JP5365050B2 - Solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell that operates with a fuel gas and an oxidant gas, and a method for manufacturing a solid oxide fuel cell.

A fuel cell is a cell that can directly convert chemical energy generated when fuel is oxidized into electric energy while continuously supplying fuel from the outside and exhausting combustion products. The types of fuel cells are classified according to the electrolyte, and those using metal oxides having ion conductivity for the electrolyte are called solid oxide fuel cells. As such a solid oxide fuel cell, for example, one disclosed in Patent Document 1 is known.

As shown in FIG. 5, this solid oxide fuel cell 101 is supported on a substrate 103 and has a sheet-like electrolyte 107 and a sheet-like air electrode laminated on the upper surface (one surface) of the electrolyte 107. 109. A sheet-like fuel electrode 105 is laminated on the lower surface (the other surface) of the electrolyte 107. In the solid oxide fuel cell 101, an electrolyte 107, a fuel electrode 105, and an air electrode 109 constitute one cell. The electrolyte 107, the fuel electrode 105, and the air electrode 109 are each formed in a rectangular shape.
JP 2006-19044 A

  By the way, in recent years, the demand for solid oxide fuel cells is further increased. For example, a small and high output fuel cell is desired.

  The present invention has been made to solve such problems, and provides a solid oxide fuel cell capable of increasing the output per unit area, and a method for manufacturing the solid oxide fuel cell. With the goal.

  A solid oxide fuel cell according to the present invention is made to solve the above-described problems, and includes an electrolyte and one electrode composed of a fuel electrode or an air electrode disposed on one surface of the electrolyte, The other electrode made of an electrode different from the one electrode, and the electrolyte and the one electrode have a boundary line between them in a cross section cut in the stacking direction. The layers are bent so that the length of the boundary line is longer than the straight line length between the end portions of the boundary line.

  According to such a configuration, the boundary line between the electrolyte and one electrode, that is, the electrolyte and one electrode are compared with a solid oxide fuel cell in which the electrolyte and one electrode are simply stacked. The contact area can be lengthened. Thereby, the contact area of an electrolyte and one electrode with respect to the unit area of a solid oxide fuel cell can be enlarged. Therefore, the reaction area per unit area of the solid oxide fuel cell can be expanded, and the output per unit area can be increased.

  In the above configuration, in the cross section cut in the stacking direction, the electrolyte and the other electrode are curved at the boundary between them, and the length of the boundary is a straight line length between the ends of the boundary. It is preferable that the layers are stacked so as to be longer.

  According to such a configuration, the contact area between the electrolyte and the other electrode can be increased, and the reaction region is expanded, so that the output per unit area can be further increased.

  The first manufacturing method of the solid oxide fuel cell according to the present invention is made to solve the above-mentioned problem, and is a fuel electrode green sheet containing a fuel electrode material or an air electrode material. A green sheet laminate is prepared by preparing one of the green sheets of the air electrode green sheet containing the green sheet and laminating the one green sheet on one surface of the electrolyte green sheet containing the electrolyte material. A sheet lamination step to be formed, a sintering step to form the electrolyte and one electrode by co-sintering the green sheet laminate, and a shaping to shape the surfaces of the electrolyte and one electrode in parallel And an electrode stacking step of disposing another electrode different from the one electrode on the other surface of the electrolyte.

  The second manufacturing method of the solid oxide fuel cell includes a preparation for preparing either a fuel electrode green sheet containing a fuel electrode material or an air electrode green sheet containing an air electrode material. A step of stacking a green sheet laminate by laminating the one green sheet on one side of an electrolyte green sheet containing an electrolyte material, and co-sintering the green sheet laminate The sintering step for forming the electrolyte and one electrode, the electrode stacking step for disposing the other electrode different from the one electrode on the other surface of the electrolyte, and the one electrode and the other electrode in parallel And a shaping step for shaping so that

  According to the first and second manufacturing methods, in the sintering step, the electrolyte green sheet and the fuel electrode green sheet have different heat shrinkage rates. Can be curved. Thereby, since the interface between the electrolyte and the electrode is curved, the contact area between the electrolyte and the electrode can be increased with respect to the unit area of the solid oxide fuel cell. Therefore, the reaction area per unit area of the solid oxide fuel cell can be expanded, and the output per unit area can be increased.

