High-rate natural graphite composite negative electrode material, preparation method and application thereof

Abstract

This invention provides a high-rate natural graphite composite anode material, its preparation method, and its application. First, silane coupling agent-grafted nano-acetylene black is embedded into the interlayer and surface of graphene oxide using electrostatic self-assembly technology. Then, the graphene embedded with nano-acetylene black is heat-treated to coat the surface of natural flake graphite. During the shaping process, the natural flake graphite curls into a spherical shape, and the graphene embedded with nano-acetylene black coated on the surface of the natural flake graphite is also curled onto the inner and outer surfaces of the curled layer of the spherical graphite, meaning that part of the graphene embedded with nano-acetylene black is encapsulated within the spherical graphite. Finally, it is coated with pitch, and the pitch coating on the surface of the spherical graphite is carbonized into amorphous carbon. Through this method, the rate performance of the obtained battery is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material preparation technology, specifically relating to a high-rate natural graphite composite anode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries possess a range of advantages, including high specific capacity, stable operating voltage, good safety, and no memory effect, making them widely used in portable electronic devices such as laptops, mobile phones, and instruments. With the rapid development of various electronic devices and electric vehicles, the demand for energy density in lithium-ion batteries is increasing. The negative electrode material is a crucial component of the battery, and together with the positive electrode material, it determines key performance characteristics such as cycle life, capacity, and safety, making it a focus of research worldwide.

[0003] Currently, the main anode materials for commercially available lithium-ion batteries are modified natural graphite and artificial graphite. Although the preparation technology is quite mature, the increasingly stringent requirements for lithium-ion batteries, especially the demanding high-rate requirements for power batteries, mean that modified natural graphite and artificial graphite cannot meet practical applications. Natural graphite is abundant and does not require an expensive graphitization process, but its rate performance remains a drawback, unable to match that of artificial graphite. Therefore, improving the rate performance of natural graphite remains a pressing technical challenge in the lithium-ion battery field. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high-rate natural graphite composite anode material, its preparation method, and its application. The natural graphite composite anode material features high rate performance.

[0005] Specifically, the present invention provides the following technical solution:

[0006] A method for preparing a natural graphite composite anode material, the method comprising the following steps:

[0007] (1) The nano-acetylene black grafted with silane coupling agent was mixed with an organic solution containing graphene oxide and reacted to obtain precursor A.

[0008] (2) The precursor A from step (1) is mixed with an organic solution containing natural flake graphite to obtain precursor B;

[0009] (3) Heat-treat the precursor B from step (2) and cool it to obtain precursor C;

[0010] (4) Shape and grade the precursor C from step (3) to obtain precursor D;

[0011] (5) The precursor D from step (4) is mixed with asphalt and then carbonized. After cooling, it is broken up and sieved to obtain the natural graphite composite anode material.

[0012] According to an embodiment of the present invention, in step (1), the average particle size of the nano-acetylene black is 10-50 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm or 50 nm.

[0013] According to an embodiment of the present invention, in step (1), the silane coupling agent is selected from silane coupling agents containing amino groups, such as 3-aminopropyltriethoxysilane (APTES).

[0014] According to an embodiment of the present invention, in step (1), the silane coupling agent-grafted nano-acetylene black is prepared by the following method: adding the silane coupling agent to an organic solution containing nano-acetylene black such as ethanol or acetone, stirring, and preparing the silane coupling agent-grafted nano-acetylene black.

[0015] According to an embodiment of the present invention, in step (1), the mass ratio of the silane coupling agent to the nano-acetylene black is 0.05 to 0.5:100, such as 0.1:100, 0.2:100, 0.3:100, 0.4:100, or 0.5:100. The introduction of the silane coupling agent can achieve the effect of having a positive charge on the surface of the nano-acetylene black, which is beneficial for the nano-acetylene black to embed into the interlayer and surface of graphene oxide.

[0016] According to an embodiment of the present invention, in step (1), the mass-to-volume ratio of graphene oxide to organic solution in the organic solution containing graphene oxide is 0.1 mg (graphene oxide): (1-5) mL (organic solution), such as 0.1 mg: 1 mL, 0.1 mg: 2 mL, 0.1 mg: 3 mL, 0.1 mg: 4 mL or 0.1 mg: 5 mL.

