JP5954528B2 - Fuel cell - Google Patents

Description

  The present invention relates to an improvement in a fuel cell such as a polymer electrolyte fuel cell (PEFC).

  An example of this type of fuel cell is described in Patent Document 1. The fuel cell described in Patent Document 1 includes a membrane electrode assembly (MEA) and two separators that sandwich the membrane electrode assembly. The membrane electrode assembly includes an electrolyte membrane sandwiched between a fuel electrode and an air electrode, and has first and second gas diffusion layers on both surfaces thereof.

  In the fuel cell, the end of the membrane electrode assembly is extended to the outside of the gas diffusion layer, and the end of the membrane electrode assembly is formed by an elastic gasket provided on both separators on the outside of the gas diffusion layer. This prevents the membrane electrode assembly from being deformed and the gas diffusion layer from being displaced. Patent Document 1 describes that a reinforcing frame may be integrally provided on the outer peripheral portion of the membrane electrode assembly.

JP 2010-108852 A

  By the way, in the fuel cell as described above, a diffuser portion having a certain area for rectifying the reaction gas is indispensable between the membrane electrode assembly and the manifold that supplies the reaction gas to the membrane electrode assembly. . A diffuser part is comprised by the flame | frame formed in the outer peripheral part of a membrane electrode assembly.

  On the other hand, in this type of fuel cell, a gas differential pressure is generated between the cathode side and the anode side depending on the operating condition of the fuel cell, and the frame forming the diffuser part is affected by the differential pressure. Cheap. That is, in a fuel cell having a diffuser portion, the frame is deformed in the thickness direction in the diffuser portion having a relatively large beam length due to the above-described differential pressure, thereby reducing the cross-sectional area of the gas flow path on one side. The pressure loss of the reaction gas increases, and the differential pressure fluctuation causes repeated stress, causing the frame to deform in the thickness direction, thereby reducing the cross-sectional area of the gas flow path on one side and reducing the pressure loss of the reaction gas. There is a problem that becomes larger.

  In recent years, research and development for thinning has been promoted as one of the measures to realize miniaturization and high performance of fuel cells, and as a result, the above differential pressure is required when thinning the frame. The problem caused by the problem becomes more prominent.

  The present invention has been made in view of the above-described conventional situation, and includes a membrane electrode assembly having a frame on the outer peripheral portion, and two separators sandwiching the frame and the membrane electrode assembly, and the frame and the separator. It is an object of the present invention to provide a fuel cell in which a diffuser portion is formed between the frames, and the deformation of the frame due to the gas pressure difference between the cathode side and the anode side can be suppressed.

  A fuel cell according to the present invention includes a membrane electrode assembly having a structure in which an electrolyte membrane is sandwiched between a pair of electrode layers, a frame disposed on the outer periphery of the membrane electrode assembly, and the membrane electrode assembly and the frame. A separator that partitions the gas flow path is provided, and a diffuser portion that is a part of the gas flow path is formed between the frame and the separator. The fuel cell includes a porous metal body having gas permeability on the surface of the electrode layer, and the porous metal body has an overhanging portion that covers the region of the diffuser portion of the frame on the outer peripheral side. Thus, the above configuration is used as a means for solving the conventional problems.

  According to the present invention, in a fuel cell comprising a membrane electrode assembly having a frame on the outer peripheral portion, and two separators sandwiching the frame and the membrane electrode assembly, and having a diffuser portion formed between the frame and the separator. The deformation of the frame due to the differential pressure of gas between the cathode side and the anode side can be suppressed. As a result, a sufficient cross-sectional area of the gas flow path can be secured, and pressure loss of the reaction gas can be prevented.

It is sectional drawing of the principal part explaining one Embodiment of the fuel cell of this invention. It is a top view of the whole fuel cell shown in FIG. FIG. 3 is a plan view of the fuel cell shown in FIG. 2 in an exploded state. It is sectional drawing of the principal part explaining other embodiment of the fuel cell of this invention.

Hereinafter, an embodiment of a fuel cell according to the present invention will be described based on the drawings.
The fuel cell FC shown in FIGS. 1 to 3 includes a membrane electrode assembly M having a structure in which the electrolyte membrane 1 is sandwiched between a pair of electrode layers (2, 3), a frame 4 disposed on the outer periphery of the electrolyte membrane 1, and In addition, separators 5 and 5 that partition the gas flow path G between the membrane electrode assembly M and the frame 4 are provided.

