JP2005129281A - Solid electrolyte fuel battery cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that as for a conventional solid electrolyte battery cell, because the contacted part of an air electrode layer and a current collector is dotted, an effective contacted area is small and the contact electrical resistance of the air electrode layer and the current collector cannot be reduced sufficiently. <P>SOLUTION: As for the solid electrolyte type fuel battery cell C1 formed with a solid electrolyte layer 1, a fuel electrode layer 2 which is a first electrode layer formed on one face of the solid electrolyte layer 1, and the air electrode layer 3 which is a second electrode layer formed on the other face of the solid electrolyte layer 1, the current collector 4 is formed at least at one of the fuel electrolyte layer 2 and the air electrode layer 3 and by joining the electrode layer and the current collector 4, the contact electrical resistance on that joining interface is reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a solid oxide fuel cell that uses a solid electrolyte and obtains electric energy by an electrochemical reaction, and in particular, reduces the contact electrical resistance between the current collector and the electrode layer used to extract current from the electrode layer. The present invention relates to a solid oxide fuel cell.

  A solid oxide fuel cell is composed of a solid electrolyte layer having ionic conductivity such as oxygen ions or protons, an air electrode layer formed on one surface of the solid electrolyte layer, and a porous material. And a fuel electrode layer provided on the other surface of the solid electrolyte layer, a fuel cell formed of the solid electrolyte layer, the air electrode layer, and the fuel electrode layer, and the fuel cell and the separator are alternately stacked. It constitutes a fuel cell stack.

  The separator separates the oxidizing gas and the fuel gas, but may also serve as an interconnector that electrically connects the air electrode layer and the fuel electrode layer to connect the fuel battery cells in series. A current collector for taking out current from each electrode layer is disposed between the air electrode layer and the fuel electrode layer. The solid oxide fuel cell supplies an oxidizing gas containing oxygen to the air electrode layer side and a fuel gas (reducing gas) containing hydrogen or hydrocarbons to the fuel electrode layer side. An electromotive force is generated by the electrochemical reaction of the gas through the solid electrolyte layer.

  The above solid oxide fuel cell has been put into practical use as a power source for homes and automobiles, for example, but particularly when used as a power source for automobiles, the volume that can be mounted is limited. Miniaturization is required with high output. In order to meet such demands, it is important not only to pursue means for improving the output performance itself, but also to eliminate factors that cause a decrease in output performance.

  Here, as a factor affecting the output performance of the fuel cell, the internal electrical resistance of the fuel cell stack occupies a large proportion, and as one of the internal electrical resistance, a current collector for taking out current from the electrode layer Contact electric resistance between the electrode layer and the electrode layer. That is, if the contact electrical resistance in the fuel cell is high, the internal electrical resistance of the fuel cell stack is increased, and as a result, the output performance of the fuel cell is lowered. For this reason, in order to improve the output performance of the fuel cell, it is necessary to reduce the contact electric resistance between the current collector and the electrode layer in the fuel cell.

In contrast, conventionally, as shown in FIG. 8, the fuel cell 100 is configured by sandwiching the solid electrolyte layer 101 between the air electrode layer 102 and the fuel electrode layer 103, and the air electrode layer 102 and the fuel electrode layer 103 are formed. Current collectors 104 and 105 are arranged on the outside of each of them, and at least a contact surface with the current collector 104 in the air electrode layer 102 is scattered with metal powder 106 having non-oxidizing properties in the operating atmosphere of the fuel cell. Adhesion increases the exchange current density at the contact interface between the air electrode layer 102 and the current collector 104, reduces the contact electrical resistance at the interface, and improves the output performance.
JP 2003-7318 A

  However, in the conventional solid oxide fuel cell as described above, since the contact portions between the air electrode layer and the current collector are scattered, the effective contact area of both is small, and the air electrode layer and the current collector are scattered. There is a problem that the contact electrical resistance with the electric body cannot be sufficiently reduced to the extent that the output performance is not affected, and it has been a problem to solve such a problem.

  The solid electrolyte fuel cell of the present invention includes a solid electrolyte layer, a first electrode layer formed on one surface of the solid electrolyte layer, and a second electrode layer formed on the other surface of the solid electrolyte layer. In the solid oxide fuel cell, the current collector is formed on at least one of the first and second electrode layers, and the electrode layer and the current collector are joined to each other. Reduce contact electrical resistance at the interface.