[0017] According to an embodiment of the present invention, in step (1), the organic solution containing graphene oxide is formed by dissolving graphene oxide in an organic solvent such as ethanol, methanol or acetone.

[0018] According to an embodiment of the present invention, in step (1), the graphene oxide in the organic solution containing graphene oxide is a single layer or multiple layers (2-10 layers) of graphene oxide.

[0019] According to an embodiment of the present invention, in step (1), the organic solvent in the organic solution containing graphene oxide is selected from ethanol, methanol or acetone.

[0020] According to an embodiment of the present invention, in step (1), the mass ratio of the nano-acetylene black to graphene oxide is (20-40):100, for example, 20:100, 25:100, 30:100, 35:100 or 40:100.

[0021] According to an embodiment of the present invention, in step (1), the reaction time is 1-10 hours, such as 2-8 hours, such as 3-6 hours.

[0022] According to an embodiment of the present invention, in step (1), the reaction is carried out under stirring conditions.

[0023] According to an embodiment of the present invention, in step (1), during the stirring process, the silane coupling agent-grafted nano-acetylene black can be embedded into the interlayer and surface of graphene oxide, that is, the precursor A is formed by the embedding of silane coupling agent-grafted nano-acetylene black into the interlayer and surface of graphene oxide.

[0024] According to an embodiment of the present invention, in step (2), the mass ratio of graphene oxide to natural flake graphite in the precursor A is (5-10):100, for example, 5:100, 6:100, 7:100, 8:100, 9:100 or 10:100.

[0025] According to an embodiment of the present invention, in step (2), the natural flake graphite is flake-shaped.

[0026] According to an embodiment of the present invention, in step (2), the mass content of fixed carbon in the natural flake graphite is ≥99.0%; the average particle size of the natural flake graphite is D. 50 The value is 12-22 μm, for example 14-20 μm, with examples being 14 μm, 16 μm, 18 μm, 20 μm or 22 μm.

[0027] According to an embodiment of the present invention, in step (2), the organic solvent in the organic solution containing natural flake graphite is selected from ethanol, methanol or acetone.

[0028] According to an embodiment of the present invention, in step (2), the mixing time is 2-8 hours, such as 3-6 hours.

[0029] According to an embodiment of the present invention, in step (2), the mixing is carried out under stirring conditions.

[0030] According to an embodiment of the present invention, step (2) further includes post-processing steps such as filtration, washing, and drying after mixing.

[0031] According to an embodiment of the present invention, in step (2), the organic solution containing natural flake graphite is formed by dissolving natural flake graphite in organic solvents such as ethanol, methanol or acetone.

[0032] According to an embodiment of the present invention, in step (2), the concentration of the organic solution containing natural flake graphite is (1-3) g / L, for example, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L or 3 g / L.

[0033] According to an embodiment of the present invention, in step (2), the natural flake graphite is preferably micro-expanded natural flake graphite. The d of the micro-expanded natural flake graphite... 002 The wavelength is 0.3360nm-0.3367nm, preferably 0.3361nm-0.3366nm, for example 0.3362nm, 0.3363nm, 0.3364nm or 0.3365nm. The micro-expanded natural flake graphite has a large interlayer spacing, which is beneficial for the rapid insertion and extraction of lithium ions during charging and discharging, thereby improving the rate performance of the battery.

[0034] According to an embodiment of the present invention, in step (3), the heat treatment is carried out under a nitrogen or argon atmosphere.

[0035] According to an embodiment of the present invention, in step (3), the temperature of the heat treatment is 500℃-800℃, such as 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃; the time of the heat treatment is 5-10 hours, such as 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0036] According to an embodiment of the present invention, in step (3), during the heat treatment process, graphene oxide grafted with silane coupling agent and surface-mounted nano-acetylene black can be coated onto the surface of natural flake graphite, and the finally obtained precursor C includes graphene, natural flake graphite and nano-acetylene black; wherein, the graphene is coated onto the surface of natural flake graphite, and the graphene is embedded with nano-acetylene black in the interlayer and on the surface.