  The membrane electrode assembly M is a so-called MEA (Membrane Electrode Assembly) in which an electrolyte membrane 1 made of a solid polymer is sandwiched between a cathode layer 2 and an anode layer 3 which are a pair of electrode layers. As shown in FIG. 1, the cathode layer 2 and the anode layer 3 are respectively provided with catalyst layers 21 and 31, porous layers 22 and 32 that function as gas diffusion layers, and porous metal bodies 23 and 33 from the electrolyte membrane 1 side. ing. The porous layers 22 and 32 may be composed of a plurality of layers.

  The frame 4 is a resin member that supports the membrane electrode assembly M and also functions as a gasket. An example of the material is polyethylene naphthalate (PEN). As shown in FIG. 3, the frame 4 has a planar rectangular shape and is integrated with an outer edge portion of the membrane electrode assembly M. As shown in FIG. 1, the frame 4 of this embodiment is obtained by sandwiching the outer edge portion of the electrolyte membrane 1 with a pair of sheet-like materials and bonding the materials together with an adhesive layer 4A. ,

  Further, the frame 4 has supply holes H1 to H3 for cathode gas (oxygen-containing gas), coolant, and anode gas (hydrogen-containing gas) on one short side on the left side in FIG. On the short side, there are discharge holes H4 to H6 for these fluids. The positional relationship between supply and discharge can be changed as appropriate.

  The separator 5 also serves as a current collector. As shown in FIG. 3, the separator 5 has a plane rectangular shape having substantially the same vertical and horizontal dimensions as the frame 4, and is formed by press-molding a metal plate such as stainless steel. . The separator 5 has a plurality of protrusions along the long side direction in parallel with each other on the inner surface of the center portion, thereby forming a gas flow path G between the separator 5 and the membrane electrode assembly M. Further, the separator 5 has supply holes H1 to H3 and discharge holes H4 to H6 similar to the frame 4 formed on both short sides. In FIG. 3, the metal porous bodies 23 and 33 are omitted.

  The membrane electrode assembly M and the frame 4 and the separators 5 and 5 are overlapped with each other to constitute the fuel cell FC. At this time, the fuel cell FC includes a power generation unit G that is a region of the membrane electrode assembly M in the center as shown in FIG. The fuel cell FC includes a manifold portion H in which reaction gas supply holes H1 to H3 and discharge holes H4 to H6 are arranged on both sides of the power generation portion G, and reaches the power generation portion G from each manifold portion H. A diffuser part D for rectifying the reaction gas is provided between them. That is, the fuel cell FC has a configuration in which a diffuser portion D that is a part of the gas flow path G is formed between the frame 4 and the separators 5 and 5.

  Here, in the separator 5, a large number of convex portions 5 </ b> A are arranged vertically and horizontally in a region corresponding to the diffuser portion D. These convex portions 5A are in contact with the frame 4 to prevent the gas flow path G from being blocked when a load in the thickness direction is applied to the fuel cell FC.

  Further, the fuel cell FC is provided with a sealing material 6 between the frame 4 and the edges of the separators 5 and 5 and around the supply holes H1 to H3 and the discharge holes H4 to H6. In a state where a plurality of fuel cells FC are stacked, the sealing material 6 is also provided between the cells, that is, between the adjacent separators 5. The sealing material 6 hermetically separates the flow areas of the cathode gas, the anode gas, and the cooling fluid between the individual layers, and supplies the supply holes H1 to H3 and the predetermined holes so that a predetermined fluid flows between the layers. Openings are provided at appropriate locations on the periphery of the discharge holes H4 to H6.

  As described above, the fuel cell FC includes the porous metal bodies 23 and 33 that have gas permeability and function as gas diffusion layers on the surfaces of the cathode layer 2 and the anode layer 3 that are electrode layers. ing. In the fuel cell FC, the metal porous bodies 23 and 33 include projecting portions 23A and 33A that cover the region of the diffuser portion D of the frame 4 on the outer peripheral side thereof.

  In the case of this embodiment, the overhang portions 23 </ b> A and 33 </ b> A of the metal porous bodies 23 and 33 only need to cover the frame 4, and need not be joined to the frame 4. Of course, it goes without saying that the same effect can be achieved even when the structure is integrated. In this embodiment, the overhang portions 23A and 33A and the convex portion 5A of the separator 5 are in contact with each other. Even in the overhang portions 23A, 33A and the convex portion 5A, it is not necessary to be joined to each other, and it is sufficient that they are simply in contact with each other. Further, the overhang portions 23A and 33A and the convex portion 5A of the separator 5 do not have to be in contact with each other. In this case, you may make it contact when the flame | frame 4 deform | transforms with a differential pressure.

  The metal porous bodies 23 and 33 are made of at least one of a foam metal, an expanded metal, a punching metal, an etching plate, a precision press working plate, a wire mesh, a metal mesh, and a metal fine wire sintered body. That is, the metal porous bodies 23 and 33 have at least gas permeability in the thickness direction.

