Manufacturing method of hard carbon-graphite sea-island structure spherical negative electrode material

Abstract

The invention provides a manufacturing method of a hard carbon-graphite sea-island structure spherical negative electrode material. Graphite micro powder is dispersed and distributed in a hard carbon component ocean as an island; the hard carbon component precursor is prepared by the following steps: heating and uniformly mixing modified asphalt and graphite micro-powder, and then carrying out water-based homogeneous emulsification, dispersion and balling on liquid-solid slurry and carrying out hot isostatic pressure cross-linking curing on the liquid-solid slurry; the modified asphalt can be subjected to controllable chemical crosslinking, has a thermoplastic processing window, and can be subjected to chemical crosslinking curing at a higher temperature to obtain a spherical particle semi-finished product which is not easy to adhere; the semi-finished product is carbonized in a loose state and subjected to subsequent CVD surface hole sealing, the modified asphalt component subjected to cross-linking and curing is converted into an ocean component with hard carbon as a main component, a finished product of the hard carbon-graphite sea-island structure spherical negative electrode material with the power characteristic and the high energy density characteristic is obtained, the average particle size D50 of the finished product is 7-15 micrometers, the true density is larger than or equal to 1.85 g / cm < 3 >, and the service life of the finished product is prolonged. The compaction density is larger than or equal to 1.35 g / cm < 3 >, the BET specific surface area is smaller than or equal to 6 m < 2 > / g, and the 5C / 1C charging capacity ratio is larger than 90%.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion secondary batteries, and in particular to a high-efficiency, low-cost, and highly consistent manufacturing method for anode materials that combine fast charging and high energy density. Background Technology

[0002] Graphite, as the negative electrode active material for lithium-ion batteries, possesses high specific capacity, good electrochemical reversibility, relatively low volume expansion rate, and high electronic conductivity. With its widely available raw materials, it is currently the mainstream negative electrode material for lithium-ion rechargeable batteries. Commercially available graphite negative electrode materials mainly include artificial graphite and pitch-coated modified natural graphite. Currently, the mainstream use of artificial graphite powder as the negative electrode active material in the power battery and energy storage battery industries exceeds 83% of the market share.

[0003] Conventional artificial graphite anode materials are made from calcined needle-shaped coke or asphalt-modified petroleum coke. The raw materials are pulverized / shaped into primary particles / coated with asphalt, or modified with asphalt to form secondary particles / carbonized, and then fed into a high-temperature graphitization furnace for high-temperature graphitization treatment in the range of 2900-3200℃. Alternatively, after high-temperature graphitization, the material is cooled and then pulverized / shaped again, followed by asphalt coating / carbonization to obtain modified artificial graphite powder. In the development of lithium-ion battery anode materials, there is also a high-end artificial graphite manufactured using mesophase carbon microspheres through high-temperature graphitization. This involves heating silicone oil to a high temperature range of approximately 300-400℃ above the softening point of the mesophase asphalt, emulsifying it into spheres, cooling it to room temperature, separating it with a centrifuge, washing it with benzene or acetone solvent, drying it, and then undergoing further high-temperature graphitization treatment to obtain spherical artificial graphite anode materials with better power characteristics. Compared to the anisotropic crystal orientation of flake-like natural graphite powder, the polycrystalline structure of artificial graphite powder exhibits better isotropic crystal orientation. The powder surface is relatively smooth, with fewer active sites and a smaller specific surface area. It has a higher initial efficiency than natural graphite, a relatively longer cycle life, and better rate performance. The main drawback of traditional methods for manufacturing artificial graphite anode materials is the requirement for high-temperature graphitization, which results in a long processing cycle, high energy consumption, and significant burn-off of the resistive material filling the graphite crucible during high-temperature graphitization. Consequently, the overall cost of artificial graphite anode materials is relatively high.

