Electrochemical cell

Abstract

This electrolysis cell (10) is provided with: a hydrogen electrode current collector layer (11) comprising an aggregate and at least one of Ni and NiO; and a beam (12) that is embedded in the hydrogen electrode current collector layer (11). The beam (12) has a first portion (R1) and a second portion (R2) that covers at least a part of the first portion (R1) and contacts the hydrogen electrode current collecting layer (11). The second portion (R2) has a porosity that is greater than the porosity of the first portion (R1).

Description

electrochemical cell

[0001] The present invention relates to electrochemical cells.

[0002] BACKGROUND ART Conventionally, electrochemical cells (electrolysis cells, fuel cells, etc.) that include an electrolyte layer disposed between a first electrode layer and a second electrode layer are known.

[0003] Here, Patent Document 1 proposes suppressing warping of an electrochemical cell due to the difference in thermal expansion coefficient between the layers by embedding a porous layer having a smaller thermal expansion coefficient than the first electrode layer in the first electrode layer having a larger thermal expansion coefficient than the electrolyte layer.

[0004] Japanese Patent Application Laid-Open No. 2008-135360

[0005] The first electrode layer described in Patent Document 1 is a sintered body made of NiO-YSZ cermet. When a reduction treatment is performed on the first electrode layer to impart electrical conductivity, the volume of the first electrode layer is reduced by reducing NiO to Ni. This results in warping of the electrochemical cell due to the reduction treatment.

[0006] An object of the present invention is to provide an electrochemical cell that can suppress warping caused by reduction treatment.

[0007] An electrochemical cell according to a first aspect of the present invention includes a current collecting layer composed of at least one of Ni and NiO and an aggregate, beam portions embedded in the current collecting layer, a first electrode layer disposed on the current collecting layer, an electrolyte layer disposed on the first electrode layer, and a second electrode layer disposed on the opposite side of the first electrode layer with respect to the electrolyte layer. The beam portions have a first portion and a second portion covering at least a part of the first portion and in contact with the current collecting layer. The porosity of the second portion is greater than the porosity of the first portion.

[0008] According to a second aspect of the present invention, there is provided an electrochemical cell according to the first aspect, wherein the current collecting layer has a third portion and a fourth portion sandwiched between the third portion and the second portion, and the fourth portion has a lower aggregate content than the third portion.

[0009] An electrochemical cell according to a third aspect of the present invention is the electrochemical cell according to the first or second aspect, wherein a first surface of the beam portion opposite to the first electrode layer is covered with the current collecting layer.

[0010] An electrochemical cell according to a fourth aspect of the present invention is the electrochemical cell according to any one of the first to third aspects, wherein second surfaces of the beam portions on the first electrode layer side are covered with the current collecting layer.

[0011] According to the present invention, it is possible to provide an electrochemical cell that can suppress warping caused by reduction treatment.

[0012] Fig. 1 is a cross-sectional view of an electrolytic cell with a separator according to an embodiment, and Fig. 2 is a partially enlarged view of Fig. 1 .

[0013] (Separator-equipped electrolytic cell 1) Fig. 1 is a cross-sectional view of a separator-equipped electrolytic cell 1 according to an embodiment. The separator-equipped electrolytic cell 1 includes an electrolytic cell 10, a separator 20, a current collecting member 25, and a sealing part 30. The electrolytic cell 10 is an example of an "electrochemical cell" according to the present invention. A cell stack (not shown) can be formed by stacking multiple separator-equipped electrolytic cells 1 in the Z-axis direction, which is perpendicular to the X-axis direction and the Y-axis direction.

[0014] (Electrolysis Cell 10) As shown in Figure 1, the electrolysis cell 10 includes a hydrogen electrode current collecting layer 11, multiple beams 12, a frame 13, a hydrogen electrode active layer 14, an electrolyte layer 15, a reaction prevention layer 16, and an oxygen electrode layer 17. The hydrogen electrode current collecting layer 11 is an example of a "current collecting layer" according to the present invention. The hydrogen electrode active layer 14 is an example of a "first electrode layer" according to the present invention. The oxygen electrode layer 17 is an example of a "second electrode layer" according to the present invention.

