electrochemical cell

Abstract

To provide an electrochemical cell capable of achieving a strong join between a metal support and an electrode.SOLUTION: An electrochemical cell 1 includes: a metal support 2; a cell part 3 including a solid electrolyte layer 30 having oxygen ion conductivity, a first electrode 31 laminated on one surface side of the solid electrolyte layer 30, and a second electrode 32 laminated on the other surface side of the solid electrolyte layer 30; and a junction layer 4 joining the metal support 2 and the first electrode 31 of the cell part 3. The junction layer 4 includes at least one of: an alloy which includes a metal support constituent element that is at least one metal element constituting the metal support 2 and a first electrode constituent element that is at least one metal element constituting the first electrode 31; and a metal oxide including the metal support constituent element and the first electrode constituent element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to electrochemical cells. [Background technology]

[0002] Conventionally, electrochemical cells in which a cell section is supported by a metal support are known. Examples of electrochemical cells include solid oxide fuel cells (hereinafter sometimes referred to as SOFCs) and solid oxide electrochemical cells (hereinafter sometimes referred to as SOECs) that include a solid electrolyte layer with oxygen ion conductivity.

[0003] For example, Patent Document 1 discloses a technology that includes a metal support cell in which an electrolyte layer is fixed to a metal support layer via an electrode layer, and a metal frame that surrounds the periphery of the metal support cell, in which the electrolyte layer has compressive residual stress along the surface direction, the metal frame is sinter-bonded to the electrolyte layer, and the linear expansion coefficient of the metal frame is approximately the same as that of the metal support layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-21646 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technology of Patent Document 1, the internal stress of the metal support cell is offset, and as a result, Patent Document 1 claims that warping due to bending moment occurring in the metal support cell is suppressed, and damage to the electrolyte layer can be suppressed.

[0006] However, the technology of Patent Document 1 does not take into consideration the difference in thermal expansion between the metal support layer and the electrode layer, and therefore, with the technology of Patent Document 1, there is a risk of peeling occurring at the interface between the metal support layer and the electrode layer due to thermal stress.

[0007] The present invention has been made in view of the above problems, and aims to provide an electrochemical cell that can realize strong bonding between a metal support and an electrode. [Means for solving the problem]

[0008] One aspect of the present invention is 、 gold a support (2); a cell section (3) including a solid electrolyte layer (30) having oxygen ion conductivity, a first electrode (31) laminated on one side of the solid electrolyte layer, and a second electrode (32) laminated on the other side of the solid electrolyte layer; a bonding layer (4) that bonds the metal support and the first electrode of the cell portion, The bonding layer is The metal support includes at least one of an alloy including a metal support constituent element, which is at least one metal element constituting the metal support, and a first electrode constituent element, which is at least one metal element constituting the first electrode, and a metal oxide including the metal support constituent element and the first electrode constituent element. fruit, The cell portion has a concentration distribution of the first electrode constituent element in the thickness direction thereof, In the concentration distribution, the concentration of the first electrode constituent element is lower on the metal support side than on the first electrode side. , In an electrochemical cell (1). [Effects of the Invention]

[0009] The electrochemical cell has the above configuration. Therefore, in the electrochemical cell, the bonding layer reduces the difference in thermal expansion between the metal support and the first electrode. Therefore, the electrochemical cell can suppress peeling of the first electrode from the metal support due to thermal stress, and can achieve strong bonding between the metal support and the first electrode. Therefore, the electrochemical cell is suitable as a SOFC cell or SOEC cell supported by a metal support.

[0010] In addition, the symbols in parentheses in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of the electrochemical cell of the first embodiment. [Figure 2] FIG. 2 is an enlarged schematic view of the area enclosed by the dotted line in FIG. [Figure 3] FIG. 3 is a diagram schematically showing the concentration distribution of the constituent elements of the metal support in the bonding layer as viewed in the thickness direction of the bonding layer. [Figure 4] FIG. 4 is an explanatory diagram that schematically shows the concentration distribution of the first electrode constituent elements in the bonding layer as viewed in the thickness direction of the bonding layer. [Figure 5] FIG. 5 shows the results of SEM-EDX analysis of a cross section along the thickness direction of the electrochemical cell of Sample 1 prepared in Experimental Example 1, in which (a) is an SEM image, (b) is O element mapping, (c) is Ni element mapping, (d) is Zr element mapping, (e) is Fe element mapping, (f) is Cr element mapping, and (g) is Al element mapping. [Figure 6]FIG. 6 shows the results of SEM-EDX analysis of a cross section along the thickness direction of the electrochemical cell of Sample 2 prepared in Experimental Example 1, in which (a) is an SEM image, (b) is O element mapping, (c) is Ni element mapping, (d) is Zr element mapping, (e) is Cr element mapping, and (f) is Al element mapping. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Embodiment 1) The electrochemical cell of embodiment 1 will be described with reference to Figs. 1 to 4. As illustrated in Figs. 1 and 2, the electrochemical cell 1 of this embodiment is a metal-supported electrochemical cell in which a cell portion 3 is supported by a metal support 2. The electrochemical cell 1 has the metal support 2, the cell portion 3, and a bonding layer 4. The cell portion 3 may be flat or cylindrical. Fig. 1 illustrates a flat cell portion 3.

[0013] The metal support 2 can be made of a metal material (including an alloy) containing at least one metal element selected from the group consisting of, for example, Fe (iron), Ni (nickel), Co (cobalt), Cu (copper), Ag (silver), Pt (platinum), Ti (titanium), Cr (chromium), Al (aluminum), Mn (manganese), Mg (magnesium), and Zn (zinc). This configuration makes it easier to achieve both strong bonding by the bonding layer 4 and electronic conductivity of the metal support 2. The metal support 2 may or may not have a natural oxide film on its surface. FIG. 2 shows an example in which a natural oxide film 201 is formed on the surface of the metal support 2.

[0014] Specifically, the metal material may contain at least Fe and Cr, at least Fe, Cr, and Al, at least Ni, at least Ni and Cr, at least Ni, Cr, and Al, at least Ni, Cr, and Fe, at least Ni, Cr, and Si, or at least Ni and Fe. This configuration makes it easier to balance electronic conductivity, corrosion resistance, structural strength, cost, etc. More specifically, the metal material may be composed of an Fe-Cr alloy, an Fe-Cr-Al alloy, a ferritic stainless steel (e.g., SUS430), an austenitic stainless steel (e.g., SU304), a Ni alloy, a Ni-Cr alloy, a Ni-Cr-Al alloy, a Ni-Cr-Si alloy, a Ni-Cr-Fe alloy, a Ni-Fe alloy, or the like. Examples of Fe-Cr alloys include alloys containing 20% to 30% by mass of Cr, 0.2% to 2% by mass of Mn, with the balance being Fe and unavoidable impurities, and alloys containing 20% to 24% by mass of Cr, 0.1% to 0.6% by mass of Si, 1% to 3% by mass of W, and 0.2% to 1% by mass of Nb, with the balance being Fe and unavoidable impurities. Examples of Fe-Cr-Al alloys include alloys containing 20% to 27% by mass of Cr, 3% to 6% by mass of Al, with the balance being Fe and unavoidable impurities. Examples of Ni-based alloys, Ni-Cr-based alloys, Ni-Cr-Al-based alloys, and Ni-Cr-Si-based alloys include alloys containing Cr: 1% by mass to 5% by mass, Al: 3% by mass to 8% by mass, Si: 1% by mass to 3% by mass, Mn: 0.5% by mass to 2% by mass, with the remainder being Ni and unavoidable impurities.

