Electrochemical reaction cell stack

Abstract

To suppress peeling between an oxide film and an insulating member in an electrochemical reaction cell stack.SOLUTION: An electrochemical reaction cell stack includes a unit cell, a first metal member, a first oxide film formed on a surface of the first metal member and mainly composed of a metal oxide containing a first metal element, and an insulating member disposed between the unit cell or a conductive member electrically connected to the unit cell and the first oxide film. The first oxide film contains a first specific element having a standard electrode potential whose absolute value is larger than that of the first metal element.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] As one of fuel cells that generate electricity using an electrochemical reaction between hydrogen and oxygen, a solid oxide fuel cell (hereinafter referred to as "SOFC") is known. SOFCs are generally used in the form of a fuel cell stack. Conventionally, a cell stack including a plurality of fuel cells (single cells), a manifold (first metal member) composed of an alloy material containing Cr, and a glass seal member (insulating member) that joins the fuel cell and the manifold is known (see, for example, Patent Document 1).

[0003] The fuel cell stack may further include a first oxide film formed on the surface of the first metal member and mainly composed of a metal oxide containing a first metal element. In such a fuel cell stack, an insulating member is disposed between a single cell or a conductive member electrically connected to the single cell and the first oxide film formed on the surface of the first metal member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Because an insulating material is interposed between a single cell or a conductive material electrically connected to a single cell and the first oxide film, a relatively large electric field is generated, for example, when a fuel cell stack generates electricity. Voltages are applied to the conductive material, the first oxide film, and the insulating material, and at this time, a redox reaction of the first metal element may occur in the first oxide film. When a redox reaction of the first metal element occurs, the volume of the first oxide film changes, cracks may occur at the interface between the first oxide film and the insulating material, and consequently, the first oxide film and the insulating material may delaminate.

[0006] Furthermore, these challenges are also common to electrolytic cell stacks, which are a form of electrolytic cell (hereinafter referred to as "SOEC") that uses the electrolysis reaction of water to produce hydrogen.In this specification, fuel cell single cells and electrolytic single cells are collectively referred to as single cells, and fuel cell stacks and electrolytic cell stacks are collectively referred to as electrochemical reaction cell stacks.In addition, these challenges are not limited to SOFCs and SOECs, but are also common to other types of electrochemical reaction cell stacks.

[0007] This specification discloses a technology capable of solving the above-mentioned problems. [Means for solving the problem]

[0008] The technologies disclosed herein can be implemented, for example, in the following forms:

[0009] (1) An electrochemical reaction cell stack disclosed herein comprises a single cell, a first metal member, a first oxide film formed on the surface of the first metal member and mainly composed of a metal oxide containing a first metal element, a conductive member electrically connected to the single cell or the single cell, and an insulating member disposed between the first oxide film. The first oxide film contains a first specific element whose absolute value of standard electrode potential is greater than that of the first metal element.

[0010] According to this electrochemical reaction cell stack, the first oxide film contains a first specific element that is less susceptible to oxidation-reduction reactions than the first metal element, which is the main component of the first oxide film. As a result, oxidation-reduction reactions are less likely to occur in the first oxide film as a whole. This improves the voltage resistance of the entire first oxide film and suppresses the occurrence of cracks at the interface between the first oxide film and the insulating material. Therefore, this electrochemical reaction cell stack can suppress delamination between the first oxide film and the insulating material.

[0011] (2) In the electrochemical reaction cell stack described in (1) above, the insulating member may be made of glass. With this configuration, since the insulating member is made of glass, peeling between the first oxide film and the insulating member can be suppressed while improving the gas sealing performance between the first oxide film and the insulating member.

[0012] (3) The electrochemical reaction cell stack described in (1) above further comprises a conductive member having a second metal member and a second oxide film formed on the surface of the second metal member, the second oxide film mainly composed of a metal oxide containing a second metal element, wherein the second oxide film may contain a second specific element whose absolute value of standard electrode potential is greater than that of the second metal element. With this configuration, by including a second specific element in the second oxide film that is less prone to oxidation-reduction than the second metal element which is the main component, oxidation-reduction reactions are less likely to occur in the second oxide film as a whole. As a result, the voltage resistance of the entire second oxide film is improved, and the occurrence of cracks at the interface between the second oxide film and the insulating member is suppressed. Therefore, with this electrochemical reaction cell stack, peeling between the second oxide film and the insulating member can be suppressed.

[0013] (4) In the electrochemical reaction cell stack described in (1) above, the first metal element may be either Al or Cr. With this configuration, by making the first metal element either Al or Cr, oxidation of the first metal component when the electrochemical reaction cell stack is operated at high temperatures can be suppressed, and high reliability can be achieved.

[0014] (5) In the electrochemical reaction cell stack described in (3) above, the second metal element may be either Al or Cr. With this configuration, by making the second metal element either Al or Cr, oxidation of the second metal component when the electrochemical reaction cell stack is operated at high temperatures can be suppressed, and high reliability can be achieved.

[0015] (6) In the electrochemical reaction cell stack described in (1) above, the concentration of the first specific element in the first oxide film may be 2 mol% or more. With this configuration, since the concentration of the first specific element in the first oxide film is 2 mol% or more, peeling between the first oxide film and the insulating member can be suppressed more effectively.

[0016] (7) In the electrochemical reaction cell stack described in (1) above, the first oxide film has a first portion which is a portion that overlaps with the insulating member in a first direction which is the direction in which the first oxide film and the insulating member are stacked, and a second portion which is a portion that does not overlap with the insulating member in the first direction and is adjacent to the first portion in a second direction which intersects the first direction, and the first specific element may be located in at least one of the first portion and a portion of the second portion which is within 100 μm of the boundary with the first portion in the second direction. With this configuration, since the first specific element is located in a portion of the first oxide film that is prone to voltage, peeling between the first oxide film and the insulating member can be suppressed more effectively.

[0017] (8) In the electrochemical reaction cell stack described in any one of (1) to (7) above, the first oxide film is mainly composed of alumina, and the first specific element may be at least one of Ba, Ca, La, Mg, and Sr. With this configuration, since the first specific element is at least one of Ba, Ca, La, Mg, and Sr, the durability of the electrochemical reaction cell stack can be improved.

[0018] (9) In the electrochemical reaction cell stack according to any one of (1) to (7) above, the first oxide film contains chromia as the main component, and the first specific element may be at least one of Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn. According to this configuration, since the first specific element is at least one of Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn, the durability of the electrochemical reaction cell stack can be improved.

[0019] Note that the technology disclosed in this specification can be realized in various forms, for example, in the form of an electrochemical reaction cell stack and its manufacturing method, etc.