[0037] According to an embodiment of the present invention, in step (4), the equipment used for shaping can be a mechanical shaping machine or an airflow shaping machine. The equipment used for grading can be a grading machine.

[0038] According to an embodiment of the present invention, in step (4), the precursor D is spherical, elliptical, or potato-shaped.

[0039] According to an embodiment of the present invention, in step (4), the median particle size D of the precursor D is... 50It is 10-20μm, for example 12-18μm, with 12μm, 14μm, 16μm or 18μm being examples.

[0040] According to an embodiment of the present invention, in step (5), the mass ratio of the asphalt to the precursor D is (1-5):100, for example, 1:100, 2:100, 3:100, 4:100 or 5:100.

[0041] According to an embodiment of the present invention, in step (5), the softening point of the asphalt is 150-200℃, for example 160-180℃, exemplarily 150℃, 160℃, 180℃, or 200℃. The carbon residue of the asphalt is ≥50%, exemplarily 50% or 60%.

[0042] According to an embodiment of the present invention, in step (5), the carbonization temperature is 800℃-1200℃, such as 800℃, 900℃, 1000℃, or 1200℃; the carbonization time is 5-10 hours, such as 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours. The carbonization is carried out under an inert atmosphere, such as a nitrogen atmosphere or an argon atmosphere. Further, after the carbonization is completed, the resulting product is allowed to cool naturally under an inert atmosphere.

[0043] According to an embodiment of the present invention, in step (5), the particle shape of the natural graphite composite negative electrode material is spherical, approximately spherical, oval, potato-shaped and / or blocky.

[0044] The present invention also provides a natural graphite composite anode material, which is prepared by the above method.

[0045] According to an embodiment of the present invention, the natural graphite composite anode material is a high-rate natural graphite composite anode material.

[0046] According to an embodiment of the present invention, the natural graphite composite negative electrode material includes nano-acetylene black, graphene, natural graphite, and amorphous carbon.

[0047] According to an embodiment of the present invention, the amorphous carbon is coated on the outer surface of the natural graphite composite negative electrode material.

[0048] According to an embodiment of the present invention, the nano-acetylene black is distributed on the surface and between layers of graphene to form graphene embedded with nano-acetylene black.

[0049] According to an embodiment of the present invention, graphene with nano-acetylene black distributed on the surface and between layers (i.e., graphene embedded with nano-acetylene black) is filled into the interior of natural graphite.

[0050] According to an embodiment of the present invention, the natural graphite is natural spherical graphite, which is prepared by shaping natural flake graphite. Exemplarily, during the shaping process, the natural flake graphite is rolled into spherical graphite, and simultaneously, the graphene embedded with nano-acetylene black, which is coated on the surface of the natural flake graphite, is also rolled onto the inner and outer surfaces of the rolled layer of the spherical graphite; that is, some of the graphene embedded with nano-acetylene black is encased inside the spherical graphite.

[0051] According to an embodiment of the present invention, the natural graphite is micro-expanded natural graphite.

[0052] According to an embodiment of the present invention, in the natural graphite composite negative electrode material, the mass percentage of nano-acetylene black is 1-3%, the mass percentage of graphene is 3-10%, the mass percentage of natural graphite is 85-92%, and the mass percentage of amorphous carbon is 1-5%.

[0053] Preferably, the mass percentage of nano-acetylene black is 1%, 2%, or 3%, the mass percentage of graphene is 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, the mass percentage of natural graphite is 85%, 86%, 87%, 88%, 90%, or 92%, and the mass percentage of amorphous carbon is 1%, 2%, 3%, 4%, or 5%.

[0054] According to an embodiment of the present invention, the initial charge-discharge efficiency of the natural graphite composite anode material is ≥91%.

[0055] According to an embodiment of the present invention, the natural graphite / composite negative electrode material retains a 3C charge-discharge capacity of over 89% at room temperature.

[0056] The present invention also provides the use of the above-mentioned natural graphite composite anode material in lithium-ion batteries, preferably as a lithium-ion battery anode material.

