Electrochemical cell and manufacturing method thereof

Abstract

To provide an electrochemical cell with excellent structural stability and electrochemical cell performance, and a manufacturing method thereof.SOLUTION: An electrochemical cell (1) according to the present invention includes an air electrode (2), a solid electrolyte layer (4), a fuel electrode (6), and a porous layer (8) in this order, the porous layer (8) is made of an alloy containing Cr and Fe, with a porosity of 15 to 50%, and a pore size (average equivalent circle diameter) of 5 to 50 μm. The solid electrolyte layer (4) preferably contains stabilized zirconia containing at least one stabilizing element selected from Sc, Y, Yb, and Ce.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrochemical cell that can be a metal-supported cell type solid oxide fuel cell or solid oxide electrolysis cell, and a method for manufacturing the same.

Background Art

[0002] As solid oxide electrochemical cells, solid oxide fuel cells and solid oxide electrolysis cells are known. Among these, a solid oxide fuel cell includes a solid electrolyte layer containing an oxygen ion-conductive solid oxide, and a fuel electrode and an air electrode disposed opposite to each other on both sides of the electrolyte layer, and is a three-layer power generation cell. A fuel gas such as hydrogen is supplied to the fuel electrode, while an oxidizing gas such as air is supplied to the air electrode to generate direct current power based on an electrochemical reaction.

[0003] In such fuel cells, in recent years, a metal-supported cell type solid oxide fuel cell in which a power generation cell is supported by a metal support part (metal support part) having gas permeability and electrical conductivity through a fuel electrode is known.

[0004] Patent Document 1 discloses a support structure of a metal support cell having a metal support cell in which an electrolyte layer is fixed to a metal support layer via an electrode layer, and a metal frame surrounding the periphery of the metal support cell. The electrolyte layer has a compressive residual stress along the plane direction, the metal frame is sintered and bonded to the electrolyte layer, and the linear expansion coefficient of the metal frame is approximately the same as that of the metal support layer.

[0005] Patent Document 2 discloses a metal support having a plurality of through holes penetrating from the front surface provided with an electrode layer to the back surface, which is formed in a plate shape as a whole, and the through holes include inclined through holes whose central axes are inclined with respect to the thickness direction. Further, an electrochemical element configured by providing an electrode layer, an electrolyte layer, and a counter electrode layer on the front surface of this metal support is disclosed.

[0006] Patent Document 3 discloses an electrochemical cell having a cell unit including a metal support, a solid electrolyte layer having oxygen ion conductivity, a first electrode laminated on one surface side of the solid electrolyte layer, and a second electrode laminated on the other surface side of the solid electrolyte layer, and a bonding layer that bonds the metal support and the first electrode of the cell unit. The bonding layer contains at least one of an alloy containing a metal support constituent element which is at least one metal element constituting the metal support and a first electrode constituent element which is at least one metal element constituting the first electrode, and a metal oxide containing the metal support constituent element and the first electrode constituent element.

[0007] Also, for example, as a method of forming a fuel electrode on a metal support, a firing method (for example, a wet method in which a firing treatment is applied at about 1100 °C), a spray coating method (a thermal spraying method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, a cold spray method, etc.), a PVD method (a sputtering method, a pulsed laser deposition method, etc.), a CVD method, etc. are known.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] When the mechanical strength of the metal support (layer) is high, that of the metal-supported cell type solid oxide electrochemical cell also becomes high. However, considering the air permeability and electrochemical performance from one side to the other side, the lower limit of the porosity is also limited. Furthermore, in order to manufacture an electrochemical cell by a firing method, as a manufacturing material, a metal plate having air permeability in the thickness direction (cross-sectional direction) is used, and a fuel electrode film and a solid electrolyte layer film are placed thereon, and when this stacked body is heat-treated (co-sintered), it may shrink, the porosity decreases and the strength of the metal support (layer) improves, while the air permeability may decrease. From the viewpoints of the performance and structural stability of the obtained metal-supported cell type solid oxide electrochemical cell, it is considered preferable that a metal support (layer) having high strength and good air permeability is formed by co-sintering.

[0010] An object of the present invention is to provide an electrochemical cell of a metal-supported cell type typified by a metal-supported cell type solid oxide fuel cell and a metal-supported cell type solid oxide electrolysis cell, which includes a porous metal layer, a fuel electrode, a solid electrolyte layer, and an air electrode, and has excellent structural stability and electrochemical cell performance, and a method for manufacturing the same.

