Interconnector and electrochemical cell

Abstract

This interconnector comprises a body part and a plurality of oxide layers. The body part has a first main surface, a second main surface, and a plurality of protrusions. The second main surface faces the opposite side from the first main surface. Each protrusion is formed on the first main surface. The oxide layers are disposed on side surfaces of the protrusions. At least one oxide layer has a thickness distribution which induces warpage such that the body part swells towards the second main surface side.

Description

Interconnector and electrochemical cell

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

[0002] Electrochemical cells such as electrolysis cells or fuel cells have a cell body, a support substrate, and an interconnector. For example, in the electrochemical cell disclosed in Patent Document 1, a gas flow path is formed by the interconnector and the support substrate, and the cell body is supported on the support substrate. A plurality of electrochemical cells configured in this manner are stacked to form an electrochemical cell stack.

[0003] International Publication No. 2018 / 181926

[0004] When stacking electrochemical cells, if unevenness is formed on the cell main body portion located below the interconnector, the interconnector may press against the unevenness, causing the load to be concentrated on the unevenness of the cell main body portion, which may result in damage to the cell main body portion.

[0005] An object of the present invention is to provide an interconnector that can suppress damage to the cell main body portion.

[0006] The interconnector according to the first aspect has a main body and a plurality of oxide layers. The main body has a first main surface, a second main surface, and a plurality of protrusions. The second main surface faces the opposite side to the first main surface. Each protrusion is formed on the first main surface. Each oxide layer is disposed on a side surface of each protrusion. At least one oxide layer has a thickness distribution that induces warpage of the main body such that the main body bulges toward the second main surface.

[0007] According to this configuration, the thickness distribution of each oxide layer causes the interconnector to warp so as to bulge toward the second main surface. Therefore, when stacking electrochemical cells, it is possible to absorb unevenness on the cell main body portion disposed below the interconnector. As a result, it is possible to prevent loads from concentrating on the protruding portions of the cell main body portion, and ultimately to prevent damage to the cell main body portion.

[0008] The interconnector according to the second aspect is the interconnector according to the first aspect, and is configured as follows: The multiple protrusions are arranged at intervals from one another in the gas flow direction. The multiple protrusions include a first protrusion and a second protrusion. The first protrusion is arranged at the most upstream position in the gas flow direction. The second protrusion is arranged at the most downstream position. Each oxide layer has an upstream portion facing the upstream side and a downstream portion facing the downstream side. The oxide layer arranged on the side surface of the first protrusion has a thickness distribution in which the upstream portion is thinner than the downstream portion.

[0009] The interconnector according to the third aspect is the interconnector according to the second aspect, and is configured as follows: The oxide layer disposed on the side surface of the second protrusion has a thickness distribution in which the upstream portion is thicker than the downstream portion.

[0010] An interconnector according to a fourth aspect is the interconnector according to the second or third aspect, and is configured as follows: the plurality of protrusions include a third protrusion. The third protrusion is arranged in a central portion between the first protrusion and the second protrusion in the gas flow direction. The difference in thickness between an upstream portion and a downstream portion of the oxide layer arranged on the side surface of the first protrusion is larger than the difference in thickness between the upstream portion and the downstream portion of the oxide layer arranged on the side surface of the third protrusion.

[0011] An interconnector according to a fifth aspect is the interconnector according to any one of the second to fourth aspects, and is configured as follows: the plurality of protrusions include a third protrusion. The third protrusion is arranged in a central portion between the first protrusion and the second protrusion in the gas flow direction. The oxide layer arranged on the side surface of the third protrusion is thicker than the oxide layer arranged on the side surface of the first protrusion and is thicker than the oxide layer arranged on the side surface of the second protrusion.

[0012] An interconnector according to a sixth aspect is the interconnector according to the first aspect, and is configured as follows: The multiple protrusions extend in the gas flow direction. The multiple protrusions are arranged at intervals from one another in a first direction perpendicular to the gas flow direction. The multiple protrusions include a first protrusion and a second protrusion. The first protrusion and the second protrusion are arranged outermost in the first direction. Each oxide layer has an outer portion facing outward in the first direction and an inner portion facing inward in the first direction. The oxide layer arranged on the side surface of the first protrusion has a thickness distribution in which the outer portion is thinner than the inner portion.

