JP2003346871A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the temperature difference between respective power generating cells in the stacked direction as much as possible and to maintain prescribed power generation. <P>SOLUTION: This fuel cell stack 10 is provided with the power generating cells 12, power collecting electrodes 14 and 16 electrically integrally connected to the prescribed number of power generating cells 12, first cooling cells 18 cooling the power generating cells 12 by cooling liquid, and sheet members 31 corresponding to the outsides of an anode side electrode 28 and a cathode side electrode 26 and disposed in a space formed between a joining body 30 and first/second separators 32 and 34 in the outside of a seal member 53. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a joined body comprising an electrolyte sandwiched between an anode electrode and a cathode electrode. The joined body is sandwiched between separators, and fuel gas is supplied to the anode electrode. The present invention relates to a fuel cell stack including a power generation cell for supplying an oxidizing gas to the cathode while supplying the gas.

[0002]

2. Description of the Related Art For example, a phosphoric acid fuel cell (PAFC)
Is a joined body (electrolyte layer / electrode layer) composed of an anode side electrode and a cathode side electrode mainly composed of carbon, on both sides of an electrolyte layer in which concentrated phosphoric acid is impregnated in porous silicon carbide (matrix). An electrode assembly is provided with a power generation cell constituted by sandwiching the electrode assembly with a separator (bipolar plate). Normally, a predetermined number of the power generation cells are stacked and used as a fuel cell stack.

On the other hand, a solid polymer fuel cell (SPFC)
Employs an electrolyte membrane composed of a polymer ion exchange membrane (cation exchange membrane). Similarly, a power generation cell provided with a separator (electrolyte membrane / electrode assembly) composed of the electrolyte membrane and a separator is provided. A predetermined number of the fuel cells are stacked and used as a fuel cell stack.

[0004] In this type of fuel cell stack, a fuel gas supplied to the anode side electrode, for example, a gas mainly containing hydrogen (hereinafter also referred to as a hydrogen-containing gas) is ionized on the catalyst electrode. It moves to the cathode side via the electrolyte. The electrons generated during that time are taken out to an external circuit and used as DC electric energy.
Since an oxidant gas, for example, a gas mainly containing oxygen or air (hereinafter also referred to as an oxygen-containing gas) is supplied to the cathode side electrode, hydrogen ions, electrons, And oxygen react to produce water.

By the way, in the above-mentioned fuel cell, an optimum operating temperature for exhibiting effective power generation performance is set. For example, in the case of a phosphoric acid fuel cell,
° C, and 60 ° C to 90 ° C for the polymer electrolyte fuel cell.
It is. For this reason, it is necessary to maintain the power generation cell at a desired operating temperature, and various cooling structures have conventionally been employed. Generally, a structure is known in which a passage for a cooling medium is formed in a separator constituting a fuel cell stack, and a cooling medium such as water is supplied to the passage to cool a power generation cell.

[0006]

In this case, in water used as a cooling medium or a general cooling medium (cooling liquid) used in a cooling structure for an automobile, impurities such as ions and metal additives are contained. The cooling medium itself has conductivity. On the other hand, even when deionized water or pure water is used as a cooling medium, metal or the like is mixed by circulating through a cooling system pipe or a radiator during operation, and conductivity is imparted to the cooling medium.

However, in the fuel cell stack, electrons generated in each power generation cell are extracted from the current collecting electrodes at both ends of the stack. Electricity flows through As a result, a problem has been pointed out that electricity flows to the cooling system piping, the radiator, and the like via the cooling medium, and a ground fault or a liquid fault occurs, thereby lowering the output of the entire fuel cell stack.

Accordingly, the present applicant has proposed a fuel cell stack that can reliably prevent leakage of electricity through a cooling medium, and that can maintain effective power generation performance with a simple configuration. (See JP-A-2001-332288).

In this fuel cell stack, a cooling cell is interposed between the current collecting electrodes, and a cooling medium supplied to the cooling cell is electrically connected to the power generating cell and the current collecting electrode via an insulating mechanism. And the power generation cells arranged with the cooling cell interposed therebetween or the power generation cells and the current collecting electrode are electrically connected to each other via a conductive mechanism. As a result, it is possible to reliably prevent the occurrence of a ground fault or a liquid shortage through the cooling medium, to effectively prevent a decrease in the output of the entire fuel cell stack, and to maintain a desired power generation function. Become.

In the fuel cell stack, as shown in FIG. 8, a plurality of sets of power generation cells 1 are stacked in the direction of arrow A, and each power generation cell 1 sandwiches the joined body 2 with the joined body 2. A set of separators 3. The joined body 2 includes an electrolyte part (including an electrolyte layer or an electrolyte membrane) 4
Are provided on both sides. In the power generation cell 1,
One set of the separator 3 and the joined body 2 are sealed by an electrically insulating sealing member 6 interposed along the outer peripheral portion of the electrode portion 5.

