Electrochemical cell

Abstract

An electrolytic cell (1) is provided with a metal support (10) and a cell body (20). The cell body (20) has a hydrogen electrode layer (6) covering each communication hole (11) formed on a first main surface (12) of the metal support (10). The hydrogen electrode layer (6) has a first region (61) within 5 μm in the thickness direction from a first surface (S1) in contact with the metal support (10), a second region (62) within 5 μm in the thickness direction from a second surface (S2) in contact with an electrolyte layer (7) and a third region (63) between the first region (61) and the second region (62). The first region (61), the second region (62) and the third region (63) each contain nickel and an oxide ion conductive material. The nickel content in the first region (61) is lower than the nickel content in the third region (63).

Description

electrochemical cell

[0001] The present invention relates to electrochemical cells.

[0002] BACKGROUND ART Conventionally, electrochemical cells (electrolysis cells, fuel cells, etc.) that include a cell body disposed on a metal support are known (see, for example, Patent Document 1).

[0003] The metal support has a plurality of communication holes formed in its main surface. The cell main body is formed on the main surface of the metal support and has a first electrode layer covering the plurality of communication holes, a second electrode layer, and an electrolyte layer disposed between the first and second electrode layers. The first electrode layer contains nickel as a metal for imparting conductivity. The nickel contained in the first electrode layer becomes nickel oxide in an oxidizing atmosphere and becomes metallic nickel in a reducing atmosphere.

[0004] JP 2020-155337 A

[0005] In the electrochemical cell described above, the first electrode layer expands and contracts due to the oxidation-reduction cycle. Specifically, when the first electrode layer is reduced before the electrochemical cell is operated, nickel oxide turns to metallic nickel, causing the first electrode layer to contract. When the operation of the electrochemical cell is stopped and the first electrode layer changes from a reducing atmosphere to an oxidizing atmosphere, the metallic nickel turns to nickel oxide, causing the first electrode layer to expand.

[0006] When the first electrode layer expands and contracts due to the oxidation-reduction cycle, the first electrode layer may peel off from the metal support.

[0007] An object of the present invention is to provide an electrochemical cell that can prevent the first electrode layer from peeling off from the metal support.

[0008] An electrochemical cell according to a first aspect of the present invention includes a metal support having a plurality of through holes formed in a main surface thereof, a first electrode layer formed on the main surface and covering the plurality of through holes, a second electrode layer, and an electrolyte layer disposed between the first and second electrode layers. The first electrode layer has a first region within 5 μm in the thickness direction from the first surface in contact with the metal support, a second region within 5 μm in the thickness direction from the second surface in contact with the electrolyte layer, and a third region between the first and second regions. The first, second, and third regions each contain nickel and an oxide ion conductive material. The nickel content in the first region is lower than the nickel content in the third region.

[0009] An electrochemical cell according to a second aspect of the present invention is the electrochemical cell according to the first aspect, wherein the nickel content in the second region is lower than the nickel content in the third region.

[0010] An electrochemical cell according to a third aspect of the present invention is the electrochemical cell according to the first or second aspect, wherein the nickel content in the second region is lower than the nickel content in the first region.

[0011] According to a fourth aspect of the present invention, there is provided an electrochemical cell according to any one of the first to fourth aspects, wherein the first electrode layer has a fourth region disposed inside at least one of the plurality of communicating holes, the fourth region containing nickel and an oxide ion conductive material, and the nickel content in the fourth region is lower than the nickel content in the third region.

[0012] According to the present invention, it is possible to provide an electrochemical cell that can prevent the first electrode layer from peeling off from the metal support.

[0013] Fig. 1 is a plan view of an electrolysis cell according to an embodiment. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. Fig. 2 is a partially enlarged view of Fig. 2. Fig. 4 is a cross-sectional view of an electrolysis cell 100 according to a first modification.

[0014] (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. The electrolytic cell 1 is an example of the "electrochemical cell" according to the present invention.

[0015] 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. The X-axis and Y-axis directions are each the surface direction of the electrolytic cell 1, and the Z-axis direction is the thickness direction of the electrolytic cell 1.

[0016] 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 .

[0017] [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.

[0018] The metal support 10 is only required to be able to support the electrolysis cell 1, and its thickness is not particularly limited, but can be, for example, 0.1 mm or more and 2.0 mm or less.

