JP2009199877A - Fuel cell, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell having excellent sealability and quality. <P>SOLUTION: The fuel cell 1 includes: catalyst layers 17 and 18 formed on both surfaces of an electrolyte membrane 16; gaskets 19 and 20 surrounding the circumferences of the catalyst layers; and porous gas diffusion layers 21 and 22 overlapping the catalyst layers; and is characterized in that porosity of peripheral parts 34 and 35 of the gas diffusion layers is lower than that inside the peripheral parts. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell and a method for manufacturing the fuel cell.

  Among fuel cells that generate electricity by electrochemical reaction of reaction gas, there is a solid polymer fuel cell that uses an ion conductive polymer membrane as an electrolyte membrane.

  In a polymer electrolyte fuel cell, a catalyst layer that catalyzes an electrochemical reaction of a reaction gas is disposed on both surfaces of an electrolyte membrane to form a membrane electrode assembly. It generally has a structure sandwiched between a pair of plate-like separators through a gas diffusion layer to be diffused. In order to prevent leakage of the reaction gas, the polymer electrolyte fuel cell includes a gasket surrounding the gas diffusion layer and the catalyst layer.

  For example, in the polymer electrolyte fuel cell described in Patent Document 1, the peripheral portion of the gas diffusion layer and the inner side surface of the gasket that are in contact with each other are molded in advance so as to be inclined at the same inclination with respect to the plane of the electrolyte membrane. .

By having such a structure, the fuel cell described in Patent Document 1 prevents the gas diffusion layers and the gaskets on both sides of the electrolyte membrane from being displaced and applying excessive shear stress to the electrolyte membrane.
JP-A-2005-79059

  However, in the portion where the gasket and the gas diffusion layer are in contact, not only the relaxation of the shear stress applied to the electrolyte membrane but also the improvement of the sealing performance against the reactive gas moving through the gas diffusion layer becomes a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel cell having excellent sealing properties and good quality, and a method for manufacturing the fuel cell.

  In order to achieve the above object, a fuel cell of the present invention has a catalyst layer formed on both surfaces of an electrolyte membrane, a gasket surrounding the periphery of the catalyst layer, and a porous gas diffusion layer overlapping the catalyst layer. The porosity of the peripheral portion of the gas diffusion layer is lower than the porosity inside the peripheral portion.

  In order to achieve the above object, a method of manufacturing a fuel cell according to the present invention includes a gasket disposing step of disposing a gasket on the periphery of both surfaces of an electrolyte membrane, and a catalyst layer forming step of forming a catalyst layer in a region surrounded by the gasket. Have.

  In addition to these steps, the fuel cell manufacturing method of the present invention includes a porous gas diffusion layer overlaid on the catalyst layer and crushing the peripheral portion of the gas diffusion layer in contact with the gasket to reduce the porosity of the peripheral portion. It has the gas diffusion layer arrangement | positioning process made to fall rather than the porosity inside a peripheral part, It is characterized by the above-mentioned.

  In the fuel cell of the present invention, the porosity of the peripheral portion of the gas diffusion layer is lower than the porosity of the inner side of the peripheral portion, so that leakage of the reaction gas can be prevented and the sealing performance is excellent. Therefore, the fuel cell of the present invention has good quality.

  In the fuel cell manufacturing method of the present invention, in the pressing step, the peripheral portion of the gas diffusion layer is brought into contact with the gasket and crushed, and the porosity of the peripheral portion is lower than the porosity inside the peripheral portion. Can be improved. Therefore, the fuel cell manufacturing method of the present invention can manufacture a fuel cell having good quality.

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

  FIG. 1 is a schematic perspective view of a fuel cell according to the present embodiment, FIG. 2 is a schematic cross-sectional view of a single cell, and FIG. 3 is a partially enlarged schematic cross-sectional view of the single cell. FIG. 4 is a schematic view for explaining a gasket disposing process, and FIG. 5 is a schematic perspective view of a supply roll wound with a gasket. FIG. 6 is a schematic sectional view when the catalyst ink is applied in the catalyst layer forming step. FIG. 7 is a schematic cross-sectional view for explaining the pressing process.

  As outlined in FIG. 1, the fuel cell 1 of the present embodiment includes a stack 3 in which a plurality of unit cells 2 as unit cells generating electromotive force are stacked and electrically connected, and a collection for taking out the electromotive force of the stack 3. It has an electric plate 4 and a holding member 5 that holds the stack 3 in a pressed state.