[0015] The linear thermal expansion coefficient of the metal support 2 is preferably 18×10 from the viewpoints of preventing destruction of the ceramic cell portion 3 due to thermal stress caused by thermal expansion and contraction of the metal support 2 during the manufacture of the electrochemical cell 1, improving the bonding between the cell portion 3 and the metal support 2, and improving the structural reliability during operation of the electrochemical cell 1. -6 / K or less, more preferably 15×10-6 / K or less, more preferably 13×10 -6 The linear thermal expansion coefficient of the metal support 2 can be preferably 9×10 / K or less from the viewpoints of preventing destruction of the ceramic cell portion 3 due to thermal stress caused by thermal expansion and contraction of the metal support 2 during the manufacture of the electrochemical cell 1, improving the bonding between the cell portion 3 and the metal support 2, and improving the structural reliability during operation of the electrochemical cell 1. -6 / K or more, more preferably 10 × 10 -6 / K or more, more preferably 11×10 -6 / K or more. The linear thermal expansion coefficient of the metal support 2 is a value at 700°C. The linear thermal expansion coefficient of the metal support 2 is a value measured using a thermomechanical analyzer according to the procedure described in JIS Z2285.

[0016] The metal support 2 is disposed on one side of the cell unit 3 to support the cell unit 3. FIG. 1 shows an example in which the metal support 2 specifically has a plate-shaped cell support part 20 with a plurality of through holes 21 penetrating between one plate surface and the other plate surface. In this metal support 2, the cell unit 3 is supported by being joined to one side surface of the cell support part 20. The through holes 21 of the cell support part 20 serve as a flow path for a gas (described later) to be supplied to the first electrode 31 of the cell unit 3.

[0017] The cell section 3 includes a solid electrolyte layer 30 having oxygen ion conductivity, a first electrode 31 stacked on one side of the solid electrolyte layer 30, and a second electrode 32 stacked on the other side of the solid electrolyte layer 30. Specifically, Fig. 1 shows an example in which the first electrode 31, the solid electrolyte layer 30, and the second electrode 32 are stacked in this order and joined to each other.

[0018] The cell unit 3 may further include an intermediate layer (not shown) between the solid electrolyte layer 30 and the second electrode 32. The intermediate layer is a layer that mainly serves to suppress reaction between the material of the solid electrolyte layer 30 and the material of the second electrode 32. In this case, the cell unit 3 may specifically have a configuration in which the first electrode 31, the solid electrolyte layer 30, the intermediate layer, and the second electrode 32 are stacked in this order and joined together.

[0019] The solid electrolyte layer 30 has oxygen ion conductivity. Specifically, the solid electrolyte layer 30 can be formed in a layered form using a solid electrolyte having oxygen ion conductivity. The solid electrolyte layer 30 is usually formed as a dense material to ensure gas tightness. As the solid electrolyte constituting the solid electrolyte layer 30, for example, zirconium oxide-based oxides such as yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) can be suitably used from the viewpoints of excellent strength and thermal stability. As the solid electrolyte constituting the solid electrolyte layer 30, yttria-stabilized zirconia is suitable from the viewpoints of oxygen ion conductivity, mechanical stability, compatibility with other materials, and chemical stability from oxidizing atmospheres to reducing atmospheres.

[0020] The first electrode 31 contains at least one metal element. Examples of the metal element contained in the first electrode 31 include at least one element selected from the group consisting of Ni (nickel), Cu (copper), Co (cobalt), Zr (zirconium), Y (yttrium), Sc (scandium), Ce (cerium), Al (aluminum), La (lanthanum), Pr (praseodymium), and Nd (neodymium). Specifically, the first electrode 31 may contain a metal, alloy, or oxide containing at least one element selected from Ni, Cu, Co, Zr, Y, Sc, Ce, Al, La, Pr, and Nd. More specifically, the first electrode 31 may contain a metal, alloy, or oxide containing at least one element selected from Ni, Cu, and Co, and / or a metal, alloy, or oxide containing at least one element selected from Zr, Y, Sc, Ce, Al, La, Pr, and Nd.

[0021] More specifically, the first electrode 31 may contain one or more electron conductors (metals or alloys, hereinafter omitted) such as Ni, Ni alloys, Cu, Cu alloys, Co, and Co alloys, or oxides of electron conductors (oxides of metals or alloys, hereinafter omitted) that become electron conductors upon reduction, such as Ni oxides (NiO, etc.), Cu oxides, and Co oxides. Electronic conductors and oxides of electron conductors are sometimes collectively referred to as "electronic conductors." Among these, Ni, Ni alloys, Ni oxides (NiO, etc.), etc. are preferred, and Ni is more preferred. Furthermore, the first electrode 31 may contain one or more oxygen ion conductors, such as yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ). Among these, yttria-stabilized zirconia is preferred. Furthermore, the first electrode 31 may contain one or more oxide-based additives, such as an oxide containing Zr and at least one element selected from the group consisting of Ce, Al, La, Pr, Nd, Y, and Sc, preferably an oxide containing Ce and Zr and at least one element selected from the group consisting of Al, La, Pr, Nd, Y, and Sc. Among these, an oxide containing Ce and Zr is preferred. Examples of oxides containing Ce and Zr include Ce-Zr-O-based oxides, Ce-Zr-La-O-based oxides, Ce-Zr-Sc-O-based oxides, Ce-Zr-YO-based oxides, and Ce-Zr-Al-O-based oxides. The above-mentioned metals, alloys, and oxides may be combined in any manner. More specifically, the first electrode 31 may contain, for example, Ni and yttria-stabilized zirconia, or Ni, yttria-stabilized zirconia, and an oxide containing Ce and Zr. The above-mentioned metals, alloys, and oxides may exist as particles in the first electrode 31. The first electrode 31 may generally be formed to be porous, including pores.

[0022] In the first electrode 31, the ratio of the electron conductor and the oxygen ion conductor, in terms of the formation of electron conduction paths and oxygen ion conduction paths, the balance between electron conductivity and oxygen ion conductivity, and the like, can be preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30, by volume. Furthermore, the content of the oxide-based additive, relative to the total mass of the electron conductor and the oxygen ion conductor, can be preferably 1 mass% or more, more preferably 2 mass% or more, even more preferably 3 mass% or more, even more preferably 4 mass% or more, and even more preferably 5 mass% or more, from the viewpoint of suppressing deterioration of the first electrode 31. The content of the oxide-based additive, relative to the total mass of the electron conductor and the oxygen ion conductor, can be preferably 30 mass% or less, more preferably 25 mass% or less, and even more preferably 20 mass% or less, from the viewpoint of suppressing deterioration of the electron conductivity and oxygen ion conductivity of the first electrode 31. The ratio of the electron conductor etc. to the oxygen ion conductor and the content of the oxide-based additive can be measured by inductively coupled plasma (ICP) emission spectroscopy of a solution in which the first electrode 31 is dissolved in a strong acid.

