JP2012124167A - Method of manufacturing composite substrate and method of manufacturing solid oxide fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a composite substrate in which a dense electrolyte layer can be formed thin and the characteristics of a solid oxide fuel cell can be enhanced, and to provide a method of manufacturing a solid oxide fuel cell.SOLUTION: The method of manufacturing a composite substrate includes a step for preparing a sheet for forming a dense electrolyte layer, a step for preparing a sheet for forming a porous electrolyte layer, a step for forming a sheet laminate by superimposing the sheet for forming a dense electrolyte layer and the sheet for forming a porous electrolyte layer, and a step for firing the sheet laminate. The powder that is heat treated in order to progress the sintering is contained more in the sheet for forming a porous electrolyte layer than in the sheet for forming a dense electrolyte layer. A method of manufacturing a solid oxide fuel cell is also provided.

Description

  The present invention relates to a method for manufacturing a composite substrate and a method for manufacturing a solid oxide fuel cell.

  In recent years, clean energy sources have been demanded due to environmental problems and resource problems. For example, a fuel cell is expected as such an energy source. A fuel cell is characterized in that energy that should be generated by combustion is extracted as electric energy instead of heat energy by electrochemically oxidizing fuel.

  Among such fuel cells, the solid oxide fuel cell is operated at an extremely high temperature of about 1000 ° C., and thus has an advantage that, for example, exhaust heat can be effectively used.

  In FIG. 7, the typical block diagram of an example of the solid oxide fuel cell used for the conventional solid oxide fuel cell is shown. Here, the solid oxide fuel cell 100 has a structure in which an air electrode 114 and a fuel electrode 113 are respectively disposed on both sides of a dense electrolyte layer 112 that is an oxide ion conductor. Then, oxygen or air is introduced to the air electrode 114 side, hydrogen is introduced to the fuel electrode 113 side, and the solid oxide fuel cell 100 is operated at about 1000 ° C.

Then, oxide ions (O ²⁻ ) are generated by the reaction of (1/2) O ₂ + 2e ⁻ → O ^{2− at} the air electrode 114, and the oxide ions (O ²⁻ ) are conducted through the dense electrolyte layer 112. It moves toward the fuel electrode 113. When the oxide ions (O ²⁻ ) reach the fuel electrode 113, electrons (e ⁻ ) are released by the reaction of H ₂ + O ²⁻ → H ₂ O + 2e ⁻ , and water (H ₂ O) is generated. (E ⁻ ) flows to the air electrode 114 through an external circuit.

  Here, in the conventional solid oxide fuel cell 100, the dense electrolyte layer 112 is made of a dense electrolyte ceramic because it needs to be configured so that the gases flowing on both sides thereof do not contact each other. Yes. In general, since a dense electrolyte ceramic has high mechanical strength, the conventional solid oxide fuel cell 100 is a solid oxide having an electrolyte support structure that maintains the strength of the solid oxide fuel cell with a dense electrolyte layer 112. Often referred to as a fuel cell.

FIG. 8 shows an equivalent electric circuit diagram of the conventional solid oxide fuel cell 100 shown in FIG. As shown in FIG. 8, the voltage V _cell generated in the conventional solid oxide fuel cell 100 is determined from the electromotive force E ₀ (difference between the oxygen potential in the air and the oxygen potential in the fuel). This corresponds to a value obtained by subtracting the overvoltage (η _c ) of 114, the voltage (iR _el ) resulting from the resistance of the dense electrolyte layer 112, and the overvoltage (η _a ) of the fuel electrode 113.

Here, the voltage due to the resistance of the dense electrolyte layer 112 (iR _el) is increased in proportion to the current i, overvoltage overvoltage of the air electrode 114 (eta _c) and the fuel electrode 113 (η _a) each current It increases in proportion to the logarithm (logi) of i. Therefore, in the solid oxide fuel cell 100, the rate at which the voltage Vcell decreases due to the resistance component of the dense electrolyte layer 112 increases as the current density during power generation increases.

  Therefore, for example, as shown in FIG. 9, while the dense electrolyte layer 112 is formed thin, the solid oxide fuel cell 101 having a fuel electrode support structure that maintains the strength of the solid oxide fuel cell at the fuel electrode 113 is also provided. (For example, refer nonpatent literatures 1-3.).

  The solid oxide fuel cell 101 having such a fuel electrode support structure is manufactured as follows. First, as shown in the schematic perspective view of FIG. 10 (a), a dense electrolyte layer forming sheet 112a formed by mixing a ceramic powder for a dense electrolyte layer and a binder or the like into a tape shape, and a ceramic powder for a fuel electrode And a fuel electrode forming sheet 113a formed in a tape shape by mixing a binder and the like.

  Next, the dense electrolyte layer forming sheet 112a and the fuel electrode forming sheet 113a are co-sintered by firing a laminate in which the dense electrolyte layer forming sheet 112a and the fuel electrode forming sheet 113a are overlapped, A composite substrate 110 having the configuration shown in the schematic perspective view of FIG. Here, the composite substrate 110 has a configuration in which a thin dense electrolyte layer 112 made of a dense electrolyte ceramic is bonded to a thick fuel electrode 113 made of a porous electrolyte ceramic.

