Copper foil coated single-walled carbon nanotube current collector and preparation method thereof

Abstract

The invention belongs to the technical field of lithium battery current collectors, and particularly relates to a copper foil coated single-walled carbon nanotube current collector and a preparation method thereof.The preparation method comprises the steps that carboxylation is conducted on a single-walled carbon nanotube, the single-walled carbon nanotube reacts with amine-terminated polyether, a flexible macromolecular chain is grafted on the surface of the single-walled carbon nanotube, and an elastic conductive unit is formed; meanwhile, the copper foil is subjected to epoxy group silane functionalization treatment, epoxy groups on the copper surface and amino groups on the single-walled carbon nanotubes are subjected to a ring-opening addition reaction through heat treatment, and a fully-chemically-bonded copper foil-buffer layer integrated structure is formed; according to the design, the strong interface bonding force is ensured through chemical bonding, and the volume expansion stress of the silicon negative electrode is actively dissipated through reversible deformation of the elastic macromolecular chain, so that the mechanical stability and the electrochemical cycle life of the electrode are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery current collector technology, specifically relating to copper foil coated single-walled carbon nanotube current collectors and their preparation methods. Background Technology

[0002] The negative electrode of a lithium-ion battery is the main body that houses lithium ions, and its performance directly determines the battery's energy density and cycle life. During battery operation, lithium ions repeatedly insert and extract between the positive and negative electrodes, while electrons are transported through the external circuitry and current collectors. The current collector, typically copper foil, functions to achieve efficient electron collection and transport, providing a mechanical carrier and support for the active material layer to maintain the structural integrity of the electrode. Therefore, the physical contact stability and electrochemical stability of the interface between the current collector and the active material layer directly determine the efficiency of charge transfer and the durability of the electrode structure, forming a key foundation affecting the overall battery performance, especially long-term cycle reliability.

[0003] Silicon-based materials have become the most promising next-generation anode material due to their extremely high theoretical specific capacity. However, silicon undergoes huge volume expansion and contraction of up to 300% or more during charging and discharging. Under repeated stress, the expansion of silicon particles will directly lead to the failure of physical contact between them and the current collector, causing the active material to peel off from the copper foil surface, resulting in a sharp decrease in capacity. The huge stress will be transmitted to the thin copper foil itself, which will not only destroy the electron conduction path, but may also cause safety hazards such as internal short circuits.

[0004] To address these challenges, the industry has undertaken numerous explorations: existing technologies mostly focus on physical mechanical interlocking or simple physical adsorption, resulting in limited interfacial bonding and susceptibility to failure under long-term drastic volume changes; ordinary carbon material coatings are inherently brittle, lack intrinsic elasticity to dissipate stress, and their bonding with copper foil substrates largely depends on physical adhesion, making the interface prone to peeling during cycling; therefore, developing a novel current collector structure that can match the expansion characteristics of high-silicon anodes, providing both strong interfacial bonding and active buffering of mechanical stress is a key technological requirement for addressing the bottlenecks in silicon-based anode applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing copper foil coated with single-walled carbon nanotube current collectors to solve the above-mentioned technical problems.

[0006] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows: A method for preparing a copper foil-coated single-walled carbon nanotube current collector includes the following steps: S1. Slurry coating: Elastic polymer grafted single-walled carbon nanotubes are dispersed in N-methylpyrrolidone, stirred evenly, and sonicated for 10-15 min to obtain a dispersion slurry; the dispersion slurry is coated on epoxy-functionalized copper foil, and the doctor blade gap is controlled to be 50-100 μm to obtain coated copper foil. S2. The coated copper foil is vacuum dried at 100~130℃ for 1.5~2.5h and cooled to room temperature to obtain a copper foil coated single-walled carbon nanotube current collector.

[0007] As a further improvement, the preparation method of the elastic polymer-grafted single-walled carbon nanotubes is as follows: carboxylated single-walled carbon nanotubes are dispersed in anhydrous DMF and sonicated for 1-2 hours to obtain a dispersion; terminal amino polyether is added to the dispersion, followed by EDC・HCl and NHS; under nitrogen protection, the mixture is stirred at a constant temperature of 50-65℃ for 20-24 hours; the precipitate is collected by centrifugation, washed twice with DMF, once with deionized water, and once with anhydrous ethanol; and then vacuum dried at 50-60℃ to constant weight to obtain elastic polymer-grafted single-walled carbon nanotubes.

[0008] As a further improvement, the mass ratio of the carboxylated single-walled carbon nanotubes, the amino-terminated polyether, and EDC·HCl is 1:30~50:0.6~1; and the number-average molecular weight of the amino-terminated polyether is 400~2000.

[0009] As a further improvement, the preparation method of the carboxylated single-walled carbon nanotubes is as follows: add single-walled carbon nanotubes to a mixed acid solution, react at 70~75℃ for 2~3h, cool to room temperature, collect the filter cake by suction filtration, wash the filter cake repeatedly with deionized water until the filtrate is neutral, and vacuum dry at 50~60℃ for 8~12h to obtain carboxylated single-walled carbon nanotubes.