However, in the above configuration, a space 7 exists between the separator 3 and the electrolyte portion 4 on the outer side of the seal member 6, and the air in the space 7 acts as a heat insulating layer, and There is a problem that heat transfer in the direction is not smoothly performed. As a result, a problem has been pointed out that the temperature difference between the power generation cells 1 is increased, and the power generation performance is reduced.

[0012] Further, the fuel cell stack is tightened with bolts between backup plates arranged at both ends. For this reason, when each member expands in the stacking direction with a rise in temperature during power generation of the power generation cell 1, the joined body 2
The pressure acting in the film thickness direction (lamination direction) increases. Thereby, phosphoric acid, which is an electrolyte, is particularly likely to seep out from the electrolyte layer in which polybenzimidazole is impregnated with phosphoric acid, and the performance of the power generation cell 1 may be deteriorated.

The present invention solves this kind of problem, and it is possible to reduce the temperature difference between the power generation cells in the stacking direction as much as possible and to maintain a desired power generation performance. An object is to provide a fuel cell stack having a compact configuration.

[0014]

In the fuel cell stack according to the first aspect of the present invention, a sheet member is formed in a space corresponding to the outer periphery of the anode and the cathode and formed between the assembly and the separator. Is arranged. Thereby, the sheet member is arranged in the space where the air, which is the heat insulating layer, was present, and heat transfer between the power generation cells in the stacking direction is favorably performed. Therefore, the temperature difference between the power generation cells in the stacking direction is reduced, so that the power generation performance of the power generation cells can be made closer to the maximum performance, and the output of the entire fuel cell stack can be improved.

Further, when the temperature of the fuel cell stack rises to the operating temperature due to the power generation of the power generation cells, even if each member expands in the stacking direction, the pressure acting on the joined body in the film thickness direction is reduced by the sheet member. Is done. So, for example,
Phosphoric acid, which is an electrolyte, can be effectively prevented from seeping out of the electrolyte layer in which polybenzimidazole is impregnated with phosphoric acid, and a decrease in power generation performance can be avoided.

In the fuel cell stack according to the second aspect of the present invention, since the sheet member is made of metal and has good thermal conductivity, the temperature difference in the stacking direction of the fuel cell stack can be effectively reduced. Reduced.

Further, in the fuel cell stack according to claim 3 of the present invention, the sheet member is made of a stainless alloy, an aluminum alloy or a copper alloy. Therefore, the thermal conductivity is further improved, and the temperature difference in the stacking direction of the fuel cell stack is reduced as much as possible.

Further, in the fuel cell stack according to a fourth aspect of the present invention, a cooling gas for cooling the power generation cells is supplied, and a predetermined number of the power generation cells are interposed between the fuel cells and the cooling cells. An auxiliary cooling cell is provided between the electrodes, and the power generation cell is cooled via cooling gas supplied to the auxiliary cooling cell.

Therefore, by supplying the cooling gas to the auxiliary cooling cell, the high-temperature power generation cell near the auxiliary cooling cell can be effectively cooled. This allows
The temperature of each power generation cell is adjusted near the optimum operation temperature, and the temperature difference between the power generation cells along the stacking direction is reduced, so that each power generation performance of the power generation cell can be effectively improved.

In addition, at the time of high output, an auxiliary cooling cell is used together with the cooling cell to cool only the power generation cells that need to be cooled. Therefore, there is no need to use a large heat exchanger for cooling, and the heat exchanger can be effectively reduced in size.

[0021]

FIG. 1 is a side view showing a schematic configuration of a fuel cell stack 10 according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view of the fuel cell stack 10. FIG. 3 is an enlarged sectional view of a main part of the fuel cell stack 10.

The fuel cell stack 10 includes power generation cells 12, and a predetermined number of the power generation cells 12 are stacked in the direction of arrow A. At both ends in the stacking direction of the power generation cell 12, current collecting electrodes 14 and 16 that are electrically connected integrally to the power generation cell 12 are arranged. A predetermined number of first cooling cells 18 are interposed between the current collecting electrodes 14 and 16, and a predetermined number of power generation cells 1 are interposed between the first cooling cells 18.
2 between the current collecting electrodes 14 and 16
A cooling cell 20 is interposed.

Outside the current collecting electrodes 14 and 16, insulating plates 19a and 19b are interposed and end plates 21a and
21b is arranged. End plates 21a, 21b
Are fastened by tie rods or the like via a backup plate (not shown), and the power generation cell 12, the current collecting electrodes 14, 16 and the first and second cooling cells 18, 20
Are integrally clamped and held in the direction of arrow A. A load 22 such as a motor is connected to the current collecting electrodes 14 and 16 (see FIG. 1).

