A nanocomposite negative electrode material and preparation method thereof

Abstract

The present invention relates to the technical field of lithium battery negative electrode materials, discloses a nanocomposite negative electrode material and its preparation method, its raw materials are measured by weight, and the composition includes: 3 4 parts of carbon nanotubes, 135 150 parts of concentrated nitric acid, 315 330 parts of concentrated sulfuric acid, 600 650 parts of dilute hydrochloric acid, 30 40 parts of anhydrous ethanol, 7.5 10 parts of polyethylene imine, 25 30 parts of molybdenum disulfide, 10 12 parts of surfactant, 3325 3600 parts of deionized water. The present invention adopts the self-assembly method assisted by electrostatic force to self-assemble the modified MoS2 nanosheets and MWCNTs in solution to obtain MoS2 / PVP / PEI / MWCNTs quaternary complex, and finally heat-treated to obtain final MoS2 / MWCNTs nanocomposite negative electrode material, with higher reversible capacity, better cycle stability and rate performance. In addition, the preparation method does not require high temperature and high pressure conditions, is efficient, convenient and energy-saving and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery negative electrode materials, and in particular to a nano composite negative electrode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are considered one of the high-energy batteries most capable of meeting the sustainable development requirements of future societies. In recent years, lithium-ion batteries have rapidly developed and are widely used in portable electronic devices such as mobile phones, laptops, and camcorders, as well as in aviation and aerospace applications. They have also gained significant attention in the electric vehicle sector. However, current lithium-ion batteries cannot meet the ever-increasing energy density demands of applications such as pure electric and hybrid electric vehicles. Therefore, the development of battery materials with high energy density and high rate performance has become a hot research topic.

[0003] Anode materials are key to the performance of lithium-ion batteries. Currently, the main anode materials for lithium-ion batteries include graphite, amorphous carbon, carbon nanotubes, silicon-based materials, tin-based materials, alloys, transition metal oxides, and two-dimensional nanomaterials. Multi-walled carbon nanotubes (MWCNTs) are a new type of carbon crystalline material discovered recently. They consist of several to thousands of coaxially arranged single-walled carbon nanotubes. The inter-tube interactions are similar to the van der Waals forces in graphite, and the radial spacing between adjacent tubes is approximately 0.34 nm. MWCNTs exhibit excellent physical and chemical properties, such as a large specific surface area and molecular-sized pores, extremely high tensile strength, excellent thermodynamic properties, high chemical stability, and excellent hydrogen storage capacity. Consequently, they have been extensively studied in areas such as catalyst supports, hydrogen storage materials, lithium-ion batteries, electric double-layer capacitors, and field emission. MWCNTs as anode materials for lithium-ion batteries offer advantages such as numerous lithium insertion sites, easy lithium deintercalation, and excellent cycling stability. However, they suffer from high irreversible capacity in the first cycle and low specific capacity.

[0004] Molybdenum disulfide (MoS2) is an important transition metal sulfide with a typical layered structure. It has a wide range of applications and can be used as an embedded electrode material for electrochemical lithium storage, offering a high theoretical specific capacity. However, its cycling stability is poor. Therefore, many researchers have hybridized it with carbon materials with excellent cycling stability, such as graphene, carbon nanotubes, and amorphous carbon, to produce composite anode materials with even better performance.

[0005] Currently, the hydrothermal synthesis method is commonly used to prepare MoS2 / CNTs nanocomposites, but its disadvantages are high temperature and high pressure, which not only places high demands on equipment, but is also extremely energy-consuming and does not meet the requirements of modern green chemistry. Summary of the Invention

[0006] In order to overcome the shortcomings and deficiencies of the existing technology, the present invention aims to provide a nanocomposite negative electrode material and a preparation method thereof. The prepared nanocomposite negative electrode material has a high reversible capacity, good cycle stability and rate performance. The preparation method is an electrostatic force-assisted self-assembly method, which is efficient, convenient, energy-saving and environmentally friendly.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A nanocomposite negative electrode material comprises, by weight, 3-4 parts of carbon nanotubes, 135-150 parts of concentrated nitric acid, 315-330 parts of concentrated sulfuric acid, 600-650 parts of dilute hydrochloric acid, 30-40 parts of anhydrous ethanol, 7.5-10 parts of polyethyleneimine, 25-30 parts of molybdenum disulfide, 10-12 parts of a surfactant, and 3325-3600 parts of deionized water.

