A high-sulfur coke-based fast-charging artificial graphite negative electrode material, a preparation method thereof and applications thereof

Abstract

The application belongs to the technical field of lithium ion battery negative electrode materials, and particularly relates to a high-sulfur coke-based fast-charging artificial graphite negative electrode material and a preparation method and application thereof. The application selects high-sulfur coke with a sulfur content of 3-8 wt% as a raw material, and simultaneously selects a heat treatment process with segmented temperature rising for desulfurization treatment, so as to cooperatively remove harmful sulfur in the high-sulfur coke and realize C-axis pore formation of graphite. By controlling the volatilization speed of sulfur, the collapse of the structure of the high-sulfur coke is avoided, and the reconstructed porous desulfurized coke can ensure the order degree of the C-axis pore formation graphite, which is beneficial to the acquisition of pore structures, active sites for lithium ion intercalation and deintercalation and transmission, and thus the rate performance of the prepared fast-charging artificial graphite negative electrode material is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material technology, specifically relating to a high-sulfur coke-based fast-charging artificial graphite anode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries achieve charge transfer and charging / discharging by the continuous shuttle of lithium ions between the positive and negative electrodes. They are mainly composed of positive and negative electrodes, a separator, and an electrolyte, assembled through a series of component processes. Kinetic performance is a very important property of the positive and negative electrodes, mainly referring to the ability of lithium ions to rapidly insert and extract, enabling the battery to charge and discharge quickly.

[0003] Currently, the main anode material for commercially available lithium-ion batteries is graphite. Graphite is a layered structure material in which carbon atoms in the same layer form relatively strong covalent bonds through sp2 hybridization, and the layers are bonded together by van der Waals forces. Due to its relatively weak interlayer bonding force and large interlayer spacing, it allows lithium ions to intercalate and deintercalate. Therefore, graphite is an important anode material for lithium-ion batteries and an active material for other ion-intercalating electrodes.

[0004] In practical applications, graphite needs to maintain its intrinsic layered structure and have a relatively large micron-sized particle size. This inevitably leads to slow diffusion kinetics of ions intercalating and deintercalating between graphite layers, resulting in low rate performance of graphite anodes. If pores can be created in a direction perpendicular to the graphite planar layers (i.e., C-axis pores), the diffusion kinetics can be improved through diffusion channels in the C-axis direction, but such C-axis pore creation is very difficult.

[0005] Compared to natural graphite, artificial graphite exhibits superior kinetic properties. Artificial graphite is generally produced by graphitizing needle coke or petroleum coke. Petroleum coke is a final byproduct of delayed coking processes in oil refineries and can be categorized into high-sulfur coke (sulfur content greater than 3%), medium-sulfur coke, and low-sulfur coke (sulfur content less than 0.5%) based on its sulfur content. Existing technologies have reported methods involving mixing small-particle high-sulfur coke with a binder (asphalt or resin), granulating, desulfurizing, and graphitizing to prepare artificial graphite anode materials with a secondary particle structure (formed by the bonding of small particles). Desulfurization is used to create C-axis pores between graphite layers, thereby improving the rate performance of artificial graphite. However, the dense structure of graphite or hard carbon converted from asphalt or resin during graphitization reduces the diffusion rate of Li+ to the graphite (C-axis pore-forming) surface; therefore, this C-axis pore-forming method can only improve rate performance to a certain extent. Therefore, a method for preparing artificial graphite with excellent kinetic properties using high-sulfur coke is urgently needed. Summary of the Invention

[0006] To effectively utilize high-sulfur coke to prepare artificial graphite with excellent kinetic properties, this invention provides a high-sulfur coke-based fast-charging artificial graphite anode material, its preparation method, and its applications. The fast-charging artificial graphite anode material features high rate capability, good cycle stability, high initial coulombic efficiency, and large initial charge-discharge capacity. The preparation method is characterized by its simple process, low cost, and wide availability of raw materials.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a fast-charging artificial graphite anode material, the method comprising the following steps:

[0009] (1) High-sulfur coke is heat-treated to prepare desulfurized coke;

[0010] (2) The desulfurized coke from step (1) is crushed, shaped and graded to prepare desulfurized coke powder;

