Lithium ion battery negative electrode material, preparation method and use thereof

Abstract

The application provides a lithium ion battery negative electrode material, a preparation method and application thereof, and the negative electrode material comprises a crystalline carbon base, nitrogen-doped and porous carbon nanotubes uniformly dispersed on the crystalline carbon base, and Co / CoO nanoparticles coated inside the carbon nanotubes and forming a pea pod structure with the carbon nanotubes. The carbon nanotubes prepared on the crystalline carbon base have high porosity, good dispersity and stable structure, and meanwhile, the high-capacity Co / CoO nanoparticles are wrapped, the expansion of the Co / CoO nanoparticles is effectively inhibited, the pea pod structure formed together with the crystalline carbon base forms a complex three-dimensional structure, thereby improving the electron and ion transmission, promoting the infiltration of the electrolyte, greatly improving the energy density, and the nitrogen doping further improves the electrochemical performance of the negative electrode material, and finally the rate performance and cycle stability of the lithium ion battery containing the negative electrode material are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, and relates to a lithium-ion battery anode material, its preparation method and application. Background Technology

[0002] Over the past thirty years, lithium-ion batteries have been widely used and extensively researched in both commercial and academic fields as a novel energy storage device. The future development of lithium-ion batteries continues to focus on high volumetric energy density and high mass energy density, long cycle life, stable rechargeability and pollution-free operation, small size and light weight, good safety, and low cost.

[0003] Currently, the main anode material for lithium-ion batteries is commercial graphite; however, the theoretical capacity of graphite anode materials is only 372 mAh g. -1 However, it is difficult to achieve the lithium storage capacity required by novel cathode materials. While novel carbon-based nanomaterials can exhibit high capacity performance as alternatives, the increased side reactions often result in an initial charge-discharge efficiency of less than 50%. Therefore, further development and optimization of novel carbon-based nanomaterials has become a hot research topic in the industry.

[0004] Transition metal oxides such as cobalt oxide have attracted widespread attention due to their high theoretical specific capacity. However, cobalt oxide materials have poor conductivity and are prone to volume expansion during lithium delithiation / intercalation, thus limiting their commercial application. For example, CN10563382A discloses a method for preparing cobalt oxide / graphene composite lithium-ion battery anode materials. This method uses an in-situ synthesis method with cobalt acetate as the cobalt source, lithium hydroxide as the precipitant, and water as the solvent. Utilizing the high cobalt precipitation rate of lithium hydroxide, a simple ultrasonication, stirring, and high-temperature calcination process is employed to prepare the cobalt oxide / graphene composite material. This method can achieve uniform cobalt oxide nanoparticle size and uniform dispersion on the graphene surface. However, the cobalt oxide component in the composite material obtained by this invention is still exposed outside the graphene, thus failing to effectively protect the cobalt oxide component and suppress its volume expansion during charge and discharge.

[0005] Currently, researchers primarily employ carbon coating, porous structures, and composite materials to address the volume expansion and conductivity issues of cobalt oxide materials. For example, CN110459740A discloses a carbon nanotube-coated cobalt oxide material, its preparation method, and its applications. A Co-PBA powder precursor is prepared using a cobalt source, polyvinylpyrrolidone, water, and potassium cobalt cyanide. Then, carbon nanotube-coated cobalt oxide is prepared using electrospinning and annealing processes. This carbon nanotube-coated cobalt oxide material has a large specific surface area, providing channels for ion transport and improving the specific capacity and charge / discharge efficiency of lithium batteries. Oxidation treatment of the carbonized nanospun fibers yields more active Co3O4 carbon nanofibers, further enhancing the overall battery capacity. However, this method is complex and cumbersome, requiring multiple steps including precursor preparation, electrospinning, carbonization, and annealing oxidation to obtain the final product, resulting in high costs and hindering large-scale production and application.

[0006] Therefore, it is necessary to develop a novel carbon anode material and a simple and low-cost preparation method to enable the anode material to have high capacity, high coulombic efficiency and long cycle stability. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of this invention is to provide a lithium-ion battery anode material, its preparation method, and its uses. The anode material includes a crystalline carbon substrate, nitrogen-doped carbon nanotubes uniformly dispersed on it, and Co / CoO nanoparticles encapsulated inside the carbon nanotubes, forming a pea-pod structure with the carbon nanotubes. The carbon nanotubes prepared on the crystalline carbon substrate by this invention have high porosity, good dispersibility, and stable structure. Simultaneously, it achieves the encapsulation of high-capacity Co / CoO nanoparticles, effectively suppressing their expansion. The resulting pea-pod structure, together with the crystalline carbon substrate, constitutes a complex three-dimensional structure, thereby improving electron and ion transport, promoting electrolyte wetting, and significantly increasing energy density. Nitrogen doping further improves the electrochemical performance of the anode material, ultimately resulting in a significant improvement in the rate performance and cycle stability of lithium-ion batteries containing this anode material.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, a lithium-ion battery anode material includes a crystalline carbon substrate, nitrogen-doped carbon nanotubes uniformly dispersed on the crystalline carbon substrate, and Co / CoO nanoparticles encapsulated inside the carbon nanotubes; the surface of the carbon nanotubes has a porous structure, and the carbon nanotubes and the Co / CoO nanoparticles form a pea pod structure.

