Cell connection member, electrochemical module, solid oxide fuel cell, solid oxide electrolysis cell, electrochemical device, and energy system

Abstract

To provide a high electron conductivity and low contact resistance while having high economical efficiency, to suppress the growth of an oxide film on the surface of a base material, and to satisfactorily suppress the scattering of Cr.SOLUTION: An inter-cell connection member 10 of an electrochemical element 30 in which an electrode layer 31, an electrolyte layer 33, and a counter electrode layer 32 are laminated in this order includes a base material 11 made of an alloy or an oxide containing at least Cr, and a coating film 13 for protecting a surface of the base material 11, and the coating film 13 is made of a metal oxide containing Al, Cu, and Mn.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an inter-cell connector for an electrochemical element in which an electrode layer, an electrolyte layer, and a counter electrode layer are stacked in the stated order, an electrochemical module, a solid oxide fuel cell, a solid oxide electrolysis cell, an electrochemical device, and an energy system. [Background technology]

[0002] In recent years, development has been underway on coating films for inter-cell connecting members such as interconnectors, separators, and current collectors for SOFC / SOEC cell stacks with metal-supported structures, such as SOFC cell stacks installed in SOFC cogeneration systems and SOEC stacks used in SOEC methanation (see Patent Documents 1 and 2). The metal components used for connecting the cells, which are mainly made of stainless steel, are coated with a ceramic film using electrochemical deposition methods such as plating and electrodeposition, or deposition methods such as PVD and aerosol deposition, to give them a durability of 12 years.

[0003] Co-based Co-Mn spinel, Zn-Co-Mn spinel, Ni-Co spinel, etc. are commonly used as coating film materials, not only to improve the durability of stainless steel but also to prevent Cr poisoning of the air electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-191928 [Patent Document 2] Japanese Patent Publication No. 2022-155183 Summary of the Invention [Problem to be solved by the invention]

[0005] However, these materials are extremely expensive, particularly the Co, which accounts for the majority of the cost of the coating material. Spinel oxides using materials other than Co, such as Ni-Mn and Cu-Mn, based on transition metals, have been investigated, but Ni-Mn does not provide sufficient electronic conductivity, and Cu-Mn has issues such as Cu volatilization during operation and insufficient resistance to Cr poisoning, and no Co-free coating material has yet been discovered.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an inter-cell connecting member, an electrochemical module, a solid oxide fuel cell, a solid oxide electrolysis cell, an electrochemical device, and an energy system that are highly economical, have high electronic conductivity and low contact resistance, can suppress the growth of an oxide film on the surface of the substrate, and can effectively suppress Cr scattering. [Means for solving the problem]

[0007] The inter-cell connection member for achieving the above object comprises: An inter-cell connection member for an electrochemical element in which an electrode layer, an electrolyte layer, and a counter electrode layer are stacked in the stated order, and characterized by the following configuration: The substrate has a base material made of an alloy or oxide containing at least Cr, and a coating film that protects the surface of the base material, The coating film is made of a metal oxide containing Al, Cu, and Mn.

[0008] The inventors of the present invention have conducted extensive research into materials for the coating film of the cell-to-cell connecting member from the perspectives of low resistance, suppression of the growth of an oxide film on the surface of the substrate, and suppression of Cr scattering from the substrate. As a result, they have discovered that a coating film made from a metal oxide containing Al, Cu, and Mn has high electronic conductivity and low contact resistance, can suppress the growth of an oxide film on the surface of the substrate, and can effectively suppress Cr scattering. In particular, the inventors have found that, as shown in test data described below, metal oxides that contain Cu and Mn but do not contain Al cannot maintain low resistivity and cannot suppress the growth of an oxide film or the scattering of Cr because Cu volatilizes over time at a specified operating temperature, whereas metal oxides that contain Al, Cu, and Mn can exhibit the desired low resistivity and can suppress the growth of an oxide film while suppressing the scattering of Cr. As described above, the above characteristic configuration makes it possible to realize an inter-cell connection member that is highly economical, has high electronic conductivity, low contact resistance, can suppress the growth of an oxide film on the surface of the substrate, and can effectively suppress Cr scattering.

[0009] Further characteristic configurations of the inter-cell connection members include: The coating film is made of the metal oxide that is substantially free of Co.

[0010] The inventors have discovered that by using a metal oxide containing Al, Cu, and Mn as the material for the coating film, it is possible to achieve the required low resistance, suppression of the growth of an oxide film on the substrate surface, and suppression of Cr scattering from the substrate, even without substantially containing the highly rare Co. In other words, by using a metal oxide containing Al, Cu, and Mn as the material of the coating film, the above-mentioned effects can be satisfactorily exhibited even without containing Co. In this specification, "substantially free of Co" means that the mass percentage of Co in the coating film material is 0.1 mass% or more and 3 mass% or less, more preferably 0.1 mass% or more and 1 mass% or less, and more preferably 0 mass%.

[0011] Further characteristic configurations of the inter-cell connection members include: The thickness of the coating film is 5 μm or more and 30 μm or less.

[0012] In the case of a coating film made of a metal oxide containing Al, Cu, and Mn, as in the present invention, it is preferable to set the film thickness to a relatively large value of 5 μm or more and 30 μm or less from the viewpoint of durability. In particular, it has been confirmed that Cr leaks from the coating film with use over time when the film thickness is less than 5 μm. The thickness of the coating film is more preferably 10 μm or more and 25 μm or less, and even more preferably 15 μm or more and 20 μm or less.

[0013] Further characteristic configurations of the inter-cell connection members include: The coating film contains Al, Cu, and Mn, and the content of Mn is 50 mass % or less.

[0014] As described above, by setting the abundance ratio of Mn among Al, Cu, and Mn contained in the coating film to 50 mass% or less, the electronic conductivity of the coating film can be made to be equal to or higher than the desired value, thereby realizing an inter-cell connecting member with good low resistance. To further explain, the abundance ratio of Mn is preferably 50 mass % or less, more preferably 33 mass % or less, from the viewpoint of low resistivity, and is preferably 16 mass % or more, more preferably 33 mass % or more, from the viewpoint of durability.

