Electrochemical reaction cell stack

Abstract

To improve durability of an electrochemical reaction cell stack.SOLUTION: An electrochemical reaction cell stack comprises: a first member; a second member that includes an overlapping part that is a part overlapping the first member in a first direction; and a bonding part that bonds the first member and the second member, and bonds the overlapping part in the second member, and a part that is opposite to the overlapping part in the first member in the first direction. The overlapping part includes an overlapping part borderline as at least one annular borderline in a first direction view. The electrochemical reaction cell stack is a combination of the bonding part and the overlapping part borderline, and a bonding part borderline as the borderline of the bonding part is similar to a shape of the overlapping part borderline in the first direction view. In the first direction view, one of the bonding part borderline and the overlapping part borderline surrounds the other one of the bonding part borderline and the overlapping part borderline. The electrochemical reaction cell stack contains a combination satisfying a condition that a center of the bonding part borderline and a center of the overlapping part borderline are different in a position form each other in the first direction view.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The technology disclosed herein relates to electrochemical reaction cell stacks. [Background technology]

[0002] Solid oxide fuel cells (hereinafter referred to as "SOFCs") are known as one type of fuel cell that generates electricity by utilizing an electrochemical reaction between hydrogen and oxygen. SOFCs are generally used in the form of a fuel cell stack. A fuel cell stack includes a certain member (hereinafter referred to as "first member"), another member (hereinafter referred to as "second member") having an overlapping portion that overlaps with the first member in a predetermined direction (hereinafter referred to as "first direction"), and a joint that joins the first member and the second member. A specific example of a combination of the first member, the second member, and the joint is a separator, an anode frame, and a weld that joins the separator and the anode frame.

[0003] 2. Description of the Related Art Conventionally, fuel cell-related components have been disclosed in which a plurality of plate-shaped workpieces are stacked and joined together with a joining material or by laser welding (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6112932 Summary of the Invention [Problem to be solved by the invention]

[0005] When stress is applied to the first and second members of a fuel cell stack, the joints may be damaged, which may lead to failure of the fuel cell stack. Therefore, there has been a demand for improving the durability of the joints in order to improve the durability of the fuel cell stack.

[0006] Such an issue is also common to, for example, an electrolysis cell stack, which is a form of an electrolysis cell (hereinafter referred to as "SOEC") that generates hydrogen by utilizing the electrolysis reaction of water. In this specification, a single fuel cell cell and a single electrolysis cell are collectively referred to as a single electrochemical reaction cell, and a fuel cell stack and an electrolysis cell stack are collectively referred to as an electrochemical reaction cell stack. Furthermore, such an issue is not limited to SOFCs and SOECs, but is also common to other types of electrochemical reaction cell stacks.

[0007] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0008] The technology disclosed in this specification can be realized, for example, in the following forms.

[0009] (1) The electrochemical reaction cell stack disclosed in the present specification includes a first member, a second member having an overlapping portion that is a portion that overlaps with the first member in a first direction, and a joint that joins the first member and the second member, the joint joining the overlapping portion of the second member and a portion of the first member that faces the overlapping portion in the first direction. The overlapping portion has at least one overlapping portion contour that is a circular contour when viewed in the first direction. The electrochemical reaction cell stack includes a combination of the joint and the overlapping portion contour that satisfies the following conditions: when viewed in the first direction, the joint contour that is the contour of the joint is similar in shape to the overlapping portion contour, when viewed in the first direction, one of the joint contour and the overlapping portion contour surrounds the other of the joint contour and the overlapping portion contour, and when viewed in the first direction, the center of the joint contour and the center of the overlapping portion contour are at different positions from each other.

[0010] According to this electrochemical reaction cell stack, in a combination of a joint and an overlapping portion contour line, the center of the joint contour line as viewed in a first direction and the center of the overlapping portion contour line are located at different positions, so that it is possible to make the stress applied to the joint non-uniform when stress is applied to the first member or the second member. Therefore, the portion of the joint to which a relatively large stress is applied becomes the initial damaged portion, but the portion other than the initial damaged portion does not receive as much stress as the initial damaged portion, so that it is possible to extend the life of the joint from the occurrence of initial damage until the entire joint is damaged.

[0011] (2) In the electrochemical reaction cell stack, the distance between the center of the joint contour line and the center of the overlapping contour line in the combination when viewed in the first direction may be 10 μm or more. With this configuration, in the combination of the joint and the overlapping contour line, the distance between the center of the joint contour line and the center of the overlapping contour line in the combination when viewed in the first direction is 10 μm or more, so that the lifespan of the joint from when initial damage occurs until the entire joint is damaged can be more effectively extended.

[0012] (3) In the electrochemical reaction cell stack, the longest distance between the joint contour and the overlapping portion contour when viewed in the first direction may be 1.01 times or more the shortest distance between the joint contour and the overlapping portion contour when viewed in the first direction. With this configuration, in the combination of the joint and the overlapping portion contour, the longest distance between the joint contour and the overlapping portion contour is 1.01 times or more the shortest distance between the joint contour and the overlapping portion contour, so that the lifespan of the joint from when initial damage occurs until the entire joint is damaged can be more effectively extended.

[0013] (4) The electrochemical reaction cell stack may further include a plurality of unit cells stacked in the first direction, a manifold for supplying gas to each of the unit cells is formed, a first through hole constituting a part of the manifold is formed in the first member, a second through hole constituting a part of the manifold is formed in the second member, at least a part of the overlapping portion contour line coincides with at least a part of a first through hole surrounding portion that is a portion surrounding the first through hole in the first member when viewed in the first direction, and the joint portion is a bonding material surrounding each of the first through hole and the second through hole. According to this configuration, when viewed in the first direction, the center of the overlapping portion contour line and the center of the contour line of the bonding material are different in position, so that the internal configuration of the manifold is non-uniform. This makes it easier for turbulence to occur in the gas flowing through the manifold, and gas can be evenly supplied to each of the unit cells.

[0014] (5) In the electrochemical reaction cell stack, a first unit and a second unit each having the first member and the second member may be stacked in the first direction, the first unit and the second unit each have the combination, at least a part of the overlapping portion contour of the combination in the first unit and at least a part of the overlapping portion contour of the combination in the second unit overlap each other in the first direction, and the center of the joint contour of the combination in the first unit and the center of the joint contour of the combination in the second unit may be positioned differently from each other when viewed in the first direction. According to this configuration, the center of the joint contour of the first unit and the center of the joint contour of the second unit are positioned differently from each other when viewed in the first direction, so that the stress of the joint can be distributed for each unit, and thus the stress can be distributed throughout the entire electrochemical reaction cell stack. Therefore, the life until the joint is damaged can be extended compared to a configuration in which the centers of the joint contours of the first unit and the second unit are positioned at the same position from each other when viewed in the first direction.

[0015] (6) In the electrochemical reaction cell stack, the first member and the second member may have a plurality of combinations, and the distance between the center of the joint contour line and the center of the overlapping portion contour line in one of the combinations when viewed in the first direction may be different from the distance between the center of the joint contour line and the center of the overlapping portion contour line in another of the combinations when viewed in the first direction. According to this configuration, the distance between the center of the joint contour line and the center of the overlapping portion contour line in one combination of the joint and the overlapping portion contour line in the first direction is different from the distance between the center of the joint contour line and the center of the overlapping portion contour line in another combination of the joint and the overlapping portion contour line in the first direction, thereby increasing the degree of freedom in designing the electrochemical reaction cell stack.

