JP2013101924A - Stack structure for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stack structure for a fuel cell which is bonded to a support plate using a jointing material so that a plurality of tabular cells are arranged in a stack, and is capable of suppressing formation of cracks in the bonding material.SOLUTION: A shape of a side surface of one edge in the longitudinal direction of each of cells 100 has a second longitudinal direction (y-axis direction). A shape of each of insertion holes 211 into which to insert the edges of a plurality of cells formed on a surface of a support plate 210 has a symmetrical axis direction (the y-axis direction) with regard to axial symmetry. One edge of each of cells is loosely fit into a corresponding insertion hole 211 so that the second longitudinal direction coincides with the symmetrical axis direction of the insertion hole 211. A bonding material 300 is provided at each of bonding parts to one edge of the cell corresponding to each of insertion holes 211 so as to fill in a gap between an inner wall of the insertion hole 211 and an exterior wall of the one edge of the cell 100. A maximal value of a tilt angle of the second longer direction with regard to the symmetrical axis direction in each of the plurality of cells is equal to or less than 5.0°.

Description

  The present invention relates to a fuel cell stack structure.

  Conventionally, “a flat cell having a longitudinal direction provided with a support substrate in which a gas flow path is formed” and “the cells protrude from the surface of the support plate along the longitudinal direction, respectively, and the plurality of cells A support plate that joins and supports one end of each cell in the longitudinal direction using a joining material so that the cells are arranged in a stack, and “the internal space of the manifold and the gas flow paths of the plurality of cells” There is known a stack structure of a solid oxide fuel cell including a gas manifold provided with the support plate so that one end of each of the fuel cell and the one end of each of the fuel cell is in communication with each other (see, for example, Patent Document 1) ).

JP 2005-1000068 A

  By the way, regarding the above-described stack structure, the present inventor considers one having the following characteristics. The shape of the side surface of one end of each cell has a second longitudinal direction. A plurality of insertion holes for communicating the internal space of the manifold and one end portions of the plurality of cells are formed on the surface of the support plate corresponding to the plurality of cells. The shape of each insertion hole (of the opening) has a direction of an axis of symmetry with respect to line symmetry. One end of each cell is loosely fitted in the corresponding insertion hole so that the corresponding second longitudinal direction is along the direction of the symmetry axis of the corresponding insertion hole. The bonding material enters (fills) at least a gap existing between the inner wall of the insertion hole and the outer wall of the one end of the cell at each of the bonding portions between the insertion holes and the corresponding one end of the cell. By being provided as described above, each insertion hole and one end of the corresponding cell are joined to each other.

  In the stack structure having the above-mentioned features, one end portion of each cell is usually inserted by solidifying the bonding material by applying heat treatment in a state where the bonding material paste is filled in the gaps of the respective bonding portions. Each is joined to a hole. Thereby, the stack structure is completed. Here, when the completed fuel cell stack structure is operated under a severe thermal stress environment, cracks may occur from the surface of the (solidified) bonding material to the inside ( (See FIG. 9 described later). The present inventor has conducted various experiments in order to deal with such problems. As a result, the present inventors have found that the occurrence of such cracks has a strong correlation with the inclination angle of the second longitudinal direction with respect to the direction of the symmetry axis.

  An object of the present invention is to provide a fuel cell stack structure having the above-described features, which can suppress the occurrence of cracks in a solidified bonding material.

  The fuel cell stack structure according to the present invention has the above-described features. That is, one end of each cell is loosely fitted into the corresponding insertion hole so that the corresponding second longitudinal direction is along the direction of the symmetry axis of the corresponding insertion hole. The bonding material enters (fills) at least a gap existing between the inner wall of the insertion hole and the outer wall of the one end of the cell at each of the bonding portions between the insertion holes and the corresponding one end of the cell. It is provided to do. Thereby, each insertion hole and the corresponding one end of the cell are joined.

  Note that one end of each cell may not be inserted (freely fitted) into the corresponding (insertion) hole. In this case, one end of each cell is positioned corresponding to the corresponding hole such that the corresponding second longitudinal direction is along the direction of the symmetry axis of the corresponding hole, and the bonding material is It is provided so that the space which exists between the said hole and the one end part of the said cell may be filled up in each junction part with the said one end part of the said cell corresponding to each said hole. Thereby, the one end of the cell corresponding to each hole is joined.

  Here, the “first longitudinal direction” refers to symmetry with respect to line symmetry when a figure having a planar (upper surface) shape of a flat cell (two-dimensional shape in a top view of the cell) has line symmetry properties. When there are a plurality of symmetric axes, the direction of the axis indicates the direction of the symmetric axis with the longest part included in the figure. Similarly, the “second longitudinal direction” refers to the symmetry axis related to the line symmetry in the case where a figure having the shape of the side surface of the one end portion of the cell (two-dimensional shape in the side view of the cell) has the property of line symmetry. When there are a plurality of symmetry axes, the direction of the symmetry axis with the longest part included in the figure is indicated. The “direction of the symmetry axis” refers to the direction of the symmetry axis with respect to the line symmetry when the figure having the shape of the insertion hole (two-dimensional shape in plan view of the support plate) has the property of line symmetry, In the case where a plurality of are present, it indicates the direction of any of the symmetry axes.

  Even if one end of each cell is inserted (freely fitted) / joined into the corresponding insertion hole so that the corresponding second longitudinal direction coincides with the direction of the symmetry axis of the corresponding insertion hole, Due to the presence of the gap, the direction of the one end of the cell (second longitudinal direction) can inevitably be inclined with respect to the direction of the insertion hole (direction of the symmetry axis) in plan view of the support plate. In other words, the second longitudinal direction does not coincide with the direction of the symmetry axis, and therefore the inclination angle of the second longitudinal direction with respect to the direction of the symmetry axis is greater than zero.

  When the maximum value of the corresponding inclination angles of the second longitudinal direction with respect to the direction of the symmetry axis of the corresponding hole for each of the plurality of cells is 5.0 ° or less, It has been found that cracks are less likely to occur in the solidified bonding material than in the case where it is not. Details of this point will be described later.

  The joined body is preferably made of crystallized glass. In this case, the joined body provided in each joined portion includes an outer portion located in the vicinity of the surface including the surface of the joined body, and the outer portion located inside the joined body from the outer portion. And an inner portion having a higher porosity. Here, the porosity of the outer portion is preferably 1 to 5%, and the porosity of the inner portion is preferably 5 to 25%.

It is a perspective view which shows one cell used for the stack structure of the fuel cell which concerns on embodiment of this invention. 1 is an overall perspective view of a stack structure of a fuel cell according to an embodiment of the present invention. FIG. 3 is a perspective view of the entire fuel gas manifold shown in FIG. 2. It is an enlarged view of the insertion hole formed in the support plate shown in FIG. It is the longitudinal cross-sectional view which showed the mode of the junction part of an insertion hole and the one end part of a cell. It is the cross-sectional view which showed the mode of the junction part of an insertion hole and the one end part of a cell. It is the figure which showed a mode that fuel gas and air were supplied and discharged | emitted with respect to the stack structure shown in FIG. FIG. 6 shows a state in which one end of the cell is joined to the insertion hole in a state where the direction of the one end of the cell (second longitudinal direction) is inclined with respect to the direction of the insertion hole (direction of the symmetry axis). It is a figure corresponding to. It is the figure which showed a mode that the crack had generate | occur | produced in the joining material in the junction part of an insertion hole and the one end part of a cell. It is a figure for demonstrating the inclination angle of the 2nd longitudinal direction with respect to the direction of a symmetrical axis. FIG. 11 is a view corresponding to FIG. 10 in a case where the shape of the insertion hole is a gourd type having a line-symmetric property. It is a figure corresponding to FIG. 5 for demonstrating the force which a cell receives from the current collection member interposed between adjacent cells. It is a figure corresponding to FIG. 10 for demonstrating the force which a cell receives from a current collection member. It is the figure which showed a mode that a joining material was comprised from the outer part and the inner part whose porosity is larger than an outer part. FIG. 7 is a view corresponding to FIG. 6 in a case where one end portions of a plurality of cells are inserted into one insertion hole. FIG. 6 is a view corresponding to FIG. 5 in the case where the cell is arranged with respect to the support plate so that one end of the cell does not enter the hole of the support plate. It is a perspective view which shows the other example of one cell used for the stack structure of the fuel cell which concerns on embodiment of this invention. It is sectional drawing corresponding to the 18-18 line of the cell shown in FIG. It is the top view which showed the state of the fuel electrode and interconnector which were embed | buried under the recessed part of the support substrate shown in FIG. It is a figure for demonstrating the operating state of the cell shown in FIG. It is a figure for demonstrating the flow of the electric current in the operating state of the cell shown in FIG. It is a perspective view which shows the support substrate shown in FIG. FIG. 18 is a cross-sectional view corresponding to FIG. 18 in a first stage in the process of manufacturing the cell shown in FIG. 17. FIG. 18 is a cross-sectional view corresponding to FIG. 18 in a second stage in the process of manufacturing the cell shown in FIG. FIG. 18 is a cross-sectional view corresponding to FIG. 18 in a third stage in the process of manufacturing the cell shown in FIG. FIG. 18 is a cross-sectional view corresponding to FIG. 18 in a fourth stage in the process of manufacturing the cell shown in FIG. FIG. 18 is a cross-sectional view corresponding to FIG. 18 in a fifth stage in the process of manufacturing the cell shown in FIG. FIG. 18 is a cross-sectional view corresponding to FIG. 18 in a sixth stage in the process of manufacturing the cell shown in FIG. FIG. 19 is a cross-sectional view corresponding to FIG. 18 in a seventh step in the process of manufacturing the cell shown in FIG. FIG. 18 is a cross-sectional view corresponding to FIG. 18 in an eighth stage in the process of manufacturing the cell shown in FIG. FIG. 18 is a cross-sectional view corresponding to FIG. 18 of a first modification of the cell shown in FIG. 17. FIG. 18 is a cross-sectional view corresponding to FIG. 18 of a second modification of the cell shown in FIG. 17. FIG. 18 is a cross-sectional view corresponding to FIG. 18 of a third modification of the cell shown in FIG. 17. It is sectional drawing corresponding to FIG. 19 of the 4th modification of the cell shown in FIG. FIG. 18 is a view corresponding to FIG. 2 when the cell shown in FIG. 17 is used in the stack structure of the fuel cell according to the embodiment of the present invention. FIG. 18 is a view corresponding to FIG. 3 when the cell shown in FIG. 17 is used in the stack structure of the fuel cell according to the embodiment of the present invention. FIG. 18 is a view corresponding to FIG. 4 when the cell shown in FIG. 17 is used in the stack structure of the fuel cell according to the embodiment of the present invention. FIG. 18 is a view corresponding to FIG. 5 when the cell shown in FIG. 17 is used in the stack structure of the fuel cell according to the embodiment of the present invention. FIG. 18 is a view corresponding to FIG. 6 when the cell shown in FIG. 17 is used in the stack structure of the fuel cell according to the embodiment of the present invention. FIG. 18 is a view corresponding to FIG. 7 when the cell shown in FIG. 17 is used in the stack structure of the fuel cell according to the embodiment of the present invention.