[0015] The hydrogen electrode current collecting layer 11, the beams 12, the hydrogen electrode active layer 14, the electrolyte layer 15, and the oxygen electrode layer 17 are essential components, while the frame 13 and the reaction prevention layer 16 are optional components.

[0016] The hydrogen electrode current collecting layer 11, the hydrogen electrode active layer 14, the electrolyte layer 15, the reaction prevention layer 16, and the oxygen electrode layer 17 are stacked in this order in the Z-axis direction. The Z-axis direction is perpendicular to both the X-axis direction and the Y-axis direction. The Z-axis direction is an example of the "stacking direction" according to the present invention.

[0017] [Hydrogen Electrode Current Collector Layer 11] The hydrogen electrode current collector layer 11 is formed in a layered shape. Beams 12 are embedded in the hydrogen electrode current collector layer 11. The hydrogen electrode current collector layer 11 is supported by the beams 12. In this embodiment, the hydrogen electrode current collector layer 11 is also supported by a frame 13. The hydrogen electrode current collector layer 11, together with the beams 12 and frame 13, functions as a support for the electrolysis cell 10. The electrolysis cell 10 according to this embodiment is a so-called electrode-supported electrochemical cell.

[0018] The hydrogen electrode current collecting layer 11 has a first main surface P1, a second main surface P2, and a side surface P3. The first main surface P1 is electrically connected to the separator 20 via a current collecting member 25. The second main surface P2 is provided on the opposite side of the first main surface P1 in the Z-axis direction. The second main surface P2 is connected to the hydrogen electrode active layer 14. The side surface P3 is continuous with the first main surface P1 and the second main surface P2. In this embodiment, the side surface P3 is covered by the frame 13. The side surface P3 may be perpendicular to the first main surface P1 and the second main surface P2, or may be inclined with respect to the first main surface P1 and the second main surface P2.

[0019] A hydrogen electrode side space S1, to which a raw material gas is supplied, is provided between the hydrogen electrode current collecting layer 11 and the separator 20. The hydrogen electrode current collecting layer 11 has a gas diffusion function in addition to a current collecting function. The hydrogen electrode current collecting layer 11 supplies the raw material gas from the hydrogen electrode side space S1 to the hydrogen electrode active layer 14 and discharges the produced gas from the hydrogen electrode active layer 14 to the hydrogen electrode side space S1.

[0020] The hydrogen electrode current collecting layer 11 is an electron-conductive porous body. The hydrogen electrode current collecting layer 11 contains nickel (Ni). In the case of co-electrolysis, Ni functions as an electron conductor and also functions as a carrier for H generated in the hydrogen electrode active layer 14. ２ and CO contained in the raw material gas ２ It also functions as a thermal catalyst that promotes the thermal reaction with HCl and maintains an appropriate gas composition for methanation, Fischer-Tropsch (FT) synthesis, etc. The Ni contained in the hydrogen electrode current collecting layer 11 is basically present in the form of metallic Ni during operation of the electrolysis cell 10, but a portion of it may also be present in the form of nickel oxide (NiO).

[0021] The hydrogen electrode current collecting layer 11 contains, in addition to Ni, a ceramic as an aggregate. The aggregate may have ion conductivity. For example, yttria (Y ２ O ３ ), magnesia (MgO), iron oxide (Fe ２ O ３ ), zirconia (ZrO ２ Examples of materials that can be used include yttria-stabilized zirconia (YSZ, partially stabilized zirconia), yttria-stabilized zirconia (YSZ), calcia-stabilized zirconia (CSZ), scandia-stabilized zirconia (ScSZ), gadolinium-doped ceria (GDC), samarium-doped ceria (SDC), and mixed materials of two or more of these.