[0004] Traditional pitch-coated modified natural graphite uses fine-particle pitch powder obtained by air jet milling to solid-phase coat natural graphite powder, followed by carbonization. The resulting pitch-coated modified natural graphite anode material has the advantages of low cost and high compaction density. However, its main disadvantage is the poor stability of the soft carbon coating layer formed after pitch coating. During the high-speed stirring process of preparing the anode slurry, the soft carbon coating layer is easily damaged by the impact of stirring. During the rolling process of making the anode sheet, the soft carbon coating layer is also easily crushed and destroyed. In actual use, the specific surface area increases again, resulting in a 3-8% lower initial efficiency for the entire battery compared to artificial graphite, and a significantly shorter cycle life. Furthermore, the anisotropic nature of the flake-like polycrystalline structure of natural graphite means that lithium ions are inserted primarily from the end face, resulting in a small effective insertion or extraction area. This leads to poor charge / discharge rate characteristics, affecting rate performance, and making lithium plating more likely during fast charging, thus compromising battery safety.

[0005] The uniformity of natural graphite powder coated with asphalt in the liquid phase is improved compared to the solid phase coating method. The liquid phase coating process often requires the use of organic solvents such as tetrahydrofuran or aromatic hydrocarbon solvents such as wash oil to dissolve the asphalt into a binder. Natural graphite powder is mixed and coated in the asphalt solution, and subsequent vacuum heating is required to remove the solvent, which poses a risk of flammability and explosion, as well as environmental pressure. The soft carbon coating layer formed after carbonization also has the problem of structural instability, and the battery performance is not enough to compete with batteries made of artificial graphite.

[0006] With the market demand for electric vehicles to solve range anxiety and reduce costs, the performance requirements for fast charging of anode active materials have increased from 1.3C in the early market to 4C or even 5C fast charging. Traditional asphalt-coated natural graphite or artificial graphite anode materials have encountered rate performance bottlenecks and are prone to lithium plating during fast charging, making it difficult to meet the market demand for 5C fast charging performance.

[0007] Hard carbon anode materials possess superior lithium-ion transport performance and excellent rate capability. However, their disadvantage lies in their nanoscale microporous structure. When used as anode materials for lithium-ion batteries, hard carbon powder exhibits low true density, low compaction density, and low initial efficiency. The true density of conventional hard carbon powder materials is generally between 1.50 and 1.65 g / cm³. While improving the rate capability of the battery, conventional hard carbon powder materials significantly reduce the compaction density of the electrode and the energy density of the battery. The compaction density of conventional hard carbon anode materials is generally below 1.25 g / cm³, falling far short of the market expectation of a compaction density of over 1.35 g / cm³, thus failing to meet the high energy density requirements of power batteries. Furthermore, when traditional hard carbon powder materials are used in lithium batteries, the large BET specific surface area results in a low initial efficiency.

[0008] In order to improve the energy density of the battery while meeting the fast charging characteristics, literature CN117012936A proposed to granulate graphite particles with modified asphalt to obtain secondary particles with hard carbon-soft carbon composite structure. In order to improve the bonding strength of the interface between the two, it is proposed to use pore-forming agents such as sodium hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate to be mixed with graphite particles and then calcined to create pores on the surface of graphite powder by high-temperature reaction etching.

[0009] Literature CN114068886A proposes to mix urea, sodium carbonate, or ammonium bicarbonate into graphite raw materials for vapor-phase etching and nitriding treatment of graphite powder surface. The calcination treatment is carried out in conventional roller kiln, pusher kiln, rotary kiln, or box furnace at a temperature between 850-1100℃. The above-mentioned atmospheric pressure treatment process for surface etching and pore-forming of graphite powder has the disadvantage of environmental pollution. In addition, the atmospheric pressure treatment process also has the disadvantage of uneven gas-phase mass transfer between powders, resulting in insufficient uniformity of reaction pore-forming and product consistency.

[0010] Literature CN 111628170A proposes a method for heat-treating petroleum coke raw powder in a carbon dioxide atmosphere at a temperature range of 600-700℃ to obtain porous petroleum coke. This porous petroleum coke is then mixed with modified asphalt and subjected to oxidation, carbonization, and high-temperature graphitization to manufacture hard carbon-graphite composite secondary particle anode materials. This process heats the petroleum coke raw powder in a carbon dioxide atmosphere at a temperature range of 600-700℃. At this temperature, the petroleum coke raw powder is not fully calcined, and the pores formed by the decomposition and gas production are uneven and have large pore sizes. The high-temperature graphitization process in this process also has the disadvantages of high energy consumption and high production costs.

