Electrochemical reaction cell and electrochemical reaction cell stack

Abstract

Provided is an electrochemical reaction cell and an electrochemical reaction cell stack capable of inhibiting stress from concentrating on a specific portion of an interlayer. The electrochemical reaction cell includes an electrolyte layer including a solid oxide; an air electrode and a fuel electrode sandwiching the electrolyte layer and facing each other in a first direction; and an interlayer formed between the electrolyte layer and the air electrode. In the electrochemical reaction cell, at least a portion of an outer edge of the interlayer is located inward of an outer edge of the electrolyte layer when viewed along the first direction. In addition, a plurality of protrusions protruding toward the outer edge of the electrolyte layer are formed at the at least a portion of the outer edge of the interlayer.

Description

Technical Field

[0001] The technology disclosed in this specification relates to electrochemical reaction single cells. Background Technology

[0002] As a type of fuel cell that generates electricity using the electrochemical reaction of hydrogen and oxygen, solid oxide fuel cells (hereinafter referred to as "SOFCs") with an electrolyte layer including a solid oxide layer are known. The fuel cell single cell (hereinafter simply referred to as "single cell"), which is the smallest constituent unit of an SOFC, includes an electrolyte layer and an air electrode and a fuel electrode sandwiching the electrolyte layer and facing each other in a predetermined direction (hereinafter referred to as "first direction").

[0003] In such fuel cell single cells, for example, there are known fuel cell single cells configured such that, in order to suppress the formation of a high-resistivity layer near the boundary between the electrolyte layer and the air electrode due to the reaction between the substance contained in the air electrode and the substance contained in the electrolyte layer, an intermediate layer is disposed between the air electrode and the electrolyte layer (for example, Patent Document 1).

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-156007 Summary of the Invention

[0007] The problem to be solved by the present invention

[0008] In existing fuel cell cells, when viewed along a first direction, the outer edge of the interlayer is located further inward than the outer edge of the electrolyte layer and extends in a straight line along the outer edge of the electrolyte layer. Therefore, stress in the interlayer, generated by the difference in thermal expansion between the interlayer and the electrolyte layer, tends to concentrate at specific locations on the outer edge of the interlayer. As a result, there is a possibility of delamination between the interlayer and the electrolyte layer, or the formation of cracks.

[0009] It should be noted that this issue is also common to the single electrolytic cell, the building block of solid oxide electrolytic cells (hereinafter referred to as "SOEC") that utilize the electrolysis reaction of water to generate hydrogen. It should also be noted that in this specification, both fuel cell single cells and single electrolytic cells are collectively referred to as electrochemical reaction single cells.

[0010] Solution for solving the problem

[0011] The techniques disclosed in this specification can be implemented, for example, as follows.

[0012] (1) The electrochemical reaction single cell disclosed in this specification comprises: an electrolyte layer containing a solid oxide; an air electrode and a fuel electrode sandwiching the electrolyte layer and facing each other in a first direction; and an intermediate layer formed between the electrolyte layer and the air electrode. In the electrochemical reaction single cell, when viewed along the first direction, at least a portion of the outer edge of the intermediate layer is located inside the outer edge of the electrolyte layer, and a plurality of protrusions protruding toward the outer edge of the electrolyte layer are formed on the at least a portion of the outer edge of the intermediate layer. In this electrochemical reaction single cell, a plurality of protrusions are formed on the outer edge of the intermediate layer. Therefore, compared with a structure in which no protrusions are formed on the outer edge of the intermediate layer, the stress generated on the outer edge of the intermediate layer is dispersed by the plurality of protrusions, thereby suppressing stress concentration at specific locations in the intermediate layer.

[0013] (2) In the above-described electrochemical reaction single cell, it can also be configured such that, when viewed along the first direction, the protrusion width of each of the plurality of protrusions is wider than the separation distance between adjacent plurality of protrusions. According to this electrochemical reaction single cell, compared with a structure in which the protrusion width of each protrusion is narrower than the separation distance between the protrusions, stress concentration on each protrusion can be suppressed, and the peeling of the intermediate layer and the electrolyte layer can be suppressed accordingly by increasing the contact area between the intermediate layer and the electrolyte layer.

[0014] (3) In the above-described electrochemical reaction single cell, the shape of the front end of the protrusion, when viewed along the first direction, can also be configured such that the shape of the front end of the protrusion is flat along the arrangement direction of the plurality of protrusions. According to this electrochemical reaction single cell, compared with, for example, a structure in which the front end of the protrusion is pointed, it is possible to suppress the concentration of stress dispersed to each protrusion at the front end of the protrusion.

[0015] (4) In the above-described electrochemical reaction single cell, it can also be configured such that, when viewed along the first direction, both ends of the front end of the protrusion are arc-shaped. According to this electrochemical reaction single cell, it is possible to more reliably suppress the concentration of stress dispersed to each protrusion at the front end of the protrusion.

[0016] (5) In the above-described electrochemical reaction single cell, the structure can also be configured such that, when viewed along the first direction, the outer edge of the intermediate layer is entirely located inside the outer edge of the electrolyte layer; and when viewed along the first direction, among the plurality of protrusions in the intermediate layer, the depth of the recess between adjacent pairs of protrusions protruding towards the second direction is different from the depth of the recess between adjacent pairs of protrusions protruding towards a third direction different from the second direction. According to this electrochemical reaction single cell, by referring to the difference in the depth of the recess between the protrusions, the orientation of the electrochemical reaction single cell can be easily determined, for example, during battery stack assembly.

[0017] (6) In an electrochemical reaction battery stack having multiple electrochemical reaction single cells, at least one of the multiple electrochemical reaction single cells may be configured as an electrochemical reaction single cell of any of the above-described embodiments. According to this electrochemical reaction battery stack, stress concentration at specific locations in the intermediate layer can be suppressed.

