Petroleum coke microstructure regulation and control and graphite negative electrode material and preparation method thereof

Abstract

The invention discloses a petroleum coke microstructure regulation and graphite negative electrode material and a preparation method thereof.The preparation method utilizes heavy oil containing polycyclic aromatic hydrocarbon to generate a petroleum coke and graphite negative electrode material, and comprises the steps that after impurities in the heavy oil are removed, a structure regulator is added under the ultrasonic action, and then upper-layer and lower-layer heavy oil is generated; the materials are respectively used as raw materials of petroleum coke and a negative electrode material. According to the method, the low-sulfur and low-nitrogen quality of petroleum coke can be achieved without complex raw material pretreatment, hydrogenation and other processes, the production cost is reduced, the method is easy to apply and popularize in common petrochemical companies, high-added-value utilization of heavy oil of the petroleum and petrochemical companies is achieved, and the method is suitable for industrial production. The high-performance preparation of petroleum coke and the overall improvement of the comprehensive performance of artificial graphite are realized.

Description

Microstructure control of petroleum coke and graphite anode material and its preparation method Technical Field

[0001] This invention relates to a method for structural regulation of petroleum coke and preparation of artificial graphite anode materials for energy storage lithium batteries. Specifically, this invention relates to a method for obtaining artificial graphite anode materials by blending specific petroleum heavy aromatic raw materials, pyrolyzing them to obtain petroleum coke, and then drying, pulverizing, surface modifying, carbonizing, and graphitizing the coke. Background Technology

[0002] Currently, the anode materials used in commercial lithium-ion batteries mainly include carbon materials and non-carbon materials. Carbon materials, particularly graphite anodes, are the most commonly used, encompassing two main categories: artificial graphite and natural graphite. Artificial graphite is produced by graphitizing easily graphitizable carbons (such as petroleum coke, needle coke, and pitch coke) at high temperatures of 2800–3000℃ in an N2 atmosphere. The raw materials for artificial graphite anode materials consist of petroleum coke, needle coke, and pitch coke. Their microstructure comprises streamlined fibrous structures, sheet-like structures, and interlocking structures of varying sizes. The proportions of these structures vary depending on the choice of raw materials and processing conditions, thus requiring separate design for the uniformity of properties, electrochemical indicators, and application areas of the manufactured artificial graphite. Generally, high-specific-capacity artificial graphite anodes use needle coke as raw material, while ordinary specific-capacity anodes use inexpensive petroleum coke (also known as sponge coke). The choice of raw materials significantly impacts the performance of artificial graphite anodes, affecting the battery's specific capacity, cycle life, rate capability, and compaction density. When artificial graphite is used in different fields such as consumer, power, and energy storage batteries, the specific type of petroleum coke required as raw material varies, and the corresponding microstructure of the petroleum coke also differs. The differences in the properties of petroleum coke largely depend on the nature of the raw materials and their processing conditions.

[0003] Petroleum coke is produced from heavy oil (residue oil) or other heavy oil mixtures obtained after crude oil distillation. This mixture is passed at high flow rates through the furnace tubes of a 500°C heated furnace, where cracking and condensation reactions occur within a coking tower. The resulting coke is then cooled and decoked over a certain period. Because the chemical molecular structures of heavy oils obtained from different crude oil sources and processing methods vary, the properties of petroleum coke produced by different refineries differ. Petroleum coke produced by the same refinery can only meet the needs of a specific application.

[0004] CN202011139089.1 describes a process where inferior raw materials are heated to 360-390℃ and then subjected to vacuum distillation to obtain light non-ideal components, heavy non-ideal components, and a fraction with a distillation range of 350-500℃. The 350-500℃ fraction is then hydrorefined with hydrogen in the presence of a hydrorefining catalyst. The resulting product is then thermally cracked to obtain petroleum coke with a sulfur content of <0.5 wt% and an ash content of <0.3 wt%. The petroleum coke is then subjected to heat treatment and graphitization to obtain a carbon anode material with an initial discharge specific capacity ≥350 mA / h and an initial coulombic efficiency ≥90%. This process represents the currently mature industrialized petroleum coke-to-graphite preparation process, but it cannot overcome the performance limitations of existing artificial graphite, such as its relatively low specific capacity and lack of long-cycle capability.

[0005] CN202010595625.2 describes a graphite matrix with carbon nanotubes and amorphous carbon coated on its surface. The carbon nanotubes and amorphous carbon constitute 0.5-5% of the graphite matrix mass. The preparation process uses petroleum coke, pitch coke, or graphite electrode connector powder as raw materials. These materials are crushed, spheroidized, purified at high temperature, and then coated with carbon via CVD vapor deposition to obtain a low-temperature fast-charging artificial graphite anode material. The nanomaterials are compounded after graphite formation. Since graphite is the main material, 95% of the material's properties are determined by the graphite matrix, and the role of the nanomaterials is relatively weak.

[0006] Existing technologies have failed to obtain artificial graphite product forming technologies with different performance characteristics by designing the physical properties of heavy oil feedstocks and adjusting the structure of corresponding petroleum coke. Summary of the Invention

[0007] The purpose of this invention is to provide a method for controlling the microstructure of petroleum coke and preparing graphite anode materials. This method flexibly prepares petroleum coke with different microstructures from heavy petroleum raw materials, and further obtains lithium battery anode materials through crushing, surface modification, and heat treatment.

[0008] To achieve the above objectives, the present invention provides a method for the microstructure regulation of petroleum coke and the preparation of graphite anode materials. This preparation method utilizes heavy oil containing polycyclic aromatic hydrocarbons to generate petroleum coke and graphite anode materials, including: after removing impurities from the heavy oil, adding a structure modifier under ultrasonic action, and then using the resulting upper and lower layers of heavy oil as raw materials for petroleum coke and anode materials, respectively.

[0009] The preparation method of the present invention includes removing impurities by settling one or more of the first type of heavy oil raw materials to obtain heavy oil one, and removing metal impurities by centrifugation of one or more of the second type of heavy oil raw materials to obtain purified heavy oil two.

[0010] The preparation method of the present invention includes at least one of the following: the first type of heavy oil feedstock: catalytic cracking slurry oil, catalytic cycle oil, and reformed heavy aromatic oil; the sedimentation and removal process uses a sedimentation agent to remove metal impurities, the sedimentation agent is a polypropylene glycol ether compound, the amount of sedimentation agent added is 200-400 ppm, the sedimentation time is 12-20 hours, and the ash content of the heavy oil obtained after sedimentation is 200-1000 ppm.

