KR102568624B1 - Gas Diffusion Layer and method thereof - Google Patents

Abstract

The present invention relates to a gas diffusion layer for a fuel cell and a method for manufacturing the same, and more particularly, to a gas diffusion layer support in which a conductive carbon black coating layer is formed on one or both sides of a carbon fiber nonwoven fabric; and a microporous layer on one surface of the gas diffusion layer support, wherein polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), and ethylene tetrafluoroethylene (ETFE) are provided on one surface of the gas diffusion layer support, and a gas diffusion layer for a fuel cell comprising the same It's about manufacturing methods.

Description

Gas diffusion layer for fuel cell and method for manufacturing the same {Gas Diffusion Layer and method thereof}

The present invention relates to a gas diffusion layer for a fuel cell and a method for manufacturing the same, and more particularly, to a gas diffusion layer for a fuel cell having excellent bonding strength and electrical conductivity between a gas diffusion layer support constituting the gas diffusion layer and a microporous layer, and a method for manufacturing the same.

A fuel cell is a kind of power generation device that converts chemical energy of fuel into electrical energy by electrochemically reacting it in a fuel cell stack.

PEMFC (Polymer Electrolyte Membrane Fuel Cell) is applied as a fuel cell for dual vehicle driving. Hundreds of unit cells are required to normally express high output performance of at least several tens of kW under various vehicle driving conditions. It is known that a stack is formed by repeated stacking and must be able to operate stably in a wide range of current densities.

Such a polymer electrolyte membrane fuel cell (PEMFC) is a membrane electrode assembly (MEA) including a polymer electrolyte membrane (PEM) and a catalyst, a gas diffusion layer (GDL), a reaction It is composed of a gasket for maintaining the airtightness of gases and cooling water and an appropriate clamping pressure, and a bipolar plate for moving reactive gases and cooling water.

The principle of generating electricity through a membrane electrode assembly (MEA) is that hydrogen supplied to the anode, the anode of the fuel cell, is separated into hydrogen ions and electrons, and then the hydrogen ions pass through the polymer electrolyte membrane to the cathode, the cathode. ), and the electrons move to the cathode through an external circuit, where oxygen molecules, hydrogen ions, and electrons react together to generate electricity and heat, as well as water as a reaction by-product.

On the other hand, water generated during the electrochemical reaction in the fuel cell plays a desirable role in maintaining the humidification of the membrane electrode assembly (MEA) if it is present in an appropriate amount, but if it is not properly removed when excessive water is generated, it " A "flooding" phenomenon occurs, and the flooded water serves to prevent the efficient supply of reactive gases to the fuel cell, so that the voltage loss increases.

The gas diffusion layer (GDL) plays a role in supplying hydrogen and oxygen evenly to the polymer electrolyte membrane (PEM), as an electrical conductor that moves electrons reacted between the catalyst layer and the separator from the separator, and as a polymer electrolyte membrane ( Since PEM) plays a very important role in a polymer electrolyte membrane fuel cell (PEMFC), such as supplying or discharging water to maintain proper moisture, it must have electrical and thermal conductivity, porosity and hydrophobicity, and thermal and chemical stability. .

The gas diffusion layer (GDL) has a two-layer structure in which a microporous layer (MPL) is formed on a gas diffusion back layer (GDBL). That is, the porous gas diffusion layer support (GDBL) is manufactured by coating a water repellent material containing a fluorine-based polymer material on carbon cloth, carbon nonwoven fabric, or carbon paper using a carbon material having good electrical conductivity, heat resistance, and chemical resistance, A solution for forming the microporous layer (MPL) also contains a fluorine-based polymer material. Therefore, when heated above a certain temperature, these fluorine-based polymer materials are melted together, and as a result, the porous gas diffusion layer support and the microporous layer are combined.

However, since PTFE (polytetrafluoroethylene) is mainly used as a fluorine-based polymer material, the gas diffusion layer support (GDBL) and the microporous layer (MPL) do not have sufficient bonding strength, so gas, electrons, and generated water move within the gas diffusion layer (GDL). There is a problem that the performance of the fuel cell is deteriorated due to instability.