(Example of cell configuration used for stack structure)
First, a cell 100 used in a stack structure of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention will be described. As shown in FIG. 1, in a cell 100, one main surface of a flat porous conductive support 11 is composed of a porous fuel electrode 12, a dense solid electrolyte 13, and porous conductive ceramics. Air electrodes 14 are sequentially stacked. Further, an intermediate film 15, an interconnector 16 made of a lanthanum-chromium oxide material, and a current collecting film 17 made of a P-type semiconductor material are sequentially formed on the main surface of the conductive support 11 opposite to the air electrode 14. Has been.

  The cell 100 has a flat plate shape having a first longitudinal direction (x-axis direction), the length L1 (length in the first longitudinal direction) of the cell 100 is 50 to 500 mm, and the width L2 is 10 to 100 mm. The thickness L3 is 1 to 5 mm (L1> L2). The shape of the side surface (length L2, oval shape of width L3, L2> L3) of one end portion of the cell 100 in the first longitudinal direction (x-axis direction) has the second longitudinal direction (y-axis direction).

  In addition, a plurality of gas flow paths (through holes) 18 parallel to each other are formed in the conductive support 11 at intervals in the width direction (y direction) along the longitudinal direction (x axis direction). Yes. The cross-sectional shape of each gas flow path 18 is a circle having a diameter D of 0.5 to 3 mm. The space | interval (pitch) P in the width direction of the adjacent gas flow paths 18 and 18 is 1-5 mm. In addition, the cross-sectional shape of each gas flow path 18 may be an ellipse, a long hole, a quadrangle having arcs at four corners, or the like.

  The cell 100 includes side end portions B and B provided on both sides in the width direction (direction perpendicular to the longitudinal direction) and a pair of flat portions A and A connecting the side end portions B and B, respectively. ing. The pair of flat portions A and A are flat and substantially parallel. On one of the flat portions A and A, the fuel electrode 12, the solid electrolyte 13, and the air electrode 14 are formed in this order on one main surface of the conductive support 11, and on the other of the flat portions A and A, On the other main surface of the conductive support 11, an intermediate film 15, an interconnector 16, and a current collecting film 17 are formed in this order.

  The width of the conductive support 11 is preferably 10 to 100 mm, and the thickness is preferably 1 to 5 mm. The aspect ratio (width / thickness) of the conductive support 11 is 5 to 100. The shape of the conductive support 11 is expressed as “thin plate shape”, but depending on the combination of the dimension in the width direction and the dimension in the thickness direction, it may be referred to as “elliptical column shape” or “flat shape”. Can be expressed.

  The conductive support 11 is composed mainly of a rare earth element oxide composed of one or more selected from Y, Lu, Yb, Tm, Er, Ho, Dy, Gd, Sm and Pr and Ni and / or NiO. It is desirable to be composed of the material In addition to Ni, Fe, Cu, or the like may be included.

The conductive support 11 can also be described as including “NiO (nickel oxide) or Ni (nickel)” and “insulating ceramics”. Insulating ceramics include CSZ (calcia stabilized zirconia), YSZ (8YSZ) (yttria stabilized zirconia), Y ₂ O ₃ (yttria), MgO (magnesium oxide), or “MgAl ₂ O ₄ (magnesia alumina spinel). ) And MgO (magnesium oxide) "or the like. The conductivity of the conductive support 11 is 10 to 2000 S / cm at 800 ° C. The porosity of the conductive support 11 is 20 to 60%.

The intermediate film 15 formed between the conductive support 11 and the interconnector 16 is made of a material mainly containing ZrO ₂ containing Ni and / or NiO and a rare earth element, or a rare earth oxide (for example, Y ₂ O ₃ ). The Ni conversion amount of the Ni compound in the intermediate film 15 is preferably 35 to 80% by volume, and more preferably 50 to 70% by volume in the total amount. When the Ni conversion amount is 35% by volume or more, the conductive path by Ni is increased, and the conductivity of the intermediate film 15 is improved. As a result, the voltage drop caused by the intermediate film 15 is reduced. Moreover, when the Ni conversion amount is 80% by volume or less, the difference in thermal expansion coefficient between the conductive support 11 and the interconnector 16 can be reduced, and the occurrence of cracks at the interface between the two can be suppressed.

  Further, from the viewpoint of reducing the voltage drop, the thickness of the intermediate film 15 is preferably 20 μm or less, and more preferably 10 μm or less.

The thermal expansion coefficient of the middle rare earth element or heavy rare earth element oxide is smaller than that of “ZrO ₂ containing Y ₂ O ₃ ” in the solid electrolyte 13. Therefore, the thermal expansion coefficient of the conductive support 11 as a cermet material with Ni can be made closer to the thermal expansion coefficient of the solid electrolyte 13. As a result, cracks in the solid electrolyte 13 and separation of the solid electrolyte 13 from the fuel electrode 12 can be suppressed. Furthermore, by using a heavy rare earth element oxide having a small thermal expansion coefficient, Ni in the conductive support 11 can be increased, and the electrical conductivity of the conductive support 11 can be increased. From this viewpoint, it is desirable to use heavy rare earth element oxides.

  If the sum of the thermal expansion coefficients of the rare earth element oxide is less than the thermal expansion coefficient of the solid electrolyte 13, the light rare earth elements La, Ce, Pr, and Nd oxides are added to the medium rare earth element and heavy rare earth element. Even if it is contained, there is no problem.

  Moreover, the raw material cost can be significantly reduced by using a complex rare earth element oxide containing a plurality of inexpensive rare earth elements in the course of purification. Also in this case, it is desirable that the thermal expansion coefficient of the complex rare earth element oxide is less than the thermal expansion coefficient of the solid electrolyte 13.

  Further, it is desirable to provide a current collector film 17 made of a P-type semiconductor, for example, a transition metal perovskite oxide, on the surface of the interconnector 16. When a current collecting member made of metal is disposed directly on the surface of the interconnector 16, the potential drop increases due to non-ohmic contact. In order to secure ohmic contact and reduce the potential drop, it is necessary to connect the current collector film 17 made of a P-type semiconductor to the interconnector 16. As the P-type semiconductor, it is desirable to use a transition metal perovskite oxide. As the transition metal perovskite oxide, it is desirable to use at least one of a lanthanum-manganese oxide, a lanthanum-iron oxide, a lanthanum-cobalt oxide, or a composite oxide thereof.

The fuel electrode 12 provided on the main surface of the conductive support 11 is composed of Ni and ZrO _{2 in} which a rare earth element is dissolved. The thickness of the fuel electrode 12 is desirably 1 to 30 μm. When the thickness of the fuel electrode 12 is 1 μm or more, a three-layer interface as the fuel electrode 12 is sufficiently formed. Further, when the thickness of the fuel electrode 12 is 30 μm or less, interfacial peeling due to a difference in thermal expansion from the solid electrolyte 13 can be prevented.

The solid electrolyte 13 provided on the main surface of the fuel electrode 12 is made of yttria-stabilized zirconia YSZ (dense ceramic) containing yttria (Y ₂ O ₃ ). The thickness of the solid electrolyte 13 is desirably 0.5 to 100 μm. Gas permeation can be prevented when the thickness of the solid electrolyte 13 is 0.5 μm or more. Moreover, the increase in a resistance component can be suppressed because the thickness of the solid electrolyte 13 is 100 micrometers or less.

The air electrode 14 is a lanthanum-manganese oxide, lanthanum-iron oxide, lanthanum-cobalt oxide of a transition metal perovskite oxide, or at least one porous conductive material of a composite oxide thereof. Made of ceramics. The air electrode 14 is preferably a (La, Sr) (Fe, Co) O ₃ system from the viewpoint of high electrical conductivity in the middle temperature range of about 800 ° C. The thickness of the air electrode 14 is preferably 10 to 100 μm from the viewpoint of current collection.

  The interconnector 16 is a dense body in order to prevent leakage of fuel gas and oxygen-containing gas between the inside and outside of the conductive support 11. Moreover, since the inner and outer surfaces of the interconnector 16 are in contact with the fuel gas and the oxygen-containing gas, respectively, they have reduction resistance and oxidation resistance.

