A method for preparing carbon fiber paper for fuel cell gas diffusion layer

Abstract

The present invention relates to the field of fuel cell technology, and in particular, to a method for preparing carbon fiber paper for a fuel cell gas diffusion layer. The method comprises the following steps: adding phenolic resin, dispersant, anti-settling agent, asphalt and graphitization template agent into a mixed solvent for mixing and dispersing to obtain a resin impregnation solution; immersing carbon fiber base paper into the resin impregnation solution for impregnation, drying, and then subjecting to hot pressing curing and graphitization treatment to obtain a final product. Asphalt is used to replace part of the phenolic resin, and a graphitization template agent is introduced to reduce the graphitization temperature of the carbon fiber paper and improve the graphitization degree of the resin carbon. By optimizing the formula of the resin impregnation solution, the problem that asphalt and graphitization template agent are difficult to disperse and easy to settle in the phenolic resin impregnation solution is solved, and the asphalt, phenolic resin and graphitization template agent are loaded on the carbon paper base paper by a one-step impregnation method. The method has the advantages of simple process, low graphitization temperature and low energy consumption, and the prepared carbon fiber paper has good conductivity.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to a method for preparing carbon fiber paper for a fuel cell gas diffusion layer. Background Art

[0002] Gas diffusion layer (GDL) is an important component of fuel cells or electrolyzers. Most common GDLs use carbon fiber paper as the base layer. The carbon fiber paper is located between the catalyst layer and the bipolar plate. It plays an important role in the operation of fuel cells or electrolyzers, such as extracting waste heat, conducting electricity, coordinating water-gas mass transfer, and providing mechanical support.

[0003] The preparation process of carbon fiber paper as the base layer of GDL mainly includes the steps of wet papermaking, resin impregnation, hot pressing curing and graphitization. Among them, the resin impregnation process usually uses a resin impregnation liquid with phenolic resin as the main component. The phenolic resin is loaded on the carbon fiber base paper through the impregnation process. After hot pressing curing, it is converted into resin carbon in the graphitization process, which plays the role of adhesive and electrical and thermal conductivity in the carbon fiber paper. In the production of carbon fiber paper for GDL, graphitization equipment and energy consumption account for a large proportion of the overall production cost, and phenolic resin belongs to difficult graphitization carbon. There is a problem of difficult graphitization in the graphitization stage, and the electrical and thermal conductivity of phenolic resin carbon is directly related to its graphitization degree. In order to make phenolic resin carbon reach a more ideal degree of graphitization, the graphitization temperature usually needs to reach 2600-3000℃, which not only puts extremely high requirements on graphitization equipment, but also consumes a lot of energy. In order to reduce equipment and energy costs and solve the problem that the difficult-to-graphitize phenolic resin carbon restricts the electrical and thermal conductivity of the graphitized GDL, a reasonable solution is to use an easily graphitized carbon precursor material to replace part of the phenolic resin.

[0004] Asphalt is a common graphitizable carbon precursor, but there are certain difficulties in using asphalt to replace phenolic resin. Specifically, if asphalt and phenolic resin are impregnated separately in steps, the process is complicated and a continuous asphalt phase will be formed. Due to the high hardness and brittleness of asphalt at room temperature, the continuous asphalt phase will lead to poor processability of carbon fiber paper. Especially in the roll-to-roll production process of carbon fiber paper, the carbon fiber base paper loaded with asphalt lacks flexibility during the winding and unwinding process, and the asphalt layer is more likely to be damaged, which is difficult to adapt to industrial production. The small cracks formed by slight damage to the asphalt phase will also affect the conductivity of the carbon paper; in addition, since asphalt is incompatible with the existing phenolic resin impregnation liquid system, if asphalt is directly added to the phenolic resin impregnation liquid for impregnation, the asphalt is difficult to disperse in the phenolic resin impregnation liquid, and it is easy to settle. The impregnation effect is poor, which will lead to a decrease in the conductivity of the carbon fiber paper. Therefore, it is of great significance to provide a method for preparing carbon fiber paper with simple process, low energy consumption and good conductivity.

