JP2012226848A - Electrode-membrane-frame assembly of polymer electrolyte fuel cell and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cross leak phenomenon in the peripheral part of a polymer electrolyte membrane and to improve performance of a polymer electrolyte fuel cell, in an electrode-membrane-frame assembly of the fuel cell.SOLUTION: Components for an electrode-membrane-frame assembly formed by closely contacting an electrolyte membrane, a first frame member arranged in a peripheral part of the electrolyte membrane, and second and third frame members with a same thickness that are alternately overlapped in a comb shape on the opposite side of the first frame member with respect to the electrolyte membrane across the peripheral edge face of the electrolyte membrane, in which the electrolyte membrane is not exposed to the outside, are provided.

Description

  The present invention relates to a solid polymer electrolyte fuel cell, and more particularly, to a structure of an electrode-membrane-frame assembly of a fuel cell and a manufacturing method thereof.

  The most typical solid polymer electrolyte fuel cell is a polymer electrolyte membrane supported by a frame having a gasket for sealing gas at the periphery, and an anode on one surface of the electrolyte membrane. An electrolyte membrane-electrode assembly (referred to as “MEA”) formed by joining and a cathode to the other surface of the electrolyte membrane, an anode side conductive separator plate sandwiching the MEA, and cathode side conductivity A gas supply part that is constituted by a separator and supplies fuel gas and oxidant gas to the anode and the cathode, respectively, is formed at the periphery of the central part that contacts the MEA in the separator.

  Such a structure of a conventional solid polymer electrolyte fuel cell is disclosed in, for example, Patent Document 1. FIG. 14 shows a partial schematic view of the electrode-membrane-frame assembly in the same document.

  In the electrode-membrane-frame assembly of Patent Document 1, the frame body 118 is disposed on the cathode surface side of the peripheral edge portion 117a of the polymer electrolyte membrane 117, and the end surface portion is alternately formed with the convex shape portions 118a and the concave shape portions 118b. It is formed in a comb-tooth shape, and a frame body 119 is disposed on the anode surface side, and a convex-shaped portion 119a and a concave-shaped portion 119b are alternately formed in a comb-tooth shape on the end surface portion.

  At this time, the shape of the frame on the anode surface side corresponding to the boundary of the polymer electrolyte membrane 117 in the convex portion 118a of the cathode surface side frame body is a concave shape 119b, and the concave portion 118b of the cathode surface side frame body. The shape of the frame on the anode surface side corresponding to the boundary of the polymer electrolyte membrane 117 is a convex shape 119a.

  FIG. 15 is a schematic diagram showing a state in which an elastic body is installed in a concave portion of a frame comb-tooth portion in the electrode-membrane-frame assembly of Patent Document 1, and FIG. AA line sectional drawing in is shown. The polymer electrolyte membrane 117 is not covered with the anode, the cathode and the frame body, and the portion where the membrane itself is exposed to the outside is covered with an elastic body. An electrode assembly (MEA) is used.

International Publication No. 2009/047908

  However, in the conventional electrolyte membrane-electrode assembly (MEA) as described above, the end surfaces of the frame body have a comb-tooth shape on both the anode surface side and the cathode surface side. The structure becomes complicated. 2) The convex shape of the cathode surface side frame must correspond to the concave shape on the anode surface side, and problems such as the need for highly accurate mold processing arise. It will be.

  Further, since the polymer electrolyte membrane 117 is exposed in the concave portions 119b and 118b of the anode / cathode side frame, the elastic bodies 120 and 121 are attached to the anode surface in the next step as shown in FIG. It must be formed in the side frame recess 119b and the cathode surface side frame recess 118b. Since the elastic bodies 120 and 121 need to be thicker than the thickness of the frame body 118, 3) the entire thickness of the electrolyte membrane-electrode assembly (MEA) is increased. Further, in the assembly process, the frame is sandwiched between the separators, but as shown in FIG. 16, the overlap portion R between the cathode-side elastic body 120 and the anode-side elastic body 121 is strongly sandwiched. 4) Polymer electrolyte A local load acts on the film, which may cause damage to the film.