  The porous metal bodies 23 and 33 more desirably have not only gas permeability in the thickness direction but also gas permeability in the in-plane direction. At this time, the metal porous bodies 23 and 33 may have a gas permeability in the in-plane direction per se, such as a foam metal, a wire mesh, and a fine metal wire sintered body, or may be three-dimensional in the thickness direction. It is also possible to secure the gas permeability in the in-plane direction by performing processing to be performed. For example, gas permeability in the in-plane direction can be ensured by processing a flat punching metal into a cross-sectional wave shape.

  Since the fuel cell FC having the above-described configuration includes the porous metal bodies 23 and 33 on the surfaces of the cathode layer 2 and the anode layer 3, the porous metal bodies 23 and 33 are responsible for differential pressure input and steady input load. As a result, the stress on the frame 4 is relaxed.

  Also, in this type of fuel cell, a gas differential pressure cycle occurs between the cathode side and the anode side depending on the operating conditions, etc., and the portion where the beam length is generally increased, that is, the frame 4 in the diffuser part D is different. It is easily affected by pressure input. On the other hand, the fuel cell FC relieves stress on the frame 4 and suppresses deformation of the frame 4 by the metal porous bodies 23 and 33 even when the above-described differential pressure cycle occurs. it can. Thereby, in the fuel cell FC, a sufficient cross-sectional area of the gas flow path G can be secured to prevent an increase in the pressure loss of the reaction gas.

  Further, since the stress on the frame 4 is relieved in the fuel cell FC as described above, the durability of the frame 4 is improved, and the membrane electrode assembly M is supported by the frame 4 even if the frame 4 is thinned. The function can be sufficiently maintained, and the overall thickness can be reduced.

  Furthermore, a plurality of fuel cells FC are stacked to constitute a fuel cell stack. This fuel cell stack can maintain high-efficiency power generation with the above-described deformation suppression of the frame 4 and securing of the cross-sectional area of the gas flow path G. Furthermore, the fuel cell stack can be reduced in size and weight as the fuel cell FC is made thinner. Such a fuel cell stack is very suitable as a power source mounted on a vehicle such as an automobile.

  Furthermore, since the fuel cell FC of this embodiment has a structure in which the convex portion 5A of the separator 5 and the overhang portions 23A and 33A of the metal porous bodies 23 and 33 are in contact with each other, the overhang portions 23A and 33A and The displacement in the thickness direction of the frame 4 is suppressed, and the deformation suppressing function of the frame 4 due to the differential pressure cycle is further enhanced.

  Further, in the fuel cell FC, the porous metal bodies 23 and 33 are made of at least one of foam metal, expanded metal, punching metal, etching plate, precision press-worked plate, wire mesh, metal mesh, and metal fine wire sintered body. Therefore, the function of relieving stress on the frame 4 can be enhanced with a simple configuration.

  Further, in the fuel cell FC, since the metal porous bodies 23 and 33 have gas permeability in the thickness direction and in the in-plane direction, the substantial gas permeation area in the diffuser portion D increases. Thereby, further reduction of the pressure loss of the reaction gas can be realized.

  FIG. 4 is a diagram for explaining another embodiment of the fuel cell of the present invention. Note that the same components as those of the previous embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The illustrated fuel cell FC includes a membrane electrode assembly M, a frame 4 disposed on the outer periphery thereof, and a separator 5 that partitions and forms a gas flow path G between the membrane electrode assembly M and the frame 4. . A diffuser portion D, which is a part of the gas flow path G, is formed between the frame 4 and the separator 5.

  The fuel cell FC includes gas permeable porous layers 22 and 32 and metal porous bodies 23 and 33 on the surface of the electrode layer (2, 3), and the metal porous body 23 of the electrode layer (2) on one side. However, on the outer peripheral side, an overhang portion 23 </ b> A joined to the frame 4 so as to cover the region of the diffuser portion D of the frame 4 is provided. In the illustrated fuel cell FC, the metal porous body 23 that forms the surface of the cathode layer 2 is provided with an overhang 23A.

  That is, in the previous embodiment, the projecting portions (23A, 33A) of the metal porous bodies (23, 33) of the cathode layer 2 and the anode layer 3 cover the region of the diffuser portion D of the frame 4. . On the other hand, in this embodiment, the protruding portion 23A of the porous metal body 23 in the cathode layer 2 not only covers the region of the diffuser portion D of the frame 4, but is joined to the frame 4.

