Electrochemical reaction single cells and electrochemical reaction cell stack

Abstract

To perform both of ensuring of electrical connection between a specific electrode and a conductive member and restraint of a decrease in gas flowability while ensuring an efficient current path between the specific electrode and the conductive member.SOLUTION: An electrochemical reaction single cell includes an electrolyte layer, an air electrode, a fuel electrode, and a metal support. The metal support has a plurality of through-holes formed therein, the through-holes penetrating from a first surface facing a specific electrode to a second surface opposite to the first surface. A conductive film that is electrically connected to the specific electrode and extends to an end portion on the second surface side of the inner circumferential surface is formed on the inner circumferential surface of the metal support that forms at least one through hole. At least a part of the peripheral portion of at least one through-hole on which the conductive film is formed, on the first surface of the metal support, faces the specific electrode without interposing the conductive film therebetween, and a gas flow path is formed that extends from the end portion on the second surface side of the at least one through-hole on which the conductive film is formed, to the specific electrode.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The technology disclosed by this specification relates to an electrochemical reaction single cell and an electrochemical reaction cell stack.

Background Art

[0002] As one type of fuel cell that generates electricity by utilizing the electrochemical reaction between hydrogen and oxygen, a solid oxide fuel cell (hereinafter referred to as "SOFC") is known. A fuel cell single cell (hereinafter simply referred to as "single cell"), which is a constituent unit of an SOFC, includes an electrolyte layer containing a solid oxide, and a fuel electrode and an air electrode that face each other in a predetermined direction with the electrolyte layer interposed therebetween.

[0003] As one form of a single cell, a metal-supported (metal support type) single cell is known. A metal-supported single cell includes, for example, a metal support disposed on the side opposite to the electrolyte layer with respect to the fuel electrode, and supports other parts (such as the electrolyte layer) in the single cell by the metal support. Generally, a metal-supported single cell is less likely to crack due to thermal shock and has high start-up performance compared to other types (for example, fuel electrode-supported type) of single cells.

[0004] In a metal-supported single cell, a plurality of through holes penetrating from the surface facing the fuel electrode (hereinafter referred to as "first surface") to the second surface on the side opposite to the first surface are formed in the metal support so that the reaction gas used for power generation can pass through the metal support.

[0005] Conventionally, a technique is known in which the fuel electrode is electrically connected to a conductive member such as an interconnector without passing through the metal support by filling the material of the fuel electrode into each through hole of the metal support (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the above conventional technology, since each through-hole of the metal support is blocked by the material of the fuel electrode, the gas flow to the fuel electrode is hindered, and as a result, for example, the performance of a single cell may deteriorate.

[0008] In addition, such a problem is a common problem also in a single cell in which a metal support is disposed on the side opposite to the electrolyte layer with respect to the air electrode, and in an electrolysis single cell which is a constituent unit of a solid oxide type electrolysis cell (hereinafter referred to as "SOEC") that generates hydrogen by utilizing the electrolysis reaction of water. In this specification, a fuel cell single cell and an electrolysis single cell are collectively referred to as an electrochemical reaction single cell.

[0009] This specification discloses a technology capable of solving the above-described problems.

Means for Solving the Problems

[0010] The technology disclosed in this specification can be realized, for example, in the following forms.

[0011] (1) The electrochemical reaction single cell disclosed in this specification includes an electrolyte layer, a fuel electrode and an air electrode that face each other in a first direction with the electrolyte layer interposed therebetween, and a metal support disposed on the side opposite to the electrolyte layer with respect to a specific electrode of either the fuel electrode or the air electrode. A plurality of through holes penetrating from a first surface facing the specific electrode to a second surface opposite to the first surface are formed in the metal support. A conductor film that is electrically connected to the specific electrode and extends to an end portion on the second surface side of the inner peripheral surface is formed on the inner peripheral surface of the metal support forming at least one of the through holes. At least a part of the peripheral portion of at least one of the through holes in which the conductor film is formed on the first surface of the metal support faces the specific electrode without passing through the conductor film. A gas flow path extending from an end portion on the second surface side of at least one of the through holes in which the conductor film is formed to the specific electrode is formed.

[0012] In this electrochemical reaction single cell, in at least one through-hole, the conductor film is electrically connected to the specific electrode and extends to the end on the second surface side on the inner peripheral surface. Therefore, compared with a configuration in which a conduction path between a conductive member (for example, a current collector) disposed on the second surface side of the metal support and the single cell is ensured without passing through the through-hole of the metal support, both can be electrically connected by a short conductive path with relatively low electrical resistance. Further, in this electrochemical reaction single cell, in at least one through-hole in which the conductor film is formed, a gas flow path extending from the second surface of the metal support to the specific electrode is formed. Therefore, it is possible to suppress a decrease in the fluidity of the gas to the specific electrode due to the conductor film, as compared with a configuration in which, for example, the through-hole is blocked by the conductor film. Furthermore, at least a part of the peripheral portion of at least one through-hole in which the conductor film is formed on the first surface of the metal support faces the specific electrode without passing through the conductor film. Therefore, an efficient current path is ensured between the specific electrode and the conductive member, as compared with a configuration in which, for example, the entire first surface of the metal support is covered with the conductor film. That is, according to this electrochemical reaction single cell, it is possible to achieve both ensuring electrical connection between the specific electrode and the conductive member and suppressing a decrease in gas fluidity while ensuring an efficient current path between the specific electrode and the conductive member.

