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 in this specification relates to an electrochemical reaction cell stack.

Background Art

[0002] As one type of fuel cell that generates electricity by utilizing the electrochemical reaction between hydrogen and oxygen, a solid oxide fuel cell (hereinafter referred to as "SOFC") is known. An SOFC is generally used in the form of a fuel cell stack. The fuel cell stack includes a certain member (hereinafter referred to as the "first member"), another member (hereinafter referred to as the "second member") having an overlapping portion that overlaps the first member in a predetermined direction (hereinafter referred to as the "first direction"), and a joining portion that joins the first member and the second member. Specific examples of the combination of the first member, the second member, and the joining portion include a separator, a fuel electrode frame, and a welded portion that joins the separator and the fuel electrode frame.

[0003] Conventionally, fuel cell-related components in which a plurality of plate-like workpieces are stacked and the plate-like workpieces are joined to each other by a joining material or laser welding have been disclosed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When stress is applied to the first member and the second member of the fuel cell stack, the joining portion may be damaged, which may also cause a failure of the fuel cell stack. Therefore, in order to improve the durability of the fuel cell stack, it has been desired to improve the durability of the joining portion.

[0006] Furthermore, these challenges are also common to electrolytic cell stacks, which are a form of electrolytic cell (hereinafter referred to as "SOEC") that produces hydrogen using the electrolysis reaction of water.In this specification, fuel cell single cells and electrolytic single cells are collectively referred to as electrochemical reaction single cells, and fuel cell stacks and electrolytic cell stacks are collectively referred to as electrochemical reaction cell stacks.In addition, these challenges are not limited to SOFCs and SOECs, but are also common to other types of electrochemical reaction cell stacks.

[0007] This specification discloses a technology capable of solving the above-mentioned problems. [Means for solving the problem]

[0008] The technologies disclosed herein can be implemented, for example, in the following forms:

[0009] (1) An electrochemical reaction cell stack disclosed herein comprises a first member, a second member having an overlapping portion which is a portion that overlaps 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 an overlapping portion contour line which is at least one annular contour line in the first direction view. The electrochemical reaction cell stack includes a combination of the joint and the overlapping portion contour line which satisfies the conditions that, in the first direction view, the joint contour line which is the contour line of the joint is similar in shape to the overlapping portion contour line, in the first direction view, one of the joint contour line and the overlapping portion contour line surrounds the other of the joint contour line and the overlapping portion contour line, and in the first direction view, the center of the joint contour line and the center of the overlapping portion contour line are in different positions from each other.

[0010] In this electrochemical reaction cell stack, in the combination of the joint and the overlapping contour lines, the centers of the joint contour line and the overlapping contour line in the first viewing direction are in different positions. Therefore, when stress is applied to the first or second member, the stress applied to the joint can be made non-uniform. As a result, the part of the joint that is subjected to relatively large stresses will be the initial point of damage, but the parts other than the initial point of damage will not be subjected to the same level of stress. Thus, the lifespan of the joint from the time initial damage occurs until the entire joint is damaged can be extended.

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

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

[0013] (4) The electrochemical reaction cell stack may further include a plurality of single cells stacked in the first direction, with a manifold formed to supply gas to each of the plurality of single cells, the first member having a first through-hole that constitutes part of the manifold, the second member having a second through-hole that constitutes part of the manifold, at least a portion of the overlapping contour line coincides with at least a portion of the first through-hole surrounding area of ​​the first member which surrounds the first through-hole in the first direction view, and the joint is a joining material that surrounds the first through-hole and the second through-hole, respectively. With this configuration, in the first direction view, the positions of the center of the overlapping contour line and the center of the contour line of the joining material are different, resulting in an uneven configuration inside the manifold. This makes it easier for turbulence to occur in the gas flowing through the manifold, and allows for an even supply of gas to each of the plurality of single cells.

[0014] (5) In the electrochemical reaction cell stack described above, a first unit and a second unit, each having the first member and the second member respectively, are stacked in the first direction, and the first unit and the second unit each have the combination, and at least a portion of the overlapping contour lines of the combination in the first unit and at least a portion of the overlapping contour lines of the combination in the second unit overlap each other in the first direction, and the center of the joint contour line of the combination in the first unit and the center of the joint contour line of the combination in the second unit are in different positions when viewed in the first direction. With this configuration, since the center of the joint contour line of the first unit and the center of the joint contour line of the second unit are in different positions when viewed in the first direction, the stress at the joint can be distributed for each unit, and consequently the stress can be distributed throughout the entire electrochemical reaction cell stack. Therefore, compared to a configuration in which the centers of the joint contour lines of the first unit and the second unit are in the same position when viewed in the first direction, the lifespan until the joint is damaged can be extended.

[0015] (6) In the electrochemical reaction cell stack described above, there may be multiple combinations of the first member and the second member, and the distance between the center of the joint contour line and the center of the overlapping contour line in the first viewing direction of one of the combinations may be different from the distance between the center of the joint contour line and the center of the overlapping contour line in the first viewing direction of other combinations. With this configuration, since the distance between the center of the joint contour line and the center of the overlapping contour line in the first viewing direction of one combination of joint and overlapping contour line is different from the distance between the center of the joint contour line and the center of the overlapping contour line in the first viewing direction of other combinations of joint and overlapping contour line, the degree of design freedom in the electrochemical reaction cell stack can be increased.

[0016] Furthermore, the technologies disclosed herein can be implemented in various forms, for example, in the form of an electrochemical reaction cell stack or a method for producing the same. [Brief explanation of the drawing]

[0017] [Figure 1] Perspective view showing the external configuration of the fuel cell stack 10 in this embodiment. [Figure 2] This diagram shows the XZ cross-sectional configuration of the fuel cell stack 10 at position II-II in Figure 1. [Figure 3] This diagram shows the XZ cross-sectional configuration of the fuel cell stack 10 at position III-III in Figure 1. [Figure 4] Diagram illustrating the YZ cross-sectional configuration of the fuel cell stack 10 at position IV-IV in Figure 1. [Figure 5] This diagram illustrates the XZ cross-sectional configuration of two adjacent power generation units 100U at the same location as the cross-section shown in Figure 2. [Figure 6] This diagram shows the XZ cross-sectional configuration of two adjacent power generation units 100U at the same location as the cross-section shown in Figure 3. [Figure 7] Figure 6 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at position VII-VII. [Figure 8]Explanatory drawing showing the XY cross-sectional configuration of the fuel cell stack 10 at the VIII-VIII position in FIG. 6 [Figure 9] Explanatory drawing showing the XY cross-sectional configuration of the fuel cell stack 10 at the IX-IX position in FIG. 6 [Figure 10] Explanatory drawing showing the XY cross-sectional configuration of the fuel cell stack 10 at the X-X position in FIG. 6 [Figure 11] Explanatory drawing showing the XY cross-sectional configuration of the fuel cell stack 10 at the XI-XI position in FIG. 2 [Figure 12] Explanatory drawing schematically showing the evaluation method of gas flow evaluation [Figure 13] Explanatory drawing showing the XY cross-sectional configuration of the fuel cell stack 10a at the VII-VII position in FIG. 6 in the modification

