JP2014179252A - Fuel cell and process of manufacturing the same - Google Patents

Abstract

The present invention provides a fuel cell capable of preventing gas from flowing around due to a separator step when integrally forming a seal on a separator and further improving power generation performance.
A polymer electrolyte membrane (11) includes a catalyst layer (13) and a gas diffusion layer (14) provided on the frame so that an outer edge of the polymer electrolyte membrane (11) is located outside an inner edge of the frame (20) when viewed from the thickness direction. In the fuel cell, the first seal member 18 is provided on the side surface 15 of the step of the separators 30 and 40 so that no gap is generated between the side surface of the step of the separator and the gas diffusion layer.
[Selection] Figure 3

Description

  The present invention relates to a fuel cell used as a drive source for a mobile object such as an automobile, a distributed power generation system, and a household cogeneration system.

  BACKGROUND ART A fuel cell (for example, a polymer electrolyte fuel cell) is an apparatus that generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. It is.

  Conventionally, as this type of fuel cell, for example, one described in Patent Document 1 (Japanese Patent Laid-Open No. 2004-47230) is known.

  As shown in FIG. 10, the fuel cell of Patent Document 1 is configured by sandwiching a membrane electrode assembly 101 (hereinafter referred to as MEA: Membrane-Electrode-Assembly) between a pair of plate-like conductive separators 102 and 102. ing.

  The MEA 101 includes a polymer electrolyte membrane 111 and a pair of electrode layers 112 and 112 formed on both surfaces of the electrolyte membrane 111. The electrode layer 112 includes a catalyst layer 113 formed on the surface of the polymer electrolyte membrane 111 and a gas diffusion layer 114 formed on the catalyst layer 113.

  The MEA 101 is held by a frame body 115 having a peripheral edge portion (also referred to as an outer peripheral region) formed in a frame shape in order to improve handling properties. The inner edge portion of the frame 115 is located between the catalyst layer 113 and the gas diffusion layer 114. In other words, the gas diffusion layer 114 is configured to run on the frame 115. Here, the MEA 101 including the frame body 115 is referred to as an electrode-membrane-frame assembly 103.

  The separator 102 is formed with a reaction gas channel 121 through which a reaction gas (fuel gas or oxidant gas) is supplied. The fuel gas is supplied to the reaction gas channel 121 of one separator 102 and the oxidant gas is supplied to the reaction gas channel 121 of the other separator 102, thereby causing an electrochemical reaction in the MEA 101, and And heat is generated.

  A resin sealing member 122 is provided at a position facing the frame 115 of the separator 102 in order to block or suppress leakage of the reaction gas to the outside.

JP 2004-47230 A

In the conventional fuel cell such as Patent Document 1, there is still room for improvement from the viewpoint of further improving the power generation performance.
Accordingly, an object of the present invention is to provide a fuel cell and a method for manufacturing the same that can further improve power generation performance.

In order to achieve the above object, the present invention is configured as follows.
According to the present invention,
A polymer electrolyte membrane;
A catalyst layer provided on the polymer electrolyte membrane;
A frame provided on an outer peripheral region of the polymer electrolyte membrane;
A gas diffusion layer provided on the catalyst layer and the frame body such that the outer edge thereof is located outside the inner edge of the frame body as viewed from the thickness direction of the polymer electrolyte membrane;
A separator that is provided on the gas diffusion layer and has a power generation region that generates power, and a region other than the power generation region that is an area outside the power generation region;
With
A step is provided at the boundary between the power generation region and the region other than the power generation region,
A side surface of the step is provided with a first seal member that fills a gap formed between the side surface of the step and the gas diffusion layer.
A fuel cell is provided.

Moreover, according to the present invention,
A polymer electrolyte membrane;
A catalyst layer provided on the polymer electrolyte membrane; a frame provided on an outer peripheral region of the polymer electrolyte membrane;
A gas diffusion layer provided on the catalyst layer and the frame body such that the outer edge thereof is located outside the inner edge of the frame body as viewed from the thickness direction of the polymer electrolyte membrane;
An electrode-membrane-frame assembly comprising:
A power generation region, which is a region where power generation is performed, and a region other than the power generation region, which is a region outside the power generation region, are partitioned by a step, and a separator provided with a seal member on a side surface of the step is prepared.
Fastening the electrode-membrane-frame assembly and the separator;
The manufacturing method of a fuel cell including this is provided.

  According to the fuel cell and the manufacturing method thereof according to the present invention, there is an effect that the power generation performance can be further improved.

It is sectional drawing which shows typically the basic structure of the fuel cell of the examination stage. It is sectional drawing which shows typically the basic structure of the fuel cell concerning 1st Embodiment of this invention. FIG. 3 is a partially enlarged cross-sectional view of the fuel cell of FIG. 2. FIG. 3 is a partially enlarged cross-sectional view showing a state before the electrode-membrane-frame assembly and the separator of the fuel cell of FIG. 2 are fastened. FIG. 3 is an exploded perspective view showing a basic structure of a fuel cell stack in which a plurality of fuel cells of FIG. 2 are connected. It is a partially expanded sectional view which shows typically the structure of the fuel cell concerning 2nd Embodiment of this invention. It is a partially expanded sectional view which shows the state before fastening the membrane electrode assembly and separator of the fuel cell of FIG. It is a top view which shows typically the structure of the fuel cell concerning 2nd Embodiment of this invention. It is a partially expanded sectional view which shows the state before fastening the electrode-membrane-frame assembly and a separator of the fuel cell concerning 2nd Embodiment of this invention. It is sectional drawing which shows the state before fastening the electrode-membrane-frame assembly and a separator of the conventional fuel cell.

(Knowledge that became the basis of the present invention)
A conventional fuel cell is manufactured by sandwiching an electrode-membrane-frame assembly 103 between a pair of separators 102 and 102 from the state shown in FIG. Each component of the fuel cell is designed such that the outer edge 114a of the gas diffusion layer 114 and the inner edge 122a of the seal member 122 are in contact with each other without a gap.