[0019] 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 .

[0020] Each communication hole 11 penetrates the metal support 10 from the first main surface 12 to the second main surface 13. Each communication hole 11 opens to both the first main surface 12 and the second main surface 13. The opening of each communication hole 11 on the first main surface 12 side is covered by the hydrogen electrode layer 6. The opening of each communication hole 11 on the second main surface 13 side is connected to a flow path 30a, which will be described later.

[0021] Each of the communication holes 11 can be formed by mechanical processing (for example, punching), laser processing, or chemical processing (for example, etching).

[0022] In this embodiment, each communication hole 11 is formed linearly 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.

[0023] 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.

[0024] 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.

[0025] 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 Al 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).

[0026] The metal support 10 may have an oxide film on its surface, which is formed by oxidation of the constituent elements of the metal support 10. A typical example of the oxide film is a chromium oxide film. The chromium oxide film covers at least a portion of the surface of the metal support 10. The chromium oxide film may also cover at least a portion of the inner wall surface of each communicating hole 11.

[0027] [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 hydrogen electrode layer 6 (cathode), an electrolyte layer 7, a reaction prevention layer 8, and an oxygen electrode layer 9 (anode).

[0028] The 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 hydrogen electrode layer 6, electrolyte layer 7, and oxygen electrode layer 9 are essential components, while the reaction prevention layer 8 is optional.

[0029] [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 between the metal support 10 and the electrolyte layer 7. The hydrogen electrode layer 6 is formed on the first main surface 12 of the metal support 10. In this embodiment, a portion of the hydrogen electrode layer 6 is disposed inside each of the communication holes 11 of the metal support 10. The detailed configuration of the hydrogen electrode layer 6 will be described later.

[0030] A source gas is supplied to the hydrogen electrode layer 6 through each of the communication holes 11. The source gas contains at least H ２ Contains O.

[0031] 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.

[0032] Hydrogen electrode layer 6: H ２ O + 2e － →H ２ +O ２－ ...(1)

[0033] 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.

[0034] 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)

[0035] The hydrogen electrode layer 6 is an electron-conductive porous body containing nickel (Ni) and an oxide ion conductive material.

[0036] Ni acts as an electron conductor. In the case of co-electrolysis, Ni acts as an electron conductor. 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.

[0037] Ni exists in the form of nickel oxide (NiO) in an oxidizing atmosphere and in the form of metallic Ni in a reducing atmosphere. The hydrogen electrode layer 6 is exposed to an oxidizing atmosphere when the electrolytic cell 1 is not in operation, and is exposed to a reducing atmosphere when the electrolytic cell 1 is in operation and during a reduction treatment performed before the operation of the electrolytic cell 1. The hydrogen electrode layer 6 expands and contracts as Ni is oxidized and reduced.

[0038] Examples of oxide ion conductive materials 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.

[0039] The thickness of the hydrogen electrode layer 6 is not particularly limited, but can be, for example, 1 μm or more and 100 μm or less.

[0040] The method for forming the hydrogen electrode layer 6 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] [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.

[0042] 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 hydrogen electrode layer 6 .

[0043] 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).

[0044] 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.

[0045] 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.

[0046] [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.

[0047] The reaction prevention layer 8 is made of an oxide ion conductive material, such as GDC or SDC.

[0048] 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.

[0049] 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.

[0050] [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.

[0051] The oxygen electrode layer 9 reacts with O 2 transferred from the hydrogen electrode layer 6 through the electrolyte layer 7 in accordance with the chemical reaction of the following formula (2): ２－ From O ２ Generate.

[0052] Oxygen electrode layer 9: 2O ２－ →O ２ +4e － ... (2)

[0053] The oxygen electrode layer 9 is made of a porous material having oxide ion conductivity and electron conductivity, such as (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).

[0054] 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.

[0055] 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.

[0056] [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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] (Configuration of hydrogen electrode layer 6) Fig. 3 is a partially enlarged view of Fig. 2. As shown in Fig. 3, the hydrogen electrode layer 6 has a first region 61, a second region 62, a third region 63, and a fourth region 64.

