Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B15/00—Operating or servicing cells
  • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/60—Constructional parts of cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the present invention relates to an interconnector and an electrochemical cell.
• the electrochemical cell disclosed in Patent Document 1 has an electrode layer, an electrolyte layer, and a counter electrode layer stacked in this order on a metal substrate.
• the metal substrate has multiple through-holes for supplying raw material gas to the electrode layer.
• the electrochemical cell has an interconnector that forms a flow path for the raw material gas supplied to the cell body.
• the interconnector has an uneven surface formed by embossing or slitting.
• the objective of this invention is to generate warping in the interconnector.
• the interconnector according to the first aspect comprises a main body portion, a first oxide layer, and a second oxide layer.
• the main body portion has a first main surface and a second main surface.
• the second main surface is the surface opposite to the first main surface.
• the first oxide layer is disposed on the first main surface.
• the second oxide layer is disposed on the second main surface.
• the second oxide layer has a thickness different from that of the first oxide layer.
• the first oxide layer and the second oxide layer have different thicknesses, so that thermal stress generated in the interconnector can cause warping in the interconnector.
• the thermal expansion coefficients of the first oxide layer and the second oxide layer smaller than that of the main body portion and making the first oxide layer thinner than the second oxide layer, it is possible to generate a warp in the interconnector such that the center protrudes toward the second oxide layer. Furthermore, by making the thermal expansion coefficients of the first oxide layer and the second oxide layer smaller than that of the main body portion and making the first oxide layer thicker than the second oxide layer, it is possible to generate a warp in the interconnector such that the center protrudes toward the first oxide layer.
• the thermal expansion coefficients of the first oxide layer and the second oxide layer larger than that of the main body portion and making the first oxide layer thinner than the second oxide layer, it is possible to generate a warp in the interconnector such that the center protrudes toward the first oxide layer. Furthermore, by making the thermal expansion coefficients of the first oxide layer and the second oxide layer larger than that of the main body portion and making the first oxide layer thicker than the second oxide layer, it is possible to generate a warp in the interconnector such that the center protrudes toward the second oxide layer.
• the interconnector according to the second aspect is the interconnector according to the first aspect, but is configured as follows:
• the main body is made of an alloy containing chromium.
• the first oxide layer and the second oxide layer are primarily composed of chromium.
• the interconnector of the third aspect is the interconnector of the first or second aspect, and is configured as follows:
• the first oxide layer and the second oxide layer each have a smaller thermal expansion coefficient than the main body portion.
• the interconnector of the fourth aspect is the interconnector of the third aspect, configured as follows: The first oxide layer is thinner than the second oxide layer.
• the interconnector according to the fifth aspect is the interconnector according to any one of the first to fourth aspects, and is configured as follows:
• the main body has a convex portion on the first main surface.
• the first oxide layer formed on the convex portion is thinner than the first oxide layer formed on portions other than the convex portion.
• the electrochemical cell of the sixth aspect comprises an interconnector of any one of the first to fifth aspects, a support substrate, and a cell main body.
• the support substrate is attached to the interconnector.
• the cell main body is disposed on the support substrate.
• the electrochemical cell of the seventh aspect is the electrochemical cell of the sixth aspect, configured as follows: The first oxide layer and the second oxide layer are each thinner than the cell main body.
• FIG. 1 is a plan view of an electrolysis cell.
• 2 is a cross-sectional view taken along line II-II in FIG. 1;
• FIG. FIG. FIG. 10 is a plan view of an interconnector according to a modified example.
• the electrolytic cell 100 (an example of an electrochemical cell) according to this embodiment will be described below with reference to the drawings.
• a solid oxide electrolytic cell SOEC
• Figure 1 is a plan view of the electrolytic cell 100.
• Figure 2 is a cross-sectional view taken along line II-II in Figure 1.
• the electrolytic cell 100 is formed in a plate shape extending in the X-axis and Y-axis directions.
• the electrolytic cell 100 is formed in a rectangular shape extending in the Y-axis direction when viewed in a plan view along the Z-axis direction, which is perpendicular to the X-axis and Y-axis directions.
• the planar shape of the electrolytic cell 100 is not particularly limited, and may be a polygon other than a rectangle, an ellipse, a circle, or the like.
• the Z-axis direction refers to the thickness direction of the electrolytic cell 100, the cell main body 2, the support substrate 3, and the interconnector 4.
