JP2023143898A - Electrochemical cell and manufacturing method thereof, electrochemical module, and electrochemical cartridge - Google Patents

Abstract

To provide an electrochemical cell reduced in the reaction resistance of an interface of an air electrode middle layer and an air electrode conductive layer in comparison to the conventional one, and its manufacturing method.SOLUTION: An electrochemical cell according to a disclosure hereof comprises: an air electrode conductive layer 113b composed of a sintered body of a material which contains a perovskite oxide represented by the general formula, ABO3 and of which A site is La, Sr and/or Ca and B site is Mn; and an air electrode middle layer 113a composed of a sintered body of a material containing Sm-doped ceria, and having pore P, a first structure S1 and a second structure S2. The first structure S1 contains Ce of 50 atom% or more, and it does not contain Ca, Sr and Mn. The second structure S2 contains an element selected from a group consisting of Ca, Sr and Mn. In a section of the air electrode middle layer 113a, the rate of an area of the second structure S2 is 20% or more and 60% or less to a total area of the first structure S1 and second structure S2.SELECTED DRAWING: Figure 9

Description

The present disclosure relates to an electrochemical cell, a method for manufacturing the same, an electrochemical module, and an electrochemical cartridge.

A solid oxide fuel cell (SOFC) consists of a single element (cell) consisting of a fuel electrode, a solid electrolyte membrane, and an air electrode, and an interconnector that electrically connects adjacent cells. We are prepared. Although the generated voltage per cell is small, by connecting multiple cells in series to form a cell stack, it is possible to increase the voltage and obtain a practical output.

In a cell stack, when fuel gas is supplied to the fuel electrode and oxidizing gas such as oxygen is supplied to the air electrode, the oxygen in the oxidizing gas supplied to the air electrode is ionized and passes through the solid electrolyte membrane. , reaches the fuel electrode. An electrochemical reaction between the oxygen ions that have reached the fuel electrode and the fuel gas generates a potential difference between the fuel electrode and the air electrode, and this potential difference is extracted to the outside to generate electricity.

The biggest feature of SOFC is its high power generation efficiency. Therefore, SOFCs are required to achieve higher output density while maintaining cell deterioration resistance during power generation. Understanding the behavior of electrode and electrolyte surfaces and interfaces is important for improving power generation performance and degrading behavior. (See Non-Patent Document 1)

Junichiro Otomo, “Improving the performance of solid electrolyte fuel cells through material development and structural control,” Surface Chemistry, Vol. 32, No. 2, pp. 93-98, 2011

In a cell, a large interfacial resistance exists at the interface between the air electrode and the solid electrolyte membrane. As described in Non-Patent Document 1, one of the measures to reduce the resistance at the interface between the air electrode and the solid electrolyte membrane is to form a dense intermediate layer of ceria-based oxide between the air electrode and the solid electrolyte membrane. Methods of introducing layers are known.

However, when an air electrode having electronic conductivity is laminated on an intermediate layer of ceria-based oxide, the interfacial resistance between the air electrode and the intermediate layer may increase.

At the interface between the solid electrolyte membrane and the air electrode, an electrode reaction occurs at the three-phase interface accompanied by adsorption and dissociation of oxygen. A three-phase interface is an interface where three phases of ionic conductivity (electrolyte), oxygen supply (gas diffusion), and electron supply (electronic conductivity) coexist.

FIG. 10 shows a schematic diagram of the air electrode side of a conventional cell. An air electrode 113' is formed on the solid electrolyte membrane 111. The air electrode 113' includes an air electrode intermediate layer 113a' and an air electrode conductive layer 113b'. Since the air electrode intermediate layer 113a' is ionic conductive in an oxidizing atmosphere, it functions as an electrolyte. Pores P included in the air electrode intermediate layer 113a' and the air electrode conductive layer 113b' can serve as an oxygen gas diffusion path. The air electrode conductive layer 113b' has electronic conductivity. In FIG. 10, the interface between the air cathode intermediate layer 113a' and the air cathode conductive layer 113b' can be a three-phase interface field.

However, the ceria-based oxide that is the main component of the air electrode intermediate layer 113a' does not have electronic conductivity. Therefore, electrons cannot pass through the air electrode intermediate layer 113a', and the three-phase interface field on the air electrode 113' side is only the interface between the air electrode intermediate layer 113a' and the air electrode conductive layer 113b', and the interfacial resistance of the electrode becomes higher.

The present disclosure has been made in view of these circumstances, and provides an electrochemical cell, a method for manufacturing the same, and an electrochemical module that have lower resistance at the interface between the oxygen electrode intermediate layer and the oxygen electrode conductive layer than before. , aims to provide an electrochemical cartridge.

In order to solve the above problems, the electrochemical cell, its manufacturing method, electrochemical module, and electrochemical cartridge of the present disclosure employ the following means.

In the present disclosure, a hydrogen electrode, a solid electrolyte membrane, and an oxygen electrode are sequentially stacked, the oxygen electrode includes an oxygen electrode intermediate layer and an oxygen electrode conductive layer in order from the solid electrolyte membrane side, and the oxygen electrode conductive layer is generally It is a sintered body of a material containing a perovskite oxide represented by the formula ABO ₃ , the A site is La, Sr and/or Ca, and the B site is Mn, and the oxygen electrode intermediate layer is doped with Sm. It is a sintered body of a material containing ceria, and has pores, a first structure, and a second structure, and the first structure contains 50 atomic % or more of Ce, and contains Ca, Sr, and Mn. The second structure contains an element selected from the group consisting of Ca, Sr, and Mn, and the area ratio of the second structure in the cross section of the oxygen electrode intermediate layer is the same as that of the first structure and the second structure. Provided is an electrochemical cell whose area is 20% or more and 60% or less of the total area of the tissue.

The present disclosure provides an electrochemical module comprising the electrochemical cell described in the above disclosure.

The present disclosure provides an electrochemical cartridge comprising the electrochemical module described in the above disclosure.

In the present disclosure, a hydrogen electrode, a solid electrolyte membrane, and an oxygen electrode are sequentially stacked, the oxygen electrode includes an oxygen electrode intermediate layer and an oxygen electrode conductive layer in order from the solid electrolyte membrane side, and the oxygen electrode conductive layer is generally It is a sintered body of a material containing a perovskite oxide represented by the formula ABO ₃ , the A site is La, Sr and/or Ca, and the B site is Mn, and the oxygen electrode intermediate layer is doped with Sm. A method for manufacturing an electrochemical cell which is a sintered body of a material containing ceria, wherein in a cross section of the oxygen electrode intermediate layer, a structure containing an element selected from the group consisting of Ca, Sr, and Mn is provided. The oxygen electrode intermediate layer and the oxygen electrode conductive layer are co-sintered according to the acquired conditions, and the oxygen A method of manufacturing an electrochemical cell forming a very intermediate layer is provided.

