JP2007227125A - Fuel cell stack and current collector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current collector to supply a reaction gas at a high concentration to an electrode on a cell outer face, and simultaneously realize superior electrical connection in a fuel battery cell stack. <P>SOLUTION: In the fuel battery cell stack in which columnar solid electrolyte fuel battery cells equipped with a first gas flow passage in the axial direction are arranged in a plurality of numbers and which is electrically connected between the mutually neighboring fuel battery cells by using the current collector, the current collector has a cylindrical body inserted between the mutually neighboring fuel battery cells and equipped with an inner space which becomes a second gas flow passage in parallel with the axial direction, and the cylindrical body is equipped with a pair of opposing cell contacting parts contacted with each of the mutually neighboring fuel battery cells and with a pair of gas sealing parts to mutually couple both ends of the pair of cell contacting parts. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell stack in which a plurality of solid oxide fuel cells are arranged, and a current collector that electrically connects the fuel cells.

In recent years, various fuel cells have been proposed in which a stack of fuel cells is accommodated in a storage case as next-generation energy.
FIG. 10 is an example of a solid oxide fuel cell conventionally presented in Patent Document 1 and the like, and is a partial perspective view including a cross section of the fuel cell 30. The fuel cell 30 has a flat columnar shape as a whole, and a fuel gas passage 31a is bored along the axial direction inside a conductive support tube 31 having gas permeability, on the outer surface of the conductive support tube 31. A fuel electrode 32 made of cermet, a solid electrolyte 33, and an oxygen electrode 34 made of conductive ceramic are sequentially laminated. An interconnector 35 made of conductive ceramics is provided on the outer surface facing the oxygen electrode 34 via a bonding layer 38, and a P-type semiconductor layer 39 for reducing contact resistance is provided thereon. For example, the fuel electrode 32 is formed of Ni and ZrO ₂ (YSZ) containing Y ₂ O ₃ , the solid electrolyte 33 is formed of ZrO ₂ (YSZ) containing Y ₂ O ₃ , and the oxygen electrode 34 is It is formed from a lanthanum manganate perovskite complex oxide.

In such a fuel cell 30, hydrogen is supplied to the fuel electrode 32 by flowing the fuel gas through the fuel gas passage 31 a, while oxygen is supplied to the oxygen electrode 34 by supplying an oxygen-containing gas around the fuel cell 30. Supply. Thus, power is generated by the following electrode reactions occurring at the oxygen electrode 34 and the fuel electrode 32, respectively. The reaction is carried out at 600-1000 ° C.
Oxygen electrode: 1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte)
Fuel electrode: O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻

Since the fuel cell of the above structure has a small amount of power generation per cell, a plurality of fuel cells are arranged in a line, one end of each fuel cell is supported and fixed to the manifold, and adjacent to each other using a current collector made of a conductive material. The fuel cell stack is configured by electrically connecting the oxygen electrode of the fuel cell and the interconnector. The conventional current collector has a structure in which the contact resistance with each fuel cell is made as small as possible and the gas supply to the oxygen electrode is not hindered. Conventional examples of current collectors such as the net-like ones of Patent Document 2 and the spiral ones of Patent Document 3 are those of a flexible type that can ensure air permeability with the surrounding space and can follow fluctuations in the distance between cells. Is often used.
Further, the fuel cell stack is housed in a housing case together with a fuel gas supply means to the fuel electrode 32 and an oxygen-containing gas supply means to the oxygen electrode 34 to constitute a fuel cell module.

