JP5826963B1 - Fuel cell - Google Patents

Abstract

To provide a fuel cell having a support substrate with a gas flow path formed therein, in which cracks are unlikely to occur at the gas discharge side end of the support substrate. In this fuel cell, a power generating element section A in which a fuel electrode 20, a solid electrolyte 40, and an air electrode 60 are sequentially laminated on the surface of a support substrate 10 in which a plurality of gas flow paths 11 are formed. It is formed. An additional member 90 is provided at the gas discharge side end of the support substrate 10 via a bonding material 80. A plurality of gas flow paths are also formed inside the additional member 90. Each gas flow path 11 of the support substrate 10 is connected to a corresponding gas flow path of the additional member 90. By providing the additional member 90, the fuel gas flowing through the gas flow path 11 in the support substrate 10 is not immediately discharged from the gas discharge side end of the support substrate 10 to the external space, but in the additional member 90. After passing through the gas flow path, the additional member 90 is discharged from the gas discharge side end to the external space. [Selection] Figure 15

Description

  The present invention relates to a fuel cell.

  Conventionally, “a porous support substrate having a longitudinal direction in which one or a plurality of gas passages penetrating in the longitudinal direction are formed” and “provided on the surface of the support substrate. In addition, a solid oxide fuel cell that is a fired body including a power generation element unit in which at least a fuel electrode, a solid electrolyte, and an air electrode are stacked in this order is widely known (see, for example, Patent Document 1). ).

  In the fuel cell which is such a fired body, heat treatment is performed to supply a reducing gas to the fuel cell at a high temperature (for example, about 800 ° C.) before operating the fuel cell in order to obtain conductivity of the fuel electrode and the like. (Hereinafter referred to as “reduction treatment”) is performed, and the fuel cell is transferred from the non-reduced form to the reduced form.

  In such a fuel cell, “the gas (fuel gas) flows in one direction (same direction) in the longitudinal direction in each gas flow path, and the excess gas discharged from the gas discharge side end of each gas flow path to the external space” A configuration in which a gas reacts with air (oxygen) in the external space and burns in the vicinity of the gas discharge side end portion can be employed.

  When this configuration is employed, cracks are likely to occur at the gas discharge side end of the support substrate. This is considered based on the following reasons. First, due to the support substrate being porous, air in the external space enters the inside of the gas discharge side end of the support substrate via the gas discharge side end of each gas flow path. The surplus gas mentioned above reacts with air and burns inside. As a result, excessive thermal stress due to heat generation due to combustion is locally generated in the inside, and cracks are generated. Secondly, the air in the external space enters the inside of the gas discharge side end of the support substrate, so that the inside which is a reductant is reoxidized. As a result, an excessive stress accompanying a dimensional change (oxidation expansion or contraction) due to re-oxidation is locally generated in the inside, and a crack is generated.

  In order to reduce the possibility of occurrence of such cracks, the gas discharge side end of the support substrate, specifically, the gas discharge side end of the inner wall surface of each gas flow path, and the longitudinal direction of the support substrate There is known a configuration in which a coating film having a lower porosity than that of a support substrate is formed on the end surface on the gas discharge side (see Patent Document 1, for example). The formation of this coating film makes it difficult for air in the external space to enter the gas discharge side end of the support substrate, and as a result, cracks may occur at the gas discharge side end of the support substrate. Can be reduced.

JP 2012-9228 A

  By the way, in the configuration in which the coating film is formed as described above, a crack may occur in the coating film depending on the operating environment of the fuel cell. When a crack occurs in the coating film, air in the external space can enter the inside of the gas discharge side end of the support substrate through the crack. As a result, cracks may eventually occur at the gas discharge side end of the support substrate.

  As described above, there is room for improvement in the method of forming the coating film when suppressing cracks at the gas discharge side end of the support substrate. The present inventor has found a new technique for suppressing cracks at the gas discharge side end of the support substrate without using a technique for forming a coating film.

  The fuel cell according to the present invention includes the same support substrate as described above and the same power generation element unit as described above. The support substrate may be flat or cylindrical. A first side in the longitudinal direction of each gas flow path of the support substrate and a second side opposite to the first side correspond to a gas inflow side and a gas discharge side, respectively.

