Graphene conductive material and preparation method thereof
By combining porous graphene and modified polyvinylidene fluoride during the graphene preparation process, the problem of graphene sheets hindering lithium-ion transport in lithium-ion batteries has been solved, thereby improving the battery's conductivity and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-12
- Publication Date
- 2026-03-13
AI Technical Summary
In existing lithium-ion batteries, when graphene is used as a conductive agent, lithium ions need to take a detour to pass through the graphene sheets, which leads to transmission obstacles. In addition, traditional conductive agents such as acetylene black have problems such as low density and easy agglomeration.
Porous graphene was prepared by etching with a strong alkali, and catechol structures were introduced onto the graphene to form a porous structure and cross-linked network. The conductivity was improved by combining it with modified polyvinylidene fluoride.
It improves the electrochemical performance and cycle stability of lithium-ion batteries, enhances conductivity and lithium-ion transport channels, and improves the battery's electrical performance and cycle stability.
Abstract
Description
Technical Field
[0001] This invention relates to the field of conductive materials technology, specifically to a graphene conductive material and its preparation method. Background Technology
[0002] Common cathode materials have low electronic conductivity, which hinders the rapid reach of electrons to the surface of the active material. Therefore, conductive agents are needed to construct an electronic conductive network. Currently, traditional conductive agents such as acetylene black and Super-P have drawbacks such as low density and a tendency to agglomerate, and their "point-to-point" conductivity is generally ineffective. Therefore, to improve energy density and meet people's needs for a better life, there is an urgent need to develop new conductive additives.
[0003] Graphene is an excellent conductive agent, possessing significant advantages in lithium-ion batteries due to its two-dimensional planar structure, unique mechanical properties, and outstanding conductivity. Graphene exhibits high specific surface area, good mechanical strength, and thermal stability, which can significantly improve the electrochemical performance and cycle life of lithium-ion batteries. Furthermore, graphene's microstructure can be modified to further enhance battery electrochemical performance, thus demonstrating broad application prospects in the field of lithium-ion batteries.
[0004] This invention uses graphene as a conductive agent. Addressing the issue of graphene's significant steric hindrance, which prevents lithium ions from directly penetrating graphene sheets and forces them to take a detour, this invention creates a porous structure on the graphene through alkaline etching. This significantly reduces the steric hindrance effect of graphene on lithium ions. Simultaneously, a catechol structure similar to that found in the adhesive proteins secreted by marine mussels is introduced into the graphene, enhancing its adhesion. This allows graphene to form a cross-linked network with other substances in the positive electrode slurry through hydrogen bonding, oxidative cross-linking, and other mechanisms, effectively improving the cycle stability of the lithium battery. Summary of the Invention
[0005] The purpose of this invention is to provide a graphene conductive material and its preparation method to solve the problems existing in the prior art.
[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a graphene conductive material, the method comprising the following steps: (1) Functionalized furan monomers were prepared by reacting 3,4-dihydroxybenzaldehyde and 2,5-bis(aminomethyl)furan; (2) Graphene was etched with a strong base to prepare porous graphene; and porous graphene was reacted with functionalized furan monomer to prepare modified porous graphene. (3) Prepare a blocked isocyanate by reacting phenol and 2-methyl-2-acrylate isocyanate; (4) Methacrylate-based pyrene was prepared by reacting 1-pyrene methanol with methacrylamide chloride; (5) Modified polyvinylidene fluoride was prepared by grafting blocked isocyanate and methacrylate-based pyrene onto polyvinylidene fluoride using a free radical grafting method. (6) A positive electrode slurry is prepared using lithium iron phosphate as the positive electrode material, modified polyvinylidene fluoride as the binder, modified porous graphene as the conductive agent, and N-methylpyrrolidone as the solvent. The positive electrode slurry is coated on aluminum foil, dried, and stamped into sheets to obtain graphene conductive material.
[0007] As an optimization, the preparation method of the functionalized furan monomer in step (1) is as follows: 3,4-dihydroxybenzaldehyde and 2,5-di(aminomethyl)furan are added to tetrahydrofuran at a molar ratio of 2:1, which is 10 to 12 times the mass of 3,4-dihydroxybenzaldehyde. The mixture is stirred at 300 to 500 r / min for 4 to 5 h at 50 to 60 °C and then vacuum dried at 50 to 60 °C for 13 to 15 h to obtain the functionalized furan monomer.
[0008] As an optimization, the reaction process of the functionalized furan monomer in step (1) is as follows: .
