Micro-nano structure carbon fiber paper for gas diffusion layer, and preparation method and application thereof

Abstract

This invention discloses a micro / nano-structured carbon fiber paper for gas diffusion layers, its preparation method, and its application. The preparation method includes the following steps: S1, adding polyacrylonitrile powder and nano-boron compounds to an organic solvent, stirring until uniformly dissolved to form a spinning solution, and obtaining boron-containing polyacrylonitrile nanofibers by high-voltage electrospinning; S2, subjecting the boron-containing polyacrylonitrile nanofibers to pre-oxidation and opening / breaking treatments to obtain boron-containing pre-oxidized nanofiber short filaments; S3, mixing the boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant, and water uniformly, and then performing wet papermaking to obtain micro / nano-structured carbon fiber base paper; S4, impregnating the micro / nano-structured carbon fiber base paper with resin, hot-pressing curing, and heat treatment to obtain micro / nano-structured carbon fiber paper for gas diffusion layers. This invention can solve the problem of insufficient mechanical strength of carbon paper in the prior art, while improving the permeability, air permeability, and electrical conductivity of the gas diffusion layer in fuel cells.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and particularly relates to a micro-nano structured carbon fiber paper for gas diffusion layer, its preparation method and application. This micro-nano structured carbon fiber paper for gas diffusion layer is mainly used in the gas diffusion layer of fuel cells. Background Technology

[0002] Against the backdrop of low-carbon development and energy transition, the hydrogen energy industry has achieved a favorable development trend in my country. Hydrogen energy is an important carrier for building a diversified energy structure dominated by renewable energy in the future, and its development and utilization technologies have become an important direction for a new round of global energy technology revolution. Among them, hydrogen fuel cells are power generation devices that directly convert the chemical energy of hydrogen and oxygen into electrical energy, enabling the mobility, lightweighting, and large-scale popularization of hydrogen energy, and can be widely used in transportation, industry, construction, military and other fields.

[0003] The membrane electrode assembly (MEA) is the site of electrochemical reactions in a hydrogen fuel cell. The gas diffusion layer, as one of the core components of the MEA, primarily provides a transport channel for the reacting gases and generated water, and supports the catalyst. Its performance directly impacts the fuel cell's performance. Developing high-performance, low-cost, and domestically produced gas diffusion layers is a key factor in accelerating the industrialization of fuel cells.

[0004] Currently, domestic carbon fiber paper manufacturing technology cannot meet the requirements of gas diffusion layers in fuel cells. Chinese patent application CN201911066598.3 describes a process where porous carbon materials are mixed into mesophase pitch and thoroughly stirred and swollen to produce porous carbon-modified mesophase pitch. The nascent fiber membrane is then prepared using melt-spinning or electrospinning, followed by pre-oxidation, carbonization, and graphitization to prepare carbon paper. Chinese patent application CN202110774730.7 discloses a process for preparing thin carbon paper, using polyacrylonitrile or pitch as raw materials and functionalized ionic liquid as a dopant. The carbon paper substrate is spun using electrospinning technology, and then impregnated with a resin solution after solvation treatment, followed by hot-press curing, pre-oxidation, carbonization, and graphitization to prepare thin carbon paper. However, the carbon paper prepared by the above methods lacks mechanical strength, and its gas and water transport performance still needs further optimization. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a micro / nano structured carbon fiber paper for gas diffusion layers, its preparation method, and its application. This invention solves the problem of insufficient mechanical strength in existing carbon paper while improving the permeability, air permeability, and electrical conductivity of the gas diffusion layer in fuel cells. The micro / nano structured carbon fiber paper prepared by the present invention has a micro / nano composite structure, and the gas diffusion layer has low resistivity and high air permeability, which can effectively improve the electrochemical performance of fuel cells.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a method for preparing micro / nano-structured carbon fiber paper for a gas diffusion layer, comprising the following steps:

[0008] S1, add polyacrylonitrile powder and nano-boron to an organic solvent, stir until uniformly dissolved to form a spinning solution, and obtain boron-containing polyacrylonitrile nanofibers by high voltage electrospinning.