Means for Solving the Problems

[0011] The present inventors used powder metallurgy technology to subject a composition containing alloy particles containing Cr and Fe and a pore former to pressure molding, and sintered the obtained thin molded body to produce a porous metal plate, which is composed of a connected structure of alloy particle portions and has a porosity of 50 to 80%. When an electrochemical cell is manufactured using this porous metal plate, it was found that the porosity and pore diameter (average of equivalent circle diameters) in the porous layer are in a specific range, and the above problems are solved.

[0012] The present invention is shown below. (1) An electrochemical cell comprising an air electrode, a solid electrolyte layer, a fuel electrode, and a porous layer in this order, wherein the porous layer is made of an alloy containing Cr and Fe, has a porosity of 15 to 50%, and a pore diameter (average of equivalent circle diameters) of 5 to 50 μm, and is characterized by an electrochemical cell. (2) The electrochemical cell according to (1) above, wherein the solid electrolyte layer contains stabilized zirconia containing at least one stabilizing element selected from Sc, Y, Yb, and Ce. (3) A method for manufacturing the electrochemical cell according to (1) above, A first carrier manufacturing step of forming or placing a fuel electrode film on the surface of a porous metal plate having a connecting structure of alloy particle portions containing Cr and Fe and having a porosity of 50 to 80% to produce a first carrier; A second carrier manufacturing step of forming or placing a solid electrolyte layer film on the surface of the fuel electrode film to produce a second carrier; A first sintering step of heat-treating the second carrier to co-sinter the fuel electrode film and the solid electrolyte layer film to produce an integrated product (A) composed of a porous layer, a fuel electrode, and a solid electrolyte layer derived from the porous metal plate; A third carrier manufacturing step of forming or placing an air electrode film on the surface of the solid electrolyte layer to produce a third carrier; An air electrode forming step of heat-treating the third carrier to bond the air electrode film to the solid electrolyte layer, characterized by sequentially comprising an electrochemical cell manufacturing method. (4) After the first sintering step, a dispersion of electrolyte particles containing stabilized zirconia containing at least one stabilizing element selected from Sc, Y, Yb, and Ce and having an average particle diameter of 150 nm or less is applied to the surface of the solid electrolyte layer in the integrated product (A), dried, and further heat-treated to densify the solid electrolyte layer. The electrochemical cell manufacturing method according to (3) above.

Advantages of the Invention

[0013] The electrochemical cell of the present invention is excellent in structural stability and electrochemical cell performance. In particular, the porous layer corresponding to the air-permeable metal support portion does not have a plurality of through-holes of a single flow path inside, but the void portions extend non-linearly to form through-holes of a plurality of paths, and has a structure excellent in gas diffusibility. Therefore, it is considered to bring excellent electrochemical cell performance. According to the method for manufacturing an electrochemical cell of the present invention, since a porous metal plate composed of a connected structure of alloy particle portions containing Cr and Fe and having a porosity of 50 to 80% is used, a suitable porous layer can be efficiently formed, and an electrochemical cell excellent in structural stability and electrochemical cell performance can be obtained. Further, when the solid electrolyte layer is densified using electrolyte particles having an average particle diameter of 150 nm or less, even more excellent electrochemical cell performance can be obtained.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0015] The electrochemical cell of the present invention includes an air electrode, a solid electrolyte layer, a fuel electrode, and a porous layer in this order. The porous layer is made of an alloy containing Cr and Fe, has a porosity of 15 to 50%, and an average pore diameter (equivalent circle diameter) of 5 to 50 μm. FIG. 1 shows an example of the electrochemical cell of the present invention, which is an electrochemical cell 1 including an air electrode 2, a solid electrolyte layer 4, a fuel electrode 6, and a porous layer 8 in this order.

[0016] The constituent material of the air electrode 2 is not particularly limited and can be those included in the air electrodes arranged in known solid oxide fuel cells and solid oxide electrolytic cells, and can be one or more selected from perovskite-type oxides such as (Ba,Sr)(Fe,Co)O 3 , (La,Sr)CoO 3 , (La,Sr)(Fe,Co)O 3 , (Sm,Sr)(Fe,Co)O 3 etc. In the present invention, (Ba,Sr)(Fe,Co)O 3 is preferable. Further, the air electrode 2 may contain a solid electrolyte (described later) that can form the solid electrolyte layer.

