Interconnector with protective layer, cell stack comprising this interconnector with protective layer, and hydrogen energy system

Abstract

To provide an interconnector with a protective layer, a cell stack, and a hydrogen energy system, the protective layer being protected from shattering of a constituting component (Cr in particular) even when exposed to a high-temperature state for a long period of time, having sufficient shattering prevention properties and protective properties even with a protective layer thinner than conventional ones, having suppressed deterioration due to use, and having excellent electrical conductivity.SOLUTION: An interconnector has a protective layer on the surface of an interconnector material. The protective layer includes a metal layer composed of elements of the 11-th genus. The interconnector with the protective layer, a cell stack including the same, and a hydrogen energy system are provided.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to an interconnector with a protective layer, a cell stack including the interconnector with the protective layer, and a hydrogen energy system.

Background Art

[0002] As one of the new energy sources, hydrogen can be mentioned. As a device that uses such hydrogen as an energy source, a fuel cell that can convert chemical energy into electrical energy by electrochemically reacting hydrogen and oxygen has attracted attention.

[0003] Since fuel cells have high energy utilization efficiency, their development is underway as large-scale distributed power sources, household power sources, and mobile power sources.

[0004] Generally, fuel cells are classified according to the temperature range, the types of materials and fuels used. When classified by the electrolyte material used, they are divided into solid polymer type, phosphoric acid type, molten carbonate type, and solid oxide type. Among these, from the viewpoint of efficiency, solid oxide fuel cells (SOFCs) using solid oxide electrolytes have attracted attention.

[0005] However, since hydrogen does not exist in nature, it is necessary to transport hydrogen to a hydrogen system including a fuel cell. In an electrochemical cell, since it is possible to cause a water electrolysis reaction which is the reverse reaction of the fuel cell reaction, it becomes possible to produce hydrogen in the hydrogen system by this.

[0006] As hydrogen production reactions, three types can be mentioned: alkaline water electrolysis, solid polymer type, and solid oxide type. Among these, the solid oxide type is said to have the highest hydrogen production efficiency. And, since a solid oxide type electrochemical cell can perform either the fuel cell or the water electrolysis electrochemical reaction with high efficiency, it has attracted attention.

[0007] Furthermore, solid oxide type electrochemical cells can be increased in capacity by stacking them through an interconnector for solid oxide type electrochemical cells. Generally, since high temperature resistance is required for the interconnector for solid oxide type electrochemical cells, stainless steels with a high chromium content are often used as the substrate. However, these alloys may form an oxide coating mainly composed of Cr2O3 on the surface at high temperatures. However, since Cr2O3 has a high electrical resistance, it is inevitable that the electrical conductivity of the interconnector decreases and the resistance of the solid oxide type electrochemical cell stack increases. In addition, when the Cr component in the Cr2O3 coating gasifies and adheres to the electrode part of the solid oxide type electrochemical cell, the performance of the solid oxide type electrochemical cell is reduced.

[0008] In order to suppress these problems, suppressing Cr scattering by a protective layer on the surface of the interconnector for solid oxide type electrochemical cells is cited as one of the countermeasures. On the other hand, since the electrical resistance of this protective layer reduces the energy efficiency as ohmic loss, measures to reduce the electrical resistance of the protective layer have been widely studied.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] In an interconnector for a solid oxide type electrochemical cell having a protective layer, a material with high electrical conductivity is adopted as the protective layer. For example, perovskite-type oxides (chemical formula: ABO3) and spinel-type oxides (AB2O4) exhibit high electrical conductivity during the operating temperature and are materials that have been widely studied. On the other hand, in an interconnector for a solid oxide type electrochemical cell having a protective layer, Cr contained in the interconnector for solid oxide type electrochemistry diffuses into the protective layer, resulting in the substitution of some metal elements constituting the protective layer with Cr, and the formation of Cr2O3 between the interconnector for solid oxide type electrochemical cell and the protective layer, which increases the electrical resistance, thus posing a problem.

