High-performance fuel cell 3D flow field and preparation method and application thereof

Abstract

The invention discloses a high-performance fuel cell 3D flow field and a preparation method and application thereof, and belongs to the technical field of fuel cells. The preparation method at least comprises the steps that a pattern layer with a 3D pattern is formed on the surface of a supporting layer through a mold suction filtration method, and the gas diffusion layer with the 3D pattern is obtained after demolding-heat treatment. The mold suction filtration method comprises a method of combining a mold reverse patterning technology and a vacuum suction filtration technology, and a mold with a 3D pattern is placed on the surface of the supporting layer to be subjected to vacuum suction filtration to form a pattern layer. The mold suction filtration combined method adopted by the invention not only is simple, but also can be combined with the prior art to carry out complex flow field structure design, and is directly matched with a general traditional bipolar plate in the prior art to construct a 3D flow field with high fuel cell performance, the optimization cost of the flow field structure does not need to be increased, the flexibility is high, and the application range is wide. Therefore, the research and development cost and the processing difficulty are greatly reduced, and the method has great market popularization and application values.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells. Specifically, it relates to a high-performance fuel cell 3D flow field and its preparation method and application. Background Art

[0002] With the rapid development of technology and industry, the demand for energy has increased day by day, resulting in serious environmental pollution and energy crisis. Proton exchange membrane fuel cells (PEMFCs) fueled by hydrogen have received great attention and have been applied in the fields of transportation, industry, and energy storage. PEMFCs use only hydrogen and oxygen as fuels, and only by-products water and a small amount of waste heat are generated during the power generation process. Compared with the huge gas emissions, waste heat, and cooling requirements in traditional power generation systems, PEMFCs are considered to be one of the most promising next-generation energy devices due to their high energy density, high energy conversion rate, and zero carbon emissions.

[0003] The flow field is a key component of traditional proton exchange membrane fuel cells, responsible for evenly distributing hydrogen and oxygen (or air) to the electrodes, ensuring that reactants can effectively reach the catalyst layer for electrochemical reactions, and removing the product water generated in the catalyst layer from the electrode area to avoid flooding, which can cause the catalyst active sites to be covered and hinder gas transport in the cell, resulting in performance degradation. Therefore, the design of the flow field is crucial for improving the performance of fuel cells. It not only requires a suitable structure to improve water management and optimize gas flow and distribution, but also needs to have good electrical conductivity and certain mechanical strength to maintain the integrity and stability of the cell components. The traditional fuel cell flow field is provided by a graphite bipolar plate, with structures such as parallel, serpentine, interdigitated, and wavy, and the manufacturing process is relatively simple, but there are problems such as uneven gas distribution and limited water drainage, making it difficult to further improve the performance of fuel cells. For example, Chinese Utility Model Patent CN220895554U discloses a new flow field for fuel cells. This flow field area consists of multiple raised ridges and multiple flow channels, where the wavy ridges and straight-channel ridges are arranged alternately, which can promote gas convection in the flow field to improve mass transfer ability, and at the same time can accelerate the discharge of liquid water in the flow field, effectively preventing flooding. This flow field can be used for both the cathode to enhance mass transfer and as the anode flow field, with good universality. However, in actual production and large-scale applications, this relatively complex flow field structure lacks a certain degree of flexibility in dealing with fuel cells of different effective areas, which will increase the difficulty and cost of the research and development and preparation of bipolar plates. Chinese Invention Patent CN118147631A discloses a method for preparing a flow field of a fuel cell metal bipolar plate. Compared with graphite bipolar plates, metal bipolar plates have excellent electrical and thermal conductivity, and are more suitable for miniaturized production, and have good application prospects in fuel cell stacks. Apply clad alloy powder on the surface of the stainless steel plate according to the set flow channel structure, and then use laser cladding to form a surface clad surface. Then, through secondary surface treatment and polishing, a straight-channel flow field of the metal bipolar plate is obtained, which alleviates the problem of reduced electrical conductivity caused by pits, cracks, etc. at the ridges of the metal flow field to a certain extent. However, due to the overall weakly acidic environment of PEMFC, this will cause the oxide film of the metal flow field to thicken, reducing the cell performance.

[0004] Therefore, the fuel cell flow field needs to have an advanced structure and suitable materials to ensure efficient mass transfer ability and stable properties to further improve the power density of the fuel cell. At present, the flow fields with traditional structures have problems such as uneven gas distribution, excessive pressure drop, and limited drainage efficiency, and can no longer meet the normal operation of fuel cells with high current density. However, although various new structures proposed in recent years, such as biomimetic flow fields and 3D flow fields with baffles, have certain improvements in mass transfer, the complex structures lead to great manufacturing difficulty and high application cost, and even most of them only stay in the stage of theoretical simulation. Chinese invention patent CN115719818A discloses a fuel cell gas diffusion layer with an ordered structure and its preparation method. The gas diffusion layer of this invention includes a main structure with ordered square holes, a mesh structure, and a microporous layer; the mesh structure is located on one side of the main structure, and the microporous layer slurry is coated on the mesh structure to obtain the microporous layer; and the main structure and the mesh structure are prepared by 3D printing technology; and the main structure and the mesh structure are carbonized; then the carbonized main structure and mesh structure are hydrophobized with a hydrophobic agent; the microporous layer slurry is coated on the mesh structure of the gas diffusion layer by screen printing to prepare the microporous layer; finally, the gas diffusion layer is obtained by carbonization treatment. However, this technology directly uses 3D printing to obtain the main structure and the mesh structure, and then coats the microporous layer on the mesh structure; but the flow field structure design of this technology is complex, resulting in high production cost and difficult to be widely promoted and applied.

[0005] In view of the above limitations, the present invention provides a 3D flow field with a new structure, which has simple preparation process, easily available raw materials, and the characteristics of low design and production cost of the flow field structure while improving the working performance of the fuel cell. Summary of the Invention

[0006] The object of the present invention is to provide a high-performance fuel cell 3D flow field, its preparation method and application to overcome the deficiencies of the prior art.

[0007] To achieve the above object of the invention, the present invention adopts the following technical solutions.

[0008] As the first aspect of the invention, the present invention provides a preparation method of a 3D patterned gas diffusion layer, which at least includes: forming a pattern layer with a 3D pattern on the surface of a support layer by using a mold suction filtration method, and obtaining a 3D patterned gas diffusion layer after demolding-thermal treatment; the mold suction filtration method includes: combining a mold reverse patterning technique with a vacuum suction filtration technique, placing a mold with a 3D pattern on the surface of the support layer, and performing vacuum suction filtration on the mold to form the pattern layer stacked on the support layer.

[0009] Preferably, the pattern layer is obtained by pouring carbon paper slurry into the mold, obtaining a wet carbon paste blank after vacuum filtration, and then performing demolding-thermal treatment.

[0010] Preferably, the carbon paper slurry includes at least carbon fibers and / or carbon nanotubes.

[0011] Preferably, the mold with a 3D pattern is prepared by any one of 3D printing technology, laser engraving technology or machining technology, but is not limited to the listed processing technologies.