  The fuel cell stack of the present invention has a structure in which the solid oxide fuel cell and the separator for separating the fuel gas and the oxidizing gas are alternately stacked, and the contact electric resistance between the electrode layer and the current collector. By adopting the fuel battery cell with reduced, the internal electrical resistance of the fuel cell stack is reduced.

  According to the solid oxide fuel cell of the present invention, a sufficient electrical connection between the electrode layer and the current collector can be secured, and the contact electrical resistance at the bonded interface can be reduced. The contact electrical resistance can be sufficiently reduced to the extent that it does not affect the output performance, thereby realizing a reduction in the internal electrical resistance of the fuel cell stack formed by stacking the fuel cells, and further The output performance of the fuel cell having the fuel cell stack as a component is improved. In addition, the fuel cell provides improved output performance by reducing the contact electrical resistance between the electrode layer and the current collector, that is, eliminating the cause of the decrease in output performance, and there are very few structural changes. Therefore, it is effective for reducing the size of the entire fuel cell, particularly when used for an automobile power source whose volume is limited.

  According to the fuel cell stack of the present invention, by using a fuel cell having a reduced contact electric resistance, the internal electric resistance can be sufficiently reduced, and the output performance of the fuel cell having the fuel cell stack as a constituent element Improvement can be realized. In addition, the fuel cell stack is designed to improve output performance by reducing internal electrical resistance, that is, eliminating the cause of lowering output performance, and the volume of the fuel cell stack is particularly limited because there are very few structural changes. When used for a power source for automobiles, it is effective for downsizing the fuel cell.

  The solid electrolyte fuel cell of the present invention includes a solid electrolyte layer, a first electrode layer formed on one surface of the solid electrolyte layer, and a second electrode layer formed on the other surface of the solid electrolyte layer. In the solid oxide fuel cell, the current collector is formed on at least one of the first and second electrode layers, and as a more preferable embodiment, An opening for exposing the electrode layer is provided. More specifically, the current collector can be patterned in a linear or lattice shape, or the current collector can be formed in a polygonal shape. .

  And the said fuel battery cell can reduce the contact electrical resistance in the joining interface by joining an electrode layer and a collector, especially when the collector is pattern-formed linearly. The current collectors can be used as gas flow paths when the fuel cell and the separator are stacked.

  In addition, when the current collector is patterned in a grid pattern or the current collector has a polygonal opening, a current path is formed by electrically connecting the current collectors in parallel to The resistance can be further reduced, especially when the current collector opening has a polygonal shape, the distance to the current collector at each opening can be made isotropic, A more uniform current collecting function can be exhibited, and the electric resistance against current extraction can be further reduced.

  Furthermore, the fuel cell stack of the present invention is a stack of the above solid oxide fuel cell and a separator that separates the fuel gas and the oxidizing gas, and as a more preferred embodiment, a linear pattern is formed. A solid oxide fuel cell having a current collector and a separator can be stacked. As a result, the fuel cell stack can reduce the internal electrical resistance, and the current collector functions as a gas flow path. Therefore, a flat separator having no gas flow path is used. Thus, the separator can be easily processed and the structure can be simplified.

  As described above, the fuel cell and the fuel cell stack of the present invention realize reduction of the contact electric resistance between the electrode layer and the current collector and the internal electric resistance of the stack, and the output performance of the fuel cell using these as constituent elements. It is possible to realize the improvement.

As a material of the solid electrolyte layer, a stabilized zirconia (ZrO ₂ ) in which a known Nd ₂ O ₃ , Sm ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O _3, Sc ₂ O ₃ or the like is dissolved, A solid oxide containing CeO ₂ , Bi ₂ O _3, LaGaO ₃ or the like as a main component can be used. As the material of the fuel electrode layer of each electrode layer, for example, Ni and solid electrolyte material cermet such as Ni—YSZ (Y ₂ O ₃ added ZrO ₂ ), or metal such as Ni or Pt should be used. Can do. On the other hand, as a material for the air electrode layer, a known solid oxide mainly composed of LaMnO ₃ , LaCoO ₃ and SmCoO ₃ , or a metal such as Ag or Pt can be used. The materials for the solid electrolyte layer, the fuel electrode layer, and the air electrode layer are not limited to the above examples.