  In addition, since the overlap R portion depends on the pitch and shape accuracy of the comb teeth on the anode side and the cathode side, variations in the R portion dimension are likely to occur. Since the junction between the anode side elastic body 121 and the anode side frame recess and the junction between the cathode side elastic body 120 and the cathode side frame recess are perpendicular to the polymer electrolyte membrane, they are easily damaged when sandwiched between separators. In addition, since the joining distance is only the thickness of the frame body, 5) the cross leak tends to occur.

  Cross leak is a phenomenon that gas leaks from one side of the anode side or cathode side to the other through a small gap generated between the inner edge of the frame and the electrode through a part of the gas supplied into the battery. Means. In order to improve the power generation efficiency in the fuel cell, it is necessary to reduce such cross leak.

  The present invention solves the above-mentioned conventional problems, and in a method of forming a frame body by injection molding around the electrode, the second frame member and the third frame member are integrated with the first frame member. The electrolyte membrane in a state of being joined and sandwiched between them can be held in a more closely contacted state, the electrode membrane is not turned over, and the electrode membrane is not exposed to the outside. It is an object of the present invention to provide an electrode-membrane-frame assembly part having the same thickness of the frame member and the third frame member.

  In order to achieve the above object, in the present invention, an electrolyte membrane, a first frame member arranged at a peripheral portion of the electrolyte membrane, and an electrolyte membrane on a side opposite to the first frame member with respect to the electrolyte membrane An electrode-membrane-frame junction where the electrolyte membrane is not exposed to the outside, in which the second and third frame members of the same thickness, which are alternately overlapped in a comb-tooth shape, with the end face of the electrode as the border Provide body parts.

  As described above, the electrolyte membrane, the first frame member arranged at the periphery of the electrolyte membrane, and the comb on the opposite side of the electrolyte membrane from the first frame member with the end face of the electrolyte membrane as a boundary. By using an electrode-membrane-frame assembly in which the electrolyte film is not exposed to the outside, in which the second frame member and the third frame member having the same thickness, which are alternately overlapped with the tooth shape, are adhered to each other, Since the airtightness with the electrode peripheral part can be improved without turning up the peripheral part of the electrolyte membrane, cross leak can be reduced.

  Further, since the electrolyte membrane is not exposed to the outside, a problem that damages the electrolyte membrane does not occur. Further, the third frame member can be molded with the same thickness as the second frame member because the portion not filled with the second frame member is injection-molded. Moreover, although the joint part of the 2nd frame member and the 3rd frame member is comb-tooth shape, since the end surface part of a 1st frame member may be linear shape, it becomes a simple metal mold | die structure.

Stack structure diagram of fuel cell Schematic diagram in the vicinity of the end face of the single cell MEA in the present invention. The schematic diagram which has arrange | positioned the 1st frame member in the peripheral part of the polymer electrolyte membrane in this invention The schematic diagram which has arrange | positioned the 2nd frame member in the peripheral part of the polymer electrolyte membrane in this invention The top view which has arrange | positioned the 2nd frame member in the peripheral part of the polymer electrolyte membrane in this invention The schematic diagram which has arrange | positioned the 3rd frame member in the peripheral part of the polymer electrolyte membrane in this invention Sectional drawing which formed the 3rd frame member in the upper surface of the 2nd frame member in this invention The schematic diagram which formed the 3rd frame member in the upper surface of the 2nd frame member in this invention The schematic diagram which made the joint surface of the 2nd and 3rd frame member in this invention the slope shape The schematic diagram which made the joining surface of the 2nd frame member in this invention the slope shape The schematic diagram of the state without the clearance gap between the anode electrode and 1st frame member in this invention Schematic diagram of a state without a gap between the cathode electrode and the second frame member in the present invention Schematic diagram when elastomer is used for frame member in the present invention Partial schematic diagram of conventional electrode-membrane-frame assembly (without elastic member) Partial schematic diagram of conventional electrode-membrane-frame assembly (with elastic member) AA line schematic cross-sectional view of a conventional electrode-membrane-frame assembly

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. Fuel cell and fuel cell stack structure:
The fuel cell is a solid polymer electrolyte fuel cell (PEFC), and electrically reacts a fuel gas containing hydrogen with an oxidant gas containing oxygen such as air, thereby generating electric power, heat, and Water is generated at the same time.

