JP4306419B2 - Polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a polymer electrolyte fuel cell, and more particularly to a technique for improving its assembly workability and stacking workability.

  The polymer electrolyte fuel cell is a clean and highly efficient power generation device, and in recent years, development competition has been developed on a global scale. In particular, in the automobile industry, there is a great expectation for a polymer electrolyte fuel cell as an alternative power source for an internal combustion engine, and technical development from various viewpoints is actively performed.

  The general configuration of the polymer electrolyte fuel cell will be described. In the polymer electrolyte fuel cell, a fuel electrode and an oxidant electrode are arranged on both sides of the polymer film, and a gas diffusion layer is in contact with each electrode. Are provided. These are collectively referred to as a membrane electrode composite. And the separator which provided the fuel gas flow path and the oxidant gas flow path on each one side is arrange | positioned so that a membrane electrode assembly may be pinched | interposed. The separator supplies the fuel gas and the oxidant gas flowing through the through holes called the fuel gas manifold and the oxidant gas manifold to the fuel electrode and the oxidant electrode through the fuel gas channel and the oxidant gas channel, respectively. It has a function. In addition to the gas supply function as described above, the separator plays a role of collecting the current flowing due to the electromotive force generated in the membrane electrode assembly via the rib portion in contact with the membrane electrode assembly. Therefore, the separator needs to be conductive at least with respect to the portion in contact with the membrane electrode assembly. Further, if the fuel gas and the oxidant gas are mixed, the electrochemical reaction in each electrode is hindered. Therefore, the fuel gas and the oxidant gas need to be sealed so as not to be mixed with each other. Therefore, a gasket is disposed between the polymer film near the outer periphery of the membrane electrode assembly and the separator.

  These are called unit cells as one unit. The polymer electrolyte fuel cell usually indicates a stack obtained by stacking a plurality of unit cells in series. Further, since the electrochemical reaction at the oxidant electrode is an exothermic reaction, a cooling plate for cooling the heat may be inserted for each predetermined number of unit cells.

  In the polymer electrolyte fuel cell as described above, the specifications of the membrane electrode assembly are various, but the polymer membrane is usually formed larger than the gas diffusion layer and exposed to the surroundings. It is comprised so that it may become a sealed structure by inserting | pinching with a gasket.

  However, in a structure in which the polymer film is formed larger than the gas diffusion layer and the polymer film projects around, the membrane electrode assembly must be aligned with reference to the thin polymer film. In other words, it is difficult to assemble unit cells and stacks, and there is a problem that stacking workability is poor. In addition, since the exposed portion of the polymer membrane is large, malfunctions of the fuel cell due to damage to the polymer membrane frequently occur. Furthermore, there is a problem that the amount of expensive polymer membranes to be used increases and the manufacturing cost is forced to increase.

Furthermore, for example, a specification has been proposed in which a peripheral portion of a membrane electrode assembly is impregnated with a resin so as to have a sealing function (see, for example, Patent Document 1). The membrane electrode assembly having the specifications described in Patent Document 1 has a fuel electrode and an oxidizer electrode on both sides of a polymer membrane, and a gas diffusion layer is arranged on the outside thereof to constitute the membrane electrode assembly. Is the same, but the gas sealing portion is formed by impregnating the resin around the gas diffusion layer. The membrane electrode assembly and the separator are in contact with each other, and a gasket is provided so as to be in contact with the gas sealing portion in the membrane electrode assembly. Thus, a unit cell is configured.
JP 2001-118592 A

  However, in the specification of the membrane electrode composite described in Patent Document 1, since the amount of the polymer membrane used is reduced, the production cost can be reduced to some extent, but eventually the membrane electrode is based on the polymer membrane. The alignment of the composite must be performed, and the problem that alignment is difficult when assembling unit cells and stacks remains. Further, the problem of damage to the polymer film cannot be solved.

  The present invention has been proposed in view of the conventional situation as described above. For example, in the assembly of unit cells or stacks in which separators and membrane electrode composites are alternately stacked, alignment of the membrane electrode composites is performed. It is an object of the present invention to provide a solid polymer fuel cell that is easy to assemble, is excellent in assembling and laminating workability, and does not cause malfunction of the fuel cell due to damage to the polymer membrane.