[0010] This invention provides a composite carbon nanomaterial consisting of one-dimensional nitrogen-doped carbon nanotubes coated with cobalt / cobalt oxide nanoparticles and crystalline carbon. Specifically, it uses inexpensive, industrially producible crystalline carbon as a substrate to facilitate the formation of one-dimensional carbon nanotubes. The carbon nanotubes prepared using this substrate are one-dimensional hollow tubular structures, belonging to hard carbon materials. They possess a large specific surface area, high porosity, good dispersibility, and structural stability, which facilitates precise control of the diameter and wall thickness of the carbon nanotubes. Furthermore, the use of crystalline carbon as a substrate improves the graphitization degree of the resulting anode material and significantly increases its conductivity. Based on this, the carbon nanotubes serve as a Co / Co composite material. The "support" and "protective shell" of the O nanoparticles allow the high-theoretical-capacity Co / CoO nanoparticles to be uniformly dispersed on the inner wall and surface of the carbon nanotubes, effectively mitigating the volume expansion of the Co / CoO nanoparticles during charge and discharge, thereby improving battery stability. It also effectively enhances the conductivity between isolated carbon nanotubes and Co / CoO nanoparticles. Simultaneously, the pea-pod-like composite structure formed by carbon nanotubes encapsulating Co / CoO nanoparticles, together with the crystalline carbon substrate, constitutes a three-dimensional electron conduction network and a stable electrode structure network, ensuring sufficient contact between particles, promoting effective electrolyte wetting, and significantly increasing energy density. Furthermore, the carbon nanotubes are nitrogen-doped, further improving the electrochemical performance of the resulting anode material. When the resulting anode material is fabricated as an anode sheet and applied in lithium-ion batteries, the rate performance and cycle stability of the battery are effectively improved.

[0011] The pea pod structure described in this invention specifically refers to a one-dimensional hollow nitrogen-doped carbon nanotube as the outer shell of a pea pod, with Co / CoO nanoparticles as the pea kernel encased within the shell. This differs from the typical core-shell structure where a carbon coating layer is simply formed on the outside of the kernel. The pea pod structure obtained in this invention is complete, without significant breakage, and maintains the large aspect ratio of the carbon nanotubes, thus exhibiting superior charge transport performance. The resulting three-dimensional structure is also more conducive to the performance of the Co / CoO nanoparticles.

[0012] The Co / CoO nanoparticles described in this invention refer to a mixed phase formed by Co metal particles and CoO metal oxide particles, where both types of particles coexist and constitute the Co / CoO nanoparticles, as well as metal / metal oxide composite nanoparticles. Furthermore, the majority (approximately 95% or more) of the Co / CoO nanoparticles exist as a core within carbon nanotubes, while a small portion (approximately 0-5%) is dispersed on the surface of the carbon nanotubes.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0014] As a preferred technical solution of the present invention, the crystalline carbon substrate includes any one or a combination of at least two of expanded graphite, graphite powder, or graphene, preferably expanded graphite. Typical but non-limiting examples of the combination include combinations of expanded graphite and graphite powder, combinations of expanded graphite and graphene, and combinations of graphite powder and graphene.

[0015] The present invention preferably uses expanded graphite as the crystalline carbon substrate, because its good crystallinity and layered structure are more conducive to serving as the substrate and the supporting structure for the synthesized one-dimensional nitrogen-doped carbon nanotubes.

[0016] Preferably, the porous structure includes micropores and mesopores.

[0017] Preferably, the pore diameter of the porous structure is 1 to 50 nm, such as 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0018] Preferably, the specific surface area of ​​the carbon nanotubes with a porous structure is 40–64 m². 2 / g, for example 40m 2 / g、44m 2 / g、48m 2 / g、52m 2 / g、56m 2 / g、60m 2 / g or 64m 2 / g, etc., but not limited to the listed values; other unlisted values ​​within the above range also apply.

[0019] Preferably, the inner diameter of the carbon nanotube is 20–100 nm, such as 20 nm, 20 nm, 20 nm, 20 nm, 20 nm, 20 nm, 20 nm, or 100 nm, and the outer diameter is 55–500 nm, such as 55 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0020] The outer and inner diameters of the carbon nanotubes described in this invention can be adjusted according to actual needs. This invention found that when the outer diameter is controlled at 50 nm, the inner diameter can be controlled at 42 nm, and the tube wall thickness is 8 nm, which is the thinnest controllable tube wall thickness. In addition, when the inner diameter is 20 nm, the outer diameter can be controlled at a minimum of 55 nm.

[0021] Preferably, the pore volume of the lithium-ion battery negative electrode material is 0.1–2 cm. 3 / g, for example, 0.1cm 3 / g, 0.2cm 3 / g, 0.5cm 3 / g, 0.8cm 3 / g, 1.1cm 3 / g, 1.4cm 3 / g, 1.7cm 3 / g or 2cm 3 / g, etc., but not limited to the listed values; other unlisted values ​​within the above range also apply.

[0022] Preferably, the content of nitrogen-doped carbon nanotubes accounts for 10% to 30% of the total mass of the lithium-ion battery anode material, such as 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, or 30%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] Preferably, the Co / CoO nanoparticles have a particle size of 10–30 nm, such as 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, or 30 nm, but are not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0024] Preferably, the content of the Co / CoO nanoparticles accounts for 5% to 15% of the total mass of the lithium-ion battery anode material, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0025] Preferably, the nitrogen doping amount accounts for 1% to 3% of the total mass of the lithium-ion battery anode material, such as 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] Preferably, the degree of graphitization of the lithium-ion battery anode material is I. G / I D The range is 1.01 to 1.1, such as 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09 or 1.1, but it is not limited to the listed values. Other unlisted values ​​within the above range also apply.

[0027] The I described in this invention G / I D The data are Raman spectroscopy results, representing the degree of graphitization that affects the conductivity of the material. This degree of graphitization is mainly influenced by the crystallinity of nitrogen-doped carbon nanotubes generated from polyvinylpyrrolidone. The crystalline carbon substrate added in this invention, such as expanded graphite, is already a well-crystallized carbon-based material with high IT. G / I D value.

