Electrochemical reaction single cell and electrochemical reaction cell stack

Abstract

It suppresses cracking in single cells of electrochemical reactions. [Solution] The electrochemical reaction single cell is a flat plate type electrochemical reaction single cell in which an air electrode, an electrolyte layer, and a fuel electrode are stacked in this order in the first direction. When viewed along a second direction perpendicular to the first direction, the electrochemical reaction single cell is curved in a convex manner toward the direction in which the air electrode is located. The corner of the fuel electrode where the first surface facing the side opposite to the side in the first direction where the electrolyte layer is located intersects with the second surface facing the second direction is chamfered.

Description

Technical Field

[0001] The technology disclosed in this specification relates to an electrochemical reaction single cell and 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 (SOFC) having an electrolyte layer containing a solid oxide is known. SOFCs are generally used in the form of a fuel cell stack including a plurality of fuel cell single cells in which an air electrode, an electrolyte layer, and a fuel electrode are stacked in this order. Conventionally, an SOFC having chamfers at the corners of the portions where other members in the electrode contact has been disclosed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The fuel cell single cell may warp in a convex state in the direction where the air electrode is located. Also, in the fuel cell single cell, the corners of the fuel electrode are likely to include chipping. Chipping at the corners of the fuel electrode is likely to be the starting point of cracking in the fuel cell single cell. Therefore, when such fuel cell single cells are stacked, if an external force is applied to the fuel cell single cells, the fuel cell single cells may crack.

[0005] Furthermore, these challenges are also common to electrolytic cell stacks that include multiple solid oxide type electrolytic cells (hereinafter referred to as "SOECs") that produce 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. Moreover, these challenges are not limited to SOFCs and SOECs, but are also common to other types of fuel cells and electrolytic cells.

[0006] This specification discloses a technology capable of solving the above-mentioned problems. [Means for solving the problem]

[0007] The technologies disclosed herein can be implemented, for example, in the following forms:

[0008] (1) The electrochemical reaction single cell disclosed herein is a flat plate type electrochemical reaction single cell in which an air electrode, an electrolyte layer, and a fuel electrode are stacked in this order in a first direction. The electrochemical reaction single cell is curved in a convex manner toward the direction in which the air electrode is located when viewed along a second direction perpendicular to the first direction. The corner of the fuel electrode where the first surface facing the side opposite to the side in which the electrolyte layer is located in the first direction intersects with the second surface facing the second direction is chamfered. With this electrochemical reaction single cell, chipping is eliminated by chamfering the corner of the intersecting first and second surfaces of the fuel electrode, and thus cracking of the electrochemical reaction single cell can be suppressed.

[0009] (2) In the electrochemical reaction single cell described above, the second surface is a plane extending in a third direction perpendicular to the first and second directions, and both ends in the third direction may be sandwiched between curved surfaces. With this configuration, the corners including the second surface, which is relatively prone to cracking and is sandwiched between curved surfaces, are chamfered, so cracking of the electrochemical reaction single cell can be suppressed more effectively.

[0010] (3) In the electrochemical reaction single cell described above, the curvature of the electrochemical reaction single cell when viewed along the second direction may be greater than the curvature of the electrochemical reaction single cell when viewed along a third direction that is perpendicular to both the first and second directions. With this configuration, the corner where the first surface and the second surface, which are corners with relatively large curvature, intersect is chamfered, so cracking of the electrochemical reaction single cell can be suppressed more effectively.

[0011] (4) In the electrochemical reaction single cell described above, the fuel electrode may have a chamfered edge around the entire circumference of the corner where the first surface and the surface intersecting the first direction intersect. With this configuration, since the entire circumference of the corner where the first surface and the surface intersecting the first direction intersect is chamfered, cracking of the electrochemical reaction single cell can be suppressed more effectively.

[0012] (5) In the electrochemical reaction single cell described above, the corners of the fuel electrode may be chamfered by a portion that is between one-quarter and three-quarters of the thickness of the fuel electrode in the first direction. This configuration suppresses cracking of the electrochemical reaction cell stack while preventing the electrochemical reaction cell stack from becoming too thin by chamfering the fuel electrode.

[0013] (6) The electrochemical reaction cell stack disclosed herein comprises a plurality of electrochemical reaction single cells arranged in the first direction, wherein at least one of the plurality of electrochemical reaction single cells may be the electrochemical reaction single cell described in any one of (1) to (5) above. With this electrochemical reaction cell stack, chipping is eliminated by chamfering the corners where the first and second surfaces of the fuel electrode intersect, thereby suppressing cracking of the electrochemical reaction single cell.

