Electrochemical cell

Abstract

An electrochemical cell (1) comprises: a metal support (2) constituted from an Fe-based alloy; a cell part (3); and a bonding layer (4). The cell part (3) is provided with: a solid electrolyte layer (30) having oxygen ion conductivity; a first electrode layer (31) disposed on one surface side of the solid electrolyte layer (30); and a second electrode layer (32) disposed on the other surface side of the solid electrolyte layer (30). The bonding layer (4) bonds the metal support (2) and the first electrode layer (31). The bonding layer (4) is constituted from an oxide having electron conductivity and containing at least one metal element from among the alloy elements of the Fe-based alloy constituting the metal support (2). The bonding layer (4) is inclined so that the concentration of at least one of said metal elements decreases from the metal support (2) side toward the first electrode layer (31) side.

Description

Cross - reference to related applications

[0001] This application is based on Japanese Application No. 2021 - 212758 filed on December 27, 2021, the contents of which are incorporated herein by reference.

Technical Field

[0002] This disclosure relates to an electrochemical cell.

Background Art

[0003] Conventionally, an electrochemical cell in which a cell part is supported by a metal support is known. Examples of the electrochemical cell include a solid oxide fuel cell (SOFC) having a solid electrolyte layer with oxygen ion conductivity and a solid oxide electrolytic cell (SOEC).

[0004] For example, Patent Document 1 discloses an SOFC having a porous metal support made of a sintered body of stainless steel powder, an anode supported by the metal support and having a perovskite - type oxide, and a mixed layer provided between the metal support and the anode. Patent Document 1 describes a technique for joining the metal support and the anode with a mixed layer obtained by mixing stainless steel powder used for the metal support and ceramic powder used for the anode in order to suppress delamination between the metal support and the anode during firing in a strongly reducing atmosphere.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] The prior art has the following problems. In an electrochemical cell including a solid electrolyte layer having oxygen ion conductivity, the electrode layer is usually made of ceramics. Therefore, in an electrochemical cell supported by a metal support, it is inherently difficult to ensure the bondability between the metal support and the electrode layer. In this regard, in the prior art, the metal support and the anode are joined by a mixed layer formed by mixing stainless steel powder used for a porous metal support and ceramic powder used for the anode.

[0007] However, in the prior art, a catalytic metal such as Ni contained in the anode is poisoned by Fe elements diffused from the metal support. Therefore, the catalytic performance of the catalytic metal deteriorates. Therefore, it is difficult to apply the above prior art to the joining between the metal support and the electrode layer in an electrochemical cell supported by a metal support containing Fe due to the problem of Fe poisoning of the catalytic metal. Therefore, a technique capable of improving the bondability between the Fe-containing metal support and the electrode layer is required.

[0008] An object of the present disclosure is to provide an electrochemical cell capable of improving the bondability between an Fe-containing metal support and an electrode layer.

[0009] One aspect of the present disclosure is a metal support made of an Fe-based alloy, a cell unit including a solid electrolyte layer having oxygen ion conductivity, a first electrode layer disposed on one surface side of the solid electrolyte layer, and a second electrode layer disposed on the other surface side of the solid electrolyte layer, and a joining layer that joins the metal support and the first electrode layer of the cell unit. The joining layer is composed of an electronically conductive oxide containing at least one metal element among the alloy elements of the Fe-based alloy, and the concentration of at least one of the metal elements is inclined to decrease from the metal support side toward the first electrode layer side and the electroconductive oxide constituting the joining layer contains a La element , and is in the electrochemical cell. In addition, another aspect of the present disclosure is a metal support composed of an Fe-based alloy, a cell unit including a solid electrolyte layer having oxygen ion conductivity, a first electrode layer disposed on one surface side of the solid electrolyte layer, and a second electrode layer disposed on the other surface side of the solid electrolyte layer, a joining layer that joins the metal support and the first electrode layer of the cell unit, the joining layer is composed of an electroconductive oxide containing at least one metal element among the alloy elements of the Fe-based alloy, the concentration of at least one of the metal elements is inclined so as to decrease from the metal support side toward the first electrode layer side, the joining layer has a coating layer covering the surface of the joining layer on the first electrode layer side, the coating layer has a lower Fe concentration than the joining layer 、 in an electrochemical cell.

[0010] The above-described electrochemical cell has the above configuration. Therefore, the above-described electrochemical cell can suppress a sudden change in the coefficient of thermal expansion in the bonding layer. Therefore, the above-described electrochemical cell can improve the bonding property between the metal support made of an Fe-based alloy and the first electrode layer of the cell part disposed on the metal support side. Further, according to the above bonding layer, diffusion of Fe element from the Fe-based alloy constituting the metal support can be suppressed, so that Fe poisoning of the catalyst metal in the first electrode layer can be suppressed.

[0011] The reference numerals in parentheses described in the claims indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the present disclosure.

Brief Description of Drawings

[0012] The above object, other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. The drawings are

FIG. 1

FIG. 2

FIG. 3

FIG. 4

FIG. 5

FIG. 6

FIG. 7

DETAILED DESCRIPTION OF THE INVENTION

[0013] The electrochemical cell of the embodiment will be described with reference to FIGS. 1 to 5. As illustrated in FIG. 1, the electrochemical cell 1 of the present embodiment is a metal-supported type electrochemical cell in which the cell unit 3 is supported by a metal support 2. The electrochemical cell 1 includes a metal support 2, a cell unit 3, and a bonding layer 4. Note that the electrochemical cell 1 may be flat or cylindrical. FIG. 1 illustrates an electrochemical cell 1 in which a flat cell unit 3 is supported by a plate-shaped metal support 2.

[0014] The metal support 2 is composed of an Fe-based alloy. In the Fe-based alloy, alloying elements are added to the base Fe. The alloying elements include at least one or more metal elements, and may also include at least one or more non-metal elements in addition to the metal elements. Note that the alloying elements do not include the Fe element. Also, the above metal elements can include semi-metal elements. Examples of the metal elements contained in the alloying elements include, for example, Cr (chromium), Mn (manganese), Ti (titanium), Ni (nickel), Al (aluminum), Cu (copper), Mo (molybdenum), Nb (niobium), V (vanadium), La (lanthanum), Ta (tantalum), Hf (hafnium), Zr (zirconium), Si (silicon), B (boron), etc. These can be used alone or in combination of two or more. Specifically, the metal elements contained in the alloying elements can include at least Cr, and more specifically, can include at least Cr and at least one selected from the group consisting of Mn, Ti, Ni, Al, Cu, Mo, Nb, V, La, Ta, Hf, Zr, Si, and B. In the metal support 2, the maximum addition metal element with the largest content among the metal elements contained in the alloying elements of the Fe-based alloy can be one selected from the group consisting of Cr, Mn, and Ti. Note that the Fe-based alloy containing Cr as the maximum addition metal element can be referred to as an Fe-Cr-based alloy. Similarly, the Fe-based alloy containing Mn as the maximum addition metal element can be referred to as an Fe-Mn-based alloy, and the Fe-based alloy containing Ti as the maximum addition metal element can be referred to as an Fe-Ti-based alloy.