[0057] The beneficial effects of this invention are:

[0058] This invention provides a high-rate composite anode material made from natural graphite, its preparation method, and its applications. First, silane coupling agent-grafted nano-acetylene black is embedded into the interlayer and surface of graphene oxide using electrostatic self-assembly technology. Then, graphene embedded with nano-acetylene black is heat-treated to coat the surface of natural flake graphite. During the shaping process, the natural flake graphite curls into spherical graphite, and simultaneously, the graphene embedded with nano-acetylene black coated on the surface of the natural flake graphite is also curled onto the inner and outer surfaces of the curled layers of the spherical graphite, meaning that part of the graphene embedded with nano-acetylene black is encapsulated within the spherical graphite. Next, it is coated with pitch, and the pitch coating on the surface of the spherical graphite is carbonized into amorphous carbon. Through this method, nano-acetylene black and graphene can be uniformly distributed within the spherical graphite, and the nano-acetylene black and graphene can exert a synergistic effect, more effectively constructing a conductive network within the composite anode material. This can significantly improve the rate performance of the composite anode material, giving it excellent application prospects. Attached Figure Description

[0059] Figure 1 This is a scanning electron microscope image of the natural graphite composite anode material prepared in Example 1 of the present invention. Detailed Implementation

[0060] The preparation method of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0061] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0062] The preparation process of the 3-aminopropyltriethoxysilane-grafted nano-acetylene black used in the following examples and comparative examples is as follows: 0.1 g of 3-aminopropyltriethoxysilane was added to 100 mL of an ethanol solution (1 g / mL) containing nano-acetylene black and stirred for 5 hours. After filtration, washing and drying, 3-aminopropyltriethoxysilane-grafted nano-acetylene black was prepared.

[0063] Example 1

[0064] (1) 40 mg of 3-aminopropyltriethoxysilane-grafted nano-acetylene black was mixed with 1000 mL of ethanol solution containing graphene oxide (0.1 mg / mL), and the reaction was stirred for 5 hours to obtain precursor A; 2 L of micro-expanded natural flake graphite (D) was added to the mixture. 50 20μm, d 002An ethanol solution (1 g / L) with a concentration of 0.3364 nm was added to precursor A, and the mixture was stirred for 10 hours. The mixture was then filtered, washed, and dried to obtain precursor B. Precursor B was placed in a rotary kiln and heated to 600 °C under N2 protection. The temperature was maintained for 4 hours, and the mixture was then cooled to obtain precursor C.

[0065] (2) The precursor C is placed in a shaping machine for shaping and grading to obtain D. 50 The precursor D with a thickness of 18 μm was mixed with isotropic pitch (carbon residue value of 60%) with a softening point of 200℃ at a mass ratio of 5:100. The mixture was treated at 1200℃ for 4 hours under N2 protection. After cooling to room temperature, it was dispersed, sieved and demagnetized to obtain a high-ratio natural graphite composite anode material.

[0066] The composition of nano-acetylene black is 1.79% by mass, graphene is 4.49% by mass, micro-expanded natural graphite is 88.96% by mass, and amorphous carbon is 4.76% by mass.

[0067] Example 2

[0068] (1) 25 mg of 3-aminopropyltriethoxysilane-grafted nano-acetylene black was mixed with 1000 mL of ethanol solution containing graphene oxide (0.1 mg / mL), and the reaction was stirred for 5 hours to obtain precursor A; 0.4 L of micro-expanded natural flake graphite (D) was added to the mixture. 50 It is 18μm, d 002 An ethanol solution (4 g / L) with a concentration of 0.3362 nm was added to precursor A, and the mixture was stirred for 8 hours. The mixture was then filtered, washed, and dried to obtain precursor B. Precursor B was placed in a rotary kiln and heated to 800 °C under N2 protection. The temperature was maintained for 6 hours, and the mixture was then cooled to obtain precursor C.

[0069] (2) The precursor C is placed in a shaping machine for shaping and grading to obtain D. 50 The precursor D with a thickness of 16 μm was mixed with isotropic pitch (carbon residue value of 50%) with a softening point of 150℃ at a mass ratio of 3:100. The mixture was treated at 1200℃ for 4 hours under N2 protection. After cooling to room temperature, it was dispersed, sieved and demagnetized to obtain a high-ratio natural graphite composite anode material.

