JP5108987B1 - Fuel cell structure - Google Patents

Abstract

[PROBLEMS] To provide a structure of a "horizontal stripe" fuel cell that can maintain a high fuel utilization rate and can easily suppress the inflow (reverse diffusion) of air from the outlet of a gas flow path to the inside. To do.
A plurality of power generation element portions A electrically connected in series to a main surface of a plate-like support substrate having a longitudinal direction in which a fuel gas flow path 11 is formed, and one or a plurality of sets One or a plurality of electrical connection portions that are respectively provided between the adjacent power generation element portions and electrically connect one inner electrode and the other outer electrode of the adjacent power generation element portions. A fuel cell structure, wherein a cross-sectional area of an outlet of the gas flow path is smaller than a cross-sectional area of an inlet of the gas flow path.
[Selection] Figure 32

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). See). Such a configuration is also called a “horizontal stripe type”.

JP 2008-226789 A

  In the structure of the “horizontal stripe type” solid oxide fuel cell described in Patent Document 1, the cross-sectional area of the gas flow path formed inside the support substrate is constant from the inlet to the outlet. The inventor conducted various experiments and the like, focusing on the relationship between the “position of the flow path in the gas flow direction” and the “cross-sectional area of the flow path” for the gas flow path formed inside the support substrate. As a result, in relation to the above relationship, compared to the case where the cross-sectional area of the gas flow path is constant from the inlet to the outlet, a high fuel utilization rate can be maintained, and the inflow of air from the gas flow path outlet to the inside ( We found an embodiment in which (diffusion) is easily suppressed.

  The present invention is a “horizontal stripe type” fuel cell structure that can maintain a high fuel utilization rate and can easily suppress the inflow (reverse diffusion) of air from the outlet to the inside of the gas flow path. The purpose is to provide.

  The structure of the fuel cell according to the present invention includes a flat plate-like porous support substrate that has a gas flow path formed therein and does not have electron conductivity, and a main surface of the flat plate-like support substrate that is separated from each other. Provided at each of a plurality of locations, `` a plurality of power generation element portions formed by laminating at least an inner electrode, a solid electrolyte, and an outer electrode '', and provided between one or a plurality of adjacent power generation element portions, One or a plurality of electrical connection portions having electronic conductivity for electrically connecting one inner electrode and the other outer electrode of the adjacent power generation element portions. That is, this structure is a “horizontal stripe type” fuel cell structure.

  The fuel cell structure according to the present invention is characterized in that the cross-sectional area of the outlet of the gas flow path is smaller than the cross-sectional area of the inlet of the gas flow path. According to this, since the cross-sectional area on the outlet side is narrow, the pressure loss in the gas channel increases, and the fuel gas is appropriately retained in the gas channel. As a result, the gas concentration distribution in the longitudinal direction in the gas flow path can be made more uniform while maintaining a high fuel utilization rate.

  In addition, since the cross-sectional area on the outlet side is narrow, the flow rate of gas at the outlet of the gas channel increases, and the inflow of air from the outlet of the gas channel to the inside of the gas channel (reverse diffusion) is suppressed. obtain. As a result, re-oxidation of the support substrate is suppressed, and the durability of the fuel cell can be maintained.

  In the fuel cell structure according to the present invention, the plurality of locations on the main surface of the flat support substrate are formed from the material of the support substrate over the entire circumference and the bottom wall made of the material of the support substrate. It is preferable that a first recess having a side wall closed in the circumferential direction is formed, and a corresponding inner electrode (the whole) of the power generation element unit is embedded in each first recess.

  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.

  In the said structure, each 1st recessed part for embedding an inner side electrode has the 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.

