JP2008257890A - Current collecting material for fuel electrode, and solid oxide fuel cell using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current collecting material for a fuel electrode, along with a solid oxide fuel cell, for improved adhesion between a current collecting body and a fuel electrode, as well as durability and outputs. <P>SOLUTION: A collecting material 4 is attached to the fuel electrode of a solid oxide fuel cell. It comprises a partial oxidized active material and an electron conductive material included in the fuel electrode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a current collector for a fuel electrode attached to a fuel electrode of a solid oxide fuel cell operated by a fuel gas and an oxidant gas, and a solid oxide fuel cell having 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 metal oxides having ion conductivity for the electrolyte are called solid oxide fuel cells.
In this solid oxide fuel cell, oxygen (air) is supplied to the air electrode side and fuel gas (H ₂ , CH _4, etc.) is supplied to the fuel electrode side. Oxygen supplied to the air electrode side passes through the pores in the air electrode and reaches the vicinity of the interface with the electrolyte. At this portion, electrons are received from the air electrode and ionized to oxygen ions (O ²⁻ ). The oxygen ions move (diffuse) in the electrolyte toward the fuel electrode. The oxygen ions that reach the vicinity of the interface with the fuel electrode react with the fuel gas at this portion to become reaction products (H ₂ O, CO _2, etc.) and simultaneously release electrons. The electrons reach the air electrode after performing electrical work through an external electric circuit. Therefore, a current collector is formed on each electrode in order to efficiently extract electrons.

As the current collector, a material made of a metal having resistance to an oxidizing or reducing atmosphere is often used, and in many cases, elasticity is given to improve contact with the electrode. Specifically, a metal spring plate of Pt, Ni, Ag, or the like, a foam metal, a metal mesh, or the like is pressed against the electrode surface to form a current collector, and an output is extracted from the current collector to an external circuit. The current collecting performance of the current collector is affected by the bonding state between the electrode layer and the current collector, and when the bonding is insufficient, the resistance between the electrode layer and the current collector increases and the output decreases. Therefore, the current collector needs to be securely bonded to the electrode layer. In order to prevent this, a method of applying a fuel electrode material to a current collector and embedding the current collector in the fuel electrode has been proposed.
Japanese Utility Model Publication No. 63-106063 JP 2005-317274 A

However, when a general metal material is used as a current collector, when the operating temperature reaches 600 to 800 ° C., the difference between the internal stress of the metal material itself and the coefficient of thermal expansion at the time of temperature rise and fall is caused by the fuel electrode. Peeling of the current collector may occur.

  The present invention has been made to solve such problems, and can prevent peeling at the interface between the current collector and the fuel electrode, and can directly introduce a hydrocarbon-based gas at a low temperature. It is an object of the present invention to provide a current collector for a fuel electrode that can also generate electricity and a solid oxide fuel cell having the same.

The present invention
A current collector attached to a fuel electrode of a solid oxide fuel cell, which is made to solve the above-mentioned problem, and contains an electronic conductive material contained in the fuel electrode and a partial oxidation active material. Yes.
According to the current collector according to the present invention, since it has the electronic conductive material contained in the fuel electrode, the adhesion with the fuel electrode can be improved and the difference in thermal expansion coefficient can be suppressed. The peeling inside can be prevented. Moreover, since the partial oxidation active material is contained together, there is an advantage that the hydrocarbon gas can be directly introduced and the output can be improved even at a low temperature.
In addition, the current collector according to the present invention contains the electronic conductive material and the partial oxidation active material contained in the fuel electrode. Since the electronic conductive material uses an oxide body, the oxide body of the electronic conductive material itself is reduced during the internal reforming reaction of the hydrocarbon-based gas, so that it becomes a porous film and the gas permeability to the fuel electrode Has the advantage of ensuring.
The electronic conductive material contained in the fuel electrode can be composed of at least one element selected from the iron group. As such an electronic conductive material, for example, nickel can be used.

  The partial oxidation active material can be composed of at least one element selected from a platinum group element and a vanadium group element.

  The partial oxidation active material can be composed of at least one element selected from, for example, platinum, ruthenium, rhodium, palladium, vanadium, niobium, and tantalum.

  Moreover, it is preferable that 60-70 weight% of partial oxidation active materials are contained. If it is less than 60% by weight, the partial oxidation activity may be reduced and the electromotive force of the battery may be reduced. If it exceeds 70% by weight, the content of the electronically conductive material is reduced, so that peeling from the fuel electrode is not possible. This is because it tends to occur.