  The current collector plate 4 is a plate-like member made of a conductive material having gas impermeability, such as dense carbon and copper, and has an output terminal 56 for electrical connection with other instruments. The current collector plates 4 are located at both ends of the stack 3 in the stacking direction of the single cells 2 and are electrically connected to the stack 3.

  The holding member 5 includes a pair of end plates 6A and 6B that are flat plates, and a rod-shaped tie rod 7 that fastens the end plates 6A and 6B. The end plates 6A and 6B and the tie rod 7 are made of a material having rigidity, for example, a metal material such as steel.

  The end plates 6A and 6B are located outside the current collecting plate 4 in the stacking direction of the single cells 2, and have through holes through which the tie rods 7 pass at the four corners. The tie rod 7 has male screw portions at both ends in the longitudinal direction, and nuts (not shown) are screwed into the male screw portions to fasten the end plates 6A and 6B. The fuel cell 1 has an insulating insulating plate 8 between the end plates 6A and 6B and the current collecting plate 4 to prevent an electrical short circuit.

  One of the pair of end plates 6 </ b> A, 6 </ b> B has a fuel gas inlet 9 for introducing fuel gas into the stack 3 and a fuel gas outlet 10 through which the fuel gas flowing through the stack 3 flows out. Further, the end plate 6B has an oxidant gas introduction port 11 for introducing the oxidant gas into the stack 3 and an oxidant gas discharge port 12 through which the oxidant gas flowing through the stack 3 flows out. The fuel gas contains hydrogen and the oxidant gas is, for example, air. Further, the end plate 6 </ b> B has a cooling water inlet 13 for introducing cooling water into the stack 3 and a cooling water outlet 14 through which the cooling water circulated through the stack 3 flows.

  As shown in FIG. 2, the single cell 2 as a unit battery constituting the stack 3 has a laminated structure in which a plurality of rectangular plate-like members are laminated. Specifically, the single cell 2 includes a pair of plate-like separators 23, through a gas diffusion layer 21, 22 that diffuses a fuel gas and an oxidant gas through a membrane electrode assembly 15 that advances an electrochemical reaction. 24.

  Each of the separators 23 and 24 includes gas flow paths 27 and 29 through which gas flows and cooling water flow paths 28 and 30 through which cooling water flows, and the surface on which the gas flow paths 27 and 29 are formed is a membrane electrode. The membrane electrode assembly 15 is sandwiched so as to face the assembly 15.

  The gas flow path 29 of one separator 23 communicates with the fuel gas inlet 9 and the fuel gas outlet 10 (see FIG. 1) of the end plate 6B, and the fuel gas flows. The gas flow path 27 of the other separator 24 communicates with the oxidant gas introduction port 11 and the oxidant gas discharge port 12 (see FIG. 1) of the end plate 6B, and the oxidant gas flows.

  The separators 23 and 24 are formed by pressing a stainless steel plate, and not only supply fuel gas and oxidant gas to the membrane electrode assembly 15 but also electrically connect adjacent single cells 2 to each other. Also plays a role.

  The membrane / electrode assembly 15 has a structure in which a pair of catalyst layers 17 and 18 exhibiting a catalytic action for the reaction of fuel gas and oxidant gas are disposed on both surfaces of an electrolyte membrane 16 having ion conductivity. The ion conductive electrolyte membrane 16 is a proton conductive ion exchange membrane made of a solid polymer material, for example, a fluororesin, and exhibits good electrical conductivity in a wet state.

  The catalyst layers 17 and 18 located on both surfaces of the electrolyte membrane 16 include catalyst-supporting carbon and proton conductive polymer. The proton conductive polymer has a binder function. The carbon material of the catalyst-supporting carbon is not particularly limited as long as it has a function capable of supporting the catalyst. For example, carbon black, activated carbon, coke, graphite, or a mixture of two or more of these can be used.

  The catalyst material of the catalyst-supporting carbon is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction in the catalyst layer 18 facing the separator 24 through which the oxidant gas flows, and a conventionally known material can be used. On the other hand, in the catalyst layer 17 facing the separator 23 through which the fuel gas flows, the catalyst-supporting carbon catalyst material is not particularly limited as long as it has a catalytic action for the oxidation reaction of hydrogen, and a conventionally known material can be used.

  The gas diffusion layers 21 and 22 are based on a sheet-like material having conductivity and porosity. Examples of the base material of the gas diffusion layers 21 and 22 include carbon woven fabric, paper-like paper body, felt, and non-woven fabric. In order to further improve the water repellency and prevent the flooding phenomenon and the like, it is preferable that the base material of the gas diffusion layers 21 and 22 contains a water repellent. An example of the water repellent is a fluorine-based polymer material.