• the electrolysis cell 100 comprises a cell main body 2, a support substrate 3, and an interconnector 4.
• the cell body 2 is disposed on a support substrate 3.
• the cell body 2 is supported by the support substrate 3.
• the cell body 2 is disposed on the support substrate 3 so as to cover a plurality of through-holes 33, which will be described later.
• the cell body 2 has a hydrogen electrode 21 (cathode), an electrolyte 22, a reaction prevention layer 23, and an oxygen electrode 24 (anode).
• the hydrogen electrode 21, electrolyte 22, reaction prevention layer 23, and oxygen electrode 24 are stacked in this order in the Z-axis direction from the support substrate 3 side.
• the hydrogen electrode 21, electrolyte 22, and oxygen electrode 24 are required components, while the reaction prevention layer 23 is optional.
• the hydrogen electrode 21 is disposed on the first main surface 31 of the support substrate 3.
• a source gas is supplied to the hydrogen electrode 21 through each through-hole 33 of the support substrate 3.
• the source gas contains at least water vapor (H 2 O).
• the hydrogen electrode 21 generates H 2 as a result of an electrolytic reaction.
• the hydrogen electrode 21 produces H 2 from the raw material gas in accordance with the electrochemical reaction of water electrolysis shown in the following formula (1).
• Hydrogen electrode 21 H 2 O + 2e ⁇ ⁇ H 2 + O 2 ⁇ (1)
• the hydrogen electrode 21 produces H 2 , CO, and O 2 ⁇ from the raw material gas in accordance with the co-electrolytic electrochemical reactions shown in the following formulas (2), (3), and (4).
• ⁇ Hydrogen electrode 21 CO 2 +H 2 O+4e - ⁇ CO+H 2 +2O 2 -...(2)
• Electrochemical reaction of H 2 O H 2 O + 2e ⁇ ⁇ H 2 + O 2 ⁇ (3)
• Electrochemical reaction of CO 2 CO 2 + 2e ⁇ ⁇ CO + O 2 ⁇ (4)
• the H 2 generated in the hydrogen electrode 21 flows out from each through-hole 33 of the support substrate 3 into an internal space 30 described later.
• the hydrogen electrode 21 is an electron-conductive porous body.
• the hydrogen electrode 21 contains nickel (Ni).
• Ni functions as an electron conductor and also as a thermal catalyst that promotes the thermal reaction between the generated H 2 and the CO 2 contained in the feed gas, thereby maintaining an appropriate gas composition for methanation, Fischer-Tropsch (FT) synthesis, and the like.
• the Ni contained in the hydrogen electrode 21 is basically present in the form of metallic Ni, but may also be present in part in the form of nickel oxide (NiO).
• the hydrogen electrode 21 may contain an ion-conductive material such as yttria-stabilized zirconia (YSZ), calcia-stabilized zirconia (CSZ), scandia-stabilized zirconia (ScSZ), gadolinium-doped ceria (GDC), samarium-doped ceria (SDC), (La, Sr)(Cr, Mn) O3 , (La, Sr) TiO3 , Sr2 (Fe, Mo) 2O6 , (La, Sr) VO3 , (La, Sr) FeO3 , or a mixture of two or more of these materials.
• YSZ yttria-stabilized zirconia
• CSZ calcia-stabilized zirconia
• ScSZ scandia-stabilized zirconia
• GDC gadolinium-doped ceria
• SDC samarium-doped ceria
• the thickness of the hydrogen electrode 21 is not particularly limited, but may be, for example, 1 ⁇ m or more and 100 ⁇ m or less.
• the thermal expansion coefficient of the hydrogen electrode 21 is not particularly limited, but may be, for example, 12 ⁇ 10 ⁇ 6 /°C or more and 20 ⁇ 10 ⁇ 6 /°C or less.
• the method for forming the hydrogen electrode 21 is not particularly limited, and methods such as firing, spray coating (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, etc.), PVD (sputtering, pulsed laser deposition, etc.), and CVD can be used.
• the electrolyte 22 is formed on the hydrogen electrode 21.
• the electrolyte 22 is disposed between the hydrogen electrode 21 and the oxygen electrode 24.
• the electrolyte 22 is sandwiched between the hydrogen electrode 21 and the reaction prevention layer 23 and connected to both of them.
• the electrolyte 22 covers the hydrogen electrode 21 and also covers the area of the first main surface 31 of the support substrate 3 that is exposed from the hydrogen electrode 21.
