Method for producing metal-supported electrochemical element, metal-supported electrochemical element, electrochemical module, and energy system

Abstract

Provided is a method for producing a metal-supported electrochemical element including a metal support, an electrode layer disposed on the metal support, and an electrolyte layer disposed on the electrode layer, the method including forming a stabilized zirconia dense membrane as an electrolyte layer by a simple sol-gel method in which a coating film formed by applying a coating composition to a surface of a substrate is calcined and fired, the stabilized zirconia dense membrane being homogeneous and dense and having few defects such as cracks.SOLUTION: The surface layer forming step includes an application step of applying the coating composition onto a substrate to obtain a coating composition-applied substrate, a calcination step of calcining the coating composition-applied substrate at a set calcination temperature after the application step, and a firing step of firing the coating composition-applied substrate at a set firing temperature higher than the set calcination temperature after the calcination step, wherein in the calcination step, the set calcination temperature is set within a range of 260 °C or higher and lower than 750 °C, and in the firing step, the set firing temperature is set within a range of higher than 950 °C and lower than 1100 °C.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing a metal-supported electrochemical device having a metal support, an electrode layer laminated on the metal support, and an electrolyte layer laminated on the electrode layer. [Background technology]

[0002] Adding yttrium, calcium, or other elements to zirconia stabilizes the dense crystalline structure that exists at high temperatures even at room temperature, making it suitable for a variety of applications. For example, it is known that dense stabilized zirconia films can be formed on the surfaces of various substrates and used in parts that require high hardness and inertness, as well as refractory parts used in jet engines, etc. In particular, yttria-stabilized zirconia dense films (YSZ) are used as electrolyte layers in solid oxide fuel cells (SOFCs), which are used at relatively high temperatures.

[0003] In recent years, in order to improve robustness and reduce costs, development has been underway to form a thin layer (thin film) of stabilized zirconia dense membrane as an electrolyte layer on the surface of a metal support in metal-supported electrochemical elements used in solid oxide fuel cells (SOFCs) and other devices. Furthermore, in the manufacturing method of a metal-supported electrochemical element, in the electrolyte layer formation step for forming a stabilized zirconia dense layer as an electrolyte layer, it is desirable to employ a simple sol-gel method in which a coating composition (sol) containing a zirconium component and a stabilizing substance component is applied to the surface of a substrate to form a coating film (gel film), and the coating film is then fired at a predetermined set firing temperature (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-133947 Summary of the Invention [Problem to be solved by the invention]

[0005] In manufacturing methods for metal-supported electrochemical elements used in SOFCs and other applications, forming a homogeneous, dense stabilized zirconia film with high gas barrier properties as an electrolyte layer generally requires firing a coating at a high temperature of approximately 1400°C. However, firing at high temperatures severely deteriorates the metal substrate with an electrode layer, which consists of a metal support and an electrode layer laminated thereon. This necessitates measures such as providing a special coating layer on the substrate surface, resulting in increased costs and performance degradation. Therefore, firing the coating at a low temperature, such as below 1100°C, is desirable to minimize substrate degradation. However, it has been difficult to form homogeneous, dense stabilized zirconia films, particularly those made of yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ), or samaria-stabilized zirconia (SSZ), at low temperatures.

[0006] Furthermore, when a simple sol-gel method is employed to produce a stabilized zirconia dense film as an electrolyte layer, particularly when the thickness or area of ​​the coating film of the coating composition is large, the coating film shrinks when the solvent component contained in the coating film evaporates, increasing internal stress and making defects such as cracks more likely to occur. In particular, when the coating composition is applied by dip coating, if the substrate is pulled up quickly in order to increase the thickness of the coating film, uneven dripping or the like will cause localized areas of thick film thickness in the coating film, making such areas of thick film thickness even more likely to produce defects such as cracks.

[0007] In view of this situation, a main object of the present invention is to provide a technology for forming a homogeneous and dense stabilized zirconia dense film with few defects such as cracks in the coating film of the coating composition, even when the thickness or area of ​​the coating film of the coating composition is increased, in a method for producing a metal-supported electrochemical element having a metal support, an electrode layer laminated on the metal support, and an electrolyte layer laminated on the electrode layer, by employing a simple sol-gel method in which a coating composition containing a zirconium component and a stabilizing substance component is applied to the surface of a substrate and the resulting coating film is calcined and fired to form a stabilized zirconia dense film as an electrolyte layer. [Means for solving the problem]

[0008] A first characteristic configuration of the present invention is a method for producing a metal-supported electrochemical element having a metal support, an electrode layer laminated on the metal support, and an electrolyte layer laminated on the electrode layer, the method comprising: an electrolyte layer forming step of forming a stabilized zirconia dense film as the electrolyte layer on the electrode layer of the electrode layer-formed metal substrate, the electrode layer being composed of the metal support and the electrode layer laminated thereon; The electrolyte layer forming step a coating step of applying a coating composition containing a zirconium component and a stabilizing substance component onto the metal substrate with an electrode layer to obtain a coating composition-coated substrate in which the metal substrate with an electrode layer and a coating film of the coating composition are laminated together; A calcination step of calcining the coating composition-coated substrate at a predetermined set calcination temperature after the coating step; A baking step of baking the coating composition-applied substrate at a predetermined set baking temperature higher than the set baking temperature after the calcination step, In the calcination step, the set calcination temperature is set within a range of 260°C or higher and lower than 750°C, In the firing step, the firing temperature is set within a range of more than 950°C and less than 1100°C.

[0009] As a result of extensive research, the present inventors have found that the occurrence of defects such as cracks due to increased internal stress in the coating film can be suppressed by carrying out a calcination step in which a coating composition-coated substrate having a coating film formed by applying a coating composition containing a zirconium component and a stabilizing substance component to the substrate is calcined at a relatively low set calcination temperature within the range of 260°C or higher and lower than 750°C to volatilize the solvent component contained in the coating film. That is, by setting the set calcination temperature in the calcination step within the range of 260°C or higher and lower than 750°C, calcination is performed at a set calcination temperature higher than the volatilization temperature of the organic solvent component present around 250°C, and the temperature is quickly passed through the volatilization temperature of the organic solvent component present around 250°C, and it is thought that a precursor of a stabilized zirconia dense film can be formed in a state in which the occurrence of defects is suppressed. Then, after the calcination step, a firing step is carried out, and firing is carried out at a relatively low firing temperature set within the range of more than 950°C and less than 1100°C, which is capable of suppressing deterioration of the metal constituting the substrate to which the coating composition is applied, and which has a coating film in which the occurrence of defects such as cracks is suppressed, thereby forming a homogeneous and dense stabilized zirconia dense film as the electrolyte layer. Therefore, the present invention provides a technique for forming a homogeneous and dense stabilized zirconia dense film with few defects such as cracks in the coating film of the coating composition, even when the thickness or area of ​​the coating film of the coating composition is increased, in a method for producing a metal-supported electrochemical element having a metal support, an electrode layer laminated on the metal support, and an electrolyte layer laminated on the electrode layer, by employing a simple sol-gel method in which a coating composition containing a zirconium component and a stabilizing substance component is applied to the surface of a substrate and the resulting coating film is calcined and fired to form a stabilized zirconia dense film as an electrolyte layer.

[0010] The set calcination temperature in the calcination step is more preferably set to 300°C or higher, and even more preferably set to 340°C or higher. In this way, by increasing the lower limit of the set calcination temperature, it becomes easier to suppress the occurrence of defects such as cracks in the coating film of the coating composition. Furthermore, the set temperature rise rate when raising the temperature to the set calcination temperature in the calcination step is more preferably set to 14°C or higher per second, and even more preferably set to 16°C or higher per second. In this way, by increasing the lower limit of the set temperature rise rate, it becomes easier to suppress the occurrence of defects such as cracks in the coating film of the coating composition. Furthermore, the set calcination temperature in the calcination step is more preferably less than 650° C., and even more preferably less than 500° C. By lowering the upper limit of the set calcination temperature in this way, it is possible to more inexpensively produce a homogeneous and dense stabilized zirconia dense film with fewer defects such as cracks in the coating film of the coating composition.

[0011] A second characteristic feature of the present invention is that the metal-supported electrochemical element has an electrode functional layer between the electrode layer and the electrolyte layer.

