Carbon paper as well as preparation method and application thereof

Abstract

The invention provides carbon paper as well as a preparation method and application thereof. The preparation method comprises the following steps: providing short carbon fibers; the short carbon fibers are evenly laid, carding and lapping are carried out, a carbon fiber net structure is obtained, and the short carbon fibers are distributed in the carbon fiber net structure in a random orientation mode; stacking the carbon fiber net structures, and performing needling treatment to obtain a carbon paper precursor; carrying out curing treatment on the carbon paper precursor to obtain carbon paper body paper; and carrying out carbonization treatment and graphitization treatment on the carbon paper body paper to obtain the carbon paper. The carbon paper precursor with isotropy is prepared through carding, lapping and needling, carbon fibers in the carbon paper can be uniformly distributed under random orientation, and the uniformity of distribution of mechanical properties and electrical properties in the carbon paper can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of carbon materials, and in particular to a carbon paper, a preparation method and application thereof. Background Art

[0002] Carbon paper is a porous material made of carbon fiber. It has high conductivity, light weight and chemical resistance. It is widely used in lithium batteries, electrochemical reactions, fuel cells and various electronic devices. The preparation scheme of carbon paper is mostly wet papermaking, with short-cut carbon fiber as the main raw material, adding dispersant and adhesive, and then beating and papermaking to obtain carbon paper precursor; then the carbon paper product is obtained by impregnation with resin, hot pressing and curing, carbonization, graphitization and other steps. However, this method has many disadvantages, such as the difficulty in dispersing short-cut carbon fiber, the difficulty in accurately controlling the porosity and thickness of the finished carbon paper, the use of a large amount of additives in production and pollution to the environment.

[0003] In contrast, dry forming can avoid the above problems. At present, the dry forming process mostly uses textile technology to prepare the felt body, and its fiber distribution is anisotropic, and the mechanical properties and conductive properties of the obtained carbon paper base paper are uneven. For example, patent CN115332545A uses a dry process to spin and weave carbon fiber preoxidized yarn to obtain preoxidized yarn cloth, and the mechanical properties of the obtained carbon paper are not isotropic; patent CN116314869A uses a weaving method to spun the preoxidized yarn multiple times, which is cumbersome and costly.

[0004] Based on this, it is necessary to propose a dry forming scheme that can achieve isotropic carbon paper performance and simple process. Summary of the invention

[0005] In view of the above problems in the prior art, the present application provides a carbon paper, a preparation method and application thereof, and the specific technical solutions are as follows:

[0006] In one aspect, the present application provides a method for preparing carbon paper, comprising:

[0007] S1: Provide chopped carbon fiber;

[0008] S2: evenly laying the chopped carbon fibers, combing them, and laying them to obtain a carbon fiber mesh structure, wherein the chopped carbon fibers are randomly oriented and distributed in the carbon fiber mesh structure;

[0009] S3: stacking the carbon fiber mesh structure and performing a needle punching treatment to obtain a carbon paper precursor;

[0010] S4: curing the carbon paper precursor to obtain a carbon paper base;

[0011] S5: performing carbonization and graphitization treatment on the carbon paper base paper to obtain carbon paper.

[0012] In a possible implementation manner, the chopped carbon fiber satisfies at least one of the following characteristics:

[0013] The chopped carbon fiber is selected from one or more of polyacrylonitrile-based carbon fiber and asphalt-based carbon fiber;

[0014] The length of the chopped carbon fiber is 40-70 mm;

[0015] The diameter of the chopped carbon fibers is 3-15 μm.

[0016] In a possible implementation manner, the carbon paper precursor satisfies at least one of the following characteristics:

[0017] The surface density of the carbon paper precursor is 30-70 g / m 2 ;

[0018] The thickness of the carbon paper precursor is 300-800 μm.

[0019] In a possible implementation manner, S3 satisfies at least one of the following characteristics:

[0020] The acupuncture treatment is a flat plate acupuncture method;

[0021] The needle density of the needle treatment is 15-30 needles / cm 2 .

[0022] In a possible implementation manner, the S4 includes:

[0023] providing a resin solution, wherein the resin solution comprises a resin and a solvent;

[0024] placing the carbon paper precursor in the resin solution, allowing the resin solution to penetrate the carbon paper precursor, and drying to obtain a carbon paper prepreg;

[0025] The carbon paper prepreg is subjected to heat pressing treatment to obtain the carbon paper base paper.

[0026] In a possible implementation manner, the preparation method satisfies at least one of the following characteristics:

[0027] The mass fraction of the resin in the resin solution is 5%-20%;

[0028] The mass ratio of the chopped carbon fiber to the resin in the carbon paper prepreg is 1:(1-1.5);

[0029] The temperature of the hot pressing treatment is 130-170°C;

[0030] The pressure of the hot pressing treatment is 1-2 MPa.

