A method for producing a gas diffusion layer for a fuel cell

Abstract

The application discloses a preparation method of a gas diffusion layer for a fuel cell and belongs to the field of fuel cells. The gas diffusion layer is composed of a substrate layer and a microporous layer. By solving the agglomeration problem of nanoscale conductive carbon materials in the dispersion process and successfully constructing a "point-line-surface" high-conductivity network microporous layer, the conductivity of the gas diffusion layer is greatly improved, and a single cell exhibits good performance and stability under high current density.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a method for preparing a gas diffusion layer for fuel cells. Background Technology

[0002] The gas diffusion layer is one of the key materials in fuel cells. It directly connects the bipolar plates and the catalyst layer, establishing a bridge between millimeter-scale mass transport in the gas flow channel and nanometer-scale mass transport in the catalyst. Its main functions include transporting the reaction medium and removing reaction products, as well as providing electrical and thermal conductivity and mechanical support. While ensuring good permeability and water management, the conductivity of the gas diffusion layer directly affects the performance of the fuel cell. A highly conductive gas diffusion layer can significantly reduce polarization, increase fuel cell output power, reduce heat generation, improve thermal management, optimize current distribution, and enhance fuel cell stability and durability.

[0003] The gas diffusion layer consists of a base layer and a microporous layer. The microporous layer is mainly composed of nanoscale conductive carbon black and hydrophobic materials. Nanoscale conductive carbon black is prone to agglomeration during dispersion, which affects the conductivity and stability of the gas diffusion layer. Furthermore, the use of conductive carbon black alone limits the performance of the gas diffusion layer at high current densities through a "point-to-point" conductive network.

[0004] To improve the performance and stability of fuel cells at high current densities, this invention effectively solves the agglomeration problem of nanoscale conductive carbon materials during dispersion by optimizing the conductive slurry dispersion process and leveraging the synergistic effect of the electrostatic repulsion of ionic surfactants and the steric hindrance of polymeric dispersants. It successfully constructs a microporous layer with a highly conductive "point-line-surface" network, significantly improving the conductivity of the gas diffusion layer to 3000 mA / cm² at RH 60%. 2 The battery has a single voltage of up to 0.54V, which is 11.57% higher than that of competing foreign products. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a gas diffusion layer for fuel cells. By solving the problem of agglomeration of nanoscale conductive carbon materials in the dispersion process of the microporous layer and successfully constructing a "point-line-surface" highly conductive network microporous layer, the performance and stability of fuel cells under high current density are effectively improved.

[0006] To achieve the above objectives, the present invention provides the following technical solutions.

[0007] This invention provides a method for preparing a gas diffusion layer for fuel cells, characterized in that: the gas diffusion layer consists of a substrate layer and a microporous layer, wherein the microporous layer is obtained by uniformly coating a conductive slurry onto the surface of the substrate layer and then sintering it.

[0008] The substrate layer refers to hydrophobic treated carbon paper, carbon cloth, nickel foam, copper foam, iron foam, aluminum foam, or nickel-iron foam.

[0009] The conductive slurry preparation process is as follows: a) Conductive carbon black, carbon nanotubes, and graphene are mixed in a certain mass ratio to obtain a homogeneous mixture; b) An ionic surfactant is added to a solvent and stirred thoroughly, followed by the addition of a polymeric dispersant at a mass ratio of 1:1 to 5:1, and the mixture is stirred and dispersed to obtain a homogeneous solution. The surfactant and dispersant have a mass fraction of 0.5% to 10% in the solution; c) The mixture is added to the solution and stirred for 10 to 30 minutes for pre-dispersion, with the mixture having a mass fraction of 5% to 40% in the slurry; d) The pre-dispersed slurry is ultrasonically dispersed to obtain a homogeneous slurry. The ultrasonic parameters are: power 50W to 500W, total effective ultrasonic time 10 to 120 minutes, and temperature controlled at 20 to 40℃; e) Finally, 5% to 60% hydrophobic emulsion is added to the homogeneous slurry and stirred thoroughly to obtain a conductive slurry, wherein the mass ratio of the hydrophobic substance to the mixture is 1:9 to 4:6.

