JPH076776A - Stack of solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To improve the power generating efficiency of a stack of a solid electrolyte fuel cell, and to reduce the consumption of fuel, and to improve the output density. CONSTITUTION:A hollow base plate 11 with bottom, which is made of the first electrode material and which has an opening only at one end thereof and which is formed with a flow passage, in which the gas to be used as a first electrode is U-turned and passed, inside thereof, and a second electrode, which is formed of a solid electrolyte layer and the second electrode material different from the first electrode material, are layered to form a cell. Plural cells are layered through each porous conductor 18 having elasticity to form a stack of a solid electrolyte fuel cell. The stack of a solid electrolyte fuel cell is formed with a partitioning plate for preventing the mixture of the gas as the gas to be used for the first electrode, which is forcedly passed along the flow passage inside of the hollow base plate and led into the flow passage inside of the hollow base plate, and the gas discharged from the flow passage inside of the hollow base plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stack structure of a solid oxide fuel cell.

[0002]

2. Description of the Related Art Solid oxide fuel cells (SOFC) are
A single cell including an electrode and a solid electrolyte is a fuel cell composed of a ceramic material, and zirconia (YSZ) whose crystal structure is stabilized by adding yttria is used as an electrolyte. This material has high oxygen ion conductivity, but its temperature dependence shows that the conductivity is low at low temperatures, and 900 to 1
By setting the temperature to 000 ° C., the sufficient electric conductivity required for constructing the fuel cell can be obtained. Therefore, the operating temperature of the SOFC is set to a high temperature of 900 to 1000 ° C. However, the conductivity of the above YSZ electrolyte is at most 0.1 S / c even at 1000 ° C.
Since it is about m, it is necessary to reduce the thickness of YSZ when forming a single cell. In the conventional SOFC, for example, as shown in FIG. 5A, a study has been made on a flat plate type single cell in which two electrodes, an air electrode 3 and a fuel electrode 2, are formed on the surface of a solid electrolyte layer 1 made of YSZ. It has been advanced. But,
As in this system, YSZ needs a sufficient mechanical strength to serve as a support for electrodes, but yttria-added 8 mol% yttria, which has a high conductivity among YSZ-added yttria, is added. YSZ has a drawback that mechanical strength is weak. Therefore, it becomes necessary to increase the thickness of the support made of YSZ. When the thickness of YSZ is increased, a voltage drop due to iR loss in the solid electrolyte portion occurs even though a highly conductive material is used. There has been a problem that the power generation characteristics are increased and a sufficiently satisfactory power generation characteristic cannot be obtained. Therefore, in order to compensate for the lack of mechanical strength of the flat plate type single cell,
A method called a cylindrical type as shown in (b) is under study. As shown in the figure, as shown in the figure, a porous body made of inert calcia-stabilized zirconia or the like is used as a support body 10, on which a fuel electrode 2, a solid electrolyte layer 1, an air electrode 3, and an interconnector 4 are formed in order of materials. The units are stacked to form a unit power generation cell. In this SOFC, power generation is performed by flowing a fuel gas and an oxidant gas to the outside and the inside of the power generation cell. With a single cell having such a structure, the solid electrolyte layer is no longer functioning as a support for the single cell, and as long as it is a dense membrane, it can be made as thin as possible. It is possible to dramatically improve the performance. However, the SOFC is not used with only one single cell, and the single cells are connected in series and, if necessary, in parallel to form a power generation stack having a predetermined output. For example, in order to connect a large number of cells of this system to obtain a predetermined output, a single cell is normally electrically connected by an interconnector 4 and a metal felt 7 as shown in FIG. 5 (c). Used vertically stacked.

[0003]

However, the above-mentioned FIG.
In the case of the conventional cylindrical power generation cell as shown in (c), (1) the generated current flows along the electrode surface as shown by the arrow, so that the current path becomes long and the internal resistance of the entire unit cell is increased. Grows larger. Further, (1) it is necessary to increase the length of the support in order to increase the output in the cylindrical structure, but there is a limit to the length and the thinness of the pipe diameter due to manufacturing restrictions. Further, (3) a space is formed inside and outside the cylindrical tube, which becomes a dead volume, and the output density is limited. There was such a problem.

