Complex

Abstract

Prevents damage to joining members in composites. [Solution] The composite comprises a first member, a second member, a joining member, and at least one stress relief portion. The second member is aligned with the first member in a first direction. The joining member is disposed between the first member and the second member in the first direction. The stress relief portion is disposed between a specific member, which is at least one of the first member and the second member, and the joining member in the first direction. The stress relief portion is joined to the specific member by at least one of welding and brazing. The stress relief portion has a displacement portion at a portion different from the joint with the specific member, which is displaceable in the first direction relative to the specific member. At least a portion of the displacement portion is joined to the joining member. The total distance from the joint with the specific member to the joint with the joining member in the stress relief portion is 100 μm or more.

Description

[Technical Field]

[0001] The technology disclosed herein relates to a composite. [Background technology]

[0002] Solid oxide fuel cells (hereinafter referred to as "SOFCs") are known as one type of fuel cell that generates electricity using the electrochemical reaction between hydrogen and oxygen. SOFCs are generally used in the form of a fuel cell stack, which has multiple fuel cell power generation units (hereinafter simply referred to as "power generation units"), which are constituent units, and each power generation unit has a single fuel cell.

[0003] A fuel cell stack includes terminal plates (first members), end plates (second members), and glass seal members (joint members). The end plates are aligned with the terminal plates, for example, in the direction in which the power generation units are stacked (hereinafter referred to as the "first direction"). The joint members are disposed between the end plates and the terminal plates in the first direction. The fuel cell stack may further include stress relief members disposed between the terminal plates and the joint members in the first direction to reduce stress applied to the joint members (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-139360 Summary of the Invention [Problem to be solved by the invention]

[0005] In the fuel cell stack described above, when a relatively large stress occurs that separates the first member and the second member, the joining member may be damaged.

[0006] Note that this issue is also common to electrolysis cell stacks that include, for example, multiple electrolysis cell units, which are constituent units of solid oxide electrolysis cells (hereinafter referred to as "SOECs") that generate hydrogen using the electrolysis reaction of water, and each electrolysis cell unit includes a single electrolysis cell. In this specification, a single fuel cell cell and a single electrolysis cell are collectively referred to as a single electrochemical reaction cell, a fuel cell power generation unit and a single electrolysis cell unit are collectively referred to as an electrochemical reaction unit, and a fuel cell stack and a single electrolysis cell stack are collectively referred to as an electrochemical reaction cell stack. Furthermore, this issue is not limited to SOFCs and SOECs, but is also common to other types of fuel cells and electrolysis cells. Furthermore, this issue is not limited to electrochemical reaction cell stacks, but is common to all composites that include a first member, a second member, a joining member, and a stress relief portion.

[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) A composite disclosed in this specification comprises a first member, a second member, a joining member, and at least one stress relief portion. The second member is aligned with the first member in a first direction. The joining member is disposed between the first member and the second member in the first direction. The stress relief portion is disposed between a specific member, which is at least one of the first member and the second member, and the joining member in the first direction. The stress relief portion is joined to the specific member by at least one of welding and brazing. The stress relief portion has a displacement portion at a portion different from the joint with the specific member, which is displaceable in the first direction relative to the specific member. At least a portion of the displacement portion is joined to the joining member. The total distance from the joint with the specific member to the joint with the joining member in the stress relief portion is 100 μm or more.

[0010] In this composite, the total distance from the joint with the specific member to the joint with the joining member in the stress relaxation portion is 100 μm or more, so that the displaceable portion is more likely to displace in the first direction relative to the specific member. Therefore, even if a relatively large stress that separates the first member and the second member occurs in the composite, damage to the joining member can be suppressed.

[0011] (2) In the composite, the portion of the stress relaxation portion from the joint with the specific member to the joint with the joining member may not be joined to the specific member. With this configuration, the displacing portion is more likely to displace in the first direction relative to the specific member, so that even if a relatively large stress that separates the first member and the second member occurs in the composite, damage to the joining member can be more effectively suppressed.

[0012] (3) In the composite, the length of the stress relaxation portion in the first direction may be shorter than the length of the joining member in the first direction. With this configuration, the rigidity of the stress relaxation portion in the first direction can be reduced, so that even when a relatively large stress that separates the first member and the second member occurs in the composite, damage to the joining member can be more effectively suppressed.

[0013] (4) In the above composite, the composite may be an electrochemical reaction cell stack including a plurality of electrochemical reaction units, each of which has an electrochemical reaction unit cell including an air electrode, an electrolyte layer, and a fuel electrode arranged in this order. This configuration can suppress damage to joining members included in the electrochemical reaction cell stack.