The oxygen electrode conductive layer formed by sintering the material containing the perovskite oxide has electronic conductivity. The oxygen electrode intermediate layer formed by sintering a material containing Sm-doped ceria has ionic conductivity. By forming the oxygen electrode into a two-layer structure consisting of the oxygen electrode conductive layer and the oxygen electrode intermediate layer, the interfacial resistance between the solid electrolyte membrane and the oxygen electrode can be reduced.

The first structure, which is mainly composed of an element derived from ceria and which is Sm-doped, has the function of ionic conduction. The second structure containing an element selected from the group consisting of Ca, Sr and Mn is responsible for the function of electronic conduction. When the total cross-sectional area of the oxygen electrode intermediate layer is constant, as the second structure increases, the proportion of the first structure decreases and the ionic conductivity of the oxygen electrode intermediate layer decreases; As the proportion of the structure decreases, the electronic conductivity of the oxygen electrode intermediate layer decreases. By setting the area ratio of the second structure in the cross section of the oxygen electrode intermediate layer to 20% or more and 60% or less of the total area of the first structure and the second structure in the cross section of the oxygen electrode intermediate layer, the oxygen electrode intermediate layer It is possible to form an electron path while ensuring an ion path within the structure.

The electrode reaction field (three-phase interface) is expanded three-dimensionally inside the oxygen electrode intermediate layer by including pores that serve as gas paths, an ionic conductive first structure, and an electronically conductive second structure. do. This reduces the resistance at the interface between the oxygen electrode conductive layer and the oxygen electrode intermediate layer.

FIG. 2 is a diagram illustrating one aspect of a cell stack according to an embodiment of the present disclosure. FIG. 1 is a diagram illustrating one aspect of a SOFC module according to an embodiment of the present disclosure. 1 is a diagram showing one aspect of a cross section of an SOFC cartridge according to an embodiment of the present disclosure. It is a scanning electron micrograph of the cross section of the air cathode intermediate layer of the test piece. It is a chart of semi-quantitative analysis results of energy dispersive X-ray analysis (EDX). It is a graph explaining the influence which Mn, Ca, and Sr have on the electronic conductivity of a test object. This is a chart summarizing the numerical values read from FIG. 6. It is a graph showing the relationship between the proportion of the second structure in the air electrode intermediate layer and the electronic conductivity. FIG. 1 is a schematic diagram of a cross section (air electrode side) of a fuel cell according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram of a cross section (air electrode side) of a conventional fuel cell.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electrochemical cell, a method for manufacturing the same, an electrochemical module, and an electrochemical cartridge according to the present disclosure will be described below with reference to the drawings. Note that the following description regarding fuel cells should be read with the term electrochemical cell being replaced as appropriate.

In the following, for convenience of explanation, the positional relationship of each component explained using the expressions "above" and "below" with respect to the paper surface indicates the vertically upper side and the vertically lower side, respectively. In addition, in this embodiment, the same effect can be obtained in the vertical direction and the horizontal direction without necessarily limiting the vertical direction in the plane of the paper to the vertical vertical direction. good.

In addition, in the following description, a cylindrical (cylindrical) cell stack will be explained as an example of a solid oxide fuel cell (SOFC) cell stack, but it is not necessarily limited to this, and for example, a flat cell stack may be used. Good too. Although a fuel cell is formed on a base, an electrode (fuel electrode or air electrode) may be formed thick instead of the base so that it also serves as the base.

(Structure of cylindrical cell stack)
First, a cylindrical cell stack using a base tube will be described as an example of the present embodiment with reference to FIG. When the base tube is not used, for example, the fuel electrode may be made thick and also serve as the base tube, and the use is not limited to the base tube. Furthermore, although the base tube in this embodiment is described as having a cylindrical shape, the base tube may be cylindrical, and the cross section is not necessarily limited to a circular shape, and may be, for example, an elliptical shape. A cell stack such as a flat cylinder in which the circumferential side of the cylinder is vertically crushed may be used. Here, FIG. 1 shows one aspect of a cell stack according to an embodiment.

The cell stack 101 includes, for example, a cylindrical base tube 103, a plurality of fuel cells 105 formed on the outer peripheral surface of the base tube 103, and an interconnector 107 formed between adjacent fuel cells 105. . The fuel cell 105 is formed by stacking a fuel electrode 109, a solid electrolyte membrane 111, and an air electrode 113. In addition, the cell stack 101 is connected to the air electrode 113 of the fuel cell 105 that is formed at one end of the plurality of fuel cells 105 formed on the outer peripheral surface of the base tube 103 in the axial direction of the base tube 103. , a lead film 115 electrically connected via an interconnector 107, and a lead film 115 electrically connected to the fuel electrode 109 of the fuel cell 105 formed at the other end.

(Explanation of materials and functions of each component of the cell stack)
The base tube 103 is made of a porous material, such as CaO-stabilized ZrO ₂ (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ+NiO), or Y ₂ O _3- stabilized ZrO ₂ (YSZ), or The main component is MgAl ₂ O ₄ etc. The base tube 103 supports the fuel cell 105, the interconnector 107, and the lead membrane 115, and also supplies fuel gas to the inner peripheral surface of the base tube 103 through the pores of the base tube 103. The fuel is diffused into the fuel electrode 109 formed on the outer peripheral surface of the fuel electrode 109.

The fuel electrode 109 is made of a composite oxide of Ni and a zirconia-based electrolyte material, and for example, Ni/YSZ is used. The thickness of the fuel electrode 109 is 50 μm to 250 μm, and the fuel electrode 109 may be formed by screen printing a slurry. In this case, in the fuel electrode 109, Ni, which is a component of the fuel electrode 109, has a catalytic effect on the fuel gas. This catalytic action causes the fuel gas supplied through the base pipe 103, for example, a mixed gas of methane (CH ₄ ) and water vapor, to react and reform into hydrogen (H ₂ ) and carbon monoxide (CO). It is something. Further, the fuel electrode 109 transfers hydrogen (H ₂ ) and carbon monoxide (CO) obtained by reforming, and oxygen ions (O ²⁻ ) supplied via the solid electrolyte membrane 111 to the solid electrolyte membrane 111. The electrochemical reaction occurs near the interface of the two to produce water (H ₂ O) and carbon dioxide (CO ₂ ). Note that the fuel cell 105 generates power using electrons released from oxygen ions at this time.
Fuel gases that can be supplied to the fuel electrode 109 of the solid oxide fuel cell include hydrogen (H ₂ ), hydrocarbon gases such as carbon monoxide (CO) and methane (CH ₄ ), city gas, and natural gas. Other examples include gasified gas produced from carbon-containing raw materials such as petroleum, methanol, and coal using gasification equipment.