[0012] Preferably, the heat treatment includes calcining at 300-400 °C for 15-60 min.

[0013] Preferably, the preparation method of the 3D patterned gas diffusion layer specifically includes the following steps:

[0014] S1. Provide carbon paper slurry;

[0015] Prepare carbon fiber dispersion liquid and carbon nanotube dispersion liquid respectively, and prepare the first carbon paste, the second carbon paste and the third carbon paste according to different ratios;

[0016] S2. Provide a filtration mold;

[0017] Design a 3D pattern as needed, and then use any one of 3D printing technology, laser engraving technology or machining technology to prepare the mold;

[0018] S3. Provide a microporous layer;

[0019] Pour the first carbon paste on the surface of the filter membrane, and dry the water by one-time filtration to form the microporous layer;

[0020] S4. Provide a support layer;

[0021] Pour the second slurry on the surface of the microporous layer, and dry the water by secondary vacuum filtration to form a support layer on the surface of the microporous layer;

[0022] S5. Provide a pattern layer;

[0023] Place the filtration mold on the surface of the support layer, pour the third slurry into the filtration mold, and perform reverse patterning by three-time vacuum filtration to form a pattern layer on the surface of the support layer;

[0024] S6. Heat treatment

[0025] Calcine the microporous layer-support layer-pattern layer obtained in S5 at 300-400 °C for 30-60 min, and the 3D patterned gas diffusion layer is obtained after demolding.

[0026] Preferably, the carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0027] Preferably, in S1, the first slurry is composed of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0028] Preferably, the mass ratio of the single-walled carbon nanotubes to the multi-walled carbon nanotubes is 1:6 - 8.

[0029] Preferably, the total loading of the microporous layer is 1 - 3 mg / cm -2 .

[0030] Preferably, the second slurry is composed of carbon fiber, single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0031] Preferably, the mass ratio of the carbon fiber, single-walled carbon nanotubes, and multi-walled carbon nanotubes is 1:1.5 - 3.5:16 - 19.

[0032] More preferably, the mass ratio of the carbon fiber, single-walled carbon nanotubes, and multi-walled carbon nanotubes is 1:2.5:17.5.

[0033] Preferably, the loading of the support layer is 2 - 4 mg / cm -2 .

[0034] More preferably, the loading of the support layer is 3.75 mg / cm -2 .

[0035] Preferably, the third slurry is composed of carbon fiber, single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0036] Preferably, the mass ratio of the carbon fiber, single-walled carbon nanotubes, and multi-walled carbon nanotubes is 4 - 8:1:7 - 11.

[0037] More preferably, the mass ratio of the carbon fiber, single-walled carbon nanotubes, and multi-walled carbon nanotubes is 6:1:9.

[0038] Preferably, the loading of the pattern layer is 5 - 8 mg / cm -2 .

[0039] More preferably, the loading of the pattern layer is 6 mg / cm -2 .

[0040] Preferably, in S3 - S5, the vacuum degrees of the first filtration, the second filtration, and the third filtration are all 0.06 Mpa - 0.1 Mpa; the filtration time is 1 - 15 min.

[0041] Preferably, the first slurry and / or the second slurry and / or the third slurry further includes a water repellent.

[0042] Preferably, the addition amount of the hydrophobic agent is 10-30 wt% of the first slurry and / or the second slurry and / or the third slurry.

[0043] Preferably, the hydrophobic agent is a polytetrafluoroethylene solution; the concentration is 10-25 wt%.

[0044] As a second aspect of the invention, the present invention also provides a 3D patterned gas diffusion layer prepared by the foregoing preparation method.

[0045] Preferably, it includes a microporous layer - a support layer - a pattern layer; the pattern layer is a 3D patterned structure laminated on the surface of the support layer.

[0046] As a third aspect of the invention, the present invention also provides a 3D flow field composed of a graphite bipolar plate and a 3D patterned gas diffusion layer prepared by the foregoing preparation method, or a composite of the 3D patterned gas diffusion layer as described above; a 3D flow field space is formed between the bipolar plate and the 3D patterned gas diffusion layer, which can achieve effective transmission of water and gas separation.

[0047] As a fourth aspect of the invention, the present invention also provides a membrane electrode including at least a 3D patterned gas diffusion layer prepared by the preparation method of the 3D patterned gas diffusion layer as described above, or the 3D patterned gas diffusion layer as described above.

[0048] As a fifth aspect of the invention, the present invention also provides a fuel cell including at least a 3D patterned gas diffusion layer prepared by the preparation method of the 3D patterned gas diffusion layer as described above, or the 3D patterned gas diffusion layer as described above; or the membrane electrode as described above.

[0049] The present invention breaks through the limitations of complex flow field structure design. Through a simple and easily available 3D patterned gas diffusion layer and a traditional graphite bipolar plate, a new 3D flow field structure is assembled. Among them, the 3D patterned gas diffusion layer is prepared by a simple method of layer-by-layer die vacuum filtration and heat treatment, using carbon fiber and carbon nanotube as raw materials, and a gas diffusion layer with a simple process and rich pores and a 3D concave-convex structure is prepared. By changing the die design drawing, the 3D pattern structure of the gas diffusion layer can be flexibly changed to match traditional bipolar plates with different flow field structures, such as parallel, serpentine, and waveform. At the same time, the traditional bipolar plate is retained, and no additional cost and burden are added for the optimization of the flow field structure. In the 3D flow field space composed of these two components, water and gas achieve highly separated and effective transmission.

[0050] Compared with the prior art, the present invention has at least the following beneficial effects:

[0051] 1. By adopting the technical solution of the present invention, a gas diffusion layer with a 3D pattern is prepared through a simple die-assisted vacuum filtration method. On the one hand, the obtained gas diffusion layer can not only achieve the separation of water vapor in the mass transfer process, with efficient mass transfer and strong drainage ability; but also can make full use of the good electrical conductivity of the carbon material itself, so that the obtained gas diffusion layer has better electrical conductivity than the commercial diffusion layer, improving the battery performance of the fuel cell.

[0052] 2. The method of die filtration combination adopted in the present invention is not only simple, but also can combine with 3D printing technology, laser engraving, machining, etc. to realize the pattern design of complex flow field structures, which is extremely flexible and can match with traditional bipolar plates with different flow field structures commonly used in the prior art, such as parallel, serpentine, waveform and other structures, to realize the construction of 3D flow fields, without increasing the cost of optimizing the flow field structure, thus greatly reducing the R & D cost and processing difficulty of 3D flow fields, and having great market promotion and application value. Brief Description of the Drawings

[0053] Figure 1 It is a schematic diagram of the preparation process of the gas diffusion layer provided by the present invention.

[0054] Figure 2 It is a SEM photo of the cross-section of the 3D flow field provided by the present invention.

[0055] Figure 3 It is a comparison diagram of the gas pressure drop between the 3D flow field provided by Example 1 of the present invention and the traditional flow field provided by Comparative Example 1.