The polymer electrolyte fuel cell according to the present invention is a membrane electrode composite in which a fuel electrode and an oxidizer electrode are disposed on both sides of a polymer membrane, and gas diffusion layers are provided adjacent to the fuel electrode and the oxidizer electrode, respectively. Body, a separator provided with gas flow paths for supplying fuel gas and oxidant gas to the fuel electrode and oxidant electrode of the membrane electrode assembly, respectively, and a gasket provided between the membrane electrode complex and the separator, The unit cell is configured by the above, and has a stacked structure in which unit cells having such a configuration are repeatedly arranged in parallel. In the polymer electrolyte fuel cell having such a structure, in the present invention, in order to achieve the above-described object , both surfaces of the polymer membrane in the membrane electrode assembly of each unit cell are covered with the gas diffusion layer over the entire area. In addition , one of the gas diffusion layers has an outer dimension larger than that of the other gas diffusion layer and the polymer film.

  The gas diffusion layer is thicker than the polymer film and has high mechanical strength against changes in temperature and humidity. Therefore, if the outer dimensions of the gas diffusion layer are made larger than the outer dimensions of the polymer membrane and the membrane electrode assembly is aligned based on the periphery of the gas diffusion layer, the alignment becomes easy. . Moreover, since the polymer film is not exposed, damage to the polymer film is avoided.

  According to the present invention, there is provided a polymer electrolyte fuel cell that can facilitate the alignment of the membrane electrode assembly, is excellent in assembling and laminating workability, and can save labor. it can. In addition, according to the present invention, it is possible to provide a highly reliable polymer electrolyte fuel cell that does not damage the polymer membrane and that does not cause malfunctions.

  Hereinafter, embodiments of a polymer electrolyte fuel cell to which the present invention is applied will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a cross-sectional structure of the polymer electrolyte fuel cell in the present embodiment. In the polymer electrolyte fuel cell of this embodiment, a fuel electrode 2a and an oxidant electrode 2b having a catalyst are arranged on both sides of the polymer film 1, respectively, and a gas is adjacent to the fuel electrode 2a and the oxidant electrode 2b. A membrane electrode assembly 4 provided with diffusion layers 3a and 3b is provided.

  Here, for example, a solid polymer electrolyte membrane is used for the polymer membrane 1 in consideration of high energy density, low cost, light weight, and the like. The solid polymer electrolyte membrane is made of an ion (proton) conductive polymer membrane such as a fluororesin ion exchange membrane, and functions as an ion conductive electrolyte when saturated with water.

  The fuel electrode 2a and the oxidant electrode 2b disposed on both surfaces of the polymer film 1 are made of platinum, carbon cloth containing a catalyst made of platinum and other metals, carbon paper, or the like, and there is a catalyst. The surface is formed so as to be in contact with the polymer film 1. The gas diffusion layers 3a and 3b are used to efficiently distribute the fuel gas and the oxidant gas to the fuel electrode 2a and the oxidant electrode 2b. For example, the gas diffusion layers 3a and 3b are formed as porous catalyst electrodes.

  In the fuel electrode 2a, the supplied hydrogen is dissociated into hydrogen ions and electrons, the hydrogen ions pass through the electrolyte (polymer film 1), the electrons pass through an external circuit to generate electric power, and are supplied to the oxidant electrode 2b. Move each one. In the oxidant electrode 2b, oxygen in the supplied air reacts with the hydrogen ions and electrons to generate water.

  A separator 6 having a fuel gas flow path 5a and an oxidant gas flow path 5b for supplying fuel gas and oxidant gas to the fuel electrode 2a and oxidant electrode 2b, respectively, in contact with the membrane electrode assembly 4 Is provided. The separator 6 not only has a function as a gas flow path but also has a function as a current collector and a function as a partition between cells, and is made of a dense carbon material that is impermeable to gas, for example. .