The solid electrolyte membrane 111 is mainly made of YSZ, which has airtightness that prevents gas from passing through and high oxygen ion conductivity at high temperatures. This solid electrolyte membrane 111 moves oxygen ions (O ²⁻ ) generated at the air electrode 113 to the fuel electrode 109. The thickness of the solid electrolyte membrane 111 located on the surface of the fuel electrode 109 is 10 μm to 100 μm, and the solid electrolyte membrane 111 may be formed by screen printing a slurry.

The air electrode 113 dissociates oxygen in the supplied oxidizing gas such as air near the interface with the solid electrolyte membrane 111 to generate oxygen ions (O ²⁻ ). The air electrode 113 is applied with slurry by screen printing or using a dispenser.

Oxidizing gas is a gas containing about 15% to 30% oxygen, and air is typically preferred, but other gases include a mixture of combustion exhaust gas and air, a mixture of oxygen and air, etc. is available.

The air electrode 113 includes an air electrode intermediate layer 113a and an air electrode conductive layer 113b. The air electrode intermediate layer 113a is placed in contact with the solid electrolyte membrane 111 and the interconnector 107. The air electrode conductive layer 113b is placed in contact with the air electrode intermediate layer 113a.

The air electrode conductive layer 113b has electronic conductivity. The film thickness of the air electrode conductive layer 113b is 20 μm or more and 1500 μm or less. When applied to a cylindrical cell stack, the thickness of the air electrode conductive layer 113b may be 500 μm or more and 1500 μm or less.

The material of the air electrode conductive layer 113b is a perovskite oxide represented by the general formula _ABO3 . In the general formula ABO ₃ , the A site is selected from the group consisting of La, Sr and Ca. The B site is Mn. Perovskite oxides of the general formula ABO ₃ are, for example, LaMnO ₃ doped with Sr and/or Ca. LaMnO ₃ doped with Sr and Ca can be produced by a general solid phase mixing method or a liquid phase mixing method. The contents of La, Mn, Sr, and Ca can be adjusted during raw material mixing.

The perovskite oxide represented by the general formula ABO ₃ may have an A-site deficient composition. In the A-site deficient composition, the A/B molar ratio is preferably 0.90 or more and 0.98 or less. For example, by setting A=0.95 mol, B=1.00 mol, and A/B molar ratio 0.95, the composition will be such that the A site is deficient and the B site is excessive.

The perovskite oxide represented by the general formula ABO ₃ may have an A-site excess composition. In the A-site excess composition, the A/B ratio is preferably 1.02 or more and 1.10 or less. For example, by setting A=1.05 mol, B=1.00 mol, and A/B ratio 1.05, the B site becomes deficient and the A site becomes excessive.

The air electrode intermediate layer 113a has ionic conductivity and electronic conductivity. The film thickness of the air electrode intermediate layer 113a is 10 μm or more and 20 μm or less.

The air electrode intermediate layer 113a has pores, a first structure, and a second structure. The area ratio of the second structure in the air electrode intermediate layer 113a is 20% or more and 60% or less, preferably 30% or more and 40% or more, with respect to the total area of the first structure and the second structure in the cross section. In the cross section of the air electrode intermediate layer 113a, the area ratio of pores may be 5% or more and 50% or less with respect to the total area of the pores, the first structure, and the second structure in the cross section.

The air electrode intermediate layer 113a is made of a material that has high ionic conductivity and excellent catalytic activity. The material of the air electrode intermediate layer 113a is Sm-doped ceria. The Sm-doped ceria may be Sm _1-x Ce _x O ₂ (0.8≦x≦0.9).

The material of the air electrode intermediate layer 113a may be added with elements at the A site and the B site of the material of the air electrode conductive layer 113b. The amount of the element added is such that the molar ratio of the element at the A site and the B site is 1.0 or less.

The first structure is mainly composed of Sm-doped ceria-derived elements. The Ce content of the first structure is 50 atomic % or more. The first structure does not contain Mn, Ca, or Sr. Here, "not containing" indicates that the content is 0.4 atomic % or less.

The second structure includes an Sm-doped ceria-derived element and an element (electronic conductive element) selected from the group consisting of Ca, Sr, and Mn. The Ce content of the second structure is less than 50 atomic %. The content of the electronic conductive element in the second structure may be 0.5 atomic % or more and 50 atomic % or less.

The interconnector 107 is made of a conductive perovskite oxide represented by M _1-x L _x TiO ₃ (M is an alkaline earth metal element, L is a lanthanide element) such as SrTiO ₃ system, and is made by screen printing a slurry. do. The interconnector 107 is a dense film to prevent fuel gas and oxidizing gas from mixing. Further, the interconnector 107 has stable durability and electrical conductivity under both an oxidizing atmosphere and a reducing atmosphere. This interconnector 107 electrically connects the air electrode 113 of one fuel cell 105 and the fuel electrode 109 of the other fuel cell 105 in the adjacent fuel cells 105, and connects the adjacent fuel cells 105 to each other. are connected in series.

The lead film 115 needs to have electronic conductivity and have a coefficient of thermal expansion close to that of other materials constituting the cell stack 101. It is composed of M1-xLxTiO ₃ (M is an alkaline earth metal element, L is a lanthanide element) such as a composite material or SrTiO ₃ system. This lead film 115 guides the DC power generated by the plurality of fuel cells 105 connected in series by the interconnector 107 to near the end of the cell stack 101.

(Method for manufacturing cylindrical cell stack)
An aqueous vehicle is mixed with each of the material powders of the fuel electrode 109, solid electrolyte membrane 111, interconnector 107, lead membrane 115, air electrode intermediate layer 113a, and air electrode conductive layer 113b to prepare a slurry of each structure.

The base tube 103 on which the slurry film of the fuel electrode 109, the solid electrolyte membrane 111, and the interconnector 107 has been formed is co-sintered in the atmosphere. The sintering temperature is specifically 1350°C to 1450°C.

Next, the base tube 103 in which the slurry films of the air electrode intermediate layer 113a and the air electrode conductive layer 113b are sequentially formed on the co-sintered base tube 103 is sintered in the atmosphere. The sintering temperature is specifically 1100°C to 1250°C. The sintering temperature here is lower than the co-sintering temperature after forming the base tube 103 to the interconnector 107.

Through the above steps, a cylindrical cell stack 101 in which fuel cells 105 are formed on a base tube 103 is obtained.

