A gas diffusion layer and a preparation method thereof and a fuel cell

Abstract

The present invention relates to the technical field of fuel cell gas diffusion layer, and in particular, to a gas diffusion layer and a preparation method thereof and a fuel cell. A carbon fiber two-dimensional matrix material is impregnated with a reinforcing resin and then coated with a release film. A first microporous layer slurry containing resin, graphite, acetylene black and an organic solvent is applied to another release film and dried, and then the two are bonded, hot pressed and cured, and then carbonized and graphitized to obtain a composite material layer including a matrix layer and a first microporous layer; the composite material layer is impregnated in a first hydrophobic agent and then dried, and then a second microporous layer slurry containing conductive carbon black, a dispersant, a second hydrophobic agent and water is applied to the surface of the first microporous layer, and then sintered to form a second microporous layer to obtain a gas diffusion layer. This method can reduce the surface roughness of the gas diffusion layer, reduce the amount of resin impregnation, increase the mass transfer channel inside the material, reduce the brittleness of the gas diffusion layer, improve the strength of the gas diffusion layer, reduce energy consumption and production costs, and the second microporous layer is not easy to fall off.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell gas diffusion layers, and in particular to a gas diffusion layer and a preparation method thereof, and a fuel cell. Background Art

[0002] The gas diffusion layer (GDL) is an important component of the membrane electrode of the proton exchange membrane fuel cell assembly. It is usually composed of a porous material with good conductivity and has an anisotropic porous microstructure. It performs multiple functions such as transporting gas, conducting electricity, supporting the catalytic layer, and improving water and heat management. It is one of the key components that affect the electrochemical performance of fuel cells.

[0003] The preparation process of the gas diffusion layer in the prior art is: impregnation, hot pressing and curing, carbonization and graphitization, hydrophobic agent impregnation, sintering, microporous layer coating, and sintering.

[0004] However, the above process has the following disadvantages: (1) One side of the microporous layer of the gas diffusion layer is rough, about 10 μm; (2) The amount of resin applied is large, which is not conducive to mass transfer (the greater the amount of impregnated resin, the more serious the blockage of the mass transfer channel inside the material); (3) The gas diffusion layer is brittle, which is not conducive to subsequent processing; (4) After the hydrophobic agent is impregnated, the material needs to be sintered at high temperature, which consumes a lot of energy and has high production costs; (5) The adhesion between the obtained microporous layer and the substrate layer is poor, and the microporous layer is easy to fall off.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first purpose of the present invention is to provide a method for preparing a gas diffusion layer. By forming a first microporous precursor layer, the surface roughness of the gas diffusion layer can be reduced, the resin impregnation amount can be reduced, the internal mass transfer channel of the material can be increased, the brittleness of the gas diffusion layer can be reduced, the strength of the gas diffusion layer can be improved, the energy consumption and production costs can be reduced, and the second microporous layer is not prone to powder falling problems.

[0007] The second object of the present invention is to provide a gas diffusion layer having the advantages of low surface roughness, high mass transfer efficiency, good flexibility, high strength, the second microporous layer is not easy to fall off powder and low production cost.

[0008] A third object of the present invention is to provide a fuel cell.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0010] The present invention first provides a method for preparing a gas diffusion layer, comprising the following steps:

[0011] (a) The carbon fiber two-dimensional matrix material is impregnated with a reinforcing resin to form a matrix material layer, and a first release film is covered on one surface of the matrix material layer to obtain a first composite layer;

[0012] (b) coating the first microporous layer slurry containing resin, graphite, acetylene black and organic solvent onto the second release film and drying the slurry to obtain a second composite layer having the first microporous precursor layer;

[0013] (c) laminating the base material layer of the first composite layer and the first microporous precursor layer of the second composite layer, performing heat pressing and curing, and then peeling off the first release film and the second release film, performing carbonization and graphitization, to obtain a composite material layer including the base layer and the first microporous layer;

[0014] (d) immersing the composite material layer in a first hydrophobic agent and drying it, then coating a second microporous layer slurry containing conductive carbon black, a dispersant, a second hydrophobic agent and water on the surface of the first microporous layer, and then sintering to form a second microporous layer, thereby obtaining the gas diffusion layer;

[0015] The gas diffusion layer includes a base layer, a first microporous layer and a second microporous layer which are stacked in sequence.

[0016] Furthermore, in step (a), the preparation method of the carbon fiber two-dimensional matrix material comprises: using wet molding technology, mixing and dispersing chopped carbon fibers, a dispersant and water, dehydrating and molding, and then drying to obtain the carbon fiber two-dimensional matrix material; wherein the dispersant comprises at least one of hydroxypropyl cellulose, hydroxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose and ethyl cellulose; the mass ratio of the chopped carbon fibers, the dispersant and the water is 2~5:1~5:1000; the average length of the chopped carbon fibers is 3~12mm; the dispersing method comprises: dispersing at a rotation speed of 1200~3000r / min for 5~15min.

[0017] Further, in step (a), the reinforcing resin is a phenolic resin. Or the reinforcing resin is an epoxy resin. Or the reinforcing resin is a mixed material of a phenolic resin and an epoxy resin. Or the reinforcing resin is a mixed material of a phenolic resin and asphalt. Or the reinforcing resin is a mixed material of an epoxy resin and asphalt. Or the reinforcing resin is a mixed material of a phenolic resin, an epoxy resin and asphalt.

[0018] Furthermore, in step (a), the mass ratio of the carbon fiber two-dimensional matrix material to the resin in the reinforced resin is 1:0.5-1.7.

[0019] Furthermore, in step (b), the resin includes phenolic resin and / or epoxy resin.

[0020] Furthermore, in step (b), in the first microporous layer slurry, the mass ratio of the resin, the graphite, the acetylene black and the organic solvent is 10:0.5~2:1~2:1~2.

[0021] Furthermore, in step (b), the organic solvent includes an alcohol solvent.

[0022] Furthermore, in step (b), the preparation method of the first microporous layer slurry includes: mixing resin, graphite, acetylene black and an organic solvent, and the mixing method includes: stirring at a rotation speed of 800-1500 r / min for 15-30 min.