[0013] An interconnector according to a seventh aspect is the interconnector according to the sixth aspect, and is configured as follows: The oxide layer disposed on the side surface of the second protrusion has a thickness distribution in which the outer portion is thinner than the inner portion.

[0014] An interconnector according to an eighth aspect is the interconnector according to the sixth or seventh aspect, and is configured as follows: the plurality of protrusions include a third protrusion. The third protrusion is arranged in a central portion between the first protrusion and the second protrusion in the first direction. The difference in thickness between an outer portion and an inner portion of the oxide layer arranged on the side surface of the first protrusion is larger than the difference in thickness between the outer portion and the inner portion of the oxide layer arranged on the side surface of the third protrusion.

[0015] An interconnector according to a ninth aspect is the interconnector according to any one of the sixth to eighth aspects, and is configured as follows: the plurality of protrusions include a third protrusion. The third protrusion is arranged in a central portion between the first protrusion and the second protrusion in the first direction. The oxide layer arranged on the side surface of the third protrusion is thicker than the oxide layer arranged on the side surface of the first protrusion. The oxide layer arranged on the side surface of the third protrusion is thicker than the oxide layer arranged on the side surface of the second protrusion.

[0016] An interconnector according to a tenth aspect is the interconnector according to any one of the first to ninth aspects, wherein the main body is made of an alloy containing chromium, and each oxide layer contains chromium as a main component.

[0017] An interconnector according to an eleventh aspect is the interconnector according to any one of the first to tenth aspects, configured as follows: Each oxide layer has a thermal expansion coefficient smaller than that of the main body portion.

[0018] An electrochemical cell according to a twelfth aspect includes the interconnector according to any one of the first to eleventh 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.

[0019] The electrochemical cell according to the thirteenth aspect is the electrochemical cell according to the twelfth aspect, and is configured as follows: each oxide layer is thinner than the cell main body portion.

[0020] According to the present invention, damage to the cell main body can be suppressed.

[0021] 12. Plan view of an electrolysis cell. Cross-sectional view taken along line II-II in FIG. 1. Plan view of an interconnector. Enlarged cross-sectional view of a first convex portion. Cross-sectional view taken along line V-V in FIG. 4. Enlarged cross-sectional view of a second convex portion. Cross-sectional view taken along line VII-VII in FIG. 6. Enlarged cross-sectional view of a third convex portion. Cross-sectional view taken along line IX-IX in FIG. 8. Enlarged cross-sectional view showing the warping direction around the first convex portion of the interconnector. Enlarged cross-sectional view showing the warping direction around the second convex portion of the interconnector. Plan view of an interconnector according to a modified example. Cross-sectional view taken along line XIII-XIII in FIG. 12. Cross-sectional view taken along line XIV-XIV in FIG. 12. Cross-sectional view taken along line XV-XV in FIG. 12. Enlarged cross-sectional view showing the warping direction around the first convex portion of the interconnector. Enlarged cross-sectional view showing the warping direction around the second convex portion of the interconnector.

[0022] 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.

[0023] 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.

[0024] As shown in FIGS. 1 and 2 , the electrolysis cell 100 includes a cell body 2 , a support substrate 3 , and an interconnector 4 .

[0025] <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).

[0026] 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.

[0027] <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.

[0028] 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.

[0029] Hydrogen electrode 21: H ２ O + 2e － →H ２ +O ２－ ... (1) The raw material gas is H２ 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.

[0030] 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)

[0031] 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.

[0032] 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).

[0033] 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)TiO３ , Sr ２ (Fe, Mo) ２ O ６ , (La, Sr)VO ３ , (La,Sr)FeO ３ and mixed materials of two or more of these.

[0034] 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.

[0035] 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.

[0036] <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.

[0037] 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 .

[0038] 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.

[0039] 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.

[0040] 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.

[0041] <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.

[0042] The reaction prevention layer 23 is made of an oxide ion conductive material, such as GDC or SDC.

[0043] 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.

[0044] 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.

[0045] <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.

[0046] 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.

[0047] Oxygen electrode 24:2O ２－ →O ２ +4e － ...(5)

[0048] 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).

