JP6856005B2 - Fuel cell manufacturing method - Google Patents

Description

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

In the manufacturing process of a fuel cell, a technique of adhering a membrane electrode assembly to a frame with an ultraviolet curable adhesive is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2015-195189

The membrane electrode assembly is adhered to the frame by irradiating the ultraviolet curable adhesive with ultraviolet rays. At this time, since the catalyst (electrode catalyst layer) of the membrane electrode assembly is also irradiated with ultraviolet rays, the catalyst generates heat by the irradiation of the ultraviolet rays, and the monomer components in the adhesive are volatilized by the heat. If the volatilized monomer component diffuses and adheres to the catalyst of the membrane electrode assembly, the catalyst may be poisoned and the power generation performance may be deteriorated, for example, a decrease in cell voltage. This problem is not limited to the ultraviolet curable adhesive, but also occurs when a thermosetting adhesive is used.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a fuel cell that suppresses poisoning of a catalyst.

The method for manufacturing a fuel cell described in the present specification is to expose the electrolyte membrane, the first electrode catalyst layer formed on one surface of the electrolyte membrane, and the peripheral region of the electrolyte membrane. A step of preparing a film electrode joint having a second electrode catalyst layer formed on the other surface, and an inner circumference larger than the second electrode catalyst layer and smaller than the electrolyte membrane, and the inner circumference and the outer circumference. A step of preparing a frame-shaped frame having one or more through holes formed between them, and forming a first adhesive layer containing a thermosetting resin or an ultraviolet curable resin along the outer peripheral end of the peripheral region. The inner peripheral end of one surface of the frame or the inner peripheral end of the frame so that a gap is formed between the step and the second adhesive layer containing an electrolyte material as a main component. A step of forming the peripheral region closer to the second electrode catalyst layer than the first adhesive layer along the inner peripheral end, and the inner peripheral end of one surface of the frame. A step of arranging the frame on the electrolyte membrane so that the peripheral region is overlapped with the peripheral region via the second adhesive layer and the one or more through holes communicate with the gap, and a step of curing the first adhesive layer. And include.

According to the present invention, poisoning of the catalyst can be suppressed.

It is a perspective view which shows an example of a fuel cell. It is an exploded perspective view which shows an example of a single cell. It is sectional drawing which shows an example of the manufacturing process of a single cell. It is sectional drawing which shows an example of the manufacturing process of a single cell. It is sectional drawing which shows an example of the manufacturing process of a single cell. It is sectional drawing which shows an example of the manufacturing process of a single cell. It is sectional drawing which shows an example of the manufacturing process of a single cell. It is sectional drawing which shows an example of the manufacturing process of a single cell. It is sectional drawing which shows an example of the manufacturing process of a single cell.

FIG. 1 is a perspective view showing an example of a fuel cell. The fuel cell 1 is used, for example, in a fuel cell vehicle, but its use is not limited.

The fuel cell 1 is, for example, a solid polymer type, and has a laminate 3 in which a plurality of single cells 2 are laminated, a pair of end plates 8, a tension plate 9, and a pair of pressure plates 12. A fuel gas (for example, hydrogen) and an oxidant gas (for example, oxygen in the air) are supplied to the single cell 2, and power is generated by a chemical reaction between the fuel gas and the oxidant gas. The configuration of the single cell 2 will be described later.

The pair of end plates 8 fasten the laminated body 3 at both ends in the laminated direction. The end plate 8 at one end is opened with a cathode side inlet manifold 15a, a cathode side outlet manifold 15b, an anode side inlet manifold 16a, an anode side outlet manifold 16b, a cooling medium inlet manifold 17a, and a cooling medium outlet manifold 17b.

Oxidizing agent gas supplied to each single cell 2 flows through the cathode side inlet manifold 15a. Oxidizing agent off gas discharged from each single cell 2 flows through the cathode side outlet manifold 15b. The fuel gas supplied to each single cell 2 flows through the anode side inlet manifold 16a. The fuel off gas discharged from each single cell 2 flows through the anode side outlet manifold 16b. A cooling medium such as cooling water supplied to each single cell 2 flows through the cooling medium inlet manifold 17a. The cooling medium discharged from each single cell 2 flows through the cooling medium outlet manifold 17b.

