JP5095878B1 - Fuel cell - Google Patents

Abstract

A fuel cell which is a fired body including a flat porous support substrate having a gas flow path formed therein, and suppresses the occurrence of cracks in the support substrate during firing.
The fuel cell includes a flat porous support substrate 11 in which a gas flow path 18 is formed, and a main surface of the support substrate 11. The fuel cell includes at least a fuel electrode 12, a solid electrolyte 13, And a power generation element unit in which the air electrode 14 is laminated in this order. Note that the occurrence of cracks in the support substrate has a strong correlation with the “surface roughness of the wall surface of the gas flow path” of the fuel cell in a non-reduced state. In a state where the fuel cell is a non-reduced body that has not been heat-treated in a reducing atmosphere, the cracks are caused when the surface roughness of the wall surface of the gas channel 18 is 0.11 to 5.1 μm in terms of arithmetic average roughness Ra. The generation of can be suppressed.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell.

  Conventionally, a power generation in which a flat porous support substrate having a gas flow path formed therein and a main surface of the support substrate are provided, and at least a fuel electrode, a solid electrolyte, and an air electrode are stacked in this order. 2. Description of the Related Art Fuel cells that are fired bodies including element portions are widely known (see, for example, Patent Documents 1 and 2).

  Such a fuel cell is manufactured, for example, by the following procedure. First, the fuel electrode molded body and the solid electrolyte molded body are sequentially laminated on the main surface of the support substrate molded body. This laminated molded body is simultaneously fired in an air atmosphere. An air electrode molded body is laminated on the surface of the solid electrolyte in the laminated fired body. A fuel cell as a fired body is manufactured by firing the molded body of the air electrode in an air atmosphere.

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

  By the way, at the time of simultaneous firing of the laminated molded body described above, cracks sometimes occurred from the wall surface of the gas flow path to the main surface inside the support substrate (see FIGS. 2 and 17 described later). The present inventor has conducted various experiments in order to deal with such problems. As a result, the present inventors have found that the occurrence of such cracks has a strong correlation with the “surface roughness of the wall surface of the gas flow path”.

  The present invention is a fuel cell that is a fired body including a flat porous support substrate having a gas flow path formed therein, and can suppress the occurrence of cracks in the support substrate during firing. The purpose is to provide things.

A fuel cell according to the present invention includes a flat porous support substrate having a gas flow path formed therein,
A fired body provided on a main surface of the support substrate, and including a power generation element portion in which at least a fuel electrode, a solid electrolyte, and an air electrode are stacked in this order. In this fuel cell, the support substrate has a longitudinal direction, and a plurality of the gas flow paths parallel to each other are formed in the support substrate at intervals in the width direction along the longitudinal direction. The outer periphery of the support substrate is covered with the dense solid electrolyte membrane. The feature of this fuel cell is that the surface of the surface composed of the material of the support substrate in the inner wall portion of the gas flow path in a state where the fuel cell is a non-reduced body that has not been heat-treated in a reducing atmosphere. However, the arithmetic average roughness Ra is 0.11 to 5.1 μm.

  Here, the porosity of the support substrate is preferably 10 to 40%. The support substrate has a longitudinal direction, and a plurality of gas flow paths parallel to each other are formed in the support substrate at intervals in the width direction along the longitudinal direction. The aspect ratio, which is the ratio of the width of the support substrate to the thickness, can be 5 or more. The thickness of the support substrate may be 1 to 5 mm, and the cross-sectional shape of each gas flow path may be a circle having a diameter of 0.5 to 3 mm. The support substrate may include nickel oxide NiO or nickel Ni and insulating ceramics.

  In general, in a solid oxide fuel cell (hereinafter referred to as “SOFC”), in order to acquire the conductivity of the fuel electrode, before operating the SOFC, the temperature is higher than that of the SOFC (fuel electrode) as a fired body. It is necessary to perform a heat treatment (hereinafter referred to as “reduction treatment”) for supplying a reducing gas at a lower temperature (for example, about 800 ° C.) to reduce NiO constituting the fuel electrode to Ni. That is, it is necessary to transfer the SOFC (the fuel electrode) from the non-reduced form to the reduced form.

  If the SOFC (reduced electrode) is continuously exposed to the reducing atmosphere until the temperature is lowered to around 400 ° C. in the process of lowering the SOFC that has been reduced by the reduction treatment from about 800 ° C. to room temperature, The SOFC (fuel electrode) is maintained in the reductant even under. On the other hand, when the SOFC (fuel electrode) is exposed to an oxidizing atmosphere before the SOFC that has been reduced by the reduction treatment is cooled down to around 400 ° C., the fuel electrode is re-oxidized and then at room temperature thereafter. The SOFC can be maintained in a non-reduced form. That is, the SOFC (the fuel electrode) can return from the reductant to the non-reducer. Further, the SOFC (the fuel electrode) is removed from the non-reduced material by performing the reduction treatment again at about 800 ° C. with respect to the SOFC in a state where the SOFC (the fuel electrode) becomes a non-reduced material by the reoxidation. It can move again to the reductant. As described above, the state of the SOFC (after production) that is a fired body can be either a reduced form or a non-reduced form depending on the subsequent use conditions.

  The present inventor has compared the case where the surface roughness of the wall surface of the gas flow path is 0.11 to 5.1 μm in arithmetic mean roughness Ra in a state where SOFC is non-reduced as compared to the case where it is not. Thus, it has been found that cracks extending from the wall surface of the gas flow path to the main surface are less likely to occur. Details of this point will be described later.

