JP2016219407A - Fuel battery single cell and fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress decline in power generation efficiency of a fuel battery single cell due to the presence of bubbles, while relaxing concentration of stress on the vicinity of the boundary of at least one of an electrolyte layer and an air electrode and an intermediate layer, by the pores of the intermediate layer.SOLUTION: In a fuel battery single cell including an electrolyte layer containing solid oxide, an air electrode and a fuel electrode facing each other while sandwiching the electrolyte layer, and an intermediate layer arranged between the electrolyte layer and air electrode, a region satisfying the following area conditions exists on at least one cross section that is parallel with the first direction, i.e., the facing direction of the air electrode and fuel electrode. Area conditions: the ratio of the number of pores satisfying first pore conditions to the number of a plurality of pores existing in the area is 50% or more. First pore conditions: dimension in the first direction/dimension in a second direction orthogonal to the first direction>1.SELECTED DRAWING: Figure 12

Description

  The technology disclosed in this specification relates to a single fuel cell.

  A solid oxide fuel cell (hereinafter also referred to as “SOFC”) using a solid oxide as an electrolyte is known. The SOFC unit cell provided in the SOFC includes an electrolyte layer and an air electrode and a fuel electrode facing each other across the electrolyte layer in a predetermined direction (hereinafter also referred to as “opposing direction”). Power is generated by supplying the agent gas and supplying the fuel gas to the fuel electrode. In such a fuel cell single cell, for example, near the boundary between the electrolyte layer and the air electrode, a substance contained in the air electrode reacts with a substance contained in the electrolyte layer to form a high resistance layer. In order to suppress this, a structure in which an intermediate layer is disposed between the air electrode and the electrolyte layer is known (for example, Patent Document 1).

  In this fuel cell unit cell, stress is concentrated near the boundary between the intermediate layer and the electrolyte layer due to the strain caused by the difference in thermal expansion coefficient and firing shrinkage between the intermediate layer and the electrolyte layer. In order to suppress the separation of the pores, pores exist in the intermediate layer.

Japanese Patent Application Laid-Open No. 2012-23018

  In the fuel cell single cell including the above-described intermediate layer having pores, the dimension in the opposing direction (hereinafter also referred to as the vertical direction) is orthogonal to the opposing direction in the cross section parallel to the opposing direction in the intermediate layer. There may be pores having shapes having different dimensions in the direction (hereinafter, also referred to as a lateral direction). Among the pores of this shape, if there are pores in the intermediate layer whose lateral dimension is longer than the longitudinal dimension, the pores will be in the way, so the linear shape from the air electrode to the electrolyte layer along the longitudinal direction. Since the number of ion conduction paths that are continuously connected to each other decreases, the power generation efficiency of the SOFC may decrease.

  The present specification discloses a technique capable of solving at least a part of the problems described above.

  The technology disclosed in this specification can be implemented as the following forms.

(1) A fuel cell single cell disclosed in this specification includes an electrolyte layer containing a solid oxide, an air electrode and a fuel electrode facing each other across the electrolyte layer, and the electrolyte layer and the air electrode. An intermediate layer disposed between the at least one cross section of the intermediate layer parallel to a first direction in which the air electrode and the fuel electrode face each other, A region that satisfies the region condition exists. The region condition: the ratio of the number of pores satisfying the first pore condition to the number of pores existing in the region is 50% or more. The first pore condition: dimension in the first direction / dimension in the second direction perpendicular to the first direction> 1. According to the present fuel cell single cell, compared to the case where no region satisfying the region condition exists in any cross section, which is parallel to the first direction in which the air electrode and the fuel electrode face each other in the intermediate layer, In the intermediate layer, the ion conduction path length continuously connected in the first direction from the air electrode side to the electrolyte layer side becomes short, and the element ions easily move linearly. It is suppressed that the power generation efficiency of a single cell falls. That is, the stress concentration in the vicinity of the boundary between at least one of the electrolyte layer and the air electrode and the intermediate layer is mitigated by the pores in the intermediate layer, and the power generation efficiency of the single fuel cell is reduced by the presence of the pores. Can be suppressed.

(2) A fuel cell single cell disclosed in this specification includes an electrolyte layer containing a solid oxide, an air electrode and a fuel electrode facing each other across the electrolyte layer, and the electrolyte layer and the air electrode. An intermediate layer disposed between the at least one cross section of the intermediate layer parallel to a first direction in which the air electrode and the fuel electrode face each other, There is a pore satisfying the second pore condition. The second pore condition: the size of the pores in the first direction / the size of the pores in the second direction orthogonal to the first direction> 2. According to the single fuel cell of the present invention, when there is no pore that satisfies the second pore condition in any cross section that is parallel to the first direction in which the air electrode and the fuel electrode face each other in the intermediate layer. In comparison, the ion conduction path length continuously connected in the first direction from the air electrode side to the electrolyte layer side in the intermediate layer becomes shorter, and element ions easily move linearly. This suppresses a decrease in power generation efficiency of the single fuel cell. That is, stress concentration near the boundary between at least one of the electrolyte layer and the air electrode and the intermediate layer is mitigated by the pores in the intermediate layer, and the power generation efficiency of the single fuel cell is reduced by the presence of the pores. Can be suppressed. In addition, since the intermediate layer has pores that satisfy the second pore condition, stress (for example, shear stress) due to thermal expansion generated between each layer adjacent to the intermediate layer in the first direction is generated. Since it is easily dispersed by the inner wall that is long in the first direction constituting the pores, it is possible to more effectively relieve stress concentration near the boundary between the electrolyte layer and / or the air electrode and the intermediate layer. it can.

(3) In the fuel cell single cell, the intermediate layer may have a porosity of 10% or more and 25% or less. According to the present fuel cell single cell, it is possible to suppress the resistance of the intermediate layer from becoming too high while alleviating stress concentration near the boundary between at least one of the electrolyte layer and the air electrode and the intermediate layer. .

(4) In the fuel cell single cell, a thickness of the intermediate layer in the first direction may be 1 μm or more and 15 μm or less. According to the present fuel cell single cell, it is possible to suppress the resistance of the intermediate layer from becoming too high while alleviating stress concentration near the boundary between at least one of the electrolyte layer and the air electrode and the intermediate layer. .

(5) In the fuel cell single cell, the intermediate layer is disposed between the first intermediate layer, the first intermediate layer, and the electrolyte layer, and is denser than the first intermediate layer. It is good also as a structure containing a 2nd intermediate | middle layer. According to this single fuel cell, since the second intermediate layer is included in the intermediate layer, it is possible to suppress the diffusion of elements from the air electrode to the electrolyte layer and the formation of the high resistance layer. When the second intermediate layer is present on the electrolyte layer side of the first intermediate layer, it is possible to suppress stress concentration near the boundary between the air electrode and the intermediate layer.

(6) In the fuel cell single cell, a thickness of the second intermediate layer in the first direction may be 0.1 μm or more and 0.9 μm or less. According to the present fuel cell single cell, it is possible to suppress the resistance of the intermediate layer from becoming too high while suppressing the diffusion of elements from the air electrode to the electrolyte layer.

(7) In the fuel cell single cell, the porosity of the first intermediate layer may be 10% or more and 25% or less. According to the present fuel cell single cell, it is possible to suppress the resistance of the intermediate layer from becoming too high while alleviating stress concentration near the boundary between at least one of the electrolyte layer and the air electrode and the intermediate layer. .

(8) In the fuel cell single cell, a thickness of the first intermediate layer in the first direction may be 1 μm or more and 15 μm or less. According to the present fuel cell single cell, it is possible to suppress the resistance of the intermediate layer from becoming too high while alleviating stress concentration near the boundary between at least one of the electrolyte layer and the air electrode and the intermediate layer. .

