JP4872250B2 - Manufacturing method of fuel cell - Google Patents

Description

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

  The fuel cell is expected as a power generation device that can reduce the environmental load. In particular, polymer electrolyte fuel cells that use polymer electrolyte membranes as electrolytes are expected to be used as in-vehicle fuel cells for automobiles, stationary fuel cells for home and business use, and portable fuel cells for personal computers. Yes.

  FIG. 2 is an explanatory cross-sectional view schematically illustrating a single cell structure of a polymer electrolyte fuel cell. The polymer electrolyte membrane 1 is sandwiched between the fuel electrode 2 and the oxidant electrode 3 and joined to produce a membrane electrode assembly 10. The fuel electrode 2 is composed of a fuel electrode catalyst layer 2a and a fuel electrode diffusion layer 2b, and the oxidant electrode 3 is composed of an oxidant electrode catalyst layer 3a and an oxidant electrode diffusion layer 3b. A membrane cell assembly 10 is sandwiched between separators 4 and 5 to constitute a single cell of a fuel cell. The separators 4 and 5 are conductive members each having a fuel channel 4a and an oxidant channel 5a.

  Fuel is supplied to the fuel flow path 4a from the inlet 4b and discharged from the outlet 4c. Oxidant is supplied to the oxidant flow path 5a from the inlet 5b and discharged from the outlet 5c. Hydrogen, hydrogen-containing gas, methanol or the like is used as the fuel. An oxygen-containing gas such as air is used as the oxidizing agent. Here, an example using hydrogen as a fuel and air as an oxidant will be described.

The hydrogen supplied to the fuel flow path 4a reaches the fuel electrode catalyst layer 2a through the fuel electrode diffusion layer 2b which is also a current collector, and the following electrode reaction occurs.

Proton H ⁺ generated at the fuel electrode 2 moves through the polymer electrolyte membrane 1 toward the oxidant electrode 3 along with water molecules. At the same time, the electrons e ⁻ generated in the fuel electrode 2 pass through the fuel electrode catalyst layer 2a and the fuel electrode diffusion layer 2b and move to the oxidant electrode 3 via an external circuit (not shown).

On the other hand, in the oxidant electrode 3, air passes through the oxidant electrode diffusion layer 3b, which is also a current collector, and reaches the oxidant electrode catalyst layer 3a, and oxygen in the air moves through an external circuit. In response to the electrons, they are reduced by the following reaction and combined with protons H ⁺ that have moved from the fuel electrode 2 through the polymer electrolyte membrane 1 to become water.

Since polymer electrolyte membranes require movement of protons or the like, ion conductivity is required. At the same time, if the fuel and oxidant permeate as they are, the power generation performance is lowered, so that shielding against them is required. Since gas is often used for fuel and oxidant, the gas shielding property will be described below. Since the fuel and oxidant are allowed to pass through the diffusion layer, the above-mentioned electron e ⁻ is used together with fluid permeability (in many cases, gas is used for the fuel and oxidant, and is described below as gas permeability). Electrical conductivity is required for conduction. For this reason, a porous body formed of conductive fibers is used. Further, since the diffusion layer is placed in a corrosive environment such as an oxidant or a corrosive environment during an electrochemical reaction, corrosion resistance is required. For this reason, carbon fibers are generally used as conductive fibers.

  Several challenges remain for full-scale practical application of polymer electrolyte fuel cells. One of the problems is that the power generation characteristics gradually deteriorate. Various causes have been discussed, but one is the problem that pinholes exist in the polymer electrolyte membrane. When pinholes exist in the polymer electrolyte membrane, the reaction gas cross-leaks during power generation of the fuel cell, and the electrode characteristics gradually deteriorate. Cross leak is a phenomenon in which fuel permeates the oxidant electrode side or oxidant permeates the fuel electrode side.

  As Prior Art 1, Patent Document 1 discloses a fuel cell in which a plurality of polymer electrolyte membranes are stacked. It is described that even if a pinhole position exists in the polymer electrolyte membrane, the positions are shifted from each other, so that cross leak can be reduced.