The tension plate 9 connects between the pair of end plates 8. The pair of pressure plates 12 sandwich a plurality of elastic bodies (not shown) in the stacking direction of the laminated body 3.

FIG. 2 is an exploded perspective view showing an example of the single cell 2. The single cell 2 has a MEGA (Membrane-Electrode-Gas diffusion layer assembly) 20, a frame 21, and separators 23 and 24 arranged along the stacking direction of the laminate 3.

The separators 23 and 24 are made of, for example, a metal plate and have a rectangular outer shape. The separators 23 and 24 are bonded to each other by an adhesive or welding, and the separator 23 is bonded to the frame 21 by an adhesive. Therefore, in the laminated body 3, the separator 24 is arranged on the anode side of the MEGA 20 of the adjacent single cell 2, and the separator 23 is arranged on the cathode side of the MEGA 20 of the same single cell 2.

The separator 23 has through holes 231 to 236 penetrating in the thickness direction and a corrugated plate-shaped cathode flow path portion 230. Through holes 231, 235, and 234 are provided at one end of the separator 23, and through holes 233, 236, 232 are provided at the other end of the separator 23.

A groove-shaped oxidant gas flow path through which the oxidant gas flows is formed on the surface of the cathode flow path portion 230 on the MEGA 20 side. The cathode flow path portion 230 is formed, for example, by bending with a press die. The oxidant gas flow path may be formed, for example, linearly or meanderingly.

Further, the separator 24 has through holes 241 to 246 and a corrugated plate-shaped anode flow path portion 240. Through holes 241, 245, 244 are provided at one end of the separator 24, and through holes 243, 246, 242 are provided at the other end of the separator 24.

A groove-shaped cooling medium flow path through which the cooling medium flows is formed on the surface of the anode flow path portion 240 on the separator 23 side, and fuel gas is formed on the other surface of the anode flow path portion 240 on the adjacent single cell 2 side. A groove-shaped fuel gas flow path is formed. The anode flow path portion 240 is formed, for example, by bending with a press die. The cooling medium flow path and the fuel gas flow path may be formed, for example, linearly or meanderingly. The separators 23 and 24 are not limited to metal, and may be formed by, for example, carbon molding.

The through holes 231 to 236 of the separator 23 overlap the through holes 241 to 246 of the separator 24, respectively. The through holes 231 and 241 are a part of the anode side inlet manifold 16a, and the fuel gas flows along the stacking direction of the laminated body 3. The through holes 232 and 242 are a part of the anode side outlet manifold 16b, and the fuel off gas flows along the stacking direction of the laminated body 3.

Through holes 241,242 are connected to the fuel gas flow path. The fuel gas is supplied to the MEGA 20 from the through hole 241 via the fuel gas flow path. Further, the fuel off gas is discharged from the MEGA 20 to the through hole 242 via the fuel gas flow path.

The through holes 233 and 243 are a part of the cathode side inlet manifold 15a, and the oxidant gas flows along the stacking direction of the laminated body 3. The through holes 234 and 244 are a part of the cathode side outlet manifold 15b, and the oxidant off gas flows along the stacking direction of the laminated body 3.

The oxidant gas is supplied to MEGA 20 from the through hole 233 via the oxidant gas flow path. Further, the oxidant off gas is discharged from MEGA 20 to the through hole 234 via the oxidant gas flow path.

The through holes 236 and 246 are a part of the cooling medium inlet manifold 17a, and the cooling medium flows along the stacking direction of the laminated body 3. The through holes 235 and 245 are a part of the cooling medium outlet manifold 17b, and the cooling medium flows along the stacking direction of the laminated body 3.

The cooling medium flows from the through hole 246 into the through hole 245 via the cooling medium flow path. As a result, the cooling medium cools the fuel cell 1.