  Furthermore, according to the second manufacturing method, since the contact area between the electrolyte and the other electrode can be increased, the output per unit area can be further increased.

  Moreover, it is preferable that the said sintering step co-sinters in the state which loads, such as a pressing board, do not act on the said green sheet laminated body. Thereby, it becomes possible to make the electrode and electrolyte interface further curved.

  According to the solid oxide fuel cell and the manufacturing method of the solid oxide fuel cell of the present invention, the output per unit area can be increased.

(First embodiment)
A first embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a solid oxide fuel cell according to a first embodiment of the present invention.

  As shown in FIG. 1, a solid oxide fuel cell (hereinafter simply referred to as a fuel cell) 1 includes an electrolyte 2 and a fuel electrode 3 (one electrode) in close contact with the lower surface (one surface) of the electrolyte 2. It has. An air electrode 4 (the other electrode) is in close contact with the upper surface (the other surface) of the electrolyte 2. The upper surface of the electrolyte 2 and the lower surface of the fuel electrode 3 are polished flat so as to be parallel to each other.

  In the fuel cell 1, a boundary line 5 is formed between the electrolyte 2 and the fuel electrode 3 in a cross section cut in the stacking direction of the electrolyte 2 and the fuel electrode 3. The boundary line 5 is curved, and its length L1 is longer than the length L2 of a virtual straight line 6 (dotted line in FIG. 1) connecting both ends 5a and 5b of the boundary line 5. In the entire fuel cell 1, the lower surface of the electrolyte 2 and the upper surface of the fuel electrode 3, that is, the interface between the electrolyte 2 and the fuel electrode 3 are curved. The length L1 of the boundary line 5 is longer than the length L2 of the straight line 6, for example, based on image data obtained by photographing a cross section of the fuel cell 1 using a scanning electron microscope (SEM). can do. In this case, by confirming that the layer thickness at both end portions of the fuel electrode 3 is thinner than the layer thickness at the center portion of the fuel electrode 3, the length of L1 and L2 can be indirectly determined.

  Subsequently, materials constituting the fuel cell 1 will be described. The electrolyte 2, the fuel electrode 3, and the air electrode 4 can be formed of a ceramic powder material. The average particle size of the powder used at this time is preferably 10 nm to 100 μm, more preferably 50 nm to 50 μm, and particularly preferably 100 nm to 10 μm. In addition, an average particle diameter can be measured according to JISZ8901, for example.

  As the material of the electrolyte 2, those known as electrolytes for solid oxide fuel cells can be used. For example, ceria oxide (GDC) doped with samarium or gadolinium, lanthanum doped with strontium or magnesium An oxygen ion conductive ceramic material such as a galide oxide, zirconia oxide (YSZ) containing scandium or yttrium can be used.

  As the fuel electrode 3, for example, a mixture of a metal catalyst and a ceramic powder material made of an oxide ion conductor can be used. As the metal catalyst used at this time, a material that is stable in a reducing atmosphere, such as nickel, iron, cobalt, or a noble metal (platinum, ruthenium, palladium, etc.) and has hydrogen oxidation activity can be used. In addition, as the oxide ion conductor, one having a fluorite structure or a perovskite structure can be preferably used. Examples of those having a fluorite structure include ceria-based oxides doped with samarium, gadolinium, and the like, and zirconia-based oxides containing scandium and yttrium. In addition, examples of those having a perovskite structure include lanthanum galide oxides doped with strontium and magnesium. Among the above materials, it is preferable to form the fuel electrode 3 with a mixture of an oxide ion conductor and nickel. The mixed form of the ceramic material made of the oxide ion conductor and nickel may be a physical mixed form, or may be a powder modification to nickel or a nickel modification to ceramic material. Good. Moreover, the ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types. Moreover, the fuel electrode 3 can also be comprised using a metal catalyst alone.