As the material of the current collector on the fuel electrode layer side, a dense material with suppressed gas permeability and lower electric resistance is desirable. For example, the same material as the fuel electrode layer material such as cermet of Ni and solid electrolyte material is used. Can be used. Moreover, low resistance metal materials, such as Ni, Pt, and Cu, can also be used and it is not limited to these. On the other hand, the material of the current collector on the air electrode layer side is preferably a dense material with suppressed gas permeability and lower electrical resistance. For example, solid oxide mainly composed of LaMnO ₃ , LaCoO _3, SmCoO _3, etc. The same material as the air electrode layer material such as an object can be used. Further, a low-resistance and oxidation-resistant metal material such as Ag, Pt, and Au can be used, but is not limited thereto.

  As a method for forming the current collector, various film forming methods such as a vapor phase film forming method such as a vacuum deposition method and a sputtering method, and a screen printing method can be used. Moreover, the method of bonding together the current collector and the fuel battery cell created in advance can also be used, and is not limited to these.

  Further, the gas supply to the portion of each electrode layer covered with the current collector is performed by gas diffusion in the electrode layer. In consideration of the gas supply capability to this electrode layer, in order not to reduce the electrode area effective for power generation, the width of the current collector in which the linear, grid, or opening is patterned in a polygonal shape is It is desirable not to exceed about twice the thickness.

(Example 1)
A fuel cell C1 shown in FIG. 1 is provided with a fuel electrode layer 2 as a first electrode layer on one surface (the lower surface in the drawing) of the solid electrolyte layer 1, and on the other surface of the solid electrolyte layer 1. The air electrode layer 3 as the second electrode layer is provided. More specifically, the solid electrolyte layer 2 made of YSZ is formed to a thickness of about 0.01 mm on the upper surface of the Ni-YSZ fuel electrode layer 2 having a thickness of 0.5 mm. An air electrode layer 3 made of LSM (LaMnO ₃ to which Sr is added) is formed on the upper surface to a thickness of about 0.05 mm. And the collector 4 which has Ag as a main component is formed in the upper surface of the air electrode layer 3, and in this Example, the linear collector 4 is pattern-formed in parallel by the fixed space | interval.

  As a manufacturing method of the fuel electrode layer 2, there is a method in which carbon powder, NiO powder, and YSZ powder as a pore forming agent for ensuring gas permeability are mixed and fired based on a known ceramic firing method. At this time, since carbon powder is removed by combustion, the gas permeability can be controlled by the ratio of the pore-forming agent, and 5-30 mass% of carbon powder having a particle size of about 0.003-0.01 mm is added. And the fuel electrode layer 2 with which the gas permeability required for electric power generation was ensured can be obtained by carrying out temporary baking at 1100 degreeC in air | atmosphere.

  A solid electrolyte layer 1 made of YSZ is formed on the fuel electrode layer 2 produced by the above method by a known screen printing method. That is, the YSZ raw material powder is made into a paste using an organic material such as polyvinyl butyral, and this is screen-printed on the fuel electrode layer 2 and baked at 1400 ° C. for about 5 hours in the atmosphere to form the solid electrolyte layer 1. . The fuel electrode layer 2 is also fired simultaneously with the firing of the solid electrolyte layer 1. At this time, the thickness of the solid electrolyte layer 1 can be controlled by the viscosity of the paste, the pressure during printing, and the like.

  Next, similarly to the method for forming the solid electrolyte layer 1, the LSM raw material powder is made into a paste, and this is screen-printed on the solid electrolyte layer 1 and then baked, for example, in the atmosphere at 1100 ° C. for about 2 hours. Layer 3 is formed. Thereby, the fuel electrode-supported fuel cell C1 can be obtained. A linear current collector is obtained by pattern-printing Ag paste on the air electrode layer 3 of the fuel battery cell C1 produced as described above by screen printing and firing in the atmosphere at 850 ° C. for about 30 minutes. 4 is formed.

  In the fuel cell C1, the electrical junction between the air electrode layer 3 and the current collector 4 is sufficiently secured, and the contact electrical resistance at the junction interface affects the output performance. It can be sufficiently reduced to the extent not given. The fuel cell C1 is configured by alternately stacking separators (not shown) to form a fuel cell stack, thereby reducing the internal electrical resistance of the fuel cell stack and further improving the output performance of the fuel cell. In addition, since the current collector 4 that is patterned in a linear shape is employed, a space between the current collectors 4 can be used as a gas flow path, and a flat plate separator that does not have a gas flow path is employed. This can contribute to the simplification of the structure.

