JP5694113B2 - Fuel cell - Google Patents

Description

  In the present invention, a first electrode having a first catalyst layer and a first gas diffusion layer and a second electrode having a second catalyst layer and a second gas diffusion layer are disposed on both surfaces of the solid polymer electrolyte membrane. The present invention relates to a fuel cell in which an electrolyte membrane / electrode structure and a separator are stacked.

  In general, a polymer electrolyte fuel cell employs a polymer electrolyte membrane made of a polymer ion exchange membrane. This fuel cell comprises an electrolyte membrane / electrode structure (MEA) in which an anode electrode and a cathode electrode each comprising a catalyst layer (electrode catalyst) and a gas diffusion layer (porous carbon) are disposed on both sides of a solid polymer electrolyte membrane. ) Is sandwiched between separators (bipolar plates). Usually, a fuel cell stack in which a predetermined number of fuel cells are stacked is used in, for example, a fuel cell electric vehicle as an in-vehicle fuel cell stack.

  In this type of electrolyte membrane / electrode structure, one gas diffusion layer is set to have a smaller surface area than the solid polymer electrolyte membrane, and the other gas diffusion layer is set to the same surface area as the solid polymer electrolyte membrane. In other words, a so-called step type MEA may be formed.

  For example, in the electrolyte membrane-electrode assembly disclosed in Patent Document 1, as shown in FIG. 7, the electrolyte membrane 1, the cathode catalyst layer 2 a disposed on one side of the electrolyte membrane 1, and the electrolyte membrane 1 is provided with an anode catalyst layer 2b disposed on the other side of 1 and gas diffusion layers 3a and 3b disposed on both sides of the electrolyte membrane 1.

  The gas diffusion layer 3b on the anode side is configured to be equal to the area of the electrolyte membrane 1 and larger than the area of the gas diffusion layer 3a on the cathode side. A gasket structure 4 is disposed in the edge region of the electrolyte membrane / electrode assembly (MEA), and the outer periphery of the electrolyte membrane 1 on the gas diffusion layer 3a side and the gasket structure 4 are bonded to each other. It is joined via.

JP 2007-66766 A

  By the way, in the above-mentioned Patent Document 1, a gap is formed between the outer peripheral end surface 3ae of the gas diffusion layer 3a and the inner peripheral end surface 4ae on the inner side of the gasket structure 4 from the relationship between processing accuracy and assembly accuracy. easy. For this reason, there is a problem that gas permeation from the gap between the gas diffusion layer 3a and the gasket structure 4 is increased, and the electrolyte membrane 1 is particularly deteriorated.

  Further, in a fuel cell, a buffer may be provided in the separator so as to communicate with the inlet and outlet of the reaction gas flow path. The buffer section is provided outside the electrode surface and has a function of diffusing the reaction gas and allowing it to uniformly flow through the reaction gas channel.

  Therefore, in the electrolyte membrane-electrode assembly, the cathode catalyst layer 2a and the anode catalyst layer 2b are usually not provided in the portion corresponding to the buffer portion. Accordingly, there is a problem that gas permeation easily increases on the tip side of the electrolyte membrane 1 corresponding to the buffer portion, and the electrolyte membrane 1 is significantly deteriorated.

  The present invention solves this type of problem, and is a fuel cell capable of preventing damage to a solid polymer electrolyte membrane as much as possible and ensuring good power generation performance with an easy and simple configuration. The purpose is to provide.

  The present invention provides a first electrode having a first catalyst layer and a first gas diffusion layer on one surface of a solid polymer electrolyte membrane, and a second catalyst layer and a second electrode on the other surface of the solid polymer electrolyte membrane. A second electrode having two gas diffusion layers is laminated with an electrolyte membrane / electrode structure and a separator, and the plane of the first gas diffusion layer is the plane of the second gas diffusion layer. The present invention relates to a fuel cell having a larger dimension and the same dimension as the plane of the solid polymer electrolyte membrane.

  In this fuel cell, a surface of the separator facing the first electrode is formed with a reaction gas flow channel for allowing one of the reaction gases to flow, and a buffer portion communicating with an inlet and an outlet of the reaction gas flow channel. The first catalyst layer is provided over the entire outer peripheral end portion of the first gas diffusion layer including a portion corresponding to the buffer portion.