[0015] As illustrated in FIGS. 1, 2, 4(a), etc., the metal support 2 may not have an oxide layer 20 derived from the Fe-based alloy on its surface, or may have an oxide layer 20 derived from the Fe-based alloy on its surface as illustrated in FIGS. 4(b), 4(c), etc. The oxide layer 20 can have conductivity under hydrogen, but according to the former configuration, the surface of the metal support 2 and the bonding layer 4 are joined without passing through the oxide layer 20 derived from the Fe-based alloy. Therefore, according to the former configuration, it is easier to reduce the electrical resistance.

[0016] The metal support 2 is disposed on one side of the cell unit 3 to support the cell unit 3. The metal support 2 can be composed of, for example, a solid Fe-based alloy having a plurality of through-holes 21. In FIG. 1, an example is shown in which the metal support 2 has a plurality of through-holes 21 penetrating between one surface and the other surface of the metal support 2. Specifically, the metal support 2 can be configured to have a plate-shaped cell support portion 22 including a plurality of through-holes 21 penetrating between one plate surface and the other plate surface. The through-holes 21 serve as gas flow paths for the gas supplied to the first electrode layer 31 (described later) of the cell unit 3. In FIG. 1, an example is shown in which the through-holes 21 are formed along the thickness direction of the metal support 2.

[0017] The cell unit 3 includes a solid electrolyte layer 30 having oxygen ion conductivity, a first electrode layer 31 laminated on one surface side of the solid electrolyte layer 30, and a second electrode layer 32 laminated on the other surface side of the solid electrolyte layer 30.

[0018] Note that the cell unit 3 can further include an intermediate layer 33 between the solid electrolyte layer 30 and the second electrode layer 32. The intermediate layer 33 is mainly a layer for suppressing the reaction between the material of the solid electrolyte layer 30 and the material of the second electrode layer 32. In this case, specifically, the cell unit 3 can be configured such that the first electrode layer 31, the solid electrolyte layer 30, the intermediate layer 33, and the second electrode layer 32 are laminated in this order and joined to each other.

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

[0020] As materials for the first electrode layer 31, for example, electronic conductors 311 such as Ni, Ni alloys, Cu, Cu alloys, Co, Co alloys (metals and alloys, hereinafter omitted), oxides of electronic conductors 311 that become electronic conductors 311 by reduction such as nickel oxide (NiO, etc.), copper oxide, cobalt oxide (metal and alloy oxides, hereinafter omitted), etc. can be exemplified. These can be used alone or in combination of two or more. Among these, preferably, Ni, Ni alloys, nickel oxide (NiO, etc.), etc. are used, and more preferably, Ni is used. Note that the electronic conductor 311 functions as a catalyst for the electrochemical reaction in the first electrode layer 31. The first electrode layer 31 can also contain, for example, one or more oxygen ion conductors 312 such as yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ). Among these, preferably, it is yttria-stabilized zirconia. The first electrode layer 31 can also contain, for example, oxides containing at least one element selected from the group consisting of Ce, Al, La, Pr, Nd, Y, and Sc and Zr, preferably, oxides containing at least one element selected from the group consisting of Al, La, Pr, Nd, Y, and Sc and Ce and Zr, ceria (CeO2), ceria-based solid solutions doped with one or more elements selected from Gd, Sm, Y, La, Nd, Yb, Ca, and Ho, etc. (oxide-based additives not shown in the figure) can be contained alone or in combination of two or more. Among these, preferably, it is an oxide containing Ce and Zr. Examples of the oxide containing Ce and Zr include Ce-Zr-O-based oxides, Ce-Zr-La-O-based oxides, Ce-Zr-Sc-O-based oxides, Ce-Zr-Y-O-based oxides, Ce-Zr-Al-O-based oxides, etc. The above-mentioned metals, alloys, and oxides can be arbitrarily combined. More specifically, the first electrode layer 31 can have, for example, a configuration containing Ni and yttria-stabilized zirconia, a configuration containing Ni, yttria-stabilized zirconia, and an oxide containing Ce and Zr, a configuration containing Ni, yttria-stabilized zirconia, and ceria, a configuration containing Ni, yttria-stabilized zirconia, and a ceria-based solid solution, etc. Note that in the first electrode layer 31, the above-mentioned metals, alloys, and oxides can exist as particles.Further, the first electrode layer 31 can usually be formed as a porous body including pores 313.

[0021] As illustrated in FIG. 1, the first electrode layer 31 may be composed of a single layer or may be composed of a plurality of layers such as a two-layer structure. When the first electrode layer 31 is composed of a plurality of layers, specifically, for example, the first electrode layer 31 can have a structure including a diffusion layer disposed on the side of the metal support 2 and a reaction layer disposed on the side of the solid electrolyte layer 30. The diffusion layer is a layer that promotes the diffusion of the gas introduced into the first electrode layer 31, and the reaction layer is a layer including a reaction field where an electrochemical reaction occurs in the first electrode layer 31.

[0022] Examples of the material of the second electrode layer 32 include transition metal perovskite-type oxides 321 such as lanthanum-strontium-cobalt-based oxides, lanthanum-strontium-cobalt-iron-based oxides, and lanthanum-strontium-manganese-iron-based oxides, or a mixture including the transition metal perovskite-type oxide 321 and a ceria-based solid solution 322 doped with one or more elements selected from Gd, Sm, Y, La, Nd, Yb, Ca, and Ho in ceria (CeO2). These can be used alone or in combination of two or more. In the second electrode layer 32, the above-mentioned transition metal perovskite-type oxide 321 and ceria-based solid solution 322 can exist as particles. Further, the second electrode layer 32 can usually be formed as a porous body including pores 323.

[0023] When the cell unit 3 has the intermediate layer 33, specifically, the intermediate layer 33 can be formed in a layered manner from a solid electrolyte having oxygen ion conductivity. Examples of the solid electrolyte used for the intermediate layer 33 include ceria (CeO2) and ceria-based solid solutions 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 of two or more. As the solid electrolyte used for the intermediate layer 33, ceria doped with Gd is preferable.

[0024] The thickness of the cell portion 3 can preferably be 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, etc., the thickness of the cell portion 3 can preferably be 20 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more.

[0025] From the viewpoints of reducing ohmic resistance, suppressing gas permeation, and preventing a decrease in electromotive force due to electron leakage, etc., the thickness of the solid electrolyte layer 30 can preferably be 3 to 20 μm, more preferably 3.5 to 15 μm, and even more preferably 4 to 10 μm. From the viewpoint of ensuring electrochemical reaction sites, etc., the thickness of the first electrode layer 31 can preferably be 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. From the viewpoints of reducing ohmic resistance and reducing gas diffusion resistance, etc., the thickness of the first electrode layer 31 can preferably be 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, reducing gas diffusion resistance, and ensuring electrochemical reaction sites, etc., the thickness of the second electrode layer 32 can preferably be 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, suppressing element diffusion from the second electrode layer 32, and suppressing gas permeation, etc., the thickness of the intermediate layer 33 can preferably be 1 to 20 μm, more preferably 2 to 10 μm. Note that the thicknesses of the cell portion 3, the solid electrolyte layer 30, the first electrode layer 31, the second electrode layer 32, and the intermediate layer 33 described above are each the arithmetic mean value of 10 thickness measurement values obtained by observing a cross section along the thickness direction of the cell portion 3 with a scanning electron microscope (SEM).