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Each through-hole 33 can be formed by mechanical processing (for example, punching), laser processing, chemical processing (for example, etching), or the like.

[0057] 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.

[0058] 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.

[0059] 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).

[0060] <Interconnector> FIG. 3 is a plan view of the interconnector 4. As shown in FIGS. 2 and 3 , 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 configured so that the source gas and the gas generated at the hydrogen electrode flow within the internal space 30. In the following description, the gas flow direction refers to the direction from the supply hole 405 toward the discharge hole 406, which will be described later. Specifically, the Y-axis direction is the gas flow direction. The first direction is a direction perpendicular to the gas flow direction. Specifically, the X-axis direction is the first direction.

[0061] 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 and a plurality of oxide layers 41.

[0062] 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.

[0063] The main body 40 has a first main surface 401, a second main surface 402, a plurality of convex portions 403, a supply hole 405, and a discharge hole 406. 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 direction in which the first main surface 401 faces. 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.

[0064] 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. The 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] Each of the protrusions 403 is formed on the first main surface 401 of the main body 40. Each of the protrusions 403 protrudes toward the support substrate 3. Each of the protrusions 403 is disposed within the internal space 30. The height of each of the protrusions 403 is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less. Each of the protrusions 403 is columnar or cylindrical.

[0067] 3, the protrusions 403 are arranged at intervals from one another in the gas flow direction. The protrusions 403 are also arranged at intervals from one another in a first direction perpendicular to the gas flow direction. Specifically, the protrusions 403 are arranged in a staggered pattern. The protrusions 403 can be formed by subjecting the interconnector 4 to press processing, cutting processing, etching processing, or the like.

[0068] The protrusions 403 are larger than the through-holes 33 in plan view. Therefore, the plurality of through-holes 33 overlap with the protrusions 403 in plan view.

[0069] The plurality of convex portions 403 includes a plurality of first convex portions 403 a, a plurality of second convex portions 403 b, and a plurality of third convex portions 403 c. In this embodiment, the plurality of convex portions 403 includes five first convex portions 403 a, five second convex portions 403 b, and four third convex portions 403 c.

[0070] Each first convex portion 403a is disposed at the most upstream position in the gas flow direction. That is, each first convex portion 403a is the convex portion 403 disposed at the upper end of the plurality of convex portions 403 in Fig. 3. Each first convex portion 403a is arranged in a first direction.

[0071] Each second convex portion 403b is disposed at the most downstream position in the gas flow direction. That is, each second convex portion 403b is one of the plurality of convex portions 403 that is disposed at the bottom in Fig. 3. Each second convex portion 403b is arranged in the first direction.

[0072] Each third convex portion 403c is disposed in the center between each first convex portion 403a and each second convex portion 403b in the gas flow direction. That is, each third convex portion 403c is the convex portion among the multiple convex portions 403 that is closest to the midpoint between the first convex portion 403a and the second convex portion 403b in the gas flow direction. Each third convex portion 403c is arranged in the first direction.

[0073] 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.

[0074] Each oxide layer 41 is formed on the side surface of each protrusion 403. Each oxide layer 41 is formed on the entire side surface of each protrusion 403. That is, each oxide layer 41 is annular in plan view. An oxide layer may be formed on the first main surface 401. In this case, the oxide layers 41 are connected to each other. An oxide layer may be formed on the tip surface of each protrusion 403. Although no oxide layer is formed on the outer periphery of the first main surface 401, an oxide layer may be formed on the outer periphery of the first main surface 401.

[0075] Each oxide layer 41 has a different thermal expansion coefficient from that of the main body portion 40. In the present embodiment, the oxide layer 41 has a smaller thermal expansion coefficient than the main body portion 40. The oxide layer 41 is composed of an oxide containing Cr as a main component (hereinafter abbreviated as "Cr oxide"). This makes it possible to suppress the diffusion of Cr from the support substrate 3 and the main body portion 40 to the oxide layer 41 during the 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 oxide layer 41, the effect on the composition of the oxide layer 41 is small, and therefore a decrease in the strength of the oxide layer 41 can also be suppressed.

[0076] 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 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.