[0017] The thickness of the air electrode 2 is preferably 5 to 100 μm.

[0018] The constituent material of the solid electrolyte layer 4 is not particularly limited and can be an electrolyte that conducts oxygen ions and is included in the solid electrolyte layers arranged in known solid oxide fuel cells and solid oxide electrolytic cells, and can be one or more selected from stabilized zirconia (scandia-stabilized zirconia, yttria-stabilized zirconia, scandia-ceria co-stabilized zirconia, scandia-yttria co-stabilized zirconia, ytterbia-stabilized zirconia, etc.) containing at least one stabilizing element selected from Sc, Y, Yb, and Ce, fluorite-type oxides having oxide ion conductivity, etc. In the present invention, from the viewpoints of thermal and chemical stability, the above-mentioned stabilized zirconia is preferable. In this specification, "stabilized zirconia" means zirconia in which a rare earth element oxide is solid-solved, and includes partially stabilized zirconia.

[0019] The thickness of the solid electrolyte layer 4 is preferably 1 to 50 μm.

[0020] The constituent material of the fuel electrode 6 is not particularly limited, and can be those included in known solid oxide fuel cells and fuel electrodes disposed in solid oxide electrolytic cells, and can be one or more selected from electronic conductors such as metallic Ni, Ni alloys, metallic Cu, Cu alloys, metallic Co, Co alloys, etc., and metallic Pt, Pt alloys, etc. In the present invention, metallic Ni and Ni alloys are preferred. Further, the fuel electrode 6 may contain a solid electrolyte (described above) that can constitute the solid electrolyte layer.

[0021] The thickness of the fuel electrode 6 is preferably 5 to 100 μm.

[0022] The porous layer 8 is made of an alloy containing Cr and Fe, and this alloy may further contain Mn, Ni, Ti, Cu, Zr, Si, Al, Mo, etc. in addition to Cr and Fe. The above alloy is preferably a ferritic stainless steel (such as SUS430).

[0023] The porous layer 8 is preferably an alloy skeleton body having a three-dimensional network structure with voids, and does not have a plurality of through-holes with a single flow path inside, and the void portion extends discontinuously from one surface side (for example, the fuel electrode 6 side) to the other surface side (for example, the surface side of the porous layer 8) to form a plurality of through-holes with a plurality of paths.

[0024] The porosity of the porous layer 8 is 15 to 50%, preferably 25 to 50%. Further, the pore diameter (average of the equivalent circle diameter) is 5 to 50 μm, preferably 15 to 50 μm. Since the porosity and pore diameter (average of the equivalent circle diameter) of the porous layer 8 are within the above ranges, the electrochemical cell of the present invention is excellent in structural stability and electrochemical cell performance.

[0025] In the present invention, the above porosity is obtained by photographing the cross-section of the electrochemical cell of the present invention with an optical microscope or the like, binarizing the obtained image, and using image analysis software to obtain the area ratio of the void portion per a predetermined area.

[0026] In the present invention, the above pore diameter (average of equivalent circle diameters) is obtained by photographing a cross-section of the electrochemical cell of the present invention with an optical microscope or the like, setting an arbitrary measurement target portion inside in the obtained image (for example, FIG. 2), measuring the areas of 100 or more void portions therein, calculating the diameters of the perfect circles corresponding to each area, and calculating the average value obtained based on each calculated value.

[0027] The thickness of the porous layer 8 is preferably 100 to 1500 μm.

[0028] The electrochemical cell of the present invention may be housed in a frame body.

[0029] The method for manufacturing an electrochemical cell of the present invention comprises a first carrier manufacturing step of forming or placing a fuel electrode film on the surface of a porous metal plate having a connected structure of alloy particle portions containing Cr and Fe and a porosity of 50 to 80% to produce a first carrier; a second carrier manufacturing step of forming or placing a solid electrolyte layer film on the surface of the fuel electrode film to produce a second carrier; a first sintering step of heat-treating the second carrier to co-sinter the fuel electrode film and the solid electrolyte layer film to produce an integrated product (A) composed of a porous layer, a fuel electrode, and a solid electrolyte layer derived from the porous metal plate; a third carrier manufacturing step of forming or placing an air electrode film on the surface of the solid electrolyte layer to produce a third carrier; and an air electrode forming step of heat-treating the third carrier to bond the air electrode film to the solid electrolyte layer, which are sequentially provided.

