JP2008084721A - Solid oxide fuel cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell capable of enhancing a yield while enhancing strength and thermal shock resistance, and to provide a manufacturing method of the solid oxide fuel cell. <P>SOLUTION: The solid oxide fuel cell includes a porous substrate 2, a hydrogen permeable filling member 6 filled in pores opened on the upper surface side of the substrate 2, a fuel electrode 3 formed on the upper surface 21 side of the substrate 2, an electrolyte 4 formed on the fuel electrode 3, and an air electrode 5 formed on the electrolyte 4, and a smooth surface 8 is formed with the upper surface 21 of the substrate 2 and the filling member 6, and at least a part of the substrate 2 adheres to the fuel electrode 3 through the smooth surface 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell and a method for producing the same.

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 a solid oxide having ionic conductivity for the electrolyte are called solid oxide fuel cells. Various types of solid oxide fuel cells have been proposed. For example, in Patent Document 1, in order to improve the strength and thermal shock resistance, a fuel electrode (anode), electrolyte, air, and the like are supported by a support. A single-chamber fuel cell that supports a single cell composed of an electrode (cathode) is disclosed.
JP 2005-174661 A

  In the fuel cell described above, the support is porous from the viewpoint of gas permeability, and the mixed gas is supplied to the fuel electrode formed on the support through the pores of the support. However, in such a porous support, when the fuel electrode is formed on the support by printing or the like, the fuel electrode penetrates into the pores of the support, and the fuel electrode is formed with a uniform film thickness. Difficult to do. For this reason, irregularities occur on the upper surface of the fuel electrode, and it becomes difficult to form an electrolyte formed on the upper surface. As a result, the stability and reproducibility of the battery performance during mass production becomes poor, and as a result, the yield decreases.

  Then, this invention makes it a subject to provide the solid oxide fuel cell which can improve a yield, improving the intensity | strength and thermal shock resistance, and its manufacturing method.

  The solid oxide fuel cell according to the present invention has been made to solve the above problems, and is a porous substrate and a hydrogen-permeable material filled in pores opened on one side of the substrate. A filling member comprising: a fuel electrode formed on one surface of the substrate; an electrolyte formed on the fuel electrode; and an air electrode formed on the electrolyte; and one surface of the substrate A smooth surface is formed with the filling member, and at least a part of the substrate is bonded to the fuel electrode through the smooth surface.

  According to this configuration, the filling member is filled in the pores opened on the one surface side of the porous substrate, and the smooth surface is formed by the one surface of the substrate and the filling member. Therefore, the fuel electrode can be formed in a uniform film thickness without causing a problem that the fuel electrode is formed in the pores of the substrate. For this reason, the electrolyte formed on the fuel electrode can be easily formed, and the yield can be improved. By the way, the hydrogen permeable material may become hydrogen embrittled due to occlusion and release of hydrogen, and as a result may be destroyed. However, according to the above configuration, the filling member is not interposed as a layer between the substrate and the fuel electrode, but is filled in the pores of the substrate. For this reason, the fuel electrode is directly bonded to the substrate on the smooth surface. That is, the portion of the substrate that is not filled with the filling member is directly bonded to the fuel electrode. Therefore, even if the hydrogen permeable material is hydrogen embrittled and destroyed, it is possible to prevent the substrate and the fuel electrode from being separated.

  The porosity of the substrate is preferably 20 to 60%. As described above, by setting the porosity to 20% or more, gas permeability can be secured, while by setting the porosity to 60% or less, a bonding area between the substrate and the fuel electrode is secured, and the substrate And the fuel electrode can be prevented more reliably.

  Various materials can be used as the filling member, and it is preferable that the filling member is made of at least one selected from the group consisting of palladium, vanadium, niobium, and tantalum.

  In order to form the fuel electrode with a uniform film thickness, the surface roughness Ra of the smooth surface is preferably within 5 μm.