[0013] (2) In the above electrochemical reaction single cell, the conductor film may be formed of a conductive oxide. According to this electrochemical reaction single cell, for example, compared with a configuration in which the conductor film is formed of a metal, the chemical stability is high, and for example, peeling of the conductor film from the metal support can be suppressed.

[0014] (3) In the above electrochemical reaction single cell, the conductor film in the at least one through-hole may be configured to cover at least a part of the second surface. According to this electrochemical reaction single cell, for example, compared with a configuration in which the conductor film does not cover the second surface of the metal support, the conductor film and the conductive member are more likely to come into contact with each other, so that a conduction path between the conductive member and the single cell can be ensured more stably.

[0015] (4) In the above-described electrochemical reaction single cell, the conductor film may be configured to contain the same material as the specific electrode. According to this electrochemical reaction single cell, for example, compared with a configuration in which the conductor film does not contain the same material as the specific electrode, the bonding property between the conductor film and the specific electrode is improved, so that the conduction path between the conductive member and the single cell can be more stably ensured.

[0016] Note that the technology disclosed in this specification can be realized in various forms. For example, it can be realized in the form of an electrochemical reaction single cell (fuel cell single cell or electrolysis single cell), an electrochemical reaction cell stack (fuel cell stack or electrolysis cell stack) including a plurality of electrochemical reaction single cells, a manufacturing method thereof, and the like.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0018] A. Embodiment: A-1. Configuration of the fuel cell stack 100: FIG. 1 is a perspective view showing the external configuration of the fuel cell stack 100 in the present embodiment, FIG. 2 is an explanatory view showing the XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II of FIG. 1, and FIG. 3 is an explanatory view showing the YZ cross-sectional configuration of the fuel cell stack 100 at the position III-III of FIG. 1. In each figure, XYZ axes orthogonal to each other for specifying directions are shown. In this specification, for convenience, the positive direction of the Z axis is referred to as the upward direction, and the negative direction of the Z axis is referred to as the downward direction, but the fuel cell stack 100 may actually be installed in a direction different from such an orientation. The same applies to FIGS. 4 and later.

[0019] The fuel cell stack 100 includes a plurality of (seven in this embodiment) fuel cell power generation units (hereinafter simply referred to as "power generation units") 102 and a pair of end plates 104 and 106. The seven power generation units 102 are arranged side by side in a predetermined arrangement direction (the Z-axis direction in this embodiment). The pair of end plates 104 and 106 are arranged so as to sandwich the assembly composed of the seven power generation units 102 from above and below. The above arrangement direction (Z-axis direction) is an example of the first direction in the claims, and the fuel cell stack 100 is an example of an electrochemical reaction cell stack in the claims.

[0020] A plurality of (eight in this embodiment) holes penetrating in the Z-axis direction are formed at the peripheral portions of each layer (power generation unit 102, end plates 104 and 106) constituting the fuel cell stack 100 in the circumferential direction around the Z axis, and the holes formed in each layer and corresponding to each other communicate with each other in the Z-axis direction to form a through hole 108 extending in the Z-axis direction 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 through hole 108 may also be referred to as the through hole 108.

[0021] A bolt 22 extending in the Z-axis direction is inserted into each through-hole 108, and the fuel cell stack 100 is fastened by the bolt 22 and nuts 24 fitted on both sides of the bolt 22. As shown in FIGS. 2 and 3, an insulating sheet 26 is interposed between the nut 24 and each end plate 104, 106 (or a gas passage member 27 described later).

[0022] A space is secured between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each through-hole 108. As shown in FIGS. 1 and 2, the space formed by one bolt 22 (bolt 22A) and the through-hole 108 through which the bolt 22A is inserted functions as an air electrode side gas supply manifold 161, which is a gas flow path for introducing an oxidant gas OG (e.g., air) from the outside of the fuel cell stack 100 and supplying the oxidant gas OG to the air chambers 166 of each power generation unit 102. The space formed by another bolt 22 (bolt 22B) and the through-hole 108 through which the bolt 22B is inserted functions as an air electrode side gas discharge manifold 162, which discharges the oxidant off-gas OOG, which is the gas discharged from the air chambers 166 of each power generation unit 102, to the outside of the fuel cell stack 100. Also, as shown in FIGS. 1 and 3, the space formed by another bolt 22 (bolt 22D) and the through-hole 108 through which the bolt 22D is inserted functions as a fuel electrode side gas supply manifold 171, which introduces a fuel gas FG (e.g., a hydrogen-rich gas) from the outside of the fuel cell stack 100 and supplies the fuel gas FG to the fuel chambers 176 of each power generation unit 102. The space formed by another bolt 22 (bolt 22E) and the through-hole 108 through which the bolt 22E is inserted functions as a fuel electrode side gas discharge manifold 172, which discharges the fuel off-gas FOG, which is the gas discharged from the fuel chambers 176 of each power generation unit 102, to the outside of the fuel cell stack 100.