[0077] The Cr content of the metal elements in the Cr oxide constituting the 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 oxide layer 41.

[0078] The Cr oxide constituting the 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 oxide layer 41 can be improved.

[0079] 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.

[0080] The Cr oxide constituting the oxide layer 41 is preferably crystalline, which can prevent the 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.

[0081] The Cr oxide constituting the oxide layer 41 preferably has a spinel or corundum crystal structure, which has high symmetry and can improve the thermal stress resistance of the oxide layer 41.

[0082] The oxide layer 41 can be formed by applying a paste containing Cr oxide to the side surfaces of the protrusions 403 and then performing a heat treatment. The conditions for the heat treatment can be set appropriately, but can be, for example, 600° C. to 1100° C. and 0.5 hours to 24 hours.

[0083] The oxide layer 41 is thinner than the cell body 2. The thickness of the oxide layer 41 can be set to, for example, 0.1 μm or more and 20 μm or less.

[0084] FIG. 4 is an enlarged cross-sectional view of the first convex portion 403a as viewed in the thickness direction, and FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4. As shown in FIGS. 4 and 5, each oxide layer 41 has an upstream portion 411 and a downstream portion 412. The upstream portion 411 is a portion of the oxide layer 41 facing the upstream side. The downstream portion 412 is a portion of the oxide layer 41 facing the downstream side. For example, assuming that the upper side of FIG. 4 is upstream and the lower side is downstream, a line extending directly upward from the center O of the convex portion 403 is defined as 0 degrees, and the range of ±45 degrees from that line is the upstream portion 411. Furthermore, a line extending directly downward from the center O of the convex portion 403 is defined as 0 degrees, and the range of ±45 degrees from that line is the downstream portion 412.

[0085] At least one of the oxide layers 41 has a thickness distribution that induces warping of the main body 40 such that the main body 40 bulges toward the second main surface 402 .

[0086] Specifically, in the oxide layer 41 formed on the side surface of each first convex portion 403a, the thickness ta1 of the upstream portion 411 is thinner than the thickness ta2 of the downstream portion 412. For example, in the oxide layer 41 formed on the side surface of each first convex portion 403a, the average value of the thickness ta1 of the upstream portion 411 is smaller than the average value of the thickness ta2 of the downstream portion 412.

[0087] In the oxide layer 41 formed on the side surface of at least one first protrusion 403a, the ratio of the thickness ta1 to the thickness ta2 (ta1 / ta2) can be 0.83 or less, and this ratio (ta1 / ta2) can be 0.1 or more.

[0088] In the oxide layer 41 formed on the side surface of each first convex portion 403a, the thickness ta1 of the upstream portion 411 and the thickness ta2 of the downstream portion 412 can be measured as follows. First, each first convex portion 403a is cut along the gas flow direction (Y-axis direction) so as to pass through the center of each first convex portion 403a, and a cut surface such as that shown in FIG. 5 is created for each first convex portion 403a. Then, images of each cut surface are taken using an electron microscope (SEM) at a magnification (200 to 20,000 times) suitable for measuring the thickness of each first convex portion 403a, for the upstream portion 411 and the downstream portion 412. Note that the images are taken near the center of each first convex portion 403a in the height direction.

[0089] Then, in each SEM image, the thickness ta1 of the upstream portion 411 and the thickness ta2 of the downstream portion 412 are measured. Note that the thickness ta1 of the upstream portion 411 and the thickness ta2 of the downstream portion 412 are measured at the center in the height direction of the first convex portion 403a.

[0090] Fig. 6 is an enlarged cross-sectional view of the second convex portion 403b as viewed in the thickness direction, and Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 6. As shown in Fig. 6 and Fig. 7, in the oxide layer 41 formed on the side surface of each second convex portion 403b, the thickness tb1 of the upstream portion 411 is thicker than the thickness tb2 of the downstream portion 412. For example, in the oxide layer 41 formed on the side surface of each second convex portion 403b, the average value of the thickness tb1 of the upstream portion 411 is greater than the average value of the thickness tb2 of the downstream portion 412.

[0091] In the oxide layer 41 formed on the side surface of at least one second protrusion 403b, the ratio of the thickness tb1 to the thickness tb2 (tb1 / tb2) can be 1.2 or more, and this ratio (tb1 / tb2) can be 10 or less.