[0018] (7) In the above-described electrochemical reaction battery stack, the structure can also be configured as follows: the electrochemical reaction battery stack includes: a separator connected to the periphery of the at least one electrochemical reaction cell for dividing the space on the air electrode side and the space on the fuel electrode side; and a junction integrally covering both the separator and at least a portion of the intermediate layer in the at least one electrochemical reaction cell. According to this electrochemical reaction battery stack, the junction covers both the portion of the separator and the portion of the intermediate layer with protrusions, thus the contact area between the junction and the intermediate layer is relatively large, thereby improving the bonding strength between the electrochemical reaction cell and the separator.

[0019] It should be noted that the technology disclosed in this specification can be implemented in various forms, such as as an electrochemical reaction single cell (fuel cell or electrolytic cell), an electrochemical reaction battery stack (fuel cell stack or electrolytic battery stack) having multiple electrochemical reaction units with electrochemical reaction single cells, and their manufacturing methods. Attached Figure Description

[0020] Figure 1 This is a perspective view showing the external structure of the fuel cell stack 100 in the embodiment.

[0021] Figure 2 It means Figure 1 An explanatory diagram of the XZ cross-sectional structure of the fuel cell stack 100 at position II-II.

[0022] Figure 3 It means Figure 1An explanatory diagram of the YZ cross-sectional structure of the fuel cell stack 100 at position III-III.

[0023] Figure 4 It means and Figure 2 The diagram illustrates the XZ cross-sectional structure of two adjacent power generation units 102 at the same location shown in the cross-section.

[0024] Figure 5 It means and Figure 3 The diagram illustrates the YZ cross-sectional structure of two adjacent power generation units 102 at the same location shown in the cross-section.

[0025] Figure 6 This is an explanatory diagram showing the shape of the outer edge of the electrolyte layer 112 and the intermediate layer 180.

[0026] Figure 7 This is an explanatory diagram that briefly shows a partial structure of the screen 200.

[0027] Symbol Explanation

[0028] 22: Bolt; 24: Nut; 26: Insulating sheet; 27: Gas passage component; 28: Main body; 29: Branch; 100: Fuel cell stack; 102: Power generation unit; 104, 106: End plate; 108: Connecting hole; 110: Single cell; 112: Electrolyte layer; 114: Air electrode; 116: Fuel electrode; 120: Separator; 121, 131, 141: Hole; 124: Joint; 130: Air electrode side frame; 132: Oxidant gas supply connecting hole; 133: Oxidant gas exhaust connecting hole; 134: Air electrode side current collector; 135: Current collector element; 140: Fuel electrode side frame; 142: Fuel gas supply connection hole 143: Fuel gas discharge connection hole 144: Fuel electrode side current collector 145: Electrode opposing part 146: Interconnector opposing part 147: Connector part 149: Gasket 150: Interconnector 161: Oxidant gas inlet manifold 162: Oxidant gas outlet manifold 166: Air chamber 171: Fuel gas inlet manifold 172: Fuel gas outlet manifold 176: Fuel chamber 180: Intermediate layer 180P: Intermediate layer paste 182: Protrusion 183: End 184, 185: Recess 187: Bottom part 200: Screen 210, 220: Wire Detailed Implementation

[0029] A. Implementation Method

[0030] A-1. Structure

[0031] (Structure of fuel cell stack 100)

[0032] Figure 1 This is a perspective view showing the external structure of the fuel cell stack 100 in this embodiment. Figure 2It means Figure 1 An explanatory diagram of the XZ cross-sectional structure of the fuel cell stack 100 at position II-II. Figure 3 It means Figure 1 An explanatory diagram of the YZ cross-sectional structure of the fuel cell stack 100 at position III-III. In each figure, mutually orthogonal XYZ axes used to determine orientation are shown. In this specification, for convenience, the positive Z-axis direction is sometimes referred to as the upward direction, and the negative Z-axis direction as the downward direction; however, the fuel cell stack 100 may actually be configured with an orientation different from these. For Figure 4 The same applies to the subsequent figures. It should be noted that the vertical direction is an example of the first direction in the claims.

[0033] The fuel cell stack 100 includes a plurality of (seven in this embodiment) power generation units 102 and a pair of end plates 104, 106. The seven power generation units 102 are arranged in a predetermined arrangement direction (vertical in this embodiment). The pair of end plates 104, 106 are arranged to clamp the assembly of the seven power generation units 102 from above and below.

[0034] Multiple holes (eight in this embodiment) extending vertically are formed at the periphery of each layer (power generation unit 102, end plates 104, 106) constituting the fuel cell stack 100 in the Z-axis direction. These corresponding holes in each layer are interconnected vertically, forming a connecting hole 108 extending vertically from one end plate 104 to the other end plate 106. In the following description, the holes formed in each layer of the fuel cell stack 100 to form the connecting hole 108 are sometimes referred to as connecting holes 108.

[0035] Bolts 22, extending vertically, are passed through the connecting holes 108, and the fuel cell stack 100 is secured using the bolts 22 and nuts 24 fitted on both sides of the bolts 22. It should be noted that, as... Figure 2 and Figure 3 As shown, insulating sheets 26 are sandwiched between the nut 24 fitted onto one side (upper side) of the bolt 22 and the upper surface of the end plate 104 constituting the upper end of the fuel cell stack 100, and between the nut 24 fitted onto the other side (lower side) of the bolt 22 and the lower surface of the end plate 106 constituting the lower end of the fuel cell stack 100. Specifically, at locations where the gas passage member 27 (described later) is provided, the gas passage member 27 and insulating sheets 26, respectively disposed on the upper and lower sides of the gas passage member 27, are sandwiched between the nut 24 and the surface of the end plate 106. The insulating sheets 26 are, for example, composed of mica sheets, ceramic fiber sheets, ceramic powder sheets, glass sheets, glass-ceramic composites, etc.