  The thickness of the interconnector 16 is desirably 30 to 200 μm. When the thickness of the interconnector 16 is 30 μm or more, gas permeation can be completely prevented, and when it is 200 μm or less, an increase in resistance component can be suppressed.

For example, a bonding layer made of Ni and ZrO ₂ or Y ₂ O ₃ may be interposed between the end portion of the interconnector 16 and the end portion of the solid electrolyte 13 in order to improve the sealing performance.

  In the cell 100, the dense solid electrolyte 13 is not only on one main surface of the conductive support 11, but also on the side end surface of the interconnector 16 on the other main surface via the side end portion of the conductive support 11. Is formed. That is, the solid electrolyte 13 is extended to the other main surface of the conductive support 11 so as to form the side ends B, B on both sides, and is joined to the interconnector 16. Note that the side ends B and B (side ends of the conductive support 11) have curved shapes that protrude outward in the width direction in order to relieve the thermal stress that occurs due to heating and cooling associated with power generation. It is desirable.

  Next, a method for manufacturing the cell 100 as described above will be described. First, rare earth element oxide powder excluding La, Ce, Pr, and Nd elements and Ni and / or NiO powder are mixed. A conductive support material in which an organic binder and a solvent are mixed is extruded into this mixed powder to produce a plate-shaped conductive support molded body. This molded body is dried and degreased.

In addition, a sheet-like solid electrolyte molded body is produced using a solid electrolyte material in which a ZrO ₂ powder in which a rare earth element (Y) is dissolved, an organic binder, and a solvent are mixed.

Next, a slurry to be the fuel electrode 12 prepared by mixing Ni and / or NiO powder, ZrO ₂ powder in which a rare earth element is solid-solved, an organic binder, and a solvent is formed into the solid electrolyte molded body. Applied to one side. Thereby, a fuel electrode molded body is formed on one surface of the solid electrolyte molded body.

  Next, the conductive support body is formed such that a laminate of the sheet-like solid electrolyte formed body and the fuel electrode body is in contact with the conductive electrode body. It is wound around the compact.

  Next, several layers of the sheet-like solid electrolyte molded body are laminated on the solid electrolyte molded body at the position where the side end portions B and B of the laminated molded body are formed, and dried. Moreover, the slurry used as the solid electrolyte 13 may be screen-printed on the solid electrolyte molded body. In addition, degreasing may be performed at this time.

  Next, a sheet-like interconnector molded body is produced using an interconnector material in which a lanthanum-chromium oxide powder, an organic binder, and a solvent are mixed.

Moreover, a sheet-like intermediate film molded body is produced using a slurry in which Ni and / or NiO powder, a ZrO ₂ powder in which a rare earth element is dissolved, an organic binder, and a solvent are mixed.

  Next, the interconnector molded body and the intermediate film molded body are laminated. The laminate is laminated on the conductive support molded body so that the intermediate film molded body side of the laminate is in contact with the exposed conductive support molded body side.

  Thereby, the fuel electrode molded body and the solid electrolyte molded body are sequentially laminated on one main surface of the conductive support molded body, and the intermediate film molded body and the interconnector molded body are laminated on the other main surface. A body is made. Each molded body can be produced by sheet molding by a doctor blade, printing, slurry dip, spraying by spraying, and the like. Moreover, each molded object can be produced by these combinations.

  Next, the laminated molded body is degreased and cofired at 1300 to 1600 ° C. in an oxygen-containing atmosphere.

  Next, a transition metal perovskite oxide powder, which is a P-type semiconductor, and a solvent are mixed to produce a paste. The laminate is immersed in this paste. An air electrode molded body and a current collector film molded body are formed on the surfaces of the solid electrolyte 13 and the interconnector 16 by dipping or direct spray application, respectively. These molded bodies are baked at 1000 to 1300 ° C., whereby the cell 100 is manufactured.

  At this time, the Ni component in the conductive support 11, the fuel electrode 12, and the intermediate film 15 is NiO by firing in an oxygen-containing atmosphere. Therefore, in order to acquire these electroconductivity, after that, reducing fuel gas is flowed from the electroconductive support body 11 side, and NiO is reduced at 800-1000 degreeC over 1 to 10 hours. This reduction process may be performed during power generation.

(Example of overall structure of stack structure)
Next, a stack structure of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention using the above-described cell 100 will be described. As shown in FIG. 2, the stack structure includes a large number of cells 100 and a fuel gas manifold 200 for supplying a fuel gas to each of the large number of cells 100. The entire manifold 200 is made of a material such as stainless steel.

  The top plate of the manifold 200 (in other words, the top plate (flat plate) of the gas tank) also serves as a support plate 210 for supporting a large number of cells 100. The manifold 200 is provided with an introduction passage 220 for introducing fuel gas from the outside into the internal space of the manifold 200. One end portion of each cell 100 in the first longitudinal direction is protruded from the surface of the support plate 210 along the first longitudinal direction (x-axis direction) and the plurality of cells 100 are arranged in a stack. It is joined and supported by the support plate 210 (details of the joining structure will be described later). The other end portion of each cell 100 in the first longitudinal direction is a free end. Therefore, this stack structure can be expressed as a “cantilever stack structure”.

  As shown in FIG. 3, a large number of insertion holes 211 communicating with the internal space of the manifold 200 are formed on the surface of the support plate 210 (the top plate of the manifold 200). One end of the corresponding cell 100 is inserted into each insertion hole 211. As shown in FIG. 4, the shape of each insertion hole 211 is an oval shape (L4> L5) having a length L4 and a width L5, and the direction of the axis of symmetry with respect to line symmetry (third longitudinal direction, y-axis direction). Have

  The length L4 of the insertion hole 211 is 0.2 to 3 mm longer than the length L2 (see FIG. 1) of the side surface of one end of the cell 100. Similarly, the width L5 of the insertion hole 211 is 0.2 to 3 mm larger than the width L3 (see FIG. 1) of the side surface of one end of the cell 100. That is, as shown in FIGS. 5 and 6, the second longitudinal direction (the length direction of the side surface of one end of the cell 100) is along the direction of the axis of symmetry of the insertion hole 211 (the length direction of the insertion hole 211). In a state where one end of the cell 100 is inserted into the insertion hole 211, a gap is formed between the inner wall of the insertion hole 211 and the outer wall of the one end of the cell 100. In other words, one end of the cell 100 is loosely fitted in the insertion hole 211. 5 and 6 (particularly, FIG. 6), the gap is exaggerated.

  As shown in FIGS. 5 and 6, the solidified bonding material 300 is provided so as to fill the gap in each of the bonding portions between the insertion hole 211 and one end of the cell 100. Thereby, each insertion hole 211 and the one end part of the corresponding cell 100 are joined and fixed, respectively. As shown in FIG. 5, one end of the gas flow path 18 of each cell 100 communicates with the internal space of the manifold 200.

  Also, as shown in FIG. 5, between adjacent cells 100, 100, between adjacent cells 100, 100 (more specifically, the fuel electrode 12 of one cell 100 and the air electrode of the other cell 100). 14) A current collecting member 400 for electrically connecting them in series is interposed. The current collecting member 400 is made of, for example, a metal mesh.

The bonding material 300 is preferably composed of crystallized glass, but may be composed of amorphous glass, metal brazing material, or the like. As the crystallized glass, for example, SiO ₂ —MgO-based glass is preferable.

  When the cantilever stack structure of the fuel cell described above is operated, as shown in FIG. 7, the fuel gas (eg, hydrogen) at a high temperature (for example, 600 to 800 ° C.) and the “gas containing oxygen (eg, air) ) ". The fuel gas introduced from the introduction passage 220 moves to the internal space of the manifold 200 and is then introduced into the gas flow path 18 of the corresponding cell 100 via each insertion hole 211. The fuel gas that has passed through each gas flow path 18 is then discharged to the outside from the other end (free end) of each gas flow path 18. Air flows in the width direction (y-axis direction) of the cells 100 along the gaps between the adjacent cells 100 in the stack structure.

  The above-mentioned cantilever stack structure is assembled by the following procedure, for example. First, a required number of completed cells 100 and a completed manifold 200 are prepared. Next, the plurality of cells 100 are aligned and fixed in a stack using a predetermined jig or the like. Next, one end of each of the plurality of cells 100 is inserted into the corresponding insertion hole 211 of the support plate 210 at a time while maintaining the state in which the plurality of cells 100 are aligned and fixed in a stack. Next, the paste for the bonding material 300 is filled in each gap of the bonding portion between the insertion hole 211 and one end of the cell 100. At that time, as shown in FIG. 5, the paste may be supplied to the joint to the extent that it protrudes upward from the surface of the support plate 210.

  Next, the bonding material 300 is solidified by applying heat treatment to the paste to solidify the paste. As a result, one end of each cell is joined and fixed to the corresponding insertion hole 211. In other words, one end of each cell 100 is joined and supported by the support plate 210 using the joining material 300. Thereafter, the predetermined jig is removed from the plurality of cells 100 to complete the above-described cantilever stack structure.

  Hereinafter, a case where crystallized glass is used as the bonding material 300 will be particularly noted. In this case, amorphous glass is used as the paste for the bonding material. Heat treatment is applied to the amorphous glass filled in the gap. When the temperature of the amorphous glass reaches the crystallization temperature by this heat treatment, a crystal phase is generated inside the amorphous glass at the crystallization temperature, and crystallization proceeds. As a result, the amorphous glass is converted into ceramic and becomes crystallized glass. Here, in the present specification, the crystallized glass has a ratio (crystallinity) of “volume occupied by the crystal phase” to the total volume of 60% or more, and the “amorphous phase and impurities occupy the total volume”. Glass (ceramics) having a volume ratio of less than 40%.