  The technology disclosed in the present specification can be realized in various forms, for example, a single cell, a fuel cell power generation unit, a fuel cell stack including a fuel cell power generation unit, and a power generation including a fuel cell stack. It can be realized in the form of a module, a fuel cell system including a power generation module, or the like.

1 is a perspective view showing an external configuration of a fuel cell stack 100 in a first embodiment. FIG. 3 is an explanatory diagram showing an XY plane configuration on the upper side of the fuel cell stack 100 in the first embodiment. FIG. 3 is an explanatory diagram showing an XY plane configuration on the lower side of the fuel cell stack 100 in the first embodiment. FIG. 4 is an explanatory diagram showing an XZ cross-sectional configuration of a fuel cell stack 100 at a position of IV-IV in FIGS. 1 to 3. FIG. 4 is an explanatory diagram showing an XZ cross-sectional configuration of a fuel cell stack 100 at a position VV in FIGS. 1 to 3. FIG. 4 is an explanatory diagram showing a YZ cross-sectional configuration of a fuel cell stack 100 at a position of VI-VI in FIGS. 1 to 3. It is explanatory drawing which shows the XZ cross-section structure of the two electric power generation units 102 adjacent to each other in the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross-section structure of the two electric power generation units 102 adjacent to each other in the same position as the cross section shown in FIG. It is explanatory drawing which shows XY cross-section structure of the electric power generation unit 102 in the position of IX-IX of FIG. It is explanatory drawing which shows XY cross-section structure of the electric power generation unit 102 in the position of XX of FIG. It is explanatory drawing which shows XY cross-sectional structure of the heat exchange part 103 roughly. FIG. 3 is an explanatory diagram showing an XZ cross-sectional configuration of a part of a single cell 110. It is explanatory drawing which shows the XZ cross-section structure of a part of single cell in a comparative example. It is explanatory drawing which shows the XZ cross-section structure of a part of single cell in 2nd Embodiment. It is explanatory drawing which shows roughly the XZ cross-sectional structure of 100 C of fuel cell stacks in 3rd Embodiment.

A. First embodiment:
A-1. Constitution:
(Configuration of fuel cell stack 100)
1 to 6 are explanatory views schematically showing the configuration of the fuel cell stack 100 in the present embodiment. FIG. 1 shows an external configuration of the fuel cell stack 100, FIG. 2 shows a planar configuration of the upper side of the fuel cell stack 100, and FIG. FIG. 4 shows a cross-sectional configuration of the fuel cell stack 100 at the position IV-IV in FIGS. 1 to 3, and FIG. 5 shows a plan configuration in FIGS. A cross-sectional configuration of the fuel cell stack 100 at a position VV is shown, and FIG. 6 shows a cross-sectional configuration of the fuel cell stack 100 at a position VI-VI in FIGS. 1 to 3. In each figure, XYZ axes orthogonal to each other for specifying the direction are shown. In this specification, for the sake of convenience, the positive direction of the Z axis is referred to as the upward direction, and the negative direction of the Z axis is referred to as the downward direction. However, the fuel cell stack 100 is actually different from such an orientation. It may be installed. The same applies to FIG.

  The fuel cell stack 100 includes a plurality of (six in this embodiment) power generation units 102, a heat exchange unit 103, and a pair of end plates 104 and 106. The six power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in the present embodiment). However, among the six power generation units 102, the three power generation units 102 are arranged adjacent to each other, and the remaining three power generation units 102 are also arranged adjacent to each other, so that the three power generation units 102 and the remaining power generation units 102 are arranged. A heat exchanging unit 103 is disposed between the three power generation units 102. That is, the heat exchanging unit 103 is arranged near the center in the vertical direction in the assembly composed of the six power generation units 102 and the heat exchanging unit 103. The pair of end plates 104 and 106 are arranged so as to sandwich an assembly composed of the six power generation units 102 and the heat exchange unit 103 from above and below.

  A plurality of (eight in this embodiment) holes penetrating in the vertical direction are formed in the peripheral portions around the Z direction of each layer (power generation unit 102, heat exchange unit 103, end plates 104, 106) constituting the fuel cell stack 100. The holes corresponding to each other formed in each layer communicate with each other in the vertical direction to form a bolt hole 108 extending in the vertical direction from one end plate 104 to the other end plate 106. In the following description, holes formed in each layer of the fuel cell stack 100 in order to form the bolt holes 108 are also referred to as bolt holes 108.

  Bolts 22 extending in the vertical direction are inserted into the respective bolt holes 108, and the fuel cell stack 100 is fastened by the bolts 22 and nuts 24 fitted on both sides of the bolts 22.

  As shown in FIGS. 4 to 6, between the nut 24 fitted on one side (upper side) of the bolt 22 and the upper surface of the end plate 104 constituting the upper end of the fuel cell stack 100, and between the bolt 22 An insulating sheet 26 is interposed between the nut 24 fitted on the other side (lower side) and the lower surface of the end plate 106 constituting the lower end of the fuel cell stack 100. However, in a place where a gas passage member 27 described later is provided, an insulating sheet disposed between the nut 24 and the surface of the end plate 106 on the upper and lower sides of the gas passage member 27 and the gas passage member 27, respectively. 26 is interposed. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder sheet, a glass sheet, a glass ceramic composite agent, or the like.

  The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each bolt hole 108. Therefore, a space is secured between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each bolt hole 108. As shown in FIGS. 2 to 4, a bolt 22 (bolt 22 </ b> A) located near one vertex (vertex on the Y-axis negative direction side and X-axis negative direction side) on the outer periphery around the Z direction of the fuel cell stack 100, The space formed by the inner peripheral surface of the bolt hole 108 functions as an oxidant gas introduction manifold 161 that is a gas flow path into which the oxidant gas OG is introduced from the outside of the fuel cell stack 100. Bolt 22 (bolt 22C) located near the midpoint of one side (the X-axis positive direction side of two sides parallel to the Y-axis) on the outer periphery around the Z direction and the inner peripheral surface of the bolt hole 108 The space formed by the above functions as an oxidant gas supply manifold 163 that is a gas flow path for carrying the oxidant gas OG discharged from the heat exchange unit 103 toward each power generation unit 102. As shown in FIGS. 2, 3, and 5, one side of the outer periphery of the fuel cell stack 100 around the Z direction (the side on the negative X-axis side of the two sides parallel to the Y axis) The space formed by the bolt 22 (bolt 22B) located near the midpoint and the inner peripheral surface of the bolt hole 108 contains an oxidant off-gas OOG that is an unreacted oxidant gas OG discharged from each power generation unit 102. It functions as an oxidant gas discharge manifold 162 that discharges to the outside of the fuel cell stack 100. In the present embodiment, for example, air is used as the oxidant gas OG.

  2, 3, and 6, one side of the outer periphery of the fuel cell stack 100 around the Z direction (the side on the Y axis positive direction side of the two sides parallel to the X axis) In the space formed by the bolt 22 (bolt 22D) located near the midpoint and the inner peripheral surface of the bolt hole 108, the fuel gas FG is introduced from the outside of the fuel cell stack 100, and the fuel gas FG is converted into each power generation unit. Bolt 22 (which functions as a fuel gas introduction manifold 171 to be supplied to 102 and is located near the midpoint of the opposite side (the side on the Y axis negative direction side of the two sides parallel to the X axis) ( The space formed by the bolts 22E) and the inner peripheral surface of the bolt hole 108 is a fuel cell that contains unreacted fuel gas FG discharged from each power generation unit 102 and fuel off-gas FOG containing gas after power generation of the fuel gas FG. Stack 100 Functions as a fuel gas exhaust manifold 172 for discharging to the outside. In the present embodiment, for example, hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG.