[0030] The first carrier manufacturing process according to the present invention is a process of manufacturing a first carrier by forming or placing a fuel electrode film on the surface of a porous metal plate having a connected structure of alloy particle portions containing Cr and Fe and a porosity of 50 to 80%. The porous metal plate is preferably an article having a porosity of 50 to 80% obtained by using powder metallurgy technology with alloy particles containing Cr and Fe as one of the manufacturing raw materials. The alloy particle portion is made of an alloy containing Cr and Fe, and this alloy may further contain Mn, Ni, Ti, Cu, Zr, Si, Al, Mo, etc. in addition to Cr and Fe. The alloy is preferably a ferritic stainless steel (such as SUS430). Although various stabilized zirconias are widely used for the solid electrolyte layer of an electrochemical cell, among stainless steels, the thermal expansion coefficient of ferritic stainless steel is close to that of stabilized zirconia. Therefore, when co-sintering is performed to join a fuel electrode and a solid electrolyte layer containing stabilized zirconia to the porous metal plate in this order, problems such as thermal shock are suppressed.

[0031] The shape of the porous metal plate is not particularly limited and may be either a flat plate or a curved plate. From the viewpoints of the productivity of the electrochemical cell and the structural stability of the formed electrochemical cell, the lower limit of the thickness is usually 0.1 mm, and the upper limit is usually 1.5 mm, preferably 1.2 mm.

[0032] As shown in FIG. 3, which is a typical example, the porous metal plate preferably has a plurality of non-linear communication holes from one surface side to the other surface side and has air permeability. According to FIG. 4, which is an enlarged view, not all of the alloy particle portions have the same size, and alloy particle portions of various different sizes form a connected structure, and alloy particle portions having a maximum diameter of usually 1 μm or more measured from its general shape are connected. The porous metal plate used in the present invention is not limited to this mode, and all of the alloy particle portions may have the same size. Also, the connection state of adjacent alloy particle portions may be either regular or irregular, but as can be seen from these typical example figures, it is usually irregular.

[0033] When co-sintering is performed in the first sintering step, the porosity of the porous metal plate is 50 to 80%, preferably 60 to 80%, and more preferably 70 to 80% because a breathable porous layer having suitable voids can be formed, and an integrated product (A) composed of the porous layer, the fuel electrode, and the solid electrolyte layer can be efficiently formed. The porosity of this porous metal plate can be measured according to JIS Z 2501.

[0034] In the porous metal plate, for example, when the thickness is 0.1 mm or more, the average value of the maximum diameters of the alloy particle portions measured from the outlines of at least 20 alloy particle portions is preferably 1 to 20 μm, more preferably 1 to 10 μm, so that the above porosity can be ensured.

[0035] FIG. 5 is an explanatory diagram showing a method for measuring the maximum diameters of a plurality of connected alloy particle portions 10. It shows a method of photographing the surface or inside of a porous metal plate with an electron microscope, drawing a contour line for each alloy particle portion from the obtained image, and measuring its maximum diameter. FIG. 5 shows that the maximum diameters of four alloy particle portions 10 are r1, r2, r3, and r4, respectively. Based on this measurement method, for example, after measuring the maximum diameters of 20 or more alloy particle portions and calculating the average value, if it is within the range of the above preferred average value, it will have suitable strength for the production of the electrochemical cell obtained by the present invention.

[0036] In the first carrier production step according to the present invention, a fuel electrode film is formed or placed on the surface of the porous metal plate to produce a first carrier. When forming a fuel electrode film on the surface of the porous metal plate, a fuel electrode forming slurry may be applied or printed (such as screen printing) at a predetermined position on the porous metal plate, and then the coating film may be dried. When placing a fuel electrode film on the surface of the porous metal plate, a fuel electrode film obtained by separately applying and drying a fuel electrode forming slurry on the surface of, for example, a release film may be placed at a predetermined position on the porous metal plate. The thickness of the fuel electrode film is not particularly limited, but is preferably 5 to 300 μm.

[0037] The slurry for forming the fuel electrode can contain particles composed of a solid electrolyte such as stabilized zirconia, nickel oxide, metal oxides such as strontium titanate, noble metals such as metallic Pt and Pt alloys, a binder, a dispersion medium, and the like.

