JP4658488B2 - Solid oxide fuel cell - Google Patents

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.

  In the flat plate-type cell, a fuel electrode and an air electrode are respectively disposed on the front and back surfaces of a plate-like electrolyte, and a plurality of cells formed in this manner are used in a state where they are stacked via separators. The separator plays a role of completely separating the fuel gas and air supplied to each cell, and a gas seal is provided between each cell and the separator (for example, Patent Document 1). However, this flat cell has a drawback in that it is vulnerable to vibration, thermal cycle, etc. because it applies a gas seal by applying pressure to the cell. 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 disadvantage 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 ohmic resistance by reducing the thickness of the electrolyte. However, if the electrolyte is too thin, it becomes vulnerable to vibration and thermal cycling. There was a problem that the vibration resistance and durability deteriorated.

  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 a 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, the conduction of oxygen ions occurs mainly near the surface layer of the solid electrolyte, and the fuel electrode and the air electrode are formed close to each other on the same surface of the solid electrolyte. The thickness of the electrolyte does not directly affect the performance of the battery as in the case of the mold or cylinder. Therefore, the thickness of the electrolyte can be increased while maintaining the performance of the battery, thereby improving the vulnerability.
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)

By the way, in the case of the solid electrolyte fuel cell shown in Patent Document 3, normally, in the fuel electrode, hydrogen gas (H ₂ ) or methane (CH ₄ ) of the fuel is an electron (e ⁻ ) at the interface between the fuel electrode and the electrolyte. Simultaneously with oxygen ions (O ²⁻ ) moving from the air electrode side to produce water molecules or carbon dioxide (CO ₂ ). At this time, electrons (e ⁻ ) emitted from hydrogen or the like pass through an external electric circuit such as an interconnector and play an electrical role, and then are supplied to the air electrode. On the other hand, oxygen (O ₂ ) in the air reacts with the supplied electrons (e ⁻ ) to become oxygen ions (O ²⁻ ) at the interface between the air electrode and the electrolyte, and these oxygen ions (O ²⁻ ). Is taken into the electrolyte and moves to the fuel electrode side. Electricity is generated by repeating the above reaction.

For example, as shown in Patent Document 3, when current is collected by forming an electrode in a comb shape and forming a current collector at the end of the electrode, electrons (e ⁻ ) generated at the fuel electrode It moves inside and is collected by a current collector formed at the end thereof. Then, after passing through the external electric circuit, the electron (e ⁻ ) reacts with oxygen in the air electrode, so that the electron (e ⁻ ) moves in the air electrode in the length direction from the current collector formed at the end.

However, when electrons (e ⁻ ) move in the fuel electrode or the air electrode, there is a problem that electron conduction loss occurs due to the internal resistance of the electrodes. More specifically, in general, it is considered preferable to lengthen both electrodes in order to increase the amount of power generation. However, as the distance from the current collector increases, the loss during electron conduction increases and the power generation efficiency There is a problem that decreases. For example, as shown in FIG. 6, if current collectors 61 and 81 are provided at the ends of electrodes 6 and 8, the distance from current collectors 61 and 81 will increase even if electrodes 6 and 8 are formed longer. Therefore, since the electrode activity is lowered, the entire electrode cannot be effectively used, and the power generation efficiency is lowered.

  On the other hand, as shown in FIG. 7, the current collectors 6 and 8 can be provided over the entire lengths of the electrodes 6 and 8. , 81 causes an extra area on the electrolyte to be used, resulting in a problem that power generation efficiency is reduced and the degree of freedom in wiring design is reduced.

  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 reducing loss during electron conduction and obtaining high power generation efficiency.

The present invention has been made to solve the above problems, and includes an electrolyte and an electrode body composed of a fuel electrode and an air electrode, the electrode body being disposed on one surface of the electrolyte, The one electrode is configured to surround the entire periphery of the other electrode at a predetermined interval, and the one electrode and the other electrode are arranged concentrically.