  However, when a conventional fuel cell is mass-produced, a gap may occur between the outer edge 114a of the gas diffusion layer 114 and the inner edge 122a of the seal member 122 due to misalignment or tolerance (about ± 0.5 mm) at the time of fastening. obtain. If a gap is generated between the outer edge 114a and the inner edge 122a, the reaction gas supplied to the inside of the fuel cell may not be passed through the reaction gas flow path 121 and may be discharged to the outside of the fuel cell through the gap. obtain. Hereinafter, this phenomenon is referred to as a gas wraparound phenomenon. When this wraparound phenomenon occurs, the utilization efficiency of the reaction gas decreases, and the power generation performance of the fuel cell decreases.

  As a method of suppressing the gas wraparound phenomenon, it is conceivable to increase the volume of the seal member 122. In this case, it is considered that the gap is filled by the seal member 122 being compressed and elastically deformed at the time of fastening. However, in this case, since the volume of the sealing member 122 is increased, it naturally increases the cost accordingly.

  Therefore, as a result of intensive studies, the present inventors have caused the above-described misalignment and tolerance by causing at least one of the seal member 122 and the gas diffusion layer 114 to be crushed in the thickness direction by the other. In addition, the present inventors have found that the gap can be filled with the crushed and deformed portion without increasing the volume of the seal member 122. Based on this knowledge, the present inventors examined the following fuel cells.

FIG. 1 is a cross-sectional view schematically showing the basic structure of a fuel cell at the examination stage. As shown in FIG. 1, the fuel cell under study is
A polymer electrolyte membrane;
A catalyst layer provided on the polymer electrolyte membrane;
A frame provided on an outer peripheral region of the polymer electrolyte membrane;
A gas diffusion layer provided on the catalyst layer and the frame body such that the outer edge thereof is located outside the inner edge of the frame body as viewed from the thickness direction of the polymer electrolyte membrane;
A separator provided on the gas diffusion layer;
A resin-made second seal member provided so as to come into contact with both the separator and the frame,
At least one of the outer peripheral portions of the second seal member and the gas diffusion layer is crushed in the thickness direction by the other.

  In addition, the fuel cell separators 30 and 40 in the examination stage include a power generation region 16 that is a region where power generation is performed and a region 17 other than the power generation region that is an outer region of the power generation region 16. And a step between the region 17 other than the power generation region. In the present specification, the power generation region means a region in the separator, and means a region that overlaps a region in which a gas flow path is provided when viewed from the thickness direction of the polymer electrolyte membrane.

  In the fuel cell at the examination stage, the second seal member 21 is provided so as to come into contact with the outer peripheral portion 14 b of the gas diffusion layer 14 and to crush the outer peripheral portion 14 b in the thickness direction of the polymer electrolyte membrane 11. As a result, no gap is formed between the second seal member 21 and the gas diffusion layer 14.

  According to the fuel cell in the present examination stage, the second seal member 21 is provided so as to contact the frame body 20 and to crush the outer peripheral portion 14b of the gas diffusion layer 14 in the thickness direction of the polymer electrolyte membrane 11. ing. Thereby, the clearance gap between the 2nd sealing member 21 and the gas diffusion layer 14 can be eliminated, the gas wraparound phenomenon can be suppressed, and the power generation performance of the fuel cell can be further improved. Furthermore, when viewed from the thickness direction of the polymer electrolyte membrane 11, the outer peripheral portion 14 b of the gas diffusion layer 14 that does not overlap with the catalyst layer 13 can be crushed. Therefore, the reaction gas can be prevented from flowing through the outer peripheral portion 14 b of the gas diffusion layer 14. Thereby, it can suppress that the reactive gas which is not supplied to the catalyst layer 13 and does not contribute to an electric power generation reaction flows through the outer peripheral part 14b of the gas diffusion layer 14, and can utilize a reactive gas more effectively.

  However, it has been found that the fuel cell in the examination stage still has room for improvement in terms of further improving the power generation performance. When mass production of the fuel cell at the examination stage, a gap may occur between the side surface 15 of the step of the separators 30 and 40 and the gas diffusion layer 14 due to misalignment or tolerance (about ± 0.5 mm) at the time of fastening. . When a gap is formed between the side surface 15 of the step of the separators 30 and 40 and the gas diffusion layer 14, a gas wraparound phenomenon occurs through the gap. When this wraparound phenomenon occurs, the utilization efficiency of the reaction gas decreases, and the power generation performance of the fuel cell decreases.

  Therefore, as a result of intensive studies, the present inventors have provided the first seal member 18 between the side surface 15 of the step of the separators 30 and 40 and the gas diffusion layer 14, so that the above-described misalignment and tolerance may occur. It has been found that the gap can be filled with the first seal member 18. Based on this knowledge, the present inventors have reached the following invention.

  According to the first aspect of the present invention, a polymer electrolyte membrane, a catalyst layer provided on the polymer electrolyte membrane, a frame provided on an outer peripheral region of the polymer electrolyte membrane, and the polymer The catalyst layer and the gas diffusion layer provided on the frame body, and the gas diffusion layer provided on the gas diffusion layer so that the outer edge thereof is located outside the inner edge of the frame body when viewed from the thickness direction of the electrolyte membrane. And a separator having a power generation region that is a region where power generation is performed and a region other than the power generation region that is an area outside the power generation region, and a boundary between the power generation region and the region other than the power generation region A fuel cell is provided in which a step is provided, and a first seal member is provided on a side surface of the step to fill a gap formed between the side surface of the step and the gas diffusion layer.

  According to the second aspect of the present invention, it further comprises a resin-made second seal member provided so as to be in contact with both the separator and the frame body, and the second seal member and the gas diffusion layer. The fuel cell according to the first aspect, wherein at least one of the outer peripheral portions is crushed by the other in the thickness direction.

According to a third aspect of the present invention, the fuel cell according to the second aspect, wherein the contact pressure between the seal member and the outer peripheral portion of the gas diffusion layer is smaller than the contact pressure between the seal member and the frame. I will provide a.