As a means for supplying the oxygen-containing gas in the housing case, for example, an oxygen-containing gas supply nozzle is provided in the vicinity of the fuel cell stack, and pressurized oxygen-containing gas (for example, air) is injected from an outlet at the end thereof There is a form. Further, as the fuel gas supply means, for example, a reformer for reforming the reformed gas is provided, and the reformed hydrogen-rich fuel gas is supplied to the fuel gas passage of the fuel cell through the internal space of the manifold. There is a form to send to.
JP 2003-317751 A JP 2005-19239 A JP 2004-228050 A

The fuel cell stack includes a plurality of fuel cells. In order to improve the power generation amount and the power generation efficiency, it is preferable to supply gas evenly to each cell. The power generation efficiency in the fuel cell is better as the difference in oxygen concentration between the oxygen electrode and the fuel electrode is larger.
However, even when pressurized oxygen-containing gas is injected around the cell stack, the oxygen is contained in the housing case at almost atmospheric pressure, so that the oxygen-containing gas does not stay around the cell stack and easily diffuses. A sufficiently high concentration of oxygen-containing gas could not be supplied. In order to prevent diffusion of the oxygen-containing gas after injection, for example, if the flow rate and flow rate are suitably controlled, the heat in the storage case is exhausted, and the fuel cell does not become self-sustaining and the power generation performance decreases. There's a problem. In addition, there is a problem that the equipment such as a compressor becomes large and the cost increases for controlling the flow rate and the like.

  The same problem can be said for a fuel cell in which the oxygen electrode and the fuel electrode are reversed. In this case, the oxygen-containing gas passes through the fuel battery cell, and the fuel gas is supplied around the cell stack. Then, since the fuel gas does not stay around the cell stack but diffuses, a sufficiently high concentration fuel gas cannot be supplied to the fuel electrode on the outer surface of the cell.

  Furthermore, for the current collector, in order to minimize the electrical resistance between the adjacent fuel cells, it is desirable that the current collector is in close contact with the electrode on the outer surface of the cell in a large area and the cells are connected at a short distance. It is required that the reaction gas can be sufficiently supplied to the electrode on the outer surface of the cell.

  In view of the above situation, the present invention provides a sufficient amount of reaction gas (oxygen-containing gas or fuel gas) to the electrode on the outer surface of the fuel cell stack in which the fuel cells are electrically connected using a current collector. An object is to reduce current collection loss and enable high-output power generation by supplying high concentration and at the same time making good electrical connection. Further, it is an object to realize this without increasing the current facilities or changing the control system without impairing the thermal independence.

In order to achieve the above object, the present invention provides the following configurations.
(1) In the fuel cell stack according to claim 1, a plurality of columnar solid electrolyte fuel cells each having a first gas flow path are arranged in the axial direction, and a current collector is disposed between adjacent fuel cells. In the fuel cell stack to be electrically connected using,
The current collector has a cylindrical body having an internal space that is inserted between the adjacent fuel cells and serves as a second gas flow path parallel to the axial direction,
The cylinder includes a pair of opposing cell contact portions that contact each of the adjacent fuel cells, and a pair of gas sealing portions that connect both ends of the pair of cell contact portions. It is characterized by doing.
(2) The fuel cell stack according to claim 2 is the fuel cell stack according to claim 1, wherein the first gas channel in the fuel cell is a fuel gas channel and the second gas channel in the current collector. Is an oxygen-containing gas flow path.
(3) The fuel cell stack according to claim 3 is the fuel cell stack according to claim 1 or 2, wherein a vent hole is formed in the cell contact portion of the current collector.
(4) The fuel cell stack according to claim 4 is characterized in that, in claim 3, the size of the vent hole is larger on the downstream side than the upstream side of the second gas flow path.
(5) The fuel cell stack according to claim 5 is the fuel cell stack according to any one of claims 1 to 4, wherein a part of the gas sealing portion of the current collector is provided with an introduction opening to the second gas flow path. It was set up.
(6) A fuel cell stack according to a sixth aspect is the fuel cell stack according to any one of the first to fifth aspects, wherein the current collector is installed in an internal space of the cylindrical body so as to connect the pair of cell contact portions. And a conductive cross-linked portion.
(7) A current collector according to claim 7 is a fuel cell adjacent to each other in a fuel cell stack in which a plurality of columnar solid electrolyte fuel cells having a first gas flow path penetrating in the axial direction are arranged. A current collector for electrically connecting
Having a cylindrical body having an internal space inserted between the adjacent fuel cells and serving as a second gas flow path parallel to the axial direction;
The cylinder includes a pair of opposed cell contact portions that contact each of the adjacent fuel cells, and a pair of gas sealing portions that connect both ends of the pair of cell contact portions. It is characterized by doing.