[0092] In the oxide layer 41 formed on the side surface of each second convex portion 403b, the thickness tb1 of the upstream portion 411 and the thickness tb2 of the downstream portion 412 can be measured as follows. First, each second convex portion 403b is cut along the gas flow direction (Y-axis direction) so as to pass through the center of each second convex portion 403b, and a cut surface such as that shown in FIG. 7 is created for each second convex portion 403b. Then, images of each cut surface are taken using an electron microscope (SEM) at a magnification (200 to 20,000 times) suitable for measuring the thickness of each second convex portion 403b, for the upstream portion 411 and the downstream portion 412. Note that the images are taken near the center of each second convex portion 403b in the height direction.

[0093] Then, in each SEM image, the thickness tb1 of the upstream portion 411 and the thickness tb2 of the downstream portion 412 are measured. Note that the thickness tb1 of the upstream portion 411 and the thickness tb2 of the downstream portion 412 are measured at the center in the height direction of the second convex portion 403b.

[0094] Fig. 8 is an enlarged cross-sectional view of the third convex portion 403c as viewed in the thickness direction, and Fig. 9 is a cross-sectional view taken along line IX-IX in Fig. 8. As shown in Fig. 8 and Fig. 9, in the oxide layer 41 formed on the side surface of each third convex portion 403c, the thickness tc1 of the upstream portion 411 and the thickness tc2 of the downstream portion 412 are substantially the same. For example, in the oxide layer 41 formed on the side surface of each third convex portion 403c, the average value of the thickness tc1 of the upstream portion 411 is substantially the same as the average value of the thickness tc2 of the downstream portion 412.

[0095] In the oxide layer 41 formed on the side surface of at least one third convex portion 403c, the ratio of the thickness tc1 to the thickness tc2 (tc1 / tc2) can be set to 0.83 or more and 1.2 or less.

[0096] The difference in thickness (tc1-tc2) between the upstream portion 411 and the downstream portion 412 of the oxide layer 41 disposed on the side surface of the third convex portion 403c is smaller than the difference in thickness (ta1-ta2) between the upstream portion 411 and the downstream portion 412 of the oxide layer 41 disposed on the side surface of the first convex portion 403a. Also, the difference in thickness (tc1-tc2) between the upstream portion 411 and the downstream portion 412 of the oxide layer 41 disposed on the side surface of the third convex portion 403c is smaller than the difference in thickness (tb1-tb2) between the upstream portion 411 and the downstream portion 412 of the oxide layer 41 disposed on the side surface of the second convex portion 403b. Here, the difference in thickness between the upstream portion 411 and the downstream portion 412 is an absolute value.

[0097] In the oxide layer 41 formed on the side surface of each third convex portion 403c, the thickness tc1 of the upstream portion 411 and the thickness tc2 of the downstream portion 412 can be measured as follows. First, each third convex portion 403c is cut along the gas flow direction (Y-axis direction) so as to pass through the center of each third convex portion 403c, and a cut surface such as that shown in FIG. 9 is created for each third convex portion 403c. Then, images of each cut surface are taken using an electron microscope (SEM) at a magnification (200 to 20,000 times) suitable for measuring the thickness of each third convex portion 403c, for the upstream portion 411 and the downstream portion 412. Note that the images are taken near the center of each third convex portion 403c in the height direction.

[0098] Then, in each SEM image, the thickness tc1 of the upstream portion 411 and the thickness tc2 of the downstream portion 412 are measured. Note that the thickness tc1 of the upstream portion 411 and the thickness tc2 of the downstream portion 412 are measured at the center in the height direction of the third convex portion 403c.

[0099] The oxide layer 41 disposed on the side surface of the third convex portion 403c is thicker than the oxide layer 41 disposed on the side surface of the first convex portion 403a. For example, the average thickness of the oxide layer 41 disposed on the side surface of each third convex portion 403a is greater than the average thickness of the oxide layer 41 disposed on the side surface of each first convex portion 403a. Furthermore, the oxide layer 41 disposed on the side surface of the third convex portion 403c is thicker than the oxide layer 41 disposed on the side surface of the second convex portion 403b. For example, the average thickness of the oxide layer 41 disposed on the side surface of each third convex portion 403a is greater than the average thickness of the oxide layer 41 disposed on the side surface of each second convex portion 403b. Here, the thickness of the oxide layer 41 can be the average value of the thickness of the upstream portion 411 and the thickness of the downstream portion 412.