The present invention uses a single cell having a structure in which a power generation section is formed on one side surface of a bottomed hollow substrate having an opening only at one end, which is made of an electrode material.
It also specifically shows the method of combining the single cells, and the purpose thereof is to completely separate the oxidant gas and the fuel gas and reduce the number of gas seal portions of each single cell. It is possible to prevent mixing of the two gases and to reuse the gases. Furthermore, in order to prevent the transverse flow phenomenon of the generated current in the conventional cylindrical power generation cell and reduce the electric resistance as a whole, a hollow substrate partially provided with pillars is used and electrodes are formed on it. It is to provide a stack structure of a solid oxide fuel cell as a single cell.

[0005]

In order to achieve the above-mentioned object, the present invention is made of a first electrode material, has an opening only at one end, and is a gas used for the first electrode inside. On the surface of a bottomed hollow substrate having a flow path through which a U-turn passes, a solid electrolyte layer and a second electrode made of a second electrode material different from the first electrode material are provided. In a stack of solid oxide fuel cells, wherein a plurality of single cells formed by stacking are stacked via an elastic porous conductor to form a power generation stack, the fuel cell stack has a first electrode as a first electrode. The gas used flows along the flow path in the hollow substrate, and the gas introduced into the flow path in the hollow substrate and the gas discharged through the flow path are not mixed with each other. A partition plate for isolation is provided. As described above, the single cell that constitutes the stack of the conventional solid oxide fuel cell has only two types, that is, the flat plate type and the cylindrical type, and as in the present invention, has an opening only at one end and has a first internal portion. A power generation stack having a structure in which a single cell is a bottomed hollow substrate having a flow path through which a gas used for the first electrode makes a U-turn and passes through has not been proposed in the prior art. The configuration of the single cell in the SOFC of the present invention is
An open portion is formed only at one end, and a bottomed hollow flat plate substrate in which a gas passage is formed by partially joining upper and lower thin plates by a pillar portion is produced, and on one surface of this hollow substrate, A solid electrolyte layer and another electrode layer are formed to form a single cell. Then, a combination of such single cells constitutes a power generation stack that can obtain a predetermined output, but when assembling the power generation stack, a partition plate forces gas to flow in the substrate, and Metallic felt with high elasticity is placed between the unit cells. By using such a hollow substrate, the strength of the single cell is ensured, and the current generated by the power generation reaction flows in the thickness direction of the substrate through the supporting columns,
The voltage drop of the current flowing along the surface of the support, which has occurred in the conventional cylindrical single cell, is also prevented, and excellent power generation performance of the single cell can be obtained. Further, since the separation of each gas is surely performed by the single cell, the thick interconnector plate as seen in the conventional flat plate type is not necessary between the single cells, which has occurred in the conventional flat plate type. It is possible to obtain a high-performance power generation stack in which no voltage drop occurs in the interconnector section. Since each unit cell having the above-mentioned excellent power generation performance is electrically connected by the metal felt having sufficient conductivity, the voltage drop due to the electric resistance of the interconnector plate and the surface of the support body are caused. It is possible to realize an SOFC stack having a single cell as it is, which has an excellent power generation performance as compared with the conventional method, without the voltage drop of the flowing current. Specifically, it is possible to obtain excellent effects such as improvement of power generation efficiency, reduction of fuel consumption and output density, and reduction of required volume due to this, and it is possible to exert enormous effects in industry. it can.