[0009] Preferably, the carbon nanotubes are multi-walled carbon nanotubes.

[0010] Preferably, the surfactant is polyvinyl pyrrolidone.

[0011] Preferably, the concentration of the concentrated nitric acid is 65%.

[0012] Preferably, the concentration of the concentrated sulfuric acid is 98%.

[0013] Preferably, the concentration of the dilute hydrochloric acid is 3%.

[0014] The method for preparing a nanocomposite negative electrode material comprises the following steps:

[0015] (1) Concentrated sulfuric acid and concentrated nitric acid were mixed and stirred evenly, and then multi-walled carbon nanotubes were added, ultrasonically dispersed for 10 minutes, and then transferred to an oil bath for reaction. After the reaction was completed, it was diluted with 1000-1200 parts of deionized water, allowed to stand overnight, filtered to remove the acid solution, and then washed with 1500 parts of deionized water for 3-4 times, washed twice with anhydrous ethanol, transferred to an oven for vacuum drying for 24 hours, and then transferred to a refrigerator for freezing for 5 hours. Then, it was freeze-dried to obtain pretreated multi-walled carbon nanotubes, which were added to 500 parts of deionized water and ultrasonically dispersed for 15 minutes to obtain a multi-walled carbon nanotube aqueous dispersion;

[0016] (2) Add polyethyleneimine to 30 times the mass of deionized water and stir evenly to form a polyethyleneimine aqueous solution, then add it dropwise to the multi-walled carbon nanotube aqueous dispersion under ultrasonic conditions. After the addition is completed, continue ultrasonication for 1.5 hours, remove a small amount of precipitate by centrifugation, and obtain a polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion;

[0017] (3) Molybdenum disulfide and polyvinyl pyrrolidone were added to 100 parts of deionized water and stirred evenly, and then ultrasonically dispersed until the dispersion turned dark green. The mixture was allowed to stand for 72 hours, and the supernatant was removed and transferred to a centrifuge tube. The mixture was centrifuged at 1500 rpm for 45 minutes, and the supernatant was removed again to obtain a polyvinyl pyrrolidone-stabilized molybdenum disulfide nanosheet dispersion.

[0018] (4) Under ultrasonic conditions, the molybdenum disulfide nanosheet dispersion was added dropwise to the polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion. After the addition was completed, the mixture was ultrasonically treated for 1.5 hours, then allowed to stand for 24 hours, filtered, and dried in a vacuum oven for 24 hours to obtain a molybdenum disulfide / polyvinyl pyrrolidone / polyethyleneimine / multi-walled carbon nanotube quaternary complex. The mixture was then heat treated at 800°C for 1.5 hours under an inert gas atmosphere to remove the polyvinyl pyrrolidone and polyethyleneimine to obtain a nanocomposite negative electrode material of molybdenum disulfide / multi-walled carbon nanotubes.

[0019] Preferably, the reaction in step (1) is carried out at 70° C. with stirring for 6 h.

[0020] Preferably, the centrifugal operation in step (2) is a centrifugal operation with a rotation speed of 8000 r / min and a time of 5 min.

[0021] Preferably, the oven in step (1) is an oven at 60°C, and the oven in step (4) is an oven at 80°C.