[0031] In a possible implementation manner, the S5 satisfies at least one of the following characteristics:

[0032] The temperature of the carbonization treatment is 800-1000°C;

[0033] The temperature of the graphitization treatment is 2000-2500°C.

[0034] In a possible implementation manner, the volume density of the carbon paper is 0.3-0.7 g / cm 3 .

[0035] On the other hand, the present application provides a carbon paper, which is prepared by the above-mentioned method for preparing carbon paper.

[0036] On the other hand, the present application provides an application of carbon paper in a fuel cell, wherein the carbon paper is prepared by the above-mentioned method for preparing carbon paper.

[0037] Based on the above technical solution, this application has the following beneficial effects:

[0038] The technical solution of the present application adopts chopped carbon fibers, and by combing and laying the chopped carbon fibers, the chopped carbon fibers are randomly oriented and distributed in the carbon fiber mesh structure, and further a carbon paper precursor is obtained by a needle punching treatment, so that the carbon paper precursor has a tight fiber overlap structure, which is conducive to forming a good conductive path; carbon paper is prepared using an isotropic carbon paper precursor, so that the carbon fibers in the carbon paper are uniformly distributed in a random orientation, can efficiently and uniformly conduct electrons, and the mechanical properties of the carbon paper are uniformly distributed, which is conducive to improving the overall performance of the carbon paper and avoiding local fractures; the needle punching process is simple, and the obtained carbon paper precursor has a large molding area, which is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 : A schematic diagram of a process for preparing carbon paper provided in an embodiment of the present application;

[0041] Figure 2 : Surface morphology of a carbon paper precursor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0043] It should be noted that in the description of the present application, for the following defined terms, unless a different definition is given in the claims or elsewhere in this specification, these definitions should be applied. All numerical values, whether or not explicitly indicated, are defined herein as being modified by the term "about". The term "about" generally refers to a numerical range that a person of ordinary skill in the art would consider to be equivalent to the stated value to produce substantially the same properties, functions, results, etc. A numerical range indicated by a low value and a high value is defined to include all numerical values ​​included in the numerical range and all subranges included in the numerical range.

[0044] It should be noted that, in the description of the present application, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0045] It should be noted that, in the description of the present application, the meaning of the terms "on", "above", "above", and "above" should be interpreted in the broadest sense, meaning that the description containing these terms is interpreted as "the component can be set on another component in direct contact, or there can be an intermediate component or layer between the components". In addition, for the convenience of description, the present application may also use spatial relative terms such as "under", "below", "under", "on", "above", "above", "lower", "upper", etc. to describe the relationship between an element or component and another element or component shown in the drawings. In addition to the orientations described in the figures, the spatially relative terms are also intended to cover different orientations of the device in use or operation. The device can be oriented in other ways (rotated 90° or in other orientations), and the spatially relative descriptors used in the present application can be interpreted accordingly.

[0046] The following combination Figure 1A method for preparing carbon paper provided in an embodiment of the present application is introduced. This specification provides method operation steps as in the embodiment, but may include more or fewer operation steps based on conventional or non-creative labor. The order of steps listed in the embodiment is only one way of executing the order of many steps and does not represent the only execution order. When the preparation method is actually executed, it can be executed in the order of the method shown in the embodiment or the accompanying drawings or in parallel. The method for preparing carbon paper may include S1-S5:

[0047] S1: Provide chopped carbon fiber.

[0048] Specifically, the chopped carbon fiber is selected from one or more of polyacrylonitrile-based carbon fiber and asphalt-based carbon fiber; preferably, the chopped carbon fiber is polyacrylonitrile-based carbon fiber, which has excellent strength and can withstand large external forces without damage during the preparation of carbon paper. The polyacrylonitrile-based carbon fiber also has good high temperature resistance and electrical conductivity. The prepared carbon paper can be used in electrode materials.

[0049] Specifically, the length of the chopped carbon fiber is 40-70mm; it is understandable that the length of the chopped carbon fiber can be any point value in the range of 40-70mm; illustratively, the length of the chopped carbon fiber can be 40mm, 45mm, 50mm, 60mm, 70mm, etc. If the length of the chopped carbon fiber is greater than the above range, the longer fibers will lead to uneven fiber distribution, thereby affecting the isotropy of the distribution of the chopped carbon fiber, causing differences in the performance of the fiber material in different directions, and the longer fibers are easily entangled and knotted during the needle punching process, which increases the difficulty of preparation and reduces production efficiency; if the length of the chopped carbon fiber is less than the above range, the overlap between the chopped carbon fibers is limited, and a mesh structure cannot be formed in the subsequent process, affecting the mechanical properties of the carbon paper. Preferably, the length of the chopped carbon fiber is 50-60mm, so that the length of the chopped carbon fiber is moderate and highly consistent, ensuring that the carbon fibers in the fiber mesh structure formed subsequently can be evenly dispersed.

