Carbon paper, its preparation methods and applications

Abstract

This application relates to the field of fuel cell technology, and provides a carbon paper, its preparation method, and its application. The carbon paper preparation method includes the following steps: performing papermaking treatment on mixed fibers to obtain carbon paper base paper, wherein the mixed fibers include carbon fibers and organic fibers, with organic fibers accounting for 5% to 20% of the total mass of carbon fibers and organic fibers; impregnating and hot-rolling the carbon paper base paper with a mixed slurry containing a binder to obtain a carbon paper precursor; and sequentially performing graphitization and hydrophobic treatment on the carbon paper precursor to obtain carbon paper. This carbon paper preparation method utilizes the high affinity between organic fibers and binders to enhance the bonding strength between binders and fibers in the carbon paper precursor, and carbonizes the organic fibers into new carbon fibers and the binder into a connecting phase, significantly improving the interlayer bonding strength, mechanical properties, and electronic conductivity of the carbon paper, and effectively inhibiting fiber delamination.

Description

Technical Field

[0001] This application belongs to the field of fuel cell technology, and in particular relates to a carbon paper, its preparation method and application. Background Technology

[0002] In a proton exchange membrane fuel cell (PEMFC), the gas diffusing layer (GDL) primarily functions to conduct current, transport gases, expel liquid water, and support the catalyst layer. It is one of the key components affecting the performance of the PEMFC and typically consists of a macroporous substrate (MPS) and a microporous layer (MPL). Carbon paper is commonly used as the material for the substrate.

[0003] To ensure the gas diffusion layer has good performance, carbon paper needs to have good air permeability, high electronic conductivity, uniform porous structure, good chemical stability and thermal stability, as well as a compact structure and a certain mechanical strength. This is to ensure the gas diffusion layer has good structural stability and prevent technical problems such as loosening or falling off of the base layer during the preparation and use of the gas diffusion layer.

[0004] In existing technologies, the main steps of carbon paper preparation methods include: first, pulping and papermaking carbon fibers to prepare carbon paper base paper; then, impregnating the carbon paper base paper in an organic resin binder solution; subsequently, curing, carbonization, and graphitization treatments are performed sequentially to finally obtain carbon paper. However, due to the smooth surface and high chemical inertness of carbon fibers, the bonding performance between carbon fibers and organic resins is poor, resulting in poor mechanical strength of the carbon paper after sintering, and making it prone to fiber peeling and insufficient interlayer bonding. Summary of the Invention

[0005] The purpose of this application is to provide a carbon paper, its preparation method, and its application, in order to solve the technical problem of poor mechanical strength of carbon paper in the prior art.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0007] Firstly, embodiments of this application provide a method for preparing carbon paper. The carbon paper preparation method of this application includes the following steps:

[0008] Step S10: The mixed fibers are subjected to papermaking treatment to obtain carbon paper base paper, wherein the mixed fibers include carbon fibers and organic fibers, and the organic fibers account for 5% to 20% of the total mass of carbon fibers and organic fibers.

[0009] Step S20: Impregnate and heat-roll the carbon paper base paper with a mixed slurry containing a binder to obtain a carbon paper precursor;

[0010] Step S30: The carbon paper precursor is subjected to graphitization and hydrophobic treatment in sequence to obtain carbon paper.

[0011] The carbon paper preparation method of this application first prepares carbon paper base paper using a mixed fiber containing carbon fiber and organic fiber. Then, the carbon paper base paper is impregnated with a binder solution and subjected to hot rolling treatment, resulting in a tight bond between the fibers and between the fibers and the binder, thus obtaining a carbon paper precursor. Due to the good affinity and adhesion between organic fibers and the binder, the binder can be more evenly distributed in the carbon paper base paper layer, greatly enhancing the interaction force between the fibers and the binder in the carbon paper precursor, effectively improving the bonding tightness between the mixed fibers in the carbon paper precursor. Simultaneously, the organic fibers have soft properties, providing good winding performance during papermaking. This allows the organic fibers to effectively wind carbon fibers, further improving the density of the fiber network and the overall structural stability. Furthermore, the organic fibers deform under heat during hot rolling, driving the carbon fibers to align horizontally, enhancing the horizontal orientation of the fibers, and improving the conductivity and mechanical strength of the carbon paper. In the subsequent sintering process, the organic fibers carbonize to form carbon fibers, and the binder forms the carbon material connecting the carbon fibers. Based on the tight bonding between fibers and between fibers and binder in the carbon paper precursor, the bonding tightness between carbon fibers in the prepared carbon paper is effectively improved. Simultaneously, the carbon fibers formed by sintering organic fibers and the carbon material formed by sintering binder also exhibit high bonding strength. This effectively enhances the fiber bonding strength and interlayer bonding performance of the carbon paper, strengthens its mechanical strength, and reduces fiber delamination during use. Furthermore, the improved bonding tightness of carbon fibers and the increased interlayer bonding tightness of the carbon paper result in higher electronic conductivity.

[0012] Furthermore, in this application embodiment, the content of organic fibers is controlled within a specific range, such that organic fibers account for 5% to 20% of the total mass of carbon fibers and organic fibers. In exemplary examples, organic fibers can account for typical but not limiting proportions such as 5%, 7%, 10%, 12%, 15%, 17%, and 20% of the total mass of carbon fibers and organic fibers. Increasing the content of organic fibers can further enhance the bonding effect between organic fibers and binders, improving the binding force between fibers and binders in the carbon paper precursor; however, organic fibers undergo carbonization shrinkage during graphitization. When the content of organic fibers increases, the shrinkage stress increases, leading to a greater risk of carbon paper deformation and cracking. The preparation method of this application controls the content of organic fibers within this range, which effectively promotes the positive effect of strong adhesion between organic fibers and binders, significantly strengthens the internal bonding of carbon paper precursor, and thus effectively improves the mechanical strength and interlayer bonding performance of carbon paper formed after carbonization; at the same time, it effectively avoids excessive shrinkage stress during graphitization caused by excessive organic fiber content, which could lead to cracking or deformation of carbon paper, thereby significantly improving its structural stability and electrical conductivity while ensuring the mechanical strength of carbon paper.

[0013] In step S10, the preparation method of this application embodiment uses papermaking treatment to fully disperse and uniformly interweave carbon fibers and organic fibers, thereby forming a stable network structure between the fibers to obtain carbon paper. The papermaking treatment effectively promotes the interweaving and entanglement of organic fibers with carbon fibers, significantly increasing the number of contact points and the contact area between fibers, enhancing the density and structural uniformity of the fiber network in the carbon paper base paper, thereby further improving the mechanical strength and electrical conductivity of the subsequently obtained carbon paper; and the interweaving and entanglement between organic fibers and carbon fibers effectively inhibits the slippage and breakage of carbon fibers in subsequent steps, improving the overall mechanical stability of the carbon paper base paper.