[0028] Secondly, the present invention provides a method for preparing the lithium-ion battery anode material described in the first aspect, the method comprising the following steps:

[0029] (1) Dissolve the cobalt source and polyvinylpyrrolidone in water to obtain a mixed solution;

[0030] (2) The mixed solution obtained in step (1) is vacuum-pressed into a crystalline carbon substrate and dried to obtain a powder precursor;

[0031] (3) The powder precursor obtained in step (2) is calcined at high temperature and then activated at high temperature to obtain lithium-ion battery anode material.

[0032] This invention utilizes polyvinylpyrrolidone (PVP) as a carbon nanotube precursor, crystalline carbon as a scaffold, and cobalt acetate as a catalyst. This allows PPVP to catalyze the formation of one-dimensional nitrogen-doped carbon nanotubes on the surface of crystalline carbon. Simultaneously, cobalt acetate gradually forms Co / CoO nanoparticles, which are then coated or loaded onto the surface of the grown carbon nanotubes. This one-step method constructs a negative electrode material with a complex three-dimensional structure. This three-dimensional structure is stable and facilitates electron conduction, ensuring sufficient contact between particles, promoting effective electrolyte wetting, and significantly improving energy density. The preparation method of this invention uses polyvinylpyrrolidone (PVP) as both a carbon source and a nitrogen source for nitrogen doping, eliminating the need for additional nitrogen-containing compounds. After nitrogen doping, nitrogen atoms are uniformly distributed on the surface of the carbon nanotube structure, which improves the conductivity and specific surface area of ​​the carbon nanotubes, thus optimizing the electrochemical performance of the resulting anode material. Furthermore, this invention obtains a complex three-dimensional anode material through a single calcination step, eliminating the need for multiple calcination processes. The high-temperature activation creates a porous structure on the surface of the carbon nanotubes, containing micropores and mesopores at different levels. This results in a highly active porous lithium-ion battery anode material with a larger specific surface area and higher porosity, promoting contact between the anode material and the electrolyte, thereby further improving electrochemical activity. The assembled lithium-ion battery exhibits higher energy density, rate performance, and cycle stability. The high-temperature activation process is simple and only aims to create pores, without affecting the morphology of the resulting anode material. The preparation method uses inexpensive raw materials, has a simple preparation process, and low cost. The resulting negative electrode material has good lithium storage performance and can be used to manufacture high-performance lithium-ion batteries, making it suitable for large-scale preparation and industrial application.

[0033] As a preferred technical solution of the present invention, the mass ratio of the cobalt source to the polyvinylpyrrolidone in step (1) is 1:(0.5~5), for example, it can also be 1:0.5, 1:1, 1:1.5, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, etc., preferably 1:2, but not limited to the listed values, other unlisted values ​​within the above range are also applicable.

[0034] Preferably, the cobalt source in step (1) includes cobalt acetate and / or cobalt citrate, with cobalt acetate being the most preferred.

[0035] Through experiments, this invention has found that when cobalt citrate is used as a catalyst, polyvinylpyrrolidone can also generate nitrogen-doped carbon nanotubes and encapsulate Co / CoO nanoparticles to form a pea pod structure. However, its ability to control the size of carbon nanotubes over a wide range is weaker than that of cobalt acetate.

[0036] As a preferred technical solution of the present invention, the vacuum pressing method in step (2) includes:

[0037] The mixed solution and the crystalline carbon were placed in a self-sealing bag, and the mixed solution was vacuum-pressed into the crystalline carbon substrate until there was no obvious liquid in the self-sealing bag. Then it was placed in an oven to dry, and the powder precursor was obtained.

[0038] The vacuum infusion refers to using the negative pressure generated by the porous structure of the crystalline carbon substrate itself to immerse the expanded crystalline carbon substrate in a solution, apply negative pressure from the outside, and then slowly release the vacuum. At this time, atmospheric pressure can force the solution into the pores of the crystalline carbon substrate. This method is different from other simple adsorption processes, which can only adsorb the solution onto the surface of expanded graphite, resulting in uneven carbon nanotube morphology and low yield.

[0039] Preferably, the mass ratio of the polyvinylpyrrolidone to the crystalline carbon substrate in the mixed solution in step (2) is 1:(1-4), preferably 1:2; for example, it can also be 1:1, 1:1.5, 1:2.5, 1:3, 1:3.5 or 1:4, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0040] Preferably, the drying temperature in step (2) is 70-90°C, such as 70°C, 75°C, 80°C, 85°C or 90°C, and the drying time is 12-48h, preferably 24h, but can also be 12h, 16h, 20h, 28h, 32h, 36h, 40h, 44h or 48h, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] As a preferred technical solution of the present invention, the high-temperature calcination temperature in step (3) is 600-1000℃, preferably 1000℃, and can also be 600℃, 700℃, 800℃, 900℃ or 1000℃, etc. The high-temperature calcination time is 2-8h, preferably 4h, and can also be 2h, 3h, 4h, 5h, 6h, 7h or 8h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0042] Preferably, the heating rate of the high-temperature calcination in step (3) is 1 to 10 °C / min, preferably 5 °C / min. For example, it can also be 1 °C / min, 3 °C / min, 7 °C / min, 9 °C / min or 10 °C / min, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] Preferably, the high-temperature calcination in step (3) is carried out under a protective atmosphere.

[0044] Preferably, the equipment used for high-temperature calcination in step (3) includes a tubular furnace.

[0045] Preferably, the protective atmosphere includes any one or a combination of at least two of nitrogen, helium, neon, argon, krypton, or xenon, with argon being the most preferred. Typical but non-limiting examples of such combinations include combinations of nitrogen and helium, nitrogen and neon, nitrogen and argon, nitrogen and xenon, and helium and argon.

