Carbon-coated slurry for aluminum foil current collector and preparation method of carbon-coated slurry

Abstract

The invention discloses carbon-coated slurry for an aluminum foil current collector and a preparation method of the carbon-coated slurry, belongs to the technical field of carbon-coated slurry preparation, and is used for solving the technical problem that the adhesion performance and the conductivity of the carbon-coated slurry for the aluminum foil current collector in the prior art need to be further improved. The composite carbon fiber comprises the following raw materials in parts by weight: 40-50 parts of a conductive substrate, 20-30 parts of isopropanol, 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, copper-silver nanoparticles are modified on carboxylated multi-walled carbon nanotubes to obtain the composite carbon fiber, and the composite carbon fiber is used as the conductive substrate. The preparation method comprises the following steps: carrying out cross-linking reaction on carboxyl on the ionic polyester and amino on the prepared ionic polyester to obtain a conductive matrix precursor, introducing a silica group into the conductive matrix precursor to obtain a conductive matrix, mixing the conductive matrix with an auxiliary material, and coating an aluminum foil activated by an aluminum foil activation solution to obtain the composite current collector.

Description

Technical Field

[0001] The invention relates to the technical field of carbon coating slurry preparation, and in particular to a carbon coating slurry for an aluminum foil current collector and a preparation method thereof. Background Art

[0002] The research and development of carbon-coated slurry for aluminum foil current collector has gone through a process from improving basic adhesion and conductivity to high-performance optimization. In the early days, the coating had poor adhesion and was easy to fall off. To solve this problem, researchers used binders such as polyvinyl alcohol and adopted water-based systems such as carboxymethyl cellulose to enhance stability. In terms of conductivity, the conductive performance was improved by introducing materials such as superconducting carbon black and graphene. With the advancement of technology, aluminum foil surface treatment technology and new conductive materials have enabled the coating to maintain good performance at high current density. Today, carbon-coated slurry has reached a high standard in adhesion and conductivity, providing important support for the performance improvement of lithium batteries.

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

[0004] However, the above patent content is to disperse conductive carbon black in deionized water and add thickeners and dispersants. However, the composition of the carbon-coated slurry is single, 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. In addition, the conductive carbon black mainly has point contact and a small contact area. The electron transmission path is easily affected by uneven dispersion or agglomeration, resulting in an overly single conductive path, which further leads to the need to improve the conductive performance of the carbon-coated slurry. Summary of the Invention

[0005] The purpose of the present invention is to provide a carbon coating slurry for aluminum foil current collector and a preparation method thereof, so as to solve the technical problem in the prior art that the adhesion performance and conductive performance of the carbon coating slurry for aluminum foil current collector need to be further improved.

[0006] The purpose of the present invention can be achieved through the following technical solution: A carbon coating slurry for an aluminum foil current collector comprises the following raw materials in parts by weight: 40-50 parts of a conductive substrate, 20-30 parts of isopropyl alcohol, 10-15 parts of deionized water, 5-6 parts of polyvinyl alcohol, 1-2 parts of polyvinyl pyrrolidone and 1-2 parts of sodium carboxymethyl cellulose.

[0007] Furthermore, the preparation method of the conductive substrate includes the following steps:

[0008] A1. Add N,N-dimethylformamide to a reactor and stir. After the temperature of the reactor drops to 0-5°C, add composite carbon fibers to the reactor, keep warm and stir for 5-10 minutes, then dropwise add N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide to the reactor, keep warm and stir for 30-40 minutes, raise the temperature of the reactor to room temperature, add ionic polyester to the reactor, keep warm and stir for 4-6 hours, and then post-treat to obtain a conductive matrix precursor.

[0009] A2. Add the conductive matrix precursor, 3-(methacryloyloxy)propyltrimethoxysilane and N,N-dimethylformamide to the reactor, increase the temperature of the reactor to 80-100°C, keep warm and stir for 10-15 minutes, add azobisisobutyronitrile to the reactor, keep warm and stir for 60-80 minutes, and post-treat to obtain the conductive matrix.

[0010] The reaction kettle equation for preparing the conductive substrate is:

[0011]

[0012] Where: Indicates composite carbon fiber.

[0013] The reaction principle for preparing the conductive matrix is as follows: by adding N,N'-dicyclohexylcarbodiimide to react with the carboxyl group to form an intermediate product, activated ester, the carboxyl group on the composite carbon fiber is activated, and N-hydroxysuccinimide enhances the stability of this intermediate product. N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide are added to the reactor under low temperature conditions. In this process, the activated carboxyl group is ready to react with the amino group on the subsequently added ionic polyester to form an amide bond to prepare a conductive matrix precursor, and through a free radical addition reaction, the siloxy group is introduced into the conductive matrix precursor to finally prepare a conductive matrix.

[0014] Furthermore, in step A1, the amount ratio of N,N-dimethylformamide, composite carbon fiber, N,N'-dicyclohexylcarbodiimide, N-hydroxysuccinimide and ionic polyester is 30-40 mL: 2-3 g: 0.3-0.5 g: 0.1-0.3 g: 8-10 g, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is transferred to a rotary evaporator, the temperature of the rotary evaporator is increased to 60-80 ° C, and the conductive matrix precursor is obtained after vacuum distillation until no liquid is extracted;

[0015] Furthermore, in step A2, the amount 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, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is transferred to a rotary evaporator, the temperature of the rotary evaporator is increased to 60-80°C, and the conductive matrix is obtained by distillation under reduced pressure until no liquid is extracted.