[0016] The technology disclosed in this specification can be realized in various forms, for example, in the form of an electrochemical reaction cell stack, a manufacturing method thereof, etc. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 10 according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 10 taken along the line II-II in FIG. [Diagram 3] FIG. 2 is an explanatory diagram showing an XZ cross-sectional configuration of the fuel cell stack 10 taken along the line III-III in FIG. 1. [Figure 4] FIG. 4 is an explanatory diagram showing a YZ cross-sectional configuration of the fuel cell stack 10 taken along the line IV-IV in FIG. [Diagram 5] FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent generating units 100U at the same position as the cross-section shown in FIG. 2. [Figure 6] FIG. 4 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 100U at the same position as the cross-section shown in FIG. [Figure 7] FIG. 7 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 taken along line VII-VII in FIG. [Figure 8]FIG. 8 is an explanatory diagram showing an XY cross-sectional configuration of the fuel cell stack 10 taken along the line VIII-VIII in FIG. 6. [Figure 9] FIG. 7 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 taken along the line IX-IX in FIG. 6. [Figure 10] FIG. 7 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at the position XX in FIG. 6. [Figure 11] FIG. 1 is an explanatory diagram showing an XY cross-sectional configuration of the fuel cell stack 10 taken along the line XI-XI in FIG. 2. [Figure 12] FIG. 1 is an explanatory diagram showing an outline of a gas flow evaluation method. [Figure 13] FIG. 7 is an explanatory diagram showing an XY cross-sectional configuration of a fuel cell stack 10a in a modified example taken along the line VII-VII in FIG. 6; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A. Embodiment: A-1. Configuration of fuel cell stack 10: FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 10 in this embodiment, FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 10 at the position II-II in FIG. 1, FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 10 at the position III-III in FIG. 1, and FIG. 4 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 10 at the position IV-IV in FIG. 1. Each figure shows mutually orthogonal XYZ axes for specifying directions. In this specification, for convenience, the Z-axis direction is called the up-down direction, the Z-axis positive direction is called the up-down direction, and the Z-axis negative direction is called the down-down direction, but the fuel cell stack 10 may actually be installed in a direction different from these directions. The fuel cell stack 10 is an example of an electrochemical reaction cell stack in the claims. The Z-axis direction (up-down direction) is an example of a first direction in the claims.

[0019] (Overall configuration of fuel cell stack 10) 1 to 4, the fuel cell stack 10 includes a power generation block 100, an end separator 230, a first plate 232, a second plate 260, a first terminal plate 240, a second terminal plate 250, an insulating section 220, a first end plate 210, a second end plate 270, a first bus bar 242, a second bus bar 252, and four gas passage members 280. The first end plate 210, the insulating section 220, the end separator 230, the first terminal plate 240, the power generation block 100, the second terminal plate 250, the second plate 260, and the second end plate 270 have rectangular outer shapes of approximately the same size, and are arranged overlapping in this order in a predetermined arrangement direction (vertical direction).

[0020] As shown in Figures 1 and 4, the fuel cell stack 10 has bolt holes BH near each of the four corners, penetrating from the first end plate 210 to the second end plate 270. A bolt B is inserted into each bolt hole BH. A nut N is screwed onto both ends of each bolt B. These bolts B and nuts N fasten the members from the first end plate 210 to the second end plate 270 together. As shown in Figures 2 to 4, the first plate 232 is supported by the end separator 230, and the four gas passage members 280 are connected to the second end plate 270.

[0021] The power generation block 100 is composed of a plurality of (seven in this embodiment) power generation units 100U arranged side by side in a predetermined arrangement direction (vertical direction) as shown in Figures 2 to 4. Among the power generation units 100U, two adjacent power generation units 100U arranged at any position (the second and third from the top in this embodiment) are referred to as the first power generation unit 100A and the second power generation unit 100B. The first power generation unit 100A is an example of the first unit in the claims, and the second power generation unit 100B is an example of the second unit in the claims.

[0022] (First end plate 210) The first end plate 210 is a member formed by pressing (bending) a single plate-shaped member, and is formed of a conductive material such as stainless steel. As shown in Figs. 1 to 4, the first end plate 210 includes a rectangular frame-shaped flat portion 211 having a through hole 212 near the center, and an outer convex portion 213 and an inner convex portion 214 that protrude from the flat portion 211 in the opposite direction to the insulating portion 220 (upward in Fig. 2). The flat portion 211 has holes that form the bolt holes BH described above. The outer convex portion 213 protrudes from the outer periphery of the flat portion 211. The outer convex portion 213 is formed around the entire circumference of the outer periphery of the flat portion 211. The inner convex portion 214 protrudes from the inner periphery of the flat portion 211. The inner convex portion 214 is formed around the entire circumference of the inner periphery of the flat portion 211.

[0023] (insulating part 220) Insulating section 220 is a rectangular frame-shaped member having a through hole near the center, and is formed of, for example, an insulating material. Insulating section 220 is sandwiched between first end plate 210 and end separator 230 as shown in Fig. 2, so that insulation between first end plate 210 and end separator 230 is ensured.

[0024] (Terminal separator 230) As shown in FIGS. 2 to 4, end separator 230 is a rectangular frame-like member having a through hole 231 near the center, and is made of, for example, metal.

[0025] (First Plate 232) The first plate 232 is a rectangular flat member and is made of a conductive material such as stainless steel. As shown in Figures 2 to 4, the first plate 232 is joined to the periphery of the through hole 231 in the end separator 230 by, for example, welding. The end separator 230 and the first plate 232 separate the power generation block 100 from the external space of the fuel cell stack 10.

[0026] The first plate 232 is connected to an interconnector 190 (described below) provided in a power generating unit 100U arranged at one end (the upper end in Figure 2) of the multiple power generating units 100U that make up the power generating block 100, via a connecting member having the same structure as the anode current collecting member 144 (described below), thereby electrically connecting the power generating unit 100U and the first plate 232.

[0027] (First terminal plate 240) The first terminal plate 240 is a rectangular frame-shaped member having a through hole 241 near the center, and is made of a conductive material such as ferritic stainless steel that forms an alumina oxide coating on its surface. The first terminal plate 240 is electrically connected to a power generating unit 100U arranged at one end (the upper end in FIG. 2) of the multiple power generating units 100U that make up the power generating block 100, via a first plate 232 and an end separator 230. One end (the right end in FIG. 2) of the first terminal plate 240 protrudes laterally from the power generating block 100.

[0028] (2nd terminal plate 250) The second terminal plate 250 is a rectangular plate-like member, and is made of a conductive material such as ferritic stainless steel that forms an alumina oxide coating on its surface. The second terminal plate 250 is electrically connected to the power generating unit 100U arranged at the other end (the lower end in FIG. 2) of the multiple power generating units 100U that make up the power generating block 100. One end (the right end in FIG. 2) of the second terminal plate 250 protrudes laterally from the power generating block 100.

[0029] (First bus bar 242 and second bus bar 252) The first bus bar 242 and the second bus bar 252 are both flat plate-shaped members made of a conductive material. The lower surface of the first bus bar 242 is connected to the upper surface of the first terminal plate 240 via a welded portion 243. The first bus bar 242 functions as a positive output terminal of the fuel cell stack 10. The lower surface of the second bus bar 252 is connected to the upper surface of the second terminal plate 250 via a welded portion 253. The second bus bar 252 functions as a negative output terminal of the fuel cell stack 10.

[0030] (Second plate 260) The second plate 260 is a rectangular flat member and is made of, for example, an insulating material. The peripheral portion of the second plate 260 is sandwiched between the second terminal plate 250 and the second end plate 270, thereby ensuring insulation between the second terminal plate 250 and the second end plate 270.

[0031] (Second end plate 270) The second end plate 270 is a member formed by pressing (bending) a single plate-shaped member, and is formed of a conductive material such as stainless steel. The second end plate 270 includes a rectangular frame-shaped flat portion 271 having a through hole 272 near the center, and an outer convex portion 273 and an inner convex portion 274 that protrude from the flat portion 271 in the opposite direction to the second terminal plate 250 (downward in FIG. 2). The flat portion 271 has holes that form the bolt holes BH described above. The outer convex portion 273 protrudes from the outer periphery of the flat portion 271. The outer convex portion 273 is formed around the entire circumference of the outer periphery of the flat portion 271. The inner convex portion 274 protrudes from the inner periphery of the flat portion 271. The inner convex portion 274 is formed around the entire circumference of the inner periphery of the flat portion 271.

[0032] (Manifolds 311, 312, 321, 322) 1, 2, and 3, the fuel cell stack 10 has four holes that penetrate from the power generation block 100 to the second end plate 270. The four holes are an oxidant gas supply manifold 311, an oxidant gas discharge manifold 312, a fuel gas supply manifold 321, and a fuel gas discharge manifold 322, respectively.

[0033] 2, the oxidant gas supply manifold 311 is a gas flow path that supplies the oxidant gas OG introduced from outside the fuel cell stack 10 to an air chamber 313 (described later) of each power generating unit 100U. The oxidant gas discharge manifold 312 is a gas flow path that discharges the oxidant off-gas OOG discharged from the air chamber 313 of each power generating unit 100U to the outside of the fuel cell stack 10. For example, air is used as the oxidant gas OG. The oxidant gas supply manifold 311 and the oxidant gas discharge manifold 312 are disposed on opposite sides of each other with the air chamber 313 in between.