[0050] Specifically, the diameter of the chopped carbon fiber is 3-15 μm; it is understandable that the diameter of the chopped carbon fiber can be any point value in 3-15 μm; illustratively, the diameter of the chopped carbon fiber can be 3 μm, 5 μm, 10 μm, 12 μm, 15 μm, etc. If the diameter of the chopped carbon fiber is greater than 15 μm, the fiber diameter is too large, which is not conducive to the overlap between the chopped carbon fibers, and the carbon fiber with too large a diameter is more likely to break during the needle punching process, resulting in a decrease in the mechanical strength of the carbon paper; if the diameter of the chopped carbon fiber is less than 3 μm, the chopped carbon fiber is softer and more fragile, which affects the combing and winding of the fiber during the needle punching process, resulting in the breakage of the carbon fiber or uneven winding. Preferably, the diameter of the chopped carbon fiber is 5-10 μm.

[0051] In some embodiments, the chopped carbon fibers may include a plurality of chopped carbon fibers with different lengths, wherein the chopped carbon fibers of different lengths have a preset ratio. Exemplarily, the chopped carbon fibers provided include two chopped carbon fibers with lengths of 25 mm and 50 mm, and the preset ratio between the two chopped carbon fibers may be any point value in the range of 1:1-1.5; in another example, two chopped carbon fibers with lengths of 35 mm and 70 mm are provided, and the preset ratio between the two chopped carbon fibers may be any point value in the range of 1:1-1.5. In this way, by combining chopped carbon fibers of different lengths, the chopped carbon fibers of different lengths are intertwined and overlapped with each other in the subsequent process, so as to form a more complex and stable fiber network structure, which is beneficial to improving the mechanical properties of the carbon paper.

[0052] S2: evenly laying the chopped carbon fibers, combing them, and laying them into a net to obtain a carbon fiber mesh structure, wherein the chopped carbon fibers are randomly oriented and distributed in the carbon fiber mesh structure.

[0053] Specifically, the chopped carbon fibers can be evenly spread by a mechanical spreading device. Specifically, the chopped carbon fibers can be combed and dispersed by a combing machine, and the combed short fibers are randomly oriented and dispersed. In this way, the chopped carbon fibers can be evenly dispersed without adding solvents and dispersants, which is conducive to simplifying the dispersion process, and can avoid the use of additives, thereby protecting the environment.

[0054] In some embodiments, the combing process includes mechanical combing, which can loosen the fiber raw material, reduce the cohesion between the fibers, disperse the fiber bundles into single fibers, and remove impurities in the fibers to improve the purity of the fibers.

[0055] In some embodiments, the combing process includes air combing, which utilizes the effect of air flow to evenly disperse the fibers, and the fibers can be directly deposited on the mesh curtain under the effect of air flow, so that the fibers are randomly oriented and distributed on the mesh curtain. Specifically, mechanical combing and air combing can be combined, the carbon fibers are loosened by mechanical combing, and then the carbon fibers are randomly oriented and distributed by air combing.

[0056] Specifically, the combed chopped carbon fibers are adsorbed on the mesh curtain, and the chopped carbon fibers are intertwined and overlapped with each other to form a carbon fiber mesh structure, so that the carbon fibers can be evenly distributed in the mesh structure.

[0057] S3: stacking the carbon fiber mesh structure and performing needle punching treatment to obtain a carbon paper precursor.

[0058] In some embodiments, the carbon fiber mesh structure is stacked at a preset frequency by a web laying machine. By controlling the stacking frequency of the carbon fiber mesh structure, the surface density of the carbon paper precursor formed in the subsequent process can be controlled. It can be understood that the preset frequency of the web laying machine can be set according to actual application requirements.

[0059] Specifically, the fluffy carbon fiber mesh structure can be formed into a compact planar structure by needle punching to obtain a carbon paper precursor having a compact fiber overlap structure. Figure 2 Moreover, the needle punching method can increase the longitudinal compression performance of the carbon fiber network structure without affecting the lateral compression performance of the carbon fiber network structure, thereby increasing the compactness of the carbon paper precursor without affecting the random orientation distribution of the carbon fibers in the carbon paper precursor.

[0060] Specifically, the needle density of the needle treatment is 15-30 needles / cm 2 It can be understood that the needle density of the needle treatment can be 15-30 needles / cm 2 For example, the acupuncture density of the acupuncture treatment can be 15 needles / cm 2 , 17 needles / cm 2 , 20 needles / cm 2 , 25 needles / cm 2 , 30 needles / cm 2 In this way, the needle punching density of the needle punching treatment is controlled within the above range, which can ensure the random distribution of the chopped carbon fibers while avoiding the damage and breakage of the fibers caused by too high acupuncture density and the low degree of interweaving between the fibers caused by too low acupuncture density, thereby affecting the mechanical properties of the carbon paper precursor.