  A feature of the fuel cell according to the present invention is that an additional member attached to the end portion on the second side in the longitudinal direction of the support substrate is provided. This additional member has one or more gas flow paths therein. Each gas flow path penetrates in the longitudinal direction and is connected to each gas flow path of the support substrate.

  Here, the additional member may be composed of porous ceramics (porosity of 10% or more), or may be composed of dense ceramics (porosity of less than 10%). When the additional member is made of porous ceramics, the outer surface of the additional member may be covered with a dense ceramic film. The material of the bonding material has a composition different from the materials of the support substrate and the additional member. The material of the support substrate and the additional member may have the same composition and microstructure, or one or both of the composition and microstructure may be different.

  Each of the gas flow paths of the additional member is preferably connected to one corresponding gas flow path of the support substrate, but is connected to a plurality of corresponding gas flow paths of the support substrate. It may be. The single said gas flow path of the said additional member may be connected with all the several said gas flow paths of the said support substrate.

  According to the above feature of the present invention, the fuel gas flowing through the gas flow path extending in the longitudinal direction in the support substrate is not immediately discharged from the gas discharge side end of the support substrate to the external space, but in the additional member. After passing through the gas flow path extending in the longitudinal direction, the gas is discharged from the gas discharge side end of the additional member to the external space. That is, the gas discharge side end of the gas flow path in the support substrate is not directly connected to the external space, but is connected to the external space via the gas flow path in the additional member. When the additional member is porous, part of the fuel gas can be discharged from the gas flow path in the additional member to the external space via the pores inside the additional member.

  Therefore, compared with the configuration in which the additional member is not provided, the air in the external space is introduced into the gas discharge side end of the support substrate through the gas discharge side end of the gas flow path in the support substrate. It becomes difficult to enter. As a result, it is possible to reduce the possibility of cracks occurring at the gas discharge side end portion of the support substrate due to the “entry of the air in the external space into the gas discharge side end portion of the support substrate”.

  In particular, when the additional member is made of a porous material, the air in the external space can enter the inside of the gas discharge side end of the additional member. There is a high possibility of cracking. However, even if a crack occurs in the additional member, there is no problem as long as the crack does not occur at the gas discharge side end of the support substrate. That is, the present invention reduces the possibility of cracks occurring at the gas discharge side end portion of the support substrate by intentionally providing a member that does not have a problem even if cracks occur in a place where cracks are likely to occur. Based on knowledge.

  In the fuel cell according to the present invention, the additional member is inserted into the end portion on the second side of the corresponding one of the gas flow paths of the support substrate and joined through the joining material. Or it may be composed of a plurality of tubular members extending in the longitudinal direction.

  Moreover, the fuel cell according to the present invention may further include a metal member interposed between the support substrate and the additional member in the longitudinal direction. The metal member has one or a plurality of gas passages penetrating in the longitudinal direction and connected to the gas passages of the support substrate.

  In the configuration in which the metal member is not interposed between the support substrate and the additional member, that is, in the configuration in which only the bonding material is interposed between the support substrate and the additional member, when a crack occurs in the additional member as described above, If the degree of growth / progress of cracks is large, the cracks may reach the gas discharge side end of the support substrate via the bonding material.

  In this respect, since the metal has ductility, it is difficult for the metal to crack. Therefore, as described above, in the configuration in which the metal member is interposed between the support substrate and the additional member, even if the degree of growth / progress of the crack generated in the additional member is large, the crack is a metal. The progress of the crack stops when it reaches the member. That is, it becomes difficult for the crack to reach the gas discharge side end of the support substrate.

  When the fuel cell according to the present invention further includes a metal member, the fuel cell according to the present invention preferably includes a coating film that covers the surface of the metal member. For example, when the metal member is made of stainless steel, the coating film covers the surface of the metal member, thereby preventing chromium from flowing out from the metal member. As a result, it is possible to prevent the problem that the air electrode and the like are poisoned by chromium volatilized from the metal member.