  A fuel cell is configured by a stack having a stacked structure in which a plurality of fuel cells (single cells) having a pair of anode and cathode electrodes are connected in series.

  FIG. 1 shows a fuel cell stack. A stack provided in a fuel cell is formed by stacking a plurality of single cells (single cell modules) 205 which are basic unit configurations, and are fastened with a predetermined load from both sides by a current collector plate 203, an insulating plate 202, and an end plate 201. Yes. Each current collecting plate 203 is provided with a current extraction terminal portion 203a from which a current, that is, a battery is extracted during power generation. Each of the insulating plates 202 insulates between the current collector plate 203 and the end plate 201, and may be provided with a gas or cooling water inlet / outlet (not shown). Each end plate 201 fastens and holds a single cell 205, a current collecting plate 203, and an insulating plate 202, which are stacked, with a predetermined load by a pressing means (not shown).

  As shown in FIG. 1, the single cell 205 is configured such that the MEA 207 is sandwiched between a pair of separators 206 and 208. The MEA 207 forms a catalyst layer (anode side catalyst layer) on the anode surface side of the polymer electrolyte membrane that selectively transports hydrogen ions, and also forms a catalyst layer (cathode side catalyst layer) on the cathode surface side. The gas diffusion layer having both the gas permeability of the fuel gas or the oxidant gas and the electron conductivity is arranged on the outer surface of the catalyst layer.

  The separators 206 and 208 may be any gas-impermeable conductive material. For example, a material obtained by cutting a resin-impregnated carbon material into a predetermined shape or a mixture of carbon powder and a resin material is generally used. . A concave groove is formed in a portion of the separators 206 and 208 that contacts the MEA 207. When the groove contacts the gas diffusion layer, fuel gas or oxidant gas is supplied to the electrode surface, and excess gas is carried away. A gas flow path is formed.

2. Structure of electrolyte membrane-electrode assembly (MEA):
FIG. 2 shows a schematic diagram in the vicinity of the end face of the single-cell MEA.

  The unit cell includes an electrode part 212 formed by joining the anode electrode 211 to one surface of the polymer electrolyte membrane 213 and joining the cathode electrode 210 to the other surface of the polymer electrolyte membrane 213, An electrode-membrane-frame assembly (MEA) formed by a frame body portion 218 disposed on the peripheral edge and having a gas supply portion for supplying fuel gas and oxidant gas to the anode electrode 211 and the cathode electrode 210, respectively. And a pair of separators sandwiching the MEA from the anode side and the cathode side. A polymer electrolyte fuel cell is formed by assembling a plurality of single cells.

  As shown in FIG. 2, the frame body portion 218 includes a first frame member 215 having a frame shape in a plan view, and a second frame member 216 and a third frame member 214 having the same frame shape, which are injection-molded. It is formed by integrally joining. Further, the first frame member 215, the second frame member 216, and the third frame member 214 are disposed so that the peripheral edge portion of the polymer electrolyte membrane 213 of the electrode portion 212 is sandwiched between them. The three members are closely joined and held. In addition, the joint surface at the boundary between the second frame member 216 and the third frame member 214 has a comb-tooth shape 217 in order to hold down the polymer electrolyte membrane 213 during injection molding.

3. Method for forming electrolyte membrane-electrode assembly (MEA):
A method for forming the MEA having the above-described configuration by injection molding will be described with reference to explanatory diagrams shown in FIGS.

  FIG. 3 shows a cross-sectional view of a state in which the polymer electrolyte membrane 213 is placed on the first frame member 215.