Brief Description of the Drawings

[0020] [Figure 1] Perspective view showing the appearance of the fuel cell stack [Figure 2] Explanatory drawing showing the XZ cross-section of the fuel cell stack at the position of II-II in FIG. 1 [Figure 3] Explanatory drawing showing the XZ cross-section of the fuel cell stack at the position of III-III in FIG. 1 [Figure 4] Explanatory drawing showing the XZ cross-section of two adjacent power generation units at the same position as the cross-section shown in FIG. 2 [Figure 5] Explanatory drawing showing the XZ cross-section of two adjacent power generation units at the same position as the cross-section shown in FIG. 3 [Figure 6] Explanatory drawing showing an enlarged view of the X1 part in FIG. 5 [Figure 7] Explanatory drawing showing an enlarged view of the X2 part in FIG. 3 [Figure 8] Top view of the test piece [Figure 9] Cross-sectional view of the test piece at the position of IX-IX in FIG. 8

Embodiments for Carrying Out the Invention

[0021] A. Embodiment: (Configuration of the fuel cell stack 10) Figure 1 is a perspective view showing the external appearance of the fuel cell stack 10, Figure 2 is an explanatory diagram showing the XZ cross-section of the fuel cell stack 10 at position II-II in Figure 1, and Figure 3 is an explanatory diagram showing the XZ cross-section of the fuel cell stack 10 at position III-III in Figure 1. Each figure shows mutually orthogonal XYZ axes for specifying direction. For convenience, in this specification, the Z-axis direction will be referred to as the up-down direction, the positive Z-axis direction as the up direction, and the negative Z-axis direction as the down direction, however, the fuel cell stack 10 may actually be installed in a different orientation. The fuel cell stack 10 is an example of an electrochemical reaction cell stack.

[0022] As shown in Figures 1 to 3, the fuel cell stack 10 comprises a power generation block 100, an end separator 230, a first plate 232, a second plate 260, a first terminal plate 240, a second terminal plate 250, an insulating section 220, a first end plate 210, a second end plate 270, and four gas passage members 280. The first end plate 210, the insulating section 220, the end separator 230, the first terminal plate 240, the power generation block 100, the second terminal plate 250, the second plate 260, and the second end plate 270 have rectangular outlines of approximately the same size and are arranged in this order overlapping in a predetermined arrangement direction (vertical direction).

[0023] As shown in Figure 1, the fuel cell stack 10 has bolt holes BH near each of its four corners, each extending from the first end plate 210 to the second end plate 270. A bolt B is inserted into each bolt hole BH. Nuts N are threaded onto both ends of each bolt B. These bolts B and nuts N fasten the components from the first end plate 210 to the second end plate 270 together. As shown in Figures 2 and 3, the first plate 232 is supported by the end separator 230. The four gas passage members 280 are connected to the second end plate 270.

[0024] As shown in Figures 2 and 3, the power generation block 100 is composed of a plurality (seven in this embodiment) of power generation units 100U arranged in a predetermined arrangement direction (vertical direction).

[0025] The first end plate 210 is a member formed by press-forming (bending) a single plate-shaped member. As shown in Figures 1 to 3, the first end plate 210 comprises a rectangular frame-shaped planar portion 211 having a through hole 212 near the center, and an outer projection 213 and an inner projection 214 projecting from the planar portion 211 in the opposite direction to the insulating portion 220 (upwards in Figure 2). The planar portion 211 has holes that constitute the bolt holes BH described above. The outer projection 213 protrudes from the outer peripheral edge of the planar portion 211. The outer projection 213 is formed around the entire circumference of the outer peripheral portion of the planar portion 211. The inner projection 214 protrudes from the inner peripheral edge of the planar portion 211. The inner projection 214 is formed around the entire circumference of the inner peripheral portion of the planar portion 211.

[0026] The insulating portion 220 is a rectangular frame-shaped member with a through hole near the center, and is made of insulating material. As shown in Figures 2 and 3, the insulating portion 220 is sandwiched between the first end plate 210 and the end separator 230, thereby ensuring insulation between the first end plate 210 and the end separator 230.

[0027] As shown in Figures 2 and 3, the end separator 230 is a rectangular frame-shaped member having a through hole 231 near the center, and is made of, for example, metal.

[0028] The first plate 232 is a rectangular, flat member made of a conductive material such as stainless steel. As shown in Figures 2 and 3, the first plate 232 is joined to the peripheral portion of the through hole 231 in the end separator 230, for example, by welding. The end separator 230 and the first plate 232 separate the power generation block 100 from the external space of the fuel cell stack 10.

[0029] The first plate 232 is connected to an interconnector 190, described later, provided on a power generation unit 100U located at one end (the upper end in Figure 2) of the multiple power generation units 100U that make up the power generation block 100, via a connecting member having the same structure as the fuel electrode current collector 144, described later. In this way, the power generation unit 100U and the first plate 232 are electrically connected.

[0030] The first terminal plate 240 is a rectangular frame-shaped member having a through hole 241 near the center, and is made of a conductive material such as ferritic stainless steel that forms an alumina oxide film on its surface. The first terminal plate 240 is electrically connected to a power generation unit 100U located at one end (upper end in Figure 2) of the multiple power generation units 100U that make up the power generation block 100, via the first plate 232 and the end separator 230. One end of the first terminal plate 240 (right end in Figure 2) protrudes laterally from the power generation block 100, and this protruding portion functions as the positive output terminal of the fuel cell stack 10.

[0031] The second terminal plate 250 is a rectangular plate-shaped member, formed from a conductive material such as ferritic stainless steel that forms an alumina oxide film on its surface. The second terminal plate 250 is electrically connected to the power generation unit 100U located at the other end (lower end in Figure 2) of the multiple power generation units 100U that make up the power generation block 100. One end of the second terminal plate 250 (right end in Figure 2) protrudes laterally from the power generation block 100, and this protruding portion functions as the negative output terminal of the fuel cell stack 10.

[0032] The second plate 260 is a rectangular, flat member, formed of, for example, an insulating material. The peripheral edge of the second plate 260 is sandwiched between the second terminal plate 250 and the second end plate 270, thereby ensuring insulation between the second terminal plate 250 and the second end plate 270.

[0033] The second end plate 270 is a component formed by press-forming (bending) a single plate-shaped member, and is made of a conductive material such as stainless steel. The second end plate 270 comprises a rectangular frame-shaped planar portion 271 having a through hole 272 near the center, and an outer projection 273 and an inner projection 274 projecting from the planar portion 271 in the opposite direction to the second terminal plate 250 (downward in Figure 2). The planar portion 271 has holes that constitute the bolt holes BH described above. The outer projection 273 protrudes from the outer peripheral edge of the planar portion 271. The outer projection 273 is formed around the entire circumference of the outer peripheral portion of the planar portion 271. The inner projection 274 protrudes from the inner peripheral edge of the planar portion 271. The inner projection 274 is formed around the entire circumference of the inner peripheral portion of the planar portion 271. An oxide film 276 is formed on the surface of the second end plate 270, as will be described in detail later (see Figure 7). The second end plate 270 is an example of the first metal member in the claims. The oxide film 276 is an example of the first oxide film in the claims.