[0022] Beneficial effects of the present invention:

[0023] The present invention uses polyvinyl pyrrolidone (PVP) as a surfactant to assist in liquid-phase ultrasonic exfoliation to prepare a PVP-stabilized MoS2 nanosheet dispersion, imparting a negative charge to the nanosheets. The acidified multi-walled carbon nanotubes (MWCNTs) are then coated with polyethyleneimine (PEI) to impart a positive surface charge. The two components are then self-assembled in solution to form a MoS2 / PVP / PEI / MWCNTs quaternary complex. Finally, heat treatment is performed to obtain the final MoS2 / MWCNTs nanocomposite anode material, which exhibits high reversible capacity, good cycle stability, and rate performance. Furthermore, the preparation method, a self-assembly method assisted by electrostatic interactions, is efficient, convenient, energy-efficient, and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the cycle performance diagram of each material electrode at the same current density;

[0025] Figure 2 This is the rate performance diagram of MoS2 / MWCNTs nanocomposite anode material at different current densities; DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments so as to fully understand the purpose, characteristics and effects of the present invention. Example 1:

[0027] A nanocomposite negative electrode material comprises, by weight, 3 parts of multi-walled carbon nanotubes, 135 parts of concentrated nitric acid, 315 parts of concentrated sulfuric acid, 600 parts of dilute hydrochloric acid, 30 parts of anhydrous ethanol, 7.5 parts of polyethyleneimine, 25 parts of molybdenum disulfide, 10 parts of polyvinylpyrrolidone, and 3325 parts of deionized water.

[0028] The method for preparing the nanocomposite negative electrode material described in this embodiment comprises the following steps, in parts by weight:

[0029] (1) Concentrated sulfuric acid and concentrated nitric acid were mixed and stirred evenly, and then multi-walled carbon nanotubes were added, ultrasonically dispersed for 10 minutes, and then transferred to an oil bath pot and stirred at 70°C for 6 hours. After the reaction was completed, it was diluted with 1000 parts of deionized water, allowed to stand overnight, filtered to remove the acid, and then washed with 1500 parts of deionized water 3-4 times, washed twice with anhydrous ethanol, transferred to a 60°C oven for vacuum drying for 24 hours, and then transferred to a refrigerator for freezing for 5 hours. Then, it was freeze-dried to obtain pretreated multi-walled carbon nanotubes, which were added to 500 parts of deionized water and ultrasonically dispersed for 15 minutes to obtain a multi-walled carbon nanotube aqueous dispersion;

[0030] (2) Add polyethyleneimine to 30 times the mass of deionized water and stir evenly to form a polyethyleneimine aqueous solution, then add it dropwise to the multi-walled carbon nanotube aqueous dispersion under ultrasonic conditions. After the addition is completed, continue ultrasonication for 1.5 hours, and centrifuge at a speed of 8000 r / min for 5 minutes to remove a small amount of precipitate to obtain a polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion;

[0031] (3) Molybdenum disulfide and polyvinyl pyrrolidone were added to 100 parts of deionized water and stirred evenly, and then ultrasonically dispersed until the dispersion turned dark green. The mixture was allowed to stand for 72 hours, and the supernatant was removed and transferred to a centrifuge tube. The mixture was centrifuged at 1500 rpm for 45 minutes, and the supernatant was removed again to obtain a polyvinyl pyrrolidone-stabilized molybdenum disulfide nanosheet dispersion.

[0032] (4) Under ultrasonic conditions, the molybdenum disulfide nanosheet dispersion was added dropwise to the polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion. After the addition was completed, the mixture was ultrasonically treated for 1.5 hours, then allowed to stand for 24 hours, filtered, and dried in a vacuum oven at 80°C for 24 hours to obtain a molybdenum disulfide / polyvinyl pyrrolidone / polyethyleneimine / multi-walled carbon nanotube quaternary complex. The mixture was then heat treated at 800°C for 1.5 hours under an inert gas atmosphere to remove the polyvinyl pyrrolidone and polyethyleneimine to obtain a nanocomposite negative electrode material of molybdenum disulfide / multi-walled carbon nanotubes. Example 2:

[0033] A nano-composite negative electrode material comprises, by weight, 3 parts of multi-walled carbon nanotubes, 140 parts of concentrated nitric acid, 325 parts of concentrated sulfuric acid, 625 parts of dilute hydrochloric acid, 35 parts of anhydrous ethanol, 9 parts of polyethyleneimine, 27 parts of molybdenum disulfide, 11 parts of polyvinylpyrrolidone, and 3470 parts of deionized water.