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

[0006] The purpose of the present invention is to provide a method for preparing carbon fiber paper for a fuel cell gas diffusion layer, using asphalt to replace part of the phenolic resin, and introducing a graphitization template, reducing the graphitization temperature of the carbon fiber paper, and improving the graphitization degree of the resin carbon. By optimizing the formula of the resin impregnation solution, the problem that the asphalt and the graphitization template are difficult to disperse and easy to settle in the phenolic resin impregnation solution is solved, and the asphalt, phenolic resin and graphitization template are impregnated in one step. The method has the advantages of simple process, low graphitization temperature and low energy consumption, and the prepared carbon fiber paper has good conductivity.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] A method for preparing carbon fiber paper for a fuel cell gas diffusion layer comprises the following steps:

[0009] The carbon fiber base paper is prepared by a wet papermaking process; phenolic resin, dispersant, anti-settling agent, asphalt and graphitization template are added into a mixed solvent for mixing and dispersing to obtain a resin impregnation solution; the carbon fiber base paper is immersed in the resin impregnation solution for impregnation, and then subjected to hot pressing curing and graphitization treatment after drying to obtain the carbon fiber base paper;

[0010] The mixed solvent includes at least two of methanol, ethanol, isopropanol, petroleum ether, n-heptane, toluene, xylene, and quinoline;

[0011] The dispersant includes at least one of methyl cellulose, polyacrylate, and polyoxyethylene ether dispersants;

[0012] The anti-settling agent includes at least one of polyurea, organic bentonite and polyvinyl pyrrolidone anti-settling agent.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] In the preparation process of carbon fiber paper, the present invention uses asphalt to replace part of the phenolic resin, and by introducing graphitizable asphalt, the graphitization degree of the carbon fiber paper resin carbon part is increased, thereby optimizing the conductive performance of the carbon fiber paper.

[0015] The present invention introduces a graphitization template agent into the carbon fiber paper system to catalyze the graphitization process of asphalt and phenolic formaldehyde, and can obtain resin carbon with a higher degree of graphitization at a lower graphitization temperature, thereby further optimizing the performance of the carbon fiber paper and saving equipment and energy costs in the graphitization stage.

[0016] The present invention solves the problem that asphalt and graphitized template are difficult to disperse and easy to settle in phenolic resin impregnation solution by optimizing the formula of resin impregnation solution. The asphalt and graphitized template particles in the prepared resin impregnation solution are evenly dispersed without agglomeration and do not settle for a long time, and have industrial feasibility. By using the resin impregnation solution to impregnate carbon fiber paper, the graphitized template, asphalt and phenolic resin can be introduced into the carbon fiber paper system in one step, thereby simplifying the process flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of a process flow for preparing carbon fiber paper for a fuel cell gas diffusion layer provided by an embodiment of the present invention;

[0019] Figure 2 A comparison chart of the stability results of different resin impregnation solutions provided in the embodiments of the present invention;

[0020] Figure 3 The morphology of the resin carbon after graphitization in Example 1-2 of the present invention and Comparative Example 1-2;

[0021] Figure 4 The morphology of the carbon fiber hot-pressed paper after hot-pressing curing in Example 1 of the present invention and Comparative Example 4 is shown. DETAILED DESCRIPTION

[0022] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0023] like Figure 1 As shown, the first aspect of the present invention provides a method for preparing carbon fiber paper for a fuel cell gas diffusion layer, which mainly involves the preparation of a resin impregnation solution, comprising the following steps:

[0024] Phenolic resin, dispersant, anti-settling agent, asphalt and graphitization template are added into a mixed solvent for mixing and dispersing to obtain a resin impregnation solution; the carbon fiber base paper is immersed in the resin impregnation solution for impregnation, and then subjected to hot pressing curing and graphitization treatment after drying to obtain a carbon fiber base paper;

[0025] The mixed solvent used includes at least two of methanol, ethanol, isopropanol, petroleum ether, n-heptane, toluene, xylene, and quinoline;

[0026] The dispersant used includes at least one of methyl cellulose, polyacrylate, and polyoxyethylene ether dispersant;

[0027] The anti-settling agent used includes at least one of polyurea, organic bentonite and polyvinyl pyrrolidone anti-settling agent.