The outer peripheral end portion of the second electrode than the outer peripheral end portion of the solid polymer electrolyte membrane disposed inwardly, and the outer peripheral edge portion of the second catalyst layer, the outer peripheral edge portion of the second gas diffusion layer the outer periphery of the well while being positioned inwardly, fuel cell, one end is disposed between the second gas diffusion layer and the outer circumferential edge portion of the second catalyst layer, and the other end of the solid polymer electrolyte membrane and a frame-shaped film member disposed at the same position as the end.

  According to the present invention, the plane of the first gas diffusion layer is set to the same size as the plane of the solid polymer electrolyte membrane, and the first catalyst layer includes a portion corresponding to the buffer portion. It is provided over the entire outer peripheral end of the gas diffusion layer, that is, over the entire outer peripheral end of the solid polymer electrolyte membrane.

  Therefore, no gap is formed in the electrolyte membrane / electrode structure corresponding to the end of the first catalyst layer, and gas permeation of the solid polymer electrolyte membrane can be suppressed as much as possible. . This makes it possible to prevent damage to the solid polymer electrolyte membrane as much as possible with an easy and simple configuration and to ensure good power generation performance.

  Moreover, the plane of the first gas diffusion layer is set to the same dimension as the plane of the solid polymer electrolyte membrane. Therefore, since the first electrode itself supports the entire surface of the solid polymer electrolyte membrane, the deformation of the solid polymer electrolyte membrane can be satisfactorily suppressed.

It is a principal part disassembled perspective explanatory drawing of the fuel cell which concerns on the 1st Embodiment of this invention. FIG. 2 is a sectional view of the fuel cell taken along line II-II in FIG. 1. FIG. 4 is a partial cross-sectional explanatory view of an electrolyte membrane / electrode structure constituting the fuel cell. It is a front view of the cathode side of the electrolyte membrane / electrode structure. It is a principal part disassembled perspective explanatory drawing of the fuel cell which concerns on the 2nd Embodiment of this invention. FIG. 4 is a partial cross-sectional explanatory view of an electrolyte membrane / electrode structure constituting the fuel cell. 6 is an explanatory diagram of an electrolyte membrane-electrode assembly disclosed in Patent Document 1. FIG.

  As shown in FIGS. 1 and 2, the fuel cell 10 according to the first embodiment of the present invention includes an electrolyte membrane / electrode structure 12, a first separator 14 that sandwiches the electrolyte membrane / electrode structure 12, and A second separator 16. The first separator 14 and the second separator 16 are made of, for example, a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, a metal plate whose surface is subjected to anticorrosion treatment, a carbon member, or the like. .

  The electrolyte membrane / electrode structure 12 integrally includes protrusions 12a and 12b corresponding to an oxidant gas inlet buffer portion and an outlet buffer portion described later. The protruding portions 12a and 12b constitute a partial region of the buffer portion as a connection flow path portion. The protrusions 12a and 12b may be provided as necessary, and may be unnecessary. The electrolyte membrane / electrode structure 12 includes a solid polymer electrolyte membrane 18, and a cathode electrode (first electrode) 20 and an anode electrode (second electrode) 22 that sandwich the solid polymer electrolyte membrane 18.

  The cathode electrode 20 has a larger surface area than the anode electrode 22 and the same surface area as the solid polymer electrolyte membrane 18. A frame-shaped reinforcing sheet member 24 is disposed on the solid polymer electrolyte membrane 18 on the surface exposed from the outer periphery of the anode electrode 22 to the outside.

  As shown in FIG. 3, the cathode electrode 20 is provided with a first catalyst layer (electrode catalyst layer) 20 a and a first gas diffusion layer 20 b that are in contact with one surface 18 a of the solid polymer electrolyte membrane 18. The anode electrode 22 is in contact with the other surface 18b of the solid polymer electrolyte membrane 18, and the second catalyst layer (electrode catalyst layer) 22a and the second gas expose the outer periphery of the solid polymer electrolyte membrane 18 in a frame shape. A diffusion layer 22b is provided. In addition, you may comprise the 1st and 2nd catalyst layers 20a and 22a from several layers.