[0010] As a further improvement, the mixed acid solution is prepared by mixing 68% concentrated nitric acid and 98% concentrated sulfuric acid at a volume ratio of 1:3.

[0011] As a further improvement, the preparation method of the epoxy-functionalized copper foil is as follows: the copper foil is ultrasonically cleaned in acetone and anhydrous ethanol for 15 min respectively, and dried with nitrogen to obtain clean copper foil; the clean copper foil is immersed in dilute nitric acid for 10-20 s, taken out, rinsed with deionized water, and vacuum dried at 60-80℃ for 15-30 min to obtain activated copper foil; the activated copper foil is immersed in an epoxy silane coupling agent solution using the dip-pull method, and after standing for 30 s, it is vertically pulled out of the liquid surface at a constant speed, and immediately vacuum dried at 80-100℃ for 15-30 min, and cooled to room temperature to obtain epoxy-functionalized copper foil.

[0012] As a further improvement, the preparation method of the epoxy silane coupling agent solution is as follows: dissolve the epoxy silane coupling agent in anhydrous ethanol at a concentration of 10 g / L and mix well; the constant speed is 1~2 cm / min.

[0013] As a further improvement, the epoxy silane coupling agent is one of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, or 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0014] As a further improvement, the ratio of the elastic polymer-grafted single-walled carbon nanotubes to N-methylpyrrolidone is 3~6 mg: 1 mL.

[0015] The present invention also provides a copper foil coated single-walled carbon nanotube current collector.

[0016] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: 1. Elastic polymer grafting modification of single-walled carbon nanotubes (SUVs) involves covalently grafting flexible polymer chains onto their surface, transforming SUVs from traditional rigid conductive units into functional units with both excellent conductivity and intrinsic elasticity. The grafted polyether chains can actively absorb and dissipate mechanical energy through reversible stretching, bending, and conformational changes, thus addressing the significant volume expansion of silicon anode materials. Excessive feeding of amino-terminated polyethers ensures sufficient grafting onto the surface of SUVs while effectively controlling the degree of cross-linking between molecules. The abundant amino functional groups at the ends of the grafted chains reserve key active reaction sites for subsequent covalent bonding with functionalized copper foil interfaces. 2. The copper foil substrate is functionalized with epoxy silane to construct a strong chemical bonding interface. The epoxy silane coupling agent forms a strong covalent bond with the hydroxyl group on the surface of the copper foil through its silane oxygen end group, thus firmly anchoring it to the copper foil. At the same time, the epoxy group at the other end of its molecule is exposed to the outside. Its interfacial bonding strength is much higher than that of traditional physical adsorption or hydrogen bonding. 3. During the integration process, the epoxy groups exposed on the copper foil surface react with the excess amino groups on the elastic polymer-grafted single-walled carbon nanotubes to form stable covalent bonds, thereby constructing a stable covalent bond between the single-walled carbon nanotube layer and the copper foil layer, solving the interlayer adhesion problem. In addition, an efficient stress transfer path from the active layer to the elastic buffer layer is constructed. The expansion stress of the silicon anode is quickly dissipated along this path to the dissipation system composed of polyether chains, thus fundamentally ensuring the structural integrity and capacity retention of the battery during long-term cycling. Attached Figure Description