[0056] Figure 4 It is a comparison diagram of the sheet resistance (R □ ) between the 3D flow field provided by Example 1 of the present invention and the traditional flow field provided by Comparative Example 1.

[0057] Figure 5 It is a comparison diagram of the polarization curve performance between the 3D flow field provided by Example 1 of the present invention and the traditional flow field provided by Comparative Example 1.

[0058] Figure 6 It is a comparison diagram of the battery impedance test between the 3D flow field provided by Example 1 of the present invention and the traditional flow field provided by Comparative Example 1.

[0059] Figure 7 It is the polarization curve of the fuel cell assembled with the 3D flow field provided by Example 1 of the present invention within different relative humidity ranges.

[0060] Figure 8 It is a comparison diagram of the power density at 0.6V under different humidities between the 3D flow field provided by Example 1 of the present invention and the traditional flow field provided by Comparative Example 1.

[0061] Figure 9 It is a graph showing the relationship between the sheet resistance changes of carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes with different loadings of the present invention and the pattern layer.

[0062] Figure 10 It is a graph showing the relationship between the gas flux coefficient changes of carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes with different loadings of the present invention and the pattern layer.

[0063] Figure 11 It is a graph showing the relationship between the power density changes at 0.6V of carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes with different loadings of the present invention and the pattern layer.

[0064] Figure 12 It is a graph showing the power density changes at 0.6V of different loadings of the pattern layer of the present invention.

[0065] Figure 13 It is a graph showing the current density changes at 0.5V of different loadings of the pattern layer of the present invention.

[0066] Figure 14 It is a SEM cross-sectional view of the 3D patterned gas diffusion layer provided in Example 1 of the present invention.

[0067] Figure 15 It is a SEM cross-sectional view of the 3D patterned gas diffusion layer provided in Example 2 of the present invention.

[0068] Figure 16 It is a SEM cross-sectional view of the planar gas diffusion layer provided in Comparative Example 2 of the present invention.

[0069] Figure 17 It is a SEM cross-sectional view of the 3D patterned gas diffusion layer provided in Example 3 of the present invention.

[0070] Figure 18 It is a graph comparing the polarization curve performances of the gas diffusion layers provided in Example 2, Example 3 and Comparative Example 2 of the present invention.

[0071] Figure 19 It is a graph comparing the polarization curve performances of the gas diffusion layers provided in Example 3 and Example 3 of the present invention. Detailed implementation manners

[0072] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Apparently, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0073] The present invention provides a method for preparing a 3D patterned gas diffusion layer, which includes combining a mold reverse patterning technique with a vacuum filtration technique. By adding a carbon paper slurry to a mold with a 3D pattern and then subjecting the carbon paper slurry to vacuum filtration to obtain a carbon paper precursor (or a wet carbon paper blank), the 3D pattern of the mold is reverse patterned on the carbon paper precursor. Finally, after carbonization treatment, a 3D patterned gas diffusion layer is obtained.

[0074] Refer to Figure 1 , which is a schematic flow diagram for the preparation of a gas diffusion layer. As can be seen from the figure, the obtained 3D patterned gas diffusion layer includes a microporous layer and a 3D patterned support layer. Among them, the 3D patterned support layer is obtained by the reverse patterning effect of the mold.

[0075] Specifically, the preparation steps include:

[0076] (1) Provide a microporous layer;

[0077] Prepare a first carbon paper slurry (or first carbon paste) containing a hydrophobic agent and pour the first carbon paper slurry onto the surface of an MCE filter membrane; perform vacuum filtration for about 2 minutes with a vacuum degree of 0.06 Mpa - 0.1 Mpa. When no water droplets flow down, the vacuum filtration is completed, and a microporous layer is obtained;

[0078] (2) Provide a support layer;

[0079] Prepare a second carbon paper slurry (or second carbon paste) containing a hydrophobic agent and pour the carbon paper slurry onto the surface of the microporous layer. Perform vacuum filtration with a vacuum degree of 0.06 Mpa - 0.1 Mpa. When no water droplets flow down, the vacuum filtration is completed, and a support layer is formed;

[0080] (3) Provide a 3D patterned mold;

[0081] Use 3D printing technology, laser engraving technology, machining technology, etc. to process a reverse mold with the required 3D pattern;

[0082] (4) 3D pattern layer;

[0083] Place the mold on the support layer, pour a third carbon paper slurry (or third carbon paste) into the mold, perform vacuum filtration with a vacuum degree of 0.06 Mpa - 0.1 Mpa. When no water droplets flow down, the vacuum filtration is completed, and the support layer is reverse patterned to obtain a 3D pattern layer with the required pattern;

[0084] (5) Heat treatment;

[0085] Heat-treat the obtained support layer and microporous layer at 350 °C for 30 minutes, and then demold to obtain a 3D patterned gas diffusion layer with the required pattern.

[0086] Furthermore, in the present invention, the first carbon paper slurry is subjected to a first vacuum filtration to obtain a microporous layer; then a second slurry is added to the surface of the microporous layer for a second vacuum filtration to obtain a support layer. Finally, a mold with a 3D pattern is covered on the support layer, a third slurry is added into the mold, and then a third vacuum filtration is carried out to achieve reverse patterning, obtaining a pattern layer with a pattern opposite to the 3D pattern of the mold; finally, through high-temperature calcination, impurities in the carbon paper precursor are removed and the strength of the carbon paper is increased, and demolding is carried out to obtain a gas diffusion layer with 3D patterning.

[0087] The gas diffusion layer of the present invention uses single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon fibers as raw materials, and a carbon paper slurry is prepared by adjusting the proportions of the three to obtain a microporous layer and a support layer. Then, combined with 3D printing technology and the method of vacuum filtration for patterning, the loading of the gas diffusion layer is optimized, thereby improving the electrochemical performance of the battery. First of all, single-walled carbon nanotubes (SWCNT) can enhance conductivity. As the content of SWCNT increases, the sheet resistance of the diffusion layer significantly decreases, showing good conductivity. However, its structure is relatively dense, and too much SWCNT will cause the gas flux of the diffusion layer to decrease and the resistance to gas permeation to increase. Therefore, the present invention optimizes the power density of the battery by optimizing the content of SWCNT in the pattern layer.

[0088] Secondly, carbon fibers (CF) mainly play two roles in the pattern layer, enhancing conductivity and increasing porosity. If the content of CF is too small, the conductivity of the pattern layer cannot be improved, while too much CF will not be embedded in the diffusion layer but float on the surface, increasing the surface roughness and resulting in an increase in contact resistance.

[0089] Finally, multi-walled carbon nanotubes (MWCNT) can increase the gas permeability of the diffusion layer. However, due to its mostly small pore structure, when the content is too low, the gas flux of the diffusion layer is limited, and when the content is too high, it will cause the thickness of the diffusion layer to be too large, that is, it cannot improve the conductivity of the entire gas diffusion layer and will further increase the sheet resistance of the battery.

