A phenol resin slurry internal addition method carbon paper and a preparation method thereof

Abstract

The present application relates to a kind of phenolic resin slurry adding method carbon paper and its preparation method.The present application adds phenolic resin and dispersing agent into water, ultrasonic oscillation, mechanical stirring, obtains phenolic resin suspension;Carbon fiber is dispersed in water stirring, adds polyvinyl alcohol fiber and polyethylene oxide, is uniformly mixed, obtains carbon fiber / polyvinyl alcohol fiber suspension.The prepared phenolic resin suspension is poured into carbon fiber / polyvinyl alcohol fiber suspension, is uniformly mixed, obtains mixed slurry, is copied into shape, is pressed, is dried, obtains carbon paper base paper.Heat pressing, carbonization, prepares a kind of phenolic resin slurry adding method carbon paper.The carbon paper prepared in the present application has high mechanical strength, low resistivity, porosity and air permeability is easy to adjust, and preparation process is simple, quality is controllable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fuel cell preparation, and particularly relates to a phenolic resin slurry internal addition method carbon paper and a preparation method thereof. BACKGROUND

[0002] Fuel cell is an energy conversion device that directly converts chemical energy into electrical energy, and the proton exchange membrane fuel cell (i.e. hydrogen fuel cell) is the most widely used fuel cell at present. The proton exchange membrane fuel cell does not involve the conversion of excess energy during operation, and is not limited by the Carnot cycle, so the energy conversion efficiency is very high. The energy conversion efficiency of a general fuel cell is between 50% and 60%, while the energy conversion efficiency of the proton exchange membrane fuel cell is as high as 90% (operating below 100℃). In addition, the proton exchange membrane fuel cell does not emit harmful gases during operation. Therefore, the proton exchange membrane fuel cell has the advantages of high power generation efficiency and no environmental pollution.

[0003] The proton exchange membrane fuel cell is currently the most promising fuel cell, but the high manufacturing cost restricts its development, so it is necessary to optimize and improve the key materials thereof. The proton exchange membrane fuel cell is composed of a bipolar plate, a gas diffusion layer, a catalyst layer and a proton exchange membrane, wherein the gas diffusion layer is composed of a substrate layer and a microporous layer. The gas diffusion layer supports the catalyst layer, stabilizes the electrode structure and conducts water, gas and electrons in the fuel cell, and is one of the key components that affect the performance of the cell.

[0004] The substrate layer needs to have a uniform void structure, a low resistivity, sufficient mechanical strength, appropriate hydrophilicity / hydrophobicity, good thermal conductivity and excellent chemical stability. At present, the materials of the substrate layer mainly include carbon fiber paper (referred to as carbon paper), carbon fiber cloth and carbon black paper, and the carbon paper is the most commonly used material for the substrate layer because it has the advantages of high mechanical strength, high air permeability, low resistivity, high production efficiency and low manufacturing cost.

[0005] The current production process of the carbon paper is as follows: carbon fibers, other fibers (such as plant fibers, polyvinyl alcohol fibers and polyacrylonitrile fibers, etc.) and dispersants (polyethylene oxide, polyacrylamide and sodium dodecylbenzenesulfonate, etc.) are mixed and dispersed in water, formed in a former, pressed, dried (to remove water), impregnated with a phenolic resin / ethanol solution, dried (to remove the ethanol solution), heat-pressed and cured, high-temperature carbonized and graphitized to produce the carbon paper.

[0006] The Chinese patent with the publication number CN103556543B and the publication date of April 20, 2016 uses short-cut carbon fibers, plant fibers, thermal bonding fibers and carbon black as raw materials, and after defibrillation, beating and pulp mixing, a wet paper web is made by wet papermaking process, and then dried, hot-pressed and hydrophobic treated to produce carbon paper. However, the carbon paper has not been carbonized, contains more plant fibers and thermal bonding fibers, resulting in high resistivity.

