JP6147606B2 - Solid oxide fuel cell stack - Google Patents

Description

  The present invention relates to a solid oxide fuel cell stack in which a plurality of single cells are stacked via an interconnector, and an interconnector with a separator included in the solid oxide fuel cell stack.

  Conventionally, a solid oxide fuel cell (SOFC) using a solid oxide as an electrolyte is known. A single cell that is a constituent unit of SOFC generates electric power by supplying a fuel gas and an oxidant gas to, for example, a fuel electrode layer and an air electrode layer arranged on both sides of a flat solid electrolyte layer. In addition, a plurality of such single cells are stacked and an interconnector is disposed between adjacent single cells to constitute a solid oxide fuel cell stack (hereinafter referred to as a fuel cell stack). Since the interconnector included in the SOFC is required to have good gas tightness and electrical conductivity, it can be formed using a metal material. For example, an interconnector using a ferritic stainless material having a thermal expansion coefficient close to that of a cell has been proposed (see Patent Document 1). On the other hand, since the use temperature range of SOFC becomes considerably high, cathode poisoning due to chromium evaporation from the metal material of the interconnector becomes a problem. Therefore, an interconnector has been proposed in which a conductive ceramic such as a spinel oxide having both conductivity and barrier property against chromium is coated on the surface of a metal material (Patent Document 2).

Japanese Patent Laid-Open No. 10-92446 Japanese Patent No. 3712733

  However, since the conventional interconnector as described above has a structure in which the whole is laminated with a single cell to form a stack and the interconnector is constrained in the stacking direction, the heat applied at the time of starting and stopping during operation of the SOFC The interconnector may be deformed by stress or mechanical stress during stack assembly. When conductive ceramic is coated on the surface of the interconnector metal material, the ceramic material is generally susceptible to cracking due to stress. There was a problem of losing.

  The present invention has been made to solve these problems. The surface of the metal material is coated with a conductive ceramic to reduce the stress applied to the interconnector while suppressing the chromium poisoning of the cathode. An object of the present invention is to provide a solid oxide fuel cell stack capable of improving durability and reliability.

In order to solve the above-described problems, a solid oxide fuel cell stack according to the present invention includes a plurality of single cells each including a fuel electrode layer, an air electrode layer, and a solid electrolyte layer stacked via an interconnector. In the solid oxide fuel cell stack, the interconnector includes an interconnector body made of a metal material having a surface coated with a conductive ceramic, and a first separator made of a flexible metal plate. And the interconnector body is joined to each other via a joint that surrounds the first separator and the entire periphery of the opening formed in the approximate center of the first separator, and The interconnector is laminated by fixing a portion of the first separator, and the first separator is in contact with a frame constituting a frame portion It is characterized in that it is fixed by state.

  According to the solid oxide fuel cell stack of the present invention, the interconnector body is joined to the first separator via the joint that surrounds the entire circumference of the central opening, and the conductive ceramic is formed on the surface of the metal material. It has a structure coated. And the several single cell is laminated | stacked by fixing the part of a 1st separator between adjacent single cells. Accordingly, when a stress is applied to the interconnector that is not constrained by the single cell, the stress can be released by the deformation of the first separator fixed to the single cell. Furthermore, while the interconnector body is formed using a metal material having a thermal expansion coefficient close to that of the fuel battery cell, the evaporation of chromium oxide can be prevented by the conductive ceramic on the surface thereof. At this time, the bonding structure between the first separator and the interconnector body can prevent problems such as cracks in the conductive ceramic.