  In addition, a method for producing a solid oxide fuel cell according to the present invention is made to solve the above-described problems, and includes a step of preparing a porous substrate and pores opened on one side of the substrate. A filling member made of a hydrogen permeable material, a step of polishing the filling member so that at least a part of the substrate is exposed, and a fuel electrode on one surface of the substrate after the polishing step. , A step of forming an electrolyte on the fuel electrode, and a step of forming an air electrode on the electrolyte.

  According to this manufacturing method, first, the filling member is formed so as to fill the pores of the substrate, and then the filling member coming out of the pores is polished, so that hydrogen permeation other than the filling member filled in the pores is performed. By removing the conductive material, the filling member can be reliably filled only into the pores of the substrate, and a smooth surface can be easily formed.

  ADVANTAGE OF THE INVENTION According to this invention, the solid oxide fuel cell which can improve a yield, improving a intensity | strength and a thermal shock resistance, and its manufacturing method can be provided.

  Embodiments of a solid oxide fuel cell and a method for manufacturing the same according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a front sectional view of a solid oxide fuel cell according to the present embodiment, and FIG. 2 is a sectional view taken along line AA of FIG. 1, and is a plan view of a substrate according to the present embodiment. For simplification of description, the proportionality of the size and shape of each component in each drawing is different from the actual product.

  As shown in FIGS. 1 and 2, the solid oxide fuel cell 1 includes a substrate 2 made of a porous material having a rectangular shape in plan view, and a thin film fuel electrode 3 and an electrolyte 4 on an upper surface (one surface) 21 thereof. And the air electrode 5 is formed in this order. The fuel electrode 3 and the electrolyte 4 are formed in a thin film shape having substantially the same shape as the substrate 2, and the air electrode 5 is formed in a thin film shape on the electrolyte 4 in a slightly small rectangular shape in plan view. In addition, since the substrate 2 is porous, it has a plurality of pores, and the porosity is set to 20 to 60% from the viewpoint of gas permeability and prevention of separation between the substrate 2 and the fuel electrode 3. Is preferred. Of the pores of the substrate 2, the pores 22 opened to the upper surface 21 side are filled with a filling member 6 made of a hydrogen permeable material. The smooth surface 8 is formed by the upper surface 21 of the substrate 2 and the filling member 6. Forming. The fuel electrode 3 is formed on the upper surface 21 of the substrate 2 so as to adhere to the filling member 6 filled in the pores 22 and a portion of the upper surface 21 of the substrate 2 where the filling member 6 is not filled. Yes.

  Next, materials constituting the fuel cell 1 will be described.

  For the filling member 6, a material having hydrogen permeability can be used. Specifically, palladium, vanadium, niobium, tantalum, or the like can be used.

The substrate 2 is made of, for example, a conductive metal such as Pt, Au, Ag, Ni, Cu, and SUS, or a metal-based material, or La (Cr, Mg) O ₃ , (La, Ca) CrO from the viewpoint of heat resistance. ₃ , (La, Sr) CrO ₃ and other conductive ceramic materials such as lanthanum and chromite. One of these may be used alone, or two or more may be mixed. May be used. The thickness of the substrate 2 is preferably 200 to 3000 μm and more preferably 500 to 1000 μm from the viewpoint of strength and the like from the viewpoint of strength and the like.

  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 a form of powder modification to nickel. 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 material of the electrolyte 4, those known as electrolytes for solid oxide fuel cells can be used. For example, ceria oxide doped with samarium or gadolinium, lanthanum galade doped with strontium or magnesium, etc. Oxygen ion conductive ceramic materials such as oxides, zirconia-based oxides containing scandium and yttrium can be used.

As the ceramic powder material forming the air electrode 5, 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) MnO ₃ is preferable. The ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types.

  When the fuel electrode 3, the electrolyte 4 and the air electrode 5 are formed from a ceramic powder material, the average particle size of the powder used is preferably 10 nm to 100 μm, more preferably 50 nm to 50 μm, and particularly preferably 100 nm. 10 μm. In addition, an average particle diameter can be measured according to JISZ8901, for example.