[0014] The technology disclosed in this specification can be realized in various forms, such as a composite, an electrochemical reaction cell stack, and a method for manufacturing the same. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing the appearance of a fuel cell stack according to an embodiment; [Figure 2] FIG. 2 is an explanatory diagram showing an XZ cross section of the fuel cell stack taken along the line II-II in FIG. 1; [Figure 3] FIG. 2 is an explanatory diagram showing an XZ cross section of the fuel cell stack taken along the line III-III in FIG. 1; [Figure 4] An explanatory diagram showing an XZ cross section of two adjacent power generating units at the same position as the cross section shown in Figure 2. [Figure 5] FIG. 4 is an explanatory diagram showing an XZ cross section of two adjacent power generating units at the same position as the cross section shown in FIG. 3. [Figure 6] FIG. 1 is an explanatory diagram showing a detailed configuration of a glass seal portion and its periphery in an embodiment; [Figure 7] FIG. 7 is an explanatory diagram showing an XY cross section of the fuel cell stack taken along line VII-VII in FIG. 6. [Figure 8] FIG. 1 is an explanatory diagram showing a detailed configuration of a glass seal portion and its periphery in an embodiment; [Figure 9] FIG. 10 is an explanatory diagram showing a detailed configuration of the periphery of a glass seal portion of a first modified example; [Figure 10] FIG. 10 is an explanatory diagram showing a detailed configuration of the periphery of a glass seal portion of a second modified example. [Figure 11] FIG. 11 is an explanatory diagram showing a detailed configuration of the periphery of a glass seal portion of a third modified example. [Figure 12] FIG. 10 is an explanatory diagram showing a detailed configuration of the periphery of a glass seal portion of a fourth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0016] A. Implementation: (Configuration of fuel cell stack 10) FIG. 1 is a perspective view showing the appearance of a fuel cell stack 10 according to an embodiment, FIG. 2 is an explanatory diagram showing an XZ cross section of the fuel cell stack 10 taken along line II-II in FIG. 1 , and FIG. 3 is an explanatory diagram showing an XZ cross section of the fuel cell stack 10 taken along line III-III in FIG. Each figure shows mutually orthogonal X, Y, and Z axes for identifying directions. For convenience, the Z-axis direction will be referred to as the up-down direction, the positive Z-axis direction as the up-down direction, and the negative Z-axis direction as the down-down direction in this specification; however, the fuel cell stack 10 may actually be installed in an orientation different from these orientations. The fuel cell stack 10 is an example of a composite. The up-down direction is an example of a first direction.

[0017] 1 to 3, 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, 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 in a stacked manner in this order in a predetermined arrangement direction (vertical direction).

[0018] As shown in FIG. 1, the fuel cell stack 10 has bolt holes BH formed 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 FIGS. 2 and 3, the first plate 232 is supported by the terminal separator 230. Four gas passage members 280 are connected to the second end plate 270.

[0019] As shown in FIGS. 2 and 3, the power generation block 100 is made up of a plurality of (seven in this embodiment) power generation units 100U arranged side by side in a predetermined arrangement direction (vertical direction).

[0020] The first end plate 210 is a member formed by pressing (bending) a single plate-like member, and is formed of a conductive material such as stainless steel. As shown in FIGS. 1 to 3 , the first end plate 210 includes a rectangular, frame-like flat portion 211 with a through-hole 212 formed near the center, and an outer convex portion 213 and an inner convex portion 214 that protrude from the flat portion 211 in the direction opposite to the insulating portion 220 (upward in FIG. 2 ). Holes that form the above-mentioned bolt holes BH are formed in the flat portion 211. 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 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 inner periphery of the flat portion 211.

[0021] Insulating section 220 is a rectangular frame-shaped member with a through hole formed near the center, and is made of, for example, an insulating material. As shown in Figures 2 and 3, insulating section 220 is sandwiched between first end plate 210 and end separator 230, thereby ensuring insulation between first end plate 210 and end separator 230.

[0022] As shown in FIGS. 2 and 3, the terminal separator 230 is a rectangular frame-shaped member having a through-hole 231 formed near the center, and is made of, for example, metal.

[0023] The first plate 232 is a rectangular, flat member made of a conductive material such as stainless steel. As shown in Figures 2 and 3, the first plate 232 is joined by welding, for example, to the periphery of the through-hole 231 in the terminal separator 230. The terminal separator 230 and the first plate 232 separate the power generating block 100 from the external space of the fuel cell stack 10.

[0024] The first plate 232 is connected to an interconnector 190 (described later) provided in a power generation unit 100U arranged 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 anode current collecting member 144 (described later), thereby electrically connecting the power generation unit 100U and the first plate 232.

[0025] The first terminal plate 240 is a rectangular frame-shaped member with a through-hole 241 formed 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 the power generating unit 100U located 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 a terminal separator 230. One end (the right end in FIG. 2) of the first terminal plate 240 protrudes laterally from the power generating block 100, and this protruding portion functions as a positive output terminal for the fuel cell stack 10.

[0026] The second terminal plate 250 is a rectangular plate-shaped member 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 that is 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, and this protruding portion functions as the negative output terminal of the fuel cell stack 10. The second terminal plate 250 is an example of a first member.

