JP2013157179A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell in which local stress concentration between a fuel cell body and a collector is reduced.SOLUTION: The fuel cell includes: a flat plate-like fuel cell body formed by laminating an air electrode layer, an electrolyte layer, and a fuel electrode layer, wherein a surface of one of the air electrode layer and the fuel electrode layer is a first main surface; and a flat plate-like collector which is in contact with the first main surface of the fuel cell body and is laminated in the laminating direction. That region of the collector which corresponds to the first main surface has a rectangular boundary having chamfered corners.

Description

  The present invention relates to a fuel cell.

Development of fuel cells is underway as a power generator. For example, a solid oxide fuel cell using a solid oxide as an electrolyte (hereinafter also referred to as “SOFC” or simply “fuel cell”) is known. The SOFC has, for example, a stack (fuel cell stack) in which a large number of fuel cell main bodies each provided with a fuel electrode and an air electrode are stacked on each surface of a plate-shaped solid electrolyte body. Electric power is generated by supplying a fuel gas and an oxidant gas (for example, oxygen in the air) to the fuel electrode and the air electrode, respectively, and causing a chemical reaction through the solid electrolyte body (see, for example, Patent Document 1). .
At this time, the electric power generated in the fuel cell body is output using a conductive current collector that contacts the fuel cell body.

JP 2009-99308 A

However, during assembly and operation of the fuel cell stack, stress is concentrated locally between the fuel cell body (fuel electrode or air electrode) and the current collector (for example, where corners are formed). The battery cell body may break.
An object of this invention is to provide the fuel cell which reduced the local stress concentration between a fuel cell main body and a collector.

  The fuel cell according to the present invention is formed by laminating an air electrode layer, an electrolyte layer, and a fuel electrode layer, and the surface of one of the air electrode layer and the fuel electrode layer is defined as a first main surface. A fuel cell body comprising: a flat plate fuel cell body; and a flat plate current collector that is in contact with the first main surface of the fuel cell body and stacked in the stacking direction; A region corresponding to the first main surface of the current collector has a rectangular boundary with chamfered corners.

  The area corresponding to the first main surface of the current collector is an area where the current collector is in contact with the first main surface, and an area between current collectors when there are a plurality of current collectors. A single continuous area. In addition, this region has a rectangular boundary with chamfered corners. For example, the corners of the current collector are chamfered. As a result, the concentration of stress at the corners of the region where the current collector and the fuel cell main body come into contact is alleviated, and cracking of the fuel cell main body can be reduced.

(1) The current collector in contact with the first main surface is composed of a plurality of first single bodies, and boundaries between regions corresponding to the first main surfaces are the plurality of first single bodies. May be defined by
That is, the current collector arranged on the air electrode or fuel electrode side may be constituted by a plurality of single units. In this case, since this region has a rectangular boundary with chamfered corners, stress concentration at the corners is alleviated.

(2) The surface of the air electrode layer of the fuel cell body and the other layer of the fuel electrode layer is a second main surface, and is in contact with the second main surface of the fuel cell body, A flat plate-like second current collector laminated in a direction, and a region corresponding to the second main surface of the second current collector is a rectangular shape with chamfered corners. It may have a boundary.

  The region corresponding to the second main surface of the second current collector is an area where the second current collector is in contact with the second main surface and a plurality of second current collectors. In some cases, it includes an area between current collectors and refers to one continuous area. In addition, this region has a rectangular boundary with chamfered corners. For example, the corners of the second current collector are chamfered. As a result, the concentration of stress at the corner of the region where the second current collector and the fuel cell body contact each other is alleviated, and cracking of the fuel cell body can be reduced.

(3) In (2), the second current collector in contact with the second main surface is composed of a plurality of second single bodies, and the boundary of the region corresponding to the second main surface is , May be defined by the plurality of second single units.
Even in this case, similarly, this region has a rectangular boundary with chamfered corners, so that stress concentration at the corners is alleviated.

(4) The chamfering can be a C chamfering. By chamfering the corner of the region corresponding to the second main surface of the second current collector, stress concentration at the corner is reduced. At this time, the amount of chamfering is preferably 5% or more of the short side length of the rectangular shape.

