JP4040863B2 - Fuel cell stack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes an electrolyte / electrode structure in which a pair of electrodes are provided on both sides of an electrolyte, and includes a laminate in which a plurality of the electrolyte / electrode structures are laminated via separators, on both sides of the laminate. The present invention relates to a fuel cell stack provided with a power extraction terminal.
[0002]
[Prior art]
In recent years, various fuel cells have been developed. For example, a polymer electrolyte fuel cell (PEFC) is known. This polymer electrolyte fuel cell employs an electrolyte membrane composed of a polymer ion exchange membrane (cation exchange membrane), and an anode side electrode composed of a catalyst electrode and porous carbon on both sides of the electrolyte membrane, and A unit cell (unit fuel cell) configured by sandwiching an electrolyte (membrane) / electrode structure configured by arranging a cathode side electrode between separators (bipolar plates) is provided. Usually, a predetermined number of unit cells are stacked and used as a fuel cell stack.
[0003]
In this type of fuel cell stack, a fuel gas supplied to the anode electrode, for example, a gas mainly containing hydrogen (hereinafter also referred to as a hydrogen-containing gas) is ionized by hydrogen on the catalyst electrode, via an electrolyte. Move to the cathode side electrode side. Electrons generated in the meantime are taken out to an external circuit and used as direct current electric energy. The cathode side electrode is supplied with an oxidant gas, for example, a gas mainly containing oxygen or air (hereinafter also referred to as an oxygen-containing gas). And oxygen react to produce water.
[0004]
By the way, in the fuel cell stack, there are unit cells in which a temperature drop is likely to be caused by heat radiation to the outside as compared with other unit cells. For example, a unit cell (hereinafter also referred to as an end cell) disposed at the end in the stacking direction is, for example, a power extraction terminal (collector plate) that collects the electric power generated by each unit cell, or a stacked unit A large amount of heat is dissipated by the end plate or the like provided to hold the cell, and the above-described temperature drop becomes significant. It has been pointed out that due to this temperature decrease, condensation is more likely to occur in the end cells than in the central portion of the fuel cell stack, and the generated water discharge performance is reduced and power generation performance is reduced.
[0005]
Therefore, as disclosed in, for example, Japanese Patent Laid-Open No. 8-130028 (hereinafter referred to as Prior Art 1), a cooling fluid flow groove is not formed in the outer separator that constitutes the end cell. A solid polymer electrolyte fuel cell having a structure in which the separator is not overcooled by a cooling fluid is known. This prevents the end cell from being overcooled.
[0006]
Further, in the solid polymer electrolyte fuel cell disclosed in Japanese Patent Application Laid-Open No. 8-167424 (hereinafter referred to as Prior Art 2), the outer surface of the separator located at at least both ends of the unit fuel cell stack is contacted. A heating element that is heated by a current output from the solid polymer electrolyte fuel cell is formed at a portion of the current collector plate. This prevents overcooling of the end cells.
[0007]
Furthermore, in the stacked fuel cell disclosed in Japanese Patent Application Laid-Open No. 7-326379 (hereinafter referred to as Prior Art 3), a gas connect plate is disposed at both ends of the cell stack, and the gas connect plate includes: A vacuum layer and an air layer are formed. For this reason, heat radiation to the outside of the cell stack is prevented under the heat insulating action of the vacuum layer and the air layer.
[0008]
[Problems to be solved by the invention]
However, in the above-described prior art 1, a separator in which a groove for cooling fluid flow is formed and a separator in which this groove is not formed are required. This increases the number of types of separators, complicates the manufacturing process of the separators, and increases the manufacturing cost.
[0009]
Furthermore, in the above-described prior art 2, a heating element made of a resistance material such as an alloy material for electric heating is provided between the current collector plate and the single battery (unit cell). For this reason, a heating element, a current collector plate, an insulating plate, and an end plate are actually laminated at both ends of the end cell, and there is a problem that the entire fuel cell stack is enlarged in the stacking direction.
[0010]
Furthermore, in the above-described prior art 3, a vacuum layer and an air layer are formed on the gas connect plate, and the gas connect plate is provided with a lattice-like groove, a circular counterbore, etc. The thickness becomes considerably large, resulting in a plate with low dimensional accuracy. Accordingly, the surface pressure distribution load of the fuel cell stack, which is a laminate, is biased, increasing the resistance between the unit cells and increasing the size of the fuel cell stack itself.
[0011]
The present invention solves this kind of problem, and with a simple configuration, it is possible to effectively prevent the temperature drop of the unit cell, improve the power generation performance of each unit cell, and easily reduce the size. An object of the present invention is to provide a simple fuel cell stack.
