JP4942064B2 - Current collector and solid oxide fuel cell stack including the same - Google Patents

Description

The present invention relates to a current collector and a solid oxide fuel cell stack including the current collector .

Conventionally, various solid oxide fuel cells (SOFC) using a solid electrolyte such as zirconia ceramics as an electrolyte have been developed. In this solid oxide fuel cell, hydrogen gas, natural gas, methanol, naphtha, coal gas containing carbon monoxide, or the like is used as a fuel gas, and usually high power generation efficiency of 50% to 60% The ratio of the amount of electric power obtained when power is generated with the same amount of fuel gas with respect to the amount), and the operating temperature is as high as about 1000 ° C., so it is necessary to use a noble metal catalyst such as platinum (Pt) In addition, since exhaust heat can be used, it is used in a combined exhaust heat power generation system with high power generation efficiency.
Generally, solid oxide fuel cells include a cylindrical type as shown in Patent Document 1 and a flat plate type as shown in Patent Document 2.
FIG. 6A is a front view of a main part showing a stack of a conventional cylindrical solid oxide fuel cell, and FIG. 6B is a perspective view of a main part showing a cell of the cylindrical solid oxide fuel cell. is there.
In FIG. 6, 60 is a cylindrical solid oxide fuel cell stack, 61 is a cell, 62 is an air electrode tube, 63 is a solid electrolyte layer, 64 is a fuel electrode layer, 65 is an interconnector layer, and 66a and 66b are nickel felts. It is. In FIG. 6, an arrow X indicates the direction of current flow.
As shown in FIG. 6 (b), a cylindrical solid oxide fuel cell 61 has a solid electrolyte layer 63 and a fuel electrode layer 64 sequentially formed on the outer surface of an air electrode tube 62 made of a porous cylinder. An interconnector layer 65 which is formed in an arc shape and extends in the longitudinal direction in contact with the outer surface of the air electrode tube 62 is formed in a portion where the arc is cut.
The solid oxide fuel cell stack 60 configured as described above is formed by connecting the cells 61 arranged in the horizontal direction in parallel by the nickel felt 66a and connecting the cells 61 connected in parallel in the vertical direction in series. Yes. The nickel felt 66b that connects the upper and lower cells 61 in series connects the interconnector layer 65 of the lower cell 61 and the fuel electrode layer 63 of the upper cell 61. When air is supplied into the air electrode tube 62 and fuel gas is supplied to the surface of the fuel electrode layer 64, a current flows in the direction indicated by the arrow X.
FIG. 7A is a perspective view of a main part showing a stack of a conventional flat plate solid oxide fuel cell, and FIG. 7B is a main view showing a current collector of a cell of the flat plate solid oxide fuel cell. FIG.
In FIG. 7, 70 is a flat solid oxide fuel cell stack, 70a is a cell, 71 is an interconnector section, 72 is a fuel flow path, 73 is an air flow path, 74 is an air electrode layer, 75 is a solid electrolyte layer, 76 is a fuel electrode layer, and 77 and 78 are current collector plates. In FIG. 7B, Y indicates the flow of air, and Z indicates the flow of fuel gas.
In the flat solid oxide fuel cell stack 70 configured as described above, a cell 70a in which an air electrode layer 74, a solid electrolyte layer 75, and a fuel electrode layer 76 are sequentially stacked is used. Further, as the interconnector portion 71, a structure in which grooves as fuel flow paths 72 and air flow paths 73 are formed on the front and back sides is used. The cell 70a and the interconnector 71 are stacked, and current collector plates 77 and 78 are provided above and below the stacked body to form the stack 70. Air is introduced into the air flow path 73 as indicated by arrow Y, and fuel gas is introduced into the fuel flow path 72 as indicated by arrow Z.

Japanese Patent Laid-Open No. 10-125346 Japanese Unexamined Patent Publication No. 7-111158

However, the above prior art has the following problems.
(1) In the cylindrical solid oxide fuel cell stack 60, since a plurality of cylindrical cells 61 are arranged in the horizontal direction and the vertical direction, it is applied to the space-saving property that a useless space is formed between the cells 61. Had problems. Further, in each cell 61, since the current flows in the circumferential direction of the fuel electrode layer 64 or the air electrode tube 62, the current path becomes longer and the internal resistance increases, so that the output becomes smaller. Therefore, there is a problem that the output density (output that can be taken out per unit volume of the stack) is small.
(2) In the solid oxide fuel cell stack 70 of the flat type, it is necessary to achieve both gas sealing and electrical connection on the upper and lower surfaces of the interconnector portion 71, which is technically difficult and gas sealing or electrical connection is required. There was a problem of lack of certainty.
(3) In both stacks of the cylindrical type and the flat plate type, a high temperature portion and a low temperature portion are generated due to a difference in concentration of hydrogen gas or the like in the fuel gas inside the stack, and an ohmic resistance and activation polarization are generated in the low temperature portion. Since the amount of power generation is reduced due to an increase in the power consumption, the power generation performance of the entire cell is reduced. Note that the difference in concentration of hydrogen gas or the like in the fuel gas occurs inside the stack in the cylindrical stack 60 when the fuel gas flows on the surface of the fuel electrode layer 64 along the axial direction of the cylinder. Since hydrogen gas is consumed and water vapor is generated by the reaction, the hydrogen gas concentration is high on the upstream side and low on the downstream side, and in the flat stack 70, the hydrogen gas concentration in the fuel gas is the same as the fuel flow. This is because it is higher on the upstream side of the path 72 and lower on the downstream side. The part where the temperature differs due to the difference in concentration of hydrogen gas, etc. is caused by the difference in concentration of hydrogen gas, etc., where the part of the electromotive force is different inside the cell. This is because when the hydrogen gas concentration is increased and the hydrogen gas concentration is low, the calorific value of the electromotive force is reduced.
(4) Further, in the flat type stack 70, the metal interconnector portion 71 is frequently used to reduce the manufacturing cost. However, the thermal expansion difference between the interconnector portion 71 and the fragile ceramic cell 70a. The cell 70a is easily damaged by the thermal stress generated during the temperature increase of the stack 70 to the operating temperature or by the temperature difference in the stack 70 during operation.