[0007] The Chinese patent with the publication number CN113774720B and the publication date of July 12, 2022 performs hydrophilic surface treatment on short-cut polyacrylonitrile carbon fibers, then disperses them in water to make a wet paper web, dries it to produce carbon paper base paper, and then immerses it in a hot-setting phenolic resin ethanol solution, dries, hot-presses, cures and carbonizes to produce carbon paper. However, the raw material of the carbon paper base paper of this patent is only carbon fiber, which is difficult to adjust the mechanical strength, porosity and electrical conductivity of the carbon paper. In addition, the process and operation of immersing the hot-setting phenolic resin ethanol solution are relatively complex, and the uneven distribution of the resin and the volatilization of ethanol will cause environmental pollution.

[0008] The Chinese patent with the publication number CN114808536B and the publication date of February 28, 2023 places the carbon paper skeleton layer (including carbon fiber base paper, carbon fiber thin felt, etc.) in a boron-containing hot-setting resin / alcohol impregnating solution, and then performs rolling, drying, hot-pressing, curing, carbonization and graphitization to produce carbon paper. In order to produce boron-containing carbon paper with good performance, this patent still needs to use the method of immersing the resin / ethanol solution to bond the carbon fibers and add boron-containing substances, so the preparation method of this patent still has the problems of complex process and operation, environmental pollution, etc.

[0009] In summary, the current carbon paper preparation method has the problems of multiple process steps, high production cost, high energy consumption and environmental pollution. In addition, the resin impregnation method using ethanol as a solvent will affect the uniformity of the resin distribution in the carbon paper, making it difficult to control the pore size and porosity of the carbon paper, and also affecting the strength of the carbon paper. Therefore, it is necessary to develop a new carbon paper preparation method with simple process, easy operation and controllable quality. SUMMARY

[0010] The technical problem to be solved by the present application is that the current carbon paper preparation needs to first produce carbon paper base paper, and then immerse it in a phenolic resin ethanol solution, which has the problems of complex process operation, difficult control of carbon paper porosity, low mechanical strength and environmental pollution. The present application proposes a phenolic resin in-pulp addition method for carbon paper and its preparation method, which cancels the phenolic resin ethanol solution immersion and drying processes, thereby simplifying the process operation, improving the product quality, reducing the production cost and reducing the environmental pollution.

[0011] The technical solution adopted by the present application to solve the technical problem is as follows:

[0012] The application provides a phenolic resin slurry internal addition method carbon paper preparation method, which comprises the following steps:

[0013] (1) adding phenolic resin into water and adding a dispersing agent to obtain a phenolic resin suspension;

[0014] placing the phenolic resin suspension into an ultrasonic cleaner for ultrasonic oscillation to obtain a uniformly dispersed phenolic resin suspension;

[0015] stirring the phenolic resin suspension with a stirrer for standby;

[0016] (2) adding carbon fibers into water to obtain a carbon fiber slurry;

[0017] adding polyvinyl alcohol fibers and polyethylene oxide;

[0018] stirring in the stirrer to obtain a uniformly mixed carbon fiber / polyvinyl alcohol fiber suspension;

[0019] (3) slowly pouring the phenolic resin suspension prepared in step (1) into the carbon fiber / polyvinyl alcohol fiber suspension prepared in step (2) and uniformly mixing to obtain a mixed slurry;

[0020] forming, pressing and drying the mixed slurry in a paper machine to obtain a carbon paper base paper;

[0021] hot-pressing the carbon paper base paper in a hot press and performing carbonization after hot-pressing to obtain a target carbon paper.

[0022] Further, the phenolic resin in step (1) is thermosetting phenolic resin or thermoplastic phenolic resin, which is in powder form and has a particle size of 0.01-200 μm.

[0023] Further, the phenolic resin suspension in step (1) is placed in an ultrasonic cleaner for ultrasonic oscillation for 5-30 min at an ultrasonic frequency of 50-500 kHz to obtain a uniformly dispersed phenolic resin suspension; and a stirrer with a rotating speed of 30-300 rpm is used to stir the phenolic resin suspension.

[0024] Further, the dispersing agent in step (1) is sodium polyacrylate or potassium polyacrylate.