Mode for Carrying Out the Invention

[0018] A. Embodiment: A-1. Configuration of the fuel cell stack 10: FIG. 1 is a perspective view showing the external configuration of the fuel cell stack 10 in the present embodiment, FIG. 2 is an explanatory drawing showing the XZ cross-sectional configuration of the fuel cell stack 10 at the II-II position in FIG. 1, FIG. 3 is an explanatory drawing showing the XZ cross-sectional configuration of the fuel cell stack 10 at the III-III position in FIG. 1, and FIG. 4 is an explanatory drawing showing the YZ cross-sectional configuration of the fuel cell stack 10 at the IV-IV position in FIG. 1. In each figure, XYZ axes orthogonal to each other for specifying directions are shown. In this specification, for convenience, the Z-axis direction is referred to as the vertical direction, the positive Z-axis direction is referred to as the upward direction, and the negative Z-axis direction is referred to as the downward direction. However, the fuel cell stack 10 may actually be installed in a direction different from such a direction. The fuel cell stack 10 is an example of an electrochemical reaction cell stack in the claims. The Z-axis direction (vertical direction) is an example of the first direction in the claims.

[0019] (Overall configuration of the fuel cell stack 10) As shown in Figures 1 to 4, the fuel cell stack 10 comprises 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 roughly the same rectangular shape and are arranged in this order overlapping 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 its four corners, each extending from the first end plate 210 to the second end plate 270. A bolt B is inserted into each bolt hole BH. Nuts N are threaded onto both ends of each bolt B. These bolts B and nuts N fasten the components 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] As shown in Figures 2 to 4, the power generation block 100 is composed of a plurality (seven in this embodiment) of power generation units 100U arranged in a predetermined arrangement direction (vertical direction). Furthermore, two adjacent power generation units 100U arranged at arbitrary positions (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 component formed by press-forming (bending) a single plate-shaped member, and is made of a conductive material such as stainless steel. As shown in Figures 1 to 4, the first end plate 210 comprises a rectangular frame-shaped planar portion 211 having a through hole 212 near the center, and an outer projection 213 and an inner projection 214 that protrude from the planar portion 211 in the opposite direction to the insulating portion 220 (upwards in Figure 2). The planar portion 211 has holes that constitute the bolt holes BH described above. The outer projection 213 protrudes from the outer peripheral edge of the planar portion 211. The outer projection 213 is formed around the entire circumference of the outer peripheral portion of the planar portion 211. The inner projection 214 protrudes from the inner peripheral edge of the planar portion 211. The inner projection 214 is formed around the entire circumference of the inner peripheral portion of the planar portion 211.

[0023] (Insulation part 220) The insulating portion 220 is a rectangular frame-shaped member having a through hole near the center, and is formed of, for example, an insulating material. As shown in Figure 2, the insulating portion 220 is sandwiched between the first end plate 210 and the end separator 230, thereby ensuring insulation between the first end plate 210 and the end separator 230.

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

[0025] (Plate 1, No. 232) The first plate 232 is a rectangular, flat member made of a conductive material such as stainless steel. As shown in Figures 2 to 4, the first plate 232 is joined to the peripheral portion of the through hole 231 in the end separator 230, for example, by 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 later, provided on a power generation unit 100U located at one end (the upper end in Figure 2) of the multiple power generation units 100U that make up the power generation block 100, via a connecting member having the same structure as the fuel electrode current collector 144, described later. In this way, the power generation unit 100U and the first plate 232 are electrically connected.

[0027] (Terminal 1 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 film on its surface. The first terminal plate 240 is electrically connected to a power generation unit 100U located at one end (upper end in Figure 2) of the multiple power generation units 100U that make up the power generation block 100, via the first plate 232 and the end separator 230. One end of the first terminal plate 240 (right end in Figure 2) protrudes laterally from the power generation block 100.

[0028] (Terminal 2 Plate 250) The second terminal plate 250 is a rectangular plate-shaped member, formed from a conductive material such as ferritic stainless steel that forms an alumina oxide film on its surface. The second terminal plate 250 is electrically connected to the power generation unit 100U located at the other end (lower end in Figure 2) of the multiple power generation units 100U that make up the power generation block 100. One end of the second terminal plate 250 (right end in Figure 2) protrudes laterally from the power generation block 100.

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

[0030] (Plate 2, page 260) The second plate 260 is a rectangular, flat member, formed of, for example, an insulating material. The peripheral edge 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 press-forming (bending) a single plate-shaped member, and is made of a conductive material such as stainless steel. The second end plate 270 comprises a rectangular frame-shaped planar portion 271 having a through hole 272 near the center, and an outer projection 273 and an inner projection 274 projecting from the planar portion 271 in the opposite direction to the second terminal plate 250 (downward in Figure 2). The planar portion 271 has holes that constitute the bolt holes BH described above. The outer projection 273 protrudes from the outer peripheral edge of the planar portion 271. The outer projection 273 is formed around the entire circumference of the outer peripheral portion of the planar portion 271. The inner projection 274 protrudes from the inner peripheral edge of the planar portion 271. The inner projection 274 is formed around the entire circumference of the inner peripheral portion of the planar portion 271.

[0032] (Manifolds 311, 312, 321, 322) As shown in Figures 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 the oxidizer gas supply manifold 311, the oxidizer gas discharge manifold 312, the fuel gas supply manifold 321, and the fuel gas discharge manifold 322, respectively.