[0026] The bonding layer 4 is a layer that bonds the metal support 2 and the first electrode layer 31 of the cell unit 3. The bonding layer 4 is composed of an electronically conductive oxide. The electronically conductive oxide contains at least one metal element among the alloy elements of the Fe-based alloy constituting the metal support 2. That is, the electronically conductive oxide contains at least one metal element derived from the alloy elements of the Fe-based alloy constituting the metal support 2. The metal element derived from the Fe-based alloy contained in the electronically conductive oxide is specifically diffused from the Fe-based alloy constituting the metal support. The metal element derived from the Fe-based alloy is incorporated into the structure of the electronically conductive oxide to form the electronically conductive oxide. The type of the electronically conductive oxide in the bonding layer 4 can be grasped from the crystal structure by thin-film XRD analysis and the like.

[0027] As illustrated in FIG. 3, in the bonding layer 4, the concentration of at least one metal element among the alloy elements of the Fe-based alloy constituting the metal support 2 is inclined so as to decrease from the metal support 2 side toward the first electrode layer 31 side. That is, in the electronically conductive oxide constituting the bonding layer 4, the concentration of at least one metal element derived from the alloy elements of the Fe-based alloy is inclined so as to decrease from the metal support 2 side toward the first electrode layer 31 side. Note that FIG. 3 shows a state in which one metal element derived from the alloy elements of the Fe-based alloy is inclined and diffused for simplification of the drawing. The concentration of the metal element derived from the alloy elements of the Fe-based alloy may gradually (slowly) decrease from the metal support 2 side toward the first electrode layer 31 side, or may decrease stepwise (for example, in a stepped manner).

[0028] The gradient of the concentration of the metal element in the bonding layer 4 can be measured by secondary ion mass spectrometry (SIMS). Specifically, sputtering is started from the surface of the bonding layer 4 on the first electrode layer 31 side, and the cation concentration distribution in the depth direction from the surface of the bonding layer 4 on the first electrode layer 31 side is obtained. The sputtering can be carried out until the sputtering depth reaches the surface layer part of the bonding layer 4 side of the metal support 2. The cation concentration distribution has the depth from the start of detection (unit: nm) on the horizontal axis and Relative Intensity (Normalized by Total ion Counts) on the vertical axis. Note that the vertical axis in the cation concentration distribution is the intensity, taking the number of detections (counts) as the intensity, and the ratio of the value of each cation to the total value obtained by summing up the number of detections as the relative intensity. In the obtained cation concentration distribution, identify the metal elements contained in the alloy elements of the Fe-based alloy constituting the metal support 2, and confirm the diffusion behavior of the identified metal elements in the bonding layer 4. As a result, when the concentration of the identified metal element is inclined so as to decrease from the metal support side towards the first electrode layer 31 side in terms of the cation ratio, it can be determined that the electronically conductive oxide constituting the bonding layer 4 has an inclined composition. Note that the cation concentration distribution can include the concentration distribution of Fe in addition to the concentration distributions of the respective metal elements contained in the alloy elements of the Fe-based alloy constituting the metal support 2. As the secondary ion mass spectrometer, a time-of-flight secondary ion mass spectrometer such as "TOF.SIMS5" manufactured by ION-TOF can be used. Also, as the irradiation ion, 209Bi1 + is used.

[0029] Specific examples of the metal elements derived from the Fe-based alloy contained in the electronically conductive oxide constituting the bonding layer 4 include Cr, Mn, Ti, etc. These can be used alone or in combination of two or more.

[0030] The bonding layer 4 can be configured such that the concentration of the maximum added metal element, which is the metal element having the highest content among the alloying elements of the Fe-based alloy constituting the metal support 2, is at least inclined. Note that the content of the metal element in the Fe-based alloy is in mass%. According to this configuration, the bonding strength of the bonding layer 4 can be enhanced. Therefore, according to this configuration, it is advantageous for improving the bondability between the metal support and the first electrode layer.

[0031] Specifically, the maximum added metal element can be one selected from the group consisting of Cr, Mn, and Ti. Cr, Mn, and Ti are elements capable of forming an electronically conductive oxide. Therefore, according to this configuration, the maximum added metal element diffused from the metal support 2 is likely to be incorporated into the structure of the electronically conductive oxide constituting the bonding layer 4. The maximum added metal element is preferably Cr. In this case, the Fe-based alloy constituting the metal support 2 becomes an Fe-Cr-based alloy. Since the Fe-Cr-based alloy is excellent in the balance of corrosion resistance, structural strength, cost, etc., it is suitable as the material of the metal support 2 in the metal-supported electrochemical cell 1.

[0032] For the bonding layer 4, for at least one kind of metal element among the alloying elements of the Fe-based alloy, when the inclination distance, which is the layer thickness direction distance of the region where the concentration of the metal element is inclined, is obtained respectively, and the maximum of each inclination distance is taken as the maximum inclination distance, the maximum inclination distance can be configured to be 0.1 μm or more. According to this configuration, as the inclination distance becomes longer, the suppression of the abrupt change in the coefficient of thermal expansion in the bonding layer 4 can be made more reliable, and the bondability by the bonding layer 4 can be enhanced.

[0033] Specifically, in the concentration distribution of the metal element of interest in the bonding layer 4, the inflection point position (reference P in FIG. 3) where the concentration of the metal element first changes to attenuation from the side of the metal support 2 is taken as the start point of the inclination, and the distance between the start point of the inclination and the surface position on the side of the first electrode layer 31 of the bonding layer 4 can be grasped by measurement. The surface position on the side of the first electrode layer 31 of the bonding layer 4 is also the start point of sputtering by the SIMS analysis described above. From the viewpoint of improving the bondability by the bonding layer 4, etc., the maximum inclination distance can preferably be 0.15 μm or more, more preferably 0.2 μm or more, and still more preferably 0.5 μm or more. The longer the maximum inclination distance is with respect to the thickness of the bonding layer 4, the better, and the upper limit is not particularly limited, but for example, it can be set to be equal to or less than the thickness of the bonding layer 4. From the viewpoint of the bonding strength of the bonding layer 4, etc., it is preferable that the maximum added metal element has the maximum inclination distance in the bonding layer 4.

[0034] The thickness of the bonding layer 4 can be 0.2 μm or more. According to this configuration, a sufficient region where the concentration of the metal element derived from the Fe-based alloy contained in the electronically conductive oxide constituting the bonding layer 4 inclines can be ensured. Therefore, according to this configuration, the bonding strength of the bonding layer 4 can be ensured more stably. From the viewpoint of stably ensuring the bonding strength of the bonding layer 4, etc., the thickness of the bonding layer 4 can preferably be 0.2 μm or more, more preferably 1 μm or more, and still more preferably 5 μm or more. Also, from the viewpoint of reducing resistance, etc., the thickness of the bonding layer 4 can preferably be 20 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less.