[0006]

Embodiments of the present invention will be described below in more detail with reference to the drawings. 1A and 1B show an example of a single cell manufactured in this example. In addition, FIG.
It is an AA arrow line view of Drawing 1 (a). The unit cell has a solid electrolyte layer 1 and a second electrode different from the above-mentioned first electrode material on one surface of a bottomed hollow substrate 11 having an opening only at one end made of the first electrode material. A fuel electrode 2 made of an electrode material is formed by stacking, and an interconnector 4 for electrically connecting the unit cells is formed on the opposite surface of the hollow substrate 11. In the remaining portion, a gas impermeable layer 9 is formed to prevent gas permeation. The hollow substrate 11
Between the upper and lower thin plates, pillars 12 for reinforcing the hollow substrate 11 and securing an electric current are formed. As an example of producing a single cell used in this example, a single cell using an air electrode material for the hollow substrate 11 will be taken as an example and described below. As an air electrode material, a (La _1-X Sr _X ) _Y MnO ₃ (0 ≦ X ≦) having a perovskite structure that is generally widely used is used.
0.6, 0 ≦ Y ≦ 0.2), and the composition is La _0.8 S
r _0.2 MnO ₃ and La _0.9 Sr _0.1 MnO ₃ are selected,
Raw material powder having an average particle diameter of 1 to 3 μm was used. And
The bottomed hollow substrate 11 having an opening only at one end was produced by a method in which sheet-shaped ceramics were thermocompression bonded and then sintered. The ceramic sheet was prepared by the doctor blade method, and the slurry required for this was prepared in the following mixing ratio. Raw material powder 100 parts by weight Binder 10 to 15 parts by weight Plasticizer 5 to 10 parts by weight Solvent 200 parts by weight As a binder, polyvinyl butyral, as a plasticizer,
Butyl phthalate was used and isobutyl alcohol as the solvent. The amount of binder and plasticizer varies depending on the particle size of the raw material powder, and the surface area also changes.Therefore, with the same amount of use, the properties of the slurry will differ. used. In addition to the above, a small amount of a dispersant and an antifoaming agent was added depending on the properties of the slurry. Such a mixture was mixed and stirred by a ball mill for about 24 to 48 hours, degassed under reduced pressure to remove the solvent and adjust the viscosity, and thereafter, a sheet molded body was produced by a doctor blade device. Next, in order to obtain a bottomed hollow substrate 11 having an opening only at one end and a column portion from this sheet molded body, a sheet of a predetermined size is cut out, heated and pressed, and hollowed. A sheet-shaped fused body was produced. FIG. 2 shows a method for producing the fused sheet. That is, the sheet-fused body was produced by thermocompression-bonding a sheet to be the pillar portion 12 and a U-shaped sheet 27 for closing the peripheral portion between the upper and lower flat sheet sheets 26. The heating / pressurizing conditions at this time need to be changed depending on the softness of the sheet, but generally 70 to 80 ° C., 30 to 70 kg /
It was performed under the condition of cm ² . The hollow substrate 11 can have any shape by selecting the shape, size, and thickness of the sheets to be stacked on each layer. Further, at this time, it is necessary to consider the shrinkage rate of the sheet molded body at the time of sintering, and the fused body was produced in consideration of the shrinkage rate of the air electrode material of 15 to 20%. Next, the produced hollow substrate 11 is degreased at about 400 ° C., and then 1200 to 1400.
It heated at ℃ and obtained the sintered compact. The manufactured hollow substrate 11 had a width and depth of 100 × 150 mm and a thickness of about 5 mm. Since the progress of sintering is affected by the particle size of the raw material powder used and the amount of the binder or plasticizer added, the temperature and time were appropriately selected according to the raw material used.
For example, since a raw material having a small particle size has a large surface area and begins to sinter in a low temperature region, firing conditions were set to a low temperature for a short time (specifically, for example, heating at 1250 ° C. for 2 hours). As described above, by appropriately selecting the firing conditions according to the addition amount of the raw material powder, the binder, etc. and firing, a sintered body having a porosity of about 30% can be obtained even if the raw material powder is changed. . The conductivity of the prepared air electrode is about 100 S / cm (10
