JP2005276536A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell (SOFC) capable of yielding a high power generating output. <P>SOLUTION: A solid oxide fuel cell includes an electrolyte 1, and at least one electrode element E having a fuel pole 3 and an air pole 5 formed in one side of the electrolyte 1. The fuel pole 3 and the air pole 5 are formed in a belt shape, as well as arranged at a predetermined interval, and the electrode width B with which the fuel pole 3 is in contact in a direction that both electrodes 3, 5 are aligned is made to be 10 to 1,000μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid oxide fuel cell (SOFC) using a solid electrolyte.

  Conventionally, as a cell design of a solid oxide fuel cell, a flat plate type (stack type), a cylindrical type (tube type), and the like have been proposed.

  A flat cell is one in which a fuel electrode and an air electrode are respectively arranged on the front and back surfaces of a plate-like electrolyte, and a plurality of cells formed in this way are used in a state where they are stacked via separators. The separator plays the role which completely isolate | separates the fuel gas and oxidant gas which are supplied to each cell, and the gas seal is given between each cell and the separator (for example, patent document 1). However, this flat cell has a drawback that the cell is vulnerable to vibration, thermal cycle, etc. because it applies pressure to the cell to provide a gas seal, and has a big problem in practical use. Yes.

  On the other hand, a cylindrical cell has a fuel electrode and an air electrode arranged on the outer peripheral surface and inner peripheral surface of a cylindrical electrolyte, and a cylindrical vertical stripe type, a cylindrical horizontal stripe type, and the like have been proposed (for example, Patent Documents). 2). However, the cylindrical cell has an advantage of excellent gas sealing properties, but has a drawback that the manufacturing process is complicated and the manufacturing cost is high because the structure is more complicated than that of the flat plate cell.

  In addition, there are the following problems. In order to improve the performance of both flat and cylindrical cells, it is necessary to reduce the internal resistance by thinning the electrolyte. However, if the electrolyte is too thin, it becomes vulnerable to vibration and thermal cycles. As a result, there is a problem that vibration resistance and durability are lowered.

  For this reason, as a fuel cell that replaces the flat plate type and the cylindrical type described above, the fuel electrode and the air electrode are arranged on the same surface of the substrate made of solid electrolyte, and power is generated by supplying a mixed gas of fuel gas and oxidant gas A non-diaphragm solid oxide fuel cell that can be used has been proposed (for example, Patent Document 3). According to this fuel cell, since it is not necessary to separate the fuel gas and the oxidant gas, the separator and the gas seal are not required, and the structure and the manufacturing process can be greatly simplified.

Further, in this non-membrane type solid oxide fuel cell, it is considered that conduction of oxygen ions occurs mainly near the surface layer of the solid electrolyte, and the fuel electrode and the air electrode are brought close to each other on the same surface of the solid electrolyte. Battery performance is improved. Therefore, it is not necessary to reduce the thickness of the electrolyte more than necessary, and it is possible to improve the fragility of the electrolyte while maintaining the battery performance.
JP-A-5-3045 (first page, FIG. 6) Japanese Patent Laid-Open No. 5-94830 (first page, FIG. 1) JP-A-8-264195 (page 2-3, FIG. 1)

  However, even the fuel cell described in Patent Document 3 cannot be said to have sufficient output, and there is room for further improvement.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a solid oxide fuel cell capable of obtaining a higher power generation output.

The present inventor has conducted research to further improve the above-described invention, and the output of the fuel cell is improved by setting the width of the air electrode formed in a strip shape (the length in the direction in which the electrodes are arranged) to a predetermined length. I found. The present invention is characterized by the following points.
1. In a solid oxide fuel cell comprising an electrolyte and at least one electrode body formed on one surface of the electrolyte and having a fuel electrode and an air electrode, the fuel electrode and the air electrode are formed in a band shape, A solid oxide fuel cell, which is arranged in parallel at a predetermined interval, and an electrode width of the air electrode in a direction in which both electrodes are arranged is 10 to 1000 μm.
2. Item 2. The solid oxide fuel cell according to Item 1, wherein the electrode width of the air electrode is 10 to 500 µm.
3. Item 3. The solid oxide fuel cell according to Item 1 or 2, wherein the electrode width of the air electrode is 20 to 200 µm, and the electrode width of the fuel electrode is larger than the electrode width of the air electrode.
4). Item 4. The solid oxide fuel cell according to any one of Items 1 to 3, wherein the fuel electrode is formed of a mixture of an oxide ion conductor having a fluorite structure or a perovskite structure and a metal catalyst.
5). 5. The solid oxide fuel cell according to claim 1, wherein the air electrode is formed of a material containing at least one of a metal oxide having a perovskite structure and a noble metal.