  According to this configuration, since one electrode is configured to surround the other electrode at a predetermined interval, when a current collector is formed at the end of each electrode as in the conventional example, In comparison, loss during electron conduction can be reduced. That is, since the one electrode is configured to surround the other electrode, even if the current collector is formed at any position of the one electrode, the electron moving distance, that is, the current collector and the current collector The distance to the position on the farthest electrode is halved even compared to the conventional strip electrode. Therefore, even if the length of the electrode is increased, the electron moving distance is half that length, so that the amount of power generation can be increased and the loss of electron conduction can be reduced. In addition, there is an advantage that the size of the electrode body can be made compact compared to the band-shaped electrode.

  When wiring is performed in the fuel cell of the present invention, a current collector is formed so as to overlap part of the fuel electrode and the air electrode as described above, and an interconnector is connected to this current collector. That's fine. Alternatively, wire bonding can be performed directly on the fuel electrode and the air electrode to form the wiring.

In the electrode body, it is preferable that the inner peripheral edge of hand electrodes, the distance between the outer peripheral edge of the other electrode is constant. That is, it is preferable that the distance between both electrodes is constant at any position, whereby stable power generation can be performed.

The present invention has been made to solve the above-described problem, and includes an electrolyte and an electrode body composed of a fuel electrode and an air electrode. The electrode body is disposed on one surface of the electrolyte, and both electrodes One of the electrodes is configured to surround the entire periphery of the other electrode at a predetermined interval, and a plurality of other electrodes are arranged in a region surrounded by the one electrode. The plurality of other electrodes can be connected to each other by, for example, an interconnector.

  Further, one electrode does not necessarily have to be formed continuously and surround the other electrode, and a discontinuous portion can be formed in a part thereof. In this case, a wiring that passes through this discontinuous portion and is connected to the other electrode can also be provided. According to this configuration, since the wiring does not pass through the discontinuous portion and does not contact the electrode, it is possible to easily perform the wiring design without causing a short circuit between the wiring and the electrode.

  The electrode body is preferably configured such that one electrode is a fuel electrode and the other electrode is an air electrode, that is, the fuel electrode surrounds the air electrode. This is because the air electrode has low electron conductivity and easily generates ohmic loss. Therefore, the air electrode is surrounded by the fuel electrode, and the air electrode is made shorter than the fuel electrode, thereby further reducing the loss during electron conduction. It is because it is thought that it can reduce.

  According to the solid oxide fuel cell according to the present invention, it is possible to reduce loss during electron conduction and to obtain high power generation efficiency.

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

  As shown in FIG. 1, the fuel cell includes an electrolyte 1 formed in a rectangular plate shape, and an electrode body E disposed on one surface of the electrolyte 1.

  Each electrode body E includes a fuel electrode 3 and an air electrode 5, and a frame-shaped fuel electrode 3 is disposed around the rectangular air electrode 5 at a predetermined interval. The outer shape of the fuel electrode 3 is rectangular according to the air electrode 5. At this time, the distance between the fuel electrode 3 and the air electrode 5 is preferably, for example, 1 to 1000 μm, and more preferably 10 to 500 μm. In addition, current collectors 51 and 31 for taking out current are formed at the center of the upper surface of the air electrode 5 and a part of the upper surface of the fuel electrode 3, respectively. An interconnector (not shown) is connected to each of the current collectors 31 and 51 so that a current flows to the outside (can be taken out).

