Electrochemical cell

Abstract

An electrolytic cell (1) is provided with: a metal support (10) having a plurality of communication holes (11) formed on a first main surface (12) thereof; and a cell body (20). The cell body (20) has a gas diffusion layer (5) disposed on the first main surface (12) of the metal support (10), and a hydrogen electrode layer (6) disposed on the gas diffusion layer (5). The gas diffusion layer (5) has a body section (5a) sandwiched in a gap between the metal support (10) and the hydrogen electrode layer (6), and a projecting part (5b) projecting from the body section (5a) into a communication hole (11). The projecting part (5b) covers part of the inner peripheral surface (14) of the communication hole (11).

Description

electrochemical cell

[0001] The present invention relates to electrochemical cells.

[0002] Patent Document 1 discloses an electrochemical cell (electrolysis cell, fuel cell, etc.) including a cell body disposed on a metal support. The metal support has a plurality of communication holes formed on a main surface. The cell body includes a gas diffusion layer formed on the main surface of the metal support, a first electrode layer and a second electrode layer disposed on the gas diffusion layer, and an electrolyte layer disposed between the first and second electrode layers.

[0003] Patent Document 1 describes that through-holes communicating with the communication holes of the metal support are formed in the gas diffusion layer in order to ensure smooth gas supply and discharge between the communication holes of the metal support and the first electrode layer.

[0004] Japanese Patent Application Laid-Open No. 2020-079189

[0005] However, in the electrochemical cell disclosed in Patent Document 1, damage (cracks and peeling) may occur in the gas diffusion layer due to distortion occurring around the through-holes of the metal support.

[0006] An object of the present invention is to provide an electrochemical cell that can suppress damage to the gas diffusion layer.

[0007] An electrochemical cell according to a first aspect of the present invention includes a metal support having a plurality of communication holes formed in a main surface thereof and a cell main body portion disposed on the main surface. The cell main body portion includes a gas diffusion layer disposed on the main surface, a first electrode layer and a second electrode layer disposed on the gas diffusion layer, and an electrolyte layer disposed between the first electrode layer and the second electrode layer. The gas diffusion layer includes a main body portion sandwiched between the metal support and the first electrode layer, and a protrusion portion protruding from the main body portion into the communication hole. The protrusion portion covers a portion of the inner circumferential surface of the communication hole.

[0008] An electrochemical cell according to a second aspect of the present invention is the electrochemical cell according to the first aspect, wherein the protrusion is tapered in a thickness direction away from the main body.

[0009] An electrochemical cell according to a third aspect of the present invention is related to the first or second aspect, wherein the protrusion covers a part of the surface of the first electrode layer facing the metal support.

[0010] An electrochemical cell according to a fourth aspect of the present invention is related to the third aspect, wherein the protrusion is tapered in a direction away from the main body in a plane direction perpendicular to the thickness direction.

[0011] An electrochemical cell according to a fifth aspect of the present invention is related to the third or fourth aspect, wherein the protrusion has an exposed surface exposed to the communication hole and the through hole, and the exposed surface is curved.

[0012] An electrochemical cell according to a sixth aspect of the present invention is the electrochemical cell according to any one of the first to fifth aspects, wherein the ratio of the coverage width in the thickness direction of the region of the inner surface of the communicating hole that is covered by the protrusion to the thickness in the thickness direction of the main body is 10 or more.

[0013] An electrochemical cell according to a seventh aspect of the present invention is the electrochemical cell according to any one of the first to sixth aspects, wherein the coverage width in the thickness direction of the region of the inner surface of the communicating hole that is covered by the protrusion is 10 μm or more.

[0014] An electrochemical cell according to an eighth aspect of the present invention relates to any one of the first to seventh aspects, wherein the metal support has a base material and an oxide film covering a surface of the base material, and a first portion of the oxide film exposed to the communicating hole has a thickness greater than a second portion of the oxide film covered by the protrusion.

[0015] An electrochemical cell according to a ninth aspect of the present invention is the electrochemical cell according to any one of the first to eighth aspects, wherein an average pore diameter of the plurality of pores in the gas diffusion layer is smaller than an average pore diameter of the plurality of pores in the first electrode layer.