  The first separator is preferably formed of a metal plate that is thinner than the interconnector body. That is, if the metal plate used for forming the first separator is thicker than the interconnector body, the stress relaxation function is lowered. Therefore, by making the metal plate thinner than the interconnector body, the stress relaxation function is enhanced. For example, the thickness of the first separator can be set to 0.05 mm or more and 0.5 mm or less. The first separator is preferably formed of an alloy containing aluminum in an amount of 1 wt% to 10 wt%. As a result, an alumina coating having high oxidation resistance can be formed on the surface of the first separator. If the aluminum content of the first separator is less than 1% by weight, the formation of the alumina film becomes insufficient, and durability cannot be obtained over a long period of time. On the other hand, if the aluminum content of the first separator exceeds 10% by weight, the first separator becomes too hard at room temperature, which hinders stress relaxation.

  The conductive ceramic coated on the surface of the interconnector body is preferably formed with a thickness of 1 μm or more and 30 μm or less. If the thickness of the conductive ceramic is less than 1 μm, it will hinder the formation of a uniform coating layer. On the other hand, if the thickness of the conductive ceramic exceeds 30 μm, the coating layer tends to break and the reliability is lowered.

  The first separator can be formed with a concave or wavy cross-sectional shape that can relieve stress. By giving such a cross-sectional shape to the first separator, the concave or wavy portion is deformed when stress is applied, thereby sufficiently enhancing the effect of relieving the stress.

  The joint can be formed using any one of welding, brazing, glass sealing, or a combination thereof. For example, the cost can be reduced by forming the joint using a laser welding machine. Moreover, the strength of the joint can be increased by forming the joint by brazing. In addition, the gas sealability can be improved by forming the bonding portion by glass sealing. By combining these, it becomes possible to further improve the reliability of the joint.

  In the present invention, a cell main body in which the fuel electrode layer is disposed on one side and the air electrode layer is disposed on the other side across the solid electrolyte layer, and a second separator made of a flexible metal plate And the cell main body and the second separator may be joined to each other via a cell joint portion that surrounds the entire circumference of the opening formed in the approximate center of the second separator. As a result, by providing a stress relaxation structure similar to that of the interconnector for the fuel cell, a stress relaxation effect can be obtained with respect to the thermal stress in the stacking direction. In addition to the interconnector, the fuel cell can be deformed or cracked. Can be effectively prevented.

  In order to solve the above problems, an interconnector with a separator according to the present invention is for a solid oxide fuel cell stack in which a plurality of unit cells each including a fuel electrode layer, an air electrode layer, and a solid electrolyte layer are stacked. An interconnector with a separator, comprising an interconnector body made of a metal material coated with a conductive ceramic on the surface, wherein the interconnector body includes a first separator made of a flexible metal plate, The separators are joined to each other through a joint portion that surrounds the entire circumference of the opening formed at substantially the center of one separator. By configuring the solid oxide fuel cell stack using the separator-equipped interconnector of the present invention, the above-described effects can be realized.

  As described above, according to the present invention, in the solid oxide fuel cell stack, the interconnector body and the first separator are joined together to form the interconnector, and the surface of the metal material of the interconnector body The structure is coated with conductive ceramic material. Therefore, the stress applied to the interconnector can be released by the deformation of the first separator, and the evaporation of chromium oxide can be prevented by the action of the conductive ceramic on the surface of the interconnector body using the metal material. Therefore, a solid oxide fuel cell stack capable of improving durability and reliability by preventing problems such as cracking of the interconnector due to stress in the stacking direction and sufficiently suppressing chrome poisoning of the cathode. Can be realized.

It is a perspective view of the fuel cell stack as a solid oxide fuel cell of this embodiment. FIG. 2 is a schematic cross-sectional view of the fuel cell stack shown in FIG. 1 as viewed from the direction of arrow A. It is a typical sectional structure figure in the state where each constituent element was disassembled about one single cell. It is a figure which shows the specific structure of the interconnector main body and the separator for interconnectors which comprise the interconnector with a separator of this embodiment. It is a figure which shows the structure of the junction part in the 3rd Example of an interconnector. It is a figure which shows the structure of the junction part in 4th Example of an interconnector. It is a figure which shows the structure of the junction part in 5th Example of an interconnector.