The present invention solves the above-described conventional problems, and since it does not form a useless space, it is excellent in space-saving properties and has high output density, and the gas seal and the electrical connection are performed in different places, so that the gas seal performance can be improved. An object of the present invention is to provide a solid oxide fuel cell stack excellent in safety.

In order to solve the above conventional problems, the present invention has the following configuration.
The current collector according to claim 1 of the present invention is a current collector used for electrical connection of a solid oxide fuel cell stack formed by stacking a plurality of solid oxide fuel cells, A three-layer structure of a layer, an insulating layer, and a lower conductive layer is formed in a shape having a waveform or a plurality of irregularities, and is arranged between the solid oxide fuel cells.
This configuration has the following effects.
(1) Since the current collector is formed into a waveform or a shape having a plurality of irregularities, the stress caused by the difference in thermal expansion between the current collector and the cell can be absorbed by the current collector.
(2) Since the current collector is formed in a waveform or a shape having a plurality of irregularities, an air channel or a fuel gas channel can be formed between the air electrode layer or the fuel electrode layer. Air or fuel gas can be supplied evenly over the entire surface of the electrode layer.
(3) Since the current collector has a three-layer structure of an upper conductive layer, an insulating layer, and a lower conductive layer, the air electrode layers of the upper and lower cells can be insulated, and the mass production is low at low cost.
(4) Since the current collector has a large surface area, heat transfer from the cell to the surrounding atmosphere (outside air) can be promoted, and thermal shocks during thermal cycles and load changes due to starting and stopping can be mitigated.
Here, a metal such as a heat-resistant alloy is used for the upper conductive layer and the lower conductive layer of the current collector. Moreover, ceramics etc. are used as an insulating layer. The current collector is formed into a waveform or a shape having a plurality of irregularities by bending a ceramic felt (ceramic fiber formed into a felt shape or the like) between a pair of flat metal materials and bending it with a press or the like. Alternatively, it is manufactured by bending a pair of flat plate materials, spraying ceramics on one side, and then bonding them together.
A solid oxide fuel cell stack according to claim 2 of the present invention is formed by stacking a plurality of solid oxide fuel cells via the current collector according to claim 1. A fuel electrode base comprising a porous body formed in a flat plate shape or an oval cross section, and a fuel electrode base that is formed parallel to the inside of the fuel electrode base. A plurality of gas introduction holes having a bottomed hole shape opened at one end surface of the electrode substrate, a fuel gas supply pipe made of a conductive material having a gas ejection hole on a tube wall and inserted into each of the gas introduction holes, A fibrous conductive material filled in a gap between a fuel gas supply pipe and an inner wall of the gas introduction hole, a solid electrolyte layer made of a solid oxide formed on an outer surface of the fuel electrode base, and a solid electrolyte layer Air electrode made of porous material laminated on the outer surface If, it has a configuration provided with a gas sealing portion for sealing the end faces on the opening side and the bottom side of the gas inlet hole of the fuel electrode substrate.
This configuration has the following effects.
(1) Since the stack is formed by stacking cells, a useless space is not formed, and space saving can be improved and the output density can be increased as compared with the cylindrical type.
(2) When air or oxygen is supplied to the air electrode layer in a state where the cell is heated to about 800 ° C. to 1000 ° C., oxygen obtains electrons and becomes oxide ions, and passes through the solid electrolyte layer. When fuel gas (hydrogen, carbon monoxide, or a gas containing these, etc.) is supplied to the inner wall of the gas introduction hole of the fuel electrode substrate, the hydrogen or carbon monoxide reacts with the oxide ions to become water or carbon dioxide and become an electron. And power is generated in the cell.
(3) Since it is provided with a fibrous conductive material and a fuel gas supply pipe made of a conductive material, electrons emitted from the fuel electrode substrate can be taken out through the fibrous conductive material and the fuel gas supply pipe. The exposed end portion of the exposed fuel gas supply pipe can be used as a negative electrode terminal. Moreover, a collector can be made to contact the upper surface or lower surface of an air electrode layer, and it can be set as the terminal of a positive electrode side.
(4) Since the cell is formed by laminating a solid electrolyte layer and an air electrode layer on a fuel electrode base having a flat plate shape or an oval cross section, it is useless when the cells are stacked to form a stack. The space saving performance of the stack can be improved without forming a space, and the output density per unit volume can be increased.
(5) Since the fuel gas supply pipe having the gas ejection holes formed in the pipe wall is provided, the number of fuel ejection holes, the position, and the diameter are appropriately set, so that the fuel can be evenly distributed over the entire fuel electrode base. Gas can be supplied, current density and temperature distribution can be made uniform, and thermal distortion can be prevented.
(6) Since the fibrous conductive material is filled in the gas introduction hole, the stress caused by the difference in thermal expansion between the fuel gas supply pipe and the fuel electrode base can be absorbed by the fibrous conductive material and can be made extremely small.
(7) The fuel seal can be surely prevented from leaking in the gas sealing portion, and the gas sealing of the cells is performed at the gas sealing portion, and the electrical connection between the cells is performed by the current collector. And electrical connection can be performed at different locations, the gas sealing performance can be easily improved, and the fuel gas and air are not mixed, and high reliability is obtained.