[0012] According to this configuration, even in a metal-supported electrochemical element having an electrode functional layer between an electrode layer and an electrolyte layer, the above-described method for manufacturing a metal-supported electrochemical element can be carried out to form a homogeneous, dense stabilized zirconia film with high gas barrier properties as the electrolyte layer.

[0013] A third characteristic feature of the present invention is that the stabilizing substance component is at least one of an yttrium compound, a scandium compound, and a samarium compound.

[0014] According to this configuration, by including at least one of an yttrium compound, a scandium compound, and a samarium compound as a stabilizing substance component in the coating composition applied in the coating step, a homogeneous and dense stabilized zirconia dense film made of yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ), or samaria-stabilized zirconia (SSZ) can be obtained as the electrolyte layer through the calcination step and the firing step. Furthermore, in forming such YSZ, ScSZ, or SSZ, a low-temperature firing method can be adopted in the firing step, in which a set firing temperature of, for example, less than 1100°C is set, which can suppress deterioration of the substrate.

[0015] A fourth characteristic feature of the present invention is that the average thickness of the dense stabilized zirconia film is in the range of 0.2 μm or more and 10 μm or less.

[0016] According to this configuration, the occurrence of defects such as cracks due to an increase in internal stress in the coating film during the calcination step can be suppressed, and therefore, by applying the coating composition to a relatively large film thickness during the coating step, and by achieving an average film thickness of 0.2 μm or more through the calcination and firing steps, a stabilized zirconia dense film with excellent durability and reliability can be formed as the electrolyte layer. Furthermore, by using a thinned stabilized zirconia dense film with an average film thickness of 10 μm or less as the electrolyte layer of a metal-supported electrochemical element, a high-performance metal-supported electrochemical element can also be manufactured.

[0017] The average thickness of the stabilized zirconia dense membrane is more preferably 0.5 μm or more, and even more preferably 1 μm or more. This is because the durability and reliability of the stabilized zirconia dense membrane can be further improved by doing so. Furthermore, the average thickness of the stabilized zirconia dense membrane is more preferably 5 μm or less, and even more preferably 4 μm or less. This is because the stabilized zirconia dense membrane can have higher ion conductivity.

[0018] A fifth characteristic configuration of the present invention is that in the electrolyte layer forming step, the coating step and the calcination step are repeated multiple times before the firing step, to form a coating film consisting of multiple layers on the coating composition-coated substrate.

[0019] According to this configuration, the coating step and the calcination step can be repeated multiple times to form a coating film of a relatively large thickness consisting of multiple layers on the coating composition-coated substrate. Then, by subjecting the coating composition-coated substrate having such a coating film consisting of multiple layers to a calcination step, a stabilized zirconia dense film of a relatively large thickness and excellent durability and reliability can be formed as an electrolyte layer.

[0020] A sixth characteristic configuration of the present invention is a metal-supported electrochemical element having a metal support, an electrode layer laminated on the metal support, and an electrolyte layer laminated on the electrode layer, The metal-supported electrochemical element having the above-mentioned characteristic configuration is manufactured by the manufacturing method thereof.

[0021] According to this configuration, by carrying out the manufacturing method for a metal-supported electrochemical element described above, a homogeneous, dense stabilized zirconia film with high gas barrier properties is formed as the electrolyte layer, thereby realizing a high-performance metal-supported electrochemical element with excellent durability and reliability.

[0022] A seventh characteristic feature of the present invention is that an electrode functional layer is provided between the electrode layer and the electrolyte layer.

[0023] According to this configuration, even in a metal-supported electrochemical element having an electrode functional layer between an electrode layer and an electrolyte layer, the above-described method for manufacturing a metal-supported electrochemical element can be carried out to form a homogeneous, dense stabilized zirconia film with high gas barrier properties as the electrolyte layer.

[0024] An eighth characteristic feature of the present invention is an electrochemical module in which a plurality of metal-supported electrochemical elements having the fifth characteristic feature are arranged in a collective state.

[0025] According to this configuration, a plurality of metal-supported electrochemical elements having, as an electrolyte layer, a homogeneous, dense stabilized zirconia membrane with high gas barrier properties are arranged in a collective state, thereby realizing a high-performance electrochemical module with excellent durability and reliability.

[0026] A ninth characteristic feature of the present invention is an energy system including a metal-supported electrochemical device having the fifth characteristic feature.

[0027] According to this configuration, by providing an electrochemical module in which a plurality of metal-supported electrochemical elements are arranged in a collective state, each of which has, as an electrolyte layer, a homogeneous, dense stabilized zirconia membrane with high gas barrier properties, it is possible to realize a high-performance energy system that is excellent in durability and reliability. [Brief explanation of the drawings]

[0028] [Figure 1] A diagram showing the schematic configuration of a metal-supported electrochemical device. [Figure 2] FIG. 1 is a diagram showing a process flow of an electrode layer forming step. [Figure 3] A diagram showing the state of a substrate coated with a coating composition. [Figure 4] Diagram showing the schematic configuration of the electrochemical module [Figure 5] Diagram showing the outline of the energy system [Figure 6] FIG. 10 is a diagram showing a schematic configuration of an energy system according to another embodiment. [Figure 7] FIG. 10 is a diagram showing a schematic configuration of an electrochemical module according to another embodiment. [Figure 8] 1 shows the conditions of the calcination step and the firing step and the results of the performance evaluation test in Examples 1 to 5 and Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0029] A method for manufacturing a metal-supported electrochemical element, a metal-supported electrochemical element, an electrochemical module, and an energy system according to embodiments of the present invention will be described. In this embodiment, the metal-supported electrochemical element is used as a component of a solid oxide fuel cell (an example of an electrochemical module and an energy system) that generates electricity by receiving a supply of a hydrogen-containing fuel gas and air (oxidant gas). Hereinafter, when describing the positional relationship between layers, for example, with reference to FIG. 1, the side of the counter electrode layer 6 as viewed from the electrolyte layer 4 may be referred to as "top" or "upper side," and the side of the electrode layer 2 may be referred to as "bottom" or "lower side." Furthermore, the surface of the metal support 1 on which the electrode layer 2 is formed may be referred to as the "front surface," and the opposite surface may be referred to as the "rear surface."

[0030] [Metal-supported electrochemical element] As shown in Figure 1, the metal-supported electrochemical element E has a metal support 1, an electrode layer 2 formed on the metal support 1, an electrode functional layer 3 formed on the electrode layer 2, an electrolyte layer 4 formed on the electrode functional layer 3, an intermediate layer 5 formed on the electrolyte layer 4, and a counter electrode layer 6 formed on the intermediate layer 5. In other words, the counter electrode layer 6 is formed on the electrolyte layer 4, and the intermediate layer 5 is formed between the electrolyte layer 4 and the counter electrode layer 6. The electrode layer 2 is porous, and the electrolyte layer 4 is dense.

[0031] (metal support) 1, the metal support 1 supports the electrode layer 2, the electrode functional layer 3, the electrolyte layer 4, the intermediate layer 5, and the counter electrode layer 6, thereby maintaining the strength of the metal-supported electrochemical element E. In other words, the metal support 1 serves as a support for supporting the components of the metal-supported electrochemical element.

[0032] A material having excellent electronic conductivity, heat resistance, oxidation resistance, and corrosion resistance is used as the material for the metal support 1. For example, ferritic stainless steel, austenitic stainless steel, nickel-based alloys, etc. are used. Note that if the metal support 1 is made of ferritic stainless steel, it is preferable because an inexpensive, high-strength metal-supported electrochemical element can be realized.

[0033] The metal support 1 has a plate shape as a whole. The metal support 1 only needs to have sufficient strength to function as a support and form the metal-supported electrochemical element E. The thickness of the metal support 1 is preferably, for example, 0.1 mm or more from the viewpoint of ensuring strength, and is preferably, for example, 2 mm or less from the viewpoint of reducing costs.

