JP5292898B2 - Solid oxide fuel cell and method for producing the same - Google Patents

Description

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

A fuel cell is a cell that can directly convert chemical energy generated when fuel is oxidized into electric energy while continuously supplying fuel from the outside and exhausting combustion products. The types of fuel cells are classified according to the electrolyte, and those using metal oxides having ion conductivity for the electrolyte are called solid oxide fuel cells. Various types of solid oxide fuel cells have been proposed. For example, Patent Document 1 discloses a solid in which a fuel electrode (anode), an electrolyte, and an air electrode (cathode) are stacked in this order. An oxide fuel cell is described.
JP 2002-175814 A

  By the way, the current of the fuel cell electrode as described above is usually arranged by taking out the current, but if the contact between the electrode and the current collector is poor, the contact resistance increases and the power generation performance is low. There was a problem. Therefore, an increase in the contact area between the current collector and the electrode has been desired.

  The present invention has been made to solve the above problem, and by increasing the area of the contact interface between the electrode and the current collector, the contact resistance can be reduced and the power generation performance can be improved. An object of the present invention is to provide a physical fuel cell and a manufacturing method thereof.

  The present invention is a solid oxide fuel cell to which a current collector having irregularities on its surface is attached, which has been made in order to solve the above problems, and is disposed on one side of the electrolyte and the electrolyte. A fuel electrode, and an air electrode disposed on the other surface of the electrolyte, wherein a current collector can be attached to at least one of the fuel electrode and the air electrode, and an electrode to which the current collector is attached Irregularities that can be engaged with the irregularities of the current collector are formed on at least a part of the surface.

  According to this configuration, since the unevenness is formed on the surface of the electrode, the contact area of the interface between the electrode and the current collector can be increased by engaging the unevenness with the unevenness of the current collector. The contact resistance can be reduced. Thereby, the power generation performance of the battery can be improved. The uneven current collector includes, for example, one formed in a mesh shape, that is, a current collector in which a large number of small holes are formed, and a fibrous material such as metal wool. In other words, the unevenness includes not only a dent but also that formed by adjoining a large number of through holes. Therefore, the current collector targeted in the present invention means a current collector whose surface in contact with the electrode is not a flat surface. In the present invention, the electrolyte, the fuel electrode, and the air electrode can be formed into a sheet shape, a block shape, or the like, and can be a so-called flat plate type solid oxide fuel cell. The present invention can also be applied to a solid oxide fuel cell.

  By the way, since fuel gas and oxidant gas are supplied to a fuel electrode and an air electrode, it is preferable that the porosity of the surface vicinity is high. However, when the porosity is increased in this way, the adhesion with the current collector may be reduced. Therefore, if irregularities are formed on the surface of the electrode to which the current collector is attached as described above, it is possible to improve the adhesion with the current collector while keeping the porosity high. Therefore, in the fuel cell, at least the electrode to which the current collector is attached among the fuel electrode and the air electrode is formed on the porous reaction layer in contact with the electrolyte and on the reaction layer, and the porosity is higher than that of the reaction layer. And a gas diffusion layer having a high height, and irregularities may be formed on the surface of the gas diffusion layer. As the porosity of each layer, for example, the porosity of the reaction layer can be in the range of 5 to 30%, and the porosity of the gas diffusion layer can be in the range of 30 to 60%. The porosity can be measured by a known method such as Archimedes method, mercury intrusion method, or gas adsorption method.

  In the present invention, the shape is not particularly limited as long as the unevenness of the electrode is engaged with the unevenness of the current collector, but, for example, the convexity of the unevenness is formed in the through hole of the current collector. Can do. As an example, when using a mesh-shaped current collector, the unevenness formed on the electrode is formed in a lattice shape, and the unevenness is smaller than the mesh opening of the current collector. It is preferable that the convex part is formed. By doing so, the uneven portions of the electrode can be easily fitted in the holes of the mesh of the current collector, and the adhesion between the current collector and the electrode can be further improved.

  In addition, when using a mesh-like current collector, the irregularities formed on the electrodes should be formed in a lattice shape, and a recess having a width larger than the wire diameter of the current collector mesh should be formed. Is preferred. By doing so, the uneven portions of the electrode can be easily fitted in the holes of the mesh of the current collector, and the adhesion between the current collector and the electrode can be further improved.