Here, as a material of the fuel electrode substrate, cermet, metal, or the like can be used. When a cermet containing a large amount of metal is used, heat transfer to the surrounding atmosphere (outside air) can be promoted, and thermal shock during a heat cycle or load change due to start / stop can be reduced. As a method of forming the fuel electrode substrate into a flat plate shape or a shape having an elliptical cross section and having a gas introduction hole, an extrusion molding method or the like is used.
As a material of the solid electrolyte layer, a solid oxide such as zirconia or lanthanum gallate is used. In particular, zirconia to which yttria or scandia is added is preferably used because of its high reliability and good conductivity of oxide ions. As the air electrode layer, for example, when zirconia is used as the solid electrolyte layer, lanthanum strontium manganite or the like is used, and it is laminated on the surface of the fuel electrode substrate by spraying or applying slurry and firing together with the solid electrolyte layer. Is done.

A solid oxide fuel cell stack according to claim 3 of the present invention is a solid oxide fuel cell formed by stacking a plurality of solid oxide fuel cells via the current collector according to claim 1. An air electrode substrate made of a porous body formed in a flat plate shape or an oval cross section, and the fuel electrode cell, which is formed in parallel with the inside of the air electrode substrate. A plurality of bottomed hole-like gas introduction holes opened on one end surface of the electrode substrate, an air supply pipe made of a conductive material having gas ejection holes on the pipe wall and inserted into the gas introduction holes, and the air A fibrous conductive material filled in a gap between the supply pipe and the inner wall of the gas introduction hole, a solid electrolyte layer made of a solid oxide formed on the outer surface of the air electrode substrate, and an outer surface of the solid electrolyte layer A fuel electrode layer made of a porous material laminated on the It has a gas sealing portion for sealing the end faces on the opening side and the bottom side of the gas inlet hole of the air electrode substrate, a structure having a.
This configuration has the following effects.
(1) Since the stack is formed by stacking cells, a useless space is not formed, and space saving can be improved and the output density can be increased as compared with the cylindrical type.
(2) When air or oxygen is supplied to the inner wall of the gas introduction hole of the air electrode substrate while the cell is heated to about 800 ° C. to 1000 ° C., oxygen obtains electrons and becomes oxide ions, and passes through the solid electrolyte layer. To do. When fuel gas (hydrogen, carbon monoxide, or a gas containing these) is supplied to the fuel electrode layer, hydrogen or carbon monoxide reacts with oxide ions to form water or carbon dioxide, releasing electrons, and in the cell Power generation is performed.
(3) Since it has a fibrous conductive material and an air supply pipe made of a conductive material, the air electrode base, the fibrous conductive material, and the air supply pipe are electrically connected to each other, and the externally exposed air supply pipe The tip can be a positive terminal. Further, the current collector can be brought into contact with the upper surface or the lower surface of the fuel electrode layer to form a terminal on the negative electrode side.
(4) Since the cell is formed by laminating the solid electrolyte layer and the fuel electrode layer on the air electrode base plate formed in a flat plate shape or an oval cross section, it is useless when the stack is formed by stacking the cells. The space saving performance of the stack can be improved without forming a space, and the output density per unit volume can be increased.
(5) Since the fibrous conductive material is filled in the gas introduction hole, the stress caused by the difference in thermal expansion between the air supply pipe and the air electrode base can be absorbed by the fibrous conductive material and can be made extremely small.
(6) Gas or gas can be reliably prevented from leaking in the gas-sealed part, and the gas sealing of the cells is performed in the gas-sealed part, and the electrical connection between the cells is performed by the current collector. Sealing and electrical connection can be performed at different locations, gas sealing performance can be easily improved, fuel gas and air are not mixed, and high reliability can be obtained.

Here, lanthanum strontium manganite or the like is used as the material of the air electrode substrate. As a method for forming the air electrode substrate into a flat plate shape or an oval cross-sectional shape having gas introduction holes, an extrusion molding method or the like is used.
As a material of the solid electrolyte layer, a solid oxide such as zirconia or lanthanum gallate is used. In particular, zirconia to which yttria or scandia is added is preferably used because of its high reliability and good conductivity of oxide ions. As the fuel electrode layer, cermet, metal or the like is used, and is laminated on the surface of the air electrode substrate together with the solid electrolyte layer by spraying or applying slurry and firing.

When the fuel gas supply pipe or air supply pipe of the solid oxide fuel cell has a bendable bellows portion outside the gas introduction hole, it is connected to the upstream side of the fuel gas supply pipe or air supply pipe. The stress generated in the fuel gas supply pipe or the air supply pipe due to the difference in thermal expansion between the header, the fuel reformer, etc. and each component can be absorbed by the bellows-like portion, and mechanical damage of the component can be prevented .
As the stress absorbing means , in addition to the bellows-like portion, a substantially U shape, a shape in which a part of the peripheral wall is bulged, or the like can be adopted.

The invention according to claim 4 of the present invention is the solid oxide fuel cell stack according to claim 2 or 3 , wherein the fuel electrode base or the air electrode base of the solid oxide fuel cell is provided. The gas discharge hole formed in the gas sealing part on the bottom side of the gas introduction hole is provided.
With this configuration, in addition to the operation of the second or third aspect , the following operation is provided.
(1) Gas exhaust holes include a part of the fuel gas introduced into the fuel gas supply pipe or a part of the air introduced into the air supply pipe, and water vapor or carbon dioxide generated by an electrochemical reaction in the fuel electrode substrate. Therefore, the inside of the cell can be maintained at a predetermined pressure so that an electrochemical reaction can be smoothly performed in the solid electrolyte layer, and the inside of the cell can be prevented from becoming a high pressure. It is possible to prevent a pressure load from being applied to the air electrode substrate, the solid electrolyte layer, the air electrode layer, the fuel electrode layer, or the like.
(2) A part of the fuel gas or air or oxygen can be recovered from the gas discharge hole and reused, and the utilization of the fuel gas or oxygen can be increased.