[0009] As an optimization, the preparation method of porous graphene in step (2) is as follows: Sodium hydroxide and potassium hydroxide are mixed in a molar ratio of 1:2 to prepare a strong alkali powder; graphene, strong alkali powder and deionized water are mixed in a mass ratio of 1:(3~4):(120~140), ultrasonically dispersed for 1~2h, vacuum dried at 80~90℃ for 20~24h, heated to 800~900℃ at a rate of 10℃ / min under nitrogen protection, washed with deionized water by vacuum filtration 4~6 times, vacuum dried at 80~90℃ for 12~16h, ground, sieved and prepared into porous graphene.
[0010] As an optimization, the preparation method of the modified porous graphene in step (2) is as follows: porous graphene and N-methylpyrrolidone are mixed evenly at a mass ratio of 1:(200~300), ultrasonically dispersed in an ice-water bath for 30~50 min, functionalized furan monomers with a mass of 20~30 times that of porous graphene are added, and the mixture is stirred at 100~110℃ and 300~500r / min for 2~3 h, centrifuged, washed 5 times with acetone, and vacuum dried at 50~60℃ for 10~12 h to obtain modified porous graphene.
[0011] As an optimization, the preparation method of the blocked isocyanate in step (3) is as follows: Phenol, dibutyltin dilaurate, and chloroform are mixed evenly in a mass ratio of 1:(0.02~0.04):(4~6) to prepare a phenol solution; 2-methyl-2-acrylate isocyanate and chloroform, which are 1~1.2 times the molar amount of phenol, are mixed evenly in a mass ratio of 1:(6~8) to prepare an isocyanate solution; Under nitrogen protection, at 40~50℃ and stirring at 200~300r / min, the isocyanate solution is added dropwise to the phenol solution at a uniform rate within 60min. After the addition is completed, the reaction is stirred for another 50~70min. The mixture is then vacuum dried at 50~60℃ for 10~12h to obtain the blocked isocyanate.
[0012] As an optimization, the reaction process of the blocked isocyanate in step (3) is as follows: .
[0013] As an optimization, the preparation method of methacrylate-based pyrene in step (4) is as follows: 1-pyrene methanol, pyridine, triethylamine, and tetrahydrofuran are mixed in a mass ratio of 1:(0.4~0.5):(0.7~0.8):(10~12), stirred at 300~500 r / min for 10~20 min at room temperature, and then added dropwise at a uniform rate over 30 min under an ice-water bath. The mixture is stirred for another 60~70 min at room temperature, and then 3~4 times the mass of 1-pyrene methanol in deionized water is added. The mixture is stirred for another 10~20 min, extracted with 1.6~2 times the volume of tetrahydrofuran in diethyl ether, and then vacuum dried at 40~50℃ for 8~10 h to obtain methacrylate-based pyrene.
[0014] As an optimization, the reaction process of the methacrylate-based pyrene in step (4) is as follows: .
[0015] As an optimization, the preparation method of the modified polyvinylidene fluoride in step (5) is as follows: the reaction monomer, polyvinylidene fluoride, and terephthaloyl peroxide are weighed at a mass ratio of 1:(15~16):(0.6~0.8); wherein the reaction monomer is obtained by mixing blocked isocyanate and methacrylate-based pyrene at a mass ratio of 1:(2~2.2); polyvinylidene fluoride and N,N-dimethylformamide are mixed at a mass ratio of 1:(14~16), and stirred at 45~55℃ and 200~300r / min for 30~40min. n, prepare a polyvinylidene fluoride solution; mix the reactant monomer and N,N-dimethylformamide at a mass ratio of 1:(12~14) to prepare a monomer solution; under nitrogen protection, heat the polyvinylidene fluoride solution to 68~74℃, add terephthaloyl peroxide, continue stirring for 20~30min, add the monomer solution dropwise at a uniform rate over 40min, continue stirring and reacting for 7~8h after the addition is complete, cool to room temperature, precipitate with anhydrous ethanol, and vacuum dry at 50~60℃ for 14~16h to obtain modified polyvinylidene fluoride.
[0016] As an optimization, the preparation method of the positive electrode slurry in step (6) is as follows: weigh lithium iron phosphate, modified polyvinylidene fluoride, and modified porous graphene in a mass ratio of 90:(6~7):(3~4); mix modified polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:(10~12), stir at 1000~1200r / min for 10~20min, add modified porous graphene, continue stirring for 10~20min, add lithium iron phosphate, adjust the solid content to 46%~50% with N-methylpyrrolidone, and continue stirring at 1800~2000r / min for 30~40min to obtain the positive electrode slurry.