  The first solid oxide fuel cell manufacturing method according to the present invention includes a step of preparing an electrolyte, a step of forming a fuel electrode on one surface of the electrolyte, and an air electrode on the other surface of the electrolyte. And at least one of the steps of forming the fuel electrode and the air electrode is formed by printing the material for the electrode by printing, drying the printed material for the electrode, and drying A step of forming irregularities on the electrode material, and a step of sintering the electrode material having irregularities formed thereon.

According to this configuration, unevenness can be easily formed on the surface of the electrode, and therefore, if a current collector having unevenness is disposed on this electrode, the contact resistance between the current collector and the electrode can be further reduced. Thus, the power generation performance of the battery can be improved. As a result, the power generation performance of the battery can be improved.
The method for forming the unevenness is not particularly limited. For example, in the step of forming the unevenness, the unevenness is formed on the surface of the electrode by pressing the transfer member on which the unevenness is formed on the dried electrode material. Can be formed. Examples of such a transfer member may include a mesh-like member such as a mesh other than a member on which irregularities are simply formed.

  Moreover, when forming the said electrode by a screen printing method, it becomes possible to directly transfer the uneven | corrugated shape of a screen mesh to an electrode by adjusting the viscosity of a paste.

  According to the present invention, it is possible to further improve the power generation performance by reducing the contact resistance between the electrode and the current collector while improving the gas diffusibility.

  An embodiment of a solid oxide fuel cell according to the present invention will be described with reference to the drawings. 1 is a front sectional view of a solid oxide fuel cell according to the present embodiment, FIG. 2 is a plan view of the solid oxide fuel cell of FIG. 1, and FIG. 3 is an enlarged view of FIG. .

  As shown in FIGS. 1 and 2, this solid oxide fuel cell has a sheet-like fuel electrode 2 and an air electrode 3 formed on the upper and lower surfaces of a plate-like electrolyte 1, respectively. Since the electrolyte 1 is for supporting both the electrodes 2 and 3, it has a mechanical strength higher than those of the electrodes 2 and 3. Each of the electrodes 2 and 3 is composed of two layers. That is, the reaction layers 21 and 31 in contact with the electrolyte 1 and the gas diffusion layers 22 and 32 formed on the reaction layers 21 and 31 are configured. The difference between the reaction layers 21 and 31 and the gas diffusion layers 22 and 32 is the porosity. That is, while the reaction layers 21 and 31 are densely formed, the gas diffusion layers 22 and 32 have a high porosity, so that gas can easily flow in. For example, the porosity of the reaction layers 21 and 31 can be 5 to 30%, and the porosity of the gas diffusion layers 22 and 32 can be 30 to 60% larger than that of the reaction layers 21 and 31. . A mesh-like current collector 4 is arranged on the surface of each electrode 2, 3.

  Irregularities are formed on the surface of each reaction layer 21, 31. The irregularities are periodically formed in a lattice shape. That is, as shown in FIG. 2, a plurality of rectangular projections 221 are arranged in a grid pattern at a predetermined interval. More specifically, as shown in FIG. 3, the mesh of the current collector 4 is configured to pass through the concave portions 222 between the convex portions 221. That is, the mesh opening (through hole diameter d1) is larger than the width d2 of the convex portion on the electrode. The wire diameter d3 of the mesh is smaller than the width d4 of the recess 222. The depth of the recess 222 in the unevenness can be set to 0.5 to 10 μm, for example.

  Subsequently, materials constituting the fuel cell 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 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. As described above, since each electrode is supported, the thickness is preferably, for example, 100 to 1000 μm.

  The fuel electrode 2 and the air 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.

  As the fuel electrode 2, for example, a mixture of a metal catalyst and a ceramic powder material made of an oxide ion conductor can be used. As the metal catalyst used at this time, a material that is stable in a reducing atmosphere, such as nickel, iron, cobalt, or a noble metal (platinum, ruthenium, palladium, etc.) and has hydrogen oxidation activity can be used. In addition, as the oxide ion conductor, one having a fluorite structure or a perovskite structure can be preferably used. Examples of those having a fluorite structure include ceria-based oxides doped with samarium, gadolinium, and the like, and zirconia-based oxides containing scandium and yttrium. In addition, examples of those having a perovskite structure include lanthanum galide oxides doped with strontium and magnesium. Among the above materials, it is preferable to form the fuel electrode with a mixture of an oxide ion conductor and nickel. The mixed form of the ceramic material made of the oxide ion conductor and nickel may be a physical mixed form, or may be a powder modification to nickel or a nickel modification to ceramic material. Good. Moreover, the ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types. The fuel electrode 2 can also be configured using a metal catalyst alone.

