A carbon paste for an aluminum foil current collector and a method of preparing the same

Abstract

The application discloses a kind of carbon paste for aluminum foil current collector and preparation method thereof, belong to carbon paste preparation technical field, for solving the technical problems that the adhesion and conductivity of existing aluminum foil current collector carbon paste need to be further improved;The application comprises the following raw material composition by weight parts: 40-50 parts of conductive matrix, 20-30 parts of isopropyl alcohol, 10-15 parts of deionized water, 5-6 parts of polyvinyl alcohol, 1-2 parts of polyvinylpyrrolidone and 1-2 parts of sodium carboxymethyl cellulose, the carboxylated multi-walled carbon nanotube is modified with copper silver nanoparticles to obtain composite carbon fiber, the carboxyl on it and the amino on the prepared ionic polyester react and crosslink to obtain a conductive matrix precursor, and by introducing siloxane groups into the conductive matrix precursor, a conductive matrix is obtained, which is mixed with adjuvants and coated on the aluminum foil activated by the aluminum foil activation solution to obtain a composite current collector.

Description

Technical Field

[0001] This invention relates to the field of carbon coating slurry preparation technology, specifically to a carbon coating slurry for aluminum foil current collectors and its preparation method. Background Technology

[0002] The development of carbon-coated slurry for aluminum foil current collectors has evolved from improving basic adhesion and conductivity to optimizing high performance. In the early stages, the coating had poor adhesion and was prone to peeling. To solve this problem, researchers used binders such as polyvinyl alcohol and water-based systems such as carboxymethyl cellulose to enhance stability. In terms of conductivity, materials such as superconducting carbon black and graphene were introduced to improve conductivity. With the advancement of technology, aluminum foil surface treatment technology and new conductive materials have enabled the coating to maintain good performance under high current density. Today, carbon-coated slurry has reached a high standard in terms of adhesion and conductivity, providing important support for improving the performance of lithium batteries.

[0003] For example, the prior art CN113140706B provides a method for preparing a lithium-ion battery, including the following steps: S1, preparing a carbon coating slurry, the carbon coating slurry comprising 10-20% conductive carbon black, 70-80% deionized water, 5-10% styrene-butadiene rubber and 2-4% dispersant by mass percentage; S2, spraying the carbon coating slurry onto the inner surface of a small cylindrical steel shell or cylindrical aluminum shell of the lithium-ion battery; this method improves the electronic conductivity of the current collector and active material of the steel or aluminum shell by carbon coating the inner surface of the small cylindrical steel shell or small cylindrical aluminum shell battery, thereby reducing the internal resistance of the lithium-ion battery, increasing the capacity of the lithium-ion battery, and increasing the internal space utilization of the lithium-ion battery.

[0004] However, the aforementioned patent describes dispersing conductive carbon black in deionized water and adding tackifiers and dispersants. However, the composition of the carbon coating slurry is simple, and the conductive carbon black lacks a dispersion medium, making it difficult to form a stable adhesion structure with metal materials that have not undergone surface activation treatment. As a result, the adhesion and wear resistance of the slurry need to be further improved. Moreover, the conductive carbon black mainly makes point contact, resulting in a small contact area. The electron transport path is easily affected by uneven dispersion or agglomeration, leading to an overly simple conductive pathway. This further results in the need to improve the conductivity of the carbon coating slurry. Summary of the Invention

[0005] The purpose of this invention is to provide a carbon coating slurry for aluminum foil current collectors and its preparation method, which solves the technical problem that the adhesion and conductivity of carbon coating slurries for aluminum foil current collectors need to be further improved in the prior art.

[0006] The objective of this invention can be achieved through the following technical solution: A carbon coating slurry for aluminum foil current collectors, comprising the following raw material components by weight: 40-50 parts conductive matrix, 20-30 parts isopropanol, 10-15 parts deionized water, 5-6 parts polyvinyl alcohol, 1-2 parts polyvinylpyrrolidone and 1-2 parts sodium carboxymethyl cellulose.

[0007] Furthermore, the method for preparing the conductive substrate includes the following steps:

[0008] A1. Add N,N-dimethylformamide to the reactor and stir. After the reactor temperature drops to 0-5℃, add composite carbon fiber to the reactor and stir for 5-10 min. Then, add N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide dropwise to the reactor and stir for 30-40 min. Raise the reactor temperature to room temperature and add ionic polyester to the reactor. After stirring for 4-6 h, the conductive matrix precursor is obtained through post-treatment.

[0009] A2. Add the conductive matrix precursor, 3-(methacryloyloxy)propyltrimethoxysilane and N,N-dimethylformamide to the reaction vessel, raise the temperature of the reaction vessel to 80-100℃, keep it warm and stir for 10-15 min, then add azobisisobutyronitrile to the reaction vessel, keep it warm and stir for 60-80 min, and then perform post-treatment to obtain the conductive matrix.

[0010] The reaction principle for preparing the conductive matrix is ​​as follows: by adding N,N'-dicyclohexylcarbodiimide to react with carboxyl groups to form an intermediate activated ester, the carboxyl groups on the composite carbon fiber are activated. N-hydroxysuccinimide enhances the stability of this intermediate product. Under low temperature conditions, N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide are added to the reaction vessel. During this process, the activated carboxyl groups are prepared to react with the amino groups on the subsequently added ionic polyester to form amide bonds, thus preparing the conductive matrix precursor. Then, through a free radical addition reaction, siloxy groups are introduced into the conductive matrix precursor, and finally the conductive matrix is ​​prepared.