[0014] Furthermore, the technologies disclosed herein can be implemented in various forms, such as single electrochemical reaction cells, electrochemical reaction cell stacks, and methods for manufacturing them. [Brief explanation of the drawing]

[0015] [Figure 1] Perspective view showing the appearance of the fuel cell stack of the first embodiment [Figure 2] XZ cross-sectional view of the fuel cell stack at the position II-II of FIG. 1 [Figure 3] XZ cross-sectional view of the fuel cell stack at the position III-III of FIG. 1 [Figure 4] YZ cross-sectional view of the fuel cell stack at the position IV-IV of FIG. 1 [Figure 5] XZ cross-sectional view of two adjacent reaction units in the first embodiment [Figure 6] XZ cross-sectional view of two adjacent reaction units in the first embodiment [Figure 7] YZ cross-sectional view of two adjacent reaction units in the first embodiment [Figure 8] Perspective view showing the structure of the fuel electrode of the first embodiment [Figure 9] Explanatory view showing the fuel electrode of the first embodiment when viewed along the Y-axis direction [Figure 10] Explanatory view showing the fuel electrode of the first embodiment when viewed along the Z-axis direction [Figure 11] XZ cross-sectional view of two adjacent reaction units in the second embodiment [Figure 12] YZ cross-sectional view of two adjacent reaction units in the second embodiment [Figure 13] Perspective view showing the structure of the fuel electrode of the second embodiment [Figure 14] Perspective view showing the structure of the fuel electrode of the third embodiment[[ID=,42]] [Figure 15] Explanatory view showing the fuel electrode of the modified example when viewed along the Y-axis direction

Mode for Carrying Out the Invention

[0016] (First Embodiment) Figure 1 is a perspective view showing the external appearance of the fuel cell stack 10 of the first embodiment. Figure 2 is an XZ cross-sectional view of the fuel cell stack 10 at position II-II in Figure 1. Figure 3 is an XZ cross-sectional view of the fuel cell stack 10 at position III-III in Figure 1. Figure 4 is a YZ cross-sectional view of the fuel cell stack 10 at position IV-IV in Figure 1. Each figure shows mutually orthogonal XYZ axes to specify the direction. The fuel cell stack 10 is an example of an electrochemical reaction cell stack. The Z-axis direction is an example of a first direction. The Y-axis direction is an example of a second direction. The X-axis direction is an example of a third direction.

[0017] 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, 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 (Z-axis direction).

[0018] As shown in Figure 1, 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.

[0019] As shown in Figures 2 to 4, the power generation block 100 is composed of a plurality of reaction units 100U arranged in a predetermined alignment direction (Z-axis direction). In this embodiment, the power generation block 100 comprises seven reaction units 100U.

[0020] Figures 5 and 6 are XZ cross-sectional views of two adjacent reaction units 100U in the first embodiment. Figure 5 is an XZ cross-sectional view of two adjacent reaction units 100U at the same position as the cross-section shown in Figure 2. Figure 6 is an XZ cross-sectional view of two adjacent reaction units 100U at the same position as the cross-section shown in Figure 3. Figure 7 is a YZ cross-sectional view of two adjacent reaction units 100U in the first embodiment. Figure 7 is a YZ cross-sectional view of two adjacent reaction units 100U at the same position as the cross-section shown in Figure 4.

[0021] As shown in Figures 5 to 7, the reaction 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, a first glass seal portion 135, and a second glass seal portion 125. 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. The single cell 110 is supported by the single cell separator 120, the two interconnectors 190 are each supported by the two IC separators 180, and the fuel electrode current collector 144 is positioned between the single cell 110 and the interconnectors 190.

[0022] As shown in Figures 5 to 7, the IC separator 180 and interconnector 190 are shared by two adjacent reaction units 100U. However, as shown in Figure 2, one of the reaction units 100U located at one end (the lower end in Figure 2) does not have an IC separator 180 and interconnector 190 adjacent to the fuel electrode frame 140, and the second terminal plate 250 is superimposed on the fuel electrode frame 140.

[0023] The single cell 110 comprises an electrolyte layer 112, an air electrode 114, and a fuel electrode 116. As shown in Figures 5 to 7, the air electrode 114, the electrolyte layer 112, and the fuel electrode 116 are arranged in this order in the Z-axis direction, with a reaction prevention layer 118 interposed between the electrolyte layer 112 and the air electrode 114. As shown in Figures 5 to 7, the single cell 110 is a flat cell. The single cell 110 of this embodiment is a fuel electrode-supported single cell in which the other layers of the single cell 110 are supported by the fuel electrode 116. In this specification, the direction in which the air electrode 114, the electrolyte layer 112, and the fuel electrode 116 are stacked is called the "stacking direction," and the direction perpendicular to the stacking direction is called the "plane direction." The single cell 110 is an example of an electrochemical reaction single cell.