[0011] The preparation method of the present invention uses at least one of the following: the second type of heavy oil feedstock includes ethylene tar, vacuum residue, thermal cracking residue, and deoiled pitch of vacuum residue; the equipment used for centrifugation to remove metal impurities includes at least one of a horizontal spiral centrifuge, a disc centrifuge, and a horizontal spiral sedimentation centrifuge; the second type of heavy oil feedstock is heated to between 130-150°C and enters the centrifuge; the centrifuge speed is 3000-4000 rpm; and the ash content of the purified heavy oil after metal impurity removal is 10-100 ppm.

[0012] The preparation method of this invention involves adding a structure modifier to the purified heavy oil II under ultrasonic action. After ultrasonic action and stirring, heavy oil III is generated. Then, heavy oil I and heavy oil III are mixed online at a weight ratio of 1 to 5:10, and the distillation range is adjusted to obtain a coking blended oil. Specifically, the process of adding the structure modifier to the purified heavy oil II under ultrasonic action includes: the purified heavy oil II is added to a blending tank equipped with an ultrasonic wave. The blending tank is equipped with a data acquisition unit, an ultrasonic modulator, and a frame stirrer. The power and action time of the ultrasonic generator are selected according to the volume of the blending tank and the mass of the heavy oil being processed. Preferably, the generator power of the blending tank is 350-400 W / L, and the ultrasonic action time is performed at a frequency of 20-30 seconds, 20-30 seconds off, 20-30 seconds on again, and 20-30 seconds off. The content of the structure modifier in the purified heavy oil II is 200-500 ppm. The structure modifier is dispersed under ultrasonication, while the mixing tank is stirred simultaneously at a rate of 300–500 r / min for 30–60 min, resulting in purified heavy oil II containing the structure modifier. Preferably, the online mixing temperature of heavy oil I and heavy oil III is 80–100°C, and the linear velocity is 0.3–0.5 m / s.

[0013] The preparation method of the present invention involves generating petroleum coke and high-temperature oil gas through a pyrolysis reaction of the coking mixed oil, and obtaining gasoline, diesel, light wax oil and heavy wax oil through separation of the high-temperature oil gas.

[0014] The preparation method of the present invention involves drying, coarsely crushing, and finely crushing the petroleum coke to obtain petroleum coke fine powder. The petroleum coke fine powder and asphalt powder are mixed, surface-composite modified, carbonized, and graphitized to obtain artificial graphite material.

[0015] Preferably, the drying process of the petroleum coke is carried out indirectly using steam in a dryer at a temperature of 150-200°C for 1-3 hours. The coarse and fine crushing process includes: first crushing to below 3mm using a jaw crusher, and then using a fine crusher, which can be an air jet mill or a mechanical grinder with crushing and grading functions. After crushing and grading, the D10 is 1-3µm, D90 is 18-27µm, and D50 is 6-18µm.

[0016] The preparation method of the present invention uses petroleum coke fine powder and asphalt powder in a mixing process by using homogeneous asphalt powder with a softening point of 250-300℃, the amount of asphalt powder being 12-15 wt% of petroleum coke fine powder, the mixing time being 30-60 min, and the mixing temperature being 40-60℃.

[0017] Preferably, the homogeneous asphalt powder includes at least one of petroleum asphalt and coal-based asphalt powder, and the particle size of the asphalt powder is D50 1-2 μm and D90 3-4 μm. Preferably, the mixing process is carried out in a conical mixer with a stirring speed of 2000-3000 r / min.

[0018] The preparation method of the present invention includes the following process: introducing a modifying gas and simultaneously introducing nitrogen as a carrier, performing surface composite modification treatment at 800-950°C for 1-3 hours.

[0019] The flow rate of the modified gas is 3-5 L / min·kg mixture, that is, each kilogram of solid material requires a mixture of gas to be introduced per minute;

[0020] The modified gas includes at least one of carbon dioxide, water vapor, oxygen, and ammonia, and the volume ratio of the modified gas to nitrogen is 1 to 2:10.

[0021] Preferably, the mixture of petroleum coke fine powder and asphalt powder undergoes composite surface modification treatment on the coke powder surface in a high-temperature surface modifier. The stirring speed in the high-temperature surface modifier is 600-800 r / min. During the modification process, at least one of carbon dioxide, water vapor, oxygen, and ammonia is introduced as the modifying gas, while nitrogen is used as the carrier. The flow rate of the modifying gas is 3-5 L / min·kg of the mixture, the volume ratio of the modifying gas to nitrogen is 1-2:10, the modification temperature is 800-950℃, and the time is 1-3 hours.

[0022] The preparation method of the present invention includes a carbonization process comprising: heating at a rate of 10-20°C / min under a nitrogen atmosphere, and carbonizing at 1500-1700°C for 0.5-1 hour.

[0023] Preferably, after the carbonization process is completed, the material is further cooled to room temperature under a nitrogen atmosphere to obtain the carbonized material.

[0024] The preparation method of the present invention includes the graphitization process comprising: heating to 2500-2700°C for 1-2 hours under a nitrogen atmosphere at a heating rate of 5-10°C / min.

[0025] Preferably, the artificial graphite material obtained after carbonization has a D50 of 16-22 μm and exhibits good capacity, cycle life, and fast charging performance after electrochemical testing. The delithiation specific capacity is 380-390 mAh / g, the initial efficiency is 95-97%, the capacity retention rate after 500 cycles at 0.1C is 93-95%, and the coin cell retention rate at 2C is 50-60%.

[0026] In the preparation method of the present invention, the removal of impurities from the heavy oil mainly refers to the removal of Fe, Ni, V, Al, Cu, Na, and Ca metallic impurities, with the ash content representing the total amount of each metallic impurity.

[0027] The preparation method of the present invention includes a structure-adjusting agent comprising porous carbon nanomaterials loaded with nano-metals.

[0028] The preparation method of the present invention involves preparing the porous carbon nanomaterial loaded with nano-metals by co-precipitation of metal salts and porous carbon nanomaterials. The preparation method includes: mixing an aqueous solution of a metal chloride and an ethylene glycol solution of the porous carbon nanomaterial, wherein the mass ratio of the metal chloride, the porous carbon nanomaterial, and the ethylene glycol is 3-7:100:500; then adding NaOH solution to adjust the pH to 9-10; slowly adding an ethylene glycol solution of dimethylamine borane at 55°C; reacting for 4 hours; cooling to room temperature and filtering; drying the product in a 70°C drying oven for 12 hours; and carbonizing at 600°C for 4 hours under an inert atmosphere to obtain the porous carbon nanomaterial loaded with nano-metals, wherein the metal particle size is 2-4 nm.

[0029] The preparation method of the present invention comprises a porous nano-carbon material including at least one of porous graphene, porous nanotubes, and porous nano-activated carbon; the metal includes at least one of nickel, cobalt, manganese, and molybdenum; the content of the nano-metal in the structure modifier is 1-3 wt%; and the specific surface area of ​​the porous nano-carbon material is 200-2000 m². 2 / g, with pore sizes between 0.4-10nm.