1 is a perspective view showing a fuel cell according to a first embodiment of the present invention. It is a figure which shows the crack which may generate | occur | produce in the electroconductive support body of the fuel cell shown in FIG. It is a perspective view which shows the fuel cell which concerns on 2nd Embodiment of this invention. FIG. 4 is a cross-sectional view corresponding to line 4-4 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. FIG. 4 is a diagram for explaining a current flow in an operating state of the fuel cell shown in FIG. 3. It is a perspective view which shows the support substrate shown in FIG. FIG. 5 is a cross-sectional view corresponding to FIG. 4 in a first stage in the manufacturing process of the fuel cell shown in FIG. 3. FIG. 5 is a cross-sectional view corresponding to FIG. 4 in a second stage in the manufacturing process of the fuel cell shown in FIG. 3. FIG. 5 is a cross-sectional view corresponding to FIG. 4 in a third stage in the manufacturing process of the fuel cell shown in FIG. 3. FIG. 5 is a cross-sectional view corresponding to FIG. 4 in a fourth stage in the manufacturing process of the fuel cell shown in FIG. 3. FIG. 5 is a cross-sectional view corresponding to FIG. 4 in a fifth stage in the manufacturing process of the fuel cell shown in FIG. 3. FIG. 5 is a cross-sectional view corresponding to FIG. 4 in a sixth stage in the manufacturing process of the fuel cell shown in FIG. 3. FIG. 5 is a cross-sectional view corresponding to FIG. 4 in a seventh stage in the manufacturing process of the fuel cell shown in FIG. 3. FIG. 5 is a cross-sectional view corresponding to FIG. 4 in an eighth stage in the manufacturing process of the fuel cell shown in FIG. 3. It is a figure which shows the crack which may generate | occur | produce in the support substrate of the fuel cell shown in FIG. It is sectional drawing corresponding to FIG. 4 of the 1st modification of the fuel cell which concerns on this invention. It is sectional drawing corresponding to FIG. 4 of the 2nd modification of the fuel cell which concerns on this invention. It is sectional drawing corresponding to FIG. 4 of the 3rd modification of the fuel cell which concerns on this invention. FIG. 6 is a cross-sectional view corresponding to FIG. 5 of a fourth modification of the fuel cell according to the present invention. It is a figure corresponding to FIG. 1 in case the cross-sectional shape of the gas flow path inside a support substrate is flat.

(First embodiment)
As shown in FIG. 1, in a first embodiment of a solid oxide fuel cell (SOFC) according to the present invention, a porous fuel electrode is formed on one main surface of a flat porous conductive support 11. 12, a dense solid electrolyte 13 and an air electrode 14 made of porous conductive ceramics are sequentially laminated. Further, an intermediate film 15, an interconnector 16 made of a lanthanum-chromium oxide material, and a current collecting film 17 made of a P-type semiconductor material are sequentially formed on the main surface of the conductive support 11 opposite to the air electrode 14. Has been.

  A plurality of gas flow paths 18 parallel to each other are formed in the conductive support 11 at intervals in the width direction (y direction) along the longitudinal direction (x axis direction). The cross-sectional shape of each gas flow path 18 is a circle having a diameter D of 0.5 to 3 mm. The space | interval (pitch) P in the width direction of the adjacent gas flow paths 18 and 18 is 1-5 mm. In addition, the cross-sectional shape of each gas flow path 18 may be an ellipse, a long hole, a quadrangle having arcs at four corners, or the like.

  In the first embodiment, side end portions B and B provided on both sides in the width direction (direction perpendicular to the longitudinal direction), and a pair of flat portions A and A connecting the side end portions B and B, It is composed of The pair of flat portions A and A are flat and substantially parallel. On one of the flat portions A and A, the fuel electrode 12, the solid electrolyte 13, and the air electrode 14 are formed in this order on one main surface of the conductive support 11, and on the other of the flat portions A and A, On the other main surface of the conductive support 11, an intermediate film 15, an interconnector 16, and a current collecting film 17 are formed in this order.

  The width W of the conductive support 11 is preferably 10 to 100 mm, and the thickness T is preferably 1 to 5 mm. The aspect ratio (W / T) of the conductive support 11 is 5 to 100. The shortest distance between the main surface of the conductive support 11 and the wall surface of the gas flow path 18 is (TD) / 2. The shape of the conductive support 11 is expressed as “thin plate shape”, but depending on the combination of the dimension in the width direction and the dimension in the thickness direction, it may be referred to as “ellipsoidal column shape” or “flat shape”. Can be expressed.

  The conductive support 11 is composed mainly of a rare earth element oxide composed of one or more selected from Y, Lu, Yb, Tm, Er, Ho, Dy, Gd, Sm and Pr and Ni and / or NiO. It is desirable to be composed of the material In addition to Ni, Fe, Cu, or the like may be included.

The conductive support 11 can also be described as including “NiO (nickel oxide) or Ni (nickel)” and “insulating ceramics”. Insulating ceramics include CSZ (calcia stabilized zirconia), YSZ (8YSZ) (yttria stabilized zirconia), Y ₂ O ₃ (yttria), MgO (magnesium oxide), or “MgAl ₂ O ₄ (magnesia alumina spinel). ) And MgO (magnesium oxide) "or the like. The conductivity of the conductive support 11 is 10 to 2000 S / cm at 800 ° C. The porosity of the conductive support 11 is 10 to 40%.

The intermediate film 15 formed between the conductive support 11 and the interconnector 16 is made of a material mainly containing ZrO ₂ containing Ni and / or NiO and a rare earth element, or a rare earth oxide (for example, Y ₂ O ₃ ). The Ni conversion amount of the Ni compound in the intermediate film 15 is preferably 35 to 80% by volume, and more preferably 50 to 70% by volume in the total amount. When the Ni conversion amount is 35% by volume or more, the conductive path by Ni is increased, and the conductivity of the intermediate film 15 is improved. As a result, the voltage drop caused by the intermediate film 15 is reduced. Moreover, when the Ni conversion amount is 80% by volume or less, the difference in thermal expansion coefficient between the conductive support 11 and the interconnector 16 can be reduced, and the occurrence of cracks at the interface between the two can be suppressed.