[0034] As shown in Figures 1 to 3, the fuel cell stack 10 has four holes that penetrate from the power generation block 100 to the second end plate 270. The four holes are the oxidizer gas supply manifold 311, the oxidizer gas discharge manifold 312, the fuel gas supply manifold 321, and the fuel gas discharge manifold 322, respectively.

[0035] As shown in Figure 2, the oxidizer gas supply manifold 311 is a gas flow path that supplies oxidizer gas OG, introduced from outside the fuel cell stack 10, to the air chambers 313 of each power generation unit 100U (described later). The oxidizer gas discharge manifold 312 is a gas flow path that discharges oxidizer off-gas OOG, discharged from the air chambers 313 of each power generation unit 100U, to the outside of the fuel cell stack 10. For example, air is used as the oxidizer gas OG. The oxidizer gas supply manifold 311 and the oxidizer gas discharge manifold 312 are located on opposite sides of the air chamber 313.

[0036] As shown in Figure 3, the fuel gas supply manifold 321 is a gas passage that supplies fuel gas FG introduced from outside the fuel cell stack 10 to the fuel chamber 323 of each power generation unit 100U, which will be described later. The fuel gas discharge manifold 322 is a gas passage that discharges fuel off-gas FOG discharged from the fuel chamber 323 of each power generation unit 100U to the outside of the fuel cell stack 10. As the fuel gas FG, for example, hydrogen-rich gas obtained by reforming city gas is used. The fuel gas supply manifold 321 and the fuel gas discharge manifold 322 are located on opposite sides of the fuel chamber 323.

[0037] The second end plate 270 is joined to the second terminal plate 250 via a glass seal portion 500. More specifically, the peripheral portions of the four manifolds 311, 312, 321, and 322 in the planar portion 271 are each joined to the second terminal plate 250 via a glass seal portion 500. The glass seal portion 500 is an example of an insulating member in the claims. The second terminal plate 250 is an example of a conductive member in the claims.

[0038] Each of the four gas passage members 280 comprises a main body portion 281 and a flange portion 282, as shown in Figures 1 to 3. The main body portion 281 has a gas through-hole 283 that penetrates vertically. The flange portion 282 is provided so as to protrude outward from the other end of the main body portion 281 (the lower end in Figures 2 and 3). The flange portion 282 has a plurality of bolt holes 284. Bolts (not shown) for connecting the fuel cell stack 10 to an external device are inserted into each bolt hole 284. One end of the main body portion 281 provided on the four gas passage members 280 (the upper end in Figures 2 and 3) is joined to the second end plate 270, for example by welding, and the gas through-holes 283 communicate with manifolds 311, 312, 321, and 322, respectively. Gas piping (not shown) for gas supply or discharge is connected to each main body portion 281.

[0039] Figure 4 is an explanatory diagram showing the XZ cross-sections of two adjacent power generation units 100U at the same location as the cross-section shown in Figure 2. Figure 5 is an explanatory diagram showing the XZ cross-sections of two adjacent power generation units 100U at the same location as the cross-section shown in Figure 3. As shown in Figures 4 and 5, the power generation unit 100U comprises a single cell 110, a single cell separator 120, an air electrode frame 130, a glass seal portion 135, a fuel electrode frame 140, a fuel electrode current collector 144, two interconnectors 190, and two IC separators 180. One IC separator 180, the air electrode frame 130, the single cell separator 120, the fuel electrode frame 140, and the other IC separator 180 are arranged in this order, overlapping each other.

[0040] The single cell 110 comprises an electrolyte layer 112, an air electrode 114, a fuel electrode 116, and a reaction prevention layer 118. As shown in Figures 4 and 5, the air electrode 114, the reaction prevention layer 118, the electrolyte layer 112, and the fuel electrode 116 are arranged in this order. The single cell 110 in this embodiment is a fuel electrode-supported single cell in which the other layers constituting the single cell 110 (electrolyte layer 112, air electrode 114, and reaction prevention layer 118) are supported by the fuel electrode 116. The single cell 110 is supported by a single cell separator 120.

[0041] The electrolyte layer 112 is a rectangular, flat member having one side on which the air electrode 114 is located (the upper side in Figures 4 and 5) and another side parallel to the air electrode 116 (the lower side in Figures 4 and 5). The electrolyte layer 112 is a layer containing a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). The air electrode 114 is a layer having a smaller rectangular shape than the electrolyte layer 112 and contains, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The fuel electrode 116 is a layer having a rectangular shape approximately the same size as the electrolyte layer 112 and contains, for example, Ni (nickel), a cermet made of Ni and ceramic particles, a Ni-based alloy, etc. The reaction prevention layer 118 is a layer having a rectangular shape approximately the same size as the air electrode 114 and contains, for example, GDC (gadolinium-doped ceria). The reaction prevention layer 118 has the function of suppressing the reaction of elements (e.g., Sr) diffused from the air electrode 114 with elements (e.g., Zr) contained in the electrolyte layer 112 to produce a highly resistive substance (e.g., SrZrO3).

[0042] The single-cell separator 120, as shown in Figures 4 and 5, is a rectangular frame-shaped member having a substantially rectangular through-hole 121 near its center, and is made of, for example, metal. The periphery of the through-hole 121 in the single-cell separator 120 is joined to the periphery of one surface of the electrolyte layer 112 (the surface on which the air electrode 114 is located: the upper surface in Figures 4 and 5) by a joint 124. The joint 124 is made of, for example, brazing material (Ag brazing). The single-cell separator 120 is an example of a conductive member within the scope of the claims.

[0043] As shown in Figures 4 and 5, the air electrode frame 130 is a rectangular frame-shaped member having a substantially rectangular through hole 131 near the center, and is formed of, for example, mica. As shown in Figure 4, the air electrode frame 130 has an oxidant gas supply communication channel 132 that connects the oxidant gas supply manifold 311 and the air chamber 313, and an oxidant gas discharge communication channel 133 that connects the air chamber 313 and the oxidant gas discharge manifold 312.

[0044] The glass seal portion 135 is provided between the single-cell separator 120 and the IC separator 180, which are vertically opposed to each other with the air electrode frame 130 in between. The glass seal portion 135 is made of glass. The glass seal portion 135 is annular and is arranged to surround the fuel gas supply manifold 321 and the fuel gas discharge manifold 322, respectively. The glass seal portion 135 suppresses leakage of fuel gas FG or fuel off-gas FOG from the fuel gas supply manifold 321 and the fuel gas discharge manifold 322 through the interface between the air electrode frame 130 and the single-cell separator 120, and the interface between the air electrode frame 130 and the IC separator 180. The glass seal portion 135 is an example of an insulating member in the claims.