[0061] Specifically, the needling depth is 5-10mm; it can be understood that the needling depth can be any point value in the range of 5-10mm; illustratively, the needling depth is 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc. In this way, the needling depth is controlled within the above range, and the needles can drive the carbon fibers to form a three-dimensional entangled structure, thereby improving the mechanical properties and overall uniformity of the carbon paper precursor, avoiding excessive needling depth leading to carbon fiber breakage and local stress concentration, and avoiding too small needling depth leading to a loose structure in the thickness direction of the carbon paper precursor.

[0062] Specifically, the needling angle is vertical, which increases the compression performance of the carbon fiber mesh structure in the thickness direction without affecting the random orientation distribution of the carbon fibers on the plane.

[0063] In some embodiments, the needling treatment adopts a flat-plate needling method. In this way, the flat-plate needling method can improve the strength of the carbon fiber in the interlayer and thickness directions; and the flat-plate needling method can make the distribution of the carbon fiber in the carbon paper precursor more uniform, reduce the defects and pores inside the carbon paper precursor, and thus improve the overall performance of the carbon paper; the flat-plate needling method can achieve continuous needling, has high production efficiency, and can meet the needs of large-scale production.

[0064] In some embodiments, the surface density of the carbon paper precursor is 30-70 g / m 2 It can be understood that the surface density of the carbon paper precursor can be 30-70g / m 2 For example, the surface density of the carbon paper precursor is 30 g / m 2 , 40g / m 2 , 50g / m 2 , 60g / m 2 , 70g / m 2 In this way, by controlling the surface density of the carbon paper precursor within the above range, it is ensured that the carbon paper precursor has sufficient lap strength, and at the same time, the thickness of the carbon paper precursor is ensured to be moderate, which is beneficial to the impregnation of the resin solution in the subsequent process.

[0065] Specifically, the thickness of the carbon paper precursor is 300-800 μm; it is understandable that the thickness of the carbon paper precursor can be any point value in the range of 300-800 μm; illustratively, the thickness of the carbon paper precursor can be 300 μm, 400 μm, 500 μm, 600 μm, 750 μm, 800 μm, etc. If the thickness of the carbon paper precursor is greater than 800 μm, the resistance of the carbon paper precursor will increase significantly, and the thickness and resistance of the carbon paper will increase, which is not conducive to the application of the carbon paper in the fuel cell; if the thickness of the carbon paper precursor is less than 300 μm, the carbon paper is too thin, and the strength of the carbon paper in the thickness direction is reduced, making it difficult for the carbon paper to play a supporting role.

[0066] In this way, by stacking carbon fiber mesh structures and performing needle punching treatment, an isotropic carbon paper precursor can be formed; compared with the existing carbon paper dry forming process, the carbon paper precursor prepared by the method provided in the present application can make the performance distribution of the carbon paper precursor more uniform, the forming efficiency higher, and the preparation process closely connected, which is conducive to industrial production; and the width of the prepared carbon paper precursor can reach more than 1m, which is conducive to large-scale production of carbon paper.

[0067] S4: curing the carbon paper precursor to obtain a carbon paper base.

[0068] In some embodiments, the curing process includes: providing a resin solution, the resin solution includes a resin and a solvent; placing a carbon paper precursor in the resin solution, allowing the resin solution to immerse the carbon paper precursor, and drying to obtain a carbon paper prepreg; performing a hot pressing treatment on the carbon paper prepreg to obtain a carbon paper base paper. In this way, the resin can fill the gaps between the carbon fibers, making the carbon fibers more tightly bonded, and the resin can form a protective layer on the surface of the carbon fibers, which is beneficial to improving the mechanical strength and stability of the carbon paper precursor; the hot pressing treatment can completely cure the resin, thereby shaping the carbon paper prepreg.

[0069] In some embodiments, the resin in the resin solution needs to show a certain fluidity at room temperature, or be soluble in a volatile solvent, and the resin needs to be a conductive material after carbonization. Specifically, the resin may include at least one of phenolic resin, polyacrylonitrile, polyimide, epoxy resin, polyvinyl alcohol, and polyaniline. Preferably, the resin is a phenolic resin, which can maintain a high residual carbon rate after carbonization, so that more carbon elements are left in the carbon paper, which is beneficial to improving the conductive properties of the carbon paper; in addition, a high residual carbon rate helps to maintain the structural integrity of the carbon paper after carbonization, thereby improving the mechanical strength of the carbon paper.

[0070] In some embodiments, the solvent in the resin solution is a volatile solvent; specifically, the solvent includes at least one of ethanol, acetone, dimethylformamide, ethyl acetate, N-methylpyrrolidone, and isopropyl acetate, which can be completely evaporated during the drying process to avoid incomplete solvent volatilization affecting the structural stability of the carbon paper.

[0071] Specifically, the mass fraction of the resin in the resin solution is 5%-20%; it is understandable that the mass fraction of the resin in the resin solution can be any point value between 5%-20%; illustratively, the mass fraction of the resin in the resin solution can be 5%, 10%, 15%, 17%, 20%, etc. Preferably, the mass fraction of the resin in the resin solution is 10-15%. In this way, controlling the mass fraction of the resin within the above range can make the resin solution have a certain fluidity, ensure that the resin can be immersed in the interior of the carbon paper precursor and filled between the fibers, ensure that the resin solution has a better wetting and filling effect on the carbon paper precursor, and avoid the resin mass fraction being too low to cause the resin to fail to protect the carbon fibers.