  The gas diffusion layers 21 and 22 are not limited to those made of carbon, and may be a porous base material made of PTFE (polytetrafluoroethylene) mixed with carbon. By doing so, the diffusibility of the gas and the drainage of the water produced by the membrane electrode assembly 15 are improved.

  In order to prevent leakage of fuel gas and oxidant gas moving through the gas diffusion layers 21 and 22 and the catalyst layers 17 and 18, the single cell 2 surrounds the catalyst layers 17 and 18 and the gas diffusion layers 21 and 22. It has frame-shaped gaskets 19 and 20. The gaskets 19 and 20 need only be impermeable to hydrogen-containing fuel gas or oxidant gas such as air, and conventionally known ones can be used. Examples of the material of the gaskets 19 and 20 include PEN (polyethylene naphthalate) and PTFE (polytetrafluoroethylene).

  The gaskets 19 and 20 serve to support the separators 23 and 24 around the gas diffusion layers 21 and 22 and the catalyst layers 17 and 18 in addition to the function of preventing leakage of fuel gas and oxidant gas. The separators 23 and 24 compress the gas diffusion layers 21 and 22 so that the porosity in a region that is supported by the gaskets 19 and 20 and overlaps the catalyst layers 17 and 18 becomes a predetermined value. Here, the porosity is the ratio of the vacancies per unit volume of the gas diffusion layers 21 and 22, and the predetermined value is the value of the porosity required to obtain a desired voltage in the single cell 2. It is.

  As shown in FIG. 3, in the frame-shaped gaskets 19 and 20 surrounding the catalyst layers 17 and 18 and the gas diffusion layers 21 and 22, the inner side surfaces 32 and 33 of the opening are inclined with respect to the electrolyte membrane 16. The inner side surfaces 32 and 33 are flat surfaces, and the angle formed between the surfaces of the inner side surfaces 32 and 33 and the electrolyte membrane 16 is an obtuse angle.

  The length in the surface direction of the gas diffusion layers 21 and 22 is longer than the length in the surface direction of the catalyst layers 17 and 18, and the peripheral portions 34A and 35A of the gas diffusion layers 21 and 22 protruding from the edges of the catalyst layers 17 and 18 are The inner surfaces 32 and 33 of the inclined gaskets 19 and 20 are crushed in close contact.

  The amount of compression at the peripheral portions 34A and 35A is larger than the amount of compression of regions 37 and 38 (hereinafter simply referred to as active areas) overlapping the catalyst layers 17 and 18, and the peripheral portions 34A and 35A compared to the active areas 37 and 38. Then, the volume of the hole 36 is small.

  For this reason, the porosity of the peripheral portions 34A and 35A is lower than that of the active areas 37 and 38, and fuel gas or oxidant gas is prevented from leaking from the peripheral portions 34A and 35A and diffuses in the active areas 37 and 38. The catalyst layers 17 and 18 are reached.

  Next, a method for manufacturing the fuel cell 1 will be described.

  The manufacturing method of the fuel cell 1 of this embodiment includes a gasket disposing step for joining the gaskets 19 and 20 to both surfaces of the electrolyte membrane, and a catalyst layer forming step for forming the catalyst layers 17 and 18 on both surfaces of the electrolyte membrane. Have. Furthermore, the manufacturing method of the fuel cell 1 according to the present embodiment includes a pressing step for assembling the single cell 9 by superimposing and pressurizing members constituting the single cell 9.

  As shown in FIG. 4, in the gasket disposing step, a pair of rolling rollers 39 and 40 incorporating a heater sandwich the gaskets 19 and 20 and the electrolyte membrane 16, and hot press them to join them. In the gasket disposing step, a pair of transport rollers 44 and 45 rotated by a motor pulls out and transports the electrolyte membrane 16 from the supply roll 41 around which the electrolyte membrane is wound, and supplies it to the rolling rollers 39 and 40. The rolling rollers 39 and 40 superimpose the gaskets 19 and 20 supplied from the supply rolls 42 and 43 wound with gaskets on the electrolyte membrane 16 and sandwich them.

  In the process in which the gaskets 19 and 20 are supplied from the supply rolls 42 and 43 to the rolling rollers 39 and 40, a coating gun (not shown) that sprays adhesive is applied to the surface of the gaskets 19 and 20 in contact with the electrolyte membrane 16. Apply. The adhesive is a hot melt of a thermoplastic adhesive.