[0011] (3) Mix asphalt and metal chloride, react, and prepare modified asphalt;

[0012] (4) Mix the desulfurized coke powder from step (2) and the modified asphalt from step (3) and react them;

[0013] (5) Carbonize the reaction product of step (4) to prepare secondary coke particles;

[0014] (6) The secondary coke particles from step (5) are graphitized to prepare the fast-charging artificial graphite anode material;

[0015] In step (1), the heat treatment employs a segmented heating process, specifically including the following steps:

[0016] First, raise the temperature to 300-500℃ at a heating rate of 10-20℃ / min and hold for 1-3 hours; then raise the temperature to 800-1200℃ at a heating rate of 5-10℃ / min and hold for 1-3 hours; finally, raise the temperature to 1700-2000℃ at a heating rate of 1-5℃ / min and hold for 1-6 hours.

[0017] According to an embodiment of the present invention, in step (1), the high-sulfur coke is a by-product obtained by coking the residue oil during the crude oil refining process, which can be obtained through commercial purchase.

[0018] According to an embodiment of the present invention, in step (1), the particle size of the high-sulfur coke is not specifically defined, and can be a conventional particle size in the art, such as millimeter-level or centimeter-level high-sulfur coke.

[0019] According to an embodiment of the present invention, in step (1), the sulfur content in the high-sulfur coke is 3-8 wt%, for example, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 7 wt%, or 8 wt%. Studies have found that when high-sulfur coke with a sulfur content of 3-8 wt% is selected, and further combined with the preparation method of the present invention, it is possible to effectively achieve C-axis pore formation in graphite and the construction of lithium-ion compatible pores, sites, and transport pathways. This helps to obtain artificial graphite anode materials with excellent fast-charging performance and other electrochemical properties (such as cycle performance, coulombic efficiency, and charge / discharge capacity). When high-sulfur coke with a sulfur content >8wt% is selected, the high sulfur content easily causes the high-sulfur coke structure to collapse during the desulfurization process, making it impossible to effectively form lithium-ion transport channels. Therefore, it is impossible to obtain artificial graphite anode materials with high rate performance. When medium-sulfur coke or low-sulfur coke with a sulfur content <3wt% is selected, the low sulfur content makes it impossible to utilize sulfur volatilization to create C-axis pores inside the medium-sulfur coke or low-sulfur coke, and to construct lithium-ion compatible pores, sites, and transport pathways. Similarly, it is impossible to obtain artificial graphite anode materials with high rate performance.

[0020] According to an embodiment of the present invention, in step (1), the heat treatment employs a segmented heating process, specifically including heating to 300-500℃ (e.g., 300℃, 350℃, 400℃, 450℃, or 500℃) at a heating rate of 10-20℃ / min (e.g., 10℃ / min, 12℃ / min, 15℃ / min, 18℃ / min, or 20℃ / min), holding at that temperature for 1-3 hours (e.g., 1 hour, 2 hours, or 3 hours); then heating to 800-1200℃ at a heating rate of 5-10℃ / min (e.g., 5℃ / min, 6℃ / min, 8℃ / min, or 10℃ / min). ℃ (e.g., 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃ or 1200℃), hold for 1-3 hours (e.g., 1 hour, 2 hours or 3 hours); finally, raise the temperature to 1700-2000℃ (e.g., 1750℃, 1800℃, 1850℃, 1900℃, 1950℃ or 2000℃) at a heating rate of 1-5℃ / min (e.g., 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min), hold for 1-6 hours (e.g., 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours). Research has found that by adopting the segmented heating process of the present invention, sulfur in high-sulfur coke can be effectively removed and C-axis pores in graphite can be created. At the same time, it can also effectively prevent the collapse of the high-sulfur coke structure caused by the rapid volatilization of sulfur during heat treatment, as well as the inability to construct lithium-ion-compatible intercalation-deintercalation and storage microporous structures and active sites.

[0021] According to an embodiment of the present invention, in step (1), the heat treatment is carried out under a nitrogen protective atmosphere.

[0022] According to an embodiment of the present invention, in step (1), the sulfur content in the desulfurized coke is <100ppm.

[0023] According to an embodiment of the present invention, in step (2), the equipment used for pulverization is not particularly limited, and equipment known in the art can be selected, such as impact pulverizer, air jet mill, high pressure mill or rod mill.