[0023] Furthermore, in step (b), the coating method includes at least one of a blade coating method and a slit coating method.

[0024] Furthermore, in step (b), the drying temperature is 120-150°C.

[0025] Furthermore, in step (b), the thickness of the first microporous precursor layer is 5-20 μm.

[0026] Furthermore, in step (c), the temperature of the hot pressing is 150-200°C.

[0027] Furthermore, in step (c), the hot pressing pressure is 0.1-0.5 MPa.

[0028] Furthermore, in step (c), the hot pressing time is 1 to 5 minutes.

[0029] Furthermore, in step (c), the temperature of carbonization and graphitization is 1000-2300°C.

[0030] Furthermore, in step (c), the carbonization and graphitization time is 30 to 120 minutes.

[0031] Furthermore, in step (d), the first hydrophobic agent includes at least one of PTFE, PVDF and FEP.

[0032] Furthermore, in step (d), the immersion time is 30 to 300 seconds.

[0033] Furthermore, in step (d), the drying method comprises: drying at 100-120° C. for 3-5 min.

[0034] Furthermore, in step (d), the dispersant includes at least one of hydroxypropyl cellulose, hydroxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose and ethyl cellulose.

[0035] Furthermore, in step (d), the second hydrophobic agent comprises polytetrafluoroethylene.

[0036] Furthermore, in step (d), the mass ratio of the dispersant, the second hydrophobic agent, the conductive carbon black and the water is 1.5-3:5-10:15-25:100.

[0037] Furthermore, in step (d), the coating method includes at least one of blade coating, extrusion and spray coating.

[0038] Furthermore, in step (d), the thickness of the second microporous layer is 20-50 μm.

[0039] Furthermore, in step (d), the sintering temperature is 350-400° C., and the sintering time is 30-60 min.

[0040] The present invention further provides a gas diffusion layer, which is prepared by the above preparation method, and comprises a substrate layer, a first microporous layer and a second microporous layer which are stacked in sequence.

[0041] Furthermore, the thickness of the base layer is 95-140 μm.

[0042] Furthermore, the thickness of the first microporous layer is 5-20 μm.

[0043] Furthermore, the thickness of the second microporous layer is 20-50 μm.

[0044] The present invention also provides a fuel cell, comprising the gas diffusion layer prepared by the preparation method of the gas diffusion layer or the gas diffusion layer.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The method for preparing a gas diffusion layer provided by the present invention forms a first microporous precursor layer and composites it with a base material layer by using a release film, thereby reducing the surface roughness of the gas diffusion layer, increasing the internal mass transfer channel of the gas diffusion layer, reducing the brittleness of the gas diffusion layer, ensuring the strength of the gas diffusion layer, and the second microporous layer prepared is not easy to fall off, and the energy consumption and production cost are significantly reduced.

[0047] (2) The method for preparing the gas diffusion layer provided by the present invention can effectively composite the first microporous layer with the reinforced two-dimensional matrix material by controlling the temperature, time and pressure of hot pressing, while making the surface roughness of the first microporous layer lower and the composite structure more stable.

[0048] (3) The gas diffusion layer provided by the present invention, wherein the substrate layer mainly serves to increase the structural stability of the gas diffusion layer, the first microporous layer mainly serves to improve the mechanical strength, reduce the surface roughness, enhance the bonding force between the second microporous layer and the substrate material layer, and increase the hydrophobic gradient, and the second microporous layer mainly serves to increase the contact area with the catalyst layer, reduce the interface resistance, improve the efficiency of the catalytic reaction, provide a more uniform water vapor transmission channel, and increase the hydrophobic gradient again. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 A schematic diagram of the structure of the gas diffusion layer provided by the present invention;

[0051] Figure 2 This is a SEM image of one side of the substrate layer of the gas diffusion layer prepared in Example 1 provided by the present invention;

[0052] Figure 3 This is a SEM image of one side of the second microporous layer of the gas diffusion layer prepared in Example 1 provided by the present invention;

[0053] Figure 4 This is a picture of the peeling coating falling off of the second microporous layer in the gas diffusion layer prepared in Example 1 of the present invention after being adhered with 3M600 peeling tape;

[0054] Figure 5 This is a picture of the peeling coating falling off of the second microporous layer in the gas diffusion layer made by directly impregnating the reinforced two-dimensional matrix material with phenolic resin - hot pressing curing - carbonization and graphitization - hydrophobic sintering - coating the microporous layer - sintering process after being pasted with 3M600 peeling tape. DETAILED DESCRIPTION

[0055] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If the specific conditions are not indicated in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0056] If there is no special explanation, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0057] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0058] If there is no special explanation, in the present invention, "one or more" or "at least one" refers to any one, any two or more of the listed items. Among them, "several" refers to any two or more of the listed items.

[0059] In a first aspect, the present invention provides a method for preparing a gas diffusion layer for a fuel cell having a multilayer structure, comprising the following steps:

[0060] (a) A carbon fiber two-dimensional matrix material is impregnated with a reinforcing resin to form a matrix material layer (the matrix material layer is a carbon fiber two-dimensional matrix material impregnated with a reinforcing resin), and a first release film is covered on one surface of the matrix material layer to obtain a first composite layer. That is, the first composite layer includes a matrix material layer and a first release film layer. The matrix material layer is carbonized and graphitized to form a matrix layer. Among them, the reinforcing resin is used to increase the strength of the matrix material.

[0061] (b) coating the first microporous layer slurry containing resin, graphite, acetylene black and organic solvent onto the second release film and drying the slurry to obtain a second composite layer having a first microporous precursor layer. That is, the second composite layer includes the first microporous precursor layer and the second release film layer. The first microporous precursor layer is carbonized and graphitized to form the first microporous layer.

[0062] (c) laminating the base material layer of the first composite layer and the first microporous precursor layer of the second composite layer, and performing heat pressing and curing, and then peeling off the first release film and the second release film respectively, and then performing carbonization and graphitization to obtain a composite material layer including a base layer and a first microporous layer.

[0063] The present invention covers the first release film and the second release film in step (a) and step (b) respectively, so as to facilitate the composite of the base material layer and the first microporous precursor layer, and the first release film and the second release film can be easily peeled off after the composite.