  Hereinafter, an embodiment of a solid oxide fuel cell to which the present invention is applied will be described in detail. FIG. 1 shows a perspective view of a fuel cell stack S as a solid oxide fuel cell of the present embodiment. FIG. 2 is a schematic cross-sectional view of the fuel cell stack S shown in FIG. In the present embodiment, a fuel cell stack S in which a plurality of single cells C, which are basic structural units, are stacked is configured. 1 and 2 show an example in which the fuel cell stack S has a structure in which four single cells C (1), C (2), C (3), and C (4) are stacked. The fuel cell stack S can be configured by stacking a larger number of single cells C.

  As shown in FIGS. 1 and 2, the fuel cell stack S is integrally fixed by a plurality of bolts B1 to B10 and a plurality of nuts N. The fuel cell stack S has through-holes H formed at positions corresponding to the plurality of bolts B1 to B10, and is fixed in a state where the four single cells C are sandwiched between a pair of upper and lower end plates P. Among the bolts B1 to B10, the four bolts B1, B4, B6, and B9 located at the four corners in the rectangular plane of FIG. 1 are used only as connecting members for fixing the fuel cell stack S. On the other hand, each of the other six bolts B2, B3, B5, B7, B8, B10 functions as a part (inlet or outlet) of the flow path of the fuel gas or oxidant gas in addition to the connecting member. To do.

  Next, the basic structure of the single cell C in FIG. 1 will be described. FIG. 3 shows a schematic cross-sectional structure of the single cell C shown in FIG. In FIG. 3, the channel structures on both sides of FIG. 2 are omitted. The single cell C shown in FIG. 3 includes two interconnector bodies 10 on the upper side and the lower side, two separators 11 for the upper and lower interconnectors (the first separator of the present invention), and the air electrode side. A current collector 12, a frame portion 13, a cell main body 14, and a fuel electrode side current collector 15 are provided. As shown in FIG. 3, the interconnector body 10 and the interconnector separator 11 function integrally as an interconnector 1 with a separator (hereinafter simply referred to as an interconnector 1). The single cell C shown in FIG. 3 corresponds to the single cells C (2) and C (3) that are not in contact with the end plate P in FIG. As described above, the two interconnectors 1 (interconnectors with separators) each including the interconnector main body 10 and the interconnector separator 11 have the same structure above and below the single cell C in FIG. Therefore, the following description is common to the two interconnectors 1 above and below the single cell C.

  The cell main body 14 responsible for the power generation function of the single cell C is formed by laminating the fuel electrode layer 20, the solid electrolyte layer 21, and the air electrode layer 22 in order from the lower layer side. The fuel electrode layer 20 is in contact with a fuel gas serving as a hydrogen source and functions as an anode of the single cell C. The material of the fuel electrode layer 20 is preferably a metal, for example, Ni, cermet made of Ni and ceramic particles, or Ni-based alloy can be used. The solid electrolyte layer 21 is made of various solid electrolytes having ionic conductivity. As the material of the solid electrolyte layer 21, for example, YSZ (yttria stabilized zirconia), ScSZ (scandia stabilized zirconia), SDC (samarium doped ceria), GDC (gadolinium doped ceria), a perovskite oxide, or the like may be used. it can. The air electrode layer 22 is in contact with an oxidant gas (air) serving as an oxygen source and functions as a cathode of the single cell C. Examples of the material of the air electrode layer 22 include perovskite oxides such as LSCF (lanthanum strontium cobalt iron oxide) and LSM (lanthanum strontium manganese oxide), various noble metals, and cermets of noble metals and ceramics. .