[0034] The method for preparing the nanocomposite negative electrode material described in this embodiment comprises the following steps, in parts by weight:

[0035] (1) Concentrated sulfuric acid and concentrated nitric acid were mixed and stirred evenly, and then multi-walled carbon nanotubes were added, ultrasonically dispersed for 10 minutes, and then transferred to an oil bath pot and stirred at 70°C for 6 hours. After the reaction was completed, it was diluted with 1100 parts of deionized water, allowed to stand overnight, filtered to remove the acid, and then washed with 1500 parts of deionized water 3-4 times, washed twice with anhydrous ethanol, transferred to a 60°C oven for vacuum drying for 24 hours, and then transferred to a refrigerator for freezing for 5 hours. Then, it was freeze-dried to obtain pretreated multi-walled carbon nanotubes, which were added to 500 parts of deionized water and ultrasonically dispersed for 15 minutes to obtain a multi-walled carbon nanotube aqueous dispersion;

[0036] (2) Add polyethyleneimine to 30 times the mass of deionized water and stir evenly to form a polyethyleneimine aqueous solution, then add it dropwise to the multi-walled carbon nanotube aqueous dispersion under ultrasonic conditions. After the addition is completed, continue ultrasonication for 1.5 hours, and centrifuge at a speed of 8000 r / min for 5 minutes to remove a small amount of precipitate to obtain a polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion;

[0037] (3) Molybdenum disulfide and polyvinyl pyrrolidone were added to 100 parts of deionized water and stirred evenly, and then ultrasonically dispersed until the dispersion turned dark green. The mixture was allowed to stand for 72 hours, and the supernatant was removed and transferred to a centrifuge tube. The mixture was centrifuged at 1500 rpm for 45 minutes, and the supernatant was removed again to obtain a polyvinyl pyrrolidone-stabilized molybdenum disulfide nanosheet dispersion.

[0038] (4) Under ultrasonic conditions, the molybdenum disulfide nanosheet dispersion was added dropwise to the polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion. After the addition was completed, the mixture was ultrasonically treated for 1.5 hours, then allowed to stand for 24 hours, filtered, and dried in a vacuum oven at 80°C for 24 hours to obtain a molybdenum disulfide / polyvinyl pyrrolidone / polyethyleneimine / multi-walled carbon nanotube quaternary complex. The mixture was then heat treated at 800°C for 1.5 hours under an inert gas atmosphere to remove the polyvinyl pyrrolidone and polyethyleneimine to obtain a nanocomposite negative electrode material of molybdenum disulfide / multi-walled carbon nanotubes. Example 3:

[0039] A nano-composite negative electrode material comprises the following raw materials by weight: 4 parts of multi-walled carbon nanotubes, 150 parts of concentrated nitric acid, 330 parts of concentrated sulfuric acid, 650 parts of dilute hydrochloric acid, 40 parts of anhydrous ethanol, 10 parts of polyethyleneimine, 30 parts of molybdenum disulfide, 10-12 parts of polyvinyl pyrrolidone, and 3600 parts of deionized water.

[0040] The method for preparing the nanocomposite negative electrode material described in this embodiment comprises the following steps, in parts by weight:

[0041] (1) Concentrated sulfuric acid and concentrated nitric acid were mixed and stirred evenly, and then multi-walled carbon nanotubes were added, ultrasonically dispersed for 10 minutes, and then transferred to an oil bath pot and stirred at 70°C for 6 hours. After the reaction was completed, it was diluted with 1200 parts of deionized water, allowed to stand overnight, filtered to remove the acid, and then washed with 1500 parts of deionized water 3-4 times, washed twice with anhydrous ethanol, transferred to a 60°C oven for vacuum drying for 24 hours, and then transferred to a refrigerator for freezing for 5 hours. Then, it was freeze-dried to obtain pretreated multi-walled carbon nanotubes, which were added to 500 parts of deionized water and ultrasonically dispersed for 15 minutes to obtain a multi-walled carbon nanotube aqueous dispersion;

[0042] (2) Add polyethyleneimine to 30 times the mass of deionized water and stir evenly to form a polyethyleneimine aqueous solution, then add it dropwise to the multi-walled carbon nanotube aqueous dispersion under ultrasonic conditions. After the addition is completed, continue ultrasonication for 1.5 hours, and centrifuge at a speed of 8000 r / min for 5 minutes to remove a small amount of precipitate to obtain a polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion;

