Interconnector, and electrochemical cell

Abstract

This interconnector comprises a body, a first oxide layer, and a second oxide layer. The body has a first primary surface and a second primary surface. The second primary surface is the surface opposite the first primary surface. The first oxide layer is disposed on the first primary surface. The second oxide layer is disposed on the second primary surface. The second oxide layer has a thickness different from the first oxide layer.

Description

Interconnector and electrochemical cell

[0001] The present invention relates to an interconnector and an electrochemical cell.

[0002] In electrochemical cells such as electrolysis cells or fuel cells, a structure in which a cell body is supported by a metal substrate is known. For example, an 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 a plurality of through holes for supplying a raw material gas to the electrode layer.

[0003] The electrochemical cell has an interconnector that forms a flow path for the source gas supplied to the cell body. The interconnector has a surface that is formed with projections and depressions by embossing, slitting, or the like.

[0004] International Publication No. 2018 / 181926

[0005] There is a demand for imparting a warp to interconnectors from the viewpoint of ensuring reliable contact, etc. However, because interconnectors have uneven portions, it has been difficult to impart a warp by press working or the like.

[0006] An object of the present invention is to prevent warping from occurring in the interconnector.

[0007] The interconnector according to a 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 a 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.

[0008] According to this configuration, since the first oxide layer and the second oxide layer have different thicknesses, warping can be caused in the interconnector by thermal stress generated in the interconnector.

[0009] Specifically, 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 thinner than the second oxide layer, it is possible to generate a warp in the interconnector such that the central portion 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 central portion 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 thinner than the second oxide layer, it is possible to generate a warp in the interconnector such that the central portion 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 central portion protrudes toward the second oxide layer.

[0010] The interconnector according to a second aspect is the interconnector according to the first aspect, wherein the main body is made of an alloy containing chromium, and the first oxide layer and the second oxide layer are mainly composed of chromium.

[0011] The interconnector according to a third aspect is the interconnector according to the first or second aspect, and is configured as follows: The first oxide layer and the second oxide layer each have a thermal expansion coefficient smaller than that of the main body portion.

[0012] The interconnector according to a fourth aspect is the interconnector according to the third aspect, wherein the first oxide layer is thinner than the second oxide layer.

[0013] An interconnector according to a fifth aspect is the interconnector according to any one of the first to fourth aspects, and is configured as follows: the main body has convex portions on a first main surface, and the first oxide layer formed on the convex portions is thinner than the first oxide layer formed on portions other than the convex portions.

[0014] An electrochemical cell according to a sixth aspect includes the interconnector according to 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.

[0015] The electrochemical cell according to the seventh aspect is the electrochemical cell according to the sixth aspect, and is configured as follows: Each of the first oxide layer and the second oxide layer is thinner than the cell main body portion.

[0016] According to the present invention, it is possible to generate warpage in the interconnector.

[0017] Fig. 2 is a plan view of an electrolysis cell. Fig. 3 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 4 is a plan view of an interconnector. Fig. 5 is an enlarged cross-sectional view of an interconnector. Fig. 6 is an enlarged cross-sectional view of an interconnector. Fig. 7 is a plan view of an interconnector according to a modified example.

[0018] An electrolytic cell 100 (an example of an electrochemical cell) according to this embodiment will be described below with reference to the drawings. In this embodiment, a solid oxide electrolytic cell (SOEC) will be used as an example of the electrolytic cell 100. FIG. 1 is a plan view of the electrolytic cell 100. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1.

[0019] 1 and 2 , the electrolytic cell 100 is formed in the shape of a plate extending in the X-axis and Y-axis directions. In the present embodiment, 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. However, 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.

[0020] As shown in FIGS. 1 and 2 , the electrolysis cell 100 includes a cell body 2 , a support substrate 3 , and an interconnector 4 .

[0021] <Cell Body> 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).

[0022] The hydrogen electrode 21, the electrolyte 22, the reaction prevention layer 23, and the oxygen electrode 24 are stacked in this order in the Z-axis direction from the support substrate 3 side. The hydrogen electrode 21, the electrolyte 22, and the oxygen electrode 24 are essential components, while the reaction prevention layer 23 is an optional component.