  A gasket 7 is provided between the membrane electrode assembly 4 and the separator 6, and these are repeatedly laminated as unit cells, thereby forming a solid polymer fuel cell having a laminated structure.

  In the polymer electrolyte fuel cell having the above-described configuration, in this embodiment, the outer dimensions of one gas diffusion layer (here, the gas diffusion layer 3a on the fuel electrode 2a side) of each unit cell are defined as those of the polymer membrane 1. The outer dimensions and the outer dimensions of the gas diffusion layer 3b on the oxidant electrode 2b side are made larger than the outer dimensions of the separator 6.

  The separator 6 has a fuel gas manifold (not shown) for flowing fuel gas and oxidant gas in the stacking direction of the unit cells, and a through-hole called an oxidant gas manifold 9b. Similarly to the separator 6, through holes corresponding to the fuel gas manifold and the oxidant gas manifold 9b are provided in the gas diffusion layer 3a on the side of the fuel electrode 2a whose outer dimensions are increased.

  Further, the gas diffusion layer 3a on the fuel electrode 2a side has an impregnation portion 10a (shaded portion in the drawing) including an impregnation material in the portion from the vicinity of the end overlapping the polymer membrane 1 to the peripheral portion through the manifold portion. It has become. Regarding the gas diffusion layer 3b on the oxidant electrode 2b side, only the vicinity of the end overlapping the polymer film 1 is the same impregnation portion 10b. Here, examples of the impregnating material include thermoplastic resins and rubber materials. By providing the impregnated portions 10a and 10b, it is possible to prevent different kinds of gas (oxidant gas in the gas diffusion layer 3a and fuel gas in the gas diffusion layer 3b) from entering from the end portions of the gas diffusion layers 3a and 3b. be able to.

  The impregnation portion 10a of the gas diffusion layer 3a on the fuel electrode 2a side is in contact with the surface of the separator 6 on the fuel electrode 2a side, and the separator 6 on the oxidant electrode 2b side that is the counter electrode is interposed through the gasket 7 and the air layer 11. Facing each other. In the present embodiment, the gasket 7 is configured separately from the separator 6 and the gas diffusion layers 3a and 3b.

  In the polymer electrolyte fuel cell of the present embodiment, the polymer membrane 1 is present only in a portion that contributes to power generation without increasing the outer shape of the separator 6, so that the size of the polymer membrane 1 is minimized. Can do. Therefore, the manufacturing cost can be reduced. Further, since the polymer film 1 is covered with the gas diffusion layers 3a and 3b and there is no exposed portion, the performance deterioration due to damage can be avoided.

  Furthermore, in the present embodiment, the outer shape of the gas diffusion layer 3a on the fuel electrode 2a side is substantially the same as the outer shape of the separator 6, so that the membrane electrode assembly 4 including the gas diffusion layer 3a and the separator 6 are repeatedly laminated. Therefore, alignment is easy. That is, by increasing only one of the gas diffusion layers 3a, the size of the polymer film 1 can be minimized as described above, and the edge portion of the membrane electrode assembly 4 is the gas diffusion layer 3a. For this reason, the end portions of the members can be easily aligned and alignment can be easily performed. Therefore, the unit cell and the stack can be easily assembled, and the labor can be saved.

  In the above description, the gas diffusion layer 3a on the fuel electrode 2a side is larger than the gas diffusion layer 3b on the oxidant electrode 2b side, but the reverse specification may be used. That is, the outer dimensions of the gas diffusion layer 3b on the oxidizer electrode 2b side are made larger than the outer dimensions of the polymer membrane 1 and the gas diffusion layer 3a on the fuel electrode 2a side, so that the outer shape of the separator 6 is approximately the same. In this case, the same effect as the above-described example can be obtained.

(Second Embodiment)
The structure of the polymer electrolyte fuel cell of this embodiment is shown in FIG. Since the structure of the polymer electrolyte fuel cell is basically the same as that of the first embodiment described above, the same members are denoted by the same reference numerals, and detailed description thereof is omitted. Only the characteristic features of this embodiment will be described.