  In the fuel cell according to the present invention, when the second side end face of the support substrate and the first side end face of the additional member are arranged to face each other, A metal member may be interposed between the end surface and the end surface on the first side of the additional member. In this case, the end surface on the second side of the support substrate and the end surface on the first side of the metal member are bonded via the bonding material, and the end surface on the first side of the additional member and the metal The additional member is joined to the end portion on the second side of the support substrate by joining the end surface on the second side of the member via the joining material.

  Each of the gas flow paths of the metal member is preferably connected to a corresponding one of the gas flow paths of the support substrate, but is connected to a plurality of the corresponding gas flow paths of the support substrate. It may be. The single gas channel of the metal member may be connected to all of the plurality of gas channels of the support substrate.

  Moreover, in the fuel cell according to the present invention, it is preferable that the additional member is made of a ceramic (fired body thereof). The additional member may be made of a metal including chromium (Cr). However, in this case, when chromium volatilized from the surface of the additional member reaches the electrode (particularly, the air electrode), the electrode can be poisoned (so-called chromium poisoning). On the other hand, as described above, if the additional member is made of ceramics (fired body thereof), chromium poisoning cannot occur.

  Further, from the viewpoint of preventing the occurrence of chromium poisoning, the outer surface of the metal member may be covered with a dense ceramic film.

  Moreover, in the fuel cell according to the present invention, the thermal conductivity of the additional member is preferably higher than the thermal conductivity of the support substrate. According to this structure, since the heat dissipation of an additional member improves, generation | occurrence | production of a crack can be effectively prevented in a gas discharge side edge part. For example, the thermal conductivity of the additional member can be improved by including a metal element or nickel in the additional member, or coating the surface of the additional member with a metal film.

1 is a perspective view showing a fuel cell according to the present invention. FIG. 2 is a cross-sectional view corresponding to line 2-2 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 operation state 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 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 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 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 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 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 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 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 shown in FIG. 1. FIG. 7 is a cross-sectional view corresponding to FIG. 2 in an eighth stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 5 is a view corresponding to FIG. 4 showing an operating state of a fuel cell provided with an additional member. It is a perspective view which shows the additional member shown in FIG. It is the top view which expanded and showed the junction part of the support substrate shown in FIG. 15, and an additional member. It is the side view which expanded and showed the junction part of the support substrate shown in FIG. 15, and an additional member. FIG. 18 is a view corresponding to FIG. 17 in another fuel cell according to the present invention. FIG. 19 is a view corresponding to FIG. 18 in another fuel cell according to the present invention. It is a perspective view which shows the metal plate shown in FIG.19 and FIG.20. It is sectional drawing which expanded and showed the joining site | part of a support substrate and an additional member. . FIG. 16 is a view corresponding to FIG. 15 in another fuel cell according to the present invention. FIG. 18 is a view corresponding to FIG. 17 in another fuel cell according to the present invention. FIG. 19 is a view corresponding to FIG. 18 in another fuel cell according to the present invention. It is sectional drawing which expanded and showed the junction part of the support substrate shown in FIG. 25, and an additional member.

(Constitution)
FIG. 1 shows a solid oxide fuel cell (SOFC) according to an embodiment (this embodiment) of the present invention. This SOFC is electrically connected in series to each of 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) (this example). In this case, the four power generation element portions A having the same shape are arranged at predetermined intervals in the longitudinal direction, so-called “horizontal stripe type”.

  The shape of the entire SOFC as viewed from above is, for example, a rectangle whose length in the longitudinal direction is 50 to 500 mm and whose length in the width direction (y-axis direction) perpendicular to the longitudinal direction is 10 to 100 mm. The total thickness of this SOFC is 1-5 mm. The entire SOFC 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 will be described with reference to FIG. 2, which is a partial cross-sectional view of the SOFC corresponding to line 2-2 shown in FIG. 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, the recesses 12 are respectively formed at positions corresponding to the plurality of power generation element portions A on the upper and lower surfaces of the support substrate 10. Each recess 12 has 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 (two side walls along the longitudinal direction and two side walls along the width direction). ) And a rectangular parallelepiped depression defined by 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 MgO (magnesium oxide) and a first oxide ceramic. The support substrate 10 contains the first oxide ceramic because the thermal expansion coefficient of MgO alone (about 14 ppm / K) is compared with the thermal expansion coefficient of normal electrode material (10-13 ppm / K). This is because the equivalent thermal expansion coefficient of the support substrate 10 is brought close to the thermal expansion coefficient of a normal electrode material due to the large size. Therefore, as the first oxide ceramic, those having a smaller thermal expansion coefficient than that of a normal electrode material (10 to 13 ppm / K) are preferable. Specifically, as the “first oxide ceramic”, Y ₂ O ₃ (yttria), YSZ (8YSZ) (yttria stabilized zirconia), CSZ (calcia stabilized zirconia) and the like are suitable. The support substrate 10 may contain “transition metal oxide or transition metal”. 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).