[0024] The electrolyte layer 112 is a rectangular, flat member having one surface on which the air electrode 114 is located (the upper surface in Figures 5 to 7) and another surface parallel to the air electrode 116 (the lower surface in Figures 5 to 7). The electrolyte layer 112 contains a solid oxide such as YSZ (yttria-stabilized zirconia). The air electrode 114 is a layer having a rectangular shape smaller than the electrolyte layer 112. The air electrode 114 contains a perovskite-type oxide such as 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 diffused from the air electrode 114 with elements contained in the electrolyte layer 112, which would otherwise result in the formation of a highly resistive substance.

[0025] As shown in Figures 5 to 7, the single-cell separator 120 is a rectangular frame-shaped member having a roughly rectangular through-hole 121 near the center. The single-cell separator 120 is conductive and is made of a metal such as ferritic stainless steel. The thickness of the single-cell separator 120 is, 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 the electrolyte layer 112 by a joint 124. The joint 124 is made of a brazing material such as silver brazing material.

[0026] The second glass seal portion 125 is positioned on the single cell 110 and covers the edge of the through hole 121 in the single cell separator 120 and its surrounding area. The second glass seal portion 125 is made of crystallized glass. The second glass seal portion 125 may be made of, for example, SiO2-B2O3-MgO glass. The second glass seal portion 125 seals the gap between the single cell 110 and the single cell separator 120, effectively suppressing gas 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.

[0027] As shown in Figures 5 to 7, the air electrode frame 130 is a rectangular frame-shaped member having a roughly rectangular through-hole 131 near the center, and is formed of an insulating ceramic such as mica. The thickness of the air electrode frame 130 is, for example, 0.5 mm or more and 5 mm or less. The air electrode frame 130 has two sealing holes 132 located on both sides of the through-hole 131 (see Figure 6).

[0028] Each air electrode frame 130 has two seal holes 132, each containing one first glass seal portion 135. The first glass seal portion 135 is a cylindrical member with openings at both ends. The first glass seal portion 135 is made of, for example, SiO2-B2O3-MgO glass. One end of the first glass seal portion 135 is joined to the single-cell separator 120, and the other end is joined to the IC separator 180.

[0029] As shown in Figures 5 to 7, the fuel electrode frame 140 is a rectangular frame-shaped member having a roughly rectangular through-hole 141 near its center. The fuel electrode frame 140 is conductive and is made of a metal such as ferritic stainless steel.

[0030] As shown in Figures 5 to 7, the IC separator 180 is a rectangular frame-shaped member having a through hole 181 near the center. The IC separator 180 is conductive and is made of a metal such as ferritic stainless steel. The thickness of the IC separator 180 is, for example, 0.05 mm or more and 0.2 mm or less.

[0031] As shown in Figures 5 to 7, the interconnector 190 comprises a rectangular flat plate portion 191, a plurality of plate-shaped air electrode current collector portions 192 protruding from one surface of the flat plate portion 191 toward the air electrode 114, and a coating layer 193. The flat plate portion 191 and the air electrode current collector portions 192 are conductive and are made of a metal such as ferritic stainless steel. The coating layer 193 is conductive and is made of a spinel-type oxide, for example. The coating layer 193 is arranged to cover the surface of the air electrode current collector portions 192 and the surface of the flat plate portion 191 on which the air electrode current collector portions 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.

[0032] 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. The fuel electrode current collector 144 includes an interconnector-facing portion 146, an electrode-facing portion 145 substantially 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. 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.

[0033] As described above, the interconnector 190 is shared by two adjacent reaction units 100U. More specifically, as shown in Figures 5 to 7, 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 reaction 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 reaction units 100U via a fuel electrode current collector member 144. This ensures electrical conductivity between the two adjacent reaction units 100U.

[0034] However, as described above, the reaction unit 100U located at one end (the lower end of Figure 2) of the multiple reaction units 100U does not have an interconnector 190 on the fuel electrode 116 side. The fuel electrode 116 provided in this reaction unit 100U is connected to the second terminal plate 250 via a fuel electrode current collector 144.

[0035] 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 reaction unit 100U due to temperature cycles and reaction gas pressure fluctuations, and the electrical connection between the fuel electrode 116 via the fuel electrode current collector 144 and the interconnect 190 or second terminal plate 250 is maintained well.

[0036] As shown in Figures 5 to 7, 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.

[0037] 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.

[0038] The single-cell separator 120 separates the air chamber 313 from the fuel chamber 323, suppressing cross-leakage of gas 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 reaction units 100U.

[0039] The first end plate 210 is a component formed by press-forming a single plate-shaped member. The first end plate 210 is made of a metal such as ferritic stainless steel. The thickness of the first end plate 210 is, for example, 0.5 mm or more and 3 mm or less. 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 project 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 arranged 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 arranged around the entire circumference of the inner peripheral portion of the planar portion 211.