As shown in FIGS. 2 and 3, the power generation cell 12 is made of silicon carbide porous or basic polymer, for example,
A joined body (electrolyte layer / electrode) in which a cathode-side electrode 26 and an anode-side electrode 28 are arranged with an electrolyte layer 24 made of polybenzimidazole impregnated with phosphoric acid and a frame-shaped member (described later) interposed therebetween 30). The cathode side electrode 26 and the anode side electrode 28
For example, a gas diffusion layer made of porous carbon paper or the like, which is a porous layer, and an electrode catalyst layer in which porous carbon particles having a platinum-based catalyst supported on the surface are uniformly applied to the surface of the gas diffusion layer. , And the electrode catalyst layer is joined to the electrolyte part 24.

On both sides of the joined body 30, first and second separators 32 and 34 made of a conductive material, for example, a dense carbon material or metal, are disposed with a sheet member 31 interposed therebetween. The power generation cell 12 is constituted by the body 30, the sheet member 31, and the first and second separators 32 and.

The power generation cell 12 has a fuel gas supply communication passage 36a for passing a fuel gas such as a hydrogen-containing gas and a oxidizing gas as an oxygen-containing gas at the lower portion of both ends in the lateral direction (the direction of arrow B). Oxidant gas supply communication passage 38 for
a. On the upper side of both ends of the power generation cell 12 in the lateral direction,
Fuel gas discharge communication passage 36b for passing fuel gas
And an oxidizing gas discharge communication passage 38b for allowing the oxidizing gas to pass therethrough are provided at diagonal positions with respect to the fuel gas supply communication passage 36a and the oxidizing gas supply communication passage 38a.

Notched portions 40a and 40b are provided at the center of both ends in the lateral direction of the power generation cell 12, and a refrigerant supply line 46 and a refrigerant discharge line 48 are arranged in the notched portions 40a and 40b. . A cooling liquid supply passage 46a is formed in the coolant supply line 46, while a coolant discharge line 48 is formed.
A cooling liquid discharge communication passage 48a is formed therein.

The cathode electrode 26 of the first separator 32
The oxidizing gas supply passage 38a and the oxidizing gas discharge communicating passage 38b are formed at both sides thereof with an oxidizing gas passage 50 for supplying the oxidizing gas to the cathode electrode 26 at both ends thereof. (See FIGS. 2 and 3). A fuel gas supply communication passage 36a and a fuel gas discharge communication passage 36b are provided on the surface of the second separator 34 facing the anode 28.
A fuel gas flow path 51 is provided at both ends thereof for supplying a fuel gas to the anode 28. The oxidizing gas flow path 50 and the fuel gas flow path 51 adopt a flow path structure that guides the oxidizing gas and the fuel gas vertically upward while meandering in the horizontal direction (the direction of arrow B).

The surfaces of the first and second separators 32 and 34 facing the cathode side electrode 26 and the anode side electrode 28 are provided with a fuel gas supply passage 36a, an oxidant gas supply passage 38a, and a fuel gas discharge passage 36b. In order to hermetically seal the oxidizing gas discharge communication passage 38b, the oxidizing gas flow passage 50, and the fuel gas flow passage 51, an electrically insulating sealing member 53 is provided by, for example, baking.

The sheet member 31 is formed of a material having a large yield surface pressure in the compression direction, for example, a resin material such as polyethylene terephthalate, or a metal material such as a stainless alloy, an aluminum alloy or a copper alloy. In consideration of the thermal conductivity, the sheet member 31 may be made of a stainless steel alloy,
Aluminum or copper alloys are preferred. As shown in FIGS. 2 and 3, the sheet member 31 is arranged corresponding to the space outside the seal member 53 and has a thickness slightly smaller than the thickness of the cathode electrode 26 and the anode electrode 28. Is set to

As shown in FIG. 1, the first cooling cell 18
1 between the current collecting electrodes 14 and 16 in the fuel cell stack 10.
Every 0 cells, that is, 10 cells between the first cooling cells 18
The power generation cells 12 are arranged and stacked. This first
As shown in FIGS. 2 and 3, the first and second separators 32 and 34 disposed on both sides of the cooling cell 18 each have a single-sided gas passage having a flat surface on the first cooling cell 18 side. The separator structure is set. The same applies to the second cooling cell 20 described later. Other first
The oxidizing gas passage 50 and the fuel gas passage 51 are formed on both surfaces of the second separators 32 and 34.