  As shown in FIGS. 4 to 6, the fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body portion 28 and a hollow cylindrical branch portion 29 branched from the side surface of the main body portion 28. The hole of the branch part 29 communicates with the hole of the main body part 28. A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27. As shown in FIG. 4, the hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> A forming the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. As shown in FIG. 5, the hole of the main body portion 28 of the gas passage member 27 arranged at the position of the bolt 22 </ b> B forming the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162. As shown in FIG. 6, the hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22D forming the fuel gas introduction manifold 171 communicates with the fuel gas introduction manifold 171 and the fuel gas discharge manifold The hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> E forming the 172 communicates with the fuel gas discharge manifold 172.

(Configuration of end plates 104 and 106)
The pair of end plates 104 and 106 are rectangular flat plate-shaped conductive members, and are made of, for example, stainless steel. One end plate 104 is disposed on the upper side of the power generation unit 102 located on the uppermost side, and the other end plate 106 is disposed on the lower side of the power generation unit 102 located on the lowermost side. The plurality of power generation units 102 and the heat exchange unit 103 are held in a pressed state by a pair of end plates 104 and 106. The upper end plate 104 functions as a positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as a negative output terminal of the fuel cell stack 100.

(Configuration of power generation unit 102)
7 to 10 are explanatory diagrams showing the detailed configuration of the power generation unit 102. FIG. FIG. 7 shows a cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 5, and FIG. 8 shows adjacent to each other at the same position as the cross section shown in FIG. 9 shows a cross-sectional configuration of the two power generation units 102. FIG. 9 shows a cross-sectional configuration of the power generation unit 102 at the position IX-IX in FIG. 7, and FIG. A cross-sectional configuration of the power generation unit 102 at the position X is shown.

  As shown in FIGS. 7 and 8, the power generation unit 102 which is the minimum unit of power generation includes a fuel cell single cell (hereinafter referred to as “single cell”) 110, a separator 120, an air electrode side frame 130, an air electrode. A side current collector 134, a fuel electrode side frame 140, a fuel electrode side current collector 144, and a pair of interconnectors 150 constituting the uppermost layer and the lowermost layer of the power generation unit 102 are provided. Bolt holes 108 into which the above-described bolts 22 are inserted are formed in the periphery of the separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the interconnector 150 around the Z direction.

  The interconnector 150 is a rectangular flat plate-shaped conductive member, and is formed of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generation units 102 and prevents reaction gas from being mixed between the power generation units 102. In the present embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. That is, the upper interconnector 150 in a power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102. Further, since the fuel cell stack 100 includes the pair of end plates 104 and 106, the power generation unit 102 located at the top in the fuel cell stack 100 does not include the upper interconnector 150 and is located at the bottom. The power generation unit 102 does not include the lower interconnector 150 (see FIGS. 4 to 6).

  The unit cell 110 includes an electrolyte layer 112, an air electrode (cathode) 114 and a fuel electrode (anode) 116 facing each other with the electrolyte layer 112 interposed therebetween, and an intermediate layer disposed between the electrolyte layer 112 and the air electrode 114. 300. The single cell 110 of this embodiment is a fuel cell-supported single cell that supports the electrolyte layer 112, the intermediate layer 300, and the air electrode 114 with the fuel electrode 116.

  The electrolyte layer 112 is a rectangular flat plate-shaped member. For example, YSZ (yttria stabilized zirconia), ScSZ (scandia stabilized zirconia), SDC (samarium doped ceria), GDC (gadolinium doped ceria), perovskite oxide, etc. The solid oxide is formed. The air electrode 114 is a rectangular flat plate-shaped member, and is formed of, for example, a perovskite oxide (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), LNF (lanthanum nickel iron)). ing. The fuel electrode 116 is a rectangular flat plate-shaped member, and is formed of, for example, Ni (nickel), cermet made of Ni and ceramic particles, Ni-based alloy, or the like. Thus, the single cell 110 (power generation unit 102) of the present embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte.

As shown in FIGS. 7 and 8, the intermediate layer 300 is disposed between the electrolyte layer 112 and the air electrode 114. The intermediate layer 300 is a rectangular flat plate-shaped member having approximately the same size as the air electrode 114, and is formed of, for example, a solid oxide having ionic conductivity such as SDC, GDC, or perovskite oxide. If there is no intermediate layer 300 between the electrolyte layer 112 and the air electrode 114, a metal element (for example, Sr or La, for example) contained in the air electrode 114 under a high temperature condition such as during operation of the fuel cell stack 100. Hereinafter, a diffusion element) and a transition element (for example, a portion Zr) included in the electrolyte layer 112 react to form a high resistance layer (for example, SrZrO ₃ ) near the boundary between the air electrode 114 and the electrolyte layer 112. As a result, the power generation efficiency of the single cell 110 may decrease. On the other hand, in the single cell 110 of this embodiment, the intermediate layer 300 is disposed between the electrolyte layer 112 and the air electrode 114. For this reason, the intermediate layer 300 functions as a reaction preventing layer that suppresses the formation of a high resistance layer by the reaction between the metal element contained in the air electrode 114 and the transition element contained in the electrolyte layer 112. Have. The intermediate layer 300 is formed of a solid oxide having ionic conductivity. For this reason, the intermediate layer 300 has a function of moving oxide ions generated at the air electrode 114 to the electrolyte layer 112 by an ionization reaction of oxygen molecules contained in the oxidant gas OG.

  The separator 120 is a frame-like member in which a square hole 121 penetrating in the vertical direction is formed near the center, and is made of, for example, metal. The peripheral part of the hole 121 in the separator 120 is opposed to the peripheral part of the surface of the electrolyte layer 112 on the air electrode 114 side. The separator 120 is bonded to the electrolyte layer 112 (single cell 110) by a bonding portion 124 formed of a brazing material (for example, Ag brazing) disposed in the facing portion. The separator 120 divides the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116, and gas leaks from one electrode side to the other electrode side in the peripheral portion of the single cell 110. It is suppressed. The single cell 110 to which the separator 120 is bonded is also referred to as a single cell with a separator.

  As shown in FIGS. 7 to 9, the air electrode side frame 130 is a frame-like member in which a square hole 131 penetrating in the vertical direction is formed near the center, and is formed of an insulator such as mica, for example. ing. The hole 131 of the air electrode side frame 130 forms an air chamber 166 that faces the air electrode 114. The air electrode side frame 130 is in contact with the peripheral edge portion of the surface of the separator 120 opposite to the side facing the electrolyte layer 112 and the peripheral edge portion of the surface of the interconnector 150 facing the air electrode 114. . That is, the air electrode side frame 130 is sandwiched between the separator 120 and the interconnector 150. Therefore, the air electrode side frame 130 realizes a seal (compression seal) for the air chamber 166. The pair of interconnectors 150 included in the power generation unit 102 is electrically insulated by the air electrode side frame 130. As described above, the bolt hole 108 into which the bolt 22 described above is inserted is formed around the hole 131 in the air electrode side frame 130. The air electrode side frame 130 has an oxidant gas supply communication hole 132 communicating the oxidant gas supply manifold 163 and the air chamber 166, and an oxidant gas communicating the air chamber 166 and the oxidant gas discharge manifold 162. A discharge communication hole 133 is formed.

  As shown in FIGS. 7, 8 and 10, the fuel electrode side frame 140 is a frame-like member in which a square hole 141 penetrating in the vertical direction is formed near the center. For example, the fuel electrode side frame 140 is made of metal. Yes. The hole 141 of the fuel electrode side frame 140 forms a fuel chamber 176 that faces the fuel electrode 116. The fuel electrode side frame 140 is in contact with the peripheral portion of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral portion of the surface of the interconnector 150 facing the fuel electrode 116. As described above, the bolt hole 108 into which the bolt 22 described above is inserted is formed around the hole 141 in the fuel electrode side frame 140. Further, the fuel electrode side frame 140 has a fuel gas supply communication hole 142 that connects the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that connects the fuel chamber 176 and the fuel gas discharge manifold 172. And are formed.