[0034] The metal support 1 has a plurality of through holes 1a that penetrate from the surface on which the electrode layer 2 is provided (front surface) to the back surface. In this embodiment, the metal support 1 is made of a metal plate. The plurality of through holes 1a are formed by mechanical, chemical, or optical perforation (hole processing) such as punching, etching, or laser processing so as to penetrate from the front surface to the back surface of the metal plate that constitutes the metal support 1. This configuration allows the fuel gas and air to be smoothly supplied from the back surface of the metal support 1 to the electrode layer 2 side through the plurality of through holes 1a. The plate-shaped metal support 1 can also be bent and deformed into a box-like, cylindrical or other shape for use.

[0035] A metal oxide layer 1b is provided on the surface of the metal support 1 as a diffusion-inhibiting layer. That is, the diffusion-inhibiting layer is formed between the metal support 1 and the electrode layer 2 (described later). The metal oxide layer 1b is provided not only on the surface exposed to the outside of the metal support 1 but also on the contact surface (interface) with the electrode layer 2 and the inner surface of the through-holes 1a. This metal oxide layer 1b can inhibit interdiffusion of elements between the metal support 1 and the electrode layer 2. For example, when ferritic stainless steel containing chromium is used as the metal support 1, the metal oxide layer 1b is mainly composed of chromium oxide. The metal oxide layer 1b, which is mainly composed of chromium oxide, inhibits the diffusion of chromium atoms and the like from the metal support 1 into the electrode layer 2, the electrolyte layer 4, and the like. The thickness of the metal oxide layer 1b may be any thickness that can achieve both high diffusion-inhibiting performance and low electrical resistance, and is preferably on the submicron order of, for example, 0.3 μm to 0.7 μm.

[0036] The metal oxide layer 1b can be formed by various methods, but a method of oxidizing the surface of the metal support 1 to form a metal oxide is preferably used. Also, methods that can be used to form the metal oxide layer 1b on the surface of the metal support 1 include PVD methods such as sputtering and PLD, CVD, and spray coating methods (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, and cold spray). Alternatively, the metal oxide layer 1b may be formed on the surface of the metal support 1 by plating and oxidation treatment. Furthermore, the metal oxide layer 1b may contain a highly conductive spinel phase or the like.

[0037] (electrode layer) As shown in FIG. 1 , the electrode layer 2 is provided as a thin layer on the surface of the metal support 1 so as to cover the region of the metal support 1 where the through holes 1 a are formed. When the electrode layer 2 is a thin layer, the thickness of the electrode layer 2 is preferably set to, for example, about 1 μm to 100 μm. With such a thickness, it is possible to reduce the amount of expensive electrode layer material used, thereby reducing costs, while ensuring sufficient electrode performance. Furthermore, the region of the metal support 1 where the through holes 1 a are provided is entirely covered by the electrode layer 2. In other words, the through holes 1 a are formed inside the region of the metal support 1 where the electrode layer 2 is formed. In other words, all of the through holes 1 a are provided facing the electrode layer 2.

[0038] Examples of materials that can be used for the electrode layer 2 include composites such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO-CeO, and Cu-CeO. In these examples, GDC, YSZ, and CeO are called aggregates of the composite.

[0039] Examples of methods for forming the electrode layer 2 include low-temperature firing (e.g., a wet method using firing at a low temperature without firing at temperatures higher than 1100°C), spray coating (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, and cold spray), PVD (sputtering and pulsed laser deposition), and CVD. These low-temperature deposition methods can be used to obtain a good electrode layer 2 without firing at temperatures higher than 1100°C. This allows for the realization of a metal-supported electrochemical element with excellent durability, while suppressing interdiffusion of elements between the metal support 1 and the electrode layer 2 and preventing damage to the metal support 1. Furthermore, the use of a low-temperature firing method facilitates the handling of raw materials.

[0040] The electrode layer 2 has a plurality of pores inside and on its surface to provide gas permeability. That is, the electrode layer 2 is formed as a porous layer. The electrode layer 2 is formed, for example, so that its density is 30% or more and less than 80%. It is preferable to select an appropriate size for smooth electrochemical reaction. 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 relative density.

[0041] (electrode functional layer) As shown in FIG. 1 , the electrode functional layer 3 is formed as a thin layer on the electrode layer 2, covering the electrode layer 2. The electrode functional layer 3 is disposed between the porous electrode layer 2 to continuously connect the two layers and form a dense electrolyte layer 4 on the porous electrode layer 2. This layer acts as a buffer to relieve various stresses applied during the manufacture and operation of the metal-supported electrochemical element E. Therefore, the electrode functional layer 3 is intentionally formed to have a smaller density than the electrolyte layer 4. The electrode functional layer 3 is also intentionally formed to have a larger density than the electrode layer 2. This allows the electrode functional layer 3 to absorb and relieve various stresses between the porous electrode layer 2 and the dense electrolyte layer 4 formed on the metal support 1, thereby improving the performance, reliability, and stability of the metal-supported electrochemical element E. When the electrode functional layer 3 is formed as a thin layer, the thickness of the electrode functional layer 3 is preferably, for example, approximately 1 μm to 100 μm. This thickness reduces the amount of expensive electrode functional layer material used, thereby reducing costs, while still ensuring sufficient performance.

[0042] Examples of materials that can be used for the electrode functional layer 3 include YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), GDC (gadolinium-doped ceria), YDC (yttrium-doped ceria), and SDC (samarium-doped ceria). Ceria-based ceramics are preferably used.

[0043] Examples of methods for forming the electrode functional layer 3 include low-temperature firing (e.g., a wet method using firing at a low temperature without firing at temperatures higher than 1100°C), spray coating (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, etc.), PVD (sputtering, pulsed laser deposition, etc.), and CVD. These low-temperature deposition methods can be used to obtain a good electrode functional layer 3 without firing at temperatures higher than 1100°C. This allows for the realization of a durable metal-supported electrochemical element without damaging the metal support 1, while suppressing interdiffusion of elements between the metal support 1 and the electrode layer 2. Furthermore, the low-temperature firing method facilitates the handling of raw materials. In this embodiment, the electrode functional layer 3 is preferably an oxygen ion (oxide ion) conductor, and more preferably a mixed conductor having both oxygen ion (oxide ion) and electron conductivity. An electrode functional layer 3 having such properties is suitable for application to a metal-supported electrochemical element E.

[0044] (electrolyte layer) As shown in Fig. 1, the electrolyte layer 4 is formed in the form of a thin layer on the electrode functional layer 3. The electrolyte layer 4 is preferably formed in the form of a thin film with an average film thickness in the range of 0.2 µm or more and 10 µm or less. In this embodiment, the electrolyte layer 4 covers the electrode layer 2 and is provided across (straddles) the electrode functional layer 3 and the surface of the metal support 1. By configuring the electrolyte layer 4 in this way and joining it to the metal support 1, the metal-supported electrochemical element E has excellent robustness as a whole.

[0045] The electrolyte layer 4 is provided on the front surface of the metal support 1 in an area larger than the area where the through-holes 1a are provided. In other words, the through-holes 1a are formed inside the area of ​​the metal support 1 where the electrolyte layer 4 is formed. This makes it possible to suppress gas leakage from the electrode layer 2 and the electrode functional layer 3 around the electrolyte layer 4. In other words, when the metal-supported electrochemical element E is used as a component of an SOFC, gas is supplied to the electrode layer 2 from the back side of the metal support 1 through the through-holes 1a during SOFC operation. In the area where the electrolyte layer 4 contacts the metal support 1, gas leakage can be suppressed without providing a separate member such as a gasket. In this embodiment, the electrolyte layer 4 covers the entire periphery of the electrode layer 2, but the electrolyte layer 4 may be provided on top of the electrode layer 2 and the electrode functional layer 3, and a gasket or the like may be provided around the periphery.

[0046] The electrolyte layer 4 is made of a dense stabilized zirconia film. That is, the material of the electrolyte layer 4 is preferably a zirconia-based ceramic such as yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ), or samaria-stabilized zirconia (SSZ).

[0047] Using zirconia-based ceramics for the electrolyte layer 4 allows for a higher operating temperature for the SOFC using the metal-supported electrochemical element E compared to using ceria-based ceramics or various hydrogen ion conductive materials. For example, when using the metal-supported electrochemical element E in an SOFC, as in this embodiment, a material such as YSZ that exhibits high electrolyte performance even at high temperatures of approximately 650°C or higher is used for the electrolyte layer 4. 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 the SOFC anode gas by steam reforming or the like. This allows for the construction of a highly efficient SOFC system in which heat generated in the SOFC cell stack is used to reform the raw fuel gas. In this embodiment, the electrolyte layer 4 contains stabilized zirconia.