[0035] The thickness of the bonding layer 4 can be measured as follows. For a cross-section along the thickness direction of the electrochemical cell 1, SEM-EDX (scanning electron microscope - energy dispersive X-ray spectroscopy) is performed to obtain an elemental mapping image containing elements derived from the bonding layer 4 as illustrated in FIG. 5. The bonding layer 4 in the obtained elemental mapping image is divided by a straight line along the thickness direction of the bonding layer 4 at arbitrary equal intervals in a direction perpendicular to the thickness direction of the bonding layer 4. The layer thickness of the bonding layer 4 in the divided portion is measured (n number = 10 or more), and the arithmetic mean value of the measured layer thicknesses is taken as the thickness of the bonding layer 4.

[0036] The electrochemical cell 1 can be configured such that the coverage rate of the metal support 2 by the bonding layer 4 is 90% or more. The bonding layer 4 composed of an electronically conductive oxide may undergo grain growth during firing and may have fine holes. When holes occur, a part of the first electrode layer 31 and a part of the metal support 2 may be in contact through the holes. According to the above configuration, the amount of contact points between the metal support 2 and the first electrode layer 31 can be reduced, and it becomes easier to further suppress the Fe poisoning of the catalyst metal contained in the first electrode layer 31. The above coverage rate is an index indicating how much the bonding layer 4 covers the surface portion of the metal support 2 corresponding to the size of the outer shape of the bonding layer 4 formed on the surface of the metal support 2. When calculating the above coverage rate, the area of the surface portion of the metal support 2 outside the outer shape position of the bonding layer 4 is not considered.

[0037] From the viewpoint of sufficiently obtaining the above effects, the above coverage rate can preferably be 92% or more, more preferably 95% or more. Although the higher the above coverage rate, the better, from the viewpoint of manufacturability, etc., it can be, for example, 98% or less.

[0038] The coverage rate of the metal support 2 by the bonding layer 4 can be measured as follows. When the outer shape of the bonding layer 4 is formed larger than the outer shape of the first electrode layer 31, or when the bonding layer 4 is exposed to the outside, SEM-EDX is performed on the surface of the bonding layer 4 in the exposed portion to obtain an elemental mapping image of the elements derived from the bonding layer 4. By image analysis of the obtained elemental mapping image, the ratio (%) of the total area of the bonding layer 4 portion to the area of the entire image (the total area of the entire area of the bonding layer 4 portion and the entire area of the hole portion) with respect to the viewing angle where only the layer of the bonding layer 4 exists can be calculated. Further, when the outer shape of the bonding layer 4 and the outer shape of the first electrode layer 31 are formed to be equivalent, or when the bonding layer 4 is not exposed to the outside, FIB (focused ion beam)-SEM-EDX is performed, the electrode portion is removed by FIB from the first electrode layer 31 side, and with respect to the viewing angle where only the layer of the bonding layer 4 exists when the bonding layer 4 is exposed, the ratio (%) of the total area of the bonding layer 4 portion to the area of the entire image (the total area of the entire area of the bonding layer 4 portion and the entire area of the hole portion) can be calculated by image analysis in the same manner as above.

[0039] As described above, the electronically conductive oxide constituting the bonding layer 4 contains at least one metal element among the alloy elements of the Fe-based alloy constituting the metal support 2. The electronically conductive oxide constituting the bonding layer 4 can further contain a La element. In this case, the electronically conductive oxide can be a composite oxide containing La and at least one metal element among the alloy elements of the Fe-based alloy constituting the metal support 2. According to the above configuration, when Cr diffuses from the metal support 2 to the bonding layer 4, a composite oxide containing La and Cr is formed, so that it becomes easy to reduce the resistance of the bonding layer 4. Note that the electronically conductive oxide can have a perovskite structure and a structure similar to the perovskite structure (a structure in which the composition is inclined and does not have a complete perovskite structure), or a structure similar to the perovskite structure. In this case, the La element will be contained in the A site.

[0040] As illustrated in FIGS. 4(c) and 5(c), etc., the bonding layer 4 can have a coating layer 40 that covers the surface of the bonding layer 4 on the side of the first electrode layer 31. That is, in this case, the coating layer 40 is interposed between the bonding layer 4 and the first electrode layer 31. The coating layer 40 can be a layer having a lower Fe concentration than the bonding layer 4. According to the above configuration, the coating layer 40 functions as a barrier film, and it becomes possible to further suppress the diffusion of Fe element, which is a poisoning substance derived from the Fe-based alloy constituting the metal support 2, into the first electrode layer 31.

[0041] The thickness of the coating layer 40 can be 1.5 μm or more. According to this configuration, it becomes possible to further suppress the diffusion of Fe element, which is a poisoning substance derived from the Fe-based alloy constituting the metal support 2, into the first electrode layer 31. From the viewpoint of suppressing the diffusion of Fe element, which is a poisoning substance, etc., the thickness of the coating layer 40 can preferably be 1.5 μm or more, more preferably 2.5 μm or more, and still more preferably 5 μm or more. Also, from the viewpoint of reducing resistance, etc., the thickness of the coating layer 40 can preferably be 50 μm or less, more preferably 20 μm or less, and still more preferably 10 μm or less.

[0042] The thickness of the coating layer 40 can be measured as follows. Perform SEM-EDX on a cross-section along the thickness direction of the electrochemical cell 1 to obtain an elemental mapping image containing elements derived from the coating layer 40. Divide the coating layer 40 in the obtained elemental mapping image by a straight line along the thickness direction of the coating layer 40 at arbitrary equal intervals in a direction perpendicular to the thickness direction of the coating layer 40. Measure the layer thickness of the coating layer 40 in the divided portion (n number = 10 or more), and the arithmetic mean value of the measured layer thicknesses is taken as the thickness of the coating layer 40.

[0043] The coating layer 40 can be composed of a ceria-based oxide containing at least Ce element. According to this configuration, the diffusivity of Fe element can be lowered. Therefore, according to this configuration, it becomes possible to reduce the resistance while suppressing the Fe poisoning of the catalyst metal such as Ni that may be contained in the first electrode layer 31. The ceria-based oxide can contain, for example, Gd, La, Mn, Cr, etc. in addition to Ce. These may be contained singly or in combination of two or more.

[0044] The electrochemical cell 1 can be manufactured, for example, as follows, but is not limited thereto.

[0045] On one surface of the metal support 2 made of an Fe-based alloy, a precursor of the joining layer precursor is laminated. The joining layer precursor is a substance before the formation of the electronically conductive oxide that finally forms the joining layer 4. Specifically, the joining layer precursor is a metal oxide containing a metal element capable of forming an electronically conductive oxide, which is different from the metal element diffused from the Fe-based alloy constituting the metal support 2. Further, the precursor of the joining layer precursor is a substance before the joining layer precursor is formed. Specifically, the precursor of the joining layer precursor is a substance such as a metal complex capable of forming the above metal oxide by firing.