The MEGA 20 includes a membrane electrode assembly (MEA) 200 and a pair of gas diffusion layers (GDL) 201 and 202 sandwiching the MEA 200. Reference numeral P indicates a laminated structure of MEA200. The MEA 200 includes an electrolyte membrane 200a, an anode electrode catalyst layer 200b sandwiching the electrolyte membrane 200a, and a cathode electrode catalyst layer 200c.

The electrolyte membrane 200a includes, for example, an ion exchange resin membrane that exhibits good proton conductivity in a wet state. Examples of such an ion exchange resin membrane include fluororesin-based membranes having a sulfonic acid group as an ion exchange group, such as Nafion (registered trademark).

The anode electrode catalyst layer 200b and the cathode electrode catalyst layer 200c are each formed as a gas-diffusible porous layer containing catalyst-supporting conductive particles and a proton-conducting electrolyte. For example, the anode electrode catalyst layer 200b and the cathode electrode catalyst layer 200c are formed as a dry coating film of a catalyst ink which is a dispersion solution containing platinum-supported carbon and a proton conductive electrolyte.

Fuel gas is supplied to the anode electrode catalyst layer 200b via one gas diffusion layer 201, and oxidant gas is supplied to the cathode electrode catalyst layer 200c via the other gas diffusion layer 202. The gas diffusion layers 201 and 202 are formed by laminating a water-repellent microporous layer on a base material such as carbon paper. The microporous layer is formed by containing, for example, a water-repellent resin such as PTFE (polytetrafluoroethylene) and a conductive material such as carbon black. The MEA200 generates electricity by an electrochemical reaction using an oxidant gas and a fuel gas.

The frame 21 is made of a resin sheet having a rectangular outer shape as an example. The frame 21 has a frame shape and is provided with an opening 210 at the center.

Further, through holes 211 to 216 penetrating in the thickness direction are provided at the end of the frame 21. The opening 210 is provided at a position corresponding to the MEGA 20, and an end portion on the outer peripheral side of the MEA 200 is adhered to the edge thereof via an adhesive layer described later. That is, the MEA 200 is fixed to the frame 21 by adhering its outer peripheral end to the inner peripheral end of the frame 21.

Through holes 211, 215, 214 are provided at one end of the frame 21, and through holes 213, 216, 212 are provided at the other end of the frame 21. The through holes 211 to 216 overlap the through holes 231 to 236 and 241 to 246 of the separators 23 and 24, respectively.

The through hole 211 is a part of the anode side inlet manifold 16a, and the fuel gas flows along the stacking direction of the laminated body 3. The through hole 212 is a part of the anode side outlet manifold 16b, and the fuel off gas flows along the stacking direction of the laminated body 3.

The through hole 213 is a part of the cathode side inlet manifold 15a, and the oxidant gas flows along the stacking direction of the laminated body 3. The through hole 214 is a part of the cathode side outlet manifold 15b, and the oxidant off gas flows along the stacking direction of the laminated body 3.

The through hole 216 is a part of the cooling medium inlet manifold 17a, and the cooling medium flows along the stacking direction of the laminated body 3. The through hole 215 is a part of the cooling medium outlet manifold 17b, and the cooling medium flows along the stacking direction of the laminated body 3.

Next, referring to the cross-sectional view taken along the line AA, a step of adhering the MEA 200 to the frame 21 of the single cell 2 will be described as a method of manufacturing the fuel cell of the embodiment.

3 to 9 show an example of the manufacturing process of the single cell 2. In this example, the manufacturing process from the state where the gas diffusion layer 201 is laminated on the anode electrode catalyst layer 200b but the gas diffusion layer 202 is not laminated on the cathode electrode catalyst layer 200c will be described.

FIG. 3 shows a step of preparing the MEA200. The MEA200 has an anode electrode catalyst layer 200b formed on one surface and a cathode electrode catalyst layer 200c formed on the other surface. Since the area of the cathode electrode catalyst layer 200c is smaller than the areas of the electrolyte film 200a and the anode electrode catalyst layer 200b, the peripheral region 200s of the electrolyte film 200a is exposed from the cathode electrode catalyst layer 200c. The peripheral region 200s is provided in a square shape around the cathode electrode catalyst layer 200c when the upper surface of the MEA 200 is viewed from the front.