[0023] Examples of materials for the second electrode 32 include transition metal perovskite oxides such as lanthanum-strontium-cobalt oxide, lanthanum-strontium-cobalt-iron oxide, and lanthanum-strontium-manganese-iron oxide, or mixtures of the above transition metal perovskite oxides with ceria (CeO) or a ceria solid solution in which ceria is doped with one or more elements selected from Gd, Sm, Y, La, Nd, Yb, Ca, and Ho. These materials can be used alone or in combination. The second electrode 32 is typically formed to be porous, including pores.

[0024] When the cell section 3 has an intermediate layer, the intermediate layer can be specifically formed in a layer shape from a solid electrolyte having oxygen ion conductivity. Examples of the solid electrolyte used in the intermediate layer include ceria (CeO2) and ceria-based solid solutions in which ceria is doped with one or more elements selected from Gd, Sm, Y, La, Nd, Yb, Ca, and Ho. These can be used alone or in combination. Gd-doped ceria is preferred as the solid electrolyte used in the intermediate layer.

[0025] The thickness of the cell portion 3 can be 200 μm or less. The bonding layer 4 has inferior conductivity compared to the first electrode 31 in terms of its material composition. If the thickness of the cell portion 3 is 200 μm or less, even a metal-supported electrochemical cell 1 can easily exhibit battery performance comparable to that of a first-electrode-supported electrochemical cell in which the first electrode 31 serves as both an electrode and a support.

[0026] The thickness of the cell portion 3 is preferably 400 μm or less, more preferably 300 μm or less, and even more preferably 150 μm or less. From the viewpoints of ensuring strength and improving startability, the thickness of the cell portion 3 is preferably 20 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more.

[0027] The thickness of the solid electrolyte layer 30 can be preferably 3 to 20 μm, more preferably 3.5 to 15 μm, and even more preferably 4 to 10 μm, from the viewpoints of reducing ohmic resistance, suppressing gas permeation, and preventing a decrease in electromotive force due to electron leakage. The thickness of the first electrode 31 can be preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, from the viewpoints of ensuring electrochemical reaction sites. The thickness of the first electrode 31 can be preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 50 μm or less, from the viewpoints of reducing ohmic resistance and gas diffusion resistance. The thickness of the second electrode 32 can be preferably 5 to 100 μm, more preferably 20 to 80 μm, and even more preferably 30 to 50 μm, from the viewpoints of reducing ohmic resistance and gas diffusion resistance and ensuring electrochemical reaction sites. The thickness of the intermediate layer can be preferably 1 to 20 μm, and more preferably 2 to 10 μm, from the viewpoints of reducing ohmic resistance, suppressing element diffusion from the second electrode 32, suppressing gas permeation, etc. The thicknesses of the cell section 3, solid electrolyte layer 30, first electrode 31, second electrode 32, and intermediate layer described above are each the arithmetic mean value of thickness measurements at 10 points obtained by observing a cross section of the cell section 3 along the thickness direction with a scanning electron microscope (SEM).

[0028] The bonding layer 4 is a layer that bonds the metal support 2 and the first electrode 31 of the cell section 3. The bonding layer 4 contains at least one of an alloy containing the metal support constituent elements and the first electrode constituent elements, and a metal oxide containing the metal support constituent elements and the first electrode constituent elements.

[0029] The metal support constituent element is at least one metal element constituting the metal support 2 and can be selected from the various metal elements constituting the metal support 2 described above. Examples of the metal support constituent element include Cr, Ni, Al, Si, Ti, Mn, etc., from the viewpoints of element diffusibility from the metal support 2 when the first electrode 31 is joined to the metal support 2, bonding strength, high-temperature strength, oxidation resistance, etc. One or more of these elements may be included. On the other hand, the first electrode constituent element is at least one metal element constituting the first electrode 31 and can be selected from the various metal elements constituting the first electrode 31 described above. Examples of the first electrode constituent element include Cr, Al, Ni, Cu, etc., from the viewpoints of element diffusibility from the first electrode 31 when the first electrode 31 is joined to the metal support 2, bonding strength, electrochemical properties, etc. One or more of these elements may be included.

[0030] Specific examples of alloys containing a metal support constituent element and a first electrode constituent element include an alloy containing Ni and Cr, an alloy containing Ni and Al, an alloy containing Ni, Cr and Al, an alloy containing Ni and Fe, an alloy containing Ni, Fe and Cr, etc. Specific examples of metal oxides containing a metal support constituent element and a first electrode constituent element include an oxide containing Ni, Cr and O (oxygen), an oxide containing Ni, Al and O, an oxide containing Ni, Cr, Al and O, an oxide containing Ni, Fe and O, an oxide containing Ni, Fe, Cr and O, etc.

[0031] The thickness of the bonding layer 4 is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 0.8 μm or more, from the viewpoints of easily achieving sufficient bonding between the metal support 2 and the first electrode 31 and suppressing excessive element diffusion during firing. The thickness of the bonding layer 4 is preferably 5 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less, from the viewpoint of suppressing ohmic resistance. The thickness of the bonding layer 4 is the arithmetic mean value of thickness measurements at 10 points obtained by observing a cross section of the cell portion 3 along the thickness direction with a scanning electron microscope (SEM).

[0032] The electrochemical cell 1 can be configured such that the metal support constituent elements are diffused in the first electrode 31. With this configuration, some of the metal support constituent elements diffused from the metal support 2 can be present in the bonding layer 4 and the first electrode 31. Therefore, with this configuration, it is easier to achieve matching in Young's modulus and thermal expansion between the first electrode 31 and the metal support 2, and peeling of the first electrode 31 from the metal support 2 due to thermal stress can be more easily suppressed. Specifically, the metal support constituent elements present in the first electrode 31 can be solid-solved in the material of the first electrode 31. In this case, the metal support constituent elements may be solid-solved in, for example, an electron conductor or an oxygen ion conductor.

[0033] In the electrochemical cell 1, the bonding layer 4 can be configured to have a concentration distribution of the metal support constituent elements in the thickness direction of the cell section 3, as illustrated in FIG. 3(a). In this case, the concentration of the metal support elements can be gradient in the bonding layer 4. Therefore, in this case, it is easier to reduce the thermal expansion difference between the metal support 2 and the first electrode 31. In this case, the bonding layer 4 can specifically contain an alloy or metal oxide with a gradient composition. Furthermore, as illustrated in FIG. 3(b), the bonding layer 4 can also be configured not to have a concentration distribution of the metal support constituent elements in the thickness direction of the cell section 3. In other words, the bonding layer 4 can be configured so that the concentration of the metal support constituent elements is approximately constant in the thickness direction of the cell section 3. In this case, the bonding layer 4 can specifically contain an alloy or metal oxide with a specific composition.

[0034] When the bonding layer 4 has a concentration distribution of the metal support constituent elements as illustrated in FIG. 3( a), the concentration of the metal support constituent elements can be configured to be lower on the first electrode 31 side than on the metal support 2 side. The concentration of the metal support constituent elements on the metal support 2 side in the bonding layer 4 refers to the concentration of the metal support constituent elements at the end position on the metal support 2 side in the concentration distribution of the metal support constituent elements. Similarly, the concentration of the metal support constituent elements on the first electrode 31 side in the bonding layer 4 refers to the concentration of the metal support constituent elements at the end position on the first electrode 31 side in the concentration distribution of the metal support constituent elements. In the concentration distribution of the metal support constituent elements in FIG. 3( a), a configuration is illustrated in which the concentration of the metal support constituent elements decreases from the metal support 2 side toward the first electrode 31 side. In this case, the concentration of the metal support constituent elements may decrease gradually (gradually) or in stages (stepwise) from the metal support 2 side toward the first electrode 31 side.