[0027] Second plate 260 is a rectangular, flat member made of, for example, an insulating material. The peripheral edge of second plate 260 is sandwiched between second terminal plate 250 and second end plate 270, thereby ensuring insulation between second terminal plate 250 and second end plate 270.

[0028] The second end plate 270 is a member formed by pressing (bending) a single plate-like member, and is formed of a conductive material such as stainless steel. The second end plate 270 has a rectangular, frame-like flat portion 271 with a through-hole 272 formed near the center, and an outer convex portion 273 and an inner convex portion 274 that protrude from the flat portion 271 in the direction opposite to the second terminal plate 250 (downward in FIG. 2). Holes that form the above-mentioned bolt holes BH are formed in the flat portion 271. 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 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 inner periphery of the flat portion 271.

[0029] The second end plate 270 is aligned with the second terminal plate 250 in the vertical direction. As shown in FIGS. 2 and 3, the second end plate 270 is joined to the second terminal plate 250 via a glass seal 262 arranged between the second terminal plate 250 and the second end plate 270 in the vertical direction. The glass seal 262 is an annular glass member that surrounds the periphery of the manifolds 311, 312, 321, and 322 (described later) (see FIG. 6). The detailed configuration of the periphery of the glass seal 262 will be described later. The second end plate 270 is an example of a second member. The glass seal 262 is an example of a joining member.

[0030] 1 to 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.

[0031] 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 arranged on opposite sides of the air chamber 313.

[0032] As shown in Fig. 3, the fuel gas supply manifold 321 is a gas flow path that supplies 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 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. For example, hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG. The fuel gas supply manifold 321 and the fuel gas discharge manifold 322 are arranged on opposite sides of the fuel chamber 323.

[0033] 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 has a gas through hole 283 formed therethrough in the vertical direction. The flange portion 282 is provided so as to protrude outward from the other end (the lower end in FIGS. 2 and 3 ) 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 hole 283 is connected to the manifolds 311, 312, 321, and 322, respectively. A gas pipe (not shown) for supplying or discharging gas is connected to each of the main body portions 281.

[0034] FIG. 4 is an explanatory diagram showing an XZ cross section of two adjacent power generating units 100U at the same position as the cross section shown in FIG. 2. FIG. 5 is an explanatory diagram showing an XZ cross section of two adjacent power generating units 100U at the same position as the cross section shown in FIG. 3. As shown in FIGS. 4 and 5, the power 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, and two IC separators 180. 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 stacked in this order. The power generating unit 100U is an example of an electrochemical reaction unit.

[0035] 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 FIGS. 4 and 5, the air electrode 114, the reaction prevention layer 118, the electrolyte layer 112, and the anode 116 are stacked in this order. The unit cell 110 of this embodiment is an anode-supported unit cell in which the other layers constituting the unit cell 110 (electrolyte layer 112, air electrode 114, and reaction prevention layer 118) are supported by the anode 116. The unit cell 110 is supported by a unit cell separator 120. The unit cell 110 is an example of an electrochemical reaction unit cell.

[0036] The electrolyte layer 112 is a rectangular, flat member having one surface (the upper surface in FIGS. 4 and 5 ) on which the air electrode 114 is disposed and another surface (the lower surface in FIGS. 4 and 5 ) parallel to the first surface on which the anode 116 is disposed. The electrolyte layer 112 is a layer containing a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). The cathode 114 is a layer having a rectangular shape smaller than that of the electrolyte layer 112 and containing, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The anode 116 is a layer having a rectangular shape and approximately the same size as the electrolyte layer 112 and containing, 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 and approximately the same size as the air electrode 114 and containing, for example, GDC (gadolinium-doped ceria). The reaction prevention layer 118 has the function of preventing elements (e.g., Sr) diffused from the air electrode 114 from reacting with elements (e.g., Zr) contained in the electrolyte layer 112 to produce a highly resistive substance (e.g., SrZrO3).

[0037] 4 and 5, 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 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 disposed: the upper surface in FIGS. 4 and 5) by a joint 124. The joint 124 is made of, for example, a brazing material (Ag brazing).

[0038] 4 and 5, the air electrode frame 130 is a rectangular frame-like member with a substantially rectangular through-hole 131 formed near the center, and is made of, for example, mica. As shown in Fig. 4, the air electrode frame 130 has an oxidant gas supply communicating channel 132 that connects the oxidant gas supply manifold 311 and the air chamber 313, and an oxidant gas discharge communicating channel 133 that connects the air chamber 313 and the oxidant gas discharge manifold 312.

[0039] 4 and 5, the anode frame 140 is a rectangular frame-like member with a substantially rectangular through-hole 141 formed near the center, and is made of, for example, metal. As shown in Fig. 5, the anode 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.

[0040] As shown in FIGS. 4 and 5, IC separator 180 is a rectangular frame-shaped member with through-hole 181 formed near the center, and is made of, for example, metal.