[0017] Figure 1These are ATR-FTIR images of the elastic polymer-grafted single-walled carbon nanotubes prepared in Example 1; Figure 2 This is an XPS image of the epoxy-functionalized copper foil prepared in Example 1. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or manufacturer's conditions shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0019] Example 1: Preparation method of copper foil coated single-walled carbon nanotube current collector, the specific steps are as follows: 1. Preparation of carboxylated single-walled carbon nanotubes: In a 250mL three-necked flask, add 120mL of mixed acid (made by mixing 30mL of 68% concentrated nitric acid and 90mL of 98% concentrated sulfuric acid), weigh 1.0g of single-walled carbon nanotubes, and slowly add them to the mixed acid with stirring; heat to 70℃ in an oil bath and react for 3h; after the reaction is completed, cool naturally to room temperature, filter the reaction mixture, collect the filter cake, wash the filter cake repeatedly with deionized water until the filtrate is neutral, transfer the filter cake to a watch glass, and dry it in a vacuum drying oven at 50℃ for 12h to obtain black powdered carboxylated single-walled carbon nanotubes; 2. Preparation of elastic polymer-grafted single-walled carbon nanotubes: In a dry 250 mL round-bottom flask, 200 mg of carboxylated single-walled carbon nanotubes and 50 mL of anhydrous DMF (N,N-dimethylformamide) were added and ultrasonically dispersed for 2 h to obtain a uniform dispersion. 10.0 g of amino-terminated polyether (D-2000, number-average molecular weight 2000), 200 mg of EDC·HCl, and 120 mg of NHS (N-hydroxysuccinimide) were added sequentially to the dispersion. Nitrogen gas was introduced for protection, and the mixture was placed in a 50 °C oil bath and stirred for 22 h. After the reaction was complete, the reaction mixture was centrifuged at 10000 rpm for 15 min. The precipitate was washed twice with DMF, once with deionized water, and once with anhydrous ethanol. It was then vacuum dried at 60 °C to constant weight to obtain elastic polymer-grafted single-walled carbon nanotubes. The chemical equation is shown below: ; The ATR-FTIR image of the elastic polymer-grafted single-walled carbon nanotubes prepared in this embodiment is as follows: Figure 1As shown; of which 1720cm -1 The disappearance of the peak around 1650 cm⁻¹ indicates that the carboxyl group has been consumed. -1 and 1550cm -1 The characteristic peak of the amide bond is 1100 cm⁻¹. -1 The peaks are characteristic of COC, indicating that an amidation condensation reaction successfully occurred between the amino-terminated polyether and the carboxyl groups on the surface of the carboxylated single-walled carbon nanotubes. 3. Preparation of epoxy-functionalized copper foil: Cut copper foil (12μm thick) into 5cm×10cm pieces, place them in acetone, sonicate for 15min, place them in anhydrous ethanol, sonicate for 15min, and dry with nitrogen to obtain clean copper foil; immerse the clean copper foil in 1wt% dilute nitric acid solution for 20s, remove and rinse with deionized water until the pH of the rinsing solution is neutral, place it in a 60℃ vacuum drying oven for 30min to obtain activated copper foil; add 1.0g of 3-glycidyl etheroxypropyltrimethoxysilane to 100mL of anhydrous ethanol and mix magnetically; vertically immerse the activated copper foil in the above silane solution, let it stand for 30s, and then vertically pull it out of the liquid surface at a constant speed of 1cm / min. Immediately place the pulled wet film copper foil into a vacuum drying oven preheated to 100℃ and vacuum dry for 20min. Cool to room temperature to obtain epoxy-functionalized copper foil; the chemical equation is shown below: ; Wherein, -R represents epoxy group; in this reaction process, the hydrolysis reaction of silane coupling agent is mainly triggered by trace water molecules physically adsorbed on the surface of activated copper foil and water vapor in the environment; its alkoxy group preferentially hydrolyzes at the solid-liquid interface to generate silanol group, and then condenses with hydroxyl group on the surface of copper foil to form a strong Si-O-Cu covalent bond, thereby anchoring silane molecules to the surface of copper foil. The epoxy group has excellent hydrolysis stability and remains intact during the bonding process, thereby constructing a stable functionalized layer with epoxy group-rich end on the surface of copper foil; The XPS detection results of the epoxy-functionalized copper foil prepared in this embodiment are shown in the figure below. Figure 2 As shown, the peak at 102.5 eV in the Si2p spectrum is attributed to the Si-O bond in the silane layer; the peaks at 284.8 eV and 286.6 eV in the fine C1s spectrum, after peak fitting, are attributed to CC / CH and COC, respectively; the significant COC peak at 286.6 eV is evidence of the presence of epoxy functional groups on the copper foil surface. 4. Preparation of current collector: Weigh 150 mg of elastic polymer-grafted single-walled carbon nanotubes and slowly add them to 30 mL of N-methylpyrrolidone. Under ice-water bath conditions, ultrasonically disperse at 300 W for 15 min to obtain a dispersion slurry. Fix the epoxy-functionalized copper foil on the platform of a doctor blade coater, take the dispersion slurry, and coat it onto the surface of the copper foil at a uniform speed using a doctor blade, controlling the doctor blade gap at 85 μm to obtain a coated copper foil. Heat-treat the coated copper foil in a vacuum drying oven at 100 °C for 1.5 h, and cool it to room temperature to obtain the copper foil coated with single-walled carbon nanotube current collector.