[0035] FIG. 3 illustrates the concentration distribution of the metal support constituent elements not only in the bonding layer 4 but also in the metal support 2 and the first electrode 31. Specifically, FIG. 3 illustrates an example in which the concentration of the metal support constituent elements in the metal support 2 is lower in the peripheral region of the bonding layer 4 than in the interior of the metal support 2. This is an example showing that some of the metal support constituent elements present in the peripheral region of the bonding layer 4 in the metal support 2 have diffused to the bonding layer 4 and the first electrode 31. FIG. 3 also illustrates an example in which the concentration of the metal support constituent elements in the first electrode 31 decreases from the interface between the bonding layer 4 and the first electrode 31 toward the solid electrolyte layer 30. This is an example showing that the metal support constituent elements have diffused from the interface between the bonding layer 4 and the first electrode 31 toward the solid electrolyte layer 30.

[0036] The electrochemical cell 1 can be configured such that the first electrode constituent elements are diffused in the metal support 2. With this configuration, some of the first electrode constituent elements diffused from the first electrode 31 can be present in the bonding layer 4 and the metal support 2. Therefore, with this configuration, it becomes easier to achieve matching in Young's modulus and thermal expansion between the first electrode 31 and the metal support 2, and peeling of the first electrode 31 from the metal support 2 due to thermal stress can be more easily suppressed. Specifically, the first electrode constituent elements present in the metal support 2 can be solid-solved in the material of the metal support 2.

[0037] In the electrochemical cell 1, the bonding layer 4 can be configured to have a concentration distribution of the first electrode constituent elements when viewed in the thickness direction of the cell section 3, as exemplified in FIG. 4(a). In this case, the concentration of the first electrode constituent elements can be gradient in the bonding layer 4. Therefore, in this case, it is easier to reduce the difference in thermal expansion between the metal support 2 and the first electrode 31. Specifically, the bonding layer 4 in this case can contain an alloy or metal oxide with a gradient composition. In addition, Fig. As illustrated in 4(b) Na , a configuration in which the concentration distribution of the first electrode constituent elements is not present when viewed in the thickness direction of the cell portion 3. , That is, the concentration of the first electrode constituent element is almost constant in the thickness direction of the cell portion 3. Electrochemical cell 1 having an adhesive layer 4teeth, It is a reference format. do.

[0038] When the bonding layer 4 has a concentration distribution of the first electrode constituent elements as illustrated in FIG. 4(a), the concentration of the first electrode constituent elements can be configured to be lower on the metal support 2 side than on the first electrode 31 side. The concentration of the first electrode constituent elements on the metal support 2 side of the bonding layer 4 refers to the concentration of the first electrode constituent elements at the end position on the metal support 2 side in the concentration distribution of the first electrode constituent elements. Similarly, the concentration of the first electrode constituent elements on the first electrode 31 side of the bonding layer 4 refers to the concentration of the first electrode constituent elements at the end position on the first electrode 31 side in the concentration distribution of the first electrode constituent elements. In the concentration distribution of the first electrode constituent elements in FIG. 4(a), a configuration is illustrated in which the concentration of the first electrode constituent elements decreases from the first electrode 31 side toward the metal support 2 side. In this case, the concentration of the first electrode constituent elements may decrease gradually (gradually) from the first electrode 31 side toward the metal support 2 side, or may decrease in stages (stepwise).

[0039] FIG. 4 illustrates the concentration distribution of the first electrode constituent element not only in the bonding layer 4 but also in the metal support 2 and the first electrode 31. Specifically, FIG. 4 illustrates an example in which the concentration of the first electrode constituent element in the first electrode 31 is lower in the peripheral region of the bonding layer 4 than in the interior of the first electrode 31. This is an example showing that a portion of the first electrode constituent element present in the peripheral region of the bonding layer 4 in the first electrode 31 has diffused into the bonding layer 4 and the metal support 2. FIG. 4 also illustrates an example in which the concentration of the first electrode constituent element in the metal support 2 decreases from the interface between the bonding layer 4 and the metal support 2 toward the side opposite the solid electrolyte layer 30. This is an example showing that the first electrode constituent element has diffused from the interface between the bonding layer 4 and the metal support 2 toward the side opposite the solid electrolyte layer 30.

[0040] The diffusion of the metal support constituent elements into the first electrode 31 and the diffusion of the first electrode constituent elements into the metal support 2 can be understood by performing element mapping of each element on a cross section along the thickness direction of the electrochemical cell 1 using TEM-EDX (transmission electron microscope-energy dispersive X-ray spectroscopy). The concentrations of the metal support constituent elements and the first electrode constituent elements can be measured as follows: A cross section along the thickness direction of the electrochemical cell 1 is created so that the bonding layer 4 can be observed. TEM-EDX measurement is performed on the cross section, and a linear concentration profile of each element is obtained across the bonding layer 4. The number of measurement points for element concentration is determined statistically (with a confidence interval of 95% and a tolerance of 15%) from the values obtained with N=5, and the average value is used.

[0041] In the electrochemical cell 1, the first electrode 31 can be configured such that the average particle size of the material particles in the region on the metal support 2 side is larger than the average particle size of the material particles in the region on the solid electrolyte layer 30 side. This configuration improves the base material strength of the region on the metal support 2 side of the first electrode 31, enhances resistance to thermal stress, and improves bonding strength. As described below, this configuration can be formed, for example, by co-firing the first electrode-forming material on the metal support 2 while in contact with the metal support 2, thereby applying heat from the metal support 2 to the first electrode 31 and causing grain growth and necking growth of the material particles of the first electrode 31. The size relationship between the material particles in the region on the solid electrolyte layer 30 side and the material particles in the region on the metal support 2 side is compared between particles of the same type. Specifically, the material particles of the first electrode 31 can be composed of electronic conductor particles, or electronic conductor particles and oxygen ion conductor particles. The electronic conductor particles include not only electronic conductors but also oxide particles of electronic conductors that become electronic conductors upon reduction. Therefore, when the material particles of the first electrode 31 are composed of electron conductor particles, the first electrode 31 can be configured so that the average particle size of the electron conductor particles in the region on the metal support 2 side is larger than the average particle size of the electron conductor particles in the region on the solid electrolyte layer 30 side. When the material particles of the first electrode 31 are composed of electron conductor particles and oxygen ion conductor particles, the first electrode 31 can be configured so that the average particle size of the electron conductor particles in the region on the metal support 2 side is larger than the average particle size of the electron conductor particles in the region on the solid electrolyte layer 30 side, and / or the average particle size of the oxygen ion conductor particles in the region on the metal support 2 side is larger than the average particle size of the oxygen ion conductor particles in the region on the solid electrolyte layer 30 side.

