KR20220153522A - Carbon fiber substrate for gas diffusion layer of fuel cell comprising recycled carbon fiber, gas diffusion layer comprising the same and fuel cell comprising the same - Google Patents

Abstract

The objective of the present invention is to provide a recycled carbon fiber substrate for a gas diffusion layer of a low-cost fuel cell having the same performance as a gas diffusion layer made of non-regenerated carbon fiber and reduced in price by using a recycled carbon fiber. One embodiment of the present invention is to provide a carbon fiber substrate for a gas diffusion layer of a fuel cell, including a regenerated carbon fiber as a carbon fiber substrate for a gas diffusion layer of a fuel cell.

Description

A carbon fiber substrate for a gas diffusion layer of a fuel cell including recycled carbon fiber, a gas diffusion layer including the same, and a fuel cell including the same FUEL CELL COMPRISING THE SAME}

The present invention relates to a carbon fiber substrate for a gas diffusion layer of a fuel cell, a gas diffusion layer including the same, and a fuel cell including the same. More specifically, it relates to a carbon fiber substrate for a gas diffusion layer of a fuel cell including regenerated carbon fibers, a gas diffusion layer including the same, and a fuel cell including the same.

A fuel cell is a device that produces electrical energy by electrochemically reacting fuel and oxygen. Depending on the type of electrolyte used, a fuel cell is a polymer electrolyte membrane (PEM), phosphoric acid, molten carbonate, or solid oxide type. oxide), alkaline aqueous solution type, etc.

Here, the polymer electrolyte membrane fuel cell (PEMFC) has a lower operating temperature and higher efficiency than other types of fuel cells, high current density and power density, short start-up time, and excellent response to load changes. It has a quick response characteristic.

Polymer electrolyte membrane fuel cells can be divided into direct methanol fuel cells using methanol as fuel and hydrogen fuel cells using hydrogen as fuel. A polymer electrolyte membrane fuel cell has a structure in which a plurality of membrane electrode assemblies (MEAs) in which a fuel electrode coated with a catalyst and an air electrode are bonded are stacked on each gas diffusion layer (GDL) formed on both sides of a polymer electrolyte membrane. have

Here, the gas diffusion layer is formed by coating a microporous layer (MPL) on a carbon fiber substrate made of a porous carbon film. Currently, an important problem of hydrogen fuel cells is to develop parts and materials that reduce the volume of existing products, increase durability, and realize high performance while reducing prices. In order to solve these problems, development of a carbon fiber substrate for a gas diffusion layer that implements high electrical conductivity is required.

Publication No. 10-2020-0076395 (2020.06.29.)

Publication No. 10-2020-0068178 (2020.06.15.)

An object of the present invention is to provide a recycled carbon fiber substrate for a gas diffusion layer of a low-cost fuel cell with the same performance as a gas diffusion layer made of non-recycled carbon fiber and reduced cost by using recycled carbon fiber. is to provide

Another object of the present invention is to provide a gas diffusion layer for a fuel cell including the regenerated carbon fiber substrate or a fuel cell including the same.

One embodiment of the present invention provides a carbon fiber substrate for a gas diffusion layer of a fuel cell, characterized in that it comprises regenerated carbon fibers.

The regenerated carbon fibers may be carbon fibers regenerated by at least one method selected from the group consisting of pyrolysis, mechanical regeneration, oxidation, chemical regeneration, and water decomposition.

The carbon fiber substrate may include a carbide of an organic polymer material in which the regenerated carbon fibers are bonded to each other between the regenerated carbon fibers.

The organic polymer material may be at least one selected from the group consisting of polyacrylonitrile (PAN), pitch, rayon, polyvinyl alcohol (PVA), and phenol resin.

The regenerated carbon fiber may have a carbon atom content of 90% or more compared to the carbon atom content of the carbon fiber before regeneration.

The regenerated carbon fiber may have a tensile strength of 50% or more compared to the tensile strength of the carbon fiber before regeneration.

The electrical conductivity of the regenerated carbon fibers before being regenerated may be 100 S/cm or more.

The carbon fiber substrate may further include a binder.

The binder is included in an amount of 1 to 20% by weight based on 100% by weight of the carbon fiber substrate, and the binder may be at least one selected from the group consisting of polyvinyl alcohol (PVA), polyester, polyethylene, polyethylene-terephthalate, and cellulose. have.