[0024] According to an embodiment of the present invention, in step (2), the equipment used for shaping is not particularly limited, and equipment known in the art, such as mechanical shaping machine or airflow shaping machine, can be selected.

[0025] According to an embodiment of the present invention, in step (2), the equipment used for grading is not particularly limited, and equipment known in the art, such as an air classifier, can be selected.

[0026] According to an embodiment of the present invention, in step (2), the median particle size D of the desulfurized coke powder is... 50 It is 5-8μm, for example, 5μm, 6μm, 7μm or 8μm.

[0027] According to an embodiment of the present invention, in step (3), the softening point of the asphalt is 65-75°C, for example, 65°C, 70°C or 75°C.

[0028] According to an embodiment of the present invention, in step (3), the water content in the asphalt is 2-3 wt%, for example, 2 wt%, 2.2 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.8 wt%, or 3 wt%.

[0029] According to an embodiment of the present invention, in step (3), the metal chloride is selected from AlCl3, SiCl4 or TiCl4.

[0030] According to an embodiment of the present invention, in step (3), the mass ratio of the metal chloride to the asphalt is (5-15):100, for example, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100 or 15:100.

[0031] According to an embodiment of the present invention, in step (3), the reaction is carried out under stirring conditions.

[0032] According to an embodiment of the present invention, in step (3), the softening point of the modified asphalt is 100-150℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃.

[0033] According to an embodiment of the present invention, step (3) specifically includes the following steps:

[0034] The asphalt is placed in a reaction vessel and heated to 120-160℃. Under stirring, metal chlorides are added to the molten asphalt and reacted for 0.5-1 hour. Then, argon gas is introduced into the reaction vessel and heated to 330-390℃ under argon protection. The temperature is maintained for 2-6 hours to prepare modified asphalt.

[0035] For example, asphalt is placed in a reaction vessel and heated to 120°C, 130°C, 140°C, 150°C, or 160°C. Reacting at this temperature for 0.5-1 hour can increase the softening point of the asphalt, which is beneficial for obtaining carbonized products with high residual carbon values ​​after carbonization, ensuring tight bonding between primary particles.

[0036] For example, under argon protection, the temperature is further heated to 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, or 390°C.

[0037] According to an embodiment of the present invention, in step (3), during the reaction process, the metal chloride reacts with water in the asphalt to generate nano-sized metal oxides (such as Al2O3, SiO2, or TiO2), and the generated nano-oxides are uniformly distributed in the asphalt, thus preparing modified asphalt. Compared with the method of directly adding nano-sized metal oxides to asphalt to obtain modified asphalt, the in-situ synthesis method of nano-sized metal oxides of the present invention can make the metal oxides uniformly distributed in the asphalt. During the graphitization process, these nano-sized metal oxides volatilize and form uniformly distributed nanopores. The presence of these nanopores can increase the diffusion channels of lithium ions and improve the rate performance of the artificial graphite anode material. At the same time, the in-situ synthesis method of nano-sized metal oxides of the present invention can also avoid the formation of large pores inside the artificial graphite anode material during the graphitization process due to uneven dispersion of metal oxides (such as agglomeration), which reduces the diffusion channels of lithium ions and thus fails to effectively improve the rate performance of the anode material.

[0038] According to an embodiment of the present invention, in step (4), the mass ratio of the modified asphalt to the desulfurized coke powder is (8-15):100, for example, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100 or 15:100.

[0039] According to an embodiment of the present invention, in step (4), the temperature of the reaction is 450-650°C, for example, 450°C, 500°C, 550°C, 600°C or 650°C; the reaction time is 3-12 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 8 hours, 10 hours or 12 hours.

[0040] According to an embodiment of the present invention, in step (4), the reaction is carried out in an air atmosphere.

[0041] According to an embodiment of the present invention, in step (4), the reaction is naturally cooled to room temperature after completion.

[0042] According to an embodiment of the present invention, in step (4), the reaction is carried out in a granulation reactor.

[0043] According to an embodiment of the present invention, in step (4), during the reaction process, the modified asphalt can bind small particles of desulfurized coke powder into a secondary particle structure, which is beneficial to obtaining artificial graphite anode material with a secondary particle structure.