• the electrolyte 22 is a dense body having oxide ion conductivity.
• the electrolyte 22 transfers O 2- generated at the hydrogen electrode 21 to the oxygen electrode 24.
• the electrolyte 22 is made of an oxide ion conductive material.
• the electrolyte 22 can be made of, for example, YSZ, GDC, ScSZ, SDC, LSGM (lanthanum gallate), or the like, with YSZ being particularly suitable.
• the thickness of the electrolyte 22 is not particularly limited, but may be, for example, 1 ⁇ m or more and 100 ⁇ m or less.
• the thermal expansion coefficient of the electrolyte 22 is not particularly limited, but may be, for example, 10 ⁇ 10 ⁇ 6 /°C or more and 12 ⁇ 10 ⁇ 6 /°C or less.
• the method for forming the electrolyte 22 is not particularly limited, and methods such as baking, spray coating, PVD, and CVD can be used.
• the reaction prevention layer 23 is disposed between the electrolyte 22 and the oxygen electrode 24.
• the reaction prevention layer 23 is disposed on the side of the electrolyte 22 opposite to the side on which the hydrogen electrode 21 is disposed.
• the reaction prevention layer 23 prevents the constituent elements of the electrolyte 22 from reacting with the constituent elements of the oxygen electrode 24 to form a layer with high electrical resistance.
• the reaction prevention layer 23 is made of an oxide ion conductive material.
• the reaction prevention layer 23 can be made of GDC, SDC, etc.
• the porosity of the reaction prevention layer 23 is not particularly limited, but can be, for example, 0.1% or more and 50% or less.
• the thickness of the reaction prevention layer 23 is not particularly limited, but can be, for example, 1 ⁇ m or more and 50 ⁇ m or less.
• reaction prevention layer 23 There are no particular restrictions on the method for forming the reaction prevention layer 23, and methods such as baking, spray coating, PVD, and CVD can be used.
• the oxygen electrode 24 is disposed on the opposite side of the electrolyte 22 from the side on which the hydrogen electrode 21 is disposed.
• the reaction prevention layer 23 is disposed between the electrolyte 22 and the oxygen electrode 24, and therefore the oxygen electrode 24 is connected to the reaction prevention layer 23. If the reaction prevention layer 23 is not disposed between the electrolyte 22 and the oxygen electrode 24, the oxygen electrode 24 is connected to the electrolyte 22.
• the oxygen electrode 24 generates O 2 from O 2 ⁇ transferred from the hydrogen electrode 21 via the electrolyte 22 in accordance with the chemical reaction of the following formula (5).
• the oxygen electrode 24 is a porous body having oxide ion conductivity and electron conductivity, and can be made of a composite material of one or more of (La,Sr)(Co,Fe) O3 , (La,Sr) FeO3 , La(Ni,Fe) O3 , (La,Sr) CoO3 , and (Sm,Sr) CoO3 and an oxide ion conductive material (such as GDC).
• the porosity of the oxygen electrode 24 is not particularly limited, but can be, for example, 20% or more and 60% or less.
• the thickness of the oxygen electrode 24 is not particularly limited, but can be, for example, 1 ⁇ m or more and 100 ⁇ m or less.
• oxygen electrode 24 There are no particular restrictions on the method for forming the oxygen electrode 24, and methods such as firing, spray coating, PVD, and CVD can be used.
• the support substrate 3 supports the cell main body 2.
• the support substrate 3 is formed in a plate shape.
• the support substrate 3 only needs to be able to support the cell main body 2, and its thickness is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less.
• the raw material gas to be supplied to the cell body 2 and the reducing gas (H 2 in this embodiment) generated at the hydrogen electrode 21 flow.
• the support substrate 3 has a first main surface 31, a second main surface 32, and a plurality of through holes 33.
• the first main surface 31 is the upper surface of the support substrate 3, and the second main surface 32 is the lower surface of the support substrate 3.
• the first main surface 31 faces the cell main body 2.
• the second main surface 32 faces the interconnector 4.
• Each through hole 33 is configured to allow gas to pass through.
• Each through hole 33 penetrates the support substrate 3 from the first main surface 31 to the second main surface 32.
• Each through hole 33 opens to the first main surface 31 and the second main surface 32, respectively. Therefore, gas passes through the support substrate 3 via each through hole 33.