[0011] Further, in step A1, the ratio of N,N-dimethylformamide, composite carbon fiber, N,N'-dicyclohexylcarbodiimide, N-hydroxysuccinimide, and ionic polyester is 30-40mL:2-3g:0.3-0.5g:0.1-0.3g:8-10g. The post-processing includes: after the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 60-80℃, and distill under reduced pressure until no liquid is collected to obtain the conductive matrix precursor.

[0012] Furthermore, in step A2, the ratio of the conductive matrix precursor, 3-(methacryloyloxy)propyltrimethoxysilane, N,N-dimethylformamide, and azobisisobutyronitrile is 8-10g:1-2g:40-60mL:0.3-0.5g. The post-treatment includes: after the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 60-80℃, and distill under reduced pressure until no liquid is collected to obtain the conductive matrix.

[0013] Furthermore, the preparation method of ionic polyester includes the following steps:

[0014] B1. Maleic anhydride, epichlorohydrin, benzoic acid and N,N-dimethylformamide are added to a round-bottom three-necked flask. The round-bottom three-necked flask is heated to 60-80℃ and stirred for 80-100 min. The modified polyester is obtained by post-treatment.

[0015] B2. Add the modified polyester, 4-aminopyridine and N,N-dimethylformamide to a round-bottom three-necked flask. Under a nitrogen atmosphere, heat the reaction system to reflux and maintain the reflux for 10-12 hours. Post-treatment yields the ionic polyester.

[0016] The reaction principle for preparing ionic polyester is as follows: under the catalysis of benzoic acid, epoxybromopropane ring-opening forms an active free radical that reacts with maleic anhydride to form a long-chain structure, resulting in modified polyester. Under heating conditions, the bromine groups on the modified polyester are removed and combine with 4-aminopyridine to form a quaternary ammonium salt, ultimately preparing the ionic polyester.

[0017] Further, in step B1, the ratio of maleic anhydride, epichlorohydrin, benzoic acid, and N,N-dimethylformamide is 0.9-1.0g:1.2-1.3g:0.1-0.2g:8-10mL. The post-treatment includes: after the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 60-80℃, and distill under reduced pressure until no liquid is collected to obtain the modified polyester.

[0018] Furthermore, in step B2, the ratio of modified polyester, 4-aminopyridine, and N,N-dimethylformamide is 4-5g:1-1.2g:20-24mL. The post-treatment includes: after the reaction is completed, the reaction vessel temperature is lowered to room temperature, the reaction solution is transferred to a rotary evaporator, the rotary evaporator temperature is raised to 60-80℃, and the solution is distilled under reduced pressure until no liquid is collected, thus obtaining ionic polyester.

[0019] Furthermore, the preparation method of composite carbon fiber includes the following steps:

[0020] C1. Carboxylated multi-walled carbon nanotubes were dispersed in an ultrasonic device containing deionized water. After ultrasonic dispersion for 10-15 min, a modification solution was added to the ultrasonic device. After ultrasonication for another 10-15 min, the pH of the reaction system was adjusted to 9-10 using a saturated sodium hydroxide aqueous solution. Hydrazine hydrate was then added dropwise to the ultrasonic device. After the addition was completed, the reaction precursor solution was obtained.

[0021] C2. Transfer the reaction precursor liquid to the reaction vessel, raise the temperature of the reaction vessel to 80-90℃, keep it at the temperature and stir for 1-2 hours, and then perform post-treatment to obtain the composite carbon fiber precursor.

[0022] C3. The composite carbon fiber precursor is dried under low temperature vacuum to obtain the composite carbon fiber.

[0023] The reaction principle for preparing composite carbon fibers is as follows: the carboxyl groups on the hydroxylated multi-walled carbon nanotubes and the hydroxides formed by the hydrolysis of copper and silver ions in the system form a complex structure. After reduction by hydrazine hydrate, copper and silver nanoparticles are embedded on the hydroxylated multi-walled carbon nanotubes. After partial reduction by hydrazine hydrate, the electrical properties of the carboxylated multi-walled carbon nanotubes are improved. After low-temperature drying, composite carbon fibers are obtained.

[0024] Furthermore, in step C1, the ratio of carboxylated multi-walled carbon nanotubes, deionized water, and modification solution is 5-6 g: 100 mL: 100 mL, wherein the modification solution is obtained by mixing copper nitrate, silver nitrate, and deionized water in a ratio of 1.6-1.8 g: 1.0-1.2 g: 100 mL.

[0025] Furthermore, in step C2, the post-processing includes: after the reaction is complete, the reaction solution is filtered to collect the filter cake, and the filter cake is washed with anhydrous ethanol and deionized water until the filter cake is neutral to obtain the composite carbon fiber precursor.

[0026] Furthermore, in step C3, the method for preparing composite carbon fiber is as follows: the composite carbon fiber precursor is transferred to a vacuum freeze dryer, the temperature of the vacuum freeze dryer is lowered to -40℃, and the mixture is kept warm and dried for 16-20 hours to obtain composite carbon fiber.

[0027] The present invention also proposes a method for preparing a carbon-coated slurry for aluminum foil current collectors: a conductive substrate, deionized water and isopropanol are added to a mixing tank and stirred for 10-15 minutes, then polyvinyl alcohol, polyvinylpyrrolidone and sodium carboxymethyl cellulose are added, and stirring is continued for 20-30 minutes to obtain the carbon-coated slurry.

[0028] Furthermore, the method of using the carbon coating slurry prepared by the present invention is as follows: aluminum foil is immersed in aluminum foil activation solution, and ultrasonically treated for 20-30 minutes at a temperature of 40-50℃ to obtain activated aluminum foil. The carbon coating slurry is uniformly coated on the surface of the activated aluminum foil and transferred to a vacuum drying oven at a temperature of 40-60℃ for vacuum drying until the material reaches constant weight to obtain a composite current collector. The coating thickness is 2-4 μm on one side.