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

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

[0035] (Gas passage member 280) Each of the four gas passage members 280 comprises a main body portion 281 and a flange portion 282, as shown in Figures 1 to 3. The main body portion 281 has a gas through-hole 283 that penetrates vertically. The flange portion 282 is provided so as to protrude outward from the other end of the main body portion 281 (the lower end in Figure 2). The flange portion 282 has a plurality of bolt holes 284. Bolts (not shown) for connecting the fuel cell stack 10 to an external device are inserted into each bolt hole 284. One end of the main body portion 281 provided on the four gas passage members 280 (the upper end in Figures 2 and 3) is joined to the second end plate 270, for example by welding, and the gas through-holes 283 communicate with manifolds 311, 312, 321, and 322, respectively. Gas piping (not shown) for gas supply or discharge is connected to each main body portion 281.

[0036] (Overall configuration of a 100U power generation unit) Figure 5 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generation units 100U at the same position as the cross-section shown in Figure 2. Figure 6 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generation units 100U at the same position as the cross-section shown in Figure 3. In Figures 5 and 6, the first power generation unit 100A and the second power generation unit 100B are shown among the multiple power generation units 100U. As shown in Figures 5 and 6, the power generation unit 100U comprises a single cell 110, a single cell separator 120, an air electrode frame 130, a fuel electrode frame 140, a fuel electrode current collector 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 fuel electrode frame 140, and the other IC separator 180 are arranged in this order on top of each other. The single cell 110 is supported by the single cell separator 120, the interconnector 190 is supported by the IC separator 180, and the fuel electrode current collector 144 is positioned between the single cell 110 and the interconnector 190.

[0037] As shown in Figures 5 and 6, the IC separator 180 and interconnector 190 are shared by two adjacent power generation units 100U. However, as shown in Figure 2, the power generation unit 100U located at the other end (the lower end of Figure 2) of the multiple power generation 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 single cell 110 comprises an electrolyte layer 112, an air electrode 114, a fuel electrode 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 fuel electrode 116 are arranged in this order. The single cell 110 of this embodiment is a fuel electrode-supported single cell in which the other layers constituting the single cell 110 (electrolyte layer 112, air electrode 114, and reaction prevention layer 118) are supported by the fuel electrode 116.

[0039] The electrolyte layer 112 is a rectangular, flat member having one side on which the air electrode 114 is located (the upper side in Figures 5 and 6) and another side parallel to the air electrode 116 (the lower side in Figures 5 and 6). 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 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 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, etc. The reaction prevention layer 118 is a layer having a rectangular shape 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 elements (e.g., Sr) diffused from the air electrode 114 with elements (e.g., Zr) contained in the electrolyte layer 112 to produce a highly resistive substance (e.g., SrZrO3).

[0040] (Single-cell separator 120) As shown in Figures 5 and 6, the single-cell separator 120 is a rectangular frame-shaped member having a substantially rectangular through-hole 121 near the center, and is made of, for example, metal. The 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 edge of the through-hole 121 in the single-cell separator 120 is joined to the peripheral edge of one surface of the electrolyte layer 112 (the surface on which the air electrode 114 is arranged: the upper surface in Figures 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 has through-holes 125 that penetrate in the vertical direction and constitute part of the manifolds 311, 312, 321, and 322. The through-hole 125 is an example of the first through-hole in the claims.

[0041] (Air pole frame 130) As shown in Figures 5 and 6, the air electrode frame 130 is a rectangular frame-shaped member having a substantially rectangular through hole 131 near the center, and is formed 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 Figure 5, the air electrode frame 130 has an oxidant gas supply communication channel 132 that connects the oxidant gas supply manifold 311 and the air chamber 313, and an oxidant gas discharge communication channel 133 that connects the air chamber 313 and the oxidant gas discharge manifold 312.

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

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

[0044] (Interconnector 190, and fuel electrode current collector 144) As shown in Figures 5 and 6, the interconnector 190 comprises 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 collectors 192 are conductive and made of metal (for example, ferritic stainless steel). The coating layer 193 is conductive and is arranged to cover the surface of the air electrode current collectors 192 and the surface of the flat plate portion 191 on which the air electrode current collectors 192 are arranged. The flat plate portion 191 is joined to the periphery of the through hole 181 in the IC separator 180, for example, by welding.

[0045] The fuel electrode current collector 144 is a member that connects the interconnector 190 and the fuel electrode 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 fuel electrode current collector 144 comprises an interconnector-facing portion 146, an electrode-facing portion 145 parallel to the interconnector-facing portion 146, and a connecting portion 147 connecting the electrode-facing portion 145 and the interconnector-facing portion 146, and is U-shaped overall. The electrode-facing portion 145 is in contact with the fuel electrode 116, and the interconnector-facing portion 146 is in contact with the flat plate portion 191 of the interconnector 190.

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

[0047] However, as described above, the power generation unit 100U located at the other end (the lower end of Figure 2) among the multiple power generation units 100U does not have an interconnector 190 on the fuel electrode 116 side. The fuel electrode 116 provided in this power generation unit 100U is connected to the second terminal plate 250 via a fuel electrode current collector 144.

[0048] A spacer 149, for example made of mica, is placed between the electrode facing portion 145 and the interconnect facing portion 146. As a result, the fuel electrode current collector 144 follows the deformation of the power generation unit 100U due to temperature cycles and reaction gas pressure fluctuations, and the electrical connection between the fuel electrode 116 and the interconnect 190 (or second terminal plate 250) via the fuel electrode current collector 144 is maintained in good condition.

[0049] (Glass seal portion 96) The glass seal portion 96 is provided between the single-cell separator 120 and the IC separator 180, which are facing each other vertically with the air electrode frame 130 in between. The glass seal portion 96 is annular in shape and is positioned to surround the fuel gas supply manifold 321 and the fuel gas discharge manifold 322, respectively. The glass seal portion 96 suppresses leakage of fuel gas FG or fuel off-gas FOG from the fuel gas supply manifold 321 and the fuel gas discharge manifold 322 through the interface between the air electrode frame 130 and the single-cell separator 120, and the interface between the air electrode frame 130 and the IC separator 180.

[0050] (Air chamber 313 and fuel chamber 323) As shown in Figures 5 and 6, the space partitioned by the single-cell separator 120 and single cell 110, the air electrode frame 130, the IC separator 180 and interconnector 190 faces the air electrode 114 and forms an air chamber 313 through which the oxidizer gas OG flows. The air electrode frame 130 partitions the air chamber 313 from the outside space around its entire circumference and seals the space between the single-cell separator 120 and the IC separator 180, preventing gas from leaking from the air chamber 313 into the outside space.