  In the fuel cell stack according to claim 1, one reaction gas (fuel gas or oxygen-containing gas) is allowed to pass through the first gas flow path in the fuel cell, and the second gas which is the cylindrical internal space of the current collector. The other reaction gas (oxygen-containing gas or fuel gas) can be passed through the flow path. Since the second gas flow path is surrounded by the cell contact portion and the gas sealing portion of the cylindrical body, it is possible to prevent diffusion of the reaction gas passing therethrough, and a high-concentration reaction gas is supplied to the fuel cell. Can supply. As a result, since the reactive gas is effectively used, the power generation amount and power generation efficiency are improved.

  According to a second aspect of the present invention, the fuel gas is supplied to the first gas passage in the fuel battery cell, and the oxygen-containing gas is supplied to the second gas passage in the current collector. Since air is usually used as the oxygen-containing gas, it is inexpensive in cost, unlike fuel gas that requires reforming treatment. Gas supply to the current collector is not performed in a state completely isolated from the surrounding space of the cell stack, and even a little gas is wasted, so the reaction gas supplied to the current collector should be an oxygen-containing gas Is preferred.

  According to the third aspect, since the air contact hole is provided in the cell contact portion of the current collector, the second gas flow path sufficiently reacts with the electrode (fuel electrode or oxygen electrode) provided on the outer surface of the fuel cell. Gas can be supplied.

  According to a fourth aspect of the present invention, the size of the vent hole on the second gas flow path is made larger on the downstream side than on the upstream side. Since the reaction gas is consumed while being transferred through the flow path, the supply amount decreases as it goes downstream. Therefore, by providing such a difference in the size of the vent hole, the concentration difference between the upstream and downstream reaction gases can be reduced, and the reaction gas concentration on the flow path can be made as uniform as possible.

  According to the fifth aspect of the present invention, since the introduction opening to the second gas channel is provided in a part of the gas sealing portion of the current collector, the reaction gas can be efficiently taken into the second gas channel from the surroundings. .

  According to the sixth aspect of the present invention, since the conductive bridging portion that connects the inner surfaces of the opposed cell contact portions is installed in the cylindrical internal space of the current collector, the current path between the opposed cell contact portions is short and thick. As a result, the electrical resistance between the fuel cells is reduced and the electrical connection is improved.

  The current collector of claim 7 is used for electrical connection between the fuel cells in the fuel cell stack, so that the same effect as that of claim 1 can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic external perspective view showing an embodiment of a fuel cell stack device 1 of the present invention. However, unlike the actual state, it is an explanatory diagram showing a state in which no pressing force is applied when assembling the cell stack (that is, a state where no force is applied to the current collector). The solid electrolyte fuel cell 30 has the same flat columnar shape as FIG. 10 described in the background art. In the following description, for the sake of convenience, the axial direction of the fuel cell 30 will be described as the vertical direction, but the axial direction may be set horizontally. A plurality of fuel gas passages (first gas passages) 31 a are formed in the fuel cell 30 in the axial direction. As described above, an oxygen electrode is provided on one flat outer surface of the flat columnar fuel cell 30, and an interconnector (conducting with the fuel electrode) is provided on the other flat outer surface.

  In the following description, the fuel gas is supplied to the gas flow path inside the fuel battery cell, and the oxygen-containing gas (for example, air) is supplied around the fuel battery cell. Even in a mode in which an oxygen-containing gas is supplied to the gas flow path inside the battery cell and fuel gas is supplied around the fuel battery cell (in this case, the fuel electrode and the oxygen electrode of the fuel battery cell are also oppositely arranged) The present invention is applicable.