[0046] Next, an unfired material for forming the first electrode layer, which will become the first electrode layer 31 upon firing, is laminated on the precursor of the bonding layer precursor. Next, an unfired material for forming the solid electrolyte layer, which will become the solid electrolyte layer 30 upon firing, is laminated on the material for forming the first electrode layer. Next, if necessary, an unfired material for forming the intermediate layer, which will become the intermediate layer upon firing, is laminated on the material for forming the solid electrolyte layer. Incidentally, if necessary, the laminate formed on the metal support 2 is pressure-bonded by a warm isostatic press or the like. Next, the laminate formed on the metal support 2 is integrally fired together with the metal support 2. Thereby, the metal support 2 and the first electrode layer 31 are joined via the bonding layer 4. During the above firing, the precursor of the bonding layer precursor is fired to form the bonding layer precursor, and metal elements such as Cr, which can form an electronically conductive oxide from the Fe-based alloy constituting the metal support 2, diffuse into the bonding layer precursor. As a result, a bonding layer made of an electronically conductive oxide having a gradient composition in which the concentration of at least one metal element among the alloy elements of the Fe-based alloy decreases from the side of the metal support 2 toward the side of the first electrode layer 31 is formed. According to the method for manufacturing the electrochemical cell 1 described above, the metal support 2 and the first electrode layer 31, which is a ceramic, can be joined without using the metal support material itself in the bonding layer 4.

[0047] Incidentally, when a laminated body is formed by initially laminating an electronically conductive composite oxide containing a metal element contained in the Fe-based alloy constituting the metal support 2 and another metal element different from the metal element on one surface of the metal support 2, since the crystal structure of the composite metal oxide is already complete, it is difficult to diffuse metal elements such as Cr, which can form an electronically conductive oxide from the Fe-based alloy constituting the metal support 2. Therefore, in this case, it is difficult to obtain the bonding layer 4 made of an electronically conductive oxide having the above-described gradient composition, and delamination is likely to occur.

[0048] Next, when the intermediate layer 33 is not formed, an unfired material for forming the second electrode layer, which will become the second electrode layer 32 by firing, is laminated on the surface of the solid electrolyte layer 30, and when the intermediate layer 33 is formed, on the surface of the intermediate layer 33. Then, this is fired. Thereby, the second electrode layer 32 is formed. Next, the first electrode layer 31 is subjected to a reduction treatment. Thereby, the metal-supported type electrochemical cell 1 can be obtained.

[0049] The above-described electrochemical cell 1 can suppress a rapid change in the coefficient of thermal expansion in the joining layer 4. Therefore, the electrochemical cell 1 can improve the joinability between the metal support 2 made of an Fe-based alloy and the first electrode layer 31 of the cell part disposed on the metal support 2 side. Further, according to the joining layer 4, diffusion of Fe elements from the Fe-based alloy constituting the metal support 2 can be suppressed, so that poisoning of catalyst metals such as Ni in the first electrode layer 31 by Fe can be suppressed.

[0050] The electrochemical cell 1 can be used as at least one of a solid oxide fuel cell (SOFC) and a solid oxide electrolysis cell (SOEC). That is, the electrochemical cell 1 may be operated as an SOFC, may be operated as an SOEC, or may be configured to be switchable between an SOFC mode of operating as an SOFC and an SOEC mode of operating as an SOEC, and may be operated as an SOFC and an SOEC.

[0051] In this embodiment, the first electrode layer 31 can be an electrode to which a fuel gas is supplied. Specifically, when the electrochemical cell 1 operates as a SOFC, the first electrode layer 31 can be used as a fuel electrode. A hydrogen-containing gas such as hydrogen gas can be supplied to the first electrode layer 31 as a fuel gas. In this case, the second electrode layer 32 can be used as an air electrode (oxidant electrode). An oxygen-containing gas such as air or oxygen gas can be supplied to the second electrode layer 32 as an oxidant gas. On the other hand, when the electrochemical cell 1 operates as a SOEC, the first electrode layer 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 layer 31 as a fuel gas. In this case, the second electrode layer 32 can be used as an oxygen electrode. A gas such as air may or may not be supplied to the second electrode layer 32. Note that the above-mentioned hydrogen-containing gas can contain water vapor for humidification or the like, and the water-containing gas can contain a reducing gas such as hydrogen gas.

[0052] In this embodiment, although the case where a fuel gas is supplied to the first electrode layer 31 has been mainly described, the electrochemical cell 1 may be configured such that the above-mentioned fuel gas is supplied to the second electrode layer 32. In this case, as the material of the first electrode layer 31, the material of the second electrode layer 32 described above can be used, and as the material of the second electrode layer 32, the material of the first electrode layer 31 described above can be used. Also, in this case, the above-mentioned oxidant gas can be supplied to the first electrode layer 31. Also, in this case, the intermediate layer can be formed between the first electrode layer 31 and the solid electrolyte layer 30.

[0053] (Experimental Example) <Electrochemical Cell of Sample 1> A plate-shaped metal support (plate thickness: 1 mm) made of an Fe-Cr alloy containing 20 mass% or more and 24 mass% or less of Cr as the maximum added metal element was prepared. Specifically, the Fe-Cr alloy contains, by mass%, Cr: 20% - 24%, C: 0.03%, Mn: 0.30% - 0.80%, Si: 0.50%, Al: 0.50%, S: 0.020%, P: 0.050%, Ti: 0.03% - 0.20%, La: 0.04% - 0.20%, and the balance consists of Fe and unavoidable impurities. A plurality of through-holes penetrating between one plate surface and the other plate surface are formed in the portion of the metal support where the cells are joined.

[0054] Next, a solution containing a precursor of La2O3 was prepared by mixing a La complex as a precursor of La2O3 (joining layer precursor), butyl acetate as a solvent, and turpentine oil. The prepared solution was dip-coated on one plate surface of the metal support and dried repeatedly a plurality of times to form a film of the precursor of La2O3.

[0055] Next, a paste for forming a first electrode layer was prepared by mixing NiO powder, yttria-stabilized zirconia (hereinafter referred to as YSZ) powder containing 8 mol% of Y2O3, ethyl cellulose as a binder, and terpineol as a solvent. The prepared paste for forming a first electrode layer was screen-printed on the precursor of La2O3. Thereby, a material for forming a first electrode layer was laminated on the precursor of La2O3.

[0056] Next, a paste for forming a solid electrolyte layer was prepared by mixing YSZ powder, ethyl cellulose as a binder, and terpineol as a solvent. The prepared paste for forming a solid electrolyte layer was applied on the material for forming a first electrode layer. Thereby, a material for forming a solid electrolyte layer was laminated on the material for forming a first electrode layer.

[0057] Next, Ce 0.9 Gd 0.1An intermediate layer-forming paste was prepared by mixing O2 (hereinafter referred to as GDC) powder, ethyl cellulose as a binder, and terpineol as a solvent. The prepared intermediate layer-forming paste was screen-printed onto the solid electrolyte layer-forming material. Thereby, the intermediate layer-forming material was laminated on the solid electrolyte layer-forming material.