Korean Patent Publication No. 2021-0087825

The present invention was derived to solve the above problems, and the gas diffusion layer for fuel cells has improved bonding strength between the gas diffusion layer support (GDBL) and the microporous layer (MPL) constituting the gas diffusion layer (GDL) and has excellent electrical conductivity. And to provide a manufacturing method thereof.

In order to solve these technical problems, the gas diffusion layer for a fuel cell according to the present invention includes a gas diffusion layer support in which a conductive carbon black coating layer is formed on one or both sides of a carbon fiber nonwoven fabric; and a microporous layer on one surface of the gas diffusion layer support, wherein polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), and ethylene tetrafluoroethylene (ETFE) are provided on one surface of the gas diffusion layer support.

Further, the gas diffusion layer for a fuel cell according to the present invention is characterized in that the electrical resistance in the thickness direction is less than 15 mΩ/cm 2 .

In addition, the gas diffusion layer for a fuel cell according to the present invention is characterized in that the adhesion between the gas diffusion layer support and the microporous layer is 3A or more when measured according to the international standard ASTM 03359-83-Method A standard.

In addition, the gas diffusion layer for a fuel cell according to the present invention has an electrical resistance in the thickness direction of less than 15 mΩ/cm 2 , and the adhesion between the gas diffusion layer support and the microporous layer is 3A or more when measured according to the international standard ASTM 03359-83-Method A. characterized by

In addition, the method for manufacturing a gas diffusion layer for a fuel cell according to the present invention includes a first step of preparing a carbon fiber nonwoven fabric; A second step of coating the carbon fiber nonwoven fabric with a conductive carbon black solution; A third step of coating a water repellent solution on the carbon fiber nonwoven fabric coated with the conductive carbon black solution; and a fourth step of forming a microporous layer on one surface of the water-repellent coated carbon fiber nonwoven fabric; wherein, the water-repellent solution in the third step contains 1800 to 2200 parts by weight of water or ultrapure water and 60 w/v% solid content. polytetrafluoroethylene (PTFE) with a melt flow index (MFR) of 3 to 5 g/10 min and PFA (polytetrafluoroethylene) with a melt flow index (MFR) of 13 to 16 g/10 min with a solid content of 50 w/v% ( Perfluoroalkoxy) in a ratio of 150 to 250 parts by weight of a fluorine-based polymer, and in the fourth step, 250 parts by weight of water or ultrapure water, 250 parts by weight of glycerin, and 70 parts by weight of conductive carbon black are mixed and stirred, and the average particle size is 70 to 80 μm It is characterized in that 30 parts by weight of ETFE (Ethylene tetrafluoroethylene) powder having a melt flow index (MFR) of 13.6 g / 10 min is additionally mixed and then stirred.

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In addition, in the gas diffusion layer manufacturing method for a fuel cell according to the present invention, the conductive carbon black solution in the second step is 300 to 700 parts by weight of water, 30 to 70 parts by weight of conductive carbon black, and 80 to 120 parts by weight of phenol resin It is characterized in that it is mixed with.
In addition, the present invention is characterized in that it is a gas diffusion layer for a fuel cell manufactured by the above-described method for manufacturing a gas diffusion layer for a fuel cell.

According to the gas diffusion layer for a fuel cell and its manufacturing method of the present invention, two or more types of fluorine-based polymer materials having different melt flow indices are used as water repellent materials and ETFE powder is added when forming the microporous layer, thereby forming a gas diffusion layer support (GDBL) and a microporous layer. A gas diffusion layer for a fuel cell in which the bonding strength of the porous layer (MPL) is improved and the electrical conductivity is excellent can be manufactured.

1 is a flowchart illustrating a method of manufacturing a gas diffusion layer according to a preferred embodiment of the present invention.
2 is a view for explaining the adhesion test criteria.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments and drawings of the present invention, but this is to explain in detail enough that a person having ordinary knowledge in the art to which the present invention belongs can easily practice the present invention. However, this does not mean that the technical spirit and scope of the present invention are limited.