The material composition, sintering temperature, and sintering procedure of the air electrode intermediate layer 113a and the air electrode conductive layer 113b are such that the air electrode intermediate layer 113a contains an element selected from the group consisting of Ca, Sr, and Mn. (Second structure) is formed in 20% or more and 60% or less of the total area of the air electrode intermediate layer excluding pores, by obtaining conditions such as a preliminary test. The air cathode intermediate layer 113a is formed according to the obtained above.

For example, by co-sintering the air electrode intermediate layer 113a and the air electrode conductive layer 113b, elements contained in the air electrode conductive layer 113b are diffused into the air electrode intermediate layer 113a. As a result, a second structure is formed in the air electrode intermediate layer 113a.

When the material of the air electrode conductive layer 113b has an A-site deficient composition, a large amount of Mn, which is excessive with respect to the stoichiometric composition of the perovskite structure, diffuses into the air electrode intermediate layer 113a.

When the material of the air electrode conductive layer 113b has an excessive A-site composition, a large amount of Ca and Sr, which are in excess of the stoichiometric composition of the perovskite structure, diffuses into the air electrode intermediate layer 113a.

By increasing the sintering temperature and making the material of the air electrode conductive layer 113b finer, it is possible to promote the diffusion of elements contained in the material of the air electrode conductive layer 113b into the air electrode intermediate layer 113a. To increase the sintering temperature, we measured the shrinkage behavior of the air electrode conductive layer material, changed the temperature in 50°C increments from the sintering shrinkage start point, fabricated a prototype cell, and determined the second structure based on the cross-sectional structure observation results. By acquiring the amount of change in area ratio, it is possible to control the rate of change in the second tissue. Furthermore, similar control is possible by extending the sintering time even at the same sintering temperature. Regarding the particle size, we can calculate the rate of change in the second structure by making trial cells using materials with different particle sizes and obtaining the amount of change in the area ratio of the second structure from the microstructure observation results of the cross section after the particle size has changed. It is possible to control.

(Explanation of SOFC module structure and functions of each element)
Next, the SOFC module and SOFC cartridge according to this embodiment will be described with reference to FIGS. 2 and 3. Here, FIG. 2 shows one aspect of the SOFC module according to this embodiment. Further, FIG. 3 shows a cross-sectional view of one aspect of the SOFC cartridge according to the present embodiment.

As shown in FIG. 2, the SOFC module (fuel cell module) 201 includes, for example, a plurality of SOFC cartridges (fuel cell cartridges) 203 and a pressure vessel 205 that accommodates the plurality of SOFC cartridges 203. Note that although FIG. 2 illustrates a cylindrical SOFC cell stack 101, this is not necessarily the case; for example, a flat cell stack may be used. The SOFC module 201 also includes a fuel gas supply pipe 207, a plurality of fuel gas supply branch pipes 207a, a fuel gas discharge pipe 209, and a plurality of fuel gas discharge branch pipes 209a. The SOFC module 201 also includes an oxidizing gas supply pipe (not shown), an oxidizing gas supply branch pipe (not shown), an oxidizing gas exhaust pipe (not shown), and a plurality of oxidizing gas exhaust branch pipes (not shown). Equipped with.

The fuel gas supply pipe 207 is provided outside the pressure vessel 205, is connected to a fuel gas supply section that supplies fuel gas with a predetermined gas composition and a predetermined flow rate in accordance with the amount of power generated by the SOFC module 201, and is connected to a plurality of It is connected to the fuel gas supply branch pipe 207a. This fuel gas supply pipe 207 branches and guides a predetermined flow rate of fuel gas supplied from the above fuel gas supply section to a plurality of fuel gas supply branch pipes 207a. Further, the fuel gas supply branch pipe 207a is connected to the fuel gas supply pipe 207 and to the plurality of SOFC cartridges 203. This fuel gas supply branch pipe 207a guides the fuel gas supplied from the fuel gas supply pipe 207 to the plurality of SOFC cartridges 203 at a substantially equal flow rate, thereby making the power generation performance of the plurality of SOFC cartridges 203 substantially uniform. .

The fuel gas discharge branch pipe 209a is connected to the plurality of SOFC cartridges 203 and also to the fuel gas discharge pipe 209. This fuel gas discharge branch pipe 209a guides the exhaust fuel gas discharged from the SOFC cartridge 203 to the fuel gas discharge pipe 209. Further, the fuel gas exhaust pipe 209 is connected to a plurality of fuel gas exhaust branch pipes 209a, and a part of the fuel gas exhaust pipe 209 is disposed outside the pressure vessel 205. This fuel gas discharge pipe 209 guides the exhaust fuel gas, which is discharged from the fuel gas discharge branch pipe 209a at a substantially uniform flow rate, to the outside of the pressure vessel 205.

The pressure vessel 205 is operated at an internal pressure of 0.1 MPa to approximately 3 MPa and an internal temperature of atmospheric temperature to approximately 550°C, so it is important to have strength and corrosion resistance against oxidizing agents such as oxygen contained in oxidizing gas. Materials in stock will be used. For example, a stainless steel material such as SUS304 is suitable.

Here, in this embodiment, a mode is described in which a plurality of SOFC cartridges 203 are collected and stored in the pressure vessel 205, but the present invention is not limited to this, and for example, the SOFC cartridges 203 are not collected and stored in the pressure vessel 205. It can also be configured to be housed within the container 205.

(Explanation of SOFC cartridge structure and functions of each element)
As shown in FIG. 3, the SOFC cartridge 203 includes a plurality of cell stacks 101, a power generation chamber 215, a fuel gas supply header 217, a fuel gas discharge header 219, an oxidizing gas (air) supply header 221, and an oxidizing gas (air) supply header 221. A gas exhaust header 223 is provided. Further, the SOFC cartridge 203 includes an upper tube sheet 225a, a lower tube sheet 225b, an upper heat insulator 227a, and a lower heat insulator 227b. In this embodiment, the SOFC cartridge 203 has a fuel gas supply header 217, a fuel gas exhaust header 219, an oxidizing gas supply header 221, and an oxidizing gas exhaust header 223 arranged as shown in FIG. Although the structure is such that the fuel gas and the oxidizing gas flow oppositely between the inside and outside of the cell stack 101, this is not necessarily necessary; for example, the fuel gas and the oxidizing gas may flow in parallel between the inside and outside of the cell stack 101. Alternatively, the oxidizing gas may flow in a direction perpendicular to the longitudinal direction of the cell stack 101.

