Electrochemical reaction cell stack

Abstract

To suppress leakage of a gas to the outside of a stack.SOLUTION: An electrochemical reaction cell stack comprises: a single cell in which an air electrode, an electrolyte layer and a fuel electrode overlap in this order; and a plurality of tabular separators adjacent in a thickness direction to at least one of a fuel gas circulation space, in which a fuel gas is circulated, and an oxidant gas circulation space in which an oxidant gas is circulated. The plurality of separators include: a separator for single cells which supports the single cell and isolates the fuel gas circulation space and the oxidant gas circulation space; and an external separator which is a member for isolating the fuel gas circulation space or the oxidant gas circulation space from an external space, and is a member electrically connected to the single cell and different from a terminal for outputting electric energy generated in the single cell to the outside or inputting electric energy from the outside to the single cell. Rigidity of the external separator is higher than rigidity of the separator for single cells.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Solid oxide fuel cells (hereinafter referred to as "SOFCs"), which have an electrolyte layer containing solid oxide, 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, in which multiple structural units (electrochemical reaction units) are arranged in a predetermined direction. Each electrochemical reaction unit includes a single cell in which an air electrode, an electrolyte layer containing solid oxide, and a fuel electrode are stacked in this order, and a cover separator (external separator) that separates the internal and external spaces of the fuel cell stack (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-17722 Summary of the Invention [Problem to be solved by the invention]

[0004] In a fuel cell stack having the above configuration, it is required to suppress leakage of gas to the outside of the stack even if the pressure in the internal space of the fuel cell increases unintentionally.

[0005] Such issues are also common to electrolysis cell stacks that include 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 are not limited to SOFCs and SOECs, but are also common to other types of electrochemical reaction cell stacks.

[0006] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0007] The technology disclosed in this specification can be realized, for example, in the following forms. (1) The electrochemical reaction cell stack disclosed in this specification comprises a unit cell in which an air electrode, an electrolyte layer, and a fuel electrode are stacked in this order, and a plurality of plate-shaped separators adjacent in the thickness direction to at least one of a fuel gas circulation space through which a fuel gas flows and an oxidizer gas circulation space through which an oxidizer gas flows, wherein the plurality of separators include a unit cell separator that supports the unit cell and separates the fuel gas circulation space from the oxidizer gas circulation space, and an external separator that is a member that separates the fuel gas circulation space or the oxidizer gas circulation space from an external space, is electrically connected to the unit cell, and is a member different from a terminal for outputting electrical energy generated in the unit cell to the outside or for inputting electrical energy from the outside to the unit cell, and wherein the rigidity of the external separator is higher than the rigidity of the unit cell separator.

[0008] According to the above configuration, compared to when the rigidity of the external separator is equivalent to that of the single cell separator, even if the pressure inside the gas flow space increases unintentionally, deformation or damage to the external separator is suppressed, and gas leakage outside the stack can be suppressed.

[0009] (2) In the electrochemical reaction cell stack described in (1) above, the thickness of the external separator may be greater than the thickness of the single cell separator.

[0010] According to this configuration, the rigidity of the external separator can be made higher than the rigidity of the single cell separator with a simple configuration, and leakage of gas to the outside of the stack can be suppressed.

[0011] (3) The electrochemical reaction cell stack described in (1) or (2) above comprises a reaction block including the single cell and the single cell separator, and a subunit arranged on the outer surface of the reaction block and including the external separator, wherein the fuel gas circulation space includes a fuel chamber arranged inside the reaction block and facing the anode, and a sub-circulation space arranged inside the subunit and separated from the external space by the external separator, and the reaction block further includes a fuel gas supply manifold that supplies the fuel gas to the fuel chamber, and a fuel gas discharge manifold that discharges the fuel gas after passing through the fuel chamber, and the sub-circulation space is connected to the fuel gas discharge manifold, but may not be connected to the fuel gas supply manifold.

[0012] For example, if a component that adversely affects the operation of the electrochemical reaction cell stack is disposed inside the sub-circulation space if oxidized, it is preferable to create a reducing atmosphere inside the sub-circulation space to suppress oxidation of the component. The fuel gas used in the electrochemical reaction cell stack is generally a reducing gas such as hydrogen, and supplying this fuel gas to the sub-circulation space can create a reducing atmosphere inside the sub-circulation space. Due to pressure loss occurring when passing through the fuel chamber, the fuel gas passing through the fuel gas exhaust manifold has a lower pressure than the fuel gas passing through the fuel gas supply manifold. Therefore, when the sub-circulation space is connected to the fuel gas exhaust manifold, the pressure inside the sub-circulation space can be lower than when the sub-circulation space is connected to the fuel gas supply manifold. This more effectively suppresses gas leakage outside the stack.

[0013] (4) The electrochemical reaction cell stack described in any one of (1) to (3) above may further include a terminal electrically connected to the single cell for outputting electrical energy generated in the single cell to the outside or for inputting electrical energy from the outside to the single cell, and the plurality of separators may include a terminal separator electrically connected to the single cell and in contact with the terminal, and the thickness of the terminal separator may be greater than the thickness of the single cell separator.

[0014] With this configuration, it is possible to reduce the power transmission loss due to the electrical resistance of the terminal separator, compared to when the thickness of the terminal separator is equal to or less than that of the unit cell separator.