[0070] The composition of nano-acetylene black is 1.41% by mass, graphene is 5.62% by mass, micro-expanded natural graphite is 90.06% by mass, and amorphous carbon is 2.91% by mass.

[0071] Example 3

[0072] (1) 20 mg of 3-aminopropyltriethoxysilane-grafted nano-acetylene black was mixed with 1000 mL of ethanol solution containing graphene oxide (0.1 mg / mL), and the mixture was stirred for 5 hours to obtain precursor A; 1.2 L of micro-expanded natural flake graphite (D) was added to the mixture. 50 It is 16μm, d 002 An ethanol solution (1 g / L) with a concentration of 0.3365 nm was added to precursor A, and the mixture was stirred for 4 hours. The mixture was then filtered, washed, and dried to obtain precursor B. Precursor B was placed in a rotary kiln and heated to 800 °C under N2 protection. The temperature was maintained for 2 hours, and the mixture was then cooled to obtain precursor C.

[0073] (2) The precursor C is placed in a shaping machine for shaping and grading to obtain D. 50 The precursor D with a thickness of 14 μm was mixed with isotropic pitch (carbon residue value of 60%) with a softening point of 200℃ at a mass ratio of 2:100. The mixture was treated at 1200℃ for 4 hours under N2 protection. After cooling to room temperature, it was dispersed, sieved and demagnetized to obtain a high-ratio natural graphite composite anode material.

[0074] The composition of nano-acetylene black is 1.49% by mass, graphene is 7.42% by mass, micro-expanded natural graphite is 89.13% by mass, and amorphous carbon is 1.96% by mass.

[0075] Example 4

[0076] (1) 30 mg of 3-aminopropyltriethoxysilane-grafted nano-acetylene black was mixed with 1000 mL of ethanol solution containing graphene oxide (0.1 mg / mL), and the reaction was stirred for 5 hours to obtain precursor A; 1 L of micro-expanded natural flake graphite (D) was added to the mixture. 50 It is 14μm, d 002 An ethanol solution (1 g / L) with a concentration of 0.3363 nm was added to precursor A, and the mixture was stirred for 4 hours. The mixture was then filtered, washed, and dried to obtain precursor B. Precursor B was placed in a rotary kiln and heated to 700 °C under N2 protection. The temperature was maintained for 6 hours, and the mixture was then cooled to obtain precursor C.

[0077] (2) The precursor C is placed in a shaping machine for shaping and grading to obtain D. 50 The precursor D with a thickness of 12 μm was mixed with isotropic pitch (carbon residue value of 55%) with a softening point of 180℃ at a mass ratio of 2:100. The mixture was treated at 1200℃ for 4 hours under N2 protection. After cooling to room temperature, it was dispersed, sieved and demagnetized to obtain a high-ratio natural graphite composite anode material.

[0078] The composition of nano-acetylene black is 2.60% by mass, graphene is 8.67% by mass, micro-expanded natural graphite is 86.77% by mass, and amorphous carbon is 1.96% by mass.

[0079] Comparative Example 1

[0080] (1) 40 mg of 3-aminopropyltriethoxysilane-grafted nano-acetylene black was mixed with 1000 mL of ethanol solution containing graphene oxide (0.1 mg / mL), and the reaction was stirred for 5 hours to obtain precursor A; 2 L of micro-expanded natural spherical graphite (D) was added. 50 20μm, d 002 An ethanol solution (1 g / L) with a concentration of 0.3364 nm was added to precursor A, and the mixture was stirred for 10 hours. The mixture was then filtered, washed, and dried to obtain precursor B. Precursor B was placed in a rotary kiln and heated to 600 °C under N2 protection. The temperature was maintained for 4 hours, and the mixture was then cooled to obtain precursor C.

[0081] (2) Isotropic pitch with a softening point of 200℃ (carbon residue value of 60%) was mixed with precursor C at a mass ratio of 5:100. The mixture was treated at 1200℃ for 4 hours under N2 protection. After cooling to room temperature, it was broken up, sieved and demagnetized to obtain natural graphite composite anode material.

[0082] The composition of nano-acetylene black is 1.79% by mass, graphene is 4.49% by mass, micro-expanded natural graphite is 88.96% by mass, and amorphous carbon is 4.76% by mass.