[0022] The porosity of the hydrogen electrode current collecting layer 11 is not particularly limited, but can be, for example, 20% or more and 40% or less.

[0023] The thickness of the hydrogen electrode current collecting layer 11 in the Z-axis direction is not particularly limited, but may be, for example, 150 μm to 1000 μm. In the Z-axis direction, the thickness of the hydrogen electrode current collecting layer 11 may be greater than the thicknesses of the hydrogen electrode active layer 14, the electrolyte layer 15, the reaction prevention layer 16, and the oxygen electrode layer 17.

[0024] The method for forming the hydrogen electrode current collecting layer 11 is not particularly limited, and tape casting, screen printing, casting, dry pressing, or the like can be used.

[0025] [Beam Portion 12] The beam portion 12 is embedded in the hydrogen electrode current collecting layer 11. In this embodiment, the beam portion 12 being embedded in the hydrogen electrode current collecting layer 11 means that at least a portion of the beam portion 12 is embedded in the hydrogen electrode current collecting layer 11. Therefore, the beam portion 12 may be partially exposed from at least one of the first main surface P1, the second main surface P2, and the side surface P3 of the hydrogen electrode current collecting layer 11.

[0026] The beams 12 support the hydrogen electrode current collecting layer 11. The beams 12 function, together with the hydrogen electrode current collecting layer 11, as a support for the electrolysis cell 10. In Fig. 1 , the beams 12 are rod-shaped members extending in the Y-axis direction. Both ends of the beams 12 in the Y-axis direction are preferably connected to the frame 13.

[0027] 1 illustrates a cross section of three beam portions 12, but the number of beam portions 12 may be one or more. Also, in FIG. 1, the beam portions 12 extend in the Y-axis direction, but they may extend in a direction perpendicular to the Z-axis direction. For example, two or more beam portions 12 may be arranged in a lattice pattern when viewed in a plan view from the Z-axis direction.

[0028] The beam portion 12 is made of forsterite (Mg ２ SiO ４ ), magnesium silicate (MgSiO ３ ), zirconia (ZrO ２ , including partially stabilized zirconia), magnesia (MgO), spinel (MgAl ２ O ４ , NiAl ２ O ４ ), yttria stabilized zirconia (YSZ), calcia stabilized zirconia (CSZ), nickel (Ni), nickel oxide (NiO), alumina (Al ２ O ３ ), nickel oxide-magnesia solid solution (Mg ｘ Ni （１－ｘ） 0[0<x<1]) and a mixed material that combines two or more of these.

[0029] The electron conductivity of the beam portion 12 may be lower than that of the hydrogen electrode current collecting layer 11. The beam portion 12 may have electron insulating properties. The electron conductivity of the beam portion 12 is not particularly limited, but is preferably 10 －１ It is possible to make it S / m or less.

[0030] Here, the beam portion 12 has a first surface T1 and a second surface T2. The first surface T1 is the surface of the beam portion 12 opposite the hydrogen electrode active layer 14. The second surface T2 is the surface of the beam portion 12 facing the hydrogen electrode active layer 14. The first surface T1 is preferably covered by the hydrogen electrode current collecting layer 11. This ensures electrical connectivity between the electrolysis cell 10 and the separator 20 even if the beam portion 12 has low electronic conductivity. The second surface T2 is preferably covered by the hydrogen electrode current collecting layer 11. This improves gas flow between the hydrogen electrode-side space S1 and the hydrogen electrode active layer 14 even if the beam portion 12 has low gas permeability.

[0031] The method for forming the beam portion 12 is not particularly limited, and may be an extrusion molding method, a tape casting method, a print lamination method, a casting method, a dry pressing method, or the like.