[0100] In the oxide layer 41 formed on the side surface of each convex portion 403 arranged between the first convex portion 403a and the third convex portion 403c, the upstream portion 411 is preferably thinner than the downstream portion 412. In addition, in the oxide layer 41 formed on the side surface of each convex portion 403 arranged between the second convex portion 403b and the third convex portion 403c, the upstream portion 411 is preferably thicker than the downstream portion 412. The difference in thickness between the upstream portion 411 and the downstream portion 412 preferably becomes smaller as it approaches the third convex portion 403c.

[0101] In the interconnector 4 configured as described above, the oxide layer 41 formed on the side surface of each first convex portion 403a is thicker in the downstream portion 412 than in the upstream portion 411. For this reason, when the temperature is lowered to room temperature after the oxide layer 41 is formed, thermal stress is generated in the region where each first convex portion 403a of the interconnector 4 is formed, which induces warping such that the region bulges toward the second main surface 402, as shown by the arrows in FIG.

[0102] Furthermore, in the oxide layer 41 formed on the side surface of each second convex portion 403 b, the upstream portion 411 is thicker than the downstream portion 412. For this reason, when the temperature is lowered to room temperature after the oxide layer 41 is formed, thermal stress is generated in the region where each second convex portion 403 b of the interconnector 4 is formed, which induces warping such that the interconnector 4 bulges toward the second main surface 402, as shown by the arrows in FIG.

[0103] As described above, since the interconnector 4 is warped so as to bulge toward the second main surface 402, when the electrolysis cells 100 are stacked, even if there are unevenness on the cell main body portion located below the interconnector 4, the unevenness can be absorbed.

[0104] [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.

[0105] (a) In the above embodiment, the convex portions 403 have a circular shape in a plan view, but the shape of the convex portions 403 is not limited to this. For example, as shown in Fig. 12, each convex portion 403 may have a rectangular shape in a plan view. Furthermore, each convex portion 403 may extend in the gas flow direction. The convex portions 403 are arranged at intervals from one another in the first direction.

[0106] The plurality of protrusions 403 include a first protrusion 403 a, a second protrusion 403 b, and a third protrusion 403 c. The first protrusion 403 a and the second protrusion 403 b are protrusions arranged on the outermost sides in the first direction. The protrusions 403 other than the first protrusion 403 a and the second protrusion 403 b are arranged between the first protrusion 403 a and the second protrusion 403 b in the first direction.

[0107] The third convex portion 403c is disposed in the center between the first convex portion 403a and the second convex portion 403b in the first direction. That is, the third convex portion 403c is the convex portion among the multiple convex portions 403 that is closest to the midpoint between the first convex portion 403a and the second convex portion 403b in the first direction.

[0108] Fig. 13 is a cross-sectional view taken along line XIII-XIII in Fig. 12. As shown in Fig. 13, the oxide layer 41 has an outer portion 413 and an inner portion 414. The outer portion 413 is a portion that faces outward in the first direction. The inner portion 414 is a portion that faces inward in the first direction. In other words, the inner portion 414 faces toward the center of the interconnector 4 in the first direction.

[0109] In the oxide layer 41 disposed on the side surface of the first convex portion 403a, the thickness ta1 of the outer portion 413 is thinner than the thickness ta2 of the inner portion 414. For example, in the oxide layer 41 formed on the side surface of the first convex portion 403a, the ratio of the thickness ta1 to the thickness ta2 (ta1 / ta2) can be 0.83 or less. Furthermore, this ratio (ta1 / ta2) can be 0.1 or more.

[0110] 14 , in the oxide layer 41 disposed on the side surface of the second convex portion 403b, the thickness tb1 of the outer portion 413 is thinner than the thickness tb2 of the inner portion 414. For example, in the oxide layer 41 formed on the side surface of the second convex portion 403b, the ratio of the thickness tb1 to the thickness tb2 (tb1 / tb2) can be 0.83 or less. Moreover, this ratio (tb1 / tb2) can be 0.1 or more.