[0023] The fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body portion 28 and a hollow cylindrical branch portion 29 branched from the side surface of the main body portion 28. The hole of the branch portion 29 communicates with the hole of the main body portion 28. The holes of the main body portions 28 of the respective gas passage members 27 communicate with the respective manifolds 161, 162, 171, 172 provided at the installation positions of the respective gas passage members 27.

[0024] (Configuration of end plates 104 and 106) The pair of end plates 104 and 106 are flat plate-shaped conductive members substantially orthogonal to the Z-axis direction, and are formed of, for example, stainless steel. One end plate 104 is disposed above the uppermost power generation unit 102 and is electrically connected to the power generation unit 102. The other end plate 106 is disposed below the lowermost power generation unit 102 and is electrically connected to the power generation unit 102. The upper end plate 104 functions as the positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as the negative output terminal of the fuel cell stack 100.

[0025] (Configuration of power generation unit 102) FIG. 4 is an explanatory view showing an XZ cross-sectional configuration of two adjacent power generation units 102 at the same position as the cross-section shown in FIG. 2, and FIG. 5 is an explanatory view showing a YZ cross-sectional configuration of two adjacent power generation units 102 at the same position as the cross-section shown in FIG. 3.

[0026] As shown in FIGS. 4 and 5, the power generation unit 102 includes a fuel cell single cell (hereinafter referred to as "single cell") 110, a separator 120, an air electrode side frame member 130, an air electrode side current collector 134, a fuel electrode side frame member 140, a fuel electrode side current collector 144, and a pair of interconnectors 150. Holes corresponding to the through holes 108 through which the bolts 22 described above are inserted are formed at the peripheral edges of the separator 120, the air electrode side frame member 130, the fuel electrode side frame member 140, and the interconnector 150. The fuel electrode side current collector 144 is an example of the conductive member in the claims.

[0027] The interconnector 150 is a flat conductive member that is substantially orthogonal to the Z-axis direction and is formed of, for example, stainless steel. The interconnector 150 ensures electrical conductivity between the power generation units 102 and prevents mixing of the reaction gases between the power generation units 102. In the present embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by the two adjacent power generation units 102. That is, the upper interconnector 150 in a certain power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of that power generation unit 102. Further, the power generation unit 102 located at the top in the fuel cell stack 100 does not include the upper interconnector 150, and the power generation unit 102 located at the bottom does not include the lower interconnector 150 (see FIGS. 2 and 3).

[0028] The single cell 110 includes an electrolyte layer 112, and an air electrode 114 and a fuel electrode 116 that face each other in the Z-axis direction with the electrolyte layer 112 interposed therebetween. The single cell 110 further includes a metal support 180 disposed on the side (lower side) opposite to the electrolyte layer 112 with respect to the fuel electrode 116. The single cell 110 is an example of an electrochemical reaction single cell in the claims, and the fuel electrode 116 is an example of a specific electrode in the claims.

[0029] The metal support 180 is a flat conductive member that is substantially orthogonal to the Z-axis direction. The metal support 180 is formed of metal. The metal support 180 is formed of, for example, stainless steel, and more specifically, is formed of, for example, ferritic stainless steel. Forming the metal support 180 of a metal containing chromium, such as ferritic stainless steel, is preferable because the heat resistance of the metal support 180 can be improved. The metal support 180 supports other components (such as the electrolyte layer 112) in the single cell 110. Thus, the single cell 110 of the present embodiment is a so-called metal support type single cell that ensures the mechanical strength of the single cell 110 by the metal support 180. Compared with other types (for example, fuel electrode support type) of single cells, the metal support type single cell is less likely to crack due to thermal shock and has high start-up performance. As will be described later, a plurality of through holes 50 for passing the fuel gas FG are formed in the metal support 180 (see FIG. 6).

[0030] The fuel electrode 116 is a flat member that is substantially orthogonal to the Z-axis direction and is a porous layer. The fuel electrode 116 is formed of, for example, a cermet composed of Ni and oxide ion conductive ceramic particles (for example, YSZ). In the present embodiment, the fuel electrode 116 is formed at the central portion of the upper surface of the metal support 180, and the outer peripheral portion surrounding the central portion of the upper surface of the metal support 180 is not covered by the fuel electrode 116. The electrolyte layer 112 is a flat member that is substantially orthogonal to the Z-axis direction and is a dense layer. In the present embodiment, the electrolyte layer 112 is formed so as to continuously cover the upper surface of the fuel electrode 116 and the above-described outer peripheral portion of the upper surface of the metal support 180 that is not covered by the fuel electrode 116. The electrolyte layer 112 is formed of, for example, a solid oxide such as YSZ (yttria stabilized zirconia). Thus, the single cell 110 of the present embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte. The air electrode 114 is a flat member that is substantially orthogonal to the Z-axis direction and is a porous layer. The air electrode 114 is formed of, for example, a perovskite-type oxide (for example, LSCF (lanthanum strontium cobalt ferrite)).