  Further, from the viewpoint of reducing the voltage drop, the thickness of the intermediate film 15 is preferably 20 μm or less, and more preferably 10 μm or less.

The thermal expansion coefficient of the middle rare earth element or heavy rare earth element oxide is smaller than that of “ZrO ₂ containing Y ₂ O ₃ ” in the solid electrolyte 13. Therefore, the thermal expansion coefficient of the conductive support 11 as a cermet material with Ni can be made closer to the thermal expansion coefficient of the solid electrolyte 13. As a result, cracks in the solid electrolyte 13 and separation of the solid electrolyte 13 from the fuel electrode 12 can be suppressed. Furthermore, by using a heavy rare earth element oxide having a small thermal expansion coefficient, Ni in the conductive support 11 can be increased, and the electrical conductivity of the conductive support 11 can be increased. From this viewpoint, it is desirable to use heavy rare earth element oxides.

  If the sum of the thermal expansion coefficients of the rare earth element oxide is less than the thermal expansion coefficient of the solid electrolyte 13, the light rare earth elements La, Ce, Pr, and Nd oxides are added to the medium rare earth element and heavy rare earth element. Even if it is contained, there is no problem.

  Moreover, the raw material cost can be significantly reduced by using a complex rare earth element oxide containing a plurality of inexpensive rare earth elements in the course of purification. Also in this case, it is desirable that the thermal expansion coefficient of the complex rare earth element oxide is less than the thermal expansion coefficient of the solid electrolyte 13.

  Further, it is desirable to provide a current collector film 17 made of a P-type semiconductor, for example, a transition metal perovskite oxide, on the surface of the interconnector 16. When a current collecting member made of metal is disposed directly on the surface of the interconnector 16, the potential drop increases due to non-ohmic contact. In order to secure ohmic contact and reduce the potential drop, it is necessary to connect the current collector film 17 made of a P-type semiconductor to the interconnector 16. As the P-type semiconductor, it is desirable to use a transition metal perovskite oxide. As the transition metal perovskite oxide, it is desirable to use at least one of a lanthanum-manganese oxide, a lanthanum-iron oxide, a lanthanum-cobalt oxide, or a composite oxide thereof.

The fuel electrode 12 provided on the main surface of the conductive support 11 is composed of Ni and ZrO _{2 in} which a rare earth element is dissolved. The thickness of the fuel electrode 12 is desirably 1 to 30 μm. When the thickness of the fuel electrode 12 is 1 μm or more, a three-layer interface as the fuel electrode 12 is sufficiently formed. Further, when the thickness of the fuel electrode 12 is 30 μm or less, interfacial peeling due to a difference in thermal expansion from the solid electrolyte 13 can be prevented.

The solid electrolyte 13 provided on the main surface of the fuel electrode 12 is made of yttria-stabilized zirconia YSZ (dense ceramic) containing yttria (Y ₂ O ₃ ). The thickness of the solid electrolyte 13 is desirably 0.5 to 100 μm. Gas permeation can be prevented when the thickness of the solid electrolyte 13 is 0.5 μm or more. Moreover, the increase in a resistance component can be suppressed because the thickness of the solid electrolyte 13 is 100 micrometers or less.

The air electrode 14 is a lanthanum-manganese oxide, lanthanum-iron oxide, lanthanum-cobalt oxide of a transition metal perovskite oxide, or at least one porous conductive material of a composite oxide thereof. Made of ceramics. The air electrode 14 is preferably a (La, Sr) (Fe, Co) O ₃ system from the viewpoint of high electrical conductivity in the middle temperature range of about 800 ° C. The thickness of the air electrode 14 is preferably 10 to 100 μm from the viewpoint of current collection.

  The interconnector 16 is a dense body in order to prevent leakage of fuel gas and oxygen-containing gas between the inside and outside of the conductive support 11. Moreover, since the inner and outer surfaces of the interconnector 16 are in contact with the fuel gas and the oxygen-containing gas, respectively, they have reduction resistance and oxidation resistance.

  The thickness of the interconnector 16 is desirably 30 to 200 μm. When the thickness of the interconnector 16 is 30 μm or more, gas permeation can be completely prevented, and when it is 200 μm or less, an increase in resistance component can be suppressed.

For example, a bonding layer made of Ni and ZrO ₂ or Y ₂ O ₃ may be interposed between the end portion of the interconnector 16 and the end portion of the solid electrolyte 13 in order to improve the sealing performance.

  In the first embodiment, the dense solid electrolyte 13 is not only on one main surface of the conductive support 11 but also on the other main surface via the side end portion of the conductive support 11. To the side end face. That is, the solid electrolyte 13 is extended to the other main surface of the conductive support 11 so as to form the side ends B, B on both sides, and is joined to the interconnector 16. Note that the side ends B and B (side ends of the conductive support 11) have curved shapes that protrude outward in the width direction in order to relieve the thermal stress that occurs due to heating and cooling associated with power generation. It is desirable.

  Next, the manufacturing method of 1st Embodiment which was demonstrated above is demonstrated. First, rare earth element oxide powder excluding La, Ce, Pr, and Nd elements and Ni and / or NiO powder are mixed. A conductive support material in which an organic binder and a solvent are mixed is extruded into this mixed powder to produce a plate-shaped conductive support molded body. This molded body is dried and degreased.

In addition, a sheet-like solid electrolyte molded body is produced using a solid electrolyte material in which a ZrO ₂ powder in which a rare earth element (Y) is dissolved, an organic binder, and a solvent are mixed.

