cell support 5 or the protective layer 7 with an insulating material.

  The protective layer 7 is made of either one of a metal plate and a ceramic plate, which can reliably prevent the metal fibers constituting the cathode side current collector 4 from penetrating the thin insulating layer 6.

  When the protective layer 7 is a metal plate, it is electrically connected to the cathode-side current collector 4, so that the protective layer 7 is formed between the single cell 1 (cell unit CU) and the cathode-side current collector 4. An extension portion extending outward can be provided integrally, and this extension portion can be used as a voltage extraction terminal, and the terminal voltage between the cell units CU can be monitored.

  Further, when the protective layer 7 is a metal plate, the material is mainly composed of one of Fe and Ni, and the main component is a heat-resistant metal containing Cr, Pt, Ni, and Ag. It is more desirable to use one containing at least one of the above, whereby oxidation resistance and low resistance can be achieved.

  Further, when the extension portion of the protective layer 7 is used as a voltage extraction terminal, it is also effective to coat at least the surface of the terminal with a noble metal material. Contact resistance with the electric body 4 can be reduced. The protective layer 7 may be made of a bulk material such as Pt, and the noble metal material coating method may be wet or dry.

  Furthermore, when the protective layer 7 is a ceramic plate, it is necessary to select a material having a high bending strength so as to exhibit insulation even at high temperatures and be difficult to crack structurally. Specifically, alumina, zirconia, It is more desirable to use any one material of mica, mullite, and macerite, and thereby it is possible to more reliably obtain the insulation between the cell support 5 and the cathode current collector 4 together with the insulating layer 6. it can.

  Furthermore, when the protective layer 7 is a metal plate and has an extension part, at least a terminal part of the extension part can be insulated. That is, the solid oxide fuel cell constitutes a fuel cell stack structure as described above, and is further accommodated in a container in the fuel cell system. At this time, the solid oxide fuel cell forms a flow path of oxidizing gas (air) between the outer peripheral end portion of the solid oxide fuel cell and the inner surface of the container.

  At this time, it is possible to insulate the protective layer 7 from the container by subjecting the end portion of the extended portion of the protective layer 7, that is, the contact portion with the container, to insulation treatment. Insulating treatment in this case includes incorporating a bulk insulating material or forming an insulating thin film by a PVD method such as sputtering.

  In addition, in the extension part of the protective layer 7, providing the voltage extraction terminal and performing the insulation treatment are electrically contradictory, but both the voltage extraction terminal and the insulation process can be provided in the extension part. Specifically, most of the outer peripheral end of the extension is insulated, and a part of the extension is appropriately bent so as not to contact the container, so that part of the extension is used as a voltage extraction terminal. Can be.

  Hereinafter, examples of the solid oxide fuel cell of the present invention will be described with reference to the drawings. The same components as those in the embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. Further, the solid oxide fuel cell of the present invention is not limited to the following examples.

  The solid oxide fuel cell shown in FIG. 4 includes a single cell 1 that is a power generation element, and an anode side that is made of a conductive porous material in which metal fibers are formed in a felt shape and is disposed on the surface of the single cell 1 on the fuel electrode side. The current collector 2 and the metal separator plate 3 covering the anode side current collector 2 constitute a cell unit CU. The separator plate 3 includes a main body 3A and a cell plate 3B, and the cell plate 3B. However, it has the cell support part 5 which supports the edge part of the surface by the side of the air electrode in the single cell 1. FIG.

  Therefore, the solid oxide fuel cell includes a cathode 1 between the single cell 1 of the cell unit CU and a cathode-side current collector (interlayer current collector) 4 made of a conductive porous material in which metal fibers are formed in a felt shape. A metal cell support portion 5 on the side opposite to the side current collector 4 is interposed,

  Therefore, the solid oxide fuel cell includes a ceramic insulating layer 6 that covers the cell support 5 and a metal protective layer 7 that covers the current collector side surface of the insulating layer 6. In the actual assembly, the insulating layer 6 is in contact with the cell support 5.

  In this embodiment, in the illustrated cross section, the insulating layer 6 and the protective layer 7 have a flat plate shape and a width from the outer peripheral end of the cell unit CU to the inner peripheral end of the cell support portion 5. This prevents a situation in which the metal fibers constituting the cathode-side current collector 4 penetrate the insulating layer 6 and prevents a short circuit between the cell support 5 and the cathode-side current collector 4. Yes.

  In addition, with the insulation by the insulating layer 6 and the protective layer 7, the cathode current collector 4 can be disposed over the entire surface of the single cell 1, thereby making the load uniform during stacking, A sufficient diffusion supply function of oxidizing gas (air) to the single cell 1 can be realized.

  The insulating layer 6 can be an insulating film formed in a sheet shape in advance, or an insulating film in which at least one of the cell support 5 and the protective layer 7 is coated with an insulating material. The insulating layer 6 can be formed very thin and is suitable for high density integration.

  The basic structure of the solid oxide fuel cell shown in FIG. 5 is the same as that shown in FIG. 4, but the inner peripheral end of the insulating layer 6 extends longer than the inner peripheral end of the cell support 5. ing. In actual assembly, the insulating layer 6 is in contact with the cell support 5.

