JP2007042442A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To regulate movement of a separator in a plane direction occurring by thermal strain under a high-temperature atmosphere at power generation, and prevent damage to power generating cells. <P>SOLUTION: In the fuel cell stack 1 of a flat lamination type made by alternately laminating power generating cells 5 and separators 8 and weighing the laminated body from a lamination direction, each separator 8 is provided with a plurality of through-holes 22 penetrating in the lamination direction, into which 22, fixing rods 23 are inserted for regulating movement of the separator 8 in a plane direction due to thermal strain at operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell stack, and more particularly to a fixing structure for preventing a separator from moving in a plane direction caused by thermal distortion in a high temperature atmosphere during operation (power generation).

  In recent years, fuel cells that directly convert chemical energy of fuel into electrical energy have attracted attention as highly efficient and clean power generators. This fuel cell has a laminated structure in which a solid electrolyte layer made of an oxide ion conductor is sandwiched between an air electrode layer (cathode) and a fuel electrode layer (anode) from both sides.

During power generation, an oxidant gas (oxygen) is supplied to the air electrode layer side and a fuel gas (H ₂ , CO, CH _4, etc.) is supplied to the fuel electrode layer side as a reaction gas. The air electrode layer and the fuel electrode layer are both porous layers so that the reaction gas can reach the interface with the solid electrolyte layer.

In the power generation cell, oxygen supplied to the air electrode layer passes through the pores in the air electrode layer and reaches the vicinity of the interface with the solid electrolyte layer. It is ionized to (O ²⁻ ). The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode layer. Oxide ions that have reached the vicinity of the interface with the fuel electrode layer react with the fuel gas at this portion to generate reaction products (H ₂ O, CO _2, etc.), and discharge electrons to the fuel electrode layer. Electrons generated by the electrode reaction can be taken out as an electromotive force at an external load on another route.

  A flat plate type fuel cell is constructed by stacking a large number of these power generation cells and separators alternately and stacking them together, and by applying a load in the stacking direction from both ends of each of the components of the stack so that they are in pressure contact with each other. Has been.

Such a stacked fuel cell is disclosed in Patent Document 1, for example.
Patent Document 1 describes a fuel cell stack for mounting on a vehicle (automobile body) in which fuel cells are stacked in a horizontal direction via a separator. Since this fuel cell stack is used horizontally, it is fixed by a fixing rod provided in the stacking direction of the stack so that the fuel cell and separator do not slip or open due to vibration or impact during vehicle operation. Yes.
JP 2002-56882 A

  By the way, as described above, the flat plate type fuel cell has a structure in which a plurality of power generation cells configured by stacking a plurality of power generation elements are further stacked via conductive members such as separators, and thus stable. In order to ensure battery performance, excellent adhesion between components is required. For this reason, a structure is generally adopted in which a load is applied in the stacking direction from both ends of the stack after assembling the stack and the components are pressed against each other. For example, a clamping plate is arranged on the upper and lower ends of the stack, and the upper and lower clamping plates are bolted. -The laminated body is collectively loaded by tightening from both ends with nuts.

  However, in such a load structure, depending on the thermal expansion coefficient of the separator in a high temperature atmosphere during power generation, particularly in the case of a metal separator, the separator itself is easily displaced in the surface direction due to thermal strain. There was a problem that the power generation cell was damaged (cracked) by the stress in the surface direction acting on the power generation cell being pressed and sandwiched.

  The present invention has been made in view of such a problem, and by restricting the movement of the separator in the plane direction caused by thermal distortion in a high temperature atmosphere during power generation, the reliability in which the power generation cell is prevented from being damaged by thermal stress. The object is to provide a highly fuel cell stack.

  That is, the present invention according to claim 1 is a flat plate type fuel cell stack in which power generation cells and separators are alternately stacked and the stacked body is weighted from the stacking direction. A plurality of through-holes are provided in the through-holes, and fixed rods for restricting the movement in the surface direction of the separator due to thermal distortion during operation are inserted into these through-holes.