[0029] The reaction principle for preparing the composite current collector is as follows: Sodium hydroxide in the aluminum foil activation solution, as a strong alkaline substance, first reacts with the metallic aluminum on the surface of the aluminum foil, dissolving the surface oxide film and corroding the aluminum substrate, generating active sites. Sodium sulfonate is electrostatically adsorbed onto the aluminum foil surface, forming a stable negative charge layer. The residual alkaline solution on the surface promotes the hydrolysis of siloxane groups in the conductive matrix of the carbon coating slurry to form silanol structures, which form cross-linked structures with the active sites on the aluminum foil surface. Furthermore, the internal quaternary ammonium salt structure and the negative charge layer are electrostatically adsorbed, promoting the adhesion of the carbon coating slurry.

[0030] Furthermore, the preparation method of the aluminum foil activation solution is as follows: sodium hydroxide powder, sodium sulfonate and deionized water are added to a stirring vessel and mixed evenly to obtain the aluminum foil activation solution, wherein the ratio of sodium hydroxide powder, sodium sulfonate and deionized water is 8-10g:2-3g:100-120g.

[0031] The present invention has the following beneficial effects:

[0032] 1. This invention first chemically modifies the polyester by introducing quaternary ammonium salts and amino groups to form a positively charged ionic polyester. The amino groups and carboxyl groups on the surface of carboxylated carbon nanotubes form stable chemical bonds through cross-linking reactions, enabling the carbon fibers to be uniformly dispersed and constructing a conductive network. Copper and silver nanoparticles modified on the surface of carbon nanotubes catalyze the bonding reaction between siloxane groups and aluminum foil during curing, enhancing the interfacial bonding efficiency. The aluminum foil is corroded by sodium hydroxide to form a porous oxide layer, and sodium sulfonate is adsorbed on the surface to form a negatively charged region, which generates electrostatic pre-adsorption with the positively charged groups of the ionic polyester, laying the foundation for subsequent chemical bonding. Subsequently, the siloxane groups introduced by free radical polymerization condense with the hydroxyl groups on the surface of the aluminum foil to form covalent bonds. At the same time, the flexible siloxane chains buffer mechanical stress, and combined with the three-dimensional interlocking structure of the carbon fiber network, they jointly resist frictional peeling. Ultimately, the charge characteristics of the polyester determine the dispersion quality of the carbon fibers, the catalytic effect of the carbon fibers accelerates the formation of siloxane bonds, and the activation of the aluminum foil provides the bonding interface. Finally, through the multiple synergies of chemical bonding, electrostatic adsorption, and mechanical interlocking, the adhesion between the coating and the aluminum foil is improved and the wear resistance of the coating is enhanced.

[0033] 2. The principle behind the improved conductivity of the carbon-coated slurry combined with aluminum foil in this invention is achieved through a multi-step synergistic process: First, the polyester is chemically modified to carry positively charged groups and active amino groups on its surface. These groups pre-bond with the activated negatively charged layer on the aluminum foil surface via electrostatic interaction, reducing interfacial resistance. Subsequently, after modification with copper and silver particles, the acidic groups on the carbon fibers react with the amino groups of the polyester to form stable chemical bonds, constructing a uniform conductive network. The aluminum foil is then corroded with an alkaline solution and treated with a charge regulator to form a rough surface and provide chemically active sites, promoting the subsequent bonding reaction between the siloxy groups and the aluminum foil. Finally, the introduced siloxy groups strengthen the interfacial bonding through chemical bonds. Their flexible structure alleviates material deformation stress and maintains the stability of the conductive pathway. Ultimately, the electrical performance is improved by enhancing interfacial charge matching through the charge characteristics of the polyester. The carbon fiber network provides a continuous path for electron transport, the activated aluminum foil enhances interfacial bonding, and the siloxy groups ensure long-term stability. Through the synergistic effect of charge matching, chemical bonding, and structural flexibility, the conductivity of the coated aluminum foil material is improved.

[0034] 3. This invention first chemically treats the aluminum foil surface, using an alkaline solution to corrode and generate a porous oxide layer. Combined with a charge regulator, this forms a stable negatively charged surface, enhancing its adhesion to subsequent coatings. Subsequently, a polyester material is chemically modified to introduce positively charged groups and active amino groups, pre-bonding with the aluminum foil through electrostatic interaction. Simultaneously, the amino groups react with the acidic groups on the carbon fiber surface, forming stable chemical bonds, allowing the carbon fibers to be uniformly dispersed within the polyester, constructing a dense physical barrier. During curing, copper and silver particles modified on the carbon fiber surface catalyze the bonding reaction between siloxane groups and the aluminum foil, generating strong chemical bonds that further seal the pores on the aluminum foil surface. The flexible properties of the siloxane groups alleviate material deformation stress, preventing the coating from cracking due to mechanical or thermal stress. Finally, the active functional groups of the polyester promote uniform dispersion of the carbon fibers. The carbon fiber network and siloxane bonds synergistically block the penetration of corrosive media, while the metal particles accelerate bonding and enhance coating stability. Through multi-level synergy of charge adsorption, chemical bonding, physical barrier, and stress buffering, the intrusion of corrosive media is effectively inhibited, thereby improving the corrosion resistance of the coating. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The carboxylated multi-walled carbon nanotubes used in this invention were purchased from Shanghai Yuanye Biotechnology Co., Ltd., with product number V34978-25g.