[0030] The working principle of porous carbon nanomaterials containing nano-metals is that, due to their small particle size, large specific surface area, and good dispersibility in heavy oil, coupled with ultrasonic treatment, they can fully contact the heavy oil, adsorbing large aromatic hydrocarbon clusters containing metals to inhibit their rapid condensation and formation of pyrolysis reaction centers, thereby generating a mesophase structure with smaller microcrystalline structures. The amount of structure modifier added can be adjusted according to the size of the metals and molecular weight in the heavy oil to achieve structural adjustment. Furthermore, during the heating process, the porous carbon nanomaterials containing nano-metals, through the injection of steam, catalyze the breaking of CS and CN bonds in the macromolecules of thiophene, pyridine, and quinoline containing impurities in the heavy oil, reducing the amount of impurities in the petroleum coke generated later. In addition, it promotes the development of graphite-like microcrystals and improves the degree of order in the subsequent high-temperature carbonization process.

[0031] Based on the performance requirements of artificial graphite anodes and lithium batteries, petroleum coke is used to adjust the aromatic molecular components differently according to different heavy oil feedstocks, and the effect of structure modifiers is combined to achieve flexible satisfaction of the requirements.

[0032] The preparation method of this invention includes the following distillation range adjustment process: mixing heavy oil I and heavy oil III and heating them using a tubular furnace with an outlet temperature of 350–370°C; setting 1–5 side-stream outlets for the heated mixture; maintaining an upper temperature of 120–150°C and a lower temperature of 360–380°C in the fractionation tower; collecting the aromatic basic components from the lower part; recovering the oil and gas from the top of the tower through a first vacuum system; the oil and gas first enter a first gas-liquid separator, and the gas phase is cooled by heat exchange in a first condenser; the pressure of the first vacuum system is 20–50 kPa, and the condensing medium is cooling water; gasoline is collected from the first side stream with a density (20°C) of 0.71–0.75 g / cm³. 3 The second line indicates diesel fuel, with a density (at 20℃) of 0.76–0.80 g / cm³. 3 The third lateral fraction is the wax oil fraction, with a density (20℃) of 0.80–0.82 g / cm³. 3 The fractionation column yields a well-balanced mixed heavy oil with a distillation range of 350–680℃ and a density (20℃) of 1.0–1.1 g / cm³. 3 It contains 0.5-2% asphaltene, 8-15% saturated hydrocarbons, 60-80% aromatics, 0.5-2% sulfur, 0.1-0.7% nitrogen, and 5-15% residual carbon.

[0033] The preparation method of this invention involves further heating the mixed heavy oil from the fractionation tower through a pyrolysis reaction to generate petroleum coke and high-temperature oil gas. The heating device is a tubular heater. According to the need to adjust the properties of the petroleum coke, steam is injected into the furnace tube. The ratio of steam flow rate to mixed heavy oil is 0.05-0.1 L steam / hr: 5 kg / hr mixed heavy oil. The outlet temperature of the heater is 480-510℃, which is a variable temperature program design. The temperature is gradually increased from one temperature point between 480-510℃ to another temperature point by 0.2-1℃ per hour. It also includes directly raising the temperature to another temperature point between 480-510℃ after stabilizing at any temperature point between 480-510℃ for a certain period of time, and then stabilizing at another temperature point between 480-510℃ for a period of time. The heated mixed heavy oil enters from the bottom of the pyrolysis reactor, where the internal temperature is 420–470°C. The residence time within the reactor is 24, 36, or 48 hours. The reactor pressure is designed with a variable pressure program of 0.1–0.7 MPa, gradually decreasing from one pressure point to another within the 0.1–0.7 MPa range by 0.01–0.02 MPa per hour. Alternatively, the pressure may be held constant at any point within the 0.1–0.7 MPa range for a certain period before being directly decreased to any other pressure point within the 0.1–0.7 MPa range and then held constant for a period. The purpose of this temperature and pressure program is to ensure the homogeneity of the generated petroleum coke.

[0034] The preparation method of this invention involves the following steps: Petroleum coke and high-temperature oil gas generated by the pyrolysis reaction are present. The petroleum coke remains in the pyrolysis reactor, while the high-temperature oil gas, at a temperature of 370–410°C, is discharged from the top of the reactor into a fractionation tower. There, it undergoes heat and mass transfer with the heavy mixed oil entering from the middle of the fractionation tower, resulting in a well-compositioned mixed heavy oil. After the petroleum coke is generated in the pyrolysis reactor, it undergoes further processing with wax oil heated to 480–510°C from the third side stream of the fractionation tower for 3–6 hours to homogenize the petroleum coke in the upper and lower parts of the reactor. The processed petroleum coke is then cooled to 100–150°C using low-temperature steam and water, and then cut out of the reactor by high-pressure water to obtain petroleum coke lumps of varying particle sizes. Testing revealed that the petroleum coke exhibits a fine mosaic structure with a proportion of 2–40%, a small flake structure with a proportion of 5–30%, a large flake structure with a proportion of 10–50%, a short fiber structure with a proportion of 3–35%, a fine fiber structure with a proportion of 20–50%, and a coarse fiber structure with a proportion of 3–15%. The above microstructure ratios can be flexibly adjusted according to the raw materials and modification conditions. The volatile matter content of petroleum coke is 8–12%, and its true density is 1.4–1.6 g / cm³. 3 Ash content 0.03–0.1%, sulfur content 0.2–0.4%, nitrogen content 0.05–0.1%.

[0035] The present invention also provides a graphite anode material obtained by the above preparation method.

[0036] The present invention also provides an application of the graphite anode material obtained by the above preparation method in lithium batteries.

[0037] This invention achieves low-sulfur and low-nitrogen quality petroleum coke without complex raw material pretreatment and hydrogenation processes, reducing production costs and making it easily applicable and widely promoted in ordinary petrochemical companies. The process technology for petroleum coke preparation has been adjusted, solving the problem of poor petroleum homogeneity in existing refineries and poor batch stability when used in lithium-ion battery anodes. Through the action of different types of heavy oil and structure modifiers, the microstructure of petroleum coke can be adjusted over a large range, overcoming the limitations of existing petroleum and petrochemical companies in terms of the limited types of raw materials and the low adjustability of some raw materials due to the inherent properties of internal equipment. The adjustment of the petroleum coke structure leads to an improvement in the capacity and cycle characteristics of the artificial graphite anode, increasing the added value of ordinary petroleum coke. Furthermore, through the design of artificial graphite composite modification, the existing asphalt coating process is adjusted, constructing a disordered carbon layer on the surface of the petroleum coke, expanding the channels for lithium-ion insertion and extraction, and improving the fast-charging performance of artificial graphite. In addition, the nano-metals in the structure modifier reduce the temperature of artificial graphitization, thus reducing the power consumption of graphitization. The method of this invention is beneficial for realizing the high-value-added utilization of heavy oil in petroleum and petrochemical companies, achieving high-performance preparation of petroleum coke, and improving the overall performance of artificial graphite.