Further, a gas diffusion layer 201 is laminated on the anode electrode catalyst layer 200b. The anode electrode catalyst layer 200b is an example of the first electrode catalyst layer, and the cathode electrode catalyst layer 200c is an example of the second electrode catalyst layer.

FIG. 4 shows a process of preparing the frame 21. The inner circumference of the frame 21 is larger than the cathode electrode catalyst layer 200c and smaller than the electrolyte membrane 200a. More specifically, the area of the opening 210 of the frame 21 is larger than the area of the cathode electrode catalyst layer 200c and smaller than the area of the electrolyte membrane 200a.

The frame 21 is formed with one or more through holes 217 for discharging the monomer component volatilized from the curable adhesive layer described later to the outside. The through hole 217 is located between the inner circumference and the outer circumference of the frame 21 and penetrates in the thickness direction of the frame 21. One through hole 217 may be provided at the center or corner of each side of the frame 21, for example.

FIG. 5 shows a step of forming a curable adhesive layer 22 containing an ultraviolet curable resin. The curable adhesive layer 22 is formed at the outer peripheral end of the peripheral region 200s of the MEA 200. The curable adhesive layer 22 is formed in a square shape around the cathode electrode catalyst layer 200c, for example, when the upper surface of the MEA 200 is viewed from the front.

Examples of the ultraviolet curable resin include cationically polymerized resins, such as epoxy-based, vinyl ether-based, and oxetane-based resins. The curable adhesive layer 22 is an example of the first adhesive layer.

FIG. 6 shows a step of forming the electrolyte adhesive layer 4 containing the electrolyte material as a main component. The electrolyte adhesive layer 4 is formed along the inner peripheral end of one surface of the frame 21 so that a gap S (see FIG. 7) is formed between the electrolyte adhesive layer 4 and the curable adhesive layer 22.

The electrolyte adhesive layer 4 is formed on the region between the through hole 217 and the opening 210 on one surface of the frame 21, and is formed in a square shape around the opening 210 when viewed from the front. That is, the electrolyte adhesive layer 4 is formed so as to surround the opening 210. As a result, the electrolyte adhesive layer 4 is provided in the single cell 2 on the side closer to the cathode electrode catalyst layer 200c than the curable adhesive layer 22.

The electrolyte adhesive layer 4 is composed of, for example, an electrolyte material, a water or alcohol solvent, and an additive, and the electrolyte material is the main component in a state after the water or alcohol solvent is dried and removed. .. Here, the mass ratio of the electrolyte material in the electrolyte adhesive layer 4 is 50% or more, and the ratio is preferably high. For example, when a large amount of curable adhesive is contained in the electrolyte adhesive layer 4, the monomer component volatilizes from the curable adhesive in the electrolyte adhesive layer 4 and adheres to the cathode electrode catalyst layer 200c of the membrane electrode assembly 200. This is because there is a risk of deterioration of power generation performance.

More specifically, the electrolyte adhesive layer 4 is formed by applying an ionomer solution to the frame 21.

The ionomer solution is an ionomer component, a fluorocarbon-based cation exchange membrane, tetrafluoroethylene as a repeating unit represented by the structural formula of the above formula (1), and a vinyl ether monomer having a sulfonic acid group at the end of a side chain. Refers to the copolymer of. In equation (1), l, m, n, and x are integers of 1 or more.

The electrolyte adhesive layer 4 adheres the electrolyte membrane 200a or the cathode electrode catalyst layer 200c to the frame 21. Therefore, the ionomer solution preferably has the same component as the ionomer component in the electrolyte film 200a or the cathode electrode catalyst layer 200c so as to improve the adhesiveness to the electrolyte film 200a or the cathode electrode catalyst layer 200c.

The ionomer solution is produced by dissolving the ionomer of the formula (1) in water or an ethanol solution. Here, examples of the components of the alcohol solution include methanol, ethanol, npropanol and the like, but since these have flammability, the ionomer solution is preferably a mixed solution with water.

FIG. 7 shows a step of arranging the frame 21 on the electrolyte membrane 200a. In this step, the MEA 200 is bonded to the frame 21 via the electrolyte adhesive layer 4. A lower jig 50 and an upper jig 51 are used to join the frame 21 and the MEA 200.