  The air electrode side current collector 134 is disposed in the air chamber 166 as shown in FIGS. 7 to 9. The air electrode side current collector 134 is composed of a plurality of substantially quadrangular columnar conductive members arranged at predetermined intervals, and is made of, for example, ferritic stainless steel. The air electrode side current collector 134 is brought into contact with the surface of the air electrode 114 opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 facing the air electrode 114, whereby the air electrode 114 and the interconnector 150 are electrically connected. The air electrode side current collector 134 and the interconnector 150 may be formed as an integral member.

  The fuel electrode side current collector 144 is disposed in the fuel chamber 176 as shown in FIGS. 7, 8 and 10. The fuel electrode side current collector 144 includes an interconnector facing portion 146, a plurality of electrode facing portions 145, and a connecting portion 147 that connects each electrode facing portion 145 and the interconnector facing portion 146. Or nickel alloy, stainless steel or the like. Each electrode facing portion 145 contacts the surface of the fuel electrode 116 opposite to the side facing the electrolyte layer 112, and the interconnector facing portion 146 contacts the surface of the interconnector 150 facing the fuel electrode 116. To do. Therefore, the fuel electrode side current collector 144 electrically connects the fuel electrode 116 and the interconnector 150. Note that a spacer 149 made of, for example, mica is disposed between the electrode facing portion 145 and the interconnector facing portion 146. Therefore, the fuel electrode side current collector 144 follows the deformation of the power generation unit 102 due to the temperature cycle or reaction gas pressure fluctuation, and the fuel electrode 116 and the interconnector 150 are electrically connected via the fuel electrode side current collector 144. Maintained well.

(Configuration of heat exchange unit 103)
FIG. 11 is an explanatory diagram schematically showing a cross-sectional configuration of the heat exchange unit 103. FIG. 11 shows a cross-sectional configuration of the heat exchange unit 103 in a direction orthogonal to the arrangement direction. As shown in FIGS. 4 to 6 and FIG. 11, the heat exchanging portion 103 is a rectangular flat plate-like member, and is formed of, for example, ferritic stainless steel. As described above, the bolt hole 108 into which the bolt 22 is inserted is formed in the peripheral portion around the Z direction of the heat exchanging portion 103. Further, a hole 182 penetrating in the vertical direction is formed near the center of the heat exchanging portion 103. Further, the heat exchanging portion 103 has a communication hole 184 that connects the central hole 182 and the bolt hole 108 that forms the oxidant gas introduction manifold 161, and a bolt that forms the central hole 182 and the oxidant gas supply manifold 163. A communication hole 186 that communicates with the hole 108 is formed. The heat exchange unit 103 includes a lower interconnector 150 included in the power generation unit 102 adjacent to the upper side of the heat exchange unit 103 and an upper interconnector 150 included in the power generation unit 102 adjacent to the lower side of the heat exchange unit 103. And is sandwiched between. A space formed by the holes 182, the communication holes 184, and the communication holes 186 between these interconnectors 150 functions as a heat exchange channel 188 through which the oxidant gas OG flows for heat exchange described later.

A-2. Operation of the fuel cell stack 100:
As shown in FIG. 4, when the oxidant gas OG is supplied via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161. The oxidant gas OG is supplied to the oxidant gas introduction manifold 161 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28. As shown in FIGS. 4 and 11, the oxidant gas OG supplied to the oxidant gas introduction manifold 161 flows into the heat exchange channel 188 formed in the heat exchange unit 103, and the heat exchange channel 188. And is discharged to the oxidant gas supply manifold 163. The heat exchanging unit 103 is adjacent to the power generation unit 102 on the upper side and the lower side. As will be described later, the power generation reaction in the power generation unit 102 is an exothermic reaction. Therefore, when the oxidant gas OG passes through the heat exchange channel 188 in the heat exchange unit 103, heat exchange is performed between the oxidant gas OG and the power generation unit 102, and the temperature of the oxidant gas OG increases. To do. Since the oxidant gas introduction manifold 161 is not in communication with the air chamber 166 of each power generation unit 102, the oxidant gas OG is supplied from the oxidant gas introduction manifold 161 to the air chamber 166 of each power generation unit 102. There is nothing.

  The oxidant gas OG discharged to the oxidant gas supply manifold 163 through the heat exchange flow path 188 is supplied from the oxidant gas supply manifold 163 to each power generation as shown in FIGS. 4, 5, 7 and 9. The air is supplied to the air chamber 166 through the oxidant gas supply communication hole 132 of the unit 102.

  Further, as shown in FIGS. 6, 8, and 10, the fuel gas is connected via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. When the FG is supplied, the fuel gas FG is supplied to the fuel gas introduction manifold 171 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28, and the fuel of each power generation unit 102 is supplied from the fuel gas introduction manifold 171. The fuel is supplied to the fuel chamber 176 through the gas supply communication hole 142.

  When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, power is generated by an electrochemical reaction between the oxidant gas OG and the fuel gas FG in the single cell 110. Is called. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to one interconnector 150 via the air electrode side current collector 134, and the fuel electrode 116 is connected via the fuel electrode side current collector 144. The other interconnector 150 is electrically connected. In addition, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series although the heat exchange unit 103 is interposed therebetween. Therefore, electrical energy generated in each power generation unit 102 is taken out from the end plates 104 and 106 that function as output terminals of the fuel cell stack 100. Since SOFC generates power at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the fuel cell stack 100 is heated by a heater (after the start-up until the high temperature can be maintained by the heat generated by the power generation. (Not shown).

  As shown in FIGS. 5, 7, and 9, the oxidant off-gas OOG that is the oxidant gas OG that has not been used for the power generation reaction in each power generation unit 102 passes from the air chamber 166 through the oxidant gas discharge communication hole 133. The gas is discharged to the oxidant gas discharge manifold 162 and further connected to the branch part 29 through the holes of the main body part 28 and the branch part 29 of the gas passage member 27 provided at the position of the oxidant gas discharge manifold 162. It is discharged to the outside of the fuel cell stack 100 through piping (not shown). Further, as shown in FIGS. 6, 8, and 10, the fuel off-gas FOG that is the fuel gas FG that has not been used in the power generation reaction in each power generation unit 102 passes through the fuel gas discharge communication hole 143 from the fuel chamber 176. Gas piping (shown in the figure) connected to the branching portion 29 through the holes of the main body portion 28 and the branching portion 29 of the gas passage member 27 that is discharged to the fuel gas discharge manifold 172 and further provided at the position of the fuel gas discharge manifold 172. Is not discharged to the outside of the fuel cell stack 100.

A-3. Detailed structure of the intermediate layer:
The intermediate layer 300 includes a first intermediate layer 310 that is adjacent to the air electrode 114 and a second intermediate layer 320 that is adjacent to the electrolyte layer 112. The first intermediate layer 310 is a porous layer, and the second intermediate layer 320 is a denser layer than the first intermediate layer 310. For example, the porosity of the first intermediate layer 310 is 10% or more, and the porosity of the second intermediate layer 320 is less than 10%.

  FIG. 12 shows a cross-sectional configuration (cross-sectional configuration parallel to the ZX plane) parallel to the vertical direction (Z direction) of a part of the single cell 110 (electrolyte layer 112, air electrode 114, intermediate layer 300). The vertical direction (Z direction) in which the air electrode 114 and the fuel electrode 116 face each other corresponds to the first direction in the claims, and is hereinafter also referred to as the “longitudinal direction”. Further, a direction orthogonal to the vertical direction (a direction parallel to the XY plane) corresponds to a second direction in the claims, and is also referred to as a “lateral direction” hereinafter.