  As prior art 2, Patent Document 2 discloses a fuel cell in which the surface of a polymer electrolyte membrane is modified by plasma treatment, crosslinking treatment, or the like. It is described that cross leak can be suppressed without causing defects such as pinholes by modifying the surface.

As a conventional technique 3, Patent Document 3, the reinforcing material of the catalyst layer in contact with the diffusion layer (porous membrane, fibrous materials, particulate) reinforced with, a fuel cell provided with a carbon layer between the diffusion layer and the catalyst layer It is disclosed. It is described that the damage to the polymer electrolyte membrane due to the fluffing or breakage of the diffusion layer can be suppressed by the reinforcing material or the carbon layer.
JP-A-6-84528 (Claim 1, paragraph [0010], FIG. 1 etc.) JP 2003-272663 A (Claims, paragraph [0010], etc.) JP, 2004-220843, A (Claims 1, 2, paragraph [0089 etc.)] The pinhole of a polymer electrolyte membrane is a pinhole originally formed in the polymer electrolyte membrane and a pin formed at the time of manufacturing the membrane electrode assembly 10 There is a hall. The pinhole formed during the manufacture of the membrane electrode assembly 10 is formed by the carbon fiber forming the gas diffusion layer being stuck into the polymer electrolyte membrane when the membrane and the electrode are bonded (when the gas diffusion layer is bonded). .

Prior arts 1 and 2 are countermeasures against pinholes originally present in the polymer electrolyte membrane, and are not countermeasures against pinholes that can be produced during the manufacture of the membrane electrode assembly 10. The pinhole gas permeation originally present in the polymer electrolyte membrane (hydrogen gas permeation 3-5 × 10 ⁻¹⁰ cm ³ · cm · cm ⁻² · sec ⁻¹ · Pa) is very small. On the other hand, the number of pinholes that can be formed during the manufacture of the membrane electrode assembly 10 is extremely large. Therefore, the conventional techniques 1 and 2 cannot prevent the cross leak.

  Prior art 3 is a countermeasure against pinholes that can be produced during the manufacture of the membrane electrode assembly 10. However, the countermeasure of the prior art 3 is not sufficient.

The present invention solves the above problems, to prevent the possible pinholes during manufacture of the membrane electrode assembly, rather small, cross leakage, breakage falling of conductive fibers to provide a method of manufacturing a small fuel cell.

In order to solve the above technical problem, in the present invention, a diffusion layer for a fuel electrode containing conductive fibers, a catalyst layer for a fuel electrode containing a catalyst for a fuel electrode, a polymer electrolyte membrane having ion conductivity, In the method for producing a fuel cell having a membrane electrode assembly in which an oxidant catalyst layer containing an oxidant electrode catalyst and an oxidant electrode diffusion layer containing conductive fibers are sequentially laminated, the fuel electrode In the manufacturing process of both diffusion layers for the oxidizer electrode and the oxidant electrode, the punching blade in which both blades having inclined surfaces on the inner side and the outer side are provided in the punching die in a separated state, and between the spaced punching blades, A sponge whose upper surface is substantially the same height as the cutting edge of the punching blade is provided, and a sheet-shaped diffusion layer base material containing conductive fibers is placed on the upper portion of the cutting edge, and is separated by the punching die. Using a double-edged blade, strike the diffusion layer substrate. There are were as the stamping process for producing the both diffusion layers provided.

In this case, it is preferable that a water-repellent treatment step for subjecting the diffusion layer substrate to a water-repellent treatment is provided before the punching step.

In this case, the water-repellent treatment step includes an impregnation step of impregnating the diffusion layer base material with polytetrafluoroethylene particles and a sintering step of sintering the impregnated polytetrafluoroethylene particles. Good to be .

Also, in this case in the impregnation step, it may be impregnated with a conductive material with polytetrafluoroethylene particles.

    According to the invention of claim 1, since the diffusion layer for the fuel cell is manufactured by punching from the base material for the diffusion layer using the double-edged blade, it is possible to reduce the break-off of the conductive fiber, and due to the broken-off conductive fiber There is an effect that it is possible to reduce the piercing to the polymer electrolyte membrane and to manufacture a fuel cell with little cross leak.