[0011] To solve this problem, in the present invention, in order to reduce the Cr diffusion rate, a structure in which a Cr diffusion barrier layer is introduced between the interconnector for a solid oxide type electrochemical cell and the protective layer is proposed.

[0012] The functions required for the above protective layer are Cr scattering suppression, electrical conductivity, and adhesiveness. Cr contained in the interconnector material diffuses through the protective layer to the surface when exposed to high temperature for a long time. Therefore, in order to improve the durability of the solid oxide type electrochemical cell stack, although the layer thickness of the protective layer can be increased to lengthen the reach distance from the interconnector to the surface of the protective layer, as a result, the electrical resistance of the protective layer increases, leading to a decrease in the reaction efficiency of the solid oxide type electrochemical cell.

[0013] For the purpose of suppressing the electrical resistance and minimizing the layer thickness of the protective layer, it is important to slow down the Cr diffusion rate in the protective layer. As one method, the present inventors focused on the morphology control of the protective layer and studied it in detail.

[0014] To solve these problems, in an embodiment of the present invention, an interconnector having a protective layer with a Cr diffusion barrier layer is proposed.

Means for Solving the Problem

[0015] The interconnector with a protective layer according to an embodiment of the present invention is an interconnector having a protective layer on the surface of an interconnector material, wherein the protective layer comprises a metal layer composed of a Group 11 element.

[0016] The interconnector with a protective layer according to an embodiment of the present invention preferably includes, as a specific example, an interconnector in which the protective layer comprises a metal layer composed of a Group 11 element and an oxide layer composed of an oxide of a metal other than the Group 11 element, and the oxide layer is disposed on the outer side.

[0017] The interconnector with a protective layer according to an embodiment of the present invention preferably includes, as a specific example, an interconnector in which the oxide layer comprises at least one element selected from the group consisting of Mn, Fe, Co, Ni, Cu, Ce, and Zn.

[0018] The interconnector with a protective layer according to an embodiment of the present invention preferably includes, as a specific example, an interconnector in which the metal layer composed of the Group 11 element has a layer thickness of 0.1 μm to 100 μm.

[0019] The interconnector with a protective layer according to an embodiment of the present invention preferably includes, as a specific example, an interconnector in which the oxide layer has a layer thickness of 0.1 μm to 100 μm.

[0020] And the cell stack according to an embodiment of the present invention is characterized by comprising a structural unit in which a solid oxide type electrochemical cell including a fuel electrode, an electrolyte layer, and an air electrode is sandwiched by the above-described interconnector with a protective layer.

[0021] The hydrogen energy system according to an embodiment of the present invention is characterized by comprising the above-described cell stack.

Advantages of the Invention

[0022] The interconnector with a protective layer according to an embodiment of the present invention prevents the scattering of constituent components (especially Cr) even when, for example, it is exposed to a high temperature state for a long time. In particular, the protective layer has sufficient scattering prevention performance and protection performance even if it is thinner than before, and deterioration due to use is effectively suppressed. Therefore, an interconnector is provided in which other characteristics such as electrical conductivity are improved while maintaining a high level of scattering prevention performance and protection performance.

[0023] In the interconnector with a protective layer according to an embodiment of the present invention, deterioration in the performance of the interconnector itself due to component scattering is prevented, and adverse effects (for example, contamination of other components and performance deterioration) due to the scattered components are prevented. And as described above, since other characteristics such as electrical conductivity are also improved, it is possible to provide a cell stack and a hydrogen energy system with higher performance and durability.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

[0025] <Interconnector with a protective layer> Hereinafter, the interconnector with a protective layer according to the present invention will be described, but the present invention is not limited to the following forms and examples. In addition, the schematic diagrams referred to in the following description are diagrams showing the positional relationship of each configuration, and the ratio of the thickness of each layer does not necessarily match the actual one.