[0038] This invention enables the preparation of petroleum coke with different microstructures through adjustments to the composition of petroleum feedstocks, design of aromatic molecular structures, and specific reaction conditions. The proportions of streamlined, embedded, and sheet-like structures can be controllably adjusted. Different artificial graphite material preparation processes are designed based on the structural differences of the petroleum coke. Through crushing, surface modification, carbonization, and graphitization, the size and morphology of graphite particles are controlled, and the microcrystalline arrangement on the graphite surface is optimized, thereby obtaining artificial graphite anode materials suitable for manufacturing consumer, power, and energy storage lithium batteries. This allows for flexible adjustment of the properties of petroleum coke and artificial graphite, improving the utilization rate of heavy oil feedstock in refineries and diversifying products, achieving customized transformation of refining byproducts into key materials for new energy batteries. Attached Figure Description

[0039] Figure 1 is a process flow diagram of heavy oil conditioning and upgrading, petroleum coke and lithium battery anode preparation.

[0040] In the attached figures, the following labels are used:

[0041] 1: First Aromatics Feed Tank

[0042] 1-1: Settling Tank

[0043] 1-2: Electric field desiccant

[0044] 2: Second Aromatics Feed Tank

[0045] 2-1: Centrifuge

[0046] 3: Structure Adjuster Tank

[0047] 4: Ultrasonic mixer

[0048] 4-1: Data Acquisition Unit

[0049] 4-2: Ultrasonic modulator

[0050] 5: Online Mixer

[0051] 6: Tubular heating furnace

[0052] 7: Pyrolysis reactor

[0053] 8: Distillation Tower

[0054] 9: Dryer

[0055] 10: Coarse crusher

[0056] 11: Fine crusher

[0057] 12: Mixer

[0058] 13: Surface Modification Machine

[0059] 14: Low-temperature carbonization furnace

[0060] 15: High-temperature graphitization furnace Detailed Implementation

[0061] The present invention will be further described below through specific embodiments, but the present invention is not limited to the following embodiments. Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional reagents, which can be purchased commercially or synthesized according to conventional methods in the art; the experimental methods, unless otherwise specified, are all conventional methods.

[0062] Figure 1 is a process flow diagram of heavy oil conditioning and upgrading, petroleum coke and lithium battery anode preparation. The first type of heavy oil raw material is stored in the first aromatic raw material tank 1. The first type of heavy oil raw material is fed into the settling tank 1-1, which is filled with a settling agent. The first type of heavy oil raw material is decomposed in the settling tank 1-1 to remove metal impurities, and then decomposed in the electric field deconsolidator 1-2 to obtain heavy oil one.

[0063] The second aromatic feedstock tank 2 stores the second type of heavy oil feedstock. After being heated to 130-150°C, the second type of heavy oil feedstock is fed into centrifuge 2-1, where metal impurities are removed by centrifugation to obtain purified heavy oil II.

[0064] Structure modifier tank 3 contains structure modifier. The structure modifier and purified heavy oil 2 in structure modifier tank 3 are input into ultrasonic mixer 4. Ultrasonic mixer 4 is equipped with data acquisition unit 4-1, ultrasonic modulator 4-2, and frame stirrer. In ultrasonic mixer 4, the structure modifier and purified heavy oil 2 are subjected to ultrasonic action and combined with stirring to generate heavy oil 3.

[0065] Heavy oil type 1 and heavy oil type 3 are both fed into online mixer 5, where they are mixed online at a weight ratio of 1 to 5:10 to obtain a mixture. The resulting mixture is then fed into tubular furnace 6 and heated. The outlet temperature of the furnace is 350–370°C. The heated mixed heavy oil is fed from the bottom of pyrolysis reactor 7, where the internal temperature is 420–470°C. The residence time in pyrolysis reactor 7 is 24, 36, or 48 hours. The pressure inside pyrolysis reactor 7 is designed to vary from 0.1 to 0.7 MPa, gradually decreasing from one pressure point to another within the 0.1–0.7 MPa range by 0.01–0.02 MPa per hour. Alternatively, the pressure may be maintained at any pressure point within the 0.1–0.7 MPa range for a certain period before being directly decreased to any other pressure point within the 0.1–0.7 MPa range and then maintained for a period.

[0066] The petroleum coke and high-temperature oil gas generated in pyrolysis reactor 7 remain in reactor 7. The high-temperature oil gas, with a temperature of 370–410°C, is discharged from the top of reactor 7 into fractionation tower 8, where it undergoes heat and mass transfer with the heavy mixed oil entering from the middle of fractionation tower 8, resulting in a well-composite heavy mixed oil in fractionation tower 8. After the petroleum coke is generated in pyrolysis reactor 7, it undergoes further processing with wax oil heated to 480–510°C from the third side stream of fractionation tower 8 for 3–6 hours to homogenize the petroleum coke in the upper and lower parts of the reactor. The processed petroleum coke is then cooled to 100–150°C using low-temperature steam and water, and cut out of pyrolysis reactor 7 by high-pressure water to obtain petroleum coke lumps of varying particle sizes.

[0067] Petroleum coke cut from pyrolysis reactor 7 is dried in dryer 9, coarsely crushed in coarse crusher 10, and finely crushed in fine crusher 11 to obtain petroleum coke fine powder. The petroleum coke fine powder and asphalt powder are mixed in mixer 12, then surface composite modified in surface modifier 13, carbonized in low temperature carbonization furnace 14, and graphitized in high temperature graphitization furnace to obtain artificial graphite material.

[0068] Evaluation method of the present invention:

[0069] The sampling and analysis methods for petroleum coke, including volatile matter, ash, and sulfur content, refer to SHT 0313-1992, "Petroleum Coke Inspection Method"; the true density refers to SHT 0033-1990, "Petroleum Coke True Density Determination Method"; the nitrogen content refers to SNT 2422-2010, "Determination of Nitrogen in Imported and Exported Petroleum Coke - Thermal Conductivity Method"; and the microstructure analysis refers to YBT 4822-2020, "Standard for Analysis of Mesophase Coke in Coal-Series Needle Coke". The testing of various indicators for graphite materials refers to GB / T24533-2019, "Test Methods for Graphite Anode Materials for Lithium-ion Batteries".