[0037] Example 1

[0038] This embodiment provides a method for preparing composite carbon fiber for carbon coating slurry preparation of aluminum foil current collectors, including the following steps:

[0039] Step ①: Preparation of the reaction precursor solution

[0040] Weigh out 16.0g of copper nitrate, 10.0g of silver nitrate and 1000.0mL of deionized water and mix them to obtain the modified solution;

[0041] Weigh out 50.0g of carboxylated multi-walled carbon nanotubes and disperse them in an ultrasonic device containing 1000.0mL of deionized water. After ultrasonic dispersion for 10min, add 1000.0mL of modification solution to the ultrasonic device and continue ultrasonication for 10min. Then, adjust the pH of the reaction system to 9 using saturated sodium hydroxide aqueous solution. Continue to add hydrazine hydrate dropwise to the ultrasonic device. After the addition is complete, the reaction precursor solution is obtained.

[0042] Step 2: Preparation of composite carbon fiber precursor

[0043] Weigh 1000.0 mL of the reaction precursor solution and transfer it to the reaction vessel. Raise the temperature of the reaction vessel to 80°C and stir for 1 hour. After the reaction is complete, filter the reaction solution and collect the filter cake. Wash the filter cake with anhydrous ethanol and deionized water until the filter cake is neutral to obtain the composite carbon fiber precursor.

[0044] Step ③: Preparation of composite carbon fibers

[0045] Weigh 50.0g of composite carbon fiber precursor and transfer it to a vacuum freeze dryer. The temperature of the vacuum freeze dryer is lowered to -40℃ and kept at that temperature for 16 hours to obtain composite carbon fiber.

[0046] Example 2

[0047] This embodiment provides a method for preparing composite carbon fiber for carbon coating slurry preparation of aluminum foil current collectors, including the following steps:

[0048] Step ①: Preparation of the reaction precursor solution

[0049] Weigh out 18.0g of copper nitrate, 12.0g of silver nitrate and 1000.0mL of deionized water and mix them to obtain the modified solution;

[0050] 60.0 g of carboxylated multi-walled carbon nanotubes were weighed and dispersed in an ultrasonic device containing 1000.0 mL of deionized water. After ultrasonic dispersion for 15 min, 1000.0 mL of modification solution was added to the ultrasonic device. After ultrasonic dispersion for another 15 min, the pH of the reaction system was adjusted to 10 using saturated sodium hydroxide aqueous solution. Hydrazine hydrate was then added dropwise to the ultrasonic device. After the addition was completed, the reaction precursor solution was obtained.

[0051] Step 2: Preparation of composite carbon fiber precursor

[0052] Weigh 1000.0 mL of the reaction precursor solution and transfer it to the reaction vessel. Raise the temperature of the reaction vessel to 90°C and stir for 2 hours. After the reaction is complete, filter the reaction solution and collect the filter cake. Wash the filter cake with anhydrous ethanol and deionized water until the filter cake is neutral to obtain the composite carbon fiber precursor.

[0053] Step ③: Preparation of composite carbon fibers

[0054] Weigh 50.0g of the composite carbon fiber precursor and transfer it to a vacuum freeze dryer. The temperature of the vacuum freeze dryer is lowered to -40℃ and kept at that temperature for 20 hours to obtain the composite carbon fiber.

[0055] Example 3

[0056] This embodiment provides a method for preparing composite carbon fiber for carbon coating slurry preparation of aluminum foil current collectors, including the following steps:

[0057] Step ①: Preparation of the reaction precursor solution

[0058] Weigh out 17.0g of copper nitrate, 11.0g of silver nitrate and 1000.0mL of deionized water and mix them to obtain the modified solution;

[0059] Weigh out 54.0g of carboxylated multi-walled carbon nanotubes and disperse them in an ultrasonic device containing 1000.0mL of deionized water. After ultrasonic dispersion for 15min, add 1000.0mL of modification solution to the ultrasonic device and continue ultrasonication for 15min. Then, adjust the pH of the reaction system to 10 using saturated sodium hydroxide aqueous solution. Continue to add hydrazine hydrate dropwise to the ultrasonic device. After the addition is complete, the reaction precursor solution is obtained.

[0060] Step 2: Preparation of composite carbon fiber precursor

[0061] Weigh 1000.0 mL of the reaction precursor solution and transfer it to the reaction vessel. Raise the temperature of the reaction vessel to 84°C and stir for 2 hours. After the reaction is complete, filter the reaction solution and collect the filter cake. Wash the filter cake with anhydrous ethanol and deionized water until the filter cake is neutral to obtain the composite carbon fiber precursor.

[0062] Step ③: Preparation of composite carbon fibers

[0063] Weigh 50.0g of the composite carbon fiber precursor and transfer it to a vacuum freeze dryer. The temperature of the vacuum freeze dryer is lowered to -40℃ and kept at that temperature for 18 hours to obtain the composite carbon fiber.

[0064] Example 4

[0065] This embodiment provides a method for preparing ionic polyester for carbon-coated slurry preparation of aluminum foil current collectors, including the following steps:

[0066] Step I: Preparation of modified polyester

[0067] Weigh out 9.0 g maleic anhydride, 12.0 g epibromopropane, 1.0 g benzoic acid and 80.0 mL N,N-dimethylformamide and add them to a round-bottom three-necked flask. Heat the round-bottom three-necked flask to 60 °C and stir for 80 min. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, then transfer the reaction solution to a rotary evaporator. Raise the temperature of the rotary evaporator to 60 °C and distill under reduced pressure until no liquid is collected to obtain the modified polyester.