  Further, a glass frit can be further added to the current collector. Thereby, the current collector can be more closely attached to the fuel electrode. This glass frit can be composed of at least one of lead borosilicate, bismuth borosilicate, lead oxide, bismuth oxide, or silicon oxide.

  In addition, a solid oxide fuel cell according to the present invention is made to solve the above problems, and includes an electrolyte, a fuel electrode disposed on the surface of the electrolyte, and the fuel on the surface of the electrolyte. And an air electrode disposed apart from the electrode, and the fuel electrode current collector disposed on the fuel electrode.

  This fuel cell may be a so-called surface conduction type in which a fuel electrode and an air electrode are arranged at a predetermined interval on the same surface of an electrolyte, or a fuel electrode and an air electrode on one surface and the other surface of a flat electrolyte. It is also possible to configure a flat plate type in which each is arranged.

  The fuel electrode current collector is preferably formed by sintering after printing and is porous with gas permeability. When the fuel electrode current collector is made porous, the porosity is preferably 5% or more.

  Further, the current collector for the fuel electrode can be printed on the fuel electrode so that at least a part of the fuel electrode is exposed to the outside. Thereby, gas diffusibility improves.

  The current collector for the fuel electrode can be formed in various forms. For example, it can be formed on the fuel electrode in a regular pattern. For example, since the fuel electrode is exposed by forming a pattern in a lattice shape, gas diffusibility can be improved.

  The thickness of the fuel electrode current collector is preferably 50 μm or less.

  According to the current collector for a fuel electrode and the solid oxide fuel cell according to the present invention, the adhesion between the current collector and the fuel electrode is improved, peeling during operation can be prevented and durability can be improved. Hydrocarbon gas can be directly introduced, and output can be improved even at low temperatures.

  Hereinafter, an embodiment of a current collector for a fuel electrode and a solid oxide fuel cell according to the present invention will be described. Here, an example in which the current collector is attached to a solid oxide fuel cell will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a solid oxide fuel cell according to this embodiment.

  As shown in FIG. 1, a solid oxide fuel cell according to this embodiment includes an electrolyte 1 as a substrate, thin film air electrodes 2 (cathodes) and fuel electrodes 3 (anodes) formed on the upper and lower surfaces, respectively. ). A current collector 4 for the fuel electrode is attached to the surface of the fuel electrode 3, and a current collector 5 for the air electrode is attached to the surface of the air electrode 2. Hereinafter, these materials will be described.

As the material of the electrolyte electrolyte 1, those known as electrolytes for solid oxide fuel cells can be used. For example, ceria oxide (GDC) doped with samarium or gadolinium, strontium or magnesium is doped. An oxygen ion conductive ceramic material such as a lanthanum galide oxide, zirconia oxide (YSZ) containing scandium or yttrium can be used. When the electrolyte 1 is used as a substrate, the thickness is preferably 100 to 3000 μm, and more preferably 200 to 1000 μm.

The fuel electrode fuel electrode 3 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. As the metal oxide, an oxide material made of an iron group is used. Specifically, nickel oxide, iron oxide, and cobalt oxide can be used, and nickel oxide is more preferable. 50% or more, preferably 70% or more. 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 2 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.

Similar to the cathode air electrode 2 also the fuel electrode 3 can be formed by ceramic powder material. The same particle diameter as that of the fuel electrode 3 can be used. Further, as the ceramic powder material forming the air electrode 2, 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 air electrode 2 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. The fuel electrode 3 and the air electrode 2 are formed to have a film thickness of 5 to 100 μm, preferably 20 to 50 μm.

Fuel Electrode Current Collector The fuel electrode current collector 4 is configured by adding an electrode material made of a conductive material contained in the fuel electrode 3 to a material having partial oxidation activity. As the partial oxidation active material, at least one element selected from the platinum group and the vanadium group can be used. For example, one or more of platinum, ruthenium, rhodium, palladium, vanadium, niobium, tantalum and the like are combined. Can be used. Further, as the conductive material contained in the fuel electrode 3, the above-described iron group is used, and materials of nickel, iron and cobalt can be mentioned. For each of the partially oxidized active material and the conductive material, it is preferable to add a binder resin or the like so that these main components are 50 to 95% by weight. And it is preferable that the partial oxidation active material contains 60 to 70 weight% as the collector 4 for fuel electrodes. Moreover, a glass frit can also be added as needed. As such a glass frit, for example, at least one of lead borosilicate, bismuth borosilicate, lead oxide, bismuth oxide, or silicon oxide can be used. The amount of glass frit added is preferably 20 to 60% by weight.