(Suppression of the occurrence of cracks in the bonding material)
As shown in FIG. 6 described above, each of the second longitudinal directions (the length direction of the side surface of one end of the cell 100) coincides with the direction of the axis of symmetry of the insertion hole 211 (the length direction of the insertion hole 211). Even if one end portion of the cell 100 is to be inserted (freely fitted) / joined into the corresponding insertion hole 211, in fact, as shown in FIG. The second longitudinal direction (the length direction of the side surface of one end of the cell 100) can inevitably be inclined with respect to the direction of the axis of symmetry of the insertion hole 211 (the length direction of the insertion hole 211). In other words, the second longitudinal direction does not coincide with the direction of the symmetry axis of the insertion hole 211, and therefore the inclination angle of the second longitudinal direction with respect to the direction of the symmetry axis of the insertion hole 211 is greater than zero.

  On the other hand, when the completed stack structure of the fuel cell is operated under a severe thermal stress environment, as shown in FIGS. 8 and 9, the (solidified) bonding material 300 is directed from the surface toward the inside. In some cases, cracks occurred. As shown in FIGS. 8 and 9, this crack is particularly likely to occur in a portion where the gap is wide due to the inclination of the second longitudinal direction with respect to the direction of the symmetry axis of the insertion hole 211.

  The inclination angle θ in the second longitudinal direction with respect to the direction of the symmetry axis of the insertion hole 211 is defined as shown in FIG. That is, in the figure having the shape of the opening (ellipse shape) of the insertion hole 211, the “symmetric axis related to line symmetry” along the length direction (y-axis direction) of the opening is a straight line L 1, and one end of the cell 100 In the figure having the shape of the side surface (ellipse shape), the “symmetric axis with respect to line symmetry” along the length direction (y-axis direction) of the side surface is defined as a straight line L2. At this time, an angle formed by the straight line L1 and the straight line L2 when viewed from the x-axis direction is defined as an “inclination angle θ”. When warping occurs in the length direction (y-axis direction) of the side surface at one end portion of the cell 100, the straight line L2 is the length of the side surface in the figure having the shape of the side surface of the one end portion of the cell 100. It can be defined as “straight line connecting the middle points in the thickness direction (z-axis direction)” at both ends in the vertical direction. The inclination angle θ for each of the plurality of cells 100 included in one stack structure varies.

  The present inventor has conducted various experiments in order to cope with the above-described problem of crack generation. As a result, the present inventor has found that the occurrence of such a crack is the maximum value of the inclination angles θ (hereinafter referred to as “maximum inclination angle θmax”) for each of the plurality of cells 100 included in one stack structure. And found a strong correlation. Hereinafter, test A in which this has been confirmed will be described.

(Test A)
In the test A, a plurality of samples having different combinations of the material of the bonding material 30 and the maximum inclination angle θmax were produced for the above-described cantilever stack structure (see FIG. 2). Specifically, as shown in Table 1, 10 types (combinations) were prepared. Ten samples (N = 10) were made for each level.

  Each sample of the stack structure (see FIG. 2) contained 10 cells 100. As the shape of the side surface of one end portion in the first longitudinal direction (x-axis direction) of the cell 100 used in each sample (see FIG. 2), the length L2 is 20 to 100 mm and the width L3 is the same as in FIG. An oval shape (L2> L3) of 2 to 4 mm was employed. As the shape of the opening of the insertion hole 211, as in FIG. 6, the length L4 is 0.5-3 mm larger than the length L2, and the width L5 is 0.5-3 mm larger than the width L3 (L4> L5). Was adopted. More specifically, four patterns of 20, 30, 50, and 100 mm were adopted as the length L2, and one pattern of 3 mm was adopted as the width L3. That is, four types of cells were used. In addition, as the amount of L4 larger than L2 and the amount of L5 larger than L3, four patterns of 0.5, 1.0, 2.0, and 3.0 mm were employed. That is, the gaps of four types were realized. Further, the inclination angle θ (and hence the maximum inclination angle θmax) for each of the cells 100 included in each sample was controlled by adjusting the “predetermined jig or the like”. Each inclination angle θ was measured by directly observing the cell junction. For each sample, the maximum value among the measured ten inclination angles θ was set as the maximum inclination angle θmax. The thermal expansion coefficient of the cell was 11.0 to 12.0 ppm / K (thermal expansion coefficient from room temperature to 1000 ° C.). The bonding material was selected so that the difference between the thermal expansion coefficient of the bonding material and the thermal expansion coefficient of the cell was 0.5 ppm / K or less.

  Stainless steel was used as the material of the support plate 210 (manifold 200). In each sample, the paste for the bonding material filled in the gap was subjected to heat treatment at a temperature of 850 ° C. for 1 to 5 hours. As a result, the bonding material 300 was solidified, and one end of each cell 100 was bonded to the support plate 210 using the bonding material 300 (a stack structure was completed).

  For each sample after the reduction treatment, “a pattern in which the ambient temperature is raised from room temperature to 750 ° C. in 2 hours and then lowered from 750 ° C. to room temperature in 4 hours while reducing fuel gas is passed through the fuel electrode 12. Was repeated 20 times. And about each sample, the presence or absence of the generation | occurrence | production of the crack in the joining material 300 was confirmed. This confirmation was made by visual observation as well as observation using a microscope. The results are as shown in Table 1.

  As can be understood from Table 1, after the thermal cycle test severe in terms of thermal stress, when the maximum inclination angle θmax exceeds 5.0 °, as shown in FIGS. ) Cracks are likely to occur from the surface of the bonding material 300 toward the inside. On the other hand, when the maximum inclination angle θmax is 5.0 ° or less, it can be said that the cracks hardly occur. This is considered based on the following reasons. That is, when the bonding material paste is subjected to heat treatment, the bonding material 300 contracts. In particular, when the bonding material 300 is made of crystallized glass, bonding is performed after the time when the temperature of the bonding material (in this stage, amorphous glass) reaches a “glass softening point” slightly lower than the “crystallization temperature”. The material starts to be restrained at the interface with the inner wall of the insertion hole 211 and the interface with the outer wall at one end of the cell 100. After that, when the temperature of the bonding material (in this stage, the amorphous glass) reaches the “crystallization temperature”, the crystallization of the amorphous glass proceeds under the “crystallization temperature”. Thus, the bonding material 300 tends to shrink (crystallization shrinkage). Therefore, after the time when crystallization shrinkage is started, the bonding material tends to shrink while being constrained by the surroundings (the joined body). As a result, internal stress (tensile stress) acts on the bonding material.

  On the other hand, when the inclination angle θ is large, the difference in the size of the gap increases between a narrow portion and a wide portion where the gap (the interval between the inner wall of the insertion hole 211 and the outer wall of one end of the cell 100) is narrow. . The larger the gap is, the larger the amount of reduction of the gap (interval) due to crystallization shrinkage (more precisely, the amount to be reduced). This means that when the inclination angle θ is large, the difference in the amount of reduction of the gap due to crystallization shrinkage increases between the narrow gap and the wide gap. Due to the large difference in the amount of reduction of the gap due to crystallization shrinkage, the internal stress described above is particularly concentrated at a location where the gap is wide, and as a result, cracks occur in the bonding material 300 at the location where the gap is wide. Is likely to occur.

  In addition, as shown in FIG. 12, the elastic force (arrow in the figure) of the current collection member 400 in the direction which expands those intervals with respect to the two cells 100 and 100 located on both sides (z-axis direction) of itself. If the inclination θ of a certain cell 100 is large, as shown in FIG. 13, two current collecting members located on both sides (in the z-axis direction) of the cell 100 are configured. An imbalance occurs in the magnitude of the elastic force that the cell 100 receives from 400 and 400. This unbalance works so that a larger tensile stress acts on the bonding material 300 at a location where the gap is narrow. Due to this, it is considered that a crack may occur in the bonding material 300 in a portion where the gap is narrow.

  In addition, the minimum value of the inclination angles θ for all the cells 100 included in the plurality of stack structure samples used in (Test A) was 0.23 °. In other words, as described above, when each inclination angle θ is determined by the adjustment of the “predetermined jig or the like”, the inclination angle θ cannot be made smaller than 0.23 °. From this point of view, when the maximum value of the inclination angles θ for each of the plurality of cells included in one stack structure is 5.0 ° or less and the minimum value is 0.23 ° or more, It can be said that cracks are less likely to occur in the bonding material 300 as compared to the case where this is not the case.

  When the stack structure is used under normal conditions / environment (for example, a pattern in which the temperature is raised from room temperature to 750 ° C. in 4 hours and then lowered from 750 ° C. to room temperature in 12 hours), Even if the maximum value of the inclination angles θ for each of the plurality of cells included in one stack structure is larger than 5.0 °, it is separately confirmed that the bonding material 300 does not crack. Yes.

  The above results correspond to the case where the shape of the side surface of one end of the cell 100 and the shape of the opening of the insertion hole 211 are oval, but have a longitudinal direction and are symmetrical with respect to the longitudinal direction. As long as the shape has properties, the same result can be obtained even if the shape of the side surface of one end of the cell 100 and the shape of the opening of the insertion hole 211 are, for example, a gourd type as shown in FIG. It has already been confirmed that it can be obtained.

  In addition, the present inventor includes the single stack structure when the maximum value of the inclination angles θ of the plurality of cells included in the single stack structure is 5.0 ° or less. It has also been found that when the standard deviation σ for the variation in the inclination angle θ for each of the plurality of cells is 0.19 ° or more and 4.2 ° or less, cracks are less likely to occur in the bonding material 300. Hereinafter, test B in which this has been confirmed will be described.