[0031] The separator 120 is a frame-shaped member in which a substantially rectangular hole 121 penetrating in the Z-axis direction is formed near the center, and is formed of, for example, stainless steel. The portion of the separator 120 surrounding the hole 121 is joined to the peripheral edge of the single cell 110 (electrolyte layer 112) by a joint portion 124 including, for example, a brazing material. The separator 120 partitions the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116.

[0032] The air electrode side frame member 130 is a frame-shaped member in which a substantially rectangular hole 131 penetrating in the Z-axis direction is formed near the center, and is formed of an insulator such as mica. The hole 131 of the air electrode side frame member 130 constitutes the air chamber 166 facing the air electrode 114. The air electrode side frame member 130 electrically insulates between a pair of interconnects 150 included in the power generation unit 102. The air electrode side frame member 130 is formed with an air electrode side gas supply communication flow path 132 that communicates the air electrode side gas supply manifold 161 and the air chamber 166, and an air electrode side gas discharge communication flow path 133 that communicates the air chamber 166 and the air electrode side gas discharge manifold 162.

[0033] The fuel electrode side frame member 140 is a frame-shaped member in which a substantially rectangular hole 141 penetrating in the Z-axis direction is formed near the center, and is formed of, for example, stainless steel. The hole 141 of the fuel electrode side frame member 140 constitutes the fuel chamber 176 facing the fuel electrode 116. The fuel electrode side frame member 140 is formed with a fuel electrode side gas supply communication flow path 142 that communicates the fuel electrode side gas supply manifold 171 and the fuel chamber 176, and a fuel electrode side gas discharge communication flow path 143 that communicates the fuel chamber 176 and the fuel electrode side gas discharge manifold 172.

[0034] The air electrode side current collector 134 is composed of a plurality of substantially quadrangular prism-shaped current collector elements 135 arranged in the air chamber 166, and is formed of, for example, stainless steel. The air electrode side current collector 134 electrically connects the air electrode 114 and the interconnector 150. However, since the power generation unit 102 located at the top in the fuel cell stack 100 does not include the upper interconnector 150, the air electrode side current collector 134 in the power generation unit 102 electrically connects the air electrode 114 and the upper end plate 104 (see FIGS. 2 and 3). Note that the air electrode side current collector 134 and the interconnector 150 may be configured as an integral member.

[0035] The fuel electrode side current collector 144 is composed of a plurality of substantially quadrangular prism-shaped current collector elements 145 arranged in the fuel chamber 176, and is formed of, for example, stainless steel. The fuel electrode side current collector 144 electrically connects the metal support 180 and the interconnector 150. However, since the power generation unit 102 located at the bottom in the fuel cell stack 100 does not include the lower interconnector 150, the fuel electrode side current collector 144 in the power generation unit 102 electrically connects the metal support 180 and the lower end plate 106 (see FIGS. 2 and 3). Note that the fuel electrode side current collector 144 and the interconnector 150 may be configured as an integral member.

[0036] A-2. Operation of the fuel cell stack 100: As shown in FIGS. 2 and 4, the oxidant gas OG is supplied from a gas pipe (not shown) connected to a branch portion 29 of a gas passage member 27 provided at the position of the air electrode side gas supply manifold 161, through the branch portion 29 of the gas passage member 27 and the holes of the main body portion 28, to the air electrode side gas supply manifold 161, and from the air electrode side gas supply manifold 161, it is supplied to the air chamber 166 through the air electrode side gas supply communication flow path 132 of each power generation unit 102. Further, as shown in FIGS. 3 and 5, the fuel gas FG is supplied from a gas pipe (not shown) connected to a branch portion 29 of a gas passage member 27 provided at the position of the fuel electrode side gas supply manifold 171, through the branch portion 29 of the gas passage member 27 and the holes of the main body portion 28, to the fuel electrode side gas supply manifold 171, and from the fuel electrode side gas supply manifold 171, it is supplied to the fuel chamber 176 through the fuel electrode side gas supply communication flow path 142 of each power generation unit 102.

[0037] In each power generation unit 102, when the oxidant gas OG supplied to the air chamber 166 enters into the porous air electrode 114, and the fuel gas FG supplied to the fuel chamber 176 enters into the porous fuel electrode 116 through the plurality of through holes 50 formed in the metal support 180, power generation by the electrochemical reaction between the oxygen contained in the oxidant gas OG and the hydrogen contained in the fuel gas FG is performed in the single cell 110. 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 one interconnector 150 through the air electrode side current collector 134, and the fuel electrode 116 is electrically connected to the other interconnector 150 through the metal support 180 and the fuel electrode side current collector 144. Also, the plurality of 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 taken out from the end plates 104, 106 that function as the output terminals of the fuel cell stack 100. Note that since the SOFC generates power at a relatively high temperature (for example, from 700°C to 1000°C), after startup, the fuel cell stack 100 may be heated by a heater (not shown) until it reaches a state where the high temperature can be maintained by the heat generated by power generation.