[0036] The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each connecting hole 108. Therefore, a space is ensured between the outer circumferential surface of the shaft portion of each bolt 22 and the inner circumferential surface of each connecting hole 108. Figure 1 and Figure 2 As shown, the space formed by the bolt 22 (bolt 22A) located near the midpoint of one side of the outer periphery of the fuel cell stack 100 in the Z-axis direction (the side on the positive X-axis direction of the two sides parallel to the Y-axis) and the connecting hole 108 through which the bolt 22A passes functions as an oxidant gas inlet manifold 161. The oxidant gas inlet manifold 161 introduces oxidant gas OG from outside the fuel cell stack 100 and distributes the oxidant gas OG to various generators. The gas flow path supplied by the power generation unit 102 functions as an oxidant gas exhaust manifold 162 through a bolt 22 (bolt 22B) located near the midpoint of the side opposite to the aforementioned side (the side on the negative X-axis direction of the two sides parallel to the Y-axis) and a connecting hole 108 through which the bolt 22B passes. The oxidant gas exhaust manifold 162 is used to exhaust the gas, i.e., oxidant exhaust gas OOG, from the air chamber 166 of each power generation unit 102 to the outside of the fuel cell stack 100. It should be noted that, in this embodiment, air is used as the oxidant gas OG, for example.

[0037] In addition, such as Figure 1 and Figure 3 As shown, the space formed by the bolt 22 (bolt 22D) located near the midpoint of one side of the outer periphery of the fuel cell stack 100 in the Z-axis direction (the side on the positive Y-axis direction of the two sides parallel to the X-axis) and the connecting hole 108 through which the bolt 22D passes functions as a fuel gas inlet manifold 171. The fuel gas inlet manifold 171 is used to introduce fuel gas FG from the outside of the fuel cell stack 100 and supply the fuel gas FG to each power generation unit 102. The space formed by the bolt 22 (bolt 22E) located near the midpoint of the opposite side (the side on the negative Y-axis direction of the two sides parallel to the X-axis) and the connecting hole 108 through which the bolt 22E passes functions as a fuel gas outlet manifold 172. The fuel gas outlet manifold 172 is used to discharge the gas discharged from the fuel chamber 176 of each power generation unit 102, i.e., fuel exhaust gas FOG, to the outside of the fuel cell stack 100. It should be noted that, in this embodiment, the fuel gas FG is, for example, a hydrogen-rich gas obtained by modifying domestic gas.

[0038] Four gas passage components 27 are provided in the fuel cell stack 100. Each gas passage component 27 has a hollow cylindrical main body 28 and hollow cylindrical branch portions 29 branching from the side of the main body 28. The holes of the branch portions 29 communicate with the holes of the main body 28. Gas pipes (not shown) are connected to the branch portions 29 of each gas passage component 27. Additionally, as... Figure 2 As shown, the hole in the main body 28 of the gas passage member 27, located at the position of bolt 22A forming the oxidant gas inlet manifold 161, communicates with the oxidant gas inlet manifold 161. Similarly, the hole in the main body 28 of the gas passage member 27, located at the position of bolt 22B forming the oxidant gas outlet manifold 162, communicates with the oxidant gas outlet manifold 162. Furthermore, as... Figure 3 As shown, the hole in the main body 28 of the gas passage member 27, which is arranged at the position of the bolt 22D forming the fuel gas inlet manifold 171, communicates with the fuel gas inlet manifold 171, and the hole in the main body 28 of the gas passage member 27, which is arranged at the position of the bolt 22E forming the fuel gas outlet manifold 172, communicates with the fuel gas outlet manifold 172.

[0039] (Structure of end plates 104 and 106)

[0040] The pair of end plates 104 and 106 are conductive components that are approximately rectangular flat plates when viewed along the Z-axis, and are made of, for example, stainless steel. One end plate 104 is disposed on the upper side of the uppermost power generation unit 102, and the other end plate 106 is disposed on the lower side of the lowermost power generation unit 102. The pair of end plates 104 and 106 clamp the multiple power generation units 102 in a pressed state. The upper end plate 104 functions as the output terminal on the positive side of the fuel cell stack 100, and the lower end plate 106 functions as the output terminal on the negative side of the fuel cell stack 100.

[0041] (Structure of power generation unit 102)

[0042] Figure 4 It means and Figure 2 The diagram illustrates the XZ cross-sectional structure of two adjacent power generation units 102 at the same location in the cross-section shown. Figure 5 It means and Figure 3 The diagram illustrates the YZ cross-sectional structure of two adjacent power generation units 102 at the same location shown in the cross-section.

[0043] like Figure 4 and Figure 5As shown, the power generation unit 102 includes a single cell 110, a separator 120, an air electrode-side frame 130, an air electrode-side current collector 134, a fuel electrode-side frame 140, a fuel electrode-side current collector 144, and a pair of interconnecting members 150 constituting the uppermost and lowermost layers of the power generation unit 102. Holes corresponding to the connecting holes 108 through which the aforementioned bolts 22 pass are formed on the periphery of the separator 120, the air electrode-side frame 130, the fuel electrode-side frame 140, and the interconnecting members 150 in the Z-axis direction.

[0044] The interconnect 150 is a conductive member with a generally rectangular flat plate shape when viewed along the Z-axis, and is formed of a chromium-containing material, such as ferritic stainless steel. The interconnect 150 ensures electrical conductivity between power generation units 102 and prevents mixing of reactant gases between power generation units 102. It should be noted that in this embodiment, when two power generation units 102 are arranged adjacently, one interconnect 150 is shared by both adjacent power generation units 102. That is, the upper interconnect 150 in one power generation unit 102 and the lower interconnect 150 in another power generation unit 102 adjacent to that upper power generation unit 102 are the same member. Furthermore, since the fuel cell stack 100 has a pair of end plates 104 and 106, the uppermost power generation unit 102 in the fuel cell stack 100 does not have an upper interconnect 150, and the lowermost power generation unit 102 does not have a lower interconnect 150 (see reference). Figure 2 and Figure 3 ).

[0045] The single cell 110 includes an electrolyte layer 112, an air electrode (cathode) 114 disposed on the upper side relative to the electrolyte layer 112, a fuel electrode (anode) 116 disposed on the lower side relative to the electrolyte layer 112, and an intermediate layer 180 disposed between the electrolyte layer 112 and the air electrode 114. It should be noted that the single cell 110 of this embodiment is a fuel electrode-supported single cell that uses the fuel electrode 116 to support the other layers constituting the single cell 110 (electrolyte layer 112, air electrode 114, and intermediate layer 180).