[0044] According to an embodiment of the present invention, in step (5), the temperature of the carbonization treatment is 800-1000℃, for example, 800℃, 850℃, 900℃, 950℃ or 1000℃; the time of the carbonization treatment is 3-12 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 8 hours, 10 hours or 12 hours.

[0045] According to an embodiment of the present invention, in step (5), during the carbonization process, the asphalt is transformed into amorphous carbon.

[0046] According to an embodiment of the present invention, in step (5), the carbonization process is completed and the material is naturally cooled to room temperature.

[0047] According to an embodiment of the present invention, in step (5), the carbonization process is carried out under a nitrogen atmosphere.

[0048] According to an embodiment of the present invention, in step (5), the median particle size D of the secondary coke particles is... 50 It is 10-15μm, for example, 10μm, 11μm, 12μm, 13μm, 14μm or 15μm.

[0049] According to an embodiment of the present invention, in step (6), the temperature of the graphitization treatment is 2850-3200℃, for example, 2850℃, 2900℃, 2950℃, 3000℃, 3050℃, 3100℃, 3150℃ or 3200℃; the time of the graphitization treatment is 8-24 hours, for example, 8 hours, 10 hours, 12 hours, 14 hours, 15 hours, 16 hours, 18 hours, 20 hours or 24 hours.

[0050] According to an embodiment of the present invention, in step (6), during the graphitization process, metal oxides (Al2O3, SiO2 or TiO2) will volatilize from the matrix, leaving nano-sized pores in the graphite particles after volatilization. These pores provide convenient channels for the transport of lithium ions, reduce the resistance of lithium ions to intercalation and intercalation between graphite layers, and reduce the impedance of artificial graphite anode materials.

[0051] The present invention also provides a fast-charging artificial graphite anode material prepared by the above method.

[0052] According to an embodiment of the present invention, the fast-charging artificial graphite anode material has a secondary particle structure.

[0053] According to an embodiment of the present invention, the secondary particle structure is composed of small particle size (D) 50 It is formed by bonding together single graphite particles (5-8 μm in size), wherein each graphite particle has nanoscale pores in a direction perpendicular to the graphite planar layer (C-axis). The nanoscale pores are formed by heat treatment of high-sulfur coke.

[0054] According to an embodiment of the present invention, the small particle size (D) 50 Single-particle graphite (5-8 μm in size) is formed from desulfurized coke powder after graphitization.

[0055] According to an embodiment of the present invention, in the secondary particle structure, the graphite structure between adjacent single graphite particles has nanoscale pores. These nanoscale pores are formed by graphitization of metal oxides.

[0056] According to an embodiment of the present invention, the median particle size D of the fast-charging artificial graphite anode material is... 50 It is 10-15 μm.

[0057] The present invention also provides the use of the above-mentioned fast-charging artificial graphite anode material for lithium-ion batteries, preferably for preparing the anode of lithium-ion batteries.

[0058] The present invention also provides a negative electrode for lithium-ion batteries, the negative electrode comprising the above-mentioned fast-charging artificial graphite negative electrode material.

[0059] The beneficial effects of this invention are:

[0060] This invention selects high-sulfur coke with a sulfur content of 3-8 wt% as raw material and uses a segmented heating heat treatment process for desulfurization. This synergistic process removes harmful sulfur from the high-sulfur coke and achieves C-axis pore formation in graphite. By controlling the volatilization rate of sulfur, the collapse of the high-sulfur coke structure is avoided. At the same time, the reconstructed porous desulfurized coke can ensure the orderliness of the C-axis porous graphite, which is beneficial to the acquisition of pore structures and active sites for lithium ion insertion-extraction and transport. This effectively improves the rate performance of the prepared fast-charging artificial graphite anode material.

[0061] Furthermore, this invention also uses modified asphalt containing metal oxides (such as nano-sized Al2O3, SiO2, or TiO2) as a binder for the secondary granulation of small-particle-size desulfurized coke powder. During the graphitization process, the volatilization of metal oxides will form nano-sized pores between individual graphite particles (formed after graphitization of small-particle-size desulfurized coke powder). This provides a convenient channel for lithium ions to be transported to graphite, reduces the resistance of lithium ions to intercalation and intercalation between graphite layers, reduces the impedance of artificial graphite anode materials, and further improves the fast-charging performance of artificial graphite anode materials. Detailed Implementation

[0062] 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.