[0020] Example 2: Preparation method of copper foil coated single-walled carbon nanotube current collector, the specific steps are as follows: 1. Preparation of carboxylated single-walled carbon nanotubes: In a 250mL three-necked flask, add 120mL of mixed acid (made by mixing 30mL of 68% concentrated nitric acid and 90mL of 98% concentrated sulfuric acid), weigh 1.0g of single-walled carbon nanotubes, and slowly add them to the mixed acid with stirring; heat to 75℃ in an oil bath and react for 2h; after the reaction is completed, cool naturally to room temperature, filter the reaction mixture, collect the filter cake, wash the filter cake repeatedly with deionized water until the filtrate is neutral, transfer the filter cake to a watch glass, and dry it in a vacuum drying oven at 60℃ for 8h to obtain black powdered carboxylated single-walled carbon nanotubes; 2. Preparation of elastic polymer-grafted single-walled carbon nanotubes: In a dry 250 mL round-bottom flask, add 200 mg of carboxylated single-walled carbon nanotubes and 50 mL of anhydrous DMF (N,N-dimethylformamide), and sonicate for 1 h to obtain a uniform dispersion; add 6.0 g of amino-terminated polyether (D-400, number average molecular weight 400), 120 mg of EDC・HCl and 72 mg of NHS (N-hydroxysuccinimide) to the dispersion in sequence, purge with nitrogen for protection, and place in an oil bath at 65 °C for stirring and reaction for 20 h; after the reaction is completed, centrifuge the reaction mixture at 10000 rpm for 15 min, wash the precipitate twice with DMF, once with deionized water, and once with anhydrous ethanol, and dry under vacuum at 50 °C to constant weight to obtain elastic polymer-grafted single-walled carbon nanotubes; 3. Preparation of epoxy-functionalized copper foil: Cut copper foil (12μm thick) into 5cm×10cm pieces, place them in acetone, sonicate for 15min, place them in anhydrous ethanol, sonicate for 15min, and dry them with nitrogen to obtain clean copper foil; immerse the clean copper foil in 1wt% dilute nitric acid solution for 10s, remove it and rinse it with deionized water until the pH of the rinsing solution is neutral, place it in an 80℃ vacuum drying oven for 15min to obtain activated copper foil; add 1.0g of 3-glycidyl etheroxypropyltriethoxysilane to 100mL of anhydrous ethanol and stir magnetically to mix well; vertically immerse the activated copper foil in the above silane solution, let it stand for 30s, and then vertically pull it out of the liquid surface at a constant speed of 2cm / min. Immediately place the pulled wet film copper foil into a vacuum drying oven preheated to 80℃, vacuum dry for 30min, and cool it to room temperature to obtain epoxy-functionalized copper foil; 4. Preparation of current collector: Weigh 150 mg of elastic polymer-grafted single-walled carbon nanotubes and slowly add them to 50 mL of N-methylpyrrolidone. Under ice-water bath conditions, ultrasonically disperse at 300 W for 10 min to obtain a dispersion slurry. Fix the epoxy-functionalized copper foil on the platform of a doctor blade coater, take the dispersion slurry, and coat it onto the surface of the copper foil at a uniform speed using a doctor blade, controlling the doctor blade gap at 100 μm to obtain a coated copper foil. Heat-treat the coated copper foil in a vacuum drying oven at 130 °C for 2 h, and cool it to room temperature to obtain a copper foil coated with single-walled carbon nanotube current collector.

[0021] Example 3: Preparation method of copper foil coated single-walled carbon nanotube current collector, the specific steps are as follows: 1. Preparation of carboxylated single-walled carbon nanotubes: In a 250mL three-necked flask, add 120mL of mixed acid (made by mixing 30mL of 68% concentrated nitric acid and 90mL of 98% concentrated sulfuric acid), weigh 1.0g of single-walled carbon nanotubes, and slowly add them to the mixed acid with stirring; heat to 73℃ in an oil bath and react for 2.5h; after the reaction is completed, cool naturally to room temperature, filter the reaction mixture, collect the filter cake, wash the filter cake repeatedly with deionized water until the filtrate is neutral, transfer the filter cake to a watch glass, and dry it in a vacuum drying oven at 55℃ for 10h to obtain black powdered carboxylated single-walled carbon nanotubes; 2. Preparation of elastic polymer-grafted single-walled carbon nanotubes: In a dry 250 mL round-bottom flask, 200 mg of carboxylated single-walled carbon nanotubes and 50 mL of anhydrous DMF (N,N-dimethylformamide) were added and ultrasonically dispersed for 1.5 h to obtain a uniform dispersion. 8.0 g of amino-terminated polyether (D-2000, number-average molecular weight 2000), 160 mg of EDC·HCl, and 96 mg of NHS (N-hydroxysuccinimide) were added sequentially to the dispersion. Nitrogen gas was introduced for protection, and the mixture was placed in a 60 °C oil bath and stirred for 24 h. After the reaction was complete, the reaction mixture was centrifuged at 10000 rpm for 15 min. The precipitate was washed twice with DMF, once with deionized water, and once with anhydrous ethanol. It was then vacuum dried at 55 °C to constant weight to obtain elastic polymer-grafted single-walled carbon nanotubes. 3. Preparation of epoxy-functionalized copper foil: Cut copper foil (12μm thick) into 5cm×10cm pieces, place them in acetone, sonicate for 15min, place them in anhydrous ethanol, sonicate for 15min, and dry them with nitrogen to obtain clean copper foil; immerse the clean copper foil in 1wt% dilute nitric acid solution for 15s, remove it and rinse it with deionized water until the pH of the rinsing solution is neutral, place it in a vacuum drying oven at 70℃ for 20min to obtain activated copper foil; add 1.0g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane to 100mL of anhydrous ethanol and stir magnetically to mix well; vertically immerse the activated copper foil in the above silane solution, let it stand for 30s, and then vertically pull it out of the liquid surface at a constant speed of 2cm / min. Immediately place the pulled wet film copper foil into a vacuum drying oven preheated to 90℃, vacuum dry for 15min, and cool it to room temperature to obtain epoxy-functionalized copper foil; 4. Preparation of current collector: Weigh 150 mg of elastic polymer-grafted single-walled carbon nanotubes and slowly add them to 25 mL of N-methylpyrrolidone. Under ice-water bath conditions, ultrasonically disperse at 300 W for 10 min to obtain a dispersion slurry. Fix the epoxy-functionalized copper foil on the platform of a doctor blade coater, take the dispersion slurry, and coat it onto the surface of the copper foil at a uniform speed using a doctor blade, controlling the doctor blade gap at 50 μm to obtain a coated copper foil. Heat-treat the coated copper foil in a vacuum drying oven at 120 °C for 2.5 h, and cool it to room temperature to obtain the copper foil coated single-walled carbon nanotube current collector.