[0058] Next, the laminate formed on the metal support was integrally fired at 1200 °C for 2 hours in an inert gas atmosphere. Thereby, a sintered body in which a bonding layer, a first electrode layer, a solid electrolyte layer, and an intermediate layer were laminated in this order was formed on the metal support.

[0059] Next, La 0.6 Sr 0.4 A second electrode layer-forming paste was prepared by mixing CoO3 (hereinafter referred to as LSC) powder, GDC powder, ethyl cellulose as a binder, and terpineol as a solvent. The prepared second electrode layer-forming paste was screen-printed onto the intermediate layer in the sintered body. Thereby, the second electrode layer-forming material was laminated on the intermediate layer.

[0060] Next, the second electrode layer-forming material was fired at 1000 °C for 2 hours in an air atmosphere. Thereby, the second electrode layer was laminated on the solid electrolyte layer.

[0061] Next, the first electrode layer was subjected to a reduction treatment at 800 °C for 3 hours in a hydrogen atmosphere. As described above, an electrochemical cell of Sample 1 was obtained in which the first electrode layer (thickness 60 μm) / solid electrolyte layer (thickness 3 μm) / intermediate layer (thickness 3 μm) / second electrode layer (thickness 10 μm) were laminated in order, and the first electrode layer in the cell part was joined to one plate surface of the metal support via the joining layer. In the electrochemical cell of Sample 1, a hydrogen-containing gas such as hydrogen gas is supplied to the first electrode layer as the fuel gas. In this experimental example, as illustrated in FIG. 6, on one plate surface of the metal support 2, the joining layer 4, the coating layer 40 (not formed in the electrochemical cell of Sample 1), the first electrode layer 31, the solid electrolyte layer 30, the intermediate layer 33, and the second electrode layer 32 were laminated so that the outer shapes of each layer gradually became smaller. Note that the electrochemical cell of the present disclosure is not limited to the form illustrated in FIG. 6.

[0062] <Electrochemical cells of Sample 2 and Sample 3> In the production of the electrochemical cell of Sample 1, an electrochemical cell of Sample 2 was produced in the same manner except that the firing time for forming the sintered body up to the intermediate layer was 0.5 hour.

[0063] In the production of the electrochemical cell of Sample 1, an electrochemical cell of Sample 3 was produced in the same manner except that the firing time for forming the sintered body up to the intermediate layer was 10 hours.

[0064] <Electrochemical cells of Sample 4 and Sample 5> A solution containing a ZnO precursor was prepared by mixing a Zn complex as a precursor of ZnO (joining layer precursor), butyl acetate as a solvent, and turpentine oil. In the production of the electrochemical cell of Sample 1, an electrochemical cell of Sample 4 was produced in the same manner except that the solution containing the ZnO precursor was used and a plate-shaped metal support made of an Fe-Mn based alloy containing 10 mass% or more and 20 mass% or less of Mn as the maximum added metal element was used.

[0065] A solution containing a precursor of TiO was prepared by mixing a Ti complex as a precursor of TiO (bonding layer precursor), butyl acetate as a solvent, and turpentine oil. In the preparation of the electrochemical cell of Sample 1, an electrochemical cell of Sample 5 was prepared in the same manner except that the solution containing the precursor of TiO was used and a plate-shaped metal support composed of an Fe-Ti based alloy containing 10 mass% or more and 20 mass% or less of Ti as the maximum added metal element was used.

[0066] <Electrochemical cells of Sample 6 and Sample 7> In the preparation of the electrochemical cell of Sample 1, an electrochemical cell of Sample 6 was prepared in the same manner except that the number of repetitions of the step of dip-coating and drying a solution containing a precursor of La2O3 on one plate surface of the metal support was reduced and the oxide layer derived from the Fe-based alloy on the surface layer of the metal support was removed.

[0067] In the preparation of the electrochemical cell of Sample 1, an electrochemical cell of Sample 7 was prepared in the same manner except that the number of repetitions of the step of dip-coating and drying a solution containing a precursor of La2O3 on one plate surface of the metal support was reduced (more reduced than in Sample 6) and the oxide layer derived from the Fe-based alloy on the surface layer of the metal support was removed.

[0068] <Electrochemical cell of Sample 8> In the preparation of the electrochemical cell of Sample 1, an electrochemical cell of Sample 8 was prepared in the same manner except that La2O3 particles were mixed and dispersed in the solution containing the precursor of La2O3.

[0069] <Electrochemical cells of Sample 9 to Sample 10> In the preparation of the electrochemical cell of Sample 1, an electrochemical cell of Sample 9 was prepared in the same manner except that a binder was mixed and dissolved in the solution containing the precursor of La2O3.

[0070] In the preparation of the electrochemical cell of Sample 1, an electrochemical cell of Sample 10 was prepared in the same manner except that a binder was mixed (the amount was increased more than in Sample 9) and dissolved in the solution containing the precursor of La2O3.

[0071] <Electrochemical cells of Sample 11 and Sample 12> A solution containing a precursor of Sr(OH)2 was prepared by mixing an Sr complex as a precursor of Sr(OH)2 (bonding layer precursor), butyl acetate as a solvent, and turpentine oil. An electrochemical cell of Sample 11 was fabricated in the same manner as in the fabrication of the electrochemical cell of Sample 1, except that the solution containing the precursor of Sr(OH)2 was used.

[0072] A solution containing a precursor of MnO2 was prepared by mixing an Mn complex as a precursor of MnO2 (bonding layer precursor), butyl acetate as a solvent, and turpentine oil. An electrochemical cell of Sample 12 was fabricated in the same manner as in the fabrication of the electrochemical cell of Sample 1, except that the solution containing the precursor of MnO2 was used.

[0073] <Electrochemical cell of Sample 13> Ce 0.9 Gd 0.1 A paste for forming a coating layer was prepared by mixing Gd2O2 (GDC) powder, ethyl cellulose as a binder, and terpineol as a solvent. An electrochemical cell of Sample 13 was fabricated in the same manner as in the fabrication of the electrochemical cell of Sample 1, except that after screen-printing the paste for forming a coating layer on the precursor of La2O3 to laminate the material for forming a coating layer, the material for forming a first electrode layer was laminated on this material for forming a coating layer. In the electrochemical cell of Sample 13, a coating layer (thickness: 2 μm) is interposed between the bonding layer and the first electrode layer.

[0074] <Electrochemical cells of Sample 14 to Sample 16> In the fabrication of the electrochemical cell of Sample 13, an electrochemical cell of Sample 14 was fabricated in the same manner, except that a paste for forming a coating layer in which Gd2O2 (GDC) powder was changed to LaFeO3 powder was used. 0.9 Gd 0.1 In the fabrication of the electrochemical cell of Sample 13, an electrochemical cell of Sample 14 was fabricated in the same manner, except that a paste for forming a coating layer in which Gd2O2 (GDC) powder was changed to LaFeO3 powder was used.

[0075] In the fabrication of the electrochemical cell of Sample 13, Ce 0.9 Gd 0.1An electrochemical cell of Sample 15 was fabricated in the same manner except that a paste for forming a coating layer in which O2(GDC) powder was changed to MnO2 powder was used.