[0034] As shown in Fig. 3, the fuel gas supply manifold 321 is a gas flow path that supplies the fuel gas FG introduced from outside the fuel cell stack 10 to a fuel chamber 323 (described later) of each power generating unit 100U. The fuel gas discharge manifold 322 is a gas flow path that discharges the fuel off-gas FOG discharged from the fuel chamber 323 of each power generating unit 100U to the outside of the fuel cell stack 10. As the fuel gas FG, for example, a hydrogen-rich gas obtained by reforming city gas is used. The fuel gas supply manifold 321 and the fuel gas discharge manifold 322 are arranged on opposite sides of the fuel chamber 323.

[0035] (Gas passage member 280) As shown in Figs. 1 to 3, each of the four gas passage members 280 includes a main body portion 281 and a flange portion 282. The main body portion 281 is formed with a gas through hole 283 that penetrates in the vertical direction. The flange portion 282 is provided so as to protrude outward from the other end (the lower end in Fig. 2) of the main body portion 281. The flange portion 282 has a plurality of bolt holes 284. A bolt (not shown) for connecting the fuel cell stack 10 to an external device is inserted into each bolt hole 284. One end (the upper end in Figs. 2 and 3) of the main body portion 281 included in each of the four gas passage members 280 is joined to the second end plate 270 by, for example, welding, and the gas through holes 283 are connected to the manifolds 311, 312, 321, and 322, respectively. A gas pipe for supplying or discharging gas is connected to each of the main body portions 281 (not shown).

[0036] (Overall configuration of 100U generating unit) FIG. 5 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent generating units 100U at the same position as the cross-section shown in FIG. 2. FIG. 6 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent generating units 100U at the same position as the cross-section shown in FIG. 3. In FIG. 5 and FIG. 6, a first generating unit 100A and a second generating unit 100B are shown among the multiple generating units 100U. As shown in FIG. 5 and FIG. 6, the generating unit 100U includes a single cell 110, a single cell separator 120, an air electrode frame 130, an anode frame 140, an anode current collecting member 144, two interconnectors 190, two IC separators 180, and a glass seal portion 96. One IC separator 180, the air electrode frame 130, the single cell separator 120, the anode frame 140, and the other IC separator 180 are arranged in this order. The unit cell 110 is supported by a unit cell separator 120 , the interconnector 190 is supported by an IC separator 180 , and the anode current collecting member 144 is disposed between the unit cell 110 and the interconnector 190 .

[0037] 5 and 6, the IC separator 180 and the interconnector 190 are shared by two adjacent power generating units 100U. However, as shown in FIG. 2, the power generating unit 100U located at the other end (the lower end in FIG. 2) of the multiple power generating units 100U does not have the IC separator 180 and interconnector 190 adjacent to the fuel electrode frame 140, and the second terminal plate 250 overlaps the fuel electrode frame 140.

[0038] (single cell 110) The unit cell 110 includes an electrolyte layer 112, an air electrode 114, an anode 116, and a reaction prevention layer 118. As shown in Figures 5 and 6, the air electrode 114, the reaction prevention layer 118, the electrolyte layer 112, and the anode 116 are arranged in this order. The unit cell 110 of this embodiment is an anode-supported unit cell in which the anode 116 supports the other layers (electrolyte layer 112, air electrode 114, and reaction prevention layer 118) constituting the unit cell 110.

[0039] The electrolyte layer 112 is a rectangular flat member, and has one surface (upper surface in Figs. 5 and 6) on which the air electrode 114 is disposed, and the other surface (lower surface in Figs. 5 and 6) on which the fuel electrode 116 is disposed and parallel to the first surface. The electrolyte layer 112 is a layer containing a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). The air electrode 114 is a layer having a rectangular shape smaller than that of the electrolyte layer 112, and contains, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The fuel electrode 116 is a layer having a rectangular shape of approximately the same size as the electrolyte layer 112, and contains, for example, Ni (nickel), a cermet made of Ni and ceramic particles, a Ni-based alloy, or the like. The reaction prevention layer 118 is a layer having a rectangular shape of approximately the same size as the air electrode 114, and contains, for example, GDC (gadolinium-doped ceria). The reaction prevention layer 118 has the function of suppressing the reaction of an element (e.g., Sr) diffused from the air electrode 114 with an element (e.g., Zr) contained in the electrolyte layer 112 to produce a highly resistive substance (e.g., SrZrO3).

[0040] (Separator for single cell 120) As shown in Figs. 5 and 6, the single cell separator 120 is a rectangular frame-like member having a substantially rectangular through hole 121 near the center, and is made of, for example, metal. The plate thickness of the single cell separator 120 is relatively thin, for example, 0.05 mm or more and 0.2 mm or less. The peripheral portion of the through hole 121 in the single cell separator 120 is joined to the peripheral portion of one surface of the electrolyte layer 112 (the surface on which the air electrode 114 is arranged: the upper surface in Figs. 5 and 6) by a connecting member 124. The connecting member 124 is made of, for example, brazing material (Ag brazing). The single cell separator 120 is formed with a through hole 125 that is a hole that penetrates in the vertical direction and constitutes a part of the manifolds 311, 312, 321, and 322. The through hole 125 is an example of a first through hole in the claims.

[0041] (Air electrode frame 130) 5 and 6, the air electrode frame 130 is a rectangular frame-like member having a substantially rectangular through-hole 131 near the center, and is made of, for example, mica. The thickness of the air electrode frame 130 is preferably 0.5 mm or more and 5 mm or less. As shown in FIG. 5, the air electrode frame 130 has an oxidant gas supply communication passage 132 that connects the oxidant gas supply manifold 311 and the air chamber 313, and an oxidant gas discharge communication passage 133 that connects the air chamber 313 and the oxidant gas discharge manifold 312.

[0042] (fuel electrode frame 140) 5 and 6, the fuel electrode frame 140 is a rectangular frame-like member having a substantially rectangular through-hole 141 near the center, and is made of, for example, metal. As shown in Fig. 6, the fuel electrode frame 140 has a fuel gas supply communication channel 142 that connects the fuel gas supply manifold 321 and the fuel chamber 323, and a fuel gas discharge communication channel 143 that connects the fuel chamber 323 and the fuel gas discharge manifold 322.

[0043] (IC separator 180) 5 and 6, IC separator 180 is a rectangular frame-like member having through hole 181 near the center, and is made of, for example, metal. IC separator 180 is formed with through hole 185, which is a hole that penetrates in the vertical direction and constitutes part of manifolds 311, 312, 321, and 322. Through hole 185 is an example of a second through hole in the claims.

[0044] (Interconnector 190 and anode current collecting member 144) 5 and 6, the interconnector 190 includes a rectangular flat plate portion 191, a plurality of plate-shaped air electrode current collectors 192 protruding from one surface of the flat plate portion 191 toward the air electrode 114, and a coating layer 193. The flat plate portion 191 and the air electrode current collector 192 are conductive and made of a metal (e.g., ferritic stainless steel). The coating layer 193 is conductive and is disposed so as to cover the surface of the air electrode current collector 192 and the surface of the flat plate portion 191 on which the air electrode current collector 192 is disposed. The flat plate portion 191 is joined to the periphery of the through hole 181 in the IC separator 180 by, for example, welding.

[0045] The anode current collecting member 144 is a member that connects the interconnector 190 and the anode 116, and is formed of a conductive material such as nickel, a nickel alloy, or stainless steel. As shown in Figures 5 and 6, the anode current collecting member 144 includes an interconnector facing portion 146, an electrode facing portion 145 parallel to the interconnector facing portion 146, and a connecting portion 147 that connects the electrode facing portion 145 and the interconnector facing portion 146, and has a U-shape overall. The electrode facing portion 145 is in contact with the anode 116, and the interconnector facing portion 146 is in contact with a flat portion 191 of the interconnector 190.

[0046] As described above, the interconnector 190 is shared by two adjacent power generating units 100U. More specifically, as shown in Fig. 5 and Fig. 6, the air electrode current collecting portion 192 is joined to the air electrode 114 of the unit cell 110 provided in one of the two adjacent power generating units 100U via a conductive bonding material 196 made of, for example, a spinel-type oxide, and is thus electrically connected to the air electrode 114. The flat plate portion 191 is electrically connected to the anode 116 of the unit cell 110 provided in the other of the two adjacent power generating units 100U via an anode current collecting member 144. This ensures electrical continuity between the two adjacent power generating units 100U.