[0090] The present invention prepares a gas diffusion layer with a 3D pattern by using a mold with a 3D pattern combined with the method of vacuum filtration. The gas diffusion layer only needs to be prepared by a carbon material with good conductivity, and can also be matched with the existing bipolar plates in the prior art to construct a 3D flow field, which can greatly simplify the R & D path of designing 3D patterns. In particular, the entire preparation method is simple and has low cost. Moreover, the mold with a 3D pattern can be designed with a 3D pattern by using 3D printing technology, laser engraving technology or machining technology. As long as the technology can obtain a mold with the required 3D pattern, it can be applied to the preparation of the gas diffusion layer, and the present invention does not make a limitation.

[0091] The technical solutions of the present invention will be explained and described in more detail below in conjunction with several embodiments.

[0092] Example 1

[0093] This example provides a method for constructing a 3D flow field, including preparing a 3D patterned gas diffusion layer using carbon materials. The carbon materials include carbon fibers, single-walled carbon nanotubes, and multi-walled carbon nanotubes. Due to the different roles and properties of the three, the ratios of the three are optimized. By adjusting the different ratios of the three, the concentrations of the single components (all mass fractions) are as follows: the proportions of SWCNT are 0%, 3%, 5%, 7%, and 9% respectively; the proportions of CF are 22%, 26%, 28%, 30%, 32%, and 35% respectively; the proportions of MWCNT are 37%, 40%, 43%, 45%, 47%, and 49% respectively; the total proportion is 80% (the remaining 20% is the binder PTFE).

[0094] The relationships between the contents of carbon fibers, single-walled carbon nanotubes, and multi-walled carbon nanotubes and the sheet resistance, gas flux coefficient, and power are investigated and analyzed respectively. See Figures 9 - 11 , which are the comparison diagrams of the changes in the sheet resistance, gas flux coefficient, and power density at 0.6V of the patterned layer when the total mass of carbon fibers, single-walled carbon nanotubes, and multi-walled carbon nanotubes is 80% (the mass fraction of the binder PTFE remains 20% unchanged). By optimizing the loading of carbon fibers (CF), the total loading of the patterned layer is increased or decreased to maintain the best porosity and hydrophobicity of the patterned layer. Specifically,

[0095] First, the loading of carbon fibers (CF) is optimized (when the area is the same, the loading ratio is the mass ratio), with SWCNT and MWCNT being 0.4mg cm -2 and 2.8mg cm -2 respectively, and remaining unchanged. PTFE always accounts for 20% of all components (SWCNT + CF + MWCNT + PTFE) in the patterned layer. Physical property characterization and battery tests are carried out on 3D patterned gas diffusion layers with different CF loadings (1.2mg cm -2 , 1.6mg cm -2 , 2.0mg cm -2 , 2.4mg cm -2 , 2.8mg cm -2 , 3.2mg cm -2 ).

[0096] CF mainly plays two roles in the pattern layer, enhancing conductivity and increasing porosity. As the CF loading increases, initially the sheet resistance of the diffusion layer remains stable because the CF content is too low to significantly improve conductivity. When the CF loading continues to increase, the sheet resistance decreases significantly, indicating a significant increase in the conductivity of the diffusion layer. Secondly, increasing CF is beneficial for constructing a pore structure with larger pores in the diffusion layer. CFs contact and build on each other, providing more pore structures in the diffusion layer. Therefore, the air permeability coefficient increases significantly with the increase in CF loading. However, more CF is not always better. 2.4 mg / cm² -2 is the optimal loading because too much CF will no longer be embedded in the diffusion layer but float on the surface, increasing the surface roughness and resulting in an increase in contact resistance.

[0097] Then, the loading of single-walled carbon nanotubes (SWCNTs) is optimized. The optimal loading of CF, which is 2.4 mg / cm² -2 , remains unchanged, and the MWCNT loading is still set at 2.8 mg / cm² -2 unchanged. The SWCNT loadings are 0 mg / cm² -2 , 0.2 mg / cm² -2 , 0.4 mg / cm² -2 , 0.6 mg / cm² -2 , 0.8 mg / cm² -2 . SWCNTs are beneficial for enhancing the conductivity of the diffusion layer. As the loading increases, the sheet resistance of the diffusion layer decreases significantly. However, its structure is relatively dense, and too many SWCNTs will reduce the air permeability of the diffusion layer and increase the resistance to gas permeation. Therefore, the optimal SWCNT loading in the pattern layer is 0.4 mg / cm² -2 , at which point the power density of the battery is the highest.

[0098] Finally, the loading of multi-walled carbon nanotubes (MWCNTs) is optimized. The optimal loadings of CF and SWCNT have been determined to be 2.4 mg / cm² -2 and 0.4 mg / cm² -2 respectively, and their loadings remain unchanged. The MWCNT loadings are 2.4 mg / cm² -2 , 2.8 mg / cm² -2 , 3.2 mg / cm² -2 , 3.6 mg / cm² -2 , 4.0 mg / cm² -2 , 4.4 mg / cm² -2。The structure of multi-walled carbon nanotubes (MWCNT) is relatively loose, which can also increase the air permeability of the diffusion layer. However, most of them are small pore structures, and the gas flux coefficient of the diffusion layer increases with the increase of its content. However, the content should not be too much, otherwise it will increase the thickness of the entire diffusion layer and has no improvement effect on the overall conductivity. Instead, it slightly increases the sheet resistance. Obviously, an appropriate MWCNT content can achieve the best performance of the battery. The loose structure of MWCNT can also increase the air permeability of the diffusion layer, and most of them are small pore structures. The gas flux coefficient of the diffusion layer increases with the increase of its loading. Similarly, the loading should not be too much, otherwise it will increase the thickness of the entire diffusion layer and has no improvement effect on the overall conductivity. Instead, it slightly increases the sheet resistance. After optimizing the MWCNT loading, the optimal MWCNT loading in the pattern layer is 3.6 mg cm -2 , and the best performance of the battery can be achieved under this condition.

[0099] Furthermore, the loading of the patterned layer is optimized.

[0100] The 3D flow field constructed with the optimal content of each component in the above-mentioned pattern layer has a total material loading of (SWCNT + CF + MWCNT + PTFE) of 8 mg cm -2 , and below, while keeping the proportion of each component unchanged, the optimal loading of the pattern layer is analyzed by adjusting the total loading. The total loading is changed to 0 mg cm -2 , 3 mg cm -2 , 5 mg cm -2 , 6 mg cm -2 , 7 mg cm -2 , 8 mg cm -2 . Refer to Figure 12 and Figure 13 . After battery testing, under three air supply conditions, namely three air stoichiometric ratios (1.5, 2.0, 2.5), both the power density at 0.6 V and the current density at 0.5 V show a trend of first increasing and then decreasing with the increase of the loading. The pattern layer with a loading of 6 mg cm -2 has the best performance and can jointly construct the most favorable 3D flow field for efficient mass transfer with the traditional bipolar plate.

[0101] After the above loading optimization, the optimal components of the pattern layer are CF (2.4 mg cm -2 ), SWCNT (0.4 mg cm -2 ), MWCNT (3.6 mg cm -2 ). At this time, the PTFE loading with a proportion of 20% is 1.6 mg cm -2, so the optimal proportion of each component in the pattern layer is 30%, 5%, 45% and 20% respectively.