[0041] As shown in FIGS. 4 and 5 , 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 collectors 192 are formed from an alloy containing Fe and Cr (e.g., ferritic stainless steel) and are electrically conductive. The coating layer 193 is electrically 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, for example, by welding. The interconnector 190 is supported by the IC separator 180.

[0042] The anode current collecting member 144 is a member that connects the interconnector 190 and the anode 116. The anode current collecting member 144 is formed of a conductive material such as nickel, a nickel alloy, or stainless steel. As shown in FIGS. 4 and 5 , the anode current collecting member 144 has an interconnector facing portion 146, an electrode facing portion 145 that is 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 an overall U-shape. 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.

[0043] As shown in FIGS. 4 and 5, the interconnector 190 is shared by two adjacent power generating units 100U. More specifically, as shown in FIGS. 4 and 5, the air electrode current collecting portion 192 is joined to the air electrode 114 of the unit cell 110 included in one of the two adjacent power generating units 100U via a conductive bonding material 196 formed, for example, of a spinel-type oxide, which bonds the air electrode 114 and the coating layer 193. This electrically connects the air electrode current collecting portion 192 to the air electrode 114. The flat plate portion 191 is electrically connected to the anode 116 of the unit cell 110 included 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.

[0044] However, as shown in Figure 2, the power generating unit 100U located at the other end (the lower end in Figure 2) of the multiple power generating units 100U does not have an interconnector 190 on the fuel electrode 116 side. The fuel electrode 116 included in this power generating unit 100U is connected to the second terminal plate 250 via the fuel electrode current collecting member 144.

[0045] A spacer 149 made of, for example, mica is disposed between the electrode facing portion 145 and the interconnector facing portion 146. This allows the anode current collecting member 144 to follow deformation of the power generating unit 100U due to temperature cycles and reactant gas pressure fluctuations, and good electrical connection is maintained between the anode 116 and the interconnector 190 (or second terminal plate 250) via the anode current collecting member 144.

[0046] 4 and 5, the space partitioned by the single cell separator 120, single cell 110, air electrode frame 130, IC separator 180, and interconnector 190 faces the air electrode 114 and serves as an air chamber 313 through which oxidant gas OG flows. The air electrode frame 130 partitions the entire periphery of the air chamber 313 from the external space 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 external space.

[0047] 4 and 5, 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 forms a fuel chamber 323 through which 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.

[0048] The single cell separator 120 separates the air chamber 313 and the fuel chamber 323, thereby preventing 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 prevent gas leakage between adjacent power generating units 100U.

[0049] (Operation of fuel cell stack 10) As shown in Figures 2 and 4, the oxidizing gas OG is supplied to the oxidizing gas supply manifold 311 via a gas pipe (not shown) and a gas passage member 280, and is supplied to the air chamber 313 via the oxidizing gas supply communicating passage 132.

[0050] As shown in FIGS. 3 and 5, the fuel gas FG is supplied to the fuel gas supply manifold 321 via a gas pipe (not shown) and a gas passage member 280, and is supplied to the fuel chamber 323 via the fuel gas supply communication passage 142.

[0051] When an oxidant gas OG is supplied to the air chamber 313 of each power generating unit 100U and a fuel gas FG is supplied to the fuel chamber 323, power is generated in the unit cell 110 by an electrochemical reaction between the oxidant gas OG and the fuel gas FG. This power generating reaction is exothermic. 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. In other words, the multiple power generating units 100U included in the fuel cell stack 10 are electrically connected in series. Furthermore, a second terminal plate 250 is electrically connected to the power generating unit 100U located at the other end (the lower end in FIG. 2 ) of the multiple power generating units 100U, and a first terminal plate 240 is electrically connected to the power generating unit 100U located at one end (the upper end in FIG. 2 ). As a result, electrical energy generated in each power generating unit 100U is extracted from the terminal plates 240, 250, which 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), after startup, the fuel cell stack 10 may be heated by a heater (not shown) until the high temperature can be maintained using the heat generated by power generation.

[0052] 2 and 4, 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 communicating 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 FIGS. 3 and 5, 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 communicating passage 143 is discharged to the outside of the fuel cell stack 10 through the internal space of the main body 281.

[0053] (Detailed configuration of the glass seal portion 262 and its surroundings) FIG. 6 is an explanatory diagram showing a detailed configuration of the periphery of a glass seal portion 262 in this embodiment. FIG. 6 shows the periphery of the glass seal portion 262 when the fuel cell stack 10 is stopped. In other words, FIG. 6 shows the periphery of the glass seal portion 262 when no stress is applied to the second end plate 270. FIG. 7 is an explanatory diagram showing an XY cross section of the fuel cell stack 10 taken along line VII-VII in FIG. 6. In FIG. 7, the second plate 260 is omitted from the XY cross section of the fuel cell stack 10 to provide a detailed description of the periphery of the glass seal portion 262.