[0016] An electrochemical cell according to a tenth aspect of the present invention is related to the ninth aspect, wherein the porosity of the gas diffusion layer is greater than the porosity of the first electrode layer.

[0017] According to the present invention, it is possible to provide an electrochemical cell that can suppress damage to the gas diffusion layer.

[0018] Fig. 1 is a plan view of an electrolysis cell according to an embodiment. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 2 is a partial enlarged view of Fig. 2. Fig. 4 is a cross-sectional view showing a modified example of a communication hole. Fig. 5 is a cross-sectional view showing a modified example of a communication hole.

[0019] (Electrolytic cell 1) Fig. 1 is a plan view of an electrolytic cell 1 according to an embodiment. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1.

[0020] The electrolytic cell 1 is an example of an "electrochemical cell" according to the present invention. The electrolytic cell 1 is a so-called metal-supported electrolytic cell.

[0021] The electrolytic cell 1 is formed in a plate shape extending in the X-axis and Y-axis directions. In the present embodiment, the electrolytic cell 1 is formed in a rectangular shape extending in the Y-axis direction when viewed in a plan view from the Z-axis direction perpendicular to the X-axis and Y-axis directions. However, the planar shape of the electrolytic cell 1 is not particularly limited, and may be a polygon other than a rectangle, an ellipse, a circle, or the like.

[0022] As shown in FIG. 2 , the electrolysis cell 1 includes a metal support 10 , a cell main body 20 , and a flow path member 30 .

[0023] [Metal Support 10] The metal support 10 supports the cell main body 20. The metal support 10 is formed in a plate shape. The metal support 10 may be in the shape of a flat plate or a curved plate.

[0024] The metal support 10 is only required to be able to support the cell main body 20, and its thickness is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less.

[0025] As shown in FIG. 2 , the metal support 10 has a plurality of through holes 11 , a first main surface 12 and a second main surface 13 .

[0026] Each communication hole 11 penetrates the metal support 10 in the Z-axis direction from the first main surface 12 to the second main surface 13. Each communication hole 11 opens to the first main surface 12 and the second main surface 13. In this embodiment, the opening of each communication hole 11 on the first main surface 12 side is covered by the cell main body 20 (specifically, the hydrogen electrode layer 6 described later). The opening of each communication hole 11 on the second main surface 13 side is connected to a flow path 30a described later.

[0027] Each of the communication holes 11 can be formed by mechanical processing (for example, punching), laser processing, or chemical processing (for example, etching).

[0028] In this embodiment, each communication hole 11 is formed along the Z-axis direction. However, each communication hole 11 may be inclined with respect to the Z-axis direction, or may not be linear. Furthermore, the communication holes 11 may be connected to each other.

[0029] The first main surface 12 is provided on the opposite side to the second main surface 13. The cell main body 20 is disposed on the first main surface 12. The flow path member 30 is bonded to the second main surface 13.

[0030] The metal support 10 is made of a metal material. For example, the metal support 10 is made of an alloy material containing Cr (chromium). Examples of such metal materials include Fe—Cr alloy steel (stainless steel, etc.) and Ni—Cr alloy steel. The Cr content in the metal support 10 is not particularly limited, but can be set to 4% by mass or more and 30% by mass or less.

[0031] The metal support 10 may contain Ti (titanium) or Zr (zirconium). The Ti content in the metal support 10 is not particularly limited, but may be 0.01 mol % or more and 1.0 mol % or less. The Zr content in the metal support 10 is not particularly limited, but may be 0.01 mol % or more and 0.4 mol % or less. The metal support 10 may contain Ti in the form of TiO ２ (titania), or Zr may be contained as ZrO ２ It may be contained as (zirconia).

[0032] [Cell Body 20] The cell body 20 is disposed on the metal support 10. The cell body 20 is supported by the metal support 10. The cell body 20 has a gas diffusion layer 5, a hydrogen electrode layer 6 (cathode), an electrolyte layer 7, a reaction prevention layer 8, and an oxygen electrode layer 9 (anode).