The power generation chamber 215 is an area formed between the upper heat insulator 227a and the lower heat insulator 227b. The power generation chamber 215 is an area where the fuel cells 105 of the cell stack 101 are arranged, and is an area where fuel gas and oxidizing gas are electrochemically reacted to generate electricity. The temperature near the longitudinal center of the cell stack 101 in the power generation chamber 215 is monitored by a temperature measurement unit (temperature sensor, thermocouple, etc.), and is approximately 700°C to 1000°C during steady operation of the SOFC module 201. This creates a high temperature atmosphere.

The fuel gas supply header 217 is an area surrounded by the upper casing 229a and the upper tube plate 225a of the SOFC cartridge 203, and is connected to the fuel gas supply branch pipe 207a by the fuel gas supply hole 231a provided in the upper part of the upper casing 229a. It is communicated with. Further, the plurality of cell stacks 101 are joined by an upper tube plate 225a and a sealing member 237a, and the fuel gas supply header 217 is connected to a fuel gas supply header 217 for receiving fuel gas supplied from the fuel gas supply branch pipe 207a through the fuel gas supply hole 231a. is introduced into the base tubes 103 of the plurality of cell stacks 101 at a substantially uniform flow rate, thereby making the power generation performance of the plurality of cell stacks 101 substantially uniform.

The fuel gas discharge header 219 is a region surrounded by the lower casing 229b and the lower tube plate 225b of the SOFC cartridge 203, and is connected to the fuel gas discharge branch pipe 209a (not shown) by the fuel gas discharge hole 231b provided in the lower casing 229b. It is communicated with. Further, the plurality of cell stacks 101 are joined by a lower tube plate 225b and a sealing member 237b, and the fuel gas exhaust header 219 passes through the inside of the base tube 103 of the plurality of cell stacks 101 to connect to the fuel gas exhaust header 219. The exhaust fuel gas supplied to the fuel gas is collected and guided to the fuel gas exhaust branch pipe 209a via the fuel gas exhaust hole 231b.

The oxidizing gas having a predetermined gas composition and a predetermined flow rate is branched to an oxidizing gas supply branch pipe in accordance with the amount of power generated by the SOFC module 201, and is supplied to the plurality of SOFC cartridges 203. The oxidizing gas supply header 221 is an area surrounded by the lower casing 229b, the lower tube plate 225b, and the lower heat insulating body 227b of the SOFC cartridge 203. , and is communicated with an oxidizing gas supply branch pipe (not shown). This oxidizing gas supply header 221 generates electricity by using a predetermined flow rate of oxidizing gas supplied from an oxidizing gas supply branch pipe (not shown) through an oxidizing gas supply hole 233a through an oxidizing gas supply gap 235a to be described later. It leads to room 215.

The oxidizing gas exhaust header 223 is an area surrounded by the upper casing 229a, the upper tube plate 225a, and the upper insulating body 227a of the SOFC cartridge 203, and is an area surrounded by the oxidizing gas exhaust hole 233b provided on the side surface of the upper casing 229a. , and is communicated with an oxidizing gas discharge branch pipe (not shown). The oxidizing gas exhaust header 223 collects the exhaust oxidizing gas supplied from the power generation chamber 215 to the oxidizing gas exhaust header 223 through an oxidizing gas exhaust gap 235b (described later) through an oxidizing gas exhaust hole 233b. This leads to an oxidizing gas discharge branch pipe (not shown).

The upper tube sheet 225a is arranged between the top plate of the upper casing 229a and the upper insulator 227a so that the upper tube sheet 225a, the top plate of the upper casing 229a, and the upper insulator 227a are approximately parallel to each other. is fixed to the side plate. Further, the upper tube plate 225a has a plurality of holes corresponding to the number of cell stacks 101 included in the SOFC cartridge 203, and the cell stacks 101 are inserted into each of the holes. This upper tube plate 225a airtightly supports one end of the plurality of cell stacks 101 via the sealing member 237a and/or the adhesive member, and also supports the fuel gas supply header 217 and the oxidizing gas discharge header. 223.

The upper insulating body 227a is arranged at the lower end of the upper casing 229a so that the upper insulating body 227a, the top plate of the upper casing 229a, and the upper tube plate 225a are substantially parallel, and is fixed to the side plate of the upper casing 229a. There is. Further, the upper heat insulator 227a is provided with a plurality of holes corresponding to the number of cell stacks 101 included in the SOFC cartridge 203. The diameter of this hole is set larger than the outer diameter of the cell stack 101. The upper insulator 227a includes an oxidizing gas discharge gap 235b formed between the inner surface of this hole and the outer surface of the cell stack 101 inserted through the upper insulator 227a.

The upper heat insulating body 227a partitions the power generation chamber 215 and the oxidizing gas discharge header 223, and prevents the atmosphere around the upper tube sheet 225a from becoming hot, resulting in a decrease in strength and corrosion due to the oxidizing agent contained in the oxidizing gas. Suppress the increase. The upper tube sheet 225a and the like are made of a metal material that is durable at high temperatures, such as Inconel. This prevents thermal deformation. Further, the upper heat insulator 227a guides the exhaust oxidizing gas that has passed through the power generation chamber 215 and been exposed to high temperature to the oxidizing gas exhaust header 223 through the oxidizing gas exhaust gap 235b.

According to this embodiment, the structure of the SOFC cartridge 203 described above allows the fuel gas and the oxidizing gas to flow oppositely between the inside and outside of the cell stack 101. As a result, heat exchange is performed between the exhaust oxidizing gas and the fuel gas supplied to the power generation chamber 215 through the inside of the base tube 103, and the upper tube plate 225a made of metal material is prevented from buckling or the like. The gas is cooled to a temperature that does not cause deformation and is supplied to the oxidizing gas discharge header 223. Further, the temperature of the fuel gas is increased by heat exchange with the exhaust oxidizing gas discharged from the power generation chamber 215, and then the fuel gas is supplied to the power generation chamber 215. As a result, fuel gas that has been preheated to a temperature suitable for power generation can be supplied to the power generation chamber 215 without using a heater or the like.

The lower tube plate 225b is attached to the side plate of the lower casing 229b between the bottom plate of the lower casing 229b and the lower heat insulating body 227b so that the bottom plate of the lower tube plate 225b, the bottom plate of the lower casing 229b, and the lower heat insulating body 227b are approximately parallel to each other. Fixed. Further, the lower tube plate 225b has a plurality of holes corresponding to the number of cell stacks 101 included in the SOFC cartridge 203, and the cell stacks 101 are inserted into each of the holes. This lower tube plate 225b airtightly supports the other end of the plurality of cell stacks 101 via the seal member 237b and/or the adhesive member, and also supports the fuel gas discharge header 219 and the oxidizing gas supply header. 221.