[0025] Further, the carbon fibers in step (2) are one or more of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers and viscose-based carbon fibers;

[0026] the carbon fibers have a diameter of 1-15 μm or are compounded with carbon fibers of multiple diameters;

[0027] the carbon fibers have a length of 1-12 mm or are compounded with carbon fibers of multiple lengths.

[0028] Further, the mass concentration of the carbon fiber slurry is 0.05%-0.5%; the adding amount of the polyvinyl alcohol fiber is 0%-15% of the mass of the carbon fiber; and the adding amount of the polyethylene oxide is 0.05%-5% of the mass of the phenolic resin.

[0029] Further, the temperature of the drying in step (3) is 80-110℃, and the time is 5-40min; the temperature of the hot pressing is 140-200℃, the pressure is 2-15MPa, and the time is 20-120min; and the temperature of the atmosphere furnace is 600-1600℃, and the carbonization time is 30-120min.

[0030] The application further provides another carbon paper prepared by the preparation method of the carbon paper. 2 .

[0031] The application provides a gas diffusion layer, which comprises the carbon paper.

[0032] The application provides a battery, which comprises the gas diffusion layer.

[0033] The application has the following beneficial effects:

[0034] (1) The adhesive used in the application is phenolic resin, and the problem of agglomeration and caking in water is solved by adding a dispersant and ultrasonic pretreatment, the water wettability is improved, and uniform dispersion in water is achieved.

[0035] (2) The use of polyvinyl alcohol fiber is beneficial to improve the strength of the carbon paper base paper and enhance the operability of the production process.

[0036] (3) The use of polyethylene oxide promotes the dispersion of carbon fibers in water, solves the problems of easy agglomeration of carbon fibers in water and uneven paper formation. Another significant effect is that polyethylene oxide and phenolic resin form a network flocculation, promote the retention of phenolic resin, avoid the loss of phenolic resin with water in the papermaking process, and achieve the dual effects of dispersion and retention.

[0037] (4) The application adopts the method of adding phenolic resin in the pulp, realizes one-time forming of the carbon paper base paper, eliminates the phenolic resin impregnation step, removes the use of organic solvents such as ethanol and related impregnation and drying equipment, saves energy consumption, and reduces production cost and environmental pollution. The production process of the carbon paper is clean and efficient, the raw materials used are economical and easy to obtain, and continuous and large-scale production can be realized.

[0038] (5) The carbon paper has good mechanical strength, excellent electrical conductivity and uniform pore structure. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1Preparation flow chart of carbon paper of the present application;

[0040] Figure 2 Physical picture of carbon paper raw paper prepared in Example 2 of the present application;

[0041] Figure 3 Physical picture of carbon paper prepared in Example 2 of the present application;

[0042] Figure 4 Scanning electron microscope picture of carbon paper prepared in Example 2 of the present application, magnification 100 times. DETAILED DESCRIPTION

[0043] Technical scheme of the present application:

[0044] (1) Phenolic resin is added into water, then 0%-1.0% dispersant (sodium polyacrylate or potassium polyacrylate) relative to the mass of phenolic resin is added, to obtain phenolic resin suspension. Then the phenolic resin suspension is placed in an ultrasonic cleaning machine for ultrasonic oscillation, the time is 5-30 min, the ultrasonic frequency is 50-500 kHz, to obtain uniformly dispersed phenolic resin suspension. Then the phenolic resin suspension is stirred using a stirrer with a rotation speed of 30-300 revolutions / minute, for standby.

[0045] (2) Carbon fibers with a diameter of 1-15 μm and a length of 1-12 mm are added into water, to obtain carbon fiber slurry with a mass concentration of 0.05%-0.5%. Then 0%-15% polyvinyl alcohol fiber relative to the mass of carbon fiber and 0.05%-5% polyethylene oxide relative to the mass of phenolic resin are added. Then the mixture is stirred in a stirrer with a rotation speed of 30-300 revolutions / minute for 1-5 min, to obtain uniformly mixed carbon fiber / polyvinyl alcohol fiber suspension.