[0033] The gas diffusion layer 5, hydrogen electrode layer 6, electrolyte layer 7, reaction prevention layer 8, and oxygen electrode layer 9 are stacked in this order in the Z-axis direction from the metal support 10 side. The gas diffusion layer 5, hydrogen electrode layer 6, electrolyte layer 7, and oxygen electrode layer 9 are essential components, while the reaction prevention layer 8 is optional.

[0034] [Gas Diffusion Layer 5] The gas diffusion layer 5 is disposed on the first main surface 12 of the metal support 10. The gas diffusion layer 5 is interposed between the metal support 10 and the hydrogen electrode layer 6. The gas diffusion layer 5 is in direct contact with both the metal support 10 and the hydrogen electrode layer 6.

[0035] The gas diffusion layer 5 has a plurality of through holes 51 , a first connecting surface 52 and a second connecting surface 53 .

[0036] Each through hole 51 penetrates the gas diffusion layer 5 in the Z-axis direction from the first connection surface 52 to the second connection surface 53. Each through hole 51 opens to the first connection surface 52 and the second connection surface 53. In this embodiment, the opening of each through hole 51 on the first connection surface 52 side is covered by the hydrogen electrode layer 6. The opening of each through hole 51 on the second connection surface 53 side is connected to each communication hole 11 of the metal support 10. Therefore, the gas diffusion layer 5 does not cover each communication hole 11 of the metal support 10.

[0037] The first connecting surface 52 is connected to the first main surface 12 of the metal support 10. The first connecting surface 52 is provided on the opposite side to the second connecting surface 53. The second connecting surface 53 is connected to the metal support side surface 61 of the hydrogen electrode layer 6.

[0038] The gas diffusion layer 5 is a porous body having electrical conductivity. The gas diffusion layer 5 electrically connects the metal support 10 and the hydrogen electrode layer 6. The gas diffusion layer 5 also supplies and exhausts gas between each of the communicating holes 11 and the hydrogen electrode layer 6. Specifically, the gas diffusion layer 5 supplies the source gas supplied from each of the communicating holes 11 to the hydrogen electrode layer 6, and exhausts the product gas generated in the hydrogen electrode layer 6 to each of the communicating holes 11.

[0039] The gas diffusion layer 5 includes a conductive material. The gas diffusion layer 5 may include a substrate for supporting the conductive material. Examples of the conductive material include metal materials such as Ni (nickel) and Fe (iron), and conductive ceramic materials. Examples of the substrate include YSZ, CSZ, ScSZ, GDC, SDC, and (La, Sr)(Cr, Mn)O. ３ , (La,Sr)TiO ３ , Sr ２ (Fe, Mo) ２ O ６ , (La, Sr)VO ３ , (La,Sr)FeO ３ , LDC (lanthanum doped ceria), LSGM (lanthanum gallate), and a mixed material of two or more of these can be used. The substrate may be insulating.

[0040] The method for forming the gas diffusion layer 5 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.

[0041] [Hydrogen Electrode Layer 6] The hydrogen electrode layer 6 is an example of a "first electrode layer" according to the present invention. The hydrogen electrode layer 6 is disposed on the gas diffusion layer 5. The hydrogen electrode layer 6 is sandwiched between the gas diffusion layer 5 and the electrolyte layer 7. The hydrogen electrode layer 6 has a metal support side surface 61 that is connected to the second connection surface 53 of the gas diffusion layer 5.

[0042] A source gas is supplied to the hydrogen electrode layer 6 through the communication holes 11 and the through holes 51. The source gas contains at least H ２ Contains O.

[0043] The raw material gas is H ２ When only O is contained, the hydrogen electrode layer 6 converts H from the raw material gas according to the electrochemical reaction of water electrolysis shown in the following formula (1): ２ Generate.

[0044] Hydrogen electrode layer 6: H ２ O + 2e － →H２ +O ２－ ...(1)

[0045] The raw material gas is H ２ O plus CO ２ In this case, the hydrogen electrode layer 6 converts the source 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.

