ELECTROCHEMICAL CELL

Abstract

An electrolysis cell (1) comprises a metal substrate (10) and a cell body (20). The cell body (20) has a gas diffusion layer (5) arranged on a first main surface (12) of the metal substrate (10). The metal substrate (10) has a gas-permeable region (10a) with a plurality of supply holes (11) and a non-gas-permeable region (10b) surrounding the gas-permeable region (10a) in plan view. The gas diffusion layer (5) has a first region (5a) formed on the gas-permeable region (10a) and a second region (5b) formed on the non-gas-permeable region (10b). The second region (5b) has a crack-preventing space (5c) in a cross-section along a thickness direction.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electrochemical cell. STATE OF THE ART

[0002] Conventional electrochemical cells (electrolysis cells, fuel cells, etc.) are known that comprise a cell body disposed on a metal substrate. The metal substrate has a plurality of vias formed in one major surface thereof. The cell body comprises a first electrode layer formed on the major surface of the metal substrate, a second electrode layer, and an electrolyte layer disposed between the first electrode layer and the second electrode layer.

[0003] Here, Patent Document 1 describes the insertion of an electrically conductive gas diffusion layer between a cell body and a metal substrate. STATE OF THE ARTPatent literature

[0004] Patent literature 1: WO 2021 / 221052 SUMMARYTECHNICAL TASK

[0005] However, in the electrochemical cell described in Patent Document 1, there is a concern that a crack in the gas diffusion layer may be caused by stress occurring between the metal substrate and the gas diffusion layer due to a difference in thermal expansion coefficient between the metal substrate and the cell body.

[0006] An object of the present invention is to provide an electrochemical cell capable of preventing a crack from occurring in the gas diffusion layer. SOLUTION TO THE TASK

[0007] An electrochemical cell according to a first aspect of the present invention comprises: a metal substrate having a main surface and a plurality of via holes formed in the main surface; and a cell body disposed on the main surface. The cell body includes: a gas diffusion layer disposed on the main surface, the gas diffusion layer being electrically conductive; a first electrode layer disposed on the gas diffusion layer; a second electrode layer; and an electrolyte layer disposed between the first electrode layer and the second electrode layer. The metal substrate includes: a gas-permeable region in which the plurality of via holes are formed; and a gas-non-permeable region surrounding the gas-permeable region in plan view.The gas diffusion layer includes a first region formed on the gas-permeable region; and a second region formed on the gas-impermeable region. The second region has a crack-preventing space in a cross-section along a thickness direction.

[0008] An electrochemical cell according to a second aspect of the present invention is the electrochemical cell of the first aspect, wherein the crack-preventing space is located in cross section on an opposite side of the first region relative to a center of the second region in a surface direction perpendicular to the thickness direction.

[0009] An electrochemical cell according to a third aspect of the present invention is the electrochemical cell of the first or second aspect, wherein a width of the crack-preventing space in cross section in a surface direction perpendicular to the thickness direction is 20% or more and 60% or less of a total width of the second region in the surface direction perpendicular to the thickness direction.

[0010] An electrochemical cell according to a fourth aspect of the present invention is the electrochemical cell of the third aspect, wherein the crack-preventing space extends in cross section in the surface direction perpendicular to the thickness direction.

[0011] An electrochemical cell according to a fifth aspect of the present invention is the electrochemical cell of any one of the first to fourth aspects, wherein an inner end surface, which is a portion on the first region side of an inner surface of the crack-preventing space, is cantilevered in cross section to form a curved shape toward the first region.

[0012] An electrochemical cell according to a sixth aspect of the present invention is the electrochemical cell of any of the first to fifth aspects, wherein the second region has a plurality of the crack-preventing spaces. The second region, in a plan view of the second region, has a large-quantity region containing a large number of the crack-preventing spaces and a small-quantity region containing a small number of the crack-preventing spaces. The large-quantity region and the small-quantity region are adjacent to each other along an outer edge of the second region. BENEFICIAL EFFECTS

[0013] According to the present invention, it is possible to provide an electrochemical cell capable of preventing a crack from occurring in the gas diffusion layer. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of an electrolytic cell according to one embodiment. Fig. 2 shows an AA cross section of Fig. 1. Fig. 3 is an enlarged partial view of Fig. 2. Fig. 4 is an enlarged partial view of Fig. 2. Fig. 5 is a plan view of the electrolytic cell according to the embodiment from which a hydrogen electrode layer, an electrolyte layer, a reaction-preventing layer, and an oxygen electrode layer are removed. DESCRIPTION OF THE EMBODIMENTS Electrolysis cell 1

[0014] Fig. 1 is a plan view of an electrolysis cell 1 according to an embodiment. Fig. 2 shows an AA cross section of Fig. 1. Fig. 2 shows a cross section passing through a geometric center CP of a metal substrate 10 in plan view.