[0111] 15 , in the oxide layer 41 disposed on the side surface of the third convex portion 403c, the thickness tc1 of the outer portion 413 is substantially the same as the thickness tc2 of the inner portion 414. For example, in the oxide layer 41 formed on the side surface of the third convex portion 403c, the ratio of the thickness tc1 to the thickness tc2 (tc1 / tc2) can be 0.83 or more and 1.2 or less. Note that when the third convex portion 403c is disposed at the center of the interconnector 4 in the first direction, the portion of the oxide layer 41 disposed on the side surface of the third convex portion 403c facing the first convex portion 403a is referred to as the outer portion 413, and the portion facing the second convex portion 403b is referred to as the inner portion 414.

[0112] The difference in thickness (tc1-tc2) between the outer portion 413 and the inner portion 414 of the oxide layer 41 disposed on the side surface of the third convex portion 403c is smaller than the difference in thickness (ta1-ta2) between the outer portion 413 and the inner portion 414 of the oxide layer 41 disposed on the side surface of the first convex portion 403a. Also, the difference in thickness (tc1-tc2) between the outer portion 413 and the inner portion 414 of the oxide layer 41 disposed on the side surface of the third convex portion 403c is smaller than the difference in thickness (tb1-tb2) between the outer portion 413 and the inner portion 414 of the oxide layer 41 disposed on the side surface of the second convex portion 403b. Here, the difference in thickness between the outer portion 413 and the inner portion 414 is an absolute value.

[0113] The thickness of each outer portion 413 and each inner portion 414 can be measured as follows. First, the interconnector 4 is cut along the first direction so as to pass through the upstream end, downstream end, and center of each convex portion 403, respectively, to create three cut surfaces. Then, at each cut surface, the outer portion 413 and the inner portion 414 of the first convex portion 403a, the second convex portion 403b, and the third convex portion 403c are photographed using an electron microscope (SEM) at a magnification (200 to 20,000 times) suitable for measuring the thickness. The photographs taken are of the vicinity of the center in the height direction of the first convex portion 403a, the second convex portion 403b, and the third convex portion 403c.

[0114] Then, in each SEM image, the thickness ta1 of the outer portion 413 and the thickness ta2 of the inner portion 414 are measured at the upstream end, downstream end, and center of the first convex portion 403a, and the average value of the thicknesses ta1 of the outer portion 413 can be set as the thickness ta1 of the outer portion 413 of the first convex portion 403a, and the average value of the thicknesses ta2 of the inner portion 414 can be set as the thickness ta2 of the inner portion 414 of the first convex portion 403a. Similarly, the thicknesses of the second convex portion 403b and the third convex portion 403c are calculated.

[0115] The oxide layer 41 disposed on the side surface of the third convex portion 403c is thicker than the oxide layer 41 disposed on the side surface of the first convex portion 403a. Also, the oxide layer 41 disposed on the side surface of the third convex portion 403c is thicker than the oxide layer 41 disposed on the side surface of the second convex portion 403b. Here, the thickness of the oxide layer 41 can be the average value of the thickness of the outer portion 413 and the thickness of the inner portion 414.

[0116] In the interconnector 4 configured as described above, in the oxide layer 41 formed on the side surface of the first convex portion 403a, the inner portion 414 is thicker than the outer portion 413. For this reason, when the temperature is lowered to room temperature after the formation of the oxide layer 41, thermal stress is generated in the region where the first convex portion 403a of the interconnector 4 is formed, which induces warping such that the interconnector 4 bulges toward the second main surface 402, as shown by the arrow in FIG.

[0117] Furthermore, in oxide layer 41 formed on the side surface of second convex portion 403b, inner portion 414 is thicker than outer portion 413. For this reason, when oxide layer 41 is cooled to room temperature after formation, thermal stress is generated in the region where second convex portion 403b of interconnector 4 is formed, which induces warping such that the interconnector 4 bulges toward second main surface 402, as shown by the arrow in FIG.