[0061] The first region 61 is a region of the hydrogen electrode layer 6 within 5 μm in the Z-axis direction (thickness direction) from the first surface S1 that contacts the metal support 10. The second region 62 is a region of the hydrogen electrode layer 6 within 5 μm in the Z-axis direction from the second surface S2 that contacts the electrolyte layer 7. The third region 63 is a region of the hydrogen electrode layer 6 between the first region 61 and the second region 62. The fourth region 64 is a region of the hydrogen electrode layer 6 that is located inside the communicating hole 11 of the metal support 10. The fourth region 64 is engaged with the communicating hole 11, thereby exerting an anchor effect on the metal support 10.

[0062] The first to third regions 61 to 63 are essential components, while the fourth region 64 is optional. The fourth region 64 only needs to be located inside at least one of the plurality of communicating holes 11 formed in the metal support 10. Therefore, the number of fourth regions 64 may be the same as or less than the number of communicating holes 11.

[0063] The first surface S1 of the hydrogen electrode layer 6 contacts the first main surface 12 of the metal support 10. When identifying the first region 61, an approximation line of the first surface S1 obtained by the least squares method is used in a cross section along the Z axis direction. Specifically, the region of the surface of the hydrogen electrode layer 6 that contacts the first main surface 12 of the metal support 10 is approximated as a straight line by the least squares method, and the obtained approximation line is defined as the first surface S1 of the hydrogen electrode layer 6. Note that the region of the surface of the hydrogen electrode layer 6 that contacts the first main surface 12 of the metal support 10 does not include the inner circumferential surfaces of the through holes 11 of the metal support 10.

[0064] The second surface S2 of the hydrogen electrode layer 6 contacts the hydrogen electrode layer-side surface S3 of the electrolyte layer 7. When identifying the second region 62, an approximation line of the second surface S2 obtained by the least squares method is used in a cross section along the Z axis direction. Specifically, the region of the surface of the hydrogen electrode layer 6 that contacts the hydrogen electrode layer-side surface S3 of the electrolyte layer 7 is approximated as a straight line by the least squares method, and the obtained approximation line is defined as the second surface S2 of the hydrogen electrode layer 6.

[0065] Each of the first to fourth regions 61 to 64 contains Ni and an oxide ion conductive material.

[0066] The Ni content in the first region 61 is lower than the Ni content in the third region 63. This reduces the expansion / contraction of the first region 61 due to the oxidation-reduction cycle, thereby preventing the hydrogen electrode layer 6 from peeling off from the metal support 10. Furthermore, the third region 63 improves the electronic conductivity and catalytic performance. This makes it possible to prevent peeling of the hydrogen electrode layer 6 while maintaining electrode performance.

[0067] The Ni content in the second region 62 is preferably lower than the Ni content in the third region 63. This reduces expansion / contraction not only in the first region 61 but also in the second region 62, making it possible to suppress an increase in internal resistance due to deterioration in adhesion between the hydrogen electrode layer 6 and the electrolyte layer 7 when oxidation-reduction cycles are repeated, while maintaining electrode performance.

[0068] The Ni content in the second region 62 is preferably lower than the Ni content in the first region 61. This makes the amount of reduction shrinkage in the second region 62 smaller than the amount of reduction shrinkage in the first region 61, improving the shrinkage balance throughout the hydrogen electrode layer 6. As a result, the hydrogen electrode layer 6 is prevented from warping convexly toward the metal support 10, thereby preventing the hydrogen electrode layer 6 (particularly the outer periphery of the hydrogen electrode layer 6 in the planar direction) from peeling off from the metal support 10.

[0069] The Ni content in the fourth region 64 is preferably lower than the Ni content in the third region 63. This reduces the expansion / contraction of the fourth region 64 caused by the oxidation-reduction cycle, thereby suppressing changes in the shape of the fourth region 64. As a result, the anchoring effect of the fourth region 64 can be maintained.

[0070] The Ni contents in the first to fourth regions 61 to 64 are calculated by the same method, as will be described next.

[0071] The Ni content in the first region 61 is calculated by measuring the Ni content at five locations (randomly selected) spaced apart in the plane direction in the center of the thickness direction of the first region 61 in a cross section of the hydrogen electrode layer 6 taken along the Z-axis direction, and averaging the five measured values. The Ni content in the first region 61 is not particularly limited, but may be 25 mol% or more and 45 mol% or less.