[0070] The battery was tested using a half-cell testing method. The negative electrode material was prepared with a weight ratio of CMC:SBR:Super-p = 95:1.5:2:1.5, mixed with an appropriate amount of deionized water to form a slurry. This slurry was then coated onto copper foil and dried in a vacuum drying oven for 12 hours to form the negative electrode sheet. The electrolyte was 1M LiPF6 / EC+DEC+DMC = 1:1:1. A polypropylene and polyethylene microporous membrane was used as the separator, and a lithium electrode was used as the counter electrode. The battery was then assembled. Constant current charge-discharge experiments were conducted using the Xinwei Battery Testing System. The initial charge-discharge and cycle performance were tested at a charge-discharge voltage of 0-3.0V and a current density of 0.1C. The coin cell retention rate was tested at a current density of 2C.

[0071] Example 1:

[0072] Using catalytic cracking slurry as the first type of heavy oil feedstock, a polypropylene glycol ether-based settling agent was first used at a dosage of 400 ppm for a settling time of 12 hours. The ash content of the clarified oil after settling was 300 ppm. The second type of heavy oil feedstock was vacuum residue, which was heated to 135°C and fed into a horizontal screw centrifuge at a speed of 3000 r / min. The purified heavy oil II, after removing metal impurities, had an ash content of 50 ppm.

[0073] A mixed solution of nickel chloride and molybdenum chloride, porous nano-activated carbon, and ethylene glycol was prepared in a mass ratio of 5:100:500. NaOH solution was then added to adjust the pH to 9.3. A dimethylamine borane solution in ethylene glycol was slowly added at 55°C, and the reaction was allowed to proceed for 4 hours. After cooling to room temperature, the mixture was filtered. The product was dried in a 70°C oven for 12 hours, followed by carbonization at 600°C under an inert atmosphere for 4 hours to obtain porous nano-activated carbon containing 1 wt% nano-nickel and molybdenum, with metal particle sizes ranging from 2 to 4 nm. The specific surface area of ​​the porous nano-activated carbon was 1800 m². 2 / g, with a pore size of 0.5-4nm. Porous nano-activated carbon containing nano-nickel and molybdenum was added to a mixing tank as a structure modifier at a mass ratio of 500ppm. The ultrasonic generator in the mixing tank was set to a power of 350W / L, with an ultrasonic treatment time of 30 seconds followed by a 30-second pause. The structure modifier was dispersed under ultrasonic treatment, and the mixing tank was stirred at a rate of 300r / min for 60min to obtain purified heavy oil II (i.e., heavy oil III) containing the structure modifier.

[0074] Heavy oil I and heavy oil III were mixed at a weight ratio of 3:10 at a mixing temperature of 80℃ and a linear velocity of 0.4 m / s. The resulting mixture was heated to 370℃ and then subjected to vacuum distillation at 30 kPa, together with the high-temperature oil and gas produced by the ongoing pyrolysis reaction at 380℃. The temperature at the top of the distillation column was 135℃, and the temperature at the bottom was 376℃. Gasoline was extracted from the first side stream, with a density (at 20℃) of 0.745 g / cm³. 3 The second line indicates diesel fuel, with a density (at 20℃) of 0.765 g / cm³. 3 The third lateral stream is the wax oil fraction, with a density (20℃) of 0.814 g / cm³. 3 The bottom of the fractionation tower yields a coking mixture with a reasonable distillation range and composition, ranging from 360 to 620°C, and a density (at 20°C) of 1.02 g / cm³. 3 The composition of the coking oil mixture is as follows: saturated content 18%, aromatic content 64%, gum content 17%, asphaltene content 2%, sulfur content 0.6%, nitrogen content 0.2%, and residual carbon content 15%. During the heating process of the coking oil mixture, a feed rate of 0.1 L / hr steam to 5 kg / hr coking oil mixture is used, with a total feeding time of 24 hours. After maintaining a constant temperature of 485℃ for 20 hours, the temperature is set to 500℃ for the last 4 hours. The pressure inside the pyrolysis reactor is 0.3 MPa for the first 20 hours and 0.2 MPa for the last 4 hours. The wax oil obtained from distillation is then heated to 500℃ to further process the generated petroleum coke for 4 hours, followed by cooling to obtain petroleum coke lumps. Testing revealed that the petroleum coke exhibits a fine mosaic structure proportion of 21%, a small flake structure proportion of 28%, a large flake structure proportion of 12%, a short fiber structure proportion of 20%, a fine fiber structure proportion of 15%, and a coarse fiber structure proportion of 4%. The volatile matter content is 10%, and the true density is 1.53 g / cm³. 3 Ash content 0.06%, sulfur content 0.25%, nitrogen content 0.12%.

[0075] Petroleum coke was indirectly dried with steam at 200℃ for 2 hours, then coarsely crushed by a jaw crusher to obtain particles smaller than 1mm. This was followed by air jet milling and classification to obtain petroleum coke micro-powder with D10 2.5µm, D90 25.2µm, and D50 15.5µm. Petroleum asphalt with a softening point of 280℃ was pulverized by an air jet mill to obtain asphalt fine powder with D50 1.3µm and D90 3.8µm. The petroleum coke fine powder and asphalt fine powder were added to a conical mixer at a mass ratio of 100:12, with a stirring speed of 2000 rpm and a mixing time of 30 min. The mixed modified raw materials were then added to a high-temperature surface modifier, with a stirring speed of 600 rpm. During the modification process, a mixture of carbon dioxide and nitrogen gas was introduced at a rate of 3 L / min·kg of material, with a carbon dioxide to nitrogen volume ratio of 1:10. The gas modification temperature was 800℃ for 1.5 hours. After modification, the mixture was cooled to room temperature under nitrogen and transferred to a carbonization furnace.

[0076] Under nitrogen atmosphere, carbonization was performed at 1500℃ for 1 hour at a heating rate of 15℃ / min, followed by graphitization at 2600℃ for 2 hours under nitrogen atmosphere in a graphitization furnace at a heating rate of 8℃ / min, yielding artificial graphite material. The graphite powder dimensions were D10 3.2µm, D90 26.1µm, and D50 16.2µm. As a lithium-ion battery anode material, the artificial graphite material, after electrochemical testing, exhibited a delithiation capacity of 382mAh / g, an initial coulombic efficiency of 96%, a capacity retention of 95% after 500 cycles at 0.1C, and a coin cell retention of 52% at 2C.

[0077] Example 2:

[0078] Using catalytic cycle oil as the first type of heavy oil feedstock, a commercially available polypropylene glycol ether-based settling agent was first added at a dosage of 200 ppm for 15 hours. The ash content of the clarified oil after settling was 400 ppm. The second type of heavy oil feedstock was ethylene tar, which was heated to 135°C and fed into a horizontal screw centrifuge at a speed of 3400 r / min. The purified heavy oil II, after removing metal impurities, had an ash content of 70 ppm.