[0026] FIG. 1 is a schematic diagram showing a cross-sectional structure of a part of the interconnector 1 with a protective layer according to an embodiment of the present invention. The interconnector 1 with a protective layer shown in FIG. 1 is an interconnector having a protective layer 110 on the surface of an interconnector material 100, wherein the protective layer 110 comprises a metal layer composed of Group 11 elements.

[0027] Here, as the interconnector material 100, the interconnector materials conventionally used in fuel cells, particularly solid oxide fuel cells, can also be used in the present invention. For example, those made of an Fe—Cr based alloy can be used. Such a Cr based alloy preferably has a Cr content of 12% by weight or more, particularly 18% by weight or more. The Fe—Cr based alloy may contain a small amount of a rare earth element or a Zr element, for example, 1.0% by weight or less.

[0028] The interconnector material 100 is preferably made of a material having a thermal expansion coefficient close to that of a solid oxide electrochemical cell, such as ferritic stainless steel. The protective layer 110 may cover one side or both sides of the interconnector material 100.

[0029] Generally, the Cr element reacts with oxygen or water vapor and vaporizes in the operating temperature range of a solid oxide electrochemical cell, which may cause a decrease in the performance of the solid oxide electrochemical cell. In order to suppress this, in the present invention, the interconnector material 100 containing Cr is covered with the protective layer 110 so that the Cr element does not reach the surface of the protective layer 110.

[0030] In the embodiment of the present invention, the protective layer functions as a barrier layer for suppressing Cr diffusion, so that the effect of suppressing Cr scattering can be improved.

[0031] Therefore, the protective layer 110 of the interconnector 1 with a protective layer according to the embodiment of the present invention comprises at least one metal layer composed of Group 11 elements.

[0032] <<Metal layer composed of Group 11 elements>> The Group 11 elements include any one of Cu, Ag, Au, and Rg. These are noble metals that are difficult to oxidize and have the characteristic that the solubility of Cr is very low. Here, when comparing the Group 11 elements with Cr in terms of the standard oxidation-reduction potential indicating the ease of oxidation, Cr 3+ has a standard oxidation-reduction potential of -0.74V vs SHE to become a metal, while Cu 2+ has a standard oxidation-reduction potential of +0.34V vs SHE to become a metal. This indicates that Cr is more easily oxidized than Cu. Comparing the standard oxidation-reduction potentials of Cu and other Group 11 elements shows that Cu is the most easily oxidized metal, and other Group 11 elements are also less easily oxidized than Cr.

[0033] These Group 11 elements exist in a metallic state under the operating environment, thus achieving low electrical resistance. Also, the metals of these Group 11 elements are characterized by a low solubility of Cr. For example, from the Hansen phase diagram, the solubility of Cr in the Cu phase shows about 0.15 mass% at 800 °C. This indicates that Cr hardly dissolves in Cu and shows a great effect as a Cr diffusion barrier layer.

[0034] The metal layer of Group 11 elements may be partially oxidized or may contain dissolved oxygen in the metal layer. Also, the metal layer of Group 11 elements may be composed of a single metal of Group 11 elements or may be composed of an alloy with Group 11 elements.

[0035] As methods for fabricating the metal layer of Group 11 elements, physical vapor deposition methods such as vacuum evaporation and ion plating methods, chemical vapor deposition methods such as sputtering and pulsed laser deposition methods, cold spray methods, thermal spraying methods, electrodeposition methods, electroless plating methods, rolling methods, spin coating methods, dip coating methods, sol-gel methods, doctor blade methods, screen printing methods, aerosol deposition methods, etc. can be mentioned.

[0036] The metal layer of Group 11 elements can form a layer by itself, or after forming an oxide layer, the metal layer can be produced by reduction. Also, after forming a layer containing a solvent, the metal layer can be formed by volatilizing and reacting the solvent with temperature, gas atmosphere, etc. Further, when producing a metal layer by forming an oxide layer and then reducing it, or when producing a metal layer by forming a layer containing a solvent and then volatilizing and reacting the solvent with temperature, gas atmosphere, etc., the production process of the metal layer can be carried out with a single interconnector with a protective layer, or can also be carried out after incorporating the interconnector with a protective layer into a cell stack or a module.