[0046] (3) The prepared phenolic resin suspension is slowly poured into the carbon fiber / polyvinyl alcohol fiber suspension (phenolic resin accounts for 50%-400% of the mass of carbon fiber), mixed uniformly, to obtain mixed slurry. The mixed slurry is formed into shape in a paper machine, pressed, dried at 80-110°C for 5-40 min, to obtain carbon paper raw paper. Then the carbon paper raw paper is hot-pressed in a hot press at 140-200°C and a pressure of 2-15 MPa for 20-120 min. Finally, the carbon paper raw paper is carbonized in an atmosphere furnace at 600-1600°C for 30-120 min, to obtain carbon paper with a basis weight of 30-150 g / m 2 A phenolic resin in-pulp addition method carbon paper.

[0047] Principle of the method of the present application:

[0048] The phenolic resin is a linear or three-dimensional condensation polymer with benzene ring structure and phenolic hydroxyl group, which is prepared by condensation of phenol and formaldehyde as main raw materials in the presence of a catalyst. The phenolic resin is insoluble in water and has poor hydrophilic ability. The present application breaks the phenolic resin lumps by ultrasonic effect, reduces the surface tension of the phenolic resin by a dispersing agent, and improves the wettability of the phenolic resin in water, so that a uniform and stable phenolic resin dispersion liquid is formed by mechanical stirring.

[0049] The carbon fiber is composed of more than 90% carbon element, has a graphite-like structure, and the carbon elements are mainly connected by sp 2 The carbon fiber surface lacks active functional groups and is not easy to combine and react with other compounds. Meanwhile, the carbon fiber has a large length-diameter ratio and is easy to agglomerate in water, so that it is difficult to uniformly disperse in water, resulting in poor uniformity of the carbon paper. In the present application, polyethylene oxide is added to the carbon fiber slurry to form a wetting film on the surface of the carbon fiber, so as to enhance the sliding energy efficiency between the carbon fibers and facilitate the dispersion of the carbon fibers in water. In addition, the polyvinyl alcohol fiber has abundant hydroxyl groups and excellent dispersion performance in water, so that the addition of the polyvinyl alcohol fiber can effectively enhance the barrier effect between the carbon fibers and promote the dispersion of the carbon fibers.

[0050] Only when the phenolic resin is combined with the carbon fiber to form a slurry, the phenolic resin has a small particle size, so that it is seriously lost during the forming process. However, when the phenolic resin is added to the slurry composed of the carbon fiber, the polyvinyl alcohol fiber and the polyethylene oxide, the ether oxygen non-shared electron pair in the polyethylene oxide has a strong affinity with the hydroxyl group of the phenolic resin, and hydrogen bond association is generated between them to form a network structure, which agglomerates the small fibers and fillers in the paper material together, so that the retention rate is greatly improved. Therefore, the ether bond oxygen atom of the polyethylene oxide and the hydroxyl group of the phenolic resin generate hydrogen bond association to form a network structure, which captures the phenolic resin in the mixed slurry, so as to greatly improve the retention rate of the phenolic resin. Therefore, the polyethylene oxide not only effectively disperses the carbon fiber, but also forms a network structure with the phenolic resin through hydrogen bond association, which provides the possibility for the retention and uniform distribution of the phenolic resin in the carbon paper.

[0051] In order to improve the bonding strength between the carbon fibers and the conductivity of the carbon paper, the conventional carbon paper adopts the method of impregnating the base paper of the carbon paper with a phenolic resin / ethanol solution. The present application introduces the phenolic resin into the water and uniformly adsorbs and retains it on the fibers by using the dispersion, addition in the slurry and retention technology of the phenolic resin in water, regulates the glass transition temperature of the phenolic resin to make it become a high elastic state and then a viscous flow state, and inlays and solidifies it at the intersection of the carbon fibers. Therefore, the addition of the phenolic resin in the slurry can improve the bonding strength of the carbon fibers, the conductivity and the porosity of the carbon paper. Compared with the traditional carbon paper, the present application optimizes the preparation process of the carbon paper, regulates the porosity of the carbon paper, and improves the strength and the conductivity of the carbon paper.