[0015] Electrolysis cell 1 is an example of an "electrochemical cell" according to the present invention. Electrolysis cell 1 is a so-called metal-supported electrolysis cell.

[0016] The electrolytic cell 1 has a plate shape extending in an X-axis direction and a Y-axis direction. The electrolytic cell 1 in the present embodiment has a rectangular shape elongated in the Y-axis direction in a plan view from a Z-axis direction perpendicular to the X-axis direction and the Y-axis direction. However, the plan view shape of the electrolytic cell 1 is not particularly limited and may alternatively be other than a rectangular shape, and may be a polygonal shape, an elliptical shape, a circular shape, or the like.

[0017] As in Fig. 2, the electrolysis cell 1 comprises a metal substrate 10, a cell body 20 and a channel element 30. Metal substrate 10

[0018] The metal substrate 10 supports the cell body 20. The metal substrate 10 has a plate shape. The metal substrate 10 can have a flat plate shape or a curved plate shape.

[0019] The metal substrate 10 only needs to be able to support the cell body 20. The thickness of the metal substrate 10 is not particularly limited, but may be, for example, 0.1 mm or more and 2.0 mm or less.

[0020] As in Fig. 2, the metal substrate 10 has a plurality of connection holes 11, a first main surface 12 and a second main surface 13.

[0021] Each connection hole 11 extends through the metal substrate 10 from the first main surface 12 to the second main surface 13. Each connection hole 11 is open in the first main surface 12 and the second main surface 13. In the present embodiment, the opening of each connection hole 11 in the first main surface 12 is covered by a gas diffusion layer 5 described later. The opening of each connection hole 11 in the second main surface 13 is continuous with a channel 30a described later.

[0022] The connecting holes 11 can be formed by mechanical processing (e.g., punching), laser processing, chemical processing (e.g., etching), or the like.

[0023] Each connection hole 11 in the present embodiment has a straight shape extending along the Z-axis direction. However, each connection hole 11 may be inclined relative to the Z-axis direction and does not necessarily have a straight shape. The connection holes 11 may be continuous with each other.

[0024] The first main surface 12 is an example of a "main surface" according to the present invention. The first main surface 12 is provided on the opposite side to the second main surface 13. The cell body 20 is arranged on the first main surface 12. The channel element 30 is connected to the second main surface 13.

[0025] As in Fig. As shown in Figure 2, the metal substrate 10 has a gas-permeable region 10a and a non-gas-permeable region 10b. The gas-permeable region 10a is a region in the metal substrate 10 in which a plurality of supply holes 11 are formed. The non-gas-permeable region 10b is a region in the metal substrate 10 that excludes the gas-permeable region 10a. The non-gas-permeable region 10b surrounds the gas-permeable region 10a in a plan view from the Z-axis direction. Thus, in the cross-section of the metal substrate 10 along the Z-axis direction, the non-gas-permeable region 10b appears on both sides of the gas-permeable region 10a, as shown in Figure 2. Fig. 2 shown.

[0026] The boundary between the gas-permeable region 10a and the non-gas-permeable region 10b is defined by first and second supply holes 11a and 11b located on the outermost sides in the X-axis direction, as shown in Fig. 2. In particular, the boundary between the gas-permeable region 10a and the non-gas-permeable region 10b is defined by a first reference line 11S and a second reference line 11T.

[0027] The first reference line 11S is a straight line passing through an outermost position P1 in the X-axis direction of an opening on the first main surface 12 side of the first supply hole 11a located at an outermost position in the X-axis direction, and is parallel to the Z-axis direction (ie, perpendicular to the first main surface 12 in Fig. 2).

[0028] The second reference line 11T is a straight line passing through an outermost position P2 in the X-axis direction of an opening on the first main surface 12 side of the second supply hole 11b, which is farthest from the first supply hole 11a in the X-axis direction, and is parallel to the Z-axis direction (ie, perpendicular to the first main surface 12 in Fig. 2).

