JP5176362B2 - Solid oxide fuel cell structure and solid oxide fuel cell using the same - Google Patents

Description

  The present invention relates to a solid oxide fuel cell structure and a solid oxide fuel cell using 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. This solid oxide fuel cell is further classified into two types of solid oxide fuel cells: a cylindrical type and a flat type. The flat solid oxide fuel cell is easy to stack because of its shape, but has a drawback that the gas sealing property is inferior to that of a cylindrical solid oxide fuel cell. Therefore, in order to improve the gas sealing property of the flat solid oxide fuel cell, for example, the fuel cell disclosed in Patent Document 1 includes a fuel electrode, an electrolyte, and an air electrode in this order on a porous substrate. Is formed. Then, by forming an electrically conductive gas impermeable film so as to cover the porous substrate and the fuel electrode, the fuel electrode and the air electrode are separated to improve the gas sealing property.
JP 2002-319413 A

  However, the above fuel cell requires a process of covering the porous substrate and the fuel electrode with a gas-impermeable membrane, which increases the number of manufacturing steps compared to conventional fuel cells, resulting in poor yield. There is.

  Accordingly, the present invention provides a solid oxide fuel cell structure capable of obtaining good gas sealing properties without increasing the number of manufacturing steps, and a solid oxide fuel cell using the same. Let it be an issue.

The structure for a solid oxide fuel cell according to the present invention is made to solve the above-described problems, and includes a porous substrate having conductivity, and a fuel electrode or air formed on one surface of the substrate. Either one of the electrodes, a dense electrolyte formed so as to cover the one electrode and further cover the side surface of the substrate, and an interconnector arranged to face the other surface of the substrate, The interconnector is provided with a gas flow path facing the other surface of the substrate.

  The structure for a solid oxide fuel cell thus configured is usually used as a solid oxide fuel cell by forming the other electrode on the electrolyte. In this fuel cell, gas is supplied to one electrode through the substrate by introducing a gas necessary for power generation from the other surface of the substrate, that is, the surface not covered with the electrolyte. At this time, since the side surface of the substrate is covered with a dense electrolyte, the gas introduced from the other surface of the substrate can be supplied to one electrode without leaking from the side surface of the substrate. As described above, since it is not necessary to separately provide a member for preventing gas leakage, it is possible to ensure good gas sealing performance without increasing the number of manufacturing steps of the conventional fuel cell. The “dense” of the dense electrolyte according to the present invention means that it is gas-impermeable and has almost no pores for gas to permeate.

  The solid oxide fuel cell can have various configurations. For example, the side surface of the substrate can be covered with one electrode and further covered with an electrolyte. By comprising in this way, the contact area of one electrode and electrolyte which is a reaction field can be enlarged, and the improvement of an output can be aimed at.

  In addition, a solid oxide fuel cell according to the present invention has been made to solve the above problems, and any one of the solid oxide fuel cell structure and the other formed on the electrolyte. Electrode.

  Since the fuel cell configured in this manner supplies gas to one electrode, when the gas is introduced from the other surface of the substrate, the side surface of the substrate is covered with a dense electrolyte when the gas enters the substrate. Therefore, it is supplied to one electrode without leaking from the side surface of the substrate. As described above, since it is not necessary to separately provide a member for preventing gas leakage, it is possible to ensure good gas sealing performance without increasing the number of manufacturing steps of the conventional fuel cell.

  According to the present invention, there is provided a solid oxide fuel cell structure capable of obtaining good gas sealing properties without increasing the number of manufacturing steps, and a solid oxide fuel cell using the same. Let it be an issue.

  Embodiments of a solid oxide fuel cell structure and a solid oxide fuel cell using the same according to the present invention will be described below with reference to the accompanying drawings. 1 is a plan view of a solid oxide fuel cell according to the present embodiment, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG.

  As shown in FIGS. 1 to 3, the solid oxide fuel cell 1 according to the present embodiment includes a porous substrate 2 having a circular shape in a plan view having conductivity, and a fuel electrode 3 on the substrate 2. The electrolyte 4 and the air electrode 5 are formed in this order. The substrate 2 has an upper surface and side surfaces covered with the fuel electrode 3, and a lower surface thereof is exposed. The substrate 2 thus covered with the fuel electrode 3 is further covered with a dense electrolyte 4 on the upper surface and side surfaces of the fuel electrode 3 from above. Like the fuel electrode 3, the electrolyte 4 does not cover the lower surface of the substrate 2, so that the lower surface of the substrate 2 is exposed. The substrate 2 covered with the fuel electrode 3 and the electrolyte 4 as described above is referred to as a solid oxide fuel cell structure 10. The air electrode 5 is formed on the upper surface of the electrolyte 4 in the solid oxide fuel cell structure 10 so as to be slightly smaller than the electrolyte 4, thereby forming the solid oxide fuel cell 1. The

  Next, the material of each member constituting the fuel cell 1 will be described.