[0064] (d) The composite material layer including the substrate layer and the first microporous layer is immersed in the first hydrophobic agent, so that the first hydrophobic agent penetrates into the substrate layer and the first microporous layer, and then dried to obtain the treated composite material layer. Then, a second microporous layer slurry containing conductive carbon black, a dispersant, a second hydrophobic agent and water is coated on the surface of the first microporous layer in the treated composite material layer, and then sintered to form a second microporous layer, that is, the gas diffusion layer including the substrate layer, the first microporous layer and the second microporous layer is obtained. Among them, the conductive carbon black in the second microporous layer slurry plays a conductive role.

[0065] Wherein, the base layer, the first microporous layer and the second microporous layer in the gas diffusion layer are stacked in sequence.

[0066] like Figure 1 Shown is a schematic diagram of the layer structure of the gas diffusion layer provided by the present invention.

[0067] The preparation method of the gas diffusion layer provided by the present invention can make up for the problem of uncontrollable penetration of the second microporous layer slurry during coating by forming a stable and thin first microporous precursor layer containing resin, so that the second microporous layer slurry can be evenly spread on the surface of the first microporous precursor layer, and at the same time, the surface flatness of the second microporous layer is more reasonably modified, thereby reducing the surface roughness of the gas diffusion layer, that is, reducing the roughness of the surface of the second microporous layer, and greatly improving the surface roughness problem of the gas diffusion layer.

[0068] In addition, the preparation method of the gas diffusion layer provided by the present invention can reduce the amount of resin impregnation, reduce the blockage of the mass transfer channel without affecting the strength of the material, thereby increasing the mass transfer channel (water vapor transmission channel) inside the material. Furthermore, reducing the resin content can reduce the brittleness of the gas diffusion layer, because the less residual carbon after the resin is carbonized, the better the softness of the material; at the same time, because the composite first microporous precursor layer has a certain strength, the strength and support performance of the gas diffusion layer will not be reduced. That is, the present invention achieves the effect of taking into account the low amount of resin impregnation, the large mass transfer channel inside the gas diffusion layer, the low brittleness of the gas diffusion layer and the high brittle strength of the gas diffusion layer.

[0069] In addition, due to the presence of the first microporous precursor layer, the second microporous layer slurry can be better spread on the surface of the first microporous precursor layer without penetrating into the carbon fiber two-dimensional matrix material or the interior of the matrix material layer. Therefore, the sintering step after impregnation with the hydrophobic agent in the existing process is omitted, significantly reducing energy consumption.

[0070] Furthermore, the first microporous precursor layer is provided, and its roughness is lower than that of the base material layer, so the second microporous layer is more firmly bonded (good adhesion) and is less likely to have the problem of powder falling off.

[0071] In some specific embodiments, the surface roughness of the gas diffusion layer (ie, the surface of the second microporous layer) is not more than 2 micrometers, preferably not more than 1 micrometer.

[0072] In some specific embodiments, the method for preparing a gas diffusion layer provided by the present invention can reduce the energy consumption of sintering equipment by 50% compared with the two-time sintering process of the prior art.

[0073] In some specific embodiments, in step (a), the method for preparing the carbon fiber two-dimensional matrix material includes: using wet molding technology to mix and disperse chopped carbon fibers, a dispersant and water (solvent), and then transferring the prepared slurry to a former for dehydration molding, and then drying to obtain the carbon fiber two-dimensional matrix material.

[0074] Furthermore, in step (a), the dispersant includes at least one of hydroxypropyl cellulose, hydroxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose and ethyl cellulose. The dispersant can promote the decomposition of the chopped carbon fibers to form single carbon fiber filaments.

[0075] Furthermore, in step (a), the mass ratio of the chopped carbon fiber, the dispersant and the water is 2-5 (eg, 3 or 4):1-5 (eg, 2, 3 or 4):1000.

[0076] Furthermore, in step (a), the average length of the chopped carbon fiber is 3-12 mm, including but not limited to any point value of 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 10 mm, 12 mm or a range value between any two of them.

[0077] Furthermore, in step (a), the debonding method includes: debonding at a speed of 1200-3000 r / min for 5-15 min. The speed includes but is not limited to any point value of 1200 r / min, 1500 r / min, 1800 r / min, 2000 r / min, 2300 r / min, 2500 r / min, 2800 r / min, 3000 r / min or any range value between two of them; the debonding time includes but is not limited to any point value of 5 min, 6 min, 8 min, 10 min, 12 min, 15 min or any range value between two of them.

[0078] In some specific embodiments, in step (a), the reinforcing resin is a phenolic resin, or an epoxy resin, or a mixture of a phenolic resin and an epoxy resin, or a mixture of a phenolic resin and asphalt, or a mixture of an epoxy resin and asphalt, or a mixture of a phenolic resin, an epoxy resin and asphalt. It is understood that asphalt itself is solid at room temperature, so it needs to be ground into powder particles and used in combination with phenolic resin and / or epoxy resin.

[0079] In some specific embodiments, in step (a), the mass ratio of the carbon fiber two-dimensional matrix material to the resin (phenolic resin and epoxy resin) in the reinforcing resin is 1:0.5~1.7, including but not limited to any one of 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.7 or the range between any two of them.

[0080] In some specific embodiments, in step (b), the resin includes phenolic resin and / or epoxy resin.

[0081] In some specific embodiments, in step (b), the resin includes phenolic resin and epoxy resin in a mass ratio of 1:0.5~1. This can not only enhance the strength and structural stability of the carbon fiber two-dimensional matrix material, but also provide conditions for combining with the phenolic resin and epoxy resin of the first microporous layer, thereby improving the structural stability of the gas diffusion layer.

[0082] In some specific embodiments, in step (b), in the first microporous layer slurry, the mass ratio of the resin, the graphite, the acetylene black and the organic solvent is 10: 0.5~2 (for example, 1 or 1.5): 1~2 (for example, 1.3, 1.5 or 1.8): 1~2 (for example, 1.3, 1.5 or 1.8). This ratio can obtain a stable resin slurry system, which is easy to achieve mass production; at the same time, this resin slurry can be stabilized and mass produced using existing mature coating technology; in addition, this ratio is also easy to achieve a uniform dispersion effect. Among them, graphite can improve conductivity. Acetylene black not only improves conductivity, but also plays a thickening role.