[0011] Literature CN115312731A proposes acid activation of graphite powder and surface oxidation etching to create pores at 200 to 500°C by introducing an oxidizing atmosphere. The oxidants for the modified asphalt include hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid, potassium dichromate, etc. The modified asphalt is then coated and carbonized to form a hard carbon-graphite composite negative electrode active material. However, this method involves acid washing and activation on the surface of the graphite core, which raises environmental concerns. Furthermore, this method is prone to generating bubbles during the oxidative crosslinking treatment of the asphalt.

[0012] Literature CN109037603A proposes a novel method for modifying hard carbon anode materials into spherical porous, pitch-based spherical shapes. The method involves pulverizing high-temperature coal-based pitch, adding terephthalaldehyde as a crosslinking agent under nitrogen protection for crosslinking, followed by the addition of ammonium persulfate as an oxidizing agent and oxygen purging for oxidation, resulting in high-temperature crosslinked oxidized pitch. This is then followed by spray granulation into spheres, carbonization, and high-temperature graphitization. The literature indicates that the modified spherical hard carbon anode material obtained using this method exhibits good rate performance, with a 30C / 1C capacity retention greater than 98%, a reversible specific capacity greater than 400 mAh / g, an initial efficiency greater than 80%, and a capacity retention greater than 85% after 500 cycles. According to the data in the literature, the true density of this pitch-crosslinked modified hard carbon anode material is 1.62 g / cm³. 3 Compacted density 1.25 g / cm³ 3 The results are all too low to meet the high energy density requirements of lithium-ion batteries. Although conventional spray granulation can achieve a certain degree of powder sphericity, many tiny bubbles are easily generated during the high-temperature cross-linking of the modified asphalt precursor, which affects the compressive strength and specific surface area of ​​the powder material. During the manufacturing process of the negative electrode sheet, the negative electrode active material powder with bubbles is easily crushed in the rolling process, the specific surface area of ​​the powder increases rapidly, the first efficiency of the battery is seriously reduced, and the cycle life of the battery will also be negatively affected.

[0013] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, this invention provides a lithium-ion battery anode material with good rate capability, high energy density, low manufacturing cost, stable product structure, good adaptability to the process requirements of lithium battery manufacturing, and stable performance. Summary of the Invention