As shown in FIGS. 3 and 4, the first cooling cell 18 includes a cooling liquid flow path plate 52, a lid plate 56 which is overlapped with the flow path plate 52 to form a cooling liquid passage 54, and The cooling liquid supplied to the cooling liquid passage 54 is supplied to the power generation cell 12 and the current collecting electrodes 14 and 16.
Sheet (insulation mechanism) 5 for electrical insulation from
8a, 58b and conductive plates 60a, 60b for electrically connecting the power generation cells 12 to each other (or the power generation cell 12 and the current collecting electrodes 14, 16) with the first cooling cell 18 interposed therebetween. Is provided. Channel plate 52
The lid plate 56 is made of, for example, a light alloy such as an aluminum alloy or a titanium alloy, or a dense carbon material.

The flow path plate 52 protrudes toward one surface toward the center of both ends in the width direction (the direction of arrow B) and has a cylindrical connecting portion 62.
a and 62b are provided, and a refrigerant supply line 46 and a refrigerant discharge line 48 are connected to the connection portions 62a and 62b.
A cooling liquid passage 54 is provided on the other surface side of the flow path plate 52.
Are formed, and a plurality of flow channel grooves 64 which constitute the cooling liquid passage 54 and are provided linearly in the direction of arrow B,
It communicates with the connecting portions 62a and 62b. Between the inlet of the flow channel 64 and the connecting portion 62a, and between the outlet of the flow channel 64 and the connecting portion 62b, the cooling liquid flows in the flow channel 64 uniformly and stably. Guides 66a, 66b
Is provided.

The lid plate 56 has cylindrical connecting portions 68a and 68b projecting outward on a surface opposite to the surface facing the flow path plate 52. These connection portions 68a, 68
“b” is provided at the same position as the connection portions 62a and 62b of the flow path plate 52, and is connected to the refrigerant supply pipe 46 and the refrigerant discharge pipe 48.

The conductive plates 60a and 60b are arranged so as to cover the flow path plate 52 and the lid plate 56, while the insulating sheets 58a and 58b are
0a and 60b are provided on the surface side in contact with the flow path plate 52 and the lid plate 56. The conductive plates 60a and 60b are made of a metal plate having excellent electrical conductivity such as a copper alloy.

The insulating sheets 58a and 58b are formed of an insulating material, for example, polytetrafluoroethylene (PTFE), and are adhered over the entire surfaces of the conductive plates 60a and 60b with an adhesive or the like. Note that an insulating material such as silicon grease may be applied to the conductive plates 60a and 60b instead of the insulating sheets 58a and 58b.

The upper ends of the conductive plates 60a and 60b are bent in the directions approaching each other to form a joint 7
0a and 70b are provided, and
Holes 72a and 72b are formed in the holes a and 70b. A fixing plate 74 is arranged so as to cover the mating portions 70a and 70b. A screw 76 is inserted from the fixing plate 74 into the holes 72a and 72b, and a nut 78 is screwed into the screw 76 to thereby form the conductive plate 60a. , 60b hold the flow path plate 52 and the lid plate 56.

The second cooling cell 20, as shown in FIG.
In the fuel cell stack 10, it is arranged between the first cooling cells 18 adjacent to each other, and every five cells between the current collecting electrodes 14 and 16 and the first cooling cells 18. Specifically, at the center between the first cooling cells 18 and between the current collecting electrodes 14 and 16 and the first cooling cells 18, five power generation cells 12 are arranged on both sides, respectively. 20 are stacked.

As shown in FIGS. 3 and 5, the second cooling cell 20 is provided with a flow path plate 8 for cooling gas (for example, air).
0, and a lid plate 84 that is superimposed on the flow path plate 80 to form a cooling air passage 82. The channel plate 80 and the lid plate 84 are formed of a light alloy material such as an aluminum alloy or a titanium alloy that is lightweight and has good thermal and electrical conductivity.

The cooling air passage 82 is provided on one surface 80a of the flow path plate 80, and includes a plurality of flow grooves 86 extending linearly in the vertical direction (the direction of arrow C).
An air inlet 90 provided with a guide 88 communicates with the lower end of the flow channel 86. The cooling air passage 82 extends in the lateral direction of the cathode electrode 26 and the anode electrode 28 (arrow B).
Direction) is set in the range of 60% to 70% of the width dimension.

In the lid plate 84, a chamber 92 communicating with the air inlet 90 is formed.
Communicate with The air inlet 94 is connected to a pipe 96 that has been subjected to electrical insulation processing. The channel plate 80 and the lid plate 84 are fixed to each other by a plurality of screws 98.

As shown in FIG. 2, the end plate 21a
A fuel gas inlet 100a communicating with the fuel gas supply communication passage 36a, a fuel gas outlet 100b communicating with the fuel gas discharge communication passage 36b, and an oxidizing gas inlet 102a communicating with the oxidizing gas supply communication passage 38a; An oxidizing gas outlet 102b communicating with the oxidizing gas discharge communication passage 38b is formed.

FIG. 6 is a schematic configuration diagram of a fuel cell system 110 incorporating the fuel cell stack 10 according to the first embodiment.