(5) The chamfer can be an R chamfer. By chamfering the corner of the region corresponding to the second main surface of the second current collector, the stress concentration at the corner is reduced. At this time, the amount of chamfering is preferably 10% or more of the short side length of the rectangular shape.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell which reduced local stress concentration between a fuel cell main body and a collector can be provided. That is, the problem that stress is likely to be concentrated at the corner of the fuel cell main body that is in contact with the air electrode or the fuel electrode and the current collector is improved, and cell cracking is reduced.

1 is a perspective view illustrating a solid oxide fuel cell 10 according to a first embodiment. 1 is a schematic cross-sectional view of a solid oxide fuel cell 10. FIG. 3 is a cross-sectional view of a fuel cell 40. FIG. 4 is a plan view illustrating a current collector 45 disposed in the interconnector 41. FIG. 4 is a plan view illustrating a current collector 46 disposed in the interconnector 43. FIG. It is a figure showing area | region A1 of C chamfering. It is a figure showing area | region A1 of R chamfering. It is the figure showing area | region A1 of other chamfering. It is a graph showing an example of the relationship between the chamfering amount M and the stress F in C chamfering. It is a graph showing an example of the relationship between chamfering amount M and stress F in R chamfering. It is a figure showing the relationship between the external shape of the collector 45G and area | region A1, when changing the number of the collectors 45 which comprise the collector 45G. It is a figure showing the relationship between the external shape of the collector 45G and area | region A1, when changing the number of the collectors 45 which comprise the collector 45G.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. The embodiments of the present invention are not limited to the following embodiments, and various forms can be adopted as long as they belong to the technical scope of the present invention.

  FIG. 1 is a perspective view showing a solid oxide fuel cell 10 according to an embodiment of the present invention. The solid oxide fuel cell 10 is a device that generates power by receiving supply of a fuel gas (for example, hydrogen) and an oxidant gas (for example, air (specifically, oxygen in the air)).

  The solid oxide fuel cell (fuel cell stack) 10 includes end plates 11 and 12 and fuel cells 40 (1) to 40 (4) stacked, and bolts 21 and 22 (22a and 22b) and 23 (23a, 23b) and the nut 35. Here, four fuel cells 40 (1) to 40 (4) are stacked for easy understanding, but in general, about 20 fuel cells 40 are often stacked.

The end plates 11 and 12 and the fuel cells 40 (1) to 40 (4) have through holes 31 and 32 (32a and 32b) corresponding to the bolts 21 and 22 (22a and 22b) and 23 (23a and 23b), 33 (33a, 33b).
The end plates 11 and 12 are holding plates that press and hold the stacked fuel battery cells 40 (1) to 40 (4), and output current from the fuel battery cells 40 (1) to 40 (4). It is also a terminal.

  FIG. 2 is a schematic cross-sectional view of the solid oxide fuel cell 10. FIG. 3 is a cross-sectional view of the fuel battery cell 40.

  As shown in FIG. 3, the fuel cell 40 is a so-called fuel electrode support membrane type fuel cell, and includes interconnectors 41 and 43, a frame portion 42, a cell body (fuel cell body) 44, a current collector. 45, (second) current collector 46.

  The interconnectors 41 and 43 are a pair of upper and lower conductive (for example, metal) plates that ensure conduction between the fuel cells 40 and block the gas flow path.

  In addition, only one interconnector (41 or 43) is disposed between the fuel cells 40 (because one interconnector is shared between two fuel cells 40 connected in series). . Further, in each of the uppermost and lowermost fuel cells 40 (1) and 40 (4), end plates 11 and 12 are arranged in place of the interconnectors 41 and 43.

  The frame part 42 has an opening 47. The inside of the opening 47 is kept airtight and is divided into an oxidant gas passage 48 and a fuel gas passage 49. The frame portion 42 includes insulating frames 51 and 55, an air electrode frame 52, a separator (its outer peripheral edge portion) 53, and a fuel electrode frame 54.