[0048] Examples of methods for forming the electrolyte layer 4 include low-temperature firing (e.g., a wet method using firing at a low temperature without firing at a high temperature above 1100°C), spray coating (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, and cold spray), PVD (sputtering and pulsed laser deposition), and CVD. These low-temperature deposition methods can be used to obtain a good electrolyte layer 4 without firing at a high temperature above 1100°C. Therefore, a metal-supported electrochemical element with excellent durability can be realized without damaging the metal support 1 while suppressing interdiffusion of elements between the metal support 1 and the electrode layer 2. In particular, low-temperature firing and spray coating methods can be used to realize a low-cost metal-supported electrochemical element E. Furthermore, spray coating can be used to easily obtain a dense electrolyte layer 4 with high airtightness and gas barrier properties at a low temperature. Although details will be described later, in this embodiment, the electrolyte layer 4 is formed by a low-temperature firing method.

[0049] The electrolyte layer 4 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 4 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. When the electrolyte layer 4 is a uniform layer, the density thereof is preferably 95% or more, and more preferably 98% or more. Furthermore, when the electrolyte layer 4 is configured as a multi-layer structure, it is preferable that at least a portion of the multi-layer structure contains a layer (a dense electrolyte layer) having a density of 98% or more, and more preferably a layer (a dense electrolyte layer) having a density of 99% or more. When such a dense electrolyte layer is included as part of the electrolyte layer 4, it is easier to form an electrolyte layer 4 that is dense and has high airtightness and gas barrier properties, even when the electrolyte layer 4 is configured as a multi-layer structure.

[0050] (middle class) 1, the intermediate layer 5 is formed as a thin layer on the electrolyte layer 4. When the intermediate layer 5 is a thin layer, the thickness of the intermediate layer 5 is preferably set to, for example, about 1 μm to 100 μm. With such a thickness, the amount of expensive intermediate layer material used can be reduced, thereby reducing costs and ensuring sufficient performance.

[0051] The intermediate layer 5 functions as a reaction prevention layer. Therefore, the material for the intermediate layer 5 may be any material that can prevent a reaction between the components of the electrolyte layer 4 and the components of the counter electrode layer 6, such as a ceria-based material. Furthermore, a material containing at least one element selected from the group consisting of Sm, Gd, and Y is preferably used for the intermediate layer 5. The total content of these elements is preferably 1.0% by mass or more and 10% by mass or less. By incorporating the intermediate layer 5 as a reaction prevention layer between the electrolyte layer 4 and the counter electrode layer 6, the reaction between the constituent materials of the counter electrode layer 6 and the electrolyte layer 4 is effectively suppressed, thereby improving the long-term stability of the performance of the metal-supported electrochemical element E.

[0052] The intermediate layer 5 preferably has oxygen ion (oxide ion) conductivity, and more preferably is a mixed conductor having both oxygen ion (oxide ion) and electron conductivity. An intermediate layer 5 having such properties is suitable for application to a metal-supported electrochemical element E.

[0053] Examples of methods for forming the intermediate layer 5 include low-temperature firing (e.g., a wet method using firing at a low temperature without firing at temperatures higher than 1100°C), spray coating (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, etc.), PVD (sputtering, pulsed laser deposition, etc.), and CVD. These low-temperature deposition methods can be used to obtain a good intermediate layer 5 without firing at temperatures higher than 1100°C. Therefore, a metal-supported electrochemical element with excellent durability can be realized without damaging the metal support 1 while suppressing interdiffusion of elements between the metal support 1 and the electrode layer 2. In particular, low-temperature firing and spray coating methods can be used to realize low-cost elements. Furthermore, low-temperature firing facilitates handling of raw materials and allows the intermediate layer 5 to be formed on the electrolyte layer 4 with high adhesion strength.

[0054] (Counter electrode layer) 1, the counter electrode layer 6 is formed as a thin layer on the intermediate layer 5. When the counter electrode layer 6 is formed as a thin layer, the thickness of the counter electrode layer 6 is preferably set to, for example, about 1 μm to 100 μm. With such a thickness, it is possible to reduce the amount of expensive counter electrode layer material used, thereby reducing costs, while ensuring sufficient electrode performance.

[0055] Examples of materials that can be used for the counter electrode layer 6 include composite oxides such as LSCF and LSM, ceria-based oxides, and mixtures thereof. In particular, the counter electrode layer 6 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 counter electrode layer 6 formed using the above materials functions as a cathode.

[0056] Examples of methods for forming the counter electrode layer 6 include low-temperature firing (e.g., a wet method using firing at a low temperature without firing at a high temperature above 1100°C), spray coating (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, and cold spray), PVD (sputtering and pulsed laser deposition), and CVD. These low-temperature deposition methods can be used to obtain a good counter electrode layer 6 without firing at a high temperature above 1100°C. Therefore, a metal-supported electrochemical element with excellent durability can be realized without damaging the metal support 1 while suppressing interdiffusion of elements between the metal support 1 and the electrode layer 2. In particular, low-temperature firing and spray coating methods can be used to realize low-cost elements. Furthermore, low-temperature firing facilitates handling of raw materials and allows the counter electrode layer 6 to be formed with high adhesion strength.

[0057] [Method for manufacturing a metal-supported electrochemical element] Next, a method for producing the metal-supported electrochemical element E will be described. The manufacturing method of the metal-supported electrochemical element E according to this embodiment includes an electrode layer forming step, an electrolyte layer forming step, an intermediate layer forming step, and a counter electrode layer forming step, and further includes an electrode functional layer forming step between the electrode layer forming step and the electrolyte layer forming step.

[0058] (Electrode layer formation step) 1, in the electrode layer formation step, an electrode layer 2 is formed in a thin film state on a metal support 1. The electrode layer 2 can be formed by the above-mentioned film formation method, but in order to suppress deterioration of the metal support 1, it is preferable to use a film formation method that can be used in a low temperature range of less than 1100°C.

[0059] When the electrode layer formation step is performed by the low-temperature firing method, it is specifically performed as follows. First, a material powder of the electrode layer 2 is mixed with a solvent (dispersion medium) to prepare a material paste, which is then applied to the front surface of the metal support 1. The electrode layer 2 is then compression-molded (electrode layer smoothing treatment) and fired at a temperature below 1100°C (electrode layer firing treatment). The compression molding of the electrode layer 2 can be performed by, for example, CIP (Cold Isostatic Pressing), roll pressing, or RIP (Rubber Isostatic Pressing). The firing of the electrode layer 2 is preferably performed at a temperature of 800°C or higher and lower than 1100°C. The order of the electrode layer smoothing treatment and the electrode layer firing treatment can also be reversed.

[0060] The electrode layer smoothing treatment and the electrode layer firing treatment may be omitted or may be included in the electrode functional layer smoothing treatment and the electrode functional layer firing treatment described below, since the electrode functional layer 3 is formed after the electrode layer 2. The electrode layer smoothing treatment can be performed by lapping, leveling, surface cutting and polishing, or the like.

[0061] Furthermore, during the firing process in the electrode layer formation step, a metal oxide layer 1b (diffusion-suppressing layer) is formed on the surface of the metal support 1. That is, the firing process includes a firing process in which the firing atmosphere is set to an atmospheric condition with a low oxygen partial pressure. This results in a high inter-diffusion suppression effect of elements and a high-quality metal oxide layer 1b with low resistance.

[0062] (Electrode functional layer formation step) 1, in the electrode functional layer formation step, the electrode functional layer 3 is formed as a thin layer on the electrode layer 2 so as to cover the electrode layer 2. The electrode functional layer 3 can be formed using the film formation methods described above, but it is preferable to use a film formation method that can be used in a low temperature range of less than 1100°C in order to suppress deterioration of the metal support 1.