[0029] The gas-permeable region 10a is a region between the first reference line 11S and the second reference line 11T in the metal substrate 10, and the non-gas-permeable region 10b is a region in the metal substrate 10 excluding the gas-permeable region 10a, that is, a region including portions on both sides of the gas-permeable region 10a.

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

[0031] The metal substrate 10 may also contain Ti (titanium) and / or Zr (zirconium). The Ti content in the metal substrate 10 is not particularly limited, but may be 0.01 mol% or more and 1.0 mol% or less. The Al content in the metal substrate 10 is not particularly limited, but may be 0.01 mol% or more and 0.4 mol% or less. The metal substrate 10 may contain Ti in the form of TiO2 (titanium dioxide) and Zr in the form of ZrO2 (zirconium dioxide).

[0032] The metal substrate 10 may have an oxide film on one surface thereof, which is formed by oxidation of components of the metal substrate 10. A typical oxide film is, for example, a chromium oxide film. The chromium oxide film covers at least a portion of the surface of the metal substrate 10. The chromium oxide film may also cover at least a portion of an inner wall surface of each connection hole 11. Cell body 20

[0033] The cell body 20 is arranged on the metal substrate 10. The cell body 20 is supported by the metal substrate 10. The cell body 20 has a gas diffusion layer 5, a hydrogen electrode layer 6 (cathode), an electrolyte layer 7, a reaction-preventing layer 8, and an oxygen electrode layer 9 (anode).

[0034] The gas diffusion layer 5, the hydrogen electrode layer 6, the electrolyte layer 7, the reaction-preventing layer 8, and the oxygen electrode layer 9 are stacked in this order from the side of the metal substrate 10 in the Z-axis direction. The gas diffusion layer 5, the hydrogen electrode layer 6, the electrolyte layer 7, and the oxygen electrode layer 9 are essential components, and the reaction-preventing layer 8 is an optional component. Gas diffusion layer 5

[0035] The gas diffusion layer 5 is disposed on the first main surface 12 of the metal substrate 10. The gas diffusion layer 5 is sandwiched between the metal substrate 10 and the hydrogen electrode layer 6. The gas diffusion layer 5 in the present embodiment covers the via holes 11 in the metal substrate 10. The gas diffusion layer 5 may be partially located within the via holes 11 of the metal substrate 10.

[0036] The gas diffusion layer 5 is an electrically conductive porous body with gas diffusion properties. The gas diffusion layer 5 supplies a source gas supplied from the via holes 11 to the hydrogen electrode layer 6 and discharges a gas generated in the hydrogen electrode layer 6 through the via holes 11. The gas diffusion layer 5 has a large number of micropores. The pore diameter of each micropore is not particularly limited, but can be, for example, 0.01 μm or more and 1 μm or less.

[0037] The gas diffusion layer 5 contains an electrically conductive material. The electrically conductive material can be a metallic material, such as Ni (nickel) or Fe (iron), or an electrically conductive ceramic material.

[0038] The gas diffusion layer 5 may also contain a base material supporting the electrically conductive material. The base material may be insulating. The base material may be YSZ, CSZ, ScSZ, GDC, SDC, (La, Sr)(Cr, Mn)O3, (La, Sr)TiO3, Sr2(Fe, Mo)2O6, (La, Sr)VO3, (La, Sr)FeO3, LDC (lanthanum-doped cerium oxide), LSGM (lanthanum gallate), or a mixed material of two or more of these materials.

[0039] The gas diffusion layer 5 may contain a metallic element contained in the metal substrate 10. This brings the gas diffusion layer 5 and the metal substrate 10 into closer contact and is therefore preferable. Note that the above-mentioned electrically conductive material is different from the metallic element contained in the metal substrate 10. Accordingly, the electrically conductive material contained in the gas diffusion layer 5 does not need to be contained in the metal substrate 10.

[0040] The porosity of the gas diffusion layer 5 is not particularly limited, but may be, for example, 20% or more and 40% or less.

[0041] The porosity of the gas diffusion layer 5 is calculated by the following method. First, a cross-section of the gas diffusion layer 5 is exposed along the Z-axis direction. Next, a backscattered electron image of the cross-section of the gas diffusion layer 5 is acquired at a magnification of 1000x using an SEM device (FE-SEM JSM-7900F, manufactured by JEOL Ltd.). Next, the black-displayed portions (corresponding to pores) in the backscattered electron image are identified using the image analysis software Image-Pro, manufactured by MEDIACYBERNETICS. Then, the porosity of the gas diffusion layer 5 is calculated by dividing the total area of ​​the pores by the total area of ​​the backscattered electron image of the gas diffusion layer 5.