[0046] Preferably, the flow rate of the protective atmosphere is 30-300 mL / min, more preferably 60 mL / min, and can also be 30 mL / min, 90 mL / min, 120 mL / min, 150 mL / min, 180 mL / min, 210 mL / min, 240 mL / min, 270 mL / min or 300 mL / min, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0047] As a preferred technical solution of the present invention, the high-temperature activation method includes placing the lithium-ion battery negative electrode material in an activation atmosphere and heating and keeping it warm.

[0048] Preferably, the activation atmosphere comprises a CO2 / Ar mixture.

[0049] Preferably, the concentration of CO2 in the CO2 / Ar mixture is 1% to 10%, preferably 2%, and can also be 1%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0050] Preferably, the flow rate of the activating atmosphere is 30-300 mL / min, more preferably 60 mL / min, and can also be 30 mL / min, 90 mL / min, 120 mL / min, 150 mL / min, 180 mL / min, 210 mL / min, 240 mL / min, 270 mL / min or 300 mL / min, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0051] Preferably, the heating and heat preservation temperature is 900-1100℃, such as 900℃, 920℃, 940℃, 960℃, 980℃, 1000℃, 1020℃, 1040℃, 1080℃ or 1100℃, etc., and the heat preservation time is 2-8h, preferably 4h, for example, it can also be 2h, 3h, 5h, 6h, 7h or 8h, etc., but it is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0052] Preferably, the heating and heat preservation rate is 1 to 10℃ / min, preferably 5℃ / min, and can also be 1℃ / min, 3℃ / min, 7℃ / min, 9℃ / min or 10℃ / min, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0053] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0054] (1) Dissolve the cobalt source and polyvinylpyrrolidone in deionized water at a mass ratio of 1:(0.5-5) to obtain a mixed solution with a concentration of 0.2-0.3 g / mL of the cobalt source; the cobalt source includes cobalt acetate and / or cobalt citrate.

[0055] (2) Place the mixed solution from step (1) and the crystalline carbon in a self-sealing bag, such that the mass ratio of the polyvinylpyrrolidone to the crystalline carbon substrate in the mixed solution is 1:(1-4). Vacuum press the mixed solution into the crystalline carbon until there is no obvious liquid in the self-sealing bag. Then place it in an oven and dry at 70-90°C for 12-48 hours to obtain the powder precursor. The crystalline carbon substrate includes any one or a combination of at least two of expanded graphite, graphite powder, or graphene.

[0056] (3) The powder precursor obtained in step (2) is calcined at 600-1000℃ for 2-8 hours under a protective atmosphere with a flow rate of 30-300 mL / min. Then it is placed in a CO2 / Ar mixture containing 2%-3% CO2, with the flow rate of the mixture set at 30-300 mL / min, and heated and kept at 900-1100℃ for 2-8 hours to perform high-temperature activation, and finally the lithium-ion battery anode material is obtained.

[0057] Thirdly, the present invention provides a negative electrode sheet containing the lithium-ion battery negative electrode material described in the first aspect.

[0058] Fourthly, the present invention provides a lithium-ion battery comprising the negative electrode sheet described in the third aspect.

[0059] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0060] This invention produces carbon nanotubes with high porosity, good dispersibility, and stable structure on a crystalline carbon substrate. Simultaneously, it encapsulates high-capacity Co / CoO nanoparticles, effectively suppressing their expansion. The resulting pea-pod-like structure, together with the crystalline carbon substrate, forms a complex three-dimensional structure, thereby improving electron and ion transport, promoting electrolyte wetting, and significantly increasing energy density. Nitrogen doping further enhances the electrochemical performance of the anode material. Further high-temperature activation creates pores on the surface of the carbon nanotubes, increasing their specific surface area and porosity, further enhancing the electrochemical activity of the resulting lithium-ion battery anode material. Ultimately, this significantly improves the rate performance and cycle stability of lithium-ion batteries containing this anode material. Attached Figure Description

[0061] Figure 1 This is a TEM image of the lithium-ion battery anode material obtained in Example 1;

[0062] Figure 2 This is a TEM image of the lithium-ion battery anode material obtained in Example 20;

[0063] Figure 3 This is a TEM image of the lithium-ion battery anode material obtained in Comparative Example 1.

[0064] Figure 4 This is a TEM image of the lithium-ion battery anode material obtained in Comparative Example 2;

[0065] Figure 5 This is an elemental distribution diagram of the lithium-ion battery anode material obtained in Example 1;

[0066] Figure 6 The X-ray photoelectron spectra of the lithium-ion battery anode materials obtained in Examples 1, 5 and 6 are shown.

[0067] Figure 7 The graph shows the rate performance test results of the lithium-ion battery anode material obtained in Example 1 at different current densities.

[0068] Figure 8 The graph shows the cycle performance test results of the lithium-ion battery anode material obtained in Example 1. Detailed Implementation

[0069] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be considered as specific limitations thereof.

[0070] Example 1

[0071] This embodiment provides a lithium-ion battery anode material and its preparation method, the preparation method including the following steps:

[0072] (1) Take 1.5g of polyvinylpyrrolidone and 0.75g of cobalt acetate and stir in 5mL of deionized water until completely dissolved to obtain a pink mixed solution;

[0073] (2) Take another 3g of expanded graphite (EG), place the mixed solution and the expanded graphite together in a self-sealing bag, and press the mixed solution into the expanded graphite for absorption in a vacuum oven at 60°C until there is no obvious liquid in the self-sealing bag. Increase the oven temperature to 80°C and seal it for 24 hours. After the end, let it cool naturally to room temperature to obtain the powder precursor.

[0074] (3) The powder precursor was placed in a ceramic boat and calcined at high temperature under a protective atmosphere of 60 mL / min argon. The temperature was increased to 1000℃ at a heating rate of 5℃ / min and held for 4 hours. The mixture was then naturally cooled to room temperature and placed in a tube furnace for high-temperature activation. A CO2 / Ar mixture with a flow rate of 60 mL / min and containing 2% CO2 was introduced as a protective atmosphere and held at 1000℃ for 4 hours at a heating rate of 5℃ / min to obtain the lithium-ion battery anode material.