According to a fourth aspect of the present invention, there is provided the fuel cell according to the second or third aspect, wherein both the sealing member and the gas diffusion layer are crushed.

According to a fifth aspect of the present invention, there is provided the fuel cell according to any one of the first to fourth aspects, wherein the seal member is formed on a surface of the separator.

According to a sixth aspect of the present invention, there is provided the fuel cell according to the fifth aspect, wherein the seal member is formed on the surface of the separator by injection molding.

According to a seventh aspect of the present invention, there is provided an annular resin-made third seal member provided between the separator and the frame body, and the second seal member is formed with respect to an outer edge of the gas diffusion layer. A fuel cell according to a fifth aspect is provided, wherein the fuel cell is disposed with a gap therebetween, and the seal member is provided so as to close a part of the gap.

According to an eighth aspect of the present invention, there is provided the fuel cell according to the seventh aspect, wherein the seal member, the second seal member, and the third seal member are integrally formed.

According to a ninth aspect of the present invention, there is provided the fuel cell according to the eighth aspect, wherein the seal member, the second seal member, and the third seal member are made of the same resin material.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the gas diffusion layer is composed of a porous member mainly composed of conductive particles and a polymer resin. A fuel cell is provided.

According to an eleventh aspect of the present invention, a polymer electrolyte membrane, a catalyst layer provided on the polymer electrolyte membrane, a frame provided on an outer peripheral region of the polymer electrolyte membrane, and the polymer An electrode-membrane-frame comprising: the catalyst layer and a gas diffusion layer provided on the frame body such that an outer edge thereof is located outside an inner edge of the frame body as viewed from the thickness direction of the electrolyte membrane. A joined body is prepared, and a power generation region that is a region where power generation is performed and a region other than the power generation region that is an area outside the power generation region are partitioned by a step, and a seal member is provided on a side surface of the step, A method for producing a fuel cell, comprising preparing a separator and fastening the electrode-membrane-frame assembly to the separator.

According to a twelfth aspect of the present invention, there is provided the fuel cell manufacturing method according to the tenth aspect, wherein the seal member is formed on the surface of the separator by injection molding.
According to a thirteenth aspect of the present invention, the gas diffusion layer is made of a porous member mainly composed of conductive particles and a polymer resin, and the fuel cell according to the eleventh or twelfth aspect is manufactured. Provide a method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all of the following drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

<< First Embodiment >>
A fuel cell according to a first embodiment of the present invention will be described. FIG. 2 is a sectional view schematically showing the basic structure of the fuel cell according to the first embodiment of the present invention, and FIG. 3 is a partially enlarged sectional view thereof.

  The fuel cell according to the first embodiment includes a polymer electrolyte that generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. This is a fuel cell. The present invention is not limited to the polymer electrolyte fuel cell, but can be applied to various fuel cells.

  As shown in FIG. 2, the fuel cell 1 according to the first embodiment includes an electrode-membrane-frame assembly 2 and a pair of separators 30 and 40 arranged with the electrode-membrane-frame assembly 2 interposed therebetween. It has. The electrode-membrane-frame assembly 2 includes an MEA (membrane electrode assembly) 10 and a frame-like frame body 20 provided on the outer peripheral region (peripheral portion) of the MEA 10.

  The MEA 10 includes a polymer electrolyte membrane 11 and a pair of electrode layers 12 and 12 formed on both surfaces of the polymer electrolyte membrane 11. One of the pair of electrode layers 12 is an anode electrode, and the other is a cathode electrode. The electrode layer 12 includes a catalyst layer 13 and a gas diffusion layer 14. The catalyst layer 13 is formed on the surface of the polymer electrolyte membrane 11, and the gas diffusion layer 14 is formed on the catalyst layer 13.

  The polymer electrolyte membrane 11 is larger in size than the catalyst layer 13 and the gas diffusion layer 14, and is provided so that the outer peripheral region protrudes from the catalyst layer 13 and the gas diffusion layer 14. A frame 20 is provided on the outer peripheral region (peripheral portion) of the polymer electrolyte membrane 11.

  The inner edge 20 a of the frame body 20 is located between the catalyst layer 13 and the gas diffusion layer 14. In other words, the gas diffusion layer 14 is configured to run on the frame body 20. In other words, the gas diffusion layer 14 is a catalyst layer such that the outer edge 14a thereof is located outside the inner edge 20a of the frame body 20 when viewed from the thickness direction of the polymer electrolyte membrane 11 (vertical direction in FIG. 2). 13 and the frame 20 are provided.

  The separator 30 is provided on one gas diffusion layer 14. The separator 40 is provided on the other gas diffusion layer 14. The separators 30 and 40 have a power generation region 16 that is a region where power generation is performed, and a region 17 other than the power generation region that is an area outside the power generation region 16, and the power generation region 16 and the region 17 other than the power generation region A step is provided at the boundary. Further, a first seal member 18 that fills a gap formed between the side surface 15 of the step and the gas diffusion layer 14 is provided on the side surface 15 of the step. The first seal member 18 is formed in an annular shape, and is provided so as to contact both the step side surface 15 and the gas diffusion layer 14 of the separator 30, or both the step side surface 15 and the gas diffusion layer 14 of the separator 40. Yes. Thereby, no gap is formed between the side surface 15 of the step of the separator 30 and the gas diffusion layer 14 or between the side surface 15 of the step of the separator 40 and the gas diffusion layer 14. Also, resin-made second seal members 21 are provided between the separator 30 and the frame body 20 and between the separator 40 and the frame body 20, respectively.

  The second seal member 21 is formed in an annular shape and is provided so as to contact both the separator 30 and the frame body 20 or both the separator 40 and the frame body 20. The contact pressure between the second seal member 21 and the frame body 20 is higher than the pressure at which the reaction gas supplied into the fuel cell 1 tends to flow to the outside. Thereby, leakage of the reaction gas to the outside is prevented.

  The second seal member 21 is provided so as to come into contact with the outer peripheral portion 14 b of the gas diffusion layer 14 and to crush the outer peripheral portion 14 b in the thickness direction of the polymer electrolyte membrane 11. As a result, no gap is formed between the second seal member 21 and the gas diffusion layer 14.