  According to the solid oxide fuel cell according to the present invention, a high output can be obtained.

  Hereinafter, an embodiment of a solid oxide fuel cell according to the present invention will be described with reference to the drawings. FIG. 1A is a plan view of a fuel cell according to the present embodiment, and FIG.

  As shown in FIG. 1, the fuel cell according to the present embodiment includes a plate-like electrolyte 1 and an electrode body E disposed on one surface of the electrolyte 1. The electrode body E has a fuel electrode 3 and an air electrode 5 formed in a band shape, and these are arranged at a predetermined interval. For example, the interval is preferably 1 to 1000 μm, and more preferably 10 to 500 μm. In addition, current collectors 31 and 51 are formed at end portions of the electrodes 3 and 5, and current is taken out therefrom. The positions of the current collectors 31 and 51 are arranged on the opposite sides of the electrodes 3 and 5, and the current collector 31 of the fuel electrode 3 is arranged at one end on the upper side of the figure, The current collector 51 is disposed at the other end which is the lower side of the drawing. The current collectors 31 and 51 can be formed at the end portions of the electrodes 3 and 5 as described above, or can be formed on the entire surfaces of the electrodes 3 and 5.

  The film thickness of the fuel electrode 3 is preferably 1 to 300 μm, and more preferably 5 to 100 μm. This is because if the film thickness is too small, the output decreases due to a decrease in the three-phase interface length. If the film thickness is too large, the overvoltage due to insufficient diffusion of the reaction gas tends to increase. This is because the output corresponding to that cannot be obtained. That is, cost performance is lowered. Another factor is the ohmic loss of the electrodes. On the other hand, the film thickness of the air electrode 5 is similarly preferably 1 to 300 μm, and more preferably 5 to 100 μm. The reason is the same as in the case of the fuel electrode.

  Further, as will be described later, the fuel electrode 3 is made of a material containing ceria oxide, the air electrode 5 is made of samarium (Sm) based cobalt-containing material, and the electrolyte 1 is made of gadolinium-doped ceria oxide (GDC). ), The thickness of the electrodes 3 and 5 is preferably 10 to 65 μm. In particular, the thickness of the fuel electrode 3 is 10 to 35 μm, and the thickness of the air electrode 5 is 10. It is preferable from a characteristic to set it as -40 micrometers.

  Further, in each of the electrodes 3 and 5, the current collectors 31 and 51 and the length L (hereinafter referred to as “electrode length”) to the end portion on the electrode farthest from the current collectors 31 and 51 are preferably 10000 μm or less. 1000 to 7000 μm is more preferable, and 4000 μm or less is particularly preferable. For example, in the case of the air electrode 5, the length from the current collector 51 to the upper end of the electrode is preferably set as described above. In the case of the fuel electrode 3, the electrode length L may be the same as or longer than the air electrode 5.

  Further, with respect to the electrodes 3 and 5, the length in the direction in which the electrodes 3 and 5 are arranged in the direction perpendicular to the electrode length L, that is, the electrode width B is preferably set as follows. That is, about the air electrode 5, it is preferable that it is 5-1000 micrometers, It is more preferable that it is 10-500 micrometers, It is especially preferable that it is 20-200 micrometers. On the other hand, the electrode width B of the fuel electrode 3 is preferably 5 to 1000 μm, and more preferably 500 to 700 μm. At this time, the electrode width of the fuel electrode 3 is preferably larger than the electrode width of the air electrode 5.

Next, the material of the fuel cell configured as described above will be described. As the material of the electrolyte 1, those known as electrolytes for solid oxide fuel cells can be used. For example, ceria-based oxides such as (Ce, Sm) O ₃ , (Ce, Gd) O ₃ , ( Oxygen ion conductive ceramic materials such as La, Sr) (Ga, Mg) O _{3 and} other lanthanum galade oxides, scandia stabilized zirconia (ScSZ), yttria stabilized zirconia (YSZ) and other zirconia oxides Can be used. Since the electrolyte 1 is used as a substrate and needs a certain level of strength, the thickness is preferably, for example, 200 to 1000 μm.

  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.

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 oxides such as (Ce, Sm) O ₃ and (Ce, Gd) O ₃ , scandia-stabilized zirconia (ScSZ), and yttria-stabilized zirconia (YSZ). A zirconia-type oxide can be mentioned. In addition, examples of those having a perovskite structure include lanthanum galide oxides such as (La, Sr) (Ga, Mg) O ₃ . Among the materials described above, the fuel electrode 5 is preferably formed of 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 5 can also be comprised using a metal catalyst alone.