[0010] The conductive carbon black is one or more of XC-72, XC-72R, Black Pearls 2000, EC-300J, EC-600JD, acetylene black, PRINTEX XE2-B, PRINTEX L6, Super P, and Super C65.

[0011] The mass ratio is 1000:1 to 100:10 for conductive carbon black to carbon nanotubes and 1:1 to 5:1 for carbon nanotubes to graphene.

[0012] The ionic surfactant is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, stearic acid, sodium dioctyl succinate sulfonate, benzalkonium chloride, hexadecyltrimethylammonium bromide, benzalkonium bromide, dodecyltrimethylammonium bromide, and dodecyl dimethyl betaine.

[0013] The polymeric dispersant is one or more of the following: sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, nitrocellulose, cellulose acetate, polyvinyl acetate, polyurethane, acrylic resin, epoxy resin, polyvinyl alcohol, polyamide, and polyvinylpyrrolidone.

[0014] The solvent is one or more of the following: deionized water, toluene, chloroform, perfluorohexane, methanol, ethanol, isopropanol, acetone, N-methylpyrrolidone, and glycerol.

[0015] The hydrophobic emulsion is one or more of the following: polytetrafluoroethylene (PTFE), fluorocarbon, perfluoropolyether (PFPE), polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), fluorinated mesophase pitch (FMP), siloxane polymers, and silane coupling agents.

[0016] The thickness of the microporous layer is 5~250μm.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention effectively solves the agglomeration problem of nanoscale conductive carbon materials during dispersion by optimizing the conductive slurry dispersion process and utilizing the synergistic effect of different dispersants. It successfully constructs a microporous layer with a highly conductive "point-line-surface" network, greatly improving the conductivity of the gas diffusion layer, reducing heat generation, and improving thermal management. Furthermore, it optimizes current distribution, enhancing the stability and durability of the fuel cell. At RH 60%, the single-cell voltage of the 3000mA / cm² battery reaches 0.54V, which is 11.57% higher than that of competing foreign products. Attached Figure Description

[0018] Figure 1 This is a comparison chart of the single-cell performance of the gas diffusion layer obtained in Example 1 under RH 60% conditions with that of a commercially available gas diffusion layer. Detailed Implementation

[0019] Example 1

[0020] A homogeneous mixture was obtained by stirring 0.9g of acetylene black, 0.05g of carbon nanotubes, and 0.05g of graphene. 0.1g of sodium dodecylbenzenesulfonate was added to 10g of deionized water and stirred thoroughly. Then, 0.1g of sodium carboxymethyl cellulose was added and stirred to disperse the mixture into a homogeneous solution. The mixture was added to the solution and stirred for 15 minutes for pre-dispersion. The pre-dispersed slurry was then ultrasonically dispersed to obtain a homogeneous slurry. The power was 200W, the total effective ultrasonic time was 60 minutes, and the temperature was controlled at 23~30℃. Finally, 0.71g of 60% PTFE emulsion was added to the homogeneous slurry and stirred thoroughly to obtain a conductive slurry. The conductive slurry was uniformly coated onto the surface of carbon paper using a slit coating method. After drying, it was treated in an oven at 350℃ for 30 minutes to obtain a gas diffusion layer with a microporous layer thickness of 10μm.