[0009] S2, the boron-containing polyacrylonitrile nanofibers are subjected to pre-oxidation treatment and opening and breaking treatment to obtain boron-containing pre-oxidized nanofiber short filaments;

[0010] S3, the boron-containing pre-oxidized nanofiber short filaments, short-cut carbon fibers, binder, dispersant and water are mixed evenly and then wet papermaking is carried out to obtain micro-nano structured carbon fiber base paper;

[0011] S4, the micro-nano structured carbon fiber base paper is impregnated with resin, hot-pressed and cured, and then heat-treated to obtain micro-nano structured carbon fiber paper for gas diffusion layer.

[0012] Preferably, in step S1:

[0013] The weight ratio of the polyacrylonitrile powder, nano-boron compound, and organic solvent is 100:(0.1-20):(500-3000); and / or

[0014] The nano-borides are selected from one or more of nano-boron nitride, nano-boron carbide, nano-zirconium boride, and nano-titanium boride; and / or

[0015] The organic solvent is selected from one of dimethylformamide, dimethyl sulfoxide, and dimethylacetamide; and / or

[0016] The stirring temperature is 30–90°C; and / or

[0017] The high-voltage electrospinning is one of the following: single-needle, multi-needle, and needleless.

[0018] Preferably, in step S1:

[0019] The weight ratio of the polyacrylonitrile powder, nano-boron compound, and organic solvent is 100:(0.5-10):(800-2000); and / or

[0020] The stirring temperature is 40–80°C.

[0021] Preferably, in step S2:

[0022] The pre-oxidation treatment is carried out in air at 180–300°C for 0.5–5 hours; and / or

[0023] The boron-containing pre-oxidized nanofiber filaments have a length of 0.5–12 cm and a diameter of 50–800 nm.

[0024] Preferably, in step S2:

[0025] In the pre-oxidation treatment, the treatment temperature is 200–280℃, and the treatment time is 1–4 hours; and / or

[0026] The boron-containing pre-oxidized nanofibers have a length of 2–8 cm and a diameter of 100–600 nm.

[0027] Preferably, in step S3:

[0028] The weight ratio of the boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant, and water is (0.1–5):(0.1–5):(0.1–4):(0.05–2):100; and / or

[0029] The chopped carbon fibers are selected from one or more of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, and viscose-based carbon fibers; and / or

[0030] The adhesive is selected from one or more of polyvinyl alcohol, epoxy resin, and carboxymethyl cellulose; and / or

[0031] The dispersant is selected from one of polyethylene oxide, polyacrylamide, and sodium polyacrylate; and / or

[0032] The thickness of the micro-nano structured carbon fiber base paper is 200–800 μm.

[0033] Preferably, in step S3:

[0034] The weight ratio of the boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant, and water is (0.2–3):(0.2–3):(0.2–2.5):(0.1–1.5):100; and / or

[0035] The thickness of the micro-nano structured carbon fiber base paper is 300–600 μm.

[0036] Preferably, in step S4:

[0037] The resin used for impregnation is selected from one or more of phenolic resin, epoxy resin, and furan resin; and / or

[0038] During the hot-press curing process, the hot-pressing temperature is 80–300℃, the pressure is 0.5–20 MPa, and the hot-pressing time is 1–30 min; and / or

[0039] The heat treatment process is carried out under a nitrogen atmosphere, at a temperature of 600–2500℃, and for a time of 0.5–4 hours; and / or

[0040] The thickness of the micro-nano structured carbon fiber paper used for the gas diffusion layer is 100–400 μm.