[0038] As shown in FIGS. 2 and 4, the oxidant off-gas OOG discharged from the air chamber 166 of each power generation unit 102 to the air electrode side gas discharge manifold 162 through the air electrode side gas discharge communication flow path 133 passes through the main body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the air electrode side gas discharge manifold 162, and is discharged to the outside of the fuel cell stack 100 from a gas pipe (not shown) connected to the branch portion 29. Further, as shown in FIGS. 3 and 5, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generation unit 102 to the fuel electrode side gas discharge manifold 172 through the fuel electrode side gas discharge communication flow path 143 passes through the main body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the fuel electrode side gas discharge manifold 172, and is discharged to the outside of the fuel cell stack 100 from a gas pipe (not shown) connected to the branch portion 29.

[0039] A-3. Detailed Configuration of Single Cell 110: FIG. 6 is an explanatory diagram showing the detailed configuration of the single cell 110 in the present embodiment. In FIG. 6, the YZ cross-sectional configuration of the single cell 110 in the X1 portion of FIG. 5 is shown enlarged.

[0040] As shown in FIG. 6, in the single cell 110 in the present embodiment, a plurality of through holes 50 are formed in the metal support 180. In the metal support 180, each through hole 50 penetrates from the upper surface S1, which is the surface facing the fuel electrode 116, to the lower surface S2, which is the opposite side of the upper surface S1. The upper surface S1 of the metal support 180 is an example of the first surface in the claims, and the lower surface S2 of the metal support 180 is an example of the second surface in the claims.

[0041] Of the surface of the metal support 180, a metal oxide layer 90 is formed on the inner peripheral surface S3 that defines each through-hole 50. The metal oxide layer 90 is an example of a conductor film. The metal oxide layer 90 is a film composed of a metal oxide. The metal oxide layer 90 preferably contains at least one of Cr, Mn, Si, Al, Ti, and Co. The metal oxide layer 90 is composed of, for example, Cr2O3 (chromia), Mn2O3, MnCr2O4, SiO2, Al2O3 (alumina), and TiO2.

[0042] The metal oxide layer 90 preferably contains the same materials as the fuel electrode 116 (an ion conductive material (such as YSZ) + an electron conductive material (such as Ni)). Note that the metal oxide layer 90 is preferably a porous body, similar to the fuel electrode 116. The porous metal oxide layer 90 can be formed, for example, by baking and baking a paste (slurry) with relatively low viscosity at a temperature that does not become dense.

[0043] The metal oxide layer 90 is electrically connected to the fuel electrode 116 and extends to the end on the lower surface S2 side of the inner peripheral surface S3. Specifically, of the fuel electrode 116, the opposing surface S5 facing the metal support 180 is an overall flat surface. The metal oxide layer 90 continuously extends from the end on the upper surface S1 side to the end on the lower surface S2 side of the inner peripheral surface S3 and contacts the opposing surface S5 of the fuel electrode 116. Thereby, the metal oxide layer 90 and the fuel electrode 116 are electrically connected. Further, the metal oxide layer 90 is formed over the entire circumference of the inner peripheral surface S3. That is, the metal oxide layer 90 covers the entire surface of the inner peripheral surface S3. The metal oxide layer 90 is electrically connected to the fuel electrode 116 over the entire circumference on the upper end opening side of the through-hole 50.

[0044] Of the upper surface S1 of the metal support 180, at least a part of the peripheral portion of the through-hole 50 faces the fuel electrode 116 without passing through the metal oxide layer 90. Specifically, the upper surface S1 of the metal support 180 is not covered by the metal oxide layer 90. Therefore, the upper surface S1 of the metal support 180 is in contact with the fuel electrode 116 in an overall manner without passing through the metal oxide layer 90.

[0045] In the metal support 180, a gas flow path FP extending from the end on the lower surface S2 side of each through hole 50 to the fuel electrode 116 is formed. The gas flow path FP is a flow path for the fuel gas FG that communicates the fuel chamber 176 and the fuel electrode 116. Specifically, in the metal support 180, the gas flow path FP is defined by the inner peripheral surface S4 of the metal oxide layer 90 formed on the inner peripheral surface S3 of each through hole 50.

[0046] In addition, in the present embodiment, in each through hole 50 of the metal support 180, the inner diameter D of the through hole 50 at each position along the vertical direction is not constant. Specifically, the inner diameter D2 of the through hole 50 on the lower surface S2 side is larger than the inner diameter D1 of the through hole 50 on the upper surface S1 side. The inner diameter D of each through hole 50 gradually decreases from the lowermost part (the position of the lower surface S2) to the uppermost part (the position of the upper surface S1). That is, each through hole 50 is formed in a tapered shape that tapers from the lowermost part to the uppermost part.

[0047] The shape of each such through hole 50 can be realized, for example, by performing laser processing or etching on the metal support 180 to form each through hole 50. Alternatively, the shape of each such through hole 50 can also be realized, for example, by constructing the metal support 180 by laminating a plurality of plate-like members in the vertical direction and making the diameters of the holes (holes that become the through holes 50) formed in each plate-like member different for each plate-like member.