  According to a second aspect of the present invention, in the fuel cell stack according to the first aspect, the power generation cell and the separator are stacked in the vertical direction.

  Further, according to a third aspect of the present invention, in the fuel cell stack according to the first or second aspect, the thermal expansion coefficient of the fixed rod is smaller than the thermal expansion coefficient of the separator. It is characterized by.

  According to a fourth aspect of the present invention, in the fuel cell stack according to any one of the first to third aspects, alumina or silica is used as a material for the fixed rod.

  According to the present invention, since the fixing rod is inserted into each of a large number of stacked separators to restrict the movement of the separator in the surface direction due to thermal strain, the separators are pressed and sandwiched between the separators in a high temperature atmosphere during power generation. It is possible to prevent thermal stress from being applied to the power generation cell, thereby preventing the power generation cell from being damaged.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of a flat plate type solid oxide fuel cell (fuel cell stack) to which the present invention is applied, and FIG. 2 is a view taken along the line AA of FIG.

  As shown in FIG. 1B, the unit cell 10 includes a circular power generation cell 5 in which a fuel electrode layer 3 and an air electrode layer 4 are arranged on both surfaces of a solid electrolyte layer 2, and an outer side of the fuel electrode layer 3. The fuel electrode current collector 6, the air electrode current collector 7 disposed outside the air electrode layer 4, and the separator 8 disposed outside each current collector 6, 7.

Among these power generation elements, the solid electrolyte layer 2 is composed of stabilized zirconia (YSZ) or the like to which yttria is added, and the fuel electrode layer 3 is composed of a metal such as Ni or a cermet such as Ni—YSZ. 4 is composed of LaMnO ₃ , LaCoO ₃ or the like, the fuel electrode current collector 6 is composed of a sponge-like porous sintered metal plate such as Ni, and the air electrode current collector 7 is a sponge-like porous material such as Ag. It consists of a sintered metal plate.

  As shown in FIG. 2, the separator 8 is composed of a rectangular stainless steel plate, and electrically connects the power generation cells 5 arranged at the center thereof, and supplies a reaction gas to the power generation cells 5. And a fuel gas passage 11 through which fuel gas flows and an oxidant gas passage 12 through which oxidant gas flows.

A pair of gas holes 13, 14 penetrating in the plate thickness direction are provided at corners on a pair of diagonal lines of the separator 8. One gas hole 13 communicates with the fuel gas passage 11, and the other gas hole 14 is oxidized. It communicates with the agent gas passage 12. Fuel gas and oxidant gas are discharged and supplied from the gas holes 13 and 14 to the electrode surfaces of the power generation cells 5 from the gas discharge ports 11a and 12a through the gas passages 11 and 12, respectively. A power generation reaction occurs at each electrode.
The gas holes of the separators 8 stacked one above the other are connected by ring-shaped insulating gaskets 15 and 16, respectively.

  Further, as shown in FIG. 2, the separator 8 of the present embodiment has connecting portions 8 a and 8 a connecting the gas holes 13 and 14 at the left and right ends and the portion where the power generation cell 5 at the center is formed as an elongated band, which will be described later. It has a structure that is flexible with respect to the load to be applied, so that the entire surface is evenly weighted by absorbing the height variation of the separator peripheral part and the central part that occur in the lamination and assembly of components. The adhesion of each power generating element constituting the laminate and the gas sealing property of the gasket portion are improved.

  A fuel cell stack 1 shown in FIG. 1 includes a plurality of single cells 10 having the above-described configuration stacked with gaskets 15 and 16 interposed therebetween, and fastening plates 20 and 20 made of stainless steel square plates at upper and lower ends thereof. The four peripheral parts are fastened with bolts and nuts 21a and 21b, and the structural elements are brought into close contact with each other by the fastening load. In addition, the gaskets 15 and 16 are connected in the stacking direction via the gas holes 13 and 14 of the separator 8 by the tightening load, respectively, so that a tubular manifold for introducing fuel gas extending in the stacking direction inside the stack and Two systems of tubular manifolds for introducing oxidant gas are formed.