[0047] However, as described above, the power generating unit 100U located at the other end (the lower end in FIG. 2) of the multiple power generating units 100U does not have an interconnector 190 on the anode 116 side. The anode 116 included in this power generating unit 100U is connected to the second terminal plate 250 via the anode current collecting member 144.

[0048] A spacer 149 made of, for example, mica is disposed between the electrode facing portion 145 and the interconnector facing portion 146. Therefore, the anode current collecting member 144 follows the deformation of the power generating unit 100U caused by temperature cycles and reactant gas pressure fluctuations, and the electrical connection between the anode 116 and the interconnector 190 (or second terminal plate 250) via the anode current collecting member 144 is maintained well.

[0049] (Glass seal part 96) The glass seal portion 96 is provided between the single cell separator 120 and the IC separator 180 which face each other in the vertical direction with the air electrode frame 130 in between. The glass seal portion 96 is annular and is disposed so as to surround each of the fuel gas supply manifold 321 and the fuel gas exhaust manifold 322. The glass seal portion 96 suppresses leakage of the fuel gas FG or fuel off-gas FOG from the fuel gas supply manifold 321 and the fuel gas exhaust manifold 322 via the interface between the air electrode frame 130 and the single cell separator 120 or the interface between the air electrode frame 130 and the IC separator 180.

[0050] (Air chamber 313 and fuel chamber 323) 5 and 6, the space partitioned by the single cell separator 120, the single cell 110, the air electrode frame 130, the IC separator 180, and the interconnector 190 faces the air electrode 114 and serves as an air chamber 313 through which the oxidant gas OG flows. The air electrode frame 130 partitions the air chamber 313 from the outside space all around, and seals the gap between the single cell separator 120 and the IC separator 180, preventing gas from leaking from the air chamber 313 to the outside space.

[0051] The space partitioned by the single cell separator 120, the single cell 110, the fuel electrode frame 140, the IC separator 180, and the interconnector 190 faces the fuel electrode 116 and serves as a fuel chamber 323 through which the fuel gas FG flows. The fuel electrode frame 140 partitions the entire periphery of the fuel chamber 323 from the external space, and seals the gap between the single cell separator 120 and the IC separator 180, thereby preventing gas from leaking from the fuel chamber 323 to the external space.

[0052] The single cell separator 120 separates the air chamber 313 and the fuel chamber 323, and suppresses gas leakage (cross leakage) from the air electrode 114 side to the fuel electrode 116 side or from the fuel electrode 116 side to the air electrode 114 side around the single cell 110. In addition, the IC separator 180 and the interconnector 190 suppress gas leakage between adjacent power generating units 100U.

[0053] A-2. Operation of fuel cell stack 10: As shown in FIGS. 2 and 5, the oxidizing gas OG is supplied to the oxidizing gas supply manifold 311 via a gas piping (not shown) and a gas passage member 280, and is supplied to the air chamber 313 via the oxidizing gas supply communicating passage 132.

[0054] As shown in FIGS. 3 and 6, the fuel gas FG is supplied to a fuel gas supply manifold 321 via a gas piping (not shown) and a gas passage member 280, and is supplied to the fuel chamber 323 via a fuel gas supply communication passage 142.

[0055] When the oxidant gas OG is supplied to the air chamber 313 of each power generating unit 100U and the fuel gas FG is supplied to the fuel chamber 323, power is generated in the single cell 110 by an electrochemical reaction between the oxidant gas OG and the fuel gas FG. This power generating reaction is an exothermic reaction. As described above, the interconnector 190 is shared by two adjacent power generating units 100U, and the interconnector 190 ensures electrical continuity between the two adjacent power generating units 100U. That is, the multiple power generating units 100U included in the fuel cell stack 10 are electrically connected in series. In addition, the second terminal plate 250 is electrically connected to the power generating unit 100U located at the other end (lower end of FIG. 2) of the multiple power generating units 100U, and the first terminal plate 240 is electrically connected to the power generating unit 100U located at one end (upper end of FIG. 2). As a result, electrical energy generated in each power generating unit 100U is extracted from bus bars 242, 252 that are connected to terminal plates 240, 250 and function as output terminals of the fuel cell stack 10. Since SOFCs generate power at relatively high temperatures (e.g., 700°C to 1000°C), the fuel cell stack 10 may be heated by a heater (not shown) after startup until the high temperature can be maintained by the heat generated by power generation.

[0056] 2 and 5, the oxidant off-gas OOG discharged from the air chamber 313 of each power generating unit 100U to the oxidant gas discharge manifold 312 via the oxidant gas discharge communication passage 133 is discharged to the outside of the fuel cell stack 10 through the internal space of the main body 281. Also, as shown in Figures 3 and 6, the fuel off-gas FOG discharged from the fuel chamber 323 of each power generating unit 100U to the fuel gas discharge manifold 322 via the fuel gas discharge communication passage 143 is discharged to the outside of the fuel cell stack 10 through the internal space of the main body 281.

[0057] A-3. Peripheral configuration of joints in fuel cell stack 10: (Peripheral configuration of IC separator 180 and fuel electrode frame 140) As shown in Figs. 5 and 6, the anode frame 140 has an overlapping portion DP1 which is a portion that overlaps with the IC separator 180 in the Z-axis direction. The IC separator 180 and the anode frame 140 are joined by a welded portion 182. The welded portion 182 joins the overlapping portion DP1 in the anode frame 140 to a portion of the IC separator 180 that faces the overlapping portion DP1 in the Z-axis direction. The welded portion 182 is formed by, for example, laser welding. The IC separator 180 is an example of a first member in the claims, the anode frame 140 is an example of a second member in the claims, and the welded portion 182 is an example of a joint in the claims.

[0058] Fig. 7 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at the position VII-VII in Fig. 6. Fig. 7 shows the peripheral configuration of the welded portion 182 at the position of the fuel gas supply manifold 321 as viewed in the Z axis direction. The overlapping portion DP1 has an overlapping portion contour line DO1 that is a ring-shaped contour line as viewed in the Z axis direction. The welded portion 182 has a joint contour line BO1 that is a contour line closer to the overlapping portion contour line DO1 as viewed in the Z axis direction. Such a combination of the welded portion 182 and the overlapping portion contour line DO1 is called a combination CM1.

[0059] The combination CM1 satisfies the following conditions (1) to (3). Condition (1): When viewed in the Z-axis direction, the joint contour line BO1, which is the contour line of the welded portion 182, is similar in shape to the overlapping portion contour line DO1. Condition (2): When viewed in the Z-axis direction, the joint contour line BO1 surrounds the overlapping contour line DO1. Condition (3): When viewed in the Z-axis direction, the center BC1 of the joint portion contour line and the center DC1 of the overlapping portion contour line are in different positions.

[0060] 5 and 6, the first generating unit 100A and the second generating unit 100B each have an IC separator 180 and an anode frame 140, and each have a combination CM1. At least a part of the overlapping portion contour line DO1 of the combination CM1 in the first generating unit 100A and at least a part of the overlapping portion contour line DO1 of the combination CM1 in the second generating unit 100B overlap with each other in the Z-axis direction. The center BC1 of the joint contour line of the combination CM1 in the first generating unit 100A and the center BC1 of the joint contour line of the combination CM1 in the second generating unit 100B are in different positions from each other when viewed in the Z-axis direction.

[0061] In this embodiment, the IC separator 180 and the fuel electrode frame 140 have a total of four combinations CM1, since they are arranged around the manifolds 311, 312, 321, and 322. Of these four combinations CM1, the distance between the center BC1 of the joint contour line and the center DC1 of the overlapping contour line as viewed in the Z-axis direction of one combination CM1 (for example, the combination CM1 arranged around the oxidizer gas supply manifold 311) is different from the distance between the center BC1 of the joint contour line and the center DC1 of the overlapping contour line as viewed in the Z-axis direction of another combination CM1 (for example, the combination CM1 arranged around the oxidizer gas discharge manifold 312).