[0028] In the preparation process of carbon fiber paper, the present invention uses asphalt to replace part of the phenolic resin, and by introducing graphitized asphalt, the graphitization degree of the resin carbon part of the carbon fiber paper is increased, thereby optimizing the conductive properties of the carbon fiber paper; in addition to the introduction of asphalt, in order to further improve the graphitization degree of the resin carbon, a carbon material with a highly graphitized crystal structure is introduced into the carbon fiber paper system as a graphitization template, which plays a nucleation role in the graphitization transformation process of the resin carbon at high temperature, and its surface crystal structure can induce the carbon atom rearrangement process of the resin carbon at high temperature, so that these carbon atoms are more easily completed along the crystal structure orientation of the template itself. Graphitization rearrangement, thereby increasing the residual carbon rate of asphalt and phenolic, and increasing the graphitization degree of the resin carbon. The method of the present invention can obtain resin carbon with a higher degree of graphitization at a lower graphitization temperature, thereby further optimizing the performance of the carbon fiber paper and saving equipment and energy costs in the graphitization stage.

[0029] The present invention solves the problem that asphalt and graphitized template are difficult to disperse and easy to settle in phenolic resin impregnation solution by optimizing the resin impregnation solution formula. The asphalt and graphitized template are introduced into the carbon fiber paper system in the impregnation stage through a one-step method, so as to achieve the purpose of improving the graphitization degree of resin carbon, optimizing the comprehensive performance of carbon fiber paper and simplifying the process flow.

[0030] The present invention adopts a specific compound of different solvents, and adds a dispersant and an anti-settling agent. The dispersant can prevent particle agglomeration, and further prevent sedimentation caused by agglomeration. The anti-settling agent is combined to achieve a better anti-settling effect. The mixed solvent, dispersant and anti-settling agent work synergistically to improve the stability of the resin impregnation solution, so that the asphalt and graphitized template particles in the prepared resin impregnation solution are evenly dispersed without agglomeration, and do not settle for a long time, and have the feasibility of industrial production. By using the resin impregnation solution to impregnate carbon fiber base paper, the graphitized template, asphalt and phenolic resin can be introduced into the carbon fiber paper system in one step, thereby simplifying the process flow.

[0031] In some specific embodiments of the present invention, the mixed solvent used includes ethanol, toluene and quinoline.

[0032] In some specific embodiments of the present invention, the mass ratio of ethanol, toluene and quinoline is 5-8:1-3:1-3. For example, the mass ratio of ethanol, toluene and quinoline can be any point value among 5:1:3, 5:2:2, 5:3:1, 6:1:3, 6:2:2, 6:3:1, 7:1:3, 7:2:2, 7:3:1, 8:1:3, 8:2:2, 8:3:1, or a range value consisting of any two point values.

[0033] The selection of mixed solvents, dispersants and anti-settling agents have an important influence on the stability of the resin impregnation solution, such as Figure 2 As shown, the present invention prepares four resin impregnation solutions with different formulas to investigate the effects of mixed solvents, dispersants and anti-settling agents on the stability of the resin impregnation solutions, wherein the first resin impregnation solution is one of the more preferred formula combinations of the present invention, wherein the dispersant is methyl cellulose, the anti-settling agent is polyurea, the asphalt is medium-temperature coal asphalt, and the graphitization template agent is multi-walled carbon nanotubes; the formula of the second resin impregnation solution does not add dispersants and anti-settling agents; the formula of the third resin impregnation solution only uses ethanol as the solvent, and the dispersants and anti-settling agents used are the same as those of the first resin impregnation solution; the fourth resin impregnation solution only uses ethanol as the solvent, and no dispersants and anti-settling agents are added. The formulas of the resin impregnation solutions are calculated by mass, as shown in Table 1.

[0034] Table 1

[0035]

[0036] After the above four resin impregnation solutions were prepared, the stability of the four groups of resin impregnation solution formulas was analyzed by using the static method. The results are as follows: Figure 2 As shown, the order of the stability of the four resin impregnation solutions from good to bad is: resin impregnation solution 1 > resin impregnation solution 3 > resin impregnation solution 2 > resin impregnation solution 4, which indicates that the compounding of the mixed solvent and the addition of the dispersant and anti-settling agent have a significant positive effect on the stability of the resin impregnation solution.

[0037] In some specific embodiments of the present invention, the graphitization template used includes at least one of artificial graphite, natural graphite, carbon black, Ketjen black, acetylene black, nano-carbon fiber, single-walled carbon nanotube, multi-walled carbon nanotube, and graphene; the above-mentioned graphitization template is a carbon material with a highly graphitized crystal structure at the micron or even nanometer scale. In addition to being able to act as a template to guide graphitization rearrangement, it is also a material with high intrinsic conductivity. Therefore, the doping of this type of conductive template can further optimize the conductivity of asphalt and phenolic resin carbon after graphitization, thereby improving the overall performance of the GDL product.