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, scandium 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 ceramic powder material forming the fuel electrode 3, for example, a mixture of nickel and an oxygen ion conductive material can be used. Examples of the oxygen ion conductive material used at this time include ceria-based oxides such as (Ce, Sm) O ₃ and (Ce, Gd) O ₃ and lanthanum such as (La, Sr) (Ga, Mg) O _3. Oxygen ion conductive ceramic materials such as galide oxides, zirconia oxides such as scandium stabilized zirconia (ScSZ) and yttria stabilized zirconia (YSZ) can be mentioned. It is preferable to form the fuel electrode 5 with a mixture of the above. Among these, it is particularly preferable to form the fuel electrode 5 with a cermet of nickel-ceria-based oxide. The mixed form of the oxygen ion conductive ceramic material and nickel may be a physical mixed form or a form of powder modification to nickel. The metal is not limited to nickel, and a metal that is chemically stable in a reducing atmosphere of cobalt or a noble metal (platinum, ruthenium, palladium, etc.) can be used. Furthermore, the ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types.

As the ceramic powder material forming the air electrode 5, for example, a perovskite metal oxide 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. These ceramic powders can be used alone or in a mixture of two or more.

The current collectors 31 and 51 are made of lanthanum such as Pt, Au, Ag, Ni, Cu, SUS, or La (Cr, Mg) O ₃ , (La, Ca) CrO ₃ , (La, Sr) CrO _3. -It can form with electroconductive ceramic materials, such as a chromite type | system | group, 1 type of these may be used independently, and 2 or more types may be mixed and used for them.

  The fuel electrode 3 and the air electrode 5 are formed by adding the appropriate amount of varnish, organic solvent, etc. with the above-described materials as the main components. The film thicknesses of the fuel electrode 3 and the air electrode 5 are formed so as to be 1 μm to 500 μm after sintering, but preferably 10 μm to 100 μm. The current collectors 31 and 51 are also formed by adding the above additives to the above-described materials.

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 varnish, photosensitive polymer, organic solvent, etc. is added to each of them and kneaded to prepare a fuel electrode paste and an air electrode paste. Create each one. The viscosity of each paste is preferably about 10 ³ to 10 ⁶ Pa · s so as to be compatible with the screen printing method described below. Similarly, the interconnector paste is prepared by adding an additive such as varnish to the above-described powder material. The viscosity of this paste is the same as that of the fuel electrode paste described above.

  Subsequently, as shown in FIG. 1, the fuel electrode paste is applied to the electrolyte 1 in a rectangular frame shape by a screen printing method, and then dried and sintered at a predetermined time and temperature to form the fuel electrode 3. Next, the air electrode 5 is formed by applying a rectangular air electrode paste to the position surrounded by the fuel electrode 3 on each electrolyte 1 by a screen printing method, and drying and sintering at a predetermined time and temperature. To do. And the electrode body E is formed by forming the electrical power collectors 31 and 51 on each fuel electrode 3 and the air electrode 5. FIG.

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

  As described above, in the fuel cell according to the present embodiment, since the fuel electrode 3 is configured to surround the air electrode 5 with a predetermined interval, a current collector is provided at the end of each electrode as in the conventional example. Compared with the case where a body is formed, loss during electron conduction can be reduced. That is, even if the current collector 31 is formed at any position of the fuel electrode 3, the distance between the current collector 31 and the position A on the electrode farthest from the current collector 31, that is, the electron moving distance, Even half compared to the electrode. Therefore, even if the length of the electrode is increased, the electron moving distance is half that length, so that the amount of power generation can be increased and the loss of electron conduction can be reduced. In addition, there is an advantage that the size of the electrode body can be made compact compared to the band-shaped electrode.

  Note that the interconnector connected to the current collectors 31 and 51 can have various configurations. For example, it may be formed of the same material as the current collectors 31 and 51 and formed on the electrolyte 1 by printing. Alternatively, the current collectors 31 and 51 can be used as an interconnector by wire bonding. At this time, an interconnector can be directly connected to the electrodes 3 and 5 without providing a current collector.

  As mentioned above, although one 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 body E can be formed not only on one surface of the electrolyte 1 but also on the other surface. By doing so, the power generation output can be increased while keeping the fuel cell compact.