[0014] In some embodiments, the organic fibers include at least one of synthetic organic fibers and natural organic fibers. The synthetic organic fibers include at least one of acrylic fibers, polyester fibers, polypropylene (PP) fibers, polyacrylonitrile fibers, polyethylene fibers, aramid fibers, polyamide fibers, polyimide fibers, polyvinyl alcohol fibers, and phenolic resin fibers. These synthetic organic fibers, such as acrylic fibers, polyester fibers, PP fibers, PE fibers, and aramid fibers, possess characteristics such as good affinity with binders, controllable pyrolysis behavior, and designable fiber morphology. The excellent affinity of these synthetic organic fibers allows them to act as efficient bonding anchors during impregnation and hot rolling, significantly enhancing the bonding force between fibers and binders in the carbon paper precursor, thereby further improving the mechanical properties and interlayer bonding strength of the carbon paper and enhancing its overall mechanical strength. After high-temperature graphitization, these synthetic organic fibers can be transformed into carbon materials with a high degree of graphitization, forming a denser and more interconnected three-dimensional conductive network together with the original carbon fibers, thereby significantly improving the electronic conductivity of the carbon paper. Meanwhile, its controllable pyrolysis shrinkage characteristics help to further strengthen the bond between fibers and further enhance the structural stability of carbon paper.

[0015] Natural organic fibers can include at least one of cellulose fibers, lignin fibers, and cellulose and lignin composite fibers. Cellulose fibers can include at least one of cotton fibers, flax fibers, and ramie fibers; fibers with high lignin content can include coconut shell fibers, etc.; cellulose and lignin composite fibers can include wood fibers, bamboo fibers, etc. Natural organic fibers containing cellulose, lignin, and other components contain abundant active groups such as hydroxyl groups, exhibiting excellent affinity with binders and better bonding performance. This significantly enhances the bonding between binders and fibers during carbon paper impregnation and promotes the uniform distribution of binders and carbon particles along the fibers in the mixed slurry, thereby further improving the density of the carbon paper precursor after hot rolling, improving the bonding strength between fibers in the carbon paper, and enhancing the conductivity of the carbon paper. During the subsequent high-temperature graphitization process, these natural fibers carbonize and transform into carbon fibers, forming a dense and stable carbon network, thereby improving the mechanical properties and structural integrity of the final carbon paper, increasing its flexibility, and reducing the occurrence of carbon paper stiffening. In addition, natural fibers are derived from renewable biomass, which reduces dependence on petroleum-based raw materials and aligns with the development direction of green materials. At the same time, many natural fibers (such as cotton linters, bamboo or agricultural by-products) are low-cost and abundant, which helps to significantly reduce the overall production cost of carbon paper while ensuring performance.

[0016] In some embodiments, the surface of the organic fiber may include a first active group, which may be a polar group and may include, but is not limited to, oxygen-containing groups, nitrogen-containing groups, sulfur-containing groups, halogen groups, etc. The oxygen-containing groups may include, but are not limited to, hydroxyl, carboxyl, carbonyl, ester, ether bonds, etc.; the nitrogen-containing groups may include, but are not limited to, amino, amide, cyano groups, etc.; the sulfur-containing groups may include, but are not limited to, thiol, disulfide bonds, etc.; and the halogen groups may include chlorine, bromine, etc. The first active group on the surface of the organic fiber can further improve the dispersibility of the organic fiber, improve the adhesion between the organic fiber and the binder, and further promote the reinforcing effect of the organic fiber on the carbon fiber network structure.

[0017] In some embodiments, the organic fiber includes a first organic fiber and a second organic fiber, wherein the first organic fiber is a long organic fiber with an average length of 10-20 mm, and the second organic fiber is a short organic fiber with an average length of 1-3 mm. In exemplary embodiments, the average length of the first organic fiber can be typical but not limited to lengths such as 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, and 20 mm; the average length of the second organic fiber can be typical but not limited to lengths such as 1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm. The first organic fiber can bond with more binders, promoting the connection between carbon fibers, improving the bonding strength between fibers in the carbon paper, and enhancing the interlayer bonding performance of the carbon paper, thus reducing the probability of fiber delamination in the carbon paper. Simultaneously, the first organic fiber can also improve the flexibility of the carbon paper base paper and the carbon paper itself, thereby enhancing the carbon paper's resistance to bending and cracking during subsequent processing and use. The second organic fiber is more easily and uniformly dispersed in the slurry system during papermaking, filling the gaps between fiber networks, enhancing the density and structural uniformity of the carbon paper precursor, and further improving the electrical conductivity of the carbon paper formed after graphitization of the base paper. Through the synergistic effect of the first and second organic fibers, during impregnation and hot rolling, the long fibers can act as the main load-bearing skeleton to strengthen the macroscopic bonding force of the overall structure, while the short fibers can penetrate deep into the micropores, fully interact with the binder, strengthen local connection points, and further enhance the bonding stability of the carbon paper precursor. In addition, this structure is retained and strengthened after graphitization. The graphitization of long fibers forms continuous conductive and supporting carbon fibers, while the graphitization products of short fibers can effectively bridge and repair microscopic defects, thereby synergistically improving the strength, toughness, and other mechanical properties of the final carbon paper, and enhancing the electrical conductivity uniformity and structural integrity of the carbon paper.

[0018] Increasing the length of the first organic fiber can further promote the formation of the cross-linking network, improve the flexibility and structural stability of the carbon paper base, and enhance the mechanical properties and conductivity of the subsequently produced carbon paper. However, increasing the length of the first organic fiber also increases the risk of entanglement during papermaking. Entanglement of the first organic fiber can easily lead to localized unevenness in the carbon paper precursor structure, thus affecting the overall performance of the carbon paper. Shortening the length of the first organic fiber is beneficial for fiber dispersion and can effectively reduce this entanglement risk. However, shortening the length of the first organic fiber can easily affect the formation of the cross-linking network between fibers, which may lead to a decrease in the structural stability of the carbon paper base and the subsequently produced carbon paper, as well as the conductivity of the carbon paper. Therefore, controlling the length of the first organic fiber within the range of 10–20 mm further fully utilizes its reinforcing role while improving processing feasibility and the structural consistency of the carbon paper precursor and carbon paper, achieving synergistic optimization of the mechanical strength and conductivity of the carbon paper.