  Further, the contact pressure between the second seal member 21 and the outer peripheral portion 14 b of the gas diffusion layer 14 is smaller than the contact pressure between the second seal member 21 and the frame body 20. Thereby, due to the reaction force generated by compressing the outer peripheral portion 14b of the gas diffusion layer 14, there is a problem such that the polymer electrolyte membrane 11 is perforated and the durability and power generation performance of the polymer electrolyte membrane 11 are reduced. It is possible to avoid the occurrence. The “contact pressure” refers to, for example, the maximum pressure (kg / cm 2 or kg / m) within the contact area.

  In the fuel cell according to the first embodiment, the first seal member 18 is provided on the side surface 15 of the step between the separators 30 and 40. Thereby, the clearance gap between the side surface 15 of the level | step difference of the separators 30 and 40 and the gas diffusion layer 14 can be eliminated. Therefore, the reaction gas can be prevented from flowing through the outer peripheral portion 14 b of the gas diffusion layer 14. Thereby, it can suppress that the reactive gas which is not supplied to the catalyst layer 13 and does not contribute to an electric power generation reaction flows through the outer peripheral part 14b of the gas diffusion layer 14, and can utilize a reactive gas more effectively. The second seal member 21 is provided so as to contact the frame body 20 and to crush the outer peripheral portion 14 b of the gas diffusion layer 14 in the thickness direction of the polymer electrolyte membrane 11. Thereby, the clearance gap between the 2nd sealing member 21 and the gas diffusion layer 14 can be eliminated, the gas wraparound phenomenon can be suppressed, and the power generation performance of the fuel cell can be further improved. Furthermore, when viewed from the thickness direction of the polymer electrolyte membrane 11, the outer peripheral portion 14 b of the gas diffusion layer 14 that does not overlap with the catalyst layer 13 can be crushed. Therefore, the reaction gas can be prevented from flowing through the outer peripheral portion 14 b of the gas diffusion layer 14. Thereby, it can suppress that the reactive gas which is not supplied to the catalyst layer 13 and does not contribute to an electric power generation reaction flows through the outer peripheral part 14b of a gas diffusion layer, and can use a reactive gas more effectively.

  Next, each member constituting the fuel cell 1 will be described in more detail.

  The polymer electrolyte membrane 11 is preferably a polymer membrane having hydrogen ion conductivity. The polymer electrolyte membrane 11 is not particularly limited. For example, a fluorine-based polymer electrolyte membrane made of perfluorocarbon sulfonic acid (for example, Nafion (registered trademark) manufactured by DuPont, USA, manufactured by Asahi Kasei Corporation) Aciplex (registered trademark), Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd.) and various hydrocarbon electrolyte membranes can be used. The material of the polymer electrolyte membrane 11 may be any material that selectively moves hydrogen ions. The shape of the polymer electrolyte membrane 11 is not particularly limited, but is substantially rectangular in the first embodiment.

  The catalyst layer 13 is preferably a layer containing a catalyst for a redox reaction of hydrogen or oxygen. The catalyst layer 13 is preferably provided such that the outer edge 13 a is located inside the center portion of the second seal member 21 when viewed from the thickness direction of the polymer electrolyte membrane 11. When the outer edge 13a of the catalyst layer 13 is outside the center of the second seal member 21, the reaction gas that has passed through the porous catalyst layer 13 is likely to escape to the outside, and (external leakage) gas loss occurs. Further, the catalyst layer 13 is not particularly limited. For example, the catalyst layer 13 is composed of a porous member mainly composed of a carbon powder carrying a platinum-based metal catalyst and a polymer material having proton conductivity. Can do. The catalyst layer 13 only needs to have conductivity and have a catalytic ability for a redox reaction of hydrogen and oxygen. The shape of the catalyst layer 13 is not particularly limited, but is substantially rectangular in the first embodiment. The catalyst layer 13 can be formed by coating or spraying a catalyst layer forming ink on the surface of the polymer electrolyte membrane 11. Further, it may be produced by a general transfer method.

  The gas diffusion layer 14 is preferably formed of a so-called base material-less gas diffusion layer that is configured without using carbon fiber as a base material. Specifically, the gas diffusion layer 14 is composed of a porous member mainly composed of conductive particles and a polymer resin. Here, the “porous member mainly composed of conductive particles and polymer resin” means a structure (so-called self-supporting structure) that is supported only by conductive particles and polymer resin without using carbon fiber as a base material. It means a porous member having a support structure. When producing a porous member with conductive particles and a polymer resin, for example, a surfactant and a dispersion solvent are used. In this case, during the production process, the surfactant and the dispersion solvent are removed by firing, but they may not be sufficiently removed and may remain in the porous member. Therefore, as long as the “porous member mainly composed of conductive particles and polymer resin” has a self-supporting structure in which carbon fiber is not used as a base material, the surfactant and the dispersion remaining in this manner are dispersed. It means that a solvent may be included in the porous member. In addition, if the self-supporting structure does not use carbon fibers as a base material, it means that other materials (for example, carbon fibers of short fibers) may be included in the porous member.

  The gas diffusion layer 14 can be manufactured by kneading, extruding, rolling, and firing a mixture containing a polymer resin and conductive particles. Specifically, carbon, which is conductive particles, a dispersion solvent, and a surfactant are introduced into a stirrer / kneader, and then kneaded, pulverized, and granulated to disperse the carbon in the dispersed solvent. Next, the fluororesin, which is a polymer resin, is further dropped into a stirrer / kneader and stirred and kneaded to disperse the carbon and the fluororesin. The obtained kneaded material is rolled to form a sheet and fired to remove the dispersion solvent and the surfactant. Thereby, the sheet-like gas diffusion layer 14 can be manufactured.

  Examples of the material of the conductive particles constituting the gas diffusion layer 14 include carbon materials such as graphite, carbon black, and activated carbon. Examples of the carbon black include acetylene black (AB), furnace black, ketjen black, vulcan, and the like. These materials may be used alone, or a plurality of materials may be used in combination. . In addition, the raw material form of the carbon material may be any shape such as powder, fiber, and granule.