[0075] Example 2

[0076] This embodiment provides a lithium-ion battery anode material and its preparation method, the preparation method including the following steps:

[0077] (1) Take 0.5g of polyvinylpyrrolidone and 1g of cobalt acetate and stir in 5mL of deionized water until completely dissolved to obtain a pink mixed solution;

[0078] (2) Take another 2g of expanded graphite, place the mixed solution and the expanded graphite together in a self-sealing bag, and press the mixed solution into the expanded graphite for absorption in a vacuum oven at 60°C through a vacuum environment until there is no obvious liquid in the self-sealing bag. Increase the oven temperature to 70°C and seal it for 48 hours. After the end, let it cool naturally to room temperature to obtain the powder precursor.

[0079] (3) The powder precursor was placed in a ceramic boat and calcined at high temperature under a protective atmosphere of nitrogen at a flow rate of 30 mL / min. The temperature was increased to 600°C at a heating rate of 1°C / min and held for 8 hours. The temperature was then naturally cooled to room temperature and placed in a tube furnace for high-temperature activation. A CO2 / Ar mixture with a flow rate of 300 mL / min and containing 5% CO2 was introduced as a protective atmosphere and the temperature was increased to 900°C at a heating rate of 1°C / min and held for 8 hours to obtain the lithium-ion battery anode material.

[0080] Example 3

[0081] This embodiment provides a lithium-ion battery anode material and its preparation method, the preparation method including the following steps:

[0082] (1) Take 2.5g of polyvinylpyrrolidone and 0.5g of cobalt acetate and stir in 5mL of deionized water until completely dissolved to obtain a pink mixed solution;

[0083] (2) Take another 2.5g of expanded graphite, place the mixed solution and the expanded graphite together in a self-sealing bag, and press the mixed solution into the expanded graphite for absorption in a vacuum oven at 60°C until there is no obvious liquid in the self-sealing bag. Increase the oven temperature to 90°C and seal it for 12 hours. After the end, let it cool naturally to room temperature to obtain the powder precursor.

[0084] (3) The powder precursor was placed in a ceramic boat and calcined at high temperature under a protective atmosphere of helium at a flow rate of 300 mL / min. The temperature was increased to 800°C at a heating rate of 10°C / min and held for 2 hours. The mixture was then naturally cooled to room temperature and placed in a tube furnace for high-temperature activation. A CO2 / Ar mixture containing 10% CO2 was introduced at a flow rate of 30 mL / min as a protective atmosphere and held at 1100°C for 2 hours at a heating rate of 10°C / min to obtain the lithium-ion battery anode material.

[0085] Example 4

[0086] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as in Example 1, except that the amount of polyvinylpyrrolidone in step (1) is adjusted from 1.5g to 0.375g, so that the mass ratio of cobalt acetate to polyvinylpyrrolidone is changed from 1:2 to 1:0.5, and the amount of expanded graphite in step (2) is adjusted from 3g to 0.75g, so that the mass ratio of polyvinylpyrrolidone to expanded graphite remains unchanged at 1:2.

[0087] Example 5

[0088] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as in Example 1, except that the amount of polyvinylpyrrolidone in step (1) is adjusted from 1.5g to 0.75g, so that the mass ratio of cobalt acetate to polyvinylpyrrolidone is changed from 1:2 to 1:1, and the amount of expanded graphite in step (2) is adjusted from 3g to 1.5g, so that the mass ratio of polyvinylpyrrolidone to expanded graphite remains unchanged at 1:2.

[0089] Example 6

[0090] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as in Example 1, except that the amount of polyvinylpyrrolidone in step (1) is adjusted from 1.5g to 3.75g, so that the mass ratio of cobalt acetate to polyvinylpyrrolidone is changed from 1:2 to 1:5, and the amount of expanded graphite in step (2) is adjusted from 3g to 7.5g, so that the mass ratio of polyvinylpyrrolidone to expanded graphite remains unchanged at 1:2.

[0091] Example 7

[0092] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as in Example 1, except that the amount of polyvinylpyrrolidone in step (1) is adjusted from 1.5g to 4g, so that the mass ratio of cobalt acetate to polyvinylpyrrolidone is changed from 1:2 to 1:5.33, and the amount of expanded graphite in step (2) is adjusted from 3g to 8g, so that the mass ratio of polyvinylpyrrolidone to expanded graphite remains unchanged at 1:2.

[0093] Example 8

[0094] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Embodiment 1, except that the high-temperature calcination temperature in step (3) is adjusted from 1000℃ to 500℃.

[0095] Example 9

[0096] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Embodiment 1, except that the high-temperature calcination temperature in step (3) is adjusted from 1000℃ to 600℃.

[0097] Example 10

[0098] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Embodiment 1, except that the high-temperature calcination temperature in step (3) is adjusted from 1000℃ to 1100℃.

[0099] Example 11

[0100] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Embodiment 1, except that the high-temperature activation temperature in step (3) is adjusted from 1000℃ to 800℃.

[0101] Example 12

[0102] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Embodiment 1, except that the high-temperature calcination temperature in step (3) is adjusted from 1000℃ to 900℃.

[0103] Example 13

[0104] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Embodiment 1, except that the high-temperature calcination temperature in step (3) is adjusted from 1000℃ to 1100℃.

[0105] Example 14

[0106] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Example 1, except that the high-temperature calcination temperature in step (3) is adjusted from 1000℃ to 1200℃.

[0107] Example 15

[0108] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Example 1, except that the expanded graphite in step (2) is replaced with graphite powder.

[0109] Example 16

[0110] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Example 1, except that the expanded graphite in step (2) is replaced with graphene.