The carbon fiber substrate may be in the form of a recycled carbon fiber nonwoven fabric, a recycled carbon fiber paper, a recycled carbon fiber filament, a recycled carbon fiber aggregate, or a recycled carbon fiber tow.

One embodiment of the present invention may provide a gas diffusion layer of a fuel cell including a carbon fiber substrate for the gas diffusion layer of the fuel cell and a microporous layer formed on a surface of the carbon fiber substrate.

The microporous layer may include at least one of carbon powder, a dispersant, a fluororesin, and conductive particles.

The fluororesin is polytetrafluoroethylene (PTFE), fluoroethyl propylene copolymer (FEP), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (E-CTFE, PCTFE), polypropylene It may be at least one selected from the group consisting of lean random copolymer (PP-R), perfluoroalkoxyalkane (PFA), and tetrafluoroethylene-ethylene (ETFE).

The dispersant may be any one or more selected from the group consisting of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.

The conductive particles may be at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, graphite, graphene, fullerenes, and conductive polymers.

In one embodiment of the present invention, a fuel cell including a gas diffusion layer of the fuel cell may be provided.

The present invention can provide a carbon fiber substrate for a gas diffusion layer of a fuel cell comprising recycled carbon fiber.

The present invention may provide a gas diffusion layer including the carbon fiber substrate and a fuel cell including the same.

The present invention can provide a gas diffusion layer at low cost.

The present invention can provide a fuel cell gas diffusion layer with excellent fuel cell performance.

1 is a microscope image of a gas diffusion layer according to Example 1 of the present invention.
2 shows the performance evaluation results of Example 1 and Comparative Example 1 of the present invention at a relative humidity of 100 RH%.

Next, the carbon fiber substrate for the gas diffusion layer of the present invention and the manufacturing method of the gas diffusion layer using the same will be described in detail.

A regenerated carbon fiber substrate and a method for manufacturing a gas diffusion layer using the same according to an embodiment of the present invention include preparing a regenerated carbon fiber substrate, impregnating and curing, carbonizing and graphitizing, water repellent treatment, and preparing a gas diffusion layer. It includes steps to

[Production of Regenerated Carbon Fiber Substrate]

A single type or two or more types of recycled carbon fibers and binders having different lengths are put into a dissociator containing a dispersion medium and sufficiently dispersed, and then the carbon fiber dispersion is supplied to a paper machine to be stacked on a wire conveyor belt. In this process, a dispersing agent may be included in the carbon fiber dispersion to lower the surface energy of the carbon fiber.

The regenerated carbon fiber is regenerated by removing the resin and matrix components of the carbon fiber composite material through pyrolysis, mechanical recycling, oxidation in fluidized bed, chemical recycling, and hydrolysis. At least one regenerated carbon fiber selected from the group consisting of carbon fibers is used. The regenerated carbon fibers are prepared from polyacrylonitrile (PAN), pitch, rayon, polyvinyl alcohol (PVA), and phenol resin as precursors.

The binder may be one or two or more selected from the group consisting of PVA, polyester, polypropylene, polyethylene, polyethylene-terephthalate, and cellulose.

As the dispersion medium, water is mainly used. The dispersion may include 60 to 90% by weight of carbon fiber and 10 to 40% by weight of the binder. The dispersion medium remaining in the paper-made dispersion is dehydrated through a dehydration process due to pressurization of the roller. The dehydrated dispersion is subjected to pressure treatment with both rollers at a temperature of 70° C. or higher and a pressure of 1 kgf/cm ² or higher, and the regenerated carbon fiber substrate is produced by winding.

At this time, the area weight and thickness of the regenerated carbon fiber base material can be controlled by the amount of regenerated carbon fiber supplied to the paper machine and the speed of the paper machine, and can be controlled by the arrangement of the regenerated carbon fiber through the direction coming out of the conveyor belt.

[Impregnated and Cured with Regenerated Carbon Fiber Substrate]

A slurry obtained by dispersing a thermosetting resin is impregnated into a regenerated carbon fiber substrate in an amount of 1 mg/cm ² or more. The thermosetting resin is mainly a phenolic resin. Water may be used as a dispersion medium of the slurry.

The regenerated carbon fiber sheet impregnated as above is dried and cured using a heating belt at a temperature between 70 and 140°C. At this time, the pressure is 10 kgf/cm ² below

[Carbonization and graphitization]

The regenerated carbon fibers that have undergone the impregnation and curing processes are carbonized and graphitized by high-temperature heat treatment in a nitrogen atmosphere through a conveyor belt. The carbonization treatment is performed for 30 minutes to 1 hour by injecting nitrogen or argon gas in a carbonization furnace at a temperature of about 700 to 900 ° C. During the carbonization process, carbides of organic polymer materials that bind the regenerated carbon fibers to each other are generated between the regenerated carbon fibers.

