JP5849418B2 - Manufacturing method of membrane electrode assembly - Google Patents

Description

  The present invention relates to a method for producing a membrane electrode assembly, and more particularly to a method for producing a membrane electrode assembly in a polymer electrolyte fuel cell.

  In the movement toward building a decarbonized society, hydrogen is attracting attention as an intermediate energy carrier. BACKGROUND ART A fuel cell is a power generation system that takes out electric power by electrochemically reacting a fuel gas such as hydrogen and an oxidizing gas such as air, and is being developed as one form of using hydrogen energy. In particular, among various fuel cells, polymer electrolyte fuel cells are expected to be put to practical use as power sources for automobiles or households because of their high power density, low temperature operation, and compact battery body. Yes.

The membrane electrode assembly in the polymer electrolyte fuel cell includes an electrolyte membrane, a catalyst layer, a gas diffusion layer, and a gasket layer. The manufacturing method of a membrane electrode assembly can be divided according to the lamination | stacking process to the electrolyte membrane of a catalyst layer. A method of manufacturing a membrane electrode assembly having the lowest interface resistance between the catalyst layer and the electrolyte membrane and having high power generation performance is a method of laminating the catalyst layer by directly applying the catalyst ink to the electrolyte membrane. However, since the solvent in the catalyst ink soaks into the electrolyte membrane, it must be applied while controlling the swelling state of the electrolyte membrane, and it is difficult to form a catalyst layer with a uniform thickness (Non-Patent Document) 1).
On the other hand, it has been proposed to stack a catalyst layer on an electrolyte membrane by such a transfer method. This is a method in which a catalyst ink is applied to a transfer substrate in advance, dried, and then the catalyst layer is adhered to the electrolyte membrane by heat and pressure using the obtained transfer substrate with a catalyst layer. As a result, it is possible to produce a membrane / electrode assembly with low power generation performance and low interface resistance between the catalyst layer and the electrolyte membrane.

  In such a transfer method, when the catalyst layer and the gasket layer are aligned, the gasket layer is generally arranged around the transferred electrolyte membrane with the catalyst layer by making the opening of the gasket layer larger than the area of the catalyst layer. doing. This is because the dimensions of the electrolyte membrane with a catalyst layer change greatly depending on humidity and temperature, and in order to stack the gaskets, it is necessary to provide a margin in advance for the area of the gasket opening. It is. For this reason, there is a gap between the catalyst layer and the gasket layer, and it is necessary to suppress this as much as possible.

  It is reported that the air gap is considered as a cause of the cross leak between the fuel gas and the oxidizing gas, and promotes the deterioration of the chemical electrolyte membrane. Furthermore, since the voids are regions where stress due to swelling and shrinkage of the electrolyte membrane that occurs due to fluctuations in temperature and humidity is likely to concentrate, it has been reported that the void promotes physical electrolyte membrane degradation (non-patent literature). 2).

  In order to suppress the gap between the catalyst layer and the gasket layer, it is necessary to align the gasket layer accurately around the catalyst layer. However, introducing equipment that enables accurate alignment into the production line increases costs. On the other hand, in Patent Document 1, a gasket layer is disposed on an electrolyte membrane, and a transfer substrate with a catalyst layer coated with a larger area than the gasket opening is disposed via a gasket. It has been reported that a membrane electrode assembly is manufactured by bonding by means of, for example. By this manufacturing method, the gasket can be accurately arranged around the catalyst layer by a simple method.

JP 2006-286430 A

I. Park, W. Li, A. Manthiram, J. Power Sorces, 195, 7078-7082, 2010. Iwata, Fuel Cell, 6 [3], 52-55, 2007

  However, when transferring the catalyst layer to the electrolyte membrane via a gasket, the transfer sheet with the catalyst layer cannot follow the gasket layer due to the gap between the gasket layer and the electrolyte membrane, and the catalyst layer is completely transferred. It was difficult to make. Therefore, the present invention has been made to solve the problem of poor transfer of the catalyst layer in the vicinity of the gasket, and provides a method for manufacturing a membrane electrode assembly in which the gap between the catalyst layer and the gasket layer is suppressed to 50 μm or less. The purpose is to do.