  The first intermediate layer 310 has a plurality of pores P having various shapes and orientations. FIG. 12 shows a region E1 where 11 pores P exist. Among the eleven pores P, the pores P1 to P7 have a vertical dimension ΔZ (opening diameter) larger than a horizontal dimension ΔX (opening diameter) (vertical dimension ΔZ / lateral dimension ΔX> 1). The pores satisfying the first pore condition (hereinafter, also referred to as “first vertically long pores”). On the other hand, the remaining pores P8 to P11 are pores whose longitudinal dimension ΔZ is smaller than the lateral dimension ΔX, that is, pores that do not satisfy the first pore condition (hereinafter also referred to as “horizontal elongated pores”). The ratio of the number of first vertically long pores to the number of pores P existing in the region E1 (= (number of first vertically long pores / number of pores P present in the region E1) × 100 or less, Is also about 63.6%.

  Further, the porosity of the first intermediate layer 310 is 10% or more and 25% or less, and the thickness of the first intermediate layer 310 in the vertical direction is 1 μm or more and 15 μm or less. The thickness of the second intermediate layer 320 in the vertical direction is not less than 0.1 μm and not more than 0.9 μm.

A-4. Manufacturing method of the single cell 110:
An example of the manufacturing method of the single cell 110 is as follows.
(Preparation of green sheet for solid electrolyte layer)
A butyral resin, dioctyl phthalate (DOP) as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added to a YSZ powder having a specific surface area of 5 to 7 m ² / g by the BET method. Then, a slurry is prepared by mixing with a ball mill. A green sheet for a solid electrolyte layer having a thickness of 10 μm is obtained by using a doctor blade method on the obtained slurry.

(Preparation of a green sheet for the fuel electrode layer)
NiO powder having a specific surface area of 3 to 4 m ² / g by BET method is weighed to be 55 parts by mass in terms of Ni weight, and the specific surface area by BET method is 5 to 7 m ² / g. Mix with 45 parts by mass of YSZ powder to obtain a mixed powder. To this mixed powder, a butyral resin, DOP as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added and mixed in a ball mill to prepare a slurry. A green sheet for a fuel electrode active layer having a thickness of 10 μm is obtained by using a doctor blade method on the obtained slurry.

(Lamination of solid electrolyte layer and fuel electrode layer)
A green sheet for the solid electrolyte layer and a green sheet for the fuel electrode layer are attached and dried. Further, firing is performed at 1400 ° C. to obtain a laminate of the electrolyte layer 112 and the fuel electrode (fuel electrode layer) 116.

(Preparation, printing, and firing of intermediate layer forming slurry)
A solvent comprising an acrylic binder and isopropyl alcohol is added to the GDC powder, and a thixo material for improving rheological properties is added and mixed to prepare a slurry for forming an intermediate layer. The prepared slurry is applied to the surface of the laminated body of the electrolyte layer 112 and the fuel electrode 116 on the solid electrolyte molded body side by screen printing using a mesh, and the laminated body after application is fired. In this way, by improving the rheological properties of the slurry for forming the intermediate layer, the longitudinal direction of the asymmetric pores P existing in the electrolyte layer 112 is set along the predetermined direction (Z direction) and the first vertically elongated pores or Second vertically long pores described later can be formed.

  Further, in the process of firing the laminate, a portion of the intermediate layer 300 on the side of the boundary B1 with the electrolyte layer 112 becomes denser than a portion on the side opposite to the electrolyte layer 112. As a result, the electrolyte layer 112 The portion on the boundary B1 side with the second intermediate layer 320 becomes the second intermediate layer 320, and the portion on the opposite side of the electrolyte layer 112 becomes the first intermediate layer 310. Note that the thickness in the vertical direction of the second intermediate layer 320 can be adjusted by appropriately changing the firing temperature and firing time when firing the laminated body after application. For example, when the firing temperature is 1250 degrees and the firing time is 8 hours, the second intermediate layer 320 having a larger vertical thickness is formed than when the firing temperature is 1250 degrees and the firing time is 1 hour. be able to.

(Formation of air electrode 114)
A mixed solution composed of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder and isopropyl alcohol was prepared. By spray-coating the prepared liquid mixture on the surface of the first intermediate layer 310 in the laminate having the intermediate layer 300 formed thereon, and firing at 1100 ° C., the air electrode 114 is formed, and the single cell 110 is obtained. Can do.

A-5. Analysis method of the intermediate layer 300:
(Acquisition method of analysis image M1)
First, for the intermediate layer 300, an analysis image M1 for analyzing the boundary B3 between the first intermediate layer 310 and the second intermediate layer 320 and the pores P is acquired as follows. That is, as shown in FIG. 12, the entire image in the vertical direction of the intermediate layer 300 can be confirmed, and a portion estimated as the boundary B <b> 1 between the intermediate layer 300 and the air electrode 114 is 10 in the vertical direction. Of the 10 divided regions obtained by equally dividing, the portion that is located in the uppermost divided region and is assumed to be the boundary B2 between the intermediate layer 300 and the electrolyte layer 112 is the lowermost divided region. The image located inside is made observable with, for example, a scanning electron microscope (SEM), and the analysis image M1 is acquired by photographing the image. The analysis image M1 may be a binarized image after binarizing the image observed by the SEM. However, when the pores P in the binarized image are significantly different from the actual form, the contrast of the image before the binarization process observed by the SEM is adjusted, and the image after the binarization process is adjusted. But you can. Moreover, the image itself before the binarization process observed by SEM may be sufficient. The magnification of the SEM image can be 5,000 to 20,000 times, but is not limited to this and can be changed as appropriate.

(Method for determining the boundary B3 between the first intermediate layer 310 and the second intermediate layer 320)
Next, the boundary B 3 between the first intermediate layer 310 and the second intermediate layer 320 is determined by the porosity Ks in the intermediate layer 300. First, a plurality of virtual lines K perpendicular to the vertical direction (Z-axis direction) are drawn in order from the upper surface of the air electrode 114 at intervals of 0.3 μm with respect to the analysis image M1, and virtual lines K1, K2, K3,..., Km,..., K (m + 9), K (m + 10),. And the length of the part which overlaps with the pore P in each virtual line K is measured, the sum total of the length of the part which overlaps with a pore is calculated, and the length of the part which overlaps with the pore P with respect to the full length of each virtual line K Is the ratio of the pores P existing on the virtual line K (porosity Ks). Next, among the porosity Ks1, Ks2, Ks3,..., Ksm,..., Ks (m + 9), Ks (m + 10),. Each data group having the porosity Ks of each virtual line K is set, and the average value (Ave) of the 10 porosity Ks of each data group and the standard deviation (σ) of the porosity Ks of each data group are calculated. To do.