[0062] (Peripheral configuration of fuel electrode frame 140 and single cell separator 120) As shown in Figs. 5 and 6, the single cell separator 120 has an overlapping portion DP2 which is a portion that overlaps with the anode frame 140 in the Z-axis direction. The anode frame 140 and the single cell separator 120 are joined by a welded portion 122. The welded portion 122 joins the overlapping portion DP2 in the single cell separator 120 to a portion of the anode frame 140 that faces the overlapping portion DP2 in the Z-axis direction. The welded portion 122 is formed by, for example, laser welding. The anode frame 140 is an example of a first member in the claims, the single cell separator 120 is an example of a second member in the claims, and the welded portion 122 is an example of a joint in the claims.

[0063] Fig. 8 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at the position VIII-VIII in Fig. 6. Fig. 8 shows the peripheral configuration of the welded portion 122 at the position of the fuel gas supply manifold 321 as viewed in the Z axis direction. The overlapping portion DP2 has an overlapping portion contour line DO2 that is a ring-shaped contour line as viewed in the Z axis direction. The welded portion 122 has a joint contour line BO2 that is a contour line closer to the overlapping portion contour line DO2 as viewed in the Z axis direction. Such a combination of the welded portion 122 and the overlapping portion contour line DO2 is referred to as a combination CM2.

[0064] The combination CM2 satisfies the following conditions (1) to (3). Condition (1): When viewed in the Z-axis direction, the joint contour line BO2, which is the contour line of the welded portion 122, is similar in shape to the overlapping portion contour line DO2. Condition (2): When viewed in the Z-axis direction, the joint contour line BO2 surrounds the overlapping contour line DO2. Condition (3): When viewed in the Z-axis direction, the center BC2 of the joint portion contour line and the center DC2 of the overlapping portion contour line are in different positions.

[0065] 5 and 6, the first power generating unit 100A and the second power generating unit 100B each have an anode frame 140 and a single cell separator 120, and each have a combination CM2. At least a part of the overlapping portion contour line DO2 of the combination CM2 in the first power generating unit 100A and at least a part of the overlapping portion contour line DO2 of the combination CM2 in the second power generating unit 100B overlap with each other in the Z-axis direction. The center BC2 of the joint contour line of the combination CM2 in the first power generating unit 100A and the center BC2 of the joint contour line of the combination CM2 in the second power generating unit 100B are in different positions from each other when viewed in the Z-axis direction.

[0066] In the fuel electrode frame 140 and the single cell separator 120 of this embodiment, there are a total of four combinations CM2 because they are arranged around the manifolds 311, 312, 321, and 322. Of these four combinations CM2, the distance between the center BC2 of the joint contour line and the center DC2 of the overlapping contour line when viewed in the Z axis direction of one combination CM2 (for example, the combination CM2 arranged around the oxidant gas supply manifold 311) is different from the distance between the center BC2 of the joint contour line and the center DC2 of the overlapping contour line when viewed in the Z axis direction of another combination CM2 (for example, the combination CM2 arranged around the oxidant gas discharge manifold 312).

[0067] (Peripheral configuration of the single cell separator 120 and the IC separator 180) As shown in Figures 5 and 6, the IC separator 180 has an overlapping portion DP3 which is a portion that overlaps with the single cell separator 120 in the Z-axis direction. The single cell separator 120 and the IC separator 180 are joined by a glass seal portion 96. The glass seal portion 96 joins the overlapping portion DP3 in the IC separator 180 to a portion of the single cell separator 120 that faces the overlapping portion DP3 in the Z-axis direction. The single cell separator 120 is an example of a first member in the claims, the IC separator 180 is an example of a second member in the claims, and the glass seal portion 96 is an example of a joint portion in the claims.

[0068] Fig. 9 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at the position IX-IX in Fig. 6. Fig. 9 shows the peripheral configuration of the glass seal portion 96 at the position of the fuel gas supply manifold 321 as viewed in the Z axis direction. The overlapping portion DP3 has an overlapping portion contour line DO3 that is a ring-shaped contour line as viewed in the Z axis direction. The glass seal portion 96 has a joint portion contour line BO3 that is a contour line closer to the overlapping portion contour line DO3 as viewed in the Z axis direction. Such a combination of the glass seal portion 96 and the overlapping portion contour line DO3 is referred to as a combination CM3.

[0069] The combination CM3 satisfies the following conditions (1) to (3). Condition (1): When viewed in the Z-axis direction, the joint portion contour line BO3, which is the contour line of the glass seal portion 96, is similar in shape to the overlap portion contour line DO3. Condition (2): When viewed in the Z-axis direction, the joint contour line BO3 surrounds the overlapping contour line DO3. Condition (3): When viewed in the Z-axis direction, a center BC3 of the joint portion contour line and a center DC3 of the overlap portion contour line are in different positions.

[0070] In this embodiment, the overlapping portion contour line DO3 coincides with a through hole surrounding portion 126, which is a portion surrounding the through hole 125 in the single cell separator 120, when viewed in the Z axis direction. The glass seal portion 96 surrounds both the through hole surrounding portion 126 and the through hole surrounding portion 186. It is sufficient that at least a portion of the overlapping portion contour line DO3 coincides with at least a portion of the through hole surrounding portion 126 when viewed in the Z axis direction. The through hole surrounding portion 126 is an example of a first through hole surrounding portion in the claims.

[0071] 5 and 6, the first generating unit 100A and the second generating unit 100B each have a single cell separator 120 and an IC separator 180, and each have a combination CM3. At least a part of the overlapping portion contour line DO3 of the combination CM3 in the first generating unit 100A and at least a part of the overlapping portion contour line DO3 of the combination CM3 in the second generating unit 100B overlap with each other in the Z-axis direction. The center BC3 of the joint contour line of the combination CM3 in the first generating unit 100A and the center BC3 of the joint contour line of the combination CM3 in the second generating unit 100B are in different positions from each other when viewed in the Z-axis direction.

[0072] In the single cell separator 120 and the IC separator 180 of this embodiment, there are two combinations CM3 in total because they are arranged around the manifolds 321, 322. Of these two combinations CM3, the distance between the center BC3 of the joint contour line and the center DC3 of the overlapping contour line in the Z-axis direction of one combination CM3 (for example, the combination CM3 arranged around the fuel gas supply manifold 321) is different from the distance between the center BC3 of the joint contour line and the center DC3 of the overlapping contour line in the Z-axis direction of the other combination CM3 (for example, the combination CM3 arranged around the fuel gas discharge manifold 322).

[0073] (Peripheral configuration of IC separator 180 and interconnector 190) As shown in Figs. 5 and 6, the interconnector 190 has an overlapping portion DP4 which is a portion overlapping with the IC separator 180 in the Z-axis direction. The IC separator 180 and the interconnector 190 are joined by a welded portion 184. The welded portion 184 joins the overlapping portion DP4 in the interconnector 190 to a portion of the IC separator 180 which faces the overlapping portion DP4 in the Z-axis direction. The welded portion 184 is formed by, for example, laser welding. The IC separator 180 is an example of a first member in the claims, the interconnector 190 is an example of a second member in the claims, and the welded portion 184 is an example of a joint in the claims.

[0074] Fig. 10 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at the position XX in Fig. 6. Fig. 10 shows the peripheral configuration of the welded portion 184 as viewed in the Z-axis direction. The overlapping portion DP4 has an overlapping portion contour line DO4, which is a ring-shaped contour line, as viewed in the Z-axis direction. The welded portion 184 has a joint contour line BO4, which is a contour line closer to the overlapping portion contour line DO4 as viewed in the Z-axis direction. The combination of the welded portion 184 and the overlapping portion contour line DO4 is referred to as a combination CM4.

[0075] The combination CM4 satisfies the following conditions (1) to (3). Condition (1): When viewed in the Z-axis direction, the joint contour line BO4, which is the contour line of the welded portion 184, is similar in shape to the overlapping portion contour line DO4. Condition (2): When viewed in the Z-axis direction, the joint contour line BO4 surrounds the overlapping contour line DO4. Condition (3): When viewed in the Z-axis direction, a center BC4 of the joint portion contour line and a center DC4 of the overlap portion contour line are in different positions.

[0076] 5 and 6, the first generating unit 100A and the second generating unit 100B each have an IC separator 180 and an interconnector 190, and each have a combination CM4. At least a part of the overlapping portion contour line DO4 of the combination CM4 in the first generating unit 100A and at least a part of the overlapping portion contour line DO4 of the combination CM4 in the second generating unit 100B overlap with each other in the Z-axis direction. A center BC4 of the joint contour line of the combination CM4 in the first generating unit 100A and a center BC4 of the joint contour line of the combination CM4 in the second generating unit 100B are in different positions from each other when viewed in the Z-axis direction.