The current collector 5 for the air electrode is a conductive metal having oxidation resistance, such as Pt, Au, Ag, Ni, Cu, SUS, or La (Cr, Mg) O ₃ , (La, Ca). ) CrO ₃ , (La, Sr) CrO ₃ and other conductive ceramic materials such as lanthanum and chromite, and one of these may be used alone, or two or more You may mix and use. And it is preferable to add binder resin etc. so that these main components may be 50 to 95 weight%.

Manufacturing Method Next, a method for manufacturing the fuel cell will be described. First, the electrolyte substrate 1 is prepared. And while forming the fuel electrode 3 in the one surface, the air electrode 2 is formed in the other surface. Furthermore, current collectors 4 and 5 are formed on the surfaces of the fuel electrode 3 and the air electrode 2, respectively. The fuel electrode 3, the air electrode 2, and the current collectors 4 and 5 can be formed by various methods. For example, spraying method, screen printing method, lithography method, electrophoresis method, doctor blade method, ink jet method, spray coating method, dip coating method, spin coating method, sputtering, CVD, EVD or so-called green body is used. Can be formed by a method.

  As mentioned above, although one Embodiment of this invention was described, a various change is possible for this invention, unless it deviates from the meaning. For example, in the battery, the electrolyte 1 is used as a support substrate, and the fuel electrode 3 and the air electrode 2 are formed on both surfaces thereof. However, the fuel electrode 3 or the air electrode 2 is used as a support substrate, or a separate porous support substrate. Various configurations are possible, such as a battery having a battery supported thereon. In any case, the above-described fuel electrode current collector can be applied to the surface of the fuel electrode.

  Next, examples of the present invention will be described. However, the present invention is not limited to the following examples.

  First, the fuel cell of FIG. 1 is created. The materials are as follows.

Electrolyte substrate First, GDC (Ce: Gd: O = 0.9: 0.1: 1.9) powder (particle size range 0.1--3μm, average particle size: 1μm) is put in a pressure-resistant container, and pressure is 1t / cm2 with a uniaxial press. After molding, the product was packaged in a vacuum pack and molded again with a hydrostatic pressure press at a pressure of 2 t / cm2. Then, sintering (1450 degreeC, 10 hours) was performed, and the electrolyte substrate was produced. In addition, an average particle diameter can be measured according to JISZ8901, for example.

Paste for fuel electrode NiO powder (average particle size: 1μm) and GDC (Ce: Gd: O = 0.9: 0.1: 1.9) are added to ethyl carbitol, and ethyl cellulose as a binder is added by mass ratio. Was added so as to be 80:20, and these were mixed by a roll to adjust a fuel electrode paste (viscosity: 5 × 10 ⁵ mPa · s) for forming a fuel electrode layer.

Air electrode paste (La, Sr) (Fe, Co) O ₃ powder (average particle size: 0.52 μm) was added to ethyl carbitol, and ethyl cellulose as a binder was added at a mass ratio of 85: Then, the air electrode paste (viscosity: 5 × 10 ⁵ mPa · s) for forming an air electrode layer was adjusted by mixing with a roll. In addition, an average particle diameter can be measured according to JISZ8901, for example.

Current collector for air electrode Gold was used as a partial oxidation active material. A gold paste to which a lead borosilicate frit was added was used as the glass frit. The amount of glass frit added is preferably 20 to 60% by weight.