  The interconnector 1 is responsible for electrical connection between the single cell C of FIG. 3 and the single cell C adjacent to the upper layer. The interconnector separator 11 is a thin metal plate having flexibility. The interconnector separator 11 is joined to the interconnector main body 10 via a joint portion 30 surrounding the opening 11a formed at the center, and the fuel gas and the oxidant gas are isolated between two adjacent single cells C. There is a role. The interconnector body 10 has a structure in which a coating layer 10a made of conductive ceramic is formed on the entire surface of a plate-like metal member. The details of the materials and structures of the interconnector body 10, the coating layer 10a on the surface thereof, and the interconnector separator 11 will be described later.

  The air electrode side current collector 12 has a role of ensuring electrical connection between the air electrode layer 22 of the cell body 14 and the upper interconnector 1. As a material of the air electrode side current collector 12, for example, a metal material such as Ag-Pd can be used. Further, the fuel electrode side current collector 15 has a role of ensuring electrical connection between the fuel electrode layer 20 of the cell body 14 and the lower interconnector 1. As a material of the fuel electrode side current collector 15, for example, nickel felt having air permeability can be used.

  The frame portion 13 has a role of fixing the cell body 14 to the single cell C, and includes a fuel electrode frame 23, a cell body separator 24 (second separator of the present invention), an insulating frame 25, and an air electrode frame 26. It is a frame-shaped member comprised by these. Among these, the fuel electrode frame 23 is disposed on the fuel electrode layer 20 side in the stacking direction, and is formed using an insulating material such as ceramic. The insulating frame 25 has a role of electrically insulating the upper and lower interconnectors 1 and is formed using an insulating material such as ceramic. The air electrode frame 26 is disposed on the air electrode layer 22 side in the stacking direction, and is formed using a metal material. The fuel electrode frame 23, the insulating frame 25, and the air electrode frame 26 all have a relatively large opening of the same size at the center, and the cell body 14 is surrounded by the opening in a plan view.

  The cell body separator 24 of the frame portion 13 is a flexible metal thin plate, similar to the interconnector separator 11 described above, and is connected to the cell via a joint portion 31 surrounding an opening formed in the center. The main body 14 is joined to the upper surface on the outer peripheral side of the solid electrolyte layer 21. Therefore, when the cell main body 14 and the cell main body separator 24 are viewed in plan view, the solid electrolyte layer 21 is formed in a rectangular shape that is smaller than the cell main body separator 24 and larger than the opening of the cell main body separator 24. The air electrode layer 22 is formed in a square size smaller than the opening of the cell body separator 24.

  Next, specific structures of the interconnector main body 10 and the interconnector separator 11 constituting the interconnector 1 (interconnector with separator) of this embodiment will be described with reference to FIG. 4A shows a plan view of the interconnector body 10 and the interconnector separator 11, and FIG. 4B shows a side sectional view corresponding to FIG.

  As shown in FIG. 4, the upper surface (coating layer 10 a) of the interconnector body 10 and the lower surface of the interconnector separator 11 are joined via a joining portion 30. Specifically, since an opening 11a having a size smaller than the interconnector main body 10 is formed in a plan view in the center of the interconnector separator 11, the joint 30 is disposed around the opening 11a. Has been. Therefore, the space between the interconnector body 10 and the interconnector separator 11 can be hermetically sealed by the joint portion 30. In this case, the coating layer 10a on the surface of the interconnector body 10 is exposed in the opening 11a.

  Since the interconnector separator 11 is a flexible metal thin plate as described above, it is necessary to form the interconnector separator 11 to a thickness that allows the stress in the stacking direction to escape. Specifically, it is desirable that the interconnector separator 11 is formed to have a thickness within a range of 0.05 to 0.5 mm (for example, a thickness of 0.1 mm), for example. When the thickness of the interconnector separator 11 exceeds 0.5 mm, it is difficult to release the stress applied to each interconnector separator 11 in a state where a plurality of single cells C are stacked. There is a risk of causing problems such as cracking. If the thickness of the interconnector separator 11 is less than 0.05 mm, the oxidation resistance and the corrosion resistance deteriorate, and sufficient durability cannot be secured. As shown in FIG. 4A, the interconnector separator 11 is formed with circular through holes at positions corresponding to the bolts B1 to B10 in FIG.