[0077] (Peripheral configuration of first terminal plate 240 and first bus bar 242) 2, first bus bar 242 has an overlapping portion DP5 which is a portion overlapping with first terminal plate 240 in the Z-axis direction. First terminal plate 240 and first bus bar 242 are joined by a welded portion 243. Welded portion 243 joins overlapping portion DP5 of first bus bar 242 to a portion of first terminal plate 240 facing overlapping portion DP5 in the Z-axis direction. Welded portion 243 is formed by, for example, laser welding. First terminal plate 240 is an example of a first member in the claims, first bus bar 242 is an example of a second member in the claims, and welded portion 243 is an example of a joint in the claims.

[0078] Fig. 11 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at the position XI-XI in Fig. 2. Fig. 11 shows the peripheral configuration of the welded portion 243 as viewed in the Z-axis direction. The overlapping portion DP5 has an overlapping portion contour line DO5, which is a ring-shaped contour line, as viewed in the Z-axis direction. The welded portion 243 also has a joint contour line BO5, which is a contour line closer to the overlapping portion contour line DO5 as viewed in the Z-axis direction. The combination of the welded portion 243 and the overlapping portion contour line DO5 is referred to as a combination CM5.

[0079] The combination CM5 satisfies the following conditions (1) to (3). Condition (1): When viewed in the Z-axis direction, the joint contour line BO5, which is the contour line of the welded portion 243, is similar in shape to the overlapping portion contour line DO5. Condition (2): When viewed in the Z-axis direction, the overlapping portion contour line DO5 surrounds the joint portion contour line BO5. Condition (3): When viewed in the Z-axis direction, a center BC5 of the joint portion contour line and a center DC5 of the overlap portion contour line are in different positions.

[0080] Although the peripheral configuration of first terminal plate 240 and first bus bar 242 has been described in detail above, second terminal plate 250 and second bus bar 252 basically have the same configuration.

[0081] In addition, in each of the above-mentioned combinations CM1 to CM5 (hereinafter simply referred to as "combination CM"), the distance between the center BC1 to BC5 of the joint contour line (hereinafter simply referred to as "center BC of the joint contour line") and the center DC1 to DC5 of the overlapping portion contour line (hereinafter simply referred to as "center DC of the overlapping portion contour line") when viewed in the Z-axis direction is 10 μm or more.

[0082] In each of the above combinations CM, the longest distance between the joint contour lines BO1 to BO5 (hereinafter simply referred to as the "joint contour line BO") and the overlap contour lines DO1 to DO5 (hereinafter simply referred to as the "overlap contour line DO") in the Z-axis direction is 1.01 times or more the shortest distance between the joint contour line BO and the overlap contour line DO in the Z-axis direction. Note that the "longest distance between the joint contour line BO and the overlap contour line DO in the Z-axis direction" refers to the longest of the shortest distances when connecting the shortest distances from each point on the overlap contour line DO to the joint contour line BO. Similarly, the "shortest distance between the joint contour line BO and the overlap contour line DO in the Z-axis direction" refers to the shortest of the shortest distances when connecting the shortest distances from each point on the overlap contour line DO to the joint contour line BO.

[0083] Note that the joint contour BO being "similar" in shape to the overlap contour DO includes not only a configuration in which they are strictly similar, but also, for example, a configuration in which the joint contour BO and the overlap contour DO are both circular when viewed in the Z-axis direction, or a configuration in which the joint contour BO and the overlap contour DO are both rectangular, etc. Also, the "center" in the terms center BC of the joint contour and center DC of the overlap contour specifically means the centroid of the joint contour BO and the overlap contour DO when viewed in the Z-axis direction.

[0084] A-4. Advantages of this embodiment: As described above, the fuel cell stack 10 of this embodiment includes the first member (the IC separator 180, the fuel electrode frame 140, the single cell separator 120, the IC separator 180, and the first terminal plate 240), the second member (the fuel electrode frame 140, the single cell separator 120, the IC separator 180, the interconnector 190, and the first bus bar 242) having overlapping parts DP1 to DP5 (hereinafter simply referred to as "overlapping parts DP") that are parts that overlap with the first member in the Z-axis direction, and joints that join the first member and the second member, and that join the overlapping part DP in the second member to a part of the first member that faces the overlapping part DP in the Z-axis direction (the welded parts 182, the welded parts 122, the glass seal part 96, the welded parts 184, and the welded parts 243). The overlapping part DP has at least one annular contour line DO as viewed in the Z-axis direction. The fuel cell stack 10 includes a combination CM of a joint and an overlapping portion contour DO, which satisfies the following conditions: when viewed in the Z-axis direction, the joint contour line BO, which is the contour line of the joint, is similar in shape to the overlapping portion contour line DO, when viewed in the Z-axis direction, one of the joint contour line BO and the overlapping portion contour line DO surrounds the other of the joint contour line BO and the overlapping portion contour line DO, and when viewed in the Z-axis direction, the center BC of the joint contour line and the center DC of the overlapping portion contour line are at different positions.

[0085] In the fuel cell stack 10, in the combination CM of the joint and the overlapping portion contour line DO, the center BC of the joint contour line as viewed in the Z-axis direction and the center DC of the overlapping portion contour line are different in position, so that it is possible to make the stress applied to the joint non-uniform when stress is applied to the first member or the second member. Therefore, the portion of the joint to which a relatively large stress is applied becomes the initial damage portion, but the portion other than the initial damage portion does not receive as much stress as the initial damage portion, so that it is possible to extend the life of the joint from the occurrence of initial damage until the entire joint is damaged.

[0086] In the fuel cell stack 10 of this embodiment, the distance between the center BC of the joint contour line and the center DC of the overlapping portion contour line in the combined CM as viewed in the Z axis direction is 10 μm or more. According to the fuel cell stack 10, since the distance between the center BC of the joint contour line and the center DC of the overlapping portion contour line in the combined CM as viewed in the Z axis direction is 10 μm or more, it is possible to more effectively extend the lifespan of the joint from when initial damage occurs until the entire joint is damaged.

[0087] Furthermore, in the fuel cell stack 10 of this embodiment, in the combination CM, the longest distance between the joint contour line BO and the overlapping contour line DO when viewed in the Z axis direction is 1.01 times or more the shortest distance between the joint contour line BO and the overlapping contour line DO when viewed in the Z axis direction. According to the fuel cell stack 10, since the longest distance between the joint contour line BO and the overlapping contour line DO when viewed in the Z axis direction is 1.01 times or more the shortest distance between the joint contour line BO and the overlapping contour line DO when viewed in the Z axis direction, it is possible to more effectively extend the lifespan of the joint from the occurrence of initial damage until the entire joint is damaged.

[0088] The fuel cell stack 10 of this embodiment further includes a plurality of unit cells 110 stacked in the Z-axis direction, and a fuel gas supply manifold 321 is formed to supply gas to each of the unit cells 110, the unit cell separator 120 is formed with a through hole 125 constituting a part of the fuel gas supply manifold 321, the IC separator 180 is formed with a through hole 185 constituting a part of the fuel gas supply manifold 321, at least a part of the overlapping portion contour line DO coincides with at least a part of the through hole surrounding portion 126 that is a portion surrounding the through hole 125 in the unit cell separator 120 as viewed in the Z-axis direction, and the joint portion is a glass seal portion 96 that surrounds each of the through hole 125 and the through hole 185. According to the fuel cell stack 10, the position of the center BC of the overlapping portion contour line and the center of the contour line of the glass seal portion 96 differ from each other as viewed in the Z-axis direction, and therefore the internal configuration of the fuel gas supply manifold 321 becomes non-uniform. This makes it easier for turbulence to occur in the gas flowing through the fuel gas supply manifold 321, making it possible to supply the gas evenly to each of the plurality of unit cells 110.