[0118] (b) In the above embodiment, the oxide layer 41 formed on the side surface of the second convex portion 403b is thicker in the upstream portion 411 than in the downstream portion 412, but the configuration of the oxide layer 41 is not limited to this. For example, the thickness of the upstream portion 411 and the thickness of the downstream portion 412 of the oxide layer 41 formed on the side surface of the second convex portion 403b may be approximately the same.

[0119] (c) 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 for 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.

[0120] 100: Electrolysis cell 2: Cell main body 3: Support substrate 4: Interconnector 40: Main body 401: First main surface 402: Second main surface 403: Convex portion 403a: First convex portion 403b: Second convex portion 403c: Third convex portion 41: Oxide layer 411: Upstream portion 412: Downstream portion 413: Outer portion 414: Inner portion

Claims

1. An interconnector comprising: a main body portion having a first main surface, a second main surface facing the opposite side to the first main surface, and a plurality of protrusions formed on the first main surface; and a plurality of oxide layers disposed on the side surfaces of each of the protrusions, wherein at least one of the oxide layers has a thickness distribution that induces warping of the main body portion such that it bulges toward the second main surface.

2. The interconnector described in claim 1, wherein the multiple protrusions are arranged at intervals from each other in the gas flow direction, the multiple protrusions include a first protrusion arranged at the most upstream position in the gas flow direction and a second protrusion arranged at the most downstream position, each of the oxide layers has an upstream portion facing the upstream side and a downstream portion facing the downstream side, and the oxide layer arranged on the side of the first protrusion has a thickness distribution in which the upstream portion is thinner than the downstream portion.

3. The interconnector according to claim 2, wherein the oxide layer disposed on the side surface of the second protrusion has a thickness distribution in which the upstream portion is thicker than the downstream portion.

4. The interconnector described in claim 2, wherein the plurality of protrusions include a third protrusion arranged in a central portion between the first protrusion and the second protrusion in the gas flow direction, and the difference in thickness between the upstream portion and the downstream portion of the oxide layer arranged on the side surface of the first protrusion is greater than the difference in thickness between the upstream portion and the downstream portion of the oxide layer arranged on the side surface of the third protrusion.

5. The interconnector described in claim 2, wherein the plurality of protrusions include a third protrusion arranged in a central portion between the first protrusion and the second protrusion in the gas flow direction, and the oxide layer arranged on the side surface of the third protrusion is thicker than the oxide layer arranged on the side surface of the first protrusion and thicker than the oxide layer arranged on the side surface of the second protrusion.

6. The interconnector described in claim 1, wherein the plurality of protrusions extend in the gas flow direction and are arranged at intervals from one another in a first direction perpendicular to the gas flow direction, the plurality of protrusions include a first protrusion and a second protrusion arranged outermost in the first direction, each of the oxide layers has an outer portion facing outward in the first direction and an inner portion facing inward in the first direction, and the oxide layer arranged on the side of the first protrusion has a thickness distribution in which the outer portion is thinner than the inner portion.

7. The interconnector according to claim 6, wherein the oxide layer disposed on the side surface of the second protrusion has a thickness distribution in which the outer portion is thinner than the inner portion.

8. The interconnector described in claim 6, wherein the plurality of protrusions include a third protrusion arranged in a central portion between the first protrusion and the second protrusion in the first direction, and the difference in thickness between an outer portion and an inner portion of the oxide layer arranged on the side surface of the first protrusion is greater than the difference in thickness between the outer portion and the inner portion of the oxide layer arranged on the side surface of the third protrusion.

9. The interconnector described in claim 6, wherein the plurality of protrusions include a third protrusion arranged in a central portion between the first protrusion and the second protrusion in the first direction, and the oxide layer arranged on the side surface of the third protrusion is thicker than the oxide layer arranged on the side surface of the first protrusion and thicker than the oxide layer arranged on the side surface of the second protrusion.

10. The interconnector according to claim 1, wherein the main body is made of an alloy containing chromium, and each of the oxide layers contains chromium as a main component.

11. The interconnector according to claim 1, wherein each of the oxide layers has a thermal expansion coefficient smaller than that of the main body portion.

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

13. The electrochemical cell of claim 12, wherein each of the oxide layers is thinner than the cell body.

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