  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, when the support substrate 10 contains insulating oxide ceramics, the insulation of the support substrate 10 can be ensured. As a result, insulation between adjacent fuel electrodes can be ensured.

  The thickness of the support substrate 10 is 1 to 5 mm. The porosity of the support substrate 10 is 15 to 55%. In addition, the value of porosity is a value after the reduction process described later (the same applies to other porosity values). The porosity was measured by polishing the cross section of the resin-embedded sample (after the reduction treatment) and analyzing the image (secondary electron image) of the cross section by SEM (scanning electron microscope). . Specifically, the ratio of the “total area of portions corresponding to the resin-filled region on the cross section” to the “total area of the cross section” was defined as the “porosity” of the cross section. The acceleration voltage of SEM was set to 5 kV, and the magnification of SEM was set to 5000 times or 7500 times. The measurement of the porosity was performed on arbitrary 10 cross-sections of the sample, and the average value thereof was adopted as the porosity value.

  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 includes a bottom wall made of the material of the fuel electrode current collector 21 and a side wall (two side walls along the longitudinal direction) closed in the circumferential direction made of the material of the fuel electrode current collector 21 over the entire circumference. And two side walls along the width direction).

  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 four side surfaces and the bottom surface 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 includes a bottom wall made of a material of the fuel electrode current collector 21 and a circumferentially closed side wall made of the material of the fuel electrode current collector 21 (two side walls along the longitudinal direction). And two side walls along the width direction).

  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 four side surfaces and the bottom surface 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 current collector 21 includes NiO (nickel oxide) and a second oxide ceramic. The anode current collector 21 contains the second oxide ceramic because the thermal expansion coefficient of NiO alone (about 14 ppm / K) is the thermal expansion coefficient of normal electrode materials (10-13 ppm / K). This is because the equivalent thermal expansion coefficient of the fuel electrode current collector 21 is brought close to the thermal expansion coefficient of a normal electrode material due to the fact that it is larger than the above. Therefore, as the second oxide ceramic, those having a smaller thermal expansion coefficient than that of a normal electrode material (10 to 13 ppm / K) are preferable. Specifically, as the “second oxide ceramic”, Y ₂ O ₃ (yttria), YSZ (8YSZ) (yttria stabilized zirconia), CSZ (calcia stabilized zirconia) and the like are suitable. The thickness of the fuel electrode current collector 21 (that is, the depth of the recess 12) is 50 to 500 μm. The porosity of the fuel electrode current collector 21 is 15 to 55%.

  The anode active part 22 includes a substance having electron conductivity and a substance having oxygen ion conductivity. As the “substance having electron conductivity”, NiO (nickel oxide) is suitable. As the “substance having oxygen ion conductivity”, YSZ (8YSZ) (yttria stabilized zirconia), GDC (gadolinium doped ceria) and the like are suitable. The thickness of the fuel electrode active part 22 is 5 to 30 μm. The porosity of the anode active portion 22 is 15 to 55%.

  Note that NiO in the fuel electrode current collector 21 and in the fuel electrode active part 22 is changed to Ni by a reduction process, which will be described later, to acquire electron 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). 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 ion 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. In the present application, “dense” means “high density so that gas does not pass”, and specifically means “porosity is 10% or less”.

  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 may 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 in order to suppress the occurrence of a phenomenon in which a reaction layer having a large electric resistance is formed at the boundary portion with 60.