[0046] Hydrogen electrode layer 6: 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)

[0047] The hydrogen electrode layer 6 is a porous body having electrical conductivity. The hydrogen electrode layer 6 has gas diffusibility. A source gas is supplied to the hydrogen electrode layer 6 from the gas diffusion layer 5. The product gas generated in the hydrogen electrode layer 6 is discharged to the flow path 30a through the communication holes 11 and the through-holes 51.

[0048] The hydrogen electrode layer 6 contains a conductive material. As the conductive material, a metal material such as Ni (nickel) or Fe (iron), or a conductive ceramic material can be used. In the case of co-electrolysis, Ni is used as the catalyst for the generated H ２ and CO contained in the raw material gas ２ It also functions as a thermal catalyst, promoting the thermal reaction with HCl to maintain an appropriate gas composition for methanation and reverse water-gas shift reactions.

[0049] When the conductive material is a metal material, the conductive material exists in an oxide state (e.g., NiO) in an oxidizing atmosphere and in a metal state (e.g., Ni) in a reducing atmosphere. The hydrogen electrode layer 6 undergoes dimensional changes due to oxidation and reduction.

[0050] The hydrogen electrode layer 6 contains an oxide ion conductive material. The oxide ion conductive material is an example of the "ion conductive material" according to the present invention. Examples of the oxide ion conductive material include YSZ, CSZ, ScSZ, GDC, SDC, and (La, Sr)(Cr, Mn)O. ３ , (La,Sr)TiO ３ , Sr ２ (Fe, Mo) ２ O ６ , (La, Sr)VO ３ , (La,Sr)FeO ３ , LDC, LSGM, and a mixed material of two or more of these can be used.

[0051] In this embodiment, the hydrogen electrode layer 6 has a single-layer structure made of a single composition, but may have a multi-layer structure made of different compositions.

[0052] The thickness of the hydrogen electrode layer 6 is not particularly limited, but can be, for example, 1 μm or more and 500 μm or less.

[0053] In this specification, the term "thickness" refers to the size in the thickness direction. The thickness direction is the direction perpendicular to the plane direction parallel to the hydrogen electrode layer side surface 71 of the electrolyte layer 7. The plane direction is the direction parallel to the approximation line of the hydrogen electrode layer side surface 71 obtained by the least squares method in the cross section of the electrolyte layer 7. The thickness direction may coincide with the Z-axis direction shown in FIGS. 1 and 2 .

[0054] The method for forming the hydrogen electrode layer 6 is not particularly limited, and may be a firing method, a spray coating method, a PVD method, a CVD method, or the like.

[0055] [Electrolyte Layer 7] The electrolyte layer 7 is disposed between the hydrogen electrode layer 6 and the oxygen electrode layer 9. In this embodiment, the reaction prevention layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9, and therefore the electrolyte layer 7 is sandwiched between the hydrogen electrode layer 6 and the reaction prevention layer 8. The electrolyte layer 7 has a hydrogen electrode layer side surface 71 that is connected to the hydrogen electrode layer 6.

[0056] The electrolyte layer 7 covers the hydrogen electrode layer 6 and also covers the region of the first main surface 12 of the metal support 10 that is exposed from the gas diffusion layer 5 .

[0057] The electrolyte layer 7 absorbs the O generated in the hydrogen electrode layer 6. ２－ The electrolyte layer 7 is made of a dense material having oxide ion conductivity. The electrolyte layer 7 can be made of, for example, YSZ (yttria-stabilized zirconia, e.g., 8YSZ), GDC (gadolinium-doped ceria), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), or LSGM (lanthanum gallate).

[0058] The porosity of the electrolyte layer 7 is not particularly limited, but may be, for example, 0.1% to 7%. The thickness of the electrolyte layer 7 is not particularly limited, but may be, for example, 1 μm to 100 μm.

[0059] The method for forming the electrolyte layer 7 is not particularly limited, and may be a baking method, a spray coating method, a PVD method, a CVD method, or the like.