The fuel cell system 110 includes a fuel gas supply section 112 for supplying fuel gas to the fuel cell stack 10.
An oxidizing gas supply unit 114 for supplying an oxidizing gas to the fuel cell stack 10;
A cooling liquid supply unit 116 for supplying a cooling liquid (liquid cooling medium) to the fuel cell stack 10, and a cooling air supply unit 118 for supplying cooling air to the fuel cell stack 10.

The fuel gas supply unit 112 includes a high-pressure hydrogen storage source 120, and a first pressure reducing valve is connected to a fuel gas pipe 122 extending from the high-pressure hydrogen storage source 120 to a fuel gas supply communication passage 36 a in the fuel cell stack 10. 124 and a fuel gas flow controller 126 are provided.

The oxidizing gas supply section 114 includes a first compressor 128, and a second decompressed gas is supplied to the oxidizing gas pipe 130 from the first compressor 128 to the oxidizing gas supply communication passage 38 a in the fuel cell stack 10. A valve 131 and an oxidizing gas flow controller 132 are provided.

The cooling liquid supply section 116 includes a cooling liquid pipe 134 connecting the cooling liquid supply communication path 46a and the cooling liquid discharge communication path 48a in the fuel cell stack 10. The cooling liquid pipe 134 has a circulation pump. 136 and a relatively small heat exchanger 138 are provided.

The cooling air supply section 118 includes a second compressor 140, which is connected to a cooling air pipe 142 connected to the second cooling cell 20 constituting the fuel cell stack 10. This cooling air pipe 1
42, a third pressure reducing valve 144 and a cooling air flow controller 14
6 are provided.

The fuel cell stack 1 configured as described above
The operation of 0 will be described below in relation to the fuel cell system 110.

First, in the fuel cell system 110, the fuel gas supply unit 1 is operated in accordance with the required current of the load 22 such as a motor.
12 and the oxidizing gas supply unit 114 are controlled.
In the fuel gas supply unit 112, a high-pressure hydrogen storage source 120 is supplied through a first pressure reducing valve 124 and a fuel gas flow controller 126.
Supplies a predetermined amount of fuel gas (hydrogen gas or hydrogen-containing gas) to the fuel cell stack 10.

On the other hand, the oxidizing gas supply section 114
The flow rate of the oxygen-containing gas (hereinafter, also referred to as air), which is an oxidizing gas introduced through the compressor 128, is controlled through the second pressure reducing valve 131 and the oxidizing gas flow controller 132. For this reason, the fuel cell stack 10 includes
A predetermined amount of oxygen-containing gas is supplied.

As shown in FIG. 2, the end plate 21a
The fuel gas supplied to the fuel gas inlet 100a is supplied to the fuel gas flow path 51 formed in the second separator 34 via the fuel gas supply communication passage 36a. Therefore, the hydrogen-containing gas in the fuel gas is supplied to the anode 28 of the power generation cell 12, and the unused fuel gas is discharged to the fuel gas discharge communication passage 36b.

The air supplied to the oxidizing gas inlet 102a of the end plate 21a is introduced into the oxidizing gas passage 50 formed in the first separator 32 through the oxidizing gas supply communication passage 38a. . Therefore, while the oxygen-containing gas in the air is supplied to the cathode electrode 26, the unused air is discharged to the oxidizing gas discharge communication passage 38b. As a result, power is generated in the power generation cell 12, and power is supplied to the load 22 such as a motor (see FIG. 1).

As described above, when power is generated in the fuel cell stack 10, heat is generated with this power generation, and the temperature of each power generation cell 12 rises. The optimum operating temperature of the power generation cell 12 is, for example, 160 ° C. when the electrolyte part 24 in which the polybenzimidazole film is impregnated with phosphoric acid is used.
It is necessary not to exceed. Therefore, in the fuel cell system 110, as shown in FIG.
The pump 136 constituting 16 is driven.

Under the action of the pump 136, the cooling liquid supplied to the cooling liquid supply passage 46 a of the fuel cell stack 10 is formed between the flow path plate 52 and the lid plate 56 constituting the first cooling cell 18. Is introduced into the cooling liquid passage 54. As shown in FIG. 4, in the flow channel plate 52, a cooling liquid is introduced into the flow channel 64 from the connection portion 62 a, and the cooling medium passes through the flow channel 64 and the power generation cell 1.
After cooling the power generation surface of No. 2, it is discharged to the cooling liquid discharge communication passage 48a.

The cooling liquid drawn from the cooling liquid discharge communication passage 48a to the cooling liquid pipe 134 takes heat from each of the power generation cells 12 and has a relatively high temperature, and is introduced into the heat exchanger 138 (FIG. 6). reference). In the heat exchanger 138, heat is released from the cooling liquid, and the cooling liquid whose temperature has decreased is circulated again to the first cooling cell 18.