[0054] The fuel cell stack 10 of this embodiment further includes a stress relief portion 710 and a stress relief portion 720. The stress relief portion 710 is disposed between the second terminal plate 250 and the glass seal portion 262 in the vertical direction. The stress relief portion 720 is disposed between the second end plate 270 and the glass seal portion 262 in the vertical direction. FIGS. 6 and 7 show the stress relief portion 710 and the stress relief portion 720 disposed around the oxidant gas supply manifold 311. The stress relief portions 710 disposed around the manifolds 311, 312, 321, and 322 have the same configuration. Similarly, the stress relief portions 720 disposed around the manifolds 311, 312, 321, and 322 have the same configuration. Hereinafter, at least one of the second terminal plate 250 and the second end plate 270 may be referred to as a "specific member."

[0055] The stress relief portion 710 is, for example, a flat plate-like member that can be elastically deformed. More specifically, the vertical rigidity of the stress relief portion 710 is lower than the vertical rigidity of the second terminal plate 250. In this embodiment, the vertical length of the stress relief portion 710 is shorter than the vertical length of the second terminal plate 250. Furthermore, in this embodiment, the vertical length of the stress relief portion 710 is shorter than the vertical length of the glass seal portion 262. The vertical length of the stress relief portion 710 is, for example, half or less of the vertical length of the glass seal portion 262. The vertical length of the second terminal plate 250 may be, for example, approximately 2 mm. The vertical length of the glass seal portion 262 may be, for example, 1 mm or more and 1.2 mm or less. The vertical length of the stress relief portion 710 may be, for example, 0.1 mm or more and 0.3 mm or less. Furthermore, in this embodiment, an alumina coating is formed on the surface of the stress relief portion 710.

[0056] In this embodiment, the stress relief portions 710 extend parallel to a direction perpendicular to the vertical direction when the fuel cell stack 10 is stopped. In other words, the stress relief portions 710 do not have any portions that extend in the vertical direction.

[0057] The stress relief portion 710 has a joint portion 712, a displacement portion 714, and a support portion 716. As shown in Fig. 6, the stress relief portion 710 has a hole 718 formed therein, which communicates with the oxidizing gas supply manifold 311. The shape of the hole 718 is elliptical when viewed from the top-bottom direction.

[0058] The joint portion 712 is a portion of the stress relief portion 710 that is joined to the second terminal plate 250 by at least one of welding and brazing. In this embodiment, the stress relief portion 710 is joined to the second terminal plate 250 by laser welding. The joint portion 712 is formed in an annular shape so as to surround the entire circumference of the hole 718. The joint portion 712 is located inside the inner circumference of the glass seal portion 262 when viewed in the Z-axis direction.

[0059] The displacement portion 714 is a portion of the stress relief portion 710 that is different from the joint portion 712 and is located on the opposite side of the joint portion 712 from the oxidant gas supply manifold 311. As described above, the stress relief portion 710 is formed of an elastically deformable material, and therefore the displacement portion 714 is vertically displaceable relative to the second terminal plate 250. In this embodiment, the displacement portion 714 is displaced vertically from a portion of the displacement portion 714 that is located on the joint portion 712 side so as to move away from the second terminal plate 250. At least a portion of the displacement portion 714 is bonded to the glass seal portion 262. That is, the displacement portion 714 has a joint portion 715 that is a joint portion with the glass seal portion 262. The portion of the stress relief portion 710 from the joint portion 712 with the second terminal plate 250 to the joint portion 715 with the glass seal portion 262 is not bonded to the second terminal plate 250.

[0060] The support portion 716 is a portion of the stress relief portion 710 that is located on the same side as the oxidant gas supply manifold 311 with respect to the joint portion 712. The support portion 716 may be displaceable in the vertical direction relative to the second terminal plate 250, or may not be displaceable in the vertical direction relative to the second terminal plate 250.

[0061] The stress relief portion 720 is, for example, a flat plate-like member that can be elastically deformed. More specifically, the vertical rigidity of the stress relief portion 720 is lower than the vertical rigidity of the flat portion 271 of the second end plate 270. In this embodiment, the vertical length of the stress relief portion 720 is shorter than the vertical length of the flat portion 271. Furthermore, in this embodiment, the vertical length of the stress relief portion 720 is shorter than the vertical length of the glass seal portion 262. The vertical length of the stress relief portion 720 is, for example, half or less of the vertical length of the glass seal portion 262. The vertical length of the flat portion 271 may be, for example, approximately 2 mm. The vertical length of the stress relief portion 720 may be, for example, 0.1 mm or more and 0.3 mm or less. Furthermore, in this embodiment, an alumina coating is formed on the surface of the stress relief portion 720.

[0062] In this embodiment, the stress absorbing portion 720 extends parallel to a direction perpendicular to the vertical direction when the fuel cell stack 10 is stopped. In other words, the stress absorbing portion 720 does not have a portion that extends in the vertical direction.

[0063] The stress relief portion 720 has a joint portion 722, a displacement portion 724, and a support portion 726. As shown in Figures 6 and 7, the stress relief portion 720 has a hole 728 formed therein that communicates with the oxidizing gas supply manifold 311. The shape of the hole 728 when viewed from above and below is elliptical (see Figure 7).