The organic high molecular substance means an organic high molecular substance contained in carbon fiber. For example, the organic polymeric material is polyacrylonitrile (PAN), pitch, rayon, polyvinyl alcohol (PVA), or phenolic resin.

The graphitization treatment is performed for 30 minutes to 1 hour by injecting nitrogen or argon gas in a graphitization furnace at a temperature of about 1500 to 2300 ° C. By going through the carbonization and graphitization processes, a regenerated carbon fiber substrate for the gas diffusion layer is finally manufactured.

[Water repellent treatment]

When the regenerated carbon fiber substrate is treated using a fluororesin suspension or emulsion, a hydrophobic carbon fiber substrate impregnated with the fluororesin can be obtained. The fluororesin is polytetrafluoroethylene (PTFE), fluoroethyl propylene copolymer (FEP), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (E-CTFE, PCTFE), polypropylene It may be at least one selected from the group consisting of lean random copolymer (PP-R), perfluoroalkoxyalkane (PFA), and tetrafluoroethylene-ethylene (ETFE).

After the regenerated carbon fiber substrate is impregnated with the dispersion containing the fluororesin through a conveyor belt, the dispersion is coated on the space formed between the regenerated carbon fibers and the surface of the regenerated carbon fibers by pressing a roller. Thereafter, when the treated recycled carbon fiber substrate is dried to remove moisture and the fluororesin is melted, a water-repellent carbon fiber substrate can be obtained.

Water is mainly used as a dispersion medium of the dispersion, and a dispersant is used to increase the dispersibility of the fluororesin. The dispersant may be at least one selected from the group consisting of Tergitol, Triton X-100, SDMS, and SDS.

At this time, the heat treatment temperature for drying is 80 ℃ ~ 150 ℃, treatment for 30 minutes to 1 hour.

[Production of Gas Diffusion Layer]

Subsequently, a gas diffusion layer (GDL) may be obtained by applying and sintering a microporous layer on the carbon fiber substrate prepared according to the above method. The thickness of the microporous layer is mainly 10 to 100 μm, and the pore size may be mainly distributed in the range of 0.05 to 20 μm.

One embodiment of the present invention may provide a gas diffusion layer of a fuel cell including a carbon fiber substrate for the gas diffusion layer of the fuel cell and a microporous layer formed on a surface of the carbon fiber substrate.

The microporous layer may include at least one of carbon powder, a dispersant, a fluororesin, and conductive particles.

The fluororesin is polytetrafluoroethylene (PTFE), fluoroethyl propylene copolymer (FEP), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (E-CTFE, PCTFE), polypropylene It may be at least one selected from the group consisting of lean random copolymer (PP-R), perfluoroalkoxyalkane (PFA), and tetrafluoroethylene-ethylene (ETFE).

The dispersant may be any one or more selected from the group consisting of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. More specifically, the dispersant is divided into nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants, specifically, nonionic surfactants: low molecular weight groups such as alkyl glycols or polyethylene glycols and polyvinyl alcohols. nonionic surfactants such as polymeric surfactants; Anionic surfactants: anionic surfactants such as alkyl polyoxyethylene sulfates, monoalkyl sulfates, alkylbenzene sulfonates, and monoalkyl phosphates; Cationic surfactants: cationic surfactants such as dialkyldimethylammonium salts, alkylbenzylmethylammonium salts, and phosphoric acid amine salts; Amphoteric surfactant: It may be an amphoteric surfactant such as alkyl sulfobetaines and alkyl carboxy betaines, and the characteristics of the dispersant may be at least one selected from the group consisting of materials that can be removed by thermal decomposition during the sintering process.

The conductive particles may be at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, graphite, graphene, fullerenes, and conductive polymers.

In one embodiment of the present invention, a fuel cell including a gas diffusion layer of the fuel cell may be provided.

Hereinafter, the present invention will be described in more detail using the following examples, but the present invention is not limited by the following examples.

Example 1

[Production of Regenerated Carbon Fiber Substrate for Gas Diffusion Layer]

95% by weight of recycled carbon fiber (Zolteck, model name: Recycled Chopped Carbon Fiber - Type 65, carbon content: 95%, fiber length: 6mm, fiber diameter: 7.2㎛, precursor: PAN) and 5% by weight of PVA as a binder were prepared. .