Next, a slurry to be the fuel electrode 12 prepared by mixing Ni and / or NiO powder, ZrO ₂ powder in which a rare earth element is solid-solved, an organic binder, and a solvent is formed into the solid electrolyte molded body. Applied to one side. Thereby, a fuel electrode molded body is formed on one surface of the solid electrolyte molded body.

  Next, the conductive support body is formed such that a laminate of the sheet-like solid electrolyte formed body and the fuel electrode body is in contact with the conductive electrode body. It is wound around the compact.

  Next, several layers of the sheet-like solid electrolyte molded body are laminated on the solid electrolyte molded body at the position where the side end portions B and B of the laminated molded body are formed, and dried. Moreover, the slurry used as the solid electrolyte 13 may be screen-printed on the solid electrolyte molded body. In addition, degreasing may be performed at this time.

  Next, a sheet-like interconnector molded body is produced using an interconnector material in which a lanthanum-chromium oxide powder, an organic binder, and a solvent are mixed.

Moreover, a sheet-like intermediate film molded body is produced using a slurry in which Ni and / or NiO powder, a ZrO ₂ powder in which a rare earth element is dissolved, an organic binder, and a solvent are mixed.

  Next, the interconnector molded body and the intermediate film molded body are laminated. The laminate is laminated on the conductive support molded body so that the intermediate film molded body side of the laminate is in contact with the exposed conductive support molded body side.

  Thereby, the fuel electrode molded body and the solid electrolyte molded body are sequentially laminated on one main surface of the conductive support molded body, and the intermediate film molded body and the interconnector molded body are laminated on the other main surface. A body is made. Each molded body can be produced by sheet molding by a doctor blade, printing, slurry dip, spraying by spraying, and the like. Moreover, each molded object can be produced by these combinations.

  Next, the laminated molded body is degreased and cofired at 1300 to 1600 ° C. in an oxygen-containing atmosphere.

  Next, a transition metal perovskite oxide powder, which is a P-type semiconductor, and a solvent are mixed to produce a paste. The laminate is immersed in this paste. An air electrode molded body and a current collector film molded body are formed on the surfaces of the solid electrolyte 13 and the interconnector 16 by dipping or direct spray application, respectively. These molded bodies are baked at 1000 to 1300 ° C., whereby the fuel cell according to the present invention is manufactured.

  At this time, the Ni component in the conductive support 11, the fuel electrode 12, and the intermediate film 15 is NiO by firing in an oxygen-containing atmosphere. Therefore, in order to acquire these electroconductivity, after that, reducing fuel gas is flowed from the electroconductive support body 11 side, and NiO is reduced at 800-1000 degreeC over 1 to 10 hours. This reduction process may be performed during power generation.

(Surface roughness of gas flow path)
As described in the above-mentioned summary of the invention, the state of the fuel cell (after production) that is a fired body can be either a reduced body or a non-reduced body depending on the subsequent use conditions. .

  As described above, when the degreased laminated molded body is co-fired at 1300 to 1600 ° C. in an oxygen-containing atmosphere, the gas flow path 18 is formed inside the conductive support 11 as shown in FIG. In some cases, cracks occurred from the wall surface to the main surface. The present inventor has found that the occurrence of such cracks has a strong correlation with the “surface roughness of the wall surface of the gas flow path” of the fuel cell in the non-reducing state. Hereinafter, test A in which this has been confirmed will be described.

(Test A)
In the test A, the fuel cell according to the first embodiment (see FIG. 1) is different in the combination of the material of the conductive support 11 and the “surface roughness of the wall surface of the gas channel” in the non-reducing state. Multiple samples were made. Specifically, as shown in Table 1, 15 types (combinations) were prepared. Twenty samples (N = 20) were made for each level. As surface roughness, JIS
“Arithmetic mean roughness Ra” defined in B 0601: 2001 was adopted. The value of the surface roughness described in Table 1 is a value (average value of N = 20) at the stage after completion of the first embodiment as a fired body and before the reduction treatment. The surface roughness was measured along the longitudinal direction of the gas flow path 18. The surface roughness meter used for this measurement is TAYLOR
It is Form Tally Surf Plus manufactured by HOBSON. The radius of curvature of the stylus is 2 μm.

  As the conductive support 11 used in each sample (the fuel cell shown in FIG. 1), the porosity of the material is 10 to 40%, and the thickness T and the width W are 2.5 mm and 50 mm, respectively ( In other words, the aspect ratio W / T is 20), the cross-sectional shape of the gas flow path 18 is a circle having a diameter of 1.5 mm, and the pitch P between the adjacent gas flow paths 18 and 18 is 5.0 mm. It was done. In each sample, as described above, the laminated molded body (a molded body in which at least a fuel electrode molded body and a solid electrolyte molded body were laminated on a conductive support molded body) was simultaneously fired.

  The adjustment of the “surface roughness of the wall surface of the gas flow path” is performed by adjusting the surface roughness of the mold used for extrusion molding of the conductive support molded body, the powder used for the molding (La, Ce, Pr, Nd). By adjusting the particle size and specific surface area of rare earth element oxide powder and Ni and / or NiO powder, etc., the amount of organic components (binder, pore former), firing temperature, firing time, etc. Achieved. The surface roughness of the mold can be adjusted by surface polishing, fluororesin coating or the like.

