JP5116182B1 - Fuel cell structure - Google Patents

Abstract

A structure of a fuel cell of “horizontal stripe type”, wherein the support substrate is difficult to be deformed when the support substrate receives an external force, and between the interconnector embedded in the inner electrode and the inner electrode. Provide a device that can adjust the current path appropriately.
A plurality of power generating element portions A that are electrically connected in series are arranged on a main surface of a flat support substrate 10 in which a gas flow path 11 is formed. A plurality of recesses 12 corresponding to the plurality of power generation element portions A are formed on the main surface of the support substrate 10, respectively. Each recess 12 is a rectangular parallelepiped recess defined by four side walls closed in the circumferential direction and a bottom wall. The fuel electrode 20 of the corresponding power generation element portion A is embedded in each recess 12, and the interconnector 30 is embedded in a rectangular parallelepiped recess 21 b formed on the outer surface of each fuel electrode 20. An intermediate film 35 having a higher conductivity than the interconnector 30 is interposed at the interface between the bottom surface of the interconnector 30 and the fuel electrode 20.
[Selection] Figure 2

Description

  The present invention relates to a fuel cell structure.

  Conventionally, “a porous support substrate having no electron conductivity in which a gas flow path is formed” and “a plurality of locations separated from each other on the surface of the support substrate, a fuel electrode, a solid A plurality of power generation element portions in which an electrolyte and an air electrode are stacked, and one fuel electrode of each of the adjacent power generation element portions provided between one or a plurality of adjacent power generation element portions, There is known a structure of a solid oxide fuel cell provided with “one or more electrical connection parts having electronic conductivity for electrically connecting the other air electrode” (for example, Patent Document 1). 2). Such a configuration is also called a “horizontal stripe type”.

JP-A-8-106916 JP 2008-226789 A

  Hereinafter, attention is focused on the shape of the support substrate. In the “horizontal stripe type” solid oxide fuel cell structure described in Patent Document 1, the support substrate has a cylindrical shape. On the surface (cylindrical surface) of the cylindrical support substrate, a plurality of “annular grooves” for embedding the fuel electrode are respectively formed at a plurality of axial positions (see FIG. 3). Therefore, the outer diameter of the portion where the “annular groove” is formed in the support substrate is small. For this reason, it can be said that this structure is a structure that is easily deformed when an external force in the bending direction or the twisting direction is applied to the support substrate.

  In the structure of the “horizontal stripe type” solid oxide fuel cell described in Patent Document 2, the support substrate has a flat plate shape having a longitudinal direction. A “long groove extending in the longitudinal direction and opened in the longitudinal direction” for embedding a fuel electrode or the like is formed on the main surface (plane) of the flat support substrate (see FIG. 3B). . Therefore, the thickness of the portion where the “long groove” is formed in the support substrate is small.

  In addition, the “long groove” has side walls extending in the longitudinal direction at both ends in the width direction orthogonal to the longitudinal direction, and does not have side walls extending in the width direction at both ends in the longitudinal direction. That is, the “long groove” does not have a side wall closed in the circumferential direction. Therefore, the frame surrounding the “long groove” is not formed on the support substrate. Due to these reasons, this structure can be said to be a structure that is easily deformed particularly when an external force in the twisting direction is applied to the support substrate. From the above, in the structure of the “horizontal stripe” fuel cell, it is desired to suppress the deformation of the support substrate when the support substrate receives an external force.

  Furthermore, as described above, the present inventor forms the inner electrodes in the plurality of first recesses formed in the main surface of the support substrate, and forms the outer electrodes on the outer surfaces of the embedded inner electrodes. In addition, a configuration in which a portion (interconnector) made of a dense material in the corresponding electrical connection portion is embedded in the second recess has been proposed (see, for example, Japanese Patent Application No. 2011-90363).

  In this configuration, each interconnector has a corresponding inner electrode “a portion extending in the plane direction of the support substrate from a portion constituting the power generation element portion (that is, a portion where the solid electrolyte and the outer electrode are laminated)”. Often embedded in the outer surface (see FIGS. 5 and 15 to be described later). In general, current flows so that the path becomes shorter. In this case, the current that has entered the interconnector from the outer surface of each interconnector tends to flow in a direction along the main surface of the support substrate toward the “part constituting the power generation element portion” of the corresponding inner electrode. To do. That is, the current that has entered each interconnector attempts to move to the internal electrode side through the interface between the side surface of the interconnector and the inner electrode (see FIG. 15 described later).

  As described above, in the configuration in which the current passes through the interface between the side surface of the interconnector and the inner electrode, when the fuel cell is operated for a long time, peeling may occur at the interface. This is considered based on the following reasons. That is, normally, in such a “horizontal stripe type” fuel cell, the support substrate is designed to be as thin as possible in order to reduce the size and weight. Due to this, the interconnector embedded in the outer surface of the inner electrode is also made as thin as possible. That is, each interconnector has a thin plate shape (a shape having a large planar shape and a small thickness), and has an extremely small side surface area. Therefore, when the current passes through the interface between the side surface of the interconnector and the inner electrode, the current is excessively concentrated and a lot of Joule heat is likely to be generated. This Joule heat generates a local temperature distribution in the vicinity of the interface, and as a result, it is considered that peeling is likely to occur at the interface.

  In order to cope with such a problem, the current path between the interconnector and the inner electrode may be positively controlled. Specifically, in the above case, it is important to control the current path so that the current passes through “the bottom surface of the interconnector having a large area” instead of “the side surface of the interconnector having a small area”.

  The present invention relates to a structure of a “horizontal stripe type” fuel cell, wherein the support substrate is difficult to deform when the support substrate receives an external force, and between the interconnector embedded in the inner electrode and the inner electrode. An object of the present invention is to provide a device that can appropriately adjust the current path.

  A structure of a fuel cell according to the present invention includes a flat porous support substrate having an electrical insulating property in which a gas flow path is formed, and a plurality of spaced apart from each other on a main surface of the flat support substrate. Provided in each of the locations, “a plurality of power generation element portions in which at least an inner electrode, a solid electrolyte, and an outer electrode are stacked” and one set or a plurality of sets of adjacent power generation element portions are provided and adjacent to each other. One or a plurality of electrical connection portions having electronic conductivity for electrically connecting one inner electrode and the other outer electrode of the power generation element portion. That is, this structure is a “horizontal stripe type” fuel cell structure.