[0076] In the fabrication of the electrochemical cell of Sample 13, Ce 0.9 Gd 0.1 An electrochemical cell of Sample 16 was fabricated in the same manner except that a paste for forming a coating layer in which O2(GDC) powder was changed to MnCr2O4 powder was used.

[0077] <Electrochemical Cells of Samples 17 to 18> In the fabrication of the electrochemical cell of Sample 13, by changing the film thickness during screen printing of the paste for forming a coating layer, electrochemical cells of Sample 17 and Sample 18 were fabricated. In the electrochemical cell of Sample 17, a coating layer (thickness 1.5 μm) is interposed between the bonding layer and the first electrode layer. Also, in the electrochemical cell of Sample 18, a coating layer (thickness 0.2 μm) is interposed between the bonding layer and the first electrode layer.

[0078] <Electrochemical Cell of Sample 1C> A solution containing a La complex and a Cr complex was prepared by mixing a La complex, a Cr complex, butyl acetate as a solvent, and turpentine oil. In the fabrication of the electrochemical cell of Sample 1, an electrochemical cell of Sample 1C was fabricated in the same manner except that a solution containing a La complex and a Cr complex was used instead of the solution containing a precursor of La2O3.

[0079] <Various Measurements> For each of the fabricated electrochemical cells, by the above-described measurement method, the type of oxide with electron conductivity in the bonding layer, the presence or absence of a gradient composition, the maximum gradient distance, the film thickness of the bonding layer, and the coverage rate of the metal support by the bonding layer were measured. Also, the electrical resistance of the bonding layer was measured by forming an electrode layer on the bonding layer and measuring the DC resistance through the metal support.

[0080] Also, for each electrochemical cell, a peel test was performed to peel the cell part from the metal support, and the peel strength was measured. Specifically, the evaluation was performed using a surface / interface physical property analyzer (SAICAS).

[0081] In addition, for each electrochemical cell, the poisoning state of Fe at the Ni sites of the catalytic metal in the first electrode layer was examined. Specifically, for the cross-section along the layer thickness direction of the first electrode layer, quantification was performed by point analysis of the Ni portion using SEM-EDX, and the mass concentrations of Fe element and Ni element were measured. Then, the value of Fe / (Fe + Ni) (mass% / mass%) at the Ni sites in the first electrode layer was calculated as the arithmetic mean value with n = 20.

[0082] The detailed configurations of each electrochemical cell and various measurement results are summarized in Table 1 and Table 2. Also, Fig. 7 shows the cation concentration distribution in the depth direction from the surface on the first electrode layer side of the bonding layer, measured by secondary ion mass spectrometry (SIMS), for the electrochemical cell of Sample 1 fabricated in Experimental Example 1. The position of A shown in Fig. 7 is the position of the surface on the first electrode layer side of the bonding layer. In this example, since the measurement is carried out at the T point in Fig. 6, that is, at the location where the bonding layer is exposed, the bonding layer has been detected since the start of detection. Also, the position of B shown in Fig. 7 is the position of the interface between the bonding layer and the metal support, and this position is where the concentration of the main diffusing element (Cr in this example) reaches an inflection point.

[0083] [Table 1]

[0084] [Table 2]

[0085] According to Table 1, Table 2, and FIG. 7, the following can be understood. In the electrochemical cell of Sample 1C, the metal support and the first electrode layer of the cell part were peeled off, and the bondability between the metal support and the first electrode layer could not be improved. This is because in the electrochemical cell of Sample 1C, LaCrO3, which was completed as a perovskite structure, was used as a material for forming the bonding layer to perform bonding. As a result, metal elements capable of forming electronically conductive oxides such as Cr derived from the Fe-based alloy constituting the metal support could not be diffused from the metal support to the bonding layer, and a rapid change in the coefficient of thermal expansion in the bonding layer could not be suppressed.

[0086] On the other hand, in the electrochemical cells of Samples 1 to 18, peeling did not occur between the metal support and the first electrode layer of the cell part, and the bondability between the metal support and the first electrode layer could be improved. This is because a bonding layer made of an electronically conductive oxide was formed by diffusing metal elements capable of forming electronically conductive oxides such as Cr derived from the Fe-based alloy constituting the metal support from the metal support to the precursor of the electronically conductive oxide during firing, so that a rapid change in the coefficient of thermal expansion in the bonding layer could be suppressed. In addition, the electrochemical cells of Samples 1 to 18 had a specific bonding layer, so that the diffusion of Fe elements from the Fe-based alloy constituting the metal support could be suppressed, and Fe poisoning of Ni, which is a catalytic metal in the first electrode layer, could be suppressed.

[0087] Moreover, according to the electrochemical cells of Samples 1 to 3, it can be seen that the greater the value of the maximum inclination distance in the bonding layer, the easier it is to increase the bonding strength of the bonding layer. And it can be seen that by setting the maximum inclination distance to 0.1 μm or more, it becomes easier to improve the bondability by the bonding layer.

[0088] Furthermore, according to the electrochemical cells of Samples 1, 4, and 5, it can be seen that when the electronically conductive oxide constituting the bonding layer contains Cr as a metal element capable of forming an electronically conductive oxide, the bonding strength of the bonding layer is easier to increase than when it contains Mn or Ti. This is because an inclination is formed by the maximum added metal element in the Fe-based alloy constituting the metal support.

[0089] Also, according to the electrochemical cells of Sample 1, Sample 6, and Sample 7, it can be seen that the greater the thickness of the bonding layer, the easier it is to increase the bonding strength of the bonding layer. And it can be seen that by setting the thickness of the bonding layer 4 to 0.2 μm or more, the bonding strength of the bonding layer can be ensured more stably.

[0090] Also, according to the electrochemical cells of Sample 1, Sample 8 to Sample 10, it can be seen that by setting the coverage rate of the metal support by the bonding layer to 90% or more, it becomes easier to suppress the Fe poisoning of the catalyst metal contained in the first electrode layer. This is because the amount of contact points where the metal support and the first electrode layer come into contact is reduced due to fewer holes in the bonding layer.

[0091] Also, according to the electrochemical cells of Sample 1, Sample 11, and Sample 12, when the electronically conductive oxide constituting the bonding layer is a composite oxide containing metal elements capable of forming electronically conductive oxides such as La and Cr, it is easier to reduce the resistance of the bonding layer compared to the case where it is a composite oxide containing metal elements capable of forming electronically conductive oxides such as Sr and Cr, or a composite oxide containing metal elements capable of forming electronically conductive oxides such as Mn and Cr.

[0092] Also, according to the electrochemical cells of Sample 1, Sample 13 to Sample 16, it can be seen that even when the coverage rate of the metal support by the bonding layer is relatively low, if the bonding layer has a coating layer, the coating layer functions as a barrier film and can suppress the diffusion of the Fe element, which is a poisoning substance, into the first electrode layer. At this time, according to the electrochemical cells of Sample 13 and Sample 14, and the electrochemical cells of Sample 15 and Sample 16, it can be seen that by reducing the Fe concentration of the coating layer, it becomes easier to suppress the diffusion of the Fe element, which is a poisoning substance, into the first electrode layer.