[0083] In some specific embodiments, in step (b), the organic solvent includes an alcohol solvent, and the alcohol solvent includes but is not limited to ethanol, propanol, butanol, etc.

[0084] In some specific embodiments, in step (b), the preparation method of the first microporous layer slurry includes: mixing resin, graphite, acetylene black and organic solvent, and the mixing method includes: stirring at a speed of 800-1500 r / min for 15-30 min. The stirring speed includes but is not limited to any one of 800 r / min, 900 r / min, 1000 r / min, 1200 r / min, 1300 r / min, 1500 r / min or any range between two of them; the stirring time includes but is not limited to any one of 15 min, 20 min, 25 min, 30 min or any range between two of them. The equipment for mixing resin, graphite, acetylene black and organic solvent includes but is not limited to a high-speed disperser.

[0085] In some specific embodiments, in step (b), the coating method includes at least one of a blade coating method and a slit coating method.

[0086] In some specific embodiments, in step (b), the drying temperature is 120-150°C, including but not limited to any one of 120°C, 130°C, 140°C, 150°C or a range between any two of them.

[0087] In some specific embodiments, in step (b), the thickness of the first microporous precursor layer is 5-20 μm, including but not limited to any point value of 5 μm, 6 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, and 20 μm, or a range value between any two of them. The low thickness of the first microporous precursor layer can save raw materials, and the amount of resin required for carbonization of the fiber is reduced, which can reduce energy consumption.

[0088] In some specific embodiments, in step (b), the mass of the resin in the first microporous layer slurry is 30% to 80% of the mass of the carbon fiber two-dimensional matrix material, such as 40%, 50%, 60% or 70%. In the present invention, the amount of resin impregnation is small, which can improve the mass transfer efficiency without affecting the strength of the gas diffusion layer.

[0089] In some specific embodiments, in step (c), the temperature of the hot pressing is 150-200° C., including but not limited to any one of 150° C., 160° C., 170° C., 180° C., 190° C., and 200° C., or any range between two of them. At this hot pressing temperature, the resin has fluidity, and the carbon fiber filaments can be tightly connected to each other.

[0090] In some specific embodiments, in step (c), the hot pressing pressure is 0.1-0.5 MPa, including but not limited to any point value of 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa or any range value between two of them. After heating, under the action of the above pressure, the resin in the carbon fiber two-dimensional matrix material can be tightly combined with the resin of the first microporous layer.

[0091] In some specific embodiments, in step (c), the heat pressing time is 1 to 5 minutes, including but not limited to any one of 1 minute, 2 minutes, 3 minutes, 4 minutes, and 5 minutes, or any range between two of them. After heating and pressurizing, the resin solidifies within 1 to 5 minutes, thereby forming a stable composite material.

[0092] By adopting the above-mentioned hot pressing parameters, on the one hand, the bonding effect between the first microporous layer and the carbon fiber two-dimensional matrix material can be improved, and on the other hand, the structural stability of the carbon fiber two-dimensional matrix material can be improved.

[0093] In some specific embodiments, in step (c), the temperature of carbonization and graphitization is 1000-2300°C, including but not limited to any one of 1000°C, 1200°C, 1300°C, 1500°C, 1800°C, 2000°C, 2300°C or a range between any two of them.

[0094] In some specific embodiments, in step (c), the carbonization and graphitization time is 30 to 120 min, including but not limited to any one of 30 min, 40 min, 60 min, 80 min, 100 min, and 120 min or a range between any two of them.

[0095] In some specific embodiments, in step (d), the first hydrophobic agent includes at least one of PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride) and FEP (fluorinated ethylene propylene copolymer).

[0096] In some specific embodiments, in step (d), the immersion time is 30 to 300 s, for example, 60 s, 120 s, 150 s, 180 s, 210 s, 240 s, 260 s or 280 s.

[0097] In some specific embodiments, in step (d), the drying method comprises: drying at 100-120°C for 3-5 min; for example, drying at 100°C for 5 min, or drying at 120°C for 3 min, or drying at 110°C for 4 min.

[0098] In some specific embodiments, in step (d), the dispersant includes at least one of hydroxypropyl cellulose, hydroxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose and ethyl cellulose.

[0099] In some specific embodiments, in step (d), the second hydrophobic agent includes polytetrafluoroethylene.

[0100] In some specific embodiments, in step (d), the mass ratio of the dispersant, the second hydrophobic agent, the conductive carbon black and the water is 1.5-3 (e.g., 2 or 2.5): 5-10 (e.g., 6, 8 or 9): 15-25 (e.g., 18, 20 or 23): 100.

[0101] In some specific embodiments, in step (d), the coating method includes at least one of blade coating, extrusion and spray coating.

[0102] In some specific embodiments, in step (d), the thickness of the second microporous layer is 20-50 μm, including but not limited to any point value of 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm, or a range value between any two of them. The second microporous layer mainly serves to increase the contact area with the proton exchange membrane to reduce the interface resistance, provide a more uniform water vapor transmission channel, and increase the hydrophobic gradient again.

[0103] In some specific embodiments, in step (d), the sintering temperature is 350-400°C, including but not limited to any one of 350°C, 360°C, 370°C, 380°C, 390°C, and 400°C, or a range between any two of them; the sintering time is 30-60 min, including but not limited to any one of 30 min, 40 min, 50 min, and 60 min, or a range between any two of them.

[0104] In some specific embodiments, in step (a), the first release film includes a high temperature resistant release film.

[0105] In some specific embodiments, in step (b), the second release film includes a high temperature resistant release film.

[0106] The high temperature resistant release film may be any conventional high temperature resistant release film, such as silicone oil release paper, PTFE sintered film, modified PET high temperature resistant release film, etc., but is not limited thereto.

[0107] In a second aspect, the present invention provides a gas diffusion layer prepared by the method for preparing a gas diffusion layer, wherein the gas diffusion layer comprises a substrate layer, a first microporous layer and a second microporous layer stacked in sequence.