In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, it should not be interpreted in an ideal or excessively formal meaning. don't

1 is a flowchart illustrating a method of manufacturing a gas diffusion layer for a fuel cell according to a preferred embodiment of the present invention. As shown in FIG. 1, the method for manufacturing a gas diffusion layer according to the present invention includes a first step of preparing a carbon fiber nonwoven fabric, a second step of coating a conductive carbon black solution on the carbon fiber nonwoven fabric, and a coating of the conductive carbon black solution. It is configured to include a third step of coating a water repellent solution on the carbon fiber nonwoven fabric, and a fourth step of forming a microporous layer on one surface of the carbon fiber nonwoven fabric coated with water repellency.

First, the carbon fiber nonwoven fabric in the first step is prepared in step 1a of preparing a second mixture by mixing a first mixture in which carbon fibers and a surfactant are mixed in an organic solvent, a thickener, a binder, and water, and the prepared in step 1a. 1b step of preparing a third mixture by mixing the first mixture and the second mixture, 1c step of preparing a raw material mixture in a slurry state by subjecting the third mixture prepared in step 1b to ultrasonic dispersion treatment, and in step 1c It may include a 1d step of stacking the prepared raw material mixture on the mesh belt, a 1e step of dewatering the raw material mixture stacked on the mesh belt, and a 1f step of drying with hot air.

Step 1a is a step of preparing a first mixture and a second mixture, wherein the first mixture contains 1 to 5 parts by weight of an organic solvent, 0.1 to 1.0 parts by weight of carbon fiber, and a nonionic interface based on 10 to 15 parts by weight of water. After mixing 0.001 to 0.005 parts by weight of the activator, dissociation is performed at 1200 to 1800 RPM for 3 to 8 minutes.

Here, as the organic solvent, one or two or more organic solvents selected from organic solvents such as hydrocarbons, halogenated hydrocarbons, aromatic chlorinated hydrocarbons, alcohols, aldehydes, ether esters, ketones, and glycol ethers may be used. Yes, preferably ethanol.

Carbon fibers are manufactured using polyacrylonitrile as a precursor, and it is preferable to chop them to have a length of 5 to 15 mm and a diameter of 1 to 10 μm, and it is more preferable not to apply a carbon fiber sizing agent such as epoxy resin. , This is to maintain dispersibility by minimizing surface tension in the solvent.

The second mixture is prepared by mixing 0.05 to 0.2 parts by weight of a thickener, 0.001 to 0.005 parts by weight of a binder, and 190 to 200 parts by weight of water. Here, the thickener is preferably carboxylmethyl cellulose.

The binder is preferably any one of polyvinyl alcohol (PVA), vinyl acetate (PVAC), and acrylate, and more preferably polyvinyl alcohol (PVA) having a length of 3 mm and a diameter of 2 μm. The second mixture composed of the above is stirred in a stirrer.

Step 1b is a step of preparing a third mixture by mixing the first mixture and the second mixture.

Step 1c is a step of preparing a raw material mixture in a slurry state by treating the prepared third mixture with ultrasonic waves. Using ultrasonic waves, it is possible to obtain a carbon fiber nonwoven fabric having uniform thickness, air permeability, and excellent electrical conductivity because carbon fibers are evenly dispersed throughout the mixture even when a small amount of thickener is added. Here, the ultrasonic wave is preferably adjusted to 20 to 200 kHz.

Step 1d is a step of stacking the prepared slurry-state raw material mixture on the mesh belt, and spraying the raw material mixture onto the mesh belt moving at a constant speed.

Step 1e is a step of dewatering the raw material mixture stacked on the mesh belt, and may include a first dehydration step and a second dehydration step. Specifically, in the first dehydration step, the moment the raw material mixture is stacked on the mesh belt, dehydration is performed under reduced pressure from the lower surface of the mesh belt. Through this, the load applied to the mesh belt can be reduced, thereby reducing the maintenance cost of the device. Since the fibers are bonded by dehydration, even if the mesh belt moves at a slight incline, the layered raw material slurry mixture is maintained as it is, and a filter having a uniform thickness can be obtained.