The invention according to claim 5 of the present invention is the solid oxide fuel cell stack according to any one of claims 2 to 4 , wherein the fuel of each of the solid oxide fuel cells. A gas supply pipe or an air supply pipe; and the upper conductive layer of the current collector disposed on an upper part of the solid oxide fuel cell, or the lower part of the current collector disposed on a lower part. It has the structure provided with the connection part which electrically connects an electroconductive layer.
With this configuration, in addition to the operation of any one of claims 2 to 4 , the following operation is provided.
(1) Each cell can be connected in series by the connection part, and a high voltage type stack can be configured.

A sixth aspect of the present invention is the solid oxide fuel cell stack according to any one of the second to fifth aspects, wherein the solid oxide fuel cell is disposed above and below each solid oxide fuel cell. Of the pair of arranged current collectors, a side end portion of the lower conductive layer of the upper current collector is connected to a side end portion of the upper conductive layer of the lower current collector. The current collector has a configuration including a current collector side portion configuration portion.
With this configuration, in addition to the operation of any one of claims 2 to 5 , the following operation is provided.
(1) Since the current collector side part constituent part is provided, an air channel or a fuel gas channel is formed between the current collector side part constituent part and the side of the air electrode layer or fuel electrode layer. Alternatively, a sufficient amount of air (oxygen) or fuel gas can be reliably supplied to the fuel electrode layer.
(2) Since the current collector side part configuration unit can electrically connect the lower conductive layer of the upper current collector of the solid oxide fuel cell and the upper conductive layer of the lower current collector, The current can easily flow through the current collector side component having a lower electrical resistance than the surface of the air electrode layer or the fuel electrode layer, and the internal resistance can be reduced.
(3) Heat generated by power generation can be dissipated through the current collector side component, and can be efficiently removed, and cooling is sufficient while reducing the supply amount of air (oxygen) and fuel gas Power generation performance can be improved.

  Here, the current collector side part component may be formed integrally with the upper conductive layer or the lower conductive layer of the current collector, and is formed by a separate member and joined to the upper conductive layer and the lower conductive layer by welding or the like. May be.

As described above, according to the present invention, the following advantageous effects can be obtained.
According to the invention of claim 1,
(1) Since the current collector is formed into a waveform or a shape having a plurality of irregularities, the current collector can absorb the stress caused by the difference in thermal expansion between the current collector and the cell and damage due to thermal expansion. It is possible to provide a solid oxide fuel cell stack with excellent durability and the like.
(2) Since the current collector is formed in a waveform or a shape having a plurality of irregularities, an air channel or a fuel gas channel can be formed between the air electrode layer or the fuel electrode layer. It is possible to provide a solid oxide fuel cell stack that can supply air or fuel gas evenly over the entire surface of the electrode layer, has excellent power generation efficiency, has no thermal distortion, and has excellent durability.
(3) Since the current collector has a three-layer structure of an upper conductive layer, an insulating layer, and a lower conductive layer, the air electrode layer or fuel electrode layer of each of the upper and lower cells can be insulated, and mass production can be achieved at low cost. An excellent solid oxide fuel cell stack can be provided.
(4) A solid oxide fuel cell stack that can promote heat transfer from the cell to the surrounding atmosphere (outside air) because the current collector has a large surface area, and can mitigate thermal shocks during start-up and shutdown thermal cycles and load fluctuations Can be provided.
According to invention of Claim 2,
(1) Since the stack is formed by stacking cells, it is possible to improve the volume efficiency in a space-saving manner, increase the output density per unit volume, and provide a compact and high output solid oxide fuel cell stack. it can.
(2) Since it is equipped with a fibrous conductive material and a fuel gas supply pipe made of a conductive material, electrical connection can be made while supplying the fuel gas from the fuel gas supply pipe to the fuel electrode substrate with the fibrous conductive material, Further, since the fuel gas can be supplied and the electric power can be taken out by the fuel gas supply pipe, it is possible to provide a solid oxide fuel cell having excellent productivity and low cost, which can reduce the number of parts.
(3) When a stack is formed by stacking cells, a compact and high-power solid oxide fuel cell that can improve the space-saving property of the stack without forming a useless space and increase the power density per unit volume. Can be provided.
(4) Since the fuel gas supply pipe having the gas ejection holes formed in the pipe wall is provided, the fuel gas can be supplied uniformly over the entire fuel electrode base, and the current density and temperature distribution are made uniform. Therefore, it is possible to provide a solid oxide fuel cell having a low thermal strain and excellent durability.
(5) A solid oxide fuel capable of absorbing stress caused by a difference in thermal expansion between the fuel gas supply pipe and the fuel electrode substrate by the fibrous conductive material so as to be very small and preventing damage due to thermal expansion and contraction. A battery cell can be provided.
(6) Gas sealing and electrical connection can be performed at different locations, gas sealing performance can be easily improved, fuel gas and air are not mixed, and safety and high reliability are obtained. A solid oxide fuel cell can be provided.

According to the invention described in claim 3 , in addition to the effects of (1), (3), (5), (6) of claim 2 ,
(1) Since it is provided with a fibrous conductive material and an air supply pipe made of a conductive material, electrical connection can be made while supplying air from the air supply pipe to the air electrode substrate by the fibrous conductive material. Since the air can be supplied and the electric power can be taken out by the pipe, it is possible to provide a solid oxide fuel cell having a low cost and excellent productivity that can reduce the number of parts.