[0079] A mixed solution of cobalt chloride and molybdenum chloride: porous graphene and ethylene glycol was prepared in a mass ratio of 6:100:500. NaOH solution was then added to adjust the pH to 9.3. A dimethylamine borane solution in ethylene glycol was slowly added at 55°C, and the reaction was allowed to proceed for 4 hours. After cooling to room temperature, the mixture was filtered. The product was dried in a 70°C oven for 12 hours, followed by carbonization at 600°C under an inert atmosphere for 4 hours to obtain porous graphene containing 1.5 wt% nano-cobalt and molybdenum, with metal particle sizes ranging from 2 to 4 nm. The specific surface area of ​​the porous graphene was 300 m². 2 / g, with pore sizes ranging from 0.5 to 4 nm. Porous graphene containing nano-cobalt and molybdenum was added to a mixing vessel as a structure modifier at a mass ratio of 300 ppm. The ultrasonic generator in the mixing vessel was set to a power of 400 W / L, with an ultrasonic treatment time of 30 seconds followed by a 30-second pause. The structure modifier was dispersed under ultrasonic treatment, and the mixing vessel was stirred at a rate of 400 r / min for 30 minutes to obtain purified heavy oil II (i.e., heavy oil III) containing the structure modifier.

[0080] Heavy oil I and heavy oil III were mixed at a weight ratio of 5:10 at a mixing temperature of 100℃ and a linear velocity of 0.3 m / s. The resulting mixture was heated to 370℃ and then distilled under reduced pressure (40 kPa) together with the high-temperature oil and gas (380℃) produced by the ongoing pyrolysis reaction. The upper temperature of the distillation column was 136℃, and the lower temperature was 375℃. Gasoline was extracted from the first side stream with a density (20℃) of 0.746 g / cm³. 3 The second line indicates diesel fuel, with a density (at 20℃) of 0.774 g / cm³. 3 The third lateral stream is the wax oil fraction, with a density (20℃) of 0.815 g / cm³. 3 The bottom of the fractionation tower yields a coking mixture with a reasonable distillation range and composition, ranging from 350 to 650°C, and a density (at 20°C) of 1.04 g / cm³. 3 The composition of the coking oil mixture is as follows: saturated content 12%, aromatic content 74%, gum content 13%, asphaltene content 1%, sulfur content 0.4%, nitrogen content 0.1%, and residual carbon content 16%. During the heating process of the coking oil mixture, a feed rate of 0.05 L / hr steam to 5 kg / hr coking oil mixture is used, with a total feeding time of 48 hours. The temperature is increased from 480℃ to 504℃ at a rate of 0.5℃ / hr. The pressure inside the pyrolysis reactor is gradually reduced from 0.6 MPa to 0.12 MPa at a rate of 0.01 MPa / h. The wax oil obtained from distillation is then heated to 500℃ to further process the generated petroleum coke for 3 hours, followed by cooling to obtain petroleum coke lumps. Testing revealed that the petroleum coke exhibits a fine mosaic structure of 3%, a small flake structure of 5%, a large flake structure of 37%, a short fiber structure of 4%, a fine fiber structure of 39%, and a coarse fiber structure of 12%. The volatile matter content is 10%, and the true density is 1.56 g / cm³. 3 Ash content 0.07%, sulfur content 0.22%, nitrogen content 0.11%.

[0081] Petroleum coke was indirectly dried with steam at 170℃ for 3 hours, then coarsely crushed by a jaw crusher to obtain particles smaller than 2mm. This was followed by air jet milling and classification to obtain petroleum coke micro-powder with D10 2.2µm, D90 19.5µm, and D50 7.3µm. Coal tar pitch with a softening point of 270℃ was pulverized by an air jet mill to obtain fine pitch powder with D50 1.7µm and D90 3.7µm. The petroleum coke fine powder and fine pitch powder were added to a conical mixer at a mass ratio of 100:15, with a stirring speed of 3000 rpm and a mixing time of 30 min. The mixed modified raw materials were then added to a high-temperature surface modifier with a stirring speed of 700 rpm. During the modification process, a mixture of steam and nitrogen was introduced at a rate of 5 L / min·kg of material, with a steam-nitrogen volume ratio of 1:10. The modification temperature was 950℃ for 1 hour. After modification, the mixture was cooled to room temperature under nitrogen and transferred to a carbonization furnace.

[0082] Under nitrogen atmosphere, carbonization was performed at 1700℃ for 0.5 hours at a heating rate of 10℃ / min, followed by graphitization at 2700℃ for 1 hour under nitrogen atmosphere in a graphitization furnace at a heating rate of 5℃ / min, yielding artificial graphite material. The graphite powder dimensions were D10 2.9µm, D90 24.5µm, and D50 15.8µm. As a lithium-ion battery anode material, the artificial graphite material, after electrochemical testing, exhibited a delithiation capacity of 387mAh / g, an initial coulombic efficiency of 95%, a capacity retention of 93% after 500 cycles at 0.1C, and a coin cell retention of 55% at 2C.

[0083] Example 3:

[0084] The selection and processing of the first and second types of heavy oil feedstocks are the same as in Example 1.

[0085] A mixed solution of cobalt chloride and molybdenum chloride: porous nanotubes and ethylene glycol was prepared in a mass ratio of 5:100:500. NaOH solution was then added to adjust the pH to 9.5. A dimethylamine borane solution in ethylene glycol was slowly added at 55°C, and the reaction was allowed to proceed for 4 hours. After cooling to room temperature, the mixture was filtered. The product was dried in a 70°C oven for 12 hours, followed by carbonization at 600°C under an inert atmosphere for 4 hours to obtain porous nanotubes containing 1.3 wt% nano-cobalt and molybdenum, with metal particle sizes ranging from 2 to 4 nm. The specific surface area of ​​the porous nanotubes was 400 m². 2 / g, with a pore size of 0.5-6nm. Porous nanotubes of cobalt and molybdenum were added as structure modifiers to a mixing vessel at a mass ratio of 200ppm. The ultrasonic generator in the mixing vessel was set to a power of 400W / L, with an ultrasonic treatment time of 20 seconds followed by a 20-second pause. The structure modifiers were dispersed under ultrasonic treatment, and the mixing vessel was stirred at a rate of 500r / min for 50min to obtain purified heavy oil II (i.e., heavy oil III) containing the structure modifiers.