Here, weight % means the composition percent (%) of the material based on the total amount of all materials.

Carbon fibers, a binder, and a dispersant were added to water and uniformly dissociated through a mechanical method at a speed between 1,500 rpm and 2,000 rpm to obtain a regenerated carbon fiber dispersion.

Subsequently, the recycled carbon fiber dispersion is supplied to the paper machine through a pump, and at this time, the supplied recycled carbon fiber dispersion is arranged in parallel in the machine direction (the direction in which the dispersion flows) by the narrowing section of the head box.

Thereafter, the paper-made regenerated carbon fiber dispersion undergoes dehydration to some extent during the transfer process, but the remaining dispersion medium is removed through an additional dehydration process. The dehydrated regenerated carbon fiber sheet was heated and pressed with both rollers at a temperature of 70° C. or higher and a pressure of 1 kgf/cm ² or higher to obtain a regenerated carbon fiber substrate.

The regenerated carbon fiber substrate obtained in this way was subjected to an impregnation process, a curing process, a carbonization and graphitization process, and a water repellent treatment process to prepare a regenerated carbon fiber substrate for a gas diffusion layer.

At this time, in the impregnation process, the regenerated carbon fiber substrate was impregnated with an amount of 1 mg/cm ² or more of the slurry in which the phenol resin was dispersed.

The regenerated carbon fiber substrate impregnated as above is dried and cured using a heating belt at a temperature between 70 and 140°C. At this time, the pressure is 10 kgf/cm ² below

The regenerated carbon fibers that have undergone the impregnation and curing processes are carbonized and graphitized by high-temperature heat treatment in a nitrogen atmosphere through a conveyor belt. The carbonization treatment is performed for 30 minutes to 1 hour by injecting nitrogen or argon gas in a carbonization furnace at a temperature of about 700 to 900 ° C. The graphitization treatment is performed for 30 minutes to 1 hour by injecting nitrogen or argon gas in a graphitization furnace at a temperature of about 1500 to 2300 ° C. By going through the carbonization and graphitization processes, a regenerated carbon fiber substrate for the gas diffusion layer is manufactured.

[Step of water repellent treatment]

A fluororesin solution (Du Pont, model name: Teflon ^TM PTFE DISP 30 Fluoropolymer Dispersion, total solution 100% by weight fluororesin 60% by weight) was mixed with water and diluted to 5% by weight, and then mixed with a stirrer and an ultrasonic disperser. A dispersion was prepared.

Thereafter, the regenerated carbon fiber substrate was impregnated with the dispersion for 5 minutes, and in the process of taking it out, pressurized with both rollers so that the dispersion was evenly coated between or inside the regenerated carbon fibers.

Subsequently, the regenerated carbon fiber substrate impregnated with the fluororesin was dried in an air atmosphere at about 80 to 110° C. for 1 hour and then heat-treated at about 350° C. for 30 minutes in an air atmosphere to obtain a water repellent regenerated carbon fiber substrate.

[Manufacture of gas diffusion layer]

Deionized water, a dispersant, carbon black (Acetylene black), and a fluororesin solution are added, and a slurry for a microporous layer (MPL) is obtained through mechanical stirring using a mixer.

The slurry for the microporous layer is applied on the water-repellent regenerated carbon fiber substrate to a thickness of about 40 to 100 μm, dried in an air atmosphere at about 100 ° C. for 1 hour, and then sintered at about 350 ° C. for 30 minutes in an air atmosphere to obtain a gas diffusion layer. .

Comparative Example 1

Except for using carbon fiber (Zolteck, model name: ZOLTEK PX35, carbon content: 95%, fiber length: 6 mm, fiber diameter: 7.2 μm) in [Manufacture of regenerated carbon fiber substrate for gas diffusion layer] of Example 1, A gas diffusion layer was prepared in the same manner as in Example 1.

[Experimental Example 1: Observation of the surface of the gas diffusion layer]

The gas diffusion layer prepared according to Example 1 was photographed with a scanning electron microscope (S-4300), and the results are shown in FIG. 1, respectively.

[Experimental Example 2: Fuel Cell Performance Evaluation]

Fuel cell performance of the gas diffusion layer prepared according to Example 1 and Comparative Example 1 was measured. And the results are shown in Figure 2 below.