As the ceramic powder material forming the air electrode 4, for example, a metal oxide made of Co, Fe, Ni, Cr, Mn or the like having a perovskite structure or the like can be used. Specifically, (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Sr) (Fe, Co , Ni) O _{3 and the} like, and (La, Sr) (Fe, Co) O ₃ is preferable. The ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types.

  Next, a manufacturing method using a green sheet will be described as an example of a manufacturing method of the fuel cell 1. First, a method for producing an electrolyte green sheet, a fuel electrode green sheet, and an air electrode green sheet will be described.

  For example, in the case of the doctor blade method, the fuel electrode or air electrode green sheet can be produced by the following method. A pore forming agent is added to the fuel electrode or air electrode powder, a binder, a dispersant and a plasticizer are added, and a slurry dispersed in a dispersion medium composed of an alcohol solvent such as ethanol or 2-propanol is prepared. As for the addition amount of a pore making material, 5-20 w% is preferable. Since the added pore former burns and vaporizes during sintering, voids are formed at the locations where the pore former was present. Examples of the pore-forming agent include carbon-based powder and resin-based powder, but other materials may be used as long as they can be vaporized during sintering to form pores.

  Moreover, there is no restriction | limiting in the kind of binder used when producing the said slurry composition or kneading | mixing composition, A well-known organic or inorganic binder can be used. Organic binders include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl acetal resins, vinyl formal resins, polyvinyl Examples include butyral resins, vinyl alcohol resins, celluloses such as ethyl cellulose, and waxes.

  Next, the prepared slurry is formed by a known doctor blade method to form a slurry layer on a film of polyethylene terephthalate or the like, and the dispersion medium is removed from the slurry layer to dry the fuel electrode or air electrode. A green sheet is formed. The dispersion medium is not limited to alcohol solvents, and other organic solvents such as toluene, xylene, and ketones may be used. In addition to the organic solvent, a slurry in which the mixed powder is dispersed in water may be used. For example, by using a predetermined dispersant, the mixed powder can be dispersed in water.

  The electrolyte green sheet is produced by the following method. A binder, a dispersant, and a plasticizer are added to the electrolyte electrode powder to prepare a slurry that is dispersed in a dispersion medium composed of an organic solvent. The produced slurry forms a slurry layer on a film such as polyethylene terephthalate by the doctor blade method in the same manner as the fuel electrode. The dispersion medium is removed from the slurry layer to dry the electrolyte green sheet.

  Next, a method for manufacturing the fuel cell 1 will be described with reference to FIG. FIG. 2 is an explanatory diagram of the fuel cell manufacturing method according to the present embodiment.

  First, as shown in FIG. 2A, a fuel electrode green sheet 13 (one green sheet) is prepared (preparation step).

  Next, as shown in FIG. 2B, the green sheet laminate 11 is formed by laminating the electrolyte green sheet 12 on the upper surface of the fuel electrode green sheet 13 (sheet lamination step). In the sheet stacking step, it is preferable to fuse the electrolyte green sheet 12 and the fuel electrode green sheet 13 by hot pressing the green sheet stack 11.