Specifically, the surface roughness Ra (JIS B 0601: 2001) of the mold was adjusted within a range of 0.1 to 6.3 μm. The average particle diameter (D50) of the powder was adjusted within the range of 0.5 to 5 μm. More specifically, the average particle size (D50) of NiO powder is 0.3 to 2.0 μm, the average particle size (D50) of Y ₂ O ₃ powder is 0.4 to 2.5 μm, and the average particle size of 8YSZ powder. (D50) was adjusted within the range of 0.5 to 1.8 μm. The specific surface area of the powder was adjusted within a range of 3 to 30 m ² / g. The amount (weight) of the organic component was adjusted within a range of 10 to 50% with respect to the total weight of the powder. Cellulose, carbon, PMMA, etc. were used as the pore former. The average particle diameter (D50) of the pore former was adjusted within the range of 0.5 to 30 μm. The firing temperature was adjusted within the range of 1300 to 1600 ° C. The firing time was adjusted within a range of 1 to 20 hours.

  In this test (the same applies to test B described later), the porosity of the support (support substrate) was measured as follows. First, a so-called “resin filling” process was performed on the support (support substrate) so that the resin entered the pores of the support (support substrate). The surface of the support (support substrate) treated with “resin filling” was mechanically polished. By performing image processing on the image obtained by observing the microstructure of the mechanically polished surface with a scanning electron microscope, the pore portion (the portion where the resin enters) and the non-pore portion ( The area of the portion where the resin did not enter was calculated. The ratio of the “area of the pore portion” to the “total area (the area of the pore portion and the area of the non-pore portion)” was defined as the “porosity” of the support (support substrate).

  And about each sample in the stage (non-reduction state) before the said reduction process, the presence or absence of the generation | occurrence | production of the crack in the electroconductive support body 11 was confirmed. This confirmation was made by visual observation as well as observation using a microscope. The results are as shown in Table 1.

  As can be understood from Table 1, when the “surface roughness of the wall surface of the gas passage” in the non-reduced state exceeds 5.1 μm in terms of arithmetic average roughness Ra, as shown in FIG. Inside the body 11, cracks are likely to occur from the wall surface of the gas flow path 18 to the main surface. This is considered based on the following reasons. In other words, as described above, the outer periphery of the conductive support of the first embodiment (see FIG. 1) is a dense membrane having a gas sealing property that prevents mixing of two types of gases (air and fuel) ( Solid electrolyte 13 and interconnector 16). When the laminated molded body is simultaneously fired, the dense film and the conductive support 11 shrink at different shrinkage rates (firing shrinkage). Therefore, the conductive support 11 is baked and shrunk while its outer periphery is restrained by a dense film having a different baking shrinkage rate. On the other hand, the aspect ratio (W / T) of the conductive support 11 is as large as 5 or more. Therefore, the firing shrinkage amount of the conductive support 11 is greatly different between the width direction and the thickness direction. As described above, the conductive support 11 has a large aspect ratio, and the outer periphery of the conductive support 11 is constrained by a dense film having different firing shrinkage rates. It will be placed under the stress environment peculiar to. At that time, the strain generated in the conductive support 11 is concentrated on the wall surface of the gas flow path 18 which is a free end with respect to deformation due to stress. From the above, it is considered that cracks are likely to occur from the wall surface to the main surface starting from the wall surface of the gas flow path 18. In the case of a SOFC of a type in which the outer periphery of the flat support is not covered with a dense film, the support can be deformed relatively freely (can be warped) during the reduction treatment, and thus the above-mentioned. The “strain concentration on the wall surface of the gas flow path” is easily relaxed. That is, since the support is not originally placed in the above-described unique stress environment, the above-described cracks are unlikely to occur.

  Furthermore, it is considered that cracks are likely to occur from the wall surface of the gas flow path 18 to the main surface based on the following reason. That is, it is considered to be based on the difference between the firing shrinkage rate in the plane direction (xy plane direction) and the firing shrinkage rate in the thickness direction (z direction) of the conductive support 11 at the time of simultaneous firing of the laminated molded body. It is done. That is, at the time of the simultaneous firing, in the thickness direction (z direction), the respective layers constituting the laminated molded body can freely contract without being constrained to each other. As a result, the shrinkage rate of each layer can be a value specific to its own material. On the other hand, in the plane direction (xy direction), each layer constituting the laminated molded body contracts while being influenced by the contraction rate inherent to the material of the adjacent layer. As a result, the shrinkage rate of each layer does not match the value specific to its own material. As described above, a difference occurs between the firing shrinkage rate in the planar direction (xy plane direction) of the conductive support 11 and the firing shrinkage rate in the thickness direction (z direction). It is considered that cracks are generated from the wall surface of the gas flow path 18 to the main surface inside the conductive support 11 due to the three-dimensional difference in shrinkage rate.

  On the other hand, as can be understood from Table 1, when the “surface roughness of the gas flow path wall surface” in the non-reduced state is 5.1 μm or less in terms of arithmetic average roughness Ra, the crack is hardly generated. it can.

  Moreover, the electroconductive support body 11 used by each sample is produced by the extrusion molding of the electroconductive support body material as mentioned above. In each sample, the surface roughness of the wall surface of the gas flow path is not finished after the formation (molding) of the conductive support 11. In this state, the “surface roughness of the wall surface of the gas flow path” in the non-reduced state could not be made less than 0.11 μm in terms of arithmetic average roughness Ra. From the above, it is preferable that the “surface roughness of the wall surface of the gas flow path” in the non-reduced state is within the range of 0.11 to 5.1 μm in terms of arithmetic average roughness Ra.

  Note that a coating film (for example, a YSZ film) may be formed on the wall surface of the gas flow path of the support for the purpose of preventing reoxidation of Ni inside the support. In this case, the surface roughness of the “surface formed of the support material on the inner wall of the gas flow path” in the reduced state (that is, the surface covered with the coating film, not the surface of the coating film) is an arithmetic average. The roughness Ra is preferably within a range of 0.11 to 5.1 μm.