[0032] [Frame 13] The frame 13 is placed on the separator 20. The frame 13 is formed in a frame shape. The frame 13 surrounds the side periphery of the hydrogen electrode current collecting layer 11. The side periphery of the hydrogen electrode current collecting layer 11 refers to the periphery of the side surface P3 of the hydrogen electrode current collecting layer 11. The frame 13 functions as a support for the electrolysis cell 10 together with the hydrogen electrode current collecting layer 11 and the beam portions 12.

[0033] In this embodiment, the shape of the frame 13 in plan view is rectangular, but it may be circular, elliptical, or polygonal with three or more sides, depending on the planar shape of the hydrogen electrode current collecting layer 11 .

[0034] The frame body 13 is preferably connected to the beam portion 12. The frame body 13 may be formed integrally with the beam portion 12.

[0035] The frame 13 is made of forsterite (Mg ２ SiO ４ ), magnesium silicate (MgSiO ３ ), zirconia (ZrO ２ , including partially stabilized zirconia), magnesia (MgO), spinel (MgAl ２ O ４ , NiAl ２ O ４ ), yttria stabilized zirconia (YSZ), calcia stabilized zirconia (CSZ), nickel (Ni), nickel oxide (NiO), alumina (Al ２ O ３ ), nickel oxide-magnesia solid solution (Mg ｘ Ni （１－ｘ） 0[0<x<1]) and a mixed material that combines two or more of these.

[0036] The porosity of the frame 13 may be lower than the porosity of the hydrogen electrode current collecting layer 11. The porosity of the frame 13 can be, for example, 0.1% or more and 15% or less. The porosity of the frame 13 is preferably 5% or less. This provides the frame 13 with gas sealing properties, thereby preventing the source gas that has flowed from the hydrogen electrode side space S1 into the hydrogen electrode current collecting layer 11 from passing through the frame 13 and returning to the hydrogen electrode side space S1. This improves the efficiency of gas supply from the hydrogen electrode current collecting layer 11 to the hydrogen electrode active layer 14.

[0037] The electronic conductivity of the frame 13 may be lower than that of the hydrogen electrode current collecting layer 11. The frame 13 may have electronic insulation. The electronic conductivity of the frame 13 is not particularly limited, but is preferably 10 －１ It is possible to make it S / m or less.

[0038] The method for forming the frame 13 is not particularly limited, and methods such as extrusion molding, tape casting, print lamination, casting, and dry pressing can be used.

[0039] [Hydrogen Electrode Active Layer 14] The hydrogen electrode active layer 14 functions as a cathode. The hydrogen electrode active layer 14 is disposed on the hydrogen electrode current collecting layer 11. The hydrogen electrode active layer 14 is covered with the electrolyte layer 15.

[0040] The source gas is supplied to the hydrogen electrode active layer 14 through the hydrogen electrode current collecting layer 11. In this embodiment, the source gas contains at least H ２ Contains O.

[0041] The raw material gas is H ２ When only O is contained, the hydrogen electrode active layer 14 converts H from the raw material gas according to the electrochemical reaction of water electrolysis shown in the following formula (1): ２ Generate.

[0042] Hydrogen electrode active layer 14: H ２ O + 2e － →H ２ +O ２－ ...(1)

[0043] The raw material gas is H ２ O plus CO ２ In this case, the hydrogen electrode active layer 14 converts H from the source gas according to the co-electrolytic electrochemical reactions shown in the following formulas (2), (3), and (4).２ , CO and O ２－ Generate.

[0044] Hydrogen electrode active layer 14: 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)

[0045] The hydrogen electrode active layer 14 is a porous body having electronic conductivity. The hydrogen electrode active layer 14 may also have ionic conductivity. The hydrogen electrode active layer 14 is made of, for example, YSZ, CSZ, ScSZ, GDC, (SDC), or (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 , a mixed material of two or more of these, or a composite of one or more of these with NiO.

[0046] The porosity of the hydrogen electrode active layer 14 is not particularly limited, but may be, for example, 20% to 40%. The thickness of the hydrogen electrode active layer 14 is not particularly limited, but may be, for example, 5 μm to 50 μm.