In this case, in the first cooling cell 18, the flow path plate 52 forming the cooling liquid passage 54 and the lid plate 5
6 are covered with conductive plates 60a and 60b provided with insulating sheets 58a and 58b (see FIG. 3). For this reason, the cooling liquid passage 54 is electrically insulated from the power generation cell 12, and the electricity generated in the power generation cell 12 does not flow into the cooling liquid in the cooling liquid passage 54.

In addition, even if the cooling liquid is provided with conductivity, the power generation performance of the power generation cell 12 is not affected. Therefore, a general water-based cooling medium containing ions or metal-based additives can be used, and there is an advantage that the entire facility is simplified and economical.

In the fuel cell stack 10, when a high load is required and a high output state is generated, the heat generation of each power generation cell 12 increases. At this time, the liquid cooling medium and the small heat exchanger 138, that is, the first cooling cell 18
Before the maximum temperature of all the power generation cells 12 cannot be maintained below the optimum operation temperature by only the above, the cooling air supply unit 118 is driven to supply the cooling air to the second cooling cells 20 (see FIG. 6).

In the cooling air supply section 118, after the flow rate of the cooling air introduced through the second compressor 140 is adjusted through the third pressure reducing valve 144 and the cooling air flow rate controller 146, the cooling air is supplied to the second cooling air supply section 118. Pipe 9 constituting cell 20
6 to the air inlet 94.

As shown in FIGS. 3 and 5, the cooling air is supplied from the air inlet 94 to the air inlet 90 through the chamber 92.
Will be introduced. The air introduction section 90 is provided with a cooling air passage 82 via a guide 88, and the cooling air is uniformly and stably introduced into the plurality of flow grooves 86 via the guide 88. And flows vertically upward. Thereby, the power generation cell 12 near the second cooling cell 20 is cooled.

Therefore, while maintaining the power generation cell 12 near the first cooling cell 18 at a temperature close to the optimum operating temperature,
The power generation cell 12 in the vicinity of the second cooling cell 20 can be cooled to the optimum operation temperature. Therefore, each power generation cell 1
The temperature of 2 is adjusted near the optimal operating temperature,
The temperature difference between the power generation cells 12 along the stacking direction is reduced, and the effect that each power generation performance of the power generation cells 12 can be effectively improved can be obtained.

In addition, at the time of high output, the first cooling cell 18
In addition, the second cooling cell 20 is used to cool only the power generation cells 12 that need to be cooled. For this reason, it is not necessary to use a large heat exchanger for cooling, and a relatively small heat exchanger 138 can cope well.

Furthermore, since the second cooling cell 20 uses cooling air, it does not use a conductive cooling liquid as in the first cooling cell 18. Therefore, there is no need to insulate between the cooling air and the power generation cell 12, and there is an advantage that the configuration of the second cooling cell 20 is effectively simplified.

Further, in the present embodiment, as shown in FIGS. 2 and 3, the outer periphery of the cathode side electrode 26 and the anode side electrode 28 is located between the joined body 30 and the first and second separators 32 and 34. The sheet member 31 is arranged in a space outside the seal member 53 corresponding to the above. For this reason, the joined body 30 and the first and second separators 32, 34
The sheet member 31 is disposed in the space where the air, which is the heat insulating layer, was present corresponding to the outside of the seal member 53 between the power generation cells. Heat transfer in the laminating direction between the layers 12 is performed well.

Therefore, each power generation cell 12 in the stacking direction
The temperature difference between the power generation cells 12 is further reduced, and the power generation performance of the power generation cells 12 can be made even closer to the maximum performance, and the output of the entire fuel cell stack 10 can be improved. In particular, by using a stainless alloy, an aluminum alloy, or a copper alloy having good thermal conductivity as the sheet member 31, each of the power generation cells 1 arranged in the stacking direction is used.
The thermal conductivity between the two is further improved, and the fuel cell stack 1
The effect that the temperature difference in the stacking direction of 0 is reduced as much as possible is obtained.

Further, the sheet member 31 is formed of a material having a large yield surface pressure in the compression direction, for example, a resin material such as polyethylene terephthalate or a metal material such as a stainless alloy, an aluminum alloy or a copper alloy. For this reason, the fuel cell stack 10
When the temperature rises to the operating temperature, even if each member expands in the laminating direction (the direction of arrow A), the pressure acting on the joined body 30 in the thickness direction of the joined body 30 is reduced by the sheet member 31.

Thus, for example, it is possible to effectively prevent the phosphoric acid, which is an electrolyte, from seeping out from the electrolyte layer in which phosphoric acid is impregnated in the polybenzimidazole film, and the power generation performance of the power generation cell 12 is reduced. Can be reliably avoided.