  In FIG. 1, only a part of one fuel battery cell stack configured by arranging a plurality of fuel battery cells 30 is shown. The lower end of each fuel cell 30 is supported and fixed by a cell fixing material 42 such as glass or cement forming the upper wall of the manifold 41. Each fuel gas passage 31 a communicates with the internal space of the manifold 41.

  A current collector 10 that electrically connects the oxygen electrode of one cell and the interconnector of the other cell is inserted between the fuel cells 30. The current collector 10 is formed of a cylinder made of a conductive material such as a refractory metal, a noble metal, or ceramics. The cylindrical body includes a pair of cell abutting portions 11 that abut against the flat outer surface of the fuel cell 30 and a pair of gas sealing portions 12 that connect both ends of each cell abutting portion 11. A vent hole 13 is formed in the cell contact portion 11. The gas sealing part 12 is a series of walls and gas cannot pass therethrough. In addition, the upper end and lower end of a cylinder are open | released. The internal space of the cylindrical body serves as a flow path (second gas flow path) for the oxygen-containing gas.

  For convenience of explanation, FIG. 1 shows a state where a part of the cell contact portion 11 and the vent hole 13 of the current collector 10 can be seen, but in actuality, as shown in FIG. In order to fix the whole by applying the pressing force, the cell contact portion 11 is in a state of being completely in close contact with the flat outer surface of the fuel cell 30, and the vent hole 13 is also not visible from the outside.

  In the illustrated example, the oxygen-containing gas supply nozzle 51 extends from above in the vicinity of the side surface of the cell stack 1, reaches a position lower than the lower end of the current collector 10, and has an outlet directed toward the cell stack 1 at its tip. To do. Therefore, the oxygen-containing gas supplied from above by the supply nozzle 51 is changed in the horizontal direction at the outlet and is injected toward the vicinity of the lower end of the current collector 10. The reason why the outlet is open in both directions is that injection is performed also on another cell stack of the same structure installed next to the outlet. The position and direction of the outlet can be set as appropriate. As an example, the outlet of the supply nozzle 51 may be provided so as to extend right below the lower end opening of the current collector 10 and to inject upward toward the internal space.

  In FIG. 1, the injected high-pressure oxygen-containing gas flows into the internal space from the cylindrical lower end opening of the current collector 10 and is consumed for the electrode reaction while rising, and surplus gas is released from the upper end opening. The Since the cylindrical body side surface of the current collector 10 is closed by the gas sealing portion 12, there is no gas in and out through the cylindrical body side surface. Conventional current collectors generally have a structure with good air permeability (such as a mesh shape or a porous shape) so that gas can be actively introduced from the side, but the current collector 10 of the present invention has a lower end. The gas is introduced only from the opening, and the side is completely closed to form a chimney-like structure. With this structure, diffusion of the oxygen-containing gas can be remarkably reduced and a high pressure state can be maintained, so that it can be supplied to the oxygen electrode of the fuel cell 30 at a high concentration.

  FIG. 2A is a plan view of a state in which three fuel cell stacks 1 are juxtaposed. Three oxygen-containing gas supply nozzles 51 are provided between the fuel cell stacks 1 along the arrangement direction of the fuel cells 30. The number and position of the supply nozzles 51 are set so that the oxygen-containing gas is distributed around the fuel battery cell 30 with a concentration as uniform as possible.

FIG. 2B is an enlarged plan view of a part of the cell stack 1 of FIG. 2A, as viewed from the upper end opening side of the cylindrical body of the current collector 10. The inner space 16 of the cylindrical body is surrounded by a pair of opposed cell contact portions 11a and 11b and a pair of gas sealing portions 12a and 12b that connect both ends thereof. One cell abutting portion 11a abuts on a flat surface on the oxygen electrode 34 side of one fuel cell 30a, and the other cell abutting portion 11b is a flat surface on the interconnector 35 side of the other fuel cell 30b. Abut. The electrical connection between the cell contact portion 11a and the oxygen electrode 34 and between the cell contact portion 11b and the interconnector 35 is performed by chemical bonding using only pressing force and / or chemical using a conductive paste or the like. Formed by mechanical adhesion.
The vent hole 13 may be provided only in the cell contact portion 11a on the side in contact with the oxygen electrode 34. The cylindrical body of the current collector 10 is not open to the outside, and the introduced oxygen-containing gas is supplied to the oxygen electrode 34 through the vent hole 13, and the remainder is forced to flow through the cylindrical internal space. It is done.