[0015] The technology disclosed in this specification can be realized in various forms, for example, in the form of an electrochemical reaction cell stack and a manufacturing method thereof. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing the external configuration of a fuel cell stack according to an embodiment; [Figure 2] FIG. 2 is a cross-sectional view of the fuel cell stack according to the embodiment taken along line II-II in FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view of the fuel cell stack according to the embodiment taken along line III-III in FIG. 1. [Figure 4] 2 is a cross-sectional view showing two adjacent electrochemical reaction units in the fuel cell stack of the embodiment, cut at the same position as line II-II in FIG. 1. [Figure 5] 3 is a cross-sectional view showing two adjacent electrochemical reaction units in the fuel cell stack of the embodiment, cut at the same position as line III-III in FIG. 1. [Figure 6] 6 is a cross-sectional view showing the fuel cell stack of the embodiment taken along line VI-VI in FIG. 4. [Figure 7] FIG. 10 is a diagram showing the flow of gas supplied to the fuel chamber and the sub-flow space in Test Example 1-2. [Figure 8] 1 is a graph showing the relationship between the flow rate of air supplied to the fuel chamber and the pressure in the fuel supply manifold, the fuel discharge manifold, and the sub-flow space in Test Example 1-1. [Figure 9] 1 is a graph showing the relationship between the flow rate of air supplied to the fuel chamber and the pressure in the fuel supply manifold, the fuel discharge manifold, and the sub-flow space in Test Example 1-2. [Figure 10] FIG. 10 is a partially enlarged cross-sectional view showing the stress relaxation portion of the external separator set in the simulation in Test Example 2. [Figure 11] Graph showing fatigue fracture curves and cumulative equivalent inelastic strains of stress relaxation portions provided in external separators, terminal separators, and other separators after a predetermined number of thermal cycles in Test Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0017] A. Implementation: A-1. Configuration of fuel cell stack 10: The embodiment will be described with reference to Figures 1 to 6. A fuel cell stack 10 (an example of an electrochemical reaction cell stack) of the present embodiment is used in a solid oxide fuel cell having an electrolyte layer 112 containing a solid oxide.

[0018] (Overall configuration of fuel cell stack 10) 1 to 3, the fuel cell stack 10 includes a power generation block 100 (an example of a reaction block), a first insulating plate 220A, a second insulating plate 220B, a terminal unit 230 (an example of a subunit), an end frame 250, an end plate 260, a first end plate 210, a second end plate 270, and four gas passage members 280A, 280B. The power generation block 100 includes a plurality of unit cells 110 and a second terminal plate 160 (an example of a terminal). The terminal unit 230 includes an external separator 231 (an example of a separator, a terminal separator), an external plate 234, and a first terminal plate 241 (an example of a terminal).

[0019] The first end plate 210, the first insulating plate 220A, the terminal unit 230, the power generation block 100, the terminal frame 250, the terminal plate 260, the second insulating plate 220B, and the second end plate 270 have rectangular outer shapes of approximately the same size and are arranged in this order, stacked in a predetermined arrangement direction (the up and down direction in Figure 2).

[0020] As shown in FIGS. 1 to 3 , the fuel cell stack 10 has four bolt holes BH that penetrate 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 components from the first end plate 210 to the second end plate 270 together. An insulating sheet IS is interposed between the nut N and the first end plate 210, and between the nut N and the second end plate 270. The insulating sheet IS is made of, for example, a mica sheet, a ceramic fiber sheet, a pressed ceramic powder sheet, a glass sheet, or a glass-ceramic composite. There is a gap between the outer surface of each bolt B and the inner surface of each bolt hole BH.

[0021] (Overall configuration of the power generation block 100) 2 and 3, the power generation block 100 is composed of a plurality of (seven in this embodiment) electrochemical reaction units 100U (hereinafter sometimes abbreviated as "reaction units 100U") arranged side by side in a predetermined arrangement direction (the vertical direction in FIG. 2). In the following explanation, when describing the plurality of reaction units 100U, the reaction unit 100U arranged at one end (the upper end in FIG. 2) close to the first end plate 210 as distinct from the others, it will be referred to as the "first reaction unit 100UP," and when describing the other end (the lower end in FIG. 2) close to the second end plate 270 as distinct from the others, it will be referred to as the "second reaction unit 100UN."

[0022] (Overall configuration of 100U electrochemical reaction units) 4 and 5, the electrochemical reaction unit 100U includes multiple separators (a single cell separator 120 and two IC separators 180), a single cell 110, an air electrode frame 130, an anode frame 140, an anode current collecting member 144, and two interconnectors 190. 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 in a predetermined arrangement direction (the vertical direction in FIG. 4). The single cell 110 is supported by the single cell separator 120, the two interconnectors 190 are supported by the two IC separators 180, and the anode current collecting member 144 is disposed between the single cell 110 and the interconnectors 190. However, the second reaction unit 100UN includes a second terminal plate 160 instead of the fuel electrode frame 140, as shown in FIGS.

[0023] 4 and 5, the IC separator 180 and the interconnector 190 are shared by two adjacent reaction units 100U. In the following description, when the IC separator 180 and the interconnector 190 provided in the first reaction unit 100UP and disposed at one end close to the first end plate 210 (the upper end in FIG. 2) are described separately, they will be referred to as the "IC separator 180P" and the "interconnector 190P," respectively. Furthermore, when the IC separator 180 (an example of a terminal separator) and the interconnector 190 provided in the second reaction unit 100UN and disposed at the other end close to the second end plate 270 (the lower end in FIG. 2) are described separately, they will be referred to as the "IC separator 180N" and the "interconnector 190N," respectively.

[0024] (single cell 110) The unit cell 110 includes an electrolyte layer 112, a cathode 114, and an anode 116. As shown in Figures 4 and 5, the cathode 114, the electrolyte layer 112, and the anode 116 are stacked in this order, with a reaction prevention layer 118 interposed between the electrolyte layer 112 and the cathode 114. The unit cell 110 of this embodiment is an anode-supported unit cell in which the anode 116 supports the other layers (electrolyte layer 112, cathode 114, and reaction prevention layer 118) that make up the unit cell 110.

[0025] The electrolyte layer 112 is a rectangular, flat-plate member and contains a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). The air electrode 114 is a layer having a rectangular shape smaller than the electrolyte layer 112 and contains, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The anode 116 is a layer having a rectangular shape and approximately the same size as the electrolyte layer 112 and contains, for example, Ni (nickel), a cermet made of Ni and ceramic particles, or a Ni-based alloy. The reaction prevention layer 118 is a layer having a rectangular shape and approximately the same size as the air electrode 114 and contains, for example, GDC (gadolinium-doped ceria). The reaction prevention layer 118 has the function of suppressing the reaction of an element (e.g., Sr) diffused from the air electrode 114 with an element (e.g., Zr) contained in the electrolyte layer 112 to produce a highly resistive substance (e.g., SrZrO).