[0042] The region on the solid electrolyte layer 30 side refers to a region extending from the interface between the first electrode 31 and the solid electrolyte layer 30 to a depth of 3 μm toward the inside of the first electrode 31. The region on the metal support 2 side refers to a region extending from the interface between the first electrode 31 and the bonding layer 4 to a depth of 3 μm toward the inside of the first electrode 31. The average particle size of the material particles in the region on the solid electrolyte layer 30 side can be, for example, 0.1 μm to 5 μm, in order to ensure a three-phase interface, which is a reaction site, and reduce the degree of curvature of the conduction path. The average particle size of the material particles in the region on the metal support 2 side can be, for example, 0.2 μm to 10 μm, in order to reduce the degree of curvature of the conduction path and improve the bonding strength with the metal support 2. More specifically, the average particle size of the electron conductor particles in the region on the solid electrolyte layer 30 side can be, for example, 0.1 μm to 5 μm, in order to ensure a three-phase interface, which is a reaction site, and reduce the degree of curvature of the conduction path. The average particle size of the oxygen ion conductor particles in the region on the solid electrolyte layer 30 side can be, for example, 0.1 μm to 5 μm, from the viewpoints of ensuring a three-phase interface, which is a reaction site, and reducing the degree of curvature of the conduction path. The average particle size of the electron conductor particles in the region on the metal support 2 side can be, for example, 0.2 μm to 10 μm, from the viewpoints of reducing the degree of curvature of the conduction path and improving the bonding strength with the metal support 2. The average particle size of the oxygen ion conductor particles in the region on the metal support 2 side can be, for example, 0.2 μm to 10 μm, from the viewpoints of reducing the degree of curvature of the conduction path and improving the bonding strength with the metal support 2. The average particle size ranges of the material particles, electron conductor particles, and oxygen ion conductor particles in the intermediate region between the region on the solid electrolyte layer 30 side and the region on the metal support 2 side can be, for example, the same as the average particle size ranges of the material particles, electron conductor particles, and oxygen ion conductor particles in the region on the solid electrolyte layer 30 side.

[0043] The average particle size of the particles can be calculated by performing image analysis on an SEM cross-sectional image taken along the thickness direction of the cell portion 3. Specifically, an SEM cross-sectional image including the first electrode 31 along the thickness direction of the cell portion 3 is acquired. The acquired SEM cross-sectional image can be magnified 3000 times. Next, image analysis software ("Image-Pro" manufactured by Media Cybernetics) is used to perform image processing by binarization or ternarization on the captured image. The binarization process is intended to distinguish between electron conductor particles and oxygen ion conductor particles, if the material particles of the first electrode 31 are either electron conductor particles or oxygen ion conductor particles, and pores present in the first electrode 31. The ternarization process is intended to distinguish between these particles and pores present in the first electrode 31, if the material particles of the first electrode 31 are either electron conductor particles or oxygen ion conductor particles. Since the particles and pores that make up the first electrode 31 have different brightness levels, the image processing involves removing noise remaining in the captured image, setting an arbitrary threshold value, and then performing binarization or ternarization. Since the threshold value differs depending on the captured image, a threshold value that can separate the particles and pores that make up the first electrode 31 is set for each captured image while visually checking the captured image. For each specified particle in the obtained processed image (binarized image or ternarized image), the circle equivalent diameter, which is the diameter of a perfect circle having the same area as the particle, is calculated for each particle, and the particle size distribution based on the number is determined. In the obtained particle size distribution of the specified particles, the particle diameter D at which the cumulative particle diameter, counting from the smallest, is 50% is calculated. 50 The particle diameter D obtained from each processed image obtained from the SEM cross-sectional images of five different arbitrary points as described above is calculated. 50 The arithmetic mean value of these is taken as the average particle size of the predetermined particles. In this way, the average particle size of the electron conductor particles and the average particle size of the oxygen ion conductor particles in the first electrode 31 can be calculated.

[0044] In the electrochemical cell 1, the first electrode 31 can be configured such that the porosity in the region on the metal support 2 side is greater than the porosity in the region on the solid electrolyte layer 30 side. With this configuration, the Young's modulus of the region on the metal support 2 side of the first electrode 31 is reduced, improving compliance with thermal stress due to the difference in thermal expansion between the first electrode 31 and the metal support 2 and facilitating relaxation of the thermal stress. The above configuration can be produced, for example, in a production example of the electrochemical cell 1 described below, by stacking, on the metal support 2, a plurality of first electrode-forming sheets containing different amounts of pore-forming material so as to form a first electrode 31 with different porosities in the thickness direction.

[0045] The porosity of the region on the solid electrolyte layer 30 side can be, for example, 20% or more and 50% or less from the viewpoints of reducing gas diffusion resistance, maintaining electronic conductivity and oxygen ion conductivity, and ensuring a three-phase interface, which is a reaction site. The porosity of the region on the metal support 2 side can be, for example, 25% or more and 50% or less from the viewpoints of reducing gas diffusion resistance, maintaining electronic conductivity and oxygen ion conductivity, etc. The porosity of the intermediate region between the region on the solid electrolyte layer 30 side and the region on the metal support 2 side can be, for example, 25% or more and 50% or less from the viewpoints of reducing gas diffusion resistance, maintaining electronic conductivity and oxygen ion conductivity, etc.

[0046] The porosity can be calculated as follows. A processed image (binarized image or ternarized image) is obtained in the same manner as for the average particle diameter described above. The area of each pore in the obtained processed image is calculated for each pore. The measured porosity value in each region is then calculated using the formula 100 × (total pore area contained in each region) / (total area of each region). The arithmetic mean value of the measured porosity values in each region obtained from each processed image obtained for SEM cross-sectional images at any five different locations as described above is taken as the porosity in each region.

[0047] In the electrochemical cell 1, the first electrode 31 may be configured such that the content of electronic conductor particles in the region on the metal support 2 side is higher than the content of electronic conductor particles in the region on the solid electrolyte layer 30 side. The greater the amount of electronic conductor particles, the greater the amount of thermal expansion, and the smaller the difference in thermal expansion with the metal support 2. Therefore, this configuration makes it easier to alleviate thermal stress caused by the difference in thermal expansion between the first electrode 31 and the metal support 2. The above configuration can be manufactured, for example, by stacking multiple first electrode-forming sheets, each having a different content of electronic conductor particles, on the metal support 2 in a manufacturing example of the electrochemical cell 1 described below, so that the first electrode 31 has a different content of electronic conductor particles in the thickness direction.

[0048] The content of electronic conductor particles in the region on the solid electrolyte layer 30 side can be, for example, 20% to 40% from the viewpoints of maintaining electronic conductivity and ionic conductivity and ensuring a three-phase interface, which is a reaction site. The content of electronic conductor particles in the region on the metal support 2 side can be, for example, 20% to 50% from the viewpoints of maintaining electronic conductivity and strengthening the bond with the metal support 2. The content of electronic conductor particles in the intermediate region between the region on the solid electrolyte layer 30 side and the region on the metal support 2 side can be, for example, 20% to 50% from the viewpoints of maintaining electronic conductivity.

[0049] The content of the electron conductor particles can be calculated as follows: A processed image (binarized image or ternarized image) is obtained in the same manner as the average particle diameter of the particles described above. The area of each electron conductor particle in the obtained processed image is calculated for each particle. The area of each electron conductor particle in the obtained processed image is then calculated for each particle. The measured area ratio of the electron conductor particles in each region is then calculated using the formula 100 × (total area of the electron conductor particles contained in each region) / (total area of each region). The arithmetic mean value of the measured area ratios of the electron conductor particles in each region obtained from each processed image obtained for SEM cross-sectional images at any five different locations in the manner described above is taken as the content of the electron conductor particles contained in each region.