[0068] Step II: Preparation of ionic polyester

[0069] Weigh 40.0 g of modified polyester, 10.0 g of 4-aminopyridine and 200.0 mL of N,N-dimethylformamide into a round-bottom three-necked flask. Under a nitrogen atmosphere, heat the reaction system to reflux and maintain the reflux temperature for 10 h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, then transfer the reaction solution to a rotary evaporator. Raise the temperature of the rotary evaporator to 60 °C and distill under reduced pressure until no liquid is collected to obtain ionic polyester.

[0070] Example 5

[0071] This embodiment provides a method for preparing ionic polyester for carbon-coated slurry preparation of aluminum foil current collectors, including the following steps:

[0072] Step I: Preparation of modified polyester

[0073] Weigh out 10.0 g maleic anhydride, 13.0 g epichlorohydrin, 2.0 g benzoic acid and 100.0 mL N,N-dimethylformamide and add them to a round-bottom three-necked flask. Heat the round-bottom three-necked flask to 80 °C and stir for 100 min. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, then transfer the reaction solution to a rotary evaporator. Raise the temperature of the rotary evaporator to 80 °C and distill under reduced pressure until no liquid is collected to obtain the modified polyester.

[0074] Step II: Preparation of ionic polyester

[0075] Weigh out 50.0 g of modified polyester, 12.0 g of 4-aminopyridine and 240.0 mL of N,N-dimethylformamide and add them to a round-bottom three-necked flask. Under a nitrogen atmosphere, heat the reaction system to reflux and keep it at reflux for 12 h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 80 °C, and distill under reduced pressure until no liquid is collected to obtain ionic polyester.

[0076] Example 6

[0077] This embodiment provides a method for preparing ionic polyester for carbon-coated slurry preparation of aluminum foil current collectors, including the following steps:

[0078] Step I: Preparation of modified polyester

[0079] Weigh out 9.6 g maleic anhydride, 12.4 g epichlorohydrin, 1.6 g benzoic acid and 100.0 mL N,N-dimethylformamide and add them to a round-bottom three-necked flask. Heat the round-bottom three-necked flask to 70 °C and stir for 90 min. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, then transfer the reaction solution to a rotary evaporator. Raise the temperature of the rotary evaporator to 70 °C and distill under reduced pressure until no liquid is collected to obtain the modified polyester.

[0080] Step II: Preparation of ionic polyester

[0081] Weigh 48.0 g of modified polyester, 10.0 g of 4-aminopyridine and 210.0 mL of N,N-dimethylformamide into a round-bottom three-necked flask. Under a nitrogen atmosphere, heat the reaction system to reflux and maintain the reflux temperature for 12 h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, then transfer the reaction solution to a rotary evaporator. Raise the temperature of the rotary evaporator to 80 °C and distill under reduced pressure until no liquid is collected to obtain ionic polyester.

[0082] Example 7

[0083] This embodiment provides a method for preparing a conductive substrate for carbon-coated paste used in aluminum foil current collectors, including the following steps:

[0084] Step 1: Preparation of conductive substrate precursor

[0085] Weigh 300.0 mL of N,N-dimethylformamide and add it to the reaction vessel. After the temperature of the reaction vessel drops to 0°C, add 20.0 g of the composite carbon fiber prepared in Example 1 to the reaction vessel. After stirring for 5 min, add 3.0 g of N,N'-dicyclohexylcarbodiimide and 1.0 g of N-hydroxysuccinimide dropwise to the reaction vessel. After stirring for 30 min, raise the temperature of the reaction vessel to room temperature and add 80.0 g of the ionic polyester prepared in Example 4 to the reaction vessel. After stirring for 4 h, after the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 60°C, and distill under reduced pressure until no liquid is collected to obtain the conductive matrix precursor.

[0086] Step 2: Preparation of conductive substrate

[0087] Weigh out 80.0 g of conductive matrix precursor, 10.0 g of 3-(methacryloyloxy)propyltrimethoxysilane and 400.0 mL of N,N-dimethylformamide and add them to a reaction vessel. Raise the temperature of the reaction vessel to 80°C and stir for 10 min. Then add 3.0 g of azobisisobutyronitrile and stir for 60 min. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 60°C, and distill under reduced pressure until no liquid is collected to obtain the conductive matrix.

[0088] Example 8

[0089] This embodiment provides a method for preparing a conductive substrate for carbon-coated paste used in aluminum foil current collectors, including the following steps:

[0090] Step 1: Preparation of conductive substrate precursor

[0091] Weigh 400.0 mL of N,N-dimethylformamide and add it to the reaction vessel. After the temperature of the reaction vessel drops to 5°C, add 30.0 g of the composite carbon fiber prepared in Example 2 to the reaction vessel. After stirring for 10 min, add 5.0 g of N,N'-dicyclohexylcarbodiimide and 3.0 g of N-hydroxysuccinimide dropwise to the reaction vessel. After stirring for 40 min, raise the temperature of the reaction vessel to room temperature and add 100.0 g of the ionic polyester prepared in Example 5 to the reaction vessel. After stirring for 6 h, after the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 80°C, and distill under reduced pressure until no liquid is collected to obtain the conductive matrix precursor.

[0092] Step 2: Preparation of conductive substrate

[0093] Weigh out 100.0 g of conductive matrix precursor, 20.0 g of 3-(methacryloyloxy)propyltrimethoxysilane and 600.0 mL of N,N-dimethylformamide and add them to a reaction vessel. Raise the temperature of the reaction vessel to 100℃ and stir for 15 min. Then add 5.0 g of azobisisobutyronitrile and stir for 80 min. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 80℃, and distill under reduced pressure until no liquid is collected to obtain the conductive matrix.