[0048] Also, in the present embodiment, the thickness t of the metal oxide layer 90 formed on the inner peripheral surface S3 defining each through hole 50 of the metal support 180 is not constant at each position along the vertical direction. Specifically, in each through hole 50, the thickness t1 of the metal oxide layer 90 at the uppermost part (the position of the upper surface S1) of the through hole 50 is thinner than the thickness t2 of the metal oxide layer 90 at the lowermost part (the position of the lower surface S2). The thickness t of the metal oxide layer 90 formed on the inner peripheral surface S3 defining each through hole 50 of the metal support 180 gradually decreases from the lowermost part (the position of the lower surface S2) to the uppermost part (the position of the upper surface S1). The thickness t of the metal oxide layer 90 is preferably less than 1 / 2 of the minimum inner diameter of the through hole 50 (in FIG. 6, the inner diameter D1 at the uppermost part). Note that the thickness t of the metal oxide layer 90 formed in one through hole 50 and the thickness t of the metal oxide layer 90 formed in another through hole 50 may be different from each other.

[0049] Adjustment of the thickness t of the metal oxide layer 90 at each position along the vertical direction of each such through hole 50 can be realized, for example, by making the formation method of the metal oxide layer 90 different at each position along the vertical direction. Here, the formation method of the metal oxide layer 90 is, for example, the number of executions of a process of impregnating the base material of the above-described metal support 180 with a solution containing a metal oxide and then drying it, the heat treatment conditions for the metal support 180, and the like. Alternatively, adjustment of the thickness t of such a metal oxide layer 90 can also be realized, for example, by mechanically or chemically removing a part of the metal oxide layer 90 after forming the metal oxide layer 90 with a uniform thickness.

[0050] In each through hole 50, the ratio (t2 / t1) of the thickness t2 of the metal oxide layer 90 at the lowermost part (the position of the lower surface S2) to the thickness t1 of the metal oxide layer 90 at the uppermost part (the position of the upper surface S1) is preferably greater than 1.01. Further, the ratio (t2 / t1) is more preferably 1.50 or more, and even more preferably 2.00 or more.

[0051] The metal oxide layer 90 covers at least a part of the lower surface S2 of the metal support 180. Specifically, the metal oxide layer 90 extends to and covers the peripheral portion of the opening of the through hole 50 on the lower surface S2 of the metal support 180. However, the metal oxide layer 90 is not formed on the portion between adjacent through holes 50 on the lower surface S2 of the metal support 180 (the portion between the peripheral portion of one through hole 50 and the peripheral portion of the other through hole 50), and is exposed to the fuel chamber 176.

[0052] The metal oxide layer 90 can be formed, for example, by performing a heat treatment on the base material of the metal support 180. Further, the metal oxide layer 90 can also be formed by performing the process of impregnating the base material of the metal support 180 with a solution containing a metal oxide and then drying it once or a plurality of times.

[0053] A-4. Effects of the present embodiment: As described above, each single cell 110 constituting the fuel cell stack 100 of the present embodiment includes an electrolyte layer 112, a fuel electrode 116 and an air electrode 114 that face each other in the vertical direction with the electrolyte layer 112 interposed therebetween, and a metal support 180 disposed on the side opposite to the electrolyte layer 112 with respect to the fuel electrode 116. A plurality of through holes 50 penetrating from the upper surface S1 facing the fuel electrode 116 to the lower surface S2 opposite to the upper surface S1 are formed in the metal support 180. A metal oxide layer 90 is formed on the inner peripheral surface S3 of the metal support 180 that defines each through hole 50. The metal oxide layer 90 is electrically connected to the fuel electrode 116 and is formed so as to extend to the end on the lower surface S2 side of the inner peripheral surface S3. At least a part of the peripheral portion of the through hole 50 on the upper surface S1 of the metal support 180 where the metal oxide layer 90 is formed faces the fuel electrode 116 without passing through the metal oxide layer 90. A gas flow path FP is formed in the metal support 180, and the gas flow path FP is formed so as to extend from the end on the lower surface S2 side of the through hole 50 to the fuel electrode 116.

[0054] Thus, in the single cell 110 of the present embodiment, in the through hole 50, the metal oxide layer 90 is electrically connected to the fuel electrode 116 and extends to the end on the lower surface S2 side of the inner peripheral surface S3. Therefore, according to the present embodiment, compared with a configuration in which a conduction path between the fuel electrode side current collector 144 disposed on the lower surface S2 side of the metal support 180 and the single cell 110 is secured without passing through the through hole 50 of the metal support 180, for example, the two can be electrically connected by a short conductive path with relatively low electrical resistance.

[0055] Further, in the present embodiment, in the through hole 50, a gas flow path FP of the fuel gas FG extending from the lower surface S2 of the metal support 180 to the fuel electrode 116 is formed. Therefore, for example, compared with a configuration in which the through hole 50 is blocked by the metal oxide layer 90, it is possible to suppress a decrease in the fluidity of the fuel gas FG to the fuel electrode 116 due to the presence of the metal oxide layer 90.