  FIG. 3 is a diagram showing an embodiment of the current collector 10 in the cell stack shown in FIG. (A) is an external view, and an open arrow indicates the flow of an oxygen-containing gas (the same applies to the following drawings). (B) is a development view. The cylinder configured by the pair of cell contact portions 11 and the pair of gas sealing portions 12 has an elliptical cross section. When the current collector 10 is incorporated into the cell stack and fixed with a predetermined pressing force, the cell contact portion 11 is deformed so as to be in close contact with the flat outer surface of the fuel cell, as shown in FIG. 2B described above. It becomes a flat shape. In the current collector 10 of FIG. 3, a plurality of vent holes 13 extending in the width direction are formed in each of the pair of cell contact portions 11. One of the cell contact portions 11 contacts an oxygen electrode provided on the outer surface of the fuel cell. Therefore, the oxygen-containing gas flowing through the cylindrical interior space is supplied to the oxygen electrode through the vent hole 13.

  The size, shape, number and position of the air holes 13 can be variously set as in another embodiment described later. However, if the total area of the vent holes 13 becomes too large, the electrical connection with the electrodes on the outer surface of the cell is hindered, leading to performance degradation. On the other hand, if the total area of the vent holes 13 is too small or unevenly arranged, the gas is not sufficiently and evenly supplied to the electrodes, which leads to performance degradation. Therefore, the vent hole 13 needs to be set optimally.

  FIG. 4 shows another embodiment of the current collector 10. A difference from the current collector shown in FIG. 3 is that only one of the pair of cell contact portions 11 has a plurality of vent holes 13 extending in the width direction. Therefore, when incorporating the current collector 10 of FIG. 4 into the cell stack, it is necessary to incorporate the current collector 10 so that the cell contact portion 11 provided with the vent hole 13 faces the oxygen electrode side of the fuel cell. In this embodiment, a large contact area with the interconnector side can be secured.

  FIG. 5 shows a modification of the current collector 10 shown in FIG. 3 or FIG. In the current collector 10 of FIG. 5, the size of the vent hole 13 provided in the cell contact portion 11 is small at the lower side and larger at the upper side. That is, the size of the vent hole 13 is larger on the downstream side than the upstream side of the flow path of the oxygen-containing gas. The oxygen-containing gas is consumed while flowing through the flow path, and the supply amount tends to decrease toward the downstream side. Therefore, by providing such a difference in the size of the vent hole on the flow path, the difference in gas concentration between the upstream side and the downstream side can be relaxed, and the gas concentration on the flow path can be made as uniform as possible.

  FIG. 6 shows still another embodiment of the current collector 10. The difference from the current collector shown in FIG. 3 described above is the shape of the vent hole 13. The vent hole 13 of the current collector 10 in FIG. 6 is divided into a plurality of parts in the width direction.

  FIG. 7 shows still another embodiment of the current collector 10. The difference from the current collector shown in FIG. 3 described above is the shape of the vent hole 13. The vent hole 13 of the current collector 10 in FIG. 7 is circular. Although not shown, the shape of the vent 13 may be a polygon.

  FIG. 8 shows still another embodiment of the current collector 10. The difference from the current collector shown in FIG. 3 is the shape of the cylinder. The cylinder of the current collector 10 in FIG. 8 has a rectangular cross section. Furthermore, the introduction opening 14 is notched at the lower end of each of the pair of gas sealing portions 12 so that the gas can easily flow into the cylindrical interior space.