[0037] The interconnector 1 with a protective layer according to an embodiment of the present invention is composed of an interconnector material 100 and a protective layer 110 that covers the surface of the interconnector material 100. The protective layer 110 may be composed of a plurality of layers. In FIG. 2, the first protective layer 111, the second protective layer 112, and the third protective layer 113 are shown in order from the layer closest to the interconnector material.

[0038] Generally, in the operating temperature range of a solid oxide fuel cell, the Cr element reacts with oxygen and water vapor to vaporize, which can be a factor in reducing the performance of the solid oxide fuel cell. To suppress this, it is necessary to cover the interconnector material 100 containing Cr with the protective layer 110 so that the Cr element does not reach the surface of the protective layer 110. Among the plurality of layers (three layers in FIG. 2) constituting the protective layer 110, by making one or more of the protective layers function as a barrier layer for suppressing Cr diffusion, the effect of suppressing Cr scattering can be improved.

[0039] The metal layer of Group 11 elements may be the first protective layer 111 that covers the surface of the interconnector material 100, or may also be the second protective layer 112.

[0040] <<Oxide layer>> The oxide constituting the oxide layer desirably exhibits low electrical resistance at 600 to 1000°C. Particularly preferred specific examples of such oxides include spinel-type oxides (AB2O4), perovskite-type oxides (ABO3), and Ruddelsden-Popper-type oxides (ABO3) n · Oxides having a crystal structure of AO can be mentioned.

[0041] When using a spinel-type oxide as the oxide, the composition of the oxide layer is preferably an oxide containing at least one selected from the group consisting of Mn, Fe, Ni, Cu, Ce, and Zn in Co3O4, or an oxide containing at least one element selected from the group consisting of Fe, Mn, and Cu as a dopant in Zn3O4, etc.

[0042] When using a perovskite-type oxide or a Ruddelsden-Popper-type oxide as the oxide, the composition of the oxide layer is preferably (La,Sr)CoO3, (La,Sr)(Co,Fe)O3, (La,Sr)MnO3, LaNiO4, Ba(CeY)O3, (BaZr)(CeY)O3, etc.

[0043] As a method for forming the oxide layer, preferably, physical vapor deposition methods such as Kahn vacuum evaporation and ion plating method, chemical vapor deposition methods such as sputtering and pulsed laser deposition method, cold spray method, thermal spraying method, electrodeposition method, electroless plating method, rolling method, spin coating method, dip coating method, sol-gel method, doctor blade method, screen printing method, aerosol deposition method, etc. may be mentioned. The oxide layer may be formed of the oxide itself, or after forming a metal layer, the oxide layer can be produced by oxidizing it, or after forming a layer containing a solvent, the oxide layer can be produced by volatilizing and reacting the solvent with temperature, gas atmosphere, etc. Further, when forming a metal layer by oxidizing after forming a metal layer, or when producing an oxide layer by volatilizing and reacting a solvent with temperature, gas atmosphere, etc. after forming a layer containing a solvent, the production process of the oxide layer may be carried out with the single interconnector with a protective layer, or can be carried out after incorporating the interconnector with a protective layer into a cell stack or a module.

[0044] When the protective layer includes a metal layer and an oxide layer composed of Group 11 elements, the oxide layer is disposed outside the metal layer composed of Group 11 elements (that is, closer to the surface of the protective layer).

[0045] Specifically, as shown in FIG. 1, (a) The oxide layer (third protective layer 113) is outside the metal layer (second protective layer 112) composed of Group 11 elements, (b) The oxide layer (second protective layer 112) is outside the metal layer (first protective layer 111) composed of Group 11 elements, (c) The oxide layer (third protective layer 113) is disposed outside the metal layer (first protective layer 111) composed of Group 11 elements.