[0060] [Reaction prevention layer 8] The reaction prevention layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9. The reaction prevention layer 8 is disposed on the opposite side of the electrolyte layer 7 from the hydrogen electrode layer 6. The reaction prevention layer 8 prevents the constituent elements of the electrolyte layer 7 from reacting with the constituent elements of the oxygen electrode layer 9 to form a layer with high electrical resistance.

[0061] The reaction prevention layer 8 is made of an oxide ion conductive material, such as GDC or SDC.

[0062] The porosity of the reaction prevention layer 8 is not particularly limited, but may be, for example, 0.1% to 50%. The thickness of the reaction prevention layer 8 is not particularly limited, but may be, for example, 1 μm to 50 μm.

[0063] The method for forming the reaction prevention layer 8 is not particularly limited, and may be a baking method, a spray coating method, a PVD method, a CVD method, or the like.

[0064] [Oxygen Electrode Layer 9] The oxygen electrode layer 9 is an example of a "second electrode layer" according to the present invention. The oxygen electrode layer 9 is disposed on the opposite side of the electrolyte layer 7 from the hydrogen electrode layer 6. In this embodiment, the reaction prevention layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9, and therefore the oxygen electrode layer 9 is connected to the reaction prevention layer 8. If the reaction prevention layer 8 is not disposed between the electrolyte layer 7 and the oxygen electrode layer 9, the oxygen electrode layer 9 is connected to the electrolyte layer 7.

[0065] The oxygen electrode layer 9 reacts with O transferred from the hydrogen electrode layer 6 through the electrolyte layer 7 in accordance with the chemical reaction of the following formula (5): ２－ From O ２ Generate.

[0066] Oxygen electrode layer 9: 2O ２－ →O ２ +4e － ...(5)

[0067] The oxygen electrode layer 9 is a porous body having oxide ion conductivity and electrical conductivity. The oxygen electrode layer 9 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).

[0068] The porosity of the oxygen electrode layer 9 is not particularly limited, but may be, for example, 20% to 60%. The thickness of the oxygen electrode layer 9 is not particularly limited, but may be, for example, 1 μm to 100 μm.

[0069] The method for forming the oxygen electrode layer 9 is not particularly limited, and may be a firing method, a spray coating method, a PVD method, a CVD method, or the like.

[0070] [Flow Channel Member 30] The flow channel member 30 is bonded to the second main surface 13 of the metal support 10. A flow channel 30a is formed between the flow channel member 30 and the metal support 10. A source gas is supplied to the flow channel 30a. The source gas supplied to the flow channel 30a is supplied to the hydrogen electrode layer 6 of the cell main body 20 via each communication hole 11 of the metal support 10.

[0071] The flow path member 30 can be made of, for example, an alloy material. The flow path member 30 may be made of the same material as the metal support 10. In this case, the flow path member 30 may be substantially integrated with the metal support 10.

[0072] The flow path member 30 has a frame 31 and an interconnector 32. The frame 31 is an annular member that surrounds the side of the flow path 30a. The frame 31 is joined to the second main surface 13 of the metal support 10. The interconnector 32 is a plate-like member for electrically connecting an external power source or another electrolytic cell to the electrolytic cell 1 in series. The interconnector 32 is joined to the frame 31.

[0073] In this embodiment, the frame body 31 and the interconnector 32 are separate members, but the frame body 31 and the interconnector 32 may be an integrated member.

[0074] (Detailed Structure of Gas Diffusion Layer 5) The detailed structure of the gas diffusion layer 5 will be described with reference to Fig. 3. Fig. 3 is a partially enlarged view of Fig. 2.

[0075] The gas diffusion layer 5 has a main body portion 5a and protruding portions 5b.

[0076] The main body portion 5a is a portion of the gas diffusion layer 5 that is sandwiched between the metal support 10 and the hydrogen electrode layer 6. The main body portion 5a is connected to the first main surface 12 of the metal support 10 and the surface 61 of the hydrogen electrode layer 6 that faces the metal support.