[0014] This invention proposes a method for manufacturing a hard carbon-graphite island-structured spherical anode material. The hard carbon component acts as the ocean within the island structure, serving as a complete, interconnected carrier or coating layer. Graphite micropowder acts as the island within the island structure, dispersed within the ocean matrix of the hard carbon component. The precursor for the hard carbon component is modified bitumen (MP), which is dispersed into spheres via water-based homogeneous emulsification and then subjected to thermostatic crosslinking curing. The modified bitumen (MP) possesses the following technical characteristics: it enables controllable chemical crosslinking, has a thermoplastic processing window, and can chemically crosslink and cure at higher temperatures to obtain non-agglomerated spherical particle semi-finished products. After initial melting, the modified bitumen (MP) forms a low-viscosity liquid melt. During the hot processing of kneading and mixing with graphite micropowder, even if some chemical crosslinking reaction occurs, it still retains thermoplasticity, ensuring uniform dispersion into a liquid-solid slurry. Furthermore, it can be dispersed into micron-sized spherical particles using hot water and a homogeneous emulsification method (partial crosslinking). Spherical Patches (hereinafter referred to as PCSP) are uniformly distributed in an aqueous emulsion. The homogenized aqueous emulsion is placed into a high-pressure vessel, and the PCSP is subjected to thermostatic crosslinking curing treatment under high temperature and high pressure. The material temperature during the thermostatic crosslinking curing treatment is between 135°C and 190°C. Compressed air, high-pressure oxygen, high-pressure nitrogen, or compressed air containing ozone, or a combination of these gases, are pumped into the high-pressure vessel to control the ambient pressure (P1) inside the high-pressure vessel to be at least 0.20 MPa to 1 MPa higher than the saturated vapor pressure (P0) of the hot water corresponding to the material temperature.At 20 MPa, using superheated water in a water-based emulsion under high temperature and pressure as the medium to transmit static pressure, and with the crosslinking time controlled between 10 minutes and 6 hours, the PCSP in the water-based emulsion was sufficiently crosslinked and cured after treatment, preventing the formation of bubbles in the PCSP. Further drying methods included spray drying or slow, stepped cooling and depressurization of the material followed by drying in an atmospheric pressure oven to obtain crosslinked and cured spherical powder particles (Wholly Cross-linked Spherical). Particles (hereinafter referred to as WCSP); WCSP is subjected to a second carbonization treatment and subsequent pulsed high-pressure CVD surface sealing treatment in a loosely packed or vibrated physical state. The modified asphalt component after cross-linking and curing of WCSP is transformed into a marine component with hard carbon structure. Graphite micropowder is distributed in an island-like manner in the marine matrix of hard carbon component. After cooling to below 300°C and exiting the furnace, it is passed through a 200-mesh vibrating screen or air classification to remove magnetic foreign matter, resulting in a finished product of hard carbon-graphite island structure spherical negative electrode material with both power characteristics and high energy density characteristics. Its average particle size D50 is between 7-15 micrometers, for example, the average particle size D50 is controlled between 7-9 micrometers, 9-11 micrometers, 11-13 micrometers, 13-15 micrometers, D90 is less than 20 micrometers, and true density is greater than or equal to 1.85 g / cm³. 3 The compacted density is greater than or equal to 1.35 g / cm³. 3 First-time coulombic efficiency greater than or equal to 85%, reversible specific capacity greater than or equal to 350 mAh / g, and BET specific surface area less than or equal to 6 m². 2 / g, 5C / 1C charging capacity ratio greater than or equal to 90%.

[0015] The raw materials for modified bitumen (MP) include: medium-temperature bitumen with a softening point between 75°C and 95°C as the main material; high-temperature bitumen with a softening point between 100°C and 180°C, viscosity modifier, peroxide crosslinking agent, and multifunctional co-crosslinking agent as auxiliary materials; the above raw materials are kneaded and mixed at high temperature; during batching, the ratio of the volume of the modified bitumen (MP) melt as the liquid portion to the sum of the volumes of the (MP) melt and the graphite powder solid is greater than or equal to 58 vol.% and less than or equal to 90 vol.%; the liquid-solid mixture of (MP) and graphite powder is mixed at a temperature above 115°C in a vacuum kneader, a BUSS type reciprocating single-screw extruder, or other types of mixing equipment. The mixture is kneaded and mixed to form a uniform thermoplastic liquid-solid slurry. During the kneading and mixing process, some chemical cross-linking occurs between the polymers inside the (MP) while the liquid-solid slurry retains its thermoplastic physical state. The liquid-solid slurry is then controlled to be cooled to between 95°C and 100°C. Using hot water containing surfactants and dispersants at a temperature between 95°C and 100°C as a medium, the liquid-solid slurry is homogenized, emulsified, and dispersed into spheres. The liquid-solid slurry is then high-speed sheared and dispersed into spherical particles, which are then distributed in the hot water to form a uniform emulsion. When homogenizing and dispersing the liquid-solid slurry into spheres in hot water at normal pressure, the chemical cross-linking reaction rate in the (MP) is relatively slow due to temperature limitations.

[0016] The manufacturing method of this invention is described in detail below, including the following process steps:

[0017] Step 1: Preparation of graphite micropowder with high specific surface area