[0083] Comparative Example 2

[0084] (1) 40 mg of 3-aminopropyltriethoxysilane-grafted nano-acetylene black and 2 L of micro-expanded natural flake graphite (D 50 20μm, d 002 Mix with an ethanol solution (1 g / L) containing 0.3364 nm, stir for 10 hours, filter, wash and dry sequentially to obtain precursor B; place precursor B in a rotary furnace, heat to 600℃ under N2 protection, hold for 4 hours, and cool to obtain precursor C.

[0085] (2) The precursor C is placed in a shaping machine for shaping and grading to obtain D. 50 The precursor D with a thickness of 18 μm was mixed with isotropic pitch (carbon residue value of 60%) with a softening point of 200℃ at a mass ratio of 5:100. The mixture was treated at 1200℃ for 4 hours under N2 protection. After cooling to room temperature, it was dispersed, sieved and demagnetized to obtain the natural graphite composite anode material.

[0086] The nano-acetylene black has a mass percentage of 1.9%, the micro-expanded natural graphite has a mass percentage of 95.2%, and the amorphous carbon has a mass percentage of 2.9%.

[0087] Comparative Example 3

[0088] (1) 40 mg of nano-acetylene black was mixed with 1000 mL of ethanol solution containing graphene oxide (0.1 mg / mL), and the mixture was stirred for 5 hours to obtain precursor A; 2 L of micro-expanded natural flake graphite (D) was added to the mixture. 50 20μm, d 002 An ethanol solution (1 g / L) with a concentration of 0.3364 nm was added to precursor A, and the mixture was stirred for 10 hours. The mixture was then filtered, washed, and dried to obtain precursor B. Precursor B was placed in a rotary kiln and heated to 600 °C under N2 protection. The temperature was maintained for 4 hours, and the mixture was then cooled to obtain precursor C.

[0089] (2) The precursor C is placed in a shaping machine for shaping and grading to obtain D. 50 The precursor D with a thickness of 18 μm was mixed with isotropic pitch (carbon residue value of 60%) with a softening point of 200℃ at a mass ratio of 5:100. The mixture was treated at 1200℃ for 4 hours under N2 protection. After cooling to room temperature, it was dispersed, sieved and demagnetized to obtain the natural graphite composite anode material.

[0090] The nano-acetylene black has a mass percentage of 1.79%, graphene has a mass percentage of 4.49%, micro-expanded natural graphite has a mass percentage of 88.96%, and amorphous carbon has a mass percentage of 4.76%.

[0091] Electrochemical performance testing:

[0092] Half-cell testing method: The composite negative electrode materials prepared in Examples 1-4 and Comparative Examples 1-3 were mixed evenly with conductive carbon black (SP): carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) in a ratio of 95:1:1.5:2.5 (mass ratio). The mixture was then coated onto copper foil, and the coated electrode was dried in a vacuum drying oven at 120°C for 12 hours. Simulated battery assembly was performed in an argon-protected Braun glove box. The electrolyte was 1M-LiPF6+EC:DEC:DMC (volume ratio 1:1:1), and lithium metal sheets were used as the counter electrode. Simulated battery testing was conducted in a 5V, 10mA Xinwei battery test cabinet with a charge / discharge voltage of 0.01-1.5V and a charge / discharge rate of 0.2C. The initial capacity and efficiency obtained from the tests are listed in Table 1.

[0093] Full cell test method: Using the composite materials prepared in Examples 1-4 and Comparative Examples 1-3 as negative electrodes, lithium cobalt oxide as positive electrodes, and 1M-LiPF6+EC:DEC:DMC (volume ratio 1:1:1) solution as electrolyte, full cells were assembled. They were charged and discharged at room temperature at rates of 0.2C and 3C, with a voltage range of 3.0-4.2V. The test results are listed in Table 1.