[0046] The electrolyte layer 112 is a roughly rectangular flat plate-shaped component viewed along the Z-axis, and is a dense (low porosity) layer. The electrolyte layer 112 comprises solid oxides (e.g., YSZ (yttrium-stabilized zirconium oxide), ScSZ (scandium oxide-stabilized zirconium oxide), CSZ (calcium oxide-stabilized zirconium oxide)). Thus, the single cell 110 of this embodiment is a solid oxide fuel cell (SOFC) using solid oxides as the electrolyte.

[0047] Air electrode 114 is a roughly rectangular plate-shaped component smaller than electrolyte layer 112 when viewed along the Z-axis, and is a porous layer with a higher porosity than electrolyte layer 112. Air electrode 114 contains perovskite-type oxides represented by ABO3 (e.g., lanthanum strontium cobalt iron oxide (LSCF), lanthanum strontium iron oxide (LSF), lanthanum strontium cobalt oxide (LSC), lanthanum strontium manganese oxide (LSM), lanthanum nickel iron oxide (LNF), etc.).

[0048] The fuel electrode 116 is a generally rectangular flat plate-shaped member of approximately the same size as the electrolyte layer 112 when viewed along the Z-axis, and is a porous layer with a higher porosity than the electrolyte layer 112. It should be noted that, although not shown, in this embodiment, the fuel electrode 116 includes a substrate layer constituting the lower surface of the fuel electrode 116 and a functional layer located between the substrate layer and the electrolyte layer 112. The functional layer of the fuel electrode 116 primarily functions to generate electrons and water vapor by reacting oxygen ions supplied from the electrolyte layer 112 with hydrogen contained in the fuel gas FG, and includes Ni as an electron-conducting material and an oxygen-ion-conducting oxide (e.g., YSZ). Furthermore, the substrate layer of the fuel electrode 116 primarily functions to support the functional layer, the electrolyte layer 112, and the air electrode 114, and includes Ni as an electron-conducting material and an oxygen-ion-conducting oxide (e.g., YSZ).

[0049] The intermediate layer (reaction prevention layer) 180 is a roughly rectangular flat plate-shaped component when viewed along the Z-axis. The intermediate layer 180 is formed, for example, from solid oxides with ion conductivity such as SDC (samarium-doped cerium oxide), GDC (gadolinium-doped cerium oxide), LDC (lanthanum-doped cerium oxide), and YDC (yttrium-doped cerium oxide).

[0050] The separator 120 is a frame-like component, for example, made of metal, with a generally rectangular hole 121 extending vertically through its center near the center. The periphery of the hole 121 in the separator 120 faces the periphery of the surface on the air electrode 114 side of the electrolyte layer 112. The separator 120 is joined to the electrolyte layer 112 (single cell 110) by a joint 124 formed of solder (e.g., Ag solder) or glass disposed in the opposing portion. By dividing the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116 by the separator 120, leakage of gas from one electrode side to the other electrode side of the periphery of the single cell 110 can be suppressed.

[0051] The air electrode side frame 130 is a frame-like component with a generally rectangular hole 131 extending vertically through its center near the center. It is formed, for example, from an insulator such as mica. The hole 131 of the air electrode side frame 130 forms an air chamber 166 facing the air electrode 114. The air electrode side frame 130 contacts the periphery of the surface opposite to the electrolyte layer 112 in the separator 120, and the periphery of the surface opposite to the air electrode 114 in the interconnect member 150. Furthermore, the air electrode side frame 130 electrically insulates the pair of interconnect members 150 included in the power generation unit 102. Additionally, the air electrode side frame 130 has an oxidant gas supply connection hole 132 for connecting the oxidant gas inlet manifold 161 and the air chamber 166, and an oxidant gas outlet connection hole 133 for connecting the air chamber 166 and the oxidant gas outlet manifold 162.

[0052] The fuel electrode side frame 140 is a frame-like component, for example, made of metal, with a generally rectangular hole 141 extending vertically through its center near the center. The hole 141 of the fuel electrode side frame 140 forms the fuel chamber 176 facing the fuel electrode 116. The fuel electrode side frame 140 contacts the periphery of the surface of the separator 120 opposite to the electrolyte layer 112, and the periphery of the surface of the interconnect 150 opposite to the fuel electrode 116. In addition, a fuel gas supply communication hole 142 for connecting the fuel gas inlet manifold 171 and the fuel chamber 176, and a fuel gas outlet communication hole 143 for connecting the fuel chamber 176 and the fuel gas outlet manifold 172 are formed on the fuel electrode side frame 140.

[0053] A fuel electrode-side current collector 144 is disposed within the fuel chamber 176. The fuel electrode-side current collector 144 includes an interconnect opposing portion 146, an electrode opposing portion 145, and a connecting portion 147 connecting the electrode opposing portion 145 and the interconnect opposing portion 146. It is formed, for example, of nickel or a nickel alloy, stainless steel, etc. The electrode opposing portion 145 contacts the surface of the fuel electrode 116 opposite to the side facing the electrolyte layer 112, and the interconnect opposing portion 146 contacts the surface of the interconnect 150 opposite to the side facing the fuel electrode 116. As described above, since the lowermost power generation unit 102 in the fuel cell stack 100 does not have a lower interconnect 150, the interconnect opposing portion 146 in this power generation unit 102 contacts the lower end plate 106. Because the fuel electrode-side current collector 144 has this structure, the fuel electrode 116 is electrically connected to the interconnect 150 (or end plate 106). It should be noted that a gasket 149, for example, formed of mica, is disposed between the electrode opposing portion 145 and the interconnect opposing portion 146. Therefore, the fuel electrode-side current collector 144 follows the deformation of the power generation unit 102 caused by temperature cycling and changes in reactant gas pressure, thereby maintaining a good electrical connection between the fuel electrode 116 and the interconnect 150 (or end plate 106) achieved via the fuel electrode-side current collector 144.