[0051] Furthermore, the space partitioned by the single-cell separator 120 and single cell 110, the fuel electrode frame 140, the IC separator 180 and interconnector 190 faces the fuel electrode 116 and forms a fuel chamber 323 through which fuel gas FG flows. The fuel electrode frame 140 partitions the fuel chamber 323 from the outside space around its entire circumference and seals the space between the single-cell separator 120 and the IC separator 180, preventing gas from leaking from the fuel chamber 323 into the outside space.

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

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

[0054] Furthermore, as shown in Figures 3 and 6, the fuel gas FG is supplied to the fuel gas supply manifold 321 via gas piping (not shown) and gas passage members 280, and then supplied to the fuel chamber 323 via the fuel gas supply communication channel 142.

[0055] When oxidizer gas OG is supplied to the air chamber 313 of each power generation unit 100U and fuel gas FG is supplied to the fuel chamber 323, power generation occurs in the single cell 110 through an electrochemical reaction between the oxidizer gas OG and fuel gas FG. This power generation reaction is an exothermic reaction. As described above, the interconnector 190 is shared by two adjacent power generation units 100U, and the interconnector 190 ensures conductivity between the two adjacent power generation units 100U. In other words, the multiple power generation units 100U included in the fuel cell stack 10 are electrically connected in series. Furthermore, the power generation unit 100U located at the other end (lower end in Figure 2) of the multiple power generation units 100U is electrically connected to the second terminal plate 250, and the power generation unit 100U located at one end (upper end in Figure 2) is electrically connected to the first terminal plate 240. As a result, electrical energy generated in each power generation unit 100U is extracted from busbars 242 and 252, which are connected to terminal plates 240 and 250 and function as output terminals of the fuel cell stack 10. Since SOFCs generate electricity 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] As shown in Figures 2 and 5, the oxidizer off-gas OOG discharged from the air chamber 313 of each power generation unit 100U to the oxidizer gas discharge manifold 312 via the oxidizer gas discharge communication channel 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 generation unit 100U to the fuel gas discharge manifold 322 via the fuel gas discharge communication channel 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 the joint in the fuel cell stack 10: (Peripheral configuration of IC separator 180 and fuel electrode frame 140) As shown in Figures 5 and 6, the fuel electrode frame 140 has an overlapping portion DP1 which overlaps with the IC separator 180 in the Z-axis direction. The IC separator 180 and the fuel electrode frame 140 are joined by a welded joint 182. The welded joint 182 joins the overlapping portion DP1 in the fuel electrode frame 140 to the portion of the IC separator 180 that faces the overlapping portion DP1 in the Z-axis direction. The welded joint 182 is formed, for example, by laser welding. The IC separator 180 is an example of the first member in the claims, the fuel electrode frame 140 is an example of the second member in the claims, and the welded joint 182 is an example of the joint in the claims.

[0058] Figure 7 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at position VII-VII in Figure 6. Figure 7 shows the peripheral configuration of the welded joint 182 at the position of the fuel gas supply manifold 321 in a view along the Z axis. The overlapping portion DP1 has an overlapping portion contour line DO1, which is an annular contour line, in a view along the Z axis. The welded joint 182 also has a joint contour line BO1, which is the contour line on the side closer to the overlapping portion contour line DO1 in a view along the Z axis. This combination of the welded joint 182 and the overlapping portion contour line DO1 is called the combination CM1.

[0059] Combination CM1 satisfies the following conditions (1) to (3). Condition (1): In a view along the Z-axis, 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): In the view along the Z-axis, the joint contour line BO1 encloses the overlapping contour line DO1. Condition (3): In the view along the Z-axis, the center BC1 of the joint contour line and the center DC1 of the overlapping contour line are in different positions.

[0060] As shown in Figures 5 and 6, the first power generation unit 100A and the second power generation unit 100B each have an IC separator 180 and a fuel electrode frame 140, and each has a combination CM1. At least a portion of the overlapping contour line DO1 of the combination CM1 in the first power generation unit 100A and at least a portion of the overlapping contour line DO1 of the combination CM1 in the second power generation unit 100B overlap each other in the Z-axis direction. The center BC1 of the joint contour line BC1 of the combination CM1 in the first power generation unit 100A and the center BC1 of the joint contour line BC1 of the combination CM1 in the second power generation unit 100B are in different positions when viewed in the Z-axis direction.

[0061] In this embodiment, there are a total of four combination CM1s in the IC separator 180 and the fuel electrode frame 140, as each combination CM1 is arranged around the manifolds 311, 312, 321, and 322. Of these four combination CM1s, the distance between the center BC1 of the joint contour line and the center DC1 of the overlapping contour line in a Z-axis view 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 in a Z-axis view 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 Figures 5 and 6, the single-cell separator 120 has an overlapping portion DP2 which overlaps with the fuel electrode frame 140 in the Z-axis direction. The fuel electrode frame 140 and the single-cell separator 120 are joined by a welded portion 122. The welded portion 122 joins the overlapping portion DP2 of the single-cell separator 120 to the portion of the fuel electrode frame 140 that faces the overlapping portion DP2 in the Z-axis direction. The welded portion 122 is formed, for example, by laser welding. The fuel electrode frame 140 is an example of the first member in the claims, the single-cell separator 120 is an example of the second member in the claims, and the welded portion 122 is an example of a joint in the claims.

[0063] Figure 8 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at position VIII-VIII in Figure 6. Figure 8 shows the peripheral configuration of the welded joint 122 at the position of the fuel gas supply manifold 321 in a view along the Z axis. The overlapping portion DP2 has an overlapping portion contour line DO2, which is an annular contour line, in a view along the Z axis. The welded joint 122 also has a joint contour line BO2, which is the contour line on the side closer to the overlapping portion contour line DO2 in a view along the Z axis. This combination of the welded joint 122 and the overlapping portion contour line DO2 is called the combination CM2.

[0064] Combination CM2 satisfies the following conditions (1) to (3). Condition (1): In a view along the Z-axis, 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): In the view along the Z-axis, the joint contour line BO2 encloses the overlapping contour line DO2. Condition (3): In the view along the Z-axis, the center BC2 of the joint contour line and the center DC2 of the overlapping contour line are in different positions.