[0018] The raw materials for graphite micron powder include natural graphite, artificial graphite, or combinations thereof, with an average particle size D50 between 2 and 8 micrometers, preferably natural graphite micron powder with an average particle size D50 between 3 and 6 micrometers. The particle size D90 of the graphite micron powder raw materials is controlled to be less than or equal to 14 micrometers, the carbon content is greater than 99.9%, and the true density is greater than or equal to 2.20 g / cm³. 3The reversible specific capacity is greater than or equal to 350 mAh / g. In order to improve the interfacial bonding strength between the hard carbon component and the graphite powder surface, in addition to the above-mentioned particle size control technology measures, for graphite powder raw materials with a small specific surface area, pulse high pressure carbon dioxide vapor phase etching is used to increase the specific surface area of ​​the graphite powder. That is, pulse high pressure carbon dioxide gas with a peak pressure between 0.50-1.00 MPa is used to perform surface vapor phase etching treatment on graphite powder raw materials in a loose or compacted state in a high temperature range between 760-830℃. Micropores are created on the surface of the graphite powder raw materials through the Bourdelle reaction. After vapor phase etching treatment, the BET specific surface area of ​​the graphite powder increases by more than 20%. The BET specific surface area of ​​the fine graphite powder used to prepare the following liquid-solid slurry is controlled to be greater than 12 m² / g. Too low a specific surface area and too large a particle size are not conducive to the interfacial bonding strength between the graphite powder and the hard carbon coating layer.

[0019] Step 2: Preparation of thermoplastic liquid-solid slurry

[0020] The thermoplastic liquid-solid slurry uses a partially cross-linked modified bitumen (MP) melt as the liquid phase component. The present invention delays the cross-linking and curing process after homogeneous emulsification into spheres by controlling the thermal decomposition kinetics of the peroxide cross-linking agent therein. The above-mentioned graphite micro powder with high specific surface area is used as the solid phase component.

[0021] The modified bitumen (MP) used in this product is made from the following raw materials:

[0022] Main raw material A: Medium-temperature asphalt with a softening point between 75℃ and 95℃ and a coking value greater than 40% is used; the weight percentage of main raw material A in (MP) raw materials is greater than or equal to 40 wt.%;

[0023] Auxiliary raw material B: As a melt strength modifier, it is a high-temperature asphalt with a relatively high molecular weight, a softening point between 100℃ and 180℃, and a coking value greater than 50%; the weight percentage of auxiliary raw material B in (MP) raw material is between 0-30 wt.%.

[0024] Auxiliary raw material C: As a viscosity modifier and participating in chemical crosslinking, it is one or a combination thereof, including naphthenic oil, coal tar, ethylene tar, vacuum residue, naphthalene pitch, ethylene-vinyl acetate (EVA) copolymer with a melting point between 55-90℃, and styrene-butadiene rubber (SBR); the weight percentage of auxiliary raw material C in the (MP) raw material is between 10-35 wt.%.

[0025] Auxiliary raw material D: Utilizes a peroxide crosslinking agent, exhibiting controllable thermal decomposition kinetics, with a 1-minute half-life temperature greater than 165℃, a 1-hour half-life temperature greater than 130℃, and a 10-hour half-life temperature between 110-125℃; including one or a combination of dicumyl peroxide (DCP), bis-tert-butyldicumyl peroxide (BIPB), and 2,5-dimethyl-2,5-di-tert-butylperoxide (BIPB); Auxiliary raw material D constitutes 1.0-4.0 wt.% of the (MP) raw material.

[0026] Auxiliary raw material E: Small molecule crosslinking agents with olefin polyfunctional groups that have grafting and bridging functions, including triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), vinyltriethoxysilane (A1522), etc.; The weight percentage of auxiliary raw material E in (MP) raw material is between 0-8 wt.%.

[0027] The raw materials A / B / C are first heated in a kneader at a temperature range of 110℃-190℃ to knead and mix evenly. Then, graphite powder preheated to 110℃-190℃ is added, and kneading continues for 30min-120min. The material temperature is then controlled to 110℃-130℃. Next, peroxide crosslinking agent and co-crosslinking agent are added, and kneading continues for 20min-240min. The free radicals generated by the thermal decomposition of the peroxide crosslinking agent and the above raw materials during heating and kneading are used to generate a three-dimensional structure of CC crosslinks through free radical addition reaction or double bond addition reaction. Alternatively, the highly active oxides formed after peroxide decomposition can perform addition reactions on the above hydrocarbon polymer raw materials through hydrogen abstraction to generate free radicals, thereby achieving partial chemical crosslinking reaction between the polymers inside (MP), while the liquid-solid slurry still maintains a thermoplastic physical state