[0045] As shown in Figures 4 and 5, the fuel electrode frame 140 is a rectangular frame-shaped member having a substantially rectangular through-hole 141 near the center, and is made of, for example, metal. As shown in Figure 5, the fuel electrode frame 140 has a fuel gas supply communication passage 142 that connects the fuel gas supply manifold 321 and the fuel chamber 323, and a fuel gas discharge communication passage 143 that connects the fuel chamber 323 and the fuel gas discharge manifold 322.

[0046] As shown in Figures 4 and 5, the IC separator 180 is a rectangular frame-shaped member having a through hole 181 near the center, and is made of, for example, metal. An oxide film 186 is formed on the surface of the IC separator 180, as will be described in detail later (see Figure 6). The IC separator 180 is an example of the first metal member in the claims. The oxide film 186 is an example of the first oxide film in the claims.

[0047] As shown in Figures 4 and 5, the interconnector 190 comprises a rectangular flat plate portion 191, a plurality of plate-shaped air electrode current collectors 192 protruding from one surface of the flat plate portion 191 toward the air electrode 114, and a coating layer 193. The flat plate portion 191 and the air electrode current collectors 192 are conductive and made of metal (for example, ferritic stainless steel). The coating layer 193 is conductive and is arranged to cover the surface of the air electrode current collectors 192 and the surface of the flat plate portion 191 on which the air electrode current collectors 192 are arranged. The flat plate portion 191 is joined to the periphery of the through hole 181 in the IC separator 180, for example, by welding. The interconnector 190 is supported by the IC separator 180.

[0048] The fuel electrode current collector 144 is a member that connects the interconnector 190 and the fuel electrode 116. The fuel electrode current collector 144 is made of a conductive material such as nickel, nickel alloy, or stainless steel. As shown in Figures 4 and 5, the fuel electrode current collector 144 comprises an interconnector-facing portion 146, an electrode-facing portion 145 parallel to the interconnector-facing portion 146, and a connecting portion 147 connecting the electrode-facing portion 145 and the interconnector-facing portion 146, and is U-shaped overall. The electrode-facing portion 145 is in contact with the fuel electrode 116, and the interconnector-facing portion 146 is in contact with the flat plate portion 191 of the interconnector 190.

[0049] As shown in Figures 4 and 5, the interconnector 190 is shared by two adjacent power generation units 100U. More specifically, as shown in Figures 4 and 5, the air electrode current collector 192 is joined to the air electrode 114 of a single cell 110 provided in one of the two adjacent power generation units 100U via a conductive bonding material 196 formed, for example, of spinel-type oxide. This electrically connects the air electrode current collector 192 to the air electrode 114. The flat plate portion 191 is electrically connected to the fuel electrode 116 of a single cell 110 provided in the other of the two adjacent power generation units 100U via a fuel electrode current collector member 144. This ensures electrical conductivity between the two adjacent power generation units 100U.

[0050] However, as shown in Figure 2, the power generation unit 100U located at the other end (the lower end in Figure 2) among the multiple power generation units 100U does not have an interconnector 190 on the fuel electrode 116 side. The fuel electrode 116 provided in this power generation unit 100U is connected to the second terminal plate 250 via a fuel electrode current collector 144.

[0051] A spacer 149, for example made of mica, is placed between the electrode facing portion 145 and the interconnect facing portion 146. As a result, the fuel electrode current collector 144 follows the deformation of the power generation unit 100U due to temperature cycles and reaction gas pressure fluctuations, and the electrical connection between the fuel electrode 116 and the interconnect 190 (or second terminal plate 250) via the fuel electrode current collector 144 is maintained in good condition.

[0052] As shown in Figures 4 and 5, the space partitioned by the single-cell separator 120 and single cell 110, the air electrode frame 130, the IC separator 180 and interconnector 190 faces the air electrode 114 and forms an air chamber 313 through which the oxidizer gas OG flows. The air electrode frame 130 partitions the air chamber 313 from the outside space around its entire circumference and seals the space between the single-cell separator 120 and the IC separator 180, preventing gas from leaking from the air chamber 313 into the outside space.

[0053] As shown in Figures 4 and 5, the space partitioned by the single-cell separator 120 and single cell 110, the fuel electrode frame 140, the IC separator 180 and interconnector 190 faces the fuel electrode 116 and forms the fuel chamber 323 through which the fuel gas FG flows. The fuel electrode frame 140 partitions the fuel chamber 323 from the outside space around its entire circumference and seals the space between the single-cell separator 120 and the IC separator 180, preventing gas from leaking from the fuel chamber 323 into the outside space.

[0054] The single-cell separator 120 separates the air chamber 313 from the fuel chamber 323, suppressing gas leakage (cross-leakage) from the air electrode 114 to the fuel electrode 116, or from the fuel electrode 116 to the air electrode 114, around the single cell 110. In addition, the IC separator 180 and interconnector 190 suppress gas leakage between adjacent power generation units 100U.

[0055] (Operation of fuel cell stack 10) As shown in Figures 2 and 4, the oxidizer gas OG is supplied to the oxidizer gas supply manifold 311 via gas piping (not shown) and gas passage member 280, and then supplied to the air chamber 313 via the oxidizer gas supply communication channel 132.

[0056] Furthermore, as shown in Figures 3 and 5, the fuel gas FG is supplied to the fuel gas supply manifold 321 via gas piping (not shown) and gas passage members 280, and then supplied to the fuel chamber 323 via the fuel gas supply communication channel 142.

[0057] When oxidant gas OG is supplied to the air chamber 313 of each power generation unit 100U and fuel gas FG is supplied to the fuel chamber 323, electricity is generated in the single cell 110 by an electrochemical reaction between the oxidant gas OG and fuel gas FG. This power generation reaction is an exothermic reaction. As described above, the interconnector 190 is shared by two adjacent power generation units 100U, and the interconnector 190 ensures conductivity between the two adjacent power generation units 100U. In other words, the multiple power generation units 100U included in the fuel cell stack 10 are electrically connected in series. Furthermore, the power generation unit 100U located at the other end (lower end in Figure 2) of the multiple power generation units 100U is electrically connected to the second terminal plate 250, and the power generation unit 100U located at the one end (upper end in Figure 2) is electrically connected to the first terminal plate 240. As a result, the electrical energy generated in each power generation unit 100U is extracted from the terminal plates 240 and 250, which function as output terminals of the fuel cell stack 10. Since SOFCs generate electricity at relatively high temperatures (for example, 700°C to 1000°C), the fuel cell stack 10 may be heated by a heater (not shown) after startup until the high temperature can be maintained by the heat generated by power generation.