[0111] Example 17

[0112] This embodiment provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Example 1, except that the cobalt acetate in step (1) is replaced with cobalt citrate.

[0113] Comparative Example 1

[0114] This comparative example provides a lithium-ion battery anode material and its preparation method. The preparation method does not include the addition of polyvinylpyrrolidone in step (1), and the other conditions are exactly the same as in Example 1.

[0115] Comparative Example 2

[0116] This comparative example provides a lithium-ion battery anode material and its preparation method. The preparation method does not include the cobalt acetate in step (1), and the other conditions are exactly the same as in Example 1.

[0117] Comparative Example 3

[0118] This comparative example provides a lithium-ion battery anode material and its preparation method. The preparation method is exactly the same as that in Example 1, except that polyvinylpyrrolidone in step (1) is replaced with urea.

[0119] Comparative Example 4

[0120] This comparative example provides a lithium-ion battery anode material and its preparation method. The preparation method does not perform high-temperature activation in step (3). Instead, the product that has been calcined at high temperature and then naturally cooled to room temperature is directly used as the lithium-ion battery anode material.

[0121] TEM tests were performed on the negative electrode materials obtained in Examples 1, 20, 1, and 2. The results are as follows: Figure 1-4 As shown in the figure, the structure of the negative electrode material obtained in Example 1 is a three-dimensional structure composed of one-dimensional carbon nanotubes encapsulating Co / CoO nanoparticles and expanded graphite. The presence of hollow structures is clearly visible in the material. The material has a large specific surface area, which is beneficial for containing the volume changes of metal nanoparticles during charging and discharging. In Example 20, graphite powder was used instead of expanded graphite. The resulting negative electrode material contained carbon nanotubes and could load and encapsulate a certain amount of Co / CoO nanoparticles. However, the overall structure was composed of a small number of non-uniform carbon nanotubes and a large amount of carbon foam-like structure composite graphite powder, and its dispersibility was slightly lower than that of the product obtained in Example 1. In Comparative Example 1, the negative electrode material obtained without the use of polyvinylpyrrolidone did not show obvious carbon nanotube formation. Its material was a composite structure of cobalt nanoparticles and expanded graphite. In Comparative Example 2, the negative electrode material obtained without the use of cobalt acetate did not show obvious carbon nanotube formation. Its material was a composite structure of nitrogen-doped carbon nanosheets and expanded graphite.

[0122] Figure 5 This is an elemental distribution diagram of the lithium-ion battery anode material obtained in Example 1. It can be seen from the diagram that nitrogen is only distributed on the surface of one-dimensional carbon nanotubes.

[0123] Figure 6 The figures show the X-ray photoelectron spectroscopy (XPS) of the anode materials obtained in Examples 1, 5, and 6. As can be seen from the figures, nitrogen doping was successfully performed on the anode materials.

[0124] The negative electrode materials obtained in each embodiment and comparative example were prepared as electrodes and batteries for electrochemical performance testing: The obtained negative electrode materials were mixed with acetylene black and PVDF at a mass ratio of 8:1:1, using NMP as a solvent, and ground to form a slurry. This slurry was then coated onto copper foil using a doctor blade as the negative electrode, and lithium metal sheets were used as the positive electrode. A Celgard 2400 separator was used. 1M LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a volume ratio of 1:1:1 to form the electrolyte. The above materials were assembled into button cells in a glove box. Constant current charge-discharge tests were performed using a Neware battery testing system, with a charge-discharge voltage range of 0.01–3.0V, yielding a result of 0.1 A·g. -1 The reversible discharge specific capacity at current density, capacity retention rate after 180 cycles, and coulombic efficiency are shown in Table 1.

[0125] Figure 7 The rate performance of the negative electrode material obtained in Example 1 at different current densities in the battery is shown in the figure: As can be seen from the figure, at 0.05 A·g -1 0.1A·g -1 0.2A·g -1 0.5A·g -1 1.0A·g -1 2.0A·g -1 5.0A·g -1 10.0 A·g -1 The reversible discharge specific capacity at current density is 1164 mAh·g. -1 1003mAh·g -1 909mAh·g -1 714mAh·g -1 597mAh·g -1 472mAh·g -1 330mAh·g -1 180mAh·g -1 It exhibits excellent rate performance; Figure 8 This is the cycle performance of the negative electrode material obtained in Example 1. As can be seen from the figure, at 0.1 A·g... -1 At current density, the capacity retention rate is above 99% after 180 cycles, and the coulombic efficiency is above 99%.

[0126] Table 1

[0127]

[0128]

[0129] As can be seen from Table 1:

[0130] (1) Compared with Comparative Examples 1-3, Example 1 produced a large number of nitrogen-doped carbon nanotube structures with controllable morphology. In Comparative Examples 1-3, no carbon nanotube structures were produced. The material obtained in Example 1, compared with the material obtained in Comparative Examples 1-3, shows obvious advantages in specific capacity and capacity retention rate in the application field of lithium-ion battery anode materials. It also shows certain advantages in charge-discharge efficiency after long cycles.

[0131] (2) Compared to Comparative Example 4, Example 1 was not subjected to high-temperature activation (pore formation). Therefore, compared to Example 1, the battery made using the unactivated material in Comparative Example 4 had a specific capacity that was 440 mAh·g less than that made using the activated material. -1 (at 0.1A·g) -1 (Charging and discharging at current density), but high-temperature activation (pore-forming process) does not affect the morphology.