[0016] Furthermore, the preparation method of the ionic polyester comprises the following steps:

[0017] B1. Add maleic anhydride, epibromopropane, benzoic acid and N,N-dimethylformamide into a round-bottom three-necked flask, heat the round-bottom three-necked flask to 60-80° C., keep stirring for 80-100 minutes, and post-treat to obtain a modified polyester;

[0018] B2. Add the modified polyester, 4-aminopyridine and N,N-dimethylformamide into a round-bottom three-necked flask, heat the reaction system to reflux under a nitrogen atmosphere, keep reflux for 10-12 hours, and post-treat to obtain an ionic polyester.

[0019] The reaction equation for preparing ionic polyester is:

[0020]

[0021] The reaction principle for preparing ionic polyesters is as follows: under the catalysis of benzoic acid, epibromohydrin ring-opens to form active free radicals that react with maleic anhydride to form a long-chain structure to obtain a modified polyester. Under heating conditions, the bromine groups on the modified polyester are removed and combined with 4-aminopyridine to form a quaternary ammonium salt, ultimately preparing an ionic polyester.

[0022] Furthermore, in step B1, the amount ratio of maleic anhydride, epibromopropane, benzoic acid and N,N-dimethylformamide is 0.9-1.0 g: 1.2-1.3 g: 0.1-0.2 g: 8-10 mL, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction solution is transferred to a rotary evaporator, the temperature of the rotary evaporator is increased to 60-80 ° C, and the modified polyester is obtained by vacuum distillation until no liquid is produced;

[0023] Furthermore, in step B2, the modified polyester, 4-aminopyridine and N,N-dimethylformamide are used in a ratio of 4-5 g: 1-1.2 g: 20-24 mL, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is transferred to a rotary evaporator, the temperature of the rotary evaporator is increased to 60-80 ° C, and the ionic polyester is obtained by distillation under reduced pressure until no liquid is extracted.

[0024] Furthermore, the preparation method of the composite carbon fiber comprises the following steps:

[0025] C1. Dispersing the carboxylated multi-walled carbon nanotubes in an ultrasonic device filled with deionized water, ultrasonically dispersing for 10-15 minutes, adding the modifying liquid to the ultrasonic device, continuing ultrasonication for 10-15 minutes, adjusting the pH of the reaction system to 9-10 with a saturated sodium hydroxide aqueous solution, and continuously adding hydrazine hydrate dropwise to the ultrasonic device to obtain a reaction precursor solution after the addition is complete;

[0026] C2. Transfer the reaction precursor liquid to a reactor, increase the temperature of the reactor to 80-90°C, keep stirring for 1-2 hours, and post-treat to obtain a composite carbon fiber precursor;

[0027] C3. Low-temperature vacuum drying is performed on the composite carbon fiber precursor to obtain the composite carbon fiber.

[0028] 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, which is then reduced with hydrazine hydrate to form copper and silver nanoparticles embedded on the hydroxylated multi-walled carbon nanotubes. After partial reduction with hydrazine hydrate, the electrical properties of the carboxylated multi-walled carbon nanotubes are improved, and composite carbon fibers are obtained after low-temperature drying.

[0029] Furthermore, in step C1, the amount ratio of carboxylated multi-walled carbon nanotubes, deionized water and modifying liquid is 5-6 g:100 mL:100 mL, wherein the modifying liquid is obtained by mixing copper nitrate, silver nitrate and deionized water in an amount ratio of 1.6-1.8 g:1.0-1.2 g:100 mL;

[0030] Furthermore, in step C2, post-processing includes: after the reaction is completed, filtering the reaction liquid to collect the filter cake, washing the filter cake with anhydrous ethanol and deionized water until the filter cake is neutral, and obtaining a composite carbon fiber precursor.

[0031] Furthermore, in step C3, the preparation method of the composite carbon fiber is: transferring the composite carbon fiber precursor to a vacuum freeze dryer, lowering the temperature of the vacuum freeze dryer to -40°C, and keeping warm and drying for 16-20 hours to obtain the composite carbon fiber.

[0032] The present invention also provides a method for preparing a carbon coating slurry for an aluminum foil current collector: a conductive substrate, deionized water and isopropyl alcohol are added to a stirring kettle and stirred for 10-15 minutes, polyvinyl alcohol, polyvinyl pyrrolidone and sodium carboxymethyl cellulose are added, and stirring is continued for 20-30 minutes to obtain a carbon coating slurry.

[0033] Furthermore, the method for using the carbon-coated slurry prepared by the present invention is as follows: immersing the aluminum foil in an aluminum foil activation solution, ultrasonicating for 20-30 minutes at a temperature of 40-50°C to obtain an activated aluminum foil, uniformly coating the carbon-coated slurry on the surface of the activated aluminum foil, and transferring it to a vacuum drying oven at a temperature of 40-60°C for vacuum drying until the material has a constant weight to obtain a composite current collector, wherein the coating thickness is 2-4 μm on a single side.

[0034] The reaction principle for preparing the composite current collector is as follows: the 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, dissolves the surface oxide film and corrodes the aluminum matrix to generate active sites. Sodium sulfonate is electrostatically adsorbed on the surface of the aluminum foil to form a stable negative charge layer. The residual alkaline liquid on its surface promotes the hydrolysis of the siloxy groups in the conductive matrix in the carbon-coated slurry to form a silanol structure, which forms a cross-linked structure with the active sites on the surface of the aluminum foil. The internal quaternary ammonium salt structure and the negative charge layer are electrostatically adsorbed to promote the adhesion effect of the carbon-coated slurry.