(Test B)
In Test B, a plurality of samples having different combinations of the material of the bonding material 30, the maximum inclination angle θmax, and the standard deviation σ were produced for the above-described cantilever stack structure (see FIG. 2). Specifically, as shown in Table 2, ten kinds of levels (combinations) were prepared. Ten samples (N = 10) were made for each level. The maximum inclination angle θmax for each sample is 5.0 ° or less.

  The dimensions, conditions, and the like for each sample are the same as those in Test A. The inclination angle θ (and therefore the maximum inclination angle θmax and the standard deviation σ) for each of the cells 100 included in each sample was controlled by adjusting the “predetermined jig or the like”.

  For each sample after the reduction treatment, a thermal cycle test that is more severe in terms of thermal stress than the thermal cycle test performed in test A, that is, “atmospheric temperature while reducing fuel gas is circulated through the fuel electrode 12. The heat cycle test was repeated 20 times. “Pattern was raised from room temperature to 750 ° C. in 1 hour and then lowered from 750 ° C. to room temperature in 2 hours”. And about each sample, the presence or absence of the generation | occurrence | production of the crack in the joining material 300 was confirmed. The results are as shown in Table 2.

  As can be understood from Table 2, when the standard deviation σ of the inclination angle θ of each of the plurality of cells included in one stack structure is 0.19 ° or more and 4.2 ° or less, compared to the case where it is not so. Although the reason is unknown, it can be said that cracks are hardly generated in the bonding material 300.

  The above results correspond to the case where the shape of the side surface of one end of the cell 100 and the shape of the opening of the insertion hole 211 are oval, but have a longitudinal direction and are symmetrical with respect to the longitudinal direction. It has already been confirmed that the same result can be obtained as long as the shape has properties.

  As described above, when the maximum value (maximum inclination angle θmax) of the inclination angles θ for each of the plurality of cells included in one stack structure is 5 ° or less based on the results of Tables 1 and 2, the bonding material 300 is difficult to crack, and when the standard deviation σ of the inclination angle θ of each of the plurality of cells included in one stack structure is 0.19 ° or more and 4.2 ° or less, the crack It can be said that it is much less likely to occur.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above-described embodiment, a so-called “vertical stripe” in which a plurality of cells each provided with only one “power generation element portion in which a fuel electrode, a solid electrolyte, and an air electrode are stacked in this order” are stacked on the surface of the support substrate. Although the structure of the "type" is adopted, the so-called "horizontal stripe type" in which the power generation element portions are respectively provided at a plurality of positions separated from each other on the surface of the support substrate and the adjacent power generation element portions are electrically connected to each other. May be adopted.

  Moreover, in the said embodiment, as shown in FIG. 14, the joined body 300 provided in each joined part joins the outer part 302 located in the vicinity of the said surface including the surface of the joined body 300, and the outer part 302. An inner portion 301 located inside the body 300 and having a higher porosity than the outer portion 302 can be configured. Here, the porosity of the outer portion 302 is 1 to 5%, and the porosity of the inner portion 301 is 5 to 25%.

  According to this, “the Young's modulus of the bonding material 300 as a whole decreases due to the porosity of the inner portion 301 and the thermal stress inside the bonding material 300 decreases”, and “the bonding material 300 decreases due to the densification of the outer portion 302. The effect | action and effect, such as a defect part (stress concentration part), such as a void exposed to the surface of this, reduce | decrease, and the frequency that a crack generate | occur | produces in the joining material 300 reduce | hangs, can be show | played. Further, by making the porosity inside the inner portion 301 uniform and making the porosity inside the outer portion 302 uniform, the Young's modulus is less biased inside each portion. As a result, it is possible to obtain a joint portion in which cracks are less likely to occur.

  As described above, in order to make the inner portion 301 porous, a powder having an average particle diameter of 1 to 10 μm is adopted as the bonding material powder, or a fine powder having an average particle diameter of 0.5 to 2.0 μm and A powder obtained by mixing a coarse powder having an average particle size of 10 to 50 μm is adopted as a bonding material powder, or a pore former (average particle size: 0.5 to 20 μm, for example, cellulose or PMMA) is arranged externally. A method of adding only 10 to 30% by weight can be employed. On the other hand, in order to densify the outer portion 302, a fine powder having an average particle size of 0.5 to 2.0 μm can be employed as the bonding material powder.

  The inner part 301 and the outer part 302 can be deposited separately. That is, first, the material to be the inner portion 301 is filled in the gap. Thereafter, a material to be the outer portion 302 is applied to the surface. And these are baked simultaneously, and the joining material 300 provided with the inner part 301 and the outer part 302 is obtained. The material of the inner part 301 and the outer part 302 may be the same or different. Also, considering that amorphous glass is a material that can easily obtain a smooth surface shape, the inner portion 301 occupying most of the bonding material 300 is made of crystallized glass, and the remaining outer portion 302 is amorphous. It is preferable to be composed of glass.

  Moreover, in the cell of the said embodiment, you may replace a fuel electrode and an air electrode. In this case, a gas flow in which the fuel gas and air are interchanged in FIG. 7 is employed. Moreover, in the said embodiment, although the one end part of one cell is inserted in one insertion hole formed in the support plate, as shown in FIG. 15, in one insertion hole 211 formed in the support plate, One end of two or more cells 100 may be inserted. In FIG. 15, the interval between the adjacent cells 100 is exaggerated. Also in the case shown in FIG. 15, the y-axis direction is used as the “direction of the symmetric axis” of the insertion hole 211, as in the case shown in FIG. 6. That is, one end portion of each cell 100 corresponds so that the “second longitudinal direction” (the length direction of the side surface of one end portion of the cell 100) coincides with the “direction of the symmetry axis” (y-axis direction) of the hole 211. Is inserted into the insertion hole 211. Furthermore, all of one end portions of the plurality of cells may be inserted into one (only) insertion hole formed in the support plate.

  In the above embodiment, one end of the cell 100 is inserted into the insertion hole 211 (that is, one end of the cell 100 enters the internal space of the insertion hole 211) (see FIG. 5 and the like). 16, one end of the cell 100 may not be inserted into the hole 211 (that is, the one end of the cell 100 may not enter the internal space of the hole 211). In this case, the bonding material 300 is provided so as to fill a space existing between the hole 211 and one end of the cell 100 at each of the bonding portions between the holes 211 and the corresponding one end of the cell 100.

  Furthermore, in the above embodiment, the top plate of the manifold also serves as a support plate for supporting a large number of cells (that is, the support plate is configured integrally with the manifold), but the internal space of the manifold As long as the gas flow paths of the plurality of cells communicate with each other, the support plate may be configured separately from the manifold.

Hereinafter, another example of the cell shown in FIG. 1 will be described with reference to FIGS.
(Constitution)
FIG. 17 shows a cell 100 according to another example of the cell shown in FIG. The cell 100 includes a plurality of (books) electrically connected in series to the upper and lower surfaces (main surfaces (planes) on both sides parallel to each other) of the flat support substrate 10 having a longitudinal direction (x-axis direction). In the example, there are four so-called power generation element portions A that are arranged at predetermined intervals in the longitudinal direction and have a so-called “horizontal stripe type” configuration.

  The shape of the entire cell 100 as viewed from above is, for example, a rectangle whose length in the longitudinal direction is 5 to 50 cm and whose length in the width direction (y-axis direction) perpendicular to the longitudinal direction is 1 to 10 cm. The total thickness of the cell 100 is 1 to 5 mm. The entire cell 100 has a vertically symmetrical shape with respect to a plane passing through the center in the thickness direction and parallel to the main surface of the support substrate 10. Hereinafter, in addition to FIG. 17, the details of the cell 100 will be described with reference to FIG. 18 which is a partial cross-sectional view of the cell 100 corresponding to line 18-18 shown in FIG. FIG. 18 is a partial cross-sectional view showing a configuration (part of) each of a typical pair of adjacent power generation element portions A and A and a configuration between the power generation element portions A and A. The configuration between the other power generation element portions A and A of the other sets is the same as the configuration shown in FIG.

  The support substrate 10 is a flat plate-like fired body made of a porous material having no electronic conductivity. As shown in FIG. 22 described later, a plurality (six in this example) of fuel gas passages 11 (through holes) extending in the longitudinal direction are provided in the support substrate 10 at predetermined intervals in the width direction. Is formed. In this example, each recess 12 includes a bottom wall made of the material of the support substrate 10 and side walls closed in the circumferential direction made of the material of the support substrate 10 over the entire circumference (two side walls along the longitudinal direction and the width direction). A rectangular parallelepiped depression defined by two side walls).

The support substrate 10 can be made of, for example, CSZ (calcia stabilized zirconia). Alternatively, it may be composed of NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia), NiO (nickel oxide) and Y ₂ O ₃ (yttria), or MgO. (Magnesium oxide) and MgAl ₂ O ₄ (magnesia alumina spinel) may be used.

  The support substrate 10 may be configured to include “transition metal oxide or transition metal” and insulating ceramics. As the “transition metal oxide or transition metal”, NiO (nickel oxide) or Ni (nickel) is suitable. The transition metal can function as a catalyst for promoting a reforming reaction of the fuel gas (hydrocarbon-based gas reforming catalyst).

Further, as the insulating ceramic, MgO (magnesium oxide) or “mixture of MgAl ₂ O ₄ (magnesia alumina spinel) and MgO (magnesium oxide)” is preferable. Further, CSZ (calcia stabilized zirconia), YSZ (8YSZ) (yttria stabilized zirconia), Y ₂ O ₃ (yttria) may be used as the insulating ceramic.