(Example 2)
The fuel cell C2 shown in FIG. 2 is formed in the same manner as in Example 1, after forming the fuel electrode layer 2 made of Ni-YSZ, the n solid electrolyte layer 1 made of YSZ, and the air electrode layer 3 made of LSM. The Ag current collector 4 is formed by a screen printing method, and in particular, the current collector 4 has a horizontal line portion arranged in parallel at a predetermined interval and a line having at least one vertical line portion intersecting with the horizontal line portion. The pattern is formed in a shape. By forming the current collector 4 in a pattern that crosses the current collector 4 vertically and horizontally, a current path is formed in which the current collector 4 is electrically connected in parallel, and the electrical resistance against current extraction can be further reduced. Become.

(Example 3)
The fuel cell C3 shown in FIG. 3 was formed in the same manner as in Example 1, after forming the fuel electrode layer 2 made of Ni-YSZ, the solid electrolyte layer 1 made of YSZ, and the air electrode layer 3 made of LSM. The current collector 4 made of Ag is formed by a screen printing method, and in particular, the current collector 4 is patterned in a lattice shape. By forming the current collectors 4 in a grid pattern in this way, a current path is formed in which the current collectors 4 are electrically connected in parallel. As in the second embodiment, the electrical resistance against current extraction is further reduced. It will be possible.

Example 4
After the fuel cell C4 shown in FIG. 4 is formed in the same manner as in Example 1, the fuel electrode layer 2 made of Ni-YSZ, the solid electrolyte layer 1 made of YSZ, and the air electrode layer 3 made of LSM are formed. The current collector 4 made of Ag is formed by a screen printing method, and in particular, the current collector 4 is patterned so that the opening thereof is a regular hexagon. In this way, by forming the openings of the current collector 4 in a regular hexagon pattern, the distance to the current collector 4 at each opening becomes more isotropic, and a more uniform current collecting function can be exhibited. Thus, the electrical resistance against current extraction can be further reduced.

(Example 5)
After forming the fuel electrode layer made of Ni-YSZ, the solid electrolyte layer made of YSZ, and the air electrode layer made of LSM in the same manner as in Example 1, the current collector was used as a current collector by a known tape casting method. A green sheet made of LSM similar to the layer was formed, and this green sheet was laminated and fired to form a predetermined pattern. The current collector is formed so as to form a line, a line intersecting vertically and horizontally, a lattice, and a shape in which the opening forms a regular hexagon, and other polygonal shapes, as in Examples 1 to 4. be able to. Also in this embodiment, the same effect as in the previous embodiment can be obtained.

(Example 6)
The fuel cell C5 shown in FIG. 5 has a fuel electrode made of Ni-SDC (Sm-added CeO ₂ ) on one surface of the solid electrolyte layer 1 made of LSGM (Sr, Mg-added LaGaO ₃ ) having a thickness of 0.5 mm. The layer 2 is formed with a thickness of about 0.05 mm, and the air electrode layer 3 made of SSC (Sr-added SmCoO ₃ ) is formed with a thickness of about 0.05 mm on the other surface. A current collector 4A made of dense Ni-SDC is linearly formed on the surface of the fuel electrode layer 2, and a current collector 4B made of dense SSC is formed on the surface of the air electrode layer 3. A pattern is formed linearly.

  In this embodiment, a Ni-SDC layer is formed by screen printing on one surface of a solid electrolyte layer 1 made of LSGM manufactured using a known ceramic technology, and is fired to a thickness of about 0.05 mm. The fuel electrode layer 2 was formed. Similarly, an SSC layer was formed on the other surface of the solid electrolyte layer 1 by screen printing and baked to form an air electrode layer 3 having a thickness of about 0.05 mm.

  Further, the current collector 4A of the fuel electrode layer 2 is formed by forming a green sheet having a thickness of 0.5 mm made of Ni-SDC similar to the fuel electrode layer 2 by a tape casting method, and forming the green sheet in a predetermined pattern. Further, the green sheet is laminated and fired to form a pattern. Similarly, the current collector 4B on the air electrode layer 3 side is formed by forming a green sheet having a thickness of 0.5 mm made of SSC similar to the air electrode layer 3 by a tape casting method, and forming this into a predetermined pattern. Further, the green sheet is laminated and fired to form a pattern. In this manner, current collectors 4A and 4B were formed on both the fuel electrode layer 2 and the air electrode layer 3. Also in this embodiment, sufficient electrical joining between the current collectors 4A and 4B is obtained in both the fuel electrode layer 2 and the air electrode layer 3, and the contact electrical resistance at the joining interface is sufficiently reduced. Can do.