[0102] The optimal mass ratio of carbon fiber, single-walled carbon nanotube, and multi-walled carbon nanotube is 6:1:9. Taking this ratio as an example, the 3D flow field is constructed below.

[0103] Furthermore, the specific steps of the 3D flow field construction method provided in this embodiment include:

[0104] 1. Dispersion of carbon materials

[0105] (1) Dispersion of carbon fiber: Weigh 500 mg of short-cut carbon fiber (CF) with a length of 150 μm and measure 50 mL of deionized water. Disperse 50 mg of short-cut carbon fiber in 50 mL of deionized water, add sodium dodecylbenzenesulfonate (SDBS) (mass ratio of CF:SDBS = 1:10), and then treat it with a 500 W ultrasonic cleaner for 10 min. Stir evenly with a glass rod while ultrasonicating to obtain a short-cut carbon fiber slurry with a concentration of 10 mg / mL. -1 of short-cut carbon fiber slurry.

[0106] (2) Dispersion of multi-walled carbon nanotubes: Weigh 500 mg of multi-walled carbon nanotubes (MWCNT), measure 250 mL of deionized water, and add sodium dodecylbenzenesulfonate (SDBS) (mass ratio of MWCNT:SDBS = 1:15). Mix the multi-walled carbon nanotubes, SDBS, and deionized water evenly and ultrasonicate with a cell disrupter for 2 h to obtain a black and uniform dispersion with a concentration of 2 mg / mL, which is the MWCNT slurry. This MWCNT slurry has good stability and can be placed for up to several weeks without obvious precipitation. -1 of the black, uniform dispersion, that is, the MWCNT slurry. This MWCNT slurry has good stability and can be placed for up to several weeks without obvious precipitation in the dispersion.

[0107] (3) Dispersion of single-walled carbon nanotubes: Weigh 500 mg of single-walled carbon nanotubes (SWCNT), measure 250 mL of deionized water, and add sodium dodecylbenzenesulfonate (SDBS) (mass ratio of SWCNT:SDBS = 1:15). Mix the multi-walled carbon nanotubes, SDBS, and deionized water evenly and ultrasonicate with a cell disrupter for 3 h to obtain a black and uniform dispersion with a concentration of 2 mg / mL and can be placed for up to several weeks. There is no obvious precipitation in the dispersion. -1 of the black and uniform dispersion and can be placed for up to several weeks. There is no obvious precipitation in the dispersion.

[0108] 2. Design of the suction filtration mold

[0109] The mold is designed by the modeling software UGNX12.0 and printed by a BlueMaker 3D printer (BlueMaker Co., Ltd.). Different structures can be changed according to requirements to obtain molds of different shapes. The 3D printing material is white resin.

[0110] 3. Preparation of the 3D patterned gas diffusion layer

[0111] See Figure 1 , which is a process flow simulation diagram for the preparation of a 3D patterned gas diffusion layer, including mixing SWCNT slurry and MWCNT slurry with a hydrophobic agent and pouring it onto an MCE filter membrane, and forming a microporous layer through vacuum filtration; then mixing CF slurry, SWCNT slurry and MWCNT slurry with a hydrophobic agent and pouring it onto the surface of the microporous layer to form a support layer through vacuum filtration; finally, placing the mold obtained by 3D printing on the surface of the support layer, and then mixing CF slurry, SWCNT slurry and MWCNT slurry with a hydrophobic agent and introducing it into the mold, followed by vacuum filtration. After demolding, a patterned layer is formed on the surface of the support layer. Thus, a 3D patterned gas diffusion layer with a microporous layer - support layer - patterned layer is formed. Specifically, the preparation steps include:

[0112] (1) Mix the treated SWCNT slurry and MWCNT slurry according to a mass ratio of 1:7, where the proportion of SWCNT is 9.4 wt%, the proportion of MWCNT is 65.6 wt%, and finally add a polytetrafluoroethylene (PTFE) solution with a proportion of 25 wt% as a hydrophobic agent and mix evenly to obtain the final carbon paper slurry. Place a mixed fiber (MCE) filter membrane with a pore size of 0.45 μm on the suction filtration device, slowly pour the obtained slurry onto the MCE filter membrane, and draw out the water through vacuum filtration. Filter for about 2 minutes, with a vacuum degree of 0.06 Mpa to 0.1 Mpa. When no water droplets flow down, the suction filtration is completed, and the first layer of the 3D patterned gas diffusion layer - the microporous layer is obtained. The total loading of the overall material is 1.067 mg cm -2 .

[0113] (2) Mix the treated CF slurry, SWCNT slurry and MWCNT slurry according to a mass ratio of 1:2.5:17.5, where the proportion of CF is 3.5 wt%, the proportion of SWCNT is 8.8 wt%, the proportion of MWCNT is 61.4 wt%, and finally add a polytetrafluoroethylene (PTFE) solution with a proportion of 25 wt% as a hydrophobic agent and mix evenly to obtain the final carbon paper slurry. On the basis of the microporous layer obtained by the first-step suction filtration, slowly pour the obtained slurry onto the microporous layer, and through vacuum filtration, filter for about 5 minutes, with a vacuum degree of 0.06 Mpa to 0.1 Mpa. When no water droplets flow down, the suction filtration is completed; after the water is drawn out, the second layer of the 3D patterned gas diffusion layer - the support layer is obtained, and the overall loading is 3.75 mg cm -2 .

[0114] (3) Mix the processed CF slurry, SWCNT slurry, and MWCNT slurry according to a mass ratio of 6:1:9, where CF accounts for 30 wt%, SWCNT accounts for 5 wt%, and MWCNT accounts for 45 wt%. Finally, add a polytetrafluoroethylene (PTFE) solution with a proportion of 20 wt% as a water repellent and mix evenly to obtain the final carbon paper slurry. Based on the support layer obtained by suction filtration in the second step, place the 3D printed mold on the support layer, slowly pour the obtained slurry into the suction filtration device, perform vacuum suction filtration for about 10 minutes, with a vacuum degree of 0.06 Mpa to 0.1 Mpa. When no water droplets flow down, the suction filtration is completed. After drying the water, the third layer of the 3D patterned gas diffusion layer - the 3D pattern layer is obtained, with an overall loading of 6 mg cm -2 . After the water is completely dried, remove the mold, and then peel it off from the MCE membrane to obtain the carbon paper precursor. Place the carbon paper precursor in a muffle furnace and calcine it at 350 °C for 30 minutes to remove impurities in the carbon paper precursor and increase its strength. Finally, the required 3D patterned gas diffusion layer is obtained. This method can flexibly prepare gas diffusion layers with various shaped patterns only by designing the mold structure. Refer to Figure 2 , which shows a gas diffusion layer with a 3D pattern of a parallel structure.