[0023] <Hydrogen Electrode> 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 The hydrogen electrode 21 contains H ２ Generate.

[0024] The raw material gas is H ２ When the raw material gas contains only O, the hydrogen electrode 21 converts H into H according to the electrochemical reaction of water electrolysis shown in the following formula (1): ２ Generate.

[0025] Hydrogen electrode 21: H ２ O + 2e － →H ２ +O ２－ ... (1) The raw material gas is H ２ O plus CO ２ In this case, the hydrogen electrode 21 converts the raw material gas into H according to the electrochemical reactions of co-electrolysis shown in the following formulas (2), (3), and (4). ２ , CO and O ２－ Generate.

[0026] Hydrogen electrode 21: CO ２ +H ２ O+4e － →CO+H ２ +20 ２－ ... (2) ・H ２ Electrochemical reaction of O: H ２ O + 2e － →H ２ +O ２－... (3) CO ２ Electrochemical reaction of: CO ２ +2e － →CO+O ２－ ...(4)

[0027] H generated at the hydrogen electrode 21 ２ flows out from each through-hole 33 of the support substrate 3 into an internal space 30 described later.

[0028] The hydrogen electrode 21 is a porous body having electron conductivity. The hydrogen electrode 21 contains nickel (Ni). In the case of co-electrolysis, Ni functions as an electron conductor and also functions as a conductor for the generated H ２ and CO contained in the raw material gas ２ It also functions as a thermal catalyst that promotes the thermal reaction with HCl and maintains an appropriate gas composition for methanation, Fischer-Tropsch (FT) synthesis, etc. The Ni contained in the hydrogen electrode 21 is basically present in the form of metallic Ni during operation of the electrolysis cell 100, but a portion of it may also be present in the form of nickel oxide (NiO).

[0029] 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)O, or the like. ３ , (La,Sr)TiO ３ , Sr ２ (Fe, Mo) ２ O ６ , (La, Sr)VO ３ , (La,Sr)FeO ３ and mixed materials of two or more of these.

[0030] The thickness of the hydrogen electrode 21 is not particularly limited, but may be, for example, 1 μm or more and 100 μm or less. The thermal expansion coefficient of the hydrogen electrode 21 is not particularly limited, but may be, for example, 12×10 ―６ / ℃ or more 20 x 10 －６ / °C or less.

[0031] The method for forming the hydrogen electrode 21 is not particularly limited, and may be a firing method, a spray coating method (such as a thermal spraying method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulsed laser deposition method), or a CVD method.

[0032] <Electrolyte> 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. In this embodiment, the electrolyte 22 is sandwiched between the hydrogen electrode 21 and the reaction prevention layer 23 and connected to both of them.

[0033] The electrolyte 22 covers the hydrogen electrode 21 and also covers the region of the first main surface 31 of the support substrate 3 that is exposed from the hydrogen electrode 21 .

[0034] The electrolyte 22 is a dense body having oxide ion conductivity. ２－ The electrolyte 22 is made of an oxide ion conductive material, such as YSZ, GDC, ScSZ, SDC, or LSGM (lanthanum gallate), with YSZ being particularly suitable.

[0035] The thickness of the electrolyte 22 is not particularly limited, but may be, for example, 1 μm or more and 100 μm or less. The thermal expansion coefficient of the electrolyte 22 is not particularly limited, but may be, for example, 10×10 ―６ / ℃ or more 12 x 10 ―６ / °C or less.

[0036] The method for forming the electrolyte 22 is not particularly limited, and a baking method, a spray coating method, a PVD method, a CVD method, or the like can be used.

[0037] <Reaction prevention layer> 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.

[0038] The reaction prevention layer 23 is made of an oxide ion conductive material, such as GDC or SDC.

[0039] The porosity of the reaction prevention layer 23 is not particularly limited, but may be, for example, 0.1% to 50%. The thickness of the reaction prevention layer 23 is not particularly limited, but may be, for example, 1 μm to 50 μm.

[0040] The method for forming the reaction prevention layer 23 is not particularly limited, and may be a baking method, a spray coating method, a PVD method, a CVD method, or the like.

[0041] <Oxygen electrode> 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. In this embodiment, 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.