The lower insulator 227b is arranged at the upper end of the lower casing 229b so that the lower insulator 227b, the bottom plate of the lower casing 229b, and the lower tube plate 225b are substantially parallel, and is fixed to the side plate of the lower casing 229b. . Further, the lower heat insulator 227b is provided with a plurality of holes corresponding to the number of cell stacks 101 included in the SOFC cartridge 203. The diameter of this hole is set larger than the outer diameter of the cell stack 101. The lower insulator 227b includes an oxidizing gas supply gap 235a formed between the inner surface of the hole and the outer surface of the cell stack 101 inserted through the lower insulator 227b.

The lower heat insulating body 227b partitions the power generation chamber 215 and the oxidizing gas supply header 221, and prevents the atmosphere around the lower tube sheet 225b from becoming hot, resulting in a decrease in strength and corrosion due to the oxidizing agent contained in the oxidizing gas. Suppress the increase. Although the lower tube sheet 225b and the like are made of a metal material such as Inconel that is durable at high temperatures, it is important to note that if the lower tube sheet 225b and the like are exposed to high temperatures and the temperature difference within the lower tube sheet 225b becomes large, thermal deformation may occur. It is something to prevent. Further, the lower heat insulator 227b guides the oxidizing gas supplied to the oxidizing gas supply header 221 to the power generation chamber 215 through the oxidizing gas supply gap 235a.

According to this embodiment, the structure of the SOFC cartridge 203 described above allows the fuel gas and the oxidizing gas to flow oppositely between the inside and outside of the cell stack 101. As a result, the exhaust fuel gas that has passed through the inside of the base tube 103 and the power generation chamber 215 undergoes heat exchange with the oxidizing gas supplied to the power generation chamber 215, and the lower tube sheet 225b made of metal material is heated. etc. are cooled to a temperature that does not cause deformation such as buckling and are supplied to the fuel gas discharge header 219. Further, the oxidizing gas is heated by heat exchange with the exhaust fuel gas, and is supplied to the power generation chamber 215. As a result, the oxidizing gas heated to a temperature necessary for power generation can be supplied to the power generation chamber 215 without using a heater or the like.

The DC power generated in the power generation chamber 215 is led to the vicinity of the end of the cell stack 101 by the lead membranes 115 made of Ni/YSZ etc. provided in the plurality of fuel cells 105, and then transferred to the current collector rod (non-conductor) of the SOFC cartridge 203. The current is collected through a current collector plate (not shown) and taken out to the outside of each SOFC cartridge 203 . The DC power led out to the outside of the SOFC cartridge 203 by the current collector rod is connected to the generated power of each SOFC cartridge 203 in a predetermined number of series and parallel numbers, and led out to the outside of the SOFC module 201. It is converted into predetermined alternating current power by a power conversion device (such as an inverter) such as a power conditioner (not shown), and is supplied to a power supply destination (for example, a load facility or a power system).

Next, the functions and effects of the fuel cell according to the above embodiment will be explained.

(Test specimen preparation)
A cross-section of a fuel cell was cut out from the cell stack produced according to the above embodiment and used as a test specimen.

The materials for each component of the cell stack are as follows.
Base tube: Calcium stabilized zirconia (Ca addition amount 15 mol%)
Fuel electrode: Ni:YSZ (Y addition amount 8 mol%) = 50:50 (mass ratio), film thickness 120 μm
Solid electrolyte membrane: YSZ (Y addition amount: 8 mol%), film thickness: 80 μm
Interconnector: Sr _0.9 La _0.1 TiO ₃
Air electrode intermediate layer: Sm _0.2 Ce _0.8 O ₂ , film thickness 15 μm
Air electrode conductive layer: La _0.5 Sr _0.25 Ca _0.25 MnO ₃ , film thickness 1000 μm, A/B ratio = 0.95

The co-sintering conditions for the base tube and the interconnector were 1400° C. for 4 hours, and the sintering conditions for the air electrode intermediate layer and the air electrode conductive layer were 1200° C. for 2 hours.

(Compositional analysis of air electrode intermediate layer)
The composition of the air cathode intermediate layer was analyzed using a scanning electron microscope (SEM) "Model SU6600" (manufactured by Hitachi High-Tech) equipped with an elemental analysis device. The elemental analysis device is an EDX (Energy Dispersive X-ray spectrometer).
The test specimen was subjected to energy dispersive X-ray analysis (EDX). The analysis results are shown in Figures 4 and 5. FIG. 4 is a SEM photograph (field size (magnification): 5000 times) of the air electrode intermediate layer portion on the surface of the test piece. FIG. 5 shows the results of semi-quantitative analysis of the air electrode intermediate layer. Since carbon was vapor-deposited, the semi-quantitative value of C was excluded in FIG. 5, and the total of Ce, Sm, O, Mn, Ca, and Sr was set to 100.

In the air cathode intermediate layer in FIG. 4, a black part (threshold value 0-60.frn), a gray part (threshold value 61-195.frn), and a white part (threshold value 196-255.frn) were observed. When the total area of the black, gray, and white parts is taken as 100%, the area ratios of the black, gray, and white parts (average value of each three points analyzed) are 17%, 26%, and 55%, respectively. Met. When the total area of the gray part and the white part was taken as 100% (without pores), the area ratios of the gray part and the white part were 32% and 68%, respectively. The black parts correspond to pores.

According to FIG. 5, Ce, Sm, and O were detected in the white part, but Mn, Ca, and Sr were not detected. The white part was a structure (first structure) mainly containing elements derived from the material of the air electrode intermediate layer. The white part contained 50 atomic % or more of Ce.

In the gray area, Mn, Ca, and Sr were detected in addition to elements (Ce, Sm, and O) originating from the material of the air electrode intermediate layer. Since Ca, Mn, and Sr are not contained in the material of the air electrode intermediate layer, it is considered that the elements contained in the material of the air electrode conductive layer were diffused into the air electrode intermediate layer during co-sintering. The gray part contained elements derived from the material of the air electrode conductive layer, and was a structure (second structure) with a different composition from the first structure. The gray part contained less Ce than the white part, which was less than 50 atomic %. According to FIG. 5, the gray area contained 12-14 at.% of Mn, 1-2.1 at.% of Ca, and 1-2.1 at.% of Sr.

Although not shown in the figure, as a result of surface analysis of the test specimen, it was found that Mn, Ca, and Sr were each diffused from the air electrode conductive layer side to the air electrode intermediate layer.