[0063] When the electrode functional layer formation step is performed using a low-temperature firing method, the process is specifically as follows. First, a material powder for the electrode functional layer 3 is mixed with a solvent (dispersion medium) to prepare a material paste, which is then applied to the front surface of the electrode layer 2. The electrode functional layer 3 is then compression-molded (electrode functional layer smoothing treatment) and fired at a temperature below 1100°C (electrode functional layer firing treatment). The compression molding of the electrode functional layer 3 can be performed, for example, by CIP molding, roll pressure molding, RIP molding, etc. Furthermore, the electrode functional layer 3 is preferably fired at a temperature of 800°C or higher but lower than 1100°C. This is because such a temperature can form a high-strength electrode functional layer 3 while suppressing damage and deterioration of the metal support 1. Furthermore, the electrode functional layer 3 is preferably fired at 1050°C or lower, and even more preferably at 1000°C or lower. This is because the lower the firing temperature of the electrode functional layer 3, the more effectively the metal-supported electrochemical element E can be formed while suppressing damage and deterioration of the metal support 1. The order of the electrode functional layer smoothing treatment and the electrode functional layer firing treatment can also be reversed. Furthermore, the electrode functional layer smoothing treatment can also be performed by lapping, leveling, cutting and polishing the surface, etc.

[0064] (Electrolyte layer formation step) In the electrolyte layer formation step, a stabilized zirconia dense film is formed as the electrolyte layer 4. That is, in the electrolyte layer formation step, as shown in FIG. 1 , on a metal substrate B with an electrode layer, which includes a metal support 1, an electrode layer 2 laminated thereon, and an electrode functional layer 3 laminated thereon, the electrolyte layer 4 is formed as a thin layer on the electrode functional layer 3 in a state where it covers the electrode layer 2 and the electrode functional layer 3. As described above, the electrolyte layer 4 is preferably formed by a low-temperature firing method (a wet method in which firing is performed in a low temperature range below 1100°C). Hereinafter, as a specific procedure for forming the electrolyte layer 4, the electrolyte layer formation step included in the method for manufacturing a metal-supported electrochemical element according to this embodiment will be described in detail.

[0065] The electrolyte layer formation step included in the manufacturing method of a metal-supported electrochemical element according to this embodiment is composed of a coating step (#01), a calcination step (#02), and a firing step (#03) performed in this order, as shown in FIG. In the coating process (#01), a coating composition containing at least a zirconium component and a stabilizing substance component for stabilizing the crystalline structure of the zirconium component is first prepared. This coating composition is prepared by dispersing at least the zirconium component and the stabilizing substance component in a solvent component such as an organic solvent. The coating composition may also contain water necessary for the hydrolysis of the zirconium component, a catalyst for inducing the hydrolysis and polycondensation reactions, a chelating compound for suppressing the hydrolysis rate and polycondensation rate, and fine particles of stabilized zirconia as a filler (aggregate). Next, as shown in Figure 3, the coating composition produced as described above is applied to the electrode layer 2 and electrode functional layer 3 laminated on the metal support 1 in the metal substrate B with an electrode layer, to obtain a coating composition-coated substrate A comprising the metal support 1, the electrode layer 2, the electrode functional layer 3, and a coating film 4a of the coating composition laminated together. As a method for applying the coating composition, it is desirable to use a dip coating method, which is advantageous in terms of cost, but coating methods other than dip coating, such as spray coating, can also be used.

[0066] In the coating step (#01), the coating composition is applied so that the coating film 4a covers the electrode layer 2 and the electrode functional layer 3 and spans the surface of the metal support 1. As a result, the stabilized zirconia dense film formed as the electrolyte layer 4 in the metal-supported electrochemical element E (see FIG. 1) is also formed so as to cover the electrode layer 2 and the electrode functional layer 3 and span the surface of the metal support 1. In this embodiment, as shown in FIG. 3, the coating composition-coated substrate A includes the electrode functional layer 3, but this electrode functional layer 3 may be omitted. The coating composition-coated substrate A obtained in this manner is sufficiently dried, for example, by heat treatment at 80°C for 10 minutes, and then the next calcination step (#02) is carried out.

[0067] The zirconium component contained in the coating composition used in the coating step (#01) is the starting material for the stabilized zirconia dense film. The content of the zirconium component in the coating composition is preferably 10 to 30 mass%. As the zirconium component, a zirconium alkoxide can be used. Examples of the zirconium alkoxide include one or more of zirconium(IV) methoxide, zirconium(IV) ethoxide, zirconium(IV) n-propoxide, zirconium(IV) i-propoxide, zirconium(IV) n-butoxide, zirconium(IV) i-butoxide, zirconium(IV) sec-butoxide, and zirconium(IV) t-butoxide.

[0068] The content of the stabilizing substance component in the coating composition is preferably 1 to 10 mass%. By using a yttrium compound, a scandium compound, a samarium compound, or the like as the stabilizing substance component, yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ), or samaria-stabilized zirconia (SSZ) can be formed as a stabilized zirconia dense film used as the electrolyte layer 4. Examples of yttrium compounds that can be used include one or more of yttrium nitrate, yttrium chloride, yttrium sulfate, yttrium phosphate, yttrium acetate, yttrium carbonate, yttrium oxalate, yttrium(III) ethoxide, yttrium(III) n-propoxide, yttrium(III) i-propoxide, and yttrium(III) butoxide. Examples of scandium compounds that can be used include one or more of scandium nitrate, scandium chloride, scandium sulfate, dodecylscandium sulfate, and scandium(III) i-propoxide. As the samarium compound, for example, one or more of samarium acetate, samarium nitrate, samarium chloride, samarium sulfate, samarium oxalate, and samarium (III) i-propoxide can be used.

[0069] Furthermore, in addition to the zirconium component and the stabilizing substance component, the coating composition may also contain a chelate compound, a polyalkylene glycol, a catalyst, water, an organic solvent, and the like. Examples of chelating compounds that can be used include 2,4-pentanedione, 2,4-hexanedione, 3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 1-phenyl-1,3-butanedione, 1,3-diphenyl-1,3-propanedione, 1,1,1-trifluoro-2,4-pentanedione, 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, and 1,3-cyclohexanedione. The content of the chelating compound in the coating composition is preferably 3 to 15% by mass. Examples of polyalkylene glycol that can be used include tetraethylene glycol, pentaethylene glycol, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, tripropylene glycol, tetrapropylene glycol, polypropylene glycol 400, polypropylene glycol 700, and polypropylene glycol 1000. The content of polyalkylene glycol in the coating composition is preferably 0.3 to 7% by mass. Examples of catalysts that can be used include hydrochloric acid, acetic acid, nitric acid, sulfuric acid, phosphoric acid, etc. The catalyst content in the coating composition is preferably 0.1 to 2 mass %. From the viewpoint of the coatability and ease of handling of the coating composition, the content of water in the coating composition is preferably 0.1 to 2 mass %. Examples of organic solvents that can be used include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, and 2-methyl-2-propanol. The content of the organic solvent in the coating composition is within the range of the remaining amounts of the other components.

[0070] In the calcination step (#02), the coating composition-coated substrate A is calcined at a predetermined set calcination temperature Ta for a predetermined time (e.g., 10 minutes). Furthermore, in the calcination step (#02), the temperature of the coating composition-coated substrate A is raised to the set calcination temperature Ta at a predetermined set temperature rise rate ΔTa. In the present embodiment, by setting the calcination temperature Ta in the range of 260°C or higher and lower than 750°C in the calcination step (#02), as demonstrated in the examples and comparative examples described later, a homogeneous and dense stabilized zirconia dense film with few defects such as cracks in the coating film 4a of the coating composition is formed as the electrolyte layer 4. The coating composition-coated substrate A thus subjected to the calcination step (#02) is then subjected to the next firing step (#03).

[0071] Furthermore, in this embodiment, in order to form a stabilized zirconia dense film having a relatively large thickness and excellent durability and reliability as the electrolyte layer 4, the above-mentioned application step (#01) and the above-mentioned calcination step (#02) are repeated multiple times to form a coating film 4a having a relatively large thickness and consisting of multiple layers on the coating composition-applied substrate A.

[0072] In the firing step (#03), the coating composition-coated substrate A is fired for a predetermined time (e.g., 60 minutes) at a predetermined set firing temperature Tb, which is higher than the set calcination temperature Ta. Then, by carrying out this firing step (#04), the zirconium component contained in the coating film 4a of the coating composition-coated substrate A is sintered, and a homogeneous and dense stabilized zirconia dense film is formed as the electrolyte layer 4. Furthermore, in this embodiment, in the firing step (#03), the firing temperature Tb is set relatively low, within the range of more than 950°C and less than 1100°C, thereby suppressing deterioration of the metal support 1.