[0035] Furthermore, the preparation method of the aluminum foil activation solution is: adding sodium hydroxide powder, sodium sulfonate and deionized water into a stirring tank and mixing them evenly to obtain the aluminum foil activation solution, wherein the usage ratio of sodium hydroxide powder, sodium sulfonate and deionized water is 8-10g:2-3g:100-120g.

[0036] The present invention has the following beneficial effects:

[0037] 1. The present invention first chemically modifies polyester by introducing quaternary ammonium salt and amino groups to form a positively charged ionic polyester. The amino groups form stable chemical bonds with the carboxyl groups on the surface of the carboxylated carbon nanotubes through a cross-linking reaction, thereby uniformly dispersing the carbon fibers and constructing a conductive network. The copper-silver nanoparticles modified on the surface of the carbon nanotubes catalyze the bonding reaction between the siloxy groups and the aluminum foil during curing, thereby 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 area, which generates electrostatic pre-adsorption with the positively charged groups of the ionic polyester, laying the foundation for subsequent chemical bonding. Subsequently, the siloxy 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 siloxy chains buffer mechanical stress and, combined with the three-dimensional interlocking structure of the carbon fiber network, 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 siloxy bonds, and the activation of the aluminum foil provides a bonding interface. Ultimately, through the multiple synergistic effects 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.

[0038] 2. The principle of improving the conductive performance after the carbon-coated slurry of the present invention is combined with aluminum foil is achieved through a multi-step synergistic approach: first, the polyester is chemically modified so that its surface carries positively charged groups and active amino groups, which are pre-bonded with the negatively charged layer activated on the surface of the aluminum foil through electrostatic action to reduce the interface resistance; then, after the carbon fiber is modified with copper and silver particles, its surface acidic groups react with the amino groups of the polyester to form a stable chemical connection and construct a uniform conductive network; the aluminum foil is corroded by an alkaline solution and treated with a charge regulator to form a rough surface and provide chemically active sites to promote the subsequent bonding reaction between the siloxy groups and the aluminum foil; finally, the introduced siloxy groups strengthen the interface bonding through chemical bonds, and their flexible structure relieves the deformation stress of the material and maintains the stability of the conductive path. Ultimately, the electrical performance is improved by enhancing the interface charge matching through the charge characteristics of the polyester, the carbon fiber network provides a continuous path for electron transmission, the aluminum foil activation enhances the interface bonding, and the siloxy groups ensure long-term stability. The conductive performance of the coated aluminum foil material is improved through the synergistic effect of charge matching, chemical bonding and structural flexibility.

[0039] 3. The present invention first chemically treats the surface of the aluminum foil, uses alkaline solution corrosion to generate a porous oxide layer, and combines with a charge regulator to form a stable negative charge surface to enhance the bonding ability with subsequent coatings. Subsequently, the polyester material is chemically modified to introduce positively charged groups and active amino groups, which are pre-bonded with the aluminum foil through electrostatic action. At the same time, its amino groups react with the acidic groups on the surface of the carbon fiber to form a stable chemical connection, so that the carbon fiber is evenly dispersed in the polyester to construct a dense physical barrier. The copper and silver particles modified on the surface of the carbon fiber catalyze the bonding reaction between the siloxy groups and the aluminum foil during the curing process to generate strong chemical bonds, further sealing the pores on the surface of the aluminum foil. The flexible properties of the siloxy groups can relieve the deformation stress of the material and prevent the coating from cracking due to mechanical or thermal stress. Finally, the active functional groups of the polyester promote the uniform dispersion of the carbon fiber, and the carbon fiber network and the siloxy bonds cooperate to block the penetration of the corrosive medium. The metal particles accelerate the bonding and improve the stability of the coating. Through the multi-level synergy of charge adsorption, chemical bonding, physical barrier and stress buffering, the intrusion of the corrosive medium is effectively suppressed, thereby improving the corrosion resistance of the coating. DETAILED DESCRIPTION

[0040] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] The carboxylated multi-walled carbon nanotubes used in the present invention were purchased from Shanghai Yuanye Biotechnology Co., Ltd. with the product number V34978-25g.

[0042] Example 1

[0043] This embodiment provides a method for preparing composite carbon fibers for preparing a carbon coating slurry for an aluminum foil current collector, comprising the following steps:

[0044] Step ①, prepare reaction precursor solution

[0045] Weigh: 16.0 g copper nitrate, 10.0 g silver nitrate and 1000.0 mL deionized water to obtain a modified solution;

[0046] Weigh: 50.0 g of carboxylated multi-walled carbon nanotubes were dispersed in an ultrasonic device containing 1000.0 mL of deionized water. After ultrasonic dispersion for 10 minutes, 1000.0 mL of the modification liquid was added to the ultrasonic device. After continuing ultrasonication for 10 minutes, the pH of the reaction system was adjusted to 9 using a saturated sodium hydroxide aqueous solution. Hydrazine hydrate was continued to be added dropwise to the ultrasonic device to obtain a reaction precursor solution after the addition was complete.