  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 “electrical connection portions”.

  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, the reformed fuel gas (hydrogen gas or the like) flows through the fuel gas flow path 11 of the support substrate 10 as shown in FIG. By exposing the upper and lower surfaces (in particular, 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), a solid is obtained. An electromotive force is generated by an oxygen partial pressure difference generated between both side surfaces of the electrolyte membrane 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 ⁻ (at the 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, from this entire SOFC (specifically, the interconnector 30 of the power generating element part A on the frontmost side in FIG. 4 and the air electrode 60 of the power generating element part A on the innermost side in FIG. Power).

(Production method)
Next, an example of a method for manufacturing the “horizontal stripe type” SOFC 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. For example, this support substrate molded body 10g uses a slurry obtained by adding a binder or the like to the powder of the material of the support substrate 10 (for example, MgO and Y ₂ O ₃ ). It can be made using. 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.

As shown in FIG. 7, when the support substrate molded body 10g is manufactured, next, as shown in FIG. 8, in each recess 12 formed on the upper and lower surfaces of the support substrate molded body 10g, the fuel electrode assembly is formed. The molded part 21g of the electric part is embedded and formed respectively. 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 fuel electrode active part 22g are, 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 Y ₂ O ₃ ). It is embedded and formed using a printing method or the like.

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 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 60 g, the solid electrolyte film 40, and the interconnector 30, the air electrode current collecting film forming film 70 g 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. Thereby, the SOFC 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 electron conductivity of the fuel electrode 20 (current collector 21 + active part 22), a reducing fuel gas is then flowed from the support substrate 10 side, and NiO is heated at 800 to 1000 ° C. for 1 to 10 hours. The reduction treatment is performed over a period of time. This reduction process may be performed during power generation. In the above, an example of the manufacturing method of SOFC shown in FIG. 1 was demonstrated.

(Suppression of cracks at the gas discharge side end of the support substrate)
As shown in FIG. 4 described above, in the fuel cell according to the present embodiment, gas (fuel gas) flows in one direction (same direction) in the longitudinal direction (x-axis direction) in each gas flow path 11. Excess gas discharged from the gas discharge side end (end in the negative x-axis direction) of each gas flow path 11 to the external space is air in the external space near the gas discharge side end. It reacts with (oxygen) and burns.

  In this configuration, as described in the above-mentioned “Background Art” section, the air in the external space passes through the gas discharge side end portions of the gas flow paths 11 to the gas discharge side end portions of the support substrate 10. Due to entering the inside, cracks are likely to occur at the gas discharge side end of the support substrate 10.

  In order to cope with this problem, as shown in FIG. 15, in this embodiment, an additional member 90 is attached to the gas discharge side end portion of the SOFC support substrate 10. For example, the additional member 90 is bonded to the gas discharge side end portion of the support substrate 10 via the bonding material 80. As illustrated in FIG. 16, the additional member 90 has a shape in which the length in the longitudinal direction (x-axis direction) is shortened in the support substrate 10. A plurality of gas passages 91 penetrating in the longitudinal direction (x-axis direction) are formed inside the additional member 90. The gas discharge side end surface of the support substrate 10 and the gas inflow side end surface of the additional member 90 are arranged so as to face each other, and these two end surfaces are bonded to each other by a bonding material 80.

  As shown in FIGS. 17 and 18, in a state where the support substrate 10 and the additional member 90 are bonded via the bonding material 80 (see also FIG. 15), each gas flow path 11 of the support substrate 10 is The additional member 90 is connected to the corresponding gas flow path 91. Note that, in the bonding material 80, gas flow paths that connect the corresponding gas flow paths 11 and the gas flow paths 91 (penetrate in the longitudinal direction) are formed.

  The material of the additional member 90 may have the same composition and microstructure as the material of the support substrate 10, or one or both of the composition and microstructure may be different. The additional member 90 may be made of porous ceramics (porosity of 10% or more) or may be made of dense ceramics (porosity of less than 10%). When the additional member 90 is made of porous ceramics, the outer surface of the additional member 90 may be covered with a dense ceramic film. The additional member 90 may be made of a metal containing chromium (Cr), but is preferably made of ceramics (fired body thereof). As a result, the chromium poisoning (see the summary of the invention) cannot occur in the electrodes (particularly the air electrode).