[0050] In the electrochemical cell 1, the first electrode 31 contains Ni-containing particles (Ni particles, Ni alloy particles, etc.) as electron conductor particles, and can be configured such that the content of Ni-containing particles in the region on the metal support 2 side is higher than the content of Ni-containing particles in the region on the solid electrolyte layer 30 side. According to this configuration, by increasing the content of Ni-containing particles in the region on the metal support 2 side of the first electrode 31, the thermal expansion of the region on the metal support 2 side of the first electrode 31 can be made closer to that of the metal support 2, which has the advantage of reducing thermal stress due to temperature changes.

[0051] In the above configuration, the content of Ni-containing particles in the region on the solid electrolyte layer 30 side can be, for example, 20% to 40% from the viewpoints of electronic conductivity and ensuring a three-phase interface, which is a reaction site. Furthermore, the content of Ni-containing particles in the region on the metal support 2 side can be, for example, 20% to 50% from the viewpoints of maintaining electronic conductivity and strengthening the bond with the metal support 2. Furthermore, the content of Ni-containing particles in the intermediate region between the region on the solid electrolyte layer 30 side and the region on the metal support 2 side can be, for example, 20% to 50% from the viewpoints of maintaining electronic conductivity. The content of Ni-containing particles can be determined according to the method for calculating the content of electronic conductor particles described above.

[0052] The first electrode 31 may be composed of a single layer or multiple layers. When the first electrode 31 is composed of multiple layers, the material ratio, average particle size of the material particles, and porosity of each layer may be the same or different. The material ratio, average particle size of the material particles, and porosity of each layer may be configured to be graded.

[0053] The electrochemical cell 1 can be configured so that voids 5 are present at at least one of the interface between the metal support 2 and the bonding layer 4 and the interface between the first electrode 31 and the bonding layer 4. According to the above configuration, the voids 5 can relieve residual stress, which is advantageous in preventing peeling of the first electrode from the metal support 2. Specifically, the voids 5 can be configured to be scattered at the interface between the metal support 2 and the bonding layer 4, as exemplified in FIG. 2 , or can be configured to be scattered at the interface between the first electrode 31 and the bonding layer 4, although not shown.

[0054] The void diameter of the voids 5 can be preferably 1 μm or more, more preferably 0.5 μm or more, and even more preferably 0.1 μm or more, from the viewpoints of suppressing peeling of the first electrode by relaxing residual stress, relaxing thermal stress, etc. Furthermore, the void diameter can be preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less, from the viewpoints of ensuring adhesion between the metal support 2 and the bonding layer 4, ensuring adhesion between the first electrode 31 and the bonding layer 4, and ensuring electronic conductivity.

[0055] The porosity of the voids 5 can be preferably 0.1 vol% or more, more preferably 0.2 vol% or more, and even more preferably 0.5 vol% or more, from the viewpoints of suppressing peeling of the first electrode by relaxing residual stress, relaxing thermal stress, etc. Furthermore, the porosity can be preferably 5 vol% or less, more preferably 2 vol% or less, and even more preferably 1 vol% or less, from the viewpoints of ensuring adhesion between the metal support 2 and the bonding layer 4, ensuring adhesion between the first electrode 31 and the bonding layer 4, and ensuring electronic conductivity.

[0056] The void diameter and the void ratio can be calculated as follows. A processed image (binarized image or ternarized image) is obtained in the same manner as the average particle diameter described above. For each void 5 in the obtained processed image, the circle equivalent diameter, which is the diameter of a perfect circle having the same area as the area of the void 5, is calculated for each void 5, and the void diameter distribution on a number basis is obtained. In the obtained void diameter distribution, the void diameter Dp at which the cumulative void diameter counting from the smallest is 50% is calculated. 50The void diameter Dp obtained from each processed image obtained from the SEM cross-sectional images of five different arbitrary locations as described above is calculated. 50 The arithmetic mean value of these is taken as the void diameter of the voids 5. In addition, in the obtained processed image, the porosity measurement value is calculated using the formula 100 × (total length of the interface cut out by the voids 5 out of the specified interface) / (total length of the specified interface). The arithmetic mean value of the porosity measurement values obtained from each processed image calculated for the SEM cross-sectional images at any five different locations as described above is taken as the porosity of the voids 5.

[0057] The electrochemical cell 1 can be manufactured, for example, as follows, but is not limited to this. First, an unfired first electrode-forming sheet, which will become the first electrode 31 upon firing, an unfired solid electrolyte layer-forming sheet, which will become the solid electrolyte layer 30 upon firing, an unfired second electrode layer-forming sheet, which will become the second electrode 32 upon firing, and, if necessary, an unfired intermediate layer-forming sheet, which will become the intermediate layer upon firing, are prepared. An unfired second electrode-forming paste, which will become the second electrode 32 upon firing, is also prepared. Next, the first electrode layer-forming sheet, the solid electrolyte layer-forming sheet, and, if necessary, the intermediate layer-forming sheet are stacked in this order on one surface of the metal support 2, and then pressed together using a warm isostatic press or the like. The pressed laminate can be degreased as needed. Multiple first electrode-forming sheets can be stacked together as needed. In this case, the plurality of first electrode-forming sheets to be stacked may be made of the same material, or may be made of materials that differ from one another in terms of material type, material particle size, compounding ratio, amount of pore-forming material, etc., so that first electrodes 31 having different chemical compositions and microstructures in the thickness direction are formed. Furthermore, the plurality of first electrode-forming sheets to be stacked may have the same thickness, or may have different thicknesses.

[0058] The laminate is then fired in an air atmosphere at a maximum temperature of 1200°C or less. The bonding layer 4 can be formed by co-firing an unfired first electrode-forming material, which will become the first electrode 31 upon firing, on the metal support 2. Specifically, the bonding layer 4 can be formed by diffusion bonding the metal support 2 and the first electrode-forming material. Therefore, the bonding layer 4 is different from a layer formed by disposing a separate bonding material between the metal support 2 and the first electrode-forming material and firing the resulting material. When the thickness of the bonding layer 4 is 1 μm or less, it becomes difficult to form a layer by sandwiching a separate material between the metal support 2 and the first electrode-forming material, making the difference between the two distinct.

[0059] If the firing temperature exceeds 1300°C, a strong insulating oxide film will be formed on the metal support 2, making it difficult to operate the electrochemical cell 1. In the firing, in order to promote the formation of a bonding layer 4 at the interface between the metal support 2 and the cell section 3, it is preferable to hold the temperature lower than the maximum temperature for a long time (for example, at 900°C for 24 hours) before firing at the maximum temperature. Next, a paste for forming a second electrode is applied to the surface of the formed solid electrolyte layer 30 (or the intermediate layer, if any) by screen printing or the like, and then fired (baked) in an air atmosphere. The firing temperature at this time can be, for example, 900°C to 950°C. Next, the first electrode 31 is subjected to a reduction treatment. This allows the metal-supported electrochemical cell 1 to be obtained.

[0060] In the above-described electrochemical cell 1, the difference in thermal expansion between the metal support 2 and the first electrode 31 is alleviated by the bonding layer 4. Therefore, the electrochemical cell 1 can prevent the first electrode 31 from peeling off from the metal support 2 due to thermal stress, and can achieve strong bonding between the metal support 2 and the first electrode 31.