[0040] The insulating portion 220 is a rectangular frame-shaped member with a through hole near the center, and is made of an insulating material. As shown in Figures 2 to 4, 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.

[0041] 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. The end separator 230 is conductive and is made of a metal such as ferritic stainless steel.

[0042] The first plate 232 is a rectangular, flat member. The first plate 232 is conductive and is made of a metal such as ferritic 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.

[0043] The first plate 232 is connected to an interconnector 190 provided on a reaction unit 100U located at the other end (upper end in Figure 2) of the multiple reaction units 100U that constitute the power generation block 100, via a connecting member with the same structure as the fuel electrode current collector 144. This electrically connects the reaction unit 100U and the first plate 232.

[0044] As shown in Figures 2 to 4, the first terminal plate 240 is a rectangular frame-shaped member having a through hole 241 near the center. The first terminal plate 240 is conductive and is made of a metal such as ferritic stainless steel. The thickness of the first terminal plate 240 is, for example, 0.2 mm or more and 3 mm or less. The first terminal plate 240 is electrically connected to the reaction unit 100U located at the other end (upper end in Figure 2) of the multiple reaction units 100U that constitute 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. This protruding portion functions as the positive output terminal of the fuel cell stack 10.

[0045] The second terminal plate 250 is a rectangular plate-shaped member. The second terminal plate 250 is conductive and is made of a metal such as ferritic stainless steel. The thickness of the second terminal plate 250 is, for example, 0.2 mm or more and 3 mm or less. As described above, the second terminal plate 250 is connected to the fuel electrode 116 provided on the reaction unit 100U located at one end (the lower end in Figure 2) of the plurality of reaction units 100U via the fuel electrode current collector 144. In this way, the reaction unit 100U and the second terminal plate 250 are electrically connected. One end of the second terminal plate 250 (the right end in Figure 2) protrudes laterally from the power generation block 100. This protruding portion functions as the negative output terminal of the fuel cell stack 10.

[0046] The second plate 260 is a rectangular, flat member made of an insulating material. As shown in Figures 2 to 4, 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.

[0047] The second end plate 270 is a component formed by press-forming a single plate-shaped member. The second end plate 270 is made of a metal such as ferritic stainless steel. The thickness of the second end plate 270 is, for example, 0.5 mm or more and 3 mm or less. As shown in Figures 2 to 4, 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 outer projection 273 protrudes from the outer peripheral edge of the planar portion 271. The outer projection 273 is arranged 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 arranged around the entire circumference of the inner peripheral portion of the planar portion 271.

[0048] As shown in Figures 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 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.

[0049] 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 chamber 313 of each reaction unit 100U. The oxidizer gas discharge manifold 312 is a gas flow path that discharges oxidizer off-gas OOG, discharged from the air chamber 313 of each reaction unit 100U, to the outside of the fuel cell stack 10. For example, air is used as the oxidizer gas OG.

[0050] 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 reaction unit 100U. The fuel gas discharge manifold 322 is a gas passage that discharges fuel off-gas FOG discharged from the fuel chamber 323 of each reaction 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.

[0051] As shown in Figure 6, the fuel gas supply manifold 321 penetrates one of the two first glass seal portions 135 located inside each air electrode frame 130. In other words, the internal space of the first glass seal portion 135 is part of the fuel gas supply manifold 321. Similarly, the fuel gas exhaust manifold 322 penetrates the other of the two first glass seal portions 135 located inside each air electrode frame 130. In other words, the internal space of the first glass seal portion 135 is part of the fuel gas exhaust manifold 322. The first glass seal portions 135 suppress leakage of fuel gas FG or fuel off-gas FOG from the fuel gas supply manifold 321 and the fuel gas exhaust 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.

[0052] 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 is cylindrical with open ends. The flange portion 282 is provided so as to protrude outward from one 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. The other 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 internal space of the main body portion 281 communicates with the manifolds 311, 312, 321, and 322, respectively. Gas piping for gas supply or discharge is connected to each main body portion 281.

[0053] The following describes the configuration of the single cell 110 in detail.

[0054] Figure 8 is a perspective view showing the configuration of the fuel electrode 116 of the first embodiment. Figure 9 is an explanatory diagram showing the fuel electrode 116 of the first embodiment as viewed along the Y-axis. Figure 10 is an explanatory diagram showing the fuel electrode 116 of the first embodiment as viewed along the Z-axis. Figure 10 shows the configuration of the fuel electrode 116 as viewed from the positive Z-axis direction. In Figures 8 to 10, components other than the fuel electrode 116 in the fuel cell stack 10 are omitted.