[0019] Shorter second organic fibers exhibit good dispersibility in the slurry, are less prone to localized agglomeration and entanglement, and can effectively fill the micropores in the fiber network, improving the density and structural uniformity of the carbon paper base. Increasing the length of the second organic fibers increases the surface area for bonding with the binder, thereby enhancing the bonding ability between the second organic fibers and the binder. It also increases the number and area of ​​contact points between the second organic fibers and other fibers, thus enhancing the reinforcing effect of the second organic fibers on the fiber network. This, in turn, promotes the construction of conductive pathways in the carbon paper and improves its mechanical properties. Therefore, controlling the length of the second organic fiber within the range of 1–3 mm can, on the one hand, improve the dispersion uniformity of the second organic fiber during the papermaking process, promote the full filling of the gaps in the fiber network by the second organic fiber, enhance the density and structural uniformity of the precursor, and thus effectively improve the conductivity and mechanical stability of the carbon paper; on the other hand, it can also effectively play its filling and bridging role, improve the density and structural stability of the carbon paper precursor, thereby improving the integrity of the carbon paper structure and the continuity of the conductive network during the subsequent graphitization process, as well as the bonding strength between fibers in the carbon paper, and improve the tensile properties of the carbon paper.

[0020] In some embodiments, the first organic fiber may account for 80% to 99% of the total mass of organic fibers; the second organic fiber may account for 1% to 20% of the total mass of organic fibers. In exemplary embodiments, the first organic fiber may account for typical but not limiting contents such as 80%, 83%, 85%, 88%, 90%, 92%, 95%, 98%, and 99% of the total mass of organic fibers; the second organic fiber may account for typical but not limiting contents such as 1%, 3%, 5%, 7%, 10%, 13%, 15%, 17%, and 20% of the total mass of organic fibers.

[0021] Increasing the content of the first organic fiber improves the continuity and integrity of the fiber network structure; increasing the content of the second organic fiber further promotes its filling effect in the fiber network, improving its density. Controlling the content of the first and second organic fibers within this range, and regulating their ratio within a reasonable range, promotes the construction of a continuous framework by the first organic fiber, while further leveraging the efficient filling effect of the second organic fiber on the pores of the fiber network, thereby further improving the tensile properties and conductivity of the carbon paper.

[0022] In some embodiments, the water contact angle of the organic fiber surface can be below 110°. In exemplary cases, the water contact angle of the organic fiber can be typical but not limiting sizes such as 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, and 110°. A lower water contact angle indicates that the organic fiber has good hydrophilicity. Controlling the water contact angle of the organic fiber surface to below 110° ensures good hydrophilicity. On the one hand, good hydrophilicity promotes uniform dispersion of the organic fiber in the aqueous dispersion system, thereby improving the uniformity of the fiber network during papermaking. On the other hand, a surface with good hydrophilicity is more easily wetted by polar mixed pulp, which can increase the penetration and adhesion of binders such as resins in subsequent impregnation processes, enhance the bonding between binders and fiber networks in the carbon paper precursor, and improve the structural stability of the fiber network in the subsequent graphitized carbon paper.

[0023] It should be noted that the water contact angle test method for organic fiber surfaces involves forming a dense, smooth sheet of organic fiber under specific pressure, and then determining the water contact angle of the organic fiber by measuring the water contact angle of the sheet. In the example, the water contact angle of the organic fiber surface can be measured using a LAUDA Scientific optical contact angle meter.

[0024] In some embodiments, the carbon fiber includes a first carbon fiber and a second carbon fiber, wherein the first carbon fiber is a long carbon fiber with an average length of 10-20 mm, and the second carbon fiber is a short carbon fiber with an average length of 1-3 mm. In exemplary embodiments, the average length of the first carbon fiber can be typical non-limiting lengths such as 10 mm, 12 mm, 15 mm, 18 mm, and 20 mm, and the average length of the second carbon fiber can be typical non-limiting lengths such as 1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm. The long carbon fiber acts as a skeletal support, providing the main mechanical load-bearing function and endowing the carbon paper with high tensile strength and structural stability. The short carbon fiber fills the gaps in the long carbon fiber interwoven network, effectively reducing porosity and improving material density, while also improving the connectivity and uniformity of conductive pathways. The synergistic effect of long and short carbon fibers optimizes the fiber network structure. Furthermore, the combination of long and short organic fibers significantly enhances the tensile properties of the carbon paper, reduces the risk of interlayer delamination, and improves the carbon paper's resistance to deformation during subsequent processing.

[0025] Longer first carbon fibers increase the number of overlap points between carbon fibers and between carbon fibers and organic fibers, increasing the continuity of the conductive pathways in the fiber network and improving the mechanical transmission efficiency of the fiber network, thereby enhancing the overall conductivity and tensile strength of the carbon paper. Shorter first carbon fibers improve dispersion, reducing agglomeration and orientation disorder. Furthermore, shorter first carbon fibers are less prone to bending and breakage during subsequent processing, thus reducing the disruption to the continuity of the conductive network caused by fiber breakage and improving the stability of the electron transport path and the structural stability of the carbon paper. Controlling the length of the first carbon fiber within the range of 10–20 mm effectively improves its dispersion, promoting uniform distribution and the formation of a stable three-dimensional skeleton structure during papermaking to construct a continuous conductive network and enhance the overall conductivity of the carbon paper. Simultaneously, first carbon fibers within this length range ensure sufficient entanglement to enhance inter-fiber bonding, further improving the mechanical strength of the carbon paper.

[0026] When the length of the second carbon fiber is too short, its filling effect is significantly weakened, making it difficult to effectively fill the tiny gaps between fibers. This results in a loose pore structure in the carbon paper, reducing the density of the carbon paper and the connectivity of the conductive network. Furthermore, excessively short carbon fibers are more susceptible to orientation deflection or migration due to fluid shear forces during dispersion, making it difficult for them to remain stably and uniformly in the gaps of the long fiber interwoven network, further weakening the filling effect of the second carbon fiber. On the other hand, if the second carbon fiber is too long, it may disrupt the uniform distribution of the original fiber network, causing local accumulation, which reduces the rheological properties of the pulp during papermaking and affects the uniformity of the forming process.