  Subsequently, the electrolyte 2 and the fuel electrode 3 are formed by co-sintering the green sheet laminate 11 (sintering step). The sintering temperature is preferably 1100 ° C to 1500 ° C. At this time, due to the difference in thermal contraction rate between the electrolyte green sheet 12 and the fuel electrode green sheet 13, the electrolyte 2 and the fuel electrode 3 are curved as the green sheet laminate 11 is sintered, and the boundary surface between the two is curved. As shown in FIG. 2C, in the cross section obtained by longitudinally cutting the sintered laminate, the boundary line 5 between the electrolyte 2 and the fuel electrode 3 is curved in an arc shape. In the sintering step, the degree of curvature of the electrolyte 2 and the fuel electrode 3 to be formed can be adjusted by adjusting the load acting on the green sheet laminate 11. From the viewpoint of increasing the degree of curvature of the electrolyte 2 and the fuel electrode 3, it is preferable that the load acting on the green sheet laminate 11 is small, and co-sintering is performed in a state where no load acts on the green sheet laminate 11. preferable.

  Subsequently, as shown in FIG. 2D, the electrolyte 2 is shaped so that the upper surface of the electrolyte 2 and the lower surface of the fuel electrode 3 are parallel (shaping step). In the shaping step, the surfaces of the electrolyte 2 and the fuel electrode 3 can be polished. As a polishing method, for example, a known method such as a lapping method, a polishing method, or a mechanochemical can be used. Further, it is preferable to cut the side surfaces of the electrolyte 2 and the fuel electrode 3 in accordance with the dimensions of the fuel cell 1. As a cutting method, ceramics can be cut mainly by a method using a cutting tool such as a diamond grindstone or a saw blade, or by a known method such as shearing, laser, or water jet.

  Subsequently, as shown in FIG. 2E, the air electrode 4 (the other electrode) is laminated on the upper surface (the other surface) of the electrolyte 2 (electrode lamination step). The air electrode 4 can be formed by, for example, a screen printing method. Thus, the fuel cell 1 is completed. However, other methods are not particularly limited, and can be formed by a wet coating method such as an electrophoretic (EPD) method, a spray coating method, an ink jet method, a spin coating method, or a dip coating method. It can also be formed by a dry coating method. Examples of dry coating methods include vapor deposition, sputtering, ion plating, chemical vapor deposition (CVD), electrochemical vapor deposition, ion beam, laser ablation, atmospheric pressure plasma deposition, and reduced pressure. It can also be formed by a plasma film formation method or the like.

  The fuel cell configured as described above generates power as follows. First, a fuel gas composed of hydrogen or a hydrocarbon such as methane or ethane is supplied to the porous fuel electrode 3. On the other hand, an oxidant gas such as air is supplied to the air electrode 4. In this way, the fuel gas and the oxidant gas are distributed individually over the fuel electrode 3 and the air electrode 4 individually. The fuel gas and the oxidant gas such as air supplied at this time are supplied at a high temperature of 400 to 1000 ° C., for example. Thus, since the fuel electrode 3 and the air electrode 4 are in contact with the fuel gas and the oxidant gas, respectively, oxygen ion conduction through the electrolyte 2 occurs between the fuel electrode 3 and the air electrode 4, and power generation is performed. It can also be used as a single-chamber solid oxide fuel cell that generates power in a mixed gas of fuel gas and oxidant gas. Even in this case, the electrodes 2 and 3 selectively react with the fuel gas or the oxidant gas, so that power generation can be performed.

  According to the present embodiment described above, since the boundary surface between the electrolyte 2 and the fuel electrode 3 is curved, the contact area between the two can be increased with respect to the area of the fuel cell. Thereby, the reaction area | region per unit area can be expanded and an output can be made high.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 3 is a cross-sectional view of a fuel cell according to the second embodiment of the present invention. 3, the same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 3, a boundary line 7 is formed between the electrolyte 2 and the air electrode 4 in a cross section in which the fuel cell 1 is cut in the stacking direction of the electrolyte 2 and the air electrode 4. The boundary line 7 is curved, and its length L3 is longer than the length L4 of a virtual straight line 8 (dotted line in FIG. 3) connecting both ends 7a and 7b of the boundary line 7. In the entire fuel cell 1, the upper surface of the electrolyte 2 and the lower surface of the air electrode 4, that is, the interface between the electrolyte 2 and the air electrode 4 are curved. The lengths of the boundary line 7 and the straight line 8 can be obtained based on image data obtained by photographing a cross section of the fuel cell 1. The upper surface of the air electrode 4 and the lower surface of the fuel electrode 3 are polished flat so as to be parallel to each other.