[0115] 4. Construction of the 3D flow field

[0116] After the 3D patterned gas diffusion layer obtained in step 3, it is combined with a traditional graphite bipolar plate. The 3D patterned gas diffusion layer and the traditional bipolar plate jointly construct a more efficient mass transfer composite 3D flow field space.

[0117] Refer to Figure 2 , which is a cross-sectional SEM photo of the 3D flow field. The 3D pattern shown in the figure has a concave-convex structure. As shown in the figure, 1 is the traditional bipolar plate, 2 is the 3D flow field space, 3 is the 3D patterned gas diffusion layer, and 4 is the catalyst-coated proton exchange membrane. Assemble the prepared 3D patterned gas diffusion layer 3 with the traditional bipolar plate 1 and the catalyst-coated proton exchange membrane 4 to construct a 3D flow field space 2 in the membrane electrode of the fuel cell. In the 3D flow field space 2, there are two types of flow channels with different functions. Gas can be efficiently transported in the waveform flow channels provided by the traditional bipolar plate 1, while the product water can be quickly discharged in the parallel direct flow channels provided by the 3D patterned gas diffusion layer 3.

[0118] Refer to Figure 14 , which is a cross-sectional SEM photo of the 3D patterned gas diffusion layer of this embodiment. It can be seen from the figure that the three-layer stacked structure of the gas diffusion layer, and the thickness of the microporous layer is about 26 μm; the thickness of the support layer is about 80 μm; the height of the pattern layer is about 210 μm.

[0119] 5. Assemble the fuel cell

[0120] Cathode: Customized waveform flow channel graphite bipolar plate, self-made 3D patterned gas diffusion layer.

[0121] The catalyst-coated proton exchange membrane was purchased from Suzhou Shengnuoke Technology Co., Ltd. (China); the proton exchange membrane was Gore M820.15 (12 μm); the catalyst was JM Hispec 9100 (55.5 - 58.5%), and the platinum loadings of the anode and cathode were 0.12 mg cm -2 and 0.48 mg cm -2 .

[0122] Anode: Customized parallel flow channel graphite bipolar plate, SGL 28BC as the diffusion layer.

[0123] The effective area of the assembled fuel cell was 3×5 cm 2 .

[0124] Example 2

[0125] The difference between this example and Example 1 is only that the height of the three-layer structure is different, and other steps and conditions are the same.

[0126] The height of the three-layer structure was adjusted by the amount of the slurry used.

[0127] Refer to Figure 15 , which is the cross-sectional SEM image of the 3D patterned gas diffusion layer prepared in this example. The thickness of the microporous layer is about 45 μm; the thickness of the support layer is about 75 μm, the total thickness of the microporous layer and the support layer is 120 μm, the height of the pattern layer is 269 μm, and the loading of the pattern layer is 8 mg cm -2 .

[0128] Example 3

[0129] The difference between this example and Example 1 is only that the height of the three-layer structure is different, and other steps and conditions are the same.

[0130] The height of the three-layer structure was adjusted by the amount of the slurry used.

[0131] Refer to Figure 17 , which is the cross-sectional SEM image of the 3D patterned gas diffusion layer prepared in this example. The total thickness is about 332 μm; among them, the thickness of the microporous layer is about 45 μm; the thickness of the support layer is about 75 μm, the total thickness of the microporous layer and the support layer is 120 μm, the height of the pattern layer is 212 μm, and the loading of the pattern layer is 6 mg cm -2 .

[0132] Comparative Example 1

[0133] This comparative example uses a commercial gas diffusion layer (SGL 28BC) and a traditional flow field structure constructed with a traditional graphite bipolar plate.

[0134] Comparative Example 2

[0135] The difference between this comparative example and Example 2 is only that it does not include a pattern layer, only includes a microporous layer and a support layer. The thickness of the microporous layer is about 45 μm; the thickness of the support layer is about 75 μm; the loading of the pattern layer is 0 mg cm -2 .

[0136] That is, after the preparation of the microporous layer and the support layer is completed, it is immediately placed in a muffle furnace and calcined at 350 °C for 30 min to obtain the gas diffusion layer.

[0137] Refer to Figure 16 , which is the cross-sectional SEM image of the planar gas diffusion layer obtained in this comparative example. The total thickness of the microporous layer and the support layer is 120 μm.

[0138] Comparative Example 3

[0139] The difference between this comparative example and Example 3 is only that this comparative example does not include a pattern layer, only includes a microporous layer and a support layer; the total thickness of the gas diffusion layer is about 330 μm; the thickness of the microporous layer is about 43 μm, and the rest is the support layer.

[0140] Performance Characterization of 3D Flow Field

[0141] Test Parameters

[0142] Gas Pressure Drop: In the fuel cell flow field design, the gas pressure drop is an important parameter for evaluating its mass transfer and water management. Its physical meaning is the difference in gas pressure between the inlet and outlet of the flow field. A certain pressure drop is required in the fuel cell flow field to generate a pressure gradient in the flow channel, so as to accelerate the discharge of excess water in the flow channel. However, although an excessive pressure drop can make the reaction gas stay in the flow channel for a longer time and improve the utilization efficiency of reactants, it will greatly increase the burden and energy consumption of the entire fuel system, and generate a large stress difference in the battery, affecting the battery life. Therefore, an appropriate pressure drop is crucial for improving the performance of fuel cells.

[0143] Here, the present invention uses a self-made detection device for detection (for the preparation method of the detection device, refer to Fu, X. et al. Highly flat and highly homogeneous carbon paper with ultra-thin thickness for high-performance proton exchange membrane fuel cell (PEMFC). J. Power Sources 520, 230832 (2022)). The specific detection steps are as follows: (1) Consistent with the assembly conditions during battery testing, fix the 3D patterned gas diffusion layer and the traditional corrugated bipolar plate in the fixture. (2) Use an air pump to introduce gas into the fixture. Connect a gas flowmeter at the gas inlet, and connect one end of the pressure gauge to the inlet and the other end to the outlet to measure the pressure difference between the inlet and outlet, that is, the gas pressure drop. (3) Turn on the air pump and adjust the air flow rate into the fixture by adjusting the flow valve on the device, increasing the air flow rate from slow to fast. Take five equally spaced points within the flow range from 200 mL min -1 to 1000 mL min -1 , and record the pressure readings (unit: Kpa) at a specific air flow rate through the pressure gauge. (4) Repeat each set of data 3 - 5 times, eliminate abnormal points, and take the average value.

[0144] Conductivity: As a gas diffusion electrode, the gas diffusion layer plays a role in transferring electrons in the fuel cell and needs to have good electron conductivity to ensure that protons can be transported from the membrane to the electrode. Therefore, its conductivity is also an important physical property parameter that we need to investigate. We measure the sheet resistance (R □ ) of the gas diffusion layer to evaluate its conductivity.

