Fuel cell composite gas diffusion layer and preparation and application thereof

Abstract

The invention relates to the technical field of fuel cells, in particular to a fuel cell composite gas diffusion layer and preparation and application thereof. The fuel cell composite gas diffusion layer provided by the invention is obtained by dipping a substrate in a filler and then carrying out stepped heating and drying, the substrate is a commercial gas diffusion layer, and the filler is a high thermal conductivity material. In the preparation process of the composite gas diffusion layer of the fuel cell provided by the invention, the used raw materials are few, the raw materials are easy to obtain, and the cost of the raw materials is low; the preparation method is simple, and can be realized by means of the cooperation of the gas diffusion layer and the high-heat-conductivity material only through stepped heating and drying treatment after dipping; compared with a commercial gas diffusion layer, the fuel cell composite gas diffusion layer provided by the invention has the advantages that the thermal conductivity is obviously improved, and the hydrophobic property is also obviously improved.

Description

Technical Field

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

[0002] The electrochemical reaction of fuel cells accounts for about 50% of the total heat, which means that a large amount of waste heat is generated during operation, causing the temperature inside the battery to rise. When the temperature exceeds the typical operating temperature window, it will affect the water content of the membrane, reduce proton conductivity, increase overpotential, and reduce performance. Therefore, effective thermal management of fuel cells is required, and high thermal conductivity materials play a vital role in maintaining temperature balance and stability. The gas diffusion layer is a key component for conducting heat out of the membrane and catalyst layer, but the through-plane thermal conductivity of the gas diffusion layer is much smaller than the in-plane thermal conductivity, which exacerbates the temperature accumulation.

[0003] Patent CN111162285A discloses a conductive gas diffusion layer for a fuel cell, which mainly includes two parts: the base layer is mainly one of a carbon fiber layer, a carbon fiber woven cloth and a carbon black paper, and the microporous layer is mainly composed of carbon black and a hydrophobic agent. Since the heat transfer process does not currently directly affect the performance of the fuel cell, the current technology does not focus on the thermal conductivity of the gas diffusion layer, but mainly focuses on gas transmission and water management, and mainly works on the construction of the gas diffusion layer layered structure and the pore structure design. In the future, the power density of fuel cells is steadily increasing, and the heat dissipation problem will become more and more prominent. The low through-plane thermal conductivity of the gas diffusion layer will become a key bottleneck problem.

[0004] Therefore, it is still very important to provide a technical solution that can solve the problem of low thermal conductivity of the gas diffusion layer. Summary of the invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a fuel cell composite gas diffusion layer and its preparation and application. The present invention directly uses a commercial gas diffusion layer as a substrate, uses a high thermal conductivity material represented by carbon nanotubes as a filler (commercial gas diffusion layer and filler are matched), and forms a fuel cell composite gas diffusion layer simply by impregnation and then drying.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The first object of the present invention is to provide a fuel cell composite gas diffusion layer, wherein the fuel cell composite gas diffusion layer is obtained by immersing a substrate in a filler solution.

[0008] The substrate is a commercial gas diffusion layer and the filler is a high thermal conductivity material.

[0009] In one embodiment of the present invention, the commercial gas diffusion layer is selected from TORAY TGL-R-060 gas diffusion layer, SGL (SGL) A gas diffusion layer, one of the following: AvCarb H14CX483 gas diffusion layer from the United States, JNTGHCP120 gas diffusion layer from South Korea, or a non-woven fabric-based gas diffusion layer from Freudenberg;

[0010] The high thermal conductivity material is selected from one of carbon nanotubes, graphene, acetylene black or carbon fiber.

[0011] In one embodiment of the present invention, the commercial gas diffusion layer is TORAY TGL-R-060 gas diffusion layer, and the high thermal conductivity material is carbon nanotubes.

[0012] In one embodiment of the present invention, the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes;

[0013] Preferably, the carbon nanotubes are multi-walled carbon nanotubes, and the inner diameter of the multi-walled carbon nanotubes is less than 8 nm and the length is 10 to 30 μm.

[0014] A second object of the present invention is to provide a method for preparing a fuel cell composite gas diffusion layer, comprising the following steps:

[0015] (S1) dissolving the filler and the hydrophobic agent and mixing them to obtain a hydrophobic agent-filler solution;

[0016] (S2) Immersing the pretreated substrate in the hydrophobic agent-filler solution prepared in step (S1), and obtaining a fuel cell composite gas diffusion layer after post-treatment.