In the present invention, if carbon fibers are used as the conductive fibers, there is an effect that a diffusion layer having excellent corrosion resistance and electrical conductivity can be produced. The carbon fiber is easily damaged by impact, and the damaged carbon fiber is likely to pierce the polymer electrolyte membrane. Therefore, it is particularly effective to punch out using a double-edged blade.

According to the present invention, since the diffusion layer base material is subjected to water repellent treatment, there is an effect that the diffusion layer is not easily clogged by the supplied fuel, the water in the oxidant, or the water generated by the electrode reaction. . Also, since the water-repellent treatment is performed before the punching process, the large-sized diffusion layer substrate is subjected to the water-repellent treatment, and a plurality of diffusion layers are punched out from the diffusion layer substrate. There is an effect that man-hours can be reduced.

Further , according to the present invention, since the diffusion layer base material contains polytetrafluoroethylene particles, there is an effect that water repellency is maintained from the surface to the inside, and water is less likely to clog.

Furthermore, according to the present invention, since the conductive material is impregnated into the base material for the diffusion layer together with the polytetrafluoroethylene particles, there is an effect of having both the conductivity through which electrons are passed and the water repellency which is difficult to cause water clogging.

In the present invention, when manufacturing a diffusion layer for a fuel cell punched using a double-edged from the diffusion layer base material, there is an effect of reducing the damage to dropout of the conductive fibers. For this reason, it is possible to reduce the influence on other members due to the conductive fibers that are broken and dropped. When used as a diffusion layer for membrane electrode assemblies of polymer electrolyte fuel cells that use polymer electrolyte membranes, membrane electrodes can reduce puncture of polymer electrolyte membranes due to damaged and dropped conductive fibers, resulting in less cross-leakage There exists an effect which can manufacture a zygote. Thereby, the reliability and durability of the fuel cell can be improved.

  The present inventors diligently researched and found the cause that the method of the prior art 3 is insufficient to prevent the conductive fibers from sticking to the polymer electrolyte membrane. The prior art 3 is effective for piercing the conductive electrolyte existing on the surface of the diffusion layer facing the polymer electrolyte membrane or damaging and falling off from this surface, but from the end surface of the diffusion layer. It turned out that it was not a measure against the piercing of the polymer electrolyte membrane of the conductive fiber that was broken and dropped. The diffusion layer is manufactured by punching a large conductive fiber sheet formed of conductive fibers into a predetermined size. It was found that the conductive fibers at the end face portion of the diffusion layer were damaged and dropped at the time of this punching, and the conductive fibers that were damaged and dropped at the time of membrane electrode bonding were stuck into the polymer electrolyte membrane. The inventor further researched and found that, when a diffusion layer is manufactured by punching, the use of a double-edged blade as a blade for punching can prevent the conductive fibers from being broken off at the end face portion of the diffusion layer.

FIG. 1 is an explanatory sectional view for explaining a punching device used in the embodiment. The thickness of the punching blade is emphasized for explanation. A punching die 20 is fixed on a lower die 6 fixed to a lower die base (not shown). The punching die 20 includes a punching blade 21 and a holder 22 for fixing the punching blade 21. Two punching blades 21 whose longitudinal direction is perpendicular to the plane of the drawing are shown on the left and right sides of the drawing. Two punching blades 21 whose longitudinal direction is parallel to the drawing are also provided before and after the drawing so as to punch out the gas diffusion layer into a rectangle. It has been. A holder 22 is fixed to the lower die 6. A sponge 9 is provided between the punching blades 21. Before the punching, the upper surface of the sponge 9 is substantially the same as the height of the cutting edge of the punching blade 21, and the sponge 9 just fits between the punching blades 21 is used.