[0061] The electrochemical cell 1 has a cell section 3 that includes a solid electrolyte layer 30 that has oxygen ion conductivity. Therefore, the electrochemical cell 1 can be used as at least one of a solid oxide fuel cell (SOFC) that includes a solid electrolyte layer 30 that has oxygen ion conductivity, and a solid oxide electrolysis cell (SOEC) that includes a solid electrolyte layer 30 that has oxygen ion conductivity. In other words, the electrochemical cell 1 may be operated as an SOFC or as an SOEC, or may be configured to be switchable between an SOFC mode in which it operates as an SOFC and an SOEC mode in which it operates as an SOEC, and may be operated as both an SOFC and an SOEC.

[0062] In this embodiment, the first electrode 31 can be an electrode to which a fuel gas is supplied. Specifically, when the electrochemical cell 1 is operated as an SOFC, the first electrode 31 can be used as a fuel electrode. A hydrogen-containing gas such as hydrogen gas can be supplied to the first electrode 31 as a fuel gas. In this case, the second electrode 32 can be used as an air electrode (oxidizer electrode). An oxygen-containing gas such as air or oxygen gas can be supplied to the second electrode 32 as an oxidizer. On the other hand, when the electrochemical cell 1 is operated as an SOEC, the first electrode 31 can be used as a hydrogen electrode. A water (H2O)-containing gas such as water vapor gas can be supplied to the first electrode 31 as a fuel gas. In this case, the second electrode 32 can be used as an oxygen electrode. A gas such as air may or may not be supplied to the second electrode 32. The hydrogen-containing gas may contain water vapor for humidification, etc., and the water-containing gas may contain a reducing gas such as hydrogen gas.

[0063] In this embodiment, the case where fuel gas is supplied to the first electrode 31 has been mainly described, but the electrochemical cell 1 may be configured so that fuel gas is supplied to the second electrode 32. In this case, the above description of the first electrode 31 can be read as a description of the second electrode 32, and the above description of the second electrode 32 can be read as a description of the first electrode 31.

[0064] (Experimental Example 1) <Preparation of electrochemical cell> A plate-shaped metal support (thickness: 1 mm) was prepared, which was made of an Fe-Cr-Al alloy containing 20% by mass to 30% by mass of Cr, 3% by mass to 8% by mass of Al, and the remainder being Fe and unavoidable impurities. The metal support had a plurality of through holes formed between its two surfaces at the portion where the cells were to be joined.

[0065] NiO powder (average particle size: 0.5 μm), yttria-stabilized zirconia (YSZ) powder (average particle size: 0.2 μm) containing 8 mol% YO, carbon (pore-forming agent), polyvinyl butyral, isoamyl acetate, and 1-butanol were mixed and crushed in a ball mill to prepare a slurry. The mass ratio of NiO powder to YSZ powder was 65:35. The slurry was applied in layers onto a resin sheet using a doctor blade method, dried, and then peeled off to prepare a first electrode-forming sheet A. The average particle size is the particle size (diameter) d50 at which the volume-based cumulative frequency distribution measured by laser diffraction and scattering is 50% (the same applies below).

[0066] A slurry was prepared by mixing YSZ powder (average particle size: 0.2 μm), polyvinyl butyral, isoamyl acetate, and 1-butanol in a ball mill. After that, a sheet for forming a solid electrolyte layer was prepared in the same manner as in the production of the sheet A for forming a first electrode.

[0067] A slurry was prepared by mixing Gd-doped CeO2 (hereinafter referred to as GDC) powder (average particle size: 0.3 μm), polyvinyl butyral, isoamyl acetate, and 1-butanol in a ball mill. In this experimental example, CeO2 doped with 10 mol% Gd was used as the GDC. Thereafter, an intermediate layer-forming sheet was prepared in the same manner as in the preparation of the first electrode-forming sheet A.

[0068] LSC(La 0.6 Sr0.4 CoO3 powder (average particle size: 2.0 μm), ethyl cellulose, and terpineol were kneaded using a triple roll mill to prepare a paste for forming a second electrode.

[0069] The first electrode-forming sheet A, the solid electrolyte layer-forming sheet, and the intermediate layer-forming sheet were stacked in this order on one surface of a metal support, and then pressed together using a warm isostatic press. The pressing conditions were a temperature of 85°C, a pressure of 50 MPa, and a pressing time of 30 minutes. The pressed laminate was then fired at approximately 500°C and degreased.

[0070] Next, the obtained compact was held at 900°C for 24 hours in an air atmosphere, and then fired at a maximum temperature of 1200°C for 20 hours to form a cohesive body.

[0071] Next, a paste for forming a second electrode was applied to the surface of the intermediate layer of the obtained fired body by screen printing, and fired (baked) in an air atmosphere at 950°C for 2 hours to form a second electrode. The outer shape of the second electrode was formed smaller than that of the first electrode.

[0072] Next, the formed cell section was appropriately sealed with glass to form a gas seal structure. The first electrode of this cell section was then reduced in a hydrogen atmosphere at 800°C for 3 hours. As a result, an electrochemical cell of Sample 1 was obtained, in which the first electrode in the cell section, in which the first electrode (thickness 30 μm), solid electrolyte layer (thickness 4 μm), intermediate layer (thickness 4 μm), and second electrode (thickness 30 μm) were stacked in this order, was bonded to one surface of the metal support via a bonding layer. In this experimental example, firing was performed in an air atmosphere (oxidizing atmosphere), but firing in a reducing atmosphere is also possible.

[0073] An electrochemical cell of Sample 2 was obtained in the same manner as in the preparation of the electrochemical cell of Sample 1, except that a plate-shaped metal support (plate thickness 1 mm) composed of a Ni-based alloy containing Cr: 1 mass % to 5 mass % inclusive, Al: 3 mass % to 8 mass % inclusive, Si: 1 mass % to 3 mass % inclusive, Mn: 0.5 mass % to 2 mass % inclusive, with the remainder being Ni and unavoidable impurities was used.

[0074] <Microstructure of electrochemical cells> A cross section along the thickness direction was taken for each electrochemical cell obtained. The cross section was taken so that the bonding layer could be observed. SEM-EDX analysis was performed on the cross section, and elemental mapping of the metal support, bonding layer, and first electrode was obtained. Figure 5 shows the results of SEM-EDX analysis of a cross section along the thickness direction of the electrochemical cell of Sample 1. Figure 6 shows the results of SEM-EDX analysis of a cross section along the thickness direction of the electrochemical cell of Sample 2. Figures 5(a) and 6(a) show that a bonding layer 4 is formed between the metal support 2 and the first electrode 31 of the cell section 3. Note that reference numeral 201 denotes a native oxide film on the surface of the metal support. Figure 5(a) also shows that voids 5 are scattered at the interface between the metal support 2 and the bonding layer 4.

[0075] 5, it can be seen that the bonding layer of the electrochemical cell of Sample 1 contains a metal oxide containing Al, which is one of the constituent elements of the metal support, and Ni, which is one of the constituent elements of the first electrode. It can also be seen that Al, a constituent element of the metal support, is diffused and dissolved in the first electrode, and Ni, a constituent element of the first electrode, is diffused and dissolved in the metal support. As described above, by firing in a reducing atmosphere, the bonding layer can be configured to contain a metal containing Al, which is one of the constituent elements of the metal support, and Ni, which is one of the constituent elements of the first electrode.