[0015] Further characteristic configurations of the inter-cell connection members include: The metal oxide used as the coating film is Al X Cu Y Mn Z The oxide is an oxide of X, Y, and Z, and the ratio of X:Y:Z is 1:1:1.

[0016] The inventors of the present invention have used a metal oxide as a coating film, such as Al X Cu Y Mn Z When the X:Y:Z ratio is 1:1:1, as shown in the test results described below, in an ASR test, it was confirmed that a low resistance comparable to that of a coating film containing Co could be achieved, and that the growth of the oxide film and the scattering of Cr could be suppressed to the same extent as a coating film containing Co.

[0017] Further characteristic configurations of the inter-cell connection members include: The bonding material that bonds the coating film to either the air electrode or oxygen evolution electrode, which is either the electrode layer or the counter electrode layer of the electrochemical element, is LSCF or the metal oxide containing Al, Cu, and Mn.

[0018] As in the above-described characteristic configuration, when the material of the coating film is a metal oxide containing Al, Cu, and Mn, the bonding material that bonds the coating film to either the air electrode or oxygen evolution electrode, which is either the electrode layer or the counter electrode layer, is either LSCF or a metal oxide containing Al, Cu, and Mn. This makes it possible to realize an inter-cell connecting member that uses a sufficiently reduced amount of Co overall, thereby achieving high cost-effectiveness.

[0019] The electrochemical module having the above-described inter-cell connection member has the following characteristic configuration: The electrochemical elements are connected together by inter-cell connecting members and arranged in a group.

[0020] According to the above-described characteristic configuration, by arranging a plurality of electrochemical elements in a cluster, it is possible to realize a compact, high-performance electrochemical module that is excellent in durability and performance while reducing material and processing costs. Furthermore, when the electrochemical module is operated as a fuel cell, for example, it is possible to obtain a large power generation output.

[0021] The characteristic configuration of a solid oxide fuel cell having the above-described inter-cell connection member is as follows: The feature is that a power generation reaction occurs in the electrochemical elements connected by the inter-cell connecting members.

[0022] According to the above-described characteristic configuration, a power generation reaction can be carried out as a solid oxide fuel cell equipped with the electrochemical element described above, and therefore, a highly economical solid oxide fuel cell can be obtained with substantially no Co usage.

[0023] The solid oxide electrolysis cell having the above-described inter-cell connector has the following characteristic configuration: The electrolytic reaction occurs in the electrochemical elements connected by the inter-cell connecting members.

[0024] According to the above characteristic configuration, a solid oxide electrolysis cell including the electrochemical element described above can generate gas through an electrolytic reaction, thereby providing a highly economical solid oxide electrolysis cell with substantially zero Co usage.

[0025] The electrochemical device having the above-described electrochemical module has the following characteristic configuration: The fuel cell system is characterized in that it comprises at least a fuel converter that generates reducing components to be supplied to the electrochemical module or that converts gas containing reducing components generated in the electrochemical module.

[0026] According to the above characteristic configuration, when the electrochemical element or electrochemical module is operated as a fuel cell, it can be configured to generate hydrogen using a fuel converter such as a reformer from natural gas or the like supplied using existing raw fuel supply infrastructure such as city gas, thereby realizing an electrochemical device equipped with the electrochemical element or electrochemical module that is highly economical with substantially no Co usage. Furthermore, it becomes easy to build a system for recycling unused fuel gas circulated from the electrochemical module, thereby realizing a highly efficient electrochemical device. On the other hand, when the electrochemical element or electrochemical module is operated as an electrolysis cell, a gas containing water vapor or carbon dioxide is passed through the electrode layer, and a voltage is applied between the electrode layer and the counter electrode layer. Then, electrons e - reacts with water H2O and carbon dioxide molecules CO2 to produce hydrogen H2, carbon monoxide CO and oxygen ions O 2- The generated oxygen ions O 2- moves through the electrolyte layer to the counter electrode layer, where oxygen ions O 2-releases electrons and becomes oxygen O2. Through the above reaction, when gas containing water vapor flows, water H2O is decomposed into hydrogen H2 and oxygen O2, and when gas containing carbon dioxide molecules CO2 flows, it is electrolyzed into carbon monoxide CO and oxygen O2. Therefore, when a gas containing water vapor and carbon dioxide molecules (CO2) is circulated, a fuel converter can be provided that synthesizes various compounds such as hydrocarbons from the hydrogen and carbon monoxide produced by the electrolysis in the electrochemical element or electrochemical module. This allows the hydrocarbons produced by the fuel converter to be circulated to the electrochemical element or electrochemical module, or extracted from this system / device and used as fuel or chemical raw materials.

[0027] The electrochemical device having the above-described electrochemical module has the following characteristic configuration: The electrochemical module is characterized by comprising at least a power converter that extracts electric power from the electrochemical module or that supplies electric power to the electrochemical module.

[0028] According to the above characteristic configuration, the power converter can extract power generated by the electrochemical device or electrochemical module or can supply power to the electrochemical device or electrochemical module, thereby allowing the electrochemical device or electrochemical module to function as a fuel cell or an electrolysis cell. Therefore, according to the above-described characteristic configuration, an electrochemical device with improved efficiency in converting chemical energy such as fuel into electrical energy or converting electrical energy into chemical energy such as fuel can be realized in a highly economical state with substantially zero Co usage. For example, when an inverter is used as a power converter, this is preferable when operating as a fuel cell, because the inverter can boost voltage or convert direct current into alternating current, making it easier to utilize the electrical output obtained from the electrochemical element or electrochemical module. Furthermore, when operating as an electrolytic cell, this is preferable because it allows for the construction of an electrochemical device that can obtain direct current from an alternating current power source and supply the direct current to the electrochemical element or electrochemical module.