[0042] The thickness of the gas diffusion layer 5 is not particularly limited, but may be, for example, 1 μm or more and 50 μm or less. The term "thickness" as used herein means the thickness in the thickness direction of the cell body 20. The term "thickness direction" refers to a direction perpendicular to a surface direction parallel to the first main surface 12 of the metal substrate 10. The thickness direction is identified using an approximate straight line of the first main surface 12 obtained by the least squares method in a cross-section of the metal substrate 10 along the Z-axis direction.

[0043] As in Fig. 2, the gas diffusion layer 5 has a first region 5a and a second region 5b. The first region 5a is a region in the gas diffusion layer 5 that is formed on the gas-permeable region 10a of the metal substrate 10. The second region 5b is a region in the gas diffusion layer 5 that is formed on the gas-impermeable region 10b of the metal substrate 10. The second region 5b surrounds the first region 5a in a plan view from the Z-axis direction. Thus, in the cross-section of the gas diffusion layer 5 along the Z-axis direction, the second region 5b appears on both sides of the first region 5a, as shown in Fig. 2 shown.

[0044] The boundary between the first region 5a and the second region 5b is defined by the above-mentioned first reference line 11S and second reference line 11T. The first region 5a is a region between the first reference line 11S and the second reference line 11T in the gas diffusion layer 5, and the second region 5b is a region in the metal substrate 5 excluding the first region 5a, that is, a region including portions on both sides of the first region 5a.

[0045] Here is Fig. 3 an enlarged partial view of Fig. 2. Fig. 3 shows a cross section of the second region 5b passing through a geometric center CP of the metal substrate 10 and taken along the thickness direction of the cell body 20.

[0046] As in Fig. As shown in FIG. 3, the second region 5b has a crack-preventing space 5c. The crack-preventing space 5c is a hollow space within the second region 5b. A crack can be prevented from occurring in the gas diffusion layer 5 by providing this crack-preventing space 5c in the second region 5b in the following manner. First, stress occurs in the surface direction between the metal substrate 10 and the gas diffusion layer 5 due to a difference in thermal expansion coefficient between the metal substrate 10 and the cell body 20. This stress may cause a crack that starts from the vicinity of an outer end surface 5S of the gas diffusion layer 5 and extends inward (i.e., toward the first region 5a).However, when the crack reaches the crack-preventing space 5c, the stress that caused the crack can be absorbed by the crack-preventing space 5c, and therefore it is possible to prevent the crack from growing beyond the crack-preventing space 5c.

[0047] It is preferable that the crack-preventing space 5c is located on the opposite side of the first region 5a relative to a center CL of the second region 5b in the surface direction, as shown in Fig. 3. That is, it is preferable that the crack-preventing space 5c be located near an outer edge of the second region 5b. This can quickly stop the growth of the crack originating from the vicinity of the outer end surface 5S of the gas diffusion layer 5. Therefore, even if a crack occurs, the crack can be prevented from elongating.

[0048] It is preferable that a width Wc of the crack-preventing space 5c in the surface direction be 20% or more and 60% or less of a total width Wb of the second region 5b in the surface direction. The width Wc of the crack-preventing space 5c being 20% ​​or more of the total width Wb of the second region 5b allows the crack-preventing space 5c to reliably absorb the stress that caused a crack. The width Wc of the crack-preventing space 5c being 60% or less of the total width Wb of the second region 5b can ensure the strength of the second region 5b.

[0049] Note that the value of the width Wc of the crack-preventing space 5c is not particularly limited, but may be, for example, 5 μm or more and 500 μm or less. The value of the width Wb of the second region 5b is not particularly limited, but may be, for example, 20 μm or more and 2000 μm or less. The equivalent circle diameter of the crack-preventing space 5c is not particularly limited, but may be, for example, 5 μm or more and 500 μm or less. The equivalent circle diameter is the diameter of a circle having the same area as the crack-preventing space 5c in a cross section of the second region 5b.

[0050] It is preferable that the crack-preventing space 5c is elongated in the surface direction as shown in Fig. 3. That is, it is preferable that the width Wc of the crack-preventing space 5c in the surface direction be greater than a height Tc of the crack-preventing space 5c in the thickness direction. This makes it easier for the crack-preventing space 5c to absorb the stress that occurs in the surface direction between the metal substrate 10 and the gas diffusion layer 5. Therefore, it is possible to prevent the crack from growing beyond the crack-preventing space 5c.