[0027] When the second carbon fiber (short fiber) is shorter, it has a higher specific surface area and better dispersibility. The high specific surface area provides more active surface, which is beneficial for bonding with binders and enhancing local interfacial strength. The good dispersibility makes the second carbon fiber easy to disperse uniformly in papermaking pulp, less prone to entanglement, and significantly improves the rheological properties of the pulp, thereby improving the structural uniformity of the carbon paper base paper. Extending the length of the second carbon fiber can improve its filling effect in the pores of the fiber network. Longer second carbon fibers can also more effectively cross and fill larger pores in the fiber network, forming a more continuous spatial support structure, thereby improving the overall rigidity and dimensional stability of the carbon paper. At the same time, its longer span distance can more reliably connect carbon fibers that are far apart, forming a more interconnected three-dimensional conductive path, which is beneficial for reducing the overall resistance of the produced carbon paper. Controlling the length of the second carbon fiber within the range of 1–3 mm effectively balances its filling effect and dispersion uniformity, preventing localized aggregation that could reduce the rheological properties of the pulp, improving the fluidity of the pulp during papermaking, and enhancing the uniformity and density of fiber distribution in the carbon paper base paper. This, in turn, improves the structural uniformity and density of the subsequently produced carbon paper. Furthermore, a suitable length of second carbon fiber effectively bridges the contact points between the first carbon fibers, increasing the connectivity of the conductive pathways and strengthening the interfacial bonding strength, thereby synergistically optimizing the conductivity, mechanical properties, and structural stability of the carbon paper.

[0028] In some embodiments, the second carbon fiber can account for 15% to 40% of the total mass of the carbon fibers. In exemplary examples, the second carbon fiber can account for typical non-limiting contents such as 15%, 20%, 25%, 30%, 35%, and 40% of the total mass of the carbon fibers. Controlling the carbon fiber content within this range further enhances the filling effect of the second carbon fiber on the fiber network structure, while further optimizing the synergistic effect of the first and second carbon fibers, improving the continuity of the fiber skeleton, reducing the contact resistance between fibers, and enhancing the integrity of the conductive network, thereby significantly improving the overall conductivity, toughness, and structural stability of the carbon paper.

[0029] In some embodiments, the surface of the carbon fiber contains a second active group. In an exemplary embodiment, the second active group can be a polar group, and may include at least one of carboxyl, hydroxyl, amino, mercapto, ester, cyano, or halogen groups. The second active group can further improve the dispersibility of the carbon fiber, giving it better formability during papermaking. It also enhances the affinity between the carbon fiber and the binder and organic fibers, further promoting the adsorption between the carbon fiber and organic fibers, thereby promoting the anchoring effect of the organic fibers in the fiber network and further improving the bonding stability of the fibers in the carbon paper and the electrical conductivity of the carbon paper. In an exemplary embodiment, the second active group can be formed by modifying the carbon fiber through processes such as oxidation or grafting, or by applying a coating containing the second active group to the surface of the carbon fiber to attach the second active group to the surface of the carbon fiber.

[0030] In a further embodiment, when the content of the second active group in the carbon fiber is low, the content of the first active group in the organic fiber can be increased, thereby further promoting the bonding between the organic fiber and the carbon fiber, improving the anchoring effect of the organic fiber on the carbon fiber, and thus enhancing the bonding force between fibers in the carbon paper and improving the structural stability of the carbon paper.

[0031] It should be noted that the content of the first active group on the surface of organic fiber and the content of the second active group on the surface of carbon fiber can be determined by common measurement methods for these groups. For example, when both the first and second active groups are hydroxyl groups, the content of hydroxyl groups can be determined by titration.

[0032] In some embodiments, the average diameter of the organic fibers can be 8–14 μm, the average diameter of the carbon fibers can be 5–8 μm, and the ratio of the average diameter of the organic fibers to the average diameter of the carbon fibers can be 1:1 to 2:1. In exemplary examples, the average diameter of the organic fibers can be typical but not limiting diameters such as 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, and 14 μm; the average diameter of the carbon fibers can be typical but not limiting diameters such as 5 μm, 6 μm, 7 μm, and 8 μm; and the ratio of the average diameter of the organic fibers to the average diameter of the carbon fibers can be typical but not limiting values ​​such as 1:1, 1.2:1, 1.5:1, 1.8:1, and 2:1. During graphitization, the organic fibers undergo carbonization shrinkage, resulting in fiber thinning. By controlling the ratio of the average diameter of the organic fibers to the carbon fibers within this range, the initial diameter of the organic fibers is equal to or slightly larger than the diameter of the carbon fibers. Even after high-temperature shrinkage, the final size of the organic fibers can still match that of the carbon fibers, effectively maintaining the uniformity and integrity of the fiber network. Furthermore, during impregnation and hot rolling processes, coarser organic fibers can more effectively bridge and support carbon fibers, forming a tightly bonded and stronger carbon paper precursor. After graphitization, the organic fibers, which shrink and become thinner, transform into carbon fibers that fill the spaces between the original carbon fiber skeleton. This enhances the electrical connections between fibers, improves overall conductivity, and reduces large pores or stress concentration points caused by excessive shrinkage of organic fibers, thereby optimizing the pore structure and reducing microscopic defects. This diameter ratio synergistically improves the mechanical strength, structural stability, electrical uniformity, and gas diffusion properties of the carbon paper.

[0033] In some embodiments, the average length of the first organic fiber is 0.9 to 2 times the average length of the first carbon fiber, preferably 1.1 to 1.5 times. In exemplary examples, the average length of the first organic fiber is typically, but not limitingly, 0.9, 1, 1.1, 1.2, 1.3, 1.4, and 1.5 times the average length of the first carbon fiber. Slightly longer organic fibers can connect multiple carbon fiber contact points, significantly improving network integrity and suppressing the risk of delamination; however, if the organic fibers are too long, they are prone to entanglement and clumping, hindering the effective bridging that should form between carbon fibers, leading to increased resistance and reduced inter-fiber bonding strength. Controlling the ratio of the average length of the first organic fiber to the average length of the first carbon fiber within this range, so that the length of the first organic fiber is similar to or slightly longer than that of the first carbon fiber, allows it to fully entangle and interweave with the carbon fiber during mixing and papermaking, effectively constructing a stable three-dimensional network skeleton and further improving the conductivity and mechanical strength of the carbon paper.

[0034] In some embodiments, the binder in the mixed slurry includes at least one of phenolic resin, epoxy resin, furan resin, polyimide resin, and pitch resin. These resins exhibit good wettability during impregnation and can tightly bond with the fiber surface through polar groups, significantly enhancing the mechanical strength and interlayer bonding of the carbon paper precursor. More importantly, in the subsequent graphitization process, these binders can be carbonized into a stable carbon material with a high residual carbon content. The resulting carbon material firmly bridges the carbon fibers, which not only further improves the structural stability of the carbon paper and the bonding force between carbon fibers, but also further constructs a continuous and dense three-dimensional conductive network, thereby significantly improving the conductivity of the carbon paper.