  For example, the interconnector separator 11 is preferably formed using a metal material whose main component is iron (Fe) and containing about 1 to 10% by weight of aluminum. That is, by forming an alumina coating on the surface of the interconnector separator 11, the oxidation resistance can be improved. However, when a metal material having an aluminum content of less than 1% by weight is used, film formation is insufficient and the above-described effects are weakened. On the other hand, when a metal material with an aluminum content exceeding 10% by weight is used, the interconnector separator 11 becomes too hard at room temperature, making it difficult to relieve stress.

  4B, the interconnector separator 11 has a structure in which the interconnector body 10 is suspended and can be deformed. Therefore, the interconnector separator 11 is thinner than the interconnector body 10. It is desirable to form. In this case, it is desirable that the thickness of the interconnector body 10 be in the range of 0.5 to 1.5 mm in consideration of the thickness of the interconnector separator 11 described above.

  On the other hand, the interconnector body 10 has a structure in which the surface of the metal material is covered with the coating layer 10a made of conductive ceramic, as already described. As a metal material of the interconnector body 10, for example, a ferritic stainless material can be used. Since the thermal expansion coefficient of the ferritic stainless steel is close to the thermal expansion coefficient of the cell main body 14, it is suitable for relaxing the thermal stress in the fuel cell stack S.

  As the coating layer 10a on the surface of the interconnector body 10, for example, a conductive ceramic such as a spinel oxide is used. Specific examples include MnCo spinel and NiCo spinel. By covering the interconnector body 10 with such a coating layer 10a, it becomes possible to prevent the evaporation of chromium oxide formed on the surface of the metallic interconnector body 10. Therefore, in this embodiment, the role of the coating layer 10a is to suppress the chromium poisoning of the cathode, which is a problem when the interconnector body 10 is exposed, while maintaining the electrical conductivity of the interconnector body 10. is there. The coating layer 10a is preferably formed with a thickness in the range of 1 to 30 μm. That is, it is difficult to form the coating layer 10a with a thickness of less than 1 μm uniformly, and the coating layer 10a with a thickness of more than 30 μm tends to break.

  Next, the specific structure of the interconnector 1 according to the present embodiment will be described sequentially with reference to five examples. The first embodiment of the interconnector 1 has a structure in which Ni solder is used as a material for forming the joint 30 shown in the side sectional view of FIG. Specifically, BNi-2, BNi-3, BNi-5 or the like can be used as a brazing material for forming the joint portion 30. By using the brazing material as the material of the joint portion 30, an effect of joining the interconnector body 10 and the interconnector separator 11 with sufficient joint strength can be obtained.

  The second embodiment of the interconnector 1 has a structure in which glass is used as a material for forming the joint portion 30 shown in the side sectional view of FIG. When forming the joint part 30 using glass, in order to prevent the crack at the time of the stress application by the difference in thermal expansion coefficient, the glass which has a thermal expansion coefficient comparatively close to the interconnector main body 10 and the interconnector separator 11 is used. It is desirable to adopt. By using glass as the material of the joint portion 30, an effect of sealing between the interconnector body 10 and the interconnector separator 11 and preventing leakage of fuel gas or oxidant gas can be obtained.

  The joint 30 in the interconnector 1 of the present embodiment is not limited to the first and second examples described with reference to FIG. 4B, and various structures can be applied. FIG. 5 shows the structure of the joint 30a in the third embodiment of the interconnector 1. As shown in FIG. The joint portion 30a of the third embodiment is formed by welding and joining the upper interconnector separator 11 and the metal portion of the lower interconnector body 10 at predetermined locations. As shown in FIG. 5, the joint portion 30 a formed by welding and joining has a tapered shape whose diameter becomes narrower from the upper side to the lower side. For example, the interconnector separator 11 and the interconnector body 10 can be integrally welded by irradiating a predetermined position from above the interconnector separator 11 with a laser welder.