[0132] (3) Compared with Example 1, Examples 4-7 adjusted the mass ratio of polyvinylpyrrolidone (PVP) and cobalt acetate, but maintained the mass ratio of PPVP to the crystalline carbon substrate. The results showed that one-dimensional nitrogen-doped carbon nanotube structures could be obtained in Examples 4-7. The difference was that the uniform and controllable carbon nanotube structure formed in Example 1, while Examples 4-8 generated different amounts of carbon foam structures. The ratios of carbon nanotubes to carbon foam were 1:0; 1:1.5; 1:1.8; 1:2.5; 1:2.2; and 1:1.3. Excessive PPVP would form more carbon foam, thus affecting the specific capacity of the lithium-ion battery anode material. However, thanks to the stability of the carbon material itself, the stability and coulombic efficiency of the anode material could remain stable. Insufficient PPVP would lead to more metal / metal oxide particles being exposed in the electrolyte. During charge and discharge, the lack of carbon structure could not protect against volume changes, thus reducing the capacity retention rate.

[0133] (5) Compared with Examples 12-14, Example 1 controlled the high-temperature calcination temperature, i.e., the pyrolysis temperature. If the temperature was too high, the nitrogen content would decrease. Although this effectively improved the degree of graphitization, the performance would decrease. If the temperature was too low, the carbon nanotubes would not form completely, and the degree of graphitization of the carbon structure would be low, resulting in decreased conductivity. Therefore, the performance of the lithium-ion battery anode material would decrease.

[0134] (6) Compared with Examples 15-18, Examples 15-18 controlled the temperature of high-temperature activation. When the activation temperature is below 1000 degrees Celsius, the reaction between CO2 and C structure is slow and cannot form obvious microporous structure. Therefore, the performance is significantly reduced. When the temperature is too high or the activation time is too long, the nitrogen content will decrease significantly, resulting in a significant performance decrease.

[0135] (7) Compared with Examples 19-20, in Examples 19 and 20, expanded graphite was replaced with graphite powder and graphene respectively. Carbon nanotubes were generated, but the uniformity and integrity were poor. Therefore, the performance of the lithium-ion battery anode was significantly reduced.

[0136] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0137] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0138] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0139] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A lithium-ion battery anode material, characterized in that, The lithium ion battery negative electrode material comprises a crystalline carbon base, nitrogen-doped carbon nanotubes uniformly dispersed on the crystalline carbon base, and Co / CoO nanoparticles coated inside the carbon nanotubes; the surface of the carbon nanotubes has a porous structure, and the carbon nanotubes and the Co / CoO nanoparticles form a pea pod structure. The preparation method of the lithium ion battery negative electrode material comprises the following steps: (1) dissolving a cobalt source and polyvinylpyrrolidone in water to obtain a mixed solution; (2) vacuum-pressing the mixed solution obtained in step (1) into a crystalline carbon base, and drying to obtain a powder precursor; (3) high-temperature calcining and high-temperature activating the powder precursor obtained in step (2) to obtain the lithium ion battery negative electrode material; The temperature of the high-temperature calcining is 600-1000°C; The temperature of the high-temperature activation is 900-1100°C.

2. The lithium-ion battery anode material of claim 1, wherein, The crystalline carbon base comprises any one or a combination of at least two of expanded graphite, graphite powder or graphene.

3. The lithium-ion battery anode material of claim 1, wherein, The porous structure comprises micropores and mesopores.

4. The lithium-ion battery anode material of claim 1, wherein, The pore diameter of the porous structure is 1-50 nm.

5. The lithium-ion battery anode material of claim 1, wherein, The specific surface area of the carbon nanotubes having a porous structure is 40 ~ 64 m 2 / g.

6. The lithium-ion battery anode material of claim 1, wherein, The inner diameter of the carbon nanotubes is 20-100 nm, and the outer diameter is 55-500 nm.

7. The lithium-ion battery anode material of claim 1, wherein, The lithium ion battery negative electrode material has a pore volume of 0.1-2 cm 3 / g.

8. The lithium-ion battery anode material of claim 1, wherein, The content of the nitrogen-doped carbon nanotubes accounts for 10%-30% of the total mass of the lithium ion battery negative electrode material.

9. The lithium-ion battery anode material of claim 1, wherein, The particle size of the Co / CoO nanoparticles is 10-30 nm.

10. The lithium-ion battery anode material of claim 1, wherein, The content of the Co / CoO nanoparticles accounts for 5%-15% of the total mass of the lithium ion battery negative electrode material.

11. The lithium-ion battery anode material of claim 1, wherein, The doping amount of the nitrogen doping accounts for 1%-3% of the total mass of the lithium ion battery negative electrode material.

12. The lithium-ion battery anode material of claim 1, wherein, Degree of graphitization I of the lithium-ion battery negative electrode material G / I D is 1.01-1.

1.

13. A method of producing the negative electrode material of any one of claims 1 to 12, characterized in that, The preparation method comprises the following steps: (1) dissolving a cobalt source and polyvinylpyrrolidone in water to obtain a mixed solution; (2) vacuum-pressing the mixed solution obtained in step (1) into a crystalline carbon base, and drying to obtain a powder precursor; (3) high-temperature calcining and high-temperature activating the powder precursor obtained in step (2) to obtain the lithium ion battery negative electrode material; The temperature of the high-temperature calcining is 600-1000°C; The temperature of the high-temperature activation is 900-1100°C.

14. The method of claim 13, wherein the lithium ion battery anode material is prepared by the method comprising: The mass ratio of the cobalt source to the polyvinylpyrrolidone in step (1) is 1:(0.5-5). ​ 15. The method of claim 13, wherein the lithium ion battery anode material is prepared by the method comprising: The mass ratio of the cobalt source to the polyvinylpyrrolidone in step (1) is 1:

2. ​ 16. The method of claim 13, wherein the lithium ion battery anode material is prepared by the method comprising: The cobalt source in step (1) comprises cobalt acetate and / or cobalt citrate. ​ 17. The method for preparing the lithium-ion battery negative electrode material according to claim 13, characterized in that, The method of the vacuum-pressing in step (2) comprises: Placing the mixed solution and the crystalline carbon in a self-sealing bag, vacuum-pressing the mixed solution into the crystalline carbon base until no obvious liquid exists in the self-sealing bag, and then drying in an oven to obtain the powder precursor.