According to invention of Claim 4 , in addition to the effect of Claim 2 or 3 ,
(1) A part of fuel gas introduced into the fuel gas supply pipe, or a part of air or oxygen introduced into the air supply pipe, and water vapor or dioxide generated by an electrochemical reaction in the fuel electrode base or air electrode base Since carbon and carbon can be discharged from the gas discharge hole, the inside of the cell can be maintained at a predetermined pressure, and the electrochemical reaction can be smoothly performed in the solid electrolyte layer. A solid oxide fuel cell that is excellent in mechanical durability and is capable of preventing pressure load from being applied to the fuel electrode base or air electrode base, solid electrolyte layer, air electrode layer or fuel electrode layer. Can be provided.
(2) A solid oxide fuel cell excellent in energy saving that can recover a part of the fuel gas or air or oxygen from the gas discharge hole and reuse it, and can increase the utilization of the fuel gas or oxygen. A cell can be provided.

According to the invention described in claim 5 , in addition to the effect of any one of claims 2 to 4 ,
(1) It is possible to provide a solid oxide fuel cell stack in which each cell can be connected in series by a connecting portion, and a high voltage type stack can be configured.

According to invention of Claim 6 , in addition to the effect of any one of Claims 2 to 5 ,
(1) A solid oxide fuel cell stack capable of reliably supplying a sufficient amount of air (oxygen) or fuel gas to the air electrode layer or the fuel electrode layer since the current collector side portion is provided. Can be provided.
(2) The solid oxide fuel that makes it easier for the current to flow through the current collector side portion constituting part having a lower electric resistance than the surface of the air electrode layer or the fuel electrode layer, and to reduce the internal resistance. A battery stack can be provided.
(3) Heat generated by power generation can be dissipated through the current collector side component, and can be efficiently removed, and cooling is sufficient while reducing the supply amount of air (oxygen) and fuel gas Therefore, it is possible to provide a solid oxide fuel cell stack that can improve the power generation performance.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1A is a front cross-sectional view of a main part of a solid oxide fuel cell used in the solid oxide fuel cell stack according to the first embodiment, and FIG. 1B is a solid diagram according to the first embodiment. FIG. 2 is a side sectional view of a main part of a solid oxide fuel cell used in an oxide fuel cell stack , and FIG. 2 is a perspective view of a main part of a fuel gas supply pipe.
In the figure, 1 is a solid oxide fuel cell, 2 is a fuel electrode base made of a porous body formed in a flat plate shape with an oval cross section, and 3 is parallel to the inside from the front of the fuel electrode base 2 in the horizontal direction. A plurality of bottomed hole-like gas introduction holes 4, 4 is a bottomed tubular fuel gas supply pipe inserted into each gas introduction hole 3, and 4 a is a gas introduction hole 3 of the fuel gas supply pipe 4. A bellows-like portion formed in a bendable portion at an externally located portion, 5 is a gas ejection hole formed in the tube wall of the fuel gas supply pipe 4, and 6 is a fuel gas supply pipe 4 and the inner wall of the gas introduction hole 3. Fibrous conductive material made of fibrous metal filled in the gap, 7 is a solid electrolyte layer made of a solid oxide formed over the upper surface, lower surface and side surface of the fuel electrode substrate 2, and 8 is on the solid electrolyte layer 7 Air electrode layers 9a and 9b made of a porous body laminated on the front and rear of the fuel electrode base 2 Gas sealing portions for sealing a 10 is a gas discharge holes formed in the gas sealing portion 9b of the rear surface of the fuel electrode substrate 2.

Here, as a material of the fuel electrode substrate 2, nickel zirconia cermet containing 25 to 50% by volume of nickel, nickel-iron / zirconia cermet, nickel-aluminum / zirconia cermet, or the like is used. As a method of forming the fuel electrode substrate 2 into a shape having a flat plate shape with an oval cross section and a gas introduction hole, an extrusion molding method or the like is used.
Further, as the material of the solid electrolyte layer 7, stable zirconia (hereinafter referred to as YSZ) to which 3 to 8 mol% of yttria is added, stabilized zirconia to which 8 to 10 mol% of scandia is added, ceria to which samaria or gadria is added, Lantern gallate or the like is used. The solid electrolyte layer 7 can be formed by spraying a powder such as YSZ on the surface of the fuel electrode substrate 2 or applying and firing a ceramic slurry. The thickness of the solid electrolyte layer 7 is preferably 10 μm to 100 μm. As the thickness of the solid electrolyte layer 7 becomes larger than 100 μm, the ohmic resistance increases and the power generation performance of the cell 1 is greatly deteriorated. Furthermore, the stress generated by the difference in thermal expansion between the fuel electrode substrate 2 and the solid electrolyte layer 7 is not preferable because the solid electrolyte layer 7 is liable to crack or peel off. Further, as the thickness of the solid electrolyte layer 7 becomes smaller than 10 μm, diffusion of the electrode material, particularly manganese in the air electrode layer 8, into the solid electrolyte layer 7 occurs during firing in the manufacturing process, and ion conduction of the solid electrolyte layer 7 occurs. This is not preferable because the performance of the cell 1 is lowered and the mechanical strength is lowered.
As the material of the air electrode layer 8, lanthanum strontium manganite, lanthanum strontium cobaltite, or the like is used. The air electrode layer 8 can be formed by spraying a powder of lanthanum strontium manganite or the like on the surface of the solid electrolyte layer 7 or applying a slurry and baking. The thickness of the air electrode layer 8 is determined in view of the ohmic resistance due to the current flow in the direction parallel to the electrode surface, the effective reaction area contributing to the electrode reaction, the stress due to the thermal expansion difference between the solid electrolyte layer 7 and the air electrode layer 8, and the like. To 50 μm to 200 μm.
The fibrous conductive material 6 is made of a metal felt-like material such as nickel, iron, or chromium. In addition, it is preferable to fill the fibrous conductive material 6 at a suitable density and uniformly so that the electric conductivity is 1000 S / cm or more and the gas permeability is 10 ⁻³ cm ⁴ / (g · s) or more.
As the gas sealing portions 9a and 9b, alumina, a mixture of magnesia and silica, or the like is used. A fuel gas supply pipe 4 is inserted into the gas sealing portion 9 a disposed on the front side of the fuel electrode base 2 so that the fuel gas can be introduced into the gas introduction hole 3.
The fuel gas supply pipe 4 is formed of a metal such as an alloy having conductivity and heat resistance.