[0026] (Single cell separator 120) As shown in FIGS. 4 and 5, the single cell separator 120 is a rectangular plate-like member having a substantially rectangular through-hole 121 near the center, and is made of a conductive material such as metal (e.g., ferritic stainless steel). The thickness of the single cell separator 120 is, for example, 0.1 mm or less. The peripheral portion of the through-hole 121 in the single cell separator 120 is joined to the peripheral portion of the electrolyte layer 112 by a joint portion 124. The joint portion 124 is formed of, for example, a brazing material (Ag brazing). A portion of the single cell separator 120 serves as a stress relief portion 122 for alleviating thermal stress caused by high temperatures inside the fuel cell stack 10 during operation. The stress relief portion 122 is, for example, a portion curved in a U-shaped groove shape, and is arranged to surround the entire periphery of the through-hole 121.

[0027] (Air electrode frame 130) As shown in FIGS. 4 and 5, the cathode frame 130 is a rectangular plate-like member having a substantially rectangular through-hole 131 near the center, and is made of, for example, insulating ceramics (mica, etc.).

[0028] (fuel electrode frame 140) As shown in FIGS. 4 and 5, the fuel electrode frame 140 is a rectangular plate-like member having a substantially rectangular through-hole 141 near the center, and is made of, for example, metal.

[0029] (IC separator 180) 4 and 5, the IC separator 180 is a rectangular plate-like member having a through-hole 181 near the center, and is made of a conductive material such as metal (e.g., ferritic stainless steel). A portion of the IC separator 180 serves as a stress relief portion 182 for alleviating thermal stress that occurs when the inside of the fuel cell stack 10 becomes hot during operation. The stress relief portion 182 is, for example, a portion curved in a U-shaped groove, and is arranged to surround the entire periphery of the through-hole 181.

[0030] (Interconnector 190 and anode current collecting member 144) 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 conductive and formed of a conductive material such as metal (e.g., ferritic stainless steel). The coating layer 193 is conductive and is disposed so as to cover the surface of the air electrode current collector 192 and the surface of the flat plate portion 191 on which the air electrode current collector 192 is disposed. The flat plate portion 191 is joined to the periphery of the through hole 181 in the IC separator 180, for example, by welding.

[0031] The anode current collecting member 144 is a member that connects the interconnector 190 and the anode 116, and is formed of a conductive material such as nickel, a nickel alloy, or stainless steel. As shown in Figures 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.

[0032] As described above, the interconnector 190 is shared by two adjacent reaction units 100U. More specifically, as shown in Figures 4 and 5, the air electrode current collecting part 192 is joined to the air electrode 114 of the unit 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, and is thereby electrically connected to the air electrode 114. The flat plate part 191 is electrically connected to the anode 116 of the unit cell 110 provided in the other of the two adjacent reaction units 100U via an anode current collecting member 144. This ensures electrical continuity between the two adjacent reaction units 100U.

[0033] 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 reaction unit 100U due to temperature cycles and fluctuations in reactant gas pressure, and good electrical connection between the anode 116 and the interconnector 190 via the anode current collecting member 144 is maintained.

[0034] (Second terminal plate 160) As shown in Figures 2 and 3, the second terminal plate 160 is a rectangular plate-shaped member having a through hole 161 near the center, and is made of a conductive material such as ferritic stainless steel that forms an alumina oxide coating on its surface.

[0035] The second terminal plate 160 is disposed between the single cell separator 120 and the IC separator 180N provided in the second reaction unit 100UN, and is electrically connected to the single cell 110 via the IC separator 180N and the interconnector 190N. The second terminal plate 160 functions as a negative output terminal for outputting the electrical energy generated by the single cell 110 to the outside.

[0036] The thickness of the IC separator 180N in contact with the second terminal plate 160 is greater than the unit cell separator 120 and the other IC separators 180. The thickness of the IC separator 180N is preferably greater than 0.1 mm and equal to or less than 0.35 mm, for example.

[0037] (Overall configuration of terminal unit 230) As described above, the terminal unit 230 includes the external separator 231, the external plate 234, and the first terminal plate 241. The first terminal plate 241 and the external separator 231 have rectangular shapes of approximately the same size, and are stacked in this order on the first reaction unit 100UP (specifically, the IC separator 180P), as shown in Figures 4 and 5. The external plate 234 is supported by the external separator 231.

[0038] (External separator 231) As shown in FIGS. 4 and 5, the external separator 231 is a rectangular plate-like member having a through-hole 232 near the center, and is made of a conductive material such as metal (e.g., ferritic stainless steel). The thickness of the external separator 231 is greater than that of the single cell separator 120. The thickness of the external separator 231 is preferably greater than 0.1 mm and not greater than 0.35 mm, for example. A part of the external separator 231 serves as a stress relief portion 233 for alleviating thermal stress caused by high temperatures inside the fuel cell stack 10 during operation. The stress relief portion 233 is, for example, a portion curved in a U-shaped groove, and is arranged to surround the entire periphery of the through-hole 232.

[0039] (External Plate 234) The external plate 234 is a rectangular, flat member made of a conductive material such as stainless steel. The thickness of the external plate 234 is greater than the thickness of the external separator 231. As shown in Figures 4 and 5, the external plate 234 is joined to the peripheral portion of the through-hole 232 in the external separator 231 by, for example, welding.

[0040] (External current collecting member 235) The external current collecting member 235 is formed of a conductive material, similar to the anode current collecting member 144, and has the same structure as the anode current collecting member 144. The external current collecting member 235 of this embodiment contains nickel or a nickel alloy. As shown in FIGS. 4 and 5, the external current collecting member 235 electrically connects the external plate 234 and the interconnector 190 provided in the first reaction unit 100UP. This electrically connects the external plate 234 and the single cell 110 provided in the first reaction unit 100UP.