[0047] Step 2: Preparation of composite carbon fiber precursor

[0048] Weigh: 1000.0mL of reaction precursor liquid was transferred to the reactor, the temperature of the reactor was raised to 80°C, and the mixture was stirred for 1 hour. After the reaction was completed, the reaction liquid was filtered to collect the filter cake, and the filter cake was washed with anhydrous ethanol and deionized water until the filter cake was neutral to obtain a composite carbon fiber precursor.

[0049] Step 3: Preparation of composite carbon fiber

[0050] Weigh 50.0 g of the composite carbon fiber precursor and transfer it to a vacuum freeze dryer. Lower the temperature of the vacuum freeze dryer to -40°C and keep it dry for 16 hours to obtain a composite carbon fiber.

[0051] Example 2

[0052] This embodiment provides a method for preparing composite carbon fibers for preparing a carbon coating slurry for an aluminum foil current collector, comprising the following steps:

[0053] Step ①, prepare reaction precursor solution

[0054] Weigh: 18.0 g copper nitrate, 12.0 g silver nitrate and 1000.0 mL deionized water to obtain a modified solution;

[0055] 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 minutes, 1000.0 mL of the modified liquid was added to the ultrasonic device. After continuing ultrasonication for 15 minutes, the pH of the reaction system was adjusted to 10 using a saturated aqueous sodium hydroxide solution. Hydrazine hydrate was continued to be added dropwise to the ultrasonic device to obtain a reaction precursor solution after the addition was completed.

[0056] Step 2: Preparation of composite carbon fiber precursor

[0057] Weigh: 1000.0mL of reaction precursor liquid was transferred to the reactor, the temperature of the reactor was raised to 90°C, and the mixture was stirred for 2 hours. After the reaction was completed, the reaction liquid was filtered to collect the filter cake, and the filter cake was washed with anhydrous ethanol and deionized water until the filter cake was neutral to obtain a composite carbon fiber precursor.

[0058] Step 3: Preparation of composite carbon fiber

[0059] Weigh 50.0 g of the composite carbon fiber precursor and transfer it to a vacuum freeze dryer. Lower the temperature of the vacuum freeze dryer to -40°C and keep it dry for 20 hours to obtain a composite carbon fiber.

[0060] Example 3

[0061] This embodiment provides a method for preparing composite carbon fibers for preparing a carbon coating slurry for an aluminum foil current collector, comprising the following steps:

[0062] Step ①, prepare reaction precursor solution

[0063] Weigh: 17.0 g copper nitrate, 11.0 g silver nitrate and 1000.0 mL deionized water to obtain a modified solution;

[0064] Weigh: 54.0 g of carboxylated multi-walled carbon nanotubes were dispersed in an ultrasonic device containing 1000.0 mL of deionized water. After ultrasonic dispersion for 15 minutes, 1000.0 mL of the modification liquid was added to the ultrasonic device. After continuing ultrasonication for 15 minutes, the pH of the reaction system was adjusted to 10 using a saturated sodium hydroxide aqueous solution. Hydrazine hydrate was continued to be added dropwise to the ultrasonic device to obtain a reaction precursor solution after the addition was complete.

[0065] Step 2: Preparation of composite carbon fiber precursor

[0066] Weigh: 1000.0mL of reaction precursor liquid was transferred to the reactor, the temperature of the reactor was raised to 84°C, and the mixture was stirred for 2 hours. After the reaction was completed, the reaction liquid was filtered to collect the filter cake, and the filter cake was washed with anhydrous ethanol and deionized water until the filter cake was neutral to obtain a composite carbon fiber precursor.

[0067] Step 3: Preparation of composite carbon fiber

[0068] Weigh 50.0 g of the composite carbon fiber precursor and transfer it to a vacuum freeze dryer. Lower the temperature of the vacuum freeze dryer to -40°C and keep it dry for 18 hours to obtain a composite carbon fiber.

[0069] Example 4

[0070] This embodiment provides a method for preparing an ionic polyester for preparing a carbon coating slurry for an aluminum foil current collector, comprising the following steps:

[0071] Step I: Preparation of modified polyester

[0072] Weigh: 9.0 g of maleic anhydride, 12.0 g of epibromopropane, 1.0 g of benzoic acid and 80.0 mL of N,N-dimethylformamide and add them into a round-bottom three-necked flask, heat the round-bottom three-necked flask to 60°C, keep stirring for 80 minutes, after the reaction is completed, wait for the temperature of the reactor to be lowered to room temperature, transfer the reaction liquid to a rotary evaporator, raise the temperature of the rotary evaporator to 60°C, and distill under reduced pressure until no liquid is produced to obtain a modified polyester.

[0073] Step II: Preparation of ionic polyester

[0074] Weigh: 40.0 g of modified polyester, 10.0 g of 4-aminopyridine and 200.0 mL of N,N-dimethylformamide were added to a round-bottom three-necked flask. Under a nitrogen atmosphere, the reaction system was heated to reflux and kept at reflux for 10 hours. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the reaction liquid was transferred to a rotary evaporator. The temperature of the rotary evaporator was raised to 60°C, and the ionic polyester was obtained after vacuum distillation until no liquid was extracted.

[0075] Example 5

[0076] This embodiment provides a method for preparing an ionic polyester for preparing a carbon coating slurry for an aluminum foil current collector, comprising the following steps:

[0077] Step I: Preparation of modified polyester

[0078] Weigh: 10.0 g of maleic anhydride, 13.0 g of epibromopropane, 2.0 g of benzoic acid and 100.0 mL of N,N-dimethylformamide are added to a round-bottom three-necked flask, the round-bottom three-necked flask is heated to 80° C., and stirred for 100 minutes. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and the reaction liquid is transferred to a rotary evaporator. The temperature of the rotary evaporator is raised to 80° C. and distilled under reduced pressure until no liquid is produced to obtain a modified polyester.