  As a result, the solid oxide fuel cell has a short-circuit preventing function between the cell support 5 and the cathode-side current collector 4 and a cathode-side current collector corresponding to the entire surface of the single cell 1 as in the previous embodiment. 4 can provide the load equalization function and the function of supplying and supplying an oxidant gas, and the insulating property can be further enhanced by the extending portion on the inner peripheral side of the insulating layer 6.

  The basic structure of the solid oxide fuel cell shown in FIG. 6 is the same as that shown in FIG. 4, but the outer peripheral ends of the insulating layer 6 and the protective layer 7 extend longer than the outer peripheral end of the cell unit CU. ing. In actual assembly, the insulating layer 6 is in contact with the cell support 5.

  As a result, the solid oxide fuel cell has a short-circuit preventing function between the cell support 5 and the cathode-side current collector 4 and a cathode-side current collector corresponding to the entire surface of the single cell 1 as in the previous embodiment. Even if the insulating layer 6 and the protective layer 7 are deformed by the extended portions on the outer peripheral side of the insulating layer 6 and the protective layer 7, Contact between the separator plate 3 and the protective layer 7 can be prevented.

  The basic structure of the solid oxide fuel cell shown in FIG. 7 is the same as that shown in FIG. 4, but the inner peripheral end of the insulating layer 6 extends longer than the inner peripheral end of the cell support 5. In addition, the outer peripheral ends of the insulating layer 6 and the protective layer 7 extend longer than the outer peripheral end of the cell unit CU. In actual assembly, the insulating layer 6 is in contact with the cell support 5.

  As a result, the solid oxide fuel cell has a short-circuit preventing function between the cell support 5 and the cathode-side current collector 4 and a cathode-side current collector corresponding to the entire surface of the single cell 1 as in the previous embodiment. 4 can provide the load equalizing function and the diffusion supply function of the oxidizing gas. Further, the insulating portion 6 can further enhance the insulating property by the extending portion on the inner peripheral side, and the insulating layer 6 and the protective layer 7. Even if the insulating layer 6 and the protective layer 7 are deformed by the extended portion on the outer peripheral side, the contact between the separator plate 3 and the protective layer 7 can be prevented.

  The basic structure of the solid oxide fuel cell shown in FIG. 8 is the same as that shown in FIG. 4, but the insulating layer 6 and the protective layer 7 are provided along the outer surface of the separator plate 3 of the cell unit CU. . In this case, the insulating layer 6 and the protective layer 7 can be formed by sequentially coating the material of each layer on the separator plate 3, and the cell support 5 and the cathode-side current collector 4 are the same as in the previous embodiment. In addition, it is possible to obtain a function of preventing a short circuit between the two, a uniform load by the cathode-side current collector 4 corresponding to the entire surface of the single cell 1, and a function of supplying and supplying an oxidizing gas.

  In the solid oxide fuel cell shown in FIG. 9, the insulating layer 6 is provided along the outer surface of the separator plate 3 of the cell unit CU, and the protective layer 7 is directly bonded to the cathode-side current collector 4. It has become. In actual assembly, the protective layer 7 is in contact with the inner peripheral portion of the insulating layer 6.

  In this case, in the solid oxide fuel cell, the insulating layer 6 can be formed by coating the separator plate 3 with an insulating material. Similarly to the previous embodiment, the cell support 5 and the cathode-side current collector 4 are formed. In addition, it is possible to obtain a function of preventing a short circuit between the two, a uniform load by the cathode-side current collector 4 corresponding to the entire surface of the single cell 1, and a function of supplying and supplying an oxidizing gas.

  The basic structure of the solid oxide fuel cell shown in FIG. 10 is the same as that shown in FIG. 4 except that the protective layer 7 extends to the outer peripheral side longer than the outer peripheral end of the cell unit CU. The fuel cell stack structure is configured by alternately stacking the cell units CU and the cathode side current collectors (interlayer current collectors) 4. In the fuel cell stack structure, an insulator (not shown) is interposed between the cathode-side current collector 4 and the separator plate 3 adjacent to the lower side in the drawing.

  In this embodiment, the extension portion 7a of the protective layer 7 is used as a voltage extraction terminal, and the extension portion 7a is coated with Pt by the PVD method to form the oxidation resistant film 8.

  In the case of this embodiment, in each solid oxide fuel cell, the same effect as in the previous embodiment can be obtained, and the terminal voltage ΔV between the cell units CU is monitored in the fuel cell stack structure. In addition, the oxidation-resistant film 8 can prevent the extension portion 7a made of metal from being oxidized and reduce the contact resistance.

  The basic configuration of the solid oxide fuel cell shown in FIG. 11 is the same as that shown in FIG. 4 except that the protective layer 7 extends to the outer peripheral side longer than the outer peripheral end of the cell unit CU. The fuel cell stack structure is configured by alternately stacking the cell units CU and the cathode side current collectors (interlayer current collectors) 4. In the fuel cell stack structure, an insulator (not shown) is interposed between the cathode-side current collector 4 and the separator plate 3 adjacent to the lower side in the drawing.