[0108] The gas diffusion layer provided by the invention has low surface roughness, high mass transfer efficiency, good softness, high strength, the second microporous layer is not easy to drop powder, and the production cost is low.

[0109] The base layer, the first microporous layer and the second microporous layer have different hydrophobicity, and the gas diffusion layer has a gradient hydrophobic structure. The hydrophobicity is ranked as follows: the first microporous layer> the second microporous layer> the base layer.

[0110] In some specific embodiments, the thickness of the substrate layer is 95-140 μm, such as 100 μm, 110 μm, 120 μm or 130 μm. The thinner the material, the more space it saves, which can reduce the volume of the battery or increase the battery power.

[0111] In some specific embodiments, the thickness of the first microporous layer is 5-20 μm, including but not limited to any point value of 5 μm, 6 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm or a range between any two of them.

[0112] In some specific embodiments, the thickness of the second microporous layer is 20-50 μm, including but not limited to any point value of 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or a range value between any two of them.

[0113] In some specific embodiments, the air permeability of the first microporous layer is 10000-50000 ml.mm, for example, 20000 ml.mm, 30000 ml.mm or 40000 ml.mm.

[0114] In some specific embodiments, the air permeability of the second microporous layer is 50-200 ml.mm, for example, 100 ml.mm, 130 ml.mm, 150 ml.mm or 180 ml.mm.

[0115] The larger the pore size, the stronger the air permeability. That is, the average pore size of the first microporous layer is greater than the average pore size of the second microporous layer.

[0116] In some specific embodiments, the average pore size of the first microporous layer is 30 μm to 50 μm, and the porosity is about 80%. The average pore size of the second microporous layer is 0.4 μm to 0.8 μm, and the porosity is about 78%.

[0117] In a third aspect, the present invention provides a fuel cell, comprising a gas diffusion layer prepared by the method for preparing the gas diffusion layer or the gas diffusion layer.

[0118] The fuel cell using the above-mentioned gas diffusion layer has the advantages of long life, good conductivity, applicability to large current and small current, high efficiency hydrophobicity, uniform air permeability, etc.

[0119] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0120] Example 1

[0121] The method for preparing the gas diffusion layer provided in this embodiment comprises the following steps:

[0122] (1) The chopped carbon fiber is made into a carbon fiber two-dimensional matrix material by wet molding technology: water is used as a solvent, hydroxypropyl cellulose is added as a dispersant, and then the chopped carbon fiber (average length is 8 mm) is added, wherein the mass ratio of the chopped carbon fiber, the dispersant and water is 4:3:1000, and the slurry is disintegrated at a speed of 2000 r / min for 10 min, and then the prepared slurry is transferred to a molding machine for dehydration molding, and the carbon fiber two-dimensional matrix material is obtained after drying.

[0123] The carbon fiber two-dimensional matrix material is impregnated in phenolic resin (i.e., reinforcing resin), and the mass ratio of the carbon fiber two-dimensional matrix material to the phenolic resin is controlled to be 1:0.7 to form a matrix material layer; then a layer of modified PET release film is covered on either side of the matrix material layer to obtain a first composite layer.

[0124] (2) A first microporous layer slurry containing resin, graphite, acetylene black and ethanol (alcohol solvent) was prepared using a high-speed disperser, wherein the resin was a phenolic resin and an epoxy resin in a mass ratio of 1:0.8, and the mass ratio of the resin, ethanol, graphite and acetylene black was 10:1:1:1. The mixing speed was 1000 r / min and the mixing time was 25 min. The mass of the resin in the first microporous layer slurry was 30% of the mass of the carbon fiber two-dimensional matrix material.

[0125] Then, the first microporous layer slurry was coated onto another release film by using a doctor blade coating method, and dried at 130° C. to obtain a second composite layer having a first microporous precursor layer.

[0126] (3) The base material layer of the first composite layer (the carbon fiber two-dimensional base material surface after impregnation with resin) is laminated with the first microporous precursor layer of the second composite layer (the layer formed after coating the first microporous layer slurry and drying it), and hot-pressed for 3 minutes at 0.3 MPa and 180°C using a hot press to perform composite curing. After curing, the two release films are peeled off to obtain a composite carbon fiber two-dimensional material.

[0127] The composite carbon fiber two-dimensional material is carbonized and graphitized at 2000° C. for 90 minutes to obtain a composite material layer having a two-layer structure including a matrix layer (having large pores) and a first microporous layer (having small pores).

[0128] (4) The composite material layer is immersed in PTFE (i.e., the first hydrophobic agent) for 180 seconds, and then dried at 120° C. for 3 minutes to obtain a treated composite material layer.

[0129] Then, a second microporous layer slurry containing conductive carbon black, methyl cellulose (dispersant), polytetrafluoroethylene (i.e., the second hydrophobic agent) and water is scraped onto the surface of the first microporous layer in the treated composite material layer, wherein the mass ratio of methyl cellulose, polytetrafluoroethylene, conductive carbon black and water is 2.3:8:20:100. Thereafter, the slurry is sintered at 380°C for 50 minutes to form a second microporous layer, thereby obtaining a gas diffusion layer including a substrate layer, a first microporous layer and a second microporous layer.

[0130] The gas diffusion layer prepared in this embodiment includes a substrate layer, a first microporous layer and a second microporous layer stacked in sequence, wherein the substrate layer has a thickness of 115 μm, the first microporous precursor layer has a thickness of 10 μm, and the second microporous layer has a thickness of 40 μm.

[0131] Figure 2 This is a SEM image of one side of the substrate layer of the gas diffusion layer prepared in Example 1; Figure 3 This is a SEM image of one side of the second microporous layer of the gas diffusion layer prepared in Example 1.

[0132] Example 2

[0133] The method for preparing the gas diffusion layer provided in this embodiment comprises the following steps:

[0134] (1) The chopped carbon fibers are made into a carbon fiber two-dimensional matrix material by wet molding technology: water is used as a solvent, hydroxypropyl cellulose is added as a dispersant, and then the chopped carbon fibers (average length of 3 mm) are added thereto, wherein the mass ratio of the chopped carbon fibers, the dispersant and water is 5:5:1000, and the slurry is disintegrated at a speed of 1200 r / min for 15 min, and then the prepared slurry is transferred to a molding machine for dehydration molding, and the carbon fiber two-dimensional matrix material is obtained after drying.