Next, a solid oxide fuel cell stack formed by stacking a plurality of solid oxide fuel cells 1 configured as described above via a current collector will be described with reference to the drawings.
FIG. 3A is a perspective view of a main part of the solid oxide fuel cell stack according to the first embodiment, and FIG. 3B is a connection showing electrical connection of each cell in the solid oxide fuel cell stack. FIG. 4 is a side view of a main part of the solid oxide fuel cell stack according to the first embodiment, FIG. 5 (a) is a main part perspective view showing a current collector, and FIG. b) is a perspective view showing a main part of another example of the current collector.
In the figure, 11 is a solid oxide fuel cell stack, 12 is a current collector formed in a wave shape, and 12 ′ (see FIG. 5B) is a current collector formed in a shape having a plurality of irregularities. As shown in FIG. 5, the current collectors 12 and 12 ′ are each formed in a three-layer structure of an upper conductive layer 13, an insulating layer 14, and a lower conductive layer 15. Reference numerals 12a and 12b (see FIG. 5) denote upward and downward convex portions formed on the upper and lower surfaces of the current collectors 12 and 12, respectively. Reference numeral 16 denotes a connection part for electrically connecting the fuel gas supply pipe 4 and the upper conductive layer 13 of the current collector 12 stacked on the upper part thereof, and 17 is provided above and below each solid oxide fuel cell 1. In the pair of current collectors 12, the solid oxide type is connected from the side end portion of the lower conductive layer 15 of the upper current collector 12 to the side end portion of the upper conductive layer 13 of the lower current collector 12. A current collector side portion that is disposed so as to cover the side of the fuel cell 1, forms an air flow path on the side of the air electrode layer 8, and is a lower portion of the current collector 12 on the upper side of the cell 1. The conductive layer 15 and the upper conductive layer 13 of the lower current collector 12 are electrically connected. 18 is a fuel flow path formed inside the fuel gas supply pipe 4, and 19 is an air flow path formed in the gap between the current collector 12 and the upper and lower surfaces of the solid oxide fuel cell 1.
The solid oxide fuel cell 1 is surrounded by a lower conductive layer 15 of an upper current collector 12, an upper conductive layer 13 of a lower current collector 12, and current collector side portion constituting portions 17 on both sides. It is arranged in the space. Further, the air electrode layer 8 on the upper surface of the solid oxide fuel cell 1 is in contact with the top of the downward convex portion 12b of the current collector 12 on the upper side, and the air electrode layer 8 on the lower surface is on the current collector on the lower side. The body 12 is in contact with the top of the upward convex portion 12a. Reference numeral 20a denotes a current extraction line connected to the upper conductive layer 13 of the uppermost current collector 12. Reference numeral 20b denotes a current extraction line connected to the lowermost current collector side part 17.

Here, the upper conductive layer 13 and the lower conductive layer 15 of the current collectors 12 and 12 ′ are formed of a refractory metal or the like, and the insulating layer is formed of ceramics or the like.
Further, the current collectors 12 and 12 'are formed to have a thickness of 3 mm or less. Further, the vertical height from the top of the upward convex portion 12a to the top of the downward convex portion 12b, that is, the thickness (height) in the vertical direction of the current collectors 12 and 12 ′ is 4 mm to 5 mm. Is formed.

The power generation method of the solid oxide fuel cell stack 11 according to the first embodiment configured as described above will be described below with reference to the drawings.
First, the entire stack 11 is heated to about 700 ° C. by a gas burner or a heater in a heat insulating container (heating process). Thereby, oxide ions can freely pass through the solid electrolyte layer 7.
Next, the fuel gas (hydrogen gas) heated to about 600 ° C. is introduced into the fuel flow path 18 of the fuel gas supply pipe 4 (fuel gas introduction process). Further, air (outside air) is introduced into the air flow path 19 (air introduction process). The fuel gas introduced into the fuel flow path 18 passes through the inside of the fuel gas supply pipe 4 and is ejected from the gas ejection hole 5 into the gas introduction hole 3 (fuel gas ejection process). Since the inside of the gas introduction hole 3 is filled with the fibrous conductive material 6, the fuel gas passes through this and is supplied to the fuel electrode substrate 2 formed of a porous body. On the other hand, the air introduced into the air flow path 19 is supplied to the air electrode layer 8 formed of a porous body (air supply process).
When air is supplied to the air electrode layer 8, oxygen in the air obtains electrons and becomes oxide ions, and passes through the solid electrolyte layer 7. Hydrogen in the fuel gas supplied to the fuel electrode substrate 2 reacts with oxide ions to become water and emit electrons. In this way, power generation is performed in each cell 1 (power generation process).
Since the electrons emitted from the fuel electrode substrate 2 are taken out via the fibrous conductive material 6 and the fuel gas supply pipe 4, the fuel gas supply pipe 4 exposed to the outside serves as a terminal on the negative electrode side. In addition, the lower conductive layer 15 of the current collector 12 is brought into contact with the upper surface of the air electrode layer 8, and the upper conductive layer 13 of another current collector 12 is brought into contact with the lower surface, so that the current collector 12 is connected to the positive terminal. Become. Note that the fuel gas supply pipe 4 serving as a negative electrode side terminal is electrically connected to the upper conductive layer 13 of the current collector 12 through a connection portion 16.
That is, of the adjacent upper and lower cells 1, the positive terminal (upper conductive conductor 13) of the upper cell 1 is connected to the negative terminal (fuel gas supply pipe 4) of the lower cell 1. 1 are connected in series to form a stack 11 (see FIG. 3B).
In this way, the stack 11 is configured, power is generated by an electrochemical reaction in the solid electrolyte layer 7 of each cell 1, and a voltage is generated between the current extraction lines 20a and 20b.
A part of the fuel gas introduced into the fuel flow path 18 of the fuel gas supply pipe 4 and water vapor generated by the electrochemical reaction in the fuel electrode base 2 are discharged from the gas discharge hole 10. A part of the fuel gas can be recovered from the gas discharge hole 10 and reused. The inner diameter of the gas discharge hole 10 is appropriately set so that the electrochemical reaction is smoothly performed in the fuel electrode base 2 and the inside of the cell 1 does not become a high pressure.
The fuel gas is not limited to hydrogen gas, and natural gas (methane), propane, butane, methanol, naphtha, coal gas containing carbon monoxide, and the like can be used.