[0093] Also, according to the electrochemical cells of Sample 13, Sample 17, and Sample 18, it can be seen that by setting the thickness of the coating layer to 1.5 μm or more, it becomes easier to suppress the diffusion of the Fe element, which is a poisoning substance, into the first electrode layer.

[0094] The present disclosure is not limited to the above-described embodiments and experimental examples, and various modifications are possible without departing from the gist thereof. In addition, the respective configurations shown in the embodiments and experimental examples can be arbitrarily combined. That is, although the present disclosure has been described in accordance with the embodiments, it is understood that the present disclosure is not limited to such embodiments, structures, etc. The present disclosure also includes various modifications and modifications within the equivalent scope. In addition, various combinations and forms, and further other combinations and forms including only one element, more than one element, or less than one element thereof, are within the scope and spirit of the present disclosure. Hereinafter, examples of reference embodiments will be appended. Item 1. A metal support (2) composed of an Fe-based alloy, a cell unit (3) including a solid electrolyte layer (30) having oxygen ion conductivity, a first electrode layer (31) disposed on one surface side of the solid electrolyte layer, and a second electrode layer (32) disposed on the other surface side of the solid electrolyte layer, a joining layer (4) that joins the metal support and the first electrode layer of the cell unit, the joining layer is composed of an electroconductive oxide containing at least one metal element among the alloy elements of the Fe-based alloy, the concentration of at least one of the metal elements is inclined so as to decrease from the metal support side toward the first electrode layer side, an electrochemical cell (1). Item 2. The metal support does not have an oxide layer derived from the Fe-based alloy on its surface, The electrochemical cell according to Item 1. Item 3. In the joining layer, when the concentration of the maximum addition metal element having the largest content among the metal elements contained in the alloy elements of the Fe-based alloy is at least inclined, The electrochemical cell according to Item 1 or Item 2. Item 4. The maximum addition metal element is Cr, The electrochemical cell according to Item 3. Item 5. The joining layer For at least one of the metal elements among the alloy elements of the Fe-based alloy, when the inclination distance, which is the layer thickness direction distance of the region where the concentration of the metal element is inclined, is obtained respectively, and the maximum of the respective inclination distances is defined as the maximum inclination distance, the maximum inclination distance is 0.1 μm or more. The electrochemical cell according to any one of Items 1 to 4. Item 6. The thickness of the bonding layer is 0.2 μm or more. The electrochemical cell according to any one of Items 1 to 5. Item 7. The coverage rate of the metal support by the bonding layer is 90% or more. The electrochemical cell according to any one of Items 1 to 6. Item 8. The electronically conductive oxide constituting the bonding layer contains a La element. The electrochemical cell according to any one of Items 1 to 7. Item 9. The bonding layer has a coating layer that covers the surface of the bonding layer on the first electrode layer side. The coating layer has a lower Fe concentration than the bonding layer. The electrochemical cell according to any one of Items 1 to 8. Item 10. The coating layer is composed of a ceria-based oxide containing at least a Ce element. The electrochemical cell according to Item 9. Item 11. The thickness of the coating layer is 1.5 μm or more. The electrochemical cell according to Item 9 or Item 10. Item 12. It is used as at least one of a solid oxide electrolysis cell and a solid oxide fuel cell. The electrochemical cell according to any one of Items 1 to 11.

Claims

1. A metal support (2) composed of an Fe-based alloy, a solid electrolyte layer (30) having oxygen ion conductivity, a first electrode layer (31) disposed on one surface side of the solid electrolyte layer, and a second electrode layer (32) disposed on the other surface side of the solid electrolyte layer, and a cell part (3) comprising: a bonding layer (4) that bonds the metal support and the first electrode layer of the cell part, wherein the bonding layer is composed of an electronically conductive oxide containing at least one metal element among the alloy elements of the Fe-based alloy, the concentration of at least one of the metal elements is inclined to decrease from the metal support side toward the first electrode layer side, the electronically conductive oxide constituting the bonding layer contains a La element, an electrochemical cell (1).

2. The bonding layer has a coating layer that covers the surface of the bonding layer on the first electrode layer side, and the coating layer has a lower Fe concentration than the bonding layer, The electrochemical cell according to Claim 1.

3. The coating layer is composed of a ceria-based oxide containing at least a Ce element, The electrochemical cell according to Claim 2.

4. The thickness of the coating layer is 1.5 μm or more, The electrochemical cell according to Claim 2 or Claim 3.

5. A metal support (2) composed of an Fe-based alloy, a solid electrolyte layer (30) having oxygen ion conductivity, a first electrode layer (31) disposed on one surface side of the solid electrolyte layer, and a second electrode layer (32) disposed on the other surface side of the solid electrolyte layer, and a cell part (3) comprising: a bonding layer (4) that bonds the metal support and the first electrode layer of the cell part, wherein the bonding layer is composed of an electronically conductive oxide containing at least one metal element among the alloy elements of the Fe-based alloy, the concentration of at least one of the metal elements is inclined to decrease from the metal support side toward the first electrode layer side, the bonding layer has a coating layer that covers the surface of the bonding layer on the first electrode layer side, and the coating layer has a lower Fe concentration than the bonding layer, an electrochemical cell (1).

6. The electronically conductive oxide constituting the bonding layer contains a La element, The electrochemical cell according to Claim 5.

7. The coating layer is composed of a ceria-based oxide containing at least a Ce element, The electrochemical cell according to Claim 5 or Claim 6.

8. The thickness of the coating layer is 1.5 μm or more. The electrochemical cell according to claim 5 or claim 6.

9. The metal support does not have an oxide layer derived from the Fe-based alloy on its surface. The electrochemical cell according to any one of claims 1, 2, 3, 5, and 6.

10. In the bonding layer, for the metal element among the alloying elements of the Fe-based alloy with the highest content rate, when the concentration of the maximum added metal element with the highest content rate is at least inclined, The electrochemical cell according to any one of claims 1, 2, 3, 5, and 6.

11. The maximum added metal element is Cr. The electrochemical cell according to claim 10.

12. The bonding layer For at least one of the metal elements among the alloying elements of the Fe-based alloy, the inclination distance, which is the distance in the layer thickness direction of the region where the concentration of the metal element is inclined, is obtained respectively, and when the maximum of each inclination distance is defined as the maximum inclination distance, the maximum inclination distance is 0.1 μm or more. The electrochemical cell according to any one of claims 1, 2, 3, 5, and 6.

13. The thickness of the bonding layer is 0.2 μm or more. The electrochemical cell according to any one of claims 1, 2, 3, 5, and 6.

14. The coverage rate of the metal support by the bonding layer is 90% or more. The electrochemical cell according to any one of claims 1, 2, 3, 5, and 6.

15. It is used as at least one of a solid oxide type electrolysis cell and a solid oxide type fuel cell. The electrochemical cell according to any one of claims 1, 2, 3, 5, and 6.

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