  The structure of the fuel cell structure according to the present invention is characterized in that each of the electrical connection portions is a first portion (interconnector) made of a dense material, and is connected to the first portion and made of a porous material. And a bottom wall made of the material of the support substrate and a circumference made of the material of the support substrate over the entire circumference. A first recess having a side wall closed in a direction is formed, and the inner electrode (the whole) of the corresponding power generation element portion is embedded in each of the first recesses. In the second concave portion formed on the side surface, the first portion (the whole or a part thereof) of the corresponding electrical connection portion is embedded.

  Thus, in the “horizontal stripe type” fuel cell structure according to the present invention, each first recess for embedding the inner electrode has a side wall closed in the circumferential direction. In other words, a frame surrounding each first recess is formed on the support substrate. Therefore, it can be said that this structure is a structure that is not easily deformed when the support substrate receives an external force.

  In addition, the first portion of the electrical connection portion is embedded in a second recess formed on the outer surface of the inner electrode. Therefore, compared with the case where the configuration in which the first portion of the electrical connection portion is laminated (contacted) on the outer plane of the internal electrode embedded in the first recess is employed, the internal electrode and the electrical connection portion The area of the interface can be increased. Therefore, the electronic conductivity between the internal electrode and the electrical connection portion can be increased. As a result, the power generation output of the fuel cell can be increased.

  In this case, each of the second recesses in which the corresponding first portion of the electrical connection portion is embedded includes a bottom wall made of the material of the inner electrode, and a circumferential direction made of the material of the inner electrode over the entire circumference. It is preferable to have closed side walls. According to this, the area of the interface between the internal electrode and the electrical connection portion can be further increased. Therefore, the electronic conductivity between the internal electrode and the electrical connection portion can be further increased.

  Here, the planar shape of the first recess (the shape when viewed from the direction perpendicular to the main surface of the support substrate) is, for example, a rectangle, a square, a circle, an ellipse, or an oval. Further, it is preferable that the support substrate has a longitudinal direction, and the plurality of first recesses are arranged at predetermined intervals along the longitudinal direction. The inner electrode and the outer electrode may be an air electrode and a fuel electrode, respectively, or may be a fuel electrode and an air electrode.

  Further, the structure of the fuel cell structure according to the present invention is characterized in that the electrical conductivity of the embedded first electrical connection portion (interconnector) and a part of the interface between the inner electrodes is higher than that of the interconnector. In some cases, a member having a larger conductivity, a member having a lower conductivity than the interconnector, or a gap is provided. According to this, the region through which current passes in the interface between the interconnector and the inner electrode is positively adjusted, and the current path between the interconnector and the inner electrode can be adjusted appropriately.

  Specifically, when each of the second recesses has a bottom wall made of the material of the inner electrode and a side wall made of the material of the inner electrode, and the interconnector has a thin plate shape, A member having higher conductivity than the interconnector can be interposed only at the interface between the bottom surface and the inner electrode. Alternatively, a member having a lower conductivity than the interconnector can be interposed only at the interface between the side surface of the interconnector and the inner electrode. Alternatively, a gap may be provided only at the interface between the side surface of the interconnector and the inner electrode.

  According to any of these, the current path can be controlled so that the current passes through “the bottom surface of the interconnector having a large area” instead of “the side surface of the interconnector having a small area”. As a result, the occurrence of peeling at the interface due to the generation of Joule heat when the current passes through the interface between the “side surface of the interconnector having a small area” and the inner electrode can be suppressed.

1 is a perspective view showing a structure of a fuel cell according to the present invention. It is sectional drawing corresponding to the 2-2 line of the structure of the fuel cell shown in FIG. It is the top view which showed the state of the fuel electrode and interconnector which were embed | buried under the recessed part of the support substrate shown in FIG. It is a figure for demonstrating the operating state of the structure of the fuel cell shown in FIG. It is a figure for demonstrating the flow of the electric current in the operating state of the structure of the fuel cell shown in FIG. It is a perspective view which shows the support substrate shown in FIG. FIG. 3 is a cross-sectional view corresponding to FIG. 2 in a first stage in the manufacturing process of the fuel cell structure shown in FIG. 1. FIG. 3 is a cross-sectional view corresponding to FIG. 2 in a second stage in the manufacturing process of the fuel cell structure shown in FIG. 1. FIG. 3 is a cross-sectional view corresponding to FIG. 2 in a third stage in the manufacturing process of the fuel cell structure shown in FIG. 1. FIG. 4 is a cross-sectional view corresponding to FIG. 2 in a fourth stage in the manufacturing process of the fuel cell structure shown in FIG. 1. FIG. 6 is a cross-sectional view corresponding to FIG. 2 in a fifth stage in the manufacturing process of the fuel cell structure shown in FIG. 1. FIG. 7 is a cross-sectional view corresponding to FIG. 2 in a sixth stage in the manufacturing process of the fuel cell structure shown in FIG. 1. FIG. 8 is a cross-sectional view corresponding to FIG. 2 in a seventh stage in the manufacturing process of the fuel cell structure shown in FIG. 1. FIG. 8 is a cross-sectional view corresponding to FIG. 2 in an eighth stage in the manufacturing process of the fuel cell structure shown in FIG. 1. In the comparative example, it is the schematic diagram which showed the path | route at the time of an electric current passing between an interconnector and an inner side electrode. In the structure of the fuel cell according to the present invention, it is a schematic diagram showing a path when current passes between an interconnector and an inner electrode. In the 1st modification of the structure of the fuel cell which concerns on this invention, it is the schematic diagram which showed the path | route at the time of an electric current passing between an interconnector and an inner side electrode. In the 2nd modification of the structure of the fuel cell which concerns on this invention, it is the schematic diagram which showed the path | route at the time of an electric current passing between an interconnector and an inner side electrode. It is sectional drawing corresponding to FIG. 2 of the 3rd modification of the structure of the fuel cell concerning this invention. It is sectional drawing corresponding to FIG. 2 of the 4th modification of the structure of the fuel cell concerning this invention. FIG. 10 is a cross-sectional view corresponding to FIG. 2 of a fifth modification of the fuel cell structure according to the present invention. FIG. 10 is a cross-sectional view corresponding to FIG. 3 of a sixth modification of the fuel cell structure according to the present invention.