[0017] The present invention also provides a graphene conductive material prepared according to the above-described method for preparing graphene conductive materials.
[0018] Compared with the prior art, the beneficial effects achieved by the present invention are: Graphene is an excellent conductive agent, possessing significant advantages in lithium-ion batteries due to its two-dimensional planar structure, unique mechanical properties, and outstanding conductivity. However, when used as a conductive agent in lithium batteries, graphene suffers from high steric hindrance. The graphene sheet structure exhibits a steric effect on lithium ions in the direction perpendicular to the sheet, hindering lithium ion transport in the electrode and increasing the ion transport resistance. Porous graphene is fabricated through strong base etching, forming a porous structure that reduces the tortuosity of lithium ion transport, providing a high-speed channel for lithium ion transport and improving the electrical performance of lithium-ion batteries. Furthermore, through the Diels-Alder reaction between graphene and functionalized furan monomers, a large number of catechol structures are introduced onto the surface of modified porous graphene. This catechol structure is similar to the adhesive protein secreted by mussels, exhibiting strong adhesion. It allows the modified graphene to form a cross-linked network with other substances in the positive electrode slurry through hydrogen bonding, oxidative cross-linking, and other mechanisms, improving the cycle stability of lithium batteries.
[0019] Secondly, a blocked isocyanate was prepared by reacting phenol and 2-methyl-2-acrylate isocyanate; methacrylate-based pyrene was prepared by reacting 1-pyrene methanol and methacryl chloride; and modified polyvinylidene fluoride (PVDF) was prepared by grafting the blocked isocyanate and methacrylate-based pyrene onto PVDF using a free radical grafting method. PVDF is a commonly used binder for cathode materials. By grafting pyrene rings onto PVDF, the pyrene rings easily self-assemble into an ordered structure, conducting electrons through π-π stacking, thereby improving the conductivity of the modified PVDF and enhancing the electrical performance of the battery. The grafted blocked isocyanate is deblocked at high temperatures, and the resulting phenol volatilizes under low pressure and high temperature conditions, forming a porous structure. The porous structure facilitates full contact between the cathode material and the electrolyte, making the charging and discharging process easier and further improving the electrical performance of the battery. Detailed Implementation
[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0021] In the following examples and comparative examples, the lithium iron phosphate used had a D50 of 0.78 μm and was purchased from Yitian Tianci High-Tech Materials Co., Ltd. The polyvinylidene fluoride used is HSV 900, manufactured by Arkema, France.
[0022] The graphene used was graphene oxide, model number MG-NGO-01, purchased from Shanghai Maoguo Nanotechnology Co., Ltd.
[0023] Example 1: A method for preparing a graphene conductive material, the method comprising the following steps: (1) 3,4-dihydroxybenzaldehyde and 2,5-bis(aminomethyl)furan were added to tetrahydrofuran at a molar ratio of 2:1, 10 times the mass of 3,4-dihydroxybenzaldehyde. The mixture was stirred at 300 r / min for 5 h at 50 °C and dried under vacuum for 15 h to obtain the functionalized furan monomer. (2) Sodium hydroxide and potassium hydroxide were mixed in a molar ratio of 1:2 to prepare a strong alkali powder; graphene, strong alkali powder and deionized water were mixed in a mass ratio of 1:3:120, ultrasonically dispersed for 1 h, vacuum dried at 80℃ for 24 h, heated to 800℃ at a rate of 10℃ / min under nitrogen protection, washed 4 times with deionized water, vacuum dried at 80℃ for 16 h, ground, passed through a 500-mesh sieve, and porous graphene was obtained; porous graphene and N-methylpyrrolidone were mixed evenly in a mass ratio of 1:200, ultrasonically dispersed in an ice-water bath for 30 min, functionalized furan monomer with a mass of 20 times that of porous graphene was added, stirred at 100℃ and 300 r / min for 3 h, centrifuged, washed 5 times with acetone, vacuum dried at 50℃ for 12 h, and modified porous graphene was obtained; (3) Phenol, dibutyltin dilaurate and chloroform are mixed evenly in