[0041] Preferably, in step S4:

[0042] During the hot-press curing process, the hot-pressing temperature is 100–240℃, the pressure is 1–10 MPa, and the hot-pressing time is 2–15 min; and / or

[0043] During the heat treatment process, the heat treatment temperature is 800–2000℃, and the heat treatment time is 1–3 hours; and / or

[0044] The thickness of the micro-nano structured carbon fiber paper used for the gas diffusion layer is 140–280 μm.

[0045] A second aspect of the present invention provides a micro / nano-structured carbon fiber paper for a gas diffusion layer prepared by the method for preparing micro / nano-structured carbon fiber paper for a gas diffusion layer according to the first aspect of the present invention.

[0046] Preferably, the gas diffusion layer uses micro / nano-structured carbon fiber paper with a vertical air permeability ≥2200 mL·mm / (cm). 2 ·h·mmAq), vertical resistivity ≤55mΩ·cm, parallel resistivity ≤4.0mΩ·cm, tensile strength ≥50MPa, flexural modulus ≥12GPa.

[0047] A third aspect of the present invention provides an application of micro / nano-structured carbon fiber paper for gas diffusion layers, prepared by the method for preparing micro / nano-structured carbon fiber paper for gas diffusion layers according to the first aspect of the present invention, in the gas diffusion layer of a flow battery.

[0048] The micro / nano structured carbon fiber paper for gas diffusion layers, its preparation method, and its applications provided by this invention have the following advantages:

[0049] Beneficial effects:

[0050] 1. The micro-nano structured carbon fiber paper prepared by this invention has both nano-scale carbon fibers and micron-scale carbon fibers, forming a micro-nano gradient pore structure, which effectively improves the permeability, air permeability and electrical conductivity of the gas diffusion layer while maintaining a certain mechanical strength.

[0051] 2. This invention adds nano-borides to the spinning solution to uniformly disperse boron in boron-containing polyacrylonitrile fibers, thereby enhancing the catalytic graphitization effect of boron, lowering the graphitization temperature, and increasing the degree of graphitization. This allows the carbonization and graphitization of boron-containing pre-oxidized nanofiber short filaments to be completed simultaneously at a lower heat treatment temperature of the carbon fiber base paper, greatly saving energy consumption costs. Attached Figure Description

[0052] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0053] Figure 1 This is a schematic flowchart of the preparation method of the micro / nano structured carbon fiber paper for the gas diffusion layer of the present invention. Detailed Implementation

[0054] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with embodiments.

[0055] Combination Figure 1 As shown, a method for preparing a micro / nano structured carbon fiber paper for a gas diffusion layer according to the present invention includes the following steps:

[0056] S1, add polyacrylonitrile powder and nano-boron to an organic solvent, stir until uniformly dissolved to form a spinning solution, and obtain boron-containing polyacrylonitrile nanofibers by high voltage electrospinning.

[0057] Specifically, polyacrylonitrile powder, nano-boron compounds, and organic solvent are mixed in a weight ratio of 100:(0.1-20):(500-3000). The polyacrylonitrile powder and nano-boron compounds are added to the organic solvent and stirred at 30-90°C until uniformly dissolved to form a spinning solution. Boron-containing polyacrylonitrile nanofibers are then prepared by high-voltage electrospinning. In a specific embodiment, the weight ratio of polyacrylonitrile powder to nano-boron compounds and organic solvent is 100:(0.5-10):(800-2000); in a further preferred embodiment, the weight ratio of polyacrylonitrile powder to nano-boron compounds and organic solvent is 100:(2-5):(900-1600). The nano-borides are selected from one or more of nano-boron nitride, nano-boron carbide, nano-zirconium boride, and nano-titanium boride; the organic solvent is selected from one of dimethylformamide, dimethyl sulfoxide, and dimethylacetamide; the stirring temperature is 40–80℃; and the high-voltage electrospinning is one of single-needle, multi-needle, and needleless.