(Constitution)
FIG. 1 shows a structure of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. This SOFC structure is electrically connected in series to the upper and lower surfaces (main surfaces (planes) on both sides parallel to each other) of the flat support substrate 10 having a longitudinal direction (x-axis direction). (In this example, four) power generation element portions A having the same shape are arranged at a predetermined interval in the longitudinal direction and have a so-called “horizontal stripe type” configuration.

  The shape of the entire SOFC structure as viewed from above is, for example, a rectangle having a length of 50 to 500 mm in the longitudinal direction and a length in the width direction (y-axis direction) perpendicular to the longitudinal direction of 10 to 100 mm. is there. The total thickness of the SOFC structure is 1 to 5 mm. The entire SOFC structure has a vertically symmetrical shape with respect to a plane passing through the center in the thickness direction and parallel to the main surface of the support substrate 10. Hereinafter, in addition to FIG. 1, the details of the SOFC structure will be described with reference to FIG. 2, which is a partial cross-sectional view of the SOFC structure corresponding to line 2-2 shown in FIG. 1. FIG. 2 is a partial cross-sectional view showing a configuration (part of) each of a typical pair of adjacent power generation element portions A and A and a configuration between the power generation element portions A and A. The configuration between the other power generation element portions A and A in other sets is the same as the configuration shown in FIG.

  The support substrate 10 is a flat plate-like fired body made of a porous material having no electronic conductivity. As shown in FIG. 6 to be described later, a plurality of (six in this example) fuel gas passages 11 (through holes) extending in the longitudinal direction are provided in the support substrate 10 at predetermined intervals in the width direction. Is formed. In this example, each recess 12 includes a bottom wall made of the material of the support substrate 10 and side walls closed in the circumferential direction made of the material of the support substrate 10 over the entire circumference (two side walls along the longitudinal direction and the width direction). A rectangular parallelepiped depression defined by two side walls). Each recess 12 has a length (dimension in the x-axis direction) of 5 to 50 mm, a width (dimension in the y-axis direction) of 2 to 95 mm, and a depth (dimension in the z-axis direction) of 0.03 to 1. .5 mm.

The support substrate 10 includes, for example, MgO (magnesium oxide), MgAl ₂ O ₄ (magnesia alumina spinel), CSZ (calcia stabilized zirconia), NiO (nickel oxide), YSZ (yttria stabilized zirconia), Y ₂ O ₃ ( It is composed of one or more materials selected from yttria.

  The support substrate 10 may be configured to include “transition metal oxide or transition metal” and insulating ceramics. As the “transition metal oxide or transition metal”, NiO (nickel oxide) or Ni (nickel) is suitable. The transition metal can function as a catalyst for promoting a reforming reaction of the fuel gas (hydrocarbon-based gas reforming catalyst).

Further, as the insulating ceramic, MgO (magnesium oxide) or “mixture of MgAl ₂ O ₄ (magnesia alumina spinel) and MgO (magnesium oxide)” is preferable. Further, CSZ (calcia stabilized zirconia), YSZ (8YSZ) (yttria stabilized zirconia), Y ₂ O ₃ (yttria) may be used as the insulating ceramic.

  As described above, since the support substrate 10 contains “transition metal oxide or transition metal”, the gas containing the residual gas component before the reforming is supplied to the fuel through the numerous pores inside the porous support substrate 10. In the process of being supplied from the gas flow path 11 to the fuel electrode, the catalytic action can promote the reforming of the residual gas component before the reforming. In addition, the insulating property of the support substrate 10 can be ensured by the support substrate 10 containing insulating ceramics. As a result, insulation between adjacent fuel electrodes can be ensured.

  The thickness of the support substrate 10 is 1 to 5 mm. Hereinafter, only the configuration on the upper surface side of the support substrate 10 will be described in consideration of the fact that the shape of the structure is vertically symmetrical. The same applies to the configuration of the lower surface side of the support substrate 10.

  As shown in FIGS. 2 and 3, the entire fuel electrode current collector 21 is embedded (filled) in each recess 12 formed in the upper surface (upper main surface) of the support substrate 10. Therefore, each fuel electrode current collector 21 has a rectangular parallelepiped shape. A recess 21 a is formed on the upper surface (outer surface) of each fuel electrode current collector 21. Each recess 21a has a rectangular parallelepiped shape defined by a bottom wall made of the material of the fuel electrode current collector 21 and side walls closed in the circumferential direction (two side walls along the longitudinal direction and two side walls along the width direction). It is a depression. Of the side walls closed in the circumferential direction, two side walls along the longitudinal direction are made of the material of the support substrate 10, and two side walls along the width direction are made of the material of the fuel electrode current collector 21.

  The entire anode active portion 22 is embedded (filled) in each recess 21a. Accordingly, each fuel electrode active portion 22 has a rectangular parallelepiped shape. A fuel electrode 20 is configured by the fuel electrode current collector 21 and the fuel electrode active unit 22. The fuel electrode 20 (fuel electrode current collector 21 + fuel electrode active part 22) is a fired body made of a porous material having electron conductivity. The two side surfaces and the bottom surface along the width direction of each anode active portion 22 are in contact with the anode current collecting portion 21 in the recess 21a.

  A recess 21b is formed in a portion of the upper surface (outer surface) of each fuel electrode current collector 21 excluding the recess 21a. Each recess 21b has a rectangular parallelepiped shape defined by a bottom wall made of the material of the fuel electrode current collector 21 and side walls closed in the circumferential direction (two side walls along the longitudinal direction and two side walls along the width direction). It is a depression. Of the side walls closed in the circumferential direction, two side walls along the longitudinal direction are made of the material of the support substrate 10, and two side walls along the width direction are made of the material of the fuel electrode current collector 21. Each recess 21b has a length (dimension in the x-axis direction) of 0.2 to 10 mm, a width (dimension in the y-axis direction) of 2 to 95 mm, and a depth (dimension in the z-axis direction) of 10 to 100 μm. It is.