[0029] The characteristic configuration of the energy system having the electrochemical device described above is as follows: The electrochemical device is characterized by comprising at least a waste heat utilization section for reusing heat discharged from the electrochemical device.

[0030] The above-described characteristic configuration makes it possible to realize an energy system that is free of Co, is economical, and has excellent energy efficiency. It is also possible to realize a hybrid system with excellent energy efficiency by combining it with a power generation system that generates electricity by utilizing the combustion heat of unused fuel gas discharged from the electrochemical device. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 2 is a schematic diagram showing an electrochemical module in which electrochemical elements and inter-cell connection members are separated in the stacking direction. [Figure 2] FIG. 2 is a cross-sectional view showing an electrochemical module in which electrochemical elements and inter-cell connection members are stacked. [Figure 3] FIG. 2 is an explanatory diagram of the reaction during operation of a solid oxide fuel cell. [Figure 4] 1 is a diagram showing the configuration of an electrochemical device including a solid oxide fuel cell and an energy system. [Figure 5] FIG. 1 is a diagram showing the configuration of an electrochemical device including a solid oxide electrolysis cell and an energy system. [Figure 6] FIG. 1 is a graph showing resistance values ​​(ASR) at each temperature for an example and a comparative example in which a predetermined inter-cell connection member is joined to a stainless steel material. [Figure 7] 1 is an SEM image showing a cross section of an example in which a predetermined inter-cell connection member is joined to a stainless steel material. [Figure 8] 10 is an SEM image showing a cross section of a comparative example in which a predetermined inter-cell connection member is joined to a stainless steel material. [Figure 9] FIG. 1 is a cross-sectional view of a metal-supported electrochemical device. [Figure 10] FIG. 10 is a schematic diagram showing an electrochemical module made up of the electrochemical device shown in FIG. [Figure 11] FIG. 10 is a schematic diagram illustrating another embodiment of an electrochemical module. DETAILED DESCRIPTION OF THE INVENTION

[0032] The inter-cell connection members, electrochemical modules, solid oxide fuel cells, solid oxide electrolysis cells, electrochemical devices, and energy systems according to the embodiments of the present invention are highly economical, yet have high electronic conductivity and low contact resistance, can suppress the growth of an oxide film on the surface of the substrate, and can effectively suppress Cr scattering. Hereinafter, an inter-cell connection member, an electrochemical module, a solid oxide fuel cell, a solid oxide electrolysis cell, an electrochemical device, and an energy system according to embodiments of the present invention will be described with reference to the drawings.

[0033] Fig. 1 is a schematic diagram of an electrochemical module M, and Fig. 3 is an explanatory diagram of reactions during operation of a solid oxide fuel cell (hereinafter sometimes abbreviated as SOFC) using the electrochemical module M. As shown in Figs. 1 and 3, the electrochemical module M used in the solid oxide fuel cell is configured to include a plurality of electrochemical elements 30 and inter-cell connection members 10 that connect the electrochemical elements 30 together. In other words, the electrochemical module M is configured as a flat-plate cell stack.

[0034] <Electrochemical element> The electrochemical element 30 includes an electrode layer 31 and a counter electrode layer 32. Specifically, the electrochemical element 30 is formed by joining a cathode (air electrode) made of an oxygen ion and electron conductive porous body as either the electrode layer 31 or the counter electrode layer 32 to one side of an electrolyte layer 33 made of a dense body of oxygen ion conductive solid oxide, and by joining an anode (fuel electrode) made of an electron conductive porous body to the other side of the electrolyte layer 33 as the other of the electrode layer 31 or the counter electrode layer 32. In this embodiment, a configuration example (solid oxide fuel cell) will be described in which the electrode layer 31 is the cathode (air electrode) and the counter electrode layer 32 is the anode (fuel electrode).

[0035] The electrochemical module M has a structure in which the electrochemical element 30 is sandwiched between a pair of electron-conductive inter-cell connection members 10, each having grooves 12 formed therein for donating and receiving electrons to and from the electrode layer 31 or counter electrode layer 32 and for supplying air and hydrogen, with a gas seal held between the outer peripheries as appropriate. By arranging the cathode and the inter-cell connection member 10 in close contact, the groove 12 on the cathode side functions as an air flow path 12a for supplying air to the cathode. By arranging the anode and the inter-cell connection member 10 in close contact, the groove 12 on the anode side functions as a fuel flow path 12b for supplying hydrogen to the anode.

[0036] To explain in more detail about the general materials used for the elements constituting the electrochemical device 30, the electrode layer 31 can be a thin layer, and its thickness can be, for example, about 1 μm to 100 μm, preferably 5 μm to 50 μm. With such a thickness, it is possible to reduce the amount of expensive material used for the electrode layer 31, thereby reducing costs, while ensuring sufficient electrode performance. Examples of materials that can be used for the electrode layer 31 include composite oxides such as LSCF and LSM, ceria-based oxides, and mixtures thereof. In particular, the electrode layer 31 preferably contains a perovskite-type oxide containing two or more elements selected from the group consisting of La, Sr, Sm, Mn, Co, and Fe. The electrode layer 31 formed using the above materials functions as a cathode.

[0037] The electrode layer 31 is preferably formed using a method capable of forming the electrode layer 31 at a processing temperature of 1100°C or less, since this can suppress the diffusion of Cr elements from the inter-cell connection member 10 (described later) to the electrode layer 31 and realize an electrochemical device 30 with excellent performance and durability. For example, a low-temperature firing method (e.g., a wet method using a firing process at a low temperature without firing at a high temperature exceeding 1100°C), a spray coating method (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, etc.), a PDV method (sputtering, pulsed laser deposition, etc.), a CVD method, etc., can be used. Low-temperature firing methods and spray coating methods are particularly preferred, since they allow for the realization of low-cost devices. Furthermore, low-temperature firing methods are even more preferred, since they facilitate the handling of raw materials.