[0022] Comparative Example 1: The method for preparing copper foil-coated single-walled carbon nanotube current collectors differs from Example 1 in that the single-walled carbon nanotubes are not grafted with elastic polymers. The specific steps are as follows: 1. Preparation of carboxylated single-walled carbon nanotubes: In a 250mL three-necked flask, add 120mL of mixed acid (made by mixing 30mL of 68% concentrated nitric acid and 90mL of 98% concentrated sulfuric acid), weigh 1.0g of single-walled carbon nanotubes, and slowly add them to the mixed acid with stirring; heat to 70℃ in an oil bath and react for 3h; after the reaction is completed, cool naturally to room temperature, filter the reaction mixture, collect the filter cake, wash the filter cake repeatedly with deionized water until the filtrate is neutral, transfer the filter cake to a watch glass, and dry it in a vacuum drying oven at 50℃ for 12h to obtain black powdered carboxylated single-walled carbon nanotubes; 2. Preparation of epoxy-functionalized copper foil: Cut copper foil (12μm thick) into 5cm×10cm pieces, place them in acetone, sonicate for 15min, place them in anhydrous ethanol, sonicate for 15min, and dry them with nitrogen to obtain clean copper foil; immerse the clean copper foil in 1wt% dilute nitric acid solution for 20s, remove it and rinse it with deionized water until the pH of the rinsing solution is neutral, place it in a vacuum drying oven at 60℃ for 30min to obtain activated copper foil; add 1.0g of 3-glycidyl etheroxypropyltrimethoxysilane (KH-560) to 100mL of anhydrous ethanol and stir magnetically to mix well; vertically immerse the activated copper foil in the above silane solution, let it stand for 30s, and then vertically pull it out of the liquid surface at a constant speed of 1cm / min. Immediately place the pulled wet film copper foil into a vacuum drying oven preheated to 100℃, vacuum dry for 20min, and cool it to room temperature to obtain epoxy-functionalized copper foil; 3. Preparation of current collector: Weigh 150 mg of carboxylated single-walled carbon nanotubes and slowly add them to 30 mL of N-methylpyrrolidone. Under ice-water bath conditions, ultrasonically disperse at 300 W for 15 min to obtain a dispersion slurry. Fix the epoxy-functionalized copper foil on the platform of a doctor blade coater, take the dispersion slurry, and coat it onto the surface of the copper foil at a uniform speed using a doctor blade, controlling the doctor blade gap at 85 μm to obtain a coated copper foil. Heat-treat the coated copper foil in a vacuum drying oven at 100 °C for 1.5 h, and cool it to room temperature to obtain the copper foil coated with single-walled carbon nanotube current collector.

[0023] Comparative Example 2: The preparation method of copper foil coated with single-walled carbon nanotube current collector differs from Example 1 in that the copper foil is not epoxy-functionalized. The specific steps are as follows: 1. Preparation of carboxylated single-walled carbon nanotubes: In a 250mL three-necked flask, add 120mL of mixed acid (made by mixing 30mL of 68% concentrated nitric acid and 90mL of 98% concentrated sulfuric acid), weigh 1.0g of single-walled carbon nanotubes, and slowly add them to the mixed acid with stirring; heat to 70℃ in an oil bath and react for 3h; after the reaction is completed, cool naturally to room temperature, filter the reaction mixture, collect the filter cake, wash the filter cake repeatedly with deionized water until the filtrate is neutral, transfer the filter cake to a watch glass, and dry it in a vacuum drying oven at 50℃ for 12h to obtain black powdered carboxylated single-walled carbon nanotubes; 2. Preparation of elastic polymer-grafted single-walled carbon nanotubes: In a dry 250 mL round-bottom flask, add 200 mg of carboxylated single-walled carbon nanotubes and 50 mL of anhydrous DMF (N,N-dimethylformamide), and sonicate for 2 h to obtain a uniform dispersion; add 10.0 g of amino-terminated polyether (D-2000, number average molecular weight of 2000), 200 mg of EDC·HCl and 120 mg of NHS (N-hydroxysuccinimide) to the dispersion in sequence, purge with nitrogen for protection, and place in an oil bath at 50 °C for stirring and reaction for 22 h; after the reaction is completed, centrifuge the reaction mixture at 10000 rpm for 15 min, wash the precipitate twice with DMF, once with deionized water, and once with anhydrous ethanol, and dry under vacuum at 60 °C to constant weight to obtain elastic polymer-grafted single-walled carbon nanotubes; 3. Preparation of the current collector: Weigh 150 mg of elastic polymer-grafted single-walled carbon nanotubes and slowly add them to 30 mL of N-methylpyrrolidone. Under ice-water bath conditions, ultrasonically disperse at 300 W for 15 min to obtain a dispersion slurry. Cut copper foil (12 μm thick) into 5 cm × 10 cm pieces, place them in acetone, ultrasonically clean for 15 min, place them in anhydrous ethanol, ultrasonically clean for 15 min, and dry them with nitrogen to obtain clean copper foil. Fix the clean copper foil on the platform of a doctor blade coater, take the dispersion slurry, and coat it onto the surface of the copper foil at a uniform speed using a doctor blade, controlling the doctor blade gap at 85 μm to obtain coated copper foil. Heat-treat the coated copper foil in a vacuum drying oven at 100 °C for 1.5 h, and cool it to room temperature to obtain the copper foil coated with single-walled carbon nanotube current collector.