[0054] An air-side current collector 134 is disposed within an air chamber 166. The air-side current collector 134 is composed of multiple generally quadrangular prism-shaped current collector elements 135, formed of a chromium-containing material, such as ferritic stainless steel. The air-side current collector 134 contacts the surface opposite to the side of the air electrode 114 and the surface opposite to the side of the interconnect 150. As described above, since the uppermost power generation unit 102 in the fuel cell stack 100 does not have an upper interconnect 150, the air-side current collector 134 in this power generation unit 102 contacts the upper end plate 104. Due to this structure, the air electrode 114 is electrically connected to the interconnect 150 (or end plate 104). A conductive bonding layer for joining the air electrode 114 and the air-side current collector 134 may also be sandwiched between them. It should be noted that the air-side current collector 134 and the interconnect 150 can also be constructed as an integral component.

[0055] A-2. Operation of fuel cell stack 100

[0056] like Figure 2 and Figure 4As shown, when oxidant gas OG is supplied via a gas piping (not shown) connected to a branch 29 of the gas passage member 27 located at the position of the oxidant gas inlet manifold 161, the oxidant gas OG is supplied to the oxidant gas inlet manifold 161 through the branch 29 of the gas passage member 27 and the holes of the main body 28, and is supplied from the oxidant gas inlet manifold 161 to the air chamber 166 through the oxidant gas supply communication holes 132 of each power generation unit 102. Additionally, as... Figure 3 and Figure 5 As shown, when fuel gas FG is supplied via a gas piping (not shown) connected to a branch 29 of a gas passage member 27 located at the fuel gas inlet manifold 171, the fuel gas FG is supplied to the fuel gas inlet manifold 171 via the branch 29 of the gas passage member 27 and the holes of the main body 28, and is supplied from the fuel gas inlet manifold 171 to the fuel chamber 176 via the fuel gas supply communication holes 142 of each power generation unit 102.

[0057] When oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and fuel gas FG is supplied to the fuel chamber 176, power generation occurs in the single cell 110 based on the electrochemical reaction between oxidant gas OG and fuel gas FG. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to an interconnect 150 via an air electrode-side current collector 134, and the fuel electrode 116 is electrically connected to another interconnect 150 via a fuel electrode-side current collector 144. Furthermore, the multiple power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, the electrical energy generated in each power generation unit 102 is extracted from the end plates 104 and 106, which function as output terminals of the fuel cell stack 100. It should be noted that since SOFC generates electricity at relatively high temperatures (e.g., 700°C to 1000°C), the fuel cell stack 100 can also be heated by a heater (not shown) after startup until the high temperature can be maintained by the heat generated by power generation.

[0058] Oxidant exhaust gas OOG discharged from air chamber 166 of each power generation unit 102, such as Figure 2 and Figure 4 As shown, the gas is discharged into the oxidant gas discharge manifold 162 via the oxidant gas discharge port 133, and then discharged to the outside of the fuel cell stack 100 via the holes of the main body 28 and branch 29 of the gas passage member 27 located at the position of the oxidant gas discharge manifold 162, and through the gas piping (not shown) connected to the branch 29. Additionally, the fuel exhaust gas FOG discharged from the fuel chamber 176 of each power generation unit 102... Figure 3 and Figure 5As shown, the gas is discharged to the fuel gas discharge manifold 172 via the fuel gas discharge communication hole 143, and then discharged to the outside of the fuel cell stack 100 via the holes of the main body 28 and branch 29 of the gas passage member 27 provided at the position of the fuel gas discharge manifold 172 and through the gas piping (not shown) connected to the branch 29.

[0059] A-3. Detailed structure of intermediate layer 180

[0060] Next, the detailed structure of the intermediate layer 180 in the single cell 110 constituting the fuel cell stack 100 of this embodiment will be described. Figure 6 This is an explanatory diagram showing the shape of the outer edge of the electrolyte layer 112 and the intermediate layer 180. Figure 6 The image shows the shape of the outer edges of the electrolyte layer 112 and the intermediate layer 180 when viewed from the top and bottom. Additionally, in... Figure 6 In the image, a portion of the outer edge of the intermediate layer 180 (X1 portion) is shown in magnification.

[0061] like Figure 6 As shown, when viewed vertically, the outer edge of the intermediate layer 180 is located more inwardly than the outer edge of the electrolyte layer 112 around the entire circumference. A plurality of protrusions 182 are formed on the outer edge of the intermediate layer 180. When viewed vertically, the protrusions 182 are formed such that they protrude toward the outer edge of the electrolyte layer 112 (the portion of the electrolyte layer 112 closest to the intermediate layer 180). Furthermore, the protrusions 182 are in contact with the surface of the electrolyte layer 112.

[0062] Viewed vertically, a plurality of protrusions 182 are arranged along the outer edge of the intermediate layer 180. It should be noted that, in this embodiment, the plurality of protrusions 182 are arranged along the outer edge of the separator 120. Furthermore, the plurality of protrusions 182 are spaced apart from each other by recesses 184. Here, viewed vertically, the protrusion width W1 (the length of the protrusion 182 in the direction orthogonal to the protrusion direction) of each of the plurality of protrusions 182 is wider than the separation distance between adjacent protrusions 182 (the opening width W2 of the recess 184). It should be noted that the protrusion width W1 of all the protrusions 182 formed in the intermediate layer 180 is approximately the same, and the opening width W2 of all the recesses 184 formed in the intermediate layer 180 is approximately the same.

[0063] It should be noted that the protrusion width W1 of the protrusion 182 can be, for example, 50 μm or more and 200 μm or less, or 70 μm or more and 150 μm or less. The opening width W2 of the recess 184 can be, for example, 15 μm or more and 60 μm or less, or 30 μm or more and 40 μm or less. Furthermore, the ratio (W1 / W2) of the protrusion width W1 of the protrusion 182 to the opening width W2 of the recess 184 can be 1.5 times or more, or 2 times or more. Additionally, the protrusion height of the protrusion 182 (the height difference between the protrusion 182 and the recess 184) can be, for example, 6.5 μm or more and 40 μm or less, or 10.5 μm or more and 20 μm or less.