The material of the bonding material 80 has a composition different from the materials of the support substrate 10 and the additional member 90. Specifically, for example, the bonding material 80 is made of amorphous glass, crystallized glass, or the like. As the crystallized glass, for example, ones such as MgO—CaO—SiO ₂ —B ₂ O ₃ and MgO—BaO—SiO ₂ —B ₂ O ₃ are preferable. In this specification, crystallized glass means that the ratio (crystallinity) of “volume occupied by crystal phase” to the total volume is 60% or more, and “volume occupied by amorphous phase and impurities relative to the total volume”. "Refers to glass (ceramics) having a ratio of less than 40%.

  The assembly of the additional member 90 to the SOFC support substrate 10 can be performed, for example, by the following procedure. First, a completed SOFC (see FIG. 1) and a completed additional member 90 (see FIG. 16) are prepared. Next, using a predetermined jig or the like, the gas discharge side end surface of the support substrate 10 and the gas inflow side end surface of the additional member 90 are arranged to face each other with a predetermined interval. Next, the paste for the bonding material 80 is filled in the space (gap) between these two end faces. At this time, in order to form the above-described “gas flow path inside the bonding material 80”, rod-shaped members may be inserted and arranged so as to penetrate the corresponding gas flow paths 11 and 91. .

  Next, heat treatment is applied to the paste filled as described above. Thereby, when the paste is dried and solidified, the function as the bonding material 80 is exhibited, and the two end surfaces are bonded and fixed to each other. Thereafter, the predetermined jig (and the rod-shaped member) is removed, and the assembly of the additional member 90 to the support substrate 10 is completed.

  Hereinafter, the operation and effect obtained by assembling the additional member 90 to the gas discharge side end of the SOFC support substrate 10 will be described. By providing this additional member 90, the fuel gas flowing through the gas flow path 11 in the support substrate 10 is not immediately discharged from the gas discharge side end portion of the support substrate 10 to the external space, but is added to the additional member 90. After passing through the inner gas flow path 91, the additional member 90 is discharged from the gas discharge side end to the external space. That is, the gas discharge side end of the gas flow path 11 in the support substrate 10 is not directly connected to the external space, but is connected to the external space via the gas flow path 91 in the additional member 90. In addition, when the additional member 90 is porous, a part of fuel gas can be discharged | emitted from the gas flow path 91 in the additional member 90 to the external space via the pore inside the additional member 90.

  Therefore, as compared with the configuration in which the additional member 90 is not provided, the air in the external space is moved to the gas discharge side end portion of the support substrate 10 through the gas discharge side end portion of the gas flow path 11 in the support substrate 10. It becomes difficult to enter inside. As a result, the possibility of occurrence of cracks at the gas discharge side end portion of the support substrate 10 due to the “entry of the air in the external space into the gas discharge side end portion of the support substrate 10” is reduced. obtain.

  In particular, when the additional member 90 is made of a porous material, air in the external space can enter the inside of the gas discharge side end of the additional member 90. Thereby, a crack is highly likely to occur at the gas discharge side end of the additional member 90. However, even if a crack occurs in the additional member 90, there is no problem as long as the crack does not occur at the gas discharge side end of the support substrate 10. That is, the present invention reduces the possibility of cracks occurring at the gas discharge side end of the support substrate 10 by intentionally providing a member that does not have a problem even if cracks occur in a place where cracks are likely to occur. Based on this knowledge.

  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, only the bonding material 80 is interposed between the gas discharge side end surface of the support substrate 10 and the gas inflow side end surface of the additional member 90 (see FIGS. 17 and 18). And as shown in FIG. 20, the metal plate (an example of a metal member) 110 may interpose between these two end surfaces. In the example shown in FIGS. 19 and 20, the gas discharge side end surface of the support substrate 10 and the gas inflow side end surface of the metal plate 110 are bonded via the bonding material 80, and the gas inflow side end surface of the additional member 90 and the metal A gas discharge side end surface of the plate 110 is bonded via a bonding material 80.