  The fuel cell stack structure is housed in a metal container 9 in the fuel cell system. At this time, in each of the solid oxide fuel cells, the fuel cell stack structure is configured such that the outer peripheral end portion of the protective layer 7 is in contact with the inner peripheral surface of the container 9 and the oxidizing gas (air) is in contact with the container 9. Although the flow path 10 is formed, since the metal protective layer 7 and the metal container 9 are in contact with each other, the extension portion 7a of the protective layer 7 is insulated by coating with an insulating material, that is, an insulating material. A coating 11 is formed.

  In the case of this embodiment, in each solid oxide fuel cell, the same effect as in the previous embodiment can be obtained, and a flow path 10 is formed between the fuel cell stack structure and the container 9. However, sufficient insulation between the extension 7a of the protective layer 7 and the container 9 can be ensured.

  Further, the insulation treatment for the extension portion 7a of the protective layer 7 can be performed over the entire circumference of the extension portion 7a, but a part of the extension portion 7a is appropriately cut or bent so as not to contact the container 9. Alternatively, a part of the voltage extraction terminal shown in FIG. 10 can be used.

  The solid oxide fuel cell and the fuel cell stack structure according to the present invention are not limited to the above embodiments, and the structure can be appropriately changed without departing from the gist of the present invention. It is.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional explanatory view with one side omitted showing an embodiment of a solid oxide fuel cell of the present invention. It is a top view of the one side omission explaining a solid oxide fuel cell provided with one single cell. It is a top view of the one side omission explaining a solid oxide fuel cell provided with a plurality of single cells. 1 is an explanatory cross-sectional view of one embodiment of a solid oxide fuel cell according to the present invention with one side omitted. FIG. 6 is a cross-sectional explanatory view of one side omitted showing another embodiment of a solid oxide fuel cell. FIG. 6 is a cross-sectional explanatory view of one side omitted showing still another embodiment of the solid oxide fuel cell. FIG. 6 is a cross-sectional explanatory view of one side omitted showing still another embodiment of the solid oxide fuel cell. FIG. 6 is a cross-sectional explanatory view of one side omitted showing still another embodiment of the solid oxide fuel cell. FIG. 6 is a cross-sectional explanatory view of one side omitted showing still another embodiment of the solid oxide fuel cell. FIG. 3 is a cross-sectional explanatory view of one side omitted showing an embodiment of a solid oxide fuel cell and a fuel cell stack structure. FIG. 5 is a cross-sectional explanatory view of one side omitted showing another embodiment of a solid oxide fuel cell and a fuel cell stack structure.

Explanation of symbols

1 single cell 2 anode side current collector 3 separator plate 4 cathode side current collector (interlayer current collector)
5 Cell support (different pole part)
6 Insulating layer 7 Protective layer 7a Extension (voltage extraction terminal)
8 Antioxidation film 10 Insulation film

Claims (9)

  A solid oxide fuel cell having a structure in which a current collector made of a porous material is interposed between a single cell as a power generation element and a separator plate, and a part of the single cell is interposed between the single cell and the current collector. A solid oxide fuel cell comprising: a cell support portion to be supported; an insulating layer that insulates between the cell support portion and the current collector; and a protective layer that covers a surface of the insulating layer on the current collector side.   2. The solid oxide fuel cell according to claim 1, wherein the insulating layer is made of an insulating film formed in a sheet shape in advance, or an insulating film in which at least one of the cell support portion and the protective layer is coated with an insulating material.   The solid oxide fuel cell according to claim 1 or 2, wherein the protective layer is made of one of a metal plate and a ceramic plate.   The protective layer is mainly composed of one of Fe and Ni, and is composed of a material containing at least one of a refractory metal containing Cr, Pt, Ni and Ag as a main component. Item 3. The solid oxide fuel cell according to Item 1 or 2.   The solid oxide fuel cell according to claim 1 or 2, wherein the protective layer is made of any one material of alumina, zirconia, mica, mullite, and macerite.   The protective layer is electrically connected to the current collector, and an extended portion extending outward from between the power generation element and the current collector is used as a voltage extraction terminal. 5. The solid oxide fuel cell according to any one of 2 and 4.   7. The solid oxide fuel cell according to claim 6, wherein the voltage extracting terminal is coated with a noble metal material.   The protective layer has an extension part extending outward from between the power generation element and the current collector, and at least a terminal part of the extension part is insulated. The solid oxide fuel cell according to any one of the above.   A fuel cell stack structure formed by stacking the solid oxide fuel cells according to any one of claims 1 to 8, comprising a single cell, a current collector disposed on one surface of the single cell, The cell unit is composed of a separator plate that covers the current collector, and the cell unit and the interlayer current collector disposed on the other surface of the single cell are alternately stacked, so that the single cell of the cell unit and the adjacent cell The cell unit has a structure in which an interlayer current collector is interposed between the separator plates of the cell unit, and the cell support part is integrated with the separator plate and supports a part of the other surface of the single cell, as well as the insulating layer and protection A fuel cell stack structure characterized in that a layer is provided between a cell support and an interlayer current collector.

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