[0073] Furthermore, in this manufacturing method, the occurrence of cracks due to increased internal stress in the coating film 4a is suppressed in the above-mentioned calcination step (#02), so by applying the coating composition to a relatively large film thickness in the above-mentioned application step (#01), it is possible to form a stabilized zirconia dense film with a relatively large film thickness, with an average film thickness in the range of 0.5 μm or more and 10 μm or less.

[0074] (Intermediate layer formation step) In the intermediate layer formation step, the intermediate layer 5 is formed in a thin layer state on the electrolyte layer 4. As a method for forming the intermediate layer 5, the above-mentioned film formation methods can be used, and it is particularly preferable to use a film formation method that can be used in a low temperature range of 1100°C or less to suppress deterioration of the metal support 1.

[0075] (Counter electrode layer formation step) In the counter electrode layer forming step, the counter electrode layer 6 is formed in a thin layer state on the intermediate layer 5. As a method for forming the counter electrode layer 6, the above-mentioned film formation methods can be used, and it is particularly preferable to use a film formation method that can be used in a low temperature range of 1100°C or less to suppress deterioration of the metal support 1.

[0076] [Examples and Comparative Examples] Next, examples and comparative examples for evaluating the performance of the stabilized zirconia dense film produced as the electrolyte layer 4 by the method for producing a metal-supported electrochemical element according to this embodiment will be described. In the following examples and comparative examples, a coating composition is used which is prepared by mixing the following components in a 150 ml glass container and stirring for 3 hours using a magnetic stirrer.

[0077] <Composition components of coating composition> Zirconium(IV) n-butoxide (zirconium component): 6.40g ·Yttrium nitrate hexahydrate (stabilizing substance component): 1.60g 4-Pentanedione: 3.34g Polyethylene glycol (average molecular weight 200): 0.67g ·60% nitric acid: 0.26g ·Water: 0.12g Ethanol: 14.42g 1-butanol: 21.59g

[0078] In the examples and comparative examples shown below, as shown in Figure 3, an electrode layer 2 was formed on part of the surface of a circular, flat metal support 1 (diameter: 25 mm, thickness: 3 mm, material: SUS403) with multiple through holes 1a, and an electrode functional layer 3 was further formed on top of that to produce a test piece of metal substrate B with an electrode layer. Specifically, 60 wt% NiO powder and 40 wt% GDC powder were mixed, and an organic binder and an organic solvent were added to prepare a paste. The paste was applied by screen printing to laminate the electrode layer 2 in a region with a radius of 3 mm from the center of the metal support 1. The metal support 1 with the laminated electrode layer 2 was then fired at 850°C. Next, an organic binder and an organic solvent were added to the GDC fine powder to prepare a paste. The paste was then applied by screen printing to form an electrode functional layer 3 in a region with a radius of 5 mm from the center of the metal support 1 on which the electrode layer 2 was laminated. The metal support 1 on which the electrode functional layer 3 was laminated was then fired at 1050°C.

[0079] The coating process is carried out in such a manner that the coating composition is applied to the surface of the metal substrate B with electrode layer produced in this manner so as to cover the electrode layer 2 and the electrode functional layer 3, and then the coating film 4a is formed by heat-treating it at 80°C for 30 minutes and drying it, thereby obtaining a coating composition-coated substrate A which is composed of a metal support 1, an electrode layer 2, an electrode functional layer 3, and a coating film 4a of the coating composition laminated together. The coating composition was applied by a so-called dip coating method in which the metal substrate B with an electrode layer was immersed in the coating composition and then pulled up, and the pulling up speed was set at 1 mm / sec.

[0080] In the examples and comparative examples shown below, after the coating step, a calcination step is carried out in which the temperature of the coating composition-coated substrate A is raised at a predetermined set temperature rise rate ΔTa and calcined for 10 minutes at a predetermined set calcination temperature Ta. The coating step and the calcination step are then repeated three times to form a coating film 4a consisting of three layers and having a relatively large thickness on the coating composition-coated substrate A. Furthermore, in the examples and comparative examples shown below, the application step and the calcination step are repeated three times, and then the coating composition-applied substrate A is calcined at a predetermined set calcination temperature Tb for 60 minutes.

[0081] In the examples and comparative examples shown below, He leakage amount and open circuit voltage were measured as performance evaluation tests. In the He leakage measurement, the periphery of the test piece after the firing process was sealed, and He gas was pressurized at 10 kPa from the back side of the test piece (the side facing the metal support 1), and the He leakage amount (ppm) leaking out from the front side of the test piece (the side facing the electrolyte layer 4) was measured. This He leakage amount (ppm) can be used to evaluate the gas barrier properties of the stabilized zirconia dense film formed as the electrolyte layer 4. The appropriate range for the He leakage amount was set to 18,000 ppm or less, and a metal-supported electrochemical element was deemed to be good when the He leakage amount was within the appropriate range (18,000 ppm or less), and not good when the He leakage amount was outside the appropriate range (more than 18,000 ppm). On the other hand, in the open circuit voltage measurement, the open circuit voltage (OCV) was measured when a solid oxide fuel cell was constructed using a metal-supported electrochemical element using the test piece, in which a power generation reaction occurred in the metal-supported electrochemical element. This open circuit voltage can be used to evaluate the performance of the metal-supported electrochemical element. The appropriate range for the open circuit voltage was set to 1.0 V or higher, and if the open circuit voltage was within the appropriate range (1.0 V or higher), the metal-supported electrochemical element was considered to be good, and if the open circuit voltage was outside the appropriate range (less than 1.0 V), the metal-supported electrochemical element was considered to be bad.

[0082] The conditions for the calcination step and firing step and the performance evaluation test results for Examples 1 to 5 and Comparative Examples 1 to 3 are shown in FIG. In the performance evaluation test, the "Judgment" column indicates that the He leak amount was within the appropriate range (18,000 ppm or less) with a "○" and that the He leak amount was outside the appropriate range (more than 18,000 ppm) with a "×".

[0083] The performance evaluation test results shown in FIG. 8 reveal that by setting the calcination temperature Ta within the range of 260°C or higher and lower than 750°C, the He leakage amount is within the appropriate range (18,000 ppm or lower), and a homogeneous and dense stabilized zirconia dense film with excellent gas barrier properties is formed as the electrolyte layer 4. Furthermore, since Examples 1 and 2 have a smaller He leakage amount and better gas barrier properties than Examples 3 and 4, it is considered that the set calcination temperature Ta is more preferably 340°C or higher, and the set temperature rise rate ΔTa is more preferably 16°C per second or higher.

[0084] [Solid oxide fuel cell] By configuring the metal-supported electrochemical element E as described above, the metal-supported electrochemical element E can be used as a power-generating cell of a solid oxide fuel cell. In other words, a solid oxide fuel cell in which a power-generating reaction occurs in the metal-supported electrochemical element E can be realized.

[0085] For example, referring to FIG. 1, while maintaining a predetermined operating temperature (for example, 500°C or higher and 900°C or lower), a fuel gas containing hydrogen as a first gas is supplied from the rear surface of the metal support 1 through the through-holes 1a to the electrode layer 2, and air as a second gas is supplied to the counter electrode layer 6. Then, oxygen ions O 2- When an electrolyte material that conducts electrons is used, oxygen O2 contained in the air is converted into electrons e - reacts with oxygen ions O 2- is generated, and the oxygen ions O 2- The hydrogen ions H2 contained in the supplied fuel gas are converted into oxygen ions O2 in the electrode layer 2. 2-reacts with water H2O and electrons e - is generated.

[0086] When an electrolyte material that conducts hydrogen ions is used for the electrolyte layer 4, hydrogen H2 contained in the fuel gas supplied to the electrode layer 2 is converted into electrons e - releases hydrogen ions H + The hydrogen ions H + moves through the electrolyte layer 4 to the counter electrode layer 6. At the counter electrode layer 6, oxygen O2 and hydrogen ions H + , electronic e - reacts to produce water H2O.