In order from the top, the data group G1 is composed of Ks1, Ks2,..., Ks10, the data group G2 is composed of Ks2, Ks3,..., Ks11, and the data group Gm is composed of Ksm, Ks (m + 1). ), Ks (m + 2),..., Ks (m + 9), and the data group G (m + 1) includes Ks (m + 1), Ks (m + 2),. That is, the data group G (m + 1) means nine porosity (Ks (m + 1),..., Ks (m + 9)) excluding the porosity Ksm of the first virtual line Km from the data group Gm. Furthermore, it means one group consisting of 10 porosity Ks, which is obtained by adding the porosity Ks (m + 10) of the virtual line K (m + 10) next to the last virtual line K (m + 9) of the data group. The “average value of the porosity Ks of G (m + 1)” is a value obtained by adding a value twice the standard deviation (σ) of 10 porosity Ks of Gm to the average value of the porosity Ks of Gm. Or the average value of the porosity Ks of G (m + 1) is 2 of the standard deviation (σ) of 10 porosity Ks of Gm from the average value of the porosity Ks of Gm. The virtual line K (m + 10) corresponding to the tenth porosity Ks (m + 10) of the data group G (m + 1) when it is below the “value obtained by subtracting the double value” for the first time, The boundary B3 with the second intermediate layer 320 is assumed. That is, when the average value of the porosity Ks of Gm is Gmave, the average value of the porosity Ks of the data group G (m + 1) is G (m + 1) Ave, and the standard deviation of the porosity Ks of the data group Gm is σm, An imaginary line K (m + 10) corresponding to the tenth porosity Ks (m + 10) of the first data group G (m + 1) satisfying the expression (1) is represented by the first intermediate layer 310, the second intermediate layer 320, The boundary B3.
| (G (m + 1) Ave) − (GmAve) |> 2σm (1)
If the boundary B3 is determined, the first intermediate layer 310 and the second intermediate layer 320 can be distinguished from each other on the analysis image M1, and each pore P has the first intermediate layer 310 and the first intermediate layer 310. It can be specified which of the two intermediate layers 320 is present.

(Measurement method of dimension of pore P)
The vertical dimension ΔZ and the horizontal dimension ΔX of the pores P are measured as follows. That is, the horizontal ferret diameter and the vertical ferret diameter are obtained by performing known image processing on the analysis image M1 (an image after the binarization processing if the analysis image M1 is before the binarization processing). Ask. The diameter of the horizontal ferret is circumscribed by a side parallel to the lateral direction of a square (hereinafter also referred to as a circumscribed square W) that is circumscribed by each pore P and is composed of two sides parallel to the vertical direction and two sides parallel to the horizontal direction. The vertical ferret diameter is the length of a side parallel to the longitudinal direction of the circumscribed square W, and corresponds to the longitudinal dimension ΔZ of the pore P.

  In the analysis image M1, for example, a predetermined number, a predetermined ratio (50 to 80%), or an opening area or an area of the circumscribed square W is a predetermined value in descending order of the opening area or the circumscribed square W. For the pores P (for example, the visible area on the analysis image M1), the vertical dimension ΔZ and the horizontal dimension ΔX are measured, and from the measurement result, each pore P satisfies the first pore condition. If it is determined that it is satisfied, it is assumed that it is the first vertically-oriented pore, and if it is determined that it is not satisfied, it is assumed that it is not the first vertically-oriented pore. And from this judgment result, the ratio of vertically long pores can be obtained. That the ratio of vertically elongated pores is 50% or more (first region condition) corresponds to the region condition in the claims.

A-6. Effects of this embodiment:
FIG. 13 shows a region EC of a cross-sectional configuration (cross-sectional configuration parallel to the ZX plane) parallel to the vertical direction (Z direction) of a part of the single cell of the comparative example (electrolyte layer 112, air electrode 114, intermediate layer 300). An analysis image MC is shown. In the single cell of this comparative example, out of 11 pores P1 to P11, only 4 pores P2 to P4 and P7 are the first vertically elongated pores, and the ratio of vertically elongated pores is 36.3%, less than 50% It is. For this reason, in the intermediate layer 300, the pores P, like the ion conductive paths R4 to R6, are included in the ion conductive paths R of the oxide ions continuously connected from the air electrode 114 side to the electrolyte layer 112 side. Since many of them are curved so as to make a detour, the power generation efficiency of the fuel cell stack 100 may decrease.

  On the other hand, in the single cell 110 of this embodiment, as shown in FIG. 12, the vertically long pore ratio is 50% or more. For this reason, in the ion conduction path R in the intermediate layer 300, the ion conduction paths R1 to R3 are continuously connected in a straight line along the vertical direction from the air electrode 114 side to the electrolyte layer 112 side. Since the number of ion conduction paths is short, the oxide ions can be efficiently transferred from the air electrode 114 to the electrolyte layer 112 as compared with the single cell of the comparative example. A decrease in efficiency can be suppressed.

  As described above, by making the intermediate layer 300 the same porous layer as the air electrode 114, stress is concentrated near the boundary between the air electrode 114 and the intermediate layer 300, or the air electrode 114 and the intermediate layer 300 are separated. Can be eased. On the other hand, the power generation efficiency of the fuel cell stack 100 may be reduced due to the ionic conduction path of oxide ions from the air electrode to the electrolyte layer being obstructed by the pores P in the intermediate layer 300. There is. However, in the fuel cell stack 100 of the present embodiment, there is a region that satisfies the region condition in the intermediate layer 300. As a result, the concentration of stress near the boundary between the air electrode 114 and the intermediate layer 300 is alleviated by the pores P of the intermediate layer 300, and the power generation efficiency of the fuel cell stack 100 is reduced due to the presence of the pores P. Can be suppressed.

In the intermediate layer 300, a second intermediate layer 320 that is denser than the first intermediate layer 310 is disposed between the first intermediate layer 310 and the electrolyte layer 112. Therefore, it is possible to suppress the diffusion element or Sr which is generated source of the high-resistance layer (e.g., SrZrO ₃₎ is diffused into the electrolyte layer 112 side. Further, the second intermediate layer 320 is present on the electrolyte layer side with respect to the first intermediate layer 310. That is, the porous first intermediate layer 310 is in contact with the porous air electrode 114, and the dense second intermediate layer 320 is in contact with the dense electrolyte layer 112. As a result, the porous first intermediate layer 310 is in contact with the dense electrolyte layer 112 and the dense second intermediate layer 320 is in contact with the porous air electrode 114. It is possible to suppress stress concentration near the boundary between the air electrode 114 and the intermediate layer 300 and separation of the air electrode 114 and the intermediate layer 300 from each other.

  The thickness of the second intermediate layer 320 in the vertical direction is not less than 0.1 μm and not more than 0.9 μm. For this reason, it is possible to suppress the resistance of the intermediate layer 300 from becoming too high while suppressing the diffusion of elements from the air electrode 114 to the electrolyte layer 112. Further, the porosity of the first intermediate layer 310 is 10% or more and 25% or less. For this reason, it can suppress that resistance of the intermediate | middle layer 300 becomes high too much, relieving that stress concentrates on the boundary vicinity of the air electrode 114 and the intermediate | middle layer 300. FIG. Furthermore, the thickness of the first intermediate layer 310 in the vertical direction is not less than 1 μm and not more than 15 μm. For this reason, it can suppress that resistance of the intermediate | middle layer 300 becomes high too much, relieving that stress concentrates on the boundary vicinity of the air electrode 114 and the intermediate | middle layer 300. FIG.

B. Second embodiment:
FIG. 14 shows a detailed configuration of a part of a single cell according to the second embodiment. Among the configurations of the fuel cell stack of the second embodiment, the same configurations as those of the fuel cell stack 100 of the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

  The single cell according to the present embodiment includes an electrolyte layer 112, an air electrode 114 and a fuel electrode 116 facing each other with the electrolyte layer 112 interposed therebetween, and an intermediate layer 300A disposed between the electrolyte layer 112 and the air electrode 114. Prepare.

  The intermediate layer 300A has a plurality of pores P having various shapes and orientations. FIG. 14 shows a region E2 where eleven pores P exist. Among the 11 pores P, the pore P1 has a second pore condition in which the longitudinal dimension ΔZ is larger than twice the lateral dimension ΔX (vertical dimension ΔZ / lateral dimension ΔX> 2). The other pores P2 to P11 have the vertical dimension ΔZ smaller than twice the horizontal dimension ΔX, and hence the second pores. The condition is not met. Accordingly, in the intermediate layer 300A, there is an area E2 where one or more second vertically long pores exist in at least one cross section parallel to the vertical direction (vertical direction). The presence of the second vertically long pores (second region condition) corresponds to the region condition in the claims. Of the 11 pores P, only four pores P1, P2, P4, and P7 are the first vertically long pores that satisfy the first pore condition, and the ratio of the vertically long pores is 36.3%. The first region condition of one embodiment is not satisfied.