[0077] The protrusion 5b is continuous with the main body 5a. The protrusion 5b is formed integrally with the main body 5a. The protrusion 5b protrudes from the main body 5a into the communicating hole 11. The protrusion 5b covers a portion of the inner circumferential surface 14 of the communicating hole 11. Specifically, the protrusion 5b continuously covers the region of the inner circumferential surface 14 of the communicating hole 11 on the hydrogen electrode layer 6 side.

[0078] In this way, the protrusions 5b cover part of the inner circumferential surface 14 of the communication holes 11, thereby suppressing distortion of the communication holes 11 and thereby suppressing damage (cracks and peeling) to the gas diffusion layer 5. Furthermore, suppressing distortion of the communication holes 11 also suppresses warping of the cell main body 20, thereby suppressing cracks in the cell main body 20.

[0079] The main body portion 5a and the protruding portion 5b do not necessarily have to be strictly separated, but can be separated using a reference line L1 as a reference. The reference line L1 is a straight line that passes through the inner end Q1 of the metal support 10 and is parallel to the thickness direction. When the inner circumferential surface 14 is defined as the region of the metal support 10 that faces each other across the communication hole 11 in a cross section along the thickness direction, the inner end Q1 of the metal support 10 is the position on the inner circumferential surface 14 that is closest to the hydrogen electrode layer 6. The portion of the gas diffusion layer 5 on the opposite side of the reference line L1 from the through hole 51 is the main body portion 5a, and the portion of the gas diffusion layer 5 on the side of the reference line L1 facing the through hole 51 is the protruding portion 5b.

[0080] 3, the protrusion 5b is preferably tapered in the thickness direction away from the main body 5a. That is, the protrusion 5b preferably becomes thinner in the thickness direction as it penetrates deeper into the communicating hole 11. This prevents stress from concentrating at the tip of the protrusion 5b in the thickness direction, thereby preventing the protrusion 5b from peeling off from the inner circumferential surface 14 of the communicating hole 11.

[0081] 3, the protrusion 5b preferably covers a part of the metal support side surface 61 of the hydrogen electrode layer 6. This allows the protrusion 5b to be sandwiched between the inner circumferential surface 14 of the communicating hole 11 and the metal support side surface 61 of the hydrogen electrode layer 6, thereby improving the strength of the protrusion 5b.

[0082] Furthermore, when the protrusion 5b covers a part of the metal support side surface 61 of the hydrogen electrode layer 6, the protrusion 5b is preferably tapered in the planar direction away from the main body 5a, as shown in Fig. 3. This prevents stress from concentrating at the tip of the protrusion 5b in the planar direction, thereby preventing the protrusion 5b from peeling off from the metal support side surface 61 of the hydrogen electrode layer 6.

[0083] Furthermore, when the protruding portion 5 b covers a part of the metal support side surface 61 of the hydrogen electrode layer 6, the exposed surface 54 of the protruding portion 5 b exposed to the communicating hole 11 and the through-hole 51 is preferably curved as shown in Fig. 3. This makes it possible to suppress localized stress concentration on the exposed surface 54, thereby suppressing the occurrence of cracks on the exposed surface 54.

[0084] The ratio of the covering width W in the thickness direction of the region of the inner circumferential surface 14 of the communicating hole 11 that is covered by the protrusion 5b to the thickness T in the thickness direction of the main body 5a is preferably equal to or greater than 10. This allows the protrusion 5b to further suppress distortion of the communicating hole 11. From this viewpoint, it is particularly preferable that the covering width W be equal to or greater than 10 μm.

[0085] The thickness T of the main body portion 5a is calculated by the following method. First, a cross section of the gas diffusion layer 5 along the thickness direction is exposed. Next, a backscattered electron image of the cross section is obtained at 3000x magnification using an SEM device (FE-SEM JSM-7900F, manufactured by JEOL Ltd.). Next, the thickness of the main body portion 5a is measured at three locations on the backscattered electron image that divide the main body portion 5a into four equal parts in the surface direction. The thickness T of the main body portion 5a is then calculated by arithmetically averaging the three measured values. The thickness T of the main body portion 5a can be, for example, 1 μm or more and 50 μm or less.

[0086] As shown in FIG. 3, the metal support 10 may have a substrate 10a and an oxide film 10b.