a mass ratio of 1:0.02:4 to prepare a phenol solution; 2-methyl-2-acrylate isocyanate and chloroform are mixed evenly in a mass ratio of 1:6 to prepare an isocyanate solution; under nitrogen protection, at 40°C and 200 r / min stirring conditions, the isocyanate solution is added dropwise to the phenol solution at a uniform rate over 60 min. After the addition is complete, the reaction is stirred for another 70 min. The solution is then dried under vacuum at 50°C for 12 h to obtain the blocked isocyanate. (4) Mix 1-pyrene methanol, pyridine, triethylamine and tetrahydrofuran in a mass ratio of 1:0.4:0.7:10, stir at 300 r / min for 10 min at room temperature, add 1-pyrene methanol equimolar amount of methacryloyl chloride dropwise over 30 min under an ice-water bath, continue stirring at room temperature for 60 min, add 3 times the mass of 1-pyrene methanol deionized water, continue stirring for 10 min, extract with 1.6 times the volume of tetrahydrofuran in diethyl ether, and dry under vacuum at 40℃ for 10 h to obtain methacrylate-based pyrene; (5) Weigh the reaction monomer, polyvinylidene fluoride, and terephthaloyl peroxide in a mass ratio of 1:15:0.6; wherein the reaction monomer is obtained by mixing blocked isocyanate and methacrylate-based pyrene in a mass ratio of 1:2; mix polyvinylidene fluoride and N,N-dimethylformamide in a mass ratio of 1:14, stir at 45°C and 200 r / min for 40 min to prepare a polyvinylidene fluoride solution; mix the reaction monomer and N,N-dimethylformamide in a mass ratio of 1:12 to prepare a monomer solution; under nitrogen protection, heat the polyvinylidene fluoride solution to 68°C, add terephthaloyl peroxide, continue stirring for 30 min, add the monomer solution dropwise at a uniform rate over 40 min, continue stirring and react for 8 h after the addition is complete, cool to room temperature, precipitate with anhydrous ethanol, and vacuum dry at 50°C for 16 h to obtain modified polyvinylidene fluoride; (6) Weigh lithium iron phosphate, modified polyvinylidene fluoride and modified porous graphene in a mass ratio of 90:6:3; mix modified polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:10, stir at 1000 r / min for 10 min, add modified porous graphene, continue stirring for 10 min, add lithium iron phosphate, adjust the solid content to 46% with N-methylpyrrolidone, continue stirring at 1800 r / min for 30 min to obtain positive electrode slurry; coat the positive electrode slurry on aluminum foil with a coating thickness of 100 μm, vacuum dry at 60℃ for 3 h, vacuum dry at 120℃ for 12 h, and press into an electrode sheet with a diameter of 13 mm to obtain modified graphene conductive material.
[0024] Example 2: A method for preparing a graphene conductive material, the method comprising the following steps: (1) 3,4-dihydroxybenzaldehyde and 2,5-di(aminomethyl)furan were added to tetrahydrofuran at a molar ratio of 2:1, which was 11 times the mass of 3,4-dihydroxybenzaldehyde. The mixture was stirred at 55°C and 400 r / min for 4.5 h, and then dried under vacuum at 55°C for 14 h to obtain the functionalized furan monomer. (2) Sodium hydroxide and potassium hydroxide were mixed in a molar ratio of 1:2 to prepare a strong alkali powder; graphene, strong alkali powder and deionized water were mixed in a mass ratio of 1:3.5:130, ultrasonically dispersed for 1.5h, vacuum dried at 85℃ for 21h, heated to 850℃ at a rate of 10℃ / min under nitrogen protection, washed 5 times with deionized water, vacuum dried at 85℃ for 14h, ground, passed through a 500-mesh sieve, and porous graphene was obtained; porous graphene and N-methylpyrrolidone were mixed evenly in a mass ratio of 1:250, ultrasonically dispersed in an ice-water bath for 40min, functionalized furan monomers with a mass of 25 times that of porous graphene were added, stirred at 105℃ and 400r / min for 2.5h, centrifuged, washed 5 times with acetone, vacuum dried at 55℃ for 11h, and modified porous graphene was obtained; (3) Phenol, dibutyltin dilaurate and chloroform are mixed evenly in a mass ratio of 1:0.03:5 to prepare a phenol solution; 2-methyl-2-acrylate isocyanate and chloroform are mixed evenly in a mass ratio of 1:7 to prepare an isocyanate solution; under nitrogen protection, at 45°C and 250 r / min stirring conditions, the isocyanate solution is added dropwise to the phenol solution at a uniform rate over 60 min. After the addition is complete, the reaction is stirred for another 60 min. The