  This result corresponds to the case where the cross-sectional shape of each gas flow path 18 is circular. It has already been confirmed that it can be obtained. This result corresponds to the case where the aspect ratio of the conductive support is 20, but it has already been confirmed that the same result can be obtained if the aspect ratio of the conductive support is in the range of 5 to 100. ing.

(Second Embodiment)
FIG. 3 shows a second embodiment of a solid oxide fuel cell (SOFC) according to 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 5 to 50 cm and whose length in the width direction (y-axis direction) perpendicular to the longitudinal direction is 1 to 10 cm. 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. 3, the details of the SOFC will be described with reference to FIG. 4, which is a partial cross-sectional view of the SOFC corresponding to line 4-4 shown in FIG. 3. FIG. 4 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. 8 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. The cross-sectional shape of each fuel gas channel 11 is a circle having a diameter D of 0.5 to 3 mm. The space | interval (pitch) P in the width direction of the adjacent fuel gas flow paths 11 and 11 is 1-5 mm. In addition, the cross-sectional shape of each fuel gas flow path 11 may be an ellipse, a long hole, a quadrangle having arcs at four corners, or the like. Further, in this example, each recess 12 includes a bottom wall made of the material of the support substrate 10 and a side wall made of the material of the support substrate 10 over the entire circumference (two side walls and a width along the longitudinal direction). Two side walls extending in the direction), and a rectangular parallelepiped-shaped depression.

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 porosity of the support substrate 10 is 10 to 40%.

  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 width W of the support substrate 10 is 10 to 100 mm, and the thickness T is 1 to 5 mm. The aspect ratio (W / T) of the support substrate 10 is 5-100. The shortest distance between the main surface of the support substrate 10 and the wall surface of the fuel gas channel 11 is (TD) / 2. 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. 4 and 5, the entire fuel electrode current collector 21 is embedded (filled) in each recess 12 formed on 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 oxidative ion (oxygen ion) conductivity. The “volume ratio of the substance having oxidative ion conductivity relative to the total volume excluding the pore portion” in the anode active portion 22 is “the oxidative ion conductivity relative to the entire volume excluding the pore portion” in the anode current collecting portion 21. Greater than the volume fraction of the substance having

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

  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. 4, 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 parts A and A, the air electrode 60 of one power generation element part A (on the left side in FIG. 4) and the interconnector of the other power generation element part A (on the right side in FIG. 4). 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, the air electrode 60 of one power generation element part A (on the left side in FIG. 4) of each pair of adjacent power generation element parts A and A, The other fuel electrode 20 (in particular, the fuel electrode current collector 21) of the power generating element part A (on the right side in FIG. 4) is connected via 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, the fuel gas (hydrogen gas or the like) flows through the fuel gas flow path 11 of the support substrate 10 and the upper and lower surfaces of the support substrate 10 (particularly with respect to the “horizontal stripe type” SOFC described above, as shown in the figure. Each of the air electrode current collector films 70) is exposed to “a gas containing oxygen” (air or the like) (or a gas containing oxygen is allowed to flow along the upper and lower surfaces of the support substrate 10). An electromotive force is generated by an oxygen partial pressure difference generated between the surfaces. 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 ⁻
(At: Fuel electrode 20) (2)

  In the power generation state, as shown in FIG. 7, 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. 6, from the entire SOFC (specifically, the interconnector 30 of the power generating element part A on the front side in FIG. 6 and the air electrode 60 of the power generating element part A on the farthest side in FIG. Power).

(Production method)
Next, an example of a method for manufacturing the “horizontal stripe type” SOFC shown in FIG. 3 will be briefly described with reference to FIGS. 8 to 16, “g” at the end of the reference numeral of each member indicates that the member is “before firing”.

  First, a support substrate molded body 10g having the shape shown in FIG. 8 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. 9 to 16 showing partial cross sections corresponding to line 9-9 shown in FIG.

  When the support substrate molded body 10g is manufactured as shown in FIG. 9, the fuel electrode current collector is then placed in each recess formed on 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. 11, 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. 12, in each recess formed in “a 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. 13, the outer periphery extending in the longitudinal direction of the molded body 10g of the support substrate in a state in which the molded bodies (21g + 22g) of the plurality of fuel electrodes and the molded bodies 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. 14, a molded film 50 g of a reaction preventing film is formed on the outer surface of the solid electrolyte membrane molded body 40 g in contact with the molded body 22 g of each fuel electrode. 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. 3 is obtained.

  Next, as shown in FIG. 15, 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. 16, for each pair of adjacent power generation element portions, air is formed so as to straddle the air electrode forming 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. In the above, an example of the manufacturing method of SOFC shown in FIG. 3 was demonstrated.

  At this time, the Ni component in the support substrate 10 and the fuel electrode 20 is NiO by firing in an oxygen-containing atmosphere. Therefore, in order to acquire the conductivity of the fuel electrode 20, thereafter, reducing fuel gas is flowed from the support substrate 10 side, and NiO is reduced at 800 to 1000 ° C. for 1 to 10 hours. This reduction process may be performed during power generation.

(Surface roughness of gas flow path)
As in the first embodiment described above, also in the second embodiment, when the laminated molded body shown in FIG. 14 is co-fired at 1500 ° C. in an oxygen-containing atmosphere, as shown in FIG. In some cases, cracks may occur from the wall surface of the gas flow path 11 to the main surface. The present inventor has found that the occurrence of such cracks also has a strong correlation with the “surface roughness of the wall surface of the gas flow path” of the fuel cell in the non-reducing state in the second embodiment. Hereinafter, test B in which this has been confirmed will be described.