18. The method for preparing the lithium-ion battery negative electrode material according to claim 13, characterized in that, The mass ratio of the polyvinylpyrrolidone in the mixed solution to the crystalline carbon base in step (2) is 1:(1-4).

19. The method of claim 13, wherein the lithium ion battery anode material is prepared by the method comprising: mixing the carbon material, the metal oxide, and the binder to form a mixture; and coating the mixture on a current collector to form the lithium ion battery anode material. The mass ratio of the polyvinylpyrrolidone in the mixed solution to the crystalline carbon base in step (2) is 1:

2.

20. The method for preparing the lithium-ion battery negative electrode material according to claim 13, characterized in that, The temperature of the drying in step (2) is 70-90°C, and the time is 12-48 h.

21. The method for preparing the lithium-ion battery negative electrode material according to claim 13, characterized in that, The time of the drying in step (2) is 24 h.

22. The method for preparing the lithium-ion battery anode material according to claim 13, characterized in that, The temperature of the high-temperature calcining in step (3) is 1000°C.

23. The method for preparing the lithium-ion battery anode material according to claim 13, characterized in that, The high-temperature calcination in step (3) is performed for 2-8 h.

24. The method for preparing the lithium-ion battery anode material according to claim 13, characterized in that, The high-temperature calcination in step (3) is performed for 4 h.

25. The method for preparing the lithium-ion battery anode material according to claim 13, characterized in that, The high-temperature calcination in step (3) is performed at a heating rate of 1-10 ℃ / min.

26. The method of making a lithium-ion battery anode material of claim 13, wherein, The high-temperature calcination in step (3) is performed at a heating rate of 5 ℃ / min.

27. The method of producing a lithium-ion battery anode material according to claim 13, wherein The high-temperature calcination in step (3) is performed under a protective atmosphere.

28. The method of producing a lithium-ion battery anode material of claim 13, wherein, The high-temperature calcination in step (3) is performed using a tube furnace.

29. The method for preparing the lithium-ion battery anode material according to claim 27, characterized in that, The protective atmosphere comprises any one or a combination of at least two of nitrogen, helium, neon, argon, krypton or xenon.

30. The method for preparing the lithium-ion battery anode material according to claim 27, characterized in that, The protective atmosphere is argon.

31. The method of making a lithium-ion battery anode material of claim 27, wherein, The flow rate of the protective atmosphere is 30-300 mL / min.

32. The method of producing a lithium-ion battery anode material of claim 27, wherein, The flow rate of the protective atmosphere is 60 mL / min.

33. The method of producing a lithium-ion battery anode material according to claim 13, wherein The high-temperature activation method comprises heating and holding the lithium-ion battery negative electrode material in an activation atmosphere.

34. The method of producing a lithium-ion battery anode material according to claim 33, wherein The activation atmosphere comprises CO2 / Ar mixed gas.

35. The method for preparing the lithium-ion battery anode material according to claim 34, characterized in that, The concentration of CO2 in the CO2 / Ar mixed gas is 1%-10%.

36. The method of making a lithium-ion battery anode material of claim 34, wherein, The concentration of CO2 in the CO2 / Ar mixed gas is 2%.

37. The method of producing a lithium-ion battery anode material of claim 33, wherein, The flow rate of the activation atmosphere is 30-300 mL / min.

38. The method of producing a lithium-ion battery anode material of claim 33, wherein, The flow rate of the activation atmosphere is 60 mL / min.

39. The method of producing a lithium-ion battery anode material of claim 33, wherein, The heating and holding is performed for 2-8 h.

40. The method of producing a lithium-ion battery anode material of claim 33, wherein, The heating and holding is performed for 4 h.

41. The method of producing a lithium-ion battery anode material of claim 33, wherein, The heating and holding is performed at a heating rate of 1-10 ℃ / min.

42. The method of producing a lithium-ion battery anode material of claim 33, wherein, The heating and holding is performed at a heating rate of 5 ℃ / min.

43. The method of producing a lithium-ion battery anode material of claim 13, wherein, The preparation method comprises the following steps: (1) dissolving a cobalt source and polyvinylpyrrolidone in deionized water at a mass ratio of 1:(0.5-5) to obtain a mixed solution, wherein the concentration of the cobalt source is 0.2-0.3 g / mL, and the cobalt source comprises cobalt acetate and / or cobalt citrate; (2) placing the mixed solution in step (1) and the crystalline carbon in a self-sealing bag, wherein the mass ratio of the polyvinylpyrrolidone in the mixed solution to the crystalline carbon substrate is 1:(1-4), vacuum-pressing the mixed solution into the crystalline carbon, and then drying the self-sealing bag in an oven at 70-90 ℃ for 12-48 h to obtain the powder precursor; the crystalline carbon substrate comprises any one or a combination of at least two of expanded graphite, graphite powder or graphene; (3) high-temperature calcining the powder precursor obtained in step (2) at 600-1000 ℃ for 2-8 h under a protective atmosphere with a flow rate of 30-300 mL / min, and then heating and holding at 900-1100 ℃ for 2-8 h in CO2 / Ar mixed gas containing 2%-3% CO2, wherein the flow rate of the mixed gas is 30-300 mL / min, to perform high-temperature activation, thereby obtaining a lithium-ion battery negative electrode material.

44. A negative electrode sheet characterized by comprising: The negative electrode sheet contains the lithium-ion battery negative electrode material according to any one of claims 1-12.

45. A lithium-ion battery, characterized in that, The lithium-ion battery contains the negative electrode sheet according to claim 44.

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