  As described above, since the support substrate 10 contains “transition metal oxide or transition metal”, the gas containing the residual gas component before the reforming is supplied to the fuel through the numerous pores inside the porous support substrate 10. In the process of being supplied from the gas flow path 11 to the fuel electrode, the catalytic action can promote the reforming of the residual gas component before the reforming. In addition, the insulating property of the support substrate 10 can be ensured by the support substrate 10 containing insulating ceramics. As a result, insulation between adjacent fuel electrodes can be ensured.

  The thickness of the support substrate 10 is 1 to 5 mm. Hereinafter, only the configuration on the upper surface side of the support substrate 10 will be described in consideration of the fact that the shape of the structure is vertically symmetrical. The same applies to the configuration of the lower surface side of the support substrate 10.

  As shown in FIGS. 18 and 19, the entire fuel electrode current collector 21 is embedded (filled) in each recess 12 formed on the upper surface (upper main surface) of the support substrate 10. Therefore, each fuel electrode current collector 21 has a rectangular parallelepiped shape. A recess 21 a is formed on the upper surface (outer surface) of each fuel electrode current collector 21. Each recess 21a has a rectangular parallelepiped shape defined by a bottom wall made of the material of the fuel electrode current collector 21 and side walls closed in the circumferential direction (two side walls along the longitudinal direction and two side walls along the width direction). It is a depression. Of the side walls closed in the circumferential direction, two side walls along the longitudinal direction are made of the material of the support substrate 10, and two side walls along the width direction are made of the material of the fuel electrode current collector 21.

  The entire anode active portion 22 is embedded (filled) in each recess 21a. Accordingly, each fuel electrode active portion 22 has a rectangular parallelepiped shape. A fuel electrode 20 is configured by the fuel electrode current collector 21 and the fuel electrode active unit 22. The fuel electrode 20 (fuel electrode current collector 21 + fuel electrode active part 22) is a fired body made of a porous material having electron conductivity. The two side surfaces and the bottom surface along the width direction of each anode active portion 22 are in contact with the anode current collecting portion 21 in the recess 21a.

  A recess 21b is formed in a portion of the upper surface (outer surface) of each fuel electrode current collector 21 excluding the recess 21a. Each recess 21b has a rectangular parallelepiped shape defined by a bottom wall made of the material of the fuel electrode current collector 21 and side walls closed in the circumferential direction (two side walls along the longitudinal direction and two side walls along the width direction). It is a depression. Of the side walls closed in the circumferential direction, two side walls along the longitudinal direction are made of the material of the support substrate 10, and two side walls along the width direction are made of the material of the fuel electrode current collector 21.

  An interconnector 30 is embedded (filled) in each recess 21b. Accordingly, each interconnector 30 has a rectangular parallelepiped shape. The interconnector 30 is a fired body made of a dense material having electronic conductivity. The two side surfaces and the bottom surface along the width direction of each interconnector 30 are in contact with the fuel electrode current collector 21 in the recess 21b.

  The upper surface (outer surface) of the fuel electrode 20 (the fuel electrode current collector 21 and the fuel electrode active unit 22), the upper surface (outer surface) of the interconnector 30, and the main surface of the support substrate 10 form one plane (recessed portion). The same plane as the main surface of the support substrate 10 when 12 is not formed) is formed. That is, no step is formed between the upper surface of the fuel electrode 20, the upper surface of the interconnector 30, and the main surface of the support substrate 10.

The fuel electrode active part 22 may be composed of, for example, NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia). Or you may comprise from NiO (nickel oxide) and GDC (gadolinium dope ceria). The fuel electrode current collector 21 can be composed of, for example, NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia). Alternatively, it may be composed of NiO (nickel oxide) and Y ₂ O ₃ (yttria), or may be composed of NiO (nickel oxide) and CSZ (calcia stabilized zirconia). The thickness of the anode active portion 22 is 5 to 30 μm, and the thickness of the anode current collecting portion 21 (that is, the depth of the recess 12) is 50 to 500 μm.

  As described above, the fuel electrode current collector 21 includes a substance having electronic conductivity. The fuel electrode active part 22 includes a substance having electron conductivity and a substance having oxidative ion (oxygen ion) conductivity. The “volume ratio of the substance having oxidative ion conductivity relative to the total volume excluding the pore portion” in the anode active portion 22 is “the oxidative ion conductivity relative to the entire volume excluding the pore portion” in the anode current collecting portion 21. Greater than the volume fraction of the substance having

The interconnector 30 can be composed of, for example, LaCrO ₃ (lanthanum chromite). Alternatively, it may be composed of (Sr, La) TiO ₃ (strontium titanate). The thickness of the interconnector 30 is 10 to 100 μm.

  The entire surface excluding the central portion in the longitudinal direction of each portion where the plurality of interconnectors 30 are formed on the outer peripheral surface extending in the longitudinal direction of the support substrate 10 in a state where the fuel electrode 20 and the interconnector 30 are embedded in the respective recesses 12. Is covered with a solid electrolyte membrane 40. The solid electrolyte membrane 40 is a fired body made of a dense material having ionic conductivity and not electron conductivity. The solid electrolyte membrane 40 can be made of, for example, YSZ (8YSZ) (yttria stabilized zirconia). Or you may comprise from LSGM (lantern gallate). The thickness of the solid electrolyte membrane 40 is 3 to 50 μm.

  That is, the entire outer peripheral surface extending in the longitudinal direction of the support substrate 10 in a state where the fuel electrode 20 is embedded in each recess 12 is covered with a dense layer composed of the interconnector 30 and the solid electrolyte membrane 40. This dense layer exhibits a gas sealing function that prevents mixing of the fuel gas flowing in the space inside the dense layer and the air flowing in the space outside the dense layer.

  As shown in FIG. 18, in this example, the solid electrolyte membrane 40 covers the upper surface of the fuel electrode 20, both side ends in the longitudinal direction on the upper surface of the interconnector 30, and the main surface of the support substrate 10. Here, as described above, no step is formed between the upper surface of the fuel electrode 20, the upper surface of the interconnector 30, and the main surface of the support substrate 10. Therefore, the solid electrolyte membrane 40 is flattened. As a result, compared with the case where a step is formed in the solid electrolyte membrane 40, the generation of cracks in the solid electrolyte membrane 40 due to stress concentration can be suppressed, and the gas sealing function of the solid electrolyte membrane 40 is reduced. Can be suppressed.

  An air electrode 60 is formed on the upper surface of a portion in contact with each fuel electrode active part 22 in the solid electrolyte membrane 40 via a reaction preventing film 50. The reaction preventing film 50 is a fired body made of a dense material, and the air electrode 60 is a fired body made of a porous material having electron conductivity. The shape of the reaction preventing film 50 and the air electrode 60 viewed from above is substantially the same rectangle as the fuel electrode active part 22.

The reaction preventing film 50 can be made of, for example, GDC = (Ce, Gd) O ₂ (gadolinium-doped ceria). The thickness of the reaction preventing film 50 is 3 to 50 μm. The air electrode 60 can be made of, for example, LSCF = (La, Sr) (Co, Fe) O ₃ (lanthanum strontium cobalt ferrite). Alternatively, from LSF = (La, Sr) FeO ₃ (lanthanum strontium ferrite), LNF = La (Ni, Fe) O ₃ (lanthanum nickel ferrite), LSC = (La, Sr) CoO ₃ (lanthanum strontium cobaltite), etc. It may be configured. Further, the air electrode 60 may be configured by two layers of a first layer (inner layer) made of LSCF and a second layer (outer layer) made of LSC. The thickness of the air electrode 60 is 10 to 100 μm.

  The reaction preventing film 50 is interposed because the YSZ in the solid electrolyte film 40 and the Sr in the air electrode 60 react with each other in the SOFC during the production or operation of the SOFC, and the solid electrolyte film 40 and the air electrode. This is to suppress the occurrence of a phenomenon in which a reaction layer having a large electric resistance is formed at the interface with the substrate 60.

  Here, the laminated body formed by laminating the fuel electrode 20, the solid electrolyte membrane 40, the reaction preventing membrane 50, and the air electrode 60 corresponds to the “power generation element portion A” (see FIG. 18). In other words, a plurality (four in this example) of power generating element portions A are arranged on the upper surface of the support substrate 10 at a predetermined interval in the longitudinal direction.

  For each pair of adjacent power generation element portions A and A, the air electrode 60 of one power generation element portion A (on the left side in FIG. 18) and the interconnector of the other power generation element portion A (on the right side in FIG. 18). The air electrode current collecting film 70 is formed on the upper surfaces of the air electrode 60, the solid electrolyte film 40, and the interconnector 30. The air electrode current collector film 70 is a fired body made of a porous material having electron conductivity. The shape of the air electrode current collector film 70 as viewed from above is a rectangle.

The air electrode current collector film 70 can be made of, for example, LSCF = (La, Sr) (Co, Fe) O ₃ (lanthanum strontium cobalt ferrite). Alternatively, LSC = (La, Sr) CoO ₃ (lanthanum strontium cobaltite) may be used. Or you may comprise from Ag (silver) and Ag-Pd (silver palladium alloy). The thickness of the air electrode current collector film 70 is 50 to 500 μm.

  By forming each air electrode current collecting film 70 in this way, for each pair of adjacent power generation element parts A and A, the air electrode 60 of one power generation element part A (on the left side in FIG. 18), The other fuel electrode 20 (particularly, the fuel electrode current collector 21) of the power generating element part A (on the right side in FIG. 18) passes through the “air electrode current collector film 70 and interconnector 30” having electronic conductivity. Are electrically connected. As a result, a plurality (four in this example) of power generation element portions A arranged on the upper surface of the support substrate 10 are electrically connected in series. Here, the “air electrode current collector film 70 and the interconnector 30” having electronic conductivity correspond to the “electrical connection part”.