  The cutting edge 21d of the punching blade 21 has a double-edged shape in which both side surfaces are formed by inclined surfaces 21a and 21b. The inclined surface 21a is an inclined surface on the inner side (the punching blade sides facing each other), that is, the side where the diffusion layer is formed. The inclination angle of the inclined surface 21a is 30 to 40 degrees, preferably 33 to 37 degrees. The inclined surface 21b is an inclined surface on the outer side, that is, the side opposite to the side where the diffusion layer is formed. As an inclination angle of the inclined surface 21b, 10 to 20 degrees, desirably 13 to 17 degrees can be exemplified. The inclination angle of the inclined surface is an angle formed by a perpendicular line dropped from the tip 21c of the blade edge 21d in FIG. 1 and the inclined surface. The inclined surfaces 21a and 21b are surfaces parallel to the longitudinal direction of the punching blade 21 (direction perpendicular to the paper surface of FIG. 1). Examples of the opening angle between the inclined surface 21a and the inclined surface 21b include 40 to 60 degrees, preferably 46 to 54 degrees. The opening angle is an angle formed by the inclined surface 21a and the inclined surface 21b. In the embodiment, the punching blade 21 having an inclination angle of the inclined surface 21a of 35 degrees, an inclination angle of the inclined surface 21b of 15 degrees, and an opening angle of the inclined surfaces 21a and 21b of 50 degrees was used. It should be noted that the inclined surfaces of the two blades of the punching blade 21 do not necessarily have to be flat, and may be any punching blade having blades formed on both.

  Examples of the thickness t of the punching blade 21 include 0.1 to 1 mm, preferably 0.2 to 0.5 mm. In the example, a punching blade 21 having a thickness t of 0.2 mm was used. Examples of the position of the blade tip 21c include 0.5 to 3 mm, preferably 1 to 2 mm from the inner surface (sponge 9 side). In the embodiment, the punching blade 21 provided at a position of 1 mm from the inner surface of the blade tip 21c was used.

  Examples of the material for forming the punching blade 21 include hardened stainless steel and high-speed steel. In the Example, the punching blade 21 formed from high-speed steel was used.

The conductive fiber board 30 which shape | molded the conductive fiber in the sheet form is used as a base material for diffusion layers. Examples of the conductive fiber include carbon fiber, metal fiber, inorganic fiber having conductivity, and resin fiber having conductivity. The metal fiber can be used if it has corrosion resistance or is coated to give corrosion resistance. Among these, carbon fiber is particularly desirable as a diffusion layer for fuel cells because it has excellent corrosion resistance and electrical conductivity. However, since the carbon fiber is easily damaged by impact, and the damaged carbon fiber is likely to pierce the polymer electrolyte membrane, it is effective to apply the present invention. The carbon fiber may be a PAN-based or pitch-based carbon fiber, a carbon nanotube, or a carbon nanofiber. As the conductive fiber board 30, any material such as a woven fabric or a non-woven fabric can be used as long as it is formed into a sheet shape using conductive fibers. Examples of carbon fibers used as the conductive fibers include carbon paper, carbon cloth, carbon nonwoven fabric, and carbon felt. Among these, carbon paper is preferable.

  When the conductive fiber board 30 is used as a diffusion layer for a fuel cell, it is desirable to perform a water repellent treatment before punching. The water repellent treatment is performed by attaching a water repellent substance in the conductive fiberboard. Examples of the water repellent treatment method include an impregnation method in which a conductive fiber board is impregnated with a liquid containing a water repellent material, and a method of applying to the surface with an applicator. Of these, the impregnation method is simple and desirable. Examples of the water-repellent substance include polytetrafluoroethylene (hereinafter also referred to as PTFE), tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, and the like. Among them, PTFE is preferable because of its high water repellency. When PTFE is used, it is desirable to impregnate a conductive fiber board with a dispersion of PTFE particles, dry and then sinter. The PTFE particles are bonded to each other by sintering, so that the PTFE can be firmly attached in the conductive fiberboard.