  After the rolling rollers 39 and 40 join the gaskets 19 and 20 to both surfaces of the electrolyte membrane 16 by hot pressing, an industrial robot equipped with a blade 46 attaches the electrolyte membrane 16 to which the gaskets 19 and 20 are joined on both sides. Cut into lengths used in cell 2, and the process moves on.

  As shown in FIG. 5, the gaskets 19 and 20 supplied by the supply rolls 42 and 43 include a plurality of manifold holes 47 for flowing fuel gas, oxidant gas, and cooling water, and catalyst layers 17 and 18 and gas diffusion. Openings 25 and 26 surrounding the layers 21 and 22 are provided. In these, a Thomson blade type (not shown) having a Thomson blade is formed in advance on the gaskets 19 and 20 before the gasket disposing step.

  As shown in FIG. 6, in the catalyst layer forming step, for example, the coating gun 48 spraying the catalyst ink 49 containing the catalyst is uniformly applied to the openings 25 and 26 of the gaskets 19 and 20 joined to both surfaces of the electrolyte membrane. 49 is applied.

  Thereafter, hot pressing is performed on the electrolyte membrane 16 in which the catalyst ink 49 is applied to the openings 25 and 26, and the membrane electrode assembly 54 with gasket in which the electrolyte membrane 16, the catalyst layers 17 and 18, and the gasket 19 are integrated. Is made.

  As shown in FIG. 7, in the pressing process, the die 53 and the punch 52 that are close to and away from each other sandwich the gasket-attached membrane electrode assembly 54, the gas diffusion layers 21 and 22, and the separators 23 and 24 and pressurize them.

  Of the die 53 and the punch 52 that are close to and away from each other, the die 53 is fixed and has a wall 55 for positioning the membrane electrode assembly with gasket 54 and the separators 23 and 24. The gas diffusion layers 21 and 22 are disposed in the openings 25 and 26 of the gaskets 19 and 20 in the membrane electrode assembly 54 with gasket. The punch 52 is moved close to and away from the die 53 by a hydraulic cylinder.

  The length of the gas diffusion layers 21 and 22 in the surface direction is longer than the length of the catalyst layers 17 and 18 in the surface direction, and when the gas diffusion layers 21 and 22 overlap the catalyst layers 17 and 18, the gas diffusion layers 21 and 22. Peripheral portions 34B and 35B protrude from the edges of the catalyst layers 17 and 18. The peripheral portions 34B and 35B are not inclined with respect to the electrolyte membrane 16 like the inner side surfaces 32 and 33 of the gasket, and have a rectangular cross section in the thickness direction.

  For this reason, when the punch 52 and the die 53 are pressurized, the peripheral portions 34B and 35B of the gas diffusion layer protruding from the edges of the catalyst layers 17 and 18 are in close contact with the inclined inner side surfaces 32 and 33 of the gaskets 19 and 20 and are crushed. .

  At this time, the amount of compression at the peripheral portions 34A and 35A of the gas diffusion layers 21 and 22 is larger than the amount of compression of the active areas 37 and 38, and the peripheral portions 34A and 35A have voids at the peripheral portions 34A and 35A. 36 is greatly crushed. Therefore, the porosity of the peripheral portions 34A and 35A of the gas diffusion layers 21 and 22 is lower than the porosity of the active areas 37 and 38 (see FIG. 3).

  Further, the thin plate-like separators 23 and 24 made of metal are warped because they have flow paths for flowing gas and cooling water on both surfaces, but the die 53 and the punch 52 pressurize with the separators 23 and 24 sandwiched therebetween. To correct and flatten this warp.

  After the membrane electrode assembly with gasket 54, the gas diffusion layers 21 and 22, and the separators 23 and 24 are pressurized to form the single cell 2, the same process is further repeated to produce a plurality of single cells 2. After the plurality of single cells 2 are manufactured, these are stacked to form the stack 3.

  Finally, the current collector plate 4, the end plates 6A and 6B, and the insulating plate 8 are arranged at both ends of the stack 3 from the stacking direction of the single cells 2, and the end plates 6A and 6B are fastened by the tie rods 7 to thereby form the fuel cell 1. Is completed.

  The effect of this embodiment will be described.