  The plane of the first gas diffusion layer 20b is set to a dimension larger than that of the second gas diffusion layer 22b and the same dimension as the plane of the solid polymer electrolyte membrane 18. 4, the first catalyst layer 20a includes the protrusions 12a and 12b and covers the entire outer peripheral end of the first gas diffusion layer 20b, that is, the outer peripheral end of the solid polymer electrolyte membrane 18. It is provided throughout.

  As shown in FIG. 3, the outer peripheral end portion 22ae of the second catalyst layer 22a is disposed inwardly of the outer peripheral end portion 22be of the second gas diffusion layer 22b. The reinforcing sheet member 24 has one end 24 a disposed between the outer peripheral edge of the second catalyst layer 22 a and the second gas diffusion layer 22 b, and the other end 24 b at the same position as the outer peripheral end of the solid polymer electrolyte membrane 18. Be placed.

  The reinforcing sheet member 24 has a frame shape and is made of a gas-impermeable material such as engineering plastics or super engineering plastics such as PPS (polyphenylene sulfide resin) or PEEK (polyether ether ketone). The material of the reinforcing sheet member 24 is polyimide, ethylenetetrafluoroethylene, polyvinylidene difluoride, polyester, polyamide, copolyamide, polyamide elastomer, polyurethane, polyurethane elastomer, silicone, thermoplastic elastomer, polyethylene naphthalate (PEN). Polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and the like are used.

  As shown in FIG. 1, one end edge of the fuel cell 10 in the direction of arrow B (horizontal direction in FIG. 1) communicates with each other in the direction of arrow A, which is the stacking direction, An oxidant gas inlet communication hole 30a for supplying gas, a cooling medium inlet communication hole 32a for supplying a cooling medium, and a fuel gas outlet communication hole 34b for discharging a fuel gas, for example, a hydrogen-containing gas, are shown by arrows. Arranged in the C direction (vertical direction).

  The other end edge of the fuel cell 10 in the direction of arrow B communicates with each other in the direction of arrow A, a fuel gas inlet communication hole 34a for supplying fuel gas, and a cooling medium outlet communication hole for discharging the cooling medium. 32b and an oxidant gas outlet communication hole 30b for discharging the oxidant gas are arranged in the direction of arrow C.

  An oxidant gas flow path (reactive gas flow path) 36 communicating with the oxidant gas inlet communication hole 30 a and the oxidant gas outlet communication hole 30 b is formed on the surface 14 a of the first separator 14 facing the electrolyte membrane / electrode structure 12. Is provided.

  The inlet buffer 37a and the outlet buffer 37b communicate with the inlet 36a side and the outlet 36b side of the oxidant gas flow path 36, respectively. The inlet buffer portion 37a and the outlet buffer portion 37b have a function of diffusing the oxidant gas to smooth and uniform the flow of the oxidant gas, and are configured by a plurality of embosses, for example. The electrolyte membrane / electrode structure 12 includes a protruding portion 12a that constitutes a partial region of the inlet buffer portion 37a as a connecting channel portion, and a protruding portion that constitutes a partial region of the outlet buffer portion 37b as a connecting channel portion. A portion 12b is provided as necessary.

  A fuel gas passage 38 communicating with the fuel gas inlet communication hole 34 a and the fuel gas outlet communication hole 34 b is formed on the surface 16 a of the second separator 16 facing the electrolyte membrane / electrode structure 12. Between the surface 14 b of the first separator 14 and the surface 16 b of the second separator 16, a cooling medium flow path 40 communicating with the cooling medium inlet communication hole 32 a and the cooling medium outlet communication hole 32 b is formed.

  As shown in FIGS. 1 and 2, the first seal member 42 is integrated with the surfaces 14 a and 14 b of the first separator 14 around the outer peripheral end of the first separator 14, and the second The second seal member 44 is integrated with the surfaces 16 a and 16 b of the separator 16 around the outer peripheral end of the second separator 16.

  As shown in FIG. 2, the second seal member 44 includes a first convex seal 44 a interposed between the reinforcing sheet member 24 and the second separator 16, the first separator 14, and the second separator 16. And a second convex seal 44b interposed therebetween. The first seal member 42 constitutes a flat seal. Instead of the second convex seal 44b, the first seal member 42 may be provided with a second convex seal (not shown).