  Thereafter, as shown in the schematic perspective view of FIG. 10C, the air electrode 114 is formed on the surface of the composite substrate 110 on the dense electrolyte layer 112 side, so that the solid oxide fuel cell having the fuel electrode support structure is formed. 101 is formed.

  A zirconia-based electrolyte ceramic such as yttria-stabilized zirconia (YSZ) is used as the dense electrolyte layer 112 of the solid oxide fuel cell 101 having the fuel electrode support structure as described above, and NiO is used as the fuel electrode 113. It is often done.

  On the other hand, in recent years, a lanthanum gallate (LSGM) -based electrolyte ceramic has been discovered, and this LSGM-based electrolyte ceramic exhibits a good oxide ion conductivity of several times that of YSZ in an intermediate temperature region of 800 ° C. or lower. Has been reported (for example, see Non-Patent Document 4).

  It has also been reported that when a dense electrolyte layer formed from an LSGM-based electrolyte ceramic is used, a solid oxide fuel cell having a very high output at 800 ° C. or lower can be obtained (for example, (See Patent Document 5).

  In addition, a solid oxide fuel cell having a fuel electrode support structure using a thin dense electrolyte layer formed of an LSGM electrolyte ceramic is expected to exhibit extremely good characteristics (for example, Non-Patent Document 6). reference).

Subhasish Mukerjee et al., “Solid Oxide Fuel Cell Development: Latest Results”, ECS Transactions, Vol.7, No.1, 2007, pp.59-65 M. Lang et al., “Characterization of SOFC Short Stacks and Stacks for Mobile Applications”, ECS Transactions, Vol.7, No.1, 2007, pp.85-94 E. Tang et al., “THE STATUS OF SOFC DEVELOPMENT AT VERSA POWER SYSTEMS”, Electrochemical Society Proceedings Volume 2005-07, pp.89-97 Tatsumi Ishihara, “Perovskite Oxide Ion Conductor”, Ceramic Data Book '98, edited by Engineering Products Technology Association, 1998, p. 50-53 Jun Akikusa et al., “SOFC Module and System Development by Means of Sealless Metallic Separators with Lanthanum Gallate Electrolyte”, Journal of The Electrochemical Society, 153 (3), 2006, pp.A589-A594 Yuanbo Lin et al., “Co-Firing of Anode-Supported SOFCs with Thin La0.9Sr0.1Ga0.8Mg0.2O3-δElectrolytes”, Electrochemical and Solid-State Letters, 9 (6), 2006, pp.A285-A288

  In order to produce a solid oxide fuel cell having a fuel electrode support structure, as described above, a dense electrolyte layer forming sheet formed by mixing ceramic powder for a dense electrolyte layer with a binder or the like and forming into a tape shape, and A method called co-sintering is used in which fuel electrode ceramic powder and a binder or the like are mixed and formed into a tape-like shape and stacked together and fired simultaneously.

  For example, as in the past, a dense electrolyte layer forming sheet formed using a ceramic powder for a dense electrolyte layer made of YSZ, and a fuel electrode forming sheet formed using a ceramic powder for a fuel electrode containing NiO, When these were co-sintered, these sheets did not react to form another phase.

However, a solid electrolyte of a fuel electrode support structure is obtained by co-sintering a dense electrolyte layer forming sheet having a ceramic powder for a dense electrolyte layer of LSGM and a fuel electrode forming sheet having a ceramic powder for a fuel electrode containing NiO. When a solid fuel cell is manufactured, when co-sintering is performed at a high temperature of 1350 ° C. or higher, a high resistance phase such as LaNiO ₃ or La ₂ NiO ₄ is formed, and there is a problem that almost no power is generated. When co-sintering is performed at a low temperature of less than, there is a problem that the dense electrolyte layer does not become dense.

  Non-Patent Document 6 discloses that the dense electrolyte layer and the fuel electrode react directly by inserting an intermediate layer between the dense electrolyte layer and the fuel electrode in order to suppress the formation of a high resistance phase. A method of suppression is described.

  However, even in the method of Non-Patent Document 6, a part of Ni in the fuel electrode is actually diffused inside the dense electrolyte layer. The characteristics are not obtained.

  Further, further improvement in characteristics is demanded for solid oxide fuel cells using a dense electrolyte layer formed of an electrolyte ceramic such as YSZ other than LSGM.

  In view of the above circumstances, an object of the present invention is to provide a composite substrate manufacturing method and a solid oxide fuel cell that can form a dense electrolyte layer thinly and improve the characteristics of the solid oxide fuel cell. The object is to provide a method for manufacturing a cell.

  The present invention provides a sheet laminate by stacking a step of producing a dense electrolyte layer forming sheet, a step of producing a porous electrolyte layer forming sheet, a dense electrolyte layer forming sheet and a porous electrolyte layer forming sheet. A composite substrate comprising: a step of forming; and a step of firing the sheet laminate, wherein the porous electrolyte layer forming sheet contains more powder that has been sintered by heat treatment than the dense electrolyte layer forming sheet. It is a manufacturing method.