[0094] Table 1. Electrochemical performance test results

[0095]

[0096] As can be seen from the comparison in Table 1 above, the anode material prepared using the present invention has better rate performance. Comparative Example 1 involves directly coating graphene embedded with nano-acetylene black onto the surface of micro-expanded natural spherical graphite; the anode material prepared in this way has poor rate performance. Comparative Example 2 involves distributing nano-acetylene black only inside the spherical graphite, but the anode material prepared in this way also has poor rate performance, mainly because the conductivity of acetylene black is inferior to that of graphene. Comparative Example 3 involves directly mixing nano-acetylene black with graphene oxide; this results in almost all of the nano-acetylene black being distributed on the surface of the graphene. Since it lacks the specific structure of this application, the synergistic effect of nano-acetylene black and graphene oxide cannot be fully utilized, resulting in poor rate performance of the prepared anode material.

[0097] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a natural graphite composite anode material, the method comprising the following steps: (1) The nano-acetylene black grafted with silane coupling agent was mixed with an organic solution containing graphene oxide and reacted to obtain precursor A. (2) The precursor A from step (1) is mixed with an organic solution containing natural flake graphite to obtain precursor B; (3) Heat-treat the precursor B from step (2) and cool it to obtain precursor C; (4) Shape and grade the precursor C from step (3) to obtain precursor D; (5) After mixing the precursor D from step (4) with asphalt, carbonize it, cool it, and then break it up and sieve it to obtain the natural graphite composite negative electrode material. In step (1), the precursor A is formed by embedding nano-acetylene black grafted with silane coupling agent into the interlayer and surface of graphene oxide. In step (3), the precursor C includes graphene, natural flake graphite and nano acetylene black; wherein the graphene is coated on the surface of the natural flake graphite, and nano acetylene black is embedded in the interlayer and surface of the graphene.

2. The method for preparing the natural graphite composite anode material according to claim 1, wherein, In step (1), the silane coupling agent is selected from silane coupling agents containing amino groups; And / or, in step (1), the mass ratio of the silane coupling agent to the nano acetylene black is 0.05~0.5:

100.

3. The method for preparing the natural graphite composite anode material according to claim 2, wherein, The silane coupling agent is selected from 3-aminopropyltriethoxysilane.

4. The method for preparing the natural graphite composite anode material according to claim 1, wherein, In step (1), the mass-to-volume ratio of graphene oxide to organic solution in the organic solution containing graphene oxide is 0.1 mg: (1-5) mL; And / or, in step (1), the mass ratio of the nano-acetylene black to graphene oxide is (20-40):100; And / or, in step (1), the reaction time is 1-10 hours.

5. The method for preparing the natural graphite composite anode material according to any one of claims 1-4, wherein, In step (2), the mass ratio of graphene oxide to natural flake graphite in precursor A is (5-10):100; And / or, in step (2), the concentration of the organic solution containing natural flake graphite is (1-3) g / L; And / or, in step (2), the natural flake graphite is micro-expanded natural flake graphite, and the d of the micro-expanded natural flake graphite 002 The wavelength range is 0.3360nm-0.3367nm.

6. The method for preparing the natural graphite composite anode material according to any one of claims 1-4, wherein, In step (3), the temperature of the heat treatment is 500℃-800℃; the time of the heat treatment is 5-10 hours.

7. The method for preparing the natural graphite composite anode material according to any one of claims 1-4, wherein, In step (4), the equipment used for shaping is a mechanical shaping machine or an airflow shaping machine, and the equipment used for grading is a grading machine; And / or, in step (4), the median particle size D of the precursor D 50 It is 10-20μm.

8. The method for preparing the natural graphite composite anode material according to any one of claims 1-4, wherein, In step (5), the mass ratio of the asphalt to the precursor D is (1-5):100; And / or, in step (5), the carbonization temperature is 800℃-1200℃; the carbonization time is 5-10 hours; and the carbonization is carried out under an inert atmosphere.

9. A natural graphite composite anode material, which is prepared by the method described in any one of claims 1-8.

10. The natural graphite composite anode material according to claim 9, wherein, The natural graphite composite anode material includes nano-acetylene black, graphene, natural graphite, and amorphous carbon; in the natural graphite composite anode material, the mass percentage of nano-acetylene black is 1-3%, the mass percentage of graphene is 3-10%, the mass percentage of natural graphite is 85-92%, and the mass percentage of amorphous carbon is 1-5%.

11. Use of the natural graphite composite anode material according to claim 9 or 10 in lithium-ion batteries.

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