  As shown in FIG. 21, the metal plate 110 has a plurality of gas flow paths 111 therethrough. As shown in FIGS. 19 and 20, in the state where the metal plate 110 is interposed between the gas discharge side end surface of the support substrate 10 and the gas inflow side end surface of the additional member 90 via the bonding material 80, Each gas flow path 11 of the support substrate 10 is connected to the corresponding gas flow paths 111 and 91 of the metal plate 110 and the additional member 90, respectively. Also in the bonding material 80, the corresponding gas flow path 11 and the gas flow path 111, and the corresponding gas flow path 111 and the gas flow path 91 are connected to each other (through the longitudinal direction). Each is formed.

  Hereinafter, the operation and effect of the metal plate 110 interposed as described above will be described. A configuration in which the metal plate 110 is not interposed between the support substrate 10 and the additional member 90, that is, a configuration in which only the bonding material 80 is interposed between the support substrate 10 and the additional member 90 (FIGS. 15, 17, and 18). In the case where a crack is generated in the additional member 90 as described above, if the crack grows and proceeds to a large extent, the crack is formed on the gas discharge side end of the support substrate 10 via the bonding material 80. It is also possible to reach it.

  In this respect, since the metal has ductility, the metal plate 110 is hardly cracked. Therefore, as described above, in the configuration in which the metal plate 110 is interposed between the support substrate 10 and the additional member 90, even if the degree of growth / progress of cracks generated in the additional member 90 is large, When the crack reaches the metal plate 110, the progress of the crack stops. That is, it becomes difficult for the crack to reach the gas discharge side end of the support substrate 10.

As shown in FIG. 22, the metal plate 110 may be covered with a coating film 130. Specifically, the coating film 130 is formed so as to cover the outer surface of the metal plate 110. When the metal plate 110 is made of stainless steel, by covering the metal member 110 with the coating film 130, it is possible to prevent chromium from flowing out from the metal plate 110 to the outside. As a result, the problem that the air electrode 60 and the like are poisoned by chromium volatilized from the metal plate 110 can be prevented. The coating film 130 may be a ceramic film that is stable at a high temperature, and may be composed of, for example, Cr ₂ O ₃ , Al ₂ O ₃ , (Mn, Co) ₃ O ₄ , ZnO, or the like.

  Further, in the above embodiment, each gas flow path 91 of the additional member 90 is connected to one corresponding gas flow path 11 of the support substrate 10, but the additional member 90 has a single gas flow path 91. The single gas flow path 91 of the additional member 90 may be connected to all of the plurality of gas flow paths 11 of the support substrate 10. Similarly, in the above embodiment, each gas flow path 111 of the metal member 110 is connected to one corresponding gas flow path 11 of the support substrate 10, but the metal member 110 is a single gas flow path 111. The single gas flow path 111 of the metal member 110 may be connected to all of the plurality of gas flow paths 11 of the support substrate 10.

  Moreover, in the said embodiment, although one member (additional member 90) is employ | adopted as said additional member, as shown in FIGS. 23-26, the several pipe 120 is employ | adopted as said additional member. Also good. In the example shown in FIGS. 23 to 26, one end portion (gas inflow side end portion) of each pipe 120 is inserted into the gas discharge side end portion of the corresponding one gas flow path 11 of the support substrate 10, and Bonded via a bonding material 80.

  By providing this pipe 120, the fuel gas flowing through the gas flow path 11 in the support substrate 10 is not immediately discharged from the gas discharge side end of the support substrate 10 to the external space, but in the pipe 120. After passing through the gas flow path 121, the gas is discharged from the gas discharge side end of the pipe 120 to the external space. Therefore, as in the above-described embodiment, the air in the external space is less likely to enter the gas discharge side end of the support substrate 10 through the gas discharge side end of the gas flow path 11 in the support substrate 10. . As a result, the possibility of cracks occurring at the gas discharge side end of the support substrate 10 can be reduced.