Here, in the method for producing a composite substrate of the present invention, the dense electrolyte layer forming sheet is La _1-x1 (A1) _x1 Ga _1-y1-z1 Mg _y1 (B1) _z1 O _3-d1 (where 0 ≦ x1 ≦ 0.2, 0.05 ≦ y1 ≦ 0.25, 0 ≦ z1 ≦ 0.1, 0.05 ≦ y1 + z1 ≦ 0.3, −0.025 ≦ d1 ≦ 0.25). comprises a metal oxide as a main component, the porous electrolyte layer forming _{sheet, La 1-x2 (A2)} x2 Ga 1-y2-z2 Mg y2 (B2) z2 O 3-d2 ( although, 0 ≦ x2 ≦ 0. 2, 0.05 ≦ y2 ≦ 0.25, 0 ≦ z2 ≦ 0.1, 0.05 ≦ y2 + z2 ≦ 0.3, −0.025 ≦ d2 ≦ 0.25) As a main component, A1 and A2 are each independently at least one alkali selected from the group consisting of Ba, Sr and Ca It indicates metalloid, in each B1 and B2 independently, Fe, it is preferable that represents at least one transition metal selected from the group consisting of Co and Mn.

  In addition, the present invention provides a sheet lamination process in which a dense electrolyte layer forming sheet, a porous electrolyte layer forming sheet, a dense electrolyte layer forming sheet, and a porous electrolyte layer forming sheet are overlaid. And forming a composite substrate by firing the sheet laminate, and forming an electrode on the composite substrate. The porous electrolyte layer forming sheet is sintered by heat treatment. Is a method for producing a solid oxide fuel cell, which contains more powder than the dense electrolyte layer forming sheet.

  Moreover, it is preferable that the manufacturing method of the solid oxide fuel cell of this invention includes the process of forming a fuel electrode in a composite substrate.

  In the present invention, “main component” means a component occupying 50% by mass or more.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the composite substrate which can form a dense electrolyte layer thinly, and can also improve the characteristic of a solid oxide fuel cell, and the manufacturing method of a solid oxide fuel cell are provided. be able to.

It is typical sectional drawing of an example of the composite substrate of this invention. It is typical sectional drawing of an example of the solid oxide fuel cell of this invention produced using the composite substrate shown in FIG. (A)-(d) is a typical perspective view illustrating an example of the manufacturing method of the solid oxide fuel cell shown in FIG. (A)-(d) is a typical enlarged plan view illustrating the ideal sintering process of the powder of a metal oxide. It is a SEM photograph of the composite substrate of Example 1 before fuel electrode formation. It is a SEM photograph of the composite substrate of Example 1 after fuel electrode formation. It is a typical block diagram of an example of the conventional solid oxide fuel cell. FIG. 8 is an equivalent electric circuit diagram of the conventional solid oxide fuel cell shown in FIG. 7. It is a typical block diagram of another example of the conventional solid oxide fuel cell. (A)-(c) is a typical perspective view illustrating an example of the manufacturing method of the solid oxide fuel cell shown in FIG.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

  FIG. 1 shows a schematic cross-sectional view of an example of the composite substrate of the present invention. The composite substrate 1 shown in FIG. 1 has a configuration in which a porous electrolyte layer 11 and a dense electrolyte layer 12 are joined. Here, the porous electrolyte layer 11 is an electrolyte layer having a porosity higher than 6%, and the dense electrolyte layer 12 is an electrolyte layer having a porosity of 6% or less. In the present invention, the porosity is determined by the following formula (1). In the following formula (1), the relative density (%) can be determined by a conventionally known method.

Porosity (%) = 100 (%) − relative density (%) (1)
As the dense electrolyte layer 12, for example, a known one that has been conventionally used as an electrolyte layer of a solid oxide fuel cell can be used. Among them, a metal oxide represented by the following formula (I) can be used. It is preferable to include a sintered body as a main component. In this case, the solid oxide fuel cell formed using the composite substrate 1 tends to be able to be driven at a lower temperature than before and to have a high output. In the following formula (I), A1 represents at least one alkaline earth metal selected from the group consisting of Ba (barium), Sr (strontium), and Ca (calcium). B1 represents at least one transition metal selected from the group consisting of Fe (iron), Co (cobalt), and Mn (manganese).

La _1-x1 (A1) _x1 Ga _1-y1-z1 Mg _y1 (B1) _z1 O _3-d1 (However, 0 ≦ x1 ≦ 0.2, 0.05 ≦ y1 ≦ 0.25, 0 ≦ z1 ≦ 0 .1, 0.05 ≦ y1 + z1 ≦ 0.3, −0.025 ≦ d1 ≦ 0.25) (I)
In the above formula (I), 1-x1 represents the composition ratio of La (lanthanum), x1 represents the composition ratio of the alkaline earth metal A1, and 1-y1-z1 represents the composition ratio of Ga (gallium). , Y1 represents the composition ratio of Mg (magnesium), z1 represents the composition ratio of the transition metal B1, and 3-d1 represents the composition ratio of O (oxygen).