In order to achieve the above object, a method for producing a membrane / electrode assembly according to the present invention is configured as follows.
First, the invention of claim 1
Laminating the first gasket layer on the peripheral portions of both surfaces located on the anode side and the cathode side of the electrolyte membrane constituting the membrane electrode assembly,
Laminating a catalyst layer on the electrolyte membrane exposed inside the first gasket layer on both sides of the electrolyte membrane;
Laminating a gas diffusion layer straddling the first gasket layer on the catalyst layer on both sides of the electrolyte membrane;
Laminating a second gasket layer on the first gasket layer exposed around the gas diffusion layer on both sides of the electrolyte membrane,
The step of laminating the catalyst layer on the electrolyte membrane includes a step of transferring the catalyst layer to the electrolyte membrane using a transfer substrate with a catalyst layer in which a catalyst ink is applied to a rubber transfer substrate.
It is a manufacturing method of the membrane electrode assembly characterized by the above-mentioned.

The invention of claim 2
The step of laminating the catalyst layer on the electrolyte membrane is carried out using the transfer substrate with a catalyst layer obtained by applying the catalyst ink to the fluorine-coded rubber transfer substrate. It is a manufacturing method.

The invention of claim 3
In the step of laminating the catalyst layer on the electrolyte membrane, the membrane electrode is formed by using the transfer substrate with a catalyst layer in which the catalyst ink is applied to the rubber transfer substrate on which a fluororesin sheet is installed. It is a manufacturing method of a joined object.

The invention of claim 4
In the step of laminating the catalyst layer on the electrolyte membrane, heat lamination is performed from above the sheet substrate with a porous sheet substrate disposed on the surface of the rubber transfer substrate opposite to the electrolyte membrane. It is a manufacturing method of the membrane electrode assembly characterized by including the process and transferring the said catalyst layer to the said electrolyte membrane.

  According to the present invention, since the rubber transfer substrate is used in transferring the catalyst layer to the electrolyte membrane, the catalyst layer can be transferred to the electrolyte membrane to the vicinity of the gasket of the electrolyte membrane with gasket. For this reason, since the space | gap of a catalyst layer and a gasket layer can be suppressed to 50 micrometers or less and deterioration of an electrolyte membrane can be suppressed, the fall of the power generation performance of a membrane electrode assembly can be prevented.

  Furthermore, when transferring the catalyst layer to the electrolyte layer by thermal lamination, the air between the transport sheet and the transfer substrate is inserted by inserting a porous sheet substrate between the transport sheet and the transfer substrate. Biting can be suppressed. For this reason, the transferability of the catalyst layer to the electrolyte membrane with gasket can be increased.

It is explanatory drawing of the membrane electrode assembly manufactured by the manufacturing method which concerns on one Embodiment of this invention. It is explanatory drawing of the detailed structure of the 1st gasket layer shown in FIG. It is explanatory drawing of the manufacturing method of the membrane electrode assembly which concerns on one Embodiment of this invention.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing referred to in the following description, components equivalent to those in the other drawings are denoted by the same reference numerals.
(Structure of membrane electrode assembly)
With reference to FIG. 1, the structure of the membrane electrode assembly manufactured by the manufacturing method which concerns on embodiment of this invention is demonstrated.
A membrane electrode assembly 10 shown in FIG. 1 includes an electrolyte membrane 1 and a catalyst layer 2a, a first gasket layer 3a, a second gasket layer 4a, and a gas diffusion layer laminated on one surface on the anode side of the electrolyte membrane 1. 5a and a catalyst layer 2c, a first gasket layer 3c, a second gasket layer 4c, and a gas diffusion layer 5c laminated on the other surface on the cathode side of the electrolyte membrane 1.

  The membrane electrode assembly 10 divides the gasket layer into first gasket layers 3a and 3c and second gasket layers 4a and 4c. This is due to the fact that the gas diffusion layers 5a and 5c are made larger in area than the catalyst layers 2a and 2c for the purpose of diffusing the fuel gas or the oxidizing gas throughout the catalyst layers 2a and 2c. This is for filling the gaps between the layers 5a and 5c and the catalyst layers 2a and 2c. Specifically, the gasket layer is divided into first gasket layers 3a and 3c and second gasket layers 4a and 4c, and the first gasket layers 3a and 3c are disposed so as to surround the catalyst layers 2a and 2c. Gas diffusion layers 5a and 5c and second gasket layers 4a and 4c surrounding the gas diffusion layers 5a and 5c are laminated on the first gasket layers 3a and 3c. As a result, the gap between the catalyst layers 2a, 2c and the gas diffusion layers 5a, 5c can be filled, and the fuel gas and the oxidizing gas can be uniformly distributed to the catalyst layers 2a, 2c, and the retention of water generated by power generation can be prevented. Therefore, the power generation performance can be improved.