[0072] In some embodiments, the resin solution may further include a conductive filler; in one example, adding carbon black to the resin solution is beneficial to improving the conductivity, mechanical properties and void distribution of the carbon paper; in one example, adding graphite powder to the resin solution is beneficial to improving the conductivity of the carbon paper, and increasing the air permeability and hydrophobicity of the carbon paper; in one example, adding nano-boron to the resin solution is beneficial to improving the thermal and conductive properties of the carbon paper.

[0073] In some embodiments, the impregnated carbon paper precursor is dried under vacuum, the drying temperature is 80-90°C, and the drying time is 30-60min; it can be understood that the drying temperature can be any point value between 80-90°C, and the drying time can be any point value between 30-60min; illustratively, the drying temperature is 80°C, 82°C, 85°C, 87°C, 90°C, etc., and the drying time is 30min, 35min, 40min, 50min, 55min, 60min, etc. In this way, the solvent can be completely volatilized, the resin in the carbon paper precursor can be fixed, and deformation or cracking of the material caused by excessive drying temperature can be avoided.

[0074] Specifically, the mass ratio of chopped carbon fiber and resin in the carbon paper prepreg is 1:(1-1.5); it can be understood that the mass ratio of chopped carbon fiber and resin in the carbon paper prepreg can be any point value in 1:(1-1.5); illustratively, the mass ratio of chopped carbon fiber and resin in the carbon paper prepreg can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc. The mass ratio of chopped carbon fiber and resin is controlled within the above range, so that the resin can effectively form a bond between the fibers, make the structure of the carbon paper prepreg more compact, improve the flexibility of the carbon paper, avoid too little resin content affecting the bonding strength between the carbon fibers and the coating effect of the resin, and avoid too much resin content affecting the difficulty of hot pressing qualitative.

[0075] Specifically, the temperature of the hot pressing treatment is 130-170°C; it can be understood that the temperature of the hot pressing treatment can be any point value in the range of 130-170°C; illustratively, the temperature of the hot pressing treatment is 130°C, 140°C, 150°C, 160°C, 170°C, etc. In this way, controlling the hot pressing temperature within the above range can completely cure the resin, improve the bonding strength between the carbon fiber and the resin, and help improve the flexibility of the carbon paper and avoid cracking of the carbon paper surface.

[0076] Specifically, the pressure of the hot pressing treatment is 1-2MPa; it can be understood that the pressure of the hot pressing treatment can be any point value in 1-2MPa; illustratively, the pressure of the hot pressing treatment is 1MPa, 1.1MPa, 1.5MPa, 1.7MPa, 2MPa, etc. Specifically, the holding time of the hot pressing treatment is 30-60min; it can be understood that the holding time of the hot pressing treatment can be any point value in 30-60min; illustratively, the holding time of the hot pressing treatment is 30min, 40min, 50min, 55min, 60min, etc. The pressure and holding time of the hot pressing treatment are controlled within the above range, so as to control the thickness of the carbon paper, ensure that the density of the carbon paper is improved while reducing the resistance of the carbon paper, and thus improve the conductive performance of the carbon paper.

[0077] S5: performing carbonization and graphitization treatment on the carbon paper base paper to obtain carbon paper.

[0078] In some embodiments, carbonization and graphitization are carried out under a protective atmosphere. It is understandable that the protective atmosphere can be one or more of argon and nitrogen, which can prevent the material from reacting with oxygen at high temperature and prevent oxidation or burning of the material surface, thereby improving the purity and quality of the carbonized product; and in an oxygen-free environment, the carbonization reaction can proceed more fully to form a more uniform carbon structure.

[0079] In some embodiments, the process of carbonization and graphitization includes: placing the carbon paper base paper in a carbonization furnace for carbonization treatment to carbonize the resin therein; when the temperature in the carbonization furnace drops to room temperature, placing the carbonized carbon paper base paper in a graphitization furnace for graphitization treatment, and obtaining carbon paper after cooling.

[0080] Specifically, the temperature of the carbonization treatment is 800-1000°C; it is understandable that the temperature of the carbonization treatment can be any point value in the range of 800-1000°C; illustratively, the temperature of the carbonization treatment is 800°C, 850°C, 900°C, 950°C, 1000°C, etc. Specifically, the holding time of the carbonization treatment is 20-40min; it is understandable that the holding time of the carbonization treatment can be any point value in the range of 20-40min; illustratively, the holding time of the carbonization treatment can be 20min, 25min, 30min, 35min, 40min, etc. In this way, the resin can be effectively decomposed and transformed, a microporous structure can be formed in the carbon paper, and the combination of the carbon fiber and the resin carbon is more closely connected, which is beneficial to improving the mechanical strength and conductive properties of the carbon paper.