[0017] In one embodiment of the present invention, in step (S1), the hydrophobic agent is a fluoride;

[0018] In the hydrophobic agent-filler solution, one or more of pure water, ethanol, acetone or isopropanol is used as solvent; the concentration of the hydrophobic agent is 1-15wt%, and the concentration of the filler is 0.1-0.8wt%.

[0019] Preferably, in the hydrophobic agent-filler solution, the concentration of the hydrophobic agent is 10 wt %, and the concentration of the filler is 0.8 wt %.

[0020] In one embodiment of the present invention, in step (S2), the pretreated substrate is obtained by the following method:

[0021] The substrate is cleaned with acid and then dried to obtain a pretreated substrate.

[0022] In one embodiment of the present invention, the acid is selected from one of sulfuric acid, hydrochloric acid or nitric acid;

[0023] During the drying process, the temperature is 60-100°C.

[0024] Preferably, during the drying process, the temperature is 100°C.

[0025] In one embodiment of the present invention, in step (S2), the impregnation is selected from one of atmospheric pressure impregnation, vacuum impregnation or ultrasonic impregnation;

[0026] During the immersion process, the time is 1h to 24h;

[0027] Preferably, during the dipping process, the time is 1 hour;

[0028] The post-treatment is a step-by-step temperature drying treatment; the step-by-step temperature drying treatment has the following advantages: 1) promoting uniform drying and avoiding stress concentration and material damage caused by sudden temperature changes; 2) gradually removing the solvent or moisture from the inside of the material, which helps to maintain or improve the mechanical strength and stability of the material and ensure its stability during the operation of the fuel cell; 3) helping to fix the hydrophobic agent, thereby improving the hydrophobic performance, promoting water transfer, and preventing the fuel cell from being flooded during operation.

[0029] In one embodiment of the present invention, the step-by-step drying includes a first drying process and a second drying process;

[0030] During the first drying process, the temperature is 80-120°C and the time is 20 minutes to 1 hour;

[0031] Preferably, during the first drying process, the temperature is 100° C. and the time is 30 min;

[0032] During the second drying process, the temperature is 340-380°C and the time is 20min-1h;

[0033] Preferably, during the second drying process, the temperature is 340° C. and the time is 1 hour.

[0034] The third object of the present invention is to provide an application of a fuel cell composite gas diffusion layer in the preparation of a high power density fuel cell.

[0035] In the present invention, the thermal conductivity and hydrophobicity of the fuel cell composite gas diffusion layer are enhanced by combining the gas diffusion layer (substrate) with the high thermal conductivity material (filler); specifically, the high thermal conductivity material usually has a high thermal conductivity. When it is impregnated into the gas diffusion layer, a better heat conduction path can be formed, so that heat can be more effectively transferred from the heat source to the cooling medium, thereby improving the overall thermal conductivity; the treatment of step-by-step heating and drying after impregnation can help the high thermal conductivity material to be evenly distributed in the microporous structure of the gas diffusion layer, making the pores more uniform, which not only increases the contact area between the high thermal conductivity material and the gas diffusion layer material, but also improves the heat conduction efficiency; impregnation forms a stronger interface bond between the filler and the gas diffusion layer material, reduces the interface thermal resistance, and helps to transfer heat more efficiently; in addition, the high thermal conductivity material used in the present invention has a certain hydrophobicity. When it is impregnated into the gas diffusion layer, a hydrophobic layer will be formed on the surface of the material; and the impregnated high thermal conductivity material can serve as a good carrier of the hydrophobic agent, helping the hydrophobic agent to be evenly distributed in the gas diffusion layer and maintain stability, thereby maintaining the hydrophobic performance for a long time.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) In the preparation process of the fuel cell composite gas diffusion layer provided by the present invention, less raw materials are used, the raw materials are easily available and the cost of the raw materials is low;

[0038] (2) In the preparation process of the composite gas diffusion layer for fuel cells provided by the present invention, the preparation method is simple, relying on the combination of the gas diffusion layer and the high thermal conductivity material, and can be achieved only by step-by-step temperature rising and drying treatment after impregnation;

[0039] (3) Compared with commercial gas diffusion layers, the thermal conductivity of the fuel cell composite gas diffusion layer provided by the present invention is significantly improved, and the hydrophobicity is also significantly improved. DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to specific embodiments.