[0012]
[Means for Solving the Problems]
The fuel cell stack according to claim 1 of the present invention has an electrolyte / electrode structure in which a pair of electrodes are provided on both sides of an electrolyte, and a plurality of the electrolyte / electrode structures are stacked via a separator. wherein the with both sides of the laminate was interposed a plate-like power takeout lead terminal provided an end plate, between the at least one power extraction terminal and one end plate is disposed the heat generation member The The heating member is an insulating film over the laminated face the entire surface on both sides of the gold Shokuhaku heater is provided.
[0013]
For this reason, the heat generating member is set to a film structure that is effectively thinned, and an insulating plate can be made unnecessary. As a result, the entire fuel cell stack can be reduced in size and weight. And since the conventional heat insulation board is not used, the bias | inclination of surface pressure distribution can be reduced and the contact resistance between unit cells can be reduced. Furthermore, since the heat capacity is small, the metal foil heater starts up quickly, and it is possible to quickly eliminate the unstartable state due to the generated water, particularly when starting at below freezing.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic perspective view of a fuel cell stack 10 according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of a main part of the fuel cell stack 10.
[0015]
The fuel cell stack 10 includes a stacked body 14 in which a plurality of unit cells 12 are stacked in the direction of arrow A, and end cells 12 a and 12 b are disposed at both ends of the stacked body 14. Heat generating members 18a and 18b are disposed outside the end cells 12a and 12b via a cathode side current collector plate (first power extraction terminal) 16a and an anode side current collector plate (second power extraction terminal) 16b. End plates 20a and 20b are disposed on the outer sides of the heat generating members 18a and 18b. The end plates 20a and 20b are integrally tightened by a tie rod or the like (not shown), whereby the fuel cell stack 10 is configured.
[0016]
The unit cell 12 and the end cells 12a and 12b are configured in the same manner, and the end cell 12a will be described below.
[0017]
As shown in FIG. 2, the end cell 12 a includes an electrolyte membrane / electrode structure 30. The electrolyte membrane / electrode structure 30 is provided with an anode side electrode 34 on one surface of a solid polymer electrolyte membrane 32 and a cathode side electrode 36 on the other surface. The anode-side electrode 34 and the cathode-side electrode 36 are configured by joining a noble metal-based catalyst electrode layer to a gas diffusion layer made of, for example, porous carbon paper that is a porous layer.
[0018]
The electrolyte membrane / electrode structure 30 is sandwiched between the conductive first and second separators 38 and 40, thereby forming the end cell 12a. An oxidant gas supply communication passage 42a, a fuel gas discharge communication passage 44b, and a cooling medium supply communication passage 46a are provided at one edge of the end cell 12a in the long side direction (arrow B direction). A cooling medium discharge communication passage 46b, a fuel gas supply communication passage 44a, and an oxidant gas discharge communication passage 42b are provided at the other edge in the long side direction of the end cell 12a.
[0019]
The first separator 38 is provided with a fuel gas channel 48 on a surface 38 a facing the anode side electrode 34. The fuel gas flow channel 48 includes a plurality of flow channel grooves that communicate with the fuel gas supply communication passage 44a at one end and communicate with the fuel gas discharge communication passage 44b at the other end.
[0020]
Similar to the first separator 38, the surface 40 a of the second separator 40 facing the cathode side electrode 36 has a plurality of oxides whose both ends communicate with the oxidant gas supply communication path 42 a and the oxidant gas discharge communication path 42 b. An agent gas flow path 50 is provided. A cooling medium flow path 52 that communicates with the cooling medium supply communication path 46 a and the cooling medium discharge communication path 46 b is provided on the surface 40 b of the second separator 40.
[0021]
The cathode side current collecting plate 16a is composed of a good conductor terminal such as gold-plated copper, for example. A terminal portion 54 is provided at one end portion in the long side direction of the cathode side current collector plate 16a so as to protrude outward.
[0022]
As shown in FIGS. 2 and 3, the heat generating member 18 a includes a metal foil heater 56, and an insulating film 58 is provided via a heat resistant adhesive layer 60 on at least one side of the metal foil heater 56, in this embodiment, both sides. It is done. The insulating film 58 is made of, for example, polyimide, polyester, polyethylene terephthalate (PET), or the like.
[0023]
The metal foil heater 56 is formed by, for example, forming a thin resistance foil such as a nickel alloy into a predetermined pattern shape P1 (see FIG. 4) by etching or pressing, and laminating it from both sides with an insulating film 58. In order to meet demands such as heating the power generation surface uniformly or imparting a thermal gradient according to the application, the metal foil heater 56, for example, in addition to the predetermined pattern shape P1 shown in FIG. The predetermined pattern shapes P2, P3, P4, and P5 shown in FIGS. 5 to 8 can be changed.