[0056] Furthermore, at least a part of the peripheral portion of the through hole 50 in the upper surface S1 of the metal support 180 faces the fuel electrode 116 without passing through the metal oxide layer 90. Therefore, for example, compared with a configuration in which the entire upper surface S1 of the metal support 180 is covered with the metal oxide layer 90, an efficient current path is secured between the fuel electrode 116 and the fuel electrode side current collector 144.

[0057] From the above, according to the single cell 110 of the present embodiment, while securing an efficient current path between the fuel electrode 116 and the fuel electrode side current collector 144, it is possible to achieve both the securing of electrical connection between the fuel electrode 116 and the fuel electrode side current collector 144 and the suppression of a decrease in gas fluidity.

[0058] In the present embodiment, the metal oxide layer 90 is formed of a conductive oxide. Therefore, according to the present embodiment, for example, compared with a configuration in which the metal oxide layer 90 is formed of a metal, the chemical stability is high, and for example, peeling of the metal oxide layer 90 from the metal support 180 can be suppressed.

[0059] In this embodiment, the metal oxide layer 90 covers at least a part of the lower surface S2 of the metal support 180. Therefore, according to this embodiment, for example, compared with a configuration in which the metal oxide layer 90 does not cover the lower surface S2 of the metal support 180, the metal oxide layer 90 and the fuel electrode side current collector 144 are more likely to come into contact with each other, so that a conduction path between the fuel electrode side current collector 144 and the single cell 110 can be more stably ensured.

[0060] In this embodiment, the metal oxide layer 90 contains the same material as the fuel electrode 116. Therefore, according to this embodiment, for example, compared with a configuration in which the metal oxide layer 90 does not contain the same material as the fuel electrode 116, the bonding strength between the metal oxide layer 90 and the fuel electrode 116 is improved, so that a conduction path between the fuel electrode side current collector 144 and the single cell 110 can be more stably ensured.

[0061] B. Modification examples: 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 gist thereof. For example, the following modifications are also possible.

[0062] The configurations of the fuel cell stack 100 and the single cell 110 in the above embodiment are merely examples, and can be variously modified. For example, the shape of each through hole 50 of the metal support 180 and the thickness of the metal oxide layer 90 in the above embodiment are merely examples, and can be variously modified.

[0063] Regarding the shape of each through-hole 50 of the metal support 180, the formation range and thickness of the metal oxide layer 90 in the above-described embodiment, it is not necessary to be realized in all the through-holes 50 formed in the metal support 180. It is sufficient if it is realized in at least one of the plurality of through-holes 50 formed in the metal support 180. Note that it is more preferable that the configuration is realized in 50% or more of the through-holes 50 among the plurality of through-holes 50 formed in the metal support 180, and it is even more preferable that the configuration is realized in 80% or more of the through-holes 50 among the plurality of through-holes 50 formed in the metal support 180. Further, among the plurality of through-holes 50 formed in the metal support 180, some of the through-holes 50 may be filled with the formation material of the metal oxide layer 90 and blocked.

[0064] In the above-described embodiment, the metal oxide layer 90 extends from the end on the lower surface S2 side to the end on the upper surface S1 side on the inner peripheral surface S3. However, the present invention is not limited to this, and it may extend to a position below the end on the upper surface S1 side from the end on the lower surface S2 side on the inner peripheral surface S3. For example, the fuel electrode 116 may have a protruding portion protruding into the through-hole 50, and the metal oxide layer 90 may be electrically connected to the protruding portion of the fuel electrode 116 in the middle of the through-hole 50 from the end on the lower surface S2 side. Further, in the above-described embodiment, the metal oxide layer 90 is formed over the entire circumference of the inner peripheral surface S3. However, the present invention is not limited to this, and it may be formed only on a part in the circumferential direction of the inner peripheral surface S3.

[0065] In the above-described embodiment, the entire upper surface S1 of the metal support 180 is not covered with the metal oxide layer 90. However, as long as at least a part of the peripheral portion of the through-hole 50 is not covered with the metal oxide layer 90 and is opposed to the fuel electrode 116, the configuration is acceptable. Further, in the above-described embodiment, the metal oxide layer 90 may cover the entire lower surface S2 of the metal support 180, or may not cover the entire lower surface S2 of the metal support 180 and may be exposed to the fuel chamber 176.

[0066] In the above-described embodiment, the configuration in which the present invention is applied to the single cell 110 in which the metal support 180 is disposed on the side opposite to the electrolyte layer 112 with respect to the fuel electrode 116 has been illustrated. However, the configuration in which the present invention is applied to a single cell in which the metal support is disposed on the side opposite to the electrolyte layer 112 with respect to the air electrode 114 may also be used. Even in such a configuration, while ensuring an efficient current path between the air electrode 114 and the conductive member (such as the air electrode side current collector 134), it is possible to achieve both ensuring the electrical connection between the fuel electrode 116 and the conductive member and suppressing the decrease in the gas fluidity of the oxidant gas OG. In this configuration, the air electrode 114 is an example of a specific electrode in the claims.