[0081] Specifically, the temperature of the graphitization treatment is 2000-2500°C; it is understandable that the temperature of the graphitization treatment can be any point value in the range of 2000-2500°C; illustratively, the temperature of the graphitization treatment can be 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, 2500°C, etc. Specifically, the holding time of the graphitization treatment is 10-20min; it is understandable that the holding time of the graphitization treatment can be any point value in the range of 10-20min; illustratively, the holding time of the carbonization treatment can be 10min, 12min, 15min, 17min, 20min, etc. In this way, controlling the temperature and holding time of the graphitization treatment within the above range can make the arrangement of carbon atoms in the carbon paper more regular, improve the graphitization degree of the carbon paper, and thus improve the conductive properties of the carbon paper.

[0082] In some embodiments, the volume density of carbon paper is 0.3-0.7 g / cm 3It can be understood that the volume density of carbon paper can be 0.3-0.7g / cm 3 For example, the volume density of carbon paper is 0.3 g / cm 3 , 0.4g / cm 3 , 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 If the volume density of carbon paper is higher than the above range, the gas permeability of carbon paper will be reduced, thus affecting the performance of fuel cells; if the volume density of carbon paper is lower than the above range, there will be more voids inside the carbon paper, resulting in a significant increase in the resistance of the carbon paper and a decrease in the flexibility of the carbon paper.

[0083] In summary, the present application adopts chopped carbon fibers, and combs and lays the chopped carbon fibers to obtain a carbon fiber mesh structure, so that the chopped carbon fibers are randomly oriented and distributed in the carbon fiber mesh structure; a carbon paper precursor is obtained by acupuncture treatment, so that the carbon paper precursor has a tight fiber overlap structure, which is helpful to form a good conductive path; carbon paper is prepared using an isotropic carbon paper precursor, which can make the carbon fibers in the carbon paper evenly distributed in a random orientation, and thus can efficiently and evenly conduct electrons, and make the mechanical properties of the carbon paper evenly distributed on a plane, which is beneficial to improving the overall performance of the carbon paper; this method has a simple process, and the obtained carbon paper precursor has a large molding area, which is conducive to large-scale production.

[0084] An embodiment of the present application further provides a carbon paper, wherein the carbon paper is prepared by the above-mentioned method for preparing carbon paper.

[0085] The embodiment of the present application also provides an application of carbon paper in a fuel cell, wherein the carbon paper is prepared by the above-mentioned method for preparing carbon paper. Among them, carbon paper is a key component of the gas diffusion layer in the fuel cell. The fuel cell can directly convert chemical energy into electrical energy through electrochemical reactions, and has the advantage of high energy conversion efficiency. The performance of the gas diffusion layer can directly affect the power density, durability and stability of the fuel cell, and the carbon paper can play the role of conducting electrons, distributing reaction gases, removing generated water and providing mechanical support in the gas diffusion layer. The carbon paper prepared in the present application has good isotropy, and the mechanical properties and electrical properties of the carbon paper are evenly distributed, which is conducive to improving the conductivity of the gas diffusion layer, providing good mechanical support for the gas diffusion layer, and thus improving the overall performance of the fuel cell.

[0086] The specific embodiments of the present application are introduced below in conjunction with the above technical scheme. The following examples describe the technical scheme of the present application in more detail, and these examples are only for illustrative purposes, because various modifications and changes within the scope of the disclosure of the present application are obvious to those skilled in the art. The reagents used in the examples can be obtained commercially or synthesized according to conventional methods, and can be used directly without further treatment, and the instruments and devices used in the examples can be obtained commercially.

[0087] Example 1

[0088] This embodiment provides a carbon paper and a preparation method thereof. The preparation method of the carbon paper specifically comprises the following steps:

[0089] 1. Provide chopped carbon fiber, the length of the chopped carbon fiber is 40mm, and the diameter of the chopped carbon fiber is 7μm;

[0090] 2. Evenly lay the chopped carbon fibers, comb them, and lay them to obtain a carbon fiber mesh structure, in which the chopped carbon fibers are randomly oriented and distributed;

[0091] 3. Stack the carbon fiber mesh structure and perform acupuncture treatment with a density of 20 needles / cm 2 , a carbon paper precursor is obtained, and the surface density of the carbon paper precursor is 42g / m 2 , thickness is 406μm;

[0092] 4. Providing a phenolic resin solution, wherein the mass fraction of the phenolic resin in the solution is 10%;

[0093] 5. Place the carbon paper precursor in a phenolic resin solution for 30 minutes to allow the phenolic resin solution to penetrate the carbon paper precursor. Take the carbon paper precursor out of the phenolic resin solution and dry it in a vacuum environment at a drying temperature of 80° C. for 60 minutes to obtain a carbon paper prepreg. The mass ratio of chopped carbon fiber to phenolic resin in the carbon paper prepreg is 1:1.2.