[0047] The method for forming the hydrogen electrode active layer 14 is not particularly limited, and tape casting, screen printing, casting, dry pressing, or the like can be used.

[0048] [Electrolyte Layer 15] The electrolyte layer 15 is disposed between the hydrogen electrode active layer 14 and the oxygen electrode layer 17. In this embodiment, the reaction prevention layer 16 is disposed between the electrolyte layer 15 and the oxygen electrode layer 17, and therefore the electrolyte layer 15 is disposed between the hydrogen electrode active layer 14 and the reaction prevention layer 16 and is connected to both the hydrogen electrode active layer 14 and the reaction prevention layer 16.

[0049] The electrolyte layer 15 covers the hydrogen electrode active layer 14. As shown in Fig. 1, the electrolyte layer 15 preferably covers the entire surface of the hydrogen electrode active layer 14. The outer periphery of the electrolyte layer 15 is connected to the frame 13.

[0050] The electrolyte layer 15 absorbs the O generated in the hydrogen electrode active layer 14. ２－ The electrolyte layer 15 has a function of transmitting the ionic current to the oxygen electrode layer 17. The electrolyte layer 15 is a dense body that has ionic conductivity but not electronic conductivity. The electrolyte layer 15 can be made of, for example, YSZ, GDC, ScSZ, SDC, lanthanum gallate (LSGM), or the like.

[0051] The porosity of the electrolyte layer 15 is not particularly limited, but may be, for example, 0.1% to 7%. The thickness of the electrolyte layer 15 is not particularly limited, but may be, for example, 1 μm to 100 μm.

[0052] The method for forming the electrolyte layer 15 is not particularly limited, and tape casting, screen printing, casting, dry pressing, or the like can be used.

[0053] [Reaction prevention layer 16] The reaction prevention layer 16 is disposed between the electrolyte layer 15 and the oxygen electrode layer 17. The reaction prevention layer 16 is disposed on the opposite side of the electrolyte layer 15 from the hydrogen electrode active layer 14. The reaction prevention layer 16 prevents the constituent elements of the electrolyte layer 15 from reacting with the constituent elements of the oxygen electrode layer 17 to form a layer with high electrical resistance.

[0054] The reaction prevention layer 16 is made of an ion-conductive material, such as GDC or SDC.

[0055] The porosity of the reaction prevention layer 16 is not particularly limited, but may be, for example, 0.1% to 50%. The thickness of the reaction prevention layer 16 is not particularly limited, but may be, for example, 1 μm to 50 μm.

[0056] The method for forming the reaction prevention layer 16 is not particularly limited, and tape casting, screen printing, casting, dry pressing, etc. may be used.

[0057] [Oxygen Electrode Layer 17] The oxygen electrode layer 17 functions as an anode. The oxygen electrode layer 17 is disposed on the opposite side of the electrolyte layer 15 from the hydrogen electrode active layer 14. In this embodiment, the reaction prevention layer 16 is disposed between the electrolyte layer 15 and the oxygen electrode layer 17, and therefore the oxygen electrode layer 17 is connected to the reaction prevention layer 16. If the reaction prevention layer 16 is not disposed between the electrolyte layer 15 and the oxygen electrode layer 17, the oxygen electrode layer 17 is connected to the electrolyte layer 15.

[0058] The oxygen electrode layer 17 reacts with O 2 transferred from the hydrogen electrode active layer 14 via the electrolyte layer 15 in accordance with the chemical reaction of the following formula (5): ２－ From O ２ The O generated in the oxygen electrode layer 17 ２ is released into the oxygen electrode side space S2.

[0059] Oxygen electrode layer 17: 2O ２－ →O ２ +4e － ...(5)

[0060] The oxygen electrode layer 17 is a porous material having ionic and electronic conductivity. The oxygen electrode layer 17 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 The conductive layer 10 may be made of a composite material of one or more of the above and an ion-conducting material (such as GDC).