  The first and second sealing members 42 and 44 include, for example, EPDM, NBR, fluorine rubber, silicone rubber, fluorosilicone rubber, butyl rubber, natural rubber, styrene rubber, chloroprene or acrylic rubber, a cushioning material, Alternatively, a packing material is used.

  As shown in FIG. 1, the second separator 16 has a supply hole portion 46 for communicating the fuel gas inlet communication hole 34a with the fuel gas flow path 38, and the fuel gas flow path 38 for communication with the fuel gas outlet communication hole 34b. A discharge hole 48 is formed.

  The operation of the fuel cell 10 configured as described above will be described below.

  First, as shown in FIG. 1, an oxidant gas such as an oxygen-containing gas is supplied to the oxidant gas inlet communication hole 30a, and a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas inlet communication hole 34a. Further, a cooling medium such as pure water, ethylene glycol, or oil is supplied to the cooling medium inlet communication hole 32a.

  For this reason, the oxidant gas is introduced into the oxidant gas flow path 36 of the first separator 14 from the oxidant gas inlet communication hole 30a and moves in the direction of arrow B to the cathode electrode 20 of the electrolyte membrane / electrode structure 12. Supplied. On the other hand, the fuel gas is introduced from the fuel gas inlet communication hole 34 a through the supply hole 46 into the fuel gas flow path 38 of the second separator 16. The fuel gas moves in the direction of arrow B along the fuel gas flow path 38 and is supplied to the anode electrode 22 of the electrolyte membrane / electrode structure 12.

  Therefore, in each electrolyte membrane / electrode structure 12, the oxidant gas supplied to the cathode electrode 20 and the fuel gas supplied to the anode electrode 22 are electrically supplied in the first catalyst layer 20a and the second catalyst layer 22a. It is consumed by chemical reaction to generate electricity.

  Next, the oxidant gas consumed by being supplied to the cathode electrode 20 is discharged in the direction of arrow A along the oxidant gas outlet communication hole 30b. Similarly, the fuel gas consumed by being supplied to the anode electrode 22 passes through the discharge hole 48 and is discharged in the direction of arrow A along the fuel gas outlet communication hole 34b.

  The cooling medium supplied to the cooling medium inlet communication hole 32a is introduced into the cooling medium flow path 40 between the first separator 14 and the second separator 16, and then flows in the direction of arrow B. The cooling medium is discharged from the cooling medium outlet communication hole 32b after the electrolyte membrane / electrode structure 12 is cooled.

  In this case, in the first embodiment, the electrolyte membrane / electrode structure constituting the so-called step MEA in which the anode electrode 22 and the cathode electrode 20 having different surface areas are disposed on both surfaces of the solid polymer electrolyte membrane 18, respectively. 12 is provided. In the electrolyte membrane / electrode structure 12, the plane of the first gas diffusion layer 20b is set to the same dimension as the plane of the solid polymer electrolyte membrane 18, and the first catalyst layer 20a includes the inlet buffer 37a and A portion corresponding to the outlet buffer portion 37b is provided over the entire outer peripheral end portion of the first gas diffusion layer 20b, that is, over the entire outer peripheral end portion of the solid polymer electrolyte membrane 18.

  For this reason, the electrolyte membrane / electrode structure 12 includes a buffer portion at the end of the first catalyst layer 20a, and particularly a portion corresponding to the protruding portions 12a and 12b. Gas permeation of the polymer electrolyte membrane 18 can be suppressed as much as possible. This makes it possible to prevent damage to the solid polymer electrolyte membrane 18 at the outer peripheral end of the solid polymer electrolyte membrane 18 as much as possible with an easy and simple configuration, and to ensure good power generation performance. The effect is obtained. Conventionally, a gap is generated between the adhesive layer of the buffer portion and the end portion of the catalyst layer to cause damage, but this gap is not formed and gas permeation can be suppressed. .

  Moreover, the plane of the first gas diffusion layer 20 b is set to the same dimension as the plane of the solid polymer electrolyte membrane 18. Therefore, the cathode electrode 20 itself supports the entire surface of the solid polymer electrolyte membrane 18, so that the deformation of the solid polymer electrolyte membrane 18 can be satisfactorily suppressed.