[0086] Heavy oil I and heavy oil III were mixed at a weight ratio of 1:10 at a mixing temperature of 100℃ and a linear velocity of 0.3 m / s. The resulting mixture was heated to 375℃ and then subjected to vacuum distillation at a pressure of 50 kPa, together with the high-temperature oil and gas (380℃) generated during the pyrolysis reaction. The upper temperature of the distillation column was 145℃, and the lower temperature was 370℃. Gasoline was extracted from the first side stream, with a density (20℃) of 0.748 g / cm³. 3 The second line indicates diesel fuel, with a density (at 20℃) of 0.782 g / cm³. 3 The third lateral stream is the wax oil fraction, with a density (20℃) of 0.810 g / cm³. 3 The bottom of the fractionation tower yields a coking mixture with a reasonable distillation range and composition, ranging from 360 to 620°C, and a density (at 20°C) of 1.06 g / cm³. 3 The composition of the coking oil mixture is as follows: saturated content 20%, aromatic content 63%, gum content 14.5%, asphaltene content 2.5%, sulfur content 0.6%, nitrogen content 0.2%, and residual carbon content 15%. During the heating process, the coking oil mixture is fed at a rate of 0.1 L / hr steam to 5 kg / hr coking oil mixture, with a total feeding time of 36 hours. After maintaining a constant temperature of 483℃ for 24 hours, the temperature is set to 502℃ for the next 12 hours. The pressure inside the pyrolysis reactor is 0.3 MPa for the first 24 hours and 0.2 MPa for the next 12 hours. The wax oil obtained from distillation is then heated to 500℃ to further process the generated petroleum coke for 4 hours, followed by cooling to obtain petroleum coke lumps. Testing revealed that the petroleum coke exhibits a fine mosaic structure of 15%, a small flake structure of 25%, a large flake structure of 27%, a short fiber structure of 4%, a fine fiber structure of 21%, and a coarse fiber structure of 8%. The volatile matter content is 9%, and the true density is 1.56 g / cm³. 3 Ash content 0.06%, sulfur content 0.25%, nitrogen content 0.12%.

[0087] Petroleum coke was indirectly dried with steam at 180℃ for 2 hours, then coarsely crushed by a jaw crusher to obtain particles smaller than 1mm. This was followed by air jet milling and classification to obtain petroleum coke micro-powder with D10 2.5µm, D90 25.2µm, and D50 14.8µm. Coal tar pitch with a softening point of 250℃ was pulverized by an air jet mill to obtain fine pitch powder with D50 1.8µm and D90 3.5µm. The petroleum coke fine powder and fine pitch powder were added to a conical mixer at a mass ratio of 100:12, with a stirring speed of 2500 r / min and a mixing time of 60 min. The mixed modified raw materials were then added to a high-temperature surface modifier, with a stirring speed of 600 r / min. A mixture of ammonia and nitrogen was introduced during the modification process at a rate of 3 L / min·kg of material, with a volume ratio of ammonia to nitrogen of 1:10. The modification temperature was 800℃ for 1 hour. After modification, the mixture was cooled to room temperature under nitrogen and transferred to a carbonization furnace.

[0088] Under nitrogen atmosphere, carbonization was performed at 1600℃ for 1 hour at a heating rate of 12℃ / min, followed by graphitization at 2600℃ for 1 hour under nitrogen atmosphere in a graphitization furnace at a heating rate of 8℃ / min, yielding artificial graphite material. The graphite powder dimensions were D10 2.9µm, D90 25.5µm, and D50 15.2µm. As a lithium-ion battery anode material, the artificial graphite material underwent electrochemical testing, exhibiting a delithiation capacity of 385mAh / g, an initial coulombic efficiency of 95%, a capacity retention of 94% after 500 cycles at 0.1C, and a coin cell retention of 56% at 2C.

[0089] Comparative Example 1:

[0090] A coking blend was obtained by mixing the same first-type heavy oil feedstock and the second-type heavy oil feedstock as in Example 1 at a weight ratio of 3:10. The distillation range was 340–580°C, and the density (at 20°C) was 1.04 g / cm³. 3The pyrolysis raw materials contained 22% saturated hydrocarbons, 58% aromatic hydrocarbons, 18% resins, 2% asphaltenes, 0.7% sulfur, 0.2% nitrogen, and 11% residual carbon. The pyrolysis reaction was carried out in an electrically heated reactor at 505℃, 0.3 MPa, and 10 hours to obtain pyrolysis coke, which was then pulverized to obtain particles with D10 of 2.7 μm, D50 of 16.8 μm, and D90 of 26.3 μm. Petroleum asphalt with a softening point of 280℃ was pulverized using an air jet mill to obtain asphalt powder with D50 of 1.3 μm and D90 of 3.8 μm. The pyrolysis coke powder and asphalt powder were mixed at a ratio of 100:12, with a stirring speed of 2000 r / min and a mixing time of 30 min. The mixed modified raw materials were added to a high-temperature surface modifier, and the stirring speed was 600 r / min. During the modification process, a mixture of carbon dioxide and nitrogen was introduced at a rate of 3 L / min·kg of material, with a carbon dioxide to nitrogen volume ratio of 1:10. The modification temperature was 800℃, and the time was 1.5 hours. After the modification was completed, the mixture was cooled to room temperature under nitrogen and then transferred to a carbonization furnace.

[0091] Under nitrogen atmosphere, carbonization was carried out at 1500℃ for 1 hour at a heating rate of 15℃ / min, followed by graphitization at 2600℃ for 2 hours under nitrogen atmosphere in a graphitization furnace at a heating rate of 8℃ / min, yielding artificial graphite material. The graphite powder dimensions were D10 2.4µm, D50 16.5µm, and D90 27.5µm. As a lithium-ion battery anode material, the artificial graphite material, after electrochemical testing, exhibited a delithiation capacity of 225mAh / g, an initial coulombic efficiency of 56%, a capacity retention of 12% after 500 cycles at 0.1C, and a coin cell retention of 8% at 2C.

[0092] Comparative Example 2

[0093] A coking blend was obtained by mixing the same first-type heavy oil feedstock and the second-type heavy oil feedstock as in Example 1 at a weight ratio of 3:10. The distillation range was 340–580°C, and the density (at 20°C) was 1.04 g / cm³. 3 The pyrolysis raw materials contained 22% saturated hydrocarbons, 58% aromatic hydrocarbons, 18% gum, 2% asphaltenes, 0.7% sulfur, 0.2% nitrogen, and 11% residual carbon. The pyrolysis reaction was carried out in an electrically heated reactor at 505℃, 0.3 MPa, and 10 hours to obtain pyrolytic coke, which was then pulverized to obtain particles with D10 of 2.7 μm, D50 of 16.8 μm, and D90 of 26.3 μm.