[0055] As shown in Figures 5 to 10, the fuel electrode 116 of this embodiment has a first surface S1, a second surface S2, and a third surface S3. The first surface S1 is the surface facing the opposite side (negative Z-axis direction) from the side where the electrolyte layer 112 is located in the Z-axis direction. The second surface S2 is the surface facing in the Y-axis direction. The second surface S2 is a plane extending in the X-axis direction. The third surface S3 is the surface facing in the X-axis direction. The third surface S3 is a plane extending in the Y-axis direction. As shown in Figures 8 and 10, the second surface S2 and the third surface S3 are connected by a curved surface CS. In other words, the second surface S2 is sandwiched at both ends in the X-axis direction by the curved surface CS, and the third surface S3 is sandwiched at both ends in the Y-axis direction by the curved surface CS. As shown in Figure 10, the fuel electrode 116 of this embodiment is substantially rectangular in shape when viewed along the stacking direction, with its corners having a curved, rounded shape.

[0056] In this embodiment, the single cell 110 is curved in a convex manner towards the direction in which the air electrode 114 is located when viewed along the Y-axis (see Figures 5 and 6). In other words, the single cell 110 is curved such that the area near the center of the single cell 110 bulges towards the side where the air electrode 114 is located. Furthermore, in this embodiment, the single cell 110 is curved in a convex manner towards the direction in which the air electrode 114 is located when viewed along the X-axis (see Figure 7). In this embodiment, the curvature of the single cell 110 when viewed along the Y-axis is equivalent to the curvature of the single cell 110 when viewed along the X-axis.

[0057] The configuration in which a single cell 110 is "curved" can be defined by the amount of curvature of the single cell 110 and the maximum width of the single cell 110 in the planar direction. The amount of curvature of the single cell 110 can be determined as follows. First, when viewing the fuel electrode 116 along the Y-axis direction, determine the end E1 that is furthest from the electrolyte layer 112 among the parts located on one side (negative X-axis direction side) relative to the center in the X-axis direction, and the end E2 that is furthest from the electrolyte layer 112 among the parts located on the other side (negative X-axis direction side) relative to the center in the X-axis direction. Then, by determining the width W2, which is the distance between the imaginary line VL connecting end E1 and end E2 and the recess DP, which is the part of the first surface S1 of the fuel electrode 116 that faces the Y-axis direction and is furthest from the imaginary line VL, the amount of curvature of the single cell 110 can be determined (see Figure 9). The maximum width of the single cell 110 in the planar direction can be determined as follows. The maximum width in the planar direction of a single cell 110 is equal to the maximum width of the component in the single cell 110 that has the greatest planar width. In other words, as shown in Figures 5 to 7, in this embodiment, the component in the planar direction that has the greatest width of a single cell 110 is the fuel electrode 116 (and electrolyte layer 112). Therefore, by determining the maximum width W1 in the planar direction of the fuel electrode 116, the maximum width in the planar direction of the single cell 110 can be determined (see Figure 10). In this specification, a configuration in which the value of W2 / W1 in a single cell 110 is 0.005 or greater is defined as the single cell 110 being "warped".

[0058] The fuel electrode 116 has a chamfered corner CP1 where the first surface S1 and the second surface S2 intersect. The corner CP1 of the fuel electrode 116 is chamfered to a portion of the fuel electrode 116's thickness T1 in the Z-axis direction that is between one-quarter and three-quarters of the total thickness T1 in the Z-axis direction. In other words, the amount of chamfering W3 in the Z-axis direction is between one-quarter and three-quarters of the fuel electrode 116's thickness T1 in the Z-axis direction. More specifically, the amount of chamfering W3 is the distance in the Z-axis direction from the first surface S1 to the second surface S2 at the point where the amount of chamfering in the Z-axis direction of the second surface S2 is maximum. In this embodiment, the corner CP1 may be formed by chamfering the first surface S1 and the second surface S2, which intersect at right angles to each other. The fuel electrode 116 may also be formed with the corner CP1 already chamfered from the beginning.

[0059] In this embodiment, similar to the corner CP1, the corner CP2 of the fuel electrode 116 where the first surface S1 and the third surface S3 intersect is also chamfered. The corner CP2 of the fuel electrode 116 is chamfered to a portion of the thickness T1 in the Z-axis direction of the fuel electrode 116 that is between one-quarter and three-quarters of the total thickness. In this embodiment, the corner CP2 may be formed by chamfering the first surface S1 and the third surface S3 which intersect at right angles to each other. The fuel electrode 116 may be formed with the corner CP2 already chamfered from the beginning. In this embodiment, the corner of the fuel electrode 116 where the first surface S1 and the curved surface CS intersect is not chamfered.

[0060] The above single cell 110 can be manufactured, for example, by the following manufacturing method.