[0035] In some embodiments, the binder content in the mixed slurry can be from 5 wt% to 30 wt%. In exemplary examples, the binder content can be typical but not limiting, such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, and 30 wt%. Controlling the binder content within this range provides sufficient bonding force to effectively enhance inter-fiber bonding and interlayer connections, while also providing sufficient carbon source to form adequate carbon material, thereby forming a complete carbon bridging structure and improving the mechanical properties of the carbon paper; forming a continuous conductive skeleton promotes the continuity and density of the conductive network, improving the conductivity of the carbon paper. Furthermore, it improves the toughness of the carbon paper, enhances its pore distribution, reduces the increase in carbon material after binder carbonization leading to increased brittleness, and avoids over-filling of pores that could affect the transport performance of gas and liquid water.

[0036] In some embodiments, the mixed slurry further includes conductive fillers, and in exemplary embodiments, the conductive fillers may include carbon materials such as carbon black, graphene, and carbon nanotubes.

[0037] In some embodiments, the content of conductive filler in the mixed slurry can be from 5 wt% to 30 wt%. In exemplary cases, the content of conductive filler can be typical but not limiting, such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, and 30 wt%. Conductive filler can fill the tiny gaps in the three-dimensional network structure, thereby further promoting the connection between fibers in the carbon paper, further optimizing the electronic conduction path inside the carbon paper, and effectively improving the conductivity of the carbon paper. Controlling the content of conductive filler within this range effectively improves the conductivity of the carbon paper while reducing the possibility of pore blockage or decreased processing performance due to conductive filler agglomeration. Furthermore, the synergistic effect of the conductive filler and binder can also alleviate the shrinkage of the carbon paper during high-temperature processing, reduce internal stress caused by shrinkage, further improve the structural stability of the carbon paper, and improve the dimensional stability of the carbon paper.

[0038] Controlling the content of binder and conductive filler in the mixed slurry within the aforementioned range can effectively improve the rheological properties of the mixed slurry. Through impregnation treatment, the mixed slurry fully penetrates the interior of the carbon paper base, filling the pores between fibers and coating the fiber surface. Subsequent carbonization treatment forms a continuous and dense conductive network structure, improving the overall conductivity of the carbon paper and effectively enhancing its mechanical strength and flexibility. Simultaneously, the impregnation treatment ensures uniform distribution of the slurry within the carbon paper base, further improving the consistency of performance in different areas after graphitization treatment, reducing localized over-density or under-density, and further optimizing gas transmission channels and drainage capacity.

[0039] After processing the carbon paper base paper, a carbon paper precursor is obtained through hot rolling. Hot rolling promotes the curing of the binder infiltrated into the carbon paper base paper, while simultaneously forming a tighter bond between the fibers, binder, and conductive filler, enhancing the bonding force between fibers and improving the overall density and uniformity of the fiber network structure.

[0040] In some embodiments, the temperature of the hot rolling treatment can be 150–200°C, optionally 180–190°C. In exemplary embodiments, the temperature of the hot rolling treatment can be typical but not limiting temperatures such as 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C. The time of the hot rolling treatment can be 3–20 minutes. In exemplary embodiments, the time of the hot rolling treatment can be typical but not limiting times such as 3 minutes, 5 minutes, 8 minutes, 10 minutes, 15 minutes, and 20 minutes. Controlling the temperature and time of the hot rolling treatment within the above range can, on the one hand, further promote the curing of the binder, enhance the bonding force between the binder and the fiber, and effectively improve the integrity of the fiber, reducing the occurrence of embrittlement or excessive shrinkage of the organic fiber due to excessively high temperature or excessive time. On the other hand, controlling the temperature and time of the hot rolling treatment within the above range improves the bulk uniformity of the carbon paper precursor, reduces defects in the carbon paper precursor, and thus further reduces defects in the carbon paper.

[0041] In some embodiments, the pressure of the hot rolling process can be 0.05–5 MPa. In exemplary cases, the pressure of the hot rolling process can be typical but not limiting pressures such as 0.05 MPa, 0.1 MPa, 0.2 MPa, 0.5 MPa, 0.8 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, and 5 MPa. Controlling the pressure of the hot rolling process within this range, combined with parameters such as the temperature of the hot rolling process, the fiber composition of the carbon paper base paper, and the composition of the mixed slurry, effectively compacts the carbon paper base paper structure, promotes close contact between fibers and binders, reduces structural collapse, and further improves the integrity of the carbon paper precursor. Furthermore, controlling the pressure of the hot rolling process within this range can also effectively regulate the compression ratio, thereby adjusting the density distribution of the carbon paper precursor, improving its mechanical stability and electrical continuity, and optimizing the pore distribution of the subsequently produced carbon paper, further improving the drainage and air permeability of the carbon paper.

[0042] In some embodiments, the compression rate of the hot rolling treatment can be 10% to 20%. In exemplary cases, the shrinkage rate of the hot rolling treatment can be typical but not limiting shrinkage rates such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%. Controlling the shrinkage rate of the carbon paper within this range effectively improves the density, uniformity, and structural stability of the carbon paper precursor while maintaining the integrity of the fiber network structure. By controlling the temperature, time, pressure, and compression rate of the hot rolling treatment within the above range, the interfacial bonding between the binder and fibers is enhanced, and the dense and orderly arrangement of fibers is promoted, further improving the overall uniformity of the material. This achieves synergistic optimization of the microstructure of the carbon paper precursor, maintains the connectivity of the pore network, and provides a good foundation for the formation of stable conductive pathways and uniform pore structures in the subsequent carbonization process. This results in carbon paper with high mechanical strength, excellent conductivity, and good air permeability and drainage performance in subsequent steps.

[0043] The carbon paper precursor is graphitized after hot rolling. Graphitization promotes the carbonization of organic fibers and binders in the carbon paper precursor and further transforms them into a graphite microcrystalline structure, thereby improving the material's electrical conductivity and structural stability.

[0044] In some embodiments, the graphitization process may include a first sintering process and a second sintering process, wherein the temperature of the first sintering process may be 600–1000°C and the time may be 15–60 min; the temperature of the second sintering process may be 2000–2500°C and the time may be 5–30 min. In an exemplary example, the temperature of the first sintering process may be a typical but not limiting temperature such as 600°C, 700°C, 800°C, 900°C, or 1000°C; the time of the first sintering process may be a typical but not limiting time such as 15 min, 20 min, 30 min, 40 min, 50 min, or 60 min; the temperature of the second sintering process may be a typical but not limiting temperature such as 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, or 2500°C; and the time of the second sintering process may be a typical but not limiting time such as 5 min, 10 min, 20 min, or 30 min. The first sintering process carbonizes the organic fibers and binders in the carbon paper precursor, while removing impurities such as N, H, and O from the organic fibers and binders, thus improving the purity of the carbonization products. Subsequently, the second sintering process promotes further graphitization of the carbon fibers and carbonization products, forming a highly ordered graphite microcrystalline structure, which significantly improves the conductivity of the material.