  An interconnector 30 is embedded (filled) in each recess 21b. Accordingly, each interconnector 30 has a (very thin) rectangular parallelepiped shape. The interconnector 30 is a fired body made of a dense material having electronic conductivity. The two side surfaces and the bottom surface along the width direction of each interconnector 30 are in contact with the fuel electrode current collector 21 in the recess 21b.

  The upper surface (outer surface) of the fuel electrode 20 (the fuel electrode current collector 21 and the fuel electrode active unit 22), the upper surface (outer surface) of the interconnector 30, and the main surface of the support substrate 10 form one plane (recessed portion). The same plane as the main surface of the support substrate 10 when 12 is not formed) is formed. That is, no step is formed between the upper surface of the fuel electrode 20, the upper surface of the interconnector 30, and the main surface of the support substrate 10.

The fuel electrode active part 22 may be composed of, for example, NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia). Or you may comprise from NiO (nickel oxide) and GDC (gadolinium dope ceria). The fuel electrode current collector 21 can be composed of, for example, NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia). Alternatively, it may be composed of NiO (nickel oxide) and Y ₂ O ₃ (yttria), or may be composed of NiO (nickel oxide) and CSZ (calcia stabilized zirconia). The thickness of the anode active portion 22 is 5 to 30 μm, and the thickness of the anode current collecting portion 21 (that is, the depth of the recess 12) is 50 to 500 μm.

  As described above, the fuel electrode current collector 21 includes a substance having electronic conductivity. The fuel electrode active part 22 includes a substance having electron conductivity and a substance having oxidative ion (oxygen ion) conductivity. The “volume ratio of the substance having oxidative ion conductivity relative to the total volume excluding the pore portion” in the anode active portion 22 is “the oxidative ion conductivity relative to the entire volume excluding the pore portion” in the anode current collecting portion 21. Greater than the volume fraction of the substance having

The interconnector 30 can be composed of, for example, LaCrO ₃ (lanthanum chromite). Alternatively, it may be composed of (Sr, La) TiO ₃ (strontium titanate). The thickness of the interconnector 30 is 10 to 100 μm.

Of the interface between the interconnector 30 and the fuel electrode 20 (current collector 21), the intermediate film 35 is interposed only at the interface between the bottom surface of the interconnector 30 and the fuel electrode 20 (current collector 21). Yes. The intermediate film 35 is composed of, for example, a mixed powder of NiO and Y ₂ O ₃ (yttria), a mixed powder of NiO and GDC (gadolinia doped ceria), and a mixed powder of NiO and LaCrO ₃ .

  The conductivity of the fuel electrode current collector 21 is 100 to 1000 S / cm, the conductivity of the interconnector 30 is 0.5 to 30 S / cm, and the conductivity of the intermediate film 35 is 200 to 2000 S / cm. That is, the conductivity of the intermediate film 35 is greater than the conductivity of the interconnector 30. The conductivity of the intermediate film 35 may be larger or smaller than the conductivity of the fuel electrode current collector 21, but is preferably larger than the conductivity of the fuel electrode current collector 21. The thickness of the intermediate film 35 is 2 to 20 μm. The intermediate film 35 may exist over the entire bottom surface of the interconnector 30 or may exist only over a portion of the bottom surface of the interconnector 30.

  The entire surface excluding the central portion in the longitudinal direction of each portion where the plurality of interconnectors 30 are formed on the outer peripheral surface extending in the longitudinal direction of the support substrate 10 in a state where the fuel electrode 20 and the interconnector 30 are embedded in the respective recesses 12. Is covered with a solid electrolyte membrane 40. The solid electrolyte membrane 40 is a fired body made of a dense material having ionic conductivity and not electron conductivity. The solid electrolyte membrane 40 can be made of, for example, YSZ (8YSZ) (yttria stabilized zirconia). Or you may comprise from LSGM (lantern gallate). The thickness of the solid electrolyte membrane 40 is 3 to 50 μm.

  That is, the entire outer peripheral surface extending in the longitudinal direction of the support substrate 10 in a state where the fuel electrode 20 is embedded in each recess 12 is covered with a dense layer composed of the interconnector 30 and the solid electrolyte membrane 40. This dense layer exhibits a gas sealing function that prevents mixing of the fuel gas flowing in the space inside the dense layer and the air flowing in the space outside the dense layer.

  As shown in FIG. 2, in this example, the solid electrolyte membrane 40 covers the upper surface of the fuel electrode 20, both end portions in the longitudinal direction on the upper surface of the interconnector 30, and the main surface of the support substrate 10. Here, as described above, no step is formed between the upper surface of the fuel electrode 20, the upper surface of the interconnector 30, and the main surface of the support substrate 10. Therefore, the solid electrolyte membrane 40 is flattened. As a result, compared with the case where a step is formed in the solid electrolyte membrane 40, the generation of cracks in the solid electrolyte membrane 40 due to stress concentration can be suppressed, and the gas sealing function of the solid electrolyte membrane 40 is reduced. Can be suppressed.

  An air electrode 60 is formed on the upper surface of a portion in contact with each fuel electrode active part 22 in the solid electrolyte membrane 40 via a reaction preventing film 50. The reaction preventing film 50 is a fired body made of a dense material, and the air electrode 60 is a fired body made of a porous material having electron conductivity. The shape of the reaction preventing film 50 and the air electrode 60 viewed from above is substantially the same rectangle as the fuel electrode active part 22.