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. It is the perspective view corresponding to FIG. 1 which showed a mode that the unevenness | corrugation was formed in the surface of the bottom wall of the recessed part of a support substrate. It is sectional drawing corresponding to the structure 16-16 line | wire of the fuel cell shown in FIG. FIG. 17 is a partially enlarged view of FIG. 16. It is a figure for demonstrating that the cross-sectional area of a support substrate becomes large compared with the comparative example whose cross-sectional shape of a recessed part bottom wall is a sine wave shape. It is sectional drawing corresponding to FIG. 16 of the modification of the unevenness | corrugation formed in the surface of a recessed part bottom wall. It is sectional drawing corresponding to FIG. 16 which shows an example of the shape of the outer surface of the fuel electrode embedded at the recessed part. It is sectional drawing corresponding to FIG. 16 which shows the other example of the shape of the outer surface of the fuel electrode embedded at the recessed part. It is sectional drawing corresponding to FIG. 2 of the 1st modification of the structure of the fuel cell concerning this invention. It is sectional drawing corresponding to FIG. 2 of the 2nd modification of the structure of the fuel cell concerning this invention. 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. 3 of the 4th modification of the structure of the fuel cell concerning this invention. FIG. 16 is a perspective view corresponding to FIG. 15 illustrating a state in which irregularities are also formed in a portion where a concave portion is not formed on the main surface of the support substrate. FIG. 27 is a cross-sectional view corresponding to the line 27-27 of the fuel cell shown in FIG. FIG. 27 is a cross-sectional view corresponding to the line 28-28 of the fuel cell shown in FIG. 26. FIG. 2 is a perspective view corresponding to FIG. 1 when the cross-sectional shape of the fuel gas channel is not a circle but a flat shape. FIG. 28 is a perspective view corresponding to FIG. 27 when the cross-sectional shape of the fuel gas channel is not a circle but a flat shape. FIG. 29 is a perspective view corresponding to FIG. 28 when the cross-sectional shape of the fuel gas channel is not a circle but a flat shape. It is a figure which shows the modification of the gas flow path formed in the inside of a support substrate.

(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).

The support substrate 10 can be made of, for example, CSZ (calcia stabilized zirconia). Alternatively, it may be composed of NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia), NiO (nickel oxide) and Y ₂ O ₃ (yttria), or MgO. (Magnesium oxide) and MgAl ₂ O ₄ (magnesia alumina spinel) may be used.

  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.

  An interconnector 30 is embedded (filled) in each recess 21b. Accordingly, each interconnector 30 has a 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 oxygen ion conductivity. The “volume ratio of the substance having oxygen ion conductivity with respect to the entire volume excluding the pore portion” in the anode active portion 22 is “having oxygen ion conductivity with respect to the entire volume excluding the pore portion” in the anode current collecting portion 21. It is larger than the “volume ratio of the substance”.

The interconnector 30 can be composed of, for example, LaCrO ₃ (lanthanum chromite). LaCrO ₃ may be Ca-doped (La, Ca) CrO ₃ (calcium-doped lanthanum chromite) or Sr-doped (La, Sr) CrO ₃ (strontium-doped 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.

  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%.

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. The interconnector molded bodies 30g are respectively embedded and 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. The example of the method for manufacturing the SOFC structure shown in FIG. 1 has been described above.

(Detailed shape of the bottom wall of the concave portion of the support substrate)
As shown in FIGS. 15 and 16, in the above embodiment, a plurality of (in this example, five) recesses extending in the longitudinal direction (x-axis direction) of the support substrate 10 are provided on the surface of the bottom wall of each recess 12. And a plurality of (in this example, five) convex portions extending in the longitudinal direction are provided such that the concave portions and the convex portions are alternately positioned in the width direction (y-axis direction) of the support substrate. In addition, when the support substrate 10 is viewed from a direction perpendicular to the main surface (z-axis direction), the corresponding recesses are located on each fuel gas channel 11, and the number of fuel gas channels 11 ( In this example, the number of the five recesses is equal to the number of the recesses (in this example, five).

  More specifically, as shown in FIG. 17, the cross-sectional shape of each fuel gas channel 11 in the cross section (yz cross section) along the width direction (y direction) and the thickness direction (z direction) of the support substrate 10. Is a circle having a diameter D of 0.5 to 3.0 mm, and the pitch (distance between the central axes) P between the fuel gas passages 11 and 11 is 1.0 to 6.0 mm. The top of each projection and the bottom of each recess each have an arc shape. The arc radius R1 at the top of each convex portion is 1.0 to 150 mm, the arc radius R2 at the bottom of each concave portion is 0.1 to 10 mm, and the relationship of R1> R2 is established. The height difference of the unevenness (the distance between the topmost portion of the convex portion and the bottommost portion of the concave portion in the thickness direction of the support substrate 10) H is 10 to 200 μm. The (shortest) distance T between the bottom of each recess and the corresponding inner wall surface of the fuel gas channel 11 is 0.1 to 2 mm.

  The bottom surface of the fuel electrode 20 (more specifically, the current collector 21) is in close contact with the bottom wall of each recess 12. Therefore, it can also be said that irregularities are formed on the bottom surface of each fuel electrode 20 (current collector 21). The concave / convex shape of the bottom wall of each concave portion 12 is “positively formed”, for example, by molding a support body molded body 10g (see FIG. 6) using a molding die provided with a corresponding concave / convex shape. Alternatively, it may be “spontaneously formed” by utilizing a difference in the amount of local firing shrinkage during firing of the molded body 10 g of the support substrate.