[0079] Step II: Preparation of ionic polyester

[0080] Weigh: 50.0g modified polyester, 12.0g 4-aminopyridine and 240.0mL N,N-dimethylformamide are added to a round-bottom three-necked flask. Under a nitrogen atmosphere, the reaction system is heated to reflux and kept at reflux for 12 hours. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and the reaction liquid is transferred to a rotary evaporator. The temperature of the rotary evaporator is raised to 80°C, and the ionic polyester is obtained by vacuum distillation until no liquid is produced.

[0081] Example 6

[0082] This embodiment provides a method for preparing an ionic polyester for preparing a carbon coating slurry for an aluminum foil current collector, comprising the following steps:

[0083] Step I: Preparation of modified polyester

[0084] Weigh: 9.6 g of maleic anhydride, 12.4 g of epibromopropane, 1.6 g of benzoic acid and 100.0 mL of N,N-dimethylformamide were added to a round-bottom three-necked flask, heated to 70°C, and stirred for 90 minutes. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the reaction liquid was transferred to a rotary evaporator. The temperature of the rotary evaporator was raised to 70°C, and vacuum distillation was carried out until no liquid was recovered to obtain a modified polyester.

[0085] Step II: Preparation of ionic polyester

[0086] Weigh: 48.0 g of modified polyester, 10.0 g of 4-aminopyridine and 210.0 mL of N,N-dimethylformamide were added to a round-bottom three-necked flask. Under a nitrogen atmosphere, the reaction system was heated to reflux and kept at reflux for 12 hours. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the reaction liquid was transferred to a rotary evaporator. The temperature of the rotary evaporator was raised to 80°C, and the ionic polyester was obtained after distillation under reduced pressure until no liquid was extracted.

[0087] Example 7

[0088] This embodiment provides a method for preparing a conductive substrate for preparing a carbon-coated slurry for an aluminum foil current collector, comprising the following steps:

[0089] Step (i) Preparation of a conductive matrix precursor

[0090] Weigh: 300.0mL N,N-dimethylformamide was added to the reactor and stirred. After the temperature of the reactor dropped to 0°C, 20.0g of the composite carbon fiber prepared in Example 1 was added to the reactor. After stirring for 5 minutes, 3.0g of N,N'-dicyclohexylcarbodiimide and 1.0g of N-hydroxysuccinimide were added dropwise to the reactor. After stirring for 30 minutes, the temperature of the reactor was raised to room temperature, and 80.0g of the ionic polyester prepared in Example 4 was added to the reactor. After stirring for 4 hours, after the reaction was completed, the temperature of the reactor was lowered to room temperature, the reaction solution was transferred to a rotary evaporator, the temperature of the rotary evaporator was raised to 60°C, and distilled under reduced pressure until no liquid was extracted to obtain a conductive matrix precursor.

[0091] Step (ii): preparing a conductive substrate

[0092] Weigh: 80.0g of conductive matrix precursor, 10.0g of 3-(methacryloyloxy)propyltrimethoxysilane and 400.0mL of N,N-dimethylformamide were added to the reactor, the temperature of the reactor was raised to 80°C, and the mixture was stirred for 10 minutes. Then, 3.0g of azobisisobutyronitrile was added to the reactor and stirred for 60 minutes. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the reaction liquid was transferred to a rotary evaporator. The temperature of the rotary evaporator was raised to 60°C, and the conductive matrix was obtained after distillation under reduced pressure until no liquid was extracted.

[0093] Example 8

[0094] This embodiment provides a method for preparing a conductive substrate for preparing a carbon-coated slurry for an aluminum foil current collector, comprising the following steps:

[0095] Step (i) Preparation of a conductive matrix precursor

[0096] Weigh: 400.0mL N,N-dimethylformamide was added to the reactor and stirred. After the temperature of the reactor dropped to 5°C, 30.0g of the composite carbon fiber prepared in Example 2 was added to the reactor. After stirring for 10 minutes, 5.0g of N,N'-dicyclohexylcarbodiimide and 3.0g of N-hydroxysuccinimide were added dropwise to the reactor. After stirring for 40 minutes, the temperature of the reactor was raised to room temperature, and 100.0g of the ionic polyester prepared in Example 5 was added to the reactor. After stirring for 6 hours, after the reaction was completed, the temperature of the reactor was lowered to room temperature, the reaction solution was transferred to a rotary evaporator, the temperature of the rotary evaporator was raised to 80°C, and the conductive matrix precursor was obtained by distillation under reduced pressure until no liquid was extracted.

[0097] Step (ii): preparing a conductive substrate

[0098] Weigh: 100.0g of conductive matrix precursor, 20.0g of 3-(methacryloyloxy)propyltrimethoxysilane and 600.0mL of N,N-dimethylformamide were added to the reactor, the temperature of the reactor was raised to 100°C, and the mixture was stirred for 15 minutes. Then, 5.0g of azobisisobutyronitrile was added to the reactor and stirred for 80 minutes. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the reaction liquid was transferred to a rotary evaporator. The temperature of the rotary evaporator was raised to 80°C, and the conductive matrix was obtained after distillation under reduced pressure until no liquid was extracted.