[0045] Understandably, graphitization can be carried out under a protective atmosphere such as nitrogen or helium.

[0046] After graphitization to obtain non-hydrophobic carbon paper, hydrophobic treatment can be applied to the non-hydrophobic carbon paper to increase its hydrophobicity, thereby effectively improving its drainage capacity and gas diffusion performance in fuel cell applications.

[0047] In some embodiments, non-hydrophobic carbon paper can be impregnated in a solution containing a hydrophobic agent, or a solution containing a hydrophobic agent can be sprayed onto non-hydrophobic carbon paper, followed by calcination treatment to uniformly deposit and sinter polytetrafluoroethylene (PTFE) onto the fiber surface. In an exemplary embodiment, the hydrophobic agent can be PTFE, the concentration of the PTFE emulsion can be 5 wt% to 20 wt%, the calcination temperature can be 350 to 450°C, and the time can be 10 to 30 minutes to further promote the decomposition of surfactants in the PTFE emulsion, while simultaneously promoting the melting of PTFE and other hydrophobic agent particles and coating the surface of carbon fibers and carbon materials in the carbon paper, forming a continuous and stable hydrophobic network.

[0048] Secondly, embodiments of this application provide a carbon paper prepared by the preparation method described above.

[0049] The carbon paper in this embodiment possesses excellent mechanical strength and interlayer bonding properties. This allows it to better withstand the pressure of the bipolar plates and the expansion and contraction stresses during operation when applied as a gas diffusion layer, reducing deformation or cracking caused by pressure and effectively extending the lifespan of the proton exchange membrane fuel cell. Simultaneously, the tight interlayer bonding in the carbon paper also improves electronic conductivity, increases electron transport efficiency, reduces heat generation during electron transport, and enhances the output power and thermal stability of the proton exchange membrane fuel cell.

[0050] The carbon paper in this embodiment possesses excellent mechanical strength and interlayer bonding properties. When applied to the gas diffusion layer, the carbon paper can better withstand the pressure of the bipolar plates during battery assembly and long-term operation, as well as the flow impact forces generated by gas transport. This reduces deformation or cracking caused by bipolar plate pressure or gas impact forces, effectively extending the lifespan of the proton exchange membrane fuel cell. Simultaneously, the tight interlayer bonding in the carbon paper also improves electronic conductivity, significantly reduces the internal resistance of the proton exchange membrane fuel cell, and enhances its energy conversion efficiency and thermal stability.

[0051] In some embodiments, the thickness of the carbon paper can be 150–300 μm. In exemplary examples, the thickness of the carbon paper can be typical but not limiting thicknesses such as 150 μm, 180 μm, 200 μm, 220 μm, 250 μm, 280 μm, and 300 μm. Controlling the thickness of the carbon paper within this range further improves its mechanical strength while shortening gas transport and drainage paths. In some embodiments, the porosity of the carbon paper can be 50%–90%. In exemplary examples, the porosity of the carbon paper can be typical but not limiting porosities such as 50%, 60%, 70%, 75%, 80%, 85%, and 90%. Controlling the porosity of the carbon paper within this range further improves its mechanical strength and electrical conductivity, while also improving its air permeability and drainage performance.

[0052] Thirdly, embodiments of this application provide the application of the carbon paper described above in proton exchange membrane fuel cells.

[0053] Based on the aforementioned carbon paper, the fibers and binder carbides exhibit excellent bonding strength, and the carbon paper possesses good tensile properties and other mechanical strengths, as well as good interlayer bonding performance. This enables the carbon paper, when applied in proton exchange membrane fuel cells, to effectively resist expansion and contraction stresses caused by humidity changes during battery operation, reducing the risk of interfacial delamination and thus maintaining the integrity of the carbon paper and gas diffusion layer structure. Furthermore, the excellent structural stability and conductivity of the carbon paper in this embodiment synergistically reduce the battery's internal resistance and improve the uniformity of current density distribution, contributing to enhanced stability and durability of the proton exchange membrane fuel cell under high-power conditions. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0055] Figure 1 Here is a carbon paper SEM image from Example 1, where... Figure 1 The magnification is 500 times; Detailed Implementation

[0056] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0057] Example 1

[0058] This embodiment provides a carbon paper, and the carbon paper preparation method of this embodiment includes the following steps:

[0059] Step S01: The carbon fiber and organic fiber are mixed to obtain a mixed fiber, which is then subjected to papermaking treatment to produce carbon paper base paper. As shown in Table 1, the organic fiber accounts for 10% of the mass of the mixed fiber. The carbon fiber has an average diameter of 7 μm and includes a first carbon fiber (long carbon fiber) and a second carbon fiber (short carbon fiber). The long carbon fiber has an average length of 12 mm and accounts for 70% of the total carbon fiber mass. The short carbon fiber has an average length of 6 mm and accounts for 30% of the total carbon fiber mass. The organic fiber is acrylic fiber with an average diameter of 10 μm. The organic fiber includes a first organic fiber (long organic fiber) and a second organic fiber (short organic fiber). The long organic fiber has an average length of 15 mm and accounts for 90% of the total organic fiber mass. The short organic fiber has an average length of 3 mm and accounts for 10% of the total organic fiber mass.

[0060] Step S02: Prepare a mixed slurry using a binder, conductive filler, and water. As shown in Table 2, the binder is phenolic resin, the mass content of the binder in the mixed slurry is 15%, the content of the conductive filler is 20%, and the conductive filler is carbon black.

[0061] Step S03: Impregnate the carbon paper base paper obtained in step S01 by impregnating it in the mixed slurry in step S02, and then take it out to obtain the impregnated carbon paper base paper.

[0062] Step S04: The carbon paper base paper obtained in step S03 is subjected to hot rolling treatment. The carbon paper base paper is hot rolled for 10 minutes at a temperature of 180℃ and a pressure of 2.5MPa to compress the carbon paper base paper by about 15% to obtain the carbon paper precursor.

[0063] Step S05: Graphitization treatment. The carbon paper precursor obtained in step S04 is subjected to two-stage sintering under a protective atmosphere to obtain non-hydrophobic carbon paper. The first sintering treatment is performed at a temperature of 800℃ for 30 minutes, and the second sintering treatment is performed at a temperature of 2200℃ for 10 minutes.

[0064] Step S06: Hydrophobic treatment. A polytetrafluoroethylene (PTFE) emulsion is sprayed onto the carbon paper obtained after graphitization treatment. The PTFE-coated carbon paper is then calcined to obtain the carbon paper of this embodiment, with a thickness of 206.2 μm. The PTFE concentration is 10 wt%, and the calcination temperature is 350°C for 20 minutes.