The second dehydration step is a step of further lowering the moisture of the first dewatered raw material slurry mixture and at the same time inducing more dense bonding between the fibers. desirable.

Step 1f is a step of hot air drying, which is a step of completely drying some remaining moisture. It is preferable to dry with hot air in a drying device maintained at a temperature of 100 to 150 ° C, and to dry once more at 200 to 300 ° C. more preferable

The second step of coating the conductive carbon black solution on the carbon fiber nonwoven fabric prepared in the first step is a step for improving electrical conductivity by increasing the bonding force between carbon fibers.

The carbon fiber nonwoven fabric obtained through the above-described process has a thickness of about 200 to 300 μm, but in the thickness direction, the bonding strength between carbon fibers may be insufficient, so it is difficult to expect sufficient electrical conductivity. Therefore, in the thickness direction of the carbon fiber nonwoven fabric Conductive carbon black solution is coated to increase the electrical conductivity by improving the bonding force between the carbon fibers.

The conductive carbon black solution includes a step 2a of preparing a primary slurry mixture by introducing water, conductive carbon black, and a phenol resin, and a step 2b of homogenizing.

Specifically, in step 2a of preparing the primary slurry mixture, 300 to 700 parts by weight of water, 30 to 70 parts by weight of conductive carbon black, and 80 to 120 parts by weight of phenol resin are preferably mixed.

The conductive carbon black has a particle size of 10 to 50 nm and a specific surface area of 150 to 270 m/g, and is not particularly limited, such as commonly known conductive carbon black or conductive carbon black made by thermal decomposition of acetylene gas. For example, Cabot's Vulcan, Mitsubishi Chemicl's ketchen black, Denka's Denka black, Birla Carbon's Conductex, etc. may be used.

Phenol resin functions as a binder to improve the dispersibility of carbon black when preparing a conductive carbon black solution and to improve the bonding force between carbon fibers when impregnating a carbon fiber nonwoven fabric. These phenolic resins can be classified into novolak-based and resol-based depending on the basic structure of phenol. Resin and resol type phenol resin are used together.

That is, resol-based phenolic resin can improve electrical conductivity through hardening reaction and cyclization reaction during high-temperature sintering, but after sintering, the material, that is, the gas diffusion layer support becomes brittle and the bending stiffness is lowered. Novolak-based phenolic resins have somewhat poor electrical conductivity due to insufficient hardening and cyclization reactions compared to resol-based phenolic resins during high-temperature sintering, but they can contribute to stabilizing the dispersion of conductive black carbon. There is an effect of improving the bending strength of the gas diffusion layer support by controlling excessive cyclization of the resol-based phenolic resin.

At this time, it is preferable that the resol-based phenolic resin and the novolak-based phenolic resin are mixed in a weight ratio of 9:1 to 4:6 among the total phenolic resins.

In addition, the weight average molecular weight of the Resol-based phenolic resin is preferably Mw 3,000 to 4,000 g/mol, and the Novolak-based phenolic resin has a weight average molecular weight Mw of 1,000 to 2,000 g/mol.

Step 2b of homogenization is a step of grinding the prepared primary slurry mixture, maximizing the dispersibility of the conductive carbon black through wet milling using an attrition mill or the like.

On the other hand, when the prepared conductive carbon black solution is coated on the carbon fiber nonwoven fabric, the process of immersing the carbon fiber nonwoven fabric in the conductive carbon black solution so that the conductive carbon black can be attached between the upper and lower surfaces or pores of the carbon fiber nonwoven fabric ( It can be coated through impregnation).

Here, the carbon fiber nonwoven fabric impregnated with conductive carbon black may be further subjected to a compression process one or more times, which is to remove excess carbon black solution.