  In the present embodiment, the peripheral portions 34B and 35B of the gas diffusion layers 21 and 22 are crushed in contact with the inner side surfaces 32 and 33 of the gaskets 19 and 20, and the pores at the peripheral portions 34A and 35A of the gas diffusion layers 21 and 22 are collapsed. The rate is smaller than the porosity in the active areas 37, 38.

  For this reason, in the peripheral portions 34A and 35A, leakage of fuel gas and oxidant gas is prevented and sealing performance is excellent, and fuel gas and oxidant gas efficiently flow in the active areas 37 and 38, and the electrochemical reaction is smoothly performed. proceed. Therefore, the fuel cell 1 has good quality.

In the present embodiment, the catalyst layers 17 and 18 formed in the openings 25 and 26 of the gaskets 19 and 20 are in contact with the entire inner side surfaces 32 and 33 of the openings 25 and 26. For this reason, this embodiment prevents hydrogen peroxide (H ₂ O ₂ ) by-produced in the catalyst layers 17 and 18 from entering the electrolyte membrane 16 through the gap between the gaskets 19 and 20 and the catalyst layers 17 and 18. And deterioration of the electrolyte membrane 16 can be suppressed.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, the inner surface of the opening of the gasket is not limited to a plane having an obtuse angle with the electrolyte membrane as long as the porosity at the periphery of the gas diffusion layer is lower than the porosity in the active area. It may be a curved surface.

  Further, the shape of the peripheral portion of the gas diffusion layer is not limited to a rectangular shape in the thickness direction, and may be a shape inclined with respect to the electrolyte membrane at an inclination angle different from the inner side surface of the gasket. In other words, any material may be used as long as it closely adheres to the inner surface of the gasket and is crushed to lower the porosity at the peripheral portion than the porosity in the active area.

It is a schematic perspective view of the fuel cell of this embodiment. It is a schematic sectional drawing of a single cell. It is a partial expansion schematic sectional drawing of a single cell. It is the schematic for demonstrating a gasket arrangement | positioning process. It is a schematic perspective view of the supply roll which wound the gasket. It is a schematic sectional drawing when apply | coating a catalyst ink in a catalyst layer formation process. It is a schematic sectional drawing for demonstrating a press process.

Explanation of symbols

1 Fuel cell,
2 single cell,
3 stacks,
4 current collector,
5 holding member,
6A, 6B end plate,
7 Tie rods
8 Insulating plate,
9 Fuel gas inlet,
10 Fuel gas outlet,
11 Oxidant gas inlet,
12 Oxidant gas outlet,
13 Cooling water inlet,
14 Cooling water outlet,
15 membrane electrode assembly,
16 electrolyte membrane,
17, 18 catalyst layer,
19, 20 gasket,
21, 22 Gas diffusion layer,
23, 24 separator,
25, 26 opening,
27, 29 Gas flow path,
28, 30 Cooling water flow path,
32, 33 inner surface,
34, 35 peripheral edge,
36 holes,
37, 38 active area (inside the periphery),
39, 40 Rolling roller,
41 A supply roll wound with an electrolyte membrane,
42, 43 A supply roll wound with a gasket,
44, 45 Conveying rollers,
46 blades,
47 Manifold hole,
48 painting gun,
49 catalyst ink,
50 Punch with built-in heater,
51 Die with built-in heater,
52 punches,
53 dies,
54 Membrane electrode assembly with gasket,
55 Wall.

Claims (5)

A catalyst layer formed on both sides of the electrolyte membrane;
A gasket surrounding the catalyst layer;
The porous gas diffusion layer has a porous gas diffusion layer that overlaps with the catalyst layer and has a peripheral edge abutted against the gasket and crushed, and the porosity of the peripheral edge is lower than the porosity inside the peripheral edge. A fuel cell.   The fuel cell according to claim 1, wherein the catalyst layer is in contact with the entire inner surface of the gasket.   3. The fuel cell according to claim 1, wherein an angle formed between an inner surface of the gasket and the electrolyte membrane is an obtuse angle. A gasket disposing step of disposing a gasket on the periphery of the electrolyte membrane;
A catalyst layer forming step of forming a catalyst layer in a region surrounded by the gasket;
A porous gas diffusion layer is overlaid on the catalyst layer, the periphery of the gas diffusion layer is brought into contact with the gasket and crushed, and the porosity of the periphery is lower than the porosity inside the periphery. A method of manufacturing a fuel cell, comprising: a pressing step.   5. The method of manufacturing a fuel cell according to claim 4, wherein, in the catalyst layer forming step, the catalyst layer is formed so as to contact the entire inner surface of the gasket.

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