[0058] S2, Boron-containing polyacrylonitrile nanofibers are pre-oxidized and opened and broken to obtain boron-containing pre-oxidized nanofiber short filaments;

[0059] Specifically, the boron-containing polyacrylonitrile nanofibers obtained in step S1 are pre-oxidized in air at 180–300°C for 0.5–5 hours, followed by a loosening and breaking process to obtain boron-containing pre-oxidized nanofiber short filaments with a length of 3–12 cm and a diameter of 50–800 nm. In a specific embodiment, the pre-oxidation process is carried out at a temperature of 200–280°C for 1–4 hours; the resulting boron-containing pre-oxidized nanofiber short filaments have a length of 5–9 cm and a diameter of 100–600 nm.

[0060] S3, after uniformly mixing boron-containing pre-oxidized nanofiber short filaments, short-cut carbon fibers, binder, dispersant and water, wet papermaking is carried out to obtain micro-nano structured carbon fiber base paper;

[0061] Specifically, the boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant, and water obtained in step S2 are mixed evenly in a weight ratio of (0.1–5):(0.1–5):(0.1–4):(0.05–2):100, and then wet-processed to form a micro / nano-structured carbon fiber base paper with a thickness of 200–800 μm. The chopped carbon fibers are selected from one or more of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, and viscose-based carbon fibers; the binder is selected from one or more of polyvinyl alcohol, epoxy resin, and carboxymethyl cellulose; and the dispersant is selected from one of polyethylene oxide, polyacrylamide, and sodium polyacrylate. In a specific embodiment, the weight ratio of boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant, and water is (0.2–3):(0.2–3):(0.2–2.5):(0.1–1.5):100; in a further preferred embodiment, the weight ratio of boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant, and water is (2–2.8):(1–2.8):(0.3–0.6):(0.2–0.3):100. The thickness of the micro / nanostructured carbon fiber base paper is 300–600 μm.

[0062] S4, micro-nano structured carbon fiber paper for gas diffusion layer is obtained by impregnating micro-nano structured carbon fiber base paper with resin, hot pressing and curing, and heat treatment.

[0063] Specifically, the micro / nano-structured carbon fiber base paper obtained in step S3 is impregnated with resin, hot-pressed and cured at 80–300℃ and 0.5–20MPa for 1–30 min, and then heat-treated under a nitrogen atmosphere at 600–2500℃ for 0.5–4 h to obtain a micro / nano-structured carbon fiber paper for a gas diffusion layer with a thickness of 100–400 μm. The resin used for impregnation is selected from one or more of phenolic resin, epoxy resin, and furan resin. In a specific embodiment, during the hot-press curing process, the hot-pressing temperature is 100–240°C, the pressure is 1–10 MPa, and the hot-pressing time is 2–15 min; during the heat treatment process, the heat treatment temperature is 800–2000°C, and the heat treatment time is 1–3 h. In a further preferred embodiment, during the hot-press curing process, the hot-pressing temperature is 130–190°C, the pressure is 1.5–5 MPa, and the hot-pressing time is 4–10 min; during the heat treatment process, the heat treatment temperature is 1200–1700°C, and the heat treatment time is 1.5–2 h. The thickness of the micro / nano-structured carbon fiber paper used for the gas diffusion layer is 140–280 μm.

[0064] This invention also provides a micro / nano-structured carbon fiber paper for gas diffusion layers prepared according to the above-described method. The vertical air permeability of this micro / nano-structured carbon fiber paper for gas diffusion layers is ≥2200 mL·mm / (cm²). 2 ·h·mmAq), vertical resistivity ≤55mΩ·cm, parallel resistivity ≤4.0mΩ·cm, tensile strength ≥50MPa, flexural modulus ≥12GPa.

[0065] The present invention also provides an application of the above-mentioned micro-nano structured carbon fiber paper for gas diffusion layer in fuel cell gas diffusion layer.