As the ceramic powder material forming the air electrode 3, 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 current collector 4 is made of a conductive metal material such as Pt, Au, Ag, Ni, Cu, or a stainless steel material, or La (Cr, Mg) O ₃ , (La, Ca) CrO ₃ , (La, Sr) CrO. It can be formed of a lanthanum chromite-based conductive metal oxide material such as _3, and one of these may be used alone or a mixture of two or more may be used. .
When a mesh is used as the current collector 4, the mesh size is preferably # 10 to # 500, for example. The size of the mesh is the number of meshes per inch (2.54 cm), and the wire diameter is preferably 10 to 2000 μm and the aperture is 10 to 15000 μm.

  The fuel electrode 2 and the air electrode 3 can be formed by, for example, a wet coating method. Examples of the wet coating method include a screen printing method, an electrophoresis (EPD) method, a doctor blade method, a spray coating method, an ink jet method, a spin coating method, and a dip coating method. At this time, the fuel electrode and the air electrode need to be made into a paste, and 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.

  As described above, the fuel electrode 2 and the air electrode 3 are composed of the reaction layers 21 and 31 and the gas diffusion layers 22 and 32, but the materials constituting each are the same. There are various methods for increasing the porosity, which is a difference. For example, the powder particle size of the material can be increased, or the binder content can be increased. Moreover, the thickness of the reaction layers 21 and 31 is preferably 0.1 to 20 μm, and more preferably 1 to 10 μm. On the other hand, the gas diffusion layers 22 and 32 are preferably 5 to 50 μm, and more preferably 10 to 30 μm.

  Next, an example of a manufacturing method of the solid oxide fuel cell configured as described above will be described with reference to the drawings. FIG. 4 is an explanatory diagram showing a method for manufacturing a solid oxide fuel cell according to this embodiment. Here, a method for forming electrodes by screen printing will be described.

  First, as shown in FIG. 4 (a), the above electrolyte powder material is press-molded, and a plate-shaped electrolyte substrate is prepared by sintering under known conditions, and a fuel electrode paste is applied to the upper surface thereof, The reaction layer 21 of the fuel electrode 2 is formed by drying and sintering for a predetermined time. The particle size of the ceramic material powder in the fuel electrode paste used here may be, for example, 0.01 to 1.0 μm. Subsequently, in order to form the gas diffusion layer 22, the fuel electrode paste is applied to the upper surface of the reaction layer 21 and dried for a predetermined time. The particle size of the ceramic material powder in the fuel electrode paste used here may be, for example, 1.0 to 100 μm. Subsequently, as shown in FIG. 4B, a transfer member 8 having a mesh of a predetermined size is prepared, and the transfer member 8 is pressed onto the fuel electrode paste with a predetermined pressure. As a result, periodic irregularities are formed in a lattice pattern on the upper surface of the fuel electrode paste, as shown in FIG. Then, if this fuel electrode paste is sintered for a predetermined time, the gas diffusion layer 22 having irregularities formed on the surface is formed. Similarly, the air electrode paste is also applied to the lower surface of the electrolyte 1, and dried and sintered at a predetermined temperature for a predetermined time to form the reaction layer 31, and then the air electrode paste is further applied and dried. Then, similarly to the fuel electrode 2, the transfer member 8 is pressed to form irregularities and then sintered to form the gas diffusion layer 32. Finally, if a mesh-like current collector is disposed on the surfaces of the fuel electrode 2 and the air electrode 3, the fuel cell shown in FIGS. 1 and 2 is completed. When forming the reaction layer 21 and the gas diffusion layer 22, as described above, the reaction layer 21 may be sintered to form the reaction layer completely, and then the gas diffusion layer paste may be applied. After the layer paste is dried, the gas diffusion layer paste can be applied.