• Each through-hole 33 is covered by the cell main body 2. Specifically, the opening of each through-hole 33 on the first main surface 31 side is covered by the hydrogen electrode 21. The opening of each through-hole 33 on the second main surface 32 side is connected to the internal space 30.
• Each through hole 33 can be formed by mechanical processing (e.g., punching), laser processing, or chemical processing (e.g., etching).
• each through hole 33 is formed linearly along the Z-axis direction.
• each through hole 33 may be inclined with respect to the Z-axis direction, or may not be linear.
• the through holes 33 may be connected to each other.
• the support substrate 3 is made of an alloy containing Cr (chromium). Examples of such alloys include Fe-Cr alloy steel (stainless steel, etc.) and Ni-Cr alloy steel. There are no particular restrictions on the Cr content of the support substrate 3, but it can be between 4% and 30% by mass.
• the support substrate 3 may contain Ti (titanium) or Zr (zirconium).
• the Ti content in the support substrate 3 is not particularly limited, but may be 0.01 mol % or more and 1.0 mol % or less.
• the Zr content in the support substrate 3 is not particularly limited, but may be 0.01 mol % or more and 0.4 mol % or less.
• the support substrate 3 may contain Ti as TiO 2 (titania) or Zr as ZrO 2 (zirconia).
• the interconnector 4 is disposed on the second main surface 32 side of the support substrate 3.
• the interconnector 4 is a member for electrically connecting the electrolytic cell 100 to an external power source or another electrolytic cell.
• the interconnector 4 is formed in a plate shape.
• the interconnector 4 is attached to the support substrate 3.
• the interconnector 4 is fixed to the support substrate 3 at its outer periphery.
• the interconnector 4 is fixed to the support substrate 3 by, for example, welding or adhesive bonding.
• the interconnector 4 has a main body 40, a first oxide layer 41, and a second oxide layer 42.
• the main body portion 40 is formed in a plate shape. There are no particular restrictions on the thickness of the main body portion 40, but it can be, for example, 0.1 mm or more and 2.0 mm or less.
• the outer periphery of the main body portion 40 protrudes toward the support substrate 3.
• the outer periphery of the main body portion 40 defines the periphery of the internal space 30. Note that the outer periphery of the main body portion 40 may be a separate member from the main body portion 40.
• the main body 40 has a first main surface 401, a second main surface 402, a plurality of first convex portions 403, and a plurality of second convex portions 404.
• the first main surface 401 is the surface facing the support substrate 3.
• the second main surface 402 is the surface opposite the first main surface 401. In other words, the second main surface 402 faces in the opposite direction to the direction in which the first main surface 401 faces.
• the first main surface 401 is the upper surface of the main body 40
• the second main surface 402 is the lower surface of the main body 40.
• Each first convex portion 403 is formed on the first main surface 401 of the main body portion 40. Each first convex portion 403 protrudes toward the support substrate 3. Each first convex portion 403 is disposed within the internal space 30.
• the height of each first convex portion 403 is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less.
• Each second protrusion 404 protrudes on the opposite side from the first protrusion 403.
• the height of each second protrusion 404 is not particularly limited, but can be, for example, between 0.1 mm and 2.0 mm.
• Figure 3 is a plan view of the interconnector 4. Note that, for ease of illustration, Figure 3 only shows the first convex portions 403, and does not show the concave portions that appear as the backsides of the second convex portions 404. As shown in Figure 3, the first convex portions 403 are arranged at intervals from one another. Specifically, the first convex portions 403 are arranged in a staggered pattern. The first convex portions 403 can be formed by subjecting the interconnector 4 to press processing, cutting processing, etching processing, or the like. The second convex portions 404 are also configured in the same manner.
• the first convex portion 403 is larger than the through-holes 33 in a plan view. Therefore, multiple through-holes 33 overlap with the first convex portion 403 in a plan view.
• the exhaust hole 406 penetrates the interconnector 4 in the Z-axis direction. H 2 generated in the hydrogen electrode 21 and flowing in the internal space 30 is exhausted to the outside via the exhaust hole 406 and collected.
• the first oxide layer 41 is formed on the first main surface 401 of the main body 40.
• the first oxide layer 41 is not formed on the outer periphery of the first main surface 401, but may be formed on the outer periphery of the first main surface 401.
• the first oxide layer 41 is in contact with the support substrate 3.