[0061] The porosity of the oxygen electrode layer 17 is not particularly limited, but may be, for example, 20% to 60%. The thickness of the oxygen electrode layer 17 is not particularly limited, but may be, for example, 1 μm to 100 μm.

[0062] The method for forming the oxygen electrode layer 17 is not particularly limited, and tape casting, screen printing, casting, dry pressing, or the like can be used.

[0063] (Separator 20) The separator 20 is electrically connected to the hydrogen electrode current collecting layer 11 via the current collecting member 25. The separator 20 has a connection portion 20a that contacts the current collecting member 25.

[0064] The separator 20 is made of a metal material having electronic conductivity. The separator 20 can be made of, for example, an alloy material containing Cr (chromium). Examples of such alloy materials include Fe—Cr alloy steel (stainless steel, etc.) and Ni—Cr alloy steel. The Cr content in the separator 20 is not particularly limited, but can be set to 4% by mass or more and 30% by mass or less.

[0065] The separator 20 may contain Ti (titanium) or Zr (zirconium). The Ti content in the separator 20 is not particularly limited, but can be 0.01 mol % or more and 1.0 mol % or less. The Al content in the separator 20 is not particularly limited, but can be 0.01 mol % or more and 0.4 mol % or less. The separator 20 may contain Ti in the form of TiO ２ (titania), or Zr may be contained as ZrO ２ It may be contained as (zirconia).

[0066] The separator 20 may have an oxide film on its surface, which is formed by oxidation of the constituent elements of the separator 20. A typical example of the oxide film is a chromium oxide film. The oxide film covers at least a portion of the surface of the separator 20.

[0067] (Current Collector 25) The current collector 25 electrically connects the hydrogen electrode current collecting layer 11 and the separator 20. As shown in Fig. 1 , the current collector 25 is disposed in the hydrogen electrode side space S1 between the hydrogen electrode current collecting layer 11 and the separator 20. The current collector 25 contacts the first main surface P1 of the hydrogen electrode current collecting layer 11 and the connection portion 20a of the separator 20.

[0068] The current collecting member 25 has electronic conductivity and air permeability. For example, nickel, a nickel alloy, stainless steel, or the like can be used as the current collecting member 25. The size, shape, and position of the current collecting member 25 can be changed as appropriate. For example, in this embodiment, the current collecting member 25 is in contact with both the hydrogen electrode current collecting layer 11 and the frame 13, but it does not have to be in contact with the frame 13.

[0069] (Sealing section 30) The sealing section 30 positions the frame 13 relative to the separator 20. The sealing section 30 is a dense body. The sealing section 30 seals the gap between the electrolytic cell 10 and the separator 20. This prevents gas from mixing between the hydrogen electrode side space S1 and the oxygen electrode side space S2 through the gap between the electrolytic cell 10 and the metal separator 20. Furthermore, when the frame 13 is breathable, the sealing section 30 prevents gas from mixing through the frame 13 itself.

[0070] In this embodiment, the sealing portion 30 is connected to the frame body 13 and the electrolyte layer 15 of the electrolysis cell 10, but if the frame body 13 is not breathable, the sealing portion 30 does not need to be connected to the electrolyte layer 15.

[0071] The sealing portion 30 preferably has electronic insulation properties, which can prevent a short circuit from occurring between the hydrogen electrode current collecting layer 11 and the separator 20. The sealing portion 30 can be made of, for example, glass, glass ceramics (crystallized glass), a composite of glass and ceramics, or the like.

[0072] (Detailed Configuration of Beam Portion 12) Fig. 2 is a partially enlarged view of Fig. 1. As shown in Fig. 2, the beam portion 12 has a first portion R1 and a second portion R2.

[0073] The first portion R1 is a central member of the beam portion 12. The second portion R2 covers at least a portion of the first portion R1. As shown in FIG. 2 , the second portion R2 may cover the entire first portion R1 in one cross section of the beam portion 12. The second portion R2 is in direct contact with the hydrogen electrode current collecting layer 11. The second portion R2 is formed in a layer shape.