[0063] 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.

[0064] Example 1

[0065] (1) High-sulfur coke with a sulfur content of 3wt% is placed in a high-temperature furnace and heated to 350℃ at 10℃ / min under nitrogen protection and held for 3 hours; then heated to 1000℃ at 5℃ / min and held for 2 hours; finally heated to 1800℃ at 1℃ / min and held for 6 hours to obtain desulfurized coke.

[0066] (2) After the desulfurized coke from step (1) is crushed in an impact crusher, it is shaped and graded to obtain desulfurized coke powder (median particle size is 5μm).

[0067] (3) Place 100g of asphalt (softening point 70℃) into a reactor and heat it to 140℃. While stirring (500r / min), gradually add 6g of AlCl3 to the molten asphalt and react for 1 hour. Then seal the reactor and introduce argon gas. Continue to heat it to 350℃ and continue to react for 4 hours to obtain modified asphalt (softening point 120℃).

[0068] (4) After mixing 100g of desulfurized coke powder from step (2) with 10g of modified asphalt from step (3) evenly, the mixture is stirred and reacted at 500℃ for 5 hours in a granulation reactor and then cooled to room temperature; subsequently, it is carbonized at 850℃ for 5 hours under nitrogen and then cooled to room temperature to obtain secondary coke particles (median particle size of 10μm).

[0069] (5) The secondary coke particles from step (4) are graphitized at a high temperature of 2950℃ for 12 hours and then cooled to room temperature to obtain the fast-charging artificial graphite anode material.

[0070] Example 2

[0071] (1) Place high-sulfur coke with a sulfur content of 4wt% into a high-temperature furnace, raise the temperature to 360℃ at 15℃ / min under nitrogen protection, and hold for 3 hours; then raise the temperature to 1000℃ at 6℃ / min and hold for 1-3 hours; finally raise the temperature to 1750℃ at 2℃ / min and hold for 6 hours.

[0072] (2) After the desulfurized coke from step (1) is crushed in an impact crusher, it is shaped and classified to obtain desulfurized coke powder (median particle size is 7μm).

[0073] (3) Place 100g of asphalt (softening point 75℃) into a reactor and heat it to 120℃. While stirring (500r / min), gradually add 8g of SiCl4 to the molten asphalt and react for 1 hour. Then seal the reactor and introduce argon gas. Continue to heat it to 380℃ and continue to react for 5 hours to obtain modified asphalt (softening point 110℃).

[0074] (4) After mixing 100g of desulfurized coke powder from step (2) with 10g of modified asphalt from step (3) evenly, the mixture is stirred and reacted in a granulation kettle at 520℃ for 5 hours and then cooled to room temperature; subsequently, it is carbonized at 1000℃ under nitrogen for 5 hours and then cooled to room temperature to obtain secondary coke particles (median particle size of 13μm).

[0075] (5) The secondary coke particles from step (4) are graphitized at a high temperature of 3050℃ for 10 hours and then cooled to room temperature to obtain the fast-charging artificial graphite anode material.

[0076] Example 3

[0077] (1) High-sulfur coke with a sulfur content of 5wt% is placed in a high-temperature furnace and heated to 500℃ at 20℃ / min under nitrogen protection and held for 1 hour; then heated to 1200℃ at 8℃ / min and held for 1 hour; finally heated to 1850℃ at 3℃ / min and held for 4 hours to obtain desulfurized coke.

[0078] (2) After the desulfurized coke from step (1) is crushed in an impact crusher, it is shaped and graded to obtain desulfurized coke powder (median particle size is 8μm).

[0079] (3) Place 100g of asphalt (softening point 68℃) into a reactor and heat it to 125℃. While stirring (500r / min), gradually add 10g of TiCl4 to the molten asphalt and react for 1 hour. Then seal the reactor and introduce argon gas. Continue to heat it to 390℃ and continue to react for 3 hours to obtain modified asphalt (softening point 140℃).