  Here, in the above formula (I), when x1 satisfies the relationship of 0 ≦ x1 ≦ 0.2, the dense electrolyte layer 12 tends to be a single phase and it is difficult to generate impurities.

  Further, in the above formula (I), when y1 satisfies the relationship of 0.05 ≦ y1 ≦ 0.25, the conductivity of the dense electrolyte layer 12 is improved and the dense electrolyte layer 12 has a single phase. Tend to be.

  Further, in the above formula (I), when z1 satisfies the relationship of 0 ≦ z1 ≦ 0.1, the electron transport number of the dense electrolyte layer 12 does not become too high and internal short circuit tends not to occur. .

  In the above formula (I), when y1 + z1 satisfies the relationship of 0.05 ≦ y1 + z1 ≦ 0.3, the dense electrolyte layer 12 tends to be a single phase.

  In the above formula (I), when x1, y1, and z1 satisfy the above relationship, d1 satisfies the relationship of −0.025 ≦ d1 ≦ 0.25.

  As the material for the dense electrolyte layer 12, in addition to the above, for example, a conventionally known electrolyte ceramic such as yttria stabilized zirconia (YSZ) can also be used.

  As the porous electrolyte layer 11, for example, a well-known material conventionally used as an electrolyte layer of a solid oxide fuel cell can be used. Among them, a metal oxide represented by the following formula (II) can be used. It is preferable to include a sintered body of the product as a main component. In this case, the solid oxide fuel cell formed using the composite substrate 1 tends to be able to be driven at a lower temperature than before and to have a high output. In the following formula (II), A2 represents at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca. B2 represents at least one transition metal selected from the group consisting of Fe, Co, and Mn.

La _1-x2 (A2) _x2 Ga _1-y2-z2 Mg _y2 (B2) _z2 O _3-d2 (where 0 ≦ x2 ≦ 0.2, 0.05 ≦ y2 ≦ 0.25, 0 ≦ z2 ≦ 0 .1, 0.05 ≦ y2 + z2 ≦ 0.3, −0.025 ≦ d2 ≦ 0.25) (II)
In the above formula (II), 1-x2 represents the composition ratio of La, x2 represents the composition ratio of the alkaline earth metal A2, 1-y2-z2 represents the composition ratio of Ga, and y2 represents Mg. Z2 represents the composition ratio of the transition metal B2, and 3-d2 represents the O composition ratio.

  Here, in the above formula (II), when x2 satisfies the relationship of 0 ≦ x2 ≦ 0.2, the porous electrolyte layer 11 tends to be a single phase and it is difficult to generate impurities.

  Moreover, in said Formula (II), when y2 satisfy | fills the relationship of 0.05 <= y2 <= 0.25, while the electrical conductivity of the porous electrolyte layer 11 improves, the porous electrolyte layer 11 becomes single phase and Tend to be.

  In the above formula (II), when z2 satisfies the relationship of 0 ≦ z2 ≦ 0.1, the electron transport number of the porous electrolyte layer 11 does not become too high, and internal short circuit tends not to occur. .

  In the above formula (II), when y2 + z2 satisfies the relationship of 0.05 ≦ y2 + z2 ≦ 0.3, the porous electrolyte layer 11 tends to be a single phase.

  In the above formula (II), when x2, y2, and z2 each satisfy the above relationship, d2 satisfies the relationship -0.025 ≦ d2 ≦ 0.25.

  As the material of the porous electrolyte layer 11, in addition to the above, for example, a conventionally known electrolyte ceramic such as YSZ can be used.

  The porous electrolyte layer 11 and the dense electrolyte layer 12 may be formed using the same material, or may be formed using different materials, but the porous electrolyte layer 11 and the dense electrolyte layer 12 are It is preferable to form using the same material. When the porous electrolyte layer 11 and the dense electrolyte layer 12 are formed using the same material, the bonding force between the porous electrolyte layer 11 and the dense electrolyte layer 12 is improved, and even when heat treatment is performed at a high temperature. There is an advantage that a chemical reaction is unlikely to occur between the porous electrolyte layer 11 and the dense electrolyte layer 12, and the alteration is difficult.

  Here, that the porous electrolyte layer 11 and the dense electrolyte layer 12 are formed using the same material means that the composition of the main component constituting the porous electrolyte layer 11 and the composition of the main component constituting the dense electrolyte layer 12 are used. In contrast, the constituent elements of these main components and the composition ratios of the constituent elements are the same, and the components other than the main components between the porous electrolyte layer 11 and the dense electrolyte layer 12 May be the same or different.

  As the case where the porous electrolyte layer 11 and the dense electrolyte layer 12 are formed using the same material, for example, the dense electrolyte layer 12 is made of a sintered metal oxide represented by the above formula (I). When the porous electrolyte layer 11 is made of a sintered metal oxide represented by the above formula (II), A1 and A2 indicate the same alkaline earth metal element, and B1 and B2 indicate the same element. The transition metal element is shown, and x1 = x2, y1 = y2, z1 = z2, and d1 = d2.