  Further, a frame-shaped reinforcing sheet member 24 is disposed on the solid polymer electrolyte membrane 18 on the surface exposed from the outer periphery of the anode electrode 22 to the outside. The reinforcing sheet member 24 has one end 24 a covering the entire outer peripheral end of the second catalyst layer 22 a and being disposed between the second gas diffusion layer 22 b and the other end 24 b being the outer peripheral end of the solid polymer electrolyte membrane 18. (See FIG. 3).

  Therefore, the anode electrode 22 is fixed to the strong reinforcing sheet member 24, and the solid polymer electrolyte membrane 18 is reliably reinforced over the entire surface. The reinforcing sheet member 24 is exposed to the solid polymer electrolyte membrane 18. Since gas permeation is suppressed by covering the portion, there is an advantage that the durability of the solid polymer electrolyte membrane 18 is improved.

  In addition, the reinforcing sheet member 24 is not used on the cathode electrode 20 side. That is, the outer peripheral edge of the first catalyst layer 20a and the outer peripheral edge of the second catalyst layer 22a are not covered with the reinforcing sheet member 24, respectively. Accordingly, it is possible to effectively suppress a decrease in gas diffusibility, and the solid polymer electrolyte membrane 18 is not exposed to a gas-mixed environment for a long time at the outer peripheral end portion. 18 can be suppressed.

  FIG. 5 is an exploded perspective view of a main part of a fuel cell 50 according to the second embodiment of the present invention. The same components as those of the fuel cell 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fuel cell 50 includes an electrolyte membrane / electrode structure 52, and a first separator 54 and a second separator 56 that sandwich the electrolyte membrane / electrode structure 52. The electrolyte membrane / electrode structure 52 corresponds to a fuel gas inlet buffer portion and an outlet buffer portion, which will be described later, and includes protrusions 52a and 52b that constitute a partial region of the buffer portion as a connection flow path portion. In one.

  The electrolyte membrane / electrode structure 52 includes a solid polymer electrolyte membrane 18, and an anode electrode (first electrode) 58 and a cathode electrode (second electrode) 60 that sandwich the solid polymer electrolyte membrane 18. The anode electrode 58 has a larger surface area than the cathode electrode 60 and the same surface area as the solid polymer electrolyte membrane 18. The magnitude relationship between the anode electrode 58 and the cathode electrode 60 is opposite to that of the first embodiment. A frame-shaped reinforcing sheet member 24 is disposed on the solid polymer electrolyte membrane 18 on the surface exposed from the outer periphery of the cathode electrode 60 to the outside.

  As shown in FIG. 6, the anode electrode 58 includes a first catalyst layer (electrode catalyst layer) 58 a and a first gas diffusion layer 58 b that are in contact with one surface 18 a of the solid polymer electrolyte membrane 18. The cathode electrode 60 is in contact with the other surface 18b of the solid polymer electrolyte membrane 18, and the second catalyst layer (electrode catalyst layer) 60a and the second gas expose the outer periphery of the solid polymer electrolyte membrane 18 in a frame shape. A diffusion layer 60b is provided.

  The plane of the first gas diffusion layer 58b is set to a dimension larger than that of the second gas diffusion layer 60b and the same dimension as the plane of the solid polymer electrolyte membrane 18. The first catalyst layer 58a is provided over the entire outer peripheral end of the first gas diffusion layer 58b including the protrusions 52a and 52b, that is, over the entire outer peripheral end of the solid polymer electrolyte membrane 18.

  The outer peripheral end portion 60ae of the second catalyst layer 60a is disposed inward of the outer peripheral end portion 60be of the second gas diffusion layer 60b. The reinforcing sheet member 24 has one end 24 a covering the entire outer peripheral end of the second catalyst layer 60 a and being disposed between the second gas diffusion layer 60 b and the other end 24 b being connected to the outer peripheral end of the solid polymer electrolyte membrane 18. Arranged at the same position.