[0024]
The heat generating member 18a is set to have the same size as the cathode side current collecting plate 16a or a size slightly larger than the outer circumference size of the cathode side current collecting plate 16a in order to prevent a short circuit due to a discharge transmitted in the air. .
[0025]
The anode-side current collecting plate 16b and the heat generating member 18b are configured in the same manner as the cathode-side current collecting plate 16a and the heat generating member 18a described above, and the same components are denoted by the same reference numerals. Detailed description thereof will be omitted.
[0026]
Similarly to the end cell 12a, the cathode side current collecting plate 16a, the anode side current collecting plate 16b, the heat generating members 18a and 18b, and the end plates 20a and 20b have an oxidant gas supply passage 42a at one end edge in the long side direction. The fuel gas discharge communication passage 44b and the cooling medium supply communication passage 46a are provided, and the coolant discharge passage 46b, the fuel gas supply communication passage 44a, and the oxidant gas discharge communication passage 42b are provided at the other edge in the long side direction. It is done.
[0027]
For example, a load (not shown) such as a motor is electrically connected to the cathode side current collector plate 16a and the anode side current collector plate 16b, and the heat generating members 18a and 18b are connected to the cathode side current collector plate. Electric power is supplied from 16a and the anode current collector 16b as required.
[0028]
The operation of the fuel cell stack 10 configured as described above will be described below.
[0029]
As shown in FIG. 1, in the fuel cell stack 10, a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas supply communication passage 44a, and an oxygen-containing gas such as air is oxidized to the oxidant gas supply communication passage 42a. The agent gas is supplied, and further, a cooling medium such as pure water, ethylene glycol, or oil is supplied to the cooling medium supply communication path 46a. Therefore, in the fuel cell stack 10, the fuel gas, the oxidant gas, and the cooling medium are supplied to the plurality of unit cells 12 and end cells 12a and 12b that are overlapped in the direction of arrow A.
[0030]
As shown in FIG. 2, the oxidant gas supplied to the oxidant gas supply communication path 42 a flows along the direction of arrow A, and the oxidant gas flow path 50 provided on the surface 40 a of the second separator 40. To be introduced. The oxidant gas introduced into the oxidant gas flow path 50 moves along the cathode side electrode 36, and the used oxidant gas is discharged from the oxidant gas discharge communication path 42b.
[0031]
On the other hand, the fuel gas supplied to the fuel gas supply communication path 44 a flows along the direction of arrow A and is introduced into the fuel gas flow path 48 provided on the surface 38 a of the first separator 38. After the fuel gas introduced into the fuel gas channel 48 moves along the anode side electrode 34, the used fuel gas is discharged to the fuel gas discharge communication path 44b. Therefore, in the electrolyte membrane / electrode structure 30, the oxidant gas supplied to the cathode side electrode 36 and the fuel gas supplied to the anode side electrode 34 are consumed by an electrochemical reaction in the catalyst electrode layer to generate power. Is done.
[0032]
The cooling medium supplied to the cooling medium supply communication path 46 a is introduced into the cooling medium flow path 52 provided on the surface 40 b of the second separator 40 to cool the power generation surface of the electrolyte membrane / electrode structure 30. After that, the refrigerant is discharged from the cooling medium discharge communication path 46b.
[0033]
By the way, when the temperature of the fuel cell stack 10 is equal to or lower than a predetermined temperature, electric power is supplied from the fuel cell stack 10 to the metal foil heater 56 constituting the heat generating members 18a and 18b. For this reason, the heat generating members 18a and 18b themselves are heated, and the end cells 12a and 12b arranged close to the heat generating members 18a and 18b are heated.
[0034]
Thereby, the generated water generated in the end cells 12a and 12b is not condensed by the heat radiation from the end cells 12a and 12b of the fuel cell stack 10. In addition, the temperature drop of the end cells 12a and 12b can be prevented, and the power generation performance of the end cells 12a and 12b can be effectively maintained.
[0035]
Here, in the present embodiment, the heat generating members 18a and 18b are configured by laminating a metal foil heater 56 from both sides with an insulating film 58. Specifically, the heat generating members 18a and 18b are set to a thin film structure having a thickness in the range of 0.1 mm to several mm.
[0036]
In addition, in the conventional stack end structure, a heat insulating plate (or heating plate) and a current collecting plate are arranged in the end cell and the end plate is laminated, and a current collecting plate and a heat insulating plate (or the end cell) (or In some cases, the end plate is laminated with a heating plate. However, in any case, since insulation to the end plate is necessary, an insulating plate made of resin is disposed inside the end plate.