[0074] The porosity of the second portion R2 is greater than the porosity of the first portion R1. That is, the Young's modulus of the second portion R2 is lower than the Young's modulus of the first portion R1. Therefore, warping of the electrolytic cell 10 due to reduction treatment can be suppressed as follows. First, prior to use of the electrolytic cell 10, reduction treatment must be performed on the hydrogen electrode current collecting layer 11 to impart electrical conductivity. When reduction treatment is performed on the hydrogen electrode current collecting layer 11, NiO contained in the hydrogen electrode current collecting layer 11 is reduced to Ni, thereby reducing the volume of the hydrogen electrode current collecting layer 11. This volume reduction causes deformation of the hydrogen electrode current collecting layer 11, making the electrolytic cell 10 prone to warping. However, in this embodiment, the Young's modulus of the second portion R2 of the beam portion 12 is low, and therefore the surface portion of the beam portion 12 is flexible. Therefore, deformation of the hydrogen electrode current collecting layer 11 can be absorbed by the second portion R2 of the beam portion 12, thereby suppressing warping of the electrolytic cell 10.

[0075] The porosity of the first portion R1 is not particularly limited, but may be, for example, 0.1% to 15%. The porosity of the second portion R2 is not particularly limited, but may be, for example, 5% to 25% as long as it is not less than the porosity of the first portion R1.

[0076] The porosity of the first portion R1 is calculated by the following method. First, the first portion R1 is subjected to a reduction treatment (750°C, 78% H2O humidified at 90°C). ２ A cross section of the hydrogen electrode current collecting layer 11 that has been subjected to a gas treatment (for 4 hours) is exposed. Next, of the beam portions 12 embedded in the hydrogen electrode current collecting layer 11, a region more than 50 μm from the surface is identified as the first portion R1, and a region within 50 μm from the surface is identified as the second portion R2. Next, a backscattered electron image of the cross section of the first portion R1 is acquired at 10,000x magnification using an SEM device. Next, using image analysis software Image-Pro manufactured by MEDIACYBERNETICS, Inc., the portions displayed in black (corresponding to pores) in the backscattered electron image are identified. The porosity of the first portion R1 is calculated by dividing the total area of ​​the pores in the backscattered electron image by the total area of ​​the first portion R1, including the pores.

[0077] The porosity of the second portion R2 is calculated in the same manner as the porosity of the first portion R1. The porosities of the first portion R1 and the second portion R2 can be controlled by adjusting the amount of pore-forming material added.

[0078] (Detailed Structure of Hydrogen Electrode Current Collecting Layer 11) As shown in FIG. 2, the hydrogen electrode current collecting layer 11 has a third portion R3 and a fourth portion R4.

[0079] The third portion R3 is a main portion of the hydrogen electrode current collecting layer 11. The fourth portion R4 is sandwiched between the third portion R3 and the second portion R2 of the beam portion 12. The fourth portion R4 is formed in a layer shape.

[0080] The aggregate (ceramic) content in the fourth portion R4 is lower than the aggregate content in the third portion R3. That is, the Ni content in the fourth portion R4 is higher than the aggregate content in the third portion R3. This provides flexibility to the fourth portion R4 of the hydrogen electrode current collecting layer 11 that contacts the beam portion 12. Therefore, deformation of the hydrogen electrode current collecting layer 11 can be absorbed by the fourth portion R4, further suppressing warpage of the electrolysis cell 10.

[0081] The volumetric content of the aggregate in the third portion R3 is not particularly limited, but may be, for example, 36 vol% to 60 vol%. The volumetric content of the aggregate in the fourth portion R4 is not particularly limited, but may be, for example, 0 vol% to 20 vol%.