[0067] In the above-described embodiment, a reaction prevention layer may be disposed between the air electrode 114 and the electrolyte layer 112 of the single cell 110 to suppress the reaction in which an element (for example, Sr) diffused from the air electrode 114 reacts with an element (for example, Zr) contained in the electrolyte layer 112 to generate a high-resistance substance (for example, SrZrO3). The reaction prevention layer is formed of, for example, a ceria-based ion conductor material.

[0068] In the above-described embodiment, it is not necessarily required that the above-described configuration be realized in all the single cells 110 included in the fuel cell stack 100. It is sufficient that the above-described configuration is realized in at least one single cell 110 included in the fuel cell stack 100.

[0069] The materials constituting the respective members in the above-described embodiment are merely examples, and each member may be constituted by other materials. For example, in the above-described embodiment, the metal oxide layer 90 is exemplified as the conductor film. However, the present invention is not limited to this, and a conductor film formed of a conductive material other than the metal oxide (such as a metal) may also be used. Further, the manufacturing method of the single cell 110 in the above-described embodiment is merely an example and can be variously modified.

[0070] In the above-described embodiment, a solid oxide fuel cell (SOFC) that generates electricity by utilizing the electrochemical reaction between hydrogen contained in fuel gas and oxygen contained in oxidant gas is targeted. However, the technology disclosed in this specification is also applicable to an electrolysis single cell, which is a constituent unit of a solid oxide electrolysis cell (SOEC) that generates hydrogen by utilizing the electrolysis reaction of water, and an electrolysis cell stack including a plurality of electrolysis single cells. Note that the configuration of the electrolysis cell stack is known as described in, for example, Japanese Patent Application Laid-Open No. 2016-81813, and thus will not be described in detail here. Generally, it has the same configuration as the fuel cell stack 100 in the above-described embodiment. That is, the fuel cell stack 100 in the above-described embodiment may be read as an electrolysis cell stack, the power generation unit 102 may be read as an electrolysis cell unit, and the single cell 110 may be read as an electrolysis single cell. However, during the operation of the electrolysis cell stack, a voltage is applied between the two electrodes such that the air electrode 114 is positive (anode) and the fuel electrode 116 is negative (cathode), and water vapor as a raw material gas is supplied through the through-hole 108. As a result, the electrolysis reaction of water occurs in each electrolysis cell unit, hydrogen gas is generated in the fuel chamber 176, and hydrogen is taken out of the electrolysis cell stack through the through-hole 108. Even in an electrolysis single cell having such a configuration, by adopting the same configuration as in the above-described embodiment, the same operational effects as in the above-described embodiment can be achieved.

[0071] In the above-described embodiment, a solid oxide fuel cell (SOFC) has been described as an example. However, the technology disclosed in this specification is also applicable to other types of fuel cells (or electrolysis cells) such as molten carbonate fuel cells (MCFC).

Description of Reference Numerals

[0072] 22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 28: Main body portion 29: Branch portion 50: Through hole 90: Metal oxide layer 100: Fuel cell stack 102: Power generation unit 104, 106: End plate 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 124: Joint portion 130: Air electrode side frame member 132: Air electrode side gas supply communication flow path 133: Air electrode side gas discharge communication flow path 134: Air electrode side current collector 135: Current collector element 140: Fuel electrode side frame member 142: Fuel electrode side gas supply communication flow path 143: Fuel electrode side gas discharge communication flow path 144: Fuel electrode side current collector 145: Current collector element 150: Interconnector 161, 162, 171, 172: Manifold 166: Air chamber 176: Fuel chamber 180: Metal support

Claims

1. In an electrochemical reaction single cell comprising an electrolyte layer, a fuel electrode and an air electrode that face each other in a first direction with the electrolyte layer therebetween, and a metal support disposed on the side opposite to the electrolyte layer with respect to one of the fuel electrode and the air electrode (specific electrode), a plurality of through holes are formed in the metal support, penetrating from a first surface facing the specific electrode to a second surface opposite to the first surface, a conductor film that is electrically connected to the specific electrode and extends to an end on the second surface side on the inner peripheral surface is formed on the inner peripheral surface of the metal support forming at least one of the through holes, at least a part of a peripheral portion of at least one of the through holes where the conductor film is formed on the first surface of the metal support faces the specific electrode without passing through the conductor film, a gas flow path is formed that extends from an end on the second surface side of at least one of the through holes where the conductor film is formed to the specific electrode, characterized in that it is an electrochemical reaction single cell.

2. In the electrochemical reaction single cell according to Claim 1, the conductor film is formed of a conductive oxide, characterized in that it is an electrochemical reaction single cell.

3. In the electrochemical reaction single cell according to Claim 1 or Claim 2, the conductor film in at least one of the through holes covers at least a part of the second surface, characterized in that it is an electrochemical reaction single cell.

4. In the electrochemical reaction single cell according to Claim 1 or Claim 2, the conductor film contains the same material as the specific electrode, characterized in that it is an electrochemical reaction single cell.

5. In an electrochemical reaction cell stack comprising a plurality of electrochemical reaction single cells arranged side by side in the first direction, at least one of the plurality of electrochemical reaction single cells is the electrochemical reaction single cell according to Claim 1 or Claim 2, characterized in that it is an electrochemical reaction cell stack.

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