  First, a first frame member 215 that holds the periphery of the polymer electrolyte membrane 213 is formed in advance by injection molding. FIG. 4 shows a state in which the second frame member is formed in the next step. In this step, the first frame member 215 is inserted into an injection mold, and the anode electrode 211 is joined to one surface of the polymer electrolyte membrane 213 and the cathode electrode 210 is joined to the other surface. An electrode part is arranged. Then, after arranging the polymer electrode membrane and the electrode part in the mold, the resin is flowed by injection molding on the side opposite to the first frame member with respect to the polymer electrolyte to form the second frame member 216. To do.

  If the resin is injected from the upper surface portion of the polymer film, the film may be damaged by the injection pressure of the resin. Therefore, the resin is injected from the lateral direction of the end surface portion of the film in the arrow shown in FIG. Further, the upper surface portion of the peripheral end surface of the polymer electrolyte membrane in the second frame member 216 has a comb-tooth shape with the end surface portion of the membrane as a boundary. FIG. 5 shows a top view of the schematic diagram of FIG.

  The end surface portions 219 of the polymer electrolyte membrane are pressed by comb-shaped mold film pressing portions (frame body portions 218) alternately arranged at predetermined intervals, and are not pressed by the mold (second portion). The resin flows into the comb-shaped boundary portion 217) of the frame member to form the second frame member. Since the end face of the polymer film is pressed with a narrow pitch comb-shaped mold and the resin flows in the meantime, the second frame material is formed without the peripheral edge of the film rising or turning up. .

  An appropriate pitch of the comb teeth is 1.0 mm to 3.0 mm. When the pitch is less than 1.0 mm, the resin does not flow easily between the concave portions of the comb teeth, causing poor filling, and the joint length between the second frame member and the third frame member becomes long. This will cause gas leakage. On the other hand, when the pitch is larger than 3.0, the wrinkles of the electrolyte membrane cannot be eliminated even by pressing the mold, which causes the film to turn up. It is necessary to adjust the pitch in the range of 1.0 mm to 3.0 mm, which is determined by the thickness and strength of the film.

  When the thickness of the film is thin and the strength is weak, it is necessary to make the pitch fine because the film is easily turned by injection molding. Further, the distance from the end face of the film to the single face of the mold holder is suitably about 0.5 mm to 2.0 mm, and the distance from the end face of the film to the end face of the second frame member is also 0.5 mm to 2 mm. A value of about 0 mm is appropriate and needs to be determined based on variations in the outer dimensions of the end face of the film and variations in the arrangement of the film on the mold. The greater the variation, the greater the distance from the film end face to the end face of the mold holder and the end face of the second frame member.

  FIG. 6 shows a schematic diagram of the next step. A third frame member 214 is formed on the upper surface of the polymer electrolyte membrane 213 by flowing resin from the upper surface of the second frame member with the same thickness as the second frame member. At this time, since the top surface of the peripheral edge of the polymer film is covered with the comb shape of the tip of the second frame member, the film is not turned over when the third frame member is formed.

  When an oxidant gas containing oxygen is supplied to the anode side and a fuel gas containing hydrogen is supplied to the cathode side to generate power as a fuel cell, the polymer film is deformed by the pressure of the gas and power generation efficiency is reduced. In the present invention, the end surface portion of the second frame member and the end surface portion of the third frame member are joined in a comb shape, and the contact area between the second frame member and the third frame member is large. Since it is in a state of being firmly joined, the strength of the frame body is strong, and deformation of the polymer film can be reduced. In addition, since the strength of the frame is strong, handling properties during assembly are also improved.

(Other embodiments)
FIG. 7 shows a cross-sectional view of an electrode-membrane-frame assembly according to another embodiment of the present invention, and FIG. 8 shows a perspective view (schematic diagram) thereof.

  In the above-described embodiment, the second frame member and the third frame member have the same thickness so as to reduce the total thickness. However, as shown in FIG. There may be a method in which the upper surface of the member 216 is covered with the third frame member 214.

  To comb the comb-shaped portions of the second frame member and the third frame member at the time of injection molding of the third frame member, so that the comb-tooth shaped portion boundary portion and the third frame member are joined in a molten state. The bonding strength between the second frame member and the third frame member is improved. When used as a fuel cell, the electrode-membrane-frame assembly (MEA) is laminated with a load applied, and therefore covers the boundary between the second frame member and the third frame member and the upper surface thereof. Since the third frame member further adheres, the airtightness is improved and the possibility of cross leak is further reduced.