[0064] When viewed vertically, the front end of each protrusion 182 is shaped to be flat along the parallel arrangement direction of the multiple protrusions 182. It should be noted that "flat" here means that the height difference in the direction orthogonal to the arrangement direction is less than 6 μm.

[0065] like Figure 6 As shown in section X1, when viewed along the vertical direction, the two ends 183 of the front end of the protrusion 182 are each arc-shaped. Additionally, the bottom portion 187 of the recess 184 is also arc-shaped.

[0066] Viewed along the vertical direction, the multiple protrusions 182 of the intermediate layer 180 face the second direction (in... Figure 6 The depth of the recess 184 (hereinafter referred to as "specific recess 185") between a pair of adjacent protrusions 182 protruding in the negative Y-axis direction, and the direction of a third direction different from the second direction (in Figure 6 The depths of the recesses 184 between adjacent pairs of protrusions 182 (in the positive Y-axis direction, positive X-axis direction, and negative X-axis direction) are different. Specifically, the depth of a particular recess 185 is deeper than the depths of the other recesses 184.

[0067] like Figure 4 and Figure 5 As shown, the power generation unit 102 also includes a junction 124. The junction 124 is used to connect the separator 120 to the single cell 110 (electrolyte layer 112). Furthermore, the junction 124 integrally covers the periphery of the surface on the air electrode 114 side of the intermediate layer 180 and the periphery of the hole 121 in the separator 120. It should be noted that the junction 124 is formed, for example, by glass or solder (e.g., Ag solder).

[0068] A-4. Manufacturing method of fuel cell stack 100

[0069] The method for manufacturing the fuel cell stack 100 in this embodiment is as follows.

[0070] (Formation of the laminate of electrolyte layer 112 and fuel electrode 116)

[0071] To prepare a slurry, butyral resin, dioctyl phthalate (DOP) as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added to YSZ powder and mixed using a ball mill. The slurry is then thinned using a doctor blade to obtain a green sheet for an electrolyte layer with a specified thickness (e.g., approximately 6 μm). Alternatively, to prepare a slurry, organic microspheres (as pore-forming elements), butyral resin, DOP as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added to a mixture of NiO powder and YSZ powder and mixed using a ball mill. The slurry is then thinned using a doctor blade to obtain a green sheet for a fuel electrode substrate with a specified thickness (e.g., approximately 400 μm). Alternatively, to prepare a slurry, butyral resin, DOP as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added to a mixture of NiO powder and YSZ powder and mixed using a ball mill. The obtained slurry is thinned using a doctor blade method to obtain a green sheet for the fuel electrode functional layer with a specified thickness (e.g., about 11 μm). By bonding and pressing the green sheets together, a molded body is obtained by sequentially stacking the green sheet for the fuel electrode substrate layer, the green sheet for the fuel electrode functional layer, and the green sheet for the electrolyte layer.

[0072] Next, the molded body is degreased at a specified temperature (e.g., about 280°C) and then fired at a specified temperature (e.g., about 1350°C) for a specified time (e.g., about 1 hour). Thus, a laminate of electrolyte layer 112 and fuel electrode 116 is obtained.

[0073] (Formation of intermediate layer 180)

[0074] Polyvinyl alcohol as an organic binder and butylcarbidol as an organic solvent are added to GDC powder, mixed, and the viscosity is adjusted to prepare an intermediate layer paste. The obtained intermediate layer paste is applied to the surface of the electrolyte layer 112 in the above-mentioned laminate using, for example, screen printing. Here, in the screen printing of the intermediate layer paste, by adjusting the thixotropic properties of the intermediate layer paste, the wire diameter LW of the screen 200, and the opening PW of the screen 200, an intermediate layer 180 with the aforementioned protrusions 182 can be formed.

[0075] Figure 7 This is a diagram illustrating a partial structure of the screen 200. (See diagram for example.) Figure 7As shown, the wire diameter LW of the screen 200 is the diameter (line width when viewed vertically) of the wires 210 and 220 constituting the screen 200. The opening PW of the screen 200 is the distance between adjacent wires 210 and 220. During screen printing of the intermediate layer paste, the portion of the intermediate layer paste 180P to be formed on the electrolyte layer 112, excluding the outer edge, is uniformly printed using a paste formed in a manner that completely closes the opening area S of the screen 200. On the other hand, at the outer edge of the intermediate layer paste 180P, the wire located on the central side of the intermediate layer paste 180P, formed only in the four wires 210 and 220 constituting the opening area S of the screen 200 (in... Figure 7 In the middle, the paste is printed on the side of the wire 220) located on the negative Y-axis side relative to the opening area S.

[0076] Therefore, by adjusting the thixotropy of the intermediate layer paste, the wire diameter LW of the sieve 200, and the opening PW of the sieve 200, a protrusion corresponding to the protrusion 182 can be formed on the outer edge of the intermediate layer paste 180P. Specifically, the higher the thixotropy of the intermediate layer paste, the better it maintains the shape of the intermediate layer paste 180P formed on the electrolyte layer 112, thus making the protrusions 182 and the recesses 184 more clearly defined. The larger the wire diameter LW of the sieve 200, the wider the opening width W2 of the recess 184. The wider the opening PW of the sieve 200, the wider the protrusion width W1 of the protrusion 182. In this embodiment, by setting the wire diameter LW of the sieve 200 to 30 μm, the opening PW to 72 μm, and appropriately adjusting the thixotropy of the intermediate layer paste, a protrusion corresponding to the desired protrusion 182 is formed. It should be noted that if the thixotropy of the intermediate layer paste is too high, it can easily lead to defects in screen printing (such as uneven printing or smudging). On the other hand, if the thixotropy of the intermediate layer paste is low, it will be unable to maintain the shape of the intermediate layer paste 180P and will be difficult to form the protrusion 182 under leveling. Considering these factors, it is preferable to adjust the thixotropy of the intermediate layer paste.