  In consideration of gas permeability and strength, the porous substrate 2 preferably has a porosity in the range of 20 to 60%. Thus, by setting the porosity to 20% or more, gas permeability can be secured, while by setting the porosity to 60% or less, the bonding area between the substrate and the fuel electrode is secured, and the substrate And the fuel electrode can be prevented more reliably. In order to satisfy such a requirement, the material constituting the porous substrate 2 can be a conductive metal such as Fe, Ti, Cr, Cu, Ni, Ag, Au, and Pt, and one kind can be used alone. It may be used in combination, or two or more types may be mixed. For example, stainless steel heat-resistant materials can be used. The heat-resistant alloy can be used.

  As the material of the electrolyte 4, 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.

  The fuel electrode 3 and the air electrode 5 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.

  The fuel electrode 3 can be made of a metal oxide and an oxide ion conductor at the time of production. Specifically, nickel oxide, iron oxide, cobalt oxide, copper oxide, ruthenium oxide and the like can be used as the metal oxide, more preferably nickel oxide, and the content is preferably 50% or more. 70% or more is preferable. When nickel oxide is reduced to nickel, hydrogen oxidation activity is higher than other metals, and by making the content rate 50% or more, voids are easily formed, and by making it 70% or more, the amount of nickel increases. To improve performance. 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, the fuel electrode 3 is preferably formed of a mixture of an oxide ion conductor and nickel oxide. Note that the mixed form of the ceramic material made of oxide ion conductor and nickel oxide may be a physical mixed form, or powder modification to nickel oxide or modification of nickel oxide to oxide ion conductor. It may be in the form of Moreover, the 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 the metal oxide used as a metal catalyst alone.

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) (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.

The fuel electrode 3 and the electrolyte 4 can be formed by, for example, a dry coating method. Examples of the dry coating method include a sputtering method. Specifically, when the sputtering method is used, the substrate 2 is placed on the substrate holder of the sputtering apparatus, the fuel electrode or the electrolyte material is placed on the baffle plate as a film forming material, and the inside of the chamber is used using a vacuum pump Is reduced to an ultimate vacuum of 3 × 10 ⁻⁴ Pa, the metal substrate is heated to 700 ° C., argon gas (1 slm) is introduced from the introduction tube into the chamber, and oxygen ( 0.5 slm) is introduced. Subsequently, 2 kW of power is applied to the film forming material by a pulse direct current power source to diffuse the film forming material, and film formation is performed until a predetermined thickness is reached. Note that the atmospheric pressure during film formation is set to 1 Pa.

  The air electrode 5 can be formed, for example, by screen printing. In this case, the air electrode 5 is formed by adding an appropriate amount of a binder resin, an organic solvent, or 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.

  Next, a method for manufacturing the above-described fuel cell 1 will be described with reference to FIG. FIG. 4 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. 4A).

  Subsequently, the fuel electrode 3 is formed by the above-described dry coating method so as to cover the substrate 2 except for its lower surface (FIG. 4B).

  Then, a dense electrolyte 4 is formed by the same method as described above so as to further cover the substrate 2 covered with the fuel electrode 3 from above (FIG. 4C). Through the above steps, the solid oxide fuel cell structure 10 is formed.

  Subsequently, an air electrode paste is applied onto the electrolyte 4 in the solid oxide fuel cell structure 10 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. 4D).

  In the above embodiment, the sputtering method is used as the film formation method for the fuel electrode 3 and the electrolyte 4, and the screen printing method is used as the film formation method for the air electrode 5. However, the present invention is not limited to this. Other general printing methods such as spray coating method, spin coating method, electrophoresis method, sol-gel method, CVD, EVD, sputtering method, printing method such as transfer method, etc. 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.

  A stack structure 20 using the solid oxide fuel cell 1 formed as described above will be described with reference to the drawings. FIG. 5 is a front sectional view showing a stack structure of the solid oxide fuel cell 1 according to the present embodiment.