[0066] The following section provides a further introduction to the micro / nano structured carbon fiber paper for the gas diffusion layer of the present invention, its preparation method, and its application, using specific examples.

[0067] Example 1

[0068] The method for preparing a micro / nano structured carbon fiber paper for a gas diffusion layer according to this embodiment includes the following steps:

[0069] (1) Weigh 10g of polyacrylonitrile powder and 0.2g of boron carbide nanoparticles, add them to 100g of dimethylformamide, stir at 50°C until uniformly dissolved to form a spinning solution, and prepare boron-containing polyacrylonitrile nanofibers by using a single-needle electrospinning device.

[0070] (2) The boron-containing polyacrylonitrile nanofibers obtained in step (1) are pre-oxidized in air at 220°C for 1.5 hours, and then opened and broken to obtain boron-containing pre-oxidized nanofiber short filaments with a length of 3 mm and a diameter of 200 nm.

[0071] (3) Weigh 2g of boron-containing pre-oxidized nanofiber short filaments, 2g of polyacrylonitrile-based short carbon fibers, 0.5g of polyvinyl alcohol, 0.2g of polyethylene oxide and 100g of water obtained in step (2), mix them evenly and then perform wet papermaking to obtain a micro-nano structure carbon fiber base paper with a thickness of 342μm.

[0072] (4) The micro-nano structured carbon fiber paper obtained in step (3) is impregnated in phenolic resin, then hot-pressed and cured at 180°C and 2MPa for 5 min, and finally heat-treated at 1500°C under nitrogen atmosphere for 2 h to obtain a micro-nano structured carbon fiber paper for fuel cell gas diffusion layer with a thickness of 190 μm.

[0073] The micro / nano structured carbon fiber paper prepared above has a vertical air permeability of 2300 mL·mm / (cm). 2 The resistivity is 50 mΩ·cm in the vertical direction and 3.8 mΩ·cm in the parallel direction. The thermal conductivity is 2.3 W / (m·K) in the vertical direction and 25 W / (m·K) in the parallel direction. The tensile strength is 55 MPa and the flexural modulus is 12 GPa, which is significantly better than commercial carbon paper.

[0074] Example 2

[0075] The method for preparing a micro / nano structured carbon fiber paper for a gas diffusion layer according to this embodiment includes the following steps:

[0076] (1) Weigh 10g of polyacrylonitrile powder and 0.3g of nano boron nitride, add them to 120g of dimethylacetamide, stir at 60℃ until uniformly dissolved to form a spinning solution, and prepare boron-containing polyacrylonitrile nanofibers by using a multi-needle electrospinning device.

[0077] (2) The boron-containing polyacrylonitrile nanofibers obtained in step (1) are pre-oxidized in air at 230°C for 1 hour, and then opened and broken to obtain boron-containing pre-oxidized nanofiber short filaments with a length of 4 mm and a diameter of 300 nm.

[0078] (3) Weigh 2g of boron-containing pre-oxidized nanofiber short filaments, 1.5g of polyacrylonitrile-based short chopped carbon fibers, 0.5g of pitch-based short chopped carbon fibers, 0.6g of carboxymethyl cellulose, 0.3g of polyacrylamide and 100g of water obtained in step (2), mix them evenly and then perform wet papermaking to obtain a micro-nano structure carbon fiber base paper with a thickness of 390μm.

[0079] (4) The micro-nano structured carbon fiber paper obtained in step (3) is impregnated in phenolic resin, then hot-pressed and cured at 150℃ and 3MPa for 7 min, and finally heat-treated at 1300℃ in a nitrogen atmosphere for 1.5 h to obtain a micro-nano structured carbon fiber paper for fuel cell gas diffusion layer with a thickness of 228 μm.