Was 00 ° C). Next, thin films of the solid electrolyte layer 1 and the fuel electrode 2 were formed on one surface of the manufactured hollow substrate 11. In this example, the plasma spraying method was used. The thermal spraying machine used was an atmospheric thermal spraying method, and 8 mol-stabilized YSZ (particle size: 10 to 50 μm) was used as the solid electrolyte material. The thickness of the prepared electrolyte is about 150 μm,
Gas permeability 1 to 5 × 10 ~ ⁶ [cc · cm / sec ·
(G / cm ² ) cm ² ]. As the fuel electrode, nickel oxide powder (particle size: 10 to 50 μm) and 8
Molar stabilized YSZ was used. Since the fuel electrode is preferably a porous body, the film formation could be performed more easily than in the case of the solid electrolyte. The film having a thickness of about 200 to 300 μm has a gas permeability of 10 to ⁴ [cc · cm / sec ·
(G / cm ² ) cm ² ], and a suitable electrode was obtained. The interconnector 4 and the gas impermeable layer 9 were also produced by the thermal spraying method, and were made of Ni-A.
l ₂ O ₃ , LaCrO ₃ , and Al ₂ O ₃ were used. In this example, a power generation stack was constructed by electrically connecting using the hollow substrate 11 on which each layer such as the solid electrolyte layer 1 and the interconnector 4 was formed as described above. FIG. 3 shows an example of the structure of the power generation stack manufactured in this example. Figure 3
FIG. 4 shows a cross-sectional structure seen from the side surface, and FIG.
-A cross section is shown. Note that the BB cross section in FIG. 4 corresponds to FIG. 3. In this embodiment, a fixing plate 14 for fixing a substrate is provided in the container 13, and each hollow substrate 11 is
The position is fixed by the fixing groove 15 provided in the fixing plate 14 and the groove 16 provided in the ceiling portion of the container 13, and in the fixing groove 15, a seal containing a glass material as a main component is used for gas sealing. The material 17 is filled. Then, a porous conductor 18 for electrically connecting the hollow substrates is arranged between the hollow substrates. As the porous conductor 18, a highly elastic material such as a metal such as Ni processed into a felt was used. The structure of the hollow substrate 11 has an opening on only one surface, as shown in FIGS. 1 (a) and 1 (b). When stacking, the partition plate 25 is provided under the hollow substrate 11 so that the gas flowing inside the hollow substrate 11 is forced to flow inside the substrate.
Was placed to assemble the power generation stack. This state is shown in FIG. That is, the oxidant gas such as air introduced from the oxidant gas inlet 19 flows into the hollow substrate 11 and makes a U-turn back inside the hollow substrate 11, and then from the oxidant gas outlet 20. It is discharged to the outside of the container 13. In order to generate electricity with the stack of the present invention,
It suffices to install the stack under a temperature condition of about 1000 ° C. and supply the oxidant gas and the fuel gas. At this time, as described above, the oxidant gas is supplied from the oxidant gas introduction port 19, reaches the inside of each hollow substrate 11 to perform the power generation reaction, and then the residual gas is discharged from the oxidant gas discharge port 20. Exhausted to the outside. On the other hand, the fuel gas is supplied from the fuel gas inlet 21, causes a power generation reaction on the substrate surface, and is then discharged to the outside. Regarding the fuel gas inlet 21,
From the viewpoint of improving the contact between the gas and the fuel electrode, there is no particular problem at a position where the gas flow is in the thickness direction of the hollow substrate 11. Further, the oxidant gas inlet 19 and the oxidant gas outlet 20 may be attached at the positions shown in FIG. At this time, since only the porous conductors 18 that do not hinder the diffusion of the fuel gas to the electrode surface are arranged between the hollow substrates 11, the fuel on the surface of each hollow substrate 11 is not disposed. Gas supply will be performed without any problems. In addition, in this embodiment, since the hollow substrate 11 having the hollow structure having the column portion 12 in the middle portion is used, the voltage drop caused when the generated current flows like the conventional cylindrical single cell is generated. The amount of electric power generated by power generation is extremely small and can be extracted from the single cell with low loss. Since each unit cell is electrically contacted by the porous conductor 18, it can be taken out to the outside without loss of generated power.