[0038] The electrode layer 31 has a plurality of pores inside and on its surface to provide gas permeability. That is, the electrode layer 31 is formed as a porous layer. The electrode layer 31 is formed, for example, so that its density is 30% or more and less than 80%. The size of the pores can be appropriately selected so that the electrochemical reaction proceeds smoothly. Note that density is the proportion of the space occupied by the material constituting the layer, and can be expressed as (1 - porosity), and is equivalent to the relative density.

[0039] The counter electrode layer 32 can be provided in the form of a thin layer, similar to the electrode layer 31, and its thickness can be, for example, about 1 μm to 100 μm, preferably 5 μm to 50 μm. With such a thickness, it is possible to reduce the amount of expensive counter electrode layer 32 material used to cut costs, while ensuring sufficient electrode performance.

[0040] The counter electrode layer 32 can be made of a composite material such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO-CeO, or Cu-CeO. In these examples, GDC, YSZ, or CeO can be referred to as the aggregate of the composite. By using such a material, the counter electrode layer 32 functions as an anode. The counter electrode layer 32 is preferably formed by a low-temperature firing method (e.g., a wet method using firing treatment in a low-temperature range that does not involve firing treatment in a high-temperature range higher than 1100°C), a spray coating method (such as a thermal spray method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulsed laser deposition method), or a CVD method.

[0041] The electrolyte layer 33 can be formed in a thin film state with a thickness of 10 μm or less. The material of the electrolyte layer 33 may be YSZ (yttria stabilized zirconia), SSZ (scandium stabilized zirconia), GDC (gadolinium doped ceria), YDC (yttrium doped ceria), SDC (samarium doped ceria), LSGM (strontium magnesium doped lanthanum gallate), LSO (lanthanum silicate, La 9.33+x SiO 26+2x / 3 For example, an electrolyte material that conducts oxygen ions, such as zirconia-based ceramics, or an electrolyte material that conducts hydrogen ions, such as perovskite-type oxides, can be used. In particular, zirconia-based ceramics are preferably used. When the electrolyte layer 33 is made of zirconia-based ceramics, the operating temperature of the SOFC using the electrochemical device 30 can be made higher than when it is made of ceria-based ceramics or various hydrogen ion conductive materials. For example, when the electrochemical element 30 is used in an SOFC, if a material such as YSZ that can exhibit high electrolyte performance even at high temperatures of approximately 650°C or higher is used as the material for the electrolyte layer 33, and if a hydrocarbon-based raw fuel such as city gas or LPG is used as the raw fuel for the system, and the raw fuel is converted into SOFC anode gas by steam reforming or the like, then a highly efficient SOFC system can be constructed in which the heat generated in the SOFC cell stack is used to reform the raw fuel gas.

[0042] The electrolyte layer 33 is preferably formed by a low-temperature firing method (e.g., a wet method using firing at a low temperature without firing at a high temperature above 1100°C), a spray coating method (such as thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, or cold spray), a PVD method (such as sputtering or pulsed laser deposition), or a CVD method. These film-forming processes that can be used at low temperatures can provide a dense electrolyte layer 33 with high airtightness and gas barrier properties without firing at a high temperature above 1100°C. Low-temperature firing methods and spray coating methods are particularly preferred because they allow for low-cost devices. Furthermore, spray coating is even more preferred because it allows for a dense electrolyte layer 33 with high airtightness and gas barrier properties to be easily obtained at low temperatures.

[0043] The electrolyte layer 33 is densely configured to prevent gas leakage of the anode gas and the cathode gas and to exhibit high ionic conductivity. The density of the electrolyte layer 33 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. When the electrolyte layer 33 is a uniform layer, the density thereof is preferably 95% or more, and more preferably 98% or more. Furthermore, when the electrolyte layer 33 is configured in a multi-layer structure, it is preferable that at least a portion of the layers includes a layer with a density of 98% or more (a dense electrolyte layer), and more preferably a layer with a density of 99% or more (a dense electrolyte layer). If such a dense electrolyte layer is included as part of the electrolyte layer 33, it is easier to form an electrolyte layer 33 that is dense and has high airtightness and gas barrier properties, even when the electrolyte layer 33 is configured in a multi-layer structure.

[0044] By configuring the electrochemical element 30 as described above, the electrochemical element 30 can be used as a power generation cell of a solid oxide fuel cell. For example, air is passed through the electrode layer 31, and a fuel gas containing hydrogen is passed through the counter electrode layer 32, which is the counter electrode of the electrode layer 31, and the electrochemical element 30 is operated at a temperature of, for example, 500°C to 900°C. In this case, oxygen O2 contained in the air is converted into electrons e in the electrode layer 31. - reacts with oxygen ions O 2- The oxygen ions O 2- moves through the electrolyte layer 33 to the counter electrode layer 32. In the counter electrode layer 32, hydrogen H2 contained in the supplied fuel gas is converted into oxygen ions O 2- reacts with water H2O and electrons e - When an electrolyte material that conducts hydrogen ions is used for the electrolyte layer 33, hydrogen H2 contained in the fuel gas flowing through the counter electrode layer 32 is converted into electrons e - releases hydrogen ions H + The hydrogen ions H + moves through the electrolyte layer 33 to the electrode layer 31. At the electrode layer 31, oxygen O2 and hydrogen ions H contained in the air + , electronic e - reacts to produce water H2O. The above reaction generates an electromotive force between the electrode layer 31 and the counter electrode layer 32. In this case, the counter electrode layer 32 functions as the anode of the SOFC, and the electrode layer 31 functions as the cathode. In this way, a solid oxide fuel cell is realized that includes the electrochemical module M and causes a power generation reaction.