[0080] (4) After mixing 100g of desulfurized coke powder from step (2) with 10g of modified asphalt from step (3), the mixture is stirred and reacted in a granulation reactor at 650℃ for 3 hours and then cooled to room temperature. Subsequently, it is carbonized at 900℃ under nitrogen for 5 hours and then cooled to room temperature to obtain secondary coke particles (median particle size of 15μm).

[0081] (5) The secondary coke particles from step (4) are graphitized at 3150°C for 16 hours and then cooled to room temperature to obtain the fast-charging artificial graphite anode material.

[0082] Comparative Example 1

[0083] (1) High-sulfur coke with a sulfur content of 3wt% is placed in a high-temperature furnace and heated to 350℃ at 10℃ / min under nitrogen protection and held for 3 hours; then heated to 1000℃ at 5℃ / min and held for 2 hours; finally heated to 1800℃ at 1℃ / min and held for 6 hours to obtain desulfurized coke.

[0084] (2) After the desulfurized coke from step (1) is crushed in an impact crusher, it is shaped and graded to obtain desulfurized coke powder (median particle size is 5μm).

[0085] (3) Put 100g of asphalt (softening point 70℃) into the reactor and heat it to 140℃. Keep it at the temperature for 1 hour. Then seal the reactor and introduce argon gas. Continue to heat it to 390℃ and continue to react for 6 hours to obtain modified asphalt (softening point 120℃).

[0086] (4) After mixing 100g of desulfurized coke powder from step (2) with 10g of modified asphalt from step (3) evenly, the mixture is stirred and reacted at 500℃ for 5 hours in a granulation reactor and then cooled to room temperature; subsequently, it is carbonized at 850℃ for 5 hours under nitrogen and then cooled to room temperature to obtain secondary coke particles (median particle size of 10μm).

[0087] (5) The secondary coke particles from step (4) are graphitized at a high temperature of 2950℃ for 12 hours and then cooled to room temperature to obtain the fast-charging artificial graphite anode material.

[0088] Comparative Example 2

[0089] (1) High-sulfur coke with a sulfur content of 3wt% is placed in a high-temperature furnace and heated to 1800℃ at 10℃ / min under nitrogen protection, and kept at the temperature for 6 hours to obtain desulfurized coke.

[0090] (2) After the desulfurized coke from step (1) is crushed in an impact crusher, it is shaped and graded to obtain desulfurized coke powder (median particle size is 5μm).

[0091] (3) Place 100g of asphalt (softening point 70℃) into a reactor and heat it to 140℃. While stirring (500r / min), gradually add 6g of AlCl3 to the molten asphalt and react for 1 hour. Then seal the reactor and introduce argon gas. Continue to heat it to 350℃ and continue to react for 4 hours to obtain modified asphalt (softening point 120℃).

[0092] (4) After mixing 100g of desulfurized coke powder from step (2) with 10g of modified asphalt from step (3) evenly, the mixture is stirred and reacted at 500℃ for 5 hours in a granulation reactor and then cooled to room temperature; subsequently, it is carbonized at 850℃ for 5 hours under nitrogen and then cooled to room temperature to obtain secondary coke particles (median particle size of 10μm).

[0093] (5) The secondary coke particles from step (4) are graphitized at a high temperature of 2950℃ for 12 hours and then cooled to room temperature to obtain the fast-charging artificial graphite anode material.

[0094] Comparative Example 3

[0095] (1) High-sulfur coke with a sulfur content of 10wt% is placed in a high-temperature furnace and heated to 350℃ at 10℃ / min under nitrogen protection and held for 3 hours; then heated to 1000℃ at 5℃ / min and held for 2 hours; finally heated to 1800℃ at 1℃ / min and held for 6 hours to obtain desulfurized coke.

[0096] (2) After the desulfurized coke from step (1) is crushed in an impact crusher, it is shaped and graded to obtain desulfurized coke powder (median particle size is 5μm).

[0097] (3) Place 100g of asphalt (softening point 70℃) into a reactor and heat it to 140℃. While stirring (500r / min), gradually add 6g of AlCl3 to the molten asphalt and react for 1 hour. Then seal the reactor and introduce argon gas. Continue to heat it to 350℃ and continue to react for 4 hours to obtain modified asphalt (softening point 120℃).