[0080] The micro / nano structured carbon fiber paper prepared above has a vertical air permeability of 2250 mL·mm / (cm). 2 The resistivity is 45 mΩ·cm in the vertical direction and 3.2 mΩ·cm in the parallel direction. The thermal conductivity is 2.4 W / (m·K) in the vertical direction and 27 W / (m·K) in the parallel direction. The tensile strength is 58 MPa and the flexural modulus is 13 GPa, which are significantly better than commercial carbon paper.

[0081] Example 3

[0082] The method for preparing a micro / nano structured carbon fiber paper for a gas diffusion layer according to this embodiment includes the following steps:

[0083] (1) Weigh 10g of polyacrylonitrile powder and 0.35g of nano-zirconium boride, add them to 150g of dimethyl sulfoxide, stir at 55°C until uniformly dissolved to form a spinning solution, and prepare boron-containing polyacrylonitrile nanofibers by needleless electrospinning device.

[0084] (2) The boron-containing polyacrylonitrile nanofibers obtained in step (1) are pre-oxidized in air at 210°C for 2 hours, and then opened and broken to obtain boron-containing pre-oxidized nanofiber short filaments with a length of 6 mm and a diameter of 400 nm.

[0085] (3) Weigh 2g of boron-containing pre-oxidized nanofiber short filaments, 2.5g of polyacrylonitrile-based short chopped carbon fibers, 0.3g of pitch-based short chopped carbon fibers, 0.5g of epoxy resin, 0.25g of sodium polyacrylate and 100g of water obtained in step (2), mix them evenly and then perform wet papermaking to obtain a micro-nano structure carbon fiber base paper with a thickness of 510μm.

[0086] (4) The micro-nano structured carbon fiber paper obtained in step (3) is impregnated in phenolic resin, then hot-pressed and cured at 130℃ and 5MPa for 4 min, and finally heat-treated at 1700℃ in a nitrogen atmosphere for 1 h to obtain a micro-nano structured carbon fiber paper for fuel cell gas diffusion layer with a thickness of 256μm.

[0087] The micro / nano structured carbon fiber paper prepared above has a vertical air permeability of 2350 mL·mm / (cm). 2The resistivity is 52 mΩ·cm in the vertical direction and 3.9 mΩ·cm in the parallel direction. The thermal conductivity is 2.1 W / (m·K) in the vertical direction and 25 W / (m·K) in the parallel direction. The tensile strength is 60 MPa and the flexural modulus is 12 GPa, which is significantly better than commercial carbon paper.

[0088] Example 4

[0089] The method for preparing a micro / nano structured carbon fiber paper for a gas diffusion layer according to this embodiment includes the following steps:

[0090] (1) Weigh 10g of polyacrylonitrile powder and 0.2g of nano-boron titanium, add them to 160g of dimethylformamide, stir at 60℃ until uniformly dissolved to form a spinning solution, and prepare boron-containing polyacrylonitrile nanofibers by needleless electrospinning device.

[0091] (2) The boron-containing polyacrylonitrile nanofibers obtained in step (1) are pre-oxidized in air at 230°C for 1.5 hours, and then opened and broken to obtain boron-containing pre-oxidized nanofiber short filaments with a length of 6 mm and a diameter of 150 nm.

[0092] (3) Weigh 2g of boron-containing pre-oxidized nanofiber short filaments, 1.5g of polyacrylonitrile-based short chopped carbon fibers, 0.2g of viscose-based short chopped carbon fibers, 0.3g of polyvinyl alcohol, 0.3g of sodium polyacrylate and 100g of water obtained in step (2), mix them evenly and then perform wet papermaking to obtain a micro-nano structure carbon fiber base paper with a thickness of 485μm.

[0093] (4) The micro-nano structure carbon fiber paper obtained in step (3) is impregnated in phenolic resin, then hot-pressed and cured at 190℃ and 1.5MPa for 8 minutes, and finally heat-treated at 1200℃ in a nitrogen atmosphere for 2 hours to obtain a micro-nano structure carbon fiber paper for fuel cell gas diffusion layer with a thickness of 268μm.