  Next, the punching process will be described. First, the conductive fiber board 30 is placed on the upper part of the punching die (on the blade tip 21c). A blade receiving plate 8 made of polypropylene resin is placed on the conductive fiber plate 30. Thereafter, the blade receiving plate 8 is pressurized by the upper die 7 fixed to the upper die base (not shown). The carbon fiber board 30 is lowered together with the blade receiving plate 8, and the conductive fiber board 30 is punched into a predetermined shape by the punching blade 21. The diffusion layer formed by punching remains on the sponge 9, but the peripheral portion of the conductive fiber board 30 (the portion other than the diffusion layer) falls on the holder 22 and the lower die 6. At this time, the sponge 9 is compressed by elastic deformation. The lowering of the upper die 7 ends when the conductive fiber board 30 comes into contact with the blade tip 21c. Thereafter, when the upper die 7 is raised, the diffusion layer returns to the position where the conductive fiber board 30 is placed by the elastic repulsive force of the sponge 9, so that the diffusion layer can be easily taken out. Hereinafter, an embodiment using this punching device will be described with reference to FIGS.

  30 carbon black (conductive substance) was mixed with water 100 by weight and stirred with a stirrer. To this, 25 polytetrafluoroethylene dispersion (hereinafter also referred to as PTFE dispersion) stock solution (produced by Daikin Industries, Ltd .: trade name POLYFLON D1 grade, PTFE-containing concentration 60% by weight) with respect to 100 water by weight is added. The carbon ink was prepared by stirring.

  Carbon paper (manufactured by Toray Industries, Inc .: trade name Torayca TGP-060, thickness 180 μm) was used as the base material for the diffusion layer. This carbon paper was put into the carbon ink prepared above, and the carbon paper was sufficiently impregnated with the carbon ink (impregnation step). Next, excess moisture of the carbon paper was evaporated in a drying furnace maintained at a temperature of 80 ° C. Then, it was held at a sintering temperature of 390 ° C. for 60 minutes to sinter PTFE (sintering process) to produce two water-repellent carbon papers (conductive fiber boards) 30 (water-repellent treatment process). The two water-repellent carbon papers 30 are each punched into a rectangular shape of 100 mm × 150 mm by a double-edged punching device shown in FIG. 1, and the gas diffusion layer for fuel electrode (diffusion layer for fuel electrode) 2b and the gas for oxidant electrode Diffusion layer (diffusion layer for oxidant electrode) 3b was manufactured (punching step). In this embodiment, since a fuel gas such as hydrogen is used as the fuel for the fuel cell and an oxidant gas such as air is used as the oxidant, they are referred to as a diffusion layer and a gas diffusion layer.

  A catalyst paste for the oxidant electrode was prepared using platinum-supported carbon (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd .: trade name TEC10E60E, platinum concentration 55 wt%). The platinum-supporting carbon is a catalyst-supporting conductive fine particle in which platinum as a catalyst is supported on a carbon fine body (conductive fine particle). Platinum-supported carbon, an ion exchange resin solution having a concentration of 5 wt% (Asahi Kasei Kogyo Co., Ltd .: trade name SS-1080), water, and isopropyl alcohol are mixed at a weight ratio of 12: 127: 23: 23 and oxidized. A catalyst paste for the agent electrode was prepared.

  The ion exchange resin solution used is mainly composed of a fluorocarbon electrolyte polymer (glass transition temperature: 120 ° C) with ion conductivity (proton conductivity), which is a mixture of water and ethanol as a liquid medium. It is dissolved or dispersed in a solution. Specifically, in this embodiment, the fluorocarbon electrolyte polymer contains perfluorosulfonic acid as a main component.

This oxidant electrode catalyst paste is applied to one surface of a PTFE sheet (a film-like member formed of PTFE) by the doctor blade method to form the oxidant electrode catalyst layer 3a, dried, and then the oxidant electrode catalyst. A sheet was produced. The oxidant electrode catalyst layer 3a is formed so that the amount of catalyst supported is 0.6 mg / cm ² .

  Next, a catalyst paste for a fuel electrode was prepared using platinum-ruthenium alloy-supported carbon (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd .: trade name TEC61E54, platinum concentration 30 wt%, ruthenium concentration 23 wt%). The platinum-ruthenium alloy-supported carbon is catalyst-supporting conductive fine particles in which platinum and ruthenium, which are catalysts, are supported on a carbon fine body (conductive fine particles). Using this platinum ruthenium alloy-supported carbon, a fuel electrode catalyst paste was prepared in the same manner as the oxidant electrode catalyst paste.