In addition, the carbon fiber nonwoven fabric coated with the conductive carbon black solution is dried with hot air for 5 to 40 minutes in the temperature range of 70 to 150 ° C, and then subjected to one or more heat treatment processes. At this time, after the first heat treatment at 150 to 250 ° C for 5 to 20 minutes It is preferable to perform a secondary heat treatment for 5 to 40 minutes in an Ar gas atmosphere and at a temperature of 1400 to 1600 ° C.

The third step is to impart hydrophobicity to the carbon fiber nonwoven fabric, and is a step of coating the carbon fiber nonwoven fabric with a water-repellent solution containing a polymer of hydrophobic material.

The water repellent solution may be mixed with a fluorine-based polymer in an amount of 150 to 250 parts by weight based on 1800 to 2200 parts by weight of water or ultrapure water.

At this time, PTFE (polytetrafluoroethylene), FEP (Fluorinated ethylene propylene), PFA (Perfluoroalkoxy), ETFE (Ethylene tetrafluoroethylene) can be used as the fluorinated polymer. PTFE (polytetrafluoroethylene), FEP (Fluorinated ethylene propylene), PFA (Perfluoroalkoxy) It is preferable to mix one or more materials of ETFE (Ethylene tetrafluoroethylene) together, and PTFE (polytetrafluoroethylene) and PFA to simultaneously satisfy excellent adhesion and high electrical conductivity of the gas diffusion layer support (GDBL) and the microporous layer (MPL) (Perfluoroalkoxy) is more preferable, and a polytetrafluoroethylene (PTFE) aqueous dispersion having a solid content of 60 w/v% and a melt flow index (MFR) of 3 to 5 g/10 min and a solid content of 50 w/v% It is most preferable that a perfluoroalkoxy (PFA) aqueous dispersion having a melt flow index (MFR) of 13 to 16 g/10 min is mixed to satisfy a weight part ratio of 1:0.4 to 1:1.1 for the solid content of PTFE and the solid content of PFA. .

If the melt flow index of PTFE (polytetrafluoroethylene) and PFA (perfluoroalkoxy) or the mixing ratio of these materials is out of the above range, the bonding strength between the gas diffusion layer support (GDBL) and the microporous layer (MPL) is not improved, or the final manufacturing The electrical conductivity of the gas diffusion layer (GDL) is lowered, resulting in deterioration in the performance of the fuel cell.

As in the case of coating the conductive carbon black solution, the carbon fiber nonwoven fabric coated with the carbon black solution is immersed in a container containing a water repellent solution, taken out, dried at 110 to 130 ° C for 20 to 40 minutes, By heat treatment at 320 to 380 ° C. for 15 to 25 minutes, a gas diffusion layer support (GDBL) coated with conductive carbon black and a water repellent material on a carbon fiber nonwoven fabric is obtained.

A fourth step is a step of forming a microporous layer (MPL) on the gas diffusion layer support (GDBL) obtained through the above-described first to third steps.

The solution for forming the microporous layer (MPL) is prepared by preparing 50 to 100 parts by weight of conductive carbon black, 220 to 280 parts by weight of water or ultrapure water, and 220 to 280 parts by weight of glycerin, and then using a planetary mixer for high viscosity. 4a step of preparing a high-viscosity first slurry by mixing at 45 to 55 RPM for 9 to 11 hours, and adding 25 to 35 parts by weight of ETFE powder to the first slurry, and mixing again at 45 to 55 RPM for 9 to 11 hours A solution for forming micropores may be prepared through step 4b of doing.

Here, the reason for separately mixing step 4a and step 4b is that when the conductive carbon black and the ETFE powder are simultaneously mixed, it takes too much time to disperse the conductive carbon black due to the releasability of the ETFE powder.

For the conductive carbon black, Denka's Li400 product with an average particle size of 48 nm and a specific surface area of 39 m2/g can be used, and ETFE powder (DAIKIN ETFE powder EC-6510) has an average particle size of 75 μm and a density of 0.75 g/ml. It has a physical property of MFR 13.6g/10min.