The MEA 200 is fixed together with the gas diffusion layer 201 by the lower side jig 50, and the frame 21 is pressed toward the MEA 200 side by the upper side jig 51. The upper jig 51 is provided with a space 511 for accommodating the MEA 200 and the gas diffusion layer 201, and is further provided with a through hole 510 whose position corresponds to the through hole 217 of the frame 21. Further, the lower jig 50 is provided with a recess 501 for fixing the MEA 200 and the gas diffusion layer 201.

In the frame 21, the inner peripheral end of one surface of the frame 21 and the inner peripheral end of the peripheral region 200s of the electrolyte membrane 200a overlap with each other via the electrolyte adhesive layer 4, and the through hole 217 is a curable adhesive layer. It is arranged so as to communicate with the gap S between the 22 and the electrolyte adhesive layer 4. As a result, the inner peripheral end of one surface of the frame 21 and the inner peripheral end of the peripheral region 200s of the electrolyte membrane 200a are bonded by the electrolyte adhesive layer 4.

The inner peripheral end of one surface of the frame 21 and the inner peripheral end of the peripheral region 200s of the electrolyte membrane 200a do not necessarily have to overlap with each other via the electrolyte adhesive layer 4, for example, the frame 21. The end portion of one surface on the inner peripheral side may be arranged so as to be outside the end portion on the inner peripheral side of the peripheral region 200s of the electrolyte membrane 200a.

FIG. 8 is a step of curing the curable adhesive layer 22 by irradiating with ultraviolet rays. In this step, the MEA 200 is adhered to the frame 21 via the curable adhesive layer 22. The adhesive force of the electrolyte adhesive layer 4 is generally weaker than that of the curable adhesive layer 22. By adhering through the curable adhesive layer 22, the MEA 200 is firmly adhered to the frame 21.

Ultraviolet rays (UV) are emitted from the light source 7 toward the curable adhesive layer 22. The upper jig 51 and the frame 21 transmit ultraviolet rays.

The curable adhesive layer 22 is cured when exposed to ultraviolet rays. As a result, one surface of the frame 21 and the peripheral region 200s of the electrolyte membrane 200a are adhered by the curable adhesive layer 22. At this time, the cathode electrode catalyst layer 200c generates heat by irradiation with ultraviolet rays, and the heat causes the monomer component (for example, acrylic monomer) in the curable adhesive layer 22 to volatilize and enter the gap S, and penetrate each through the gap S. It is discharged to the outside through holes 217 and 510. When the monomer component adheres to the cathode electrode catalyst layer 200c, for example, the ester bond in the monomer component acts on the platinum in the cathode electrode catalyst layer 200c, so that the power generation performance of the MEA 200 deteriorates.

However, since the cathode electrode catalyst layer 200c is separated from the gap S by the electrolyte adhesive layer 4, the monomer component is suppressed from reaching the cathode electrode catalyst layer 200c. That is, the electrolyte adhesive layer 4 protects the cathode electrode catalyst layer 200c from the monomer component as a mask of the cathode electrode catalyst layer 200c. Further, the electrolyte adhesive layer 4 does not volatilize the monomer component or the like even when it is irradiated with ultraviolet rays. Therefore, according to the production method of this example, poisoning of the catalyst is suppressed.

Further, if the frame 21 is not provided with the through hole 217, if the internal pressure increases due to the accumulation of the volatilized monomer component in the gap S, the monomer component causes the electrolyte adhesive layer 4 or the curable adhesive layer 22 to move from the gap S. By penetrating and blowing through to the outside, a part of the electrolyte adhesive layer 4 or the curable adhesive layer 22 may be divided, and the sealing performance or the adhesive performance may be deteriorated. However, in the fuel cell 1 of this example, since the monomer component is discharged from the through hole 217, deterioration of the sealing performance and the adhesive performance is suppressed.

As indicated by reference numeral D, the monomer component is discharged from the gap S to the outside through the through holes 217 and 510. Therefore, since the monomer component is suppressed from staying in the single cell 2, the poisoning of the catalyst by the staying monomer component in the single cell 2 is suppressed.