  Materials for the polymer resin constituting the gas diffusion layer 14 include PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), PVDF (polyvinylidene fluoride), ETFE (tetrafluoroethylene). -Ethylene copolymer), PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) and the like. Among these, PTFE is preferably used as the polymer resin material from the viewpoints of heat resistance, water repellency, and chemical resistance. Examples of the raw material form of PTFE include dispersion and powder. Among these, it is preferable from the viewpoint of workability that a dispersion is adopted as a raw material form of PTFE. The polymer resin constituting the gas diffusion layer 14 functions as a binder that binds the conductive particles. Further, since the polymer resin has water repellency, it also has a function (water retention) for confining water in the system inside the fuel cell.

  In addition, as described above, the gas diffusion layer 14 may contain a trace amount of a surfactant, a dispersion solvent, and the like used during production in addition to the conductive particles and the polymer resin. Examples of the dispersion solvent include water, alcohols such as methanol and ethanol, and glycols such as ethylene glycol. Examples of the surfactant include nonionic compounds such as polyoxyethylene alkyl ethers and zwitterionic compounds such as alkylamine oxides. What is necessary is just to set suitably the quantity of the dispersion solvent used at the time of manufacture, and the quantity of surfactant according to the kind of electroconductive particle, the kind of polymer resin, those compounding ratios, etc. In general, as the amount of the dispersion solvent and the amount of the surfactant increases, the polymer resin and the conductive particles tend to be uniformly dispersed, but the fluidity increases and the sheet of the gas diffusion layer is increased. It tends to be difficult. The surfactant can be appropriately selected depending on the material of the conductive particles and the type of the dispersion solvent. Moreover, it is not necessary to use a surfactant.

  In addition, the gas diffusion layer 14 may use a gas diffusion layer having the same structure or a gas diffusion layer having a different structure on the cathode electrode side and the anode electrode side. For example, a gas diffusion layer using carbon fiber as a base material may be used on either the cathode electrode side or the anode electrode side, and the above-described base material-less gas diffusion layer may be used on either side.

  The frame body 20 is a member provided for improving the handleability of the MEA 10. As a material of the frame body 20, a general thermoplastic resin, a thermosetting resin, or the like can be used. For example, as a material of the frame 20, silicon resin, epoxy resin, melamine resin, polyurethane resin, polyimide resin, acrylic resin, ABS resin, polypropylene, liquid crystalline polymer, polyphenylene sulfide resin, polysulfone, glass fiber reinforced resin, etc. Can be used. The shape of the frame 20 is not particularly limited, but in the first embodiment, it is a substantially rectangular ring.

  The separators 30 and 40 are preferably members for mechanically fixing the MEA 10. The separators 30 and 40 are preferably made of a material containing carbon or a material containing metal. In the case where the separators 30 and 40 are made of a material containing carbon, the separators 30 and 40 supply raw material powder in which carbon powder and a resin binder are mixed into the mold, and the raw material powder supplied into the mold Can be formed by applying pressure and heat. When the separators 30 and 40 are made of a material containing metal, the separators 30 and 40 may be made of a metal plate. Further, as the separators 30 and 40, those obtained by performing gold plating on the surface of a plate made of titanium or stainless steel can be used.

  A gas flow path 31 for fuel gas is provided on a main surface (hereinafter also referred to as an electrode surface) that contacts the gas diffusion layer 14 of the separator 30. A gas flow path 41 for oxidant gas is provided on a main surface (hereinafter also referred to as an electrode surface) that contacts the gas diffusion layer 14 of the separator 40. The fuel gas is supplied to one electrode layer 12 through the gas flow path 31 and the oxidant gas is supplied to the other electrode layer 12 through the gas flow path 41, so that an electrochemical reaction occurs and electric power and heat are generated. To do.

  The first seal member 18 and the second seal member 21 are preferably made of a synthetic resin having appropriate mechanical strength and flexibility. As a material constituting the first seal member 18 and the second seal member 21, for example, a compound such as a rubber material, a thermoplastic elastomer, or an adhesive can be used. Specific examples of the sealing material constituting the second sealing member 21 include fluorine rubber, silicone rubber, natural rubber, EPDM, butyl rubber, butyl rubber, butyl bromide rubber, butadiene rubber, styrene-butadiene copolymer, and ethylene-vinyl acetate rubber. Acrylic rubber, polyisopropylene polymer, perfluorocarbon, polybenzimidazole, polystyrene-based, polyolefin-based, polyester-based and polyamide-based thermoplastic elastomers, or isoprene rubber and butadiene rubber latex-based adhesives, liquid Examples of the adhesive include polybutadiene, polyisoprene, polychloroprene, silicone rubber, fluororubber, and acrylonitrile-butadiene rubber, but are not limited to these compounds. These compounds may be used alone or in combination of two or more. Further, as the sealing material constituting the first sealing member 18 and the second sealing member 21, specifically, Santoprene 8101-55, which is a polyolefin-based thermoplastic elastomer having polypropylene and EPDM, can be used. . Although the shape of the 1st seal member 18 and the 2nd seal member 21 is not specifically limited, In this 1st Embodiment, it shall be a substantially rectangular ring shape.

  Next, a method for manufacturing the fuel cell 1 according to the first embodiment will be described.

  First, as shown in FIG. 3, an electrode-membrane-frame assembly 2 and separators 30 and 40 are prepared. In the first embodiment, the second seal member 21 has a semi-elliptical cross section. The first seal member 18 is formed on the surface of the side surface 15 of the step between the separators 30 and 40. The second seal member 21 is formed on the surfaces of the separators 30 and 40.

  Next, when viewed from the thickness direction of the polymer electrolyte membrane 11, the inner peripheral portion 21b located on the inner side (left side in FIG. 3) of the second seal member 21 and the outer peripheral portion 14b of the gas diffusion layer 14 overlap each other. Align so that.