[0042] The oxygen electrode 24 converts O 2 transferred from the hydrogen electrode 21 through the electrolyte 22 in accordance with the chemical reaction of the following formula (5): ２－ From O ２ Generate.

[0043] Oxygen electrode 24:2O ２－ →O ２ +4e － ...(5)

[0044] The oxygen electrode 24 is a porous body having oxide ion conductivity and electron conductivity. The oxygen electrode 24 is made of, for example, (La, Sr)(Co, Fe)O ３ , (La,Sr)FeO ３ , La(Ni,Fe)O ３ , (La,Sr)CoO ３ , and (Sm,Sr)CoO ３ and an oxide ion conductive material (such as GDC).

[0045] The porosity of the oxygen electrode 24 is not particularly limited, but may be, for example, 20% to 60%. The thickness of the oxygen electrode 24 is not particularly limited, but may be, for example, 1 μm to 100 μm.

[0046] The method for forming the oxygen electrode 24 is not particularly limited, and may be a baking method, a spray coating method, a PVD method, a CVD method, or the like.

[0047] 2 , the support substrate 3 supports the cell main body 2. In this embodiment, 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.

[0048] In the internal space 30 defined by the support substrate 3 and the interconnector 4, the raw material gas supplied to the cell body 2 and the reducing gas (H ２ ) will be played.

[0049] The support substrate 3 has a first main surface 31, a second main surface 32, and a plurality of through holes 33. In this embodiment, 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.

[0050] 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.

[0051] 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.

[0052] Each through-hole 33 can be formed by mechanical processing (for example, punching), laser processing, chemical processing (for example, etching), or the like.

[0053] In this embodiment, each through hole 33 is formed linearly along the Z-axis direction. However, each through hole 33 may be inclined with respect to the Z-axis direction, or may not be linear. Furthermore, the through holes 33 may be connected to each other.

[0054] 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. The Cr content in the support substrate 3 is not particularly limited, but can be set to 4% by mass or more and 30% by mass or less.

[0055] The support substrate 3 may contain Ti (titanium) or Zr (zirconium). The Ti content in the support substrate 3 is not particularly limited, but can be set to 0.01 mol % or more and 1.0 mol % or less. The Zr content in the support substrate 3 is not particularly limited, but can be set to 0.01 mol % or more and 0.4 mol % or less. The support substrate 3 may contain Ti in the form of TiO ２ (titania), or Zr may be contained as ZrO ２ It may be contained as (zirconia).

[0056] <Interconnector> 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.

[0057] The interconnector 4 is formed in a plate shape. The interconnector 4 is attached to a 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. The interconnector 4 has a main body 40, a first oxide layer 41, and a second oxide layer 42.

[0058] The main body 40 is formed in a plate shape. There are no particular restrictions on the thickness of the main body 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 40 protrudes toward the support substrate 3. The outer periphery of the main body 40 defines the periphery of the internal space 30. Note that the outer periphery of the main body 40 may be a separate member from the main body 40.

[0059] 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 a surface facing the support substrate 3. The second main surface 402 is a surface opposite to the first main surface 401. In other words, the second main surface 402 faces in the opposite direction to the facing direction of the first main surface 401. In this embodiment, the first main surface 401 is an upper surface of the main body 40, and the second main surface 402 is a lower surface of the main body 40.

[0060] 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.

[0061] Each second protrusion 404 protrudes to the opposite side from the first protrusion 403. The height of each second protrusion 404 is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less.

[0062] FIG. 3 is a plan view of the interconnector 4. Note that, for ease of illustration, FIG. 3 only shows the first convex portions 403, and does not show the concave portions that appear as the back surfaces of the second convex portions 404. As shown in FIG. 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. Note that the second convex portions 404 are configured in the same manner.

[0063] The first convex portions 403 are larger than the through holes 33 in a plan view. Therefore, the plurality of through holes 33 overlap with the first convex portions 403 in a plan view.

[0064] The interconnector 4 has a supply hole 405 and a discharge hole 406. The supply hole 405 and the discharge hole 406 are in communication with the internal space 30. The supply hole 405 penetrates the interconnector 4 in the Z-axis direction. A raw material gas supplied to the electrolysis cell 100 from an external gas supply source flows through the supply hole 405 in the Z-axis direction. The raw material gas is supplied into the internal space 30 through the supply hole 405.