[0076] Furthermore, the Al concentration distribution was measured for the cross section of each bonding layer using the method described above. As a result, the Al concentration in each bonding layer was lower on the first electrode side than on the metal support side. Specifically, the Al concentration in each bonding layer decreased from the metal support side toward the first electrode side. Furthermore, the Ni concentration in each bonding layer was lower on the metal support side than on the first electrode side. Specifically, the Ni concentration in each bonding layer decreased from the first electrode side toward the metal support side. From these results, it was confirmed that each bonding layer had a gradient composition.

[0077] Furthermore, the particle size of the material particles was examined for the cross section of each first electrode using the method described above. As a result, it was confirmed that the average particle size of the material particles in the region on the metal support side of each first electrode was larger than the average particle size of the material particles in the region on the solid electrolyte layer side. More specifically, the average particle size of the Ni particles in the region on the metal support side of each first electrode was larger than the average particle size of the Ni particles in the region on the solid electrolyte layer side of each first electrode. This is because the Ni particles in the first electrode were more likely to grow due to the heat from the metal support when the first electrode-forming material was sintered in contact with the metal support.

[0078] Furthermore, in each electrochemical cell, no peeling was observed between the metal support and the first electrode due to co-firing. This result confirmed that each electrochemical cell can suppress peeling of the first electrode due to thermal stress when the cell part is co-firing on the metal support.

[0079] <Electrochemical cell operation test> Each electrochemical cell was operated as an SOEC, and the state of delamination between the metal support and the first electrode was investigated. Specifically, water electrolysis was performed using each electrochemical cell at a constant voltage of 1.3 V. During this operation, a mixed gas of H2O, H2, and N2 (volume ratio of H2O:H2:N2 = 30:30:40) was supplied to the first electrode, and air was supplied to the second electrode. The cell operating temperature was 700°C. The operating time was 1 hour. As a result, each electrochemical cell was able to suppress delamination of the first electrode due to thermal stress caused by the difference in thermal expansion between the metal support and the first electrode during operation.

[0080] Furthermore, each electrochemical cell was operated as an SOFC, and the state of peeling between the metal support and the first electrode was investigated. Specifically, each electrochemical cell was operated at a current of 0.5 A / cm 2 Power generation was carried out under these conditions. A mixed gas of H2O and H2 (volume ratio of H2O:H2 = 1:9) was supplied to the first electrode, and air was supplied to the second electrode. The cell operating temperature was 700°C. The operating time was 1 hour. As a result, each electrochemical cell was able to suppress peeling of the first electrode due to thermal stress caused by the difference in thermal expansion between the metal support and the first electrode during operation.

[0081] From the above, it can be seen that each electrochemical cell achieved strong bonding between the metal support and the first electrode.

[0082] (Experimental Example 2) An electrochemical cell was fabricated in the same manner as in the fabrication of the electrochemical cell of Sample 1 in Experimental Example 1, except that a first electrode-forming sheet B was prepared in the same manner as in the fabrication of the electrochemical cell of Sample 1 in Experimental Example 1, except that the amount of carbon (pore-forming agent) was increased compared to that in the first electrode-forming sheet A, and the first electrode-forming sheet B, the first electrode-forming sheet A, the solid electrolyte layer-forming sheet, and the intermediate layer-forming sheet were laminated in this order on one surface of a metal support. The thickness of the first electrode was 30 μm.

[0083] As a result, an electrochemical cell of Sample 3 was obtained, which had a first electrode in which the porosity in the region on the metal support side was greater than the porosity in the region on the solid electrolyte layer side.

[0084] An electrochemical cell was fabricated in the same manner as in the fabrication of the electrochemical cell of Sample 1 in Experimental Example 1, except that a first electrode-forming sheet C was prepared in the same manner as in the fabrication of the electrochemical cell of Sample 1 in Experimental Example 1, except that the mass ratio of NiO powder to YSZ powder was set to 75:25, and the first electrode-forming sheet C, first electrode-forming sheet A, solid electrolyte layer-forming sheet, and intermediate layer-forming sheet were laminated in this order on one surface of a metal support. The thickness of the first electrode was 30 μm.

[0085] As a result, an electrochemical cell of Sample 4 was obtained, which had a first electrode in which the content of Ni particles in the region on the metal support side was higher than the content of Ni particles in the region on the solid electrolyte layer side.

[0086] Furthermore, in each electrochemical cell, no peeling was observed between the metal support and the first electrode due to co-firing. Each electrochemical cell was operated as an SOEC or SOFC in the same manner as in Experimental Example 1. As a result, similar to Experimental Example 1, each electrochemical cell was able to suppress peeling of the first electrode due to thermal stress caused by the difference in thermal expansion between the metal support and the first electrode during operation.

[0087] The present invention is not limited to the above-described embodiments and experimental examples, and various modifications are possible without departing from the spirit of the present invention. Furthermore, the configurations shown in the embodiments and experimental examples can be combined in any manner. [Explanation of symbols]

[0088] 1. Electrochemical cell 2 Metal support 3 Cell section 30 Solid electrolyte layer 31 1st electrode 32 2nd electrode 4 Bonding layer

Claims

1. a metal support (2); a cell section (3) including a solid electrolyte layer (30) having oxygen ion conductivity, a first electrode (31) stacked on one side of the solid electrolyte layer, and a second electrode (32) stacked on the other side of the solid electrolyte layer; a bonding layer (4) that bonds the metal support and the first electrode of the cell portion, The bonding layer is the metal support includes at least one of an alloy including a metal support constituent element, which is at least one metal element constituting the metal support, and a first electrode constituent element, which is at least one metal element constituting the first electrode, and a metal oxide including the metal support constituent element and the first electrode constituent element; The cell portion has a concentration distribution of the first electrode constituent element in the thickness direction thereof, In the concentration distribution, the concentration of the first electrode constituent element is lower on the metal support side than on the first electrode side. Electrochemical cell (1).

2. the metal support constituent elements are diffused in the first electrode; 10. The electrochemical cell of claim 1.

3. the bonding layer has a concentration distribution of the metal support constituent elements when viewed in a thickness direction of the cell portion, In the concentration distribution, the concentration of the metal support constituent element is lower on the first electrode side than on the metal support side.

3. The electrochemical cell of claim 1 or claim 2.

4. the first electrode constituent element is diffused in the metal support; 4. An electrochemical cell according to any one of claims 1 to 3.

5. The first electrode is the average particle size of the material particles in the region on the metal support side is larger than the average particle size of the material particles in the region on the solid electrolyte layer side; 5. An electrochemical cell according to any one of claims 1 to 4.

6. The first electrode is the porosity in the region on the metal support side is greater than the porosity in the region on the solid electrolyte layer side; 6. An electrochemical cell according to any one of claims 1 to 5.

7. The first electrode is the content of the electron conductor particles in the region on the metal support side is higher than the content of the electron conductor particles in the region on the solid electrolyte layer side; 7. An electrochemical cell according to any one of claims 1 to 6.

8. a gap is present in at least one of an interface between the metal support and the bonding layer and an interface between the first electrode and the bonding layer; 8. An electrochemical cell according to any one of claims 1 to 7.

9. The total thickness of the cell portion is 200 μm or less.

9. An electrochemical cell according to any one of claims 1 to 8.

10. Used as at least one of a solid oxide electrolysis cell and a solid oxide fuel cell, 10. An electrochemical cell according to any one of claims 1 to 9.

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