The ceramic powder material forming the air electrode 5 can be formed of a metal oxide having a perovskite structure, for example. 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. These ceramic powders can be used singly or in combination of two or more. In addition, the air electrode 5 can be formed of a noble metal such as Pt, Pd, or Au, and further, the air electrode 5 can be formed of a mixture of such a noble metal and the above metal oxide.

The current collectors 31 and 51 are made of conductive metals such as Pt, Au, Ag, Ni, Cu, and SUS, or conductive metal-based materials, or La (Cr, Mg) O ₃ , (La, Ca) CrO. 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 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. The film thickness of the fuel electrode 3 and the air electrode 5 is set to the above-described film thickness after sintering. The current collectors 31 and 51 are also formed by adding the above additives to the above-described materials. The current collector may be formed of a conductive metal, a wire made of a metal-based material, a mesh-like material, or the like.

Next, an example of a method for manufacturing the above-described fuel cell will be described. First, a plate-like electrolyte 1 made of the above-described material is prepared. Subsequently, the powder material for the fuel electrode 3 and the air electrode 5 described above is used as a main component, and an appropriate amount of a binder resin, a photosensitive polymer, an organic solvent, etc. is added to each of them and kneaded to produce a fuel electrode paste and an air electrode paste. Create each. The viscosity of each paste is preferably about 10 ³ to 10 ⁶ mPa · s so as to be compatible with the screen printing method described below. Similarly, the current collector paste is prepared by adding an additive such as a binder resin to the above-described powder material. The viscosity of this paste is the same as that of the fuel electrode paste described above.

  Subsequently, the fuel electrode paste is applied to the position shown in FIG. 1A on the electrolyte 1 in a strip shape by screen printing, and then dried and sintered at a predetermined time and temperature to form the fuel electrode 3. Next, a strip-shaped air electrode paste is applied to the position facing the fuel electrode 3 on the electrolyte 1 by a screen printing method at a predetermined interval, and dried and sintered at a predetermined time and temperature, whereby the air electrode 5 Form. Then, a current collector paste is applied on each fuel electrode 3 and air electrode 5, and then dried and sintered to form current collectors 31 and 51. Through the above steps, a fuel cell as shown in FIG. 1 is completed. In addition, when using a photosensitive polymer, it is necessary to sinter after a paste application | coating and through a drying and exposure process.

  The fuel cell configured as described above generates power as follows. First, on one surface of the electrolyte 1 on which the electrode body E is arranged, a mixed gas of hydrogen or a fuel gas made of hydrocarbon such as methane or ethane and an oxidant gas such as air is in a high temperature state (for example, 400 to 1000 ° C). Thereby, oxygen ion conduction occurs between the fuel electrode 3 and the air electrode 5 in each electrode body E, and power generation is performed.

  As described above, according to the present embodiment, favorable battery performance can be obtained by setting the width of each electrode as described above. The reason is as follows. That is, when the electrode width B of both the electrodes 3 and 5 is too short, the area of the electrode is reduced and the battery reaction region is narrowed, so that the amount of power generation is reduced. On the other hand, if the electrode width B is too long, the ends S2 opposite to the opposing ends S1 of both electrodes are far from each other. Since the battery reaction normally proceeds at the three-phase interface, if the opposite ends S2 that are part of the three-phase interface are far from each other, oxygen ions are difficult to reach due to ohmic resistance, and the reaction is difficult to proceed. As a result, the portion that does not contribute to power generation increases, apparently the output density decreases, and the battery performance decreases. For the above reasons, it is preferable to adjust the width of each electrode as described above. At this time, since the fuel electrode 3 needs to increase the hydrogen oxidation activity, it is preferable to make it larger than the electrode width of the air electrode 5.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible unless it deviates from the meaning. For example, the electrode length is preferably short as described above, but from this point of view, the current collector can be formed on the entire surface of each electrode. If it does in this way, since the length from an electrical power collector to an electrode edge part can be shortened, maintaining the area of an electrode, a high output can be obtained.

  Moreover, in the said embodiment, although only one electrode body E is formed, after forming the several electrode body E on the electrolyte 1, these can also be connected by an interconnector. In this case, the interconnector can be formed of the same material as the current collectors 31 and 51.