[0052] Example 1

[0053] First step: phenolic resin was added into water, then 0.01% of polyacrylic acid sodium was added into the water, which was relative to the mass of phenolic resin. The phenolic resin suspension was obtained. Then the phenolic resin suspension was put into an ultrasonic cleaner and was ultrasonically vibrated for 5 minutes with a frequency of 50 kHz. The uniformly dispersed phenolic resin suspension was obtained. Then the phenolic resin suspension was stirred by a stirrer with a rotation speed of 30 revolutions per minute for standby.

[0054] Second step: carbon fibers were added into water to obtain a carbon fiber slurry with a mass concentration of 0.05%. Then 5% of polyvinyl alcohol fibers and 0.1% of polyethylene oxide were added into the carbon fiber slurry, which was relative to the mass of carbon fibers and the mass of phenolic resin, respectively. The mixture was stirred in a stirrer with a rotation speed of 30 revolutions per minute for 1 minute to obtain a uniformly mixed carbon fiber / polyvinyl alcohol fiber suspension.

[0055] Third step: the prepared phenolic resin suspension was slowly poured into the carbon fiber / polyvinyl alcohol fiber suspension (the mass of phenolic resin was 50% of the mass of carbon fibers), and the mixture was uniformly mixed to obtain a mixed carbon fiber slurry. The mixed carbon fiber slurry was formed into a carbon paper base paper in a paper machine, was pressed, and was dried at 80°C for 40 minutes to obtain a carbon paper base paper. Then the carbon paper base paper was hot-pressed in a hot press at 140°C and a pressure of 13 MPa for 120 minutes. Finally, the carbon paper base paper was carbonized in an atmosphere furnace at 800°C for 120 minutes to obtain a carbon paper with a basis weight of 80 g / m 2 A carbon paper for a gas diffusion layer of a fuel cell.

[0056] Example 2

[0057] First step: phenolic resin was added into water, then 0.25% of a dispersant polyacrylic acid sodium was added into the water, which was relative to the mass of phenolic resin. The phenolic resin suspension was obtained. Then the phenolic resin suspension was put into an ultrasonic cleaner and was ultrasonically vibrated for 10 minutes with a frequency of 100 kHz. The uniformly dispersed phenolic resin suspension was obtained. Then the phenolic resin suspension was stirred by a stirrer with a rotation speed of 100 revolutions per minute for standby.

[0058] Second step: carbon fibers were added into water to obtain a carbon fiber slurry with a mass concentration of 0.15%. Then 10% of polyvinyl alcohol fibers and 2% of polyethylene oxide were added into the carbon fiber slurry, which was relative to the mass of carbon fibers and the mass of phenolic resin, respectively. The mixture was stirred in a stirrer with a rotation speed of 100 revolutions per minute for 3 minutes to obtain a uniformly mixed carbon fiber / polyvinyl alcohol fiber suspension.

[0059] Third step: The prepared phenolic resin suspension was slowly poured into the carbon fiber / polyvinyl alcohol fiber suspension (phenolic resin was 200% of the mass of carbon fiber), mixed uniformly to obtain a carbon fiber mixed slurry. The mixed slurry was formed into a carbon paper base paper in a paper machine, pressed, dried at 100°C for 20 min, and then hot-pressed in a hot press at 170°C and a pressure of 10 MPa for 60 min. Finally, the carbon paper base paper was carbonized in an atmosphere furnace at 1200°C for 60 min to obtain a carbon paper with a basis weight of 80 g / m 2 A carbon paper for a gas diffusion layer of a fuel cell.

[0060] The carbon paper base paper prepared in this example is shown in Figure 2 , and the target carbon paper is shown in Figure 3 In addition, it can be seen from Figure 4 that the carbon fibers in the carbon paper of the present application are distributed in disorder, which can effectively ensure the overall uniformity of the carbon paper matrix. The phenolic resin in the conventional phenolic resin impregnation method carbon paper is distributed unevenly, and a large amount of phenolic resin is aggregated on one side of the carbon paper during the drying process, causing the voids to be blocked. The phenolic resin in this example is uniformly distributed in the carbon paper (inside and surface), especially at the contact points between the carbon fibers and the carbon fibers. The bonding strength between the carbon fibers is increased through the hot pressing and carbonization processes, and therefore the strength of the carbon paper is also improved. In addition, the carbon paper of this example has good porosity and air permeability, which can ensure the smooth passage of gas.