  FIG. 2 shows a schematic cross-sectional view of an example of the solid oxide fuel cell of the present invention produced using the composite substrate 1 shown in FIG. The solid oxide fuel cell 10 shown in FIG. 2 has a fuel electrode 13 formed by adhering a fuel electrode material inside the porous electrolyte layer 11 of the composite substrate 1 shown in FIG. In addition to being provided on one surface, the air electrode 14 is provided on the other surface of the dense electrolyte layer 12.

  Here, as the fuel electrode material constituting the fuel electrode 13, for example, a known material conventionally used as a fuel electrode material of a solid oxide fuel cell can be used. Moreover, as the air electrode 14, the well-known thing conventionally used, for example as an air electrode of a solid oxide fuel cell can be used.

  Hereinafter, an example of a method for manufacturing the solid oxide fuel cell 10 shown in FIG. 2 will be described with reference to schematic perspective views of FIGS. 3 (a) to 3 (d). First, as shown in FIG. 3A, a dense electrolyte layer forming sheet 12a is superposed on a porous electrolyte layer forming sheet 11a to form a sheet laminate.

  As the porous electrolyte layer forming sheet 11a, for example, a metal oxide powder constituting the porous electrolyte layer 11 shown in FIG. 1 and a slurry containing a binder and a pore-forming agent for binding the powder are formed into a sheet shape. Things can be used. Note that the pore expander is a material for forming voids, and for example, carbon can be used as the pore expander.

  Further, as the dense electrolyte layer forming sheet 12a, for example, a sheet formed from a slurry containing a metal oxide powder constituting the dense electrolyte layer 12 and a binder for binding the powder is used. Can do.

  Here, it is preferable that the porous electrolyte layer forming sheet 11a contains more powder processed at a high temperature than the dense electrolyte layer forming sheet 12a. The porous electrolyte layer forming sheet 11a contains a pore-forming agent for forming voids, and the amount of powder per unit volume may be smaller than that of the dense electrolyte layer forming sheet 12a. Without firing, when the above-mentioned sheet laminate is fired at the same temperature, the shrinkage amount of the porous electrolyte layer forming sheet 11a is larger than the shrinkage amount of the dense electrolyte layer forming sheet 12a and cracks. There is.

  4A to 4D are schematic enlarged plan views showing an ideal sintering process of the metal oxide powder. Here, first, the powder 41 such as a metal oxide shown in FIG. 4A is rearranged so that the contact surface of the powder 41 is as large as possible, for example, as shown in FIG. 4B. And as shown in FIG.4 (c), the contact surfaces of the powder 41 are connected, and neck formation progresses, and finally, as shown in FIG.4 (d), the space | gap between the powder 41 which generate | occur | produced in neck formation exists. The sintered body 42 is formed by closing. In such a sintering process, the gap between the powders 41 decreases with the progress of sintering, and the progress of the sintering becomes faster as the temperature during the sintering process becomes higher.

  Therefore, for example, at least a part of the metal oxide powder used for the porous electrolyte layer forming sheet 11a is treated at a high temperature without any treatment for the metal oxide powder used for the dense electrolyte layer forming sheet 12a. By proceeding with the above-described sintering, the amount of shrinkage of the porous electrolyte layer forming sheet 11a during firing of the sheet laminate can be reduced.

  Therefore, the porous electrolyte layer forming sheet 11a and the dense electrolyte layer when the sheet laminate is fired by including more powder processed at a high temperature than the dense electrolyte layer forming sheet 12a in the porous electrolyte layer forming sheet 11a. Since the difference in shrinkage from the forming sheet 12a can be reduced, the occurrence of cracks due to the difference in shrinkage can be effectively suppressed.

  Next, the composite substrate 1 having the configuration shown in FIG. 3B is formed by firing the sheet laminate shown in FIG. Here, the composite substrate 1 shown in FIG. 3B has the same configuration as the composite substrate 1 shown in FIG. 1 and is included in, for example, the porous electrolyte layer forming sheet 11a by firing the above-mentioned sheet laminate. The metal oxide powder is sintered to form the porous electrolyte layer 11, and for example, the metal oxide powder contained in the dense electrolyte layer forming sheet 12 a is sintered to form the dense electrolyte layer 12. The porous electrolyte layer 11 and the dense electrolyte layer 12 are joined.

  Here, baking of said sheet | seat laminated body can be implemented by exposing a sheet | seat laminated body to a 1400 degreeC-1500 degreeC air atmosphere, for example for 6 hours-12 hours.

  Next, by attaching a fuel electrode material to the inside of the porous electrolyte layer 11 formed by firing the above-mentioned sheet laminate, as shown in FIG. 3 (c), on one surface of the dense electrolyte layer 12 A fuel electrode 13 is formed. Here, the fuel electrode 13 introduces the fuel electrode material from the pores of the porous electrolyte layer 11 into the porous electrolyte layer 11 by immersing the porous electrolyte layer 11 in a slurry in which the fuel electrode material is dispersed, for example. 11 can be formed by adhering to the inside.

  Next, as shown in FIG. 3D, the solid oxide fuel cell 10 is produced by forming the air electrode 14 on the surface of the dense electrolyte layer 12 opposite to the side on which the fuel electrode 13 is formed. Is done. Here, the air electrode 14 can be formed by, for example, applying a conventionally known air electrode material to the surface of the dense electrolyte layer 12 and then baking it.