[0041] (1st Terminal Plate 241) The first terminal plate 241 is a rectangular plate-shaped member having a through-hole 242 near the center, and is made of a conductive material such as ferritic stainless steel having an alumina oxide coating formed on its surface. The first terminal plate 241 is in contact with the external separator 231, and is electrically connected to the first reaction unit 100UP via the external current collecting member 235, the external plate 234, and the external separator 231. The first terminal plate 241 functions as a positive output terminal for outputting the electrical energy generated by the single cell 110 to the outside.

[0042] (First end plate 210) The first end plate 210 is a rectangular plate-shaped member having a through-hole 211 near the center, and is made of a conductive material such as stainless steel.

[0043] (End frame 250) The terminal frame 250 is a rectangular frame-like member having a substantially rectangular through-hole 251 near the center, and is made of, for example, insulating ceramics (mica, etc.).

[0044] (End Plate 260) The end plate 260 is a rectangular flat member made of a conductive material such as stainless steel.

[0045] (Second end plate 270) The second end plate 270 is a rectangular plate-shaped member having a through-hole 271 near the center, and is made of a conductive material such as stainless steel.

[0046] (insulating plates 220A, 220B) Insulating plates 220A and 220B are rectangular plate-shaped members made of insulating material. As shown in Fig. 2, first insulating plate 220A is sandwiched between first end plate 210 and terminal unit 230, thereby ensuring insulation between first end plate 210 and terminal unit 230. Second insulating plate 220B is sandwiched between end plate 260 and second end plate 270, thereby ensuring insulation between end plate 260 and second end plate 270.

[0047] (Air chamber 313 and fuel chamber 323) 4 and 5, there is a space between the single cell separator 120 and one of the IC separators 180 and interconnector 190 adjacent to the single cell separator 120. This space faces the air electrode 114 and serves as an air chamber 313 (an example of an oxidant gas flow space) through which the oxidant gas OG flows. The air electrode frame 130 separates the air chamber 313 from the external space along the entire periphery 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.

[0048] There is also a space between the unit cell separator 120 and the other IC separator 180 and interconnector 190 adjacent to this unit cell separator 120. This space faces the fuel electrode 116 and serves as a fuel chamber 323 (an example of a fuel gas flow space) through which fuel gas FG flows. The fuel electrode frame 140 separates the entire periphery of the fuel chamber 323 from the external space and seals the gap between the unit cell separator 120 and the IC separator 180, thereby preventing gas from leaking from the fuel chamber 323 to the external space. In the following description, the fuel chamber 323 disposed in the first reaction unit 100UP and between the unit cell separator 120 and the IC separator 180P will be referred to as the "fuel chamber 323P."

[0049] One side of the single cell separator 120 faces the air chamber 313, and the other side faces the fuel chamber 323. In other words, the single cell separator 120 is adjacent to the air chamber 313 and the fuel chamber 323 in the thickness direction, separating the air chamber 313 from the fuel chamber 323. This prevents 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.

[0050] Furthermore, each of the IC separators 180 other than the IC separator 180P has one surface facing the air chamber 313 arranged in one of two adjacent reaction units 100U, and the other surface facing the fuel chamber 323 arranged in the other reaction unit 100U. In other words, the IC separator 180 is adjacent to the air chamber 313 and the fuel chamber 323 in the thickness direction, and separates the two adjacent reaction units 100U together with the interconnector 190. The IC separator 180 and the interconnector 190 prevent gas leakage between the adjacent reaction units 100U.

[0051] (Sub-circulation space 331) As shown in FIGS. 4 and 5, there is a space between the external separator 231 and the external plate 234 and the power generation block 100 (specifically, the IC separator 180P and the interconnector 190P). This space serves as a sub-circulation space 331 (an example of a fuel gas circulation space) through which the fuel gas FG flows. One side of the external separator 231 faces the sub-circulation space 331, and the other side faces the external space. That is, the external separator 231 is adjacent to the sub-circulation space 331 in the thickness direction, and together with the external plate 234, separates the sub-circulation space 331 from the external space. The first terminal plate 241 separates the sub-circulation space 331 from the external space along its entire periphery. Furthermore, the IC separator 180P has one side facing the sub-circulation space 331 and the other side facing the air chamber 313P. That is, the IC separator 180P is adjacent to the sub-flow space 331 and the air chamber 313P in the thickness direction, and separates the sub-flow space 331 and the air chamber 313P together with the interconnector 190P.

[0052] (Manifolds 311, 312, 321, 322) As shown in Figures 1-3, the fuel cell stack 10 has four manifolds (oxidant gas supply manifold 311, oxidant gas discharge manifold 312, fuel gas supply manifold 321, and fuel gas discharge manifold 322) that extend from the first end plate 210 to the second end plate 270.

[0053] 2, the oxidant gas supply manifold 311 is in communication with the air chamber 313 of each reaction unit 100U, and is a gas flow path that supplies the oxidant gas OG introduced from outside the fuel cell stack 10 to the air chamber 313. The oxidant gas discharge manifold 312 is in communication with the air chamber 313 of each reaction unit 100U, and is a gas flow path that discharges the oxidant off-gas OOG discharged from the air chamber 313 to the outside of the fuel cell stack 10. As the oxidant gas OG, for example, air is used.

[0054] As shown in Fig. 3, the fuel gas supply manifold 321 is connected to the fuel chamber 323 of each reaction unit 100U and is a gas flow path that supplies fuel gas FG introduced from outside the fuel cell stack 10 to the fuel chamber 323. The fuel gas discharge manifold 322 is connected to the fuel chamber 323 of each reaction unit 100U and is a gas flow path that discharges fuel off-gas FOG, which is fuel gas after passing through the fuel chamber 323, to the outside of the fuel cell stack 10. For example, a hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG. The fuel gas FG and fuel off-gas FOG are gases with reducing properties.