[0094] Example 9

[0095] This embodiment provides a method for preparing a conductive substrate for carbon-coated paste used in aluminum foil current collectors, including the following steps:

[0096] Step 1: Preparation of conductive substrate precursor

[0097] Weigh 360.0 mL of N,N-dimethylformamide and add it to the reaction vessel. After the temperature of the reaction vessel drops to 3°C, add 24.0 g of the composite carbon fiber prepared in Example 3 to the reaction vessel. After stirring for 10 min, add 4.0 g of N,N'-dicyclohexylcarbodiimide and 2.0 g of N-hydroxysuccinimide dropwise to the reaction vessel. After stirring for 36 min, raise the temperature of the reaction vessel to room temperature and add 90.0 g of the ionic polyester prepared in Example 6 to the reaction vessel. After stirring for 6 h, after the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 72°C, and distill under reduced pressure until no liquid is collected to obtain the conductive matrix precursor.

[0098] Step 2: Preparation of conductive substrate

[0099] Weigh out 90.0 g of conductive matrix precursor, 16.0 g of 3-(methacryloyloxy)propyltrimethoxysilane and 500.0 mL of N,N-dimethylformamide and add them to a reaction vessel. Raise the temperature of the reaction vessel to 90 °C and stir for 12 min. Then add 4.0 g of azobisisobutyronitrile and stir for 70 min. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, transfer the reaction solution to a rotary evaporator, raise the temperature of the rotary evaporator to 70 °C, and distill under reduced pressure until no liquid is collected to obtain the conductive matrix.

[0100] Example 10

[0101] This embodiment provides a method for preparing a composite current collector, including the following steps:

[0102] Step 1: Preparation of aluminum foil activation solution

[0103] Weigh out 80.0g of sodium hydroxide powder, 20.0g of sodium sulfonate and 1000.0g of deionized water and add them to a stirring vessel. Mix well to obtain an aluminum foil activation solution.

[0104] Step 2: Preparation of carbon coating slurry

[0105] Weigh out 40.0g of the conductive substrate prepared in Example 7, 10.0g of deionized water and 20.0g of isopropanol and add them to a mixing tank. Stir for 10.0min, then add 5.0g of polyvinyl alcohol, 1.0g of polyvinylpyrrolidone and 1.0g of sodium carboxymethyl cellulose. Continue stirring for 20min to obtain the carbon coating slurry.

[0106] Step 3: Preparation of composite current collector

[0107] Aluminum foil was immersed in an aluminum foil activation solution and ultrasonicated at 40°C for 20 minutes to obtain activated aluminum foil. Carbon coating paste was uniformly coated on the surface of the activated aluminum foil with a coating thickness of 2μm on one side. The foil was then transferred to a vacuum drying oven at 40°C and vacuum dried until the material reached constant weight to obtain a composite current collector.

[0108] Example 11

[0109] This embodiment provides a method for preparing a composite current collector, including the following steps:

[0110] Step 1: Preparation of aluminum foil activation solution

[0111] Weigh out 100.0g of sodium hydroxide powder, 30.0g of sodium sulfonate and 1200.0g of deionized water and add them to a stirring vessel. Mix them evenly to obtain an aluminum foil activation solution.

[0112] Step 2: Preparation of carbon coating slurry

[0113] Weigh out 50.0g of the conductive substrate prepared in Example 8, 15.0g of deionized water and 30.0g of isopropanol and add them to a mixing tank. After stirring for 15 minutes, add 6.0g of polyvinyl alcohol, 2.0g of polyvinylpyrrolidone and 2.0g of sodium carboxymethyl cellulose. Continue stirring for 30 minutes to obtain the carbon coating slurry.

[0114] Step 3: Preparation of composite current collector

[0115] Aluminum foil was immersed in an aluminum foil activation solution and ultrasonicated at 50°C for 30 minutes to obtain activated aluminum foil. Carbon coating paste was uniformly coated on the surface of the activated aluminum foil with a coating thickness of 4μm on one side. The foil was then transferred to a vacuum drying oven at 50°C and vacuum dried until the material reached constant weight to obtain a composite current collector.

[0116] Example 12

[0117] This embodiment provides a method for preparing a composite current collector, including the following steps:

[0118] Step 1: Preparation of aluminum foil activation solution

[0119] Weigh out 90.0g of sodium hydroxide powder, 25.0g of sodium sulfonate and 1080.0g of deionized water and add them to a stirring vessel. Mix well to obtain an aluminum foil activation solution.

[0120] Step 2: Preparation of carbon coating slurry

[0121] Weigh out 48.0g of the conductive substrate prepared in Example 9, 12.0g of deionized water and 24.0g of isopropanol and add them to a mixing tank. After stirring for 12 minutes, add 5.4g of polyvinyl alcohol, 1.6g of polyvinylpyrrolidone and 1.6g of sodium carboxymethyl cellulose and continue stirring for 24 minutes to obtain the carbon coating slurry.

[0122] Step 3: Preparation of composite current collector

[0123] Aluminum foil was immersed in an aluminum foil activation solution and ultrasonicated at 48°C for 24 minutes to obtain activated aluminum foil. Carbon coating paste was uniformly coated on the surface of the activated aluminum foil with a coating thickness of 3μm on one side. The foil was then transferred to a vacuum drying oven at 50°C and vacuum dried until the material reached constant weight to obtain a composite current collector.

[0124] Comparative Example 1

[0125] The difference between this comparative example and Example 12 is that, in the preparation of the conductive matrix, step II of the ionic polyester used in the preparation process is omitted.

[0126] Comparative Example 2

[0127] The difference between this comparative example and Example 12 is that step (ii) is omitted in the preparation of the conductive substrate, and the aluminum foil activation solution is omitted in the preparation of the composite current collector.