[0041] In the following examples, unless otherwise specified, all reagents used are commercially available reagents, and all detection means and methods used are conventional detection means and methods in the art.

[0042] Example 1

[0043] This embodiment provides a method for preparing a composite gas diffusion layer for a fuel cell, which specifically includes the following steps:

[0044] (S1) washing a commercial gas diffusion layer (TORAY TGL-R-060 gas diffusion layer) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 100° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0045] (S2) preparing a hydrophobic agent-filler solution containing 10 wt % polytetrafluoroethylene (PTFE) and 0.8 wt % carbon nanotubes by ultrasound;

[0046] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0047] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after ultrasonic immersion for 1 hour, it is placed in an oven for a first drying treatment (100°C, 30 minutes to remove moisture), and then the temperature is increased for a second drying treatment (340°C, 1 hour) to obtain a fuel cell composite gas diffusion layer.

[0048] Comparative Example 1

[0049] This comparative example provides a method for preparing a composite gas diffusion layer, which specifically comprises the following steps:

[0050] (S1) washing a commercial gas diffusion layer (TORAY TGL-R-060 gas diffusion layer) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 100° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0051] (S2) preparing a hydrophobic agent solution containing 10 wt % polytetrafluoroethylene (PTFE) by ultrasound, and simultaneously preparing a hydrophobic agent solution without carbon nanotubes;

[0052] Wherein, pure water is used as solvent in the hydrophobic agent solution;

[0053] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent solution prepared in step (S2), and after ultrasonic immersion for 1 hour, it is placed in an oven for the first drying treatment (100°C, 30 minutes to remove moisture), and then the temperature is increased for the second drying treatment (340°C, 1 hour) to obtain a composite gas diffusion layer.

[0054] Example 2

[0055] This embodiment provides a method for preparing a composite gas diffusion layer for a fuel cell, which specifically includes the following steps:

[0056] (S1) washing a commercial gas diffusion layer (TORAY TGL-R-060 gas diffusion layer) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 100° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0057] (S2) preparing a hydrophobic agent-filler solution containing 10 wt % polytetrafluoroethylene (PTFE) and 0.8 wt % carbon nanotubes by ultrasound, and simultaneously preparing a hydrophobic agent-filler solution without carbon nanotubes;

[0058] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0059] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after being immersed at normal pressure for 1 hour, it is placed in an oven for a first drying treatment (100°C, 30 minutes to remove moisture), and then the temperature is increased for a second drying treatment (340°C, 1 hour) to obtain a fuel cell composite gas diffusion layer.

[0060] The gas diffusion layers prepared in the above-mentioned Example 1, Comparative Example 1 and Example 2 were subjected to thermal conductivity tests (as shown in Table 1) and contact angle tests (as shown in Table 2). It can be found from Tables 1 and 2 that, compared with the gas diffusion layer prepared in Comparative Example 1, the thermal conductivity of the fuel cell composite gas diffusion layers prepared in Example 1 and Example 2 were effectively improved, and the contact angles were increased to more than 150°, and the hydrophobicity of the material was improved to super hydrophobicity.

[0061] Table 1 Thermal conductivity test results

[0062] Thermal conductivity λ(W / mK) <![CDATA[接触热阻(K / cm 2 W)]]> Example 1 0.500 1.491 Comparative Example 1 0.444 1.628 Example 2 0.474 1.638

[0063] Table 2 Contact angle test results

[0064] Contact angle (°) Example 1 151.594 Comparative Example 1 146.830 Example 2 150.575

[0065] Example 3

[0066] This embodiment provides a method for preparing a composite gas diffusion layer for a fuel cell, which specifically includes the following steps:

[0067] (S1) Commercial gas diffusion layer (SGL, Germany) The gas diffusion layer was washed with sulfuric acid to remove impurities, and then washed with deionized water for three times, and then placed in an oven at 80° C. to dry and remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0068] (S2) preparing a hydrophobic agent-filler solution containing 1 wt % polytetrafluoroethylene (PTFE) and 0.7 wt % carbon nanotubes by ultrasound;

[0069] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0070] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after ultrasonic immersion for 12 hours, it is placed in an oven for a first drying treatment (80°C, 60 minutes to remove moisture), and then the temperature is increased for a second drying treatment (340°C, 60 minutes) to obtain a fuel cell composite gas diffusion layer.