[0145] In the experiment, a four-probe resistance meter is used. Take out the gas diffusion layer sample, sample at different points, measure 20 points and then take the average value to obtain the sheet resistance (R □ ) of the gas diffusion layer. Since the sheet resistance is also called the film resistance, its value is only related to the resistivity and thickness of the sample itself and has nothing to do with the sample size. The unit is ohm / sq, which can be directly translated as sheet resistance or surface resistance. Therefore, the smaller its value, the faster the electrons transfer within the diffusion layer. The calculation formula for the sheet resistance is: Rs = ρ / t (where ρ is the resistivity of the material and t is the thickness of the material).

[0146] Battery Performance: The prepared 3D patterned gas diffusion layer and traditional graphite bipolar plate are used for the cathode of the fuel cell, and the anode is an ordinary commercial carbon paper and traditional bipolar plate. The catalyst layer is a commercially purchased proton exchange membrane coated with platinum-carbon catalyst. The performance test of the obtained fuel cell is carried out under the hydrogen-air condition with a battery temperature of 80 °C, 60% relative humidity, a back pressure of 100 kPa, an air stoichiometry of 2.5, and a hydrogen stoichiometry of 1.5. The polarization curve test is recorded by scanning the voltage at intervals of 0.05 V, and the recorded voltage range is from 0.2 V to 1.0 V. The polarization curve is obtained by plotting. The electrochemical impedance test is carried out under the condition of a voltage of 0.6 V in a scanning frequency mode. The test frequency range is from 10 kHz to 0.1 Hz. The amplitude of the AC signal is maintained at 10% of the DC current, and the impedance diagram is obtained by plotting.

[0147] Moisture Resistance: The broad application prospects of fuel cells determine that they are very likely to face various complex environments. Under different environmental humidity conditions, the battery performance will be correspondingly affected. At lower humidity, the proton exchange membrane may be too dry, resulting in a decrease in conductivity and a reduction in electron transport efficiency. At higher humidity, if the gas diffusion layer and flow field fail to drain the excess water in the battery in time, it will lead to the occurrence of electrode flooding, thereby reducing the electrochemistry reaction rate and battery performance. We change the relative humidity in the range of 30% - 100% under the hydrogen-air condition with a battery temperature of 80 °C, a back pressure of 100 kPa, an air stoichiometry of 1.5, and a hydrogen stoichiometry of 1.5, and test the battery performance of the 3D flow field at different humidities. At this time, the air stoichiometry is reduced to 1.5. Under the condition of a lower air stoichiometry, the amount of air supplied to the fuel cell is reduced. With a small amount of air purge, the air mass transfer efficiency and water management ability of the 3D flow field can be analyzed more accurately through performance tests.

[0148] Test Results:

[0149] Refer to Figure 3 , which is a comparison chart of the gas pressure drop between the 3D flow field provided in Example 1 and the traditional flow field provided in Comparative Example 1. As can be seen from the figure, the 3D flow field structure is composed of a traditional graphite bipolar plate and a 3D patterned gas diffusion layer, and the traditional flow field structure is composed of a traditional graphite bipolar plate and an ordinary commercial gas diffusion layer. The gas pressure drops of the two flow fields at five different air flow rates are as Figure 1 shown. Compared with the traditional flow field, the 3D flow field has a lower gas pressure drop at any air flow rate, indicating that the stress distribution inside the battery is relatively uniform, and the system auxiliary power loss in actual applications is also smaller.

[0150] Refer to Figure 4 , which is the sheet resistance (R □) The comparison chart shows that the average sheet resistance (R □ ) of the ordinary commercial gas diffusion layer is 1.08 ohms / sq, while that of the 3D patterned gas diffusion layer is only 0.31 ohms / sq, which is 71% lower than that of the traditional gas diffusion layer. This indicates that the 3D patterned gas diffusion layer prepared by a simple vacuum filtration method using various carbon materials has better conductivity, ensuring that electrons can be efficiently transported from the proton exchange membrane to the electrode.

[0151] Refer to Figure 5 , for the comparison of the polarization curve performance between the 3D flow field provided in Example 1 and the traditional flow field provided in Comparative Example 1. The peak power density of the traditional flow field is 1.1 W / cm 2 , while the peak power density of the 3D flow field is 1.7 W / cm 2 , showing a significant 51% improvement in performance compared to the traditional flow field. That is, the 3D flow field can provide a more efficient path for the mass transfer in the battery, accelerating the transport of reaction gases from the outside to the catalytic layer to participate in the electrochemical reaction, and at the same time having a strong anti-flooding ability, enabling it to transport sufficient air and timely discharge a large amount of product water generated in the battery at a higher current density, thus significantly improving the battery performance.

[0152] Refer to Figure 6 , for the comparison of the battery impedance test between the 3D flow field provided in Example 1 and the traditional flow field provided in Comparative Example 1. In the high-frequency region dominated by electron transfer, the electron transfer resistance of the 3D flow field is close to that of the traditional flow field, indicating that they have similar electron transfer efficiencies; however, in the low-frequency region dominated by mass transfer, the mass transfer resistance of the 3D flow field is much smaller than that of the traditional flow field, about 0.3 times that of the traditional flow field, which shows that the excellent battery performance of the 3D flow field benefits from its superior mass transfer efficiency.

[0153] Refer to Figure 7 , for the polarization curve of the fuel cell assembled with the 3D flow field under the condition of an air stoichiometry of 1.5 within the range of relative humidity of 30% - 60%. As can be seen from the figure, the performance is slightly lower at 30% and 40% humidity, which is due to the lack of water in the proton exchange membrane of the battery, resulting in a slower conduction electron rate and slightly affecting the electrochemical reaction rate. When the humidity reaches 60% and above, the battery performance hardly changes, indicating that the proton exchange membrane is no longer dry and reaches the best conductivity at this time. More importantly, even when the humidity is increased to 100% and under the condition of low stoichiometry air supply, there is no flooding in the battery, which reflects the excellent drainage ability of the 3D flow field. The constructed water-gas separation and transport channels can efficiently discharge the excess water in the battery without adversely affecting the reaction rate of the catalytic layer.

[0154] Refer to Figure 8, Power density comparison at 0.6V of the 3D flow field provided in Example 1 and the traditional flow field provided in Comparative Example 1 under different humidities. Under the same conditions of humidity, air stoichiometry, back pressure and temperature, the same battery polarization curve test was carried out on the traditional flow field, and its power density at 0.6V was compared with that of the 3D flow field. First of all, the power density of the 3D flow field at any humidity is much higher than that of the traditional flow field, which shows the efficient mass transfer ability of the 3D flow field, and can transfer air to the catalyst layer more quickly and fully to participate in the electrochemical reaction; secondly, in the range of relative humidity of 30% - 60%, the performance fluctuation of the 3D flow field is only 7%, while that of the traditional flow field is 10%, which reflects the excellent moisture resistance of the 3D flow field, and can still maintain a high and stable power density to ensure the efficient working state of the battery under humidity changes.

[0155] Refer to Figure 18 , which are respectively the polarization curve performance comparison diagrams of Example 2, Example 3 and Comparative Example 2. As can be seen from the figure, the battery performance is the best when the height of the pattern layer is ~210μm, that is, when the loading is 6mg cm -2 , the battery performance is the best; and the performance of the gas diffusion layer with a patterned structure is significantly higher than that of the gas diffusion layer with a planar structure.