solution is then dried under vacuum at 55°C for 11 h to obtain the blocked isocyanate. (4) Mix 1-pyrene methanol, pyridine, triethylamine and tetrahydrofuran in a mass ratio of 1:0.45:0.75:11, stir at 400 r / min for 15 min at room temperature, add 1-pyrene methanol equimolar amount of methacryloyl chloride dropwise over 30 min in an ice-water bath, continue stirring at room temperature for 65 min, add 3.5 times the mass of 1-pyrene methanol of deionized water, continue stirring for 15 min, extract with 1.8 times the volume of tetrahydrofuran of diethyl ether, and dry under vacuum at 45℃ for 9 h to obtain methacrylate-based pyrene; (5) Weigh the reactant monomer, polyvinylidene fluoride, and terephthaloyl peroxide in a mass ratio of 1:15.5:0.7; wherein the reactant monomer is obtained by mixing blocked isocyanate and methacrylate-based pyrene in a mass ratio of 1:2.1; mix polyvinylidene fluoride and N,N-dimethylformamide in a mass ratio of 1:15, stir at 50℃ and 250r / min for 35min to prepare a polyvinylidene fluoride solution; mix the reactant monomer and N,N-dimethylformamide in a mass ratio of 1:13 to prepare a monomer solution; under nitrogen protection, heat the polyvinylidene fluoride solution to 72℃, add terephthaloyl peroxide, continue stirring for 25min, add the monomer solution dropwise at a uniform rate over 40min, continue stirring and reacting for 7.5h after the addition is complete, cool to room temperature, precipitate with anhydrous ethanol, and vacuum dry at 55℃ for 15h to obtain modified polyvinylidene fluoride; (6) Weigh lithium iron phosphate, modified polyvinylidene fluoride, and modified porous graphene in a mass ratio of 90:6.5:3.5; mix modified polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:11, stir at 1100 r / min for 15 min, add modified porous graphene, continue stirring for 15 min, add lithium iron phosphate, adjust the solid content to 48% with N-methylpyrrolidone, and continue stirring at 1900 r / min for 35 min to obtain positive electrode slurry; coat the positive electrode slurry on aluminum foil with a coating thickness of 100 μm, vacuum dry at 65℃ for 2.5 h, vacuum dry at 125℃ for 11 h, and press into an electrode sheet with a diameter of 13 mm to obtain modified graphene conductive material.
[0025] Example 3: A method for preparing a graphene conductive material, the method comprising the following steps: (1) 3,4-dihydroxybenzaldehyde and 2,5-di(aminomethyl)furan were added to tetrahydrofuran at a molar ratio of 2:1, which was 12 times the mass of 3,4-dihydroxybenzaldehyde. The mixture was stirred at 500 r / min for 4 h at 60 °C and then dried under vacuum at 60 °C for 13 h to obtain the functionalized furan monomer. (2) Sodium hydroxide and potassium hydroxide were mixed in a molar ratio of 1:2 to prepare a strong alkali powder; graphene, strong alkali powder and deionized water were mixed in a mass ratio of 1:4:140, ultrasonically dispersed for 2 hours, vacuum dried at 90°C for 20 hours, heated to 900°C at a rate of 10°C / min under nitrogen protection, washed 6 times with deionized water, vacuum dried at 90°C for 12 hours, ground and passed through a 500-mesh sieve to obtain porous graphene; porous graphene and N-methylpyrrolidone were mixed evenly in a mass ratio of 1:300, ultrasonically dispersed in an ice-water bath for 50 minutes, functionalized furan monomers with a mass of 30 times that of porous graphene were added, stirred at 110°C and 500 r / min for 2 hours, centrifuged, washed 5 times with acetone, and vacuum dried at 60°C for 10 hours to obtain modified porous graphene; (3) Phenol, dibutyltin dilaurate and chloroform are mixed evenly in a mass ratio of 1:0.04:6 to prepare a phenol solution; 2-methyl-2-acrylate isocyanate and chloroform are mixed evenly in a mass ratio of 1:8 to prepare an isocyanate solution; under nitrogen protection, at 50°C and 300 r / min stirring conditions, the isocyanate solution is added dropwise to the phenol solution at a uniform rate over 60 min. After the addition is complete, the reaction is stirred for another 50 min. The solution is then dried under vacuum at 60°C for 10 h to obtain the blocked isocyanate. (4) Mix 1-pyrene methanol, pyridine, triethylamine and tetrahydrofuran in a mass ratio of 1:0.45:0.75:11, stir at 500 r / min for 20 min at room temperature, add 1-pyrene methanol equimolar amount of methacryloyl chloride dropwise over 30 min in an ice-water bath, continue stirring at room