[0061] To the YSZ powder, butyral resin, dioctyl phthalate (DOP) as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added and mixed in a ball mill to prepare a slurry. The obtained slurry is thinned using the doctor blade method to obtain, for example, a green sheet for the electrolyte layer with a thickness of approximately 10 μm. Alternatively, NiO powder and YSZ powder are mixed to obtain a mixed powder. To this mixed powder, butyral resin, DOP as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added and mixed in a ball mill to prepare a slurry. The obtained slurry is thinned using the doctor blade method to obtain, for example, a green sheet for the fuel electrode with a thickness of 270 μm. Each green sheet is attached, degreased at a predetermined temperature (e.g., approximately 280°C), and then fired at a predetermined temperature (e.g., approximately 1350°C) for a predetermined time (e.g., approximately 1 hour). This obtains a laminate of the electrolyte layer 112 and the fuel electrode 116. Furthermore, the warping of the single cell 110 may be caused by the degreasing or firing process described above.

[0062] A reaction-preventing layer paste is prepared by adding polyvinyl alcohol as an organic binder and butyl carbitol as an organic solvent to GDC powder, mixing the mixture, and adjusting the viscosity. The obtained reaction-preventing layer paste is applied to the surface of the electrolyte layer 112 in the laminate described above, for example by screen printing, and fired at a predetermined temperature (e.g., 1200°C). This forms a reaction-preventing layer 118, and a laminate of the reaction-preventing layer 118, the electrolyte layer 112, and the fuel electrode 116 is obtained.

[0063] A mixed powder of perovskite oxide powder (e.g., LSCF) and sulfate powder (e.g., SrSO4) is prepared. Polyvinyl alcohol as an organic binder and butyl carbitol as an organic solvent are added to this mixed powder and mixed to adjust the viscosity, thereby preparing an air electrode paste. The obtained air electrode paste is applied to the surface of the reaction prevention layer 118 in the laminate of the reaction prevention layer 118, electrolyte layer 112, and fuel electrode 116, for example by screen printing, and dried. The laminate coated with the air electrode paste is then fired at a predetermined temperature (e.g., about 1100°C). This forms the air electrode 114. For the fuel electrode 116, the corner where the first surface facing the side opposite to the side where the electrolyte layer 112 is located in the lamination direction intersects with the second surface facing in a direction perpendicular to the lamination direction is chamfered. Chamfering may be performed by known methods such as cutting or polishing. Based on the above, a single cell 110 comprising a fuel electrode 116, an electrolyte layer 112, a reaction prevention layer 118, and an air electrode 114 is manufactured.

[0064] The basic operation of the fuel cell stack 10 described above will now be explained. As shown in Figures 2 and 5, the oxidizer gas OG is supplied from the oxidizer gas supply manifold 311 to the air chamber 313 via the gas passage member 280. Also, as shown in Figures 3 and 6, the fuel gas FG is supplied from the fuel gas supply manifold 321 to the fuel chamber 323 via the gas passage member 280.

[0065] When oxidant gas OG is supplied to the air chamber 313 of each reaction unit 100U and fuel gas FG is supplied to the fuel chamber 323, electricity is generated in the single cell 110 by an electrochemical reaction between the oxidant 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 reaction units 100U, and the interconnector 190 ensures conductivity between the two adjacent reaction units 100U. In other words, the multiple reaction units 100U included in the fuel cell stack 10 are electrically connected in series. Furthermore, the second terminal plate 250 is electrically connected to the reaction unit 100U located at one end (the lower end of Figure 2), and the first terminal plate 240 is electrically connected to the reaction unit 100U located at the other end (the upper end of Figure 2). As a result, the electrical energy generated in each reaction unit 100U is extracted from the terminal plates 240 and 250, which function as output terminals of the fuel cell stack 10. Since SOFCs generate electricity at relatively high temperatures (for example, 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.

[0066] As shown in Figures 2 and 5, the oxidizer off-gas OOG discharged from the air chamber 313 of each reaction unit 100U to the oxidizer gas discharge manifold 312 is discharged to the outside of the fuel cell stack 10 through the inside 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 reaction unit 100U to the fuel gas discharge manifold 322 is discharged to the outside of the fuel cell stack 10 through the inside of the main body 281.

[0067] As described above, the single cell 110 of this embodiment is a flat-plate type single cell 110 in which an air electrode 114, an electrolyte layer 112, and a fuel electrode 116 are stacked in this order along the Z-axis. When viewed along the Y-axis, which is perpendicular to the Z-axis, the single cell 110 is curved in a convex manner toward the direction in which the air electrode 114 is located. The corner CP1 where the first surface S1, which faces the side opposite to the side in the Z-axis direction where the electrolyte layer 112 is located, and the second surface S2, which faces the Y-axis direction, intersect is chamfered. According to the single cell 110 of this embodiment, chipping is eliminated by chamfering the corner CP1 where the first surface S1 and the second surface S2 intersect on the fuel electrode 116, and thus cracking of the single cell 110 can be suppressed.