[0046] In cases (b) and (c), when the metal layer of Group 11 elements is used as the first protective layer 111, the structure in which the second protective layer 112, or further outer third protective layer 113, or fourth and higher protective layers have an oxide layer is considered to reduce the degree of oxidation of the metal layer of Group 11 elements.

[0047] <<Other requirements (layer thickness, porosity)>> Since the metal layer needs to cover the entire interconnector material 100, a certain layer thickness is required. On the other hand, if the layer thickness is unnecessarily large, it will cause an increase in electrical resistance. Considering these factors, the layer thickness of the metal layer is preferably 0.1 μm to 100 μm, and more preferably 0.5 μm to 20 μm.

[0048] It is desirable that the oxide layer covers the entire interconnector material 100, and for this purpose, a certain layer thickness is required. On the other hand, if the layer thickness is unnecessarily large, it may cause an increase in electrical resistance. Considering these factors, the layer thickness of the oxide layer is preferably 1 μm to 100 μm, and more preferably 1 μm to 50 μm.

[0049] A metal layer with a small porosity is preferable because it exhibits a high Cr diffusion barrier effect. The porosity of the metal layer is preferably 0 to 40%, and more preferably 0 to 15%.

[0050] An oxide layer with a small porosity is expected to have a low electrical resistance. The porosity of the oxide layer is preferably 0 to 60%, and more preferably 0 to 20%.

[0051] <Cell stack> The cell stack according to the embodiment of the present invention is characterized in that it comprises a structural unit in which a solid oxide type electrochemical cell including a fuel electrode, an electrolyte layer, and an air electrode is sandwiched by the above-described interconnector with a protective layer.

[0052] Figure 2 is a schematic diagram showing a part of the cross-sectional structure of the cell stack 0 according to the embodiment. Note that this schematic diagram shows the positional relationship of each component, and the ratio of the thickness of each layer is not necessarily the same as the actual one.

[0053] The cell stack 0 has a stacked body in which a solid oxide type electrochemical cell 2 including a fuel electrode 201, an electrolyte layer 202, and an air electrode 203 is sandwiched by the aforementioned interconnector with a protective layer (the first interconnector or the second interconnector) 1 as one structural unit (Fig. 2a). Generally, this structural unit has a stacked structure (Fig. 2b) in which the structural unit is repeatedly stacked in the stacking direction of the fuel electrode, air electrode, etc. Here, as shown in Fig. 2b, the stacked upper "interconnector 1 with a protective layer on the lower side of the stacked structure" and the stacked lower "interconnector 1 with a protective layer on the upper side of the stacked structure" can be shared by the upper "stacked structure" and the lower "stacked structure". That is, one interconnector 1 with a protective layer can be used as the upper "interconnector 1 with a protective layer on the lower side of the stacked structure" and can also be used as the lower "interconnector 1 with a protective layer on the upper side of the stacked structure".

[0054] Note that it is possible to exhibit the function as a cell stack of a fuel cell even with only one structural unit as shown in Fig. 2a. However, as shown in Fig. 2b, by adopting a stacked structure in which the structural unit is repeatedly stacked, it becomes possible to increase the amount of electrochemical reaction.

[0055] The cell stack according to the embodiment of the present invention is not limited to those having only a fuel electrode, an electrolyte layer, an air electrode, and an interconnector with a protective layer, and includes cell stacks having other constituent members, materials, etc. in addition to the exemplified constituent members (i.e., fuel electrode, electrolyte layer, air electrode, interconnector with a protective layer). Preferred specific examples of the above other constituent members include, for example, a fuel electrode current collecting member, an air electrode current collecting member, etc. For example, a cell stack in which a fuel electrode current collecting member 3 is disposed between the interconnector 1 with a protective layer and the fuel electrode 201 as shown in Fig. 2c, or a cell stack in which an air electrode current collecting member 4 is disposed between the air electrode 203 and the interconnector 1 with a protective layer is a preferred specific example of the cell stack according to the present invention.