[0135] The carbon fiber two-dimensional matrix material is impregnated in epoxy resin (i.e., reinforcing resin), and the mass ratio of the carbon fiber two-dimensional matrix material to the epoxy resin is controlled to be 1:1 to form a matrix material layer; then a layer of modified PET release film is covered on either side of the matrix material layer to obtain a first composite layer.

[0136] (2) A first microporous layer slurry containing resin, graphite, acetylene black and propanol (alcohol solvent) was prepared using a high-speed disperser, wherein the resin was a phenolic resin and an epoxy resin in a mass ratio of 1:0.5, and the mass ratio of the resin, propanol, graphite and acetylene black was 10:2:1:1. The mixing speed was 800 r / min and the mixing time was 30 min. The mass of the resin in the first microporous layer slurry was 50% of the mass of the carbon fiber two-dimensional matrix material.

[0137] Then, the first microporous layer slurry was coated onto another release film by a slit coating method and dried at 120° C. to obtain a second composite layer having a first microporous precursor layer.

[0138] (3) The base material layer of the first composite layer (the carbon fiber two-dimensional base material surface after impregnation with resin) is laminated with the first microporous precursor layer of the second composite layer (the layer formed after coating the first microporous layer slurry and drying it), and hot-pressed for 2 minutes at 0.1 MPa and 200°C using a hot press to perform composite curing. After curing, the two release films are peeled off to obtain a composite carbon fiber two-dimensional material.

[0139] The composite carbon fiber two-dimensional material is carbonized and graphitized at 1500° C. for 120 min to obtain a composite material layer having a two-layer structure including a matrix layer (having large pores) and a first microporous layer (having small pores).

[0140] (4) The composite material layer is immersed in PVDF (i.e., the first hydrophobic agent) for 60 seconds, and then dried at 100° C. for 5 minutes to obtain a treated composite material layer.

[0141] Then, a second microporous layer slurry containing conductive carbon black, ethyl cellulose (dispersant), polytetrafluoroethylene (i.e., the second hydrophobic agent) and water is sprayed onto the surface of the first microporous layer in the treated composite material layer, wherein the mass ratio of ethyl cellulose, polytetrafluoroethylene, conductive carbon black and water is 1.5:10:15:100, and then sintered at 350°C for 60 minutes to form a second microporous layer, thereby obtaining a gas diffusion layer including a substrate layer, a first microporous layer and a second microporous layer.

[0142] The gas diffusion layer prepared in this embodiment includes a substrate layer, a first microporous layer and a second microporous layer stacked in sequence, wherein the substrate layer has a thickness of 140 μm, the first microporous precursor layer has a thickness of 5 μm, and the second microporous layer has a thickness of 20 μm.

[0143] Example 3

[0144] The method for preparing the gas diffusion layer provided in this embodiment comprises the following steps:

[0145] (1) The chopped carbon fiber is made into a carbon fiber two-dimensional matrix material by wet molding technology: water is used as a solvent, hydroxypropyl cellulose is added as a dispersant, and then the chopped carbon fiber (average length is 12 mm) is added, wherein the mass ratio of the chopped carbon fiber, dispersant and water is 2:1:1000, and the slurry is disintegrated at a speed of 3000 r / min for 5 min, and then the prepared slurry is transferred to a molder for dehydration molding, and the carbon fiber two-dimensional matrix material is obtained after drying.

[0146] The carbon fiber two-dimensional matrix material is immersed in a mixed material (i.e., reinforced resin) of epoxy resin and asphalt in a mass ratio of 1:0.5, and the mass ratio of the carbon fiber two-dimensional matrix material to the epoxy resin is controlled to be 1:0.5 to form a matrix material layer; then, a layer of modified PET release film is covered on either side of the matrix material layer to obtain a first composite layer.

[0147] (2) A first microporous layer slurry containing resin, graphite, acetylene black and butanol (alcohol solvent) was prepared using a high-speed disperser, wherein the resin was a phenolic resin and an epoxy resin in a mass ratio of 1:1, and the mass ratio of the resin, butanol, graphite and acetylene black was 10:1:1:1. The mixing speed was 1500 r / min and the mixing time was 15 min. The mass of the resin in the first microporous layer slurry was 80% of the mass of the carbon fiber two-dimensional matrix material.

[0148] Then, the first microporous layer slurry is coated onto another release film by using a doctor blade coating method, and dried at 150° C. to obtain a second composite layer having a first microporous precursor layer.

[0149] (3) The base material layer of the first composite layer (the carbon fiber two-dimensional base material surface after impregnation with resin) is laminated with the first microporous precursor layer of the second composite layer (the layer formed after coating the first microporous layer slurry and drying it), and hot-pressed for 5 minutes at 0.5 MPa and 150°C using a hot press to perform composite curing. After curing, the two release films are peeled off to obtain a composite carbon fiber two-dimensional material.

[0150] The composite carbon fiber two-dimensional material is carbonized and graphitized at 2300° C. for 30 minutes to obtain a composite material layer having a two-layer structure including a matrix layer (having large pores) and a first microporous layer (having small pores).

[0151] (4) The composite material layer is immersed in PTFE (i.e., the first hydrophobic agent) for 300 seconds, and then dried at 110° C. for 5 minutes to obtain a treated composite material layer.

[0152] Then, a second microporous layer slurry containing conductive carbon black, ethyl cellulose (dispersant), polytetrafluoroethylene (i.e., the second hydrophobic agent) and water is scraped onto the surface of the first microporous layer in the treated composite material layer, wherein the mass ratio of ethyl cellulose, polytetrafluoroethylene, conductive carbon black and water is 3:5:25:100, and then sintered at 400°C for 30 minutes to form a second microporous layer, thereby obtaining a gas diffusion layer including a substrate layer, a first microporous layer and a second microporous layer.