temperature for 70 min, add 4 times the mass of 1-pyrene methanol deionized water, continue stirring for 20 min, extract with 2 times the volume of tetrahydrofuran diethyl ether, and dry under vacuum at 50 °C for 8 h to obtain methacrylate-based pyrene; (5) Weigh the reaction monomer, polyvinylidene fluoride, and terephthaloyl peroxide in a mass ratio of 1:15.5:0.7; wherein the reaction monomer is obtained by mixing blocked isocyanate and methacrylate-based pyrene in a mass ratio of 1:2.2; mix polyvinylidene fluoride and N,N-dimethylformamide in a mass ratio of 1:16, stir at 55°C and 300 r / min for 30 min to prepare a polyvinylidene fluoride solution; mix the reaction monomer and N,N-dimethylformamide in a mass ratio of 1:14 to prepare a monomer solution; under nitrogen protection, heat the polyvinylidene fluoride solution to 74°C, add terephthaloyl peroxide, continue stirring for 20 min, add the monomer solution dropwise at a uniform rate over 40 min, continue stirring and react for 7 h after the addition is complete, cool to room temperature, precipitate with anhydrous ethanol, and vacuum dry at 60°C for 14 h to obtain modified polyvinylidene fluoride; (6) Weigh lithium iron phosphate, modified polyvinylidene fluoride and modified porous graphene in a mass ratio of 90:7:4; mix modified polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:12, stir at 1200 r / min for 20 min, add modified porous graphene, continue stirring for 20 min, add lithium iron phosphate, adjust the solid content to 50% with N-methylpyrrolidone, continue stirring at 2000 r / min for 40 min to obtain positive electrode slurry; coat the positive electrode slurry on aluminum foil with a coating thickness of 100 μm, vacuum dry at 70℃ for 2 h, vacuum dry at 130℃ for 10 h, and press into an electrode sheet with a diameter of 13 mm to obtain modified graphene conductive material.
[0026] Comparative Example 1: The difference between the preparation method of the graphene conductive material in Comparative Example 1 and Example 2 is that step (1) is omitted, and step (2) is modified as follows: sodium hydroxide and potassium hydroxide are mixed in a molar ratio of 1:2 to prepare a strong alkali powder; graphene, strong alkali powder, and deionized water are mixed in a mass ratio of 1:3.5:130, ultrasonically dispersed for 1.5 h, vacuum dried at 85°C for 21 h, heated to 850°C at a rate of 10°C / min under nitrogen protection, washed 5 times with deionized water, vacuum dried at 85°C for 14 h, ground, and passed through a 500-mesh sieve to obtain modified porous graphene. The remaining steps are the same as in Example 2.
[0027] Comparative Example 2: The difference between the preparation method of the graphene conductive material in Comparative Example 2 and Example 2 lies in step (2). Step (2) is modified as follows: graphene and N-methylpyrrolidone are mixed evenly at a mass ratio of 1:250, ultrasonically dispersed in an ice-water bath for 40 min, functionalized furan monomer with a mass of 25 times that of graphene is added, and the mixture is stirred at 105°C and 400 r / min for 2.5 h. After centrifugation, the mixture is washed 5 times with acetone and vacuum dried at 55°C for 11 h to obtain modified porous graphene. The remaining steps are the same as in Example 2.
[0028] Comparative Example 3: The preparation method of the graphene conductive material in Comparative Example 3 differs from that in Example 2 in that step (3) is omitted, and step (5) is modified as follows: the reaction monomers, polyvinylidene fluoride, and terephthaloyl peroxide are weighed in a mass ratio of 1:15.5:0.7; wherein the reaction monomers are obtained by mixing n-butyl acrylate and methacrylate-based pyrene in a mass ratio of 1:2.1; polyvinylidene fluoride and N,N-dimethylformamide are mixed in a mass ratio of 1:15 and stirred at 50°C and 250 r / min. Stir for 35 min to prepare a polyvinylidene fluoride (PVDF) solution; mix the reactant monomer and N,N-dimethylformamide at a mass ratio of 1:13 to prepare a monomer solution; under nitrogen protection, heat the PVDF solution to 72°C, add terephthaloyl peroxide, continue stirring for 25 min, and then uniformly add the monomer solution dropwise over 40 min. After the addition is complete, continue stirring and react for 7.5 h, cool to room temperature, precipitate with anhydrous ethanol, and dry under vacuum at 55°C for 15 h to obtain modified PVDF. The remaining steps are the same as in Example 2.