[0068] In the single cell 110 of this embodiment, the second surface S2 is a plane extending in the X-axis direction, which is perpendicular to the Z-axis direction and the Y-axis direction, respectively, and is sandwiched at both ends in the X-axis direction by curved surfaces CS. According to the single cell 110 of this embodiment, the corner CP1 including the second surface S2, which is relatively prone to cracking and is sandwiched at both ends by curved surfaces CS, is chamfered, so cracking of the single cell 110 can be suppressed more effectively.

[0069] In the single cell 110 of this embodiment, the corner portion CP1 of the fuel electrode 116 is chamfered to a portion that is between one-quarter and three-quarters of the thickness of the fuel electrode 116 in the Z-axis direction. According to the single cell 110 of this embodiment, the chamfering of the fuel electrode 116 suppresses the single cell 110 from becoming too thin, while also suppressing cracking of the single cell 110.

[0070] The fuel cell stack 10 of this embodiment comprises a plurality of single cells arranged in a line along the Z-axis, and at least one of the plurality of single cells is the single cell 110 described above. According to the fuel cell stack 10 of this embodiment, chipping is eliminated by chamfering the corner CP1 where the first surface S1 and the second surface S2 of the fuel electrode 116 intersect, thereby suppressing cracking of the single cell 110.

[0071] (Second Embodiment) Figure 11 is an XZ cross-sectional view of two adjacent reaction units 100U in the second embodiment. Figure 11 shows a cross-section at the same location as the cross-section shown in Figure 5 in the fuel cell stack 10 of the second embodiment. Figure 12 is a YZ cross-sectional view of two adjacent reaction units 100U in the second embodiment. Figure 12 shows a cross-section at the same location as the cross-section shown in Figure 7 in the fuel cell stack 10 of the second embodiment. Figure 13 is a perspective view showing the configuration of the fuel electrode 116a in the second embodiment. Hereinafter, for the configuration of the fuel electrode 116a in this embodiment, components that are common with the fuel electrode 116 of the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted.

[0072] The fuel cell stack 10 of this embodiment includes a single cell 110a. The single cell 110a of this embodiment is curved in a convex manner towards the direction in which the air electrode 114 is located when viewed along the Y-axis direction (see Figure 11). The single cell 110a of this embodiment does not have any curvature when viewed along the X-axis direction (see Figure 12). That is, the curvature of the single cell 110a when viewed along the Y-axis direction is greater than the curvature of the single cell 110a when viewed along the X-axis direction.

[0073] The single cell 110a of this embodiment includes a fuel electrode 116a. The corner CP1 where the first surface S1 and the second surface S2 intersect of the fuel electrode 116a is chamfered. The corner CP1 of the fuel electrode 116a is chamfered to a portion of the thickness T1 in the Z-axis direction of the fuel electrode 116a that is between one-quarter and three-quarters. The corner CP2 where the first surface S1 and the third surface S3 intersect of the fuel electrode 116a is not chamfered.

[0074] As explained above, in the single cell 110a of this embodiment, the curvature of the single cell 110a when viewed along the Y-axis is greater than the curvature of the single cell 110a when viewed along the X-axis, which is perpendicular to the Z-axis and Y-axis. In the single cell 110a of this embodiment, the corner CP1 where the first surface S1 and the second surface S2, which are corners with relatively large curvature, intersect is chamfered, so cracking of the single cell 110a can be suppressed more effectively.

[0075] (Third embodiment) Figure 14 is a perspective view showing the configuration of the fuel electrode 116b of the third embodiment. In the following description, components of the fuel electrode 116b of this embodiment that are common with the fuel electrode 116 of the first embodiment will be denoted by the same reference numerals and their explanations will be omitted.

[0076] The single cell 110b of this embodiment includes a fuel electrode 116b. The fuel electrode 116b has chamfered edges at corner CP1, corner CP2, and the corner where the first surface S1 and the curved surface CS intersect. That is, in the single cell 110b of this embodiment, the entire circumference of the corner where the first surface S1 and the surface intersecting in the Z-axis direction intersect is chamfered. The width of the chamfer may differ in each part.

[0077] As described above, in the single cell 110b of this embodiment, the entire circumference of the corner where the first surface S1 and the surface intersecting in the Z-axis direction intersect is chamfered. According to the single cell 110b of this embodiment, since the entire circumference of the corner where the first surface S1 and the surface intersecting in the Z-axis direction intersect is chamfered, cracking of the single cell 110b can be suppressed more effectively.

[0078] (modified version) 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.

[0079] Figure 15 is an explanatory diagram showing a modified fuel electrode 116c as viewed along the Y-axis. In the following, components of the fuel electrode 116c of this modified example that are common with the fuel electrode 116 of the first embodiment will be denoted by the same reference numerals and their explanations will be omitted.