  The fuel cell configured as described above generates power as follows. First, a fuel gas made of hydrogen or a hydrocarbon such as methane or ethane is supplied to the fuel electrode 2. At the same time, an oxidant gas such as air is supplied to the air electrode 3. Since the electrolyte 1 is dense, no gas flows between the upper and lower surfaces of the electrolyte 1. Thus, since the fuel electrode 2 and the air electrode 3 are in contact with the fuel gas and the oxidant gas, respectively, oxygen ion conduction through the electrolyte 1 occurs between the fuel electrode 2 and the air electrode 3, and power generation is performed. It can also be used as a single-chamber solid oxide fuel cell that generates power in a mixed gas of fuel gas and oxidant gas. Even in this case, the electrodes 2 and 3 selectively react with the fuel gas or the oxidant gas, so that power generation can be performed.

  As described above, according to the present embodiment, since the unevenness is formed on the surface of each electrode 2, 3, by engaging this unevenness with the through hole of the mesh of the current collector 4, The contact area between 3 and the current collector 4 increases, and the reaction resistance can be reduced. Thereby, the power generation performance of the battery can be improved. In particular, the electrodes 2 and 3 of the present embodiment are composed of reaction layers 21 and 31 and gas diffusion layers 22 and 32, and the gas diffusion layers 22 and 32 have a high porosity. It is considered that the contact area of the gas diffusion layer decreases and the contact resistance increases. As described above, the diffusivity of the supplied gas is maintained by forming irregularities on the surfaces of the gas diffusion layers 22 and 32. However, the power generation performance of the battery can be further improved by increasing the contact area with the mesh current collector 4 and decreasing the contact resistance.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention. For example, in the above embodiment, the concavo-convex structure composed of the convex portions arranged in a grid pattern is formed on the surfaces of the electrodes 2 and 3, but the concavo-convex structure is not limited to this, and various modes are available. Is possible. That is, as long as the uneven structure formed on the current collector 4 and at least a part of the uneven structure on the electrode surface can be engaged to improve adhesion, the protrusions do not necessarily have to be arranged in a lattice pattern. Therefore, for example, a structure in which unevenness is randomly arranged may be used.

  In addition, the current collector to be used may be made of a fibrous body such as metal wool other than the mesh structure. In short, it is only necessary that the surface is not flat and irregularities are formed. In the case of metal wool, since fine fibers enter the concave portions of the concave-convex structure on the electrode surface, adhesion is improved.

Next, examples of the present invention will be described. In addition, this invention is not limited to this Example.
(Example)
First, a GDC (Ce: Gd: O = 0.9: 0.1: 1.9) electrolyte substrate having a thickness of 500 μm was prepared by the above manufacturing method. Subsequently, the fuel electrode was prepared as follows. First, SDC (Ce: Sm: O = 0.8: 0.2: 1.9) powder (average particle size 0.5 μm) and NiO (average particle size 0.8 μm) are set to 7: 3 as a reaction layer. Then, a solvent was added to the powder and the cellulose-based binder resin so that the mass ratio was 80:20 to prepare a fuel electrode reaction layer paste. Further, as the gas diffusion layer, SDC (Ce: Sm: O = 0.8: 0.2: 1.9) powder (average particle size 4 μm) and NiO (average particle size 4 μm) are set to 7: 3. The powder and cellulose binder resin were mixed and a solvent was added so that the mass ratio was 80:20 to prepare a fuel electrode gas diffusion layer paste. Thereafter, the reaction layer paste was printed on the electrolyte substrate by screen printing and dried at 130 ° C. for 15 minutes to form a reaction layer green sheet. Following this, the gas diffusion layer paste was printed on the reaction layer green sheet by screen printing and dried at 130 ° C. for 15 minutes. Thereafter, a screen mesh of # 150 mesh (aperture 0.104 mm) was pressed on the gas diffusion layer to form irregularities, and then sintered at 1450 ° C. for 1 hour to form a reaction layer having a thickness of 10 μm and the surface. A 20 μm thick gas diffusion layer having irregularities was formed.

  Subsequently, an air electrode was formed as follows. First, a reaction layer paste and a gas diffusion layer paste were prepared. As a reaction layer, LSCF (La: Sr: Co: Fe: O = 0.6: 0.4: 0.2: 0.8: 3) (average particle size 0.5 μm) was added to ethyl carbitol, A solvent was added to the powder and the cellulose-based binder resin so that the mass ratio was 80:20 to prepare a reaction layer paste.