The reaction preventing film 50 can be made of, for example, GDC = (Ce, Gd) O ₂ (gadolinium-doped ceria). The thickness of the reaction preventing film 50 is 3 to 50 μm. The air electrode 60 can be made of, for example, LSCF = (La, Sr) (Co, Fe) O ₃ (lanthanum strontium cobalt ferrite). Alternatively, from LSF = (La, Sr) FeO ₃ (lanthanum strontium ferrite), LNF = La (Ni, Fe) O ₃ (lanthanum nickel ferrite), LSC = (La, Sr) CoO ₃ (lanthanum strontium cobaltite), etc. It may be configured. Further, the air electrode 60 may be configured by two layers of a first layer (inner layer) made of LSCF and a second layer (outer layer) made of LSC. The thickness of the air electrode 60 is 10 to 100 μm.

  The reaction preventing film 50 is interposed because the YSZ in the solid electrolyte film 40 and the Sr in the air electrode 60 react with each other in the SOFC during the production or operation of the SOFC, and the solid electrolyte film 40 and the air electrode. This is to suppress the occurrence of a phenomenon in which a reaction layer having a large electric resistance is formed at the interface with the film.

  Here, the laminated body formed by laminating the fuel electrode 20, the solid electrolyte membrane 40, the reaction preventing membrane 50, and the air electrode 60 corresponds to the “power generation element portion A” (see FIG. 2). In other words, a plurality (four in this example) of power generating element portions A are arranged on the upper surface of the support substrate 10 at a predetermined interval in the longitudinal direction.

  For each pair of adjacent power generation element portions A and A, the air electrode 60 of one power generation element portion A (on the left side in FIG. 2) and the interconnector of the other power generation element portion A (on the right side in FIG. 2). The air electrode current collecting film 70 is formed on the upper surfaces of the air electrode 60, the solid electrolyte film 40, and the interconnector 30. The air electrode current collector film 70 is a fired body made of a porous material having electron conductivity. The shape of the air electrode current collector film 70 as viewed from above is a rectangle.

The air electrode current collector film 70 can be made of, for example, LSCF = (La, Sr) (Co, Fe) O ₃ (lanthanum strontium cobalt ferrite). Alternatively, LSC = (La, Sr) CoO ₃ (lanthanum strontium cobaltite) may be used. Or you may comprise from Ag (silver) and Ag-Pd (silver palladium alloy). The thickness of the air electrode current collector film 70 is 50 to 500 μm.

  By forming each air electrode current collecting film 70 in this way, for each pair of adjacent power generation element portions A and A, the air electrode 60 of one power generation element portion A (on the left side in FIG. 2), The other fuel electrode 20 (particularly, the fuel electrode current collector 21) of the power generating element part A (on the right side in FIG. 2) passes through the “air electrode current collector film 70 and interconnector 30” having electronic conductivity. Are electrically connected. As a result, a plurality (four in this example) of power generation element portions A arranged on the upper surface of the support substrate 10 are electrically connected in series. Here, the “air electrode current collector film 70 and the interconnector 30” having electronic conductivity correspond to the “electrical connection part”.

  The interconnector 30 corresponds to the “first portion made of a dense material” in the “electrical connection portion” and has a porosity of 10% or less. The air electrode current collecting film 70 corresponds to the “second portion made of a porous material” in the “electrical connection portion”, and has a porosity of 20 to 60%. The porosity of the intermediate film 35 is 20 to 60%.

As described above, as shown in FIG. 4, the fuel gas (hydrogen gas or the like) flows through the fuel gas flow path 11 of the support substrate 10 with respect to the “horizontal stripe” SOFC structure described above. By exposing the upper and lower surfaces (particularly, each air electrode current collecting film 70) to “gas containing oxygen” (air or the like) (or flowing a gas containing oxygen along the upper and lower surfaces of the support substrate 10), the solid electrolyte An electromotive force is generated by an oxygen partial pressure difference generated between both side surfaces of the film 40. Furthermore, when this structure is connected to an external load, chemical reactions shown in the following formulas (1) and (2) occur, and current flows (power generation state).
(1/2) · O ₂ + 2e ⁻ → O ²⁻ (where: air electrode 60) (1)
H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (in the fuel electrode 20) (2)

  In the power generation state, as shown in FIG. 5, a current flows as indicated by an arrow in each pair of adjacent power generation element portions A and A. As a result, as shown in FIG. 4, the SOFC structure as a whole (specifically, the interconnector 30 of the power generating element part A on the frontmost side in FIG. 4 and the air electrode of the power generating element part A on the innermost side in FIG. The power is extracted (via 60).

(Production method)
Next, an example of a manufacturing method of the “horizontal stripe type” SOFC structure shown in FIG. 1 will be briefly described with reference to FIGS. 6 to 14, “g” at the end of the reference numeral of each member represents that the member is “before firing”.

  First, a support substrate molded body 10g having the shape shown in FIG. 6 is produced. The molded body 10g of the support substrate is manufactured by using a method such as extrusion molding or cutting using a slurry obtained by adding a binder or the like to the material of the support substrate 10 (for example, CSZ). obtain. Hereinafter, the description will be continued with reference to FIGS. 7 to 14 showing partial cross sections corresponding to line 7-7 shown in FIG. 6.

  When the support substrate molded body 10g is manufactured as shown in FIG. 7, the fuel electrode current collector is then placed in each recess formed in the upper and lower surfaces of the support substrate molded body 10g as shown in FIG. Each of the molded parts 21g is embedded and formed. Next, as shown in FIG. 9, a molded body 22g of the fuel electrode active portion is embedded and formed in each recess formed in the outer surface of the molded body 21g of each fuel electrode current collector. The molded body 21g of each fuel electrode current collector and each of the fuel electrode active parts 22g use, for example, a slurry obtained by adding a binder or the like to the powder of the material of the fuel electrode 20 (for example, Ni and YSZ), It is embedded and formed using printing methods.

Subsequently, as shown in FIG. 10, in each concave portion formed in “the portion excluding the portion where the molded body 22 g of the fuel electrode active portion is embedded” on the outer surface of the molded body 21 g of each fuel electrode current collector. First, the intermediate film molded body 35g is embedded and formed, and then the interconnector molded body 30g is embedded and formed. The molded body 35g of each intermediate film is embedded, for example, using a slurry obtained by adding a binder or the like to the material of the intermediate film 35 (mixed powder of NiO and Y ₂ O ₃ ) using a printing method or the like. It is formed. The molded body 30g of each interconnector is embedded and formed by using a slurry obtained by adding a binder or the like to the material of the interconnector 30 (for example, LaCrO ₃ ), using a printing method or the like. .