As described above, the solid oxide fuel cell 1 and the solid oxide fuel cell stack 11 according to the first embodiment are configured, and thus have the following operations.
(1) Since the solid oxide fuel cell 1 is formed by laminating the solid electrolyte layer 7 and the air electrode layer 8 on the fuel electrode base 2 having a flat plate shape or an oval cross section, the cell 1 is When the stack 11 is formed by stacking, a useless space is not formed, and the space saving performance of the stack 11 can be improved and the output density can be increased as compared with the cylindrical type.
(2) Since the fuel gas supply pipe 4 having the gas ejection holes 5 formed in the pipe wall is provided, the number, position, and diameter of the gas ejection holes 5 are set as appropriate so that the entire fuel electrode base 2 can be provided. The fuel gas can be supplied evenly, and the current density and temperature distribution can be made uniform.
(3) Since the fibrous conductive material 6 is filled in the gas introduction hole 3, the fibrous conductive material 6 absorbs the stress caused by the thermal expansion difference between the fuel gas supply pipe 4 and the fuel electrode base 2. Can be very small.
(4) The gas sealing portions 9a and 9b can reliably prevent fuel gas from leaking, and the gas sealing of the cell 1 is performed by the gas sealing portions 9a and 9b to collect the electrical connection between the cells 1. By using the bodies 12 and 12 ', the gas seal and the electrical connection can be performed at different locations, the gas seal performance can be easily improved, the fuel gas and the air are not mixed, and high reliability is achieved. can get.
(5) Since the current collectors 12 and 12 'are formed in a waveform or a shape having a plurality of irregularities, the current collector absorbs stress caused by the difference in thermal expansion between the current collectors 12 and 12' and the cell 1. In addition, an air flow path 19 can be formed between the current collectors 12 and 12 ′ and the air electrode layer 8, and air (oxygen) can be supplied evenly over the entire surface of the air electrode layer 8. it can.
(6) Since the current collectors 12 and 12 'have a three-layer structure of the upper conductive layer 13, the insulating layer 14, and the lower conductive layer 15, the air electrode layers 8 of the upper and lower cells 1 can be insulated from each other, Low cost, mass production is possible, and mass productivity is excellent.
(7) Current transfer from the cell 1 to the ambient atmosphere (outside air) can be promoted by the current collectors 12 and 12 ', and thermal shock during thermal cycle or load change due to start and stop can be reduced.
(8) The bellows-like portion 4a can absorb the stress generated in the fuel gas supply pipe 4 due to the difference in thermal expansion between the constituent members and the header and fuel reformer connected to the upstream side of the fuel gas supply pipe 4. It is possible to prevent mechanical damage of the constituent members.
(9) Since part of the fuel gas introduced into the fuel gas supply pipe 4 and water vapor generated by an electrochemical reaction in the fuel electrode base 2 can be discharged from the gas discharge hole 10, the inside of the cell 1 is predetermined. The solid electrolyte layer 7 can be allowed to smoothly perform an electrochemical reaction while maintaining the pressure, and the inside of the cell 1 can be prevented from becoming a high pressure, and the fuel electrode substrate 2, the solid electrolyte layer 7, and the air electrode layer 8 can be prevented. It is possible to prevent a pressure load from being applied.
(10) A part of the fuel gas can be recovered from the gas discharge hole 10 and reused, and the fuel gas can be used without waste.
(11) Each cell 1 can be connected in series by the connecting portion 16, and a high voltage type stack 11 can be configured.
(12) Since the current collector side part constituting part 17 formed so as to cover the side part of the solid oxide fuel cell 1 is provided, an air flow path is formed on the side part of the air electrode layer 8 and air A sufficient amount of air (oxygen) can be reliably supplied to the electrode layer 8, and the lower conductive layer 15 of the upper current collector 12 of the cell 1 and the lower current collector are collected by the current collector side portion constituting unit 17. By electrically connecting the upper conductive layer 13 of the body 12, the current can easily flow through the current collector side component 17 having a lower electrical resistance than the surface of the air electrode layer 8, and the internal resistance can be reduced. . Further, the heat generated with the power generation in the cell 1 can be dissipated through the current collector 12 and the current collector side component 17 and can be efficiently removed. Thereby, cooling can fully be performed, reducing the supply amount of air (oxygen), and the power generation performance of the cell 1 can be improved.

  In the first embodiment, the solid oxide fuel cell 1 including the fuel electrode base 2, the solid electrolyte layer 7, and the air electrode layer 8 has been described. However, the present invention is not limited to this. The electrode substrate and the air electrode layer can be interchanged. That is, a solid oxide fuel cell including an air electrode substrate, a solid electrolyte layer, and a fuel electrode layer can be obtained. In this case, an air electrode substrate formed in the same shape as the fuel electrode substrate 2 by using lanthanum strontium manganite, lanthanum strontium cobaltite, or the like instead of the fuel electrode substrate 2 is used, and nickel zirconia cermet or nickel -Solid oxide type described in the first embodiment, except that a fuel electrode layer formed of iron / zirconia cermet or the like is used, air or oxygen is supplied to the air electrode substrate, and fuel gas is supplied to the fuel electrode layer. Since it is the same as that of the fuel cell 1 and the solid oxide fuel cell stack 11, the description thereof is omitted.