  The intermediate layer 300A is composed of one porous layer, and the porosity thereof is 10% or more and 25% or less. The intermediate layer 300A has a thickness in the vertical direction of 1 μm or more and 15 μm or less.

  According to the single cell of the present embodiment, the second vertically long pores exist in the cross section parallel to the vertical direction in the intermediate layer 300A. As a result, the ion conductive paths R7 and R8 that are continuously connected in a straight line along the vertical direction from the air electrode 114 side to the electrolyte layer 112 side are relatively long around the second vertically long pores. It is formed over a range. Therefore, the oxide ions are efficiently moved from the air electrode 114 to the electrolyte layer 112 as compared with the case where the second vertically long pores are not present in any cross section of the intermediate layer 300A that is parallel to the vertical direction. be able to. That is, the stress concentration in the vicinity of the boundary between the air electrode 114 and the intermediate layer 300A is mitigated by the pores P of the intermediate layer 300A, and the power generation efficiency of the fuel cell stack is suppressed from being lowered due to the presence of the pores P. be able to.

  Moreover, since the intermediate layer 300A has the second vertically elongated pores, a lateral stress (for example, shear stress) due to thermal expansion generated between each layer adjacent to the intermediate layer 300A in the vertical direction is generated. It becomes easy to disperse | distribute by the inner wall long in the vertical direction which comprises the 2nd vertically long pore. For this reason, it is possible to more effectively alleviate stress concentration near the boundary between the electrolyte layer 112 and the air electrode 114 and the intermediate layer 300A.

  The porosity of the intermediate layer 300A is 10% or more and 25% or less. For this reason, it can suppress that resistance of intermediate | middle layer 300A becomes high too much, relieving that stress concentrates on the boundary vicinity of the air electrode 114 and intermediate | middle layer 300A. Furthermore, the thickness of the intermediate layer 300A in the vertical direction is not less than 1 μm and not more than 15 μm. For this reason, it can suppress that resistance of intermediate | middle layer 300A becomes high too much, relieving that stress concentrates on the boundary vicinity of the air electrode 114 and intermediate | middle layer 300A.

C. Third embodiment:
FIG. 15 shows a fuel cell stack 100C having a plurality of power generation units 102C having a so-called cylindrical flat plate shape. The fuel cell stack 100C includes a plurality of power generation units 102C that are arranged side by side at a predetermined interval. The plurality of power generation units 102C are electrically connected in series via a current collector 870 arranged between adjacent power generation units 102C. Each power generation unit 102 </ b> C has a flat columnar appearance and includes an electrode support 830, a single cell 110 </ b> C, and an interconnector 810.

  The electrode support 830 is a columnar body having an elliptical cross section, and is formed of a porous material. A plurality of fuel gas passages 820 extending in the extending direction of the columnar body are formed inside the electrode support 830. Single cell 110 </ b> C includes a fuel electrode 840, a solid electrolyte layer 850, an air electrode 860, and an intermediate layer 900. The fuel electrode 840 is provided so as to cover one of a pair of parallel flat surfaces among the side surfaces of the electrode support 830 and two curved surfaces connecting the ends of the flat surfaces. The solid electrolyte layer 850 is provided so as to cover the side surface of the fuel electrode 840. The air electrode 860 is provided so as to cover a portion of the side surface of the solid electrolyte layer 850 located on the flat surface of the electrode support 830. The intermediate layer 900 has a porous layer, and is disposed between the solid electrolyte layer 850 and the air electrode 860. The interconnector 810 is provided on the flat surface of the electrode support 830 on the side where the fuel electrode 840 and the solid electrolyte layer 850 are not provided. The power collection unit 870 described above electrically connects the air electrode 860 of the power generation unit 102C and the interconnector 810 of the power generation unit 102C adjacent to the power generation unit 102C.

  In the fuel cell stack 100C having such a configuration, the first region condition and the second region are defined on at least one cross section parallel to the first direction (Z direction) in which the fuel electrode 840 and the air electrode 860 face each other. There is a region that satisfies at least one of the region conditions. As a result, stress concentration near the boundary between the air electrode 860 and the intermediate layer 900 is mitigated by the pores of the intermediate layer 900, and the power generation efficiency of the fuel cell stack 100C is suppressed from being reduced due to the presence of the pores. be able to.

D. Variations:
The technology disclosed in the present specification is not limited to the above-described embodiment, and can be modified into various forms without departing from the gist thereof. For example, the following modifications are possible.

  In the first embodiment, the intermediate layer 300 including the first intermediate layer 310 and the second intermediate layer 320 is illustrated as the intermediate layer. However, the intermediate layer is not limited to this, and the intermediate layer includes the first intermediate layer 310 and the second intermediate layer 320. An intermediate layer composed of one or three or more layers may be used as long as a layer including a region satisfying the first region condition is included in at least one cross section parallel to one direction.

  In the second embodiment, the intermediate layer 300A composed of one layer is illustrated as the intermediate layer. However, the intermediate layer is not limited to this, and the intermediate layer has at least one cross section parallel to the first direction. An intermediate layer composed of two or more layers may be used as long as a layer including a region satisfying the second region condition is included.

  In the above-described embodiment, the intermediate layer 300 in which the first intermediate layer 310 and the second intermediate layer 320 having different porosities by changing the firing conditions and the like for the same material is illustrated. However, the present invention is not limited to this, and an intermediate layer in which the first intermediate layer and the second intermediate layer are formed by co-firing two members having different porosities may be used.

  The thickness in the longitudinal direction of the second intermediate layer 320 may be less than 0.1 μm or greater than 0.9 μm. The porosity of the first intermediate layer 310 (intermediate layer 300A) may be less than 10% or greater than 25%. The thickness of the first intermediate layer 310 (intermediate layer 300A) in the first direction may be less than 1 μm or thicker than 15 μm.

  In each of the above embodiments, a region satisfying the first region condition (second region condition) exists in one cross section parallel to the first direction of the first intermediate layer 310 (intermediate layer 300A). Although the example has been described, the present invention is not limited to this, and the first region condition (second region condition) is applied to a plurality of cross sections parallel to the first direction of the first intermediate layer 310 (intermediate layer 300A). There may be a region that fills. For example, the first intermediate layer 310 (intermediate layer 300A) is at least 30%, 40%, 50%, or more of a plurality of cross-sections arranged at equal intervals in a direction orthogonal to the first direction, or In addition, there may be a region that satisfies the first region condition (second region condition) in a cross section of 60% or more. In one cross section, there may be a region that satisfies both the first region condition and the second region condition.

  The ratio of vertically long pores in the first embodiment is less than 100%, may be 80% or less, 70% or less, or 60% or less. If the ratio of vertically long pores is 80% or less, it is possible to suppress the occurrence of cracks near the boundary between the air electrode 114 and the first intermediate layer 310 compared to the case where the ratio of vertically long pores exceeds 80%, It is possible to more effectively suppress the diffusion element from diffusing from the air electrode 114 to the electrolyte layer 112 side.

  In the above embodiment, the number of power generation units 102 included in the fuel cell stack 100 is merely an example, and the number of power generation units 102 is appropriately determined according to the output voltage required for the fuel cell stack 100 or the like.

  In the present specification, the term “perpendicular / vertical” means that the angle between each other is 89 degrees or more and 91 degrees or less. Moreover, the parallel means that the angle between each other is -1 degree or more and 1 degree or less.