[0099] Example 9

[0100] This embodiment provides a method for preparing a conductive substrate for preparing a carbon-coated slurry for an aluminum foil current collector, comprising the following steps:

[0101] Step (i) Preparation of a conductive matrix precursor

[0102] Weigh: 360.0mL N,N-dimethylformamide was added to the reactor and stirred. After the temperature of the reactor dropped to 3°C, 24.0g of the composite carbon fiber prepared in Example 3 was added to the reactor. After stirring for 10 minutes, 4.0g of N,N'-dicyclohexylcarbodiimide and 2.0g of N-hydroxysuccinimide were added dropwise to the reactor. After stirring for 36 minutes, the temperature of the reactor was raised to room temperature, and 90.0g of the ionic polyester prepared in Example 6 was added to the reactor. After stirring for 6 hours, after the reaction was completed, the temperature of the reactor was lowered to room temperature, the reaction solution was transferred to a rotary evaporator, the temperature of the rotary evaporator was raised to 72°C, and the conductive matrix precursor was obtained by distillation under reduced pressure until no liquid was extracted.

[0103] Step (ii): preparing a conductive substrate

[0104] Weigh: 90.0g of conductive matrix precursor, 16.0g of 3-(methacryloyloxy)propyltrimethoxysilane and 500.0mL of N,N-dimethylformamide were added to the reactor, the temperature of the reactor was raised to 90°C, and the mixture was stirred for 12 minutes. Then, 4.0g of azobisisobutyronitrile was added to the reactor and stirred for 70 minutes. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the reaction liquid was transferred to a rotary evaporator. The temperature of the rotary evaporator was raised to 70°C, and the mixture was distilled under reduced pressure until no liquid was extracted to obtain a conductive matrix.

[0105] Example 10

[0106] This embodiment provides a method for preparing a composite current collector, comprising the following steps:

[0107] Step 1: Prepare aluminum foil activation solution

[0108] Weigh 80.0 g of sodium hydroxide powder, 20.0 g of sodium sulfonate and 1000.0 g of deionized water into a stirring tank, and mix well to obtain an aluminum foil activation solution.

[0109] Step 2: Prepare carbon coating slurry

[0110] Weigh: 40.0 g of the conductive substrate prepared in Example 7, 10.0 g of deionized water and 20.0 g of isopropyl alcohol are added to a stirring tank and stirred for 10.0 min. Then, 5.0 g of polyvinyl alcohol, 1.0 g of polyvinyl pyrrolidone and 1.0 g of sodium carboxymethyl cellulose are added and stirred for 20 min to obtain a carbon coating slurry.

[0111] Step 3: Preparation of composite current collector

[0112] The aluminum foil was immersed in the aluminum foil activation solution and ultrasonicated at 40°C for 20 minutes to obtain the activated aluminum foil. The carbon-coated slurry was evenly coated on the surface of the activated aluminum foil with a coating thickness of 2 μm on one side. The foil was then transferred to a vacuum drying oven at 40°C and vacuum dried until the material had a constant weight to obtain a composite current collector.

[0113] Example 11

[0114] This embodiment provides a method for preparing a composite current collector, comprising the following steps:

[0115] Step 1: Prepare aluminum foil activation solution

[0116] Weigh 100.0 g of sodium hydroxide powder, 30.0 g of sodium sulfonate and 1200.0 g of deionized water into a stirring tank, and mix them evenly to obtain an aluminum foil activation solution.

[0117] Step 2: Prepare carbon coating slurry

[0118] Weigh: 50.0 g of the conductive substrate prepared in Example 8, 15.0 g of deionized water and 30.0 g of isopropyl alcohol are added to a stirring tank and stirred for 15 minutes, then 6.0 g of polyvinyl alcohol, 2.0 g of polyvinyl pyrrolidone and 2.0 g of sodium carboxymethyl cellulose are added and stirred for 30 minutes to obtain a carbon coating slurry.

[0119] Step 3: Preparation of composite current collector

[0120] The aluminum foil was immersed in the aluminum foil activation solution and ultrasonicated at a temperature of 50°C for 30 minutes to obtain the activated aluminum foil. The carbon-coated slurry was evenly coated on the surface of the activated aluminum foil with a coating thickness of 4 μm on one side, and then transferred to a vacuum drying oven at a temperature of 50°C and vacuum dried until the material had a constant weight to obtain a composite current collector.

[0121] Example 12

[0122] This embodiment provides a method for preparing a composite current collector, comprising the following steps:

[0123] Step 1: Prepare aluminum foil activation solution

[0124] Weigh 90.0 g of sodium hydroxide powder, 25.0 g of sodium sulfonate and 1080.0 g of deionized water into a stirring tank, mix well to obtain an aluminum foil activation solution.

[0125] Step 2: Prepare carbon coating slurry

[0126] Weigh: 48.0 g of the conductive substrate prepared in Example 9, 12.0 g of deionized water and 24.0 g of isopropyl alcohol are added to a stirring tank and stirred for 12 minutes, then 5.4 g of polyvinyl alcohol, 1.6 g of polyvinyl pyrrolidone and 1.6 g of sodium carboxymethyl cellulose are added, and stirring is continued for 24 minutes to obtain a carbon coating slurry.