[0024] Comparative Example 3 describes a method for preparing a copper foil-coated single-walled carbon nanotube current collector. The difference between this method and Example 1 is that the single-walled carbon nanotubes were not grafted with elastic polymers and the copper foil was not epoxy-functionalized. The specific steps are as follows: 1. Prepare the dispersion slurry: Weigh 150mg of single-walled carbon nanotubes and slowly add them to 30mL of N-methylpyrrolidone. Under ice-water bath conditions, ultrasonically disperse at 300W for 15min to obtain the dispersion slurry. 2. Prepare clean copper foil: Cut the copper foil (12μm thick) into 5cm×10cm pieces, put it in acetone, sonicate for 15min, put it in anhydrous ethanol, sonicate for 15min, and dry it with nitrogen to obtain clean copper foil. 3. Fix the clean copper foil on the platform of the doctor blade coater, take the dispersed slurry, and coat it onto the copper foil surface at a uniform speed using a doctor blade, controlling the doctor blade gap at 85μm to obtain the coated copper foil; heat-treat the coated copper foil in a vacuum drying oven at 100℃ for 1.5h, and cool it to room temperature to obtain the copper foil coated single-walled carbon nanotube current collector.

[0025] Comparative Example 4: The method for preparing copper foil coated with single-walled carbon nanotube current collectors differs from Example 1 in that graphene and SBR aqueous coatings are used to coat the copper foil. The specific steps are as follows: 1. Preparation of water-based coating: Weigh graphene powder, aminosilane coupling agent (KH-550), and styrene-butadiene rubber (SBR) emulsion at a mass ratio of 95:2.5:2.5; first, disperse the graphene powder and KH-550 in deionized water and stir at high speed for 30 min; then add the SBR emulsion and continue stirring for 60 min, controlling the total solids content of the slurry to 5%, to form a uniform and stable water-based slurry; 2. Prepare clean copper foil: Cut the copper foil (12μm thick) into 5cm×10cm pieces, put it in acetone, sonicate for 15min, put it in anhydrous ethanol, sonicate for 15min, and dry it with nitrogen to obtain clean copper foil. 3. Fix the clean copper foil on the platform of the doctor blade coating machine, take the water-based slurry, and coat it onto the copper foil surface at a uniform speed using a doctor blade, controlling the doctor blade gap at 85μm to obtain the coated copper foil; heat-treat the coated copper foil in a vacuum drying oven at 100℃ for 1.5h to remove moisture and allow SBR to form a film, and cool it to room temperature to obtain the graphene / SBR coated modified copper foil current collector.

[0026] Performance testing The above examples and comparative examples were prepared into standardized batteries for performance testing. All samples of the examples and comparative examples were prepared into negative electrode sheets, assembled into batteries, and tested under the same conditions.

[0027] Preparation of the negative electrode sheet: Using the current collector prepared in the above examples and comparative examples as a substrate, a silicon-based negative electrode active layer is coated: Silicon powder, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber are mixed in a mass ratio of 80:10:5:5, with deionized water as a solvent, to achieve a total solid content of 50% in the slurry. The mixture is stirred evenly to obtain a negative electrode active slurry. Using an automatic coating machine, the negative electrode active slurry is coated onto the current collector, controlling the areal density of the active material to be 1.5 mg / cm³. 2(Based on silicon) The coated electrode is dried in a forced-air dryer at 100°C for 2 hours, and then rolled under a pressure of 10 MPa to be punched into a round sheet with a diameter of 14 mm to obtain the negative electrode.

[0028] Preparation of assembled batteries: In an argon atmosphere glove box, button batteries are assembled: negative electrode sheet (active material side up), Celgard 2400 separator, 60μL electrolyte, lithium metal sheet, gasket and spring are placed in sequence in the negative electrode shell, and finally the positive electrode shell is covered. The battery is sealed with a sealing machine and left to stand at room temperature for 12 hours to obtain the assembled battery.