[0051] It should be noted that the value of the height Tc of the crack-preventing space 5c is not particularly limited, but may be, for example, 1 µm or more and 50 µm or less.

[0052] It is preferable that an inner end surface Sc, which is a portion on the first region 5a side of the inner surface of the crack-preventing space 5c, is projected to form a curved shape toward the first region 5a, as shown in Fig. 3. This makes it easier for the inner end face Sc to absorb the stress occurring in the surface direction between the metal substrate 10 and the gas diffusion layer 5, compared to the case where the inner end face Sc has a straight shape. It is therefore possible to prevent the crack from growing beyond the crack-preventing space 5c.

[0053] It is preferable that the crack-preventing space 5c is separated from the outer end face 5S of the gas diffusion layer 5, as shown in Fig. 3. That is, it is preferable that the crack-preventing space 5c is not exposed from the outer end surface 5S. This can ensure the strength of the gas diffusion layer 5.

[0054] The crack-preventing space 5c in the present embodiment is separated from the hydrogen electrode layer 6 and the metal substrate 10, as shown in Fig. 3, but may alternatively be in contact with at least either the hydrogen electrode layer 6 or the metal substrate 10. For example, the crack-preventing space 5c may be in contact with the hydrogen electrode layer 6 and the metal substrate 10, as shown in Fig. 4. That is, the crack-preventing space 5c can extend through the gas diffusion layer 5 in the thickness direction. In this case, it is possible to reliably prevent a crack from growing across gaps between the hydrogen electrode layer 6 and the crack-preventing space 5c and between the metal substrate 10 and the crack-preventing space 5c.

[0055] Here is Fig. 5 is an enlarged plan view of the electrolytic cell 1 in which the hydrogen electrode layer 6, the electrolyte layer 7, the reaction-preventing layer 8 and the oxygen electrode layer 9 are removed from the cell body 20.

[0056] The second area 5b contains, in plan view of the second area 5b, a plurality of crack-preventing spaces 5c, as in Fig. 5 shown.

[0057] The second area 5b may comprise a large quantity area M1 and a small quantity area M2, as shown in Fig. 5. The large quantity region M1 and the small quantity region M2 are adjacent to each other along an outer edge 5d of the second region 5b.

[0058] The large-quantity region M1 is a region in the second region 5b that contains a large number of crack-preventing spaces 5c. The small-quantity region M1 is a region in the second region 5b that contains a small number of crack-preventing spaces 5c.

[0059] As used herein, "including a large number of crack-preventing spaces 5c" means that there are 10 or more crack-preventing spaces 5c per unit area (1 cm2). "Including a small number of crack-preventing spaces 5c" means that there are fewer than 10 crack-preventing spaces 5c per unit area (1 cm2) or no crack-preventing space 5c.

[0060] Cracking can be prevented in the second region 5b by providing the large-quantity region M1 at portions of the second region 5b where particularly large stress occurs (particularly corners). Furthermore, the strength of the second region 5b can be ensured by providing the small-quantity region M2 at portions other than the large-quantity region M1. Therefore, it is possible to both prevent cracking and ensure strength by appropriately disposing the large-quantity region M1 and the small-quantity region M2.

[0061] The number, position and size of the large quantity area M1 and the small quantity area M2 can be set appropriately.

[0062] The method for forming the gas diffusion layer 5 is not particularly limited and may be a sintering method, a spray coating method, a PVD method, a CVD method, or the like. For example, in the case of forming the gas diffusion layer 5 by the sintering method, a compact of the gas diffusion layer 5 can be formed by applying a slurry containing the constituent material of the gas diffusion layer 5 to the gas-permeable region 10a of the metal substrate 10, and then applying a slurry containing a pore former and the constituent material of the gas diffusion layer 5 to the gas-permeable region 10a of the metal substrate 10. The crack-preventing space 5c is formed in the second region 5b as a result of the pore former disappearing in the process of sintering the compact of the gas diffusion layer 5.

[0063] In the case of providing the large amount region M1 and the small amount region M2 in the second region 5b, it is possible that a slurry containing a large amount of pore-forming agent and a slurry containing a small amount of pore-forming agent (or a slurry containing no pore-forming agent) are prepared and each type of slurry is applied separately to the gas-permeable region 10a of the metal substrate 10. Hydrogen electrode layer 6

[0064] The hydrogen electrode layer 6 is an example of a "first electrode layer" according to the present invention. The hydrogen electrode layer 6 is formed on the gas diffusion layer 5. The hydrogen electrode layer 6 is arranged between the gas diffusion layer 5 and the electrolyte layer 7.