[0094] 6. The carbon paper prepreg is subjected to hot pressing treatment at a temperature of 150° C., a pressure of 1 MPa, and a holding time of 60 min to obtain a carbon paper base.

[0095] 7. The carbon paper base is carbonized at a temperature of 1000°C and a holding time of 30 minutes. After the temperature drops to room temperature, the carbonized carbon paper base is graphitized at a temperature of 2500°C and a holding time of 20 minutes. After the temperature drops to room temperature, carbon paper is obtained.

[0096] The thickness of the carbon paper prepared by the above steps is 211 μm, and the volume density of the carbon paper is 0.39 g / cm 3The average resistivity of carbon paper is 10.5 mΩ·cm, and the average tensile strength of carbon paper is 0.53 MPa.

[0097] Example 2

[0098] This embodiment provides a carbon paper and a preparation method thereof. The preparation method of the carbon paper specifically comprises the following steps:

[0099] 1. Provide chopped carbon fiber, the length of the chopped carbon fiber is 50mm, and the diameter of the chopped carbon fiber is 7μm;

[0100] 2. Evenly lay the chopped carbon fibers, comb them, and lay them to obtain a carbon fiber mesh structure, in which the chopped carbon fibers are randomly oriented and distributed;

[0101] 3. Stack the carbon fiber mesh structure and perform acupuncture treatment with a density of 22 needles / cm 2 , a carbon paper precursor is obtained, and the surface density of the carbon paper precursor is 45g / m 2 , thickness is 498μm;

[0102] 4. Providing a phenolic resin solution, wherein the mass fraction of the phenolic resin in the solution is 10%;

[0103] 5. Place the carbon paper precursor in a phenolic resin solution for 30 minutes to allow the phenolic resin solution to penetrate the carbon paper precursor. Take the carbon paper precursor out of the phenolic resin solution and dry it in a vacuum environment at a drying temperature of 80° C. for 60 minutes to obtain a carbon paper prepreg. The mass ratio of chopped carbon fiber to phenolic resin in the carbon paper prepreg is 1:1.2.

[0104] 6. The carbon paper prepreg is subjected to hot pressing treatment at a temperature of 150° C., a pressure of 1 MPa, and a holding time of 60 min to obtain a carbon paper base.

[0105] 7. The carbon paper base is carbonized at a temperature of 1000°C and a holding time of 30 minutes. After the temperature drops to room temperature, the carbonized carbon paper base is graphitized at a temperature of 2500°C and a holding time of 20 minutes. After the temperature drops to room temperature, carbon paper is obtained.

[0106] The thickness of the carbon paper prepared by the above steps is 253 μm, and the volume density of the carbon paper is 0.43 g / cm 3 The average resistivity of carbon paper is 9.1mΩ·cm, and the average tensile strength of carbon paper is 0.66MPa.

[0107] Example 3

[0108] This embodiment provides a carbon paper and a preparation method thereof. The preparation method of the carbon paper specifically comprises the following steps:

[0109] 2. Provide chopped carbon fiber, the length of the chopped carbon fiber is 60mm, and the diameter of the chopped carbon fiber is 7μm;

[0110] 2. Evenly lay the chopped carbon fibers, comb them, and lay them to obtain a carbon fiber mesh structure, in which the chopped carbon fibers are randomly oriented and distributed;

[0111] 3. Stack the carbon fiber mesh structure and perform acupuncture treatment with a density of 24 needles / cm 2 , a carbon paper precursor is obtained, and the surface density of the carbon paper precursor is 50g / m 2 , thickness is 583μm;

[0112] 4. Providing a phenolic resin solution, wherein the mass fraction of the phenolic resin in the solution is 10%;

[0113] 5. The carbon paper precursor is immersed in the phenolic resin solution for 30 minutes, so that the phenolic resin solution is immersed in the carbon paper precursor, and the carbon paper precursor is taken out from the phenolic resin solution and then dried in a vacuum environment at a drying temperature of 80° C. for 60 minutes to obtain a carbon paper prepreg, wherein the mass ratio of the chopped carbon fiber and the phenolic resin in the carbon paper prepreg is 1:1.2;

[0114] 6. The carbon paper prepreg is subjected to hot pressing treatment at a temperature of 150° C., a pressure of 1 MPa, and a holding time of 60 min to obtain a carbon paper base.

[0115] 7. The carbon paper base is carbonized at a temperature of 1000°C and a holding time of 30 minutes. After the temperature drops to room temperature, the carbonized carbon paper base is graphitized at a temperature of 2500°C and a holding time of 20 minutes. After the temperature drops to room temperature, carbon paper is obtained.

[0116] The thickness of the carbon paper prepared by the above steps is 320 μm, and the volume density of the carbon paper is 0.47 g / cm 3 The average resistivity of carbon paper is 8.2mΩ·cm, and the average tensile strength of carbon paper is 0.74MPa.