  Next, as shown in FIG. 11, the outer periphery extending in the longitudinal direction of the molded body 10g of the support substrate in a state in which the molded body (21g + 22g) of the plurality of fuel electrodes and the molded body 30g of the plurality of interconnectors are respectively embedded and formed. A solid electrolyte membrane molded film 40g is formed on the entire surface excluding the central portion in the longitudinal direction of each portion where the plurality of interconnector molded bodies 30g are formed. The molded membrane 40g of the solid electrolyte membrane is formed using, for example, a printing method, a dipping method, etc., using a slurry obtained by adding a binder or the like to the powder of the material of the solid electrolyte membrane 40 (for example, YSZ). The

  Next, as shown in FIG. 12, a reaction prevention film molding film 50g is formed on the outer surface of the solid electrolyte membrane molding body 40g in contact with the fuel electrode molding body 22g. The molded film 50g of each reaction preventing film is formed using a slurry obtained by adding a binder or the like to the powder of the material (for example, GDC) of the reaction preventing film 50, using a printing method or the like.

  Then, 10 g of the support substrate molded body in which various molded films are thus formed is fired in air at 1500 ° C. for 3 hours. As a result, a structure in which the air electrode 60 and the air electrode current collector film 70 are not formed in the SOFC structure shown in FIG. 1 is obtained.

  Next, as shown in FIG. 13, an air electrode forming film 60 g is formed on the outer surface of each reaction preventing film 50. The molded film 60g of each air electrode is formed using a slurry obtained by adding a binder or the like to the powder of the material of the air electrode 60 (for example, LSCF), using a printing method or the like.

  Next, as shown in FIG. 14, for each pair of adjacent power generation element portions, air is formed so as to straddle the air electrode molding film 60 g of one power generation element portion and the interconnector 30 of the other power generation element portion. On the outer surface of the electrode forming film 60g, the solid electrolyte film 40, and the interconnector 30, a formed film 70g of the air electrode current collecting film is formed. The forming film 70g of each air electrode current collector film is obtained by using a slurry obtained by adding a binder or the like to the powder of the material of the air electrode current collector film 70 (for example, LSCF), using a printing method or the like. It is formed.

  Then, the support substrate 10 in which the molded films 60g and 70g are thus formed is baked in air at 1050 ° C. for 3 hours. As a result, the SOFC structure shown in FIG. 1 is obtained. At this point, the Ni component in the fuel electrode 20 (current collector 21 + active portion 22) is NiO due to firing in an oxygen-containing atmosphere. Therefore, in order to acquire the conductivity of the fuel electrode 20 (the current collector 21 + the active part 22), thereafter, a reducing fuel gas is flowed from the support substrate 10 side, and NiO is heated at 800 to 1000 ° C. for 1 to 10 hours. Reduction processing is performed over the entire area. This reduction process may be performed during power generation. The example of the method for manufacturing the SOFC structure shown in FIG. 1 has been described above.

(Action / Effect)
As described above, in the “horizontal stripe type” SOFC structure according to the embodiment of the present invention, the plurality of recesses 12 formed in the upper and lower surfaces of the support substrate 10 for embedding the fuel electrode 20 are embedded. Each has a side wall closed in the circumferential direction made of the material of the support substrate 10 over the entire circumference. In other words, the support body 10 is formed with a frame surrounding each recess 12. Therefore, this structure is not easily deformed when the support substrate 10 receives an external force.

  Further, the support substrate 10 and the embedded member are co-sintered in a state in which the members such as the fuel electrode 20 and the interconnector 30 are filled and embedded in the recesses 12 of the support substrate 10 without any gap. Therefore, a sintered body having high bondability between members and high reliability can be obtained.

  The interconnector 30 is embedded in a recess 21b formed on the outer surface of the fuel electrode current collector 21, and as a result, two side surfaces and a bottom surface along the width direction (y-axis direction) of the rectangular interconnector 30 Are in contact with the anode current collector 21 in the recess 21b. Therefore, the fuel electrode 20 (the current collector 21) and the interconnector 30 are compared to the case where a configuration in which the rectangular parallelepiped interconnector 30 is laminated (contacted) on the outer plane of the fuel electrode current collector 21 is employed. The area of the interface with can be increased. Therefore, the electronic conductivity between the fuel electrode 20 and the interconnector 30 can be increased, and as a result, the power generation output of the fuel cell can be increased.

  Further, in the above-described embodiment, a plurality of power generation element portions A are provided on each of the upper and lower surfaces of the flat support substrate 10. Thereby, compared with the case where a plurality of power generation element portions are provided only on one side surface of the support substrate, the number of power generation element portions in the structure can be increased, and the power generation output of the fuel cell can be increased.

  In the above embodiment, the solid electrolyte membrane 40 covers the outer surface of the fuel electrode 20, both end portions in the longitudinal direction of the outer surface of the interconnector 30, and the main surface of the support substrate 10. Here, no step is formed between the outer surface of the fuel electrode 20, the outer surface of the interconnector 30, and the main surface of the support substrate 10. Therefore, the solid electrolyte membrane 40 is flattened. As a result, compared with the case where a step is formed in the solid electrolyte membrane 40, the generation of cracks in the solid electrolyte membrane 40 due to stress concentration can be suppressed, and the gas sealing function of the solid electrolyte membrane 40 is reduced. Can be suppressed.

  In the above embodiment, as described above, the intermediate film 35 having a higher conductivity than the interconnector 30 is interposed at the interface between the bottom surface of the interconnector 30 and the fuel electrode 20 (current collector 21). . The effect | action and effect by this are demonstrated. First, as a preparation for explaining this operation and effect, as shown in FIG. 15, a comparative example different from the above embodiment only in that the intermediate film 35 is not interposed is assumed.