[0037]
On the other hand, in the embodiment of the present invention, the metal foil heater 56 is laminated by the insulating film 58. For this reason, the heat generating members 18a and 18b themselves have a function of insulating the cathode side current collecting plate 16a and the anode side current collecting plate 16b from the end plates 20a and 20b, and a conventional resin insulating plate is unnecessary. Can be.
[0038]
Therefore, in the present embodiment, the entire fuel cell stack 10 can be effectively reduced in size and weight. Moreover, since a heat insulating plate is not used, it is possible to reduce the uneven surface pressure distribution of the fuel cell stack 10 and reduce the contact resistance between the unit cells 12. As a result, the fuel cell stack 10 can reliably maintain good power generation performance.
[0039]
Furthermore, since the heat capacity is small, the metal foil heater 56 rises quickly, and it becomes possible to quickly eliminate the start-up impossible state due to the generated water, particularly at the time of starting below the freezing point. Further, since the insulating film 58 is laminated with the metal foil heater 56, water resistance and insulation can be improved.
[0040]
Furthermore, in the present embodiment, for example, by selecting the metal foil heater 56 to a predetermined pattern shape P1 (see FIG. 4), it is possible to uniformly heat the power generation surface. In addition, the thermal gradient in the power generation surface can be changed to preferentially heat the portion where the generated water is likely to condense. For example, by selecting the predetermined pattern shape P4 shown in FIG. 7, it is possible to effectively heat a portion where condensation easily occurs particularly near the outlet of the reaction gas, while the predetermined pattern shape P5 shown in FIG. 8 is selected. By doing, it becomes possible to heat the outer peripheral part which is especially easy to radiate heat.
[0041]
In addition, by adjusting the amount of current supplied to the metal foil heater 56, it becomes possible to maintain the inside of the laminate 14 at an optimum temperature that can suppress the condensation of generated water, and at the time of starting below sub-freezing, more By passing an electric current, the frozen product water is rapidly melted and a quick start is performed.
[0042]
【The invention's effect】
In the fuel cell stack according to the present invention, the heat generating member is set to a film structure that is effectively thinned, an insulating plate can be eliminated, and the entire fuel cell stack can be reduced in size and weight. become. In addition, since no heat insulating plate is used, it is possible to reduce the unevenness of the surface pressure distribution and reduce the contact resistance between the unit cells, and it is possible to reliably maintain good power generation performance.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a fuel cell stack according to an embodiment of the present invention.
FIG. 2 is an exploded perspective view of a main part of the fuel cell stack.
FIG. 3 is a partially enlarged cross-sectional view of a heat generating member constituting the fuel cell stack.
FIG. 4 is an explanatory diagram of a pattern shape of a metal foil heater constituting the heat generating member.
FIG. 5 is an explanatory diagram of another pattern shape of the metal foil heater.
FIG. 6 is an explanatory diagram of another pattern shape of the metal foil heater.
FIG. 7 is an explanatory diagram of still another pattern shape of the metal foil heater.
FIG. 8 is an explanatory diagram of still another pattern shape of the metal foil heater.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack 12 ... Unit cell 12a, 12b ... End cell 14 ... Laminated body 16a ... Cathode side current collecting plate 16b ... Anode side current collecting plate 18a, 18b ... Heat generating member 20a, 20b ... End plate 30 ... Electrolyte membrane -Electrode structure 32 ... Solid polymer electrolyte membrane 34 ... Anode side electrode 36 ... Cathode side electrode 38, 40 ... Separator 42a ... Oxidant gas supply communication passage 42b ... Oxidant gas discharge communication passage 44a ... Fuel gas supply communication passage 44b ... fuel gas discharge communication path 46a ... cooling medium supply communication path 46b ... cooling medium discharge communication path 48 ... fuel gas flow path 50 ... oxidant gas flow path 52 ... cooling medium flow path 56 ... metal foil heater 58 ... insulating film 60 ... Heat-resistant adhesive layer P1 to P5 ... Pattern shape

Claims (2)

An electrolyte / electrode structure having a pair of electrodes on both sides of an electrolyte, and a laminate in which a plurality of the electrolyte / electrode structures are stacked via separators, and a plate-like power on both sides of the stack A fuel cell stack provided with an end plate through a takeout terminal,
Between the at least one power extraction terminal and one end plate, with the heat generation member are disposed,
The heat generating member, a fuel cell stack according to claim Rukoto insulating film is provided over the laminated face the entire surface on both sides of the gold Shokuhaku heater. 2. The fuel cell stack according to claim 1, wherein the metal foil heater is set in a pattern shape that imparts a thermal gradient to the power generation surface.

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