[0089] In addition, in the fuel cell stack 10 of this embodiment, a first power generating unit 100A and a second power generating unit 100B each having a first component (IC separator 180, fuel electrode frame 140, single cell separator 120, IC separator 180) and a second component (fuel electrode frame 140, single cell separator 120, IC separator 180, interconnector 190) are stacked in the Z-axis direction, and the first power generating unit 100A and the second power generating unit 100B each have a combination CM, and at least a portion of the overlapping contour line DO of the combination CM in the first power generating unit 100A and at least a portion of the overlapping contour line DO of the combination CM in the second power generating unit 100B overlap with each other in the Z-axis direction, and the center BC of the joint contour line of the combination CM in the first power generating unit 100A and the center BC of the joint contour line of the combination CM in the second power generating unit 100B are in different positions from each other when viewed in the Z-axis direction. In the fuel cell stack 10, the center BC of the joint contour of the first generating unit 100A and the center BC of the joint contour of the second generating unit 100B are located at different positions when viewed in the Z axis direction, so that the stress of the joint can be distributed for each generating unit, and ultimately the stress can be distributed throughout the fuel cell stack 10. Therefore, the life until the joints are damaged can be extended compared to a configuration in which the centers BC of the joint contours of the first generating unit 100A and the second generating unit 100B are located at the same positions when viewed in the Z axis direction.

[0090] In addition, in the fuel cell stack 10 of this embodiment, there are multiple combinations CM between the first member (IC separator 180, fuel electrode frame 140, single cell separator 120) and the second member (fuel electrode frame 140, single cell separator 120, IC separator 180), and the distance between the center BC of the joint contour line and the center DC of the overlapping portion contour line in the Z-axis direction of one combination CM is different from the distance between the center BC of the joint contour line and the center DC of the overlapping portion contour line in the Z-axis direction of another combination CM. According to the fuel cell stack 10, the distance between the center BC of the joint contour line and the center DC of the overlapping portion contour line in the Z-axis direction of one combination CM is different from the distance between the center BC of the joint contour line and the center DC of the overlapping portion contour line in the Z-axis direction of another combination CM, so that the design freedom of the fuel cell stack 10 can be increased.

[0091] A-5.Performance evaluation: Next, performance evaluation of this embodiment will be described. A plurality of samples (S1 to S26) in which a first member and a second member are joined by a joint, in which the distance between the center BC of the joint contour and the center DC of the overlapping portion contour when viewed from the direction in which the first member and the second member overlap (hereinafter referred to as "deviation amount") is different from one another, were produced, and performance evaluation was carried out using each sample. Tables 1 and 2 show the results of the performance evaluation.

[0092] (Durability rating (1)) In durability evaluation (1), the durability against peel load was evaluated for the first and second members joined by a joint. Specifically, samples in which the first and second members were joined by a joint were prepared, and for each sample, the first and second members were fixed by a jig, and a load of 150 N was applied in the direction of peeling the first and second members using the jig until the first and second members were completely peeled off. The evaluation criteria were as follows: for a sample with a displacement of 0 μm, the number of times a load was applied from when initial damage was observed until the first and second members were completely peeled off was set as the standard number of times of application. For each sample, samples in which the number of times a load was applied from when initial damage was observed until the first and second members were completely peeled off was 1.2 times or more and less than 1.5 times the standard number of times of application were evaluated as acceptable (△), and samples in which the number of times of application was 1.5 times or more the standard number of times of application were evaluated as good (○). For samples in which the joints were formed by welding, initial damage was identified by an increase in resistance value, and for samples in which the joints were formed from glass, initial damage was identified by gas leakage between the first or second component and the joint.

[0093] (Gas flow evaluation) In the gas flow evaluation, the distribution of gas flowing through the manifold was evaluated in a configuration in which a first through hole constituting a part of the manifold was formed in the first member, a second through hole constituting a part of the manifold was formed in the second member, and a joint surrounded each of the first through hole and the second through hole. FIG. 12 is an explanatory diagram showing a schematic evaluation method for the gas flow evaluation. As shown in FIG. 12, the gas flow evaluation was performed using a sample in which two power generation units 100U were stacked. Specifically, the gas GA was sent from the inlet side (Z-axis negative direction side) to the outlet side (Z-axis positive direction side) of a manifold (referred to as "manifold MA" in this performance evaluation) formed in the two power generation units 100U. At this time, the distribution of the gas GA flowing through the manifold MA was evaluated by measuring the difference in flow rate of the gas GA flowing between the inlet side and the outlet side of the manifold MA. That is, the larger the difference in flow rate of the gas GA flowing between the inlet side and the outlet side of the manifold MA, the better the distribution of the gas GA, and the smaller the difference in flow rate of the gas GA flowing between the inlet side and the outlet side of the manifold MA, the worse the distribution of the gas GA. The evaluation criteria were based on the difference in flow rate of the gas GA flowing between the inlet side and the outlet side of the manifold MA of the sample with the deviation of 0 μm, and the sample with improved flowability of the gas GA was evaluated as good (○). Although not shown in FIG. 12, each sample was provided with a throttle on the outlet side of the manifold MA, and the gas GA was distributed by narrowing the flow path on the outlet side of the manifold MA. The throttles provided in each sample all had the same hole diameter.

[0094] (Durability rating (2)) In durability evaluation (2), the durability against peel load of two stacked units, each including a first member and a second member joined by a joint, was evaluated. Specifically, samples were prepared in which two stacked generating units 100U, each including a first member and a second member and a joint, were prepared, and for each sample, one generating unit 100U and the other generating unit 100U were fixed by a jig, and a load of 150N was applied using the jig in a direction to peel one generating unit 100U from the other generating unit 100U, until the first member and the second member included in the generating unit 100U were completely peeled off. The evaluation criteria were as follows: in a sample in which the distance between the center BC of the joint contour of the combined CM of one generating unit 100U and the center BC of the joint contour of the combined CM of the other generating unit 100U (hereinafter referred to as the "distance between the centers BC") is 0 μm when viewed in the direction in which the two generating units 100U are stacked, the number of times a load was applied from when initial damage was observed until the first member and the second member completely peeled off was set as the standard number of load applications, and samples in which the number of times a load was applied from when initial damage was observed until the first member and the second member completely peeled off was greater than the standard number of load applications were evaluated as good (○). Note that initial damage was recognized for each sample by gas leakage from between the first member or the second member and the joint.

[0095] (Performance evaluation results) Table 1 shows the performance evaluation results. [Table 1]

[0096] Table 1 shows for each sample the first component, second component, and joint that were evaluated, the amount of misalignment, and the evaluation results, etc. The "longest distance / shortest distance" in the table shows the value of the longest distance between the joint contour line BO and the overlapping contour line DO as viewed in the Z-axis direction relative to the shortest distance between the joint contour line BO and the overlapping contour line DO as viewed in the Z-axis direction; the larger the amount of misalignment, the larger this value becomes.

[0097] Samples S1 to S4 correspond to combination CM1 in the fuel cell stack 10, samples S5 to S8 correspond to combination CM2 in the fuel cell stack 10, samples S9 to S12 correspond to combination CM3 in the fuel cell stack 10, samples S13 to S16 correspond to combination CM4 in the fuel cell stack 10, and samples S17 to S20 correspond to combination CM5 in the fuel cell stack 10. Also, although not shown in the fuel cell stack 10 of this embodiment, samples S21 to 24 use an electrolyte layer 112 as the first member, an interconnector 190 as the second member, and a glass bonding material as the bonding portion.

[0098] In the durability evaluation (1), the samples (Samples S2, S6, S10, S14, S18, S22) in which the maximum distance / minimum distance in each combination CM was 1.01 and the deviation was 5 μm were evaluated as fair (△). In addition, the samples (Samples S3, S7, S11, S15, S19, S23) in which the maximum distance / minimum distance in each combination CM was 1.1 and the deviation was 10 μm, and the samples (Samples S4, S8, S12, S16, S20, S24) in which the maximum distance / minimum distance in each combination CM was 10 and the deviation was 500 μm were evaluated as good (○). From these results, it was confirmed that durability was improved in samples with a relatively large deviation.

[0099] In the gas flow evaluation, the samples (Samples S10, S11, and S12) in which the maximum distance / minimum distance ratio in combination CM3 was 1.01 or more and the deviation was 5 μm or more were all evaluated as good (○). From this result, it was confirmed that the gas flow property was improved in samples with a relatively large deviation.

[0100] Table 2 shows the performance evaluation results. [Table 2]

[0101] Table 2 shows the first member, second member, and joint that were evaluated for each sample, the amount of misalignment, and the results of the durability evaluation (2).