  In this comparative example, each interconnector 30 is connected to the support electrode 10 from the “part constituting the power generation element part A (that is, the part where the solid electrolyte 40 and the air electrode 60 are laminated) in the corresponding fuel electrode current collector 21. It is embedded in the outer surface of the “part extending in the plane direction”. In general, the conductivity of the air electrode current collector film 70 and the fuel electrode current collector 21 is about 1 to 2 digits greater than the conductivity of the interconnector 30. Furthermore, since the interface between the interconnector 30 and the fuel electrode current collector 21 is a region where different materials are joined, there is an interface resistance. Under these conditions, in this comparative example, current flows in the interconnector 30 so that the path in the interconnector 30 is the shortest. That is, as indicated by the black arrow in FIG. 15, the current flowing through the air electrode current collector film 70 is “at the interface between the side surface of the interconnector 30 and the fuel electrode current collector 21” (see the Z portion in the figure). After entering the interconnector 30 from a close position and passing through the interconnector 30 through the shortest path, it passes through the “interface between the side surface of the interconnector 30 and the fuel electrode current collector 21” (see Z in the figure). Thus, it tends to flow to the fuel electrode current collector 21 (as a result, the “part constituting the power generation element portion A” in the fuel electrode current collector 21, rightward in the drawing).

  As described above, in the configuration in which the current passes through the interface between the side surface of the interconnector 30 and the fuel electrode current collector 21, when the fuel cell is operated for a long time, the interface sometimes peels off. . This is considered based on the following reasons. That is, as described above, in this example, each interconnector 30 has a very thin plate shape (a shape having a large planar shape and a small thickness), and has an extremely small side surface area. Therefore, when the current passes through the interface between the side surface of the interconnector 30 and the fuel electrode current collector 21, the current is excessively concentrated and a lot of Joule heat is likely to be generated. This Joule heat generates a local temperature distribution in the vicinity of the interface, and as a result, it is considered that peeling is likely to occur at the interface.

  In contrast, in the above-described embodiment, as shown in FIG. 16, an intermediate film 35 having higher conductivity than the interconnector 30 is provided on the bottom surface of the interconnector 30. By inserting this layer, the interface resistance existing between the interconnector 30 and the fuel electrode current collector 21 can be greatly reduced. Therefore, the current path can be controlled so that the current passes through “the bottom surface of the interconnector 30 having a large area” instead of “the side surface of the interconnector 30 having a small area” (see the black arrow in FIG. 16). . As a result, the occurrence of peeling of the interface due to the generation of Joule heat when the current passes through the interface between the “side surface of the interconnector 30 having a small area” and the fuel electrode current collector 21 can be suppressed.

  In addition, this invention is not limited to the said embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, in the above-described embodiment, the intermediate film 35 having higher conductivity than the interconnector 30 is provided only on the bottom surface of the interconnector 30 (see FIG. 16), but as shown in FIG. An air gap may be provided only in. Alternatively, as illustrated in FIG. 18, a member (for example, an electrical insulator) having a lower conductivity than the interconnector 30 may be provided only on the side surface of the interconnector 30. Also by these, as in the above embodiment, the current path can be controlled so that the current passes through “the bottom surface of the interconnector 30 having a large area” instead of “the side surface of the interconnector 30 having a small area”. (See the black arrows in FIGS. 17 and 18), the same actions and effects as in the above embodiment can be achieved.

  Moreover, in the said embodiment, as shown in FIG. 6 etc., the planar shape (shape when it sees from the direction perpendicular | vertical to the main surface of the support substrate 10) of the recessed part 12 formed in the support substrate 10 becomes a rectangle. However, it may be, for example, a square, a circle, an ellipse, or a long hole shape.

  In the above embodiment, the entire interconnector 30 is embedded in each recess 12, but only a part of the interconnector 30 is embedded in each recess 12, and the remaining portion of the interconnector 30 is recessed 12. May protrude outside (that is, protrude from the main surface of the support substrate 10).

  Moreover, in the said embodiment, although the angle (theta) which the bottom wall and side wall in the recessed part 12 make is 90 degrees, as shown in FIG. 19, angle (theta) may be 90-135 degrees. In the above embodiment, as shown in FIG. 20, the portion of the recess 12 where the bottom wall and the side wall intersect with each other has an arc shape with a radius R, and the ratio of the radius R to the depth of the recess 12 is 0. .01 to 1 may be used.

  Moreover, in the said embodiment, although the several recessed part 12 is formed in each of the upper and lower surfaces of the flat support substrate 10, and the several electric power generation element part A is provided, as shown in FIG. A plurality of recesses 12 may be formed only on one side of the ten and a plurality of power generation element portions A may be provided.

  Further, in the above embodiment, the fuel electrode 20 is composed of two layers of the fuel electrode current collector 21 and the fuel electrode active portion 22, but the fuel electrode 20 is a single layer corresponding to the fuel electrode active portion 22. It may be configured. In addition, in the above embodiment, the “inner electrode” and the “outer electrode” are the fuel electrode and the air electrode, respectively, but they may be reversed.

  In addition, in the above embodiment, as shown in FIG. 3, the recess 21 b formed on the outer surface of the anode current collector 21 has a bottom wall made of the material of the anode current collector 21 and the circumferential direction. It is a rectangular parallelepiped depression defined by closed side walls (two side walls along the longitudinal direction made of the material of the support substrate 10 and two side walls along the width direction made of the material of the fuel electrode current collector 21). ing. As a result, the two side surfaces and the bottom surface along the width direction of the interconnector 30 embedded in the recess 21b are in contact with the fuel electrode current collector 21 in the recess 21b.

  On the other hand, as shown in FIG. 22, the recess 21b formed on the outer surface of the fuel electrode current collector 21 has a bottom wall made of the material of the fuel electrode current collector 21 and the fuel electrode current collector over the entire circumference. It may be a rectangular parallelepiped recess defined by circumferentially closed side walls (two side walls along the longitudinal direction and two side walls along the width direction) made of the material of the electric part 21. According to this, all four side surfaces and the bottom surface of the interconnector 30 embedded in the recess 21b are in contact with the fuel electrode current collector 21 in the recess 21b. Therefore, the area of the interface between the fuel electrode current collector 21 and the interconnector 30 can be further increased. Therefore, the electronic conductivity between the fuel electrode current collector 21 and the interconnector 30 can be further increased, and as a result, the power generation output of the fuel cell can be further increased.