[0061] Example 3

[0062] First step: Phenolic resin was added to water, and then 0.8% of polyacrylic acid potassium based on the mass of the phenolic resin was added to obtain a phenolic resin suspension. The phenolic resin suspension was then placed in an ultrasonic cleaner for ultrasonic vibration for 30 min at an ultrasonic frequency of 500 kHz to obtain a uniformly dispersed phenolic resin suspension. The phenolic resin suspension was then stirred using a stirrer at a speed of 300 revolutions per minute for standby.

[0063] Second step: Carbon fibers were added to water to obtain a carbon fiber slurry with a mass concentration of 0.4%. Then 15% of polyvinyl alcohol fiber based on the mass of the carbon fiber and 5% of polyethylene oxide based on the mass of the phenolic resin were added, and the mixture was stirred in a stirrer at a speed of 300 revolutions per minute for 5 minutes to obtain a uniformly mixed carbon fiber / polyvinyl alcohol fiber suspension.

[0064] Third step: The prepared phenolic resin suspension was slowly poured into the carbon fiber / polyvinyl alcohol fiber suspension (400% of the mass of the carbon fiber was phenolic resin), and mixed uniformly to obtain a carbon fiber mixed slurry. The mixed slurry was formed into a shape in a paper machine, pressed, dried at 110°C for 40 min, and a carbon paper base paper was obtained. Then the carbon paper base paper was hot-pressed in a hot press at 200°C and a pressure of 15 MPa for 20 min. Finally, carbonization was performed at 1600°C in an atmosphere furnace for 30 min, and a carbon paper with a basis weight of 80 g / m 2 A carbon paper for a fuel cell gas diffusion layer.

[0065] Comparative Example 1

[0066] First step: Carbon fibers were added to water to obtain a carbon fiber slurry with a mass concentration of 0.15%. Then 10% of polyvinyl alcohol fibers and 1% of polyethylene oxide relative to the mass of the carbon fibers were added, and stirred in a stirrer at a speed of 100 revolutions per minute for 3 min to obtain a mixed and uniform carbon fiber / polyvinyl alcohol fiber suspension.

[0067] Second step: The mixed slurry was formed into a shape in a paper machine, pressed, dried at 100°C for 20 min, and a carbon paper base paper was obtained. Then the carbon paper base paper was hot-pressed in a hot press at 170°C and a pressure of 10 MPa for 60 min. Finally, carbonization was performed at 1200°C in an atmosphere furnace for 60 min, and a carbon paper with a basis weight of 80 g / m 2 A carbon paper for a fuel cell gas diffusion layer.

[0068] Comparative Example 2

[0069] First step: Carbon fibers were added to water to obtain a carbon fiber slurry with a mass concentration of 0.15%. Then 10% of polyvinyl alcohol fibers relative to the mass of the carbon fibers and 2% of polyethylene oxide relative to the mass of the phenolic resin were added, and stirred in a stirrer at a speed of 100 revolutions per minute for 3 min to obtain a mixed and uniform carbon fiber / polyvinyl alcohol fiber suspension.

[0070] Second step: The mixed slurry was formed into a shape in a paper machine, pressed, dried at 100°C for 20 min, and a carbon paper base paper was obtained. Then the carbon paper base paper was hot-pressed in a hot press at 170°C and a pressure of 10 MPa for 60 min. Finally, carbonization was performed at 1200°C in an atmosphere furnace for 60 min, and a carbon paper with a basis weight of 80 g / m

[0071] Comparative Example 3

[0072] (1) Phenolic resin was added into water, and then 0.25% of sodium polyacrylate was added with respect to the mass of phenolic resin to obtain a phenolic resin suspension. The phenolic resin suspension was then placed in an ultrasonic cleaner and ultrasonically vibrated for 10 minutes at a frequency of 100 kHz to obtain a uniformly dispersed phenolic resin suspension. The phenolic resin suspension was then stirred using a stirrer at a speed of 100 revolutions per minute and was ready for use.