• the first oxide layer 41 has a thermal expansion coefficient different from that of the main body 40. In this embodiment, the first oxide layer 41 has a smaller thermal expansion coefficient than the main body 40.
• the first oxide layer 41 is composed of an oxide containing Cr as its main component (hereinafter referred to as "Cr oxide"). This prevents Cr from diffusing from the support substrate 3 and the main body 40 to the first oxide layer 41 during manufacture or operation of the electrolysis cell 100. Even if Cr diffuses from the support substrate 3 and the main body 40 to the first oxide layer 41, the effect on the composition of the first oxide layer 41 is small, and therefore a decrease in the strength of the first oxide layer 41 can also be prevented.
• "mainly composed of Cr” means that when the composition of the Cr oxide that makes up the first oxide layer 41 is analyzed using an energy dispersive spectroscopy (EDS) device, the Cr content is the highest among the metal elements.
• EDS energy dispersive spectroscopy
• the Cr content in the Cr oxide can be, for example, 20 mol % or more and 100 mol % or less of the metal elements.
• the Cr content of the metal elements in the Cr oxide that constitutes the first oxide layer 41 is preferably 50 mol% or more. This significantly prevents the Cr contained in the support substrate 3 and main body portion 40 from diffusing into the first oxide layer 41.
• the Cr oxide that makes up the first oxide layer 41 is preferably composed of at least one of chromium oxide and chromium manganese oxide. These oxides have the property that Cr is particularly resistant to diffusion, which can improve the durability of the first oxide layer 41.
• chromium oxides examples include Cr 2 O 3.
• chromium manganese oxides examples include MnCr 2 O 4 (spinel) and Mn 1,5 Cr 1,5 O 4 (spinel).
• the Cr oxide that constitutes the first oxide layer 41 is preferably crystalline. This prevents the first oxide layer 41 from being damaged by a phase transition of the Cr oxide from amorphous to crystalline, even if the electrolysis cell 100 is operated for a long period of time.
• the Cr oxide that constitutes the first oxide layer 41 preferably has a spinel or corundum crystal structure. These crystal structures have high symmetry, which can improve the thermal stress resistance of the first oxide layer 41.
• the first oxide layer 41 can be formed by applying a paste containing Cr oxide to the first main surface 401 of the main body 40, followed by heat treatment.
• the heat treatment conditions can be set as appropriate, but can be, for example, 600°C to 1100°C and 0.5 hours to 24 hours.
• the second oxide layer 42 is formed on the second main surface 402 of the main body 40. When the electrolysis cells 100 are stacked, the second oxide layer 42 comes into contact with the cell main body (not shown) located below.
• the second oxide layer 42 has a different thermal expansion coefficient than the main body 40. In this embodiment, the second oxide layer 42 has a smaller thermal expansion coefficient than the main body 40. Specifically, the second oxide layer 42 has substantially the same thermal expansion coefficient as the first oxide layer 41.
• the second oxide layer 42 is composed of an oxide whose main component is Cr.
• the material of the second oxide layer 42 is substantially the same as that of the first oxide layer 41 described above, so a detailed description will be omitted.
• the first oxide layer 41 is thinner than the cell main body 2.
• the second oxide layer 42 is thinner than the cell main body 2.
• the thickness of the first oxide layer 41 can be, for example, 0.1 ⁇ m or more and 20 ⁇ m or less.
• the thickness of the second oxide layer 42 can be, for example, 0.12 ⁇ m or more and 100 ⁇ m or less.
• the first oxide layer 41 has a different thickness from the second oxide layer 42. Specifically, the first oxide layer 41 is thinner than the second oxide layer 42. Specifically, the ratio (t2/t1) of the thickness t2 of the second oxide layer 42 to the thickness t1 of the first oxide layer 41 can be 1.2 or greater. Furthermore, the ratio (t2/t1) of the thickness t2 of the second oxide layer 42 to the thickness t1 of the first oxide layer 41 can be 20 or less.
• the thicknesses of the first oxide layer 41 and the second oxide layer 42 can be measured as follows. First, the interconnector 4 is cut in the width direction (X-axis direction) so as to pass through the center of the interconnector 4, creating a cut surface as shown in Figure 2. Then, multiple images of the vicinity of the center of this cut surface are taken with an electron microscope (SEM) at a magnification suitable for measuring the thickness (200 to 20,000 times) for each of the first oxide layer 41 and the second oxide layer 42.