[0029] Comparative Example 4: The preparation method of the graphene conductive material in Comparative Example 4 differs from that in Example 2 in that step (4) is omitted, and step (5) is modified as follows: the reaction monomers, polyvinylidene fluoride, and terephthaloyl peroxide are weighed in a mass ratio of 1:15.5:0.7; wherein the reaction monomers are obtained by mixing blocked isocyanate and n-butyl acrylate in a mass ratio of 1:2.1; polyvinylidene fluoride and N,N-dimethylformamide are mixed in a mass ratio of 1:15 and stirred at 50°C and 250 r / min. For 35 minutes, prepare a polyvinylidene fluoride (PVDF) solution. Mix the reactant monomer and N,N-dimethylformamide at a mass ratio of 1:13 to prepare a monomer solution. Under nitrogen protection, heat the PVDF solution to 72°C, add terephthaloyl peroxide, and continue stirring for 25 minutes. Add the monomer solution dropwise at a uniform rate over 40 minutes. After the addition is complete, continue stirring for 7.5 hours. Cool to room temperature, precipitate with anhydrous ethanol, and dry under vacuum at 55°C for 15 hours to obtain modified PVDF. The remaining steps are the same as in Example 2.
[0030] Test Example 1 Electrical performance testing Preparation of button cells: CR2050 button cells were assembled in an argon-filled glove box. The positive electrode of the button cell was used in the examples and comparative examples, the negative electrode was a high-purity lithium metal sheet, the battery separator was polypropylene (PP), Celgard 2400 type, and the electrolyte was 1 mol / L LiPF6 dissolved in a 1:1 VEC:VDMC mixed solvent.
[0031] The prepared button cells were subjected to charge-discharge experiments at 25℃ and 0.1C current density to test the initial discharge capacity. The prepared button cells were then subjected to charge-discharge experiments at 25℃ and 1C current density for 400 cycles, and the capacity retention rate was recorded. Capacity retention rate = capacity after 400 discharge cycles / initial discharge capacity. The results are shown in Table 1.
[0032] Table 1 Initial capacitance Capacity retention Example 1 163Ah / g 97.4% Example 2 165Ah / g 98.9% Example 3 164Ah / g 98.6% Comparative Example 1 162Ah / g 88.3% Comparative Example 2 157Ah / g 95.2% Comparative Example 3 154Ah / g 95.8% Comparative Example 4 156Ah / g 96.1% A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 1 reveals that the graphene conductive material prepared by this invention has excellent electrical properties.
[0033] By comparison, the initial capacity of Examples 1-3 is greater than that of Comparative Example 2, indicating that the porous graphene prepared by strong alkali etching and the formation of a pore structure on the graphene can reduce the tortuosity in the lithium-ion transport process, provide a high-speed channel for lithium-ion transport, and improve the electrical performance of lithium-ion batteries.
[0034] By comparison, the initial capacity of Examples 1-3 was greater than that of Comparative Examples 3-4, indicating that the blocked isocyanate was prepared by reacting phenol and 2-methyl-2-acrylate isocyanate; methacrylate-based pyrene was prepared by reacting 1-pyrene methanol and methacryloyl chloride; and modified polyvinylidene fluoride (PVDF) was prepared by grafting the blocked isocyanate and methacrylate-based pyrene onto PVDF using a free radical grafting method. PVDF is a commonly used binder. Grafting pyrene rings onto PVDF allows the pyrene rings to easily self-assemble into an ordered structure, conducting electrons through π-π stacking, thus improving the conductivity of the modified PVDF and enhancing the battery's electrical performance. The grafted blocked isocyanate deblocks at high temperatures, and the resulting phenol volatilizes under low pressure and high temperature conditions, forming a porous structure. This porous structure facilitates full contact between the cathode material and the electrolyte, making the charging and discharging process easier and further improving the battery's electrical performance.
[0035] By comparison, the capacity retention rates of Examples 1-3 are greater than those of Comparative Example 1, indicating that the Diels-Alder reaction between graphene and functionalized furan monomers introduces a large number of catechol structures onto the surface of modified porous graphene. This catechol structure has a similar structure to the mussel adhesive protein secreted by marine mussels and has strong adhesion. It can enable the modified graphene to form a cross-linked network with other substances in the positive electrode slurry through hydrogen bonding, oxidative cross-linking, etc., thereby improving the cycle stability of lithium batteries.
[0036] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a graphene conductive material, characterized in that, The preparation method of the graphene conductive material includes the following preparation steps: (1) Functionalized furan monomers were prepared by reacting 3,4-dihydroxybenzaldehyde and 2,5-bis(aminomethyl)furan; (2) Graphene was etched with a strong base to prepare porous graphene; and porous graphene was prepared by reacting functionalized furan monomers. (3) Prepare a blocked isocyanate by reacting phenol and 2-methyl-2-acrylate isocyanate; (4) Methacrylate-based pyrene was prepared by reacting 1-pyrene methanol with methacrylamide chloride; (5) Modified polyvinylidene fluoride was prepared by grafting blocked isocyanate and methacrylate-based pyrene onto polyvinylidene fluoride using a free radical grafting method. (6) A positive electrode slurry is prepared using lithium iron phosphate as the positive electrode material, modified polyvinylidene fluoride as the binder, modified porous graphene as the conductive agent, and N-methylpyrrolidone as the solvent. The positive electrode slurry is coated on aluminum foil, dried, and stamped into sheets to obtain graphene conductive material.