This fuel electrode catalyst paste was applied to one surface of a PTFE sheet by a doctor blade method to form a fuel electrode catalyst layer 2a and dried to prepare a fuel electrode catalyst sheet. The fuel electrode catalyst layer 2a is formed so that the amount of catalyst supported is 0.6 mg / cm ² .

  Next, an oxidant electrode catalyst layer 3a is formed on one surface of a polymer electrolyte membrane 1 made of an ion exchange membrane having ion conductivity (proton conductivity) (manufactured by DuPont: trade name Nafion 111, thickness 25 μm). The oxidant electrode catalyst sheet was brought into contact with the membrane 1, and the fuel electrode catalyst sheet was brought into contact with the other surface so that the fuel electrode catalyst layer 2a became the polymer electrolyte membrane 1, thereby forming an intermediate laminate. After hot pressing from outside the PTFE sheets of the oxidant electrode catalyst sheet and the fuel electrode catalyst sheet at a temperature of 120 ° C. and a pressure of 8 MPa for 1 minute, the PTFE sheet was peeled off and the polymer electrolyte membrane 1 was coated with the oxidant electrode The catalyst layer 3a for fuel and the catalyst layer 2a for fuel electrode were transferred.

  Subsequently, the fuel electrode gas diffusion layer 2b produced above is brought into contact with the fuel electrode catalyst layer 2a, the oxidant electrode gas diffusion layer 3b is brought into contact with the oxidant electrode catalyst layer 3a, and the fuel electrode The gas diffusion layer 2b for the fuel electrode and the gas diffusion layer 3b for the oxidant electrode are hot-pressed from outside the gas diffusion layer 2b and the gas diffusion layer 3b for the oxidant electrode at a temperature of 140 ° C. and a pressure of 8 MPa for 3 minutes. The membrane electrode assembly 10 was manufactured by bonding.

  The produced membrane electrode assembly 10 was evaluated by a cross leak test. A separator 4 having a fuel flow path 4a on the fuel electrode 2 side and a separator 5 having an oxidant flow path 5b on the oxidant electrode 3 side are arranged on the membrane electrode assembly 10. The polymer electrolyte membrane 1 and the separators 4 and 5 are sealed so as not to leak gas from the outer peripheral portions. First, nitrogen gas was flowed into the fuel flow path 4a and the oxidant flow path 5b for purging. Next, nitrogen gas was supplied to the fuel flow path 4a to seal the pressure at 20 KPa (gauge pressure). The oxidant flow path 5b was opened to the atmosphere. The cross pressure was evaluated by measuring the differential pressure between the fuel channel 4a and the oxidant channel 5b one minute after the fuel channel 4a was sealed.

Comparative Example 1

  A membrane electrode assembly was produced in the same manner as in Example 1 except that a single-edged punching die was used instead of the double-edged punching die. FIG. 4 is an explanatory sectional view for explaining the punching device used in the comparative example. Except for using a single-blade punching blade 41 instead of the punching blade 21, it is the same as the punching device of FIG.

  The punching die 40 includes a punching blade 41 and a holder 42 for fixing the punching blade 41. In the punching die 40, as in the punching die 20, the holder 42 is fixed on the lower die 6. The punching blade 41 has a single-edged shape in which one side is formed by an inclined surface 41a. The inclined surface 41a is provided on the side where the diffusion layer is formed as shown in FIG. The inclination angle of the inclined surface 41a is 45 degrees. As in the case of the embodiment, the inclination angle is an angle formed between the perpendicular line dropped from the tip of the blade edge and the inclined surface in FIG.

  A cross leak test was performed in the same manner as in Example 1 using the manufactured membrane electrode assembly.