[0038] In some specific embodiments of the present invention, the mass fraction of the graphitized template in the resin impregnation solution is 0.01%-5%. For example, it can be any point value among 0.01%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range value consisting of any two point values.

[0039] In some specific embodiments of the present invention, the mass fraction of the dispersant in the resin impregnation solution is 0.1%-3%. For example, it can be any point value among 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, or a range value consisting of any two point values.

[0040] In some specific embodiments of the present invention, the mass fraction of the anti-settling agent in the resin impregnation solution is 0.1%-3%. For example, it can be any point value among 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, or a range value consisting of any two point values.

[0041] In some specific embodiments of the present invention, the total mass fraction of phenolic resin and asphalt in the resin impregnation solution is 5%-40%, preferably 15%-30%. For example, it can be any point value among 5%, 10%, 15%, 18%, 20%, 22.5%, 25%, 27.5%, 28.6%, 32%, 35%, 40% or a range value consisting of any two point values.

[0042] In some specific embodiments of the present invention, in the resin impregnation solution, the mass ratio of phenolic resin to asphalt is 1:2-15:1. For example, it can be any point value among 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, and 15:1, or a range value consisting of any two point values.

[0043] The present invention optimizes the ratio of asphalt to phenolic resin and the geometric distribution between the two, alleviates the problem that asphalt affects the processability of impregnated carbon fiber paper, and provides a new solution for the industrialization of asphalt-modified carbon fiber paper. In addition, if the mass ratio of phenolic resin to asphalt is too large or too small, it will affect the conductive properties of carbon fiber paper. Therefore, the ratio of phenolic resin to asphalt needs to be reasonably controlled.

[0044] In some specific embodiments of the present invention, the phenolic resin used is a resole type thermosetting phenolic resin made from phenol and formaldehyde, with a free phenol content of 10%-20% and a solid content of 40%-70%.

[0045] In some specific embodiments of the present invention, the asphalt used includes at least one of natural asphalt, coal asphalt, and petroleum asphalt.

[0046] In some specific embodiments of the present invention, the softening point of the asphalt used is 80-160°C, and the quinoline insoluble content is less than 10%. This type of asphalt has excellent graphitization performance and can also be melted with phenolic formaldehyde during the hot pressing stage to form a better interface effect between phenolic formaldehyde and asphalt.

[0047] In some specific embodiments of the present invention, the dispersion method in the process of preparing the resin dispersion includes at least one of stirring dispersion, high-speed shear dispersion, ultrasonic dispersion, and wet ball milling dispersion, wherein the stirring dispersion can be any one or more combinations of magnetic stirring dispersion, stirring paddle stirring dispersion, and dispersion disk stirring dispersion, etc.; and / or, the dispersion time is 3-360min depending on the dispersion time, for example, it can be any point value among 3min, 30min, 60min, 90min, 120min, 150min, 180min, 240min, 300min, and 360min, or a range value composed of any two point values.

[0048] In some specific embodiments of the present invention, the average thickness of the carbon fiber base paper used is 100-400 μm, for example, it can be any point value among 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, or a range value consisting of any two point values.

[0049] In some specific embodiments of the present invention, the average surface density of the carbon fiber base paper used is 10-50 g / m 2 , for example, it can be 10g / m 2 , 20g / m 2 , 30g / m 2 , 40g / m 2 , 50g / m 2 Any point value or a range of values ​​consisting of any two point values ​​in .

[0050] In some specific embodiments of the present invention, carbon fiber base paper is prepared by a wet papermaking process; the preparation method comprises the following steps:

[0051] The short-cut carbon fiber and sodium methyl cellulose are dispersed in water to prepare a carbon fiber suspension slurry, and then a stainless steel mesh is used for papermaking. After drying, the fiber paper is removed to obtain the carbon fiber base paper.

[0052] In some specific embodiments of the present invention, the drying temperature in the process of preparing carbon fiber base paper is 100-160°C; for example, it can be any point value among 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, and 160°C, or a range value composed of any two point values; the drying time is 1-60min, for example, it can be any point value among 1min, 10min, 20min, 30min, 40min, 50min, and 60min, or a range value composed of any two point values.

[0053] In some specific embodiments of the present invention, the chopped carbon fiber used to prepare the carbon fiber base paper includes at least one of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber, and viscose-based carbon fiber.