  Even if the current collector or interconnector is not formed or connected, the fuel cell of the present invention may be used and can be used. In that case, the fuel of the present invention If a current collector or interconnector is provided in a battery setting device, etc., and the fuel cell is set in the device, the current collector or interconnector is connected to the required location of each electrode. Good.

  Moreover, in the said embodiment, although the fuel electrode 3 and the air electrode 5 were formed in the rectangular shape, it is not limited to this, The air electrode 3 is formed so that a fuel electrode may be surrounded at predetermined intervals. If it is, the shape is not particularly limited. For example, as shown in FIG. 2, each electrode can be formed in a circular shape (FIG. 2 (a)) or in a polygonal shape (FIG. 2 (b)). For stable power generation, the fuel electrode 3 and the air electrode 5 are arranged concentrically, and the distance between the outer peripheral edge of the air electrode 5 and the inner peripheral edge of the fuel electrode 3 is constant at any position. From this point of view, it is preferable to form each electrode in a circular shape as shown in FIG. 2 (a). In addition, when a plurality of electrodes are arranged, the polygonal shape can be arranged without a gap, and from this viewpoint, the polygonal shape is preferable, and it may be properly used depending on the use state or the like.

  Further, when a current is taken out from the air electrode current collector by the interconnector, a discontinuous portion can be formed in a part of the fuel electrode so that the fuel electrode and the interconnector are not short-circuited. That is, as shown in FIG. 3, if the fuel electrode 3 is formed in a C shape, the interconnector 9 can be formed in the discontinuous portion 33, and wiring design is facilitated.

  Furthermore, as shown in FIG. 4, a plurality of air electrodes 5 can be formed in a region surrounded by the fuel electrode 3, and these air electrodes 5 can be connected by an interconnector. Further, as shown in FIG. 5A, a plurality of air electrodes 5 are formed in a region surrounded by the fuel electrode 3 (four in the figure), and these air electrodes 5 are connected to each other by an interconnector 9. It can also be done. Alternatively, as shown in FIG. 5B, a plurality of closed regions (two in the figure) can be formed in the fuel electrode 3, and the air electrode 5 can be formed in each region.

  In the above embodiment, the screen printing method is used for applying each paste. However, the present invention is not limited to this. The doctor blade method, the spray coating method, the lithography method, the electrophoretic electrodeposition method, the roll coating method, the dispenser coating. Other general printing methods such as a printing method such as a CVD method, a CVD method, an EVD method, a sputtering method, and a transfer method can be used. Moreover, as a post-process after printing, a hydrostatic press, a hydraulic press, and other general press processes can be used.

  In the above embodiment, a plate-like electrolyte is used, but a base material may be disposed on the other surface of the electrolyte, and each electrolyte may be supported by this substrate. By doing so, even if the electrolyte 1 is thinned, the fuel cell can be prevented from becoming weak. The substrate used at this time can be made of, for example, a ceramic material such as alumina, silica, or titanium, or SUS. In addition, the electrolyte can be formed on the substrate after being thinned by printing.

  Further, in each of the above embodiments, the electrode body is configured so that the fuel electrode surrounds the air electrode. However, it is possible to reverse this, that is, the air electrode can surround the fuel electrode.

  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.

As a solid oxide fuel cell according to the example, a battery as shown in FIG. 1 was prepared. A commercially available plate-like electrolyte having a thickness of 1 mm was prepared as the electrolyte. This electrolyte is a ceria-based electrolyte, and its material is GDC [(Ce, Cd) O ₃ ] and gadolinium is doped. As fuel electrode materials, nickel oxide (NiO) powder (particle size 0.01 to 10 μm, average particle size 1 μm) and SDC [(Ce, Sm) O ₃ ] powder (particle size 0.01 to 10 μm, average particle size) 0.1 μm) to a weight ratio of 7: 3, and then a cellulosic varnish 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. Moreover, SSC [(Sm, Sr) CoO ₃ ] powder (0.1 to 10 μm, average particle size 3 μm) was used as an air electrode material, and a cellulosic varnish was mixed to prepare an air electrode paste. Similarly, the viscosity of the air electrode paste was set to 5 × 10 ⁵ mPa · s suitable for the screen printing method.