[0072] The Ni content in the second region 62 is calculated by measuring the Ni content at five locations (randomly selected) spaced apart in the plane direction in the center of the thickness direction of the second region 62 in a cross section of the hydrogen electrode layer 6 taken along the Z-axis direction, and averaging the five measured values. The Ni content in the second region 62 is not particularly limited, but may be 20 mol% or more and 45 mol% or less.

[0073] The Ni content in the third region 63 is calculated by measuring the Ni content at four locations in a cross section of the hydrogen electrode layer 6 taken along the Z-axis direction, dividing the third region 63 into five equal parts in the Z-axis direction, and averaging the four measured values. The Ni content in the third region 63 is not particularly limited, but may be 30 mol% or more and 50 mol% or less.

[0074] The Ni content in the fourth region 64 is calculated by measuring the Ni content at five locations (randomly selected) spaced apart in the plane direction in the center of the thickness direction of the fourth region 64 in the cross section of the hydrogen electrode layer 6 taken along the Z-axis direction, and averaging the five measured values. The value of the Ni content in the fourth region 64 is not particularly limited, but may be 20 mol% or more and 45 mol% or less.

[0075] The Ni content is calculated by the following method. First, a Ni composition mapping image on a cross section is obtained at 5,000 to 10,000 magnifications using an SEM device (FE-SEM JSM-7900F, manufactured by JEOL Ltd.) and an EDS device (JED-2300) attached to the SEM device. Next, Ni particle portions are identified in the Ni composition mapping image by performing binarization processing through image analysis using image analysis software Image-Pro manufactured by MEDIACYBERNETICS. The Ni content is then calculated by dividing the total area of ​​the Ni particle portions by the total area of ​​the backscattered electron image.

[0076] (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.

[0077] [Variation 1] In the above embodiment, when the first main surface 12 of the metal support 10 is planar (i.e., linear in a cross section along the Z-axis direction as shown in FIG. 3 ), the first surface S1 of the hydrogen electrode layer 6 is defined by the first main surface 12 of the metal support 10.

[0078] However, if the first main surface 12 of the metal support 10 is not planar (for example, if the metal support 10 is made of porous metal), it is difficult to identify the first surface S1 of the hydrogen electrode layer 6 using the first main surface 12 of the metal support 10.

[0079] A method for identifying the first surface S1 of the hydrogen electrode layer 6 when the first main surface 12 of the metal support 10 is not planar will now be described with reference to Fig. 4. Fig. 4 is a cross section of the electrolysis cell 100 taken along the Z-axis direction (thickness direction).

[0080] The electrolysis cell 100 has the same configuration as the electrolysis cell 1 according to the above embodiment, except that the metal support 110 is made of porous metal. The metal support 110 has metal particles 111 connected in a three-dimensional network and a plurality of interconnected communication holes 112. The first main surface 113 of the metal support 10 has projections and recesses formed along the outer edges of the metal particles 111.

[0081] In the electrolysis cell 100, first, the second surface S2 of the hydrogen electrode layer 6 is identified by the hydrogen electrode layer-side surface S3 of the electrolyte layer 7. Next, when the second surface S2 of the hydrogen electrode layer 6 is moved horizontally in the Z-axis direction toward the metal support 110, the intersection points P where the second surface S2 intersects with the metal particles 111 are identified. At this time, the intersection points P are identified for each cluster of metal particles 111 that are separated on the cross section. In the example shown in FIG. 4, the metal particles 111 are divided into three clusters, and therefore intersection points P1 to P3 are identified in FIG. 4. Finally, the lines sequentially connecting the intersection points P1 to P3 are defined as the first surface S1 of the hydrogen electrode layer 6.

[0082] As described above, when the first main surface 113 of the metal support 110 is not flat, the first surface S1 of the hydrogen electrode layer 6 can be identified based on the hydrogen electrode layer-side surface S3 of the electrolyte layer 7.

[0083] [Modification 2] In the above embodiment, the hydrogen electrode layer 6 has the fourth region 64 , but it does not have to have the fourth region 64 .

[0084] [Variation 3] 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.

[0085] Examples of the electrochemical cell according to the present invention will be described below, but the present invention is not limited to the examples described below.