  The interconnector 30 corresponds to the “first portion made of a dense material” in the “electrical connection portion” and has a porosity of 10% or less. The air electrode current collecting film 70 corresponds to the “second portion made of a porous material” in the “electrical connection portion”, and has a porosity of 20 to 60%.

As described above, as shown in FIG. 20, the fuel gas (hydrogen gas or the like) flows through the fuel gas flow path 11 of the support substrate 10 to the “horizontal stripe type” cell 100 shown in FIG. 10 by exposing the upper and lower surfaces (in particular, each air electrode current collecting film 70) to “gas containing oxygen” (air or the like) (or flowing a gas containing oxygen along the upper and lower surfaces of the support substrate 10), An electromotive force is generated by an oxygen partial pressure difference generated between both side surfaces of the solid electrolyte membrane 40. Furthermore, when this structure is connected to an external load, chemical reactions shown in the following formulas (1) and (2) occur, and current flows (power generation state).
(1/2) · O ₂ + 2e ⁻ → O ²⁻ (where: air electrode 60) (1)
H ₂ + O ²⁻ → H ₂ O + 2e ⁻
(At: Fuel electrode 20) (2)

  In the power generation state, as shown in FIG. 21, current flows as indicated by an arrow in each pair of adjacent power generation element portions A and A. As a result, as shown in FIG. 20, from the entire cell 100 (specifically, in FIG. 20, the interconnector 30 of the power generating element part A on the foremost side and the air electrode 60 of the power generating element part A on the farthest side) The power is removed.

(Production method)
Next, an example of a manufacturing method of the “horizontal stripe type” cell 100 shown in FIG. 17 will be briefly described with reference to FIGS. 22 to 30, “g” at the end of the reference numeral of each member indicates that the member is “before firing”.

  First, a support substrate molded body 10g having the shape shown in FIG. 22 is produced. The molded body 10g of the support substrate is manufactured by using a method such as extrusion molding or cutting using a slurry obtained by adding a binder or the like to the material of the support substrate 10 (for example, CSZ). obtain. Hereinafter, the description will be continued with reference to FIGS. 23 to 30 showing partial cross sections corresponding to line 23-23 shown in FIG.

  As shown in FIG. 23, when the support substrate molded body 10g is manufactured, next, as shown in FIG. 24, fuel electrode current collectors are formed in the recesses formed on the upper and lower surfaces of the support substrate molded body 10g. Each of the molded parts 21g is embedded and formed. Next, as shown in FIG. 25, the molded body 22g of the fuel electrode active portion is embedded and formed in each recess formed in the outer surface of the molded body 21g of each fuel electrode current collector. The molded body 21g of each fuel electrode current collector and each of the fuel electrode active parts 22g use, for example, a slurry obtained by adding a binder or the like to the powder of the material of the fuel electrode 20 (for example, Ni and YSZ), It is embedded and formed using printing methods.

Subsequently, as shown in FIG. 26, in each concave portion formed in “the portion excluding the portion where the molded body 22g of the fuel electrode active portion is embedded” on the outer surface of the molded body 21g of each fuel electrode current collector. The interconnector molded bodies 30g are respectively embedded and formed. The molded body 30g of each interconnector is embedded and formed by using a slurry obtained by adding a binder or the like to the material of the interconnector 30 (for example, LaCrO ₃ ), using a printing method or the like. .

  Next, as shown in FIG. 27, the outer periphery extending in the longitudinal direction of the molded body 10g of the support substrate in a state in which the molded bodies (21g + 22g) of the plurality of fuel electrodes and the molded body 30g of the plurality of interconnectors are respectively embedded and formed. A solid electrolyte membrane molded film 40g is formed on the entire surface excluding the central portion in the longitudinal direction of each portion where the plurality of interconnector molded bodies 30g are formed. The molded membrane 40g of the solid electrolyte membrane is formed using, for example, a printing method, a dipping method, etc., using a slurry obtained by adding a binder or the like to the powder of the material of the solid electrolyte membrane 40 (for example, YSZ). The

  Next, as shown in FIG. 28, a reaction preventing film forming film 50g is formed on the outer surface of the solid electrolyte film forming body 40g in contact with the fuel electrode forming body 22g. The molded film 50g of each reaction preventing film is formed using a slurry obtained by adding a binder or the like to the powder of the material (for example, GDC) of the reaction preventing film 50, using a printing method or the like.

  Then, 10 g of the support substrate molded body in which various molded films are thus formed is fired in air at 1500 ° C. for 3 hours. As a result, a structure in which the air electrode 60 and the air electrode current collector film 70 are not formed in the cell 100 shown in FIG. 17 is obtained.

  Next, as shown in FIG. 29, an air electrode forming film 60 g is formed on the outer surface of each reaction preventing film 50. The molded film 60g of each air electrode is formed using a slurry obtained by adding a binder or the like to the powder of the material of the air electrode 60 (for example, LSCF), using a printing method or the like.

  Next, as shown in FIG. 30, for each pair of adjacent power generation element portions, air is formed so as to straddle the forming film 60 g of the air electrode of one power generation element portion and the interconnector 30 of the other power generation element portion. On the outer surface of the electrode forming film 60 g, the solid electrolyte film 40, and the interconnector 30, the air electrode current collecting film forming film 70 g is formed. The forming film 70g of each air electrode current collector film is obtained by using a slurry obtained by adding a binder or the like to the powder of the material of the air electrode current collector film 70 (for example, LSCF), using a printing method or the like. It is formed.

  Then, the support substrate 10 in which the molded films 60g and 70g are thus formed is baked in air at 1050 ° C. for 3 hours. Thereby, the cell 100 shown in FIG. 17 is obtained. In the above, an example of the manufacturing method of the cell 100 shown in FIG. 17 was demonstrated.

(Action / Effect)
As described above, in the “horizontal stripe type” cell 100 shown in FIG. 17, each of the plurality of recesses 12 embedded in the upper and lower surfaces of the support substrate 10 for embedding the fuel electrode 20 is completely formed. A circumferentially closed side wall made of the material of the support substrate 10 is provided over the circumference. In other words, the support body 10 is formed with a frame surrounding each recess 12. Therefore, this structure is not easily deformed when the support substrate 10 receives an external force.

  Further, the support substrate 10 and the embedded member are co-sintered in a state in which the members such as the fuel electrode 20 and the interconnector 30 are filled and embedded in the recesses 12 of the support substrate 10 without any gap. Therefore, a sintered body having high bondability between members and high reliability can be obtained.

  The interconnector 30 is embedded in a recess 21b formed on the outer surface of the fuel electrode current collector 21, and as a result, two side surfaces and a bottom surface along the width direction (y-axis direction) of the rectangular interconnector 30 Are in contact with the anode current collector 21 in the recess 21b. Therefore, the fuel electrode 20 (the current collector 21) and the interconnector 30 are compared to the case where a configuration in which the rectangular parallelepiped interconnector 30 is laminated (contacted) on the outer plane of the fuel electrode current collector 21 is employed. The area of the interface with can be increased. Therefore, the electronic conductivity between the fuel electrode 20 and the interconnector 30 can be increased, and as a result, the power generation output of the fuel cell can be increased.

  In the cell 100 shown in FIG. 17, a plurality of power generation element portions A are provided on the upper and lower surfaces of the flat support substrate 10. Thereby, compared with the case where a plurality of power generation element portions are provided only on one side surface of the support substrate, the number of power generation element portions in the structure can be increased, and the power generation output of the fuel cell can be increased.

  In the cell 100 shown in FIG. 17, the solid electrolyte membrane 40 covers the outer surface of the fuel electrode 20, both side ends in the longitudinal direction of the outer surface of the interconnector 30, and the main surface of the support substrate 10. Here, no step is formed between the outer surface of the fuel electrode 20, the outer surface of the interconnector 30, and the main surface of the support substrate 10. Therefore, the solid electrolyte membrane 40 is flattened. As a result, compared with the case where a step is formed in the solid electrolyte membrane 40, the generation of cracks in the solid electrolyte membrane 40 due to stress concentration can be suppressed, and the gas sealing function of the solid electrolyte membrane 40 is reduced. Can be suppressed.

  In the cell 100 shown in FIG. 17, as shown in FIG. 22 and the like, the planar shape of the recess 12 formed in the support substrate 10 (shape when viewed from the direction perpendicular to the main surface of the support substrate 10) is Although it is rectangular, for example, it may be a square, a circle, an ellipse, a long hole, or the like.

  Further, in the cell 100 shown in FIG. 17, the entire interconnector 30 is embedded in each recess 12, but only a part of the interconnector 30 is embedded in each recess 12, and the remaining portion of the interconnector 30. May protrude outside the recess 12 (that is, protrude from the main surface of the support substrate 10).

  In the cell 100 shown in FIG. 17, the angle θ between the bottom wall and the side wall in the recess 12 is 90 °, but the angle θ is 90 to 135 ° as shown in FIG. Also good. In the cell 100 shown in FIG. 17, as shown in FIG. 32, the portion of the recess 12 where the bottom wall and the side wall intersect has an arc shape with a radius R, and the radius R with respect to the depth of the recess 12 The ratio may be 0.01 to 1.

  In the cell 100 shown in FIG. 17, a plurality of recesses 12 are formed on each of the upper and lower surfaces of the flat support substrate 10 and a plurality of power generating element portions A are provided. As shown in FIG. The plurality of recesses 12 may be formed only on one side of the support substrate 10 and the plurality of power generation element portions A may be provided.