  As shown in FIG. 5, the stack structure 20 of the solid oxide fuel cell 1 includes four fuel cells 1 and five interconnectors 6, and the fuel cell 1 is interposed between the interconnectors 6. As shown, the interconnectors 6 and the fuel cells 1 are alternately arranged. Each interconnector 6 has a first gas channel 61 formed on the upper surface and a second gas channel 62 formed on the lower surface. And the 1st gas flow path 61 of each interconnector 6 has opposed the porous substrate 2 of the fuel cell 1 arrange | positioned on it, and the 2nd gas flow path 62 is the fuel arrange | positioned under it. It faces the air electrode 5 of the battery 1. In addition, by making the interconnector 6 conductive, the fuel cells 1 are connected in series via the interconnectors 6.

  The solid oxide fuel cell 1 stacked as described above generates power as follows. First, a fuel gas composed of hydrocarbons such as hydrogen, methane, and ethane is introduced into the first gas flow path 61 of each interconnector 6 in a high temperature state (for example, 400 to 1000 ° C.). Further, an oxidant gas such as air is introduced into the second gas flow path 62 of each interconnector 6 at a high temperature. Since the substrate 2 is porous, the fuel gas introduced into the first gas flow path 61 enters the substrate 2, travels to the fuel electrode 3, and comes into contact with the fuel electrode 3. Further, the mixed gas introduced into the second gas flow path 62 is in direct contact with the air electrode 5 facing the second gas flow path 62. Thus, since the fuel electrode 3 of each fuel cell 1 is in contact with the fuel gas and the air electrode 5 is in contact with the oxidant gas, the electrolyte 4 is formed between the fuel electrode 3 and the air electrode 5 in each fuel cell 1. Oxygen ion conduction occurs, and power generation is performed.

  As described above, according to the present embodiment, the side surface of the substrate 2 is covered with the electrolyte 4. Therefore, the fuel gas introduced into the first gas flow path 61 enters the substrate 2, but the fuel gas that has entered the substrate 2 is supplied to the fuel electrode 3 without leaking from the side surface of the substrate 2. The Thus, since it is not necessary to separately provide a material for preventing gas leakage in the fuel cell, a good gas sealing property can be secured without increasing the number of manufacturing steps of the conventional fuel cell, and the electromotive force Loss can be minimized.

  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-described embodiment, the two-chamber solid oxide fuel cell 1 has been described. However, the single-chamber solid oxide fuel cell 1 can be used. In this case, a mixed gas of fuel gas and oxidant gas is introduced into the first gas flow path 61 and the second gas flow path 62 of the interconnector 6, and the mixed gas is brought into contact with the fuel electrode 3 and the air electrode 5. Power generation.

  In the above embodiment, the fuel electrode 3, the electrolyte 4 and the air electrode 5 are formed in this order on the substrate 2. However, as shown in FIG. 6, the air electrode 5, the electrolyte 4 and the fuel electrode 3 are formed. They can also be formed in order. In this case, the substrate 2 covered with the air electrode 5 and the electrolyte 4 becomes the solid oxide fuel cell structure 10.

  Moreover, in the said embodiment, although the fuel electrode 3 is formed so that the side surface of the board | substrate 2 may be covered, it can also be formed so that only the upper surface of the board | substrate 2 may be covered as shown in FIG. In this case, the electrolyte 4 is formed so as to directly cover the side surface of the substrate 2.

  Moreover, in the said embodiment, although the board | substrate 2, the fuel electrode 3, the electrolyte 4, and the air electrode 5 are planar circular shapes, it is not limited to this in particular, For example, various shapes, such as making it planar-view rectangular shape, are shown. Can be.

1 is a plan 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. FIG. 3 is a sectional view taken along line B-B in FIG. 2. 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 stack structure of the solid oxide fuel cell which concerns on this embodiment. It is front sectional drawing which shows other embodiment of the solid oxide fuel cell which concerns on this invention. It is front sectional drawing which shows other embodiment of the solid oxide fuel cell which concerns on this invention.

Explanation of symbols

1 Solid Oxide Fuel Cell 2 Substrate 3 Fuel Electrode 4 Electrolyte 5 Air Electrode 10 Solid Oxide Fuel Cell Structure

Claims (3)

A porous substrate having electrical conductivity;
Either the fuel electrode or the air electrode formed on one surface of the substrate;
A dense electrolyte formed to cover the one electrode and further cover the side surface of the substrate;
An interconnector arranged to face the other surface of the substrate,
A structure for a solid oxide fuel cell , wherein the interconnector is formed with a gas flow path facing the other surface of the substrate . The one electrode is formed so as to cover a side surface of the substrate,
2. The solid oxide fuel cell structure according to claim 1, wherein the electrolyte is formed so as to further cover a side surface of the substrate from above the one electrode. A structure for a solid oxide fuel cell according to claim 1 or 2,
A solid oxide fuel cell comprising: the other electrode formed on the electrolyte.

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