As described above, the present invention relates to a solid oxide fuel cell stack in which solid oxide fuel cells using a solid electrolyte such as zirconia-based ceramics as an electrolyte are assembled. Therefore, it is possible to provide a solid oxide fuel cell stack that is excellent in space saving and has high output density, and can be improved in gas sealing performance and safety because gas sealing and electrical connection are performed in different places. it can.

(A) used in the solid oxide fuel cell stack in Embodiment 1 of the solid oxide fuel partial front sectional view of a battery cell (b) a solid oxide used in solid oxide fuel cell stack in Embodiment 1 Side sectional view of the main part of a fuel cell Perspective view of main part of fuel gas supply pipe (A) Perspective view of main part of solid oxide fuel cell stack in Embodiment 1 (b) Connection state diagram showing electrical connection of each cell in solid oxide fuel cell stack Side view of main part of solid oxide fuel cell stack according to Embodiment 1 (A) Main part perspective view showing a current collector (b) Main part perspective view showing another example of the current collector (A) Main part front view showing a stack of a cylindrical solid oxide fuel cell (b) Perspective perspective view of a main part showing a cell of a cylindrical solid oxide fuel cell (A) Main part perspective view showing a stack of a flat plate type solid oxide fuel cell (b) Main part perspective view showing a current collector of a cell of the flat plate type solid oxide fuel cell

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 2 Fuel electrode base | substrate 3 Gas introduction hole 4 Fuel gas supply pipe 4a Bellows-shaped part 5 Gas ejection hole 6 Fibrous conductive material 7 Solid electrolyte layer 8 Air electrode layer 9a, 9b Gas sealing part 10 Gas exhaust hole 11 Solid oxide fuel cell stack 12, 12 'Current collector 12a Upward convex portion 12b Downward convex portion 13 Upper conductive layer 14 Insulating layer 15 Lower conductive layer 16 Connection portion 17 Current collector side component 18 Fuel flow Path 19 Air flow path 20a, 20b Current extraction line 60 Cylindrical solid oxide fuel cell stack 61 Cell 62 Air electrode tube 63 Solid electrolyte layer 64 Fuel electrode layer 65 Interconnector layer 66a, 66b Nickel felt 70 Flat solid oxide Type fuel cell stack 70a cell 71 interconnector part 72 fuel flow path 73 air flow path 74 air electrode layer 75 Solid electrolyte layer 76 Fuel electrode layer 77, 78 Current collector plate

Claims (6)

A current collector used for electrical connection of a solid oxide fuel cell stack formed by stacking a plurality of solid oxide fuel cells,
A current collector formed of a three-layer structure of an upper conductive layer, an insulating layer, and a lower conductive layer, having a waveform or a plurality of irregularities and disposed between the solid oxide fuel cells. A solid oxide fuel cell stack formed by stacking a plurality of solid oxide fuel cells via the current collector according to claim 1,
The solid oxide fuel cell is
A fuel electrode substrate made of a porous body formed in a flat plate shape or an elliptical cross section; and
A plurality of bottomed hole-like gas introduction holes that are formed in parallel with the inside of the fuel electrode substrate and open at one end surface of the fuel electrode substrate;
A fuel gas supply pipe made of a conductive material having a gas ejection hole in the pipe wall and inserted into each of the gas introduction holes;
A fibrous conductive material filled in a gap between the fuel gas supply pipe and the inner wall of the gas introduction hole;
A solid electrolyte layer made of a solid oxide formed on the outer surface of the fuel electrode substrate;
An air electrode layer composed of a porous body laminated on the outer surface of the solid electrolyte layer;
A gas sealing portion that seals both the opening side and bottom side surfaces of the gas introduction hole of the fuel electrode base;
A solid oxide fuel cell stack comprising: A solid oxide fuel cell stack formed by stacking a plurality of solid oxide fuel cells via the current collector according to claim 1,
The solid oxide fuel cell is
An air electrode substrate made of a porous body formed in a flat plate shape or an elliptical cross section; and
A plurality of bottomed hole-like gas introduction holes that are drilled in parallel to the inside of the air electrode substrate and open to one end surface of the fuel electrode substrate;
An air supply pipe made of a conductive material having a gas ejection hole in the pipe wall and inserted into each of the gas introduction holes;
A fibrous conductive material filled in a gap between the air supply pipe and the inner wall of the gas introduction hole;
A solid electrolyte layer made of a solid oxide formed on the outer surface of the air electrode substrate;
A fuel electrode layer comprising a porous body laminated on the outer surface of the solid electrolyte layer;
A gas sealing portion that seals both the opening side and bottom side of the gas introduction hole of the air electrode base;
A solid oxide fuel cell stack comprising: The gas discharge hole formed in the gas sealing part on the bottom side of the gas introduction hole of the fuel electrode base or the air electrode base of the solid oxide fuel cell is provided. 4. The solid oxide fuel cell stack according to 2 or 3 . The fuel gas supply pipe or the air supply pipe of each of the solid oxide fuel cells, and the upper conductive layer of the current collector disposed above the solid oxide fuel cells, or 5. The solid oxide according to claim 2 , further comprising a connecting portion that electrically connects the lower conductive layer of the current collector disposed in a lower portion. 6. Physical fuel cell stack. Of the pair of current collectors disposed above and below each of the solid oxide fuel cells, side end portions of the lower conductive layer of the upper current collector and the current collector on the lower side 6. The solid oxide fuel cell stack according to claim 2 , further comprising a current collector side portion constituting a side end portion of the upper conductive layer. .

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