[0073] (2) Carbon fibers were added into water to obtain a carbon fiber slurry having a mass concentration of 0.15%. Then 10% of polyvinyl alcohol fibers were added with respect to the mass of carbon fibers, and the mixture was stirred in a stirrer at a speed of 100 revolutions per minute for 3 minutes to obtain a uniformly mixed carbon fiber / polyvinyl alcohol fiber suspension.

[0074] (3) The prepared phenolic resin suspension was slowly poured into the carbon fiber / polyvinyl alcohol fiber suspension (phenolic resin was 200% of the mass of carbon fibers), and the mixture was uniformly mixed to obtain a mixed slurry of carbon fibers. The mixed slurry was formed into a sheet on a paper machine, was pressed, and was dried at 100°C for 20 minutes to obtain a carbon paper base paper. The carbon paper base paper was then hot-pressed in a hot press at 170°C and a pressure of 10 MPa for 60 minutes. Finally, the carbon paper was carbonized in an atmosphere furnace at 1200°C for 60 minutes to obtain a carbon paper for a gas diffusion layer of a fuel cell.

[0075] Performance test of the gas diffusion layer carbon paper:

[0076] The carbon papers prepared in the above examples and comparative examples were respectively subjected to performance tests of tensile strength, resistivity, air permeability, and porosity. The test results are shown in Table 1.

[0077] Table 1 Comparison of the performance of the gas diffusion layer carbon paper

[0078]

[0079]

[0080] As can be seen from the comparison of the examples and Comparative Example 1 (without the addition of phenolic resin) in Table 1, the addition of phenolic resin can significantly increase the tensile strength of the carbon paper, reduce the resistivity, air permeability, and porosity. This is mainly because the presence of phenolic resin increases the bonding sites between the carbon fibers, forms a space network structure in the carbon paper, thereby increasing the tensile strength of the carbon paper and enhancing the electrical conductivity. The network structure hinders the passage of a portion of the gas, and thus the air permeability is slightly reduced.

[0081] The comparison between Example 2 and Comparative Example 2 (adding phenolic resin without dispersion treatment) shows that adding phenolic resin with dispersion treatment can improve the tensile strength of the carbon paper, reduce the resistivity, and improve the air permeability and porosity, which further indicates that adding pre-dispersion treated phenolic resin (compared to phenolic resin without dispersion treatment) during the preparation of the carbon paper can effectively improve the performance of the carbon paper. This is mainly because the pretreatment can effectively disperse the phenolic resin, making it more uniformly combined with polyethylene oxide, which promotes the formation of high uniformity carbon paper. Carbon paper with uneven uniformity will cause the tensile strength to decrease, the resistivity to increase, and the air permeability and porosity to decrease.

[0082] The comparison between Example 2 and Comparative Example 3 (without adding polyethylene oxide) shows that the presence of polyethylene oxide can significantly improve the tensile strength and conductivity of the carbon paper, and the air permeability and porosity will decrease. This is mainly because polyethylene oxide can improve the retention rate of phenolic resin and the uniformity of slurry dispersion, promoting the close combination of phenolic resin and fibers. The carbon paper without adding polyethylene oxide lacks phenolic resin, resulting in weak inter-fiber bonding force, which causes low tensile strength of the carbon paper, and the loose structure is the main reason for high air permeability and porosity.

[0083] The application also provides a carbon paper prepared by the above-mentioned method for preparing a carbon paper. For more technical details, please refer to the relevant description of the above-mentioned method for preparing a carbon paper, which will not be repeated here.

[0084] The application also provides a battery comprising the above-mentioned gas diffusion layer. For more technical details, please refer to the relevant description of the above-mentioned gas diffusion layer, which will not be repeated here.

[0085] In summary, the carbon paper prepared by the application has high mechanical strength, low resistivity, and easily adjustable porosity and air permeability, and the preparation process is simple, the quality is controllable, and it has practical application value.