[0094] The micro / nano structured carbon fiber paper prepared above has a vertical air permeability of 2300 mL·mm / (cm). 2 The resistivity is 49 mΩ·cm in the vertical direction and 3.6 mΩ·cm in the parallel direction. The thermal conductivity is 2.2 W / (m·K) in the vertical direction and 25 W / (m·K) in the parallel direction. The tensile strength is 53 MPa and the flexural modulus is 13 GPa, which are significantly better than commercial carbon paper.

[0095] Example 5

[0096] The method for preparing a micro / nano structured carbon fiber paper for a gas diffusion layer according to this embodiment includes the following steps:

[0097] (1) Weigh 10g of polyacrylonitrile powder and 0.5g of boron carbide nanoparticles, add them to 90g of dimethylformamide, stir at 60℃ until uniformly dissolved to form a spinning solution, and prepare boron-containing polyacrylonitrile nanofibers by a single needle electrospinning device.

[0098] (2) The boron-containing polyacrylonitrile nanofibers obtained in step (1) are pre-oxidized in air at 215°C for 2 hours, and then opened and broken to obtain boron-containing pre-oxidized nanofiber short filaments with a length of 4 mm and a diameter of 450 nm.

[0099] (3) Weigh 2.8g of boron-containing pre-oxidized nanofiber short filaments, 1g of polyacrylonitrile-based short carbon fiber, 0.4g of polyvinyl alcohol, 0.25g of polyacrylamide and 100g of water obtained in step (2), mix them evenly and then perform wet papermaking to obtain a micro-nano structure carbon fiber base paper with a thickness of 420μm.

[0100] (4) The micro-nano structured carbon fiber paper obtained in step (3) is impregnated in phenolic resin, then hot-pressed and cured at 175℃ and 2MPa for 10 min, and finally heat-treated at 1400℃ in a nitrogen atmosphere for 2.5 h to obtain a micro-nano structured carbon fiber paper for fuel cell gas diffusion layer with a thickness of 213 μm.

[0101] The micro / nano structured carbon fiber paper prepared above has a vertical air permeability of 2500 mL·mm / (cm). 2 The resistivity is 45 mΩ·cm in the vertical direction and 3.2 mΩ·cm in the parallel direction. The thermal conductivity is 2.3 W / (m·K) in the vertical direction and 24 W / (m·K) in the parallel direction. The tensile strength is 50 MPa and the flexural modulus is 12 GPa, which is significantly better than commercial carbon paper.