[0055] (Communicating flow path 243) 6, the first terminal plate 241 has first manifold holes 321A that constitute the fuel gas supply manifold 321, second manifold holes 322A that constitute the fuel gas discharge manifold 322, and communication passages 243 that connect the second manifold holes 322A and the through-holes 242. The communication passages 243 connect the sub-circulation space 331 and the fuel gas discharge manifold 322, and fuel off-gas FOG is supplied into the sub-circulation space 331. The sub-circulation space 331 and the first manifold holes 321A are separated from each other, and the sub-circulation space 331 and the fuel gas supply manifold 321 do not communicate with each other.

[0056] (Gas passage members 280A, 280B) Two of the four gas passage members 280A, 280B are gas passage members 280A connected to the oxidizing gas supply manifold 311 and the oxidizing gas discharge manifold 312, respectively. As shown in FIGS. 1 and 2, each gas passage member 280A has a cylindrical main body 281A and a cylindrical branch portion 282A branching off from the side surface of the main body 281A. The internal space of the branch portion 282A is in communication with the internal space of the main body 281A. A gas pipe (not shown) is connected to the branch portion 282A. The two gas passage members 280A are each connected to the second end plate 270. The internal spaces of the two gas passage members 280A are in communication with the oxidizing gas supply manifold 311 and the oxidizing gas discharge manifold 312, respectively.

[0057] The other two of the four gas passage members 280A, 280B are gas passage members 280B connected to the fuel gas supply manifold 321 and the fuel gas discharge manifold 322, respectively. As shown in FIGS. 1 and 3, each gas passage member 280B has a cylindrical main body 281B and a cylindrical branch portion 282B branching off from the side surface of the main body 281B. The internal space of the branch portion 282B is in communication with the internal space of the main body 281B. A gas pipe (not shown) is connected to the branch portion 282B. The two gas passage members 280B are each connected to the second end plate 270. The internal spaces of the two gas passage members 280B are in communication with the fuel gas supply manifold 321 and the fuel gas discharge manifold 322, respectively.

[0058] As shown in FIG. 2, a bolt B is inserted into the oxidant gas supply manifold 311 and the internal space of the main body 281A that communicates with it. Nuts N are threaded onto both ends of the bolt B. This fastens the components from the first end plate 210 to the gas passage member 280A together. Insulating sheets IS are interposed between the nut N and the first end plate 210, and between the nut N and the gas passage member 280A. Gaps are present between the outer circumferential surface of the bolt B and the inner circumferential surface of the oxidant gas supply manifold 311, and between the outer circumferential surface of the bolt B and the inner circumferential surface of the main body 281A, and these gaps serve as passages for the oxidant gas. The same applies to the oxidant gas discharge manifold 312 and the gas passage member 280A, the fuel gas supply manifold 321 and the gas passage member 280B, and the fuel gas discharge manifold 322 and the gas passage member 280B.

[0059] A-2. Operation of fuel cell stack 10: 2 and 4, the oxidizing gas OG is supplied to the air chamber 313 through the gas passage member 280A and the oxidizing gas supply manifold 311. Also, as shown in FIGS. 3 and 5, the fuel gas FG is supplied to the fuel chamber 323 through the gas passage member 280B and the fuel gas supply manifold 321.

[0060] When an oxidant gas OG is supplied to the air chamber 313 of each reaction unit 100U and a fuel gas FG is supplied to the fuel chamber 323, power is generated in the single cell 110 through an electrochemical reaction between the oxidant gas OG and the fuel gas FG. This power generation reaction is exothermic. As described above, the interconnector 190 is shared by two adjacent reaction units 100U, and the interconnector 190 ensures electrical continuity 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. In addition, a first terminal plate 241 is electrically connected to the first reaction unit 100UP, and a second terminal plate 160 is provided to the second reaction unit 100UN. As a result, electrical energy generated in each reaction unit 100U is extracted from the terminal plates 160, 241, 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.

[0061] 2 and 4, the oxidant off-gas OOG discharged from the air chamber 313 of each reaction unit 100U to the oxidant gas discharge manifold 312 passes through the internal space of the gas passage member 280A and is discharged to the outside of the fuel cell stack 10. Also, as shown in FIGS. 3 and 5, the fuel off-gas FOG discharged from the fuel chamber 323 of each reaction unit 100U to the fuel gas discharge manifold 322 passes through the internal space of the gas passage member 280B and is discharged to the outside of the fuel cell stack 10.

[0062] As shown in FIGS. 3, 5, and 6, a portion of the fuel off-gas FOG discharged to the fuel gas discharge manifold 322 flows into the sub-flow space 331 through the communication passage 243.

[0063] It is preferable that the inside of the sub-circulation space 331 be a reducing atmosphere to prevent a decrease in electrical connection reliability due to oxidation of the components disposed inside the sub-circulation space 331. Since the external current collecting member 235 of this embodiment contains nickel or a nickel alloy, there is a concern that it may be oxidized when it comes into contact with water (water vapor) generated by the power generation reaction occurring in the unit cell 110, which may adversely affect the operation of the fuel cell stack 10.

[0064] The fuel gas FG used in the fuel cell stack 10 is a reducing gas such as hydrogen, and the fuel off-gas FOG that is generated after the fuel gas FG passes through the fuel chamber 323 is also a reducing gas. By supplying this fuel gas FG or fuel off-gas FOG to the sub-circulation space 331, the inside of the sub-circulation space 331 can be made into a reducing atmosphere.

[0065] During operation of the fuel cell stack 10, for example, sudden unintended fluctuations may occur in the flow rates of the oxidant gas OG and fuel gas FG being supplied. For example, the fuel gas FG is produced by adding water vapor to a raw material gas to reform it. If water bumps during this process, the pressure in the flow path of the fuel gas FG may increase unintendedly. In such a case, there is a concern that the gas may leak outside the fuel cell stack 10.

[0066] In this embodiment, the external separator 231 is thicker than the single cell separator 120. In other words, the external separator 231, which constitutes the outermost layer of the fuel cell stack 10, is more rigid than the single cell separator 120 disposed inside the fuel cell stack 10, and is able to withstand relatively high pressure. As a result, deformation and damage to the external separator 231 are suppressed, and gas leakage to the outside of the fuel cell stack 10 can be suppressed, even if the pressure inside the fuel cell stack 10 unintentionally increases, compared to when the thickness of the external separator 231 is the same as the thickness of the single cell separator 120.