[0064] The joint portion 722 is a portion of the stress relief portion 720 that is joined to the second end plate 270 by at least one of welding and brazing. In this embodiment, the stress relief portion 720 is joined to the second end plate 270 by laser welding. The joint portion 722 is formed in an annular shape so as to surround the entire periphery of the hole 728. The joint portion 722 is located outside the outer periphery of the glass seal portion 262 when viewed in the Z-axis direction.

[0065] The displacement portion 724 is a portion of the stress relief portion 720 that is different from the joint portion 722 and is located on the same side of the joint portion 722 as the oxidant gas supply manifold 311. As described above, the stress relief portion 720 is formed of an elastically deformable material, and therefore the displacement portion 724 is vertically displaceable relative to the second end plate 270. In this embodiment, the displacement portion 724 is displaced vertically from a portion of the displacement portion 724 that is located on the joint portion 722 side, away from the second end plate 270. At least a portion of the displacement portion 724 is bonded to the glass seal portion 262. That is, the displacement portion 724 has a joint portion 725 that is a joint portion with the glass seal portion 262. The portion of the stress relief portion 720 from the joint portion 722 with the second end plate 270 to the joint portion 725 with the glass seal portion 262 is not bonded to the second end plate 270.

[0066] The support portion 726 is a portion of the stress relief portion 720 that is located on the opposite side of the joint portion 722 from the oxidant gas supply manifold 311. The support portion 726 may be displaceable in the vertical direction relative to the second end plate 270, or may not be displaceable in the vertical direction relative to the second end plate 270.

[0067] Fig. 8 is an explanatory diagram showing a detailed configuration of the periphery of the glass seal portion 262 of the embodiment. In the fuel cell stack 10, as shown in Fig. 8, for example, when oxidant gas OG flows through the gas through-holes 283, stress is applied to the second end plate 270, which may cause deformation of the second end plate 270. In other words, Fig. 8 shows the periphery of the glass seal portion 262 when the fuel cell stack 10 is operating and the second end plate 270 is deformed so that the second terminal plate 250 and the second end plate 270 are separated in the vertical direction.

[0068] In the fuel cell stack 10, the total distance from the joints 712, 722 with the specific members in the stress mitigation portions 710, 720 to the joints 715, 725 with the glass seal portion 262 is 100 μm or more. More specifically, in this embodiment, the total of the distance from the joint 712 with the second terminal plate 250 to the joint 715 with the glass seal portion 262 in the stress mitigation portion 710 (hereinafter referred to as the "first distance") and the distance from the joint 722 with the second end plate 270 to the joint 725 with the glass seal portion 262 in the stress mitigation portion 720 (hereinafter referred to as the "second distance") is 100 μm or more. More specifically, the "first distance" refers to the length of the stress mitigation portion 710 from point P1 on the joint 712 to point P2 on the joint 715, when these points are determined so that the distance from the joint 712 to the joint 715 is shortest when viewed in the vertical direction. More specifically, the second distance means the length of stress relaxation section 720 from point P3 to point P4 when point P3 on joint 722 and point P4 on joint 725 are determined so that the distance from joint 722 to joint 725 is shortest when viewed from the top to bottom.

[0069] 8, when stress is applied to the fuel cell stack 10 to separate the second terminal plate 250 and the second end plate 270 in the vertical direction, the displacement portion 714 of the stress absorbing portion 710 is displaced downward relative to the second terminal plate 250, and the displacement portion 724 of the stress absorbing portion 720 is displaced upward relative to the second end plate 270. This reduces the stress applied to the glass seal portion 262, and prevents damage to the glass seal portion 262.

[0070] (Effects of this embodiment) As described above, the fuel cell stack 10 of this embodiment includes the second terminal plate 250, the second end plate 270, the glass seal portion 262, and the stress relief portions 710 and 720. The second end plate 270 is aligned with the second terminal plate 250 in the vertical direction. The glass seal portion 262 is disposed between the second terminal plate 250 and the second end plate 270 in the vertical direction. The stress relief portions 710 and 720 are disposed between the glass seal portion 262 and a specific member, which is at least one of the second terminal plate 250 and the second end plate 270, in the vertical direction. The stress relief portions 710 and 720 are joined to the specific member by at least one of welding and brazing. The stress relief portions 710 and 720 have displacement portions 714 and 724 at locations different from the joint portions 712 and 722 with the specific member, which are displaceable in the vertical direction relative to the specific member. At least a part of the displacement portions 714, 724 is bonded to the glass seal portion 262. The total distance from the bonding portions 712, 722 with the specific member in the stress mitigation portions 710, 720 to the bonding portions 715, 725 with the glass seal portion 262 is 100 μm or more.