The insulating frames 51 and 55 are ceramic frames that electrically insulate the interconnectors 41 and 43, and are disposed on the air electrode 56 side and the fuel electrode 58 side. Note that one of the insulating frames 51 and 55 may be omitted.
The air electrode frame 52 is a metal frame disposed on the oxidant gas flow path 48 side.
The separator 53 is a metal frame that joins the cell main body 44 and blocks the oxidant gas passage 48 and the fuel gas passage 49.
The fuel electrode frame 54 is a metal frame disposed on the fuel gas flow path 49 side.

  The frame part 42 has through holes 31, 32 (32a, 32b), 33 (33a, 33b) corresponding to the bolts 21, 22 (22a, 22b), 23 (23a, 23b).

  The cell body (fuel cell body) 44 is formed by laminating an air electrode (also referred to as a cathode or an air electrode layer) 56, a solid electrolyte body (electrolyte layer) 57, and a fuel electrode (also referred to as an anode or fuel electrode layer) 58. Composed. An air electrode 56 and a fuel electrode 58 are disposed on the oxidant gas channel 48 side and the fuel gas channel 49 side of the solid electrolyte body 57, respectively. As the air electrode 56, perovskite oxides, various noble metals, and cermets of noble metals and ceramics can be used. As the solid electrolyte body 57, materials such as YSZ, Sc, SZ, SDC, GDC, and perovskite oxide can be used. As the fuel electrode 58, Ni and a cermet of Ni and ceramic can be used.

  As shown in FIGS. 2 and 3, in the upper part of the interconnectors 41 and 43, the through hole 32a and the opening 47 are spatially connected by a notch 61 to allow the oxidant gas to flow between them. . In the lower part of the interconnectors 41 and 43, the through hole 33a and the opening 47 are spatially connected by a notch 62, and the fuel gas can flow between them.

The current collector 45 on the air electrode 56 side is for ensuring electrical connection between the cell main body 44 (air electrode 56) and the interconnector 41. For example, the current collector 45 is made of a dense metal material such as SUS (stainless steel). Become.
The current collector 46 on the fuel electrode 58 side is for ensuring electrical connection between the cell main body 44 (fuel electrode 58) and the interconnector 43. For example, nickel can be used so that fuel gas can pass therethrough. It is made of a porous metal material made of or the like.

  Here, an adhesion layer made of, for example, a silver palladium alloy (palladium content of 1 to 10 mol%) or the like may be formed between the air electrode 56 and the current collector 45. The adhesion layer ensures the electrical connection between the air electrode 56 and the current collector 45 and allows the air electrode 56 and the current collector 45 to be joined.

  This adhesion layer can be formed as follows, for example. Specifically, an Ag-Pd conductive paste containing Ag-Pd powder (Pd: 1 mol%), ethyl cellulose, and an organic solvent is applied to the surface of the current collector 45 (the surface on the air electrode 56 side) (or Print. This conductive paste removes ethyl cellulose and the like at the operating temperature of the solid oxide fuel cell 10 (for example, 700 ° C.) and softens the Ag—Pd alloy to adhere to the air electrode 56 and the current collector 45. It becomes a state to do. When the operation is stopped, the adhesion layer is firmly joined and integrated with the air electrode 56 and the current collector 45. In this way, an adhesion layer is formed between the air electrode 56 and the current collector 45, and the reliability of conduction between them can be improved.

The bolt 21 is a member for pressing and fixing the stacked end plates 11 and 12 and the fuel cells 40 (1) to 40 (4).
The bolts 22 (22a, 22b) are members for circulating the fuel gas, and have holes (fuel gas flow paths) through which the fuel gas flows. The bolts 23 (23a, 23b) are members for circulating the oxidant gas, and have holes (oxidant gas flow paths) through which the oxidant gas flows.

Fuel gas and oxidant gas flow into and out of the fuel cell 40 as follows.
That is, the fuel gas flows into and out of the fuel gas channel 49 from the holes in the bolt 22 (22a, 22b). Oxidant gas flows into and out of the oxidant gas flow path 48 from the holes in the bolts 23 (23a, 23b).

4 and 5 are plan views showing the current collector 45 and the second current collector 46 disposed in the interconnectors 41 and 43, respectively. A plurality of current collectors 45 and a plurality of second current collectors 46 are disposed on the interconnectors 41 and 43.
In order to more clearly distinguish each of the individual current collectors 45 and the second current collectors 46 from the plurality of current collectors 45 and the second current collectors 46, the following names can also be used. And That is, the individual current collector 45 and the second current collector 46 are also referred to as a first single unit 45 and a second single unit 46. The plurality of current collectors 45 and the entire second current collector 46 are referred to as a current collector 45G and a second current collector 46G.