[0067] Furthermore, the sub-flow space 331 communicates with the fuel gas discharge manifold 322 but does not communicate with the fuel gas supply manifold 321 .

[0068] The fuel off-gas FOG discharged from the fuel chamber 323 has a lower pressure than the fuel gas FG before entering the fuel chamber 323 due to pressure loss that occurs when the fuel off-gas FOG passes through the fuel chamber 323. Therefore, by connecting the sub-circulation space 331 to the fuel gas discharge manifold 322, the pressure inside the sub-circulation space 331 can be lower than when the sub-circulation space 331 is connected to the fuel gas supply manifold 321. This effectively prevents deformation and damage to the external separator 231.

[0069] Furthermore, the external separator 231 and the IC separator 180N are in contact with the first terminal plate 241 and the second terminal plate 160, respectively, and contribute more to power transmission efficiency than the other separators 120, 180. In this embodiment, these separators 180N, 231 are thicker than the single cell separator 120. With this configuration, power transmission loss due to the electrical resistance of the separators 180N, 231 can be reduced compared to when the thickness of the separators 180N, 231 is the same as the thickness of the single cell separator 120.

[0070] A-3. Advantages of this embodiment: As described above, the fuel cell stack 10 of this embodiment includes a unit cell 110 in which the air electrode 114, the electrolyte layer 112, and the fuel electrode 116 are stacked in this order, and a plurality of plate-shaped separators 120, 180, 231 adjacent in the thickness direction to at least one of the fuel chamber 323 and the sub-flow space 331 through which the fuel gas FG or the fuel off-gas FOG flows, and the air chamber 313 through which the oxidizer gas OG flows. The plurality of separators 120, 180, 231 support the unit cell 110 and include a unit cell separator 120 that separates the fuel chamber 323 from the air chamber 313, and an external separator 231 that is a member electrically connected to the unit cell 110 and separates the sub-flow space 331 from the external space, and is a member different from the terminal plates 160, 241 that outputs electrical energy generated in the unit cell 110 to the outside or inputs electrical energy from the outside to the unit cell 110. The thickness of the outer separator 231 is greater than the thickness of the single cell separator 120 .

[0071] According to the above configuration, compared to when the rigidity of the external separator 231 is equivalent to the rigidity of the single cell separator 120, even if the pressure inside the air chamber 313, the fuel chamber 323 or the sub-circulation space 331 unintentionally increases, deformation or damage to the external separator 231 is suppressed, and leakage of gas outside the fuel cell stack 10 can be suppressed.

[0072] Furthermore, by making the thickness of the external separator 231 greater than the thickness of the single cell separator 120, the rigidity of the external separator 231 can be made greater than the rigidity of the single cell separator 120 with a simple configuration, thereby suppressing gas leakage outside the fuel cell stack 10.

[0073] The fuel cell stack 10 also includes a power generation block 100 including a single cell 110 and a single cell separator 120, and a terminal unit 230 disposed on the outer surface of the power generation block 100 and including an external separator 231. A space through which fuel gas (FG) or fuel off-gas (FOG) flows (fuel gas flow space) is disposed inside the power generation block 100 and includes a fuel chamber 323 facing the anode 116, and a sub-flow space 331 disposed inside the terminal unit 230 and separated from the external space by the external separator 231. The power generation block 100 further includes a fuel gas supply manifold 321 that supplies fuel gas (FG) to the fuel chamber 323, and a fuel gas discharge manifold 322 that discharges fuel off-gas (FOG) after passing through the fuel chamber 323. The sub-flow space 331 is in communication with the fuel gas discharge manifold 322 but not with the fuel gas supply manifold 321.

[0074] The fuel off-gas FOG passing through the fuel gas discharge manifold 322 has a lower pressure than the fuel gas FG passing through the fuel gas supply manifold 321 due to pressure loss that occurs when the fuel gas passes through the fuel chamber 323. Therefore, when the sub-circulation space 331 is connected to the fuel gas discharge manifold 322, the pressure inside the sub-circulation space 331 can be lower than when the sub-circulation space 331 is connected to the fuel gas supply manifold 321. This more effectively prevents gas from leaking out of the fuel cell stack 10.

[0075] The fuel cell stack 10 further includes a first terminal plate 241 and a second terminal plate 160 that are electrically connected to the unit cell 110 and that output electrical energy generated in the unit cell 110 to the outside. The multiple separators 120, 180, 231 are electrically connected to the unit cell 110 and include an external separator 231 that contacts the first terminal plate 241 and an IC separator 180N that contacts the second terminal plate 160. The thicknesses of the external separator 231 and the IC separator 180N are greater than the thickness of the unit cell separator 120.

[0076] With this configuration, the transmission loss due to the electrical resistance of the external separator 231 and the IC separator 180N can be reduced compared to when the thickness of the external separator 231 and the IC separator 180N is equal to or less than that of the unit cell separator 120.

[0077] A-4. Performance evaluation: [Test Example 1] A fuel cell stack 10 having the same configuration as the above embodiment was prepared. Pressure gauges capable of measuring the pressure at the inlet of the fuel gas supply manifold 321, the outlet of the fuel gas discharge manifold 322, and inside the sub-flow space 331 were attached to this fuel cell stack 10, and the stack was used for testing.

[0078] 1) Test Example 1-1 Air was supplied to the air chamber 313 at a flow rate of 25 L / min via the oxidizing gas supply manifold 311 and discharged from the oxidizing gas discharge manifold 312 (see FIGS. 2 and 4).