[0065] As shown in Figures 5 and 6, the first power generation unit 100A and the second power generation unit 100B each have a fuel electrode frame 140 and a single-cell separator 120, and each has a combination CM2. At least a portion of the overlapping contour line DO2 of the combination CM2 in the first power generation unit 100A and at least a portion of the overlapping contour line DO2 of the combination CM2 in the second power generation 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 generation unit 100A and the center BC2 of the joint contour line of the combination CM2 in the second power generation unit 100B are in different positions when viewed in the Z-axis direction.

[0066] In this embodiment, the fuel electrode frame 140 and the single-cell separator 120 have a total of four combination CM2s, each of which is located around one of the manifolds 311, 312, 321, and 322. Of these four combination CM2s, the distance between the center BC2 of the joint contour line and the center DC2 of the overlapping contour line in a Z-axis view of one combination CM2 (for example, the combination CM2 located around the oxidizer 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 in a Z-axis view of another combination CM2 (for example, the combination CM2 located around the oxidizer gas discharge manifold 312).

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

[0068] Figure 9 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at the IX-IX position in Figure 6. Figure 9 shows the peripheral configuration of the glass seal portion 96 at the position of the fuel gas supply manifold 321 in a view along the Z axis. The overlapping portion DP3 has an overlapping portion contour line DO3, which is an annular contour line, in a view along the Z axis. The glass seal portion 96 also has a joint contour line BO3, which is the contour line on the side closer to the overlapping portion contour line DO3 in a view along the Z axis. This combination of the glass seal portion 96 and the overlapping portion contour line DO3 is called the combination CM3.

[0069] Combination CM3 satisfies the following conditions (1) to (3). Condition (1): In a view along the Z-axis, the joint contour line BO3, which is the contour line of the glass seal portion 96, is similar in shape to the overlapping portion contour line DO3. Condition (2): In the view along the Z-axis, the joint contour line BO3 encloses the overlapping contour line DO3. Condition (3): In the view along the Z-axis, the center BC3 of the joint contour line and the center DC3 of the overlapping contour line are in different positions.

[0070] In this embodiment, the overlapping contour line DO3 coincides with the through-hole periphery 126, which is the 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 periphery 126 and the through-hole periphery 186. It is sufficient that at least a portion of the overlapping contour line DO3 coincides with at least a portion of the through-hole periphery 126 when viewed in the Z-axis direction. The through-hole periphery 126 is an example of the first through-hole periphery in the claims.

[0071] As shown in Figures 5 and 6, the first power generation unit 100A and the second power generation unit 100B each have a single-cell separator 120 and an IC separator 180, and each has a combination CM3. At least a portion of the overlapping contour line DO3 of the combination CM3 in the first power generation unit 100A and at least a portion of the overlapping contour line DO3 of the combination CM3 in the second power generation 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 power generation unit 100A and the center BC3 of the joint contour line of the combination CM3 in the second power generation unit 100B are in different positions when viewed in the Z-axis direction.

[0072] In this embodiment, there are a total of two combination CM3s for the single-cell separator 120 and the IC separator 180, as each combination CM3 is arranged around the respective manifolds 321 and 322. Of these two combination CM3s, the distance between the center BC3 of the joint contour line and the center DC3 of the overlapping contour line in a Z-axis view 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 a Z-axis view 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 Figures 5 and 6, the interconnector 190 has an overlapping portion DP4 which overlaps 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 the portion of the IC separator 180 that faces the overlapping portion DP4 in the Z-axis direction. The welded portion 184 is formed, for example, by laser welding. The IC separator 180 is an example of the first member in the claims, the interconnector 190 is an example of the second member in the claims, and the welded portion 184 is an example of the joint in the claims.

[0074] Figure 10 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10 at position XX in Figure 6. Figure 10 shows the peripheral configuration of the welded joint 184 in view along the Z axis. The overlapping portion DP4 has an overlapping portion contour line DO4, which is an annular contour line, in view along the Z axis. The welded joint 184 also has a joint contour line BO4, which is the contour line on the side closer to the overlapping portion contour line DO4 in view along the Z axis. This combination of the welded joint 184 and the overlapping portion contour line DO4 is called the combination CM4.

[0075] Combination CM4 satisfies the following conditions (1) to (3). Condition (1): In a view along the Z-axis, 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): In the view along the Z-axis, the joint contour line BO4 surrounds the overlapping contour line DO4. Condition (3): In the view along the Z-axis, the center BC4 of the joint contour line and the center DC4 of the overlapping contour line are in different positions.

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

[0077] (Surrounding configuration of the first terminal plate 240 and the first bus bar 242) As shown in Figure 2, the first busbar 242 has an overlapping portion DP5 which overlaps with the first terminal plate 240 in the Z-axis direction. The first terminal plate 240 and the first busbar 242 are joined by a welded portion 243. The welded portion 243 joins the overlapping portion DP5 of the first busbar 242 to the portion of the first terminal plate 240 that is opposite to the overlapping portion DP5 in the Z-axis direction. The welded portion 243 is formed, for example, by laser welding. The first terminal plate 240 is an example of the first member in the claims, the first busbar 242 is an example of the second member in the claims, and the welded portion 243 is an example of the joint in the claims.

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

[0079] Combination CM5 satisfies the following conditions (1) to (3). Condition (1): In a view along the Z-axis, 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): In the view along the Z-axis, the overlapping contour line DO5 surrounds the joint contour line BO5. Condition (3): In the view along the Z-axis, the center BC5 of the joint contour line and the center DC5 of the overlapping contour line are in different positions.

[0080] While the above describes in detail the surrounding configuration of the first terminal plate 240 and the first busbar 242, the second terminal plate 250 and the second busbar 252 basically have a similar configuration.

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

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

[0083] Furthermore, the statement that the joint contour line BO is "similar" to the shape of the overlapping contour line DO includes not only configurations that are strictly similar, but also configurations where, for example, in the view along the Z axis, both the joint contour line BO and the overlapping contour line DO are circular, or where both are rectangular. In addition, the term "center" in the terms "center BC of the joint contour line" and "center DC of the overlapping contour line" specifically refers to the centroid of the joint contour line BO or overlapping contour line DO in the view along the Z axis.