  At this time, the outer circumferences (contour lines) of the plurality of current collectors 45 as a whole (current collector 45G) and the second current collector 46 as a whole (second current collector 46G) define the regions A1 and A2. That is, the region A1 includes an area occupied by the first single unit 45 and an area between the first single units 45, and the region A2 includes an area occupied by the second single unit 46 and the second single unit 46. It is comprised including the area between each other.

  Specifically, each of the areas A1 and A2 has a substantially rectangular shape, but does not have the areas A11 and A21 at the corners of the four corners. That is, the areas A1 and A2 have rectangular “boundaries” with chamfered corners. The current collector 45G and the second current collector 46G are arranged inside the “boundary” so as not to enter the regions A11 and A21.

  Thus, the corners of the regions A1 and A2 corresponding to the main surfaces of the current collector 45G and the second current collector 46G on the cell body 44 are chamfered. As a result, the current collector 45G and the second current collector 46G alleviate stress concentration at the corners of the regions A1 and A2 corresponding to the fuel cell body 44 (air electrode, fuel electrode), and the fuel cell. The crack of the main body 44 can be reduced.

  In this embodiment, the corners of both the regions A1 and A2 are chamfered. However, even if the corners of only one of the regions A1 and A2 are chamfered, stress concentration is reduced, and the fuel cell main body 44 is cracked. Can be reduced.

  6 to 8 are diagrams showing the region A1 excluding the current collector 45 for easy understanding. In FIG. 6, the corners of the region A1 are chamfered linearly (C chamfering). In FIG. 7, the corners of the region A1 are chamfered in an arc shape (R chamfering). In FIG. 8, the corners of the area A1 are chamfered into a shape combining two straight lines (other chamfers).

As shown in FIGS. 6 and 7, the stress concentration is alleviated regardless of whether the chamfered shape is a C chamfer or an R chamfer. In this regard, even in the area A2, the concentration of stress is alleviated regardless of whether the chamfering shape is C chamfering or R chamfering.
Furthermore, as shown in FIG. 8, the chamfer has an intermediate shape such as a straight line or an arc, for example, a shape in which a plurality of straight lines are connected (a shape in which two straight lines are connected in FIG. 8), or a straight line and an arc are connected Even with the shape, the stress concentration is reduced.

Here, the chamfering amount M (%) can be defined by the following equation (1).
M = (ΔL / L) * 100 (1)
L: Side length in region A1 ΔL: Width of chamfered region A11

  As shown in FIGS. 6 to 8, this definition can be applied to either C chamfering or R chamfering. Here, the region A1 is substantially square (the lengths of adjacent sides are equal). When the region A1 is substantially rectangular (having long sides and short sides having different lengths), the length of the short side is used as the length L.

9 and 10 are graphs showing an example of the relationship between the chamfering amount M (%) and the stress F (%) in each of the C chamfering and the R chamfering. The stress F (%) is defined by the following formula (2).
F = (F1 / F0) * 100 (2)
F1: Maximum value of stress in region A1 when chamfered F0: Maximum value of stress in region A1 when not chamfered

Here, the simulation results under the following conditions are shown.
The chamfering amount M is the same in both the areas A1 and A2. The areas A1 and A2 are each composed of one current collector 45 and 46 (corresponding to FIG. 11A described later, the shapes of the areas A1 and A2). And the shape of the outer periphery of the current collectors 45 and 46 of one coincide with each other)
・ Pressure is applied to the current collectors 45 and 46 by applying pressure in the negative Z direction in FIG.

As shown in FIG. 9, in the case of C chamfering, the stress F increases as the chamfering amount M increases (0 to 5%), and the degree of stress relaxation increases. The effect is seen. Therefore, it is preferable that the chamfering amount M is 5% or more.
On the other hand, the upper limit of the amount C of chamfering is not particularly specified because of the electrical characteristics (current collection area), but can be, for example, 20% or less.