[0021] Example 2

[0022] A homogeneous mixture was obtained by stirring 1g XC-72, 0.08g carbon nanotubes, and 0.05g graphene. 0.2g stearic acid was added to 10g N-methylpyrrolidone and stirred thoroughly. Then, 0.1g polyvinylpyrrolidone was added and stirred to disperse the mixture into a homogeneous solution. The mixture was added to the solution and stirred for 10 minutes for pre-dispersion. The pre-dispersed slurry was then ultrasonically dispersed to obtain a homogeneous slurry. The power was 200W, the total effective ultrasonic time was 50 minutes, and the temperature was controlled at 25~30℃. Finally, 4.26g of 10% PTFE emulsion was added to the homogeneous slurry and stirred thoroughly to obtain a conductive slurry. The conductive slurry was uniformly coated onto the surface of carbon paper by spraying, dried, and then treated in an oven at 350℃ for 30 minutes to obtain a gas diffusion layer with a microporous layer thickness of 20μm.

Claims

1. A method for preparing a gas diffusion layer for a fuel cell, characterized in that: The gas diffusion layer consists of a base layer and a microporous layer. The microporous layer is obtained by uniformly coating a conductive paste onto the surface of the base layer and then sintering it.

2. The preparation method according to claim 1, characterized in that: The substrate layer refers to hydrophobic treated carbon paper, carbon cloth, nickel foam, copper foam, iron foam, aluminum foam, or nickel-iron foam.

3. The preparation method according to claim 1, characterized in that: The conductive slurry preparation process is as follows: a) Conductive carbon black, carbon nanotubes, and graphene are mixed in a certain mass ratio to obtain a homogeneous mixture; b) An ionic surfactant is added to a solvent and stirred thoroughly, then a polymeric dispersant is added, with a mass ratio of 1:1 to 5:1, and the mixture is stirred and dispersed to obtain a homogeneous solution, with the surfactant and dispersant having a mass fraction of 0.5% to 10% in the solution; c) The mixture is added to the solution and stirred for 10 to 30 minutes for pre-dispersion, with the mixture having a mass fraction of 5% to 40% in the slurry; d) The pre-dispersed slurry is ultrasonically dispersed to obtain a homogeneous slurry, with ultrasonic parameters of 50W to 500W power, a total effective ultrasonic time of 10 to 120 minutes, and a temperature controlled at 20 to 40℃; e) Finally, 5 to 60% hydrophobic emulsion is added to the homogeneous slurry and stirred thoroughly to obtain a conductive slurry, wherein the mass ratio of the hydrophobic substance to the mixture is 1:9 to 4:

6.

4. The preparation method according to claim 3, characterized in that: The conductive carbon black is one or more of XC-72, XC-72R, Black Pearls 2000, EC-300J, EC-600JD, acetylene black, PRINTEX XE2-B, PRINTEX L6, Super P, and Super C65.

5. The preparation method according to claim 3, characterized in that: The mass ratio is 1000:1 to 100:10 for conductive carbon black to carbon nanotubes and 1:1 to 5:1 for carbon nanotubes to graphene.

6. The preparation method according to claim 3, characterized in that: The ionic surfactant is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, stearic acid, sodium dioctyl succinate sulfonate, benzalkonium chloride, hexadecyltrimethylammonium bromide, benzalkonium bromide, dodecyltrimethylammonium bromide, and dodecyl dimethyl betaine.

7. The preparation method according to claim 3, characterized in that: The polymeric dispersant is one or more of the following: sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, nitrocellulose, cellulose acetate, polyvinyl acetate, polyurethane, acrylic resin, epoxy resin, polyvinyl alcohol, polyamide, and polyvinylpyrrolidone.

8. The preparation method according to claim 3, characterized in that: The solvent is one or more of the following: deionized water, toluene, chloroform, perfluorohexane, methanol, ethanol, isopropanol, acetone, N-methylpyrrolidone, and glycerol.

9. The preparation method according to claim 3, characterized in that: The hydrophobic emulsion is one or more of the following: polytetrafluoroethylene (PTFE), fluorocarbon, perfluoropolyether (PFPE), polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), fluorinated mesophase pitch (FMP), siloxane polymers, and silane coupling agents.

10. The preparation method according to claim 1, characterized in that: The thickness of the microporous layer is 5~250μm.

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