(Test B)
In the test B, for the fuel cell according to the second embodiment (see FIG. 3), the combination of the material of the insulating support substrate 10 and the “surface roughness of the wall surface of the gas flow path” in the non-reducing state is Different samples were made. Specifically, as shown in Table 2, 15 kinds of levels (combinations) were prepared. Twenty samples (N = 20) were made for each level. As surface roughness, JIS
“Arithmetic mean roughness Ra” defined in B 0601: 2001 was adopted. The value of the surface roughness described in Table 2 is a value after completion of the second embodiment, which is a fired body, and before the reduction treatment (average value of N = 20). The measurement of the surface roughness was performed along the longitudinal direction of the fuel gas channel 11. In this measurement, the same surface roughness meter as that used in the test A was used.

  As the support substrate 10 used in each sample (fuel cell shown in FIG. 3), the porosity of the material is 10 to 40%, and the thickness T and the width W are 2.5 mm and 50 mm, respectively (that is, The aspect ratio W / T is 20), the cross-sectional shape of the fuel gas channel 11 is a circle having a diameter of 1.5 mm, and the pitch P between adjacent fuel gas channels 11 and 11 is 5.0 mm. It was done. In each sample, the laminated molded body (see FIG. 14) was simultaneously fired as described above.

  The adjustment of the “surface roughness of the wall surface of the gas flow path” is performed by adjusting the surface roughness of the mold used for extrusion molding of the support substrate molding, the particle size of the powder (CSZ powder, etc.) used for the molding, and This was achieved by adjusting the specific surface area, the amount of organic components (binder, pore former), firing temperature, firing time and the like. The surface roughness of the mold can be adjusted by surface polishing, fluororesin coating or the like.

Specifically, the surface roughness Ra (JIS B 0601: 2001) of the mold was adjusted within a range of 0.1 to 6.3 μm. The average particle diameter (D50) of the powder was adjusted within the range of 0.5 to 5 μm. More specifically, the average particle size (D50) of NiO powder is 0.3 to 2.0 μm, the average particle size (D50) of Y ₂ O ₃ powder is 0.4 to 2.5 μm, and the average particle size of 8YSZ powder. (D50) was adjusted within the range of 0.5 to 1.8 μm. The specific surface area of the powder was adjusted within a range of 3 to 30 m ² / g. The amount (weight) of the organic component was adjusted within a range of 10 to 50% with respect to the total weight of the powder. Cellulose, carbon, PMMA, etc. were used as the pore former. The average particle diameter (D50) of the pore former was adjusted within the range of 0.5 to 30 μm. The firing temperature was adjusted within the range of 1300 to 1600 ° C. The firing time was adjusted within a range of 1 to 20 hours.

  The presence or absence of cracks in the insulating support substrate 10 was confirmed for each sample before the reduction treatment (non-reduction state). This confirmation was made by visual observation as well as observation using a microscope. The results are as shown in Table 2.

  As can be understood from Table 2, when the “surface roughness of the wall surface of the gas flow path” in the non-reduced state exceeds 5.0 μm in terms of arithmetic average roughness Ra, as shown in FIG. In the inside, cracks tend to occur from the wall surface of the fuel gas passage 11 to the main surface. This is also the same as the first embodiment described above, because the aspect ratio of the support substrate 10 is large, and the outer periphery of the support substrate 10 is constrained by the dense film 40 having different firing shrinkage rates. When the body (see FIG. 14) is co-fired, the support substrate 10 is placed in a specific stress environment, and the wall surface of the fuel gas channel 11 where the strain generated in the support substrate 10 becomes a free end Concentrating on, is thought to be based on. Furthermore, the firing shrinkage rate in the plane direction (xy plane direction) and the firing shrinkage rate in the thickness direction (z direction) of the support substrate 10 at the time of simultaneous firing of the laminated molded body (see FIG. 14). Based on the difference, a “three-dimensional difference” occurs between the firing shrinkage rate in the plane direction (xy plane direction) of the support substrate 10 and the firing shrinkage rate in the thickness direction (z direction). It is thought to be caused.

  On the other hand, as can be understood from Table 2, when the “surface roughness of the wall surface of the gas flow path” in the non-reduced state is an arithmetic average roughness Ra of 5.0 μm or less, the crack is hardly generated. it can.

  Further, as described above, the support substrate 10 used in each sample is manufactured by extrusion molding of a support substrate material. In each sample, after the support substrate 10 is formed (molded), the surface roughness of the wall surface of the gas channel is not finished. In this state, the “surface roughness of the wall surface of the gas flow path” in the non-reduced state could not be reduced to an arithmetic average roughness Ra of less than 0.15 μm. From the above, it is preferable that the “surface roughness of the wall surface of the gas channel” in the non-reduced state is within the range of 0.15 to 5.0 μm in terms of arithmetic average roughness Ra.

  A coating film (for example, a YSZ film) may be formed on the wall surface of the gas flow path of the support substrate for the purpose of preventing reoxidation of Ni inside the support substrate. In this case, the surface roughness of the “surface formed of the material of the support substrate in the inner wall portion of the gas flow path” in the non-reduced state (that is, the surface covered with the coating film, not the surface of the coating film) is arithmetic. The average roughness Ra is preferably in the range of 0.15 to 5.0 μm.

  This result corresponds to the case where the cross-sectional shape of each fuel gas channel 11 is circular, but the cross-sectional shape of each fuel gas channel 11 is an ellipse, a long hole, a quadrangle having arcs at four corners, etc. Has already been confirmed to produce the same results. This result corresponds to the case where the aspect ratio of the support substrate is 20, but it has already been confirmed that the same result can be obtained if the aspect ratio of the support substrate is in the range of 5 to 100.

(Operations and effects peculiar to the second embodiment)
In the second embodiment described above, the circumferential direction in which each of the plurality of recesses 12 for embedding the fuel electrode 20 formed on the upper and lower surfaces of the support substrate 10 is made of the material of the support substrate 10 over the entire circumference. Have closed side walls. In other words, the support body 10 is formed with a frame surrounding each recess 12. Therefore, this structure is not easily deformed when the support substrate 10 receives an external force.