[0098] (4) After mixing 100g of desulfurized coke powder from step (2) with 10g of modified asphalt from step (3) evenly, the mixture is stirred and reacted at 500℃ for 5 hours in a granulation reactor and then cooled to room temperature; subsequently, it is carbonized at 850℃ for 5 hours under nitrogen and then cooled to room temperature to obtain secondary coke particles (median particle size of 10μm).

[0099] (5) The secondary coke particles from step (4) are graphitized at a high temperature of 2950℃ for 12 hours and then cooled to room temperature to obtain the fast-charging artificial graphite anode material.

[0100] Comparative Example 4

[0101] (1) High-sulfur coke with a sulfur content of 3wt% is placed in a high-temperature furnace and heated to 350℃ at 10℃ / min under nitrogen protection and held for 3 hours; then heated to 1000℃ at 5℃ / min and held for 2 hours; finally heated to 1800℃ at 1℃ / min and held for 6 hours to obtain desulfurized coke.

[0102] (2) After the desulfurized coke from step (1) is crushed in an impact crusher, it is shaped and graded to obtain desulfurized coke powder (median particle size is 5μm).

[0103] (3) Place 100g of asphalt (softening point 70℃) into a reactor and heat it to 140℃. While stirring (500r / min), gradually add 6g of Al2O3 (median particle size 20nm) to the molten asphalt and react for 1 hour. Then seal the reactor and introduce argon gas. Continue to heat it to 350℃ and continue to react for 4 hours to obtain modified asphalt (softening point 120℃).

[0104] (4) After mixing 100g of desulfurized coke powder from step (2) with 10g of modified asphalt from step (3) evenly, the mixture is stirred and reacted at 500℃ for 5 hours in a granulation reactor and then cooled to room temperature; subsequently, it is carbonized at 850℃ for 5 hours under nitrogen and then cooled to room temperature to obtain secondary coke particles (median particle size of 10μm).

[0105] (5) The secondary coke particles from step (4) are graphitized at a high temperature of 2950℃ for 12 hours and then cooled to room temperature to obtain the fast-charging artificial graphite anode material.

[0106] Test Example 1

[0107] Electrochemical performance testing

[0108] Half-cell testing method: The negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-4 were mixed evenly with conductive carbon black (SP): carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) in a mass ratio of 95:1:1.5:2.5. 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 1C. The initial discharge capacity and initial coulombic efficiency obtained from the tests are shown in Table 1.

[0109] Full cell test method: Using the graphite materials prepared in Examples 1-3 and Comparative Examples 1-4 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 and charged and discharged at room temperature at a rate of 6C, with a voltage range of 3.0-4.2V. The cycle performance obtained is shown in Table 1.

[0110] Table 1 Electrochemical performance test results

[0111]

[0112] As can be seen from Table 1, the artificial graphite anode material prepared in this invention has better rate performance, while the artificial graphite anode materials of Comparative Examples 1-4 cannot achieve good rate performance. This is mainly due to:

[0113] The pitch used in the secondary granulation of the artificial graphite anode material in Comparative Example 1 does not contain nano-sized metal oxides. This results in a more compact graphite structure formed by the pitch that binds single-particle graphite during graphitization, which reduces the diffusion rate of Li+ to the graphite (C-axis pore formation) surface. Therefore, it can only improve its rate performance to a certain extent.

[0114] The high-sulfur coke used in Comparative Example 2 exhibits rapid sulfur volatilization during desulfurization heat treatment, making it difficult to effectively create C-axis pores on the graphite surface. This hinders the acquisition of pore structures and active sites for lithium-ion insertion-extraction and transport. Furthermore, although nanopores exist between single graphite particles in the artificial graphite anode material, these nanopores only provide convenient channels for lithium-ion transport to the graphite, but cannot create C-axis pores in the artificial graphite anode material. This results in slow diffusion kinetics for lithium-ion insertion and extraction between graphite layers, leading to very low rate performance of the artificial graphite anode material.

[0115] The high sulfur content in the high-sulfur coke used in Comparative Example 3 was too high. Although the C-axis of the prepared artificial graphite anode material had pores, the volatilization of a large amount of sulfur caused the collapse of the petroleum coke structure, resulting in lower capacity, first coulombic efficiency and lower rate performance, making it difficult to apply to lithium-ion batteries.