[0084] A4. Effects of this embodiment: As described above, the fuel cell stack 10 of this embodiment comprises a first member (IC separator 180, fuel electrode frame 140, single cell separator 120, IC separator 180, first terminal plate 240), a second member (fuel electrode frame 140, single cell separator 120, IC separator 180, interconnector 190, first busbar 242) having overlapping portions DP1 to DP5 (hereinafter simply referred to as "overlapping portions DP") which overlap with the first member in the Z-axis direction, and a joint that joins the first member and the second member, the joint (welded portion 182, welded portion 122, glass seal portion 96, welded portion 184, welded portion 243) that joins the overlapping portions DP of the second member and the portion of the first member that faces the overlapping portions DP in the Z-axis direction. The overlapping portions DP have at least one annular contour line DO in a view along the Z-axis direction. The fuel cell stack 10 includes a combination CM of a joint and an overlapping contour line DO, which satisfies the following conditions: in a view along the Z-axis, the joint contour line BO, which is the contour line of the joint, is similar in shape to the overlapping contour line DO; in a view along the Z-axis, one of the joint contour line BO and the overlapping contour line DO surrounds the other of the joint contour line BO and the overlapping contour line DO; and in a view along the Z-axis, the center BC of the joint contour line and the center DC of the overlapping contour line are in different positions from each other.

[0085] In the fuel cell stack 10, in the combination CM of the joint and the overlapping contour line DO, the center BC of the joint contour line and the center DC of the overlapping contour line are in different positions when viewed in the Z-axis direction. Therefore, when stress is applied to the first or second member, the stress applied to the joint can be made non-uniform. As a result, the part of the joint that is subjected to relatively large stresses becomes the initial point of damage, but the parts other than the initial point of damage are not subjected to the same level of stress as the initial point of damage. Thus, the lifespan of the joint from the time initial damage occurs until the entire joint is damaged can be extended.

[0086] Furthermore, 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 contour line in the Z-axis view of the combined CM 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 contour line in the Z-axis view of the combined CM is 10 μm or more, the lifespan of the joint, from when initial damage occurs until the entire stack is damaged, can be more effectively extended.

[0087] Furthermore, in the fuel cell stack 10 of this embodiment, in the combined CM, the longest distance between the joint contour line BO and the overlapping section contour line DO in the Z-axis direction view is 1.01 times or more the shortest distance between the joint contour line BO and the overlapping section contour line DO in the Z-axis direction view. According to the fuel cell stack 10, in the combined CM, the longest distance between the joint contour line BO and the overlapping section contour line DO is 1.01 times or more the shortest distance between the joint contour line BO and the overlapping section contour line DO, so the lifespan of the joint from when initial damage occurs until the entire structure is damaged can be more effectively extended.

[0088] Furthermore, the fuel cell stack 10 of this embodiment further includes a plurality of single cells 110 stacked in the Z-axis direction, and a fuel gas supply manifold 321 is formed to supply gas to each of the plurality of single cells 110. The single cell separator 120 has a through hole 125 which constitutes part of the fuel gas supply manifold 321, and the IC separator 180 has a through hole 185 which constitutes part of the fuel gas supply manifold 321. At least a portion of the overlapping contour line DO coincides with at least a portion of the through hole surrounding portion 126 which surrounds the through hole 125 in the single cell separator 120 when viewed in the Z-axis direction, and the joint is a glass seal portion 96 which surrounds the through hole 125 and the through hole 185, respectively. With the fuel cell stack 10, when viewed in the Z-axis direction, the position of the center BC of the overlapping contour line and the position of the center of the contour line of the glass seal portion 96 are different, resulting in an uneven configuration inside the fuel gas supply manifold 321. This makes it easier for turbulence to occur in the gas flowing through the fuel gas supply manifold 321, allowing the gas to be supplied evenly to each of the multiple single cells 110.

[0089] Furthermore, in the fuel cell stack 10 of this embodiment, a first power generation unit 100A and a second power generation unit 100B, each having a first member (IC separator 180, fuel electrode frame 140, single cell separator 120, IC separator 180) and a second member (fuel electrode frame 140, single cell separator 120, IC separator 180, interconnector 190), are stacked in the Z-axis direction. The first power generation unit 100A and the second power generation 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 generation unit 100A and at least a portion of the overlapping contour line DO of the combination CM in the second power generation unit 100B overlap each other in the Z-axis direction. The center BC of the joint contour line of the combination CM in the first power generation unit 100A and the center BC of the joint contour line of the combination CM in the second power generation unit 100B are in different positions when viewed in the Z-axis direction. In the fuel cell stack 10, the center BC of the joint contour line of the first power generation unit 100A and the center BC of the joint contour line of the second power generation unit 100B are located at different positions in the Z-axis direction view. This allows the stress at the joint to be distributed among the power generation units, and consequently, the stress to be distributed throughout the entire fuel cell stack 10. Therefore, compared to a configuration where the center BC of the joint contour lines of the first power generation unit 100A and the second power generation unit 100B are located at the same position in the Z-axis direction view, the lifespan before the joint is damaged can be extended.

[0090] Furthermore, in the fuel cell stack 10 of this embodiment, there are multiple combinations CM of 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). The distance between the center BC of the joint contour line and the center DC of the overlapping contour line in a Z-axis view 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 contour line in a Z-axis view of another combination CM. With the fuel cell stack 10, since the distance between the center BC of the joint contour line and the center DC of the overlapping contour line in a Z-axis view 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 contour line in a Z-axis view of another combination CM, the degree of design freedom in the fuel cell stack 10 can be increased.

[0091] A-5. Performance evaluation: Next, the performance evaluation of this embodiment will be described. Multiple samples (S1 to S26) were prepared in which a first member and a second member were joined by a joint, and the distance between the center BC of the joint contour line and the center DC of the overlapping contour line in a view in the direction in which the first member and the second member overlap (hereinafter referred to as "amount of deviation") differed from one another. Performance evaluations were performed using each sample. Tables 1 and 2 show the results of the performance evaluation.

[0092] (Durability evaluation (1)) In the durability evaluation (1), the durability against peeling load was evaluated for the first and second members joined by a joint. Specifically, samples were prepared in which the first and second members were joined by a joint. For each sample, the first and second members were fixed with jigs, and a load of 150N was applied using the jigs in the direction of peeling the first and second members apart until the first and second members were completely separated. The evaluation criteria were as follows: for a sample with a displacement of 0 μm, the number of times the load was applied from the observation of initial damage until the first and second members were completely separated was set as the standard number of applications. For each sample, samples where the number of applications from the observation of initial damage until the first and second members were completely separated was 1.2 times or more but less than 1.5 times the standard number of applications was rated as "acceptable" (△), and samples where the number of applications was 1.5 times or more the standard number of applications were rated as "good" (○). For samples where the joint is formed by welding, initial damage was identified by an increase in resistance, and for samples where the joint is formed by glass, initial damage was identified by gas leakage from between the first or second member and the joint.