[0029] 1. Interface bonding test The negative electrode sheets prepared in the above embodiments and comparative samples were subjected to interfacial bonding strength tests: The dried negative electrode sheet was pasted onto a rigid steel plate with the active layer facing down. The current collector was peeled off at a speed of 100 mm / min in a 180° direction. The average force value (F) during the peeling process was recorded. The peeling strength was calculated according to the following formula: Peeling strength (σ) = F / b; where F is the average force value during the peeling process, and b is the electrode diameter of 14 mm. The experimental results are shown in Table 1. Table 1. Test results of interfacial adhesion of coatings

[0030] As can be seen from Table 1, the samples of Examples 1 to 3 have extremely high peel strength, which is significantly higher than that of all comparative examples. This indicates that the covalent bonds between the epoxy groups and amino groups of the present invention form a strong interface and exert a good anti-peel effect.

[0031] The peel strength of Comparative Example 1 decreased by about 50% compared to Example 1, which illustrates the importance of elastic polymer grafting in enhancing the cohesion and toughness of the coating. The peel strength of Comparative Example 2 was even lower than that of Comparative Example 1, which demonstrates the core role of epoxy functionalization in achieving strong interfacial bonding. Without the bridging effect of epoxy groups, the coating relies solely on physical adsorption of copper foil, resulting in very weak bonding. The coating of Comparative Example 3 rapidly peeled off over a large area during testing, exhibiting extremely low peel strength, indicating that the physical coating bonding without any chemical modification completely failed and could not form a usable current collector. The peel strength of Comparative Example 4 was lower than that of Examples 1-3, indicating that the bonding strength of traditional physical adhesives has limitations and cannot form high-strength interfacial bonding.

[0032] 2. Battery cycle performance test The battery's charge and discharge behavior was recorded using a Blue Electric constant current charge and discharge test system. Testing was conducted in a constant temperature environment of 30°C. After activation at 0.1C for two weeks, long-cycle testing was performed at a constant current charge and discharge rate of 0.5C, with a voltage window of 0.01~1.5V (for Li). +( / Li), record the initial discharge specific capacity and the discharge specific capacity after 100 cycles, calculate the capacity retention rate, and the test results are shown in Table 2: Table 2 Battery Cycle Performance Test Results

[0033] As shown in Table 2, in the long-cycle test at a constant current charge-discharge rate of 0.5C, the battery prepared by the current collector of the present invention has a capacity retention rate of over 83%, which is higher than all comparative examples.

[0034] Comparative Example 1 uses untreated single-walled carbon nanotubes, which have a low capacity retention rate. This indicates that the carbon nanotube network grafted with an inelastic polymer is brittle and cannot effectively buffer the huge volume expansion of silicon particles during cycling. Repeated stress leads to the breakage of the brittle conductive network, a sharp increase in electrode impedance, and failure of electrical contact between the active material and the current collector, resulting in rapid capacity decay. Comparative Example 2 lacks the chemical bridging of epoxy silanes. During cycling, the coating is prone to local peeling or slippage, which leads to the failure of some active materials and loss of electrochemical activity, thereby limiting the capacity retention rate. Comparative Example 3 combines the two failure mechanisms mentioned above. It has neither an elastic buffer layer to dissipate internal stress nor a strong interface to resist external peeling. The physically coated coating fails rapidly, resulting in a rapid decline in battery performance. Comparative Example 4 shows that the SBR relying on physical bonding is prone to fatigue under long-term cyclic stress, and the insulating bonding phase hinders electron transport; in addition, it lacks elastic design in the outward direction, and the interlayer is prone to slippage, making it difficult to build a long-term, stable three-dimensional network to adapt to the volume changes of the silicon anode. The above results demonstrate that the present invention has a positive effect on improving the cycle stability of high-silicon anodes through the synergistic effect of chemical bonding and elastic buffering.

[0035] 3. Ratio Performance Test The rate performance was tested using the Blue Electric constant current charge-discharge test system in a constant temperature environment of 30°C. After activation at 0.1C for 2 weeks, the battery was sequentially charged and discharged at current densities of 0.1C, 0.2C, 0.5C, 1C, and 2C, with each rate stabilized for 5 weeks. Finally, the battery was returned to 0.1C to evaluate capacity recovery. The voltage window was 0.01~1.5V (for Li...). + / Li), record the discharge specific capacity at each rate in the 5th week, and use the discharge capacity at 0.1C rate as the baseline (100%) to calculate the capacity retention rate at each high rate, so as to evaluate the charge transport capability and structural stability of the current collector under different currents. The experimental results are shown in Table 3: Table 3 Battery Rate Performance Test Results

[0036] As shown in Table 3, the capacity retention rates of Examples 1-3 at various rates from 0.2C to 2C were significantly higher than those of all comparative examples. At the high rate of 2C, the capacity retention rates of Examples 1-3 were still maintained above 75%, indicating that the current collector of the present invention has excellent electron transport capability and stable structural strength. Furthermore, the capacity recovery rate of the samples of Examples 1-3 at 0.1C was higher than 94%, indicating that the chemical bonding interface and elastic buffer network of the present invention synergistically construct a current collector with excellent stability, which can still maintain structural stability under the drastic volume changes and current shocks brought about by high rates.