  In the cell 100 shown in FIG. 17, the fuel electrode 20 is composed of two layers of the fuel electrode current collector 21 and the fuel electrode active part 22. The fuel electrode 20 corresponds to the fuel electrode active part 22. It may be composed of one layer. In addition, in the cell 100 shown in FIG. 17, the “inner electrode” and the “outer electrode” are the fuel electrode and the air electrode, respectively, but they may be reversed.

  In addition, in the cell 100 shown in FIG. 17, as shown in FIG. 19, the recess 21 b formed on the outer surface of the anode current collector 21 has a bottom wall made of the material of the anode current collector 21, A rectangular parallelepiped shape defined by side walls closed in the circumferential direction (two side walls along the longitudinal direction made of the material of the support substrate 10 and two side walls along the width direction made of the material of the fuel electrode current collector 21). It is a depression. As a result, the two side surfaces and the bottom surface along the width direction of the interconnector 30 embedded in the recess 21b are in contact with the fuel electrode current collector 21 in the recess 21b.

  On the other hand, as shown in FIG. 34, a recess 21b formed on the outer surface of the fuel electrode current collector 21 has a bottom wall made of the material of the fuel electrode current collector 21 and the fuel electrode current collector over the entire circumference. It may be a rectangular parallelepiped recess defined by circumferentially closed side walls (two side walls along the longitudinal direction and two side walls along the width direction) made of the material of the electric part 21. According to this, all four side surfaces and the bottom surface of the interconnector 30 embedded in the recess 21b are in contact with the fuel electrode current collector 21 in the recess 21b. Therefore, the area of the interface between the fuel electrode current collector 21 and the interconnector 30 can be further increased. Therefore, the electronic conductivity between the fuel electrode current collector 21 and the interconnector 30 can be further increased, and as a result, the power generation output of the fuel cell can be further increased.

  FIGS. 35 to 40 are views corresponding to FIGS. 2 to 7 when the cell shown in FIG. 17 is used in the stack structure of the fuel cell according to the embodiment of the present invention. 35 to 40, members and configurations that are the same as or equivalent to the members and configurations shown in FIGS. 2 to 7 are denoted by the same reference numerals as those used in FIGS. As shown in FIG. 38, in this case, in order to electrically connect adjacent cells 100, 100 in series, each cell is added to the current collecting member 400 corresponding to the current collecting member 400 shown in FIG. A current collecting member 500 for electrically connecting the front side and the back side of 100 in series is also provided.

  DESCRIPTION OF SYMBOLS 11 ... Electroconductive support body, 12 ... Fuel electrode, 13 ... Solid electrolyte, 14 ... Air electrode, 18 ... Gas flow path, 100 ... Cell, 200 ... Manifold, 210 ... Support plate, 211 ... Insertion hole, 300 ... Joining material , 400 ... current collecting member, 10 ... support substrate, 11 ... fuel gas flow path, 12 ... recess, 20 ... fuel electrode, 21 ... fuel electrode current collector, 21a, 21b ... recess, 22 ... fuel electrode active part, 30 ... Interconnector, 40 ... Solid electrolyte membrane, 50 ... Reaction prevention film, 60 ... Air electrode, 70 ... Air electrode current collector film, A ... Power generation element part

Claims (10)

Each of which has a flat plate shape having a first longitudinal direction and in which a gas flow path along the first longitudinal direction is formed, a support substrate provided on the surface of the support substrate, and at least an inner electrode and a solid electrolyte And a plurality of plate-like cells including a power generation element portion in which outer electrodes are laminated in this order,
A bonding material is used for one end of each of the cells in the first longitudinal direction so that each of the cells protrudes from the surface of the support plate along the first longitudinal direction and the plurality of cells are arranged in a stack. A support plate for joining and supporting each,
A gas manifold provided with the support plate so that the internal space of the manifold communicates with one end of each of the gas flow paths of the plurality of cells;
A fuel cell stack structure comprising:
The shape of the side surface of one end of each cell has a second longitudinal direction,
One or a plurality of holes for communicating the internal space of the manifold and one end of the plurality of cells are formed on the surface of the support plate,
The shape of each hole has a direction of an axis of symmetry with respect to line symmetry,
One end of each cell is positioned corresponding to the corresponding hole so that the corresponding second longitudinal direction is along the direction of the symmetry axis of the corresponding hole;
The bonding material is provided so as to fill a space existing between the hole and one end of the cell at each of the bonding portions between the holes and the corresponding one end of the cell. The hole and the corresponding one end of the cell are joined together,
A stack structure of a fuel cell, wherein a maximum value of a corresponding inclination angle of the second longitudinal direction with respect to a direction of the symmetry axis of each of the plurality of cells is 5.0 ° or less. Each of which has a flat plate shape having a first longitudinal direction and in which a gas flow path along the first longitudinal direction is formed, a support substrate provided on the surface of the support substrate, and at least an inner electrode and a solid electrolyte And a plurality of plate-like cells including a power generation element portion in which outer electrodes are laminated in this order,
A bonding material is used for one end of each of the cells in the first longitudinal direction so that each of the cells protrudes from the surface of the support plate along the first longitudinal direction and the plurality of cells are arranged in a stack. A support plate for joining and supporting each,
A gas manifold provided with the support plate so that the internal space of the manifold communicates with one end of each of the gas flow paths of the plurality of cells;
A fuel cell stack structure comprising:
The shape of the side surface of one end of each cell has a second longitudinal direction,
In the surface of the support plate, a plurality of insertion holes for communicating the internal space of the manifold and one end of the plurality of cells are formed corresponding to each of the plurality of cells,
The shape of each insertion hole has a direction of a symmetry axis with respect to line symmetry,
One end of each cell is loosely fitted into the corresponding insertion hole so that the corresponding second longitudinal direction is along the direction of the symmetry axis of the corresponding insertion hole,
The bonding material is provided so as to enter at least a gap existing between the inner wall of the insertion hole and the outer wall of the one end of the cell at each of the bonding portions between the insertion holes and the corresponding one end of the cell. The one end of each cell corresponding to each insertion hole is joined,
The stack structure of the fuel cell, wherein the maximum value of the corresponding inclination angles of the second longitudinal direction with respect to the direction of the symmetry axis of the insertion hole for each of the plurality of cells is 5.0 ° or less. . In the fuel cell stack structure according to claim 1 or 2,
A stack structure of a fuel cell, wherein a minimum value of the inclination angles for each of the plurality of cells is 0.23 ° or more. The fuel cell stack structure according to any one of claims 1 to 3,
A stack structure of a fuel cell, wherein a standard deviation of the tilt angle for each of the plurality of cells is 0.19 ° or more and 4.2 ° or less. The fuel cell stack structure according to any one of claims 1 to 4,
The joined body is a stack structure of a fuel cell made of crystallized glass. The fuel cell stack structure according to claim 5,
The joined body provided in each joined portion includes an outer portion located in the vicinity of the surface including the surface of the joined body, a position located inside the joined body from the outer portion, and a porosity from the outer portion. A fuel cell stack structure, comprising a large inner portion. The fuel cell stack structure according to claim 6,
The fuel cell stack structure, wherein the outer portion has a porosity of 1 to 5% and the inner portion has a porosity of 5 to 25%. The stack structure of the fuel cell according to any one of claims 1 to 7,
A current collecting member for electrically connecting the adjacent cells in series is interposed in the space between the adjacent cells, and the current collecting member is provided for each of the adjacent cells. A fuel cell stack structure configured to provide an elastic force in a direction of widening the interval between adjacent cells. The fuel cell stack structure according to any one of claims 1 to 8,
The flat cell is
A flat porous support substrate having a gas flow path formed therein;
A plurality of power generating element portions provided respectively at a plurality of locations separated from each other on the main surface of the flat support substrate, wherein at least an inner electrode, a solid electrolyte, and an outer electrode are laminated in this order;
One or a plurality of electrical connections that are respectively provided between one set or a plurality of sets of adjacent power generation element portions and electrically connect one inner electrode and the other outer electrode of the adjacent power generation element portions And
With
Recesses having a bottom wall made of the material of the support substrate and side walls closed in the circumferential direction made of the material of the support substrate all around the plurality of locations on the main surface of the flat support substrate, respectively. Formed,
A fuel cell stack structure in which the corresponding inner electrode of the power generation element portion is embedded in each of the recesses. The fuel cell stack structure according to any one of claims 1 to 8,
The flat cell is
A flat porous support substrate having a gas flow path formed therein;
A plurality of power generating element portions provided respectively at a plurality of locations separated from each other on the main surface of the flat support substrate, wherein at least an inner electrode, a solid electrolyte, and an outer electrode are laminated in this order;
One or a plurality of electrical connections that are respectively provided between one set or a plurality of sets of adjacent power generation element portions and electrically connect one inner electrode and the other outer electrode of the adjacent power generation element portions And
With
Each of the electrical connection portions includes a first portion made of a dense material, and a second portion made of a porous material connected to the first portion,
A first recess having a bottom wall made of the material of the support substrate and a side wall made of the material of the support substrate over the entire circumference at the plurality of locations on the main surface of the flat support substrate. Each formed,
In each of the first recesses, a corresponding inner electrode of the power generation element portion is embedded,
Second recesses having a bottom wall made of the material of the inner electrode and a circumferentially closed side wall made of the material of the inner electrode are formed on the outer surface of each embedded inner electrode. ,
A fuel cell stack structure in which the first portions of the corresponding electrical connection portions are embedded in the second recesses, respectively.