Next, the electrode-membrane-frame assembly 2 and the separators 30 and 40 are fastened. At this time, the first seal member 18 contacts the gas diffusion layer 14. Thereby, a gap is not generated between the side surface 15 of the step of the separators 30 and 40 and the gas diffusion layer 14.
Further, the electrode-membrane-frame assembly 2 and the separators 30 and 40 are fastened, whereby the inner peripheral portion 21b of the second seal member 21 is replaced with the outer peripheral portion 14b of the gas diffusion layer 14 by the thickness of the polymer electrolyte membrane 11. While crushing in the vertical direction, the top portion 21 a of the second seal member 21 contacts the frame body 20. At this time, the outer peripheral portion 14 b of the gas diffusion layer 14 is deformed, so that no gap is generated between the second seal member 21 and the gas diffusion layer 14.

  As described above, the fuel cell 1 shown in FIG. 3 is manufactured.

  According to the fuel cell manufacturing method of the first embodiment, a fuel cell in which the first seal member 18 is provided on the side surface 15 of the step of the separators 30 and 40 can be manufactured. Thereby, the clearance gap between the side surface 15 of the level | step difference of the separators 30 and 40 and the gas diffusion layer 14 can be eliminated, the gas entrainment phenomenon can be suppressed, and the power generation performance can be further improved. The electrode-membrane-frame assembly 2 and the separator 30 so that the second seal member 21 contacts the frame body 20 and crushes the outer peripheral portion 14b of the gas diffusion layer 14 in the thickness direction of the polymer electrolyte membrane 11. , 40. Thereby, the clearance gap between the 2nd seal member 21 and the gas diffusion layer 14 can be eliminated, the gas wraparound phenomenon can be suppressed, and the power generation performance can be further improved.

  The gas diffusion layer 14 is preferably composed of a porous member mainly composed of conductive particles and a polymer resin as described above. In this case, since the porous member has elasticity, it is elastically deformed when the porous member is crushed, and a gap is formed between the first seal member 18 and the second seal member 21 and the gas diffusion layer 14. Can be prevented more reliably.

  In addition, when a highly rigid member is used as the gas diffusion layer 14, the first seal member is generated by a reaction force generated when the gas diffusion layer 14, the first seal member 18, and the second seal member 21 come into contact with each other. 18 and the second seal member 21, the separators 30 and 40, and the frame body 20 may be cracked or chipped. For this reason, it is preferable to comprise the gas diffusion layer 14 with a member with low rigidity.

  In the above description, the outer peripheral portion 14b of the gas diffusion layer 14 is crushed, but the present invention is not limited to this. At least one of the outer peripheral portion 18a of the first seal member 18 and the inner peripheral portion 21b of the second seal member 21 is crushed, and the first seal member 18, the second seal member 21, the gas diffusion layer 14, It may be possible to prevent a gap from being generated. In this case, a highly rigid member can be used as the gas diffusion layer 14. Further, both the outer peripheral portion 14b of the gas diffusion layer 14, the outer peripheral portion 18a of the first seal member 18 and the inner peripheral portion 21b of the second seal member 21 may be crushed. In this case, it is more reliable that the outer peripheral portion 18a of the first seal member 18 and the second seal member 21 and the gas diffusion layer 14 are in close contact with each other and a gap is generated between the second seal member 21 and the gas diffusion layer 14. Can be suppressed. Moreover, the selection range of the material of the gas diffusion layer 14, the outer peripheral portion 18a of the first seal member 18, and the second seal member 21 can be expanded.

  Further, the first seal member 18 and the second seal member 21 are preferably formed on the surfaces of the separators 30 and 40 as described above. In this case, since the separators 30 and 40 have higher dimensional accuracy and less warpage than the frame 20, there is an advantage that the yield is high. Further, when the first seal member 18 and the second seal member 21 are formed on the surfaces of the separators 30 and 40 by injection molding, there is an advantage that the injection molding is easy because the separators 30 and 40 have high rigidity. In addition, when the 1st seal member 18 and the 2nd seal member 21 are formed in the frame 20 by injection molding, there exists a possibility that the polymer electrolyte membrane 11 may deteriorate with the heat | fever generate | occur | produced at the time of injection molding. In this case, the power generation performance is reduced.

  Next, a structure when a plurality of fuel cells (unit cells) 1 shown in FIG. 2 are connected in series and used as a so-called fuel cell stack will be described. FIG. 5 is an exploded perspective view showing a basic structure of a fuel cell stack 3 in which a plurality of fuel cells 1 are connected.

  When a plurality of fuel cells 1 are used as the fuel cell stack 3, in order to supply the reaction gas (fuel gas or oxidant gas) to the gas flow paths 31, 41, a pipe for supplying the reaction gas is provided with a separator 30. , 40, and manifolds that branch to the gas flow paths 31 and 41 are required.

  Therefore, in the first embodiment, as shown in FIG. 5, fuel gas manifold holes 22, 32, which are a pair of through holes for supplying fuel gas to the frame 20 and the pair of separators 30, 40, respectively. 42 is provided. The frame 20 and the pair of separators 30 and 40 are provided with oxidant gas manifold holes 23, 33, and 43, which are a pair of through holes through which the oxidant gas flows. In a state where the frame 20 and the pair of separators 30 and 40 are connected as the fuel cell 1, the fuel gas manifold holes 22, 32 and 42 are connected to form a fuel gas manifold. Similarly, in a state where the frame 20 and the pair of separators 30 and 40 are connected as the fuel cell 1, the oxidant gas manifold holes 23, 33 and 43 are connected to form an oxidant gas manifold.

  The frame body 20 and the pair of separators 30 and 40 are provided with cooling medium manifold holes 24, 34, and 44, which are two pairs of through holes, respectively, through which a cooling medium (for example, pure water or ethylene glycol) flows. Yes. In the state where the frame 20 and the pair of separators 30 and 40 are connected as the fuel cell 1, the cooling medium manifold holes 24, 34 and 44 are connected to form two pairs of cooling medium manifolds.