The relationship between the presence / absence of the sheet member 31 and the cell voltage was obtained using the fuel cell stack 10 according to the present embodiment (Example) and a fuel cell stack not using the sheet member 31 (Comparative Example). An experiment was performed to detect.

In the fuel cell stack 10 of the embodiment, thirty power generation cells 12 are stacked, and current collecting electrodes 14, 1 are provided at both ends.
6 and a polycarbonate or epoxy resin plate for insulation and heat insulation was placed outside the current collecting electrodes 14 and 16, and end plates 21 a and 21 b were further placed outside the plate. End plate 21
The fuel cell stack 10 was constructed by installing a disc spring and a backup plate (not shown) in a, and inserting and tightening a bolt between the backup plate and a backup plate (not shown) on the end plate 21b side.

The electrolyte layer constituting the electrolyte part 24 is formed from the weight of the polybenzimidazole film before phosphoric acid impregnation and the molecular weight per polybenzimidazole repeating unit.
The number of moles of the polybenzimidazole repeating unit in the polybenzimidazole film was previously calculated.

Then, the polybenzimidazole film having a thickness of 50 μm was immersed in an 85% phosphoric acid solution for 24 hours or more until the phosphoric acid concentration in the polybenzimidazole film reached equilibrium. Next, the polybenzimidazole film impregnated with phosphoric acid was taken out, vacuum-dried at 80 ° C., and the number of moles of phosphoric acid in the polybenzimidazole film after immersion was calculated from the weight and the molecular weight of phosphoric acid. .

From the number of moles of the polybenzimidazole repeating unit and the number of moles of phosphoric acid in the polybenzimidazole film, the number of phosphoric acid molecules per polybenzimidazole repeating unit was calculated. The number was 10.2.

On the other hand, the cathode 26 and the anode 28 were manufactured as follows.

First, a solution prepared by dispersing carbon fine particles and fine powder of polytetrafluoroethylene (hereinafter referred to as PTFE) in ethylene glycol is applied to one surface of a carbon paper having a thickness of 270 μm, followed by drying. By removing the ethylene glycol, a carbon / PTFE layer was formed. Further, after a porous carbon fine particle carrying a platinum alloy-based catalyst was moistened with pure water, it was mixed and stirred with ethylene glycol to obtain a supported catalyst / ethylene glycol solution.

The supported catalyst / ethylene glycol solution was applied to a carbon / PTFE formed on a carbon cloth surface.
The catalyst layer was formed by uniformly coating the layer by screen printing and removing ethylene glycol by drying to obtain an electrode with a gas diffusion layer. The layer thickness of the electrode with the gas diffusion layer after the formation of the catalyst layer was 300 μm. In the cathode 26 and the anode 28, the electrode area contributing to power generation was 268 cm ² .

Next, the polyimide film having a thickness of 25 μm was punched to form a frame member.
This frame-shaped member is overlapped so as to overlap the outer periphery of an electrolyte layer having substantially the same dimensions as the cathode-side electrode 26 and the anode-side electrode 28, and the cathode-side electrode 26 and the anode-side electrode are provided on both sides of the electrolyte layer. 28
Was arranged and pressurized and heated using a press device to integrate them. Thereby, the joined body (electrolyte layer / electrode joined body)
30 were formed.

On the other hand, the first and second separators 32, 3
In No. 4, a sealing member 53 was formed by applying a liquid sealing material and performing a drying process in order to seal the outer peripheral portion of the electrolyte layer. Outside the sealing member 53, both sides of the joined body 30 and the first and second separators 32, 3
The sheet members 31 are arranged on both sides of the frame member so as to fill the space between the four. The sheet member 31 was made of a stainless alloy (SUS304) having a thickness slightly smaller than the thickness of the cathode side electrode 26 and the anode side electrode 28, for example, a thickness of 0.25 mm.

Therefore, the first cooling cells 18 are arranged for every ten power generation cells 12 and the power generation cells 1
The second cooling cell 20 was disposed every 5 cells. That is, the second cooling cell 20 was interposed at the center between the first cooling cells 18.

The fuel cell stack 1 configured as described above
At 0, the gas utilization is 50% and the pressure is 201.3k
The hydrogen gas set at Pa (absolute pressure) and the air set at a gas utilization rate of 50% and the pressure set at 201.3 kPa have a load current density of 0.02 A / cm ^{2 to} 1.2 A / c.
m ² , 5A to 321A for the fuel cell stack 10
The flow rate of each cell was adjusted so as to change between the above, and the generated cell voltage was measured.

First, a cooling liquid for automobiles is supplied to the first cooling cell 18 without using the second cooling cell 20 so that the temperature of the separator in contact with the second cooling cell 20 becomes 160 ° C. Was. At this time, the relationship between the cell voltage and the current is shown in FIG.