[0071] Example 4

[0072] This embodiment provides a method for preparing a composite gas diffusion layer for a fuel cell, which specifically includes the following steps:

[0073] (S1) washing a commercial gas diffusion layer (US AvCarb H14CX483 gas diffusion layer) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 60° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0074] (S2) preparing a hydrophobic agent-filler solution containing 15 wt % polytetrafluoroethylene (PTFE) and 0.8 wt % carbon nanotubes by ultrasound;

[0075] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0076] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after ultrasonic immersion for 24 hours, it is placed in an oven for a first drying treatment (120°C, 20 minutes to remove moisture), and then the temperature is increased for a second drying treatment (340°C, 60 minutes) to obtain a fuel cell composite gas diffusion layer.

[0077] Example 5

[0078] This embodiment provides a method for preparing a composite gas diffusion layer for a fuel cell, which specifically includes the following steps:

[0079] (S1) washing a commercial gas diffusion layer (JNTGHCP120 gas diffusion layer from Korea) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 80° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0080] (S2) preparing a hydrophobic agent-filler solution containing 5 wt % polytetrafluoroethylene (PTFE) and 0.6 wt % carbon nanotubes by ultrasound;

[0081] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0082] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after ultrasonic immersion for 6 hours, it is placed in an oven for a first drying treatment (100°C, 20 minutes to remove moisture), and then the temperature is increased for a second drying treatment (380°C, 20 minutes) to obtain a fuel cell composite gas diffusion layer.

[0083] The performance (thermal conductivity and hydrophobicity) of the fuel cell composite gas diffusion layer prepared in Examples 3 to 5 is substantially the same as that of the fuel cell composite gas diffusion layer prepared in Example 2.

[0084] Comparative Example 2

[0085] This comparative example provides a method for preparing a composite gas diffusion layer, which specifically comprises the following steps:

[0086] (S1) washing a commercial gas diffusion layer (TORAY TGL-R-060 gas diffusion layer) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 100° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0087] (S2) preparing a hydrophobic agent-filler solution containing 10 wt % polytetrafluoroethylene (PTFE) and 0.8 wt % carbon nanotubes by ultrasound;

[0088] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0089] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after ultrasonic immersion for 1 hour, it is placed in an oven for drying treatment (100°C, 30 minutes to remove moisture) to obtain a composite gas diffusion layer.

[0090] Comparative Example 3

[0091] This comparative example provides a method for preparing a composite gas diffusion layer, which specifically comprises the following steps:

[0092] (S1) washing a commercial gas diffusion layer (TORAY TGL-R-060 gas diffusion layer) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 100° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0093] (S2) preparing a hydrophobic agent-filler solution containing 10 wt % polytetrafluoroethylene (PTFE) and 0.8 wt % carbon nanotubes by ultrasound;

[0094] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0095] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after ultrasonic immersion for 1 hour, it is placed in an oven for drying treatment (100°C, 60 minutes to remove moisture) to obtain a gas diffusion layer.

[0096] Comparative Example 4

[0097] This comparative example provides a method for preparing a composite gas diffusion layer, which specifically comprises the following steps:

[0098] (S1) washing a commercial gas diffusion layer (TORAY TGL-R-060 gas diffusion layer) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 100° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0099] (S2) preparing a hydrophobic agent-filler solution containing 10 wt % polytetrafluoroethylene (PTFE) and 0.8 wt % carbon nanotubes by ultrasound;

[0100] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0101] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after ultrasonic immersion for 1 hour, it is placed in an oven for drying treatment (340°C, 30 minutes to remove moisture) to obtain a gas diffusion layer.