[0007]

As described above in detail, the S of the present invention
In OFC, a bottomed hollow substrate having an opening only at one end made of a first electrode material, and upper and lower thin plates partially joined by a pillar is produced, and a solid substrate is formed on one surface of the substrate. A second electrode is formed of an electrolyte layer and a second electrode material different from the first electrode material to form a single cell,
The unit cells are combined to form a power generation stack capable of obtaining a predetermined output, and the gas used for the first electrode flows along the flow path in the hollow substrate and the flow path in the hollow substrate. The partition plate is provided so as to prevent the gas introduced into the gas and the gas discharged through the flow path from being mixed with each other, and the gas is configured to forcibly flow in the hollow substrate, and Since the metallic felt having high elasticity is arranged between the unit cells, a stack having extremely high power generation performance can be realized. In addition, the use of the hollow substrate ensures the mechanical strength of the unit cell, and the current generated by the power generation reaction flows through the support column in the thickness direction of the substrate, so that the surface of the support in the conventional cylindrical unit cell is Excellent single-cell performance can be obtained without causing a voltage drop of the current flowing along. Furthermore, the separation of each gas is ensured by the single cell, and the thick interconnector plate seen in the conventional flat plate type is not necessary between the single cells, and the interface generated in the conventional flat plate type single cell is not necessary. A stack with no voltage drop at the connector can be obtained. Furthermore, since each cell with excellent power generation performance is electrically connected by the metal felt having sufficient conductivity, the voltage drop due to the electrical resistance of the interconnector plate and the flow along the support surface It is possible to realize an SOFC stack in which there is no voltage drop of current and single cell performance with excellent power generation performance is directly obtained as compared with the conventional method. Specifically, there are excellent effects such as improvement in power generation efficiency, reduction in fuel consumption, improvement in output density, and reduction in required volume due to this, and a great industrial effect is obtained.

[Brief description of drawings]

FIG. 1 is an external view (a) of a single cell produced in an example of the present invention and a schematic view (b) showing a cross-sectional structure taken along line AA of FIG. 1 (a).

FIG. 2 is a schematic diagram showing the configuration of a hollow substrate used in a single cell produced in an example of the present invention.

FIG. 3 is a schematic diagram showing an example of the structure of a stack of a solid oxide fuel cell produced in an example of the present invention.

4 is a sectional view taken along line AA of FIG.

FIG. 5 is an exploded view (a) showing a configuration of a single cell of a conventional flat plate fuel cell, a schematic diagram (b) showing a structure of a single cell of a conventional cylindrical fuel cell, and a single cell of a conventional cylindrical fuel cell. Schematic diagram (c) showing the configuration of a power generation stack using.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte layer 2 ... Fuel electrode 3 ... Air electrode 4 ... Interconnector 5 ... Fuel gas flow path 6 ... Oxidant gas flow path 7 ... Metal felt 8 ... Current collector 9 ... Gas impermeable layer 10 ... Support Body 11 ... Hollow substrate 12 ... Strut portion 13 ... Container 14 ... Fixing plate 15 ... Fixing groove 16 ... Groove 17 ... Sealing material 18 ... Porous conductor 19 ... Oxidizing gas introduction port 20 ... Oxidizing gas discharge port 21 ... Fuel gas inlet 22 ... Fuel gas outlet 23 ... Terminal plate 24 ... Conductive wire 25 ... Partition plate 26 ... Flat sheet 27 ... U-shaped sheet

Claims (1)

[Claims] 1. A bottomed hollow, which is made of a first electrode material, has an opening only at one end, and has therein a flow path through which a gas used for the first electrode makes a U-turn and passes. An elastic porous conductor having a unit cell formed by laminating a solid electrolyte layer and a second electrode made of a second electrode material different from the first electrode material on the surface of a substrate In the stack of the solid oxide fuel cell in which a plurality of cells are superposed through the stack to form a power generation stack, in the stack of the fuel cell, the gas used for the first electrode is distributed along the flow path in the hollow substrate. A solid characterized in that a partition plate is provided so as to separate the gas that flows and is introduced into the channel in the hollow substrate from the gas discharged through the channel. Electrolyte fuel cell stack.