  The fuel electrode 3 and the air electrode 5 are formed by adding appropriate amounts of a binder resin, an organic solvent, and the like with the above-described material as a main component. More specifically, it is preferable to add a binder resin or the like so that the main component is 50 to 95% by weight in the mixing of the main component and the binder resin. Similarly to the fuel electrode 3 and the air electrode 5, the electrolyte 4 is molded by adding an appropriate amount of a binder resin, an organic solvent, or the like with the above-described material as a main component. In the mixing, it is preferable to mix so that the ratio of the main component is 80% by weight or more. And it is preferable to form so that the film thickness of the fuel electrode 3 and the air electrode 5 may become 5-100 micrometers after sintering, and it is more preferable to set it as 10-30 micrometers. The film thickness of the electrolyte 4 is preferably 1 to 100 μm, and more preferably 10 to 50 μm.

  Next, a method for manufacturing the above-described fuel cell 1 will be described with reference to FIG. FIG. 3 is an explanatory view showing a method for manufacturing the fuel cell 1.

  First, the porous substrate 2 made of the above-described material is prepared (FIG. 3A).

  The filling member 6 is formed on the upper surface 21 of the substrate 2. More specifically, the pores 22 are filled with a hydrogen permeable material by sputtering, screen printing, dip coating, or the like, and the filling member 6 is formed in the pores 22. Since the volume of the pores 22 is actually very small when forming the filling member 6 in this way, the filling member 6 overflows from the pores 22 after filling the pores 22 in an instant, and the substrate 2 is formed as a layer on the upper surface 21 (FIG. 3B).

  Next, the filling member 6 formed as a layer on the upper surface 21 of the substrate 2 is polished by a known polishing process such as grindstone polishing or buffing until a part of the upper surface 21 of the substrate 2 is exposed, A smooth surface 8 is formed by the upper surface 21 of the substrate 2 and the filling member 6 filled in the pores 22 (FIG. 3C). The surface roughness Ra of the smooth surface 8 is preferably within 5 μm.

  After the fuel electrode paste is applied by screen printing on the smooth surface 8 formed in this way, the fuel electrode 3 is formed by drying and sintering at a predetermined time and temperature (FIG. 3D). .

  Then, an electrolyte paste is applied onto the fuel electrode 3 by a screen printing method, and dried and sintered at a predetermined time and temperature to form the electrolyte 4 (FIG. 3E). The electrolyte 4 can be formed by various methods, but in order to form the fuel electrode 3 and the air electrode 5 as porous bodies, it is preferable to sinter at a lower temperature than these, for example, vacuum method, thermal spraying, etc. It can be formed by a low-temperature firing method such as a method.

  Subsequently, an air electrode paste is applied on the electrolyte 4 by a screen printing method, and dried and sintered at a predetermined time and temperature to form the air electrode 5. Through the above steps, the solid oxide fuel cell 1 is formed (FIG. 3F).

  Next, the power generation operation of the fuel cell 1 configured as described above will be described with reference to FIG.

  First, the fuel electrode 3 and the air electrode 5 are vertically separated by the partition wall 6 and the electrolyte 4 by a known method such as providing the partition wall 7. In this way, the solid oxide fuel cell 1 is configured as a two-chamber type, and a fuel gas composed of hydrogen or a hydrocarbon such as methane or ethane is provided on the fuel electrode 3 side, and an oxidant gas such as air is provided on the air electrode 5 side. Are supplied at a high temperature (for example, 400 to 1000 ° C.). The oxidant gas supplied to the air electrode 5 side is directly supplied to the air electrode 5. The fuel gas supplied to the fuel electrode 3 side passes through the substrate 2 and proceeds to the upper surface 21. The pores 22 in the upper surface 21 of the substrate 2 are filled with the filling member 6. Since the filling member 6 is made of a hydrogen permeable material, hydrogen in the fuel gas passes through the filling member 6 and passes through the fuel electrode. 3 is supplied. When the fuel gas is supplied to the fuel electrode 3 and the oxidant gas is supplied to the air electrode 5 in this way, oxygen ion conduction through the electrolyte 4 occurs between the fuel electrode 3 and the air electrode 5 to generate power.