(Cross leak test results)
Table 1 shows the cross leak test results. In Example 1 using both blades, the differential pressure remained the sealed pressure. On the other hand, in Comparative Example 1 using a single blade, the differential pressure is 10 kPa, which is half. When the gas diffusion layers manufactured in Example 1 and Comparative Example 1 were observed, in Comparative Example 1, the surface of the outer peripheral portion (periphery of the punched portion) of the gas diffusion layer was cracked to form conductive paper. (Carbon fiber) was broken and dropped off. Moreover, the burr | flash of the shape as shown in FIG. 5 was seen. On the other hand, the surface of the outer peripheral portion of the gas diffusion layer of Example 1 was clean, and no burr was observed as shown in FIG. 3, and no breakage and dropping of the conductive fibers were observed.

  As described above, the fuel cell diffusion layer is manufactured by punching the diffusion layer for the fuel cell from the base material for the diffusion layer using a double-edged blade, so that the breakage and dropping of the conductive fibers can be reduced. This is because, in the case of a diffusion layer substrate formed of conductive fibers, if a double-blade punching die is used, cutting becomes easy and the cut surface becomes clean. According to the test of the present inventor, it has been found that there is a difference in each step as compared with a single-blade punching die. As a result, it is possible to prevent cracking of the diffusion layer and breakage of the conductive fibers that occurred with the single-blade punching die, and to prevent the conductive fibers forming the diffusion layer from piercing the polymer electrolyte membrane. Electrolyte membrane pinholes could be reduced. And a membrane electrode assembly with few cross leaks can be manufactured, and the reliability and durability of a fuel cell can be improved. The present invention is an invention that is motivated to reduce the cross leak of the polymer electrolyte membrane of the polymer electrolyte fuel cell. However, it is possible to prevent the conductive fibers of the diffusion layer from being broken and dropped. Since the influence on other members due to breakage and dropping can be reduced, it can be applied to all fuel cells having a diffusion layer containing conductive fibers.

Explanatory cross-sectional view explaining the punching device used in the examples Cross-sectional view schematically explaining a single cell structure of a polymer electrolyte fuel cell Sectional schematic diagram of the gas diffusion layer produced in Example 1 Cross-sectional view for explaining the punching device used in the comparative example Cross-sectional schematic diagram of the gas diffusion layer produced in Comparative Example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Polymer electrolyte membrane 2 ... Fuel electrode 2a ... Fuel electrode catalyst layer 2b ... Diffusion layer 3 for fuel electrode ... Oxidant electrode 3a ... Catalyst layer 3b for oxidant electrode ... Diffusion layer 10 for oxidant electrode ... Membrane Electrode assembly 20 ... punching die 21 ... punching blade 22 ... holder 30 ... conductive fiber board (base material for diffusion layer)

Claims (4)

A fuel electrode diffusion layer containing conductive fibers, a fuel electrode catalyst layer containing a fuel electrode catalyst, a polymer electrolyte membrane having ion conductivity, and an oxidant catalyst layer containing an oxidant electrode catalyst In the method for producing a fuel cell having a membrane electrode assembly in which a diffusion layer for an oxidant electrode containing conductive fibers is sequentially laminated,
In the manufacturing process of both diffusion layers for the fuel electrode and the oxidant electrode, a punching blade having a double-sided blade having inclined surfaces on the inner side and the outer side is provided in the punching die in a separated state. In between, provided a sponge whose upper surface is substantially the same height as the cutting edge of the punching blade,
A sheet-shaped diffusion layer base material containing conductive fibers is placed on the top of the blade edge, and the diffusion layer base material is punched out by the punching die using the spaced apart blades to produce both diffusion layers. A method of manufacturing a fuel cell, characterized in that a punching step is provided. The method for producing a fuel cell according to claim 1, wherein a water repellent treatment step of performing a water repellent treatment on the diffusion layer base material is provided before the punching step.
The water repellent treatment step includes an impregnation step of impregnating the diffusion layer base material with polytetrafluoroethylene particles;
The method for producing a fuel cell according to claim 2 , further comprising a sintering step of sintering the impregnated polytetrafluoroethylene particles. In the impregnation step,
The method for producing a fuel cell according to claim 3 , wherein the conductive material is impregnated with the polytetrafluoroethylene particles.

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