[0054] In some specific embodiments of the present invention, the average length of the chopped carbon fiber used is 1-20 mm, for example, it can be any point value among 1 mm, 4 mm, 8 mm, 10 mm, 15 mm, and 20 mm, or a range value consisting of any two point values; the average diameter of the chopped carbon fiber is 1-20 μm, for example, it can be any point value among 1 μm, 4 μm, 7 μm, 10 μm, 15 μm, and 20 μm, or a range value consisting of any two point values.

[0055] In some specific embodiments of the present invention, the carbon fiber base paper is immersed in the resin impregnation solution for 10-300s. For example, it can be any point value among 10s, 50s, 80s, 100s, 120s, 150s, 180s, 200s, 250s, and 300s, or a range value consisting of any two point values.

[0056] In some specific embodiments of the present invention, the drying temperature after impregnation is 60-150°C, for example, it can be any point value among 60°C, 80°C, 100°C, 120°C, 150°C, or a range value consisting of any two point values; the drying time is 1-30min, for example, it can be any point value among 1min, 5min, 10min, 15min, 20min, 25min, 30min, or a range value consisting of any two point values.

[0057] In some specific embodiments of the present invention, the temperature of hot pressing curing is 100-180°C, for example, it can be any point value among 100°C, 120°C, 140°C, 160°C, and 180°C, or a range value consisting of any two point values; the pressure of hot pressing curing is 0-5MPa, for example, it can be any point value among 0.5MPa, 1MPa, 2MPa, 3MPa, 4MPa, and 5MPa, or a range value consisting of any two point values; the time of hot pressing curing is 2-120min, for example, it can be any point value among 2min, 30min, 60min, 90min, and 120min, or a range value consisting of any two point values.

[0058] In some specific embodiments of the present invention, the graphitization temperature is 1400-2600°C, for example, it can be any point value among 1400°C, 1600°C, 1800°C, 2000°C, 2200°C, 2400°C, 2600°C, or a range value consisting of any two point values.

[0059] In some specific embodiments of the present invention, the heating rate of the graphitization process is 10-100°C / min, for example, it can be any point value among 10°C / min, 15°C / min, 30°C / min, 50°C / min, 75°C / min, 100°C / min, or a range value consisting of any two point values.

[0060] In some specific embodiments of the present invention, the protective gas used in the graphitization process includes argon and / or nitrogen.

[0061] The following is a detailed description of some embodiments of the present invention in conjunction with specific examples. The raw materials used in the examples can be purchased from the market unless otherwise specified.

[0062] Example 1

[0063] S1. In the wet papermaking stage, short-cut polyacrylonitrile-based carbon fibers with an average length of 4 mm and an average diameter of 7 μm are used. The carbon fibers are dispersed in water using a paddle-type high-speed shearing disperser. The formula of the carbon fiber dispersion slurry is composed of 0.25 parts of sodium methylcellulose, 1 part of short-cut carbon fibers, and 100 parts of water in a mass ratio. After papermaking, it is dried at 100°C for 30 minutes to obtain a surface density of 20 g / m 2 , carbon fiber paper (carbon fiber base paper) with an average thickness of 220 μm;

[0064] S2. In the impregnation stage, a mixed solvent is first prepared, 6 parts of ethanol are weighed according to the mass ratio, and then 2 parts of toluene and 1 part of quinoline are added to the ethanol in sequence under stirring to obtain a mixed solvent; 3 parts of phenolic resin are first added to the mixed solvent, and then 0.1 parts of dispersant and 0.2 parts of anti-settling agent are added, and finally 0.8 parts of asphalt and 0.2 parts of graphitization template are added, and then the mixed solution is dispersed using a specific dispersion method to obtain a resin impregnation solution; carbon fiber paper 1 is immersed in the prepared resin impregnation solution for 120 seconds, and after taking out, it is dried at 80°C for 10 minutes to obtain carbon fiber paper 2 (carbon fiber impregnated paper);

[0065] S3 hot pressing curing stage, the carbon fiber paper two in a flat vulcanizer for hot pressing and curing, hot pressing temperature, pressure, time were 140 ℃, 4MPa, 30min, to obtain carbon fiber paper three (carbon fiber hot pressing paper);

[0066] S4. In the graphitization stage, the carbon fiber paper 3 is heated to 2000° C. at a heating rate of 15° C. / min under the protection of argon gas for graphitization to obtain the carbon fiber paper 4 (carbon fiber graphitized paper, i.e., carbon fiber paper for fuel cell gas diffusion layer).