  Next, a method for manufacturing a fuel cell according to another embodiment will be described. FIG. 4 is an explanatory diagram of a fuel cell manufacturing method according to another embodiment. 4, the same components as those in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 4D, after the electrolyte 2 and the fuel electrode 3 are formed by the sintering step in the above embodiment, the upper surface of the electrolyte 2 is not polished flat and is left in a curved state. . The lower surface of the fuel electrode 3 is preferably polished flat. Further, it is preferable to cut the side surfaces of the electrolyte 2 and the fuel electrode 3 in accordance with the dimensions of the fuel cell 1.

  Subsequently, as shown in FIG. 4E, the air electrode 4 is laminated on the upper surface of the electrolyte 2 (electrode lamination step).

  Subsequently, shaping is performed so that the upper surface of the air electrode 4 and the lower surface of the fuel electrode 3 are parallel to each other (shaping step). In the shaping step, it is preferable to polish the upper surface of the air electrode 4. Thus, the fuel cell 1 is completed.

  As described above, according to the fuel cell and the manufacturing method thereof according to another embodiment, not only the contact area between the electrolyte 2 and the fuel electrode 3 (one electrode) but also the electrolyte 2 and the air electrode 4 (the other electrode). ) Can be increased, and the reaction area is expanded, so that the output per unit area can be further increased.

  Although the first and second embodiments of the present invention have been described above, specific aspects of the present invention are not limited to the above-described embodiments.

  For example, in the above-described embodiment, the fuel electrode 3 is disposed on the lower surface (one surface) of the electrolyte 2 and the air electrode 4 is disposed on the upper surface (other surface). It can be changed. Further, the green sheet disposed on the lower surface (one surface) of the electrolyte green sheet 12 may be either the fuel electrode green sheet 13 or the air electrode green sheet.

  Moreover, in the said embodiment, although the green sheet of the electrolyte 2 and the fuel electrode 3 showed the form curved downward at the sintering stage, you may curve upward. In this case, by confirming that the layer thickness at both ends of the fuel electrode 3 is thicker than the layer thickness at the center of the fuel electrode 3, the length of L1 and L2 can be determined indirectly.

1 is a cross-sectional view of a solid oxide fuel cell according to an embodiment of the present invention. It is explanatory drawing of the manufacturing method of the solid oxide fuel cell which concerns on one Embodiment of this invention. It is sectional drawing of the solid oxide fuel cell which concerns on other embodiment of this invention. It is explanatory drawing of the manufacturing method of the solid oxide fuel cell which concerns on other embodiment of this invention. It is sectional drawing of the conventional solid oxide fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 2 Electrolyte 3 Fuel electrode 4 Air electrode 11 Green sheet laminated body 12 Electrolyte green sheet 13 Fuel electrode green sheet

Claims (1)

Electrolyte,
One electrode composed of a fuel electrode or an air electrode disposed on one surface of the electrolyte;
The other electrode made of an electrode different from the one electrode, disposed on the other surface of the electrolyte,
The electrolyte and the one electrode are laminated such that a boundary line between the electrolyte and the one electrode is curved in a laminating direction, and the length of the boundary line is longer than a straight line length between end portions of the boundary line. It is,
The electrolyte and the other electrode are laminated so that a boundary line between them is curved in a cross section cut in the lamination direction, and the length of the boundary line is longer than the straight line length between the ends of the boundary line. And
Surface and the surface of the other electrode of the one electrode is a solid oxide fuel cell Ru parallel flat surfaces der each other.

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