[0087] The above reaction generates an open circuit voltage as an electrochemical output between the electrode layer 2 and the counter electrode layer 6. In this case, the electrode layer 2 functions as the fuel electrode (anode) of the fuel cell, and the counter electrode layer 6 functions as the air electrode (cathode).

[0088] [Electrochemical Module] Next, the electrochemical module M will be described with reference to FIGS. 1 and 4, the electrochemical module M includes a metal-supported electrochemical element E in a state where a cylindrical support is formed by a metal support 1 and a U-shaped member 7 attached to the back surface of the metal support 1. The electrochemical module M is constructed by stacking (assembling) a plurality of these metal-supported electrochemical elements E with a current collecting member 26 sandwiched therebetween. In this embodiment, the current collecting member 26 is joined to the counter electrode layer 6 of the metal-supported electrochemical element E and the U-shaped member 7 to electrically connect them together, but the counter electrode layer 6 of the metal-supported electrochemical element E and the U-shaped member 7 may also be directly electrically connected together.

[0089] The electrochemical module M has a gas manifold 17, a termination member, and a current draw-out section. One open end of the cylindrical support of the metal-supported electrochemical element E, which is stacked, is connected to the gas manifold 17, and the gas is supplied from the gas manifold 17. The supplied gas flows through the inside of the cylindrical support and is supplied to the electrode layer 2 through the through-holes 1a of the metal support 1.

[0090] [Energy Systems] Next, an energy system Z1 constructed using the electrochemical module M will be described with reference to FIGS. 1 and 5. FIG. FIG. 5 shows an example of an electrochemical device Y1 and an energy system Z1 in which the metal supported electrochemical element E is operated as a solid oxide fuel cell that generates electricity through the above-described power generation reaction.

[0091] As shown in FIG. 5, the energy system Z1 includes an electrochemical device Y1 and a heat exchanger 53 that is a waste heat utilization unit that reuses heat discharged from the electrochemical device Y1.

[0092] In this embodiment, the electrochemical device Y1 includes an electrochemical module M, a fuel converter consisting of a desulfurizer 31 and a reformer 34, a fuel supply unit 46 that supplies fuel gas containing reducing components generated in the fuel converter to the electrochemical module M, and an inverter 38, which is a type of power converter, as an output unit that extracts electric power from the electrochemical module M.

[0093] The electrochemical device Y1 includes a desulfurizer 31, a reforming water tank 32, a vaporizer 33, a reformer 34, a blower 37, a combustion unit 36, an inverter 38, a control unit 39, an electrochemical module M, a storage container 40, and the like.

[0094] The desulfurizer 31 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 31 can suppress the effects of the sulfur compounds on the reformer 34 or the metal-supported electrochemical element E. The vaporizer 33 generates steam from the reforming water supplied from the reforming water tank 32. The reformer 34 uses the steam generated in the vaporizer 33 to steam reform the raw fuel desulfurized in the desulfurizer 31, generating a reformed gas containing hydrogen.

[0095] The electrochemical module M generates electricity by electrochemical reaction using the reformed gas supplied from the reformer 34 and the air supplied from the blower 37. The combustion section 36 mixes the reaction exhaust gas discharged from the electrochemical module M with air and combusts combustible components in the reaction exhaust gas.

[0096] The electrochemical module M has a plurality of metal-supported electrochemical elements E and a gas manifold 17. The plurality of metal-supported electrochemical elements E are arranged in parallel while electrically connected to each other, and one end (lower end) of each metal-supported electrochemical element E is fixed to the gas manifold 17. The metal-supported electrochemical element E generates electricity by causing an electrochemical reaction between the reformed gas supplied through the gas manifold 17 and air supplied from a blower 37.

[0097] The inverter 38 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 39 controls the operation of the electrochemical device Y1 and the energy system Z1.

[0098] The vaporizer 33, the reformer 34, the electrochemical module M, and the combustion section 36 are housed in a housing 40. The reformer 34 uses combustion heat generated by the combustion of the reaction exhaust gas in the combustion section 36 to carry out a reforming process of the raw fuel.

[0099] The raw fuel is supplied to the desulfurizer 31 through a raw fuel supply path 42 by operation of a booster pump 41. The reforming water in the reforming water tank 32 is supplied to the vaporizer 33 through a reforming water supply path 44 by operation of a 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 31, and the reforming water and raw fuel that have merged outside the storage container 40 are supplied to the vaporizer 33 provided inside the storage container 40.

[0100] The reforming water is vaporized in the vaporizer 33 to become water vapor. The raw fuel containing water vapor produced in the vaporizer 33 is supplied to the reformer 34 through a water vapor-containing raw fuel supply path 45. The raw fuel is steam reformed in the reformer 34 to produce a reformed gas (first gas having a reducing component) mainly composed of hydrogen gas. The reformed gas produced in the reformer 34 is supplied to the gas manifold 17 of the electrochemical module M through a fuel supply unit 46.

[0101] The reformed gas supplied to the gas manifold 17 is distributed to the plurality of metal-supported electrochemical elements E and supplied to the metal-supported electrochemical elements E from the lower end, which is the connection between the metal-supported electrochemical elements E and the gas manifold 17. Mainly hydrogen (reducing component) in the reformed gas is used in the electrochemical reaction in the metal-supported electrochemical elements E. The reaction exhaust gas, which contains the remaining hydrogen gas not used in the reaction, is discharged from the upper end of the metal-supported electrochemical elements E to the combustion section 36.

[0102] The reaction exhaust gas is combusted in the combustion section 36 to become combustion exhaust gas, which 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 reduces the reducing components contained in the combustion exhaust gas, such as carbon monoxide and hydrogen, by combustion. 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.

[0103] The heat exchanger 53 exchanges heat between the combustion exhaust gas generated by combustion in the combustion section 36 and the supplied cold water to generate hot water. That is, the heat exchanger 53 operates as a waste heat utilization section that reuses the heat discharged from the electrochemical device Y1.

[0104] 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 the residual hydrogen gas that was not used in the reaction in the metal-supported electrochemical element E. 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.

[0105] [Another embodiment of the energy system] Next, an energy system Z2 according to another embodiment constructed using the electrochemical module M will be described with reference to FIGS. 1 and 6. FIG.

[0106] The metal-supported electrochemical element E can also be used in a solid oxide electrolysis cell, an oxygen sensor using a solid oxide, or the like. For example, referring to FIG. 1, when the metal-supported electrochemical element E is operated as an electrolysis cell, a gas containing water vapor and carbon dioxide is supplied to the electrode layer 2, and a voltage is applied between the electrode layer 2 and the counter electrode layer 6. Then, electrons e - and water H2O and carbon dioxide molecules CO 2 reacts to produce hydrogen H2, carbon monoxide CO, and oxygen ions O 2- Oxygen ions O 2- The oxygen ions O migrate through the electrolyte layer 4 to the counter electrode layer 6. 2- releases electrons and becomes oxygen O2. Through the above reaction, water H2O is electrolyzed into hydrogen H2 and oxygen O2. If gas containing carbon dioxide molecules CO2 is supplied, it will be electrolyzed into carbon monoxide CO and oxygen O2. FIG. 6 shows an example of an electrochemical device Y2 and an energy system Z2 in the case where the metal-supported electrochemical element E is operated as an electrolytic cell that produces gas through the above-mentioned electrolytic reaction.

[0107] As shown in FIG. 6, the energy system Z2 includes an electrochemical device Y2 and two heat exchangers 91 and 93 as exhaust heat utilization units that reuse heat circulated from the electrochemical device Y2. In this embodiment, the electrochemical device Y2 includes an electrochemical module M, a fuel converter 92 that synthesizes hydrocarbons based on hydrogen and other fuels produced in the electrochemical module M, and a power converter 95 that supplies power to the electrochemical module M.

[0108] In the electrochemical apparatus Y2, the electrochemical module M has a plurality of metal-supported electrochemical elements E and two gas manifolds 17, 171. The plurality of metal-supported electrochemical elements E are arranged in parallel and electrically connected to each other. One end (lower end) of each metal-supported electrochemical element E is fixed to the gas manifold 17, and the other end (upper end) is fixed to the gas manifold 171. The gas manifold 17 at one end of the metal-supported electrochemical element E receives a supply of water vapor and carbon dioxide. Hydrogen, carbon monoxide, and the like produced by the above-described reactions in the metal-supported electrochemical element E are collected by the gas manifold 171, which communicates with the other end.