(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.

  Further, unevenness is formed on the surface of the bottom wall of each recess 12 of the support substrate. Thereby, the rigidity of the support substrate 10 is further increased as compared with the case where the unevenness is not formed on the surface of the bottom wall of each recess 12. As a result, the support substrate 10 becomes more difficult to deform when it receives an external force.

  In addition, regarding the unevenness, a plurality of concave portions and a plurality of convex portions extending in the longitudinal direction (x-axis direction) are arranged on the surface of the bottom wall of each concave portion 12 such that the concave portions and the convex portions are alternately positioned in the width direction. Is provided. Thereby, especially the bending rigidity about the longitudinal direction (x-axis direction) of the support substrate 10 becomes high. As a result, warpage of the main surface in the longitudinal direction of the support substrate 10 (warpage of the support substrate 10 appearing in the xz section along the longitudinal direction and the thickness direction) is particularly difficult to occur.

  Further, in the cross section (yz cross section) along the width direction (y direction) and the thickness direction (z direction) of the support substrate 10, the arc radius R1 at the top of each convex portion is larger than the arc radius R2 at the bottom of each concave portion. (See FIG. 17). Thereby, as shown in FIG. 18, compared with the comparative example (typically the comparative example in which the cross-sectional shape has a sinusoidal shape) in which the arc radius of the top of the convex portion and the arc radius of the bottom of the concave portion coincide with each other, When the height difference of the unevenness is the same, the thickness of the support substrate 10 between the fuel gas passages 11 and 11 increases (see the region indicated by fine dots in FIG. 18). As a result, the rigidity of the support substrate 10 is further increased.

  Further, when the support substrate 10 is viewed from a direction perpendicular to the main surface (z-axis direction), corresponding recesses are located on the respective fuel gas flow paths 11. As a result, the number of the fuel gas passages 11 and the number of the recesses coincide. Thus, a mode in which the corresponding concave portion is not positioned on each fuel gas flow channel 12 (typically, as shown in FIG. 19, the corresponding convex portion is positioned on each fuel gas flow channel 11, respectively. The distance between the bottom wall of the recess 12 and the inner wall surface of the fuel gas channel 11 at each position corresponding to each fuel gas channel 12 in the width direction of the support substrate 10 is shorter than . Accordingly, the gas in the fuel gas channel 11 passes from the inner wall surface of the fuel gas channel 11 to the bottom wall of the recess 12 through the numerous pores in the support substrate 10 (therefore, the fuel electrode 20 embedded in the recess 12). The resistance (diffusion resistance) when diffusing to) decreases. This leads to an improvement in the power generation output of the entire SOFC.

  In addition, the outer surface of the fuel electrode 20 embedded in the concave portion 12 in which irregularities are formed on the surface of the bottom wall may be flat as shown in FIG. 20, or the concave surface of the concave portion 12 as shown in FIG. You may have the shape where the unevenness | corrugation corresponding to the unevenness | corrugation of a bottom wall exists. As can be understood from FIGS. 20 and 21, the inner surface of the solid electrolyte membrane 40 is in close contact with the outer surface of the fuel electrode 20. Therefore, in the aspect shown in FIG. 20, the part laminated | stacked on the fuel electrode 20 in the solid electrolyte membrane 40 becomes flat. In the embodiment shown in FIG. 21, the portion of the solid electrolyte membrane 40 laminated on the fuel electrode 20 has a shape in which there are irregularities corresponding to the outer surface of the fuel electrode 20. In the embodiment shown in FIG. 21, the arc radii R1 at the tops of the protrusions are related to the unevenness of the bottom wall of the recess 12, the unevenness of the outer surface of the fuel electrode 20, and the unevenness of the outer surface of the solid electrolyte membrane 40 (see FIG. 17) are substantially the same, and the arc radii R2 at the bottom of the recesses are substantially the same (see FIG. 17).

  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 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 embodiment, as shown in FIG. 6 and the like, the planar shape of the recess 12 formed in the support substrate 10 (the shape when viewed from the direction perpendicular to the main surface of the support substrate 10) is 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. 22, angle (theta) may be 90-135 degrees. Moreover, in the said embodiment, as shown in FIG. 23, the part in which the bottom wall and side wall in the recessed part 12 cross | intersect is the circular arc shape of the radius R, and the ratio of the radius R with respect to the depth of the recessed part 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. 25, 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.