[0102] In durability evaluation (2), the sample (sample S26) in which the distance between the centers BC was 10 μm was evaluated as good (○). This result confirmed that durability was improved in a sample in which the center BC of the joint contour of one generating unit 100U and the center BC of the joint contour of the other generating unit 100U are positioned differently from each other when viewed in the direction in which the two generating units 100U are stacked.

[0103] B. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0104] Fig. 13 is an explanatory diagram showing an XY cross-sectional configuration of a fuel cell stack 10a in a modified example taken along line VII-VII in Fig. 6. In the following, the same components of the fuel cell stack 10a in the modified example as those in the fuel cell stack 10 in the above-described embodiment are denoted by the same reference numerals and will not be described. In the fuel cell stack 10a in the modified example, the configuration of a welded portion 182a is different from that of the welded portion 182 in the embodiment.

[0105] As shown in FIG. 13, the welded portion 182a is missing a part of a complete ring. In this way, the welded portion 182a does not necessarily have to be a complete ring, and less than 50% of the complete ring may be missing. Specifically, as viewed in the Z-axis direction, a ring-shaped figure may be formed by virtually combining or overlapping the shape of the welded portion 182a with a virtual welded portion 182av, which is a shape obtained by rotating the welded portion 182a at a specific angle of 180 degrees or less around the Z-axis direction. In such a case, when the combination of the welded portion 182a and the overlapping portion contour line DO1 is defined as a combination CM1a, the combination CM1a may satisfy the following conditions. Condition (1): When viewed in the Z-axis direction, the joint contour line BO1a, which is the contour line of the welded portion 182a, is similar in shape to 50% or more of the entire circumference of the overlapping portion contour line DO1. Condition (2): When viewed in the Z-axis direction, the joint contour BO1a surrounds 50% or more of the entire circumference of the overlapping contour DO1 in each direction from the center DC1 of the overlapping contour DO1 toward the overlapping contour DO1. Condition (3): When viewed in the Z-axis direction, the virtual joint contour line BO1av is the contour line closer to the overlap contour line DO1 in the virtual welded joint 182av, and the center BC1a of the figure combining the joint contour line BO1a and the virtual joint contour line BO1av is in a different position from the center DC1 of the overlap contour line.

[0106] In the above modified example, the welded portion 182 is not in a complete annular shape, but similarly, the other joints do not necessarily have to be in a complete annular shape.

[0107] The first member, the second member, and the joint portion shown in the above embodiment are merely examples, and the first member, the second member, and the joint portion may be other members that constitute the fuel cell stack 10.

[0108] The configurations of the fuel cell stack 10 and the power generating units 100U in the above embodiment are merely examples and can be modified in various ways. For example, the number of unit cells 110 (the number of power generating units 100U) included in the fuel cell stack 10 in the above embodiment is merely an example, and the number of unit cells 110 is appropriately determined depending on the output voltage required for the fuel cell stack 10.

[0109] The materials constituting each member in the above embodiment are merely examples, and each member may be made of other materials.

[0110] The fuel cell stack 10 in the above embodiment is a co-flow type SOFC, but the technology disclosed in this specification is also applicable to a counter-flow type SOFC.

[0111] In the above embodiment, the unit cell 110 is an anode-supported unit cell, but it may be another type of unit cell, such as an electrolyte-supported type or a metal-supported type.

[0112] In the above embodiment, the electrochemical reaction cell stack is a cell stack used in a solid oxide fuel cell (SOFC), but the above configuration is also applicable to cell stacks used in other types of fuel cells such as a polymer electrolyte fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), and a molten carbonate fuel cell (MCFC), or an electrolysis cell stack having an electrolysis cell unit, which is a constituent unit of a solid oxide electrolysis cell (SOEC), as a single cell. [Explanation of symbols]

[0113] 10, 10a: fuel cell stack 96: glass seal portion 100: power generation block 100U: power generation unit 100A: first power generation unit 100B: second power generation unit 110: single cell 112: electrolyte layer 114: air electrode 116: fuel electrode 118: reaction prevention layer 120: single cell separator 121: through hole 122: welded portion 124: connection member 125: through hole 126: through hole surrounding portion 130: air electrode frame 131: through hole 132: oxidant gas supply communication channel 133: oxidant gas discharge communication channel 140: fuel electrode frame 141: through hole 142: fuel gas supply communication channel 143: fuel gas discharge communication channel 144: fuel electrode current collecting member 145: electrode facing portion 146: interconnector facing portion 147: Connection portion 149: Spacer 180: IC separator 181: Through hole 182, 182a: Welded portion 182av: Virtual welded portion 184: Welded portion 185: Through hole 186: Periphery of through hole 190: Interconnector 191: Flat plate portion 192: Air electrode current collecting portion 193: Coating layer 196: Conductive bonding material 210: First end plate 220: Insulating portion 230: Terminal separator 231: Through hole 232: First plate 240: First terminal plate 241: Through hole 242: First bus bar 243: Welded portion 250: Second terminal plate 252: Second bus bar 253: Welded portion 260: Second plate 270: Second end plate 280: Gas passage member 281: Main body portion 282: Flange 284: Bolt hole 311: Oxidizer gas supply manifold 312: Oxidizer gas exhaust manifold 313: Air chamber 321: Fuel gas supply manifold 322: Fuel gas exhaust manifold 323: Fuel chamber B: Bolt BH: Bolt hole N: Nut FG: Fuel gas FOG: Fuel off-gas OG: Oxidizer gas OOG: Oxidizer off-gas CM: Combination BO: Joint contour DO: Overlap contour DP: Overlap

Claims

1. A first member; A second member having an overlapping portion that is a portion that overlaps with the first member in a first direction; a joint that joins the first member and the second member, the joint joining the overlapping portion of the second member and a portion of the first member that faces the overlapping portion in the first direction; Equipped with In the electrochemical reaction cell stack, the overlapping portion has at least one overlapping portion contour line that is an annular contour line when viewed in the first direction, The electrochemical reaction cell stack includes: A combination of the joint and the overlap contour, When viewed in the first direction, a joint contour line that is a contour line of the joint portion is similar in shape to the overlapping portion contour line, When viewed in the first direction, one of the joint contour line and the overlapping contour line surrounds the other of the joint contour line and the overlapping contour line, a combination that satisfies a condition that, when viewed in the first direction, a center of the joint portion contour line and a center of the overlapping portion contour line are positioned differently from each other; An electrochemical reaction cell stack comprising:

2. 2. The electrochemical reaction cell stack according to claim 1 , In the combination, a distance between a center of the joint contour line and a center of the overlapping contour line when viewed in the first direction is 10 μm or more. An electrochemical reaction cell stack comprising:

3. 2. The electrochemical reaction cell stack according to claim 1 , In the combination, a longest distance between the joint contour line and the overlapping contour line when viewed in the first direction is 1.01 times or more a shortest distance between the joint contour line and the overlapping contour line when viewed in the first direction. An electrochemical reaction cell stack comprising:

4. 2. The electrochemical reaction cell stack according to claim 1, further comprising: a plurality of unit cells stacked in the first direction; A manifold is formed to supply gas to each of the plurality of unit cells, The first member has a first through hole that constitutes a part of the manifold, The second member has a second through hole that constitutes a part of the manifold. At least a portion of the overlapping portion contour line coincides with at least a portion of a first through hole surrounding portion that is a portion surrounding the first through hole in the first member when viewed in the first direction, The bonding portion is a bonding material surrounding each of the first through hole and the second through hole. An electrochemical reaction cell stack comprising:

5. 2. The electrochemical reaction cell stack according to claim 1 , a first unit and a second unit each having the first member and the second member are stacked in the first direction; the first unit and the second unit each have the combination, At least a portion of the overlapping contour of the combination in the first unit and at least a portion of the overlapping contour of the combination in the second unit overlap each other in the first direction, a center of the joint contour line of the combination in the first unit and a center of the joint contour line of the combination in the second unit are positioned differently from each other when viewed in the first direction; An electrochemical reaction cell stack comprising:

6. 2. The electrochemical reaction cell stack according to claim 1 , There are a plurality of combinations of the first member and the second member, a distance between a center of the joint contour line and a center of the overlapping portion contour line of one of the combinations when viewed in the first direction is different from a distance between a center of the joint contour line and a center of the overlapping portion contour line of another of the combinations when viewed in the first direction; An electrochemical reaction cell stack comprising:

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