  The membrane electrode assembly 10 of the present embodiment configured as described above is manufactured by a manufacturing method described later, so that the gap between the catalyst layers 2a and 2c and the first gasket layers 3a and 3c is 50 μm or less. As a result, the cross leak between the fuel gas and the oxidizing gas is reduced, the deterioration of the chemical electrolyte membrane is suppressed, and the stress due to the swelling and shrinkage of the electrolyte membrane 1 caused by the temperature and humidity fluctuations is easily concentrated. Degradation of the physical electrolyte membrane 1 due to this can also be suppressed.

The electrolyte membrane 1 may be an electrolyte membrane that is generally used for solid polymer fuel cells. For example, a fluorine-based electrolyte membrane or a hydrocarbon film can be suitably used as the electrolyte membrane 1, and a fluorine-based electrolyte membrane is particularly desirable.
The area of the electrolyte membrane 1 is preferably larger than the area of both the anode-side and cathode-side catalyst layers 2a, 2c. This is because when the electrolyte membrane 1 having the same area as the catalyst layers 2a and 2c is used, there is a concern about gas leak from the end portions of the catalyst layers 2a and 2c.

  The catalyst layers 2a and 2c may be catalyst layers that are generally used for polymer electrolyte fuel cells. For example, platinum or other metal (for example, Ru, Rh, Mo, Cr, Co, Fe, etc.) and fine particles of an alloy (an average particle size of 10 nm or less is desirable) is a conductive material such as carbon black supported on the surface. Can be used which is made from an ink in which carbonaceous fine particles (average particle size: about 20 to 100 nm) and a polymer such as a perfluorosulfonic acid resin solution are uniformly mixed in an appropriate solvent (ethanol or the like). .

As shown in FIG. 2, the first gasket layers 3a and 3c include thermoplastic resin layers 31a and 31c and adhesive layers 32a and 32c. For example, the thermoplastic resin layers 31a and 31c may use PET (polyethylene terephthalate), PEN (polyethylene naphthalate), SPS (syndiotactic polystyrene), PTFE (polytetrafluoroethylene), Pi (polyimide), or the like. it can. In particular, a thermoplastic resin having a high elastic modulus is desirable, and a fiber reinforced one may be used.
The adhesive layers 32a and 32c are made of an adhesive, an adhesive, or a heat seal agent. As the pressure-sensitive adhesive or adhesive, those having a main skeleton such as a polysiloxane skeleton, a polyether skeleton, a fluoroether skeleton, and a polyolefin skeleton can be used. A heat sealing agent having a heat sealing temperature of about 120 to 150 ° C. can be used.
The thickness of the first gasket layers 3a and 3c is desirably 300 μm or less. This is because, in the transfer of the catalyst layers 2a and 2c to the electrolyte membrane 1, if the thickness of the first gasket layers 3a and 3c is 300 μm or less by the method for manufacturing the membrane electrode assembly 10 of the present invention, the gasket is attached. This is because the catalyst layers 2a and 2c can be completely transferred to the electrolyte membrane 1 up to the vicinity of the gasket of the electrolyte membrane.

  Although not shown in detail in the drawing, the second gasket layers 4a and 4c are made of a thermoplastic resin layer and an adhesive layer in the same manner as the first gasket layers 3a and 3c.

The gas diffusion layers 5a and 5c only need to have at least gas permeability (breathability) and conductivity. For example, woven fabrics, non-woven fabrics (felts obtained by entanglement of carbon fibers, etc.) and papers (carbon papers etc.) made of carbon material are widely used.
The gas diffusion layers 5a and 5c have a larger area than the catalyst layers 2a and 2c. As a result, since the fuel gas or the oxidizing gas is supplied to the entire catalyst layers 2a and 2c, an expensive platinum catalyst can be used up to the end.