[0065] Examples 2 to 3

[0066] Examples 2 and 3 each provide a carbon paper. The carbon paper and its preparation method in Examples 2 and 3 are basically the same as those in Example 1, except that:

[0067] (1) As shown in Table 1, in the preparation of carbon paper in Example 2, the mass percentage of organic fibers in the mixed fibers was 5%;

[0068] (2) As shown in Table 1, in the preparation of carbon paper in Example 3, the mass ratio of organic fiber in the mixed fiber is 20%.

[0069] Example 4

[0070] Example 4 provides a carbon paper. The carbon paper and its preparation method in Example 4 are basically the same as those in Example 1, except that the carbon paper in Example 4 does not contain short organic fibers.

[0071] Examples 5 to 10

[0072] Examples 5 to 10 each provide a carbon paper. The carbon paper and its preparation method in Examples 5 to 10 are basically the same as those in Example 1, except that:

[0073] (1) In Example 5, the average length of the long organic fibers in the organic fibers during the preparation of carbon paper was 8 μm;

[0074] (2) In Example 6, the average length of the long organic fibers in the organic fibers during the preparation of carbon paper was 12 μm;

[0075] (3) In Example 7, the average length of the long organic fibers in the organic fibers during the preparation of carbon paper was 13.5 μm;

[0076] (4) In Example 8, the average length of the long organic fibers in the organic fibers during the preparation of carbon paper was 18 μm;

[0077] (5) In Example 9, the average length of the long organic fibers in the organic fibers during the preparation of carbon paper was 24 μm;

[0078] (6) In Example 10, the average length of the long organic fibers in the organic fibers during the preparation of carbon paper was 30 μm.

[0079] In addition, the organic fiber content and organic fiber parameters during the preparation of carbon paper in Examples 5 to 10 are shown in Table 1, the diameter, length, and long and short fiber content of carbon fibers are shown in Table 2, and the composition of the mixed slurry, hot rolling conditions and compression ratio are shown in Table 3.

[0080] Examples 11 to 13

[0081] Examples 11 to 13 each provide a carbon paper. The carbon paper and its preparation method in Examples 11 to 13 are basically the same as those in Example 1, except that:

[0082] (1) The organic fiber used in the preparation of carbon paper in Example 11 is polyester fiber. The content, diameter, and distribution of long and short fibers of polyester fiber are shown in Table 1.

[0083] (2) The organic fiber used in the preparation of carbon paper in Example 12 is PP fiber. The content, diameter, and distribution of long and short fibers of PP fiber are shown in Table 1.

[0084] (3) In Example 13, the organic fiber used in the preparation of carbon paper was cellulose fiber. The content, diameter, and distribution of long and short fibers of cellulose fiber are shown in Table 1.

[0085] In addition, the parameters such as the diameter, length, and long and short fiber content of carbon fibers during the preparation of carbon paper in Examples 11 to 13 are shown in Table 2, and the composition of the mixed slurry, hot rolling conditions, and compression ratio are shown in Table 3.

[0086] Examples 14 to 15

[0087] Examples 14 and 15 each provide a carbon paper. The carbon paper and its preparation method in Examples 14 and 15 are basically the same as those in Example 1, except that:

[0088] (1) The diameter of the organic fibers used in the preparation of carbon paper in Example 14 was 7 μm;

[0089] (2) The diameter of the organic fibers used in the preparation of carbon paper in Example 15 was 5 μm.

[0090] In addition, the organic fiber content and organic fiber parameters during the preparation of carbon paper in Examples 14 and 15 are shown in Table 1, the diameter, length, and long and short fiber content of carbon fibers are shown in Table 2, and the composition of the mixed slurry, hot rolling conditions and compression ratio are shown in Table 3.

[0091] Comparative Examples 1 to 3

[0092] Comparative Examples 1 to 3 each provide a carbon paper. The carbon papers and their preparation methods in Comparative Examples 1 to 3 are basically the same as those in Example 1, except that:

[0093] (1) As shown in Table 1, carbon paper in Comparative Example 1 was prepared by using carbon fiber for papermaking, and the carbon paper base paper did not contain organic fibers.

[0094] (2) As shown in Table 1, in the carbon paper preparation process of Comparative Example 2, the content of organic fiber in the mixed fiber used in the papermaking process is 2%.

[0095] (3) As shown in Table 1, in the preparation of carbon paper in Comparative Example 3, the content of organic fiber in the mixed fiber used in the papermaking process is 30%.

[0096] Table 1

[0097]

[0098]

[0099] Table 2

[0100]

[0101] Table 3

[0102]

[0103] Carbon paper performance evaluation

[0104] 1. Morphological examination of carbon paper

[0105] The thickness and morphology of the carbon paper were examined under an electron microscope, and the results are as follows: Figure 1 As shown in Table 4.

[0106] like Figure 1 As shown, the carbon paper in Example 1 includes stacked carbon fibers with pores between them. A carbon material formed by a binder coats the surface of the carbon fibers and fills the tiny pores between the carbon fibers with conductive filler. The carbon paper structures of Examples 2 to 15, Comparative Examples 1 and 2 are similar to those of Example 1, but the carbon paper in Comparative Example 3 shows significantly more cracks than that in Example 1.

[0107] 2. Resistivity test

[0108] The resistivity of the carbon paper from Examples 1 to 21 and Comparative Examples 1 to 3 was measured, and the results are shown in Table 4. The resistivity testing method is as follows:

[0109] Resistivity testing method: Cut the sample into a regular size and place it between two measuring electrodes in the resistivity tester. The measuring electrodes are gold electrodes or gold-plated copper electrodes. Wait 100 seconds after the pressure reaches 1 MPa, and calculate the resistivity using the following formula:

[0110] ρt= [(Rm*S) -2Rc] / d Formula (2)

[0111] In the formula:

[0112] d: Average thickness of the sample at 1 MPa;

[0113] ρt: Sample resistivity, in milliohm-cm (mΩ·cm);

[0114] Rm: The instrument's measured value, which is the sum of the sample's vertical resistance, the copper electrode's body resistance, and the contact resistance between the two samples and the electrode, in milliohms (mΩ).