[0038] In the second carrier manufacturing process according to the present invention, a solid electrolyte layer film is formed or placed on the surface of the fuel electrode film on the first carrier to manufacture a second carrier. When forming the solid electrolyte layer film on the surface of the fuel electrode film, the slurry for forming the solid electrolyte layer may be applied or printed (such as screen printing) at a predetermined position of the fuel electrode film, and then the coating film may be dried. When placing the solid electrolyte layer film on the surface of the fuel electrode film, a solid electrolyte layer film obtained by separately applying and drying the slurry for forming the solid electrolyte layer on the surface of, for example, a release film or the like may be placed at a predetermined position of the fuel electrode film. The thickness of the solid electrolyte layer film is not particularly limited, but is preferably 1 to 150 μm.

[0039] The slurry for forming the solid electrolyte layer preferably contains particles composed of stabilized zirconia containing at least one stabilizing element selected from Sc, Y, Yb, and Ce as the solid electrolyte. Examples of this stabilized zirconia include scandia-stabilized zirconia, yttria-stabilized zirconia, scandia-ceria co-stabilized zirconia, scandia-yttria co-stabilized zirconia, ytterbia-stabilized zirconia, Gd-doped ceria, Sm-doped ceria, La-doped ceria, and the like. The stabilized zirconia contained in this slurry for forming the solid electrolyte layer can be either only one kind or two or more kinds. The average particle diameter of the stabilized zirconia particles is preferably 0.5 to 20 μm.

[0040] The slurry for forming the solid electrolyte layer can further contain particles composed of metal oxides such as nickel oxide and iron oxide, a binder, a dispersion medium, and the like.

[0041] In the first sintering step according to the present invention, the second carrier is heat-treated, the fuel electrode film and the solid electrolyte layer film are co-sintered, and an integrated product (A) composed of a porous layer derived from a porous metal plate, a fuel electrode, and a solid electrolyte layer is produced. The heat treatment conditions of the second carrier are not particularly limited. The atmosphere can be a hydrogen gas atmosphere, an inert gas atmosphere, a low oxygen partial pressure atmosphere, etc. A reduced pressure condition may also be used. The heat treatment temperature is preferably 900 °C or higher, more preferably 1100 °C or higher, and the upper limit temperature is usually 1400 °C. Further, the second carrier may be heat-treated while being pressed in the thickness direction.

[0042] As described above, by the first sintering step, an integrated product (A) composed of a porous layer, a fuel electrode, and a solid electrolyte layer is obtained. In this porous layer, the porous metal plate shrinks (usually 15 to 25% in the width direction) due to the heat treatment of the second carrier, and the porosity in the porous layer also decreases, so that an integrated product (A) excellent in mechanical strength can be obtained.

[0043] In the method for manufacturing an electrochemical cell of the present invention, the integrated product (A) obtained in the first sintering step can be subjected to the third carrier manufacturing step. However, in order to further densify the solid electrolyte layer in the integrated product (A), after the first sintering step, on the surface of the solid electrolyte layer in the integrated product (A), a dispersion liquid of electrolyte particles containing stabilized zirconia containing at least one stabilizing element selected from Sc, Y, Yb, and Ce and having an average particle diameter of 150 nm or less is applied, dried, and further heat-treated. Hereinafter, this method will be described as the "densification step".

[0044] The constituent material of the electrolyte particles used in the densification process can be one type or two or more types, and the constituent material may be the same as or different from the stabilized zirconia contained in the slurry for forming the solid electrolyte layer that can be used in the above-described second carrier production process. In the present invention, it is preferable to contain at least one selected from (S1) stabilized zirconia particles composed of 3.0 to 10.0 mol% of scandium oxide, 0 to 2.0 mol% of cerium oxide, and 88.0 to 97.0 mol% of zirconium oxide, (S2) stabilized zirconia particles composed of 0.5 to 15.0 mol% of yttrium oxide and 85.0 to 99.5 mol% of zirconium oxide, and (S3) stabilized zirconia particles composed of 0.5 to 15.0 mol% of ytterbium oxide and 85.0 to 99.5 mol% of zirconium oxide.