[0045] <Inter-cell connection member 10> 1 and 2 show an interconnector that connects electrochemical elements 30 as an example of the inter-cell connection member 10. The inter-cell connection member 10 is provided in a form that joins between the electrode layer 31 and the counter electrode layer 32 of the electrochemical element 30 that constitutes the electrochemical module M. The inter-cell connection member 10 has a substrate 11 made of an alloy or oxide containing at least Cr, and a coating film 13 that protects the surface of the substrate 11. The coating film 13 can be provided so as to cover the entire outer peripheral surface of the substrate 11, but in this embodiment, it is provided on the entire surface of the inter-cell connection member 10 that faces the electrode layer 31, which serves as the cathode. More specifically, in addition to the surface that faces and is joined to the electrode layer 31, the coating film 13 is also provided on the entire inner surface of the air flow path 12a, which serves as the groove 12.

[0046] In this embodiment, the substrate 11 is made of stainless steel such as general-purpose SUS. More specifically, ferritic stainless steel is often used as the material for the substrate 11, but austenitic stainless steels with superior heat resistance, such as Fe-Cr-Ni alloys and Ni-Cr alloys, may also be used. Furthermore, instead of alloys, metal oxides such as (La,Ca)CrO3 (calcium-doped lanthanum chromite) may also be used.

[0047] The inventors have confirmed through the test described below that by forming the coating film 13 from a metal oxide containing Al, Cu, and Mn, it is possible to effectively suppress the scattering of Cr from the substrate 11 to the electrode layer 31 serving as the cathode. More specifically, the metal oxide used as the coating film 13 is Al X Cu Y Mn Zand X:Y:Z is 1:1:1. To further explain, the coating film 13 is made of a metal oxide that does not substantially contain Co, and the Co content in the coating film 13 is 0.1 mass% or more and 3 mass% or less, more preferably 0.1 mass% or more and 1 mass% or less, and even more preferably 0 mass%. The coating film 13 can have a variety of thicknesses, but from the viewpoint of durability, a relatively thick film thickness of 5 μm to 30 μm is preferably used. It has been confirmed that if the film thickness is less than 5 μm, Cr leaks from the coating film over time. More preferably, the film thickness can be 10 μm to 25 μm, and even more preferably, the film thickness can be 15 μm to 20 μm.

[0048] Among Al, Cu, and Mn contained in the coating film 13, the abundance ratio of Mn is 50 mass % or less. To further explain, the abundance ratio of Mn is preferably 50 mass % or less, more preferably 33 mass % or less, from the viewpoint of low resistivity, and is preferably 16 mass % or more, more preferably 33 mass % or more, from the viewpoint of durability.

[0049] The coating film 13 may be formed by the following methods. For example, the film can be formed by a wet coating method or a dry coating method. Examples of wet coating methods include screen printing, doctor blade coating, spray coating, inkjet coating, spin coating, dip coating, electroplating, electroless plating, and electrodeposition coating. Examples of dry coating methods include vapor deposition, sputtering, ion plating, chemical vapor deposition (CVD), electrochemical vapor deposition (EVD), ion beam deposition, laser ablation, atmospheric pressure plasma deposition, low-pressure plasma deposition, and thermal spraying.

[0050] However, dry coating methods such as CVD / EVD and thermal spraying have drawbacks, such as a complicated process for forming the protective film and an unstable composition of the coating film 13, so instead of these methods, laser ablation is being considered to form the coating film 13. Furthermore, since the laser ablation method increases the manufacturing costs compared to CVD / EVD and thermal spraying, in reality, wet coating is often adopted as a technology that can manufacture the coating film 13 inexpensively.

[0051] For example, if an electrodeposition coating method is applied, the coating film 13 can be formed by the following method. A mixed solution containing 100 g of metal oxide particles dispersed in 1 liter of electrodeposition solution and an anionic resin such as polyacrylic acid is used. Here, the mass ratio of (metal oxide particles:anionic resin) is set to 1:1. Using the mixed solution, an electric current is applied with the substrate 11 of the cell-cell connection member 10 as the positive electrode and the SUS304 electrode plate as the negative electrode, forming an uncured electrodeposition coating on the surface of the substrate 11 that is to be bonded to the electrode layer 31, which serves as the cathode of the electrochemical device 30. Electrodeposition coating is performed according to a known method, for example, by completely or partially immersing the substrate 11 in a current-carrying tank filled with the mixed solution to serve as the anode and then applying current. The electrodeposition coating conditions are not particularly limited and can be appropriately selected from a wide range depending on various conditions, such as the type of metal used as the substrate 11, the type of mixed solution, the size and shape of the current-carrying tank, and the intended use of the resulting intercell connection member 10. Typically, the bath temperature (mixed solution temperature) is approximately 10 to 40°C, the applied voltage is approximately 10 to 450 V, the voltage application time is approximately 1 to 10 minutes, and the mixed solution temperature is 10 to 40°C. The thickness of the electrodeposition coating can be controlled by changing the electrodeposition voltage and electrodeposition time. Various pretreatments can also be performed on the substrate 11. A cured electrodeposition coating is formed on the surface of the substrate 11 by heat-treating the substrate 11 on which the uncured electrodeposition coating has been formed. The heat treatment includes pre-drying to dry the electrodeposition coating and curing heating to cure the electrodeposition coating. The curing heating is performed after pre-drying. The resulting product is then baked in an electric furnace at 1000°C for 2 hours, followed by slow cooling to obtain the intercell connection member 10.

[0052] As the metal oxide fine particles, metal oxide particles containing Al, Cu, and Mn are used, as described above.

[0053] The electrochemical module M is formed by sequentially joining in series the inter-cell connection members 10 prepared as described above and the electrochemical elements 30. More specifically, the surface of the inter-cell connection member 10 on which the coating film 13 is formed, which faces the electrode layer 31 serving as the cathode, is adhesively joined to the electrode layer 31 serving as the cathode of the electrochemical element 30 using a bonding material 14. The bonding material 14 can be preferably made of either LSCF or a metal oxide containing Al, Cu, and Mn.