[0065] The discharge hole 406 penetrates the interconnector 4 in the Z-axis direction. ２ is discharged to the outside through the discharge hole 406 and collected.

[0066] 2, the main body 40 is made of an alloy containing Cr. Examples of such alloys include Fe—Cr alloy steel and Ni—Cr alloy steel. The Cr content in the main body 40 is not particularly limited, but can be set to 4% by mass or more and 30% by mass or less. The composition of the main body 40 may be the same as or different from that of the support substrate 3.

[0067] The first oxide layer 41 is formed on the first main surface 401 of the main body portion 40. Note that the first oxide layer 41 is not formed on the outer periphery of the first main surface 401, but the first oxide layer 41 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 portion 40. In the present embodiment, the first oxide layer 41 has a smaller thermal expansion coefficient than that of the main body portion 40. The first oxide layer 41 is composed of an oxide containing Cr as its main component (hereinafter abbreviated as "Cr oxide"). This makes it possible to suppress diffusion of Cr from the support substrate 3 and the main body portion 40 to the first oxide layer 41 during manufacture or operation of the electrolysis cell 100. Furthermore, even if Cr diffuses from the support substrate 3 and the main body portion 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 suppressed.

[0068] In this embodiment, "mainly composed of Cr" means that the Cr content is the highest among the metal elements when the composition of the Cr oxide constituting the first oxide layer 41 is analyzed by an energy dispersive spectroscopy (EDS) device. The Cr content in the Cr oxide is not particularly limited, but can be, for example, 20 mol % to 100 mol % of the metal elements.

[0069] The Cr content of the metal elements in the Cr oxide constituting the first oxide layer 41 is preferably 50 mol % or more, which significantly suppresses the diffusion of Cr contained in the support substrate 3 and the main body portion 40 into the first oxide layer 41.

[0070] The Cr oxide constituting the first oxide layer 41 is preferably composed of at least one of chromium oxide and chromium manganese oxide, which have the property that Cr is particularly difficult to diffuse into these oxides, and therefore the durability of the first oxide layer 41 can be improved.

[0071] Chromium oxides include Cr ２ O ３ Examples of chromium manganese oxide include MnCr ２ O ４ (Spinel), Mn １，５ Cr １，５ O ４ (Spinel), etc.

[0072] The Cr oxide constituting the first oxide layer 41 is preferably crystalline, which can prevent the first oxide layer 41 from being damaged due to a phase transition of the Cr oxide from amorphous to crystalline even when the electrolysis cell 100 is operated for a long period of time.

[0073] The Cr oxide constituting the first oxide layer 41 preferably has a spinel or corundum crystal structure, which has high symmetry and can improve the thermal stress resistance of the first oxide layer 41.

[0074] The first oxide layer 41 can be formed by applying a paste containing Cr oxide onto the first main surface 401 of the main body 40, followed by heat treatment. The conditions for the heat treatment can be set as appropriate, but can be, for example, 600° C. or higher and 1100° C. or lower, and 0.5 hours or higher and 24 hours or lower.

[0075] The second oxide layer 42 is formed on the second main surface 402 of the main body portion 40. When the electrolysis cells 100 are stacked, the second oxide layer 42 comes into contact with the cell main body portion (not shown) disposed below. The second oxide layer 42 has a thermal expansion coefficient different from that of the main body portion 40. In this embodiment, the second oxide layer 42 has a smaller thermal expansion coefficient than the main body portion 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 containing Cr as a main component.

[0076] The material of the second oxide layer 42 is substantially the same as that of the first oxide layer 41 described above, and therefore a detailed description thereof will be omitted.

[0077] The first oxide layer 41 is thinner than the cell body 2. The second oxide layer 42 is thinner than the cell body 2. The thickness of the first oxide layer 41 can be, for example, 0.1 μm or more and 20 μm or less. The thickness of the second oxide layer 42 can be, for example, 0.12 μm or more and 100 μm or less.

[0078] 4 , 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 more. 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.

[0079] 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, to prepare a cut surface as shown in Fig. 2. Then, a plurality of images of the vicinity of the center of this cut surface are taken with an electron microscope (SEM) at a magnification (200 to 20,000 times) suitable for measuring the thickness of each of the first oxide layer 41 and the second oxide layer 42.