As shown in FIG. 10, in the case of R chamfering, the stress F increases with increasing chamfering amount M (0 to 10%), and the degree of stress relaxation increases. The effect is seen. Therefore, the chamfering amount M is preferably 10% or more.
On the other hand, the upper limit of the amount C of chamfering is not particularly specified because of the electrical characteristics (current collection area), but can be, for example, 25% or less.

11 and 12 show the relationship between the outer shapes of the current collector 45G and the second current collector 46G and the areas A1 and A2 when the numbers of the current collector 45 and the second current collector 46 are changed. FIG.
In FIG. 11A, the number of current collectors 45G and current collectors (first single unit) 45 and (second single unit) 46 constituting the second current collector 46G is 1 (one single unit). Yes, the outer shapes of the current collector 45 and the second current collector 46 coincide with the areas A1 and A2.
In each of FIGS. 11B and 11C, two or three current collectors (first single body) 45 and (second single body) 46 are arranged in the vertical direction of the drawing, and current collector 45G, second Current collector 46G.

In each of FIGS. 12A to 12C, the current collectors 45G and 46G are configured by arranging a plurality of current collectors 45 and a second current collector 46 as follows.
(A) Two each vertically and horizontally (total of 4)
(B) 3 vertically and 2 horizontally (6 in total)
(C) 3 vertically and 9 (total 9)

  As described above, an arbitrary number of current collectors 45 and second current collectors 46 can correspond to the areas A1 and A2, respectively. That is, the number of the first single body 45 and the second single body 46 constituting the current collector 45G and the second current collector 46G may be any number. In addition, regardless of whether the current collector 45G or the second current collector 46G, the regions A1 and A2 have rectangular boundaries with chamfered corners, so that stress concentration at the corners is reduced. Alleviated.

(Other embodiments)
Embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.
In the above embodiment, the chamfering shape and the chamfering amount M at the four corners are the same, but a part or all of the chamfering shape or the chamfering amount M may be different.

DESCRIPTION OF SYMBOLS 10 Solid oxide fuel cell 11, 12 End plate 21-23 Bolt 31-33 Through hole 35 Nut 40 Fuel cell 41, 43 Interconnector 42 Frame 44 Cell main body 44 Fuel cell main body 45 Current collector, 1st Single body 46 (second) current collector, second single body 47 opening 48 oxidant gas flow path 49 fuel gas flow path 51, 55 insulating frame 52 air electrode frame 53 separator 54 fuel electrode frame 56 air electrode 57 solid electrolyte Body 58 Fuel electrode 61, 62 Notch

Claims (8)

A flat plate fuel cell main body, which is formed by laminating an air electrode layer, an electrolyte layer, and a fuel electrode layer, and has a surface of one of the air electrode layer and the fuel electrode layer as a first main surface. When,
A flat plate current collector that contacts the first main surface of the fuel cell body and is stacked in the stacking direction;
A fuel cell comprising:
The region corresponding to the first main surface of the current collector has a rectangular boundary with chamfered corners. The current collector in contact with the first main surface is composed of a plurality of first single bodies;
2. The fuel cell according to claim 1, wherein a boundary of a region corresponding to the first main surface is defined by the plurality of first single bodies. The surface of the air electrode layer of the fuel cell body and the other layer of the fuel electrode layer is a second main surface,
A flat plate-like second current collector that is in contact with the second main surface of the fuel cell body and is stacked in the stacking direction;
3. The fuel cell according to claim 1, wherein a region corresponding to the second main surface of the second current collector has a rectangular boundary with chamfered corners. The second current collector in contact with the second main surface is composed of a plurality of second single bodies;
4. The fuel cell according to claim 3, wherein a boundary of a region corresponding to the second main surface is defined by the plurality of second single bodies. The fuel cell according to any one of claims 1 to 4, wherein the chamfering is C chamfering. The fuel cell according to claim 5, wherein the amount of the chamfer is 5% or more of the length of the short side of the rectangular shape. The fuel cell according to any one of claims 1 to 4, wherein the chamfering is R chamfering. The fuel cell according to claim 7, wherein an amount of the chamfer is 10% or more of a length of a short side of the rectangular shape.

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