[0054] <Electrochemical devices, energy systems> FIG. 4 is a diagram showing the configuration of the energy system Z and the electrochemical device Y. As shown in FIG. The energy system Z has an electrochemical device Y and a heat exchanger 53 as a waste heat utilization unit that reuses heat discharged from the electrochemical device Y. The electrochemical device Y has at least an electrochemical module M and a reformer 56 as a fuel converter that circulates a gas containing a reducing component to the electrochemical module M. In addition, the electrochemical device Y has an electrochemical module M and an inverter 54 as a power converter that extracts electric power from the electrochemical module M. The fuel supply module of the electrochemical device Y is composed of a desulfurizer 20, a vaporizer 57, a reformer 56, etc., and supplies a fuel gas containing a reducing component to the electrochemical module M.

[0055] In addition, the electrochemical device Y includes a reforming water tank 21, a blower 59, a combustion section 58, a control section 55, a storage container 40, a booster pump 41, a reforming water pump 43, and the like.

[0056] The vaporizer 57, the reformer 56, the electrochemical module M, and the combustion section 58 are housed in the housing 40. The reformer 56 uses the combustion heat generated by the combustion of the reaction exhaust gas in the combustion section 58 to carry out a reforming process of the raw fuel.

[0057] The raw fuel is supplied to the desulfurizer 20 through the raw fuel supply path 42 by the operation of the boost pump 41. The reforming water in the reforming water tank 21 is supplied to the vaporizer 57 through the reforming water supply path 44 by the operation of the reforming water pump 43. The raw fuel supply path 42 merges with the reforming water supply path 44 at a location downstream of the desulfurizer 20, and the reforming water and raw fuel that have merged outside the storage container 40 are supplied to the vaporizer 57 provided inside the storage container 40.

[0058] The desulfurizer 20 removes (desulfurizes) sulfur compounds contained in hydrocarbon raw fuel such as city gas. When sulfur compounds are contained in the raw fuel, the provision of the desulfurizer 20 can suppress the effects of the sulfur compounds on the reformer 56 or the electrochemical elements 30 that constitute the electrochemical module M. The vaporizer 57 generates steam from the reforming water supplied from the reforming water tank 21. The raw fuel containing the steam generated in the vaporizer 57 is supplied to the reformer 56 through the steam-containing raw fuel supply path 45.

[0059] The reformer 56 uses the steam generated in the vaporizer 57 to steam reform the raw fuel desulfurized in the desulfurizer 20 to generate a reformed gas containing hydrogen. The reformed gas generated in the reformer 56 is supplied to the gas manifold 22 of the electrochemical module M through the reformed gas supply path 46.

[0060] The electrochemical elements 30 that make up the electrochemical module M are arranged in parallel while electrically connected to each other, and one end (lower end) of each electrochemical element 30 is fixed to the gas manifold 22. The reformed gas supplied to the gas manifold 22 is distributed to the multiple electrochemical elements 30. The electrochemical elements 30 that make up the electrochemical module M generate electricity by electrochemical reaction using the reformed gas supplied from the reformer 56 and air supplied from the blower 59. Reaction exhaust gas containing residual hydrogen gas not used in the reaction is discharged from the upper end of the electrochemical module M to a combustion section 58. The combustion section 58 mixes the reaction exhaust gas discharged from the electrochemical module M with air to combustible components in the reaction exhaust gas.

[0061] The reaction exhaust gas combusted in the combustion section 58 becomes combustion exhaust gas and is discharged to the outside of the storage container 40 through the combustion exhaust gas outlet 50. A combustion catalyst section 51 (e.g., a platinum-based catalyst) is arranged in the combustion exhaust gas outlet 50, and combusts and removes reducing components such as carbon monoxide and hydrogen contained in the combustion exhaust gas. The combustion exhaust gas discharged from the combustion exhaust gas outlet 50 is sent to a heat exchanger 53 through a combustion exhaust gas discharge path 52.

[0062] The heat exchanger 53 exchanges heat between the combustion exhaust gas generated by combustion in the combustion section 58 and the supplied cold water to generate hot water. In other words, the heat exchanger 53 operates as a waste heat utilization section that reuses the heat discharged from the electrochemical device Y.

[0063] Instead of the exhaust heat utilization section, a reaction exhaust gas utilization section may be provided that utilizes the reaction exhaust gas discharged (without being combusted) from the electrochemical module M. The reaction exhaust gas contains residual hydrogen gas that was not used in the reaction in the electrochemical elements 30 that constitute the electrochemical module M. In the reaction exhaust gas utilization section, the residual hydrogen gas is utilized to utilize heat through combustion or to generate electricity using a fuel cell or the like, thereby making effective use of energy.

[0064] The inverter 54 adjusts the output power of the electrochemical module M to the same voltage and frequency as the power received from a commercial grid (not shown). The control unit 55 controls the operation of the electrochemical device Y and the energy system Z.

[0065] <Test Results> Next, the test results for the ASR resistance of the coating film explained above are shown. In the example, a general-purpose stainless steel material 11 was coated with a coating film 13 made of AlCuMnO by electrodeposition coating, as shown in the cross-sectional SEM image of Fig. 7, and in the comparative example, a general-purpose stainless steel material 11 similar to the example was coated with a coating film 13 made of CoMnO by electrodeposition coating, as shown in the cross-sectional SEM image of Fig. 8. In both the example and the comparative example, after the coating was baked (1000°C), LSCF was applied as a bonding material 14 to the surface of the coating film 13, and then baked at 800°C.

[0066] To add further explanation, in the cross-sectional SEM images of Figures 7 and 8, a layer made of bonding material 14 is formed on the side of the coating film 13 opposite to the side where the general-purpose stainless steel material 11 is provided, and an oxide film 11a is formed between the coating film 13 and the general-purpose stainless steel material 11. As shown in FIGS. 7 and 8, the layer of the coating film 13 adjacent to the general-purpose stainless steel material 11 is a dense layer 13a, and the layer adjacent to the layer made of the bonding material 14 is a porous layer 13b.