  As shown in FIG. 5, on the surface 54a of the first separator 54 facing the electrolyte membrane / electrode structure 52, a fuel gas flow path (reactive gas) communicating with the fuel gas inlet communication hole 34a and the fuel gas outlet communication hole 34b. Channel) 38 is formed.

  An inlet buffer unit 39a and an outlet buffer unit 39b communicate with the inlet 38a side and the outlet 38b side of the fuel gas flow path 38, respectively. The inlet buffer unit 39a and the outlet buffer unit 39b have a function of diffusing the fuel gas and smoothing and uniforming the flow of the fuel gas, and are configured by a plurality of embosses, for example. The electrolyte membrane / electrode structure 52 includes a protruding portion 52a that constitutes a partial region of the inlet buffer portion 39a as a connecting channel portion, and a protruding portion that constitutes a partial region of the outlet buffer portion 39b as a connecting channel portion. Part 52b.

  An oxidant gas flow path 36 communicating with the oxidant gas inlet communication hole 30a and the oxidant gas outlet communication hole 30b is provided on the surface 56a of the second separator 56 facing the electrolyte membrane / electrode structure 12. Between the surface 54 b of the first separator 54 and the surface 56 b of the second separator 56, a cooling medium flow path 40 communicating with the cooling medium inlet communication hole 32 a and the cooling medium outlet communication hole 32 b is formed.

  In the second embodiment configured as described above, the plane of the first gas diffusion layer 58b is set to the same dimension as the plane of the solid polymer electrolyte membrane 18, and the first catalyst layer 58a is formed of the inlet buffer. Including the portion corresponding to the portion 39a and the outlet buffer portion 39b, it is provided over the entire outer peripheral end of the first gas diffusion layer 58b, that is, over the entire outer peripheral end of the solid polymer electrolyte membrane 18.

  Thereby, it is possible to prevent damage to the solid polymer electrolyte membrane 18 as much as possible with an easy and simple configuration, and to ensure good power generation performance. An effect is obtained.

DESCRIPTION OF SYMBOLS 10, 50 ... Fuel cell 12, 52 ... Electrolyte membrane and electrode structure 12a, 12b, 52a, 52b ... Projection part 14, 16, 54, 56 ... Separator 18 ... Solid polymer electrolyte membrane 20, 60 ... Cathode electrode 20a, 22a, 58a, 60a ... catalyst layers 20b, 22b, 58b, 60b ... gas diffusion layers 22, 58 ... anode electrode 24 ... reinforcing sheet member 30a ... oxidant gas inlet communication hole 30b ... oxidant gas outlet communication hole 32a ... cooling medium Inlet communication hole 32b ... Cooling medium outlet communication hole 34a ... Fuel gas inlet communication hole 34b ... Fuel gas outlet communication hole 36 ... Oxidant gas flow path 37a, 39a ... Inlet buffer part 37b, 39b ... Outlet buffer part 38 ... Fuel gas flow Path 40 ... cooling medium flow path

Claims (1)

A first electrode having a first catalyst layer and a first gas diffusion layer on one surface of the solid polymer electrolyte membrane, and a second catalyst layer and a second gas diffusion layer on the other surface of the solid polymer electrolyte membrane. The electrolyte membrane / electrode structure provided with the second electrode having the separator and the separator are stacked, and the plane of the first gas diffusion layer is larger than the plane of the second gas diffusion layer. And a fuel cell set to the same dimensions as the plane of the solid polymer electrolyte membrane,
On the surface of the separator facing the first electrode, a reaction gas flow channel for allowing one reaction gas to flow,
A buffer unit communicating with an inlet and an outlet of the reaction gas channel;
Is formed,
The first catalyst layer is provided over the entire outer peripheral end of the first gas diffusion layer including a portion corresponding to the buffer portion ,
The outer peripheral end of the second electrode is disposed inward of the outer peripheral end of the solid polymer electrolyte membrane, and the outer peripheral end of the second catalyst layer is the outer peripheral end of the second gas diffusion layer. Is placed inward than,
The fuel cell has one end disposed between the outer peripheral edge of the second catalyst layer and the second gas diffusion layer, and the other end disposed at the same position as the outer peripheral end of the solid polymer electrolyte membrane. fuel cell according to claim Rukoto includes a picture frame-shaped film member.

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