[0079] Gas was supplied to the fuel chamber 323 via the fuel gas supply manifold 321 and discharged from the fuel gas discharge manifold 322 (see FIGS. 3 and 5). In this test, the fuel cell stack 10 was not operated (power generation) and therefore air was used instead of fuel gas as the gas supplied to the fuel chamber 323. The flow rate of the air supplied to the fuel chamber 323 was changed within a range of 11-110 L / min, and the pressure at the inlet of the fuel gas supply manifold 321, the outlet of the fuel gas discharge manifold 322, and inside the sub-circulation space 331 was measured.

[0080] 2) Test Example 1-2 The flow direction of the gas supplied to the fuel chamber 323 was opposite to that of Test Example 1-1. That is, air was supplied to the fuel chamber 323 via the fuel gas exhaust manifold 322 and exhausted from the fuel gas supply manifold 321 (see FIG. 7). Otherwise, the test was conducted in the same manner as Test Example 1-1, and the pressure was measured.

[0081] 3) Results In Test Example 1-1, the air that had passed through the fuel chamber 323 was discharged to the fuel gas discharge manifold 322, and a portion of the air was supplied to the sub-circulation space 331 (see FIG. 5). As shown in FIG. 8, the pressure measured at the outlet of the fuel gas discharge manifold 322 was lower than the pressure measured at the inlet of the fuel gas supply manifold 321. Furthermore, the pressure inside the sub-circulation space 331 was approximately the same as the pressure measured at the outlet of the fuel gas discharge manifold 322.

[0082] In addition, in Test Example 2-2, air supplied from the fuel gas discharge manifold 322 was supplied to the fuel chamber 323, and a portion of the air was supplied to the sub-circulation space 331 (see FIG. 7). As shown in FIG. 9, the pressure measured at the inlet of the fuel gas supply manifold 321 was lower than the pressure measured at the outlet of the fuel gas discharge manifold 322. The pressure inside the sub-circulation space 331 was approximately the same as the pressure measured at the outlet of the fuel gas discharge manifold 322.

[0083] That is, it was confirmed that the internal pressure of the manifold out of the two manifolds 321, 322, from which the gas is discharged after passing through the fuel chamber 323, is lower than the internal pressure of the manifold through which the gas passes before being supplied to the fuel chamber 323. It was also confirmed that the pressure in the sub-circulation space 331 is approximately the same as the internal pressure of the manifold out of the two manifolds 321, 322 to which the sub-circulation space 331 is connected.

[0084] Therefore, when the sub-circulation space is connected to a manifold through which gas is discharged after passing through the fuel chamber, the pressure inside the sub-circulation space can be made relatively low, which is preferable from the standpoint of "more effectively suppressing gas leakage outside the fuel cell stack."

[0085] [Test Example 2] The inelastic strain and lifespan of the separator were evaluated by simulating a thermal cycle test. A fuel cell stack having a configuration similar to that of the above embodiment was used as the simulation model. As shown in FIG. 10, the stress relaxation portion 233S provided in the external separator was set to a U-shaped groove shape having a bottom wall 233S1 and two side walls 233S2 and 233S3 extending obliquely from both ends of the bottom wall 233S1. The stress relaxation portions provided in the other separators were also set to a similar shape. The material of each separator was ferritic stainless steel, and the thickness of the external separator and terminal separator (corresponding to the IC separator 180N in the above embodiment) was set to 0.3 mm, and the thickness of the other separators was set to 0.1 mm.

[0086] The simulation was performed on the above simulation model by placing a stack inside an electric furnace and, while maintaining the set temperature of the electric furnace constant, repeatedly applying a cycle of increasing the current from 0 amperes to the rated current, and then decreasing the current back to 0 amperes after the stack temperature had stabilized at the rated current.

[0087] The strain of the external separator after 10 cycles was greatest at the most bent portion of the stress relaxation portion 233S, that is, at the boundary position 233S4 between the bottom wall 233S1 and the side wall 233S2.

[0088] Figure 11 plots the cumulative equivalent inelastic strain of the stress relaxation portion after a predetermined number of thermal cycles for the external separator and the terminal separator. For reference, the cumulative equivalent inelastic strain of the stress relaxation portion after a predetermined number of thermal cycles for another separator with a smaller thickness than the two separators mentioned above is also plotted. For both the external separator and the terminal separator, the cumulative equivalent inelastic strain of the stress relaxation portion after a predetermined number of thermal cycles was located below the fatigue fracture curve, which indicates the cumulative equivalent inelastic strain leading to fatigue fracture, confirming that the external separator and the terminal separator did not reach fatigue fracture.

[0089] In addition, the life expectancy (the ratio of accumulated strain during cycling to the accumulated strain leading to fatigue fracture) of the external separator and the terminal separator after a predetermined number of thermal cycles was calculated to be 43% and 59%, respectively, which did not reach 100%.

[0090] From the above, it was confirmed that when a portion of the separator is a curved stress relaxation portion, the stress relaxation function of the stress relaxation portion is not impaired even if the separator thickness is increased to 0.3 mm. Furthermore, even if the bending shape of the stress relaxation portion differs from the shape set by the simulation, it is thought that the strain of the separator will be greatest at the most curved part of the stress relaxation portion, and that if the separator thickness is approximately the same, the same stress relaxation function will be achieved.

[0091] The terminal separators showed a larger cumulative equivalent inelastic strain than the external separators. This is thought to be because the terminal separators, which are located closer to the inlets of the oxidant gas supply manifold and the fuel gas supply manifold, tend to reach higher temperatures than the external separators.