[0067] The results of the ASR test carried out in the range of 600 to 850°C are shown in the graph of FIG. As shown in Figure 6, it was confirmed that the Example exhibited a sufficiently small resistance value comparable to that of the Comparative Example. From the viewpoint of resistance value, it was confirmed that a significant reduction in raw material costs can be expected by using AlCuMnO4 instead of the commonly used Co2MnO4 coating film. It was also confirmed that in the low temperature range of 600 to 750°C, the resistance of the example tended to be smaller than that of the comparative example.

[0068] Next, for both the example and the comparative example, the thickness of the oxide film was measured at the initial point and after 50 hours had elapsed from the initial point with the atmospheric temperature set to 900°C. In addition, for both the example and the comparative example, the amount of Cr leaking to the bonding material 14 side was measured after 50 hours had elapsed from the initial time point with the ambient temperature set to 900°C. The measurement results are shown in Table 1 below.

[0069] [Table 1]

[0070] As shown in Table 1, when looking at the change (increase) in the thickness of the oxide film from the initial point to the point after 50 hours has elapsed, it can be seen that the Examples are kept to a sufficiently small value that is comparable to that of the Comparative Examples. It can also be seen that the amount of Cr leakage in the example is kept to a sufficiently small value that is comparable to that of the comparative example.

[0071] [Another embodiment] (1) In the above embodiment, an example was described in which the electrochemical module M is used in a solid oxide fuel cell. However, the electrochemical module M can also be used in a solid oxide electrolysis cell, an oxygen sensor using a solid oxide, or the like.

[0072] In the above embodiment, a configuration capable of improving the efficiency of converting chemical energy such as fuel into electrical energy has been described. Here, however, a case will be described in which a solid oxide electrolysis cell is realized that includes an electrochemical module M and causes an electrolytic reaction in a single cell as the electrochemical element 30. In the energy system Z shown in FIG. 5, when the electrochemical element 30 constituting the electrochemical module M is operated as an electrolysis cell, a gas containing water vapor and carbon dioxide is circulated through the counter electrode layer 32 serving as the cathode (hydrogen generating electrode), and a voltage is applied between the counter electrode layer 32 and the electrode layer 31 serving as the anode (oxygen generating electrode). Then, electrons e - The water molecule H2O and the carbon dioxide molecule CO2 react to form hydrogen molecules H2, carbon monoxide CO, and oxygen ions O 2- Oxygen ions O 2- moves to the electrode layer 31, where oxygen ions O 2- releases an electron and becomes an oxygen molecule, O2.

[0073] When gas containing water vapor HO and carbon dioxide molecules CO2 is circulated, a fuel converter 91 can be provided to synthesize various compounds such as hydrocarbons from the hydrogen and carbon monoxide produced by the electrolysis in the electrochemical module M. The hydrocarbons produced by the fuel converter 91 can be circulated to the electrochemical module M via a fuel supply unit (not shown), or can be extracted outside the system / device and used separately as fuel or chemical raw materials.

[0074] 5 , the electrochemical device Y at least includes an electrochemical module M and a fuel converter 91 that converts a gas containing a reducing component produced in the electrochemical module M. The electrochemical device Y also includes at least an electrochemical module M and a power converter 93 that supplies power to the electrochemical module M.

[0075] The electrochemical module M has a plurality of electrochemical elements 30, a gas manifold 22, and a gas manifold 171. The plurality of electrochemical elements 30 are arranged in parallel while being electrically connected to one another, and one end (lower end) of each electrochemical element 30 is fixed to the gas manifold 22, and the other end (upper end) is fixed to the gas manifold 171. The gas manifold 22 at one end (lower end) of each electrochemical element 30 is supplied with water vapor and carbon dioxide. Hydrogen, carbon monoxide, and the like produced by the above-described reactions in the electrochemical elements 30 are collected by the gas manifold 171, which communicates with the other end (upper end) of each electrochemical element 30.

[0076] Energy efficiency can be improved by configuring heat exchanger 90 in FIG. 5 to operate as a waste heat utilization unit that exchanges heat between the reaction heat generated by the reaction in fuel converter 91 and water to vaporize it, and heat exchanger 92 in FIG. 5 to operate as a waste heat utilization unit that exchanges heat between the waste heat generated by electrochemical element 30 and water vapor and carbon dioxide to preheat them. Furthermore, the power converter 93 supplies power to the single cell serving as the electrochemical device 30. As a result, the electrochemical device 30 functions as an electrolysis cell as described above.

[0077] (2) The coating film 13 described above can also be suitably applied to a metal-supported electrochemical element 30, as shown in FIGS. 9 and 10, a metal-supported electrochemical device 30 according to another embodiment (2) includes a metal support 60, an electrode layer 31 formed on the metal support 60, an intermediate layer 61 formed on the electrode layer 31, an electrolyte layer 33 formed on the intermediate layer 61, a reaction prevention layer 62 formed on the electrolyte layer 33, and a counter electrode layer 32 formed on the reaction prevention layer 62. The metal support 60 serves as a support for supporting the electrode layer 31, the intermediate layer 61, the electrolyte layer 33, the reaction prevention layer 62, and the counter electrode layer 32. As shown in FIGS. 9 and 10, the metal support 60 is provided with through-holes 60a that penetrate in a direction perpendicular to the electrode layer 31 and the counter electrode layer 32. As shown in FIG. 10, the electrochemical module M is configured by interposing a U-shaped member 63 and an alloy member 64 between the electrochemical devices 30 and between the metal support 60 and the counter electrode layer 32.