[0116] In Comparative Example 4, nano-alumina was directly added to asphalt to prepare modified asphalt. During the addition process, the nano-alumina exhibited significant agglomeration problems, which prevented it from being evenly distributed in the modified asphalt. This resulted in the inability to form nano-sized pores between individual graphite particles during the graphitization process, reducing the diffusion rate of Li+ to the graphite (C-axis pore formation) surface. Therefore, it could only improve the rate performance to a certain extent.

[0117] 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 fast-charging artificial graphite anode material, the method comprising the following steps: (1) High-sulfur coke is heat-treated to prepare desulfurized coke; (2) The desulfurized coke from step (1) is crushed, shaped and graded to prepare desulfurized coke powder; (3) Mix asphalt and metal chloride, react, and prepare modified asphalt; (4) Mix the desulfurized coke powder from step (2) and the modified asphalt from step (3) and react them; (5) Carbonize the reaction product of step (4) to prepare secondary coke particles; (6) The secondary coke particles from step (5) are graphitized to prepare the fast-charging artificial graphite anode material; In step (1), the heat treatment employs a segmented heating process, specifically including the following steps: First, raise the temperature to 300-500℃ at a heating rate of 10-20℃ / min and hold for 1-3 hours; then raise the temperature to 800-1200℃ at a heating rate of 5-10℃ / min and hold for 1-3 hours; finally, raise the temperature to 1700-2000℃ at a heating rate of 1-5℃ / min and hold for 1-6 hours. In step (1), the sulfur content in the high-sulfur coke is 3-8 wt%. In step (3), the water content in the asphalt is 2-3 wt%; In step (3), the metal chloride is selected from AlCl3, SiCl4 or TiCl4; In step (4), the reaction temperature is 450-650℃; the reaction time is 3-12 hours. The fast-charging artificial graphite anode material has a secondary particle structure.

2. The preparation method according to claim 1, wherein, In step (1), the heat treatment is carried out under a nitrogen protective atmosphere; And / or, in step (1), the sulfur content in the desulfurized coke is <100ppm; And / or, in step (2), the median particle size D 50 of the desulfurized coke powder is 5-8 μm.

3. The preparation method according to claim 1, wherein, In step (3), the softening point of the asphalt is 65-75℃; And / or, in step (3), the mass ratio of the metal chloride to the pitch is (5-15):100; And / or, in step (3), the softening point of the modified asphalt is 100-150℃.

4. The preparation method according to any one of claims 1-3, wherein, Step (3) specifically includes the following steps: The asphalt is placed in a reaction vessel and heated to 120-160℃. Under stirring, metal chlorides are added to the molten asphalt and reacted for 0.5-1 hour. Then, argon gas is introduced into the reaction vessel and heated to 330-390℃ under argon protection. The temperature is maintained for 2-6 hours to prepare modified asphalt.

5. The preparation method according to any one of claims 1-3, wherein, In step (4), the mass ratio of the modified asphalt to the desulfurized coke powder is (8-15):

100.

6. The preparation method according to any one of claims 1-3, wherein, In step (5), the carbonization temperature is 800-1000℃; the carbonization time is 3-12 hours. And / or, in step (5), the carbonization process is carried out under a nitrogen atmosphere; And / or, in step (6), the temperature of the graphitization treatment is 2850-3200℃; the time of the graphitization treatment is 8-24 hours.

7. The fast-charging artificial graphite negative electrode material prepared by the method of any one of claims 1-6, wherein the fast-charging artificial graphite negative electrode material has a secondary particle structure formed by D 50 single-particle graphites with nanometer-sized pores in the direction perpendicular to the graphite plane layer, wherein the single-particle graphites have a particle size of 5-8 μm.​ 8. The fast-charging artificial graphite anode material according to claim 7, wherein, In the secondary particle structure, the graphite structure between adjacent single graphite particles has nano-sized pores.

9. Use of the fast-charging artificial graphite anode material according to claim 7 or 8, for use in lithium-ion batteries.

10. A negative electrode for a lithium-ion battery, the negative electrode comprising the fast-charging artificial graphite negative electrode material as described in claim 7 or 8.

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