  Next, the interconnector separator 11 in the interconnector 1 of the present embodiment is not limited to the first to third examples described above, and various structures can be applied. FIG. 6 shows the structure of the interconnector separator 11 in the fourth embodiment of the interconnector 1. As shown in FIG. 6, the interconnector separator 11 of the fourth embodiment is formed with a concave portion 11 b having a cross-sectional shape protruding downward in the vicinity of the outer edge of the interconnector body 10. The concave portion 11b is disposed so as to surround the entire opening portion 11a in plan view. By adopting the structure of the fourth embodiment, when stress is applied to the interconnector separator 11, there is an effect of relieving the stress by letting it escape by deformation of the concave portion 11b. In addition, what is necessary is just to use press work, for example, in order to form the recessed part 11b in the separator 11 for interconnectors.

  FIG. 7 shows the structure of the interconnector separator 11 in the fifth embodiment. The fifth embodiment is a modification of the fourth embodiment. As shown in FIG. 7, the interconnector separator 11 has a wavy cross section projecting upward and downward instead of the concave portion 11 b of FIG. 6. A wavy portion 11c having a shape is formed. Similarly to the concave portion 11b described above, the wavy portion 11c is also arranged so as to surround the entire opening portion 11a in plan view. By adopting the structure of the fifth embodiment, as in the fourth embodiment, there is an effect of relieving stress by deformation of the wavy portion 11c. In addition, in order to form the waved part 11c in the interconnector separator 11, for example, press work may be used as in the fourth embodiment.

  In the fourth and fifth embodiments, the material and structure of the joint portion 30 are not particularly limited. For example, the first to third embodiments can be freely applied. When the fourth and fifth structures are employed, the interconnector separator 11 is formed with the same thickness as in the first to third embodiments as long as the concave portion 11b and the corrugated portion 11c can be processed. be able to.

  With respect to the fuel cell stack S of the present embodiment, an outline of a manufacturing method of the interconnector 1 (interconnector with interconnector body 10 and interconnector separator 11 joined together) will be supplementarily described. First, a metal plate made of ferritic stainless steel containing aluminum in the above-described ratio is formed by a known technique. And after attaching the material of the coating layer 10a with respect to the surface of this metal plate by plating, an oxide is formed by the heat processing of 800-1000 degreeC, and the interconnector main body 10 covered with the coating layer 10a is obtained. On the other hand, for example, the interconnector separator 11 having the opening 11a (FIG. 4) is formed by punching a plate made of a ferritic stainless steel containing aluminum at the above-described ratio.

  Next, the joint portion 30 for joining the interconnector body 10 and the interconnector separator 11 to each other is formed. For example, taking the third embodiment (FIG. 5) as an example, in a state in which the interconnector body 10 and the interconnector separator 11 are arranged as shown in FIG. Using a machine, the laser is sequentially irradiated at predetermined intervals from a position above the interconnector separator 11 in a plan view to a predetermined portion surrounding the opening 11a. As a result, a plurality of joint portions 30a having a cross-sectional structure as shown in FIG. 5 are formed, and the interconnector 1 is completed. In addition, the interconnector 1 provided with the joining part 30 of another Example can also be formed by a well-known method.

  As described above, in the fuel cell stack S of the present embodiment, when the interconnector 1 is interposed between the adjacent single cells C, a so-called hanging structure is employed to connect the interconnector body 10 to the interconnector. Since it joined to the separator 11, the crack of the interconnector main body 10 can be suppressed and reliability can be improved. In this case, since the interconnector body 10 has a structure in which a conductive ceramic is coated on the surface of the metal material, it is possible to reliably suppress the chromium poisoning of the cathode caused by chromium evaporation. Since the above-described suspension structure and the conductive ceramic coating layer 10a in the interconnector body 10 are combined, when thermal stress or mechanical stress is applied to the interconnector, it is deformed by the separator 11 for the interconnector. By absorbing the above, cracks and the like generated in the coating layer 10a can be effectively prevented. Further, the structure of the joint portion 30 enables the interconnector body 10 and the interconnector separator 11 to be integrally joined while reliably separating the fuel gas and the oxidant gas.