  In the above, the fuel electrode material is introduced into the porous electrolyte layer 11 to form the fuel electrode 13 in the above. However, in the present invention, the air electrode material is introduced into the porous electrolyte layer 11 to form the air electrode 13. In addition, the fuel electrode 13 may be formed by applying a fuel electrode material to the surface of the dense electrolyte layer 12 opposite to the side on which the air electrode 14 is formed and then firing it.

  That is, in the solid oxide fuel cell 10 of the present invention, the fuel electrode 13 is installed on the porous electrolyte layer 11 side of the composite substrate 1 and the air electrode 14 is installed on the dense electrolyte layer 12 side. In addition, the air electrode 14 may be installed on the porous electrolyte layer 11 side of the composite substrate 1 and the fuel electrode 13 may be installed on the dense electrolyte layer 12 side.

  Since the solid oxide fuel cell 10 of the present invention produced as described above is formed using the composite substrate 1 of the present invention having the above-described configuration, the dense electrolyte layer 12 is formed thin. However, the strength of the solid oxide fuel cell 10 can be maintained by the porous electrolyte layer 11 thicker than the dense electrolyte layer 12.

  The solid oxide fuel cell of the present invention has electrode reaction activity improved because the electrode material (fuel electrode material, air electrode material) is dispersed and adhered inside the porous electrolyte layer. Can suppress the formation of electrodes (fuel electrode, air electrode) at a high temperature of 1350 ° C. or higher as in the prior art, and thus can suppress the reaction between the electrolyte and the electrode material. Therefore, it is considered that the characteristics of the solid oxide fuel cell of the present invention are improved.

  Further, for example, the fuel electrode 13 of the solid oxide fuel cell 10 formed using the composite substrate 1 and another solid oxide fuel cell 10 formed using the composite substrate 1. A solid oxide fuel cell of the present invention having a configuration in which a plurality of solid oxide fuel cells 10 of the present invention are electrically connected can be manufactured by electrically connecting the air electrode 14 to the air electrode 14. it can. The solid oxide fuel cell according to the present invention includes a plurality of solid oxide fuel cells 10 according to the present invention with improved characteristics, and characteristics obtained by combining the improved characteristics in a superimposed manner are obtained. As compared with a solid oxide fuel cell produced using a conventional solid oxide fuel cell, the characteristics can be greatly improved.

  In the solid oxide fuel cell of the present invention, the electrical connection between the fuel electrode 13 of the solid oxide fuel cell 10 and the air electrode 14 of another solid oxide fuel cell 10 is, for example, Although it can be performed using a conventionally known conductive member such as an interconnector, it goes without saying that the present invention is not limited to this, and the fuel electrode 13 of the solid oxide fuel cell 10 and other solid oxide fuels. What is necessary is just to be electrically connected with the air electrode 14 of the battery cell 10 in some form.

(Preparation of dense electrolyte layer forming sheet)
A powder of a metal oxide represented by a formula of La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _2.85 (hereinafter, a metal oxide having a composition represented by this formula is referred to as “LSGM”) is used in a general solid-phase reaction method. Was synthesized. That is, first, lanthanum oxide (La ₂ O ₃ ) powder, strontium carbonate (SrCO ₃ ) powder, gallium oxide (Ga ₂ O ₃ ) powder, and magnesium oxide (MgO) powder each have a molar ratio of metal elements of 9: 1: The mixture was weighed to 8: 2, added to a ball mill together with ethanol, and wet mixed and ground for 24 hours to obtain a mixture. And after removing ethanol from the mixture after the wet mixing and pulverization, LSGM powder having the composition represented by the above formula was obtained by heat treatment at 1200 ° C. for 10 hours to react.

When the crystal structure of this LSGM powder was confirmed with an X-ray diffractometer, most X-ray diffraction peaks were X-ray diffraction peaks corresponding to the crystal structure of LSGM, but slightly corresponding to impurities such as LaSrGa ₃ O ₇ X-ray diffraction peaks were also included.

  To 240 g of this LSGM powder, 2.4 g of Marialim (manufactured by NOF Corporation) as a dispersant, 24 g of polyvinyl butyral (PVB, average polymerization degree 700) as a binder, 8.4 g of di-n-butyl phthalate as a plasticizer, As a solvent, 70.8 g of n-butanol and 70.8 g of toluene were added to a kneader, respectively, and stirred and degassed with the kneader to prepare a slurry.

  And after pouring the slurry produced as mentioned above into a doctor blade apparatus and shape | molding in the sheet form, the sheet | seat for dense electrolyte layer formation was obtained by making it dry for 16 hours.

(Preparation of porous electrolyte layer forming sheet)
Until the LSGM powder was obtained, the same steps as those for producing the dense electrolyte layer forming sheet were performed.

  Next, the LSGM powder obtained as described above was further heat-treated at 1450 ° C. for 10 hours to advance the sintering.