[0067] It should be noted that in Example 1, the dispersant used is methyl cellulose, the anti-settling agent used is polyurea, the asphalt used is medium-temperature coal tar with a softening point of 90°C, the graphitization template used is multi-walled carbon nanotubes, and the specific dispersion method used is specifically to first use a dispersion disk mixer to disperse for 15 minutes at a speed of 800r / min, and then disperse it with a high-speed shearing machine for 30 minutes at a speed of 10000r / min. Since the replacement of the above raw materials will lead to certain changes in the performance of the final carbon fiber paper, in order to illustrate the effectiveness of the scheme of the present invention, in the subsequent embodiments or comparative examples, the raw materials involved remain unchanged without indication. The range of raw materials mentioned above is still within the scope of protection of the present invention. In addition, it should also be noted that in all embodiments and comparative examples, due to the different residual carbon rates of asphalt and phenolic aldehyde after graphitization, when adjusting the amount of asphalt and phenolic aldehyde, it is not an equal replacement, and the total number of asphalt and phenolic aldehyde will have a certain difference, the purpose is to ensure that the resin carbon mass fraction in the final graphitized carbon fiber paper is basically the same.

[0068] Example 2

[0069] Example 2 is similar to Example 1, with the only difference being that in step S2, when preparing the resin impregnation solution, the amount of phenolic resin added is 1.6 parts and the amount of asphalt added is 1.6 parts; the other conditions are the same as those in Example 1.

[0070] Example 3

[0071] Example 3 is similar to Example 1, with the only difference being that in step S2, when preparing the resin impregnation solution, the amount of phenolic resin added is 3.2 parts and the amount of asphalt added is 0.4 parts; the other conditions are the same as those in Example 1.

[0072] Example 4

[0073] Example 4 is similar to Example 1, with the only difference being that in step S2, when preparing the resin impregnation solution, polyoxyethylene ether is used as the dispersant, organic bentonite is used as the anti-settling agent, and spherical artificial graphite with an average particle size of 3 μm is used as the graphitization template agent; the remaining conditions are the same as those in Example 1.

[0074] Comparative Example 1

[0075] Comparative Example 1 is similar to Example 1, with the only difference being that in step S2, when preparing the resin impregnation solution, no asphalt is added, and the amount of phenolic resin added is 4 parts; the other conditions are the same as those in Example 1.

[0076] Comparative Example 2

[0077] Comparative Example 2 is similar to Example 1, with the only difference being that in step S2, when preparing the resin impregnation solution, no graphitization template is added; and the other conditions are the same as those in Example 1.

[0078] Comparative Example 3

[0079] Comparative Example 3 is similar to Example 1, except that in step S2, only 9 parts of ethanol are used as the solvent when preparing the resin impregnation solution; the other conditions are the same as those in Example 1.

[0080] The resin impregnation liquid prepared in this comparative example has poor stability and will settle after being left standing for a short time. It has a poor impregnation effect on the carbon fiber base paper. After impregnation, spots and lace will appear, which may be the settled asphalt.

[0081] Comparative Example 4

[0082] Comparative Example 4 is similar to Example 1, except that the asphalt used is mesophase asphalt with a softening point of 240°C; since the residual carbon rate of the mesophase asphalt is relatively high, in step S2, 0.5 parts of mesophase asphalt is used when preparing the resin impregnation liquid; the other conditions are the same as in Example 1.

[0083] Test example

[0084] According to the test standard GB / T20042.7-2014, proton exchange membrane fuel cell part 7: carbon paper property test method, the performance of the carbon fiber graphitized paper obtained in the above embodiments and comparative examples was tested, and the plane resistivity and vertical resistivity of the sample were calculated, and the carbonization rate was calculated as carbon fiber paper three mass / carbon fiber paper four mass. The test results are shown in Table 2.

[0085] Table 2

[0086]

[0087]

[0088] As can be seen from the data in Table 1, the preparation method of the present invention can introduce a suitable proportion of asphalt into the resin impregnation liquid during the impregnation process of the carbon fiber paper for GDL, replace part of the phenolic resin, and then cooperate with the graphitization template to catalyze the graphitization process of the resin carbon in the graphitization stage, thereby optimizing the plane and vertical surface conductivity of the carbon fiber paper, reducing the graphitization temperature, and achieving the purpose of saving equipment and graphitization energy consumption costs. In addition, the method of the present invention also optimizes the formula of the resin impregnation liquid by using solvent compounding and dispersants and anti-settling agents, thereby improving the stability of the resin impregnation liquid, and introducing asphalt and graphitization templates into the carbon fiber paper system by impregnation at the same time through a one-step method, thereby simplifying the process flow.