[0077] Next, the laminate printed with intermediate layer paste 180P is fired at a specified temperature (e.g., 1200°C). Thus, an intermediate layer 180 with protrusions 182 is formed, resulting in a laminate of intermediate layer 180, electrolyte layer 112, and fuel electrode 116.

[0078] (Formation of Air Pole 114)

[0079] A mixture of perovskite oxide (e.g., LSCF) powder and sulfate (e.g., SrSO4) powder is prepared. Polyvinyl alcohol as an organic binder and butylcarbitol as an organic solvent are added to this mixture, and the mixture is mixed and the viscosity is adjusted to obtain an air electrode paste. The obtained air electrode paste is applied to the surface of the intermediate layer 180 in a laminate of the intermediate layer 180, electrolyte layer 112, and fuel electrode 116 using, for example, screen printing, and then dried. The laminate coated with the air electrode paste is then fired at a specified temperature (e.g., about 1100°C). Thus, an air electrode 114 is formed, and a single cell 110 having a fuel electrode 116, electrolyte layer 112, intermediate layer 180, and air electrode 114 is manufactured.

[0080] After multiple individual cells 110 are manufactured according to the above method, an assembly process is performed (such as installing spacers 120 and other components on each individual cell 110, stacking multiple individual cells 110, and fastening them with bolts 22). This completes the manufacturing of the fuel cell stack 100.

[0081] A-5. Effects of this implementation method

[0082] As explained above, in the single cell 110 of the fuel cell stack 100 constituting this embodiment, a plurality of protrusions 182 are formed on the outer edge of the intermediate layer 180. Therefore, in this embodiment, even if stress is generated on the outer edge of the intermediate layer 180 due to the difference in thermal expansion between the electrolyte layer 112 and the intermediate layer 180, or due to long-term durability, this stress will be dispersed by the plurality of protrusions 182. Therefore, according to this embodiment, compared with a structure in which no protrusions 182 are formed on the outer edge of the intermediate layer 180, stress concentration in specific parts of the intermediate layer 180 can be suppressed. In addition, by having a plurality of protrusions 182 that are separated from each other on the outer edge of the intermediate layer 180, the transmission of stress generated in the intermediate layer 180 along the outer edge of the intermediate layer 180 can be suppressed. As a result, peeling and cracking of the intermediate layer 180 from the electrolyte layer 112 can be suppressed.

[0083] It should be noted that, in order to suppress the delamination and cracking of the intermediate layer 180 from the electrolyte layer 112, efforts were also made to optimize the forming material and porosity of the intermediate layer 180. However, since the intermediate layer 180 needs to function as described above to suppress the formation of a high-resistivity layer, the forming material and porosity of the intermediate layer 180 must be determined within the range that enables this function. In contrast, in this embodiment, efforts were made to optimize the shape of the intermediate layer 180, which forms multiple protrusions 182, thereby more effectively suppressing the delamination and cracking of the intermediate layer 180 from the electrolyte layer 112.

[0084] In the above embodiment, when viewed along the vertical direction, the protrusion width W1 of each of the plurality of protrusions 182 is wider than the opening width W2 of the recess 184. Therefore, according to this embodiment, compared with a structure in which the protrusion width W1 of the protrusion 182 is narrower than the opening width W2 of the recess 184, it is possible to suppress the concentration of stress on each protrusion 182, and the peeling of the intermediate layer 180 and the electrolyte layer 112 can be suppressed accordingly by increasing the contact area between the intermediate layer 180 and the electrolyte layer 112.

[0085] In the above embodiment, when viewed along the vertical direction, the front end of each protrusion 182 is flat along the arrangement direction of the plurality of protrusions 182. Therefore, according to this embodiment, compared with a structure in which, for example, the front end of the protrusion 182 is pointed, it is possible to suppress the concentration of stress dispersed to each protrusion 182 at the front end of the protrusion 182.

[0086] In the above embodiment, when viewed along the vertical direction, the two ends 183 of the front end of the protrusion 182 are each arc-shaped. Therefore, according to this embodiment, it is possible to more reliably suppress the concentration of stress dispersed to each protrusion 182 towards the front end of the protrusion 182.

[0087] In the above embodiment, when viewed along the vertical direction, the depth of a specific recess 185 is different from the depths of the other recesses 184. Therefore, according to this embodiment, by referring to the difference in depth of the recesses 184 and 185 between the protrusions 182, the orientation of the single cell 110 can be easily determined, for example, during the assembly of the fuel cell stack 100. Furthermore, in the above manufacturing method, by referring to the difference in depth of the recesses 184 and 185 between the protrusions 182, the orientation of the laminate of the intermediate layer 180, the electrolyte layer 112, and the fuel electrode 116 can be easily determined, thus making it easy to determine the printing direction of the paste for the air electrode.

[0088] In the above embodiment, the joint portion 124 for joining the separator 120 and the single cell 110 integrally covers the periphery of the surface of the air electrode 114 side of the intermediate layer 180 and the periphery of the hole 121 in the separator 120. Therefore, according to this embodiment, the contact area between the joint portion 124 and the intermediate layer 180 is relatively large, thereby improving the bonding strength between the single cell 110 and the separator 120.

[0089] B. Variations

[0090] The technology disclosed in this specification is not limited to the above-described embodiments and can be modified in various forms without departing from its spirit. For example, the following modifications can also be made.

[0091] The structure of the single cell 110 or fuel cell stack 100 in the above embodiments is merely one example and can be modified in various ways. In the above embodiments, the number of single cells 110 included in the fuel cell stack 100 is merely one example, and the number of single cells 110 can be appropriately determined according to the required output voltage of the fuel cell stack 100, etc.

[0092] In the above embodiment, the space between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each connecting hole 108 is used as a manifold. However, alternatively, an axial hole can be formed in the shaft portion of each bolt 22 and used as a manifold. Alternatively, each manifold and each connecting hole 108 for insertion of each bolt 22 can be provided separately.