• SEM electron microscope
• the thickness t1 of the first oxide layer 41 and the thickness t2 of the second oxide layer 42 are measured.
• the average value of the thicknesses t1 of the first oxide layer 41 can be defined as the thickness t1 of the first oxide layer 41
• the average value of the thicknesses t2 of the second oxide layer 42 can be defined as the thickness t2 of the second oxide layer 42.
• the thicknesses t1 and t2 are measured at a point where both the first oxide layer 41 and the second oxide layer 42 extend in the X-axis direction.
• Figure 5 is an enlarged cross-sectional view of the first convex portion 403 of the interconnector 4.
• the first oxide layer 41 has a first portion 41a formed on the first convex portion 403 and a second portion 41b formed elsewhere than on the first convex portion 403.
• the thickness t11 of the first portion 41a is thinner than the thickness t12 of the second portion 41b. This makes it possible to prevent the electrical resistance between the interconnector 4 and the support substrate 3 from increasing.
• the thickness t11 of the first portion 41a and the thickness t12 of the second portion 41b can be measured as follows. First, the interconnector 4 is cut near the center of the interconnector 4 in the width direction (X-axis direction) so as to pass through the multiple first convex portions 403, creating a cut surface as shown in Figure 2. Then, the first portion 41a and the second portion 41b are photographed near the center of this cut surface using an electron microscope (SEM) at a magnification (200 to 20,000 times) suitable for measuring the thickness of the first oxide layer 41. Note that, as shown in Figure 5, adjacent first portion 41a and second portion 41b are photographed. The second portion 41b is measured from the first convex portion 403 at which the first portion 41a was measured to a position spaced apart by the width of the first convex portion 403.
• SEM electron microscope
• the thickness t11 of the first portion 41a of the first oxide layer 41 can be measured at any number of points (e.g., 10 points), and the average value can be used as the thickness t11 of the first portion 41a.
• the thickness t12 of the second portion 41b of the first oxide layer 41 can be measured at any number of points (e.g., 10 points), and the average value can be used as the thickness t12 of the second portion 41b.
• the first oxide layer 41 is thinner than the second oxide layer 42. Therefore, when the temperature is lowered to room temperature after the first oxide layer 41 and the second oxide layer 42 are formed, the thermal stress generated in the interconnector 4 causes the interconnector 4 to warp downward. As a result, when the electrolysis cells 100 are stacked, the interconnector 4 can reliably contact the electrolysis cell located below it. Note that warping downward means that the central portion of the interconnector 4 warps downward so that it protrudes.
• the first convex portion 403 has a circular shape in a planar view, but the shape of the first convex portion 403 is not limited to this.
• the first convex portion 403 may have a rectangular shape in a planar view.
• the first convex portion 403 may extend in the Y-axis direction or the X-axis direction.
• the second convex portion 404 may also have a rectangular shape in a planar view.
• the first oxide layer 41 is configured to be thinner than the second oxide layer 42, but the configuration of the interconnector 4 is not limited to this.
• the first oxide layer 41 may be configured to be thicker than the second oxide layer 42. In this case, if it is desired to warp the interconnector 4 so as to protrude downward, the thermal expansion coefficients of the first oxide layer 41 and the second oxide layer 42 are made greater than the thermal expansion coefficient of the main body portion 40.
• the interconnector 4 was configured to warp downward, but the configuration of the interconnector 4 is not limited to this. That is, the interconnector 4 may be configured to warp upward.
• the thermal expansion coefficients of the first oxide layer 41 and the second oxide layer 42 are configured to be smaller than the thermal expansion coefficient of the main body portion 40, and the first oxide layer 41 is configured to be thicker than the second oxide layer 42.
• the thermal expansion coefficients of the first oxide layer 41 and the second oxide layer 42 are configured to be larger than the thermal expansion coefficient of the main body portion 40, and the first oxide layer 41 is configured to be thinner than the second oxide layer 42.
• electrochemical cells were described as an example of an electrochemical cell, but electrochemical cells are not limited to electrolytic cells.
• An electrochemical cell is a general term that refers to an element in which a pair of electrodes are arranged so that an electromotive force is generated from an overall oxidation-reduction reaction in order to convert electrical energy into chemical energy, and an element for converting chemical energy into electrical energy. Therefore, electrochemical cells also include, for example, fuel cells that use oxide ions or protons as carriers.

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