  And, to 160 g of LSGM powder after the above-described sintering, 90 g of activated carbon (manufactured by Wako Pure Chemical Industries, Ltd.) as a pore-increasing agent, 2.5 g of Marialim (manufactured by NOF Corporation) as a dispersing agent, 26 g of polyvinyl butyral (PVB, average polymerization degree 700) as a binder, 9 g of di-n-butyl phthalate as a plasticizer, 75.75 g of n-butanol and 75.75 g of toluene as solvents are added to a kneader, and the kneading is performed. A slurry for forming a dense electrolyte layer sheet was prepared by stirring and defoaming with a machine.

  After that, the same process as the production of the dense electrolyte layer forming sheet was performed to obtain a porous electrolyte layer forming sheet.

(Production of composite substrates of Examples 1 and 2)
The sheet laminate obtained by stacking the above-mentioned dense electrolyte layer forming sheet and porous electrolyte layer forming sheet and then cutting out into a cylindrical shape is left in an air atmosphere at 1450 ° C. for 6 hours to be fired. A dense electrolyte layer was formed from the electrolyte layer forming sheet, a porous electrolyte layer was formed from the porous electrolyte layer forming sheet, and a composite substrate of Example 1 having a configuration in which the dense electrolyte layer and the porous electrolyte layer were joined was produced. .

  The sheet laminate obtained by stacking the above-mentioned dense electrolyte layer forming sheet and the porous electrolyte layer forming sheet and then cutting out into a cylindrical shape is left in an air atmosphere at 1500 ° C. for 6 hours to be fired. A dense electrolyte layer was formed from the electrolyte layer forming sheet, a porous electrolyte layer was formed from the porous electrolyte layer forming sheet, and a composite substrate of Example 2 having a configuration in which the dense electrolyte layer and the porous electrolyte layer were joined was produced. .

(Evaluation of composite substrates of Examples 1 and 2)
(I) Composite substrate of Example 1 In the preparation of the composite substrate of Example 1, the diameter of the circular surface of the sheet laminate before firing was 41.31 mm on average, whereas The diameter of the circular surface of the composite substrate of Example 1 after firing was 35.90 mm on average. Therefore, in the composite substrate of Example 1, the average linear shrinkage rate in the diameter direction of the circular surface was 13.1%.

  In the production of the composite substrate of Example 1, the thickness of the sheet laminate before firing was 1.232 mm on average, whereas the thickness of the composite substrate of Example 1 after firing was as described above. The average thickness was 0.850 mm. Therefore, in the composite substrate of Example 1, the average linear shrinkage rate in the thickness direction was 31.0%.

  Moreover, when the laminated structure of the composite substrate of Example 1 was investigated using a transmission electron microscope, the dense electrolyte layer of the composite substrate of Example 1 was composed of a dense sintered body, and the porous electrolyte layer was It was confirmed that it was composed of a porous sintered body.

  Moreover, about the composite substrate of Example 1, by calculating the volume from the measurement results of the diameter and thickness of the circular surface described above, and measuring the mass of the composite substrate of Example 1, these volumes and masses The density of the composite substrate of Example 1 was calculated from the value. Then, the apparent density of the composite substrate of Example 1 is obtained by dividing the calculated density by the theoretical density of LSGM to obtain a relative density (%) and subtracting the relative density (%) from 100 (%). (%) Was calculated.

  The apparent porosity of the composite substrate of Example 1 obtained by this method was 76.9%. Since the composite substrate of Example 1 has a dense electrolyte layer, it is considered that the porosity of the porous electrolyte layer of the composite substrate of Example 1 is higher than 76.9%.

  Therefore, the porous electrolyte layer of the composite substrate of Example 1 is immersed in a slurry containing an electrode material (fuel electrode material, air electrode material), for example. Fuel electrode, air electrode) can be formed.

(Ii) Composite substrate of Example 2 In the production of the composite substrate of Example 2, the diameter of the circular surface of the sheet laminate before firing was 41.45 mm on the average, whereas The diameter of the circular surface of the composite substrate of Example 2 after firing was 35.75 mm on average. Therefore, in the composite substrate of Example 2, the average linear shrinkage rate in the diameter direction of the circular surface was 13.8%.

  In the production of the composite substrate of Example 2, the thickness of the sheet laminate before firing was 1.138 mm on average, whereas the thickness of the composite substrate of Example 2 after firing was as described above. The average length was 0.680 mm. Therefore, in the composite substrate of Example 2, the average linear shrinkage rate in the thickness direction was 40.2%.

  Moreover, when the laminated structure of the composite substrate of Example 1 was investigated using a transmission electron microscope, the dense electrolyte layer of the composite substrate of Example 1 was composed of a dense sintered body, and the porous electrolyte layer was It was confirmed that it was composed of a porous sintered body.

  For the composite substrate of Example 2, the apparent porosity (%) of the composite substrate of Example 2 was determined in the same manner as the composite substrate of Example 1, and the porosity was 81.0%. there were. Since the composite substrate of Example 2 also has a dense electrolyte layer, it is considered that the porosity (%) of the porous electrolyte layer of the composite substrate of Example 2 is larger than 81.0%.

  Therefore, by immersing the porous electrolyte layer of the composite substrate of Example 2 in a slurry containing, for example, an electrode material (fuel electrode material, air electrode material), an electrode having a good microstructure ( Fuel electrode, air electrode) can be formed.