When applying the solution for forming micropores on the gas diffusion layer support (GDBL), use a Micro Film Applicator and an automatic coating machine (core tech CT-AF300) to apply the solution so that the film thickness is 0.2 mm, and then at 110 to 130 ° C. Drying for 25 to 35 minutes, and heat treatment at 330 to 370 ° C. for 15 to 25 minutes, a gas diffusion layer (GDL) having a microporous layer (MPL) formed on one surface is prepared.

Hereinafter, the present invention will be described in more detail through examples and experimental examples. However, these examples are only for helping the understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

Example

(1) Manufacture of carbon fiber non-woven fabric

A carbon fiber nonwoven fabric was prepared as follows. After mixing 10 kg of water with 2 kg of ethanol, 0.45 kg of carbon fiber having a length of 5 to 7 mm and 0.0025 kg of a nonionic surfactant were mixed to prepare a first mixture, and dissociation was performed at 1500 RPM for 5 minutes.

Separately, a second mixture was prepared by mixing 2 kg of carboxylmethylcellulose, 0.05 kg of PVA, and 2000 kg of water.

After mixing the first mixture and the second mixture, after stirring at 800 RPM for 10 minutes, ultrasonic waves were applied at 160 kHz for 5 minutes, and then the prepared raw material mixture was laminated on a microfiber mesh belt conveying at 30 m/min. The moment the raw material mixture is laminated on the mesh belt, the first dehydration is performed under a vacuum pressure of 10 cmHg, and the second dehydration is performed under a vacuum pressure of 30 cmHg, followed by primary drying at 150 ° C and secondary drying at 250 ° C, resulting in an average thickness of 250 μm. And a carbon fiber nonwoven fabric having a basis weight of 30 g / m 2 was prepared.

(2) conductive carbon black solution coating

The conductive carbon black solution was prepared by mixing 500 g of water, 50 g of conductive carbon black, 70 g of Resol-based phenolic resin with a solid content of 60 w/v%, and Novolak with a solid content of 60 w/v% in an Attrition Mill with a capacity of 3 L. After adding 30 g of )-based phenol resin, the mixture was stirred at 300 rpm for 30 minutes to prepare a primary slurry mixture.

At this time, the conductive carbon black was Cabot's Vulcan XC 72R product with an average particle size of 30 nm and a specific surface area of 254 m2/g, and the Resol-based phenolic resin had a weight average molecular weight of 3,511 g/mol and a Novolak-based Phenol resin has a weight average molecular weight Mw of 1,110 g/mol.

Then, after injecting a zirconia ball with a diameter of 0.8 mm into the primary slurry mixture, the conductive carbon black solution was prepared by high-speed stirring at 500 rpm for about 5 hours in a vacuum atmosphere, and the obtained conductive carbon black solution was measured with a Brook Field viscometer. The viscosity was 65 cps, (Spindle 61, 20 RPM), the particle size by the particle size zeta potential analyzer (ELSZ-2000, Otsuka Electronics) was D50 350 nm, and the zeta potential was -37 mV.

The carbon fiber nonwoven fabric was coated with the conductive carbon black solution prepared through the above process. That is, after the carbon fiber nonwoven fabric was immersed in the reaction tank containing the conductive carbon black solution once and taken out, a compression process was performed at a pressure of 80 kPa to remove the excess conductive carbon black solution. Then, drying at 120 ° C. for 30 minutes, first heat treatment at 170 ° C. for 10 minutes, and second heat treatment at 1500 ° C. for 30 minutes were sequentially performed.

(3) Water-repellent solution coating

A carbon fiber nonwoven fabric coated with conductive carbon black was immersed in a water-repellent solution and pulled out, dried at 120° C. for 30 minutes, and heat-treated at 350° C. for 20 minutes to prepare a gas diffusion layer support (GDBL) having a water-repellent surface.