  Also, as shown in FIG. 9, there may be a method of improving the bonding strength and airtightness of the second frame member and the third frame member without increasing the thickness of the frame member.

  The bonding state from the plane of the second frame member and the third frame member is a comb-tooth shape, but the bonding surface in the cross-sectional view is not a vertical surface as shown in FIG. Can be improved. FIG. 10 shows a state where the second frame member is injection-molded. The cross-sectional shape at the comb tooth tip of the second frame member is formed to be a slope or a step shape. After that, the third frame member is formed with the same thickness as the second frame member, so that the tip portion of the second frame member that contacts the third frame member has a vertical shape, as compared with the case where the tip is in a vertical shape. In the embodiment, the contact area is increased and the bonding strength and airtightness are improved.

(Other embodiment 2)
Even with the configuration of the electrode-membrane-frame assembly (MEA) as described above, cross-leakage can be sufficiently reduced. As a better method, a cross-sectional view of other embodiment 2 is shown in FIG. FIG. 12 shows a perspective view (schematic diagram).

  Since gaps are set between the anode electrode 211 and the first frame member 215 and between the cathode electrode 210 and the third frame member 214, the gap is eliminated.

  FIG. 11 is a schematic diagram showing a state in which the gap between the anode electrode side and the cathode electrode side is eliminated, and FIG.

  As shown in FIG. 11 on the cathode electrode side, a second frame member 216a is formed by injection molding on the opposite side of the first frame member 215 with respect to the polymer electrolyte membrane. The resin 216b is caused to flow also between 211 and the first frame member 215, filling the gap between the anode electrode and the first frame member. In this second frame member, the anode electrode side and the cathode electrode side can be formed in separate steps, but the number of steps can be reduced by forming them simultaneously.

  Thereafter, as shown in FIG. 12, the resin is caused to flow between the cathode electrode 210 and the second frame member 216a, and the third frame member 214 is formed so as to cover the polymer film. By this method, the polymer film is completely covered with the frame member, and the exposed portion is eliminated, so that the cross leak can be further reduced.

(Other embodiment 3)
FIG. 13 is a schematic diagram in the case where a material having a sealing function of an elastic body (elastomer or the like) is used for the second frame member, the third frame member, and the fourth frame member according to the third embodiment. Indicates.

  As a manufacturing process, the polymer electrolyte membrane 213 in which the anode electrode 211 and the cathode electrode 210 are joined is placed on the first frame member 215. Next, the first sealing member 220 having an elastic function such as an elastomer is brought into close contact with the end face of the anode electrode, and the protrusion shape 221 is formed on the upper surface of the polymer electrolyte membrane 213 or the upper surface of the first frame member 215. Injection molding as possible.

  An elastomer is a thermoplastic resin having a rubber-like elastic function and can be injection-molded. Therefore, an elastomer is a suitable material for forming various shapes. Next, the second frame member 222 is formed in a comb shape so that the polymer electrolyte membrane 213 does not turn up. At this time, since the polymer electrolyte membrane 213 or the first frame member 215 exists between the first seal member 220 and the second frame member 222, the material of the second frame member 222 By making the same as the material of the first seal member 220, it is possible to perform injection molding at the same time and to reduce the molding process.

  Next, the second seal member 224 is shaped so as to form a projection shape 224 on the upper surface portion of the polymer electrolyte membrane 213 so as to be in close contact with the cathode electrode 210 and the second frame member 222. Since the peripheral edge portion 213a of the polymer electrolyte membrane 213 is in close contact with the first frame member at the convex portion of the comb teeth of the second frame member 222, when the second seal member is injection molded, the membrane Turn-over is unlikely to occur.