[0094] The coal tar pitch with a softening point of 270℃ was then pulverized by an air jet mill to a fine powder with a D50 of 1.7µm and a D90 of 3.7µm. This powder was added to a conical mixer at a ratio of 100:15 (petroleum coke powder to fine asphalt powder) at a stirring speed of 3000 rpm for 30 minutes. The mixed modified raw material was then added to a high-temperature surface modifier at a stirring speed of 700 rpm, with nitrogen gas introduced during the process. The modification temperature was 800℃ for 18 hours. After completion, the mixture was cooled to room temperature under nitrogen gas and then transferred to a carbonization furnace.

[0095] Under nitrogen atmosphere, carbonization was performed at 1700℃ for 0.5 hours at a heating rate of 10℃ / min, followed by graphitization at 2700℃ for 1 hour under nitrogen atmosphere in a graphitization furnace at a heating rate of 5℃ / min, yielding artificial graphite material. The graphite powder dimensions were D10 2.2µm, D50 16.2µm, and D90 27.1µm. As a lithium-ion battery anode material, the artificial graphite material, after electrochemical testing, exhibited a delithiation capacity of 335mAh / g, an initial coulombic efficiency of 92%, a capacity retention of 85% after 500 cycles at 0.1C, and a coin cell retention of 32% at 2C.

[0096] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the microstructure of petroleum coke and preparing graphite anode materials, characterized in that, The preparation method utilizes heavy oil containing polycyclic aromatic hydrocarbons to generate petroleum coke and graphite anode materials, including: after removing impurities from the heavy oil, adding a structure modifier under ultrasonic action, and then using the resulting upper and lower layers of heavy oil as raw materials for petroleum coke and anode materials, respectively.

2. The preparation method according to claim 1, characterized in that, The impurity removal includes removing metal impurities from one or more of the first type of heavy oil feedstock by sedimentation to obtain heavy oil one, and removing metal impurities from one or more of the second type of heavy oil feedstock by centrifugation to obtain purified heavy oil two.

3. The preparation method according to claim 2, characterized in that, The first type of heavy oil feedstock includes at least one of catalytic cracking slurry oil, catalytic cycle oil, and reformed heavy aromatic oil; the sedimentation and removal process uses a sedimentation agent to remove metal impurities, the sedimentation agent is a polypropylene glycol ether compound, the amount of sedimentation agent added is 200-400 ppm, the sedimentation time is 12-20 hours, and the ash content of the heavy oil obtained after sedimentation is 200-1000 ppm.

4. The preparation method according to claim 2, characterized in that, The second type of heavy oil feedstock includes at least one of ethylene tar, vacuum residue, thermal cracking residue, and deoiled pitch from vacuum residue; the equipment used for centrifugation to remove metal impurities includes at least one of horizontal screw centrifuge, disc centrifuge, and horizontal screw sedimentation centrifuge; the second type of heavy oil feedstock is heated to between 130-150°C and enters the centrifuge; the centrifuge speed is 3000-4000 rpm; and the ash content of the purified heavy oil after metal impurity removal is 10-100 ppm.

5. The preparation method according to claim 4, characterized in that, The purified heavy oil II is added to a structure modifier under ultrasonic treatment. After ultrasonic treatment and stirring, heavy oil III is generated. Then, heavy oil I and heavy oil III are mixed online at a weight ratio of 1 to 5:

10. After that, the distillation range is adjusted to obtain coking mixed oil.

6. The preparation method according to claim 5, characterized in that, The coking mixture is pyrolyzed to produce petroleum coke and high-temperature oil gas, which is then separated to obtain gasoline, diesel, light wax oil, and heavy wax oil.

7. The preparation method according to claim 6, characterized in that, The petroleum coke is dried, coarsely crushed, and finely pulverized to obtain petroleum coke fine powder. The petroleum coke fine powder and asphalt powder are mixed, surface-composite modified, carbonized, and graphitized to obtain artificial graphite material.

8. The preparation method according to claim 7, characterized in that, The mixing process of the petroleum coke fine powder and the asphalt powder uses homogeneous asphalt powder with a softening point of 250-300℃, the amount of the asphalt powder is 12-15 wt% of the petroleum coke fine powder, the mixing time is 30-60 min, and the mixing temperature is 40-60℃.

9. The preparation method according to claim 7, characterized in that, The surface composite modification process includes: introducing a modifying gas and simultaneously introducing nitrogen as a carrier, performing surface composite modification treatment at 800-950℃ for 1-3 hours; the flow rate of the modifying gas is 3-5 L / min·kg mixture; wherein the modifying gas includes at least one of carbon dioxide, water vapor, oxygen, and ammonia, and the volume ratio of the modifying gas to nitrogen is 1-2:

10.

10. The preparation method according to claim 7, characterized in that, The carbonization process includes: heating at a rate of 10-20°C / min under a nitrogen atmosphere, heating to 1500-1700°C for 0.5-1 hour.

11. The preparation method according to claim 7, characterized in that, The graphitization process includes: heating to 2500-2700℃ under a nitrogen atmosphere at a heating rate of 5-10℃ / min for 1-2 hours for graphitization treatment.

12. The preparation method according to claim 1, characterized in that, The removal of impurities from heavy oil mainly refers to the removal of metallic impurities such as Fe, Ni, V, Al, Cu, Na, and Ca.

13. The preparation method according to claim 1, characterized in that, The structure modifier includes porous carbon nanomaterials loaded with nano-metals.

14. The preparation method according to claim 13, characterized in that, The porous carbon nanomaterial loaded with nano-metals is prepared by co-precipitation of metal salts and porous carbon nanomaterials. The preparation method includes: mixing an aqueous solution of metal chloride and an ethylene glycol solution of porous carbon nanomaterials, wherein the mass ratio of metal chloride, porous carbon nanomaterials and ethylene glycol is 3-7:100:500; then adding NaOH solution to adjust the pH to 9-10; adding an ethylene glycol solution of dimethylamine borane; reacting; cooling; filtering; drying; and carbonizing under an inert atmosphere to obtain the porous carbon nanomaterial loaded with nano-metals.

15. The preparation method according to claim 14, characterized in that, The porous nanocarbon material comprises at least one of porous graphene, porous nanotubes, and porous activated carbon nanotubes; the metal comprises at least one of nickel, cobalt, manganese, and molybdenum; the content of the nanometal in the structure modifier is 1-3 wt%; and the specific surface area of ​​the porous nanocarbon material is 200-2000 m². 2 / g, with pore sizes between 0.4-10nm.

16. The preparation method according to claim 5, characterized in that, The distillation range adjustment process includes: mixing heavy oil I and heavy oil III and heating them, then feeding them into a fractionation tower to obtain coking mixed oil.

17. A graphite anode material obtained by the preparation method according to any one of claims 1-16.

18. The application of a graphite anode material obtained by the preparation method according to any one of claims 1-16 in a lithium battery.

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