[0092] B. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified into various forms without departing from the spirit thereof, for example, the following modifications are also possible. (1) In the above embodiment, the fuel cell stack 10 includes the terminal unit 230. However, the electrochemical reaction stack does not necessarily have to include a subunit. In this case, the external separator may be, for example, one of the separators included in the reaction block that faces the external space. (2) In the above embodiment, the thickness of the external separator was greater than the thickness of the single-cell separator. However, the rigidity of the external separator may be made greater than the rigidity of the single-cell separator by using different materials or shapes for the external separator and the single-cell separator. (3) In the above embodiment, the external separator 231 has the through-hole 232 near the center, but the external separator does not have to have a through-hole. (4) In the above embodiment, a part of the external separator 231 is a U-groove-shaped stress relief portion 233, but the stress relief portion may have any shape as long as it can relieve thermal stress by deforming in accordance with the thermal expansion of the external separator, and may be, for example, a V-groove-shaped portion or a portion that is thinner than the other portions. The same applies to the stress relief portions of the other separators. (5) In the above embodiment, the stress relief portion 233 of the outer separator 231 is disposed so as to surround the entire periphery of the through-hole 232. However, the arrangement of the stress relief portion is arbitrary, and for example, it may be disposed only in a portion of the periphery of the through-hole. The same applies to the stress relief portions of the other separators. (6) In the above embodiment, the external separator 231 has the stress relief portion 233, but the external separator does not have to have a stress relief portion. The same applies to the other separators. Also, only some of the separators may have stress relief portions. (7) In the above embodiment, the external plate 234 is joined to the external separator 231 having the through-holes 232. However, the external separator may be a plate-like member without through-holes. In this case, the external plate is not necessary. (8) In the above embodiment, the interconnector 190 is joined to the IC separator 180 having the through hole 181, but the IC separator may be a plate-like member without a through hole and may also serve as the interconnector. (9) In the above embodiment, the sub-circulation space 331 communicates with the fuel gas discharge manifold 322 but not with the fuel gas supply manifold 321. However, the sub-circulation space may communicate with the fuel gas supply manifold but not with the fuel gas discharge manifold. Alternatively, the sub-circulation space may communicate with both the fuel gas supply manifold and the fuel gas discharge manifold. (10) In the above embodiment, the IC separator 180P stacked on the terminal unit 230 had the same configuration as the other IC separators, but the thickness of the separator stacked on the subunit may be greater than the thickness of the other separators. (11) 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), or to electrolysis cell stacks that include electrolysis cell units, which are constituent units of solid oxide electrolysis cells (SOECs), as unit cells. For example, when the electrochemical reaction cell stack is an electrolysis cell stack, the terminals are components for inputting electrical energy from the outside to the unit cells. [Explanation of symbols]

[0093] 10: Fuel cell stack 100: Power generation block (reaction block) 100U: Electrochemical reaction unit 100UN: Second reaction unit 100UP: First reaction unit 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Anode 118: Reaction prevention layer 120: Separator for single cell (separator) 121: Through hole 122: Stress relaxation part 124: Joint part 130: Air electrode frame 131: Through hole 140: Anode frame 141: Through hole 144: Anode current collecting member 145: Electrode opposing part 146: Interconnector opposing part 147: Connection part 149: Spacer 160: Second terminal plate (terminal) 161: Through hole 180, 180P: Separator for IC (separator) 180N: IC separator (terminal separator) 181: Through hole 182: Stress relief portion 190, 190N, 190P: Interconnector 191: Flat plate portion 192: Air electrode current collecting portion 193: Coating layer 196: Conductive bonding material 210: First end plate 211: Through hole 220A: First insulating plate 220B: Second insulating plate 230: Terminal unit (subunit) 231: External separator (separator, terminal separator) 232: Through hole 233, 233S: Stress relief portion 233S1: Bottom wall 233S2, 233S3: Side wall 233S4: Boundary position 234: External plate 235: External current collecting member 241: First terminal plate (terminal) 242: Through hole 243: Communication flow path 250: End frame 251: Through hole 260: End plate 270: Second end plate 271: Through hole 280A, 280B: Gas passage member 281A, 281B: Main body 282A, 282B: Branching section 311: Oxidizer gas supply manifold 312: Oxidizer gas discharge manifold 313, 313P: Air chamber (oxidizer gas circulation space) 321: Fuel gas supply manifold 321A: First manifold hole 322: Fuel gas discharge manifold 322A: Second manifold hole 323, 323P: Fuel chamber (fuel gas circulation space) 331: Sub-circulation space (fuel gas circulation space) B: Bolt BH: Bolt hole FG: Fuel gas FOG: Fuel off-gas (fuel gas) IS: Insulation sheet N: Nut OG: Oxidizer gas OOG: Oxidizer off-gas

Claims

1. a single cell in which an air electrode, an electrolyte layer, and a fuel electrode are stacked in this order; a plurality of plate-shaped separators adjacent in a thickness direction to at least one of a fuel gas flow space through which a fuel gas flows and an oxidant gas flow space through which an oxidant gas flows, The plurality of separators are a single cell separator that supports the single cell and separates the fuel gas flow space from the oxidant gas flow space; an external separator, which is a member that separates the fuel gas circulation space or the oxidant gas circulation space from an external space, is electrically connected to the unit cell, and is a member different from a terminal for outputting electrical energy generated in the unit cell to the outside or for inputting electrical energy from the outside to the unit cell; Including, the rigidity of the external separator is higher than the rigidity of the unit cell separator; Electrochemical reaction cell stack.

2. The thickness of the external separator is greater than the thickness of the single cell separator. The electrochemical reaction cell stack according to claim 1 .

3. a reaction block including the unit cell and the unit cell separator; a subunit disposed on the outer surface of the reaction block and including the external separator; Equipped with The fuel gas flow space is a fuel chamber, which is a space disposed inside the reaction block and facing the fuel electrode; a sub-flow space disposed inside the sub-unit and separated from an external space by the external separator; Including, The reaction block comprises: a fuel gas supply manifold for supplying the fuel gas to the fuel chamber; a fuel gas discharge manifold that discharges the fuel gas after passing through the fuel chamber; further comprising the sub-flow space communicates with the fuel gas discharge manifold but does not communicate with the fuel gas supply manifold; The electrochemical reaction cell stack according to claim 1 or 2.

4. a terminal electrically connected to the unit cell for outputting electrical energy generated in the unit cell to the outside or for inputting electrical energy from the outside to the unit cell; the plurality of separators include a terminal separator electrically connected to the unit cell and in contact with the terminal, The thickness of the terminal separator is greater than the thickness of the unit cell separator. The electrochemical reaction cell stack according to claim 1 or 2.

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