[0128] Comparative Example 3

[0129] The difference between this comparative example and Example 12 is that, in step (i) of the preparation process of the conductive substrate, the composite carbon fiber is omitted and replaced with an equal amount of carboxylated multi-walled carbon nanotubes.

[0130] Performance testing:

[0131] The adhesion level between the composite current collector layers prepared in Examples 10-12 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 31586.2-2015 "Evaluation and acceptance criteria for adhesion / cohesion (breaking strength) of protective coating systems for steel structures - Part 2: cross-cut test and cross-cut test".

[0132] The mass loss of the composite current collector surface coatings prepared in Examples 10-12 and Comparative Examples 1-3 after 100 cycles of cyclic abrasion was tested in accordance with the standard YY / T 0988.15-2016 "Surgical Implant Coatings Part 15: Test Method for Abrasion Resistance of Metal Thermal Spray Coatings".

[0133] The corrosion resistance of the composite current collectors prepared in Examples 10-12 and Comparative Examples 1-3 was tested in accordance with the standard JB / T 6073-1992 "Laboratory Full Immersion Corrosion Test of Metal Coatings".

[0134] The volume resistivity of the composite current collectors prepared in Examples 10-12 and Comparative Examples 1-3 was compared with that in accordance with the standard GB / T 3048.2-2007 "Test Methods for Electrical Properties of Wires and Cables - Part 2: Test for Resistivity of Metallic Materials". The specific data are shown in Table 1.

[0135] Table 1 - Performance Test Data for Each Sample

[0136]

[0137] Data Analysis:

[0138] Comparative analysis of the data in Table 1 reveals that when the carbon-coated slurry prepared in this invention is coated onto the surface of aluminum foil activated by the aluminum foil activation solution and cured, the adhesion level between the carbon-coated slurry and the aluminum foil is grade 0, the mass loss of the cured material after 100 cycles of abrasion is 2.3 mg, the corrosion rate is 0.17%, and the volume resistivity of the composite current collector formed by the carbon-coated slurry and the aluminum foil on the aluminum foil surface is 2.4 × 10⁻⁶. -8 Ω·m, all data are better than the comparative example;

[0139] This invention first chemically treats the aluminum foil surface, using an alkaline solution to corrode and generate a porous oxide layer. A charge regulator is then used to create a stable negatively charged surface, enhancing its adhesion to subsequent coatings. Subsequently, a polyester material is chemically modified to introduce positively charged groups and active amino groups, pre-bonding with the aluminum foil through electrostatic interaction. Simultaneously, the amino groups react with the acidic groups on the carbon fiber surface, forming stable chemical bonds. This allows the carbon fibers to be uniformly dispersed within the polyester, constructing a dense physical barrier. During curing, copper and silver particles modified on the carbon fiber surface catalyze the bonding reaction between siloxane groups and the aluminum foil, generating strong chemical bonds that further seal the pores on the aluminum foil surface. The flexible properties of the siloxane groups alleviate material deformation stress, preventing the coating from cracking due to mechanical or thermal stress. Finally, the active functional groups of the polyester promote uniform dispersion of the carbon fibers. The carbon fiber network and siloxane bonds synergistically block the penetration of corrosive media, while the metal particles accelerate bonding and enhance coating stability. Through multi-level synergy of charge adsorption, chemical bonding, physical barrier, and stress buffering, the intrusion of corrosive media is effectively inhibited, thereby improving the corrosion resistance of the coating.

[0140] The principle behind the improved conductivity of the carbon-coated slurry combined with aluminum foil in this invention is achieved through a multi-step synergistic process: First, the polyester is chemically modified to carry positively charged groups and active amino groups on its surface. These groups pre-bond with the activated negatively charged layer on the aluminum foil surface via electrostatic interaction, reducing interfacial resistance. Subsequently, carbon fibers are modified with copper and silver particles, and their surface acidic groups react with the amino groups of the polyester to form stable chemical bonds, constructing a uniform conductive network. The aluminum foil is then corroded with an alkaline solution and treated with a charge regulator to form a rough surface and provide chemically active sites, promoting the subsequent bonding reaction between the siloxane groups and the aluminum foil. Finally, the introduced siloxane groups strengthen the interfacial bonding through chemical bonds, and their flexible structure alleviates material deformation stress, maintaining the stability of the conductive pathway. Ultimately, the electrical performance is improved by enhancing interfacial charge matching through the charge characteristics of the polyester, the carbon fiber network provides a continuous path for electron transport, the activated aluminum foil enhances interfacial bonding, and the siloxane groups ensure long-term stability. Through the synergistic effect of charge matching, chemical bonding, and structural flexibility, the conductivity of the coated aluminum foil material is improved.

[0141] This invention first chemically modifies polyester by introducing quaternary ammonium salts and amino groups to form a positively charged ionic polyester. The amino groups and carboxyl groups on the surface of carboxylated carbon nanotubes form stable chemical bonds through a cross-linking reaction, resulting in uniform dispersion of carbon fibers and the construction of a conductive network. Copper-silver nanoparticles modified on the carbon nanotube surface catalyze the bonding reaction between siloxane groups and aluminum foil during curing, enhancing interfacial bonding efficiency. The aluminum foil is etched with sodium hydroxide to form a porous oxide layer, and sodium sulfonate is adsorbed on the surface to form a negatively charged region, generating electrostatic pre-adsorption with the positively charged groups of the ionic polyester, laying the foundation for subsequent chemical bonding. Subsequently, the siloxane groups introduced by free radical polymerization condense with the hydroxyl groups on the aluminum foil surface to form covalent bonds. Simultaneously, the flexible siloxane chains buffer mechanical stress, and combined with the three-dimensional interlocking structure of the carbon fiber network, they jointly resist frictional peeling. Ultimately, the charge characteristics of the polyester determine the dispersion quality of the carbon fibers, the catalytic effect of the carbon fibers accelerates the formation of siloxane bonds, and the activation of the aluminum foil provides the bonding interface. Finally, through the synergistic effect of chemical bonding, electrostatic adsorption, and mechanical interlocking, the adhesion between the coating and the aluminum foil is improved, and the wear resistance of the coating is enhanced.