[0082] The aggregate content in the third portion R3 and the fourth portion R4 is calculated by the following method. First, the aggregate is subjected to reduction treatment (750°C, 78% H2O humidified at 90°C). ２ A cross section of the hydrogen electrode current collecting layer 11 that has been subjected to a gas treatment (heat treatment, 4 hours) is exposed. Next, a region of the hydrogen electrode current collecting layer 11 that is more than 5 μm from the surface of the beam portion 12 is identified as a third portion R3, and a region of the hydrogen electrode current collecting layer 11 that is within 5 μm from the surface of the beam portion 12 is identified as a fourth portion R4. Next, EDS (Energy Dispersive x-ray spectroscopy) is used to perform line analysis in a direction perpendicular to the surface of the beam portion 12, thereby obtaining the aggregate content in the third portion R3 and the fourth portion R4.

[0083] The content of the aggregate in each of the third portion R3 and the fourth portion R4 can be controlled by adjusting the compounding ratio of Ni and ceramics.

[0084] (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.

[0085] [Variation 1] In the above embodiment, the first surface T1 and the second surface T2 of the beam portion 12 are each covered by the hydrogen electrode current collecting layer 11. However, at least one of the first surface T1 and the second surface T2 does not have to be covered by the hydrogen electrode current collecting layer 11.

[0086] [Variation 2] In the above embodiment, the frame 13 is arranged on the separator 20, but it may be arranged on the sealing portion 30. Furthermore, if the frame 13 does not have air permeability, the sealing portion 30 may be connected to the frame 13 and not connected to the electrolyte layer 15.

[0087] [Variation 3] In the above embodiment, the electrolysis cell 10 includes the frame 13, but the electrolysis cell 10 does not necessarily include the frame 13. In this case, the hydrogen electrode current collecting layer 11 and the beams 12 function as a support for the electrolysis cell 10.

[0088] [Variation 4] In the above embodiment, the hydrogen electrode active layer 14 functions as the cathode and the oxygen electrode layer 17 functions as the anode. However, the hydrogen electrode active layer 14 may function as the anode and the oxygen electrode layer 17 as the cathode. In this case, the constituent materials of the hydrogen electrode active layer 14 and the oxygen electrode layer 17 are interchanged, and a source gas is passed over the outer surface of the hydrogen electrode active layer 14. The hydrogen electrode current collecting layer 11 functions as an oxygen electrode current collecting layer, but the configuration and function of the oxygen electrode current collecting layer are the same as those of the hydrogen electrode current collecting layer 11 described in the above embodiment.

[0089] [Variation 5] In the above embodiment, the electrolysis cell 10 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.

[0090] REFERENCE SIGNS LIST 10 Electrolytic cell 11 Hydrogen electrode current collecting layer R3 Third portion R4 Fourth portion 12 Beam portion R1 First portion R2 Second portion 13 Frame 14 Hydrogen electrode active layer 15 Electrolyte layer 16 Reaction prevention layer 17 Oxygen electrode layer

Claims

1. An electrochemical cell comprising: a current collecting layer composed of at least one of Ni and NiO and an aggregate; a beam portion embedded in the current collecting layer; a first electrode layer disposed on the current collecting layer; an electrolyte layer disposed on the first electrode layer; and a second electrode layer disposed on the opposite side of the electrolyte layer from the first electrode layer, wherein the beam portion has a first portion and a second portion covering at least a part of the first portion and in contact with the current collecting layer, and the porosity of the second portion is greater than the porosity of the first portion.

2. The electrochemical cell according to claim 1, wherein the current collecting layer has a third portion and a fourth portion sandwiched between the third portion and the second portion, and the content of the aggregate in the fourth portion is lower than the content of the aggregate in the third portion.

3. The electrochemical cell according to claim 1, wherein a first surface of the beam portion opposite to the first electrode layer is covered with the current collecting layer.

4. The electrochemical cell according to claim 1, wherein a second surface of the beam portion on the side of the first electrode layer is covered with the current collecting layer.

Images