(Example 7)
A fuel cell stack S1 shown in FIG. 6 has fuel cells C produced in any of Examples 1 to 5 (see FIGS. 1 to 4) and separators 5 that separate fuel gas and oxidizing gas alternately. Laminated. The separator 5 is made of a heat-resistant metal such as Inconel, and a protrusion 5a that contacts the fuel electrode layer 2 of the upper fuel cell C is formed on one surface, and the lower surface on the other surface. A protrusion 5b that contacts the current collector 4 of the fuel cell C is formed, and gas flow paths 6A and 6B are formed between the upper and lower fuel electrode layers 2 and the air electrode layer 3, respectively. The uppermost and lowermost separators 5 may have protrusions only on the inside of the stack. The protrusions 5a and 5b of the separator 5 are continuous in a predetermined direction so as to form a gas flow path, and can be formed by machining, for example.

  In this embodiment, a fuel cell stack S1 having five fuel cells C is installed in an electric furnace maintained at 600 ° C., and air is supplied as an oxidizing gas and hydrogen gas is supplied as a fuel. The power generation characteristics were evaluated. In addition, as a comparative example, a conventional porous current collector was used to create a fuel cell stack composed of fuel cells not equipped with the current collector of the present invention, and the fuel cell stack S1 of this example and the comparative example were compared. The output characteristics of the fuel cell stack were compared.

As a result, at a current density of 0.2 A / cm ² , the output voltage of the fuel cell stack S1 of the example is 0.65 V per cell, while the output voltage of the fuel cell stack of the comparative example is 0.60 V per cell. The fuel cell stack S1 of the example had a higher output voltage. That is, in this embodiment, the current output density at a density 0.2 A / cm ² was increased nearly 10% from 0.12 W / cm ² to 0.13 W / cm ^2. This effect is remarkable under operating conditions with higher current density, and it was confirmed that a high-performance fuel cell stack S1 can be provided.

(Example 8)
The fuel cell stack S2 shown in FIG. 7 is obtained by alternately stacking the fuel cell C5 prepared in Example 6 (see FIG. 5) and the separator 5 that separates the fuel gas and the oxidizing gas. The separator 5 is a flat heat-resistant metal plate that does not form a gas flow path. That is, in this embodiment, the current collectors 4A and 4B patterned on both sides of the fuel cell C5 form a linear shape, and therefore the current collectors 4A and 4B form the gas flow paths 6A and 6B. It has a function. Even in this example, as a result of evaluating the power generation characteristics together with the comparative example as in the case of Example 7, it was confirmed that a high-performance fuel cell stack S2 could be provided.

It is a perspective view which shows one Example of the fuel battery cell of this invention. It is a perspective view which shows the other Example of the fuel cell of this invention. It is a perspective view which shows the further another Example of the fuel cell of this invention. It is a perspective view which shows the further another Example of the fuel cell of this invention. It is a perspective view which shows the further another Example of the fuel cell of this invention. It is sectional drawing which shows one Example of the fuel cell stack of this invention. It is sectional drawing which shows the other Example of the fuel cell stack of this invention. It is sectional drawing which shows the conventional fuel cell.

Explanation of symbols

1 Solid electrolyte layer 2 Fuel electrode layer (first electrode layer)
3 Air electrode layer (second electrode layer)
4 4A 4B Current collector 5 Separator C C1 to C5 Fuel cell S1 S2 Fuel cell stack

Claims (7)

  In a solid electrolyte fuel cell comprising: a solid electrolyte layer; a first electrode layer formed on one surface of the solid electrolyte layer; and a second electrode layer formed on the other surface of the solid electrolyte layer. A solid oxide fuel cell, wherein a current collecting layer is formed on at least one of the second electrode layer and the second electrode layer.   2. The solid oxide fuel cell according to claim 1, wherein an opening for exposing the electrode layer is provided in the current collecting layer.   The solid oxide fuel cell according to claim 2, wherein the current collecting layer is linearly patterned.   3. The solid oxide fuel cell according to claim 2, wherein the current collecting layer is patterned in a lattice pattern.   The solid oxide fuel cell according to claim 2 or 4, wherein the opening of the current collecting layer has a polygonal shape.   6. A fuel cell stack comprising the solid oxide fuel cell according to claim 2 and a separator for separating a fuel gas and an oxidizing gas.   7. The fuel cell stack according to claim 6, wherein a solid oxide fuel cell having a current collecting layer patterned in a line and a separator are stacked.

Images