  Moreover, in the said embodiment, as shown in FIG.15 and FIG.16, the plurality (in this example, five) extended in the longitudinal direction (x-axis direction) of the support substrate 10 only on the surface of the bottom wall of each recessed part 12. FIG. And a plurality of (in this example, five) convex portions extending in the longitudinal direction are provided such that the concave portions and the convex portions are alternately positioned in the width direction (y-axis direction) of the support substrate. However, as shown in FIG. 26 to FIG. 28, in addition to the surface of the bottom wall of the recess 12, a similar plurality (in this example, 5 in the main surface of the support substrate 10 where the recess 12 is not formed). May be provided so as to be alternately positioned in the width direction (y-axis direction) of the support substrate. In the configuration shown in FIGS. 26 to 28, when the support substrate 10 is viewed from the direction (z-axis direction) perpendicular to the main surface, the bottom wall of the recess 12 and the main substrate 10 are formed on each fuel gas channel 11. The corresponding concave portions of the surface are respectively positioned, and the number of fuel gas passages 11 (in this example, five) and the number of concave portions (in this example, five) coincide.

  Similar to the concavo-convex shape of the bottom wall of each concave portion 12, the concavo-convex shape of the main surface of the support substrate 10 is formed using a molding die provided with a corresponding concavo-convex shape to form a support substrate molded body 10g (see FIG. 6). It may be “positively formed” by, for example, or may be “spontaneously formed” by utilizing a difference in the amount of local firing shrinkage at the time of firing the molded body 10 g of the support substrate. 26 to 28, the bottom wall of each recess 12 may not be provided with unevenness, and the unevenness may be provided only on the main surface of the support substrate 10.

  In FIG. 27, regarding the unevenness of the bottom wall of the recess 12, the unevenness of the outer surface of the fuel electrode 20, and the unevenness of the outer surface of the solid electrolyte membrane 40, the arc radius R 1 of the top of the protrusion and the bottom of the recess Arc radius R2 (see FIG. 17) is substantially the same. Similarly, in FIG. 28, regarding the unevenness of the main surface of the support substrate 10 and the unevenness of the outer surface of the solid electrolyte membrane 40, the arc radius R1 at the top of the protrusion and the arc radius R2 at the bottom of the recess (FIG. 17). Are substantially the same.

  Moreover, in the said embodiment, as shown in FIG. 1 etc., although the cross-sectional shape of the fuel gas flow path 11 formed in the support substrate 10 was circular, as shown in FIG. The cross-sectional shape may be a flat shape (expanded in the width direction of the support substrate). 27 and 28, the cross-sectional shape of the fuel gas channel 11 is circular. However, as shown in FIGS. 30 and 31, the cross-sectional shape of the fuel gas channel 11 is flat ( It may be in the shape of spreading in the width direction of the support substrate.

  Moreover, in the said embodiment, the cross-sectional area of each gas flow path 11 extended in the longitudinal direction (x-axis direction) formed in the support substrate 10 is an exit (x-axis negative direction) from an inlet (x-axis positive direction side). 32, the cross-sectional area of the outlet (the left end in the figure) is smaller than the cross-sectional area of the inlet (the right end in the figure) for each gas channel 11 as shown in FIG. Also good.

According to this, the following actions and effects can be expected.
1. Since the cross-sectional area on the outlet side is narrow, the pressure loss in the gas flow path 11 is increased, and the fuel gas is appropriately retained in the gas flow path 11. As a result, the gas concentration distribution in the longitudinal direction in the gas flow path 11 can be made more uniform while maintaining a high fuel utilization rate.
2. Since the cross-sectional area on the outlet side is narrow, the flow velocity of the gas at the outlet of the gas flow path 11 is increased, and the inflow (back diffusion) of air from the outlet of the gas flow path 11 to the inside of the gas flow path 11 is suppressed. obtain. As a result, re-oxidation of the support substrate 10 is suppressed, and the durability of the fuel cell can be maintained.

  Hereinafter, as shown in FIG. 32, for each gas flow path 11, the range from the inlet of the gas flow path 11 to “the end face on the outlet side of the power generation element portion A closest to the outlet of the gas flow path 11” It is called “effective part” and the remaining range is called “exit part”. In this case, as shown in FIG. 32, each gas flow path 11 has a constant cross-sectional area at the effective portion (a slight variation may exist in the longitudinal direction), and a cross-sectional area at the outlet portion as it approaches the outlet. May be formed so as to include a portion where the diameter gradually decreases. Each gas flow path 11 may be formed so that the cross-sectional area gradually decreases over the entire region in the longitudinal direction at the outlet portion, or a portion where the cross-sectional area gradually decreases is only part of the longitudinal direction. It may be formed to exist. In addition, the effective portion may be formed so as to include a portion whose cross-sectional area gradually decreases as it approaches the outlet, like the outlet portion. In this case, the effective portion may be formed so that the cross-sectional area gradually decreases over the entire area in the longitudinal direction, or a portion where the cross-sectional area gradually decreases is present only in a part in the longitudinal direction. It may be formed.