The gas diffusion layer prepared in Example 1 and Comparative Example 1 was used for the anode side and the cathode side, respectively, and attached to a commercial membrane (manufacturer: Vina tech, model name: VFP-A2A009-G00). Then, a fuel cell unit cell was assembled by inserting a gasket and combining with the separator plate.

The operating temperature was 65 °C, the electrode area was 9 cm ² , the relative humidity was 100%, and hydrogen was supplied to the anode at 200 cc/min and oxygen to the cathode at 600 cc/min, respectively, and the voltage change of the fuel cell according to the current density was measured. And the results are shown in Figure 2 below.

2 is a current voltage graph of a fuel cell unit cell to which the gas diffusion layer of Example 1 and Comparative Example 1 is applied.

Claims (16)

As a carbon fiber substrate for a gas diffusion layer of a fuel cell,
A carbon fiber substrate for a gas diffusion layer of a fuel cell, characterized in that it comprises regenerated carbon fiber. According to claim 1,
The carbon fiber substrate for the gas diffusion layer of a fuel cell, characterized in that the regenerated carbon fiber is a carbon fiber regenerated by at least one method selected from the group consisting of pyrolysis, mechanical regeneration, oxidation, chemical regeneration and water decomposition. According to claim 1 or 2,
The carbon fiber substrate for a gas diffusion layer of a fuel cell, characterized in that the carbon fiber substrate comprises a carbide of an organic polymer material in which the regenerated carbon fibers are bonded to each other between the regenerated carbon fibers. According to claim 3,
The organic polymer material is at least one selected from the group consisting of polyacrylonitrile (PAN), pitch, rayon, polyvinyl alcohol (PVA), and phenol resin Gas of a fuel cell, characterized in that Carbon fiber substrate for the diffusion layer. According to claim 1 or 2,
The regenerated carbon fiber is a carbon fiber substrate for a gas diffusion layer of a fuel cell, characterized in that it has a carbon atom content of 90% or more compared to the carbon atom content of the carbon fiber before regeneration. According to claim 1 or 2,
The carbon fiber substrate for a gas diffusion layer of a fuel cell, characterized in that the regenerated carbon fiber has a tensile strength of 50% or more compared to the tensile strength of the carbon fiber before regeneration. According to claim 1 or 2,
The regenerated carbon fiber is a carbon fiber substrate for a gas diffusion layer of a fuel cell, characterized in that the electrical conductivity of the carbon fiber before regeneration is 100 S / cm or more. According to claim 1,
The carbon fiber substrate for a gas diffusion layer of a fuel cell, characterized in that the carbon fiber substrate further comprises a binder. According to claim 8,
The binder is included in 1 to 20% by weight of 100% by weight of the carbon fiber substrate,
The carbon fiber substrate for the gas diffusion layer of a fuel cell, characterized in that the binder is at least one selected from the group consisting of polyvinyl alcohol (PVA), polyester, polyethylene, polyethylene-terephthalate and cellulose. According to claim 1,
A carbon fiber substrate for a gas diffusion layer of a fuel cell, characterized in that it is in the form of a recycled carbon fiber nonwoven fabric, a recycled carbon fiber paper, a recycled carbon fiber filament, a recycled carbon fiber aggregate or a recycled carbon fiber tow. A gas diffusion layer of a fuel cell comprising the carbon fiber substrate for a gas diffusion layer of claim 1 or 2 and a microporous layer formed on a surface of the carbon fiber substrate. According to claim 11,
The microporous layer is a gas diffusion layer of a fuel cell, characterized in that it contains at least one of carbon powder, a dispersant, a fluororesin and conductive particles. According to claim 12,
The fluororesin is polytetrafluoroethylene (PTFE), fluoroethyl propylene copolymer (FEP), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (E-CTFE, PCTFE), polypropylene A gas diffusion layer of a fuel cell, characterized in that it is at least one selected from the group consisting of lean random copolymer (PP-R), perfluoroalkoxyalkane (PFA) and tetrafluoroethylene-ethylene (ETFE). According to claim 12,
The gas diffusion layer of a fuel cell, characterized in that the dispersant is at least one selected from the group consisting of nonionic surfactants, anionic surfactants, cationic surfactants and amphoteric surfactants. According to claim 12,
The gas diffusion layer of a fuel cell, characterized in that the conductive particles are at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, graphite, graphene, fullerenes, and conductive polymers. A fuel cell comprising the gas diffusion layer of claim 11.

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