[0093] In the above embodiment, it can also be configured such that, when viewed along the vertical direction, only a portion of the outer edge of the intermediate layer 180 is located inside the outer edge of the electrolyte layer 112. In the above embodiment, the plurality of protrusions 182 are arranged at equal intervals, but are not limited thereto. The plurality of protrusions 182 can also be arranged regularly in a prescribed pattern other than at equal intervals, or the plurality of protrusions 182 can be arranged irregularly.

[0094] In the above embodiment, at least a portion of the protrusion width W1 of the plurality of protrusions 182 formed in the intermediate layer 180 may be uneven, and at least a portion of the opening width W2 of the plurality of recesses 184 formed in the intermediate layer 180 may also be uneven. The protrusion width W1 of the protrusion 182 may be the same as the opening width W2 of the recess 184, or it may be narrower than the opening width W2 of the recess 184.

[0095] In the above embodiment, when viewed in the vertical direction, the shape of the front end of each protrusion 182 is not limited to a flat shape, but may also be other shapes (such as an arc). Furthermore, when viewed in the vertical direction, the shapes of the two ends 183 of the front end of the protrusion 182 are not limited to an arc, but may also be other shapes (such as an obtuse angle). In the above embodiment, when viewed in the vertical direction, the depth of a specific recess 185 may be the same as the depth of other recesses 184.

[0096] In the above embodiments, the joint 124 may partially cover the periphery of the surface on the air electrode 114 side of the intermediate layer 180 and the area around the hole 121 in the separator 120, rather than covering the entire circumference. Alternatively, in the above embodiments, the joint 124 may not cover the intermediate layer 180.

[0097] The materials used to construct the components in the above embodiments are merely illustrative, and the components may also be constructed from other materials.

[0098] In the above embodiments, it is not necessary for all the individual cells 110 included in the fuel cell stack 100 to have a protrusion 182 formed on the outer edge of the intermediate layer 180. As long as at least one individual cell 110 included in the fuel cell stack 100 has a protrusion 182 formed on the outer edge of the intermediate layer 180, stress concentration in specific parts of the intermediate layer 180 can be suppressed.

[0099] In the above embodiment, a flat single cell 110 is used as the object, but the technology disclosed in this specification is also applicable to other single cells besides flat ones (such as cylindrical single cells).

[0100] In the above embodiments, SOFCs that generate electricity through the electrochemical reaction of hydrogen contained in fuel gas and oxygen contained in oxidant gas are taken as examples. However, the technology disclosed in this specification is also applicable to the constituent units of solid oxide electrolytic cells (SOECs) that generate hydrogen through the electrolysis of water, namely, single electrolytic cells, and electrolytic cell stacks having multiple single electrolytic cells. It should be noted that the structure of an electrolytic cell stack is known, for example, as described in Japanese Patent Application Publication No. 2016-81813, and therefore will not be described in detail here, but it is generally the same structure as the fuel cell stack 100 in the above embodiments. That is, the fuel cell stack 100 in the above embodiments can be referred to as an electrolytic cell stack, the power generation unit 102 as an electrolytic cell unit, and the single cell 110 as an electrolytic cell. When the electrolytic cell stack is operating, a voltage is applied between the two electrodes such that the air electrode 114 is the positive electrode (anode) and the fuel electrode 116 is the negative electrode (cathode), and water vapor, as the feed gas, is supplied through the connecting hole 108. Thus, an electrolysis reaction of water occurs in each electrolytic cell unit, generating hydrogen gas in the fuel chamber 176, which is then extracted to the outside of the electrolytic cell stack via the connecting hole 108. In such an electrolytic cell and electrolytic cell stack, if a structure with a protrusion 182 formed on the outer edge of the intermediate layer 180 is adopted in the same manner as in the above embodiment, the same effect can be achieved.

[0101] The method for manufacturing the fuel cell stack 100 in the above embodiment is merely one example and can be modified in various ways. For example, in the above embodiment, after the stack of the intermediate layer 180, electrolyte layer 112 and fuel electrode 116 without the protrusion 182 is fired, the protrusion 182 can be formed by processing the outer edge of the intermediate layer 180 using, for example, laser processing.

Claims

1. An electrochemical reaction single cell, comprising: An electrolyte layer comprising a solid oxide; an air electrode and a fuel electrode sandwiching the electrolyte layer and opposing each other in a first direction; and an intermediate layer formed between the electrolyte layer and the air electrode. The electrochemical reaction single cell is characterized by the following: When viewed along the first direction, at least a portion of the outer edge of the intermediate layer is located further inward than the outer edge of the electrolyte layer. At least a portion of the outer edge of the intermediate layer is formed with a plurality of protrusions projecting toward the outer edge of the electrolyte layer. The intermediate layer is a reaction prevention layer that inhibits the reaction between the electrolyte layer and the air electrode.

2. The electrochemical reaction single cell according to claim 1, characterized in that, When viewed along the first direction, the width of each of the plurality of protrusions is wider than the distance between adjacent plurality of protrusions.

3. The electrochemical reaction single cell according to claim 1 or 2, characterized in that, When viewed along the first direction, the front end of the protrusion is flat along the arrangement direction of the plurality of protrusions.

4. The electrochemical reaction single cell according to claim 3, characterized in that, When viewed along the first direction, the two ends of the front end of the protrusion are arc-shaped.

5. The electrochemical reaction single cell according to claim 1 or 2, characterized in that, When viewed along the first direction, the outer edge of the intermediate layer is located entirely inside the outer edge of the electrolyte layer. When viewed along the first direction, among the plurality of protrusions in the intermediate layer, the depth of the recess between adjacent pairs of protrusions protruding toward the second direction is different from the depth of the recess between adjacent pairs of protrusions protruding toward a third direction different from the second direction.

6. An electrochemical reaction battery stack comprising multiple electrochemical reaction single cells, characterized in that, 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.

7. The electrochemical reaction battery stack according to claim 6, characterized in that, The electrochemical reaction battery stack has the following features: A separator, connected to the periphery of the at least one electrochemical reaction cell, for dividing the space on the air electrode side from the space on the fuel electrode side; and A junction that integrally covers both the separator and at least a portion of the intermediate layer in the at least one electrochemical reaction single cell.

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