FIG. 9A shows yet another embodiment of the current collector 10. The difference from the current collector shown in FIG. 3 described above is that a conductive bridging portion 15 is provided in the internal space 16 of the cylindrical body. (B) is A sectional drawing of (a), and the electroconductive bridge | crosslinking part 15 erected in the internal space 16 of the cylinder has connected the inner surfaces of a pair of cell contact part 11. FIG. The connection portion is bonded with, for example, a conductive paste. The pair of cell contact portions 11 are electrically connected to each other by the gas sealing portions 12 at both ends. However, by providing a conductive bridging portion 15, the electrical connection path is further shortened and thickened to increase the electrical resistance. Can be reduced.
Note that the size, number, shape, and position of the conductive bridging portion 15 can be variously set as long as they do not hinder the flow of gas in the internal space.

  FIG. 9B is another embodiment of the conductive bridge 15 shown in FIG. 9A. The conductive bridging portion 15 in FIG. 9B is formed as a protrusion that protrudes from the one cell abutting portion 11b to the cylindrical inner space 16 and can abut against the inner surface of the other cell abutting portion 11a. In this case, it is not necessary to attach the conductive bridging portion 15 which is a separate member, and it can be provided by stamping the cylindrical body.

1 is a schematic external perspective view of a fuel cell stack device showing a basic embodiment of the present invention. FIG. 2 is a plan view of a state in which three fuel cell stack devices of FIG. 1 are juxtaposed. 2B is an enlarged plan view of a part of the fuel cell stack shown in FIG. 2A. FIG. It is a figure which shows one Embodiment of the collector of the cell stack shown in FIG. (A) is an external view, (b) is an expanded view. 3 shows another embodiment of the current collector in the present invention. 10 shows still another embodiment of the current collector according to the present invention. It is a figure which shows another embodiment of the electrical power collector in this invention. It is a figure which shows another embodiment of the electrical power collector in this invention. It is a figure which shows another embodiment of the electrical power collector in this invention. It is a figure which shows another embodiment of the electrical power collector in this invention. (A) is a perspective external view, (b) is A sectional drawing of (a). It is a figure which shows another embodiment of the electrical power collector in this invention. It is a fragmentary perspective view containing the cross section of the conventional solid oxide form fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 10 Current collector 11 Cell contact part 12 Gas sealing part 13 Vent 30 Fuel cell 41 Manifold

Claims (7)

In a fuel cell stack in which a plurality of columnar solid electrolyte fuel cells each having a first gas flow path are arranged in the axial direction and electrically connected between adjacent fuel cells using a current collector,
The current collector has a cylindrical body having an internal space that is inserted between the adjacent fuel cells and serves as a second gas flow path parallel to the axial direction,
The cylinder includes a pair of opposing cell contact portions that contact each of the adjacent fuel cells, and a pair of gas sealing portions that connect both ends of the pair of cell contact portions. A fuel cell stack characterized in that:   The first gas channel in the fuel battery cell is a fuel gas channel, and the second gas channel in the current collector is an oxygen-containing gas channel. Fuel cell stack.   The fuel cell stack according to claim 1, wherein a vent hole is formed in the cell contact portion of the current collector.   4. The fuel cell stack according to claim 3, wherein the size of the vent hole is larger on the downstream side than the upstream side of the second gas flow path. 5.   The fuel cell stack according to any one of claims 1 to 4, wherein an introduction opening to the second gas passage is formed in a part of the gas sealing portion of the current collector.   The current collector further includes a conductive bridging portion constructed in an internal space of the cylindrical body so as to connect the pair of cell contact portions. The fuel cell stack described. A current collector for electrically connecting adjacent fuel cells in a fuel cell stack in which a plurality of columnar solid electrolyte fuel cells having a first gas flow path penetrating in the axial direction are arranged. ,
A cylindrical body having an internal space inserted between the adjacent fuel cells and serving as a second gas flow path parallel to the axial direction;
The cylinder includes a pair of opposed cell contact portions that contact each of the adjacent fuel cells, and a pair of gas sealing portions that connect both ends of the pair of cell contact portions. A current collector.

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