  The interconnector separator 11 may be formed of the same material and the same structure as the cell body separator 24. This is effective in improving the manufacturability and cost reduction of the fuel cell stack S.

  The contents of the present invention have been specifically described above based on the present embodiment, but the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, as long as the interconnector separator 11 uses a flexible metal plate, the metal material and shape can be freely changed. In addition, there are various methods for forming the bonding portion 30 as long as the function can be maintained. Further, other components such as the interconnector 1, the air electrode side current collector 12, the frame portion 13, the cell main body 14, the fuel electrode side current collector 15, etc. may be implemented as long as the object of the present invention can be achieved. Various materials and structures can be adopted without being limited to the content of the form.

1 ... interconnector (interconnector with separator)
DESCRIPTION OF SYMBOLS 10 ... Interconnector main body 10a ... Coating layer 11 ... Interconnector separator 11a ... Opening part 12 ... Air electrode side collector 13 ... Frame part 14 ... Cell main body 15 ... Fuel electrode side collector 20 ... Fuel electrode layer 21 ... Solid electrolyte layer 22 ... Air electrode layer 23 ... Fuel electrode frame 24 ... Cell body separator 25 ... Insulating frame 26 ... Air electrode frame 30, 30a, 31 ... Junction S ... Fuel cell stack C ... Single cells B1-B10 ... Volt N ... Nut H ... Through hole P ... End plate

Claims (8)

A solid oxide fuel cell stack in which a plurality of unit cells each including a fuel electrode layer, an air electrode layer, and a solid electrolyte layer are stacked via an interconnector,
The interconnector is
An interconnector body made of a metal material coated with conductive ceramic on the surface;
A first separator made of one flexible metal plate;
With
And the said interconnector main body is mutually joined via the 1st separator and the junction part surrounding the perimeter of the opening formed in the approximate center of the said 1st separator,
And the said interconnector is laminated | stacked by fixing the part of a said 1st separator,
And the said 1st separator is being fixed in the state which contact | connected the flame | frame which comprises a frame part, The solid oxide fuel cell stack characterized by the above-mentioned. The frame portion includes a fuel electrode frame disposed on the fuel electrode layer side, and an air electrode frame disposed on the air electrode layer side,
2. The solid oxide fuel cell stack according to claim 1, wherein the first separator is fixed while being sandwiched between the fuel electrode frame and the air electrode frame. 3.   The solid oxide fuel cell stack according to claim 1 or 2, wherein the first separator is made of a metal plate thinner than the interconnector body.   The solid oxide fuel cell stack according to any one of claims 1 to 3, wherein the first separator is formed of an alloy containing aluminum in an amount of 1 wt% to 10 wt%.   5. The solid oxide fuel cell stack according to claim 1, wherein a thickness of the conductive ceramic coated on a surface of the interconnector body is 1 μm or more and 30 μm or less. 6. .   6. The solid oxide fuel cell stack according to claim 1, wherein the first separator has a concave or wavy cross-sectional shape that can relieve stress. 6.   The solid oxide form according to any one of claims 1 to 6, wherein the joint is formed by using any one of welding, brazing, glass sealing, or a combination thereof. Fuel cell stack. A cell body in which the fuel electrode layer is disposed on one side and the air electrode layer is disposed on the other side across the solid electrolyte layer;
A second separator made of a flexible metal plate;
Further comprising
2. The cell main body and the second separator are joined to each other via a cell joining portion that surrounds the entire circumference of an opening formed at substantially the center of the second separator. 8. The solid oxide fuel cell stack according to any one of items 7 to 7.

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