[0045] The average particle diameter of the above electrolyte particles is preferably 50 to 150 nm, more preferably 60 to 120 nm. This average particle diameter is the volume average particle diameter measured using the laser diffraction method. Specifically, it is the particle diameter at which the cumulative frequency becomes 50% in the particle size distribution based on volume.

[0046] The dispersion medium of the electrolyte particle dispersion is not particularly limited as long as the electrolyte particles are not likely to settle. In the present invention, alcohol is preferable, and ethanol is particularly preferable. The concentration of the electrolyte particles in the dispersion is preferably 0.01 to 20% by mass, more preferably 0.01 to 1% by mass.

[0047] The method of applying the electrolyte particle dispersion to the solid electrolyte layer of the above integrated product (A) is not particularly limited. Examples include a method of spraying or dropping the electrolyte particle dispersion on the surface of the solid electrolyte layer. The electrolyte particle dispersion to be used is not limited to only one type, and a plurality of dispersions having different concentrations of electrolyte particles can also be used. For example, a method of sequentially contacting from a low-concentration electrolyte particle dispersion can be applied.

[0048] The amount of electrolyte particles to be applied to the solid electrolyte layer of the integrated product (A) is appropriately set according to the surface area or thickness of the solid electrolyte layer or the like.

[0049] In the densification step, after applying the electrolyte particle dispersion and drying it, a part of the electrolyte particles fills the voids in the solid electrolyte layer of the integrated product (A), and in this state, it is subjected to heat treatment. The heat treatment conditions are not particularly limited. The atmosphere can be a hydrogen gas atmosphere, an inert gas atmosphere, a low oxygen partial pressure atmosphere, etc. Reduced pressure conditions may also be used. The heat treatment temperature is preferably 900 °C or higher, more preferably 1000 °C or higher, and the upper limit temperature is usually 1300 °C. Further, the integrated product (A) may be heat-treated while being pressed in the thickness direction.

[0050] Next, in the third carrier manufacturing step according to the present invention, an air electrode film is formed or placed on the surface of the solid electrolyte layer to manufacture a third carrier. When forming an air electrode film on the surface of the solid electrolyte layer, an air electrode forming slurry containing an air electrode forming material is applied or printed (such as screen printing) at a predetermined position on the solid electrolyte layer, and then the coating film may be dried. When placing an air electrode film on the surface of the solid electrolyte layer, separately, an air electrode film obtained by applying and drying an air electrode forming slurry on the surface of, for example, a release film or the like, or a molded body made of an air electrode forming material composed of solid components may be placed at a predetermined position on the solid electrolyte layer. The thickness of the air electrode film is not particularly limited, but is preferably 5 to 300 μm.

[0051] As the air electrode forming material, particles composed of perovskite-type oxides such as (Ba,Sr)(Fe,Co)O 3 , (La,Sr)CoO 3 , (La,Sr)(Fe,Co)O 3 , (Sm,Sr)(Fe,Co)O 3 etc. can be used. Particles composed of a solid electrolyte that can constitute the solid electrolyte layer may be included. When using an air electrode forming slurry, a binder, a dispersion medium, etc. can be further included.

[0052] Thereafter, in the air electrode forming step according to the present invention, the third carrier is heat-treated, the air electrode film is joined to the solid electrolyte layer, and an electrochemical cell is obtained. The heat treatment conditions of the third carrier are not particularly limited. The atmosphere can be an oxidizing gas atmosphere such as air or oxygen, or a reduced pressure condition may be used. The heat treatment temperature is preferably 500°C or higher, more preferably 700°C or higher, and the upper limit temperature is usually 1200°C. Further, the third carrier may be heat-treated while being pressed in the thickness direction.

[0053] The electrochemical cell obtained by the present invention can realize an efficient electrochemical reaction as a solid oxide fuel cell or a solid oxide electrolysis cell.