  At this time, in the second frame member 222, the second seal member 223 is injection-molded while partially pressing the upper surface of the comb-shaped convex portion holding the end surface portion of the film with a mold, The problem of film turning is further eliminated. The mold is partially convex and pressed to such an extent that a slight press mark is attached to the second frame member. The pressing amount (projection height in the mold) from the surface of the second frame member is about 0.01 to 0.02 mm for a hard resin such as PP material, and 0.05 to 0 for an elastic body such as an elastomer. About 1 mm is appropriate.

  By forming such an electrode-membrane-frame assembly, lip shapes on the protrusions of the elastic body are formed on the anode side and the cathode side of the electrolyte membrane, respectively. By sandwiching the electrode-membrane-frame assembly from the anode side and the cathode side with the separator, the apexes of the lip shapes 221 and 224 are strongly pressed against the separator, so that the portion becomes a sealing mechanism against the gas, and the cathode electrode The gas generated from 210 and the anode electrode 211 can be prevented from leaking outside.

  If the construction method in the present invention is used, it can be applied to a cogeneration system fuel cell for home use, a fuel cell for automobiles, a fuel cell for a power source for base stations such as a mobile phone and the like.

210 Cathode electrode 211 Anode electrode 212 Electrode portion 117, 213 Polymer electrolyte membrane 214 Third frame member 215 First frame member 216, 216a, 222 Second frame member 217 Comb shape (comb of second frame member) (Tooth shape boundary)
218 Frame part

Claims (8)

An anode electrode is disposed on one surface of the polymer electrolyte membrane, a cathode electrode is disposed on the other surface, and is provided at a peripheral portion of the polymer electrolyte membrane. The anode and the cathode electrode are respectively provided with fuel gas and oxidation. An electrode-membrane-frame assembly of a polymer electrolyte fuel cell having a frame body having a gas supply section for supplying an agent gas,
The upper and lower surfaces of the polymer electrolyte membrane among the peripheral portions of the polymer electrolyte membrane are configured to be covered with a resin,
An electrode-membrane-frame assembly of a polymer electrolyte fuel cell characterized by   A first frame member is disposed on the first surface side of the polymer electrolyte membrane, and a comb-shaped second frame member is disposed on the second surface side of the periphery of the polymer electrolyte membrane. The electrode-membrane-frame assembly of a polymer electrolyte fuel cell according to claim 1.   The third frame member is disposed on a surface on the second surface side of the polymer electrolyte membrane, and the second frame member and the third frame member are closely joined and held. 3. An electrode-membrane-frame assembly of a polymer electrolyte fuel cell according to 2.   The third frame member is disposed on a second surface side surface of the polymer electrolyte membrane, and the third frame member is configured to be covered with an upper surface of the second frame member. 3. An electrode-membrane-frame assembly of a polymer electrolyte fuel cell according to 2.   3. The electrode-membrane-frame assembly of a polymer electrolyte fuel cell according to claim 2, wherein, of the comb-shaped second frame member, the convex portion is formed of a plurality of steps.   The polymer electrolyte membrane according to any one of claims 3 to 5, wherein the polymer electrolyte membrane is configured not to be exposed by the anode electrode, the cathode electrode, and the first to third frame members. Electrode-membrane-frame assembly of an electrolyte fuel cell.   The electrode-membrane-frame assembly of the polymer electrolyte fuel cell according to claim 1 is sandwiched between a pair of separators, and a plurality of unit cell modules are stacked and assembled. A polymer electrolyte fuel cell. An anode electrode is disposed on one surface of a polymer electrolyte membrane, a cathode electrode is disposed on the other surface, and a polymer electrolyte fuel cell comprising a frame body provided on a peripheral portion of the polymer electrolyte membrane. In a method for producing an electrode-membrane-frame assembly,
A portion of the polymer electrolyte membrane is placed on the first frame member, a peripheral portion of the polymer electrolyte membrane is fixed with the first frame member and a mold, and the first frame A second frame member is injection-molded on the periphery of the polymer electrolyte membrane opposite to the side where the member is disposed;
Injection molding a third frame member between a peripheral portion of the polymer electrolyte membrane and the second frame member;
A method for producing an electrode-membrane-frame assembly of a polymer electrolyte fuel cell, characterized in that:

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