At this time, the water repellent solution is obtained by mixing 2000 g of ultrapure water with 100 g of PTFE (polytetrafluoroethylene) aqueous dispersion (solid content of 60 w/v%, MFR of 4 g/10 min) and 100 g of PFA (Perfluoroalkoxy) aqueous dispersion (solid content of 50 w/v%, MFR of 15 g/10 min). prepared.

(4) Formation of microporous layer

A gas diffusion layer (GDL) having a microporous layer (MPL) was prepared by applying a solution for forming micropores on one surface of the gas diffusion layer support (GDBL) obtained through the above-described water-repellent treatment.

For the solution for forming the microporous layer, 70 g of conductive carbon black, a product of Denka's Li400 with an average particle size of 48 nm and a specific surface area of 39 m2/g, and 250 g of glycerin were added to 250 g of ultrapure water, and then mixed at 50 RPM with a high-viscosity mixing mixer (industrial Planetary Mixer). A high-viscosity slurry was prepared by stirring for 10 hours.

Thereafter, 30 g of powder made of ETFE was added and stirred at 50 RPM for 10 hours.

Here, the ETFE powder (DAIKIN ETFE powder EC-6510) has physical properties of average particle size of 75 μm, density of 0.75 g/ml, and MFR of 13.6 g/10 min.

When applying the solution for forming micropores on one side of the gas diffusion layer support (GDBL), it was applied so that the film thickness was 0.2 mm using a Micro Film Applicator and an automatic coating machine (core tech CT-AF300), and then dried at 120 ° C for 30 minutes. , heat treatment at 350 ° C. for 20 minutes.

Comparative Example 1

When preparing the solution for forming micropores, a gas diffusion layer (GDL) was prepared under the same conditions as in Example except that the amount of ETFE powder was changed to 10 g.

Comparative Example 2

When preparing the solution for forming micropores, a gas diffusion layer (GDL) was prepared under the same conditions as in Example except that the amount of ETFE powder was changed to 20 g.

Comparative Example 3

When preparing the solution for forming micropores, a gas diffusion layer (GDL) was prepared under the same conditions as in Example except for changing the addition amounts of 75 g of conductive carbon black and ETFE powder to 65 g.

Comparative Example 4

When preparing the solution for forming micropores, a gas diffusion layer (GDL) was prepared under the same conditions as in Example except that the addition amounts of 75 g of conductive carbon black and ETFE powder were changed to 70 g.

Comparative Example 5

It is a gas diffusion layer (GDL) from company A that is currently on the market.

Comparative Example 6

It is the gas diffusion layer (GDL) of company B that is currently on the market.

Furtherance Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 ultrapure water (g) 250 250 250 250 250 - - Carbon black (g) 70 70 70 75 75 - - Glycerin (g) 250 250 250 250 250 - - ETFE (g) 30 10 20 65 70 - - ETFE (g) content (%) 5 1.7 3.4 10.1 10.8 - -

Experimental example

The electrical resistance of the gas diffusion layer (GDL) prepared under the conditions of Example and Comparative Example and the adhesive force between the gas diffusion layer support (GDBL) and the microporous layer (MPL) were evaluated, and the results are shown in Table 1.

Electrical resistance was measured in the thickness direction in a state where a pressure of 1 Mpa was applied to the gas diffusion layer (GDL) (TSURUGA, AC mΩ Meter, MODEL 3566).

The adhesion test was evaluated according to the paint adhesion test (international standard ASTM 03359-83-Mmthod A) as shown in FIG. 2, and the adhesion test was determined by comparing the area removed with the adhesive test tape (3M #610).

As a solution for forming micropores, the gas diffusion layer (GDL) prepared by mixing 30 g of ETFE powder with an MFR of 13.6 g/10 min in 250 g of ultrapure water, 70 g of conductive carbon black, and 250 g of glycerin has an electrical resistance of 12 mΩ/cm 2 and adhesive strength at this time. was determined to be 3A.

On the other hand, the electrical resistance of the gas diffusion layer (GDL) prepared according to Comparative Example 1 in which 10 g of ETFE powder with an MFR of 13.6 g/10 min was mixed was excellent at 10 mΩ/cm 2 , but the adhesive strength was only 1 A.