  Moreover, in the said embodiment, the position of the heat exchange part 103 in the arrangement direction of the fuel cell stack 100 is an example to the last, and the position of the heat exchange part 103 can be changed to arbitrary positions. However, the position of the heat exchanging unit 103 is a position adjacent to the power generation unit 102 having a higher temperature among the plurality of power generation units 102 included in the fuel cell stack 100, so that the heat in the arrangement direction of the fuel cell stack 100 is determined. It is preferable for the relaxation of the distribution. For example, when the power generation unit 102 near the center in the arrangement direction of the fuel cell stack 100 is likely to be hotter, the heat exchange unit 103 is provided near the center in the arrangement direction of the fuel cell stack 100 as in the above embodiment. preferable. Further, the fuel cell stack 100 may include two or more heat exchange units 103.

  In the above embodiment, the heat exchange unit 103 is configured to increase the temperature of the oxidant gas OG. However, the heat exchange unit 103 increases the temperature of the fuel gas FG instead of the oxidant gas OG. Alternatively, the temperature of the fuel gas FG may be increased together with the oxidant gas OG.

  In the above embodiment, the nuts 24 are fitted on both sides of the bolt 22, but the bolt 22 has a head, and the nut 24 is fitted only on the opposite side of the head of the bolt 22. Also good. Moreover, in the said embodiment, although the volt | bolt 22 is used as a fastening member, the fuel cell stack 100 may be fastened by other fastening members other than the bolt 22.

  In the above embodiment, the end plates 104 and 106 function as output terminals. However, instead of the end plates 104 and 106, separate members (for example, the end plate 104) connected to the end plates 104 and 106, respectively. , 106 and the power generation unit 102) may function as output terminals.

  Moreover, in the said embodiment, although the space between the outer peripheral surface of the axial part of each bolt 22 and the inner peripheral surface of each bolt hole 108 is utilized as each manifold, it replaces with this and the axis | shaft of each bolt 22 is used. An axial hole may be formed in the part, and the hole may be used as each manifold. Further, each manifold may be provided separately from the bolt hole 108 into which each bolt 22 is inserted.

  In the above embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. Two power generation units 102 may be provided with respective interconnectors 150. In the above embodiment, the upper interconnector 150 of the uppermost power generation unit 102 in the fuel cell stack 100 and the lower interconnector 150 of the lowermost power generation unit 102 are omitted. These interconnectors 150 may be provided without being omitted.

  Further, in the above embodiment, the fuel electrode side current collector 144 may have the same configuration as the air electrode side current collector 134, and the fuel electrode side current collector 144 and the adjacent interconnector 150 are an integral member. It may be. Further, the fuel electrode side frame 140 instead of the air electrode side frame 130 may be an insulator. The air electrode side frame 130 and the fuel electrode side frame 140 may have a multilayer structure.

  Moreover, the material which forms each member in the said embodiment is an illustration to the last, and each member may be formed with another material.

  In the above embodiment, the city gas is reformed to obtain the hydrogen-rich fuel gas FG, but the fuel gas FG may be obtained from other raw materials such as LP gas, kerosene, methanol, gasoline, Pure hydrogen may be used as the fuel gas FG.

  Further, in the above embodiment, a reaction preventing layer containing, for example, ceria is provided between the electrolyte layer 112 and the air electrode 114 so that zirconium or the like in the electrolyte layer 112 reacts with strontium or the like in the air electrode 114. An increase in electrical resistance between the electrolyte layer 112 and the air electrode 114 may be suppressed. In this specification, B and C facing each other across A do not require that A and B or C be adjacent to each other, and there are other components between A and B or C. Including intervening forms. For example, even in a configuration in which a reaction preventing layer is provided between the electrolyte layer 112 and the air electrode 114, it can be said that the air electrode 114 and the fuel electrode 116 face each other with the electrolyte layer 112 interposed therebetween.

  In the above embodiment, the example in which the present invention is applied to the fuel cell stack 100 has been described. However, the present invention is not limited to this, and by applying the present invention to the power generation unit 102 alone or the single cell 110 alone, pores in the intermediate layer can be obtained. It can suppress that the electric power generation efficiency of a fuel cell falls resulting from this.

22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 28: Body portion 29: Branch portion 45: Powder 100, 100C: Fuel cell stack 102, 102C: Power generation unit 103: Heat exchange portion 104, 106: End plate 108: Bolt hole 110, 110C: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 121: Hole 124: Joint part 130: Air electrode side frame 131: Hole 132: Oxidant gas supply communication hole 133 : Oxidant gas discharge communication hole 134: Air electrode side current collector 140: Fuel electrode side frame 141: Hole 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144: Fuel electrode side current collector 145: Opposite electrode Part 146: Interconnector facing part 147: Connection part 149: Spacer 150: interconnector 161: oxidant gas introduction manifold 162: oxidant gas discharge manifold 163: oxidant gas supply manifold 166: air chamber 171: fuel gas introduction manifold 172: fuel gas discharge manifold 176: fuel chamber 182: hole 184: Communication hole 186: Communication hole 188: Heat exchange flow path 300, 300A: Intermediate layer 310: First intermediate layer 320: Second intermediate layer 810: Interconnector 820: Fuel gas flow path 830: Electrode support 840: Fuel Electrode 850: Solid electrolyte layer 860: Air electrode 870: Current collector 900: Intermediate layer B1: Boundary B2: Boundary B3: Boundary E1, E2: Region EC: Region FG: Fuel gas FOG: Fuel off-gas M1: Analysis image MC: Analysis image OG: Oxidant gas OOG: Acid Containing off gas P: pore R: ion conductive path

Claims (9)

An electrolyte layer comprising a solid oxide;
An air electrode and a fuel electrode facing each other across the electrolyte layer;
In a fuel cell single cell comprising an intermediate layer disposed between the electrolyte layer and the air electrode,
A region satisfying the following region condition exists in at least one cross section parallel to the first direction in which the air electrode and the fuel electrode face each other in the intermediate layer. cell.
The region condition: the ratio of the number of pores satisfying the first pore condition to the number of pores existing in the region is 50% or more.
The first pore condition: dimension in the first direction / dimension in the second direction orthogonal to the first direction> 1 An electrolyte layer comprising a solid oxide;
An air electrode and a fuel electrode facing each other across the electrolyte layer;
In a fuel cell single cell comprising an intermediate layer disposed between the electrolyte layer and the air electrode,
In the intermediate layer, pores satisfying the following second pore condition are present in at least one cross section parallel to the first direction in which the air electrode and the fuel electrode face each other. Fuel cell single cell.
The second pore condition: the pore size in the first direction / the size of the pore in the second direction orthogonal to the first direction> 2. In the fuel cell single cell according to claim 1 or 2,
The fuel cell single cell, wherein the porosity of the intermediate layer is 10% or more and 25% or less. In the fuel cell single cell as described in any one of Claim 1- Claim 3,
A fuel cell single cell, wherein the thickness of the intermediate layer in the first direction is not less than 1 μm and not more than 15 μm. In the fuel cell single cell according to claim 1 or 2,
The intermediate layer includes a first intermediate layer, and a second intermediate layer that is disposed between the first intermediate layer and the electrolyte layer and is denser than the first intermediate layer. A fuel cell unit cell. The fuel cell single cell according to claim 5,
The fuel cell single cell, wherein a thickness of the second intermediate layer in the first direction is 0.1 μm or more and 0.9 μm or less. The single fuel cell according to claim 5 or 6,
The fuel cell single cell, wherein the porosity of the first intermediate layer is 10% or more and 25% or less. In the fuel cell single cell according to any one of claims 5 to 7,
The fuel cell single cell, wherein a thickness of the first intermediate layer in the first direction is not less than 1 μm and not more than 15 μm. In a fuel cell stack including a plurality of fuel cell single cells,
The fuel cell stack, wherein at least one of the plurality of fuel cell single cells is the fuel cell single cell according to any one of claims 1 to 8.

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