[0056] In the cell stack of FIG. 2c, the fuel electrode current collector member 3 and the air electrode current collector member 4 function as flow paths for fuel gas, air, product gas (e.g., water vapor), etc., enabling highly efficient supply of fuel gas and air to the cell stack 0, and discharge of product gas and heat, etc. from the cell stack 0, and enhancing the electrical contact between the solid oxide type electrochemical cell 2 and the interconnector 1 with a protective layer, greatly contributing to performance improvement of the cell stack or the hydrogen energy system.

[0057] <Hydrogen energy system> The hydrogen energy system according to an embodiment of the present invention is characterized by comprising the above-described cell stack.

[0058] The embodiments of the present invention have been described above with reference to specific examples. However, the above examples are given as examples of the present invention and do not limit the present invention.

[0059] In addition, in the description of each of the above embodiments, there are parts where descriptions of parts not directly required for the description of the present invention in the interconnector with a protective layer, the cell stack, and the hydrogen energy system are omitted. For these, other elements can be appropriately selected and used as necessary.

[0060] Furthermore, all interconnectors, cell stacks, and hydrogen energy systems that have the configuration of the present invention and can be appropriately designed and modified by those skilled in the art without departing from the spirit of the present invention are included in the scope of the present invention. The scope of the present invention is defined by the scope of the claims and the scope of their equivalents.

Example

[0061] <Example 1> Ag layers with a thickness of 1 μm were formed on both surfaces of a stainless steel sample piece, and Co layers with a thickness of 2 μm were further formed thereon. This was subjected to high-temperature air exposure at a temperature of 700°C for 10 hours. Thereafter, it was allowed to radiate heat until room temperature, and Sample A (Example 1) having a protective layer composed of an Ag metal layer and a Co oxide layer on the surface of stainless steel was obtained. Pt electrodes were formed on both sides of this Sample A (Example 1), and electrical resistance measurement was carried out on this sample piece at 700 °C by the four-terminal method. The results are as shown in FIG. 3.

[0062] <Example 2> Except that a 1-μm-thick Ag layer and a 4-μm-thick Co-Ni layer were formed on the surface of a stainless-steel sample piece instead of a 1-μm-thick Ag layer and a 2-μm-thick Co layer, in the same manner as in Example 1, Sample B (Example 2) having a protective layer composed of an Ag metal layer and a Co oxide layer on the surface of stainless steel was obtained. Similar to Example 1, Pt electrodes were formed on both sides of this Sample B, and electrical resistance measurement was carried out on this sample at 700 °C by the four-terminal method. The results are as shown in FIG. 3.

[0063] <Comparative Example 1> Except that a 2-μm-thick Co layer was formed on the surface of a stainless-steel sample piece instead of a 1-μm-thick Ag layer and a 2-μm-thick Co layer, in the same manner as in Example 1, Sample C (Comparative Example 1) having a Co oxide layer on the surface of stainless steel was obtained. Similar to Example 1, Pt electrodes were formed on both sides of this Sample C, and electrical resistance measurement was carried out on this sample at 700 °C by the four-terminal method. The results are as shown in FIG. 3.

[0064] <Comparative Example 2> Except that a 4-μm-thick Co-Ni layer was formed on the surface of a stainless-steel sample piece instead of a 1-μm-thick Ag layer and a 2-μm-thick Co layer, in the same manner as in Example 1, Sample D (Comparative Example 2) having a Co-Ni oxide layer on the surface of stainless steel was obtained. Similar to Example 1, Pt electrodes were formed on both sides of this Sample D, and electrical resistance measurement was carried out on this sample at 700 °C by the four-terminal method. The results are as shown in FIG. 3.