  As described above, according to the present embodiment, the filling member 6 is filled in the pores 22 opened on the upper surface 21 side of the porous substrate 2, and the smooth surface 8 is formed by the upper surface 21 and the filling member 6 of the substrate 2. Therefore, the problem that the fuel electrode 3 formed on the upper surface 21 of the substrate 2 penetrates into the pores 22 of the substrate 2 does not occur, and the fuel electrode 3 can be formed with a uniform film thickness. . For this reason, the electrolyte 4 formed on the fuel electrode 3 can be easily formed, and the yield can be improved. Further, the filling member 6 is not interposed as a layer between the substrate 2 and the fuel electrode 3, but is filled only in the pores 22 of the substrate 2. In 21, the filling member 6 is directly bonded to the portion not filled. For this reason, even if the filling member 6, which is a hydrogen permeable material, is broken due to hydrogen embrittlement, it is possible to prevent the substrate 2 and the fuel electrode 3 from being separated.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention.

  For example, in the above embodiment, a two-chamber fuel cell is used, but the single-chamber solid oxide fuel cell 1 can be used. In this case, it is not necessary to separate the fuel electrode 3 and the air electrode 5 by the partition wall 7 or the like as in the above embodiment, and a mixed gas of fuel gas and oxidant gas can be supplied to the fuel cell 1.

  Moreover, in the said embodiment, although the screen printing method is used for application | coating of each paste, it is not limited to this, A doctor blade method, a spray coat method, a spin coat method, an electrophoresis method, CVD, EVD, Other general printing methods such as a sputtering method and a printing method such as a transfer method can be used. Moreover, as a post-process after printing, CIP (hydrostatic pressure press), HIP (hot isostatic press), hot press, and other general press processes can be used.

1 is a front sectional view showing an embodiment of a solid oxide fuel cell according to the present invention. It is the sectional view on the AA line of FIG. It is explanatory drawing which shows the manufacturing method of the solid oxide fuel cell which concerns on this embodiment. It is front sectional drawing which shows the time of use of the solid oxide fuel cell which concerns on this embodiment.

Explanation of symbols

1 Solid oxide fuel cell 2 Substrate 21 Upper surface (one surface)
22 Pore 3 Fuel electrode 4 Electrolyte 5 Air electrode 6 Filling member 8 Smooth surface

Claims (5)

A porous substrate;
A filling member made of a hydrogen permeable material filled in pores opened on one side of the substrate;
A fuel electrode formed on one side of the substrate;
An electrolyte formed on the fuel electrode;
An air electrode formed on the electrolyte,
A smooth surface is formed by the one surface of the substrate and the filling member,
A solid oxide fuel cell, wherein at least a part of the substrate is bonded to the fuel electrode through the smooth surface.   The solid oxide fuel cell according to claim 1, wherein the porosity of the substrate is 20 to 60%.   3. The solid oxide fuel cell according to claim 1, wherein the filling member is made of at least one selected from the group consisting of palladium, vanadium, niobium, and tantalum.   The solid oxide fuel cell according to any one of claims 1 to 3, wherein the smooth surface has a surface roughness Ra of 5 µm or less. Preparing a porous substrate; and
Filling the pores opened on one side of the substrate with a filling member made of a hydrogen permeable material;
Polishing the filling member such that at least a portion of the substrate is exposed;
Forming a fuel electrode on one surface of the substrate after the polishing step;
Forming an electrolyte on the fuel electrode;
Forming an air electrode on the electrolyte;
A method for producing a solid oxide fuel cell.

Images