  In this embodiment, the gas diffusion layer 3a on the fuel electrode 2a side is made larger than the gas diffusion layer 3b on the oxidant electrode 2b side and the polymer film 1, and further, the outer peripheral edge of the gas diffusion layer 3a on the fuel electrode 2a side The portion was formed to overlap with a part of the peripheral edge of the gas manifold (oxidant gas manifold 9b in FIG. 2) in the stacking direction.

  Further, the gas diffusion layers 3a and 3b of both electrodes have the impregnated portions 10a and 10b at the ends overlapping with the polymer film 1, respectively. Further, a portion of the gas diffusion layer 3a on the fuel electrode 2a side that is larger than the gas diffusion layer 3b on the oxidant electrode 2b side and the polymer membrane 1 is also an impregnation portion 10a, and a separator on the oxidant electrode 2b side of the impregnation portion 10a. An insulating layer 12 is provided on the surface facing 6. Here, a thermoplastic resin, a rubber material, or the like can be used as the impregnation material, and a tape, a rubber layer, a resin layer, or the like made of tetrafluoroethylene can be used for the insulating layer 12. The surface side of the impregnated portion 10a where the insulating layer 12 is not formed is in contact with the surface of the separator 6 on the fuel electrode 2a side. The separator 6 on the oxidant electrode 2b side which is the counter electrode is separated from the insulating layer 12 and the gasket 7. And facing each other through the air layer 11. In the present embodiment, the gasket 7 is configured separately from the separator 6 and the gas diffusion layers 3a and 3b.

  In the polymer electrolyte fuel cell of the present embodiment, the counter electrode side surface of the impregnated portion 10a of the gas diffusion layer 3a on the fuel electrode 2a side that is not in contact with the polymer film 1 (the separator 6 on the oxidant electrode 2b side). Since the insulating layer 12 is provided on the surface facing each other), even when conductive particles or liquid enter the air layer 11, a short circuit does not occur via the particles. In addition, since the polymer film 1 exists only in a portion that contributes to power generation without increasing the outer shape of the separator 6, the size of the polymer film 1 can be minimized also in this embodiment. Furthermore, since a part of the outer periphery of the gas diffusion layer 3a on the fuel electrode 2a side is substantially overlapped with a part of the periphery of the gas manifold 9b in the separator 6, the membrane electrode assembly 4 including the gas diffusion layer 3a and the separator 6 are formed. Positioning becomes easy when repeatedly laminating. Therefore, also in this embodiment, it becomes excellent in the assembly property of a unit cell and a stack, and it becomes possible to aim at labor saving of work.

  In the above description, the gas diffusion layer 3a on the fuel electrode 2a side is larger than the gas diffusion layer 3b on the oxidant electrode 2b side, but the reverse specification may be used. That is, the outer dimensions of the gas diffusion layer 3b on the oxidant electrode 2b side are made larger than the outer dimensions of the polymer film 1 and the gas diffusion layer 3a on the fuel electrode 2a side, and the gas diffusion layer on the oxidant electrode 2b side. Even when a part of the outer periphery of 3b is substantially overlapped with a part of the peripheral edge of the gas manifold 9b in the separator 6, the same effect as the above-described example can be obtained.

  In addition to the gas manifold, in the case where a coolant through hole is provided for circulating the coolant in the stacking direction of the unit cells in order to cool the polymer electrolyte fuel cell, the gas diffusion layer 3a , 3b is larger than the other, and a part of the outer periphery of the larger gas diffusion layer is substantially overlapped with a part of the periphery of the coolant through hole in the separator 6, The same effect as the above-described example can be obtained.

(Third embodiment)
The structure of the polymer electrolyte fuel cell of this embodiment is shown in FIG. The structure of the polymer electrolyte fuel cell according to this embodiment is almost the same as that of the polymer electrolyte fuel cell according to the second embodiment, but in this embodiment, the insulating layer 12 described in the second embodiment is used. The gas diffusion layer 3a on the fuel electrode 2a side is provided not on the surface of the impregnation part 10a but on the surface of the separator 6 on the oxidant electrode 2b side. Here, as the insulating layer 12, a tape made of tetrafluoroethylene (so-called Teflon tape), a rubber layer, a resin layer, or the like can be used as in the second embodiment. Since other configurations are the same as those of the second embodiment described above, detailed description thereof is omitted here.