[0065] <Example 3> On both surfaces of a sample piece made of stainless steel, an Ag layer with a thickness of 1 μm was formed, and three samples were obtained in which a Co-Ni layer with a thickness of 4 μm was further formed thereon. Each sample was subjected to a high-temperature air exposure test at a temperature of 700 °C with different holding times to obtain three samples ((Example 3-1), (Example 3-2), (Example 3-3)) having a protective layer composed of an Ag metal layer and a Co oxide layer on the surface of the stainless steel. SEM-EDS analysis was performed on the cross-section of each sample, line analysis of the elemental analysis of the cross-section of the protective layer was carried out, and the Cr diffusion distance from the surface of the stainless steel was investigated. The results are as shown in Figure 4.

[0066] <Comparative Example 3> Three samples (Comparative Example 3) were obtained in which a Co-Ni layer with a thickness of 4 μm was formed on both surfaces of a sample piece made of stainless steel. Each sample was subjected to a high-temperature air exposure test at a temperature of 700 °C with different holding times to obtain three samples ((Comparative Example 3-1), (Comparative Example 3-2), (Comparative Example 3-3)) having a Co-Ni oxide layer on the surface of the stainless steel. SEM-EDS analysis was performed on the cross-section of each sample, line analysis of the elemental analysis of the cross-section of the oxide layer was carried out, and the Cr diffusion distance from the surface of the stainless steel was investigated. The results are as shown in Figure 4.

[0067] <Summary> In Example 3 having an Ag metal layer, the Cr diffusion distance was significantly reduced compared to Comparative Example 3 having no Ag metal layer. And the suppression of Cr diffusion is maintained at a sufficient level even when the heating holding time is prolonged. From this, it was confirmed that the Ag metal layer functions as a Cr diffusion barrier layer for a long time.

[0068] In addition, in Examples 1 and 2 having an Ag metal layer, the electrical resistance is significantly reduced compared to Comparative Examples 1 and 2 without an Ag metal layer. Since the electrical resistance of Cr-based oxides is generally large, it can be inferred that the formation rate of Cr-based oxides was reduced by suppressing Cr diffusion. This is considered to be the factor that reduced the electrical resistance. Since the Cr diffusion effect can be confirmed for a long time by introducing a Cr diffusion barrier layer, an effect of reducing the electrical resistance over a long time can be expected.

[0069] From the above, it was found that by introducing an Ag layer, the Ag layer functions as a Cr diffusion barrier layer for a long time and suppresses the diffusion of Cr. It was also found that the electrical resistance is reduced, and an effect over a long time is expected. From this, by introducing an Ag layer, not only can Cr diffusion be suppressed, but also the electrical resistance can be reduced. The proposed structure having a configuration with a Cr diffusion barrier layer introduced can provide a cell stack and a hydrogen energy system with higher performance and durability.

Explanation of Symbols

[0070] 1: Interconnector with protective layer, 100: Interconnector material, 110: Protective layer, 0: Cell stack, 201: Fuel electrode, 202: Electrolyte layer, 203: Air electrode, 2: Solid oxide type electrochemical cell, 3: Fuel electrode current collector member, 4: Air electrode current collector member.

Claims

1. An interconnector having a protective layer on the surface of an interconnector material, wherein the protective layer includes a metal layer and an oxide layer, and the oxide layer is disposed outwardly, the metal layer is made of Ag, has a layer thickness of 0.5 to 20 μm, and a porosity of 0 to 15%, the oxide layer is made of a spinel-type oxide, has a layer thickness of 1 to 50 μm, and a porosity of 0 to 20%, characterized in that it is an interconnector with a protective layer.

2. The interconnector with a protective layer according to claim 1, wherein the oxide layer comprises at least one element selected from the group consisting of Mn, Fe, Co, Ni, Cu, Ce, and Zn.

3. The interconnector with a protective layer according to claim 1 or 2, wherein the oxide layer is made of Co or a Co-Ni oxide.

4. A solid oxide type electrochemical cell including a fuel electrode, an electrolyte layer, and an air electrode, characterized in that it comprises a structural unit sandwiched by the interconnector with a protective layer according to any one of claims 1 to 3.

5. A hydrogen energy system, characterized in that it comprises the cell stack according to claim 4.

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