[0080] Then, at each of the 10 equal points in the width direction of each SEM image, the thickness t1 of the first oxide layer 41 and the thickness t2 of the second oxide layer 42 are measured, and 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, and 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. That is, if at least one of the first oxide layer 41 and the second oxide layer 42 extends in the Z-axis direction at each of the 10 equal points, the thickness is measured at the point nearest to that point where both the first oxide layer 41 and the second oxide layer 42 extend in the X-axis direction.

[0081] 5 is an enlarged cross-sectional view of the first protrusion 403 of the interconnector 4. As shown in Fig. 5, the first oxide layer 41 has a first portion 41a formed on the first protrusion 403 and a second portion 41b formed other than on the first protrusion 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.

[0082] 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 along the width direction (X-axis direction) so as to pass through the multiple first protrusions 403, creating a cut surface as shown in FIG. 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 FIG. 5, the first portion 41a and the second portion 41b are photographed adjacent to each other. The second portion 41b is measured between the first protrusion 403 at which the first portion 41a was measured and a position spaced apart by the width of the first protrusion 403.

[0083] The thickness t11 of the first portion 41a of the first oxide layer 41 can be measured at any number of points (for example, 10 points), and the average value can be used as the thickness t11 of the first portion 41a. Similarly, the thickness t12 of the second portion 41b of the first oxide layer 41 can be measured at any number of points (for example, 10 points), and the average value can be used as the thickness t12 of the second portion 41b.

[0084] In the interconnector 4 configured as described above, the first oxide layer 41 is thinner than the second oxide layer 42. Therefore, when the temperature is lowered to room temperature after the formation of the first oxide layer 41 and the second oxide layer 42, 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 disposed below it. Note that warping downward means that the central portion of the interconnector 4 warps downward so as to protrude.

[0085] [Modifications] Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention.

[0086] (a) In the above embodiment, the first convex portion 403 has a circular shape in a plan view, but the shape of the first convex portion 403 is not limited to this. For example, as shown in Fig. 6, the first convex portion 403 may have a rectangular shape in a plan view. The first convex portion 403 may extend in the Y-axis direction or the X-axis direction. Note that the second convex portion 404 may also have a rectangular shape in a plan view.

[0087] (b) In the above embodiment, 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. For example, 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 larger than the thermal expansion coefficient of the main body portion 40.

[0088] (c) In the above embodiment, the interconnector 4 is 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. In this case, for example, the thermal expansion coefficients of the first oxide layer 41 and the second oxide layer 42 are set 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. Alternatively, the thermal expansion coefficients of the first oxide layer 41 and the second oxide layer 42 are set 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.

[0089] (d) In the above embodiment, an electrolytic cell has been described as an example of an electrochemical cell, but the electrochemical cell is not limited to an electrolytic cell. 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.

[0090] 2: Cell main body 3: Support substrate 31: First main surface 32: Second main surface 4: Interconnector 40: Main body 401: First main surface 402: Second main surface 403: First convex portion 41: First oxide layer 42: Second oxide layer 100: Electrolytic cell

Claims

1. An interconnector comprising: a body portion having a first major surface and a second major surface opposite the first major surface; a first oxide layer disposed on the first major surface; and a second oxide layer disposed on the second major surface, the second oxide layer having a thickness different from that of the first oxide layer.

2. The interconnector according to claim 1, wherein the main body is made of an alloy containing chromium, and the first oxide layer and the second oxide layer are mainly composed of chromium.

3. The interconnector according to claim 1, wherein each of the first oxide layer and the second oxide layer has a thermal expansion coefficient smaller than that of the main body portion.

4. The interconnector according to claim 3, wherein the first oxide layer is thinner than the second oxide layer.

5. The interconnector according to claim 1, wherein the main body has a convex portion on a first main surface, and the first oxide layer formed on the convex portion is thinner than the first oxide layer formed on portions other than the convex portion.

6. An electrochemical cell comprising: the interconnector according to claim 1; a support substrate attached to said interconnector; and a cell body portion disposed on said support substrate.

7. The electrochemical cell according to claim 6, wherein each of the first oxide layer and the second oxide layer is thinner than the cell body portion.

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