  DESCRIPTION OF SYMBOLS 10 ... Support substrate, 11 ... Fuel gas flow path, 12 ... Recessed part, 20 ... Fuel electrode, 21 ... Fuel electrode current collecting part, 21a, 21b ... Recessed part, 22 ... Fuel electrode active part, 30 ... Interconnector, 35 ... Middle Membrane, 40 ... Solid electrolyte membrane, 50 ... Reaction prevention membrane, 60 ... Air electrode, 70 ... Air electrode current collector membrane, A ... Power generation element section

Claims (4)

A flat porous support substrate having a gas flow path formed therein;
A plurality of power generating element portions each provided at a plurality of positions separated from each other on the main surface of the flat support substrate, and a laminate of at least an inner electrode, a solid electrolyte, and an outer electrode;
One or a plurality of electrical connections that are respectively provided between one set or a plurality of sets of adjacent power generation element portions and electrically connect one inner electrode and the other outer electrode of the adjacent power generation element portions And
In a fuel cell structure comprising:
Each of the electrical connection parts is composed of a first part and a second part connected to the first part and made of a porous material, and the first part has a gas sealing function. The first portion has a porosity smaller than the porosity of the second portion, the first portion is connected to one inner electrode of the adjacent power generation element portion and the second portion, and the second portion is adjacent to the adjacent portion. Connected to the other outer electrode and the first part of the matching power generation element part,
It said plurality of locations on the main surface of the plate-shaped support substrate, a first recess having a side wall made of a material of the bottom wall and the supporting substrate made of a material of the supporting substrate are formed respectively, the main of the support substrate When viewed from the outside in a direction perpendicular to the surface, the side wall of the first recess is made of the material of the support substrate over the entire circumference and is closed in the circumferential direction,
In each of the first recesses, a corresponding inner electrode of the power generation element portion is embedded,
A second recess having a bottom wall made of the material of the inner electrode and a side wall made of the material of the inner electrode is formed on a surface opposite to the bottom surface of the first recess in each of the embedded inner electrodes . ,
In each of the second recesses , the corresponding first portion of the electrical connection portion is embedded,
Only in the portion corresponding to the bottom wall of the second recess at the interface between the first portion of each of the embedded electrical connection portions and the inner electrode, the conductivity is higher than that of the first portion of the electrical connection member. A fuel cell structure in which members are interposed .   A flat porous support substrate having a gas flow path formed therein;
  A plurality of power generating element portions each provided at a plurality of positions separated from each other on the main surface of the flat support substrate, and a laminate of at least an inner electrode, a solid electrolyte, and an outer electrode;
  One or a plurality of electrical connections that are respectively provided between one set or a plurality of sets of adjacent power generation element portions and electrically connect one inner electrode and the other outer electrode of the adjacent power generation element portions And
  In a fuel cell structure comprising:
  Each of the electrical connection parts is composed of a first part and a second part connected to the first part and made of a porous material, and the first part has a gas sealing function. The first portion has a porosity smaller than the porosity of the second portion, the first portion is connected to one inner electrode of the adjacent power generation element portion and the second portion, and the second portion is adjacent to the adjacent portion. Connected to the other outer electrode and the first part of the matching power generation element part,
  First recesses each having a bottom wall made of a material of the support substrate and a side wall made of a material of the support substrate are formed at the plurality of locations on the main surface of the flat support substrate, respectively. When viewed from the outside in a direction perpendicular to the surface, the side wall of the first recess is made of the material of the support substrate over the entire circumference and is closed in the circumferential direction,
  In each of the first recesses, a corresponding inner electrode of the power generation element portion is embedded,
  A second recess having a bottom wall made of the material of the inner electrode and a side wall made of the material of the inner electrode is formed on a surface opposite to the bottom surface of the first recess in each of the embedded inner electrodes. ,
  In each of the second recesses, the corresponding first portion of the electrical connection portion is embedded,
  A member having a lower conductivity than the first portion of the electrical connection member only in the portion corresponding to the side wall of the second recess at the interface between the first portion of each of the embedded electrical connection portions and the inner electrode. A fuel cell structure in which is interposed.   A flat porous support substrate having a gas flow path formed therein;
  A plurality of power generating element portions each provided at a plurality of positions separated from each other on the main surface of the flat support substrate, and a laminate of at least an inner electrode, a solid electrolyte, and an outer electrode;
  One or a plurality of electrical connections that are respectively provided between one set or a plurality of sets of adjacent power generation element portions and electrically connect one inner electrode and the other outer electrode of the adjacent power generation element portions And
  In a fuel cell structure comprising:
  Each of the electrical connection parts is composed of a first part and a second part connected to the first part and made of a porous material, and the first part has a gas sealing function. The first portion has a porosity smaller than the porosity of the second portion, the first portion is connected to one inner electrode of the adjacent power generation element portion and the second portion, and the second portion is adjacent to the adjacent portion. Connected to the other outer electrode and the first part of the matching power generation element part,
  First recesses each having a bottom wall made of a material of the support substrate and a side wall made of a material of the support substrate are formed at the plurality of locations on the main surface of the flat support substrate, respectively. When viewed from the outside in a direction perpendicular to the surface, the side wall of the first recess is made of the material of the support substrate over the entire circumference and is closed in the circumferential direction,
  In each of the first recesses, a corresponding inner electrode of the power generation element portion is embedded,
  A second recess having a bottom wall made of the material of the inner electrode and a side wall made of the material of the inner electrode is formed on a surface opposite to the bottom surface of the first recess in each of the embedded inner electrodes. ,
  In each of the second recesses, the corresponding first portion of the electrical connection portion is embedded,
  A fuel cell structure in which the gap is provided only in a portion corresponding to a side wall of the second recess at an interface between the first portion of each of the embedded electrical connection portions and the inner electrode. In the structure of the fuel cell according to any one of claims 1 to 3 ,
When viewed from the outside in a direction perpendicular to the main surface of the support substrate, the side wall of the second recess is made of the material of the inner electrode over the entire circumference .

Images