[0065] The starting gas is supplied to the hydrogen electrode layer 6 from the connecting holes 11 via the gas diffusion layer 5. The starting gas contains at least H2O.

[0066] When the starting gas contains only H2O, the hydrogen electrode layer 6 generates H2 from the starting gas according to the electrochemical reaction of water electrolysis, which is expressed by the following chemical equation (1). Hydrogen electrode layer 6: H2O + 2e - → H2 + O 2- (1)

[0067] If the starting gas contains CO2 in addition to H2O, the hydrogen electrode layer 6 produces H2, CO and O 2- from the starting gas according to the electrochemical reaction of co-electrolysis, which is expressed by the following chemical equations (2), (3) and (4). Hydrogen electrode layer 6: CO2 + H2O + 4e - → CO + H2 + 2O 2- (2) Electrochemical reaction of H2O: H2O + 2e- → H2 + O 2- (3) Electrochemical reaction of CO2: CO2 + 2e - → CO + O 2- (4)

[0068] The hydrogen electrode layer 6 is an electrically conductive porous body with gas diffusion properties. The starting gas is supplied to the hydrogen electrode layer 6 from the gas diffusion layer 5. A gas generated in the hydrogen electrode layer 6 is discharged toward the gas diffusion layer 5.

[0069] The hydrogen electrode layer 6 contains an electrically conductive material. The electrically conductive material can be a metallic material, such as Ni (nickel) or Fe (iron), or an electrically conductive ceramic material. In the case of co-electrolysis, Ni also acts as a thermal catalyst to promote the thermal reaction between the generated H2 and the CO2 contained in the feed gas, maintaining a gas composition suitable for methanation, reverse water-gas shift reactions, or the like.

[0070] The electrically conductive material is present in an oxide state (e.g., NiO) in an oxidizing atmosphere and in a metallic state (e.g., Ni) in a reducing atmosphere. The present embodiment provides that the electrolysis cell 1 is exposed to a reducing atmosphere.

[0071] The hydrogen electrode layer 6 contains an oxide ion conductive material. The oxide ion conductive material may be YSZ, CSZ, ScSZ, GDC, SDC, (La, Sr)(Cr, Mn)O3, (La, Sr)TiO3, Sr2(Fe, Mo)2O6, (La, Sr)VO3, (La, Sr)FeO3, LDC, LSGM, or a mixed material of two or more of these materials.

[0072] In the present embodiment, the hydrogen electrode layer 6 has a single-layer structure formed by a single composition, but may alternatively have a multi-layer structure formed by different compositions.

[0073] The porosity of the hydrogen electrode layer 6 is not particularly limited, but may be, for example, 20% or more and 40% or less. The porosity of the hydrogen electrode layer 6 is calculated by dividing the total area of ​​the pores by the total area of ​​the backscattered electron image of the hydrogen electrode layer 6, similar to the porosity of the gas diffusion layer 5 mentioned above.

[0074] The thickness of the hydrogen electrode layer 6 is not particularly limited, but may be, for example, 1 µm or more and 500 µm or less.

[0075] The method for forming the hydrogen electrode layer 6 is not particularly limited and may be a sintering method, a spray coating method, a PVD method, a CVD method, or the like. Electrolyte layer 7

[0076] The electrolyte layer 7 is disposed between the hydrogen electrode layer 6 and the oxygen electrode layer 9. In the present embodiment, the reaction-preventing layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9, and the electrolyte layer 7 is therefore disposed between the hydrogen electrode layer 6 and the reaction-preventing layer 8.

[0077] The electrolyte layer 7 covers the hydrogen electrode layer 6 and also covers a portion of the first main surface 12 of the metal substrate 10 exposed by the gas diffusion layer 5.

[0078] The electrolyte layer 7 transfers O 2-, which is generated in the hydrogen electrode layer 6, toward the oxygen electrode layer 9. The electrolyte layer 7 is made of an oxide ion-conductive dense material. The electrolyte layer 7 can be made of, for example, YSZ (yttria-stabilized zirconia; e.g., 8YSZ), GDC (gadolinium-doped cerium oxide), ScSZ (scandium oxide-stabilized zirconia), SDC (samarium solid solution cerium oxide), LSGM (lanthanum gallate), or the like.