[0127] Step 3: Preparation of composite current collector

[0128] The aluminum foil was immersed in the aluminum foil activation solution and ultrasonicated at 48°C for 24 minutes to obtain the activated aluminum foil. The carbon-coated slurry was evenly coated on the surface of the activated aluminum foil with a coating thickness of 3 μm on one side. The foil was then transferred to a vacuum drying oven at 50°C and vacuum dried until the material had a constant weight to obtain a composite current collector.

[0129] Comparative Example 1

[0130] The difference between this comparative example and Example 12 is that step II is omitted during the preparation of the ionic polyester used in the conductive substrate.

[0131] Comparative Example 2

[0132] The difference between this comparative example and Example 12 is that step (ii) is omitted during the preparation of the conductive substrate used, and the use of aluminum foil activation solution is omitted during the preparation of the composite current collector.

[0133] Comparative Example 3

[0134] The difference between this comparative example and Example 12 is that in the preparation process step (i) of the conductive substrate used, the composite carbon fibers are eliminated and an equal amount of carboxylated multi-walled carbon nanotubes are used to replace the composite carbon fibers.

[0135] Performance testing:

[0136] The adhesion level between the composite current collector layers prepared in Examples 10-12 and Comparative Examples 1-3 was tested with reference to the standard GB / T 31586.2-2015 "Evaluation and acceptance criteria for adhesion / cohesion (fracture strength) of protective coating systems for anti-corrosion protective coatings on steel structures - Part 2: Cross-hatch test and cross-hatch test";

[0137] 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 wear was tested in accordance with standard YY / T 0988.15-2016 "Surgical Implant Coatings Part 15: Test Method for Wear Resistance of Metal Thermal Spray Coatings."

[0138] The corrosion resistance of the composite current collectors prepared in Examples 10-12 and Comparative Examples 1-3 was tested with reference to the standard JB / T 6073-1992 "Laboratory Full Immersion Corrosion Test of Metal Coverings".

[0139] The volume resistivity of the composite current collectors prepared in Examples 10-12 and Comparative Examples 1-3 was determined with reference to the standard GB / T 3048.2-2007 "Test methods for electrical properties of wires and cables - Part 2: Test for resistivity of metallic materials". Specific data are shown in Table 1.

[0140] Table 1 - Performance test data of each sample

[0141]

[0142]

[0143] Data Analysis:

[0144] A comparative analysis of the data in Table 1 shows that the carbon-coated slurry prepared by the present invention is coated on the surface of the aluminum foil activated by the aluminum foil activation solution. After curing, the adhesion level between the carbon-coated slurry and the aluminum foil is 0, the mass loss of the cured material after 100 cycles of wear is 2.3 mg, the corrosion rate is 0.17%, and the volume resistivity of the composite current collector composed of the carbon-coated slurry on the aluminum foil surface and the aluminum foil is 2.4×10 -8 Ω·m, all data are better than those of the comparative example;

[0145] Description: The present invention first chemically treats the surface of the aluminum foil, uses alkaline solution corrosion to generate a porous oxide layer, and combines with a charge regulator to form a stable negative charge surface to enhance the bonding ability with subsequent coatings. Subsequently, the polyester material is chemically modified to introduce positively charged groups and active amino groups, which are pre-bonded with the aluminum foil through electrostatic action. At the same time, its amino groups react with the acidic groups on the surface of the carbon fiber to form a stable chemical connection, so that the carbon fiber is evenly dispersed in the polyester, and a dense physical barrier is constructed. The copper and silver particles modified on the surface of the carbon fiber catalyze the bonding reaction between the siloxy groups and the aluminum foil during the curing process to generate strong chemical bonds, further sealing the pores on the surface of the aluminum foil. The flexible properties of the siloxy groups can relieve the deformation stress of the material and avoid cracking of the coating due to mechanical or thermal stress. Finally, the active functional groups of the polyester promote the uniform dispersion of the carbon fiber, and the carbon fiber network and the siloxy bonds cooperate to block the penetration of the corrosive medium. The metal particles accelerate the bonding and improve the stability of the coating. Through the multi-level synergy of charge adsorption, chemical bonding, physical barrier and stress buffering, the intrusion of the corrosive medium is effectively suppressed, thereby improving the corrosion resistance of the coating.

[0146] It is explained that the principle of improving the conductive performance after the carbon-coated slurry of the present invention is combined with aluminum foil is achieved through a multi-step synergistic approach: first, the polyester is chemically modified so that its surface carries positively charged groups and active amino groups, which are pre-bonded with the negatively charged layer activated on the surface of the aluminum foil through electrostatic action to reduce the interface resistance; then, after the carbon fiber is modified with copper and silver particles, its surface acidic groups react with the amino groups of the polyester to form a stable chemical connection and construct a uniform conductive network; the aluminum foil is corroded by an alkaline solution and treated with a charge regulator to form a rough surface and provide chemically active sites to promote the subsequent bonding reaction between the siloxy groups and the aluminum foil; finally, the introduced siloxy groups strengthen the interface bonding through chemical bonds, and their flexible structure relieves the deformation stress of the material and maintains the stability of the conductive path. Finally, the electrical performance is improved by enhancing the interface charge matching through the charge characteristics of the polyester, the carbon fiber network provides a continuous path for electron transmission, the aluminum foil activation enhances the interface bonding, and the siloxy groups ensure long-term stability. Through the synergistic effect of charge matching, chemical bonding and structural flexibility, the conductive performance of the coated aluminum foil material is improved;