[0093] (Gas flow evaluation) In the gas flow evaluation, the distribution of gas flowing through a manifold was evaluated in a configuration where a first through-hole forming part of the manifold is formed in the first member, a second through-hole forming part of the manifold is formed in the second member, and the joint surrounds the first and second through-holes, respectively. Figure 12 is a schematic diagram illustrating the evaluation method for gas flow evaluation. As shown in Figure 12, the gas flow evaluation was performed using a sample consisting of two stacked power generation units 100U. Specifically, gas GA was sent from the inlet side (negative Z-axis side) to the outlet side (positive Z-axis side) of the manifold (referred to as "manifold MA" in this performance evaluation) formed in the two power generation units 100U. At this time, the distribution of gas GA flowing through manifold MA was evaluated by measuring the difference in flow rate of gas GA flowing between the inlet side and the outlet side of manifold MA. In other words, the greater the difference in the flow rate of gas GA flowing between the inlet and outlet sides of the manifold MA, the better the distribution of gas GA was evaluated, and the smaller the difference in the flow rate of gas GA flowing between the inlet and outlet sides of the manifold MA, the worse the distribution of gas GA was evaluated. The evaluation criterion was based on the difference in the flow rate of gas GA flowing between the inlet and outlet sides of the manifold MA of a sample with a displacement of 0 μm, and samples with improved gas GA flowability were marked as good ("○"). Although not shown in Figure 12, each sample has a throttling chamber on the outlet side of the manifold MA, and the gas GA is distributed by narrowing the flow path on the outlet side of the manifold MA. The throttling chambers in each sample all have the same pore diameter.

[0094] (Durability evaluation (2)) In durability evaluation (2), the durability against peeling load of two stacked units, each containing a first member and a second member joined by a joint, was evaluated. Specifically, a sample was prepared in which two power generation units 100U, each having a joint connecting the first member and the second member, were stacked. For each sample, one power generation unit 100U and the other power generation unit 100U were fixed with a jig, and a load of 150N was applied using the jig in a direction that peeled the two power generation units 100U apart until the first member and the second member contained in the power generation unit 100U were completely separated. The evaluation criteria were as follows: For samples where the distance BC between the center BC of the joint contour line of the combined CM in one power generation unit 100U and the center BC of the joint contour line of the combined CM in the other power generation unit 100U (hereinafter referred to as "distance between each center BC") is 0 μm in a view of two power generation units 100U stacked, the number of times a load was applied from the time initial damage was observed until the first and second members completely separated was set as the standard number of load applications. Samples where the number of load applications from the time initial damage was observed until the first and second members completely separated was greater than the standard number of load applications were judged as good ("○"). For each sample, initial damage was determined by gas leakage from between the first or 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 member, second member, and joint being evaluated, along with the amount of displacement and the evaluation results. The "Longest Distance / Shortest Distance" in the table represents the longest distance between the joint contour line BO and the overlapping contour line DO in the Z-axis direction relative to the shortest distance between the joint contour line BO and the overlapping contour line DO in the Z-axis direction. This value increases as the amount of displacement increases.

[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. Samples S21 to S24 are not shown in the fuel cell stack 10 of this embodiment, but use an electrolyte layer 112 as the first member, an interconnector 190 as the second member, and a glass bonding material as the joint.

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

[0099] In the gas flow evaluation, samples (Samples S10, S11, S12) with a maximum distance / minimum distance of 1.01 or greater in combination CM3 and a displacement of 5 μm or greater were all evaluated as "good" (○). From these results, it was confirmed that gas flowability improved in samples with relatively large displacements.

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

[0101] Table 2 shows, for each sample, the first member, second member, and joint being evaluated, as well as the amount of displacement and the results of the durability evaluation (2).

[0102] In the durability evaluation (2), the sample (Sample S26) with a distance of 10 μm between each center BC was evaluated as good ("○"). From this result, it was confirmed that durability is improved in samples where the center BC of the junction contour line of one power generation unit 100U and the center BC of the junction contour line of the other power generation unit 100U are in different positions when viewed in the direction in which the two power generation units 100U are stacked.

[0103] B. Variations: The technologies disclosed herein are not limited to the embodiments described above and can be modified in various forms without departing from their essence, for example, the following modifications are possible.

[0104] Figure 13 is an explanatory diagram showing the XY cross-sectional configuration of the fuel cell stack 10a at position VII-VII in Figure 6 in the modified example. In the following, for the modified fuel cell stack 10a, components identical to those of the fuel cell stack 10 in the embodiment described above will be denoted by the same reference numerals and their descriptions will be omitted. In the modified fuel cell stack 10a, the configuration of the welded portion 182a differs from that of the welded portion 182 in the embodiment.

[0105] As shown in Figure 13, the weld 182a is missing a portion of a complete annular shape. Thus, the weld 182a does not necessarily have to be a complete annular shape, and it may be missing less than 50% of a complete annular shape. Specifically, in a view along the Z axis, an annular shape can be formed by virtually joining or superimposing a virtual weld 182av, which is the shape obtained by rotating the weld 182a around the Z axis by a specific angle of 180 degrees or less, onto the shape of the weld 182a. In such cases, when the combination of the weld 182a and the overlapping contour line DO1 is called combination CM1a, it is sufficient that combination CM1a satisfies the following conditions. Condition (1): In a view along the Z-axis, the joint contour line BO1a, which is the contour line of the welded portion 182a, is similar in shape to more than 50% of the entire circumference of the overlapping portion contour line DO1. Condition (2): In the view along the Z axis, in each direction from the center DC1 of the overlapping contour line toward the overlapping contour line DO1, the joint contour line BO1a encloses more than 50% of the entire circumference of the overlapping contour line DO1. Condition (3): When viewed in the Z-axis direction, if the virtual joint contour line BO1av is the contour line on the side closer to the overlapping contour line DO1 in the virtual weld 182av, then the center BC1a of the figure formed by joining the joint contour line BO1a and the virtual joint contour line BO1av and the center DC1 of the overlapping contour line are in different positions from each other.