  Similar to the additional member 90, the pipe 120 may be made of porous ceramics (porosity of 10% or more) or may be made of dense ceramics (porosity of less than 10%). When the pipe 120 is made of porous ceramics, the outer surface of the pipe 120 may be covered with a dense ceramic film. Moreover, the pipe 120 may be comprised with the metal containing chromium (Cr). In this case, from the viewpoint of preventing the occurrence of the chromium poisoning, the outer surface of the pipe 120 may be covered with a dense ceramic film.

Moreover, in the said embodiment, although the several gas flow path 11 is formed in the support substrate 10, the single gas flow path 11 may be formed. In this case, a single gas passage 91 (and a single gas passage 111) is formed in the additional member 90 (and the metal plate 110).
In this case, a single pipe 120 is provided.

  Further, in the above embodiment, a plurality of recesses 12 are formed on each of the upper and lower surfaces of the flat support substrate 10 and a plurality of power generation element portions A are provided, but a plurality of recesses 12 are provided only on one side of the support substrate 10. , And a plurality of power generating element portions A may be provided. Furthermore, the support substrate 10 may have a cylindrical shape. Further, in the above-described embodiment, a so-called “horizontal stripe type” configuration in which a plurality of power generation element portions A electrically connected in series is disposed on one main surface of the support substrate 10 is employed. However, a configuration in which one power generation element portion A is disposed on one main surface of the support substrate 10 (so-called “vertical stripe type”) may be employed.

  DESCRIPTION OF SYMBOLS 10 ... Support substrate, 11 ... Fuel gas flow path, 20 ... Fuel electrode, 30 ... Interconnector, 40 ... Solid electrolyte membrane, 50 ... Reaction prevention membrane, 60 ... Air electrode, 70 ... Air electrode current collection membrane, 80 ... Joining 90 ... additional member, 91 ... gas flow path, 110 ... metal plate, 111 ... gas flow path, 120 ... pipe, 121 ... gas flow path, A ... power generation element part

Claims (9)

A support substrate having a longitudinal direction and having one or more gas flow paths penetrating in the longitudinal direction therein, wherein a first side of each gas flow path in the longitudinal direction corresponds to a gas inflow side. The second side opposite to the first side in the longitudinal direction of each gas flow path corresponds to the gas discharge side, and a support substrate;
A power generating element portion provided on the surface of the support substrate, wherein at least a fuel electrode, a solid electrolyte, and an air electrode are laminated in this order;
One or more gases that are additional members attached to the end of the support substrate in the longitudinal direction on the second side and that pass through the longitudinal direction and are connected to the gas flow paths of the support substrate. An additional member having a flow path therein;
A fuel cell. The fuel cell according to claim 1, wherein
The additional member is bonded to the support substrate via a bonding material. The fuel cell according to claim 1 or 2,
Each gas channel of the additional member is a fuel cell connected to one gas channel corresponding to the support substrate. The fuel cell according to any one of claims 1 to 3, wherein
A metal member interposed between the support substrate and the additional member in the longitudinal direction;
The metal member has one or a plurality of gas passages penetrating in the longitudinal direction and connected to the gas passages of the support substrate.
Fuel cell. The fuel cell according to claim 4, wherein
A fuel cell further comprising a coating film covering a surface of the metal member. The fuel cell according to claim 4 or 5 dependent on claim 2 ,
The second side end surface of the support substrate and the first side end surface of the additional member are arranged to face each other.
The metal member is interposed between the end surface on the second side of the support substrate and the end surface on the first side of the additional member,
The end surface on the second side of the support substrate and the end surface on the first side of the metal member are bonded via the bonding material, and the end surface on the first side of the additional member and the metal member The fuel cell, wherein the additional member is joined to the second-side end portion of the support substrate by joining the second-side end surface via the joining material. The fuel cell according to any one of claims 4 to 6, wherein
Each of the gas flow paths of the metal member is a fuel cell connected to a corresponding one of the gas flow paths of the support substrate. The fuel cell according to claim 1, wherein
The additional member, the is the end of the second side of the corresponding one of the gas flow path of the supporting substrate is inserted respectively bonded via且one junction member, to one or more of the longitudinal A fuel cell, which is a tubular member extending. The fuel cell according to any one of claims 1 to 8, wherein
The additional member is a fuel cell made of porous ceramics.

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