[0153] The gas diffusion layer prepared in this embodiment includes a substrate layer, a first microporous layer and a second microporous layer stacked in sequence, wherein the thickness of the substrate layer is 95 μm, the thickness of the first microporous precursor layer is 20 μm, and the thickness of the second microporous layer is 50 μm.

[0154] Example 4

[0155] The preparation method of the gas diffusion layer provided in this embodiment is basically the same as that in Embodiment 1, except that in step (2), the mass ratio of the resin, ethanol, graphite and acetylene black in the first microporous layer slurry is replaced with 10:1.5:2:2.

[0156] Example 5

[0157] The preparation method of the gas diffusion layer provided in this embodiment is basically the same as that in embodiment 1, except that in step (3), a hot press is used at 0.4 MPa and 170° C. for 2 minutes.

[0158] Comparative Example 1

[0159] The preparation method of the gas diffusion layer provided in this comparative example comprises the following steps:

[0160] (1) A carbon fiber two-dimensional matrix material was prepared according to the method of Example 1.

[0161] (2) The carbon fiber two-dimensional matrix material is carbonized and graphitized at 2000° C. for 90 minutes to obtain a composite material layer, i.e., a matrix layer.

[0162] (3) Same as step (4) of Example 1.

[0163] The gas diffusion layer prepared in this comparative example includes a laminated substrate layer (with the same thickness as the substrate layer in Example 1) and a microporous layer (with the same thickness as the second microporous layer in Example 1).

[0164] Comparative Example 2

[0165] The preparation method of the gas diffusion layer provided in this comparative example is basically the same as that of comparative example 1, except that in step (1), the mass ratio of the carbon fiber two-dimensional matrix material to the phenolic resin is controlled to be 1:2.

[0166] Comparative Example 3

[0167] The preparation method of the gas diffusion layer provided in this comparative example is basically the same as that of Example 1, except that in step (2), the mass ratio of the resin, ethanol, graphite and acetylene black in the first microporous layer slurry is replaced with 10:1:0.1:0.1.

[0168] Comparative Example 4

[0169] The preparation method of the gas diffusion layer provided in this comparative example is basically the same as that in Example 1, except that in step (2), the dry film thickness of the first microporous precursor layer is controlled to be 40 μm. That is, the thickness of the first microporous precursor layer of the gas diffusion layer prepared in this comparative example is 40 μm.

[0170] Comparative Example 5

[0171] The preparation method of the gas diffusion layer provided in this comparative example is basically the same as that of Example 1, except that, in step (3), a hot press is used at 2 MPa and 140° C. for 5 min.

[0172] Experimental example

[0173] The test results of the total thickness of the gas diffusion layer prepared in each embodiment and each comparative example (the sum of the thickness of the substrate layer, the first microporous layer and the second microporous layer), the surface roughness of the second microporous layer or the microporous layer (Comparative Example 1 and Comparative Example 2) side of the gas diffusion layer, the plane resistance and vertical resistance of the gas diffusion layer, the hydrophobic angle of the second microporous layer or the microporous layer (Comparative Example 1 and Comparative Example 2) side of the gas diffusion layer, and the hydrophobic angle of the substrate layer side of the gas diffusion layer are shown in Table 1. Among them, the surface roughness is measured using a roughness tester. The plane resistance is measured using a four-probe tester, and the vertical resistance is measured using a penetration resistance tester. The hydrophobic angle is measured using a water drop angle tester.

[0174] Table 1 Performance test results

[0175]

[0176] It can be seen from Table 1 that the surface roughness of the gas diffusion layer prepared in each embodiment is lower, the conductivity is better, and the tensile strength is higher. The hydrophobicity test results of each embodiment have a gradient difference of 10°.

[0177] Among them, low resistance indicates that the gas diffusion layer has good electrical conductivity, so the battery made therefrom has good electrical performance.

[0178] It can be seen from Table 1 above that the hydrophobic gradient of Example 1 reaches 12.5°. While ensuring the hydrophobicity of the gas diffusion layer, the increase in the hydrophobic gradient can enhance the drainage capacity of the gas diffusion layer, thereby avoiding flooding. At the same time, it can be seen from Table 1 above that the tensile strength of Example 1 is the highest, and the enhancement of the strength can increase the supporting performance of the GDL for the proton exchange membrane.

[0179] Furthermore, by comparing the strength data of Example 1 and Comparative Example 2, it can be seen that the strength of Comparative Example 2 after increasing the resin impregnation amount is basically consistent with that of Example 1. This shows that the present invention provides a first microporous precursor layer with a certain strength, and even if the resin impregnation amount is reduced, the strength of the gas diffusion layer will not be reduced.

[0180] However, in Comparative Example 1, the first microporous layer is not provided, resulting in increased resistance and significantly reduced conductive performance.

[0181] In Comparative Example 3, the ratio of resin, ethanol, graphite and acetylene black in the first microporous layer slurry is not suitable, resulting in the material being unable to form a film, that is, unable to form a uniform coating.

[0182] In Comparative Example 4, the thickness of the first microporous precursor layer is too large, resulting in reduced electrical performance.

[0183] In Comparative Example 5, the hot pressing conditions were not suitable, resulting in a decrease in electrical properties and a decrease in tensile strength.

[0184] Figure 4 This is a picture of the peeling coating falling off of the second microporous layer in the gas diffusion layer prepared in Example 1 after being pasted with 3M600 peeling tape. Figure 5 The gas diffusion layer is directly made of a reinforced two-dimensional matrix material impregnated with phenolic resin-hot pressing solidification-carbonization graphitization-hydrophobic sintering-microporous layer coating-sintering process. Compared with the technical solution of the present invention, Figure 5 The preparation method does not coat the second microporous layer on the release film, that is, it is not a two-layer microporous layer. Figure 4 and Figure 5 In the figure, the lower figure is the gas diffusion layer, and the upper figure is the coating peeled off with tape. Figure 4 and Figure 5 It can be seen that Figure 4 Less powder loss, Figure 5 Severe powdering occurs, which indicates that the present invention has a significant improvement effect on the powdering problem of the second microporous layer. The second microporous layer in the gas diffusion layer prepared by the present invention is not prone to powdering.