(Method for producing membrane electrode assembly)
Next, with reference to FIG.2 and FIG.3, the manufacturing method of the membrane electrode assembly which concerns on embodiment of this invention is demonstrated.
As shown in FIG. 2, first gasket layers 3 c and 3 a are formed on the electrolyte membrane 1. In forming the first gasket layers 3a and 3c, an adhesive, an adhesive, or a heat sealant is applied to one side of the thermoplastic resin layers 31c and 31a as the adhesive layers 32c and 32a by screen printing. The attached thermoplastic resin layers 31 a and 31 c are installed and fixed on the electrolyte membrane 1. The thickness of the first gasket layers 3a and 3c is desirably equal to or close to that of the adjacent catalyst layers 2a and 2c.
If the thickness of the first gasket layers 3a, 3c and the thickness of the catalyst layers 2a, 2c are different, voids are generated between the two layers when the gas diffusion layers 5a, 5c are laminated on the first gasket layers 3a, 3c. The power generation performance will be reduced.
Further, as the thickness of the electrolyte membrane 1 is thinner, resistance due to proton conduction is suppressed, and improvement in power generation performance can be expected. However, as the thickness of the electrolyte membrane 1 is reduced, handling properties are reduced and yield is reduced. On the other hand, the first gasket layers 3a and 3c are placed on the electrolyte membrane 1 and then fixed, whereby the electrolyte membrane 1 can be handled at the first gasket layers 3a and 3c. Thereby, the handleability of the electrolyte membrane 1 is improved.

After the first gasket layers 3 a and 3 c are formed on the electrolyte membrane 1, the catalyst layers 2 a and 2 c applied to the rubber transfer substrate are transferred to each surface of the electrolyte membrane 1. When the rubber-based transfer substrate has a Shore A hardness of less than 40, distortion due to shear is large during transfer by thermal lamination, resulting in transfer failure. On the other hand, when the Shore A hardness is higher than 80, the followability to the gap between the heights of the first gasket layers 3a and 3c and the electrolyte membrane 1 is low, and it is difficult to transfer the catalyst layer to the electrolyte membrane to the vicinity of the gasket. Therefore, the gap between the transferred catalyst layers 2a and 2c and the gasket layers 3a and 3c becomes large.
Of the silicone rubber and fluororubber base materials, those having a Shore A hardness of 40 to 70 as the rubber-based transfer base material have the ability to follow the gap between the heights of the first gasket layers 3a and 3c and the electrolyte membrane 1. It is desirable as a transfer substrate because of its high transferability and good transferability. When the wettability of the rubber-based transfer substrate with respect to the catalyst ink becomes a problem, a known surface treatment method such as corona treatment, plasma treatment, or fluorine coating may be used.

  Further, a transfer substrate with a catalyst layer may be formed by installing a fluororesin sheet on the electrolyte membrane 1 side of the rubber transfer substrate and applying a catalyst ink on the fluororesin sheet.

  In addition, as shown in FIG. 3, when transferring the catalyst layers 2a and 2c by thermal lamination, a sheet base made of a porous material is provided on the surface of the rubber transfer substrate 6 opposite to the electrolyte membrane 1 with the first gasket layer. The material 7 is arranged. As a result, air contact between the rubber transfer substrate 6 and the transport sheet (SUS plate 9) used for thermal lamination can be avoided, and transfer defects can be suppressed.

  The mask sheet 8 may be laminated in advance on the surface of the first gasket layers 3a and 3c opposite to the electrolyte membrane 1 side. As a result, after the transfer of the catalyst layers 2 a and 2 c by thermal lamination, the catalyst transferred onto the first gasket layers 3 a and 3 c can be removed by removing the mask sheet 8.

  Subsequently, as shown in FIG. 1, the second gasket layers 4a and 4c are disposed on the first gasket layers 3a and 3c, and exposed to the openings of the formed second gasket layers 4a and 4c. Gas diffusion layers 5a and 5c are laminated on a portion straddling 2c and the surrounding first gasket layers 3a and 3c. However, the order in which the second gasket layers 4a and 4c and the gas diffusion layers 5a and 5c are stacked is not limited to this, and the second gasket layers 4a and 4c are disposed after the gas diffusion layers 5a and 5c are stacked first. May be. Finally, the membrane electrode assembly 10 can be integrated by performing thermal lamination or hot pressing.

Hereinafter, the membrane electrode assembly and the production method thereof in the polymer electrolyte fuel cell of the present invention will be described with specific examples, but the present invention is not limited to the examples.
A platinum-supported carbon catalyst having a platinum loading of 60% and Nafion (registered trademark, manufactured by DuPont), which is a 20% by mass polymer electrolyte solution, were added to a mixed solvent of water and ethanol = 1: 2. Subsequently, a dispersion treatment was performed with a planetary ball mill to prepare a catalyst ink.