2. The method for preparing a graphene conductive material according to claim 1, characterized in that, The preparation method of the functionalized furan monomer in step (1) is as follows: 3,4-dihydroxybenzaldehyde and 2,5-di(aminomethyl)furan are added to tetrahydrofuran, stirred at 50~60℃ for 4~5h, and dried under vacuum to obtain the functionalized furan monomer.
3. The method for preparing a graphene conductive material according to claim 1, characterized in that, The method for preparing porous graphene in step (2) is as follows: Sodium hydroxide and potassium hydroxide are mixed to prepare a strong alkali powder; graphene, strong alkali powder and deionized water are mixed, ultrasonically dispersed, vacuum dried, and heated to 800~900℃ at a rate of 10℃ / min under nitrogen protection, washed, vacuum dried, ground, sieved and prepared into porous graphene.
4. The method for preparing a graphene conductive material according to claim 1, characterized in that, The modified porous graphene in step (2) is prepared by mixing porous graphene and N-methylpyrrolidone evenly, ultrasonically dispersing them in an ice-water bath, adding functionalized furan monomers, reacting at 100~110℃ for 2~3h, centrifuging, washing, and vacuum drying to obtain modified porous graphene.
5. The method for preparing a graphene conductive material according to claim 1, characterized in that, The method for preparing the blocked isocyanate in step (3) is as follows: Phenol, dibutyltin dilaurate and chloroform are mixed evenly to prepare a phenol solution; 2-methyl-2-acrylate isocyanate and chloroform are mixed evenly to prepare an isocyanate solution; under nitrogen protection and stirring at 40~50℃, the isocyanate solution is added dropwise to the phenol solution. After the addition is complete, the reaction is continued to be stirred for 50~70 min, and then dried under vacuum to obtain the blocked isocyanate.
6. The method for preparing a graphene conductive material according to claim 1, characterized in that, The preparation method of methacrylate-based pyrene in step (4) is as follows: 1-pyrene methanol, pyridine, triethylamine and tetrahydrofuran are mixed and stirred at room temperature for 10-20 min. Methacryl chloride is added dropwise under an ice-water bath and stirred at room temperature for 60-70 min. Deionized water is added and stirring is continued for 10-20 min. The mixture is extracted with diethyl ether and dried under vacuum to obtain methacrylate-based pyrene.
7. The method for preparing a graphene conductive material according to claim 1, characterized in that, The preparation method of the modified polyvinylidene fluoride in step (5) is as follows: polyvinylidene fluoride and N,N-dimethylformamide are mixed and stirred at 45~55℃ for 30~40min to prepare a polyvinylidene fluoride solution; the reaction monomer and N,N-dimethylformamide are mixed to prepare a monomer solution; under nitrogen protection, the polyvinylidene fluoride solution is heated to 68~74℃, terephthaloyl peroxide is added, and stirring is continued for 20~30min. The monomer solution is added dropwise, and after the addition is completed, the reaction is continued to be stirred for 7~8h. The mixture is cooled to room temperature, precipitated with anhydrous ethanol, and dried under vacuum to obtain modified polyvinylidene fluoride.
8. The method for preparing a graphene conductive material according to claim 7, characterized in that, The reaction monomer is obtained by mixing blocked isocyanate and methacrylate-based pyrene in a mass ratio of 1:(2~2.2).
9. The method for preparing a graphene conductive material according to claim 1, characterized in that, The preparation method of the positive electrode slurry in step (6) is as follows: weigh lithium iron phosphate, modified polyvinylidene fluoride, and modified porous graphene in a mass ratio of 90:(6~7):(3~4); mix the modified polyvinylidene fluoride and N-methylpyrrolidone evenly, stir at 1000~1200r / min for 10~20min, add the modified porous graphene, continue stirring for 10~20min, add lithium iron phosphate, adjust the solid content to 46%~50% with N-methylpyrrolidone, and continue stirring at 1800~2000r / min for 30~40min to obtain the positive electrode slurry.
10. A graphene conductive material prepared by the method of any one of claims 1 to 9.