[0080] In this modified example, the single cell 110c has two convex portions in the direction of the air electrode 114 when viewed along the Y-axis. That is, as shown in Figure 15, the fuel electrode 116c has a recess DP1, a recess DP2, and a convex portion PP. Recess DP1 is the portion furthest from the imaginary line VL among the portions located on one side (negative X-axis direction side) of the center in the X-axis direction when the fuel electrode 116c is viewed along the Y-axis. Recess DP2 is the portion furthest from the imaginary line VL among the portions located on the other side (positive X-axis direction side) of the center in the X-axis direction when the fuel electrode 116c is viewed along the Y-axis. The convex portion PP is located between recess DP1 and recess DP2 in the X-axis direction and is closer to the imaginary line VL than recesses DP1 and DP2. Thus, an electrochemical reaction single cell may have two or more convex portions in the direction of the air electrode.

[0081] The configuration of the fuel cell stack 10 and reaction unit 100U in the above embodiment is merely an example and can be modified in various ways. Furthermore, the manufacturing method of the single cell 110 in the above embodiment is merely an example.

[0082] In the above embodiment, the second surface S2 is sandwiched at both ends in the X-axis direction by curved surfaces CS, but is not necessarily limited to this. That is, the electrochemical reaction single cell and the fuel electrode may be rectangular when viewed along the stacking direction.

[0083] In the second embodiment described above, the curvature of the single cell 110a when viewed along the Y-axis is greater than the curvature of the single cell 110a when viewed along the X-axis, but this is not necessarily limited to this. That is, the corners of the single cell, where the curvature is relatively small, may be chamfered.

[0084] In the above embodiment, the corner portion CP1 of the fuel electrode 116 is chamfered to a portion that is between one-quarter and three-quarters of the thickness T1 in the Z-axis direction of the fuel electrode 116, but is not necessarily limited to this.

[0085] The above configuration can also be applied 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), as well as to electrolytic cell stacks that incorporate electrolytic cell units, which are constituent units of solid oxide electrolytic cells (SOECs), as single cells. [Explanation of symbols]

[0086] 10: Fuel cell stack 100: Power generation block 100U: Reaction unit 110,110a~110c: Single cell 112: Electrolyte layer 114: Air electrode 116,116a~116c: Fuel electrode 118: Reaction prevention layer 120: Separator for single cell 124: Joint 125: Second glass seal 130: Air electrode frame 135: First glass seal 140: Fuel electrode frame 144: Fuel electrode current collector 149: Spacer 180: Separator for IC 190: Interconnector 196: Conductive bonding material 210: First end plate 220: Insulation part 230: End separator 232: First plate 240: First terminal plate 250: Second terminal plate 260: Second plate 270: Second end plate 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 B: Bolt BH: Bolt hole N: Nut S1: First surface S2: Second surface S3: Third surface CS: Curved surface CP1: Corner CP2: Corner T1: Thickness W1: Maximum width W2: Width W3: Chamfer amount

Claims

1. In a flat-plate type electrochemical reaction single cell in which the air electrode, electrolyte layer, and fuel electrode are stacked in this order in the first direction, The electrochemical reaction single cell is curved in a convex manner toward the direction in which the air electrode is located when viewed along a second direction perpendicular to the first direction. The fuel electrode has a first surface facing the side opposite to the side where the electrolyte layer is located in the first direction, and a second surface facing the second direction, and the corner where these surfaces intersect is chamfered. A single cell for electrochemical reactions, characterized by the following features.

2. In the electrochemical reaction single cell according to claim 1, The second surface is a plane extending in a third direction perpendicular to the first and second directions, and is sandwiched at both ends of the third direction by curved surfaces. A single cell for electrochemical reactions, characterized by the following features.

3. In the electrochemical reaction single cell according to claim 1, The curvature of the electrochemical reaction single cell when viewed along the second direction is greater than the curvature of the electrochemical reaction single cell when viewed along a third direction perpendicular to both the first and second directions. A single cell for electrochemical reactions, characterized by the following features.

4. In the electrochemical reaction single cell according to claim 1, The fuel electrode has a chamfered edge around the entire circumference of the corner where the first surface and the surface intersecting in the first direction intersect. A single cell for electrochemical reactions, characterized by the following features.

5. In the electrochemical reaction single cell according to claim 1, The corners of the fuel electrode are chamfered to a portion that is between one-quarter and three-quarters of the thickness of the fuel electrode in the first direction. A single cell for electrochemical reactions, characterized by the following features.

6. In an electrochemical reaction cell stack comprising a plurality of electrochemical reaction single cells arranged in the first direction, At least one of the plurality of electrochemical reaction single cells is an electrochemical reaction single cell according to any one of claims 1 to 5. An electrochemical reaction cell stack characterized by the following features.

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