After fixing a silicone rubber film as a transfer substrate on the plate, a catalyst ink was applied onto the transfer substrate with an applicator. The transfer sheet on which the coating film made of catalyst ink is formed is placed in an oven (hot air circulating constant temperature dryer 41-S5H / Satake Chemical Machinery Co., Ltd.), the oven temperature is set to 50 ° C. and dried for 5 minutes. A catalyst layer was formed on the transfer substrate. At this time, the amount of platinum supported was adjusted so that the cathode catalyst layer was about 0.5 mg / cm ² and the anode catalyst layer was about 0.3 mg / cm ² .

Next, an adhesive was pattern printed by screen printing on a PEN film (thickness: 25 μm, inner frame area 25 cm ² ) cut into a frame shape as a first gasket layer, and arranged on both surfaces of the electrolyte membrane. Further, Nafion 211 was used as the electrolyte membrane. Subsequently, hot pressing was performed at 120 ° C. and 120 kgf / cm ² for 5 minutes to cure and bond the first gasket layer.

  Next, heat transfer was performed to transfer the catalyst layer in a configuration in which a transfer substrate having a catalyst layer formed on the electrolyte membrane with the first gasket layer and a porous film (thickness: 350 μm) on the outside were disposed. . After the transfer, the transfer substrate and the mask sheet were removed.

Subsequently, the second gasket layer was disposed on the first gasket layer, and a gas diffusion layer in which MPL-treated carbon paper (manufactured by Toray Industries, Inc.) was bonded to the opening of the formed second gasket layer was laminated. Next, hot pressing was performed at 120 ° C. and 120 kgf / cm ² for 5 minutes to integrate the membrane electrode assembly.

  The obtained membrane / electrode assembly was punched out with a blade mold, and the clearance between the catalyst layer and the first gasket layer was observed, and was about 30 μm.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for a polymer electrolyte fuel cell single cell or a stack in a polymer electrolyte fuel cell, particularly a fuel cell automobile or a household fuel cell.

DESCRIPTION OF SYMBOLS 1 ... Electrolyte membrane 2a ... Anode side catalyst layer 2c ... Cathode side catalyst layer 3a ... Anode side first gasket 3c ... Cathode side first gasket 4a ... Anode side second gasket 4c ... Cathode side second gasket 5a ... Anode side gas diffusion Layer 5c ... Cathode side gas diffusion layer 31a ... Anode side thermoplastic resin layer 31c ... Cathode side thermoplastic resin layer 32a ... Anode side adhesive layer 32c ... Cathode side adhesive layer 6 ... Rubber transfer substrate 7 ... Sheet substrate made of porous material 8 ... Mask sheet 9 ... SUS plate 10 ... Membrane electrode assembly

Claims (4)

Laminating the first gasket layer on the peripheral portions of both surfaces located on the anode side and the cathode side of the electrolyte membrane constituting the membrane electrode assembly,
Laminating a catalyst layer on the electrolyte membrane exposed inside the first gasket layer on both sides of the electrolyte membrane;
Laminating a gas diffusion layer straddling the first gasket layer on the catalyst layer on both sides of the electrolyte membrane;
Laminating a second gasket layer on the first gasket layer exposed around the gas diffusion layer on both sides of the electrolyte membrane,
The step of laminating the catalyst layer on the electrolyte membrane includes a step of transferring the catalyst layer to the electrolyte membrane using a transfer substrate with a catalyst layer in which a catalyst ink is applied to a rubber transfer substrate.
A method for producing a membrane electrode assembly, comprising:   The said process of laminating | stacking the said catalyst layer on the said electrolyte membrane is performed using the said transfer base material with a catalyst layer which apply | coated the said catalyst ink to the said rubber transfer base material which carried out the fluorine coding. The manufacturing method of the membrane electrode assembly.   The step of laminating the catalyst layer on the electrolyte membrane is performed using the transfer substrate with a catalyst layer in which the catalyst ink is applied to the rubber transfer substrate on which a fluororesin sheet is installed. 2. A method for producing a membrane electrode assembly according to 1.   In the step of laminating the catalyst layer on the electrolyte membrane, heat lamination is performed from above the sheet substrate with a porous sheet substrate disposed on the surface of the rubber transfer substrate opposite to the electrolyte membrane. The method for producing a membrane / electrode assembly according to claim 1, further comprising a step of transferring the catalyst layer to the electrolyte membrane.

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