[0106] In the above modified example, the welded joint 182 is not shown to be a perfect annular shape, but other joints do not necessarily have to be a perfect annular shape either.

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

[0108] The configuration of the fuel cell stack 10 and the power generation unit 100U in the above embodiment is merely an example and can be modified in various ways. For example, the number of single cells 110 (number of power generation units 100U) included in the fuel cell stack 10 in the above embodiment is merely an example, and the number of single cells 110 can be appropriately determined according to the output voltage required for the fuel cell stack 10.

[0109] The materials constituting each component in the above embodiment are merely examples, and each component 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 herein is also applicable to counter-flow type SOFCs.

[0111] In the above embodiment, the single cell 110 is a fuel electrode-supported single cell, but it may be other types of single cells such as an electrolyte-supported or metal-supported type.

[0112] In the above embodiment, the electrochemical reaction cell stack was a cell stack used in a solid oxide fuel cell (SOFC). However, the above configuration is also applicable to cell stacks used in other types of fuel cells such as polymer electrolyte fuel cells (PEFCs), phosphoric acid fuel cells (PAFCs), and molten carbonate fuel cells (MCFCs), or to electrolytic cell stacks that include electrolytic cell units, which are constituent units of solid oxide electrolytic cells (SOECs), as single cells. [Explanation of symbols]

[0113] 10,10a: Fuel cell stack 96: Glass seal section 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: Separator for single cell 121: Through hole 122: Welded section 124: Connecting member 125: Through hole 126: Area around the through hole 130: Air electrode frame 131: Through hole 132: Oxidizer gas supply communication channel 133: Oxidizer 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 collector 145: Electrode facing section 146: Interconnector facing section 147: Connecting part 149: Spacer 180: IC separator 181: Through hole 182,182a: Welded part 182av: Virtual welded part 184: Welded part 185: Through hole 186: Periphery of through hole 190: Interconnector 191: Flat plate part 192: Air electrode current collector part 193: Coating layer 196: Conductive bonding material 210: First end plate 220: Insulation part 230: End separator 231: Through hole 232: First plate 240: First terminal plate 241: Through hole 242: First bus bar 243: Welded part 250: Second terminal plate 252: Second bus bar 253: Welded part 260: Second plate 270: Second end plate 280: Gas passage member 281: Main body part 282: Flange section 284: Bolt hole 311: Oxidizer gas supply manifold 312: Oxidizer gas discharge manifold 313: Air chamber 321: Fuel gas supply manifold 322: Fuel gas discharge 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. First member and A second member having an overlapping portion which is a portion that overlaps with the first member in a first direction, A joint for joining the first member and the second member, the joint for joining the overlapping portion of the second member and the portion of the first member facing the overlapping portion in the first direction, Equipped with, In an electrochemical reaction cell stack, the overlapping portion has an overlapping portion contour line which is at least one annular contour line in the first viewing direction, The electrochemical reaction cell stack is A combination of the joint portion and the overlapping portion contour line, In the first direction view described above, the joint contour line, which is the contour line of the joint, is similar in shape to the contour line of the overlapping portion. In the first direction view described above, one of the joint contour line and the overlapping contour line surrounds the other of the joint contour line and the overlapping contour line. In the first viewing direction, the combination includes one in which the center of the joint contour line and the center of the overlapping contour line are in different positions from each other. A first unit and a second unit, each having the first member and the second member respectively, are stacked in the first direction. The first unit and the second unit each have the aforementioned combination, At least a portion of the overlapping contour lines of the combination in the first unit and at least a portion of the overlapping contour lines of the combination in the second unit overlap each other in the first direction. The center of the joint contour line of the combination in the first unit and the center of the joint contour line of the combination in the second unit are in different positions from each other in the first direction view. An electrochemical reaction cell stack characterized by the following features.

2. The first member and, A second member having an overlapping portion which is a portion that overlaps with the first member in a first direction, A joint for joining the first member and the second member, the joint for joining the overlapping portion of the second member and the portion of the first member facing the overlapping portion in the first direction, Equipped with, In an electrochemical reaction cell stack, the overlapping portion has an overlapping portion contour line which is at least one annular contour line in the first viewing direction, The electrochemical reaction cell stack is A combination of the joint portion and the overlapping portion contour line, In the first direction view described above, the joint contour line, which is the contour line of the joint, is similar in shape to the contour line of the overlapping portion. In the first direction view described above, one of the joint contour line and the overlapping contour line surrounds the other of the joint contour line and the overlapping contour line. In the first viewing direction, the combination includes one in which the center of the joint contour line and the center of the overlapping contour line are in different positions from each other. There are multiple combinations of the first member and the second member. The distance between the center of the joint contour line and the center of the overlapping contour line in the first direction view of one of the aforementioned combinations is different from the distance between the center of the joint contour line and the center of the overlapping contour line in the first direction view of the other aforementioned combinations. An electrochemical reaction cell stack characterized by the following features.

3. An electrochemical reaction cell stack according to claim 1 or claim 2, In the above combination, the distance between the center of the joint contour line and the center of the overlapping contour line in the first viewing direction is 10 μm or more. An electrochemical reaction cell stack characterized by the following features.

4. An electrochemical reaction cell stack according to claim 1 or claim 2, In the above combination, the longest distance between the joint contour line and the overlapping contour line in the first viewing direction is 1.01 times or more the shortest distance between the joint contour line and the overlapping contour line in the first viewing direction. An electrochemical reaction cell stack characterized by the following features.

5. An electrochemical reaction cell stack according to claim 1 or claim 2, further comprising: The device comprises a plurality of single cells stacked in the first direction, A manifold is formed to supply gas to each of the aforementioned plurality of single cells. The first member is connected to a first through-hole that constitutes a part of the manifold, The second member has a second through-hole that forms part of the manifold. At least a portion of the overlapping contour line coincides with at least a portion of the first through-hole periphery, which is the portion surrounding the first through-hole in the first member, in the first viewing direction. The aforementioned joint is a joining material that surrounds the first through hole and the second through hole, respectively. An electrochemical reaction cell stack characterized by the following features.

6. An electrochemical reaction cell stack according to Claim 1, The joint in the first unit is formed of glass. An electrochemical reaction cell stack characterized by the following features.

7. An electrochemical reaction cell stack according to Claim 2, The joint in the above combination is formed of glass. An electrochemical reaction cell stack characterized by the following features.

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