(Fabrication of fuel electrode on composite substrates of Examples 1 and 2)
The slurry for fuel electrode formation for immersing the porous electrolyte layer of the composite substrate of Examples 1-2 was produced. Here, the slurry for forming the fuel electrode is a material for a fuel electrode comprising a mixture of nickel oxide (NiO) powder and gadolinia-added ceria (GDC) powder in a mass ratio of 8: 2, and a mixture of these powders. Was added to an organic solvent three times as much as the fuel electrode material.

  And after immersing the porous electrolyte layer of the composite board | substrate of Examples 1-2 in the slurry for fuel electrode formation produced as mentioned above, the organic solvent was dried by heating at 120 degreeC for 1 hour. And by immersing the porous electrolyte layer of the composite substrate of Examples 1-2 in the slurry for fuel electrode formation and drying with the organic solvent alternately three times, the composite substrate of Examples 1-2 The fuel electrode was formed by adhering the above fuel electrode material to the inside of the porous electrolyte layer.

  After that, the composite substrate after the formation of the fuel electrode was heat-treated in air at 1200 ° C. for 3 hours, and then reduced in a hydrogen atmosphere at 750 ° C. for 1 hour, and the microstructure of the composite substrate was observed with a scanning electron microscope (SEM). did.

  FIG. 5 shows an SEM photograph of the composite substrate of Example 1 before forming the fuel electrode, and FIG. 6 shows an SEM photograph of the composite substrate of Example 1 after forming the fuel electrode. As shown in FIGS. 5 and 6, it was confirmed that Ni and GDC were uniformly dispersed and adhered to the inside of the porous electrolyte layer of the composite substrate of Example 1.

  Further, the SEM photograph of the composite substrate of Example 2 before the formation of the fuel electrode is the same as that shown in FIG. 5, and the SEM photograph of the composite substrate of Example 2 after the formation of the fuel electrode is the same as that shown in FIG. Therefore, it was confirmed that Ni and GDC were uniformly dispersed and adhered to the inside of the porous electrolyte layer of the composite substrate of Example 2.

  Therefore, a solid oxide fuel cell formed using the composite substrate of Examples 1 and 2 and a solid oxide fuel cell having a configuration in which a plurality of these solid oxide fuel cells are electrically connected are provided. It is considered that it shows good power generation characteristics.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the composite substrate which can form the dense electrolyte layer thinly, and can also improve the characteristic of a solid oxide fuel cell, and the manufacturing method of the solid oxide fuel cell are provided. can do.

  1,110 Composite substrate, 10,100,101 Solid oxide fuel cell, 11 Porous electrolyte layer, 11a Porous electrolyte layer forming sheet, 12,112 Dense electrolyte layer, 12a, 112a Dense electrolyte layer forming sheet, 13 , 113 Fuel electrode, 113a Fuel electrode forming sheet, 14, 114 Air electrode, 41 Powder, 42 Sintered body.

Claims (4)

Producing a dense electrolyte layer forming sheet;
Producing a porous electrolyte layer forming sheet;
A step of superposing the dense electrolyte layer forming sheet and the porous electrolyte layer forming sheet to form a sheet laminate;
Firing the sheet laminate,
The said porous electrolyte layer forming sheet is a manufacturing method of a composite substrate containing more powder which sintered by heat-processing than the said dense electrolyte layer forming sheet. The dense electrolyte layer forming sheet is composed of La _1-x1 (A1) _x1 Ga _1-y1-z1 Mg _y1 (B1) _z1 O _3-d1 (where 0 ≦ x1 ≦ 0.2, 0.05 ≦ y1 ≦ 0.25, 0 ≦ z1 ≦ 0.1, 0.05 ≦ y1 + z1 ≦ 0.3, −0.025 ≦ d1 ≦ 0.25) as a main component,
The porous electrolyte layer forming sheet is composed of La _1-x2 (A2) _x2 Ga _1-y2-z2 Mg _y2 (B2) _z2 O _3-d2 (where 0 ≦ x2 ≦ 0.2, 0.05 ≦ y2 ≦ 0.25, 0 ≦ z2 ≦ 0.1, 0.05 ≦ y2 + z2 ≦ 0.3, −0.025 ≦ d2 ≦ 0.25) as a main component,
A1 and A2 each independently represent at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca;
The method for producing a composite substrate according to claim 1, wherein B1 and B2 each independently represent at least one transition metal selected from the group consisting of Fe, Co, and Mn. Producing a dense electrolyte layer forming sheet;
Producing a porous electrolyte layer forming sheet;
A step of superposing the dense electrolyte layer forming sheet and the porous electrolyte layer forming sheet to form a sheet laminate;
Producing a composite substrate by firing the sheet laminate;
Forming an electrode on the composite substrate,
The method for producing a solid oxide fuel cell, wherein the porous electrolyte layer forming sheet contains a larger amount of powder that has been sintered by heat treatment than the dense electrolyte layer forming sheet.   The method for producing a solid oxide fuel cell according to claim 3, wherein the step of forming the electrode includes a step of forming a fuel electrode on the composite substrate.