[0086] Comparative Example 1 An electrolytic cell according to Comparative Example 1 was prepared as follows.

[0087] First, a metal support made of Fe-Cr-Mn alloy steel and having a plurality of communicating holes formed therein was prepared.

[0088] Next, a slurry for the hydrogen electrode layer was prepared by mixing GDC powder, NiO powder, butyral resin, polymethyl methacrylate beads as a pore-forming material, a plasticizer, a dispersant, and a solvent, and the slurry for the hydrogen electrode layer was then printed onto the first main surface of the metal support by a doctor blade method to form a green body for the hydrogen electrode layer.

[0089] Next, a slurry for the electrolyte layer was prepared by mixing YSZ powder, butyral resin, a plasticizer, a dispersant, and a solvent, and then the slurry for the electrolyte was printed by a doctor blade method so as to cover the green body for the hydrogen electrode layer, thereby forming a green body for the electrolyte layer.

[0090] Next, a slurry for the reaction prevention layer was prepared by mixing GDC powder, polyvinyl alcohol, and a solvent, and the slurry for the reaction prevention layer was then printed on the green body of the electrolyte layer by a doctor blade method to form a green body of the reaction prevention layer.

[0091] Next, the molded bodies of the hydrogen electrode layer, electrolyte layer, and reaction prevention layer arranged in this order on the metal support were fired in air (1050°C, 1 hour) to form the hydrogen electrode layer, electrolyte layer, and reaction prevention layer.

[0092] Next, (La,Sr)(Co,Fe)O ３ The powder, polyvinyl alcohol, and a solvent were mixed to prepare a slurry for the oxygen electrode layer, which was then printed onto the reaction prevention layer by a doctor blade method to form a green body for the oxygen electrode layer.

[0093] Next, the compact for the oxygen electrode layer was fired in air (1000° C., 1 hour) to form an oxygen electrode.

[0094] Finally, a flow path member made of Fe-Cr-Mn alloy steel was connected to the second main surface of the metal support using crystallized glass. In this way, the electrolytic cells according to Examples 1 to 9 were completed.

[0095] Comparative Example 2 and Examples 1 to 9 Electrolytic cells according to Comparative Example 2 and Examples 1 to 9 were fabricated using the same process as in Comparative Example 1, except that the hydrogen electrode layer had a multilayer structure.

[0096] Specifically, a slurry for the first region was prepared by mixing GDC powder, NiO powder, butyral resin, polymethyl methacrylate beads as a pore-forming material, a plasticizer, a dispersant, and a solvent. The amount of NiO powder added was adjusted to change the Ni content in the first region as shown in Table 1. The slurry for the first region was then printed on the first main surface of the metal support by a doctor blade method to form a compact for the first region of the hydrogen electrode layer.

[0097] Next, a slurry for the third region was prepared by mixing GDC powder, NiO powder, butyral resin, polymethyl methacrylate beads as a pore-forming material, a plasticizer, a dispersant, and a solvent. The amount of NiO powder added was adjusted to change the Ni content in the third region as shown in Table 1. The slurry for the third region was then printed onto the compact for the first region by a doctor blade method to form a compact for the third region of the hydrogen electrode layer.

[0098] Next, a slurry for the second region was prepared by mixing GDC powder, NiO powder, butyral resin, polymethyl methacrylate beads as a pore-forming material, a plasticizer, a dispersant, and a solvent. The amount of NiO powder added was adjusted to change the Ni content in the second region as shown in Table 1. The slurry for the second region was then printed on the compact for the third region by a doctor blade method to form a compact for the second region of the hydrogen electrode layer.

[0099] (Initial Evaluation of Electrolytic Cell Performance) First, the electrolytic cells of Examples 1 to 9 and Comparative Examples 1 and 2 were heated to 750°C, and hydrogen was supplied to the hydrogen electrode layer from the flow path in the flow path member, thereby reducing NiO contained in the hydrogen electrode layer to Ni.

[0100] Next, a mixed gas of water vapor and hydrogen (mixing ratio 90:10) was supplied to the hydrogen electrode layer, and the current density per hydrogen electrode layer area was adjusted to 0.5 A / cm ２ The cell voltage was measured when electrolysis was performed by passing a current so that the voltage was constant at 1.300 V. In Table 1, a cell voltage of less than 1.300 V was evaluated as "Good," and a cell voltage of 1.300 V or more was evaluated as "Poor."