  The frame body 20 and the pair of separators 30 and 40 are provided with four bolt holes 50 in the vicinity of each corner. Fastening bolts are inserted into the respective bolt holes 50, and a plurality of fuel cells 1 are fastened by coupling nuts to the fastening bolts.

  The gas flow path 31 is provided so as to connect the pair of fuel gas manifolds 32, 32. The gas flow path 41 is provided so as to connect the pair of oxidant gas manifolds 43, 43. In addition, in FIG. 5, although the gas flow paths 31 and 41 were shown as a serpentine type flow path, the flow path of another form (for example, linear type) may be sufficient.

  Moreover, although not shown in figure in the main surface on the opposite side to the electrode surface of the separator 30, and the main surface on the opposite side to the electrode surface of the separator 40, Preferably, a cooling medium flow path is each formed. The cooling medium flow path is formed so as to connect the two pairs of cooling medium manifold holes 34 and 44. That is, the cooling medium is configured to branch from the cooling medium manifold on the supply side to the cooling medium flow path and to flow to the cooling medium manifold on the discharge side. Thus, the fuel cell 1 is kept at a predetermined temperature suitable for the electrochemical reaction by utilizing the heat transfer capability of the cooling medium.

  In the above description, the manifolds for the fuel gas, the oxidant gas, and the cooling water are provided in the separators 30 and 40, and the supply manifolds for the fuel gas, the oxidant gas, and the cooling water are formed when they are stacked. The so-called internal manifold type fuel cell configured as described above has been described as an example, but the present invention is not limited to this. For example, a so-called external manifold type fuel cell in which supply manifolds of fuel gas, oxidant gas, and cooling water are provided on the side surface of the fuel cell stack 3 may be used. Even in this case, the same effect can be obtained. Further, the separators 30 and 40 are formed of a porous conductive material, and cooling is performed so that the pressure of the cooling water flowing through the cooling medium flow path is higher than the pressure of the reaction gas flowing through the gas flow paths 31 and 41. A so-called internal humidification type fuel cell in which a part of water is allowed to pass through the separators 30 and 40 to the electrode surface side to wet the polymer electrolyte membrane 11 may be used.

  In the above description, the gas flow paths 31 and 41 are provided in the separators 30 and 40. However, the present invention is not limited to this. For example, the gas flow path 31 may be provided in one gas diffusion layer 14 and the gas flow path 41 may be provided in the other gas diffusion layer 14. Further, the gas flow path 31 may be formed in both the separator 30 and the one gas diffusion layer 14. Further, the gas flow path 41 may be formed in both the separator 40 and the other gas diffusion layer 14.

<< Second Embodiment >>
Next, a fuel cell according to a second embodiment of the present invention will be described. FIG. 6 is a partially enlarged cross-sectional view schematically showing the configuration of the fuel cell according to the second embodiment of the present invention. The fuel cell of the second embodiment is different from the fuel cell of the first embodiment in that a third seal member 60 is provided between the separators 30 and 40 and the frame body 20.

  The third seal member 60 is formed in an annular shape and is provided so as to contact both the separator 30 and the frame body 20 or both the separator 40 and the frame body 20. The third seal member 60 is provided so as to be adjacent to the second seal member 21 on the outside. The contact pressure between the second seal member 21 and the frame body 20 is higher than the pressure at which the reaction gas supplied into the fuel cell 1 tends to flow to the outside.

  According to the fuel cell according to the second embodiment, by further including the third seal member 60, the gap between the separators 30 and 40 and the frame body 20 can be sufficiently sealed by the third seal member 60. . Thereby, leakage of the reaction gas to the outside can be prevented more reliably. Furthermore, when viewed from the thickness direction of the polymer electrolyte membrane 11, the outer peripheral portion 14 b of the gas diffusion layer 14 that does not overlap with the catalyst layer 13 can be crushed by the second seal member 21. Therefore, the reaction gas can be prevented from flowing through the outer peripheral portion 14 b of the gas diffusion layer 14. Thereby, it can suppress that the reactive gas which is not supplied to the catalyst layer 13 and does not contribute to an electric power generation reaction flows through the outer peripheral part 14b of a gas diffusion layer, and can use a reactive gas more effectively. In the case where the second seal member 21 is provided so as to close the entire gap C <b> 1 between the third seal member 60 and the gas diffusion layer 14, the separators 30 and 40 are formed by the second seal member 21 and the third seal member 60. And the frame 20 can be double sealed. Thereby, leakage of the reaction gas to the outside can be further prevented.

  Since the third sealing member 60 can prevent leakage of the reaction gas to the outside, the second sealing member 21 does not have to prevent leakage of the reaction gas to the outside, and the gas diffusion layer 14 What is necessary is just to be able to fill the gap between the first seal member 60 and the third seal member 60. For this reason, as shown in FIG. 7, before joining the separators 30 and 40 and the electrode-membrane-frame assembly 2, the second seal member 21 has a top portion 21 a that is more than the top portion 60 a of the third seal member 60. You may form so that it may become low.

  Further, the second seal member 21 and the third seal member 60 may be made of different resin materials. For example, the second seal member 21 may be made of a softer resin material than the third seal member 60. In this case, since the second seal member 21 is easily elastically deformed, the gap between the gas diffusion layer 14 and the third seal member 60 can be filled more reliably.

  Further, the second seal member 21 and the third seal member 60 may be integrally formed of the same resin material. In this case, since the 2nd seal member 21 and the 3rd seal member 60 can be formed simultaneously, the increase in a manufacturing process can be suppressed.

Moreover, as shown in FIG. 9, the 1st seal member 18, the 2nd seal member 21, and the 3rd seal member 60 may be integrally formed with the same resin material. In this case, since the first seal member 18 and the second seal member 21 are continuous, the gap between the side surface 15 of the step of the separators 30 and 40 and the gas diffusion layer 14 is more surely independent of the rigidity of the gas diffusion layer 14. Can be buried. Furthermore, since the 1st seal member 18, the 2nd seal member 21, and the 3rd seal member 60 can be formed simultaneously, the increase in a manufacturing process can be suppressed.