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

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

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

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

  In addition, this invention is not limited to the said 2nd Embodiment, A various modification is employable within the scope of the present invention. For example, in the second embodiment, as shown in FIG. 8 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. 18, angle (theta) may be 90-135 degrees. Moreover, in the said embodiment, as shown in FIG. 19, the part where the bottom wall and side wall in the recessed part 12 cross | intersect is 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, as shown in FIG. 5, the recess 21 b 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 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. 21, the recess 21 b 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, although the cross-sectional shape of the gas flow path of a support body (support substrate) is circular (refer FIG.1, FIG.3 etc.), as shown in FIG. The cross-sectional shape of the gas flow path may not be circular. Specifically, as shown in FIG. 22, the width direction of the support (support substrate) with respect to the length Z2 in the thickness direction (z-axis direction) of the support (support substrate) in the cross-sectional shape of the gas flow path ( The ratio of the length Z1 in the y-axis direction may be 1.1 or more.

  In the case of a gas flow path having a flat cross-sectional shape in which the ratio is 1.1 or more (expanded in the width direction of the support), the greater the ratio (that is, the greater the degree of flatness), the above-mentioned. It has been separately found that cracks are likely to occur. This is considered to be based on the fact that the above-described “concentration of strain on the wall surface of the gas flow path” is more likely to occur as the ratio is larger (that is, the degree of flatness is larger). Therefore, the greater the ratio (that is, the greater the degree of flatness), the greater the importance of managing the “surface roughness of the wall surface of the gas flow path”.

DESCRIPTION OF SYMBOLS 11 ... Electroconductive support body, 12 ... Fuel electrode, 13 ... Solid electrolyte, 14 ... Air electrode,
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 (7)

A flat porous support substrate having a gas flow path formed therein;
A power generation element portion provided on the main surface of the support substrate, wherein at least a fuel electrode, a solid electrolyte, and an air electrode are laminated in this order;
In a fuel cell which is a fired body provided with
The support substrate has a longitudinal direction, and a plurality of the gas flow paths parallel to each other are formed in the support substrate at intervals in the width direction along the longitudinal direction,
The outer periphery of the support substrate is covered with a dense solid electrolyte membrane,
In a state where the fuel cell is a non-reduced body that has not been heat-treated in a reducing atmosphere, the surface roughness of the surface made of the material of the support substrate in the inner wall portion of the gas flow path is an arithmetic average roughness Ra. A fuel cell having a thickness of 0.11 to 5.1 μm. The fuel cell according to claim 1, wherein
The fuel cell, wherein the support substrate has a porosity of 10 to 40%. The fuel cell according to claim 1 or 2,
The support substrate has a longitudinal direction, and a plurality of the gas flow paths parallel to each other are formed in the support substrate at intervals in the width direction along the longitudinal direction,
A fuel cell, wherein an aspect ratio, which is a ratio of a width of the support substrate to a thickness of the support substrate, is 5 or more. The fuel cell according to any one of claims 1 to 3, wherein
The support substrate is a fuel cell including nickel oxide NiO or nickel Ni and insulating ceramics. 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 at least a fuel electrode, a solid electrolyte, and an air electrode are stacked in this order;
One or a plurality of electrical connections that are respectively provided between one or a plurality of adjacent power generation element portions and electrically connect one fuel electrode and the other air electrode of the adjacent power generation element portions. And
In a fuel cell which is a fired body provided with
Recesses having a bottom wall and a side wall closed in the circumferential direction are formed at the plurality of locations on the main surface of the flat support substrate, respectively.
In each of the recesses, the corresponding fuel electrode of the power generation element portion is embedded,
The support substrate has a longitudinal direction, and a plurality of the gas flow paths parallel to each other are formed in the support substrate at intervals in the width direction along the longitudinal direction,
The outer periphery of the support substrate is covered with a dense solid electrolyte membrane,
In a state where the fuel cell is a non-reduced body that has not been heat-treated in a reducing atmosphere, the surface roughness of the surface made of the material of the support substrate in the inner wall portion of the gas flow path is an arithmetic average roughness Ra. A fuel cell having a thickness of 0.15 to 5.0 μm. 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 at least a fuel electrode, a solid electrolyte, and an air electrode are stacked in this order;
One or a plurality of electrical connections that are respectively provided between one or a plurality of adjacent power generation element portions and electrically connect one fuel electrode and the other air electrode of the adjacent power generation element portions. And
In a fuel cell which is a fired body provided with
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,
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,
In each of the first recesses, the corresponding fuel electrode of the power generation element unit is embedded,
Second recesses each having a bottom wall made of the fuel electrode material and a circumferentially closed side wall made of the fuel electrode material are formed on the outer surface of each buried fuel electrode. ,
In each of the second recesses, the corresponding first portion of the electrical connection portion is embedded,
The support substrate has a longitudinal direction, and a plurality of the gas flow paths parallel to each other are formed in the support substrate at intervals in the width direction along the longitudinal direction,
The outer periphery of the support substrate is covered with a dense solid electrolyte membrane,
In a state where the fuel cell is a non-reduced body that has not been heat-treated in a reducing atmosphere, the surface roughness of the surface made of the material of the support substrate in the inner wall portion of the gas flow path is an arithmetic average roughness Ra. A fuel cell having a thickness of 0.15 to 5.0 μm. The fuel cell according to any one of claims 1 to 6, wherein
The fuel cell, wherein a ratio of the length in the width direction of the support substrate to the length in the thickness direction of the support substrate in the cross-sectional shape of the gas flow path is 1.1 or more.

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