  Subsequently, LSCF (La: Sr: Co: Fe: O = 0.6: 0.4: 0.2: 0.8: 3) (average particle diameter of 3 μm) was added to ethyl carbitol as a gas diffusion layer. A gas diffusion layer paste was prepared by adding a solvent to the powder and the cellulose-based binder resin so that the mass ratio was 80:20.

Next, the reaction layer paste was printed on the surface of the electrolyte substrate opposite to the fuel electrode by screen printing. Thereafter, these were dried in an oven at 130 ° C. for 15 minutes to form a reaction layer reaction layer green sheet. Next, the gas diffusion layer paste was screen-printed on the reaction layer green sheet and dried at 130 ° C. for 15 minutes. Subsequently, a screen mesh of # 150 mesh (aperture 0.104 mm) was pressed onto the gas diffusion layer, and then sintered at 1200 ° C. for 1 hour to obtain a reaction layer having a thickness of 10 μm and a thickness having irregularities on the surface. A gas diffusion layer having a thickness of 20 μm was formed. Thereafter, a # 100 mesh (opening 0.144 mm) current collector was disposed on each gas diffusion layer of the fuel electrode and the air electrode. This current collector is made of platinum.
(Comparative Example 1)
As Comparative Example 1, a solid oxide fuel cell having no gas diffusion layer in Example 1 was prepared.
(Comparative Example 2)
As Comparative Example 2, a solid oxide fuel cell in which unevenness was not formed on the surface of the gas diffusion layer in Example 1 was prepared. That is, after printing the gas diffusion layer paste, drying and sintering were performed under the above-described conditions, and no irregularities were formed by the mesh.
(Evaluation test)
The battery performance of the above-described Examples and Comparative Examples was evaluated by the following method. At an operating temperature of 600 ° C., hydrogen is supplied from the fuel electrode side at 30 ml / min (3% H ₂ O), and air is supplied from the air electrode side at 60 ml / min (3% H ₂ O). The power density (PPD) was measured. As a result, in the embodiment, a PPD = 135 mW / cm ^2, in Comparative Example 1, a PPD = 103mW / cm ^2, in Comparative Example 2 was PPD = 120mW / cm ^2. From this result, it can be seen that the output density of the battery provided with the gas diffusion layer is high, and the output density of the battery provided with unevenness is high.

1 is a front sectional view showing an embodiment of a solid oxide fuel cell according to the present invention. It is a top view of FIG. FIG. 3 is an enlarged view of FIG. 2. It is a figure which shows the manufacturing method of the solid oxide fuel cell of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte 2 Fuel electrode 21 Reaction layer 22 Gas diffusion layer 3 Air electrode 31 Reaction layer 32 Gas diffusion layer 4 Current collector

Claims (4)

A solid oxide fuel cell to which a current collector having irregularities on its surface is attached,
Electrolyte,
A fuel electrode disposed on one side of the electrolyte;
An air electrode disposed on the other surface of the electrolyte,
A current collector can be attached to at least one of the fuel electrode and the air electrode,
At least a part of the surface of the electrode to which the current collector is attached is provided with irregularities that can be engaged with the irregularities of the current collector ,
Of the fuel electrode and the air electrode, at least an electrode to which a current collector is attached is
A porous reaction layer in contact with the electrolyte;
A gas diffusion layer formed on the reaction layer and having a higher porosity than the reaction layer, and
A solid oxide fuel cell , wherein the irregularities are formed on a surface of the gas diffusion layer .   The solid oxide fuel according to claim 1, wherein the porosity of the reaction layer is in the range of 5 to 30%, and the porosity of the gas diffusion layer is in the range of 30 to 60%. battery. The unevenness formed on the electrode is formed in a lattice shape, and the unevenness is formed with a width smaller than the mesh opening of the current collector formed in a mesh shape. Or a solid oxide fuel cell according to 2; The unevenness formed in the electrode is formed in a lattice shape, and the recesses in the unevenness are formed with a width larger than the wire diameter of the mesh of the current collector formed in a mesh shape. 4. The solid oxide fuel cell according to any one of 3 .

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