[0102] Comparative Example 5

[0103] This comparative example provides a method for preparing a composite gas diffusion layer, which specifically comprises the following steps:

[0104] (S1) washing a commercial gas diffusion layer (TORAY TGL-R-060 gas diffusion layer) with sulfuric acid to remove impurities, then washing it with deionized water for three times, and drying it in an oven at 100° C. to remove moisture, thereby obtaining a pretreated gas diffusion layer;

[0105] (S2) preparing a hydrophobic agent-filler solution containing 10 wt % polytetrafluoroethylene (PTFE) and 0.8 wt % carbon nanotubes by ultrasound;

[0106] The carbon nanotubes are multi-walled carbon nanotubes with an inner diameter of less than 8 nm, a length of 10 to 30 μm, and a purity of 95%, and pure water is used as a solvent in the hydrophobic agent-filler solution;

[0107] (S3) The pretreated gas diffusion layer prepared in step (S1) is immersed in the hydrophobic agent-filler solution prepared in step (S2), and after ultrasonic immersion for 1 hour, it is placed in an oven for drying treatment (340°C, 60 minutes to remove moisture) to obtain a gas diffusion layer.

[0108] The performance (thermal conductivity and hydrophobicity) of the composite gas diffusion layer prepared in Comparative Examples 2 to 5 is much worse than that of the fuel cell composite gas diffusion layer prepared in Example 1. It can be found from Example 1 and Comparative Examples 2 to 5 that the step-by-step temperature drying treatment can avoid stress concentration and material damage caused by sudden temperature changes, help maintain or improve the mechanical strength and stability of the material, and further improve the hydrophobicity to prevent the fuel cell from being flooded during operation.

[0109] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the explanation of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A fuel cell composite gas diffusion layer, characterized in that: The fuel cell composite gas diffusion layer is obtained by immersing the substrate in a filler solution and then drying it by step-by-step heating. The substrate is a commercial gas diffusion layer and the filler is a high thermal conductivity material.

2. A fuel cell composite gas diffusion layer according to claim 1, characterized in that: The commercial gas diffusion layer is selected from TORAY TGL-R-060 gas diffusion layer, German SGL Gas diffusion layer, one of the following: AvCarb H14CX483 gas diffusion layer from the United States, JNTGHCP120 gas diffusion layer from South Korea, or Freudenberg nonwoven-based gas diffusion layer; The high thermal conductivity material is selected from one of carbon nanotubes, graphene, acetylene black or carbon fiber.

3. A fuel cell composite gas diffusion layer according to claim 2, characterized in that: The commercial gas diffusion layer is TORAY TGL-R-060 gas diffusion layer, and the high thermal conductivity material is carbon nanotube.

4. A method for preparing a fuel cell composite gas diffusion layer according to any one of claims 1 to 3, characterized in that: The following steps are involved: (S1) dissolving the filler and the hydrophobic agent and mixing them to obtain a hydrophobic agent-filler solution; (S2) Immersing the pretreated substrate in the hydrophobic agent-filler solution prepared in step (S1), and then performing a stepwise temperature-raising drying process to obtain a fuel cell composite gas diffusion layer.

5. The method for preparing a fuel cell composite gas diffusion layer according to claim 4, characterized in that: In step (S1), the hydrophobic agent is a fluoride; In the hydrophobic agent-filler solution, one or more of pure water, ethanol, acetone or isopropanol is used as solvent; the concentration of the hydrophobic agent is 1-15wt%, and the concentration of the filler is 0.1-0.8wt%.

6. The method for preparing a fuel cell composite gas diffusion layer according to claim 4, characterized in that: In step (S2), the pretreated substrate is obtained by the following method: The substrate is cleaned with acid and then dried to obtain a pretreated substrate.

7. The method for preparing a fuel cell composite gas diffusion layer according to claim 6, characterized in that: The acid is selected from one of sulfuric acid, hydrochloric acid or nitric acid; During the drying process, the temperature is 60-100°C.

8. The method for preparing a fuel cell composite gas diffusion layer according to claim 4, characterized in that: In step (S2), the impregnation is selected from one of normal pressure impregnation, vacuum impregnation or ultrasonic impregnation; The soaking time is 1 to 24 hours.

9. The method for preparing a fuel cell composite gas diffusion layer according to claim 4, characterized in that: In step (S2), the step-by-step drying includes a first drying process and a second drying process; During the first drying process, the temperature is 80-120°C and the time is 20 minutes to 1 hour; During the second drying process, the temperature is 340-380°C and the time is 20 minutes to 1 hour.

10. Use of the fuel cell composite gas diffusion layer according to any one of claims 1 to 3 in preparing a high power density fuel cell.