[0079] The porosity of the electrolyte layer 7 is not particularly limited, but may be, for example, 0.1% or more and 7% or less. The thickness of the electrolyte layer 7 is not particularly limited, but may be, for example, 1 μm or more and 100 μm or less.

[0080] The method for forming the electrolyte layer 7 is not particularly limited and may be a sintering method, a spray coating method, a PVD method, a CVD method, or the like. Reaction-preventing layer 8

[0081] The reaction-preventing layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9. The reaction-preventing layer 8 is disposed on the opposite side to the hydrogen electrode layer 6 with respect to the electrolyte layer 7. The reaction-preventing layer 8 prevents a component of the electrolyte layer 7 from reacting with a component of the oxygen electrode layer 9 to form a high-electrical-resistance layer.

[0082] The reaction-preventing layer 8 is formed by an oxide-ion conductive material. The reaction-preventing layer 8 can be made of GDC, SDC, or the like.

[0083] The porosity of the reaction-preventing layer 8 is not particularly limited, but may be, for example, 0.1% or more and 50% or less. The thickness of the reaction-preventing layer 8 is not particularly limited, but may be, for example, 1 μm or more and 50 μm or less.

[0084] The method for forming the reaction-preventing layer 8 is not particularly limited and may be a sintering method, a spray coating method, a PVD method, a CVD method, or the like. Oxygen electrode layer 9

[0085] 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 to the hydrogen electrode layer 6 with respect to the electrolyte layer 7. In the present embodiment, the reaction-preventing layer 8 is disposed between the electrolyte layer 7 and the oxygen electrode layer 9, and the oxygen electrode layer 9 is therefore bonded to the reaction-preventing layer 8. When the reaction-preventing layer 8 is not disposed between the electrolyte layer 7 and the oxygen electrode layer 9, the oxygen electrode layer 9 is bonded to the electrolyte layer 7.

[0086] The oxygen electrode layer 9 generates O2 from O 2-which is transferred from the hydrogen electrode layer 6 via the electrolyte layer 7, according to the chemical reaction expressed by the following chemical equation (5). Oxygen electrode layer 9: 20 2- → O2 + 4e - ... (5)

[0087] The oxygen electrode layer 9 is an oxide ion-conductive and electrically conductive porous body. The oxygen electrode layer 9 can be made, for example, of a composite material comprising an oxide ion-conductive material (GDC, etc.) and at least one of (La, Sr)(Co, Fe)O3, (La, Sr)FeO3, La(Ni, Fe)O3, (La, Sr)CoO3, and (Sm, Sr)CoO3.

[0088] The porosity of the oxygen electrode layer 9 is not particularly limited, but may be, for example, 20% or more and 60% or less. The thickness of the oxygen electrode layer 9 is not particularly limited, but may be, for example, 1 μm or more and 100 μm or less.

[0089] The method for forming the oxygen electrode layer 9 is not particularly limited and may be a sintering method, a spray coating method, a PVD method, a CVD method, or the like. Channel element 30

[0090] The channel element 30 is connected to the second main surface 13 of the metal substrate 10. The channel element 30 forms a channel 30a between the channel element 30 and the metal substrate 10. The source gas is supplied to the channel 30a. The source gas supplied to the channel 30a is supplied to the hydrogen electrode layer 6 of the cell body 20 via the connection holes 11 in the metal substrate 10.

[0091] The channel element 30 may, for example, be made of an alloy material. The channel element 30 may be made of the same material as the metal substrate 10. In this case, the channel element 30 may be substantially integrated with the metal substrate 10.

[0092] The channel element 30 includes a frame 31 and a connector 32. The frame 31 is an annular element that surrounds the sides of the channel 30a. The frame 31 is connected to the second main surface 13 of the metal substrate 10. The connector 32 is a plate-shaped element for electrically connecting an external power source or another electrolysis cell in series with the electrolysis cell 1. The connector 32 is connected to the frame 31.