[0071] In the fuel cell stack 10 of this embodiment, the total distance from the joints 712, 722 with the specific member in the stress absorbing portions 710, 720 to the joints 715, 725 with the glass seal portion 262 is 100 μm or more, which makes it easier for the displacement portions 714, 724 to be displaced in the vertical direction relative to the specific member. Therefore, even if a relatively large stress that separates the second terminal plate 250 and the second end plate 270 occurs in the fuel cell stack 10, damage to the glass seal portion 262 can be suppressed.

[0072] In the fuel cell stack 10 of this embodiment, the portions of the stress absorbing portions 710, 720 from the joints 712, 722 with the specific member to the joints 715, 725 with the glass seal portion 262 are not joined to the specific member. According to the fuel cell stack 10 of this embodiment, the displacement portions 714, 724 are more likely to be displaced in the vertical direction relative to the specific member, and therefore damage to the glass seal portion 262 can be more effectively suppressed even when a relatively large stress that separates the second terminal plate 250 and the second end plate 270 is generated in the fuel cell stack 10.

[0073] In the fuel cell stack 10 of this embodiment, the vertical length of the stress absorbing portions 710, 720 is shorter than the vertical length of the glass seal portion 262. According to the fuel cell stack 10 of this embodiment, the vertical rigidity of the stress absorbing portions 710, 720 can be reduced, and therefore damage to the glass seal portion 262 can be more effectively suppressed even when a relatively large stress that separates the second terminal plate 250 and the second end plate 270 occurs in the fuel cell stack 10.

[0074] The fuel cell stack 10 of this embodiment is a fuel cell stack that includes a plurality of power generation units 100U, each of which has a single cell 110 that includes an air electrode 114, an electrolyte layer 112, and an anode 116 arranged in this order. The fuel cell stack 10 of this embodiment can suppress damage to the glass seal portion 262 included in the fuel cell stack.

[0075] 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 thereof, for example, the following modifications are also possible.

[0076] 9 is an explanatory diagram showing the detailed configuration of the periphery of the glass seal portion 262 of the first modified example. In the following, parts of the fuel cell stack 10 of the first modified example that are common to the fuel cell stack 10 of the above-described embodiment are denoted by the same reference numerals and descriptions thereof will be omitted as appropriate.

[0077] The fuel cell stack 10 of the first modified example differs from the stress relief portion 710 of the fuel cell stack 10 of the embodiment in the configuration of the stress relief portion 710a. The stress relief portion 710a has a joint portion 712a, a displacement portion 714a, and a support portion 716a. The joint portion 712a differs from the joint portion 712 of the embodiment in that it is located outside the outer periphery of the glass seal portion 262 when viewed in the up-down direction. The displacement portion 714a differs from the displacement portion 714 of the embodiment in that it is located on the same side as the oxidant gas supply manifold 311 with respect to the joint portion 712a. The support portion 716a differs from the support portion 716 in that it is located on the opposite side of the manifold 311 with respect to the joint portion 712a. As in the first modified example, the joint portion of the stress relief portion disposed between the first member and the joint member may be located outside the outer periphery of the joint member when viewed in the first direction. Similarly, the joint portion of the stress relaxation portion disposed between the second member and the joint member may be located inside the inner periphery of the joint member when viewed in the first direction.

[0078] 10 is an explanatory diagram showing the detailed configuration of the periphery of the glass seal portion 262 of the second modified example. In the following, parts of the fuel cell stack 10 of the second modified example that are common to the fuel cell stack 10 of the above-described embodiment are denoted by the same reference numerals and their description will be omitted as appropriate.

[0079] In the fuel cell stack 10 of the second modified example, the configuration of the stress relaxation portion 720b differs from the configuration of the stress relaxation portion 720 in the fuel cell stack 10 of the embodiment. The stress relaxation portion 720b has a portion that extends in the vertical direction when the fuel cell stack 10 is stopped. More specifically, the displacement portion 724b of the stress relaxation portion 720b has a portion that extends so as to bend upward between the joint 722 and the joint 725. As in the second modified example, the stress relaxation portion may have a portion that extends in the first direction.

[0080] 11 is an explanatory diagram showing the detailed configuration of the periphery of the glass seal portion 262 of the third modified example. In the following, parts of the fuel cell stack 10 of the third modified example that are common to the fuel cell stack 10 of the above-described embodiment are denoted by the same reference numerals and their description will be omitted as appropriate.

[0081] In the fuel cell stack 10 of the third modified example, the configuration of the stress relief portion 720c differs from the configuration of the stress relief portion 720 in the fuel cell stack 10 of the embodiment. The stress relief portion 720c has a portion that extends in the vertical direction when the fuel cell stack 10 is stopped. More specifically, the displacement portion 724c of the stress relief portion 720c has a portion that extends downward between the joint 722 and the joint 725. The displacement portion 724c of the stress relief portion 720c also has portions that overlap with each other in the vertical direction between the joint 722 and the joint 725. As in the third modified example, the stress relief portion may have a portion that extends in the first direction, or may have portions that overlap with each other in the first direction between the joint with the specific member and the joint with the joining member.