[0087] The substrate 10a is made of the above-mentioned metal material (such as Fe--Cr alloy steel or Ni--Cr alloy steel).

[0088] The oxide film 10b covers the surface of the substrate 10a. The oxide film 10b can be made of an oxide of an element constituting the substrate 10a. A typical example of such an oxide is chromium oxide.

[0089] The thickness of the first portion b1 of the oxide coating 10b exposed in the communicating hole 11 of the metal support 10 is preferably greater than the thickness of the second portion b2 of the oxide coating 10b facing the hydrogen electrode layer 6. This improves the strength of the region of the metal support 10 surrounding the communicating hole 11, thereby further suppressing distortion of the communicating hole 11.

[0090] The thickness of the first portion b1 is determined by arithmetically averaging the thicknesses of the first portion b1 measured at three positions that divide the first portion b1 into four equal parts in the thickness direction on a backscattered electron image at 3000 magnification, similar to the thickness T of the gas diffusion layer 5. Similarly, the thickness of the second portion b2 is determined by arithmetically averaging the thicknesses of the second portion b2 measured at three positions that divide the second portion b2 into four equal parts in the surface direction on a backscattered electron image at 3000 magnification.

[0091] Here, the gas diffusion layer 5 and the hydrogen electrode layer 6 each have a plurality of pores therein. The average pore size of the pores in the gas diffusion layer 5 is preferably smaller than the average pore size of the pores in the hydrogen electrode layer 6. In other words, the gas diffusion layer 5 preferably contains more pores with small diameters than the hydrogen electrode layer 6. This improves the gas diffusibility of the gas diffusion layer 5, thereby enabling smoother gas supply and discharge between the through-holes 51 and the hydrogen electrode layer 6 via the gas diffusion layer 5.

[0092] Furthermore, the porosity of the gas diffusion layer 5 is preferably larger than the porosity of the hydrogen electrode layer 6. That is, the volume ratio of the gas flow paths in the gas diffusion layer 5 is preferably larger than the volume ratio of the gas flow paths in the hydrogen electrode layer 6. This further improves the gas diffusibility of the gas diffusion layer 5, thereby enabling even smoother gas supply and discharge between the through-holes 51 and the hydrogen electrode layer 6 via the gas diffusion layer 5.

[0093] The average pore size and porosity of the gas diffusion layer 5 can be obtained as follows. First, the electrolytic cell 1 is heated to 750°C, and hydrogen is supplied to the gas diffusion layer 5 and the hydrogen electrode layer 6, thereby reducing the gas diffusion layer 5 and the hydrogen electrode layer 6. Next, the electrolytic cell 1 is cooled while maintaining the reducing atmosphere, and the electrolytic cell 1 is cut along the thickness direction to expose cross sections of the gas diffusion layer 5 and the hydrogen electrode layer 6. Next, the cross sections are precision-machined and then subjected to ion milling processing using an IM4000 manufactured by Hitachi High-Technologies Corporation. Next, an FE-SEM (Field Emission Scanning Electron Microscope) using an in-lens secondary electron detector is used to obtain an SEM image at a magnification sufficient to confirm pores (for example, 5,000 to 30,000 times). Next, image analysis is performed using HALCON image analysis software manufactured by MVTec (Germany) to obtain an analysis image in which the black areas (corresponding to pores) on the SEM image are highlighted. The average pore diameter in the gas diffusion layer 5 is calculated by arithmetically averaging the circle-equivalent diameters of each pore (the diameter of a circle having the same area as the pore). The porosity of the gas diffusion layer 5 is calculated by dividing the total area of ​​the pores (gas phase) by the area of ​​the entire analysis image (solid phase).

[0094] The average pore size and porosity of the hydrogen electrode layer 6 can be calculated in the same manner as for the gas diffusion layer 5 .