[0093] The frame 31 and the connector 32 in the present embodiment are separate members, but the frame 31 and the connector 32 may alternatively be an integrated member. Modifications of the embodiment

[0094] Although the embodiment of the present invention has been described above, the present invention is not limited thereto, and various changes may be made without departing from the gist of the invention. Variation 1

[0095] The crack-preventing space 5c in the above embodiment is located on the opposite side of the first region 5a relative to the center CL of the second region 5b in the surface direction, as shown in Fig. 3. However, this need not be the case. At least a portion of the crack-preventing space 5c may be located on the side of the first region 5a relative to the center CL of the second region 5b in the surface direction. Variation 2

[0096] The crack-preventing space 5c in the above embodiment extends in the surface direction as shown in Fig. 3. However, this need not be the case. The crack-preventing space 5c may alternatively extend in the thickness direction. That is, the width Wc of the crack-preventing space 5c in the surface direction may be smaller than the height Tc of the crack-preventing space 5c in the thickness direction. Variation 3

[0097] The inner end face Sc of the crack-preventing space 5c in the above embodiment is projected to form a curved shape toward the first region 5a as shown in Fig. 3. However, this need not be the case. Alternatively, at least a portion of the inner end surface Sc of the crack-preventing space 5c may be straight. Variation 4

[0098] The second region 5b in the above embodiment includes the large amount region M1 and the small amount region M2 as shown in Fig. 5. However, this need not be the case. In the case where the second region 5b has a plurality of crack-preventing spaces 5c, the crack-preventing spaces 5c may be uniformly arranged in a plan view of the second region 5b. Variation 5

[0099] In the present embodiment, the opening of each connection hole 11 in the metal substrate 10 on the first main surface 12 side is covered by the gas diffusion layer 5. However, this is not necessary. The gas diffusion layer 5 does not need to cover the opening of each connection hole 11 on the first main surface 12 side. In this case, the gas diffusion layer 5 has through holes connected to the respective connection holes 11, and the gas can thus be supplied and discharged more efficiently through these through holes. Variation 6

[0100] In the above embodiment, the electrolytic cell 1 was described as an example of an electrochemical cell. However, the electrochemical cell is not limited to an electrolytic cell. The term "electrochemical cell" is a general term for elements in which a pair of electrodes is arranged to generate electromotive force from the overall redox reaction to convert electrical energy into chemical energy, and elements for converting chemical energy into electrical energy. Accordingly, electrochemical cells include, for example, fuel cells that use oxide ions or protons as carriers. LIST OF REFERENCE SYMBOLS 1 electrolysis cell 10 Metal substrate 11 Connection hole 12 first main area 13 second main area 20 cell bodies 5 Gas diffusion layer 5S outer face of the gas diffusion layer 5a first area 5b second area 5c crack-preventing space Sc inner face of the crack-preventing space M1 area with large quantity M2 area with small amount 6 Hydrogen electrode layer 7 Electrolyte layer 8 reaction-preventing layer 9 Oxygen electrode layer 30 channel element 30a Canal

Claims

[1] Electrochemical cell comprising: a metal substrate having a main surface and a plurality of via holes formed in the main surface; and a cell body arranged on the main surface, where the cell body has: a gas diffusion layer disposed on the main surface, the gas diffusion layer being electrically conductive; a first electrode layer disposed on the gas diffusion layer; a second electrode layer, and an electrolyte layer disposed between the first electrode layer and the second electrode layer, wherein the metal substrate has a gas-permeable region in which the plurality of supply holes are formed, and a non-gas-permeable region surrounding the gas-permeable region in plan view, the gas diffusion layer has a first region formed on the gas-permeable region and a second region formed on the non-gas-permeable region, and the second region has a crack-preventing space in a cross-section along a thickness direction. [2] The electrochemical cell according to claim 1, wherein the crack-preventing space is located in cross section on an opposite side of the first region relative to a center of the second region in a surface direction perpendicular to the thickness direction. [3] The electrochemical cell according to claim 1 or 2, wherein a width of the crack-preventing space in cross section in a surface direction perpendicular to the thickness direction is 20% or more and 60% or less of a total width of the second region in the surface direction perpendicular to the thickness direction. [4] The electrochemical cell according to claim 3, wherein the crack-preventing space extends in cross section in the surface direction perpendicular to the thickness direction. [5] The electrochemical cell according to claim 1 or 2, wherein an inner end face, which is a portion on the first region side of an inner surface of the crack-preventing space, is cantilevered in cross section to form a curved shape toward the first region. [6] Electrochemical cell according to claim 1 or 2, wherein the second area has a large number of crack-preventing spaces, the second region, in a plan view of the second region, has a large quantity region containing a large number of the crack-preventing spaces and a small quantity region containing a small number of the crack-preventing spaces, and the large quantity area and the small quantity area are adjacent to each other along an outer edge of the second area.

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