  Furthermore, in the fuel cell according to the present invention, the current collector and the interconnector are not necessarily arranged on the electrolyte. The current collector is formed on the device side where the fuel cell is set, and the fuel cell is installed in the fuel cell. When set to, current collectors and interconnectors can be arranged at portions corresponding to the respective electrodes. In this case, the length from the position where the current collector or the interconnector is arranged to the farthest end on the electrode is the above-mentioned “electrode length”.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example. Here, four types of fuel cells having the structure shown in FIG. 1 were prepared, and the electrode width and electrode length of each cell were as shown in Table 1 below.

First, materials used for the four types of samples will be described. As the electrolyte material, a 1 mm thick plate made of GDC (Ce _0.9 Gd _0.1 O _1.9 ) was used. Further, NiO powder (0.01 to 10 μm, average 1 μm) and SDC (Ce _0.8 Sm _0.2 O _1.9 ) powder (particle size 0.01 to 10 μm, average 0.1 μm) as a fuel electrode material at a weight ratio of 7: 3 Then, the cellulose binder resin was mixed to prepare a fuel electrode paste. The viscosity of the fuel electrode paste was 5 × 10 ⁵ mPa · s suitable for screen printing. SSC (Sm _0.5 Sr _0.5 CoO ₃ ) powder (0.1 to 10 μm, average 3 μm) was used as an air electrode material, and a cellulose binder resin was mixed to prepare an air electrode paste. The viscosity of the air electrode paste was 5 × 10 ⁵ mPa · s suitable for screen printing as in the fuel electrode. Moreover, Au powder (0.1-5 micrometers, average particle diameter 2.5 micrometers) was mixed with the cellulose-type binder resin as a collector material, and the collector paste was created. These viscosities were set to 5 × 10 ⁵ mPa · s as described above.

  Next, four samples are made using the above materials. Although the following description is common to each sample, Samples 1 to 3 are different only in electrode width, and Sample 4 is different from Sample 3 only in electrode length. The fuel electrode material paste was applied by screen printing so that the electrode width was 50 μm and the electrode width was the same, and then dried at 130 ° C. for 15 minutes. Thereafter, sintering was performed at 1450 ° C. for 1 hour. Next, the air electrode material paste was applied by the screen printing method so that the electrode width and the electrode thickness were 50 μm to the electrode width. At this time, the distance between both electrodes was set to 200 μm. And after drying for 15 minutes at 130 degreeC, it sintered at 1200 degreeC for 1 hour. The film thickness of each electrode after sintering was 25 μm. Finally, a current collector paste was applied to each electrode, dried at 150 ° C. for 20 minutes, and then sintered at 900 ° C. for 2 hours to obtain four types of fuel cells.

  A mixed gas of methane: oxygen = 2: 1 was introduced at 800 ° C. into the solid oxide fuel cell produced by the above method, and current-voltage characteristics were evaluated. The results are shown in FIGS. FIG. 2 is a diagram showing the relationship between the current density, voltage, and output density in Samples 1 to 3, and FIG. 3 is a diagram showing the relationship between the current density, voltage, and output density in Samples 3 and 4.

  According to FIG. 2, it can be seen that the shorter the electrode width, the higher the battery performance. On the other hand, according to FIG. 3, it can be seen that high battery performance is exhibited when the electrode width is short and the electrode length is short.

It is the top view (a) of one Embodiment of the solid oxide fuel cell which concerns on this invention, and its AA sectional view (b). It is a figure which shows the relationship between a current density, a voltage, and an output density regarding samples 1-3. It is a figure which shows the relationship between a current density regarding a sample 3 and 4, a voltage, and an output density.

Explanation of symbols

1 Electrolyte 3 Fuel electrode 5 Air electrode 31, 51 Current collector

Claims (5)

In a solid oxide fuel cell comprising an electrolyte and at least one electrode body formed on one surface of the electrolyte and having a fuel electrode and an air electrode,
The fuel electrode and the air electrode are formed in a strip shape and are arranged in parallel at a predetermined interval.
The solid oxide fuel cell, wherein an electrode width of the air electrode in a direction in which both the electrodes are arranged is 5 to 1000 μm.   2. The solid oxide fuel cell according to claim 1, wherein an electrode width of the air electrode is 10 to 500 μm.   3. The solid oxide fuel cell according to claim 1, wherein an electrode width of the air electrode is 20 to 200 μm, and an electrode width of the fuel electrode is larger than an electrode width of the air electrode.   4. The solid oxide fuel cell according to claim 1, wherein the fuel electrode is formed of a mixture of an oxide ion conductor having a fluorite structure or a perovskite structure and a metal catalyst. 5. 5. The solid oxide fuel cell according to claim 1, wherein the air electrode is formed of a material containing at least one of a metal oxide having a perovskite structure and a noble metal.

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