  In the polymer electrolyte fuel cell of this embodiment, the same operation and effect as in the case of the second embodiment can be obtained by installing the insulating layer 12 as described above. That is, in the polymer electrolyte fuel cell of the present embodiment, the surface of the separator 6 facing the impregnated portion 10a of the portion of the gas diffusion layer 3a on the fuel electrode 2a side that is not in contact with the polymer film 1 is disposed on the surface on the oxidant electrode side. Since the insulating layer 12 is provided so as to be adjacent to the gas diffusion layer 3b, even when conductive particles or liquid enter the air layer 11, a short circuit does not occur via the particles. In addition, since the polymer film 1 exists only in a portion that contributes to power generation without increasing the outer shape of the separator 6, the size of the polymer film 1 can be minimized also in this embodiment. Furthermore, since a part of the outer periphery of the gas diffusion layer 3a on the fuel electrode 2a side is substantially overlapped with a part of the periphery of the gas manifold 9b in the separator 6, the membrane electrode assembly 4 including the gas diffusion layer 3a and the separator 6 are formed. Positioning becomes easy when repeatedly laminating. Therefore, also in this embodiment, it becomes excellent in the assembly property of a unit cell and a stack, and it becomes possible to aim at labor saving of work.

(Fourth embodiment)
The polymer electrolyte fuel cell of this embodiment is characterized in that the gasket 7 of each unit cell is integrated with the separator 6 before lamination. Other configurations are the same as those of the first embodiment described above, and thus detailed description thereof is omitted here.

  In the polymer electrolyte fuel cell of this embodiment, the gasket 7 of each unit cell is integrated with the separator 6 before the unit cells are stacked, as shown in FIG. As an integration method, for example, a separate gasket 7 may be integrated with the separator 6 in advance using an adhesive or a double-sided tape, or a rubber gasket may be baked on the separator 6 and integrally formed.

  According to the polymer electrolyte fuel cell of the present embodiment, by integrating the gasket 7 with the separator 6 in advance, the following operational effects can be obtained in addition to the operational effects of the first embodiment described above. . That is, by integrating the gasket 7 with the separator 6 in advance, the stacking workability is further improved, and erroneous work during stacking assembly can be reduced. Therefore, the yield can be further improved and further labor saving can be achieved.

(Fifth embodiment)
In the polymer electrolyte fuel cell of the present embodiment, when the impregnated portions 10a and 10b are formed in the gas diffusion layers 3a and 3b, the gasket 7 is formed integrally with the impregnated portions 10a and 10b, and the gas diffusion layer 3a. This is characterized in that the insulating layer 12 is formed integrally with the impregnated portion 10a of the portion not in contact with the polymer film 1. About another structure, it is the same as that of the thing of 1st Embodiment mentioned above. That is, also in the polymer electrolyte fuel cell of the present embodiment, the outer shape of the gas diffusion layer 3a on the fuel electrode 2a side is made larger than that of the gas diffusion layer 3b on the oxidant electrode 2b side, and is substantially the same shape as the outer shape of the separator 6 It is said. Further, as shown in FIG. 5, the gas diffusion layer 3a is provided with a through hole corresponding to the gas manifold, and the portion from the vicinity of the end overlapping the polymer film 1 to the peripheral portion through the manifold portion is The impregnated portion 10a containing the impregnating material (shaded portion in the figure).

  In the polymer electrolyte fuel cell having the above-described configuration, in the present embodiment, when the impregnation portion 10a is formed in the gas diffusion layer 3a, the gasket 7 is also integrally formed. Here, the impregnating material is preferably a rubber material. Although not shown, the gas diffusion layer 3b on the oxidant electrode 2b side has an impregnation portion 10b only in the vicinity of the end overlapping the polymer film 1, but also when forming the impregnation portion 10b. The gaskets 7 are combined and integrally molded.