In addition, as an interconnector material for connecting the electrode bodies, Au powder (0.1 to 5 μm, average particle diameter 2.5 μm) is used, and a cellulose-based varnish is mixed therewith to form an interconnector paste. Produced. The viscosity of the interconnector paste was 5 × 10 ⁵ mPa · s suitable for screen printing. The current collector was formed in the same manner as the interconnector.

  Next, the fuel electrode paste was applied onto the electrolyte 1 by screen printing. At this time, the fuel electrode paste was applied so as to form a rectangular frame having an outer side of 2700 μm and an inner side of 1950 μm. The coating thickness was 30 μm. And after drying at 130 degreeC for 15 minutes, it sintered at 1450 degreeC for 1 hour. Subsequently, an air electrode paste was applied on the same surface of the electrolyte 1 by a screen printing method. At this time, the air electrode paste was applied so as to form a rectangle with a side of 1550 μm inside the frame formed by the fuel electrode. And like the fuel electrode 3, after drying for 15 minutes at 130 degreeC, it sintered at 1200 degreeC for 1 hour.

Furthermore, a paste containing Au as a main component was applied so as to overlap a part of the air electrode to obtain a current collector. Subsequently, sol-gel SiO ₂ containing R—Si (OC ₂ H ₅ ) ₃ (R: alkyl group) as a main component is printed at a position on the fuel electrode different from the current collector, and then dried at 150 ° C. An insulating layer was formed. Thereafter, an Au paste was applied so as not to protrude from the insulating layer, thereby forming an interconnector extending from the air electrode to the outside of the electrode body. In addition, a paste mainly composed of Au was applied so as to overlap a part of the fuel electrode to obtain a current collector. After applying the Au paste, it was dried at 150 ° C. for 20 minutes and sintered at 900 ° C. for 2 hours. Thus, the fuel cell according to the example having one electrode body was obtained.

1 is a plan view of an embodiment of a solid oxide fuel cell according to the present invention. It is a top view which shows the other example of the solid oxide fuel cell which concerns on this invention. It is a top view which shows the other example of the solid oxide fuel cell which concerns on this invention. It is a top view which shows the other example of the solid oxide fuel cell which concerns on this invention. It is a top view which shows the other example of the solid oxide fuel cell which concerns on this invention. It is a top view which shows the conventional electrode body. It is a top view which shows the conventional electrode body.

Explanation of symbols

1 Electrolyte 3 Fuel electrode 5 Air electrode 7 Interconnector

Claims (6)

Electrolyte,
An electrode body comprising a fuel electrode and an air electrode,
The electrode body is disposed on one surface of the electrolyte, and one electrode of both electrodes is configured to surround the entire periphery of the other electrode at a predetermined interval ,
The solid oxide fuel cell, wherein the one electrode and the other electrode are arranged concentrically. Inner peripheral edge and the distance between the outer peripheral edge of the other electrode is constant, a solid oxide fuel cell according to claim 1 of the one electrode. Electrolyte,
An electrode body comprising a fuel electrode and an air electrode,
The electrode body is disposed on one surface of the electrolyte, and one electrode of both electrodes is configured to surround the entire periphery of the other electrode at a predetermined interval ,
A solid oxide fuel cell, wherein a plurality of the other electrodes are arranged in a region surrounded by the one electrode. The solid oxide fuel cell according to any one of claims 1 to 3 , wherein a discontinuous portion is formed in a part of the one electrode. The solid oxide fuel cell according to claim 4 , wherein a wiring that passes through the discontinuous portion and is connected to the other electrode is provided. 6. The solid oxide fuel cell according to claim 1, wherein the one electrode is a fuel electrode and the other electrode is an air electrode.

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