  Here, the fuel cell FC constitutes a fuel cell stack as described above. This fuel cell stack is operated by a predetermined fuel cell system. Some fuel cell systems are called anode dead end systems in which the flow of anode gas is unidirectional from the supply side to the discharge side. In such a fuel cell system, the anode gas supply pressure is pulsated in order to efficiently supply the anode gas and discharge the generated water. At this time, the pressure of the cathode gas is substantially constant, and the upper and lower pressures of the anode gas can be designed to be larger than the pressure of the cathode gas.

  In such a fuel cell system, in the fuel cell FC, a differential pressure is repeatedly generated between the cathode side and the anode side, and a portion where the beam length is particularly increased by such a differential pressure cycle, that is, a diffuser portion D. The frame 4 corresponding to this area is repeatedly deformed.

  Therefore, in the fuel cell FC of this embodiment, the overhanging portion 23A is provided on the metal porous body 23 of the electrode layer (2) on one side, and the overhanging portion 23A and the frame 4 are joined together, thereby the overhanging portion 23A. Thus, deformation of the frame 4 is suppressed. Thereby, the fuel cell FC can obtain the same operation and effect as the previous embodiment.

  Since the fuel cell FC joins the overhang 23A and the frame 4, if the overhang 23A is provided on one electrode layer, a certain effect of suppressing the deformation of the frame 4 can be obtained. it can. However, the fuel cell FC may have a configuration in which an overhang portion (23A) is provided in the porous metal body (23) in the electrode layer (2) on the cathode side and the anode side where the gas pressure is low. More desirable.

  This is because, when an overhang portion is provided on the electrode layer on the side where the gas pressure is high, the frame 4 and the separator protrusion 5A abut on the structure, and creep deformation occurs depending on the characteristics of the frame 4. Become. On the other hand, if an overhang portion is provided in the electrode layer on the low gas pressure side, creep deformation occurs depending on the characteristics of the metal porous body. The lateral displacement can be reduced. That is, the displacement can be structurally prevented.

  Therefore, as a more preferable embodiment, the fuel cell FC is provided with an overhang portion on the electrode layer on the low gas pressure side. When applied to the fuel cell system described above, the electrode layer on the low gas pressure side is provided. The overhanging portion 23A is provided in the metal porous body 23 of the cathode layer 2 as described above. As a result, the fuel cell FC can more reliably prevent the deformation of the frame 4 due to the gas pressure difference between the cathode side and the anode side, and the durability and power generation function can be improved as in the previous embodiment. In addition to making the entire battery thinner, it contributes to reducing the size and weight of the fuel cell stack.

  The configuration of the fuel cell according to the present invention is not limited to only the above-described embodiments, and includes the shape of the entire fuel cell, the shape and material of each component, and the like without departing from the gist of the present invention. The details of the configuration can be changed as appropriate.

D Diffuser part FC Fuel cell G Gas flow path M Membrane electrode assembly 1 Electrolyte membrane 2 Cathode layer (electrode layer)
3 Anode layer (electrode layer)
4 Frame 5 Separator 23 Metal porous body 23A Overhang 33 Metal porous body 33A Overhang

Claims (6)

A membrane electrode assembly having a structure in which an electrolyte membrane is sandwiched between a pair of electrode layers, a frame disposed on an outer peripheral portion of the membrane electrode assembly, and a separator that forms a gas flow path between the membrane electrode assembly and the frame And a fuel cell in which a diffuser part which is a part of a gas flow path is formed between the frame and the separator,
Provided with a porous metal body having gas permeability on the surface of the electrode layer,
A fuel cell, characterized in that the porous metal body has an overhanging portion that covers the region of the diffuser portion of the frame on the outer peripheral side. A membrane electrode assembly having a structure in which an electrolyte membrane is sandwiched between a pair of electrode layers, a frame disposed on an outer peripheral portion of the membrane electrode assembly, and a separator that forms a gas flow path between the membrane electrode assembly and the frame And a fuel cell in which a diffuser part which is a part of a gas flow path is formed between the frame and the separator,
Provided with a porous metal body having gas permeability on the surface of the electrode layer,
A fuel cell, wherein the porous metal body of the electrode layer on one side includes an overhanging portion bonded to the frame so as to cover a region of the diffuser portion of the frame on the outer peripheral side.   3. The fuel cell according to claim 2, wherein the electrode layer on one side is an electrode layer on a cathode gas side or an anode side on which a gas pressure is low. 4. Wherein the metal porous body, foamed metal, expanded metal, punching metal, etching plates, gold network, to any one of claims 1-3, characterized in that it consists of at least one of the metal mesh and the metal thin wire The fuel cell as described.   The fuel cell according to claim 1, wherein the porous metal body has gas permeability in a thickness direction and an in-plane direction.   A fuel cell stack comprising a plurality of the fuel cells according to any one of claims 1 to 5 stacked together.

Images