In addition, the electrical resistance of the gas diffusion layer (GDL) prepared according to Comparative Example 2 in which 20 g of ETFE powder with an MFR of 13.6 g / 10 min was mixed and Comparative Example 3 in which 65 g was mixed was excellent at 12 to 14 mΩ / cm 2, but the adhesive strength was 2A, which is sufficient Adhesion is difficult to expect.

In addition, the electrical resistance and adhesive strength of the gas diffusion layer (GDL) prepared according to Comparative Example 4 in which 70 g of ETFE powder having an MFR of 13.6 g/10 min was mixed were only 15 mΩ/cm 2 and 1 A, respectively.

On the other hand, the gas diffusion layer (GDL) of company A currently on the market had an electrical resistance of 20 mΩ/cm 2 and adhesive strength of only 1 A (Comparative Example 5), and the gas diffusion layer (GDL) of company B had a relatively good electrical resistance of 17 mΩ/cm 2 , The adhesive strength was only 2A (Comparative Example 6).

As a result of the above results, when preparing a solution for forming micropores, by mixing 30g of ETFE powder with an MFR of 13.6g/10min in 250g of ultrapure water, 70g of conductive carbon black and 250g of glycerin, It can be confirmed that the gas diffusion layer (GDL) having improved adhesion of the porous layer (MPL) can be obtained.

Amount of ETFE powder added (g) ETFE (g) content
(%) electrical resistance in the thickness direction
(mΩ/cm2, 1Map) adhesion Example 30 5 12 3A Comparative Example 1 10 1.7 10 1A Comparative Example 2 20 3.4 12 2A Comparative Example 3 65 10.1 14 2A Comparative Example 4 70 10.8 15 1A Comparative Example 5 - - 20 1A Comparative Example 6 - - 17 2A

So far, the present invention has been looked at with respect to its preferred embodiments. Those skilled in the art to which the present invention pertains will be able to understand that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative rather than a limiting point of view. The scope of the present invention is shown in the claims rather than the foregoing description, and the scope equivalent thereto should be construed as being included in the present invention.

Claims (8)

delete delete delete delete A first step of preparing a carbon fiber nonwoven fabric;
A second step of coating the carbon fiber nonwoven fabric with a conductive carbon black solution;
A third step of coating a water repellent solution on the carbon fiber nonwoven fabric coated with the conductive carbon black solution; and
A fourth step of forming a microporous layer on one surface of the water-repellent coated carbon fiber nonwoven fabric; including,
In the water repellent solution in the third step, 1800 to 2200 parts by weight of water or ultrapure water, polytetrafluoroethylene (PTFE) having a solid content of 60 w / v% and a melt flow index (MFR) of 3 to 5 g / 10 min, and solid content It is mixed in a ratio of 150 to 250 parts by weight of a fluorine-based polymer made of PFA (Perfluoroalkoxy) having a melt flow index (MFR) of 13 to 16 g / 10 min with a content of 50 w / v%,
In the fourth step, after mixing and stirring 250 parts by weight of water or ultrapure water, 250 parts by weight of glycerin, and 70 parts by weight of conductive carbon black, the average particle size is 70 to 80 μm and the melt flow index (MFR, Melt Flow Index) is 13.6g/10min A gas diffusion layer manufacturing method for a fuel cell, characterized in that 30 parts by weight of phosphorus ETFE (Ethylene tetrafluoroethylene) powder is additionally mixed and then stirred.
According to claim 5,
The conductive carbon black solution in the second step is mixed in a ratio of 300 to 700 parts by weight of water, 30 to 70 parts by weight of conductive carbon black, and 80 to 120 parts by weight of phenol resin Method for manufacturing a gas diffusion layer for a fuel cell .
A gas diffusion layer for a fuel cell manufactured by the method for manufacturing a gas diffusion layer for a fuel cell according to claim 5 or 6. delete