[0058] As shown in Figures 2 and 4, the oxidizer off-gas OOG discharged from the air chamber 313 of each power generation unit 100U to the oxidizer gas discharge manifold 312 via the oxidizer gas discharge communication channel 133 is discharged to the outside of the fuel cell stack 10 through the internal space of the main body 281. Also, as shown in Figures 3 and 5, the fuel off-gas FOG discharged from the fuel chamber 323 of each power generation unit 100U to the fuel gas discharge manifold 322 via the fuel gas discharge communication channel 143 is discharged to the outside of the fuel cell stack 10 through the internal space of the main body 281.

[0059] (Detailed configuration around oxide film 186) Figure 6 is an enlarged explanatory diagram showing part X1 of Figure 5. Figure 6 shows a part of the single-cell separator 120, a part of the air electrode frame 130, a part of the glass seal part 135, and a part of the IC separator 180.

[0060] An oxide film 186 is formed on the surface of the IC separator 180. The air electrode frame 130 and the glass seal portion 135 are positioned between the single-cell separator 120, which is electrically connected to the single cell 110 via a joint portion 124, and the oxide film 186. Due to this configuration, a relatively large electric field is generated around the oxide film 186, for example, when the fuel cell stack 10 generates power. In a configuration in which the fuel cell stack 10 does not include the single-cell separator 120, such as when a part of the single cell 110 extends to the outer edge of the power generation block 100, the air electrode frame 130 and the glass seal portion 135 may be directly connected to the single cell 110 and positioned between the single cell 110 and the oxide film 186.

[0061] The oxide film 186 is mainly composed of a metal oxide containing a first metal element. The IC separator 180 is formed of a metal containing the first metal element. In this embodiment, the first metal element is either Al (aluminum) or Cr (chromium). When the first metal element is Al, the metal oxide containing the first metal element is alumina. When the first metal element is Cr, the metal oxide containing the first metal element is chromia.

[0062] The oxide film 186 contains a first specific element whose absolute value of standard electrode potential is greater than that of the first metal element. More specifically, when the first metal element is Al and the oxide film 186 is mainly composed of alumina, the first specific element is at least one of, for example, Ba (barium), Ca (calcium), La (lanthanum), Mg (magnesium), and Sr (strontium). When the first metal element is Cr and the oxide film 186 is mainly composed of chromia, the first specific element is at least one of, for example, Al, Ba, Ca, La, Mg, Mn (manganese), Sr, Ti (titanium), and Zn (zinc). The concentration of the first specific element in the oxide film 186 is preferably 2 mol% or more, and more preferably 3 mol% or more.

[0063] As shown in Figure 6, the oxide film 186 has an overlapping portion 186d and a non-overlapping portion 186n. The overlapping portion 186d is the portion that overlaps with the glass seal portion 135 in the Z-axis direction, which is the direction in which the oxide film 186 and the glass seal portion 135 are stacked. The non-overlapping portion 186n is the portion that does not overlap with the glass seal portion 135 in the Z-axis direction and is adjacent to the overlapping portion 186d in the Y-axis direction, which intersects the Z-axis direction. In the oxide film 186, the first specific element is located in at least one of the overlapping portion 186d and the portion of the non-overlapping portion 186n within 100 μm of the boundary with the overlapping portion 186d in the Y-axis direction. The overlapping portion 186d is an example of the first portion. The non-overlapping portion 186n is an example of the second portion. The Z-axis direction is an example of the first direction. The Y-axis direction is an example of the second direction.

[0064] Furthermore, the single-cell separator 120 has a flat plate portion 125 and an oxide film 126. The flat plate portion 125 is a metal flat plate member. The oxide film 126 is a coating formed on the surface of the flat plate portion 125. Around the oxide film 126, similar to the area around the oxide film 186, a relatively large electric field is generated, for example, when the fuel cell stack 10 generates electricity. The flat plate portion 125 is an example of a second metal member. The oxide film 126 is an example of a second oxide film.

[0065] The oxide film 126 is mainly composed of a metal oxide containing a second metal element. The flat plate portion 125 is formed of a metal containing a second metal element. In this embodiment, the second metal element is either Al or Cr. When the second metal element is Al, the metal oxide containing the second metal element is alumina. When the second metal element is Cr, the metal oxide containing the second metal element is chromia.

[0066] The oxide film 126 contains a second specific element whose absolute value of standard electrode potential is greater than that of the second metal element. More specifically, when the second metal element is Al and the oxide film 126 is mainly composed of alumina, the second specific element is at least one of, for example, Ba, Ca, La, Mg, and Sr. When the second metal element is Cr and the oxide film 126 is mainly composed of chromia, the second specific element is at least one of, for example, Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn.

[0067] (Detailed configuration around oxide film 276) Figure 7 is an enlarged explanatory diagram showing part X2 of Figure 3. Figure 7 shows a part of the second end plate 270, a part of the second plate 260, a part of the glass seal part 500, and a part of the second terminal plate 250.

[0068] An oxide film 276 is formed on the surface of the second end plate 270. The second plate 260 and the glass seal portion 500 are positioned between the oxide film 276 and the second terminal plate 250. Due to this configuration, a relatively large electric field is generated around the oxide film 276, for example, when the fuel cell stack 10 generates electricity.

[0069] The oxide film 276 is mainly composed of a metal oxide containing a first metal element. The second end plate 270 is formed of a metal containing the first metal element. In this embodiment, the first metal element is either Al or Cr. When the first metal element is Al, the metal oxide containing the first metal element is alumina. When the first metal element is Cr, the metal oxide containing the first metal element is chromia.

[0070] The oxide film 276 contains a first specific element whose absolute value of standard electrode potential is greater than that of the first metal element. More specifically, when the first metal element is Al and the oxide film 276 is mainly composed of alumina, the first specific element is at least one of, for example, Ba, Ca, La, Mg, and Sr. When the first metal element is Cr and the oxide film 276 is mainly composed of chromia, the first specific element is at least one of, for example, Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn. The concentration of the first specific element in the oxide film 276 is preferably 2 mol% or more, and more preferably 3 mol% or more.

[0071] As shown in Figure 7, the oxide film 276 has an overlapping portion 276d and a non-overlapping portion 276n. The overlapping portion 276d is the portion that overlaps with the glass seal portion 500 in the Z-axis direction, which is the direction in which the oxide film 276 and the glass seal portion 500 are stacked. The non-overlapping portion 276n is the portion that does not overlap with the glass seal portion 500 in the Z-axis direction and is adjacent to the overlapping portion 276d in the Y-axis direction, which intersects the Z-axis direction. In the oxide film 276, the first specific element is located in at least one of the overlapping portion 276d and the portion of the non-overlapping portion 276n within 100 μm of the boundary with the overlapping portion 276d in the Y-axis direction. The overlapping portion 276d is an example of the first portion. The non-overlapping portion 276n is an example of the second portion. The Z-axis direction is an example of the first direction. The Y-axis direction is an example of the second direction.