[0185] In addition, the gas diffusion layer manufactured by the process of directly impregnating an enhanced two-dimensional matrix material with phenolic resin - hot pressing and curing - carbonization and graphitization - hydrophobic sintering - coating of a microporous layer - sintering began to crack when bent at 56°, while the gas diffusion layer manufactured in Example 1 of the present invention can be bent to 70°.

[0186] It can be seen that the preparation method of the gas diffusion layer provided by the present invention can significantly reduce the surface roughness of the gas diffusion layer, improve the mass transfer of the gas diffusion layer, reduce the brittleness of the gas diffusion layer, and improve the softness of the gas diffusion layer without reducing the strength of the gas diffusion layer. In addition, the second microporous layer is more firmly bonded to the first microporous layer and the substrate layer.

[0187] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a gas diffusion layer, characterized in that: The steps include: (a) The carbon fiber two-dimensional matrix material is impregnated with a reinforcing resin to form a matrix material layer, and a first release film is covered on one surface of the matrix material layer to obtain a first composite layer; (b), coating a first microporous layer slurry containing resin, graphite, acetylene black and an organic solvent onto a second release film and then drying, the drying temperature being 120-150°C, to obtain a second composite layer having a first microporous precursor layer; in the first microporous layer slurry, the mass ratio of the resin, the graphite, the acetylene black and the organic solvent is 10:0.5-2:1-2:1-2; in step (b), the mass of the resin in the first microporous layer slurry is 30%-80% of the mass of the carbon fiber two-dimensional matrix material in step (a); in step (b), the thickness of the first microporous precursor layer is 5-15 μm; (c), laminating the base material layer of the first composite layer and the first microporous precursor layer of the second composite layer, performing heat pressing and curing, then peeling off the first release film and the second release film, and performing carbonization and graphitization to obtain a composite material layer including a base layer and a first microporous layer; in step (c), the pressure of the heat pressing is 0.1-0.5 MPa; the temperature of the heat pressing is 150-200°C; the thickness of the base layer is 95-140 μm; (d), immersing the composite material layer in a first hydrophobic agent and then drying it, then coating a second microporous layer slurry containing conductive carbon black, a dispersant, a second hydrophobic agent and water on the surface of the first microporous layer, and then sintering to form a second microporous layer to obtain the gas diffusion layer; in step (d), the mass ratio of the dispersant, the second hydrophobic agent, the conductive carbon black and the water is 1.5-3:5-10:15-25:100; the thickness of the second microporous layer is 25-50 μm; The gas diffusion layer includes a base layer, a first microporous layer and a second microporous layer which are sequentially stacked.

2. The method for preparing a gas diffusion layer according to claim 1, characterized in that: In step (a), the preparation method of the carbon fiber two-dimensional matrix material comprises: using wet molding technology, mixing and dispersing short carbon fibers, a dispersant and water, dehydrating and molding, and then drying to obtain the carbon fiber two-dimensional matrix material; wherein the dispersant comprises at least one of hydroxypropyl cellulose, hydroxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose and ethyl cellulose; the mass ratio of the short carbon fibers, the dispersant and the water is 2~5:1~5:1000; the average length of the short carbon fibers is 3~12mm; the dispersing method comprises: dispersing at a rotation speed of 1200~3000r / min for 5~15min.

3. The method for preparing a gas diffusion layer according to claim 1, characterized in that: In step (a), at least one of the following conditions is met: (1) The reinforcing resin is a phenolic resin; (2) The reinforcing resin is epoxy resin; (3) The reinforcing resin is a mixture of phenolic resin and epoxy resin; (4) The reinforcing resin is a mixture of phenolic resin and asphalt; (5) The reinforcing resin is a mixture of epoxy resin and asphalt; (6) The reinforcing resin is a mixture of phenolic resin, epoxy resin and asphalt; (7) The mass ratio of the carbon fiber two-dimensional matrix material to the resin in the reinforcing resin is 1:0.5-1.

7.

4. The method for preparing a gas diffusion layer according to claim 1, characterized in that: In step (b), at least one of the following conditions is met: (1) The resin includes phenolic resin and / or epoxy resin; (2) The organic solvent includes an alcohol solvent; (3) The preparation method of the first microporous layer slurry includes: mixing resin, graphite, acetylene black and an organic solvent, and the mixing method includes: stirring at a speed of 800-1500 r / min for 15-30 min; (4) The coating method includes at least one of a blade coating method and a slit coating method.

5. The method for preparing a gas diffusion layer according to claim 1, characterized in that: In step (c), at least one of the following conditions is met: (1) The hot pressing time is 1 to 5 minutes; (2) The temperature of carbonization and graphitization is 1000~2300℃; (3) The carbonization and graphitization time is 30 to 120 minutes.

6. The method for preparing a gas diffusion layer according to claim 1, characterized in that: In step (d), at least one of the following conditions is met: (1) The first hydrophobic agent includes at least one of PTFE, PVDF and FEP; (2) The immersion time is 30 to 300 seconds; (3) The drying method comprises: drying at 100-120°C for 3-5 minutes.

7. The method for preparing a gas diffusion layer according to claim 1, characterized in that: In step (d), at least one of the following conditions is met: (1) The dispersant comprises at least one of hydroxypropyl cellulose, hydroxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose and ethyl cellulose; (2) the second hydrophobic agent comprises polytetrafluoroethylene; (3) The coating method includes at least one of scraping, extruding and spraying; (4) The sintering temperature is 350-400°C, and the sintering time is 30-60 minutes.

8. A gas diffusion layer, characterized in that: The gas diffusion layer is prepared by the method for preparing the gas diffusion layer according to any one of claims 1 to 7, wherein the gas diffusion layer comprises a substrate layer, a first microporous layer and a second microporous layer stacked in sequence; The thickness of the substrate layer is 95-140 μm; The thickness of the first microporous layer is 5-15 μm; The thickness of the second microporous layer is 25-50 μm.

9. A fuel cell, characterized in that: It comprises a gas diffusion layer prepared by the method for preparing a gas diffusion layer according to any one of claims 1 to 7 or a gas diffusion layer according to claim 8.

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