[0109] In this embodiment, the heat exchanger 91 operates as a waste heat utilization unit that exchanges heat between the reaction heat generated by the reaction occurring in the fuel converter 92 and water to vaporize it, and the heat exchanger 93 operates as a waste heat utilization unit that exchanges heat between the waste heat generated by the metal-supported electrochemical element E and water vapor and carbon dioxide to preheat them. This configuration improves energy efficiency. The power converter 95 supplies power to the metal-supported electrochemical element E of the electrochemical module M. This allows the metal-supported electrochemical element E to function as an electrolysis cell. Therefore, with the above configuration, it is possible to realize an electrochemical device Y1 and an energy system Z1 that can improve the efficiency of converting electrical energy into chemical energy such as fuel.

[0110] [Another embodiment] Other embodiments of the present invention will be described below. Note that the configurations of the embodiments described below are not limited to being applied independently, but can also be applied in combination with the configurations of other embodiments.

[0111] (1) In the above embodiment, the metal-supported electrochemical element E is described as having an electrode functional layer 3 and an intermediate layer 5, but the metal-supported electrochemical element E may be one in which the electrode functional layer 3 and the intermediate layer 5 are omitted. When the electrode functional layer 3 is omitted, the metal-supported electrochemical element E has the electrolyte layer 4 formed on the electrode layer 2. When the intermediate layer 5 is omitted, the metal-supported electrochemical element E has the counter electrode layer 6 formed on the electrolyte layer 4 .

[0112] (2) In the above embodiment, a plurality of metal-supported electrochemical elements E are used in combination as an electrochemical module M, but this is not limited to this, and it is also possible to use a single metal-supported electrochemical element E.

[0113] (3) In the above embodiment, the energy systems Z1 and Z2 are provided with a waste heat utilization unit that reuses the heat emitted from the electrochemical devices Y1 and Y2, but this is not limited to this and the energy systems Z1 and Z2 may not be provided with a waste heat utilization unit.

[0114] (4) In the above embodiment, a composite material such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO-CeO, or Cu-CeO is used as the material for electrode layer 2, a composite oxide such as LSCF or LSM is used as the material for counter electrode layer 6, hydrogen gas is passed through electrode layer 2 to form the fuel electrode (anode), and air is passed through counter electrode layer 6 to form the air electrode (cathode), and the device is used as a power generating cell for a solid oxide fuel cell. However, this configuration is not limited thereto. The metal-supported electrochemical element E may be configured such that the electrode layer 2 serves as the air electrode and the counter electrode layer 6 serves as the fuel electrode. That is, a composite oxide such as LSCF or LSM is used as the material for electrode layer 2, and a composite material such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO-CeO, or Cu-CeO is used as the material for counter electrode layer 6. In the case of the metal-supported electrochemical element E configured in this manner, air is passed through the electrode layer 2 to form an air electrode, and hydrogen gas is passed through the counter electrode layer 6 to form a fuel electrode, and the metal-supported electrochemical element E can be used as a power generation cell of a solid oxide fuel cell.

[0115] (5) In the above embodiment, the electrochemical module M includes a metal-supported electrochemical element E in a state where a cylindrical support is formed by a metal support 1 (see FIG. 1) and a U-shaped member 7 (see FIG. 4) attached to the rear surface of the metal support 1, but the present invention is not limited to this. For example, as shown in FIG. 7, the electrochemical module M may be configured by stacking metal-supported electrochemical elements E with inter-cell connection members 71 sandwiched therebetween. In this case, the inter-cell connection member 71 is a plate-like member that is conductive and gas impermeable, and has grooves 72 formed on the front and back surfaces that are perpendicular to each other. The inter-cell connection member 71 can be made of a metal such as stainless steel or a metal oxide. When metal-supported electrochemical elements E are stacked with this inter-cell connecting member 71 sandwiched therebetween, gas can be supplied to the metal-supported electrochemical elements E through the grooves 72. Specifically, the grooves 72 formed on one surface serve as first gas flow paths 72a, which supply gas to the front side of the metal-supported electrochemical element E, i.e., to the counter electrode layer 6. The grooves 72 formed on the other surface serve as second gas flow paths 72b, which supply gas to the back side of the metal-supported electrochemical element E, i.e., from the back surface of the metal support 1 as shown in FIG. 1, through the through-holes 1a to the electrode layer 2. When the electrochemical module M configured in this manner is operated as a power generation cell of a solid oxide fuel cell, air is supplied to the first gas flow path 72a and hydrogen is supplied to the second gas flow path 72b. This causes a power generation reaction to proceed in the metal-supported electrochemical elements E, generating an open-circuit voltage and current. The generated power is extracted from the electrochemical module M through the inter-cell connection members 71 at both ends of the stacked metal-supported electrochemical elements E. The grooves 72 formed on the front surface and the rear surface of the inter-cell connection member 71 may be parallel to each other.

[0116] (6) In the above embodiment, the metal-supported electrochemical element E is mainly used in flat-plate or cylindrical-plate solid oxide fuel cells, but this is not limited thereto and it can also be used in elements such as cylindrical solid oxide fuel cells.

[0117] (7) In the above embodiment, the electrochemical devices Y1 and Y2 are each provided with an electrochemical module M having a plurality of metal-supported electrochemical elements E, but this is not limiting. For example, the electrochemical device may be provided with a single metal-supported electrochemical element E. [Explanation of symbols]

[0118] 1 Metal support 2 electrode layer 3 Electrode functional layer 4 Electrolyte layer 4a Coating film A. Coating composition application substrate E. Metal-supported electrochemical element M Electrochemistry Module Ta Pre-calcination temperature ΔTa Set temperature rise rate Tb Set firing temperature Z1 Energy System Z2 Energy System

Claims

1. A method for producing a metal-supported electrochemical element having a metal support, an electrode layer laminated on the metal support, and an electrolyte layer laminated on the electrode layer, the method comprising: an electrolyte layer forming step of forming a stabilized zirconia dense film as the electrolyte layer on the electrode layer of the electrode layer-formed metal substrate, the electrode layer being composed of the metal support and the electrode layer laminated thereon; The electrolyte layer forming step a coating step of applying a coating composition containing a zirconium component and a stabilizing substance component onto the metal substrate with an electrode layer to obtain a coating composition-coated substrate in which the metal substrate with an electrode layer and a coating film of the coating composition are laminated together; A calcination step of calcining the coating composition-coated substrate at a predetermined set calcination temperature after the coating step; A baking step of baking the coating composition-applied substrate at a predetermined set baking temperature higher than the set baking temperature after the calcination step, In the calcination step, the set calcination temperature is set within a range of 260°C or higher and lower than 750°C, In the firing step, the firing temperature is set within a range of more than 950°C and less than 1100°C.

2. 2. The method for producing a metal-supported electrochemical element according to claim 1, wherein the metal-supported electrochemical element has an electrode functional layer between the electrode layer and the electrolyte layer.

3. 3. The method for producing a metal-supported electrochemical element according to claim 1, wherein the stabilizing substance component is at least one of an yttrium compound, a scandium compound, and a samarium compound.

4. 3. The method for producing a metal-supported electrochemical element according to claim 1, wherein the average thickness of the dense stabilized zirconia film is in the range of 0.2 μm or more and 10 μm or less.

5. 3. The method for producing a metal-supported electrochemical element according to claim 1 or 2, wherein, in the electrolyte layer formation step, the coating step and the calcination step are repeated multiple times before the firing step, to form a coating film consisting of multiple layers on the coating composition-coated substrate.

6. A metal-supported electrochemical element having a metal support, an electrode layer laminated on the metal support, and an electrolyte layer laminated on the electrode layer, A metal-supported electrochemical element produced by the method for producing a metal-supported electrochemical element according to claim 1 or 2.

7. 7. The metal-supported electrochemical element according to claim 6, further comprising an electrode functional layer between the electrode layer and the electrolyte layer.

8. An electrochemical module in which a plurality of metal-supported electrochemical elements according to claim 6 are arranged in a group.

9. An energy system comprising the metal-supported electrochemical device according to claim 6.

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