  By the way, as described above, in the flat plate type fuel cell stack having the above-described configuration, when thermal distortion occurs in the separator 8 due to Joule heat or the like generated in the power generation cell during power generation, power is generated by displacement in the surface direction. There was a problem that the power generation cell 5 was damaged due to the stress in the horizontal direction acting on the cell 5.

  Therefore, in the present invention, as shown in FIGS. 1 and 2, the through holes 22 are respectively provided in the upper and lower fastening plates 20 and 20 and each of the plurality of separators 8 sandwiched between the fastening plates 20 and 20. The fixing rods 23 are inserted into the through holes 22 in the stacking direction (vertical direction) of the laminated body, and the movement of the separator in the surface direction due to thermal strain is regulated by the fixing rods 23, thereby The power generation cell 5 was prevented from being damaged.

  In this embodiment, the fixing rod 23 is inserted by providing four through holes 22 in the vicinity of the outer periphery and diagonally so as to surround a portion where the power generation cell 5 is located on the surface of the separator 8. Incidentally, the diameter of the through hole 22 is 3φ, and the outer diameter of the fixed rod 23 inserted through the through hole 22 is 3.5φ.

  These fixed rods 23 are inserted through the through holes 22 of the upper end fastening plate 20, and the lower ends thereof are supported by the lower end fastening plate 20. Accordingly, all the fixing rods 23 are loosely fitted in the respective through holes 22, do not contribute to the load in the stacking direction of the stacked body, and merely move in the surface direction of the separator 8. Is regulated.

Further, as the material of the fixing rod 23, for example, alumina, silica, or the like, which has insulation and high heat resistance and has a smaller thermal expansion coefficient than the material of the separator 8 (stainless steel), is used.
The reason why the thermal expansion coefficient of the fixed rod 23 is made smaller than the thermal expansion coefficient of the separator 8 is to eliminate the mechanical influence of the thermal strain of the fixed rod 23 on the separator 8 during power generation. The reason for this is to prevent the separators from being short-circuited by the fixing rod 23.

  Note that the number of the through holes 22 is not limited to the four positions in the plane direction described above, and it is sufficient that at least three positions are provided, and the movement of the separator 8 in the plane direction can be reliably regulated. In particular, when it is provided at three places, it is desirable that the power generation cells 5 are arranged at equal intervals (regular triangles) in the vicinity of the outer periphery so as to surround the portion where the power generation cells 5 are located.

  As described above, according to the fixing structure of the fuel cell stack 1 using the fixing rod 23, the fixing rod 23 is inserted into each of a large number of stacked separators 8, and the displacement of the separator 8 due to thermal distortion of power generation, that is, the movement in the surface direction. Therefore, in the high temperature atmosphere during power generation, it is possible to prevent the power generation cells 5 being pressed and sandwiched between the separators 8 from being subjected to thermal stress in the surface direction and to prevent the power generation cells 5 from being damaged. it can. Thereby, the lifetime of the power generation cell 5 is improved, and a highly reliable fuel cell stack 1 that can obtain stable power generation performance can be realized.

The structure of the fuel cell stack to which this invention was applied is shown, (a) is a top view, (b) is a side view. The AA arrow directional view of FIG.

Explanation of symbols

1 Fuel cell stack (solid oxide fuel cell)
5 Power generation cell 8 Separator 22 Through hole 23 Fixed rod

Claims (4)

In the flat plate type fuel cell stack in which the power generation cells and the separators are alternately stacked, and this stacked body is configured by weighting from the stacking direction,
A fuel cell stack, wherein a plurality of through holes penetrating in the stacking direction are provided in each of the separators, and a fixing rod for restricting movement in the surface direction of the separator due to thermal strain during operation is inserted into the through holes. The fuel cell stack according to claim 1, wherein the power generation cell and the separator are stacked in a vertical direction. The fuel cell stack according to claim 1, wherein a thermal expansion coefficient of the fixing rod is smaller than a thermal expansion coefficient of the separator. The fuel cell stack according to any one of claims 1 to 3, wherein alumina or silica is used as a material of the fixing rod.

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