  One surface of the impregnation portion 10a is in contact with the surface of the separator 6 on the fuel electrode 2a side, and the surface facing the separator 6 on the oxidant electrode 2b side that is the counter electrode is formed of the same material as the gasket component and the impregnation component. An insulating layer 12 is integrally provided. Therefore, the gas diffusion layer 3a faces the separator 6 on the side of the oxidant electrode 2b, which is the counter electrode, through the gasket 7, the insulating layer 12, and the air layer 11 that are integrally formed.

  In the polymer electrolyte fuel cell of the present embodiment, the gasket 7 and the insulating layer 12 are previously impregnated and integrally formed in the gas diffusion layers 3a and 3b, so that the following effects are obtained in addition to the effects of the first embodiment. The effect is obtained. That is, since the gasket 7 and the insulating layer 12 are formed in accordance with the impregnation of the gas diffusion layers 3a and 3b, the number of processes can be reduced, and the workability is further improved. Further, since the insulating layer 12 is provided, even when conductive particles or liquid enters the air layer 11, no short circuit occurs through the particles. Therefore, safety and reliability can be improved, the yield can be further improved, and further labor saving can be achieved.

It is a schematic sectional drawing which shows the structure of the polymer electrolyte fuel cell of 1st Embodiment. It is a schematic sectional drawing which shows the structure of the polymer electrolyte fuel cell of 2nd Embodiment. It is a schematic sectional drawing which shows the structure of the polymer electrolyte fuel cell of 3rd Embodiment. It is a schematic sectional drawing which shows the structure of the separator and gasket in the polymer electrolyte fuel cell of 4th Embodiment. It is a schematic sectional drawing which shows the structure of the gas diffusion layer in the polymer electrolyte fuel cell of 5th Embodiment, a gasket, and an insulating layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymer membrane 2a Fuel electrode 2b Oxidant electrode 3a, 3b Gas diffusion layer 4 Membrane electrode assembly 5a Fuel gas channel 5b Oxidant gas channel 6 Separator 7 Gasket 8 Solid polymer fuel cell 9b Oxidant gas manifold 10a 10b Impregnation part 11 Air layer 12 Insulating layer

Claims (8)

A membrane electrode assembly in which a fuel electrode and an oxidant electrode are disposed on both sides of the polymer film, and a gas diffusion layer is provided adjacent to the fuel electrode and the oxidant electrode; A unit cell is constituted by a separator provided with a gas flow path for supplying an oxidant gas, and a gasket provided between the membrane electrode assembly and the separator, and the unit cells are repeatedly arranged in parallel. In a polymer electrolyte fuel cell having a structure,
The polymer membrane in the membrane electrode assembly is covered with the gas diffusion layer on both sides of the fuel electrode side and the oxidant electrode side, and one of the gas diffusion layers is the other polymer electrolyte fuel cell characterized by larger outer dimensions than the gas diffusion layer and the polymer film.   2. The solid polymer fuel cell according to claim 1, wherein an outer dimension of the larger gas diffusion layer is substantially equal to an outer dimension of the separator. The separator has a through-hole for allowing at least one of fuel gas, oxidant gas, and refrigerant to flow in the stacking direction of the polymer electrolyte fuel cell, and the larger gas diffusion layer has an outer peripheral edge. 2. The polymer electrolyte fuel cell according to claim 1, wherein the polymer electrolyte fuel cell is positioned with respect to the separator so that a position thereof coincides with an opening edge of the through hole .   2. The polymer electrolyte fuel cell according to claim 1, wherein an insulating layer is provided on the surface of the larger gas diffusion layer that is not in contact with the polymer film on the counter electrode side.   2. The polymer electrolyte fuel according to claim 1, wherein an insulating layer is provided adjacent to the gas diffusion layer on the counter electrode side on the surface of the separator on the counter electrode side of the larger gas diffusion layer. battery.   The solid polymer fuel cell according to claim 1, wherein the gasket is integrated with the separator.   2. The polymer electrolyte fuel cell according to claim 1, wherein the gasket is integrated with the gas diffusion layer.   6. The polymer electrolyte fuel cell according to claim 4, wherein the insulating layer is integrated with the gasket.

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