[0037] In Comparative Example 1, the carbon nanotubes were not grafted with elastic polymers, making them prone to breakage or contact failure under the additional stress generated by high-flux ion migration, leading to irreversible damage. In Comparative Example 2, the copper foil was not functionalized, resulting in weak interfacial bonding, which made the coating easy to peel off and increased contact resistance. Comparative Example 3 performed the worst, demonstrating that the lack of buffering and strong interfacial bonding led to rapid battery failure under high load. Comparative Example 4 used a physical bonding and layer stacking scheme, which made it difficult to construct a network that balanced high conductivity and excellent mechanical stability, failing to meet the requirements of the battery at high rates with a high-silicon anode.

[0038] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a copper foil-coated single-walled carbon nanotube current collector, characterized in that, Includes the following steps: S1. Slurry coating: Elastic polymer grafted single-walled carbon nanotubes are dispersed in N-methylpyrrolidone, stirred evenly, and sonicated for 10-15 min to obtain a dispersion slurry; the dispersion slurry is coated on epoxy-functionalized copper foil, and the doctor blade gap is controlled to be 50-100 μm to obtain coated copper foil. S2. The coated copper foil is vacuum dried at 100~130℃ for 1.5~2.5h and cooled to room temperature to obtain a copper foil coated single-walled carbon nanotube current collector.

2. The method for preparing a copper foil-coated single-walled carbon nanotube current collector according to claim 1, characterized in that, The preparation method of the elastic polymer-grafted single-walled carbon nanotubes is as follows: carboxylated single-walled carbon nanotubes are dispersed in anhydrous DMF and sonicated for 1-2 hours to obtain a dispersion; terminal amino polyether is added to the dispersion, followed by EDC・HCl and NHS; under nitrogen protection, the mixture is stirred at a constant temperature of 50-65℃ for 20-24 hours; the precipitate is collected by centrifugation, washed twice with DMF, once with deionized water, and once with anhydrous ethanol; and then vacuum dried at 50-60℃ to constant weight to obtain elastic polymer-grafted single-walled carbon nanotubes.

3. The method for preparing a copper foil-coated single-walled carbon nanotube current collector according to claim 2, characterized in that, The mass ratio of the carboxylated single-walled carbon nanotubes, the amino-terminated polyether, and EDC·HCl is 1:30~50:0.6~1; the number-average molecular weight of the amino-terminated polyether is 400~2000.

4. The method for preparing a copper foil-coated single-walled carbon nanotube current collector according to claim 2, characterized in that, The method for preparing the carboxylated single-walled carbon nanotubes is as follows: single-walled carbon nanotubes are added to a mixed acid solution and reacted at 70-75℃ for 2-3 hours. After cooling to room temperature, the filter cake is collected by suction filtration. The filter cake is repeatedly washed with deionized water until the filtrate is neutral. The filter cake is then vacuum dried at 50-60℃ for 8-12 hours to obtain carboxylated single-walled carbon nanotubes.

5. The method for preparing a copper foil-coated single-walled carbon nanotube current collector according to claim 4, characterized in that, The mixed acid solution is prepared by mixing 68% concentrated nitric acid and 98% concentrated sulfuric acid at a volume ratio of 1:

3.

6. The method for preparing a copper foil-coated single-walled carbon nanotube current collector according to claim 1, characterized in that, The preparation method of the epoxy-functionalized copper foil is as follows: the copper foil is ultrasonically cleaned in acetone and anhydrous ethanol for 15 min respectively, and dried with nitrogen to obtain clean copper foil; the clean copper foil is immersed in dilute nitric acid for 10-20 s, taken out, rinsed with deionized water, and vacuum dried at 60-80℃ for 15-30 min to obtain activated copper foil; the activated copper foil is immersed in epoxy silane coupling agent solution by dip-pull method, and after standing for 30 s, it is vertically pulled out of the liquid surface at a constant speed, and immediately vacuum dried at 80-100℃ for 15-30 min, and cooled to room temperature to obtain epoxy-functionalized copper foil.

7. The method for preparing a copper foil-coated single-walled carbon nanotube current collector according to claim 6, characterized in that, The epoxy silane coupling agent solution is prepared by dissolving the epoxy silane coupling agent in anhydrous ethanol at a concentration of 10 g / L and mixing thoroughly; the constant speed is 1~2 cm / min.

8. The method for preparing a copper foil-coated single-walled carbon nanotube current collector according to claim 7, characterized in that, The epoxy silane coupling agent is one of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, or 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

9. The method for preparing a copper foil-coated single-walled carbon nanotube current collector according to claim 1, characterized in that, The ratio of the elastic polymer-grafted single-walled carbon nanotubes to N-methylpyrrolidone is 3~6 mg: 1 mL.

10. The copper foil coated single-walled carbon nanotube current collector prepared by the method of claim 1 to 9.

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