Examples

[0054] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[0055] Example 1 Nickel oxide powder and scandia-stabilized zirconia powder were mixed at a mass ratio of 60:40. The obtained mixed powder, dibutyl phthalate, an acrylic binder, and a mixed solvent of toluene and 2-propanol were mixed using a ball mill to prepare a slurry for forming a fuel electrode. Then, this slurry for forming a fuel electrode was subjected to sheet forming to produce a preliminary sheet for a fuel electrode. Thereafter, this preliminary sheet for a fuel electrode was placed on the surface of a porous metal plate (thickness: 1 mm) made of a connected structure of alloy particle portions made of SUS430, having a porosity of 71% and an average value of the maximum diameter measured from the general shape of the alloy particle portions of 8 μm, and this was heated and pressed to be crimped. Thereafter, in an argon gas atmosphere, degreasing was performed at 850°C for 0.5 hours to obtain a first carrier composed of a porous metal plate and a degreased fuel electrode layer. Next, in order to adjust the thickness of the fuel electrode, a separately prepared slurry was screen-printed on the surface of the above-mentioned degreased fuel electrode layer. The slurry for this screen printing was obtained by mixing nickel oxide powder and scandia-stabilized zirconia powder at a mass ratio of 60:40, and mixing the resulting mixed powder with a mixed solution in which ethyl cellulose was diluted with terpineol using a ball mill. Thereafter, a slurry for forming an electrolyte layer was screen-printed and formed into a film on the surface of the screen-printed fuel electrode to obtain a second carrier. The slurry for forming this electrolyte layer was obtained by mixing scandia-stabilized zirconia powder and a mixed solution in which ethyl cellulose was diluted with terpineol using a ball mill. Next, while pressurizing the second carrier, heat treatment (co-sintering) was performed at 1150 °C for 1 hour in a hydrogen gas atmosphere, and then at 1240 °C and 1260 °C for 3 hours separately in an argon gas atmosphere under reduced pressure conditions, to bond a solid electrolyte layer to the fuel electrode, and an integrated body (hereinafter referred to as "integrated body A1") composed of a porous layer derived from a porous metal plate, a fuel electrode, and a solid electrolyte layer was obtained. Thereafter, on the surface of the solid electrolyte layer in the integrated body A1, a film body for an air electrode (thickness: 0.12 mm) composed of a mixed powder of (Ba,Sr)(Co,Fe)O 3 and (Ce,Gd)O 2 at a mass ratio of 7:3 was placed to produce a third carrier.

[0056] Next, platinum current collector layers with a diameter of 6 mm were formed on the surface of the air electrode film body and the surface of the porous layer in the third carrier, respectively, and two platinum wires were connected from each of these platinum current collector layers. Then, pure hydrogen was passed through the fuel electrode using the pores of the porous layer, and air was passed through the air electrode film body. Heat treatment was performed at 750°C for 1 hour to bond the air electrode film body to the solid electrolyte layer to form an air electrode. Two types of electrochemical cells (an electrochemical cell when the solid electrolyte layer was bonded at 1240°C and an electrochemical cell when the solid electrolyte layer was bonded at 1260°C), both having excellent mechanical strength and a stable layer structure, were obtained. Thereafter, for battery performance evaluation, while maintaining the same gas flow conditions, the open circuit voltage (OCV) was measured at 750°C in each electrochemical cell. Also, the current flowing through the external circuit was measured when the terminal voltage was changed in the range from the open circuit voltage to 0.3V.

[0057] In the electrochemical cell when the solid electrolyte layer was bonded at 1240°C, the cross-section of the porous layer was photographed with an optical microscope, the obtained image was binarized, and the area ratio (porosity) of the voids in the porous layer per a predetermined area was calculated using image analysis software, and it was 26%. Also, the porosity in the electrochemical cell when the solid electrolyte layer was bonded at 1260°C was 16%.

[0058] Furthermore, the cross-section of the porous layer was photographed with an optical microscope, an arbitrary measurement target part was set inside the obtained image, the areas of 100 or more voids were measured therein, and then the diameter of the perfect circle corresponding to each area was calculated, and the average value (pore diameter) was calculated based on each calculated value. As a result, it was 38 μm in the electrochemical cell when the solid electrolyte layer was bonded at 1240°C and 38 μm in the electrochemical cell when the solid electrolyte layer was bonded at 1260°C.