Further, even after the completion of the fuel cell 1, the monomer component may volatilize due to the heating of the curable adhesive layer 22. Therefore, the through hole 217 may be closed after the frame 21 and the MEA 200 are joined so that the adhesion of the monomer component to the cathode electrode catalyst layer 200c and the anode electrode catalyst layer 200b is suppressed during the operation of the fuel cell 1. Alternatively, on the upper surface of the frame 21, a gasket may be provided around the through hole 217, and the through hole 217 may be sealed by sandwiching the frame 21 with the separators 23 and 24. At this time, if a through hole is provided in the corresponding portion of the separators 23 and 24, the monomer component can be discharged to the outside.

FIG. 9 shows a step of arranging the gas diffusion layer 202 on the cathode electrode catalyst layer 200c. The gas diffusion layer 202 is housed in the opening 210 of the frame 21. In this way, the single cell 2 is manufactured.

As described above, in this example, the frame 21 and the MEA200 are bonded after the electrolyte adhesive layer 4 is formed on the frame 21, but the electrolyte adhesive layer 4 may be formed on the MEA200 prior to the bonding. In this case, the electrolyte adhesive layer 4 is formed, for example, along the inner peripheral end of the peripheral region 200s of the electrolyte membrane 200a.

The electrolyte adhesive layer 4 is formed by applying an ionomer solution to the end of the cathode electrode catalyst layer 200c, for example, with a dispenser. At this time, the ionomer solution is applied at a position away from the curable adhesive layer 22 on the peripheral region 200s so that a gap S is formed at the time of joining. Since the ionomer solution is a solution containing water or ethanol as described above, the thermosetting resin does not dissolve even if it comes into contact with the curable adhesive layer 22.

Therefore, even when the electrolyte adhesive layer 4 is formed on the MEA200, the same effect as described above can be obtained.

Further, in this example, an ultraviolet curable resin is used as the curable adhesive layer 22 for adhering the frame 21 and the MEA 200, but a thermosetting resin can be used instead. In this case, the curable adhesive layer 22 is cured by being heated by a heater or the like, and the monomer component is volatilized, but the cathode electrode catalyst layer 200c is protected by the electrolyte adhesive layer 4.

Therefore, even when a thermosetting resin is used, the same effect as described above can be obtained.

The embodiments described above are examples of preferred embodiments of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.

1 Fuel cell 2 Single cell 4 Electrolyte adhesive layer (second adhesive layer)
7 Light source 21 Frame 22 Curable adhesive layer (first adhesive layer)
200 MEA
200a Electrolyte membrane 200b Anode electrode catalyst layer (first electrode catalyst layer)
200c Cathode electrode catalyst layer (second electrode catalyst layer)
200s outer edge area 217 through hole S gap

Claims (1)

The electrolyte membrane, the first electrode catalyst layer formed on one surface of the electrolyte membrane, and the second electrode catalyst layer formed on the other surface of the electrolyte membrane so as to expose the peripheral region of the electrolyte membrane. And the process of preparing a membrane electrode assembly
A step of preparing a frame-shaped frame having an inner circumference larger than the second electrode catalyst layer and smaller than the electrolyte membrane and having one or more through holes formed between the inner circumference and the outer circumference.
A step of forming a first adhesive layer containing a thermosetting resin or an ultraviolet curable resin along the outer peripheral end of the peripheral region, and a step of forming the first adhesive layer.
The inner peripheral end or the peripheral region of one surface of the frame is formed so that a gap is formed between the second adhesive layer containing an electrolyte material as a main component and the first adhesive layer. A step of forming along the peripheral end portion closer to the second electrode catalyst layer than the first adhesive layer, and a step of forming the layer closer to the second electrode catalyst layer.
The inner peripheral end of one surface of the frame overlaps the peripheral region via the second adhesive layer, and the one or more through holes communicate with the gap on the electrolyte membrane. The process of arranging the frame and
A method for manufacturing a fuel cell, which comprises a step of curing the first adhesive layer.

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