[0089] Figure 3Optical microscope photographs of the resin carbon of the carbon fiber graphitized paper prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the present invention. It can be seen from the figures that there are some differences in the microscopic morphology of the resin carbon of asphalt and phenolic formaldehyde, corresponding to the differences in the graphitization process and degree of the two. The graphitization template can guide part of the resin carbon to transform into a graphitized crystal structure at the interface between the template and the resin carbon.

[0090] Figure 4 Optical microscope photographs of carbon fiber hot-pressed paper prepared in Example 1 and Comparative Example 4 of the present invention are shown. It can be seen from the figures that for Example 1, when a medium-temperature coal tar pitch raw material with a lower softening point is used, a fused interface will exist between the phenolic formaldehyde and the asphalt after curing; while for Comparative Example 4, when an intermediate phase asphalt raw material with a higher softening point is used, the asphalt and phenolic formaldehyde cannot form a fused interface after curing, and the particles of the intermediate phase asphalt can be clearly observed.

[0091] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing carbon fiber paper for a fuel cell gas diffusion layer, characterized in that: The following steps are involved: Phenolic resin, dispersant, anti-settling agent, asphalt and graphitized template are added into a mixed solvent for mixing and dispersing to prepare a resin impregnation solution; The carbon fiber base paper is immersed in the resin impregnation solution, and then subjected to hot pressing curing and graphitization treatment after drying to obtain the product; The mixed solvent includes ethanol, toluene and quinoline; the mass ratio of the ethanol, the toluene and the quinoline is 5-8:1-3:1-3; The softening point of the asphalt is 80-160°C; The dispersant includes at least one of methyl cellulose, polyacrylate, and polyoxyethylene ether; The anti-settling agent includes at least one of polyurea, organic bentonite and polyvinyl pyrrolidone.

2. The method for preparing carbon fiber paper for fuel cell gas diffusion layer according to claim 1, characterized in that: The graphitization template comprises at least one of artificial graphite, natural graphite, carbon black, Ketjen black, acetylene black, nano-carbon fiber, single-walled carbon nanotube, multi-walled carbon nanotube, and graphene; And / or, the mass fraction of the graphitized template in the resin impregnation solution is 0.01%-5%.

3. The method for preparing carbon fiber paper for fuel cell gas diffusion layer according to claim 1, characterized in that: The mass fraction of the dispersant in the resin impregnation liquid is 0.1%-3%.

4. The method for preparing carbon fiber paper for fuel cell gas diffusion layer according to claim 1, characterized in that: The mass fraction of the anti-settling agent in the resin impregnation solution is 0.1%-3%.

5. The method for preparing carbon fiber paper for fuel cell gas diffusion layer according to claim 1, characterized in that: The total mass fraction of the phenolic resin and the asphalt in the resin impregnation liquid is 5%-40%; And / or, the mass ratio of the phenolic resin to the asphalt is 1:2-15:

1.

6. The method for preparing carbon fiber paper for fuel cell gas diffusion layer according to claim 1, characterized in that: The asphalt includes at least one of natural asphalt, coal asphalt and petroleum asphalt; And / or, the quinoline insoluble matter content of the asphalt is less than 10%.

7. The method for preparing carbon fiber paper for fuel cell gas diffusion layer according to claim 1, characterized in that: The dispersion method comprises at least one of stirring dispersion, shearing dispersion, ultrasonic dispersion and wet ball milling dispersion; and / or the dispersion time is 3-360 min.

8. The method for preparing carbon fiber paper for fuel cell gas diffusion layer according to claim 1, characterized in that: Contains at least one of the following characteristics: (1) The average thickness of the carbon fiber base paper is 100-400 μm; (2) The average surface density of the carbon fiber base paper is 10-50 g / m 2 ; (3) The immersion time is 10-300s; (4) The drying temperature is 60-150° C. and the drying time is 1-30 min; (5) The temperature of the hot pressing curing is 100-180°C, the pressure is 0-5MPa, and the time is 2-120min; (6) The graphitization temperature is 1400-2600°C.

Images