[0147] The invention first chemically modifies polyester by introducing quaternary ammonium salt and amino group to form positively charged ionic polyester, wherein the amino group forms a stable chemical bond with the carboxyl group on the surface of carboxylated carbon nanotubes through a cross-linking reaction, so that the carbon fibers are evenly dispersed and a conductive network is constructed; the copper-silver nanoparticles modified on the surface of the carbon nanotubes catalyze the bonding reaction between the siloxy groups and the aluminum foil during curing, thereby enhancing the interface 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 area, which generates electrostatic pre-adsorption with the positively charged groups of the ionic polyester, laying the foundation for subsequent chemical bonding; subsequently, the siloxy groups introduced by free radical polymerization condense with the hydroxyl groups on the surface of the aluminum foil to form covalent bonds, while the flexible siloxy chains buffer mechanical stress and combine with the three-dimensional interlocking structure of the carbon fiber network to jointly resist friction peeling, and finally 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 siloxy bonds, and the activation of the aluminum foil provides a bonding interface, and finally, through the multiple synergy 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.

[0148] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A carbon coating slurry for aluminum foil current collector, characterized in that: The invention comprises the following raw materials in parts by weight: 40-50 parts of a conductive matrix, 20-30 parts of isopropyl alcohol, 10-15 parts of deionized water, 5-6 parts of polyvinyl alcohol, 1-2 parts of polyvinyl pyrrolidone and 1-2 parts of sodium carboxymethyl cellulose.

2. The carbon coating slurry for aluminum foil current collector according to claim 1, characterized in that: The preparation method of the conductive substrate comprises the following steps: A1. Add N,N-dimethylformamide to a reactor and stir. After the temperature of the reactor drops to 0-5°C, add composite carbon fibers to the reactor, keep warm and stir for 5-10 minutes, then dropwise add N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide to the reactor, keep warm and stir for 30-40 minutes, raise the temperature of the reactor to room temperature, add ionic polyester to the reactor, keep warm and stir for 4-6 hours, and then post-treat to obtain a conductive matrix precursor. A2. Add the conductive matrix precursor, 3-(methacryloyloxy)propyltrimethoxysilane and N,N-dimethylformamide to the reactor, increase the temperature of the reactor to 80-100°C, keep warm and stir for 10-15 minutes, add azobisisobutyronitrile to the reactor, keep warm and stir for 60-80 minutes, and post-treat to obtain the conductive matrix.

3. The carbon coating slurry for aluminum foil current collector according to claim 2, characterized in that: In step A1, the amount 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; in step A2, the amount ratio of conductive matrix precursor, 3-(methacryloyloxy)propyltrimethoxysilane, N,N-dimethylformamide and azobisisobutyronitrile is 8-10g:1-2g:40-60mL:0.3-0.5g.

4. The carbon coating slurry for aluminum foil current collector according to claim 1, characterized in that: The preparation method of the ionic polyester comprises the following steps: B1. Add maleic anhydride, epibromopropane, benzoic acid and N,N-dimethylformamide into a round-bottom three-necked flask, heat the round-bottom three-necked flask to 60-80° C., keep stirring for 80-100 minutes, and post-treat to obtain a modified polyester; B2. Add the modified polyester, 4-aminopyridine and N,N-dimethylformamide into a round-bottom three-necked flask, heat the reaction system to reflux under a nitrogen atmosphere, keep reflux for 10-12 hours, and post-treat to obtain an ionic polyester.

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

6. The carbon coating slurry for aluminum foil current collector according to claim 1, characterized in that: The preparation method of the composite carbon fiber comprises the following steps: C1. Dispersing the carboxylated multi-walled carbon nanotubes in an ultrasonic device filled with deionized water, ultrasonically dispersing for 10-15 minutes, adding the modifying liquid to the ultrasonic device, continuing ultrasonication for 10-15 minutes, adjusting the pH of the reaction system to 9-10 with a saturated sodium hydroxide aqueous solution, and continuously adding hydrazine hydrate dropwise to the ultrasonic device to obtain a reaction precursor solution after the addition is complete; C2. Transfer the reaction precursor liquid to a reactor, increase the temperature of the reactor to 80-90°C, keep stirring for 1-2 hours, and post-treat to obtain a composite carbon fiber precursor; C3. Low-temperature vacuum drying is performed on the composite carbon fiber precursor to obtain the composite carbon fiber.

7. The carbon coating slurry for aluminum foil current collector according to claim 6, characterized in that: In step C1, the amount ratio of carboxylated multi-walled carbon nanotubes, deionized water and modifying liquid is 5-6g:100mL:100mL, wherein the modifying liquid is obtained by mixing copper nitrate, silver nitrate and deionized water in a ratio of 1.6-1.8g:1.0-1.2g:100mL; in step C3, the preparation method of composite carbon fiber is: transferring the composite carbon fiber precursor to a vacuum freeze dryer, lowering the temperature of the vacuum freeze dryer to -40°C, and keeping warm and drying for 16-20h to obtain composite carbon fiber.

8. A method for preparing the carbon coating slurry for aluminum foil current collector according to any one of claims 1 to 7, characterized in that: The conductive substrate, deionized water and isopropyl alcohol are added to a stirring kettle and stirred for 10-15 minutes, and then polyvinyl alcohol, polyvinyl pyrrolidone and sodium carboxymethyl cellulose are added and stirred for 20-30 minutes to obtain a carbon coating slurry.

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