[0142] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A carbon-coating slurry for an aluminum foil current collector, characterized by, The raw material composition comprises the following ingredients by weight: 40-50 parts of an electrically conductive matrix, 20-30 parts of isopropyl alcohol, 10-15 parts of deionized water, 5-6 parts of polyvinyl alcohol, 1-2 parts of polyvinylpyrrolidone, and 1-2 parts of sodium carboxymethyl cellulose; The preparation method of the electrically conductive matrix comprises the following steps: A1, N,N-dimethylformamide is stirred in a reaction kettle, after the temperature of the reaction kettle is lowered to 0-5℃, composite carbon fiber is added to the reaction kettle, after 5-10min of heat preservation and stirring, N,N'-dicyclohexyl carbodiimide and N-hydroxysuccinimide are added dropwise to the reaction kettle, after 30-40min of heat preservation and stirring, the temperature of the reaction kettle is raised to room temperature, and ionic polyester is added to the reaction kettle, after 4-6h of heat preservation and stirring, the electrically conductive matrix precursor is obtained after post-treatment; A2, the electrically conductive matrix precursor, 3-(methacryloyloxy) propyl trimethoxysilane and N,N-dimethylformamide are added to the reaction kettle, the temperature of the reaction kettle is raised to 80-100℃, after 10-15min of heat preservation and stirring, azobisisobutyronitrile is added to the reaction kettle, after 60-80min of heat preservation and stirring, the electrically conductive matrix is obtained after post-treatment; The preparation method of the ionic polyester comprises the following steps: B1, maleic anhydride, epoxy bromopropane, benzoic acid and N,N-dimethylformamide are added to a round-bottom three-necked flask, the round-bottom three-necked flask is heated to 60-80℃, heat preservation and stirring are performed for 80-100min, and the modified polyester is obtained after post-treatment; B2, the modified polyester, 4-aminopyridine and N,N-dimethylformamide are added to a round-bottom three-necked flask, the reaction system is heated to reflux under the atmosphere of nitrogen, heat preservation and reflux are performed for 10-12h, and the ionic polyester is obtained after post-treatment; The preparation method of the composite carbon fiber comprises the following steps: C1, the carboxylated multi-walled carbon nanotube is dispersed in an ultrasonic device containing deionized water, after 10-15min of ultrasonic dispersion, the modified liquid is added to the ultrasonic device, after 10-15min of continuous ultrasonic, the pH value of the reaction system is adjusted to 9-10 by using saturated sodium hydroxide aqueous solution, and hydrazine hydrate is continuously added dropwise to the ultrasonic device, and the reaction precursor liquid is obtained after the dropwise addition is completed, wherein the modified liquid is obtained by mixing copper nitrate, silver nitrate and deionized water in a use amount ratio of 1.6-1.8g:1.0-1.2g:100mL; C2, the reaction precursor liquid is transferred to a reaction kettle, the temperature of the reaction kettle is raised to 80-90℃, heat preservation and stirring are performed for 1-2h, and the composite carbon fiber precursor is obtained after post-treatment; C3, the composite carbon fiber precursor is subjected to low-temperature vacuum drying to obtain the composite carbon fiber.

2. The carbon paste slurry for an aluminum foil current collector according to claim 1, characterized by, In step A1, the use amount ratio of N,N-dimethylformamide, composite carbon fiber, N,N'-dicyclohexyl carbodiimide, N-hydroxysuccinimide and ionic polyester is 30-40mL:2-3g:0.3-0.5g:0.1-0.3g:8-10g; in step A2, the use amount ratio of the electrically conductive matrix precursor, 3-(methacryloyloxy) propyl trimethoxysilane, N,N-dimethylformamide and azobisisobutyronitrile is 8-10g:1-2g:40-60mL:0.3-0.5g.

3. The carbon paste slurry for an aluminum foil current collector according to claim 1, wherein In step B1, the ratio of maleic anhydride, epoxy bromopropane, benzoic acid and N,N-dimethylformamide is 0.9-1.0g:1.2-1.3g:0.1-0.2g:8-10mL; in step B2, the ratio of modified polyester, 4-aminopyridine and N,N-dimethylformamide is 4-5g:1-1.2g:20-24mL.

4. The carbon paste slurry for an aluminum foil current collector according to claim 1, wherein In step C1, the ratio of carboxylated multi-walled carbon nanotubes, deionized water and modification solution is 5-6g:100mL:100mL; in step C3, the preparation method of the composite carbon fiber is: transferring the composite carbon fiber precursor into a vacuum freeze dryer, reducing the temperature of the vacuum freeze dryer to-40℃, and keeping the temperature for 16-20h to obtain the composite carbon fiber.

5. A method for producing a carbon paste for an aluminum foil current collector as claimed in any one of claims 1 to 4, characterized by, After adding the conductive substrate, deionized water and isopropyl alcohol into the stirred tank and stirring for 10-15min, adding polyvinyl alcohol, polyvinylpyrrolidone and sodium carboxymethyl cellulose, and continuing to stir for 20-30min, a carbon coating slurry is obtained.

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