[0072] Furthermore, the second terminal plate 250 has a flat plate portion 255 and an oxide film 256. The flat plate portion 255 is a metal flat plate member. The oxide film 256 is a coating formed on the surface of the flat plate portion 255. Around the oxide film 256, similar to around the oxide film 276, a relatively large electric field is generated, for example, when the fuel cell stack 10 generates electricity. The flat plate portion 255 is an example of a second metal member. The oxide film 256 is an example of a second oxide film.

[0073] The oxide film 256 is mainly composed of a metal oxide containing a second metal element. The flat plate portion 255 is formed of a metal containing a second metal element. In this embodiment, the second metal element is either Al or Cr. When the second metal element is Al, the metal oxide containing the second metal element is alumina. When the second metal element is Cr, the metal oxide containing the second metal element is chromia.

[0074] (Effects of this embodiment) As described above, the fuel cell stack 10 of this embodiment comprises a single cell 110, a first metal member (IC separator 180, second end plate 270), a first oxide film (oxide film 186, oxide film 276) formed on the surface of the first metal member and mainly composed of a metal oxide containing a first metal element, a conductive member (single cell separator 120, second terminal plate 250) electrically connected to the single cell 110 or the single cell 110, and an insulating member (glass seal portion 135, glass seal portion 500) disposed between the first oxide film and the first oxide film. The first oxide film contains a first specific element whose absolute value of standard electrode potential is greater than that of the first metal element.

[0075] According to the fuel cell stack 10 of this embodiment, the first oxide film contains a first specific element that is less susceptible to oxidation-reduction than the first metal element which is the main component, thereby making the entire first oxide film less prone to oxidation-reduction reactions. This improves the voltage resistance of the entire first oxide film and suppresses the occurrence of cracks at the interface between the first oxide film and the insulating material. Therefore, the fuel cell stack 10 can suppress delamination between the first oxide film and the insulating material.

[0076] Furthermore, in the fuel cell stack 10 of this embodiment, the insulating member is made of glass. According to the fuel cell stack 10 of this embodiment, since the insulating member is made of glass, it is possible to suppress peeling between the first oxide film and the insulating member while improving the gas sealing performance between the first oxide film and the insulating member.

[0077] Furthermore, the fuel cell stack 10 of this embodiment further comprises conductive members (single cell separator 120, second terminal plate 250), which include a second metal member (flat plate portion 125, flat plate portion 255) and a second oxide film (oxide film 126, oxide film 256) formed on the surface of the second metal member, mainly composed of a metal oxide containing a second metal element. The second oxide film contains a second specific element whose absolute value of standard electrode potential is greater than that of the second metal element. According to the fuel cell stack 10 of this embodiment, by including a second specific element that is less prone to oxidation-reduction than the second metal element which is the main component of the second oxide film, oxidation-reduction reactions are less likely to occur in the second oxide film as a whole. As a result, the voltage resistance of the entire second oxide film is improved, and the occurrence of cracks at the interface between the second oxide film and the insulating member is suppressed. Therefore, according to this electrochemical reaction cell stack, peeling between the second oxide film and the insulating member can be suppressed.

[0078] Furthermore, in the fuel cell stack 10 of this embodiment, the first metal element is either Al or Cr. According to the fuel cell stack 10 of this embodiment, by using either Al or Cr as the first metal element, oxidation of the first metal component when the fuel cell stack 10 is operated at high temperatures can be suppressed, thereby achieving high reliability.

[0079] Furthermore, in the fuel cell stack 10 of this embodiment, the second metal element is either Al or Cr. According to the fuel cell stack 10 of this embodiment, by using either Al or Cr as the second metal element, oxidation of the second metal component when the fuel cell stack 10 is operated at high temperatures can be suppressed, thereby achieving high reliability.

[0080] Furthermore, in the fuel cell stack 10 of this embodiment, the concentration of the first specific element in the first oxide film is 2 mol% or more. According to the fuel cell stack 10 of this embodiment, since the concentration of the first specific element in the first oxide film is 2 mol% or more, delamination between the first oxide film and the insulating member can be suppressed more effectively.

[0081] Furthermore, in the fuel cell stack 10 of this embodiment, the first oxide film has a first portion (overlapping portion 186d, overlapping portion 276d) which is a portion that overlaps with the insulating member in the Z-axis direction, which is the direction in which the first oxide film and the insulating member (glass seal portion 135, glass seal portion 500) are stacked, and a second portion (non-overlapping portion 186n, non-overlapping portion 276n) which is a portion that does not overlap with the insulating member in the Z-axis direction and is adjacent to the first portion in the Y-axis direction that intersects the Z-axis direction. The first specific element is located in at least one of the first portion and a portion of the second portion that is within 100 μm of the Y-axis distance from the boundary with the first portion. According to the fuel cell stack 10 of this embodiment, since the first specific element is located in a portion of the first oxide film that is easily subjected to voltage, peeling between the first oxide film and the insulating member can be suppressed more effectively.

[0082] Furthermore, in the fuel cell stack 10 of this embodiment, the first oxide film is mainly composed of alumina, and the first specified element is at least one of Ba, Ca, La, Mg, and Sr. According to the fuel cell stack 10 of this embodiment, since the first specified element is at least one of Ba, Ca, La, Mg, and Sr, corrosion of the first metal member is suppressed compared to, for example, the case in which Na is included as the first specified element, and the durability of the fuel cell stack 10 can be improved.

[0083] Furthermore, in the fuel cell stack 10 of this embodiment, the first oxide film is mainly composed of chromia, and the first specified element is at least one of Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn. According to the fuel cell stack 10 of this embodiment, since the first specified element is at least one of Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn, corrosion of the first metal member is suppressed compared to, for example, the case in which Na is included as the first specified element, and the durability of the fuel cell stack 10 can be improved.

[0084] In the fuel cell stack 10 of this embodiment, the concentration of the third specific element, which has a lower absolute value of standard electrode potential than the first metal element contained in the first oxide film, may be 10 mol% or less, or 2 mol% or less. By setting the concentration of the third specific element in the first oxide film to 10 mol% or less, or 2 mol% or less, oxidation-reduction reactions become less likely to occur in the first oxide film as a whole, and the voltage resistance of the first oxide film as a whole is more effectively improved. When the main component of the first oxide film is alumina, the third specific element is, for example, at least one of Mn, Cr, Fe, Co, Ni, and Cu. When the main component of the first oxide film is chromia, the third specific element is, for example, at least one of Fe, Co, Ni, and Cu.