On the other hand, in the fuel cell stack of the comparative example, power generation was performed under the same configuration and under the same conditions as the fuel cell stack 10 of the example, except that the sheet member 31 was not provided. Similarly, the relationship between cell voltage and current is shown in FIG.

As a result, in the high current side region exceeding 214 A, the result that the cell voltage was improved in the present example as compared with the comparative example was obtained. This is because phosphoric acid seeps out of the electrolyte layer even at an operating temperature of 160 ° C. because the sheet member 31 is provided in the space between the joined body 30 and the first and second separators 32 and 34. Is suppressed, and the gas diffusibility of the electrode catalyst layer and the gas diffusion layer is not hindered.

In this embodiment, the first and second cooling cells 18 and 20 are arranged evenly in the stacking direction, that is, at equal intervals.
The arrangement position can be appropriately adjusted so that the temperature distribution in the stacking direction is reduced.

[0085]

In the fuel cell stack according to the present invention, the sheet member is arranged in a space formed between the assembly and the separator, corresponding to the outer periphery of the anode electrode and the cathode electrode. Thereby, the sheet member is arranged in the space where the air as the heat insulating layer was present, and the heat transfer in the stacking direction between the power generation cells is improved. Therefore, the temperature difference between the power generation cells in the stacking direction is reduced, so that the power generation performance of each power generation cell can be made even closer to the maximum performance, and the output of the entire fuel cell stack can be improved.

Further, when the temperature of the fuel cell stack rises to the operating temperature due to the power generation of the power generation cells, even if each member expands in the stacking direction, the pressure acting on the joined body in the film thickness direction is reduced by the sheet member. You. For this reason, for example, it is possible to effectively prevent phosphoric acid, which is an electrolyte, from seeping out from an electrolyte layer in which polybenzimidazole is impregnated with phosphoric acid, and it is possible to avoid a decrease in power generation performance.

[Brief description of the drawings]

FIG. 1 is an explanatory side view showing a schematic configuration of a fuel cell stack according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the fuel cell stack.

FIG. 3 is an enlarged sectional view of a main part of the fuel cell stack.

FIG. 4 is an exploded perspective view of a first cooling cell constituting the fuel cell stack.

FIG. 5 is an exploded perspective view of a second cooling cell constituting the fuel cell stack.

FIG. 6 is a schematic structural explanatory view of a fuel cell system incorporating the fuel cell stack.

FIG. 7 is an explanatory diagram showing the relationship between the presence or absence of a sheet member of the fuel cell stack and the cell voltage.

FIG. 8 is an explanatory sectional view of a main part of a conventional fuel cell stack.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack 12 ... Power generation cells 14, 16 ... Current collecting electrodes 18, 20 ... Cooling cells 19a, 19b, 58a, 58b ... Insulating sheets 21a, 21b ... End plate 24 ... Electrolyte part 26 ... Cathode side electrode 28 ... Anode-side electrode 30 ... Joint body 31 ... Sheet members 32 and 34 ... Separator 46 ... Refrigerant supply line 48 ... Refrigerant discharge line 50 ... Oxidant gas flow path 51 ... Fuel gas flow path 52, 80 ... Flow path plate 53 ... Sealing member 54 Cooling liquid passages 56, 84 Lid plates 60a, 60b
Conductive plate 82 Cooling air passage 86 Flow path groove 90 Air introduction section 94 Air introduction port 110 Fuel cell system 112 Fuel gas supply section 114 Oxidant gas supply section 116 Cooling liquid supply section 118 Cooling air Supply unit

Claims (4)

[Claims] An assembly comprising an electrolyte sandwiched between an anode electrode and a cathode electrode, wherein the assembly is sandwiched between separators and fuel gas is supplied to the anode electrode, A power generation cell in which an oxidant gas is supplied to the cathode side electrode; a pair of current collecting electrodes electrically connected integrally to a predetermined number of the power generation cells; and cooling for cooling the power generation cells A medium is supplied, a cooling cell provided between the current collecting electrodes by providing an insulating mechanism, and corresponding to the outer periphery of the anode-side electrode and the cathode-side electrode, between the joined body and the separator. A fuel cell stack comprising: a sheet member disposed in a space formed. 2. The fuel cell stack according to claim 1, wherein said sheet member is made of metal. 3. The fuel cell stack according to claim 2, wherein said sheet member is made of a stainless steel alloy, an aluminum alloy or a copper alloy. 4. The fuel cell stack according to claim 1, wherein a cooling gas for cooling the power generation cells is supplied, and a predetermined number of the power generation cells are provided between the fuel cells and the cooling cells. A fuel cell stack, comprising: an auxiliary cooling cell interposed between the current collecting electrodes with the fuel cell interposed therebetween.