[0086] The above-mentioned is only the preferred embodiment of the application, and is not intended to limit the application in other forms. Any skilled person in the art can use the disclosed technical content to make changes or modifications to equivalent embodiments, as long as they do not deviate from the technical solution of the application, and any simple modification, equivalent change and modification of the above-mentioned embodiments based on the technical essence of the application are still within the protection scope of the technical solution of the application.

Claims

1. A method for preparing carbon paper by adding phenolic resin slurry, characterized in that: (1) Add phenolic resin to water and add dispersant to obtain phenolic resin suspension; The phenolic resin suspension was placed in an ultrasonic cleaner and ultrasonically vibrated to obtain a uniformly dispersed phenolic resin suspension. Stir the phenolic resin suspension with a stirrer and set aside. (2) Add carbon fiber to water to obtain carbon fiber slurry; Add polyvinyl alcohol fiber and polyethylene oxide; The mixture was stirred in a stirrer to obtain a uniformly mixed carbon fiber / polyvinyl alcohol fiber suspension. (3) Slowly pour the phenolic resin suspension obtained in step (1) into the carbon fiber / polyvinyl alcohol fiber suspension obtained in step (2), mix evenly, and obtain a mixed slurry. The ether bond oxygen atoms of the polyethylene oxide and the hydroxyl groups of the phenolic resin form hydrogen bonds to form a network structure, which captures the phenolic resin in the mixed slurry, thereby improving the retention rate of phenolic resin. The mixed pulp is formed, pressed, and dried in a paper machine to obtain carbon paper base paper; The carbon paper base paper is hot-pressed in a hot press, and then carbonized in an atmosphere furnace to obtain the target carbon paper.

2. The method for preparing carbon paper by adding phenolic resin slurry according to claim 1, characterized in that: The phenolic resin mentioned in step (1) is a thermosetting phenolic resin or a thermoplastic phenolic resin, in powder form, with a particle size of 0.01-200μm.

3. The method for preparing carbon paper by adding phenolic resin slurry according to claim 2, characterized in that: In step (1), the phenolic resin suspension is placed in an ultrasonic cleaner and ultrasonically vibrated for 5-30 minutes at an ultrasonic frequency of 50-500 kHz to obtain a uniformly dispersed phenolic resin suspension; the phenolic resin suspension is stirred using a stirrer with a speed of 30-300 rpm.

4. The method for preparing carbon paper by adding phenolic resin slurry according to claim 1, characterized in that: The dispersant mentioned in step (1) is sodium polyacrylate or potassium polyacrylate.

5. The method for preparing carbon paper by internal addition of phenolic resin slurry according to claim 1, characterized in that: The carbon fiber mentioned in step (2) is one or more of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and viscose-based carbon fiber; The carbon fibers mentioned are 1-15μm in diameter or a blend of carbon fibers of various diameters; The carbon fiber is 1-12mm in length or a blend of carbon fibers of various lengths.

6. The method for preparing carbon paper by adding phenolic resin slurry according to claim 5, characterized in that: The carbon fiber slurry has a mass concentration of 0.05%-0.5%; the amount of polyvinyl alcohol fiber added is 0%-15% of the carbon fiber mass; and the amount of polyethylene oxide added is 0.05%-5% of the phenolic resin mass.

7. The method for preparing carbon paper by adding phenolic resin slurry according to claim 1, characterized in that: In step (3), the drying temperature is 80-110℃ and the time is 5-40min; the hot pressing temperature is 140-200℃, the pressure is 2-15MPa, and the time is 20-120min; the atmosphere furnace temperature is 600-1600℃ and the carbonization time is 30-120min.

8. A type of carbon paper, characterized in that, The carbon paper is prepared using the method described in any one of claims 1-7, and its basis weight is 30-150 g / m³. 2 .

9. A gas diffusion layer, characterized in that, The gas diffusion layer comprises the carbon paper as described in claim 8.

10. A battery, characterized in that, The battery includes the gas diffusion layer as described in claim 9.

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