[0085] Furthermore, in the fuel cell stack 10 of this embodiment, the concentration of the fourth specific element, which has a lower absolute value of standard electrode potential than the second metal element contained in the second oxide film, may be 10 mol% or less, or 2 mol% or less. By setting the concentration of the fourth specific element in the second oxide film to 10 mol% or less, or 2 mol% or less, oxidation-reduction reactions become less likely to occur in the second oxide film as a whole, and the voltage resistance of the second oxide film as a whole is more effectively improved. When the main component of the second oxide film is alumina, the fourth specific element is, for example, at least one of Mn, Cr, Fe, Co, Ni, and Cu. When the main component of the second oxide film is chromia, the fourth specific element is, for example, at least one of Fe, Co, Ni, and Cu.

[0086] (Performance evaluation) Next, the performance evaluation of this embodiment will be described. Multiple fuel cell stack samples (SA1 to SA24) with different compositions of the first oxide film were prepared, and the performance was evaluated using these samples.

[0087] The resistance to delamination between the first oxide film and the insulating member was evaluated using a test piece simulating a fuel cell stack 10. Figure 8 shows a top view of the test piece, and Figure 9 shows a cross-sectional view of the test piece at position IX-IX in Figure 8. The test piece comprises a first metal member ME1, a second metal member ME2, an insulating member IM, two metal plates PL, two insulators IN, a bolt B, and two nuts N. A first oxide film OM1 is formed on the surface of the first metal member ME1. The insulating member IM is made of glass. Through holes are formed near the center of each of the first metal member ME1, the second metal member ME2, the insulating member IM, the metal plates PL, and the insulators IN.

[0088] In the above test piece, the first metal member ME1 corresponds to the second end plate 270 and IC separator 180 in the fuel cell stack 10, the second metal member ME2 corresponds to the second terminal plate 250 and single cell separator 120 in the fuel cell stack 10, and the insulating member IM corresponds to the glass seal portion 500 and glass seal portion 135 in the fuel cell stack 10. In addition, the insulator IN does not correspond to any of the components in the fuel cell stack 10, but is used to insulate the metal plate PL and the nut N.

[0089] First, test pieces were prepared. First, a metal oxide powder was applied to the surface of a first metal member ME1 containing either Al or Cr. Specifically, when the first metal member ME1 contained Al, at least one powder from among La2O3, MgO, BaO, CaO, and Sr2O3 was applied. When the first metal member ME1 contained Cr, at least one powder from among La2O3, MgO, BaO, CaO, Sr2O3, Al2O3, MnO, TiO, and ZnO was applied. Next, a first oxide film OM1 was formed on the surface of the first metal member ME1 by heat treatment at, for example, 1000°C. Next, one insulator IN, one metal plate PL, the first metal member ME1, the insulator IM, the second metal member ME2, the other metal plate PL, and the other insulator IN were stacked in this order so that their through holes were in communication. Bolts B were inserted into the through holes and all the members were fastened together using nuts N. Next, a test piece was fabricated by heat treatment at a temperature above the softening temperature of the glass contained in the insulator IM (for example, 850°C) to bond the first oxide film OM1 and the insulator IM.

[0090] Next, the composition of the first oxide film OM1 in the test piece prepared by the above method was analyzed. First, the test piece prepared by the above method was embedded in resin and mirror-polished so that a cross-section perpendicular to the interface between the first oxide film OM1 and the insulating material IM was exposed. The composition of the first oxide film OM1 was analyzed by energy-dispersive X-ray spectroscopy (SEM / EDX) in the area of ​​thickness direction: total thickness of the first oxide film OM1 × width direction: 5 μm. The "thickness direction" is the direction perpendicular to the interface between the first oxide film OM1 and the insulating material IM, and the "width direction" is the direction along the interface between the first oxide film OM1 and the insulating material IM.

[0091] Next, the test piece prepared by the above method was subjected to a voltage application test. First, the test piece prepared by the above method was heated to 700°C in an atmospheric environment, for example, by placing it in an electric furnace. After the test piece reached a temperature of 700°C, a predetermined voltage was applied for 10 hours. The voltage was applied by connecting a cord connected to an external power source to each of the two metal plates PL. After that, the voltage was stopped, the test piece was allowed to cool to room temperature, and the bolt B, nut N, insulator IN, and metal plate PL were removed. Then, a tensile test was performed in the direction of separating the first metal member ME1 and the second metal member ME2 to confirm whether or not delamination occurred between the first oxide film OM1 and the insulating member IM.

[0092] The results of the performance evaluation are described below. Table 1 shows the performance evaluation results.

[0093] [Table 1]

[0094] In the "Voltage Application Test" column of Table 1, samples in which delamination between the first oxide film OM1 and the insulating material IM was not observed in the tensile test are marked with "○", and samples in which delamination between the first oxide film OM1 and the insulating material IM was observed in the tensile test are marked with "×".

[0095] The first oxide film OM1 of samples SA1 to SA14 shown in Table 1 is mainly composed of alumina. Therefore, the main component of the first oxide film OM1 of samples SA1 to SA14 shown in Table 1, excluding oxygen (element O), is Al. Furthermore, La, Mg, Ba, Ca, and Sr, which are listed as components of the first oxide film OM1, are all elements whose absolute values ​​of standard electrode potential are greater than Al. In other words, in samples SA1 to SA14, La, Mg, Ba, Ca, and Sr correspond to the first specified element.

[0096] Of the samples shown in Table 1, samples SA2 to SA14 contain the first specified element, while sample SA1 does not. Furthermore, in the voltage application test, no delamination between the first oxide film OM1 and the insulating member IM was observed in samples SA2 to SA14 at an applied voltage of at least 1.2V, while delamination between the first oxide film OM1 and the insulating member IM was observed in sample SA1 at an applied voltage of 1.2V. From this, it was confirmed that the presence of the first specified element in the first oxide film suppresses delamination between the first oxide film and the insulating member.

[0097] Furthermore, among the samples containing the first specified element, sample SA7 contained 1 mol% or more but less than 2 mol% of the first specified element, samples SA2 to SA6 and SA8 contained 2 mol% or more but less than 3 mol%, and samples SA9 to SA14 contained 3 mol% or more of the first specified element. In addition, in the voltage application test, delamination between the first oxide film OM1 and the insulating material IM was confirmed in sample SA7 at an applied voltage of 2.0V, delamination between the first oxide film OM1 and the insulating material IM was confirmed in samples SA2 to SA6 and SA8 at an applied voltage of 5.0V, and no delamination between the first oxide film OM1 and the insulating material IM was confirmed in samples SA9 to SA14 at any applied voltage. From this, it was confirmed that the concentration of the first specified element in the first oxide film is preferably 2 mol% or more, and preferably 3 mol% or more.

[0098] Table 2 shows the performance evaluation results. [Table 2]

[0099] In the "Voltage Application Test" column of Table 2, samples in which delamination between the first oxide film OM1 and the insulating material IM was not observed in the tensile test are marked with "○", and samples in which delamination between the first oxide film OM1 and the insulating material IM was observed in the tensile test are marked with "×".