Platinum was used as the fuel electrode current collector partial oxidation active material, nickel was used as the electronic conductive material, and nickel oxide was used as the oxide body. In a platinum paste to which a lead borosilicate frit is added as a glass frit, a paste prepared by adjusting NiO (average particle size 1 μm) and ethyl carbitol at a mass ratio of 80:20 is as follows: Added at. At this time, five types of current collectors for the fuel electrode were prepared. That is, current collectors for fuel electrodes having platinum content (% by weight) of 100%, 80%, 70%, 60%, and 50% were prepared. The nickel oxide content at this time is 0%, 20%, 30%, 40%, and 50%, respectively. In addition, an average particle diameter can be measured according to JISZ8901, for example. The amount of glass frit added is preferably 20 to 60% by weight.
Manufacturing Method A fuel electrode paste having a film thickness of about 40 μm is applied to one surface of an electrolyte substrate by screen printing, dried at 130 ° C. for 15 minutes, and then sintered at 1450 ° C. for 1 hour to form a fuel electrode. Subsequently, an air electrode paste with a film thickness of about 40 μm is applied to the other surface of the electrolyte by screen printing, dried at 130 ° C. for 15 minutes, and then a fuel electrode current collector is applied to the fuel electrode by printing. Sinter the air electrode and the fuel electrode current collector together at 1 ° C. for 1 hour. Subsequently, a current collector for the air electrode is applied on the air electrode by printing and baked at 1000 ° C. for 1 hour.
Evaluation Test The fuel cell prepared as described above was operated. That is, a mixed gas of methane and air was supplied at 600 ° C. and a total gas flow rate of 300 cc / min. And the electromotive force at this time and the presence or absence of peeling of the collector material for fuel electrodes were examined. In addition, peeling of the current collector was also examined. 2 and 3 are SEM photographs of current collectors with platinum content of 80% and 50%, respectively. The results are as follows.

According to the evaluation test, when the platinum content was 80% or more, as shown in FIG. 2, part of the current collector was peeled off. On the other hand, peeling of the current collector could not be confirmed at 70% or less. FIG. 3 shows a current collector with a platinum content of 50%, but peeling was not confirmed. Moreover, about the electromotive force, when the content rate of platinum became 50% or less, it was confirmed that it falls rapidly. As mentioned above, it is preferable that the content rate of platinum is 60 to 70%.

1 is a cross-sectional view showing an embodiment of a solid oxide fuel cell according to the present invention. It is a SEM photograph of a current collector with a platinum content of 80%. It is a SEM photograph of a current collector with a platinum content of 50%.

Explanation of symbols

1 Electrolyte 2 Air electrode 3 Fuel electrode 4 Current collector for fuel electrode 5 Current collector for air electrode

Claims (14)

A current collector attached to a fuel electrode of a solid oxide fuel cell,
A current collector for a fuel electrode, comprising an electronic conductive material contained in the fuel electrode and a partial oxidation active material.   The current collector for a fuel electrode according to claim 1, wherein the electronic conductive material contained in the fuel electrode is composed of at least one element selected from an iron group.   The current collector for a fuel electrode according to claim 2, wherein the electronic conductive material is nickel.   The current collector for a fuel electrode according to any one of claims 1 to 3, wherein the partial oxidation active material is composed of at least one element selected from a platinum group element and a vanadium group element.   The current collector for a fuel electrode according to any one of claims 1 to 4, wherein the partial oxidation active material is composed of at least one element selected from platinum, ruthenium, rhodium, palladium, vanadium, niobium, and tantalum. .   The current collector for a fuel electrode according to any one of claims 1 to 5, wherein the partial oxidation active material is contained in an amount of 60 to 70% by weight.   The current collector for a fuel electrode according to any one of claims 1 to 6, wherein a glass frit is further added to the partially oxidized active material.   The fuel electrode according to claim 7, wherein the glass frit is made of at least one of lead borosilicate, bismuth borosilicate, lead oxide, bismuth oxide, or silicon oxide. Current collector. Electrolyte,
A fuel electrode disposed on the surface of the electrolyte;
An air electrode disposed on the surface of the electrolyte and spaced apart from the fuel electrode;
The current collector for a fuel electrode according to any one of claims 1 to 8, which is disposed on the fuel electrode,
A solid oxide fuel cell.   The solid oxide fuel cell according to claim 9, wherein the fuel electrode current collector is formed by sintering after printing and is porous having gas permeability.   The solid oxide fuel cell according to claim 9 or 10, wherein the anode current collector has a porosity of 5% or more.   The solid oxide fuel cell according to claim 9, wherein the fuel electrode current collector is printed on the fuel electrode so that at least a part of the fuel electrode is exposed to the outside.   The solid oxide fuel cell according to claim 9, wherein the fuel electrode current collector is formed in a pattern having regularity.   14. The solid oxide fuel cell according to claim 9, wherein the fuel electrode current collector has a thickness of 50 μm or less.