[0101] Next, one oxidation-reduction cycle was carried out, which sequentially included a step of supplying a mixed gas of water vapor and hydrogen (mixing ratio 90:10) to the hydrogen electrode layer for 10 hours, a step of supplying a mixed gas of water vapor and hydrogen (mixing ratio 98:2) to the hydrogen electrode layer for 10 hours, and a step of supplying a mixed gas of water vapor and hydrogen (mixing ratio 90:10) to the hydrogen electrode layer for 10 hours.

[0102] Then, in a cross section along the thickness direction of the hydrogen electrode layer and the metal support, 10 visual fields were observed at 500 μm intervals in the planar direction from each end of the interface between the two using an SEM (magnification 1000x) to check for the presence or absence of interfacial delamination (portions where the non-bonded region at the interface continued in the planar direction for 50 μm or more). In Table 1, cases where delamination was observed in two or more visual fields were judged as "×", cases where delamination was observed in only one visual field were judged as "△", and cases where no delamination was observed were judged as "◯".

[0103] (Durability evaluation of electrolytic cell performance) After the initial evaluation, the above-described oxidation-reduction cycle was performed 100 times for the electrolytic cells of Examples 1 to 9. Then, similar to the initial evaluation, the cell voltage was measured and judged, and the presence or absence of peeling was confirmed.

[0104]

[0105] As shown in Table 1, in Examples 1 to 9, in which the Ni content in the first region of the hydrogen electrode layer was lower than the Ni content in the third region, interfacial peeling in the initial evaluation was suppressed compared to Comparative Example 1. These results were obtained because the expansion / contraction of the first region due to the redox cycle was reduced. Furthermore, in Examples 1 to 9, the electrolytic cell performance in the initial evaluation was improved compared to Comparative Example 2. These results were obtained because the electronic conductivity and catalytic performance in the third region were improved. In this way, in Examples 1 to 9, it was possible to achieve both suppression of peeling and maintenance of electrode performance.

[0106] Furthermore, in Examples 6 to 9, in which the Ni content in the second region was lower than the Ni content in the third region, interfacial peeling after the durability evaluation could be suppressed and electrolysis cell performance could be improved compared to Examples 1 to 5. These results were obtained because the expansion / contraction caused by the oxidation-reduction cycle could be reduced not only in the first region but also in the second region.

[0107] Furthermore, in Examples 8 and 9, in which the Ni content in the second region was lower than the Ni content in the first region, interfacial peeling after the durability evaluation was more effectively suppressed than in Examples 6 and 7. Such results were obtained because the reduction shrinkage amount of the second region was made smaller than the reduction shrinkage amount of the first region, thereby suppressing the hydrogen electrode layer from warping convexly toward the metal support.

[0108] REFERENCE SIGNS LIST 1 electrolysis cell 10 metal support 11 communicating hole 12 first main surface 13 second main surface 20 cell main body 6 hydrogen electrode layer 61 first region 62 second region 63 third region 64 fourth region 7 electrolyte layer 8 reaction prevention layer 9 oxygen electrode layer 30 flow path member 30a flow path

Claims

1. a metal support having a plurality of communicating holes formed on a main surface thereof; a cell main body portion including a first electrode layer formed on the main surface and covering the plurality of communication holes, a second electrode layer, and an electrolyte layer disposed between the first electrode layer and the second electrode layer; Equipped with The first electrode layer is a first region within 5 μm in a thickness direction from a first surface in contact with the metal support; a second region within 5 μm in a thickness direction from a second surface in contact with the electrolyte layer; a third region between the first region and the second region; having each of the first region, the second region, and the third region contains nickel and an oxide ion conductive material; the nickel content in the first region is lower than the nickel content in the third region; The nickel content in the second region is lower than the nickel content in the first region. Electrochemical cell.

2. The nickel content in the second region is lower than the nickel content in the third region.

10. The electrochemical cell of claim 1.

3. the first electrode layer has a fourth region disposed inside at least one of the plurality of communication holes, the fourth region contains nickel and an oxide ion conductive material; The nickel content in the fourth region is lower than the nickel content in the third region.

3. An electrochemical cell according to claim 1 or 2.