[0156] Refer to Figure 19 , which are respectively the polarization curve performance comparison diagrams of Example 3 and Comparative Example 3. As can be seen from the figure, the performance of the gas diffusion layer with a patterned structure is significantly higher than that of the gas diffusion layer with a planar structure.

[0157] From the above test results, it can be known that the present invention uses a simple mold-assisted vacuum filtration method to prepare a gas diffusion layer with a 3D pattern. The materials used are all carbon materials with good conductivity, so that the prepared gas diffusion layer has better conductivity than the commercial diffusion layer, and successfully realizes the water-vapor separation in the mass transfer process, and has efficient mass transfer and strong drainage ability.

[0158] On the other hand, the present invention can realize the design and preparation of a complex flow field structure through a simple method by 3D printer technology. Only using the 3D patterned gas diffusion layer, and can also be used in combination with a commercial and easily available traditional graphite bipolar plate, which has the advantages of simple process and low cost, and can also greatly reduce the research and development and production costs of the design method and preparation process of the flow field structure.

[0159] The present invention uses carbon nanotubes and carbon fibers as raw materials, and adopts the die suction filtration method and 3D printer technology to complete the preparation of the 3D patterned gas diffusion layer. The method is not only simple, but also can integrate the traditional graphite bipolar plate in the existing technology, and can greatly reduce the preparation cost of the 3D flow field structure. In particular, by adjusting single-walled carbon nanotubes, multi-walled carbon nanotubes and carbon fibers, the electrochemical performance of the battery can be improved.

[0160] It should be noted that the above is only the preferred embodiment of the present invention. The present invention has been described in detail with reference to the foregoing embodiments. For the embodiments, they are not used to limit the present application. Although for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a 3D patterned gas diffusion layer, characterized in that, At least including: forming a pattern layer with a 3D pattern on the surface of the support layer by the die suction filtration method, and obtaining a gas diffusion layer with 3D patterning after demolding-thermal treatment; The die suction filtration method includes: combining the die reverse patterning technology and the vacuum suction filtration technology, placing a die with a 3D pattern on the surface of the support layer, and performing vacuum suction filtration on the die to form the pattern layer stacked on the support layer.

2. The preparation method of the 3D patterned gas diffusion layer according to claim 1, wherein The pattern layer is a wet carbon paste blank obtained by pouring carbon paper slurry into the die and performing vacuum suction filtration. And / or, the carbon paper slurry at least includes carbon fiber and / or carbon nanotube; And / or, the die is prepared by any one of 3D printing technology, laser engraving technology or machining technology; And / or, the heat treatment includes calcining at 300-400 °C for 15-60 min.

3. The preparation method of the 3D patterned gas diffusion layer according to claim 1, characterized in that, The specific steps include: S1. Provide carbon paper slurry; Prepare carbon fiber dispersion liquid and carbon nanotube dispersion liquid respectively, and prepare carbon paste according to different ratios; the carbon paste includes the first carbon paste, the second carbon paste and the third slurry; S2. Provide a suction filtration die; Design a 3D pattern according to needs, and then use any one of 3D printing technology, laser engraving technology or machining technology to prepare a suction filtration die with a 3D pattern; S3. Provide a microporous layer; Pour the first carbon paste on the surface of the filter membrane, and dry the water by one-time suction filtration to form the microporous layer; S4. Provide a support layer; Pour the second slurry on the surface of the microporous layer, and dry the water by secondary vacuum suction filtration to form a support layer on the surface of the microporous layer; S5. Provide a pattern layer; Place the suction filtration die on the surface of the support layer, pour the third slurry into the suction filtration die, perform three-time vacuum suction filtration to achieve reverse patterning, and form a pattern layer on the surface of the support layer; S6. Heat treatment Calcine the microporous layer-support layer-pattern layer obtained in S5 at 300-400 °C for 30-60 min, and the 3D patterned gas diffusion layer is obtained after demolding.

4. The preparation method of the 3D patterned gas diffusion layer according to claim 3, characterized in that, Carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes; In S1, the first slurry is composed of single-walled carbon nanotubes and multi-walled carbon nanotubes; And / or, the mass ratio of the single-walled carbon nanotubes to the multi-walled carbon nanotubes is 1:6-8; and / or, the total loading of the microporous layer is 1 to 3 mg cm -2 ; The second slurry is composed of carbon fiber, single-walled carbon nanotubes and multi-walled carbon nanotubes; And / or, the mass ratio of carbon fiber, single-walled carbon nanotubes, multi-walled carbon nanotubes is 1:(1.5-3.5):(16-19); And / or, the mass ratio of carbon fiber, single-walled carbon nanotubes, multi-walled carbon nanotubes is 1:2.5:17.5; and / or, the loading of the support layer is 2 to 4 mg cm -2 ; and / or, the loading of the support layer is 3.75 mg cm -2 ; The third slurry is composed of carbon fiber, single-walled carbon nanotubes and multi-walled carbon nanotubes; And / or, the mass ratio of carbon fiber, single-walled carbon nanotubes, multi-walled carbon nanotubes is 4-8:1:7-11; And / or, the mass ratio of carbon fiber, single-walled carbon nanotubes, multi-walled carbon nanotubes is 6:1:9; and / or, the loading of the pattern layer is 5 to 8 mg cm -2 ; and / or, the loading of the pattern layer is 6 mg cm -2 ; And / or, in S3-S5, the vacuum degree of the one-time suction filtration, the secondary suction filtration and the three-time suction filtration is 0.06 Mpa-0.1 Mpa; the suction filtration time is 1-15 min.

5. The method for preparing a 3D patterned gas diffusion layer according to claim 3, wherein The first slurry and / or the second slurry and / or the third slurry further includes a water repellent; The addition amount of the water repellent is 10-30 wt% of the first slurry and / or the second slurry and / or the third slurry respectively; and / or, the water repellent is a polytetrafluoroethylene solution; the concentration is 10-25 wt%.

6. A 3D patterned gas diffusion layer is prepared by using the preparation method according to any one of claims 1-5.

7. The 3D patterned gas diffusion layer according to claim 6, wherein It sequentially includes a microporous layer - a support layer - a pattern layer from bottom to top; the pattern layer has a 3D patterned structure and is laminated on the surface of the support layer; the support layer is laminated on the surface of the microporous layer.

8. A 3D flow field, characterized in that, It is composed of a bipolar plate and a 3D patterned gas diffusion layer prepared by using the preparation method according to any one of claims 1-5, or is composed of a 3D patterned gas diffusion layer according to claim 6 or 7.

9. A membrane electrode at least includes a 3D patterned gas diffusion layer prepared by using the preparation method according to any one of claims 1-5, or a 3D patterned gas diffusion layer according to claim 6 or 7.

10. A fuel cell at least includes a 3D patterned gas diffusion layer prepared by using the preparation method according to any one of claims 1-5, or a 3D patterned gas diffusion layer according to claim 6 or 7, or a membrane electrode according to claim 9.

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