[0043] (3) Molybdenum disulfide and polyvinyl pyrrolidone were added to 100 parts of deionized water and stirred evenly, and then ultrasonically dispersed until the dispersion turned dark green. The mixture was allowed to stand for 72 hours, and the supernatant was removed and transferred to a centrifuge tube. The mixture was centrifuged at 1500 rpm for 45 minutes, and the supernatant was removed again to obtain a polyvinyl pyrrolidone-stabilized molybdenum disulfide nanosheet dispersion.

[0044] (4) Under ultrasonic conditions, the molybdenum disulfide nanosheet dispersion was added dropwise to the polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion. After the addition was completed, the mixture was ultrasonically treated for 1.5 hours, then allowed to stand for 24 hours, filtered, and dried in a vacuum oven at 80°C for 24 hours to obtain a molybdenum disulfide / polyvinyl pyrrolidone / polyethyleneimine / multi-walled carbon nanotube quaternary complex. The mixture was then heat treated at 800°C for 1.5 hours under an inert gas atmosphere to remove the polyvinyl pyrrolidone and polyethyleneimine to obtain a nanocomposite negative electrode material of molybdenum disulfide / multi-walled carbon nanotubes.

[0045] Comparative Example 1:

[0046] The only difference between this comparative example and Example 1 is that MWCNTs are not added during the preparation process. The remaining raw materials and steps are the same as those in Example 1, and a MoS2 single-component negative electrode material is prepared.

[0047] Comparative Example 2:

[0048] The only difference between this comparative example and Example 1 is that MoS2 is not added during the preparation process. The remaining raw materials and steps are the same as those in Example 1, and a MWCNTs single-component negative electrode material is prepared.

[0049] Anode material performance test:

[0050] An electrode paste was prepared using the negative electrode materials prepared in Example 1 and Comparative Examples 1-2, carbon black as a conductive agent, and PVDF as a binder in a mass ratio of 85:10:5. PVDF was first dissolved in NMP, followed by the addition of carbon black and the negative electrode materials, thoroughly mixed, and diluted with NMP to an appropriate viscosity. The paste was then evenly coated onto a 0.1 nm thick copper foil current collector, dried in a 110°C oven for 4 hours, and pressed firmly on a double-roll press. The resulting copper foil was then cut into 1.2 cm diameter circular pieces for testing. A homemade battery was assembled under an inert atmosphere using lithium foil as the counter electrode, Celgard-2300 lithium-ion battery separator, and a 1.0 M LiPF6 solution in EC / EMC / DMC (1:1:1 by volume) as the electrolyte. Performance testing was then conducted on a LAND CT2001A charge-discharge tester. The charge and discharge tests were conducted at a current density of 100 mA / g and a voltage range of 3.0-0.0 V. The cyclic voltammetry tests were conducted at a scan rate of 0.2 mV / s and a voltage range of 3.0-0.0 V.

[0051] Figure 1The following graph shows the cycling performance of three negative electrode materials at 100 mA / g. As can be seen from the figure, the MoS2 material exhibits low specific capacity and poor cycling stability, while the MWCNTs material exhibits low specific capacity and excellent cycling stability. This is because MoS2 has a typical layered structure, making it suitable as an embedded electrode material for electrochemical lithium storage, providing a high theoretical specific capacity, but its cycling stability is poor. MWCNTs, used as negative electrode materials for lithium-ion batteries, have advantages such as numerous lithium insertion sites, easy lithium removal, and good cycling stability, but their irreversible capacity in the first cycle is large and their specific capacity is low. The MoS2 / MWCNTs nanocomposite negative electrode material, on the other hand, organically combines the two components and interacts with each other, exhibiting a high specific capacity and good cycling stability.