[0078] To explain further, as shown in Figure 10, an alloy member 64 is joined to the counter electrode layer 32 of the electrochemical element 30, a U-shaped member 63 is joined to the back side of the metal support 60 of the electrochemical element 30 on the side where the electrode layer 31 is provided, and the alloy member 64 is joined to the U-shaped member 63. That is, the alloy member 64 is joined to the counter electrode layer 32 of the electrochemical element 30 and the U-shaped member 63, electrically connecting them. The metal support 60 and the U-shaped member 63 form a cylindrical support, and gas flowing through the internal space of the cylindrical support is supplied to the electrode layer 31 through the through-holes 60a of the metal support 60. From the viewpoints of reducing the thermal expansion difference with the metal support 60 and ensuring the reliability of joining, such as welding, the material of the U-shaped member 63 is preferably the same metal material as the metal support 60.

[0079] The alloy member 64 is a material containing Fe and Cr. For example, ferritic stainless steel, an Fe-Cr-Ni alloy which is an austenitic stainless steel having excellent heat resistance, or a nickel-based alloy may be used as the alloy member 64. Note that the material of the alloy member 64 is preferably the same as that of the metal support 60 from the viewpoint of reducing the difference in thermal expansion between the alloy member 64 and the metal support 60. For the intermediate layer 61 and the reaction prevention layer 62, materials known as electrochemical elements can be suitably used.

[0080] 9 and 10, the metal support 60 is provided with the above-described coating film 13 on at least the entire surface facing the electrode layer 31 serving as the air electrode or oxygen evolution electrode. Preferably, the coating film 13 is also provided on the entire surface of the inner wall of the through-hole 60a. Incidentally, the above-mentioned bonding material 14 is interposed on the outer surface of the coating film 13 (the surface opposite to the metal support 60) on the side of the electrode layer 31. In this case, the metal support 60, the coating film 13, and the bonding material 14 function as the inter-cell connection member 10.

[0081] Furthermore, when the counter electrode layer 32 is an air electrode or an oxygen evolution electrode, it is preferable to provide a coating film 13 on the entire surface of the alloy member 64 on the side facing the counter electrode layer 32, as shown in FIG. The coating film 13 and the counter electrode layer 32 are bonded together with the bonding material 14 interposed therebetween. In this case, the alloy member 64, the coating film 13, and the bonding material 14 function as the inter-cell connection member 10.

[0082] (3) In the solid oxide fuel cell according to the above embodiment, the electrode layer 31 is the cathode (air electrode), the counter electrode layer 32 is the anode (fuel electrode), and a configuration example has been shown in which the coating film 13 (and bonding material 14) is provided on the entire surface of the side of the substrate 11 of the cell-to-cell connection member facing the electrode layer 31. As another configuration, a configuration may be adopted in which the counter electrode layer 32 is a cathode (air electrode), the electrode layer 31 is an anode (fuel electrode), and the coating film 13 (and bonding material 14) is provided on the entire surface of the side of the substrate 11 of the cell-to-cell connection member facing the counter electrode layer 32.

[0083] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0084] The cell-to-cell connecting member, electrochemical module, solid oxide fuel cell, solid oxide electrolysis cell, electrochemical device, and energy system of the present invention can be effectively used as a cell-to-cell connecting member, electrochemical module, solid oxide fuel cell, solid oxide electrolysis cell, electrochemical device, and energy system that is highly economical, has high electronic conductivity and low contact resistance, can suppress the growth of an oxide film on the surface of the substrate, and can effectively suppress Cr scattering. [Explanation of symbols]

[0085] 10: Inter-cell connection member 11: Base material 13: Coating film 14: Bonding material 30: Electrochemical element 31: Electrode layer 32: Counter electrode layer 33: Electrolyte layer 60: Metal support 64: Alloy material M: Electrochemical module Y: Electrochemical device Z: Energy System

Claims

1. An inter-cell connection member for an electrochemical device in which an electrode layer, an electrolyte layer, and a counter electrode layer are stacked in the stated order, a substrate made of an alloy or oxide containing at least Cr, and a coating film protecting the surface of the substrate; The coating film is an inter-cell connecting member made of a metal oxide containing Al, Cu, and Mn.

2. The inter-cell connection member according to claim 1 , wherein the coating film is made of the metal oxide that is substantially free of Co.

3. The inter-cell connection member according to claim 1 or 2, wherein the coating film has a thickness of 5 μm or more and 30 μm or less.

4. 3. The cell-cell connection member according to claim 1, wherein the coating film contains Al, Cu, and Mn, and the Mn content is 50 mass % or less.

5. The metal oxide coating film is Al Ｘ Cu Ｙ Mn Ｚ 3. The cell-cell connecting member according to claim 1, wherein the oxide is an oxide of the formula: and X:Y:Z is 1:1:

1.

6. 3. The cell-cell connection member according to claim 1, wherein a bonding material that bonds the coating film to either the air electrode or the oxygen evolution electrode, which is either the electrode layer or the counter electrode layer of the electrochemical element, is either LSCF or the metal oxide containing Al, Cu, and Mn.

7. An electrochemical module in which a plurality of the electrochemical elements are connected by the inter-cell connecting member according to claim 1 or 2 and arranged in a collective state.

8. A solid oxide fuel cell in which a power generation reaction occurs in the electrochemical elements connected by the inter-cell connector according to claim 1 or 2.

9. A solid oxide electrolysis cell in which an electrolytic reaction occurs in the electrochemical elements connected by the inter-cell connector according to claim 1 or 2.

10. The electrochemical module of claim 7 ; a fuel converter that generates reducing components to be supplied to the electrochemical module or that converts gas containing reducing components generated in the electrochemical module.

11. The electrochemical module of claim 7 ; and a power converter that extracts power from the electrochemical module or passes power to the electrochemical module.

12. The electrochemical device according to claim 10; and a waste heat utilization unit that reuses heat discharged from the electrochemical device.

13. The electrochemical device according to claim 11; and a waste heat utilization unit that reuses heat discharged from the electrochemical device.

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