[0059] Example 2 On the surface of the solid electrolyte layer in the integrated product A1 produced in Example 1, the volume-based 50% frequency diameter D measured using a laser diffraction / scattering particle size distribution measuring device "LA-960V2" (model name) manufactured by Horiba, Ltd. 50A dispersion of scandia-stabilized zirconia nanoparticles with a size of 85 nm (dispersion medium: ethanol, nanoparticle concentration: 0.134 mass%) was dropped 5 times (the dropping amount per time: 100 μL). Further, a dispersion of these nanoparticles in ethanol with a nanoparticle concentration of 0.670 mass% was dropped 5 times (the dropping amount per time: 100 μL). Then, the ethanol as the dispersion medium was removed. And then, heat treatment was carried out at 1200 °C for 3 hours in a hydrogen 20% argon balance atmosphere to obtain a densified solid electrolyte layer. Through the above operations, an integrated product (hereinafter referred to as "integrated product A2") with a densified solid electrolyte layer containing nanoparticles was obtained. Thereafter, in the same manner as in the integrated product A1 of Example 1, an air electrode was formed by bonding an air electrode membrane body to the densified solid electrolyte layer of the integrated product A2, and two types of electrochemical cells (an electrochemical cell when the solid electrolyte layer was bonded at 1240 °C, and an electrochemical cell when the solid electrolyte layer was bonded at 1260 °C), both having excellent mechanical strength and a stable layer structure, were obtained. Thereafter, battery performance evaluation was carried out in the same manner as in Example 1.

[0060] The evaluation results of the battery performance (current-voltage characteristics) of the four types of electrochemical cells obtained in the above Examples 1 and 2 are shown in the graphs of FIG. 6 (electrochemical cells of Examples 1 and 2 when the solid electrolyte layer was bonded at 1240 °C) and FIG. 7 (electrochemical cells of Examples 1 and 2 when the solid electrolyte layer was bonded at 1260 °C).

[0061] From FIG. 6, the open circuit voltages (OCV) of the electrochemical cells of Example 1 and Example 2 are 0.875 V and 0.978 V, respectively, and the extracted output densities are 0.367 W / cm 2 and 0.621 W / cm 2 respectively. Compared with the electrochemical cell of Example 1, in the electrochemical cell of Example 2, the circuit voltage at 750 °C was improved by 0.103 V, and the maximum output density was improved by 0.254 W / cm 2 . Furthermore, from FIG. 7, compared with the electrochemical cell of Example 1, in the electrochemical cell of Example 2, the circuit voltage at 750 °C was improved by 0.186 V, and the maximum output density was 0.318 W / cm2 The improvement was confirmed.

Industrial Applicability

[0062] The electrochemical cell of the present invention is suitable as a metal-supported cell type solid oxide fuel cell or a metal-supported cell type solid oxide electrolytic cell in which a solid electrolyte layer contains stabilized zirconia or the like.

Explanation of Signs

[0063] 1: Electrochemical cell 2: Air electrode 4: Solid electrolyte layer 6: Fuel electrode 8: Porous layer 10: Alloy particle part

Claims

1. An electrochemical cell comprising an air electrode, a solid electrolyte layer, a fuel electrode, and a porous layer in this order, wherein the porous layer is made of an alloy containing Cr and Fe, has a porosity of 15 to 50%, and an average pore diameter (average of equivalent circle diameters) of 5 to 50 μm. The electrochemical cell is characterized by this.

2. The electrochemical cell according to claim 1, wherein the solid electrolyte layer contains stabilized zirconia containing at least one stabilizing element selected from Sc, Y, Yb, and Ce.

3. A method for manufacturing the electrochemical cell according to claim 1, On the surface of a porous metal plate composed of a connected structure of alloy particles containing Cr and Fe and having a porosity of 50 to 80%, a fuel electrode film is formed or placed to produce a first carrier. A first carrier production step, On the surface of the fuel electrode film, a solid electrolyte layer film is formed or placed to produce a second carrier. A second carrier production step, The second carrier is heat-treated to co-sinter the fuel electrode film and the solid electrolyte layer film to produce an integrated product (A) composed of a porous layer, a fuel electrode, and a solid electrolyte layer derived from the porous metal plate. A first sintering step, On the surface of the solid electrolyte layer, an air electrode film is formed or placed to produce a third carrier. A third carrier production step, And a method for manufacturing an electrochemical cell, characterized by sequentially comprising a heat treatment of the third carrier and a step of joining the air electrode film to the solid electrolyte layer to form an air electrode.

4. After the first sintering step, on the surface of the solid electrolyte layer in the integrated product (A), a dispersion of electrolyte particles containing stabilized zirconia containing at least one stabilizing element selected from Sc, Y, Yb, and Ce and having an average particle diameter of 150 nm or less is coated, dried, and further heat-treated to densify the solid electrolyte layer. The method for manufacturing an electrochemical cell according to claim 3.

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