  Further, as shown in FIG. 8, the first seal member 18 does not block the entire gap C2 between the side surface 15 of the step of the separators 30 and 40 and the gas diffusion layer 14, but blocks a part of the gap C2. It may be provided as follows. Even in this case, since the reaction gas can be prevented from being discharged to the outside of the fuel cell through the gap C2 (gas wraparound phenomenon), the power generation performance can be improved as compared with the conventional fuel cell.

  Further, as shown in FIG. 8, the second seal member 21 is provided not to cover the entire gap C <b> 1 between the third seal member 60 and the gas diffusion layer 14 but to partially close the gap C <b> 1. May be. Even in this case, since the reaction gas can be prevented from being discharged to the outside of the fuel cell through the gap C1 (gas wraparound phenomenon), the power generation performance can be improved as compared with the conventional fuel cell. When viewed from the thickness direction of the polymer electrolyte membrane 11, a part of the outer peripheral portion 14b of the gas diffusion layer 14, which is a portion not overlapping with the catalyst layer 13, can be crushed. By crushing a part of the outer peripheral portion 14 b of the gas diffusion layer 14, it is possible to suppress the reaction gas from flowing through the outer peripheral portion 14 b of the gas diffusion layer 14. Thereby, it can suppress that the reactive gas which is not supplied to the catalyst layer 13 and does not contribute to an electric power generation reaction flows through the outer peripheral part 14b of a gas diffusion layer, and can use a reactive gas more effectively. Moreover, when the electrode-membrane-frame assembly 2 and the separators 30 and 40 are fastened by reducing the area where the second seal member 21 is disposed, it is necessary to crush the second seal member 21. An increase in the fastening load can be suppressed. Thereby, a low intensity | strength member can be used for the separators 30 and 40, and cost can be held down.

  Although FIG. 8 shows an example in which the plurality of second seal members 21 are provided in the gap C1, the present invention is not limited to this. Even when one second seal member 21 is provided in the gap C1, it is possible to suppress the gas wraparound phenomenon and improve the power generation performance as compared with the conventional fuel cell.

In addition, by appropriately combining any of the various embodiments, the effects possessed by them can be produced.
For example, the first seal member or the like may be provided only on either the anode side or the cathode side.

  Since the power generation performance of the fuel cell according to the present invention can be further improved, the fuel cell is useful as a fuel cell used as a drive source for a mobile body such as an automobile, a distributed power generation system, a household cogeneration system, and the like. is there.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Electrode-membrane-frame assembly 3 Fuel cell stack 10 MEA (membrane electrode assembly)
DESCRIPTION OF SYMBOLS 11 Polymer electrolyte membrane 12 Electrode layer 13 Catalyst layer 13a Outer edge 14 Gas diffusion layer 14a Outer edge 14b Outer peripheral part 15 Side surface of level | step difference 16 Power generation area | region 17 Area | regions other than a power generation area | region 18 20a Inner edge 20b Projection part 21 Second seal member 21a Top part 21b Inner peripheral part 30, 40 Separator 31, 41 Gas flow path 60 Third seal member 60a Top part C1, C2 Gap

Claims (13)

A polymer electrolyte membrane;
A catalyst layer provided on the polymer electrolyte membrane;
A frame provided on an outer peripheral region of the polymer electrolyte membrane;
A gas diffusion layer provided on the catalyst layer and the frame body such that the outer edge thereof is located outside the inner edge of the frame body as viewed from the thickness direction of the polymer electrolyte membrane;
A separator that is provided on the gas diffusion layer and has a power generation region that generates power, and a region other than the power generation region that is an area outside the power generation region;
With
A step is provided at the boundary between the power generation region and the region other than the power generation region,
A side surface of the step is provided with a first seal member that fills a gap formed between the side surface of the step and the gas diffusion layer.
Fuel cell. Furthermore, a resin-made second seal member provided so as to come into contact with both the separator and the frame,
2. The fuel cell according to claim 1, wherein at least one of the second seal member and the outer peripheral portion of the gas diffusion layer is crushed in the thickness direction by the other.   The fuel cell according to claim 2, wherein a contact pressure between the seal member and an outer peripheral portion of the gas diffusion layer is smaller than a contact pressure between the seal member and the frame.   The fuel cell according to claim 2 or 3, wherein both the sealing member and the gas diffusion layer are crushed.   The fuel cell according to claim 1, wherein the seal member is formed on a surface of the separator.   The fuel cell according to claim 5, wherein the seal member is formed on a surface of the separator by injection molding. An annular resin-made third seal member provided between the separator and the frame;
The second seal member is disposed with a gap with respect to an outer edge of the gas diffusion layer,
The fuel cell according to claim 5, wherein the seal member is provided so as to close a part of the gap.   The fuel cell according to claim 7, wherein the seal member, the second seal member, and the third seal member are integrally formed.   The fuel cell according to claim 8, wherein the seal member, the second seal member, and the third seal member are made of the same resin material.   The fuel cell according to any one of claims 1 to 9, wherein the gas diffusion layer is composed of a porous member mainly composed of conductive particles and a polymer resin. A polymer electrolyte membrane, a catalyst layer provided on the polymer electrolyte membrane, a frame provided on an outer peripheral region of the polymer electrolyte membrane, and a thickness of the polymer electrolyte membrane as viewed from the thickness direction. Preparing an electrode-membrane-frame assembly comprising the catalyst layer and a gas diffusion layer provided on the frame so that the outer edge is positioned outside the inner edge of the frame;
A power generation region, which is a region where power generation is performed, and a region other than the power generation region, which is a region outside the power generation region, are partitioned by a step, and a separator provided with a seal member on a side surface of the step is prepared.
Fastening the electrode-membrane-frame assembly and the separator;
The manufacturing method of a fuel cell including this.   The fuel cell manufacturing method according to claim 10, wherein the seal member is formed on a surface of the separator by injection molding.   The method for producing a fuel cell according to claim 11 or 12, wherein the gas diffusion layer is composed of a porous member mainly composed of conductive particles and a polymer resin.

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