  In this case, the maximum value and the minimum value of the variation range of the cross-sectional area Se of the gas flow path 11 in the effective part are Semax and Semin, respectively, and “the power generation element part A closest to the outlet of the gas flow path 11 in the outlet part”. If the cross-sectional area at the “end face of the outlet side” is Sb, the cross-sectional area of the outlet is So, and ΔS1 = Semax−Semin and ΔS2 = Sb−So are defined, then the relationship “ΔS2 ≧ ΔS1” holds Thus, each gas flow path 11 may be formed.

  Further, the inventor of the present invention, when the ratio of So to Semin (So / Semin) is 80% or less, compared to the case where it is not so, “maintenance of high fuel utilization rate” and “gas flow path 11” described above. It was found that “suppression of back diffusion of air into the inside” can be achieved more reliably. Hereinafter, a test for confirming this will be described.

(test)
In this test, with respect to the fuel cell according to the above-described embodiment (see FIG. 1 and the like), a plurality of samples having different combinations of Semin and So (accordingly, ratio (So / Semin)) with respect to the fuel gas flow path 11 are obtained. It was made. Specifically, as shown in Table 1, six kinds of levels (combinations) were prepared. Ten samples (N = 10) were made for each level.

  The supporting substrate 10 used in each sample (the fuel cell shown in FIG. 1) has a material porosity of 40%, and a thickness and width of 3.0 mm and 40 mm, respectively (that is, an aspect ratio of 13). The fuel gas flow path 11 has a circular cross-sectional shape and a pitch between the adjacent fuel gas flow paths 11 and 11 of 3.0 mm.

For each sample, the operating conditions are constant at a temperature of 750 ° C., a current density of 0.3 A / cm ² , an air utilization factor (Ua) of 30%, and the dependence of the fuel utilization factor (Uf). Evaluated. The results are as shown in Table 1.

  As can be understood from Table 1, when (So / Semin) exceeds 80%, the voltage drop in an operating state with a high fuel utilization rate is large. On the other hand, when (So / Semin) is 80% or less, stable operation was possible even in an operation state with a high fuel utilization rate (Uf = 75%).

  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, 40 ... Solid Electrolyte membrane, 50 ... reaction preventing 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:
In the structure of the fuel cell, wherein the cross-sectional area of the gas channel outlet is smaller than the cross-sectional area of the gas channel inlet ,
A first recess having a bottom wall made of the material of the support substrate and a side wall made of the material of the support substrate over the entire circumference at the plurality of locations on the main surface of the flat support substrate. Each formed,
A fuel cell structure in which the corresponding inner electrode of the power generation element portion is embedded in each first recess. The fuel cell structure according to claim 1,
The gas flow path has a constant cross-sectional area at the effective portion that is a range from the inlet to the end face on the outlet side of the power generation element portion that is closest to the outlet, or is cut off as the outlet approaches. It is formed so as to include a portion where the area gradually decreases, and is formed so as to include a portion where the cross-sectional area gradually decreases as it approaches the outlet, at the outlet portion that is the range from the end face to the outlet. ,
The maximum value and the minimum value of the variation range of the cross-sectional area Se of the gas flow path in the effective part are Semax and Semin, respectively, the cross-sectional area at the end face in the outlet part is Sb, and the cross-sectional area of the outlet is So. A fuel cell structure in which a relationship of ΔS2 ≧ ΔS1 is established when ΔS1 = Semax−Semin and ΔS2 = Sb−So. The fuel cell structure according to claim 2,
A structure of a fuel cell, wherein a ratio of So to Semin (So / Semin) is 80% or less. In the structure of the fuel cell according to any one of claims 1 to 3 ,
Each of the electrical connection portions includes a first portion made of a dense material, and a second portion made of a porous material connected to the first portion,
Second recesses having a bottom wall made of the material of the inner electrode and a circumferentially closed side wall made of the material of the inner electrode are formed on the outer surface of each embedded inner electrode. ,
The structure of a fuel cell, wherein the first portion of the corresponding electrical connection portion is embedded in each second recess.

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