(electronic conductivity)
FIG. 6 shows the influence of Mn, Ca, and Sr on the electronic conductivity of the test specimen (Source: Matsui et al., J. Mater. Chem. A, 2020, 8, 11867-11873). In the figure, the upper horizontal axis is temperature (° C.), the lower horizontal axis is temperature (1000T ⁻¹ /K ⁻¹ ), and the vertical axis is electronic conductivity (log[σ/Scm ⁻¹ ]). FIG. 7 is a chart summarizing the numerical values read from FIG. 6.

The electronic conductivity of SmMnO ₃ was 0.3 Scm ⁻¹ at 600 °C. This value is higher than the electronic conductivity of SmCeO ₂ without Mn. This suggests that the inclusion of Mn can increase the electronic conductivity of the test specimen.

According to FIG. 6, the inclusion of Ca or Sr increased the electronic conductivity. As the content of Ca increased, the electronic conductivity also increased. When the Ca content was low, the higher the temperature, the higher the electronic conductivity tended to be. It is presumed that Sr also shows the same tendency as Ca. When the amount of Ca or Sr added was the same as the amount of Sm, the electronic conductivity was approximately constant regardless of temperature.

Sm-doped ceria, which is the material of the air electrode intermediate layer, has high ionic conductivity, but low electronic conductivity in the oxidizing atmosphere on the air electrode side. According to FIGS. 4 to 7, it is considered that the second structure (gray area) that may be generated due to the diffusion of Mn, Ca, and/or Sr from the air electrode conductive layer to the air electrode intermediate layer has electronic conductivity. .

The electron path of a composite material containing an electronically conductive material in an electronically insulating material can be considered using percolation theory. According to percolation theory, electronic conductors are thought to aggregate at a certain concentration (threshold) or higher, forming clusters that connect the entire system, thereby developing electronic conductivity. This threshold is called the percolation threshold. Percolation is a theory that focuses on how the target substances are connected within a system and how their characteristics are reflected in the properties of the diameter. A group of connected substances is called a cluster.

FIG. 8 shows the relationship between the proportion of the second structure and the electronic conductivity in the air electrode intermediate layer according to the above embodiment. In FIG. 8, the horizontal axis represents the proportion of the second tissue (vol%), and the horizontal axis represents the electronic conductivity (S/cm). The proportion of the second tissue was calculated by setting the total volume of the first tissue and the second tissue as 100%.

FIG. 8 was estimated from Bruggeman's equation (1).
σ _c is the electronic conductivity of the air electrode intermediate layer, V _f is the volume fraction of the second structure, σ _f is the electronic conductivity of the second structure, and σ _m is the electronic conductivity of the first structure. The electronic conductivity of the first structure was assumed to be 0.001 Scm ⁻¹ . For the electronic conductivity of the second tissue, an approximate equation is created for each specimen data in the graph of FIG. 6, and an interpolated equation is used based on the correlation between the slope of the approximate equation and the Ca content of the EXP coefficient. The electronic conductivity of Sr was made equal to that of Ca.

According to FIG. 8, as the volume ratio of the second tissue increased, the electronic conductivity also increased. When the volume ratio of the second tissue was 20% or more, electronic conductivity greater than a linear effect was exhibited. The slope of the graph was greatest when the volume percentage of the second tissue was 30% or more and 40% or less. According to FIG. 8, the percolation threshold is approximately 33% in volume of the second tissue. The volume ratio can be considered in place of the area ratio. The results in FIG. 8 are consistent with the results in FIGS. 4-7.

In the air electrode intermediate layer, electronic conductivity and ionic conductivity are in a trade-off relationship. As the electronically conductive second structure increases, the proportion of the ionically conductive first structure decreases, and the ionic conductivity of the air electrode intermediate layer decreases. Since ionic conductivity is required for the air electrode intermediate layer, the proportion of the second structure is preferably 60% or less.

FIG. 9 is a schematic cross-sectional view of the air electrode side of the fuel cell according to the above embodiment in which the air electrode intermediate layer includes the second structure.

The air electrode intermediate layer 113a of the fuel cell according to the above embodiment includes pores P, a first structure _S1 , and a second structure _S2 . The pores P can serve as oxygen gas diffusion paths. Since the air electrode intermediate layer 113a is ionic conductive in an oxidizing atmosphere, it functions as an electrolyte. The air electrode intermediate layer 113a including the second structure _S2 has electronic conductivity in addition to ionic conductivity. Therefore, a three-phase interface is formed inside the air electrode intermediate layer 113a including the second structure _S2 . By imparting electronic conductivity to the air cathode intermediate layer 113a, the three-phase interface (electrode reaction field) can be expanded three-dimensionally, so that the reaction resistance can be reduced more than before.

Note that the above embodiment can also be applied to a high temperature steam electrolysis (SOEC) cell that has the same configuration as the fuel cell 105 and produces hydrogen by applying electric power. In that case, the fuel cell 105 in the above embodiment may be replaced with a hydrogen generating section that generates hydrogen without generating electricity.

〈Additional notes〉
The electrochemical cell, its manufacturing method, electrochemical module, and electrochemical cartridge described in the embodiments described above can be understood, for example, as follows.

The electrochemical cell (105) according to the present disclosure has a hydrogen electrode (109), a solid electrolyte membrane (111), and an oxygen electrode (113) stacked in sequence, and the oxygen electrode is arranged in the middle of the oxygen electrode in order from the solid electrolyte membrane side. layer (113a) and an oxygen electrode conductive layer (113b), the oxygen electrode conductive layer is represented by the general formula _ABO3 , the A site is La, Sr and/or Ca, and the B site is Mn. a sintered body of a material containing perovskite oxide, the oxygen electrode intermediate layer being a sintered body of a material containing Sm-doped ceria, and having pores, a first structure, and a second structure; The first structure contains 50 atomic % or more of Ce and does not contain Ca, Sr, and Mn, and the second structure contains an element selected from the group consisting of Ca, Sr, and Mn, and the oxygen The area ratio of the second structure in the cross section of the extreme intermediate layer is 20% or more and 60% or less of the total area of the first structure and the second structure.

The oxygen electrode conductive layer formed by sintering the material containing the perovskite oxide has electronic conductivity. The oxygen electrode intermediate layer formed by sintering a material containing Sm-doped ceria has ionic conductivity. By forming the oxygen electrode into a two-layer structure consisting of the oxygen electrode conductive layer and the oxygen electrode intermediate layer, the interfacial resistance between the solid electrolyte membrane and the oxygen electrode can be reduced.