[0117] In Examples 1-3, resistivity tests were performed on the carbon paper surface in specific directions of 0°, 30°, 60°, 90°, 120°, and 150°, respectively. The resistivity results obtained in the tests in various directions were summarized and the average resistivity was calculated. It can be seen that the resistivity of the carbon paper of the present application is less than or equal to 10.5 mΩ·cm, which proves that the carbon paper has good conductive properties; and the difference between the resistivity result obtained in each direction and the average resistivity is within 3%, which proves that the conductive properties of the carbon paper are evenly distributed in the plane.

[0118] By selecting several specific directions of 0°, 30°, 60°, 90°, 120°, and 150° on the carbon paper surface to perform tensile performance tests, summarizing the tensile strength results obtained in the tests in each direction, and calculating the average resistivity, it can be seen that the tensile strength of the carbon paper of the present application is greater than or equal to 0.53 MPa, proving that the carbon paper has good mechanical properties; and the difference between the tensile strength obtained in each direction and the average tensile strength is within 5%, proving that the mechanical properties of the carbon paper are evenly distributed in the plane.

[0119] In summary, the present invention prepares a carbon paper precursor by carding, web laying and needle punching, and the surface density of the carbon paper precursor is 42-50 g / m 2 The carbon paper precursor is cured, carbonized and graphitized to obtain a carbon paper with a thickness of 211-320 μm and a volume density of 0.39-0.47 g / cm 3 The average resistivity of carbon paper is less than or equal to 10.5mΩ·cm, and the average tensile strength of carbon paper is greater than or equal to 0.53MPa, which has good conductive and mechanical properties. At the same time, the difference between the resistivity and the average resistivity in all directions on the carbon paper surface is within 3%, and the difference between the tensile strength and the average tensile strength is within 5%. The carbon paper has good isotropy, and the electrical and mechanical properties are evenly distributed on the carbon paper surface.

[0120] The above description has fully disclosed the specific implementation methods of the present application. It should be pointed out that any changes made by technicians familiar with the field to the specific implementation methods of the present application do not deviate from the scope of the claims of the present application. Accordingly, the scope of the claims of the present application is not limited to the above specific implementation methods.

Claims

1. A method for preparing carbon paper, characterized in that: The preparation method comprises: S1: Provide chopped carbon fiber; S2: evenly laying the chopped carbon fibers, combing them, and laying them to obtain a carbon fiber mesh structure, wherein the chopped carbon fibers are randomly oriented and distributed in the carbon fiber mesh structure; S3: stacking the carbon fiber mesh structure and performing a needle punching treatment to obtain a carbon paper precursor; S4: curing the carbon paper precursor to obtain a carbon paper base; S5: performing carbonization and graphitization on the carbon paper base to obtain carbon paper.

2. The preparation method according to claim 1, characterized in that: The chopped carbon fiber meets at least one of the following characteristics: The chopped carbon fiber is selected from one or more of polyacrylonitrile-based carbon fiber and asphalt-based carbon fiber; The length of the chopped carbon fiber is 40-70 mm; The diameter of the chopped carbon fibers is 3-15 μm.

3. The preparation method according to claim 1, characterized in that: The carbon paper precursor satisfies at least one of the following characteristics: The surface density of the carbon paper precursor is 30-70 g / m 2 ; The thickness of the carbon paper precursor is 300-800 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that The S3 satisfies at least one of the following characteristics: The acupuncture treatment is a flat plate acupuncture method; The needle density of the needle treatment is 15-30 needles / cm 2 .

5. The preparation method according to any one of claims 1 to 3, characterized in that: The S4 includes: providing a resin solution, wherein the resin solution comprises a resin and a solvent; placing the carbon paper precursor in the resin solution, allowing the resin solution to penetrate the carbon paper precursor, and drying to obtain a carbon paper prepreg; The carbon paper prepreg is subjected to heat pressing treatment to obtain the carbon paper base paper.

6. The preparation method according to claim 5, characterized in that: The preparation method meets at least one of the following characteristics: The mass fraction of the resin in the resin solution is 5%-20%; The mass ratio of the chopped carbon fiber to the resin in the carbon paper prepreg is 1:(1-1.5); The temperature of the hot pressing treatment is 130-170°C; The pressure of the hot pressing treatment is 1-2 MPa.

7. The preparation method according to any one of claims 1 to 3, characterized in that: The S5 satisfies at least one of the following characteristics: The temperature of the carbonization treatment is 800-1000°C; The temperature of the graphitization treatment is 2000-2500°C.

8. The preparation method according to any one of claims 1 to 3, characterized in that: The volume density of the carbon paper is 0.3-0.7 g / cm 3 .

9. A carbon paper, characterized in that: The carbon paper is prepared by the method for preparing carbon paper according to any one of claims 1 to 8.

10. Application of carbon paper in a fuel cell, characterized in that: The carbon paper is prepared by the method for preparing carbon paper according to any one of claims 1 to 8.

Images