[0115] S: The contact area between the sample and the two electrodes, in square centimeters (cm2);

[0116] Rc: The sum of the bulk resistance of the two copper electrodes and the contact resistance between the sample and the two electrodes, in milliohms per square centimeter (mΩ·cm). 2 );

[0117] 3. Tensile strength test

[0118] The tensile strength of the carbon paper from Examples 1 to 21 and Comparative Examples 1 to 3 was measured, and the results are shown in Table 4. The method for measuring tensile strength is as follows:

[0119] The specimen is cut into strips of a certain size, and the tensile strength is tested using a universal testing machine. The tensile strength of the specimen is calculated using the following formula:

[0120]

[0121] In the formula:

[0122] Ts: Tensile strength of the sample, in megapascals (MPa);

[0123] Fb: The load recorded when the sample is disconnected, in Newtons (N);

[0124] Wcp: Width of the sample, in millimeters (mm);

[0125] d: The average thickness of the sample under a certain pressure, in millimeters (mm).

[0126] 4. Adhesion test

[0127] Adhesion tests were conducted on the carbon paper of Examples 1 to 21 and Comparative Examples 1 to 3, and the results are shown in Table 4. The adhesion test method is as follows:

[0128] A 5cm × 5cm sample was obtained by cutting, with a mass of M1 and an adhesive strength of 2N / cm. 2 The tape was applied to the surface of the carbon paper. After applying a pressure of 1.5 N / cm2 for 10 seconds, it was peeled off at a 90° angle. The mass was M2. The percentage of mass loss was calculated as (M1-M2) / M1×100%. The results are shown in Table 4.

[0129] Table 4

[0131] As shown in Table 4, the thicknesses of the carbon paper in Examples 1 to 15 and Comparative Examples 1 to 2 were similar, all within the range of 182–215 μm. The resistivity of the carbon paper in Examples 1 to 15 was significantly lower than that in Comparative Examples 1 to 3; the tensile strength of the carbon paper in Examples 1 to 15 was significantly better than that in Comparative Examples 1 to 3. The percentage of mass loss after the adhesion test of the carbon paper in Examples 1 to 15 was significantly lower than that after the adhesion test of the carbon paper in Comparative Examples 1 to 3.

[0132] The main difference between Examples 1 to 3 and Comparative Examples 1 to 3 lies in the content of organic fibers in the mixed fibers during the papermaking process. As shown in Table 4, the resistivity and tensile strength of the carbon paper in Examples 1 to 3 are significantly better than those in Comparative Examples 1 to 3. Furthermore, the percentage of adhesive mass loss of the carbon paper in Examples 1 to 3 is significantly lower than that in Comparative Examples 1 to 3. This indicates that the preparation method of this application, by adding organic fibers during the papermaking process and controlling the content of organic fibers within a specific range, effectively promotes the bonding between the binder and fibers, increases the bonding strength between the fibers and the binder, and thus produces carbon paper with good interlayer bonding performance, high mechanical strength, and resistance to fiber peeling after graphitization and hydrophobic treatment.

[0133] Compared to Example 1, the carbon paper in Example 4 did not contain short organic fibers, resulting in increased resistivity. The addition of short organic fibers improved the conductivity of the carbon paper. The average length of the long organic fibers, the content of short organic fibers, and the diameter of the carbon fibers used in the preparation of the carbon paper in Examples 5 to 10 differed from those in Example 1. Compared to Example 1, the conductivity, tensile strength, and peel resistance of the carbon paper in Examples 5 to 10 were somewhat reduced, but all were superior to the carbon paper in Comparative Example 1.

[0134] Examples 11 to 13 are carbon papers prepared using different organic fibers. The conductivity, tensile strength and peel resistance of the carbon papers in Examples 11 to 13 are better than those in Comparative Example 1. This shows that different natural organic fibers and synthetic organic fibers can be used as organic fibers in the carbon paper preparation method of this application.

[0135] The diameter of the organic fibers and the content of short carbon fibers in the preparation of carbon paper in Examples 14 and 15 differ from those in Example 1. The conductivity, tensile strength and peel resistance of the carbon paper in Examples 14 and 15 are slightly lower than those in Example 1. At the same time, the conductivity, tensile strength and peel resistance of the carbon paper in Examples 14 and 15 are better than those of the carbon paper in Comparative Example 1.

[0136] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing carbon paper, characterized in that, Includes the following steps: The mixed fibers are subjected to papermaking treatment to obtain carbon paper base paper, wherein the mixed fibers include carbon fibers and organic fibers, and the organic fibers account for 5% to 20% of the total mass of the carbon fibers and the organic fibers; The carbon paper base paper is impregnated and hot-rolled using a mixed slurry containing a binder to obtain a carbon paper precursor; The carbon paper precursor is subjected to graphitization and hydrophobic treatment in sequence to obtain the carbon paper.

2. The preparation method according to claim 1, characterized in that, The ratio of the average diameter of the organic fiber to the average diameter of the carbon fiber is 1:1 to 2:1; and / or The average diameter of the organic fiber can be 8 to 14 μm.

3. The preparation method according to claim 1, characterized in that, The organic fiber comprises a first organic fiber and a second organic fiber, wherein the average length of the first organic fiber is 10-20 mm, the average length of the second organic fiber is 1-3 mm, and the second organic fiber accounts for 1%-20% of the total mass of the organic fiber; and / or The organic fiber includes at least one of synthetic organic fiber and natural organic fiber; and / or The water contact angle of the organic fiber surface is below 110°.

4. The preparation method according to claim 3, characterized in that, The carbon fiber includes a first carbon fiber and a second carbon fiber, wherein the average length of the first carbon fiber is 10-15 mm, the average length of the second carbon fiber is 3-8 mm, and the second carbon fiber accounts for 15%-40% of the total mass of the carbon fiber.

5. The preparation method according to claim 4, characterized in that, The average length of the first organic fiber is 0.9 to 2 times the average length of the first carbon fiber.

6. The preparation method according to claim 1, characterized in that, The compression rate of the hot rolling process is 10% to 20%; and / or The hot rolling temperature is 150–200°C; and / or The pressure of the hot rolling process is 0.05–5 MPa; and / or The hot rolling process takes 3 to 20 minutes.

7. The preparation method according to claim 1, characterized in that, The binder content in the mixed slurry is 5 wt% to 30 wt%; and / or The adhesive includes at least one of phenolic resin, epoxy resin, furan resin, polyimide resin, and asphalt resin; The mixed slurry includes conductive filler, and the content of the conductive filler is 5wt% to 30wt%.

8. The preparation method according to claim 1, characterized in that, The graphitization process includes a first sintering process and a second sintering process. The temperature of the first sintering treatment is 600-1000℃, and the time is 15-60 min; The second sintering treatment is performed at a temperature of 2000–2500℃ for 5–30 minutes.

9. A type of carbon paper, characterized in that, The carbon paper is prepared by the method described in any one of claims 1-8.

10. The carbon paper prepared by any one of claims 1-8, or the application of the carbon paper of claim 9 in a proton exchange membrane fuel cell.

Images