[0082] In an embodiment in which the stress relief portion has a portion extending in the first direction, as in the second and third modifications, the distance from the joint with the specific member to the joint with the joining member in the stress relief portion can be determined as follows: That is, a line segment is drawn connecting the joint with the specific member and the joint with the joining member so that the distance from the joint with the specific member to the joint with the joining member is the shortest when viewed in the first direction, and when a cross section parallel to the first direction and the line segment is obtained, the length of the stress relief portion from the joint with the specific member to the joint with the joining member in the cross section can be determined as the distance from the joint with the specific member to the joint with the joining member in the stress relief portion.

[0083] 12 is an explanatory diagram showing the detailed configuration of the periphery of the glass seal portion 262 of the fourth modified example. In the following, parts of the fuel cell stack 10 of the fourth modified example that are common to the fuel cell stack 10 of the above-described embodiment are denoted by the same reference numerals and descriptions thereof will be omitted as appropriate.

[0084] The fuel cell stack 10 of the fourth modified example does not include a member equivalent to the stress relief portion 710 in the fuel cell stack 10 of the embodiment. That is, the fuel cell stack 10 of the fourth modified example includes only a stress relief portion 720 disposed between the second end plate 270 and the glass seal portion 262 as the stress relief portion. As in the fourth modified example, at least one stress relief portion is sufficient. When there is one stress relief portion, it is sufficient that the distance from the joint portion with the specific member in the stress relief portion to the joint portion with the joining member is 100 μm or more.

[0085] The length of the stress relaxation portion in the first direction may be longer than the length of the joining member in the first direction.

[0086] The joining material may be other materials such as mica.

[0087] The number of unit cells (number of power generation units) included in the fuel cell stack is merely an example, and the number of unit cells is determined appropriately depending on the output voltage required for the fuel cell stack.

[0088] The fuel cell stack 10 of the above embodiment is a co-flow type SOFC, but the technology disclosed in this specification is also applicable to counter-flow type SOFCs and cross-flow type SOFCs.

[0089] 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.

[0090] In the above embodiment, the fuel cell stack 10 is configured to have a plurality of flat-type unit cells 110, but the technology disclosed in this specification is equally applicable to fuel cell stacks having a plurality of unit cells of other types (e.g., cylindrical, flat cylindrical, etc.).

[0091] The features described in the above embodiments are not limited to electrochemical reaction cell stacks, etc., but are applicable to any composite body that includes a first member, a second member, a joining member, and a stress relaxation portion. [Explanation of symbols]

[0092] 10: Fuel cell stack 100: Power generation block 100U: Power generation unit 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Anode 118: Reaction prevention layer 120: Single cell separator 130: Air electrode frame 132: Oxidant gas supply communication channel 133: Oxidant gas discharge communication channel 140: Anode frame 142: Fuel gas supply communication channel 143: Fuel gas discharge communication channel 144: Anode current collecting member 149: Spacer 180: IC separator 190: Interconnector 210: First end plate 220: Insulation section 230: Terminal separator 232: First plate 240: First terminal plate 250: Second terminal plate 260: Second plate 262: Glass seal section 270: Second end plate 271: Flat portion 280: Gas passage member 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 710, 710a: Stress relief portion 712, 712a: Joint portion 714, 714a: Displacement portion 715: Joint portion 716, 716a: Support portion 718: Hole 720, 720b, 720c: Stress relief portion 722: Joint portion 724, 724b, 724c: Displacement portion 725: Joint portion 726: Support portion 728: Hole B: Bolt BH: Bolt hole N: Nut FG: Fuel gas FOG: Fuel off-gas OG: Oxidizer gas OOG: Oxidizer off-gas

Claims

1. A first member; a second member aligned with the first member in a first direction; a joining member disposed between the first member and the second member in the first direction; At least one stress relief portion, The stress relaxation portion is a specific member that is at least one of the first member and the second member in the first direction and is disposed between the joining member, The specific member is joined by at least one of welding and brazing, a displacement portion that is displaceable in the first direction relative to the specific member at a portion different from a joint portion with the specific member; a stress relaxation portion, at least a part of which is joined to the joining member; In a composite comprising: a total distance from a joint portion with the specific member to a joint portion with the joining member in the stress relaxation portion is 100 μm or more; A complex characterized by:

2. 2. The composite of claim 1 , a portion of the stress relaxation portion from a joint with the specific member to a joint with the joining member is not joined to the specific member; A complex characterized by:

3. 2. The composite of claim 1 , a length of the stress relaxation portion in the first direction is shorter than a length of the joining member in the first direction; A complex characterized by:

4. The composite according to any one of claims 1 to 3, The complex is It has a plurality of electrochemical reaction units, Each of the electrochemical reaction units is an electrochemical reaction cell stack having an electrochemical reaction unit cell in which an air electrode, an electrolyte layer, and a fuel electrode are arranged in this order. A complex characterized by:

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