[0095] The gas diffusion layer 5 can be formed as follows. First, the base material 10a of the metal support 10 is prepared, and a paste containing a desired oxide is applied to the surface of the base material 10a. In this case, the thickness of the applied paste may be thicker in areas of the surface of the base material 10a other than those covered by the gas diffusion layer 5. Next, a pore-forming material corresponding to the shape of the protrusions 5b is packed into the through-holes 11 of the metal support 10. Next, a paste containing the constituent materials of the gas diffusion layer 5 is applied to the first main surface 12 of the metal support 10, thereby forming a compact of the gas diffusion layer 5. Next, the hydrogen electrode layer 6 is placed on the compact of the gas diffusion layer 5, and the resulting mixture is fired (800 to 1500°C, 1 to 5 hours), thereby forming the gas diffusion layer 5 having the main body 5a and the protrusions 5b.

[0096] (Modifications of the Embodiment) Although the embodiment of the present invention has 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.

[0097] (Variation 1) In the above embodiment, as shown in Fig. 3, the communicating holes 11 of the metal support 10 are formed to have a tapered shape in the thickness direction toward the hydrogen electrode layer 6, but the cross-sectional shape of the communicating holes 11 can be modified as appropriate. The communicating holes 11 of the metal support 10 may be formed linearly along the thickness direction as shown in Fig. 4, or may be formed to have a tapered shape in the thickness direction away from the hydrogen electrode layer 6 as shown in Fig. 5.

[0098] (Variation 2) In the above embodiment, the electrolysis cell 1 has been described as an example of an electrochemical cell, but the electrochemical cell is not limited to an electrolysis 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 include, for example, fuel cells that use oxide ions or protons as carriers.

[0099] REFERENCE SIGNS LIST 1 Electrolysis cell 10 Metal support 11 Communication hole 12 First main surface 13 Second main surface 14 Inner peripheral surface 20 Cell main body 5 Gas diffusion layer 51 Through hole 52 First connection surface 53 Second connection surface 54 Exposed surface 6 Hydrogen electrode layer 61 Metal support side surface 7 Electrolyte layer 71 Hydrogen electrode layer side surface 8 Reaction prevention layer 9 Oxygen electrode layer 30 Flow path member 30a Flow path

Claims

1. An electrochemical cell comprising: a metal support having a plurality of communication holes formed in a main surface; and a cell main body portion disposed on the main surface, wherein the cell main body portion has: a gas diffusion layer disposed on the main surface; a first electrode layer and a second electrode layer disposed on the gas diffusion layer; and an electrolyte layer disposed between the first electrode layer and the second electrode layer, wherein the gas diffusion layer has a main body portion sandwiched in the gap between the metal support and the first electrode layer, and a protrusion portion protruding from the main body portion into the communication hole, and the protrusion portion covers a portion of the inner circumferential surface of the communication hole.

2. The electrochemical cell according to claim 1, wherein the protrusion is tapered in the thickness direction in a direction away from the main body.

3. The electrochemical cell according to claim 1 or 2, wherein the protrusion covers a part of the surface of the first electrode layer facing the metal support.

4. The electrochemical cell according to claim 3, wherein the protrusion is tapered in a direction away from the main body in a plane direction perpendicular to the thickness direction.

5. The electrochemical cell according to claim 3, wherein the protrusion has an exposed surface exposed to the communicating hole and the through-hole, and the exposed surface is curved.

6. The electrochemical cell according to claim 1, wherein the ratio of the coverage width in the thickness direction of the region of the inner circumferential surface of the communicating hole that is covered by the protrusion to the thickness in the thickness direction of the main body is 10 or more.

7. The electrochemical cell according to claim 1, wherein the coverage width in the thickness direction of the region of the inner circumferential surface of the communicating hole that is covered by the protrusion is 10 μm or more.

8. The electrochemical cell according to claim 1, wherein the metal support has a base material and an oxide film covering the surface of the base material, and a first portion of the oxide film exposed in the communicating hole has a thickness greater than a second portion of the oxide film covered by the protruding portion.

9. The electrochemical cell according to claim 1, wherein the average pore size of the plurality of pores in the gas diffusion layer is smaller than the average pore size of the plurality of pores in the first electrode layer.

10. The electrochemical cell according to claim 9, wherein the porosity of the gas diffusion layer is greater than the porosity of the first electrode layer.

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