[0102] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing micro / nano-structured carbon fiber paper for a gas diffusion layer, characterized in that, Includes the following steps: S1, polyacrylonitrile powder and nano-boron compounds are added to an organic solvent and stirred until uniformly dissolved to form a spinning solution. Boron-containing polyacrylonitrile nanofibers are then obtained by high-voltage electrospinning. The weight ratio of the polyacrylonitrile powder, nano-boron compound, and organic solvent is 100:(0.1-20):(500-3000). The nano-borides are selected from one or more of nano-boron nitride, nano-boron carbide, nano-zirconium boride, and nano-titanium boride; The organic solvent is selected from one of dimethylformamide, dimethyl sulfoxide, and dimethylacetamide; The stirring temperature is 30–90°C; The high-voltage electrospinning is one of single-needle, multi-needle, and needleless types; S2, the boron-containing polyacrylonitrile nanofibers are subjected to pre-oxidation treatment and opening and breaking treatment to obtain boron-containing pre-oxidized nanofiber short filaments. The pre-oxidation treatment is carried out in an air atmosphere at 180–300°C for 0.5–5 hours. The boron-containing pre-oxidized nanofiber short filaments have a length of 0.5–12 cm and a diameter of 50–800 nm; S3, the boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant and water are mixed evenly and then wet-processed to form paper, thereby obtaining micro-nano structured carbon fiber base paper. The weight ratio of the boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant and water is (0.1-5):(0.1-5):(0.1-4):(0.05-2):100; The chopped carbon fibers are selected from one or more of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, and viscose-based carbon fibers; The adhesive is selected from one or more of polyvinyl alcohol, epoxy resin and carboxymethyl cellulose; The dispersant is selected from one of polyethylene oxide, polyacrylamide, and sodium polyacrylate; The thickness of the micro / nano structured carbon fiber base paper is 200–800 μm; S4, the micro / nano-structured carbon fiber base paper is impregnated with resin, hot-pressed and cured, and then heat-treated to obtain a micro / nano-structured carbon fiber paper for gas diffusion layer. The resin used for impregnation is selected from one or more of phenolic resin, epoxy resin, and furan resin; During the hot-press curing process, the hot-pressing temperature is 80–300℃, the pressure is 0.5–20MPa, and the hot-pressing time is 1–30min. The heat treatment process is carried out under a nitrogen atmosphere, with a heat treatment temperature of 600–2500℃ and a heat treatment time of 0.5–4 hours. The thickness of the micro / nano structured carbon fiber paper used for the gas diffusion layer is 100–400 μm. The gas diffusion layer uses micro / nano-structured carbon fiber paper with a vertical air permeability ≥2200 mL∙mm / (cm). 2 (H·mmAq), vertical resistivity ≤55mΩ·cm, parallel resistivity ≤4.0 mΩ·cm, tensile strength ≥50 MPa, flexural modulus ≥12GPa.

2. The method for preparing micro / nano-structured carbon fiber paper for gas diffusion layer according to claim 1, characterized in that, In step S1: The weight ratio of the polyacrylonitrile powder, nano-boron compound, and organic solvent is 100:(0.5-10):(800-2000); and / or The stirring temperature is 40–80°C.

3. The method for preparing micro / nano-structured carbon fiber paper for gas diffusion layer according to claim 1, characterized in that, In step S2: In the pre-oxidation treatment, the treatment temperature is 200–280℃, and the treatment time is 1–4 hours; and / or The boron-containing pre-oxidized nanofibers have a length of 2–8 cm and a diameter of 100–600 nm.

4. The method for preparing micro / nano-structured carbon fiber paper for gas diffusion layer according to claim 1, characterized in that, In step S3: The weight ratio of the boron-containing pre-oxidized nanofiber short filaments, chopped carbon fibers, binder, dispersant, and water is (0.2–3):(0.2–3):(0.2–2.5):(0.1–1.5):100; and / or The thickness of the micro-nano structured carbon fiber base paper is 300–600 μm.

5. The method for preparing micro / nano-structured carbon fiber paper for gas diffusion layer according to claim 1, characterized in that, In step S4: During the hot-press curing process, the hot-pressing temperature is 100–240℃, the pressure is 1–10 MPa, and the hot-pressing time is 2–15 min; and / or During the heat treatment process, the heat treatment temperature is 800–2000℃, and the heat treatment time is 1–3 hours; and / or The thickness of the micro-nano structured carbon fiber paper used for the gas diffusion layer is 140–280 μm.

6. A micro / nano-structured carbon fiber paper for gas diffusion layer prepared by the method of preparing micro / nano-structured carbon fiber paper for gas diffusion layer according to any one of claims 1 to 5. The gas diffusion layer uses micro / nano-structured carbon fiber paper with a vertical air permeability ≥2200 mL∙mm / (cm). 2 (H·mmAq), vertical resistivity ≤55mΩ·cm, parallel resistivity ≤4.0 mΩ·cm, tensile strength ≥50 MPa, flexural modulus ≥12GPa.

7. The application of a micro / nano-structured carbon fiber paper for gas diffusion layer prepared by the method of preparing micro / nano-structured carbon fiber paper for gas diffusion layer according to any one of claims 1 to 5 in the gas diffusion layer of a flow battery.

Images