[0100] The first oxide film OM1 of samples SA15 to SA24 shown in Table 2 is mainly composed of chromia. Therefore, the main component of the first oxide film OM1 of samples SA15 to SA24 shown in Table 2, excluding oxygen (element O), is Cr. Furthermore, Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn, which are listed as components of the first oxide film OM1, are all elements whose absolute values ​​of standard electrode potential are greater than those of Cr. In other words, in samples SA15 to SA24, Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn correspond to the first specified element.

[0101] Of the samples shown in Table 2, samples SA16 to SA24 contain the first specified element, while sample SA15 does not. Furthermore, in the voltage application test, no delamination between the first oxide film OM1 and the insulating member IM was observed in samples SA16 to SA24 at an applied voltage of 1.0V, while delamination between the first oxide film OM1 and the insulating member IM was observed in sample SA15 at an applied voltage of 1.0V. From this, it was confirmed that the presence of the first specified element in the first oxide film suppresses delamination between the first oxide film and the insulating member.

[0102] B. Variations: The technologies disclosed herein are not limited to the embodiments described above and can be modified in various forms without departing from their essence, for example, the following modifications are possible.

[0103] The configuration of the fuel cell stack 10 and the power generation unit 100U in the above embodiment is merely an example and can be modified in various ways. For example, the number of single cells (number of power generation units) included in the fuel cell stack is merely an example, and the number of single cells can be appropriately determined according to the output voltage required for the fuel cell stack.

[0104] In the above embodiment, the first metal element contained in the first oxide film is either Al or Cr, but the first metal element may be a metal element other than Al or Cr. Also, in the above embodiment, the second metal element contained in the second oxide film is either Al or Cr, but the second metal element may be a metal element other than Al or Cr.

[0105] In the above embodiment, the insulating members (glass seal portion 135 and glass seal portion 500) are both made of glass, but the insulating members may be made of other insulating materials such as mica or insulating ceramics, or they may be made of multiple insulating materials.

[0106] In the above embodiment, the first specific element is located in at least one of the first portion of the first oxide film and the portion of the second portion within 100 μm of the boundary between the first portion and the first portion in the second portion. However, the first specific element may be included in any position in the first oxide film.

[0107] Although the fuel cell stack 10 in the above embodiment is a co-flow type SOFC, the technologies disclosed herein are also applicable to counter-flow type SOFCs and cross-flow type SOFCs.

[0108] In the above embodiment, the single cell 110 is a fuel electrode-supported single cell, but it may be other types of single cells such as an electrolyte-supported or metal-supported type.

[0109] In the above embodiment, the fuel cell stack 10 is configured to include a plurality of flat-plate single cells 110, but the technology disclosed herein is equally applicable to fuel cell stacks that include a plurality of other types of single cells (e.g., cylindrical, flat cylindrical, etc.).

[0110] In the above embodiment, the electrochemical reaction unit was a fuel cell power generation unit, which is a constituent unit of a solid oxide fuel cell (SOFC), but it can also be applied to an electrolytic cell unit, which is a constituent unit of a solid oxide electrolytic cell (SOEC). [Explanation of Symbols]

[0111] 10: Fuel cell stack 100: Power generation block 100U: Power generation unit 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 118: Reaction prevention layer 120: Separator for single cell 124: Joint 125: Flat plate section 126: Oxide film 130: Air electrode frame 132: Oxidant gas supply communication channel 133: Oxidant gas exhaust communication channel 135: Glass seal section 140: Fuel electrode frame 142: Fuel gas supply communication channel 143: Fuel gas exhaust communication channel 149: Spacer 180: Separator for IC 186: Oxide film 186d: Overlap section 186n: Non-overlap section 190: Interconnector 191: Flat plate section 192: Air electrode current collector section 193: Coating layer 196: Conductive bonding material 210: First end plate 216: Oxide film 220: Insulation part 230: End separator 232: First plate 240: First terminal plate 250: Second terminal plate 255: Flat plate part 256: Oxide film 260: Second plate 270: Second end plate 276: Oxide film 276d: Overlap part 276n: Non-overlap part 280: Gas passage member 311: Oxidizer gas supply manifold 312: Oxidizer gas discharge manifold 313: Air chamber 321: Fuel gas supply manifold 322: Fuel gas discharge manifold 323: Fuel chamber 500: Glass seal part B: Bolt BH: Bolt hole N: Nut FG: Fuel gas FOG: Fuel off-gas OG: Oxidizer gas OOG: Oxidizer off-gas

Claims

1. Single cell and, First metal member and A first oxide film formed on the surface of the first metal member, the first oxide film mainly composed of a metal oxide containing a first metal element, An insulating member disposed between the single cell or a conductive member electrically connected to the single cell and the first oxide film, In an electrochemical reaction cell stack comprising, The first oxide film contains a first specific element whose absolute value of standard electrode potential is greater than that of the first metal element. An electrochemical reaction cell stack characterized by the following features.

2. In the electrochemical reaction cell stack according to claim 1, The insulating member is made of glass. An electrochemical reaction cell stack characterized by the following features.

3. In the electrochemical reaction cell stack according to claim 1, further, The conductive member, The second metal member and The conductive member comprises a second oxide film formed on the surface of the second metal member, the second oxide film having a metal oxide containing a second metal element as its main component, The second oxide film contains a second specific element whose absolute value of standard electrode potential is greater than that of the second metal element. An electrochemical reaction cell stack characterized by the following features.

4. In the electrochemical reaction cell stack according to claim 1, The first metal element is either Al or Cr. An electrochemical reaction cell stack characterized by the following features.

5. In the electrochemical reaction cell stack according to claim 3, The second metal element is either Al or Cr. An electrochemical reaction cell stack characterized by the following features.

6. In the electrochemical reaction cell stack according to claim 1, The concentration of the first specific element in the first oxide film is 2 mol% or more. An electrochemical reaction cell stack characterized by the following features.

7. In the electrochemical reaction cell stack according to claim 1, The first oxide film is A first portion which is the portion that overlaps with the insulating member in the first direction which is the direction in which the first oxide film and the insulating member are laminated, It has a second portion which does not overlap with the insulating member in the first direction and is adjacent to the first portion in a second direction intersecting the first direction, The first specified element is located in at least one of the first portion and a portion of the second portion that is within 100 μm of the boundary between the first portion and the second portion in the second direction. An electrochemical reaction cell stack characterized by the following features.

8. In the electrochemical reaction cell stack according to any one of claims 1 to 7, The first oxide film mainly consists of alumina, The first specified element is at least one of Ba, Ca, La, Mg, and Sr. An electrochemical reaction cell stack characterized by the following features.

9. In the electrochemical reaction cell stack according to any one of claims 1 to 7, The first oxide film mainly consists of chromia, The first specified element is at least one of Al, Ba, Ca, La, Mg, Mn, Sr, Ti, and Zn. An electrochemical reaction cell stack characterized by the following features.

Images