[0052] Figure 2 The figure shows the rate performance of three anode materials at different current densities. The current densities for cycles 1-5, 6-10, 11-15, 16-20, and 21-30 are 100mA / g, 200mA / g, 400mA / g, 800mA / g, and 200mA / g, respectively. The figure shows that when the current density changes from 800mA / g to 200mA / g, the MoS2 / MWCNTs nanocomposite anode material can recover over 90% of its initial specific capacity, demonstrating excellent rate performance and good reversible capacity. Furthermore, there is little capacity decay in subsequent cycling tests, demonstrating good cycling stability.

[0053] The above embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

Claims

1. A nanocomposite negative electrode material, characterized in that: The raw materials are calculated by weight and comprise: 3-4 parts of carbon nanotubes, 135-150 parts of concentrated nitric acid, 315-330 parts of concentrated sulfuric acid, 600-650 parts of dilute hydrochloric acid, 30-40 parts of anhydrous ethanol, 7.5-10 parts of polyethyleneimine, 25-30 parts of molybdenum disulfide, 10-12 parts of a surfactant, and 3325-3600 parts of deionized water; The carbon nanotubes are multi-walled carbon nanotubes, the surfactant is polyvinyl pyrrolidone, the concentration of the concentrated nitric acid is 65%, the concentration of the concentrated sulfuric acid is 98%, and the concentration of the dilute hydrochloric acid is 3%; The method for preparing the nanocomposite negative electrode material comprises the following steps: (1) Concentrated sulfuric acid and concentrated nitric acid were mixed and stirred evenly, and then multi-walled carbon nanotubes were added, ultrasonically dispersed for 10 minutes, and then transferred to an oil bath for reaction. After the reaction was completed, it was diluted with 1000-1200 parts of deionized water, allowed to stand overnight, filtered to remove the acid solution, and then washed with 1500 parts of deionized water for 3-4 times, washed twice with anhydrous ethanol, transferred to an oven for vacuum drying for 24 hours, and then transferred to a refrigerator for freezing for 5 hours. Then, it was freeze-dried to obtain pretreated multi-walled carbon nanotubes, which were added to 500 parts of deionized water and ultrasonically dispersed for 15 minutes to obtain a multi-walled carbon nanotube aqueous dispersion; (2) Add polyethyleneimine to 30 times the mass of deionized water and stir evenly to form a polyethyleneimine aqueous solution, then add it dropwise to the multi-walled carbon nanotube aqueous dispersion under ultrasonic conditions. After the addition is completed, continue ultrasonication for 1.5 hours, remove a small amount of precipitate by centrifugation, and obtain a polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion; (3) Molybdenum disulfide and polyvinyl pyrrolidone were added to 100 parts of deionized water and stirred evenly, and then ultrasonically dispersed until the dispersion turned dark green. The mixture was allowed to stand for 72 hours, and the supernatant was removed and transferred to a centrifuge tube. The mixture was centrifuged at 1500 rpm for 45 minutes, and the supernatant was removed again to obtain a polyvinyl pyrrolidone-stabilized molybdenum disulfide nanosheet dispersion. (4) Under ultrasonic conditions, the molybdenum disulfide nanosheet dispersion was added dropwise to the polyethyleneimine-coated multi-walled carbon nanotube aqueous dispersion. After the addition was completed, the mixture was ultrasonically treated for 1.5 hours, then allowed to stand for 24 hours, filtered, and dried in a vacuum oven for 24 hours to obtain a molybdenum disulfide / polyvinyl pyrrolidone / polyethyleneimine / multi-walled carbon nanotube quaternary complex. The mixture was then heat treated at 800°C for 1.5 hours under an inert gas atmosphere to remove the polyvinyl pyrrolidone and polyethyleneimine to obtain a nanocomposite negative electrode material of molybdenum disulfide / multi-walled carbon nanotubes.

2. The method for preparing a nanocomposite negative electrode material according to claim 1, wherein: The reaction in step (1) is carried out by stirring at 70° C. for 6 h.

3. The method for preparing a nanocomposite negative electrode material according to claim 2, wherein: The centrifugal operation in step (2) is a centrifugal operation with a rotation speed of 8000 r / min and a time of 5 min.

4. The method for preparing a nanocomposite negative electrode material according to claim 3, wherein: The oven in step (1) is a 60°C oven, and the oven in step (4) is an 80°C oven.

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