The first structure, which is mainly composed of an element derived from ceria and which is Sm-doped, has the function of ionic conduction. The second structure containing an element selected from the group consisting of Ca, Sr and Mn is responsible for the function of electronic conduction. When the total cross-sectional area of the oxygen electrode intermediate layer is constant, as the second structure increases, the proportion of the first structure decreases and the ionic conductivity of the oxygen electrode intermediate layer decreases; As the proportion of the structure decreases, the electronic conductivity of the oxygen electrode intermediate layer decreases. The area ratio of the second structure in the cross section of the oxygen electrode intermediate layer is 20% or more and 60% or less, preferably 30% or more and 40% or less, with respect to the total area of the first structure and the second structure in the cross section of the oxygen electrode intermediate layer. By doing so, it is possible to form an electron path while ensuring an ion path within the oxygen electrode intermediate layer.

The electrode reaction field (three-phase interface) is expanded three-dimensionally inside the oxygen electrode intermediate layer by including pores that serve as gas paths, an ionic conductive first structure, and an electronically conductive second structure. do. This reduces the reaction resistance at the interface between the oxygen electrode conductive layer and the oxygen electrode intermediate layer.

In one aspect of the above disclosure, the area ratio of the pores in the cross section of the oxygen electrode intermediate layer may be 20% or more with respect to the total area of the pores, the first structure, and the second structure.

By setting the area ratio of pores within the above range, a three-phase interface can be more reliably formed within the oxygen electrode intermediate layer.

The electrochemical module equipped with the electrochemical cell according to the above disclosure and the electrochemical cartridge equipped with the electrochemical module have improved power generation efficiency than conventional ones.

In the method for manufacturing an electrochemical cell according to the present disclosure, a hydrogen electrode (109), a solid electrolyte membrane (111), and an oxygen electrode (113) are sequentially stacked, and the oxygen electrode is stacked in order from the solid electrolyte membrane side to the oxygen electrode intermediate layer. layer (113a) and an oxygen electrode conductive layer (113b), the oxygen electrode conductive layer is represented by the general formula _ABO3 , the A site is La, Sr and/or Ca, and the B site is Mn. A method for manufacturing an electrochemical cell, wherein the oxygen electrode intermediate layer is a sintered body of a material containing perovskite oxide, and the oxygen electrode intermediate layer is a sintered body of a material containing Sm-doped ceria. Conditions are set such that in a cross section, a structure containing an element selected from the group consisting of Ca, Sr, and Mn is formed in 20% or more and 60% or less of the total area of the cross section of the oxygen electrode intermediate layer excluding pores. and co-sintering the oxygen electrode intermediate layer and the oxygen electrode conductive layer according to the acquired conditions to form the oxygen electrode intermediate layer.

In one aspect of the disclosure, the conditions include any of the material composition of the oxygen electrode conductive layer, the material composition of the oxygen electrode intermediate layer, the sintering temperature of the oxygen electrode intermediate layer and the oxygen electrode conductive layer, and the sintering procedure. It could be.

101 Cell stack (fuel cell)
103 Base tube (base body)
105 Fuel cell (power generation element) (electrochemical cell)
107 Interconnector 109 Fuel electrode (hydrogen electrode)
111 Solid electrolyte membrane 113 Air electrode (oxygen electrode)
113a Air electrode intermediate layer (oxygen electrode intermediate layer)
113b Air electrode conductive layer (oxygen electrode conductive layer)
115 Lead membrane 201 SOFC (fuel cell) module (electrochemical module)
203 SOFC (fuel cell) cartridge (electrochemical cartridge)
205 Pressure vessel 207 Fuel gas supply pipe 207a Fuel gas supply branch pipe 209 Fuel gas discharge pipe 209a Fuel gas discharge branch pipe 215 Power generation chamber 217 Fuel gas supply header 219 Fuel gas discharge header 221 Oxidizing gas supply header 223 Oxidizing gas discharge header 225a Upper tube sheet 225b Lower tube sheet 227a Upper insulator 227b Lower insulator 229a Upper casing 229b Lower casing 231a Fuel gas supply hole 231b Fuel gas discharge hole 233a Oxidizing gas supply hole 233b Oxidizing gas exhaust hole 235a Oxidizing gas supply gap 235b Oxidizing gas discharge gap 237a, 237b Seal member

Claims (7)

A hydrogen electrode, a solid electrolyte membrane, and an oxygen electrode are sequentially stacked,
The oxygen electrode includes an oxygen electrode intermediate layer and an oxygen electrode conductive layer in order from the solid electrolyte membrane side,
The oxygen electrode conductive layer is a sintered body of a material containing a perovskite oxide represented by the general formula ABO ₃ , whose A site is La, Sr and/or Ca, and whose B site is Mn,
The oxygen electrode intermediate layer is a sintered body of a material containing Sm-doped ceria, and has pores, a first structure, and a second structure,
The first structure contains 50 atomic % or more of Ce and does not contain Ca, Sr, and Mn,
The second structure contains an element selected from the group consisting of Ca, Sr and Mn,
An electrochemical cell, wherein the area ratio of the second structure in the cross section of the oxygen electrode intermediate layer is 20% or more and 60% or less with respect to the total area of the first structure and the second structure. The electrochemical cell according to claim 1, wherein the area ratio of the second structure in the cross section of the oxygen electrode intermediate layer is 30% or more and 40% or less with respect to the total area of the first structure and the second structure. The electrochemical cell according to claim 2, wherein the area ratio of the pores in the cross section of the oxygen electrode intermediate layer is 5% or more with respect to the total area of the pores, the first structure, and the second structure. An electrochemical module comprising the electrochemical cell according to any one of claims 1 to 3. An electrochemical cartridge comprising the electrochemical module according to claim 4. A hydrogen electrode, a solid electrolyte membrane, and an oxygen electrode are sequentially stacked,
The oxygen electrode includes an oxygen electrode intermediate layer and an oxygen electrode conductive layer in order from the solid electrolyte membrane side,
The oxygen electrode conductive layer is a sintered body of a material containing a perovskite oxide represented by the general formula ABO ₃ , whose A site is La, Sr and/or Ca, and whose B site is Mn,
The method for manufacturing an electrochemical cell, wherein the oxygen electrode intermediate layer is a sintered body of a material containing Sm-doped ceria,
Conditions under which, in the cross section of the oxygen electrode intermediate layer, a structure containing an element selected from the group consisting of Ca, Sr, and Mn is formed in 20% or more and 60% or less of the total area of the cross section excluding pores. and
A method for manufacturing an electrochemical cell, comprising co-sintering the oxygen electrode intermediate layer and the oxygen electrode conductive layer according to the acquired conditions to form the oxygen electrode intermediate layer. 7. The conditions are any one of the material composition of the oxygen electrode conductive layer, the material composition of the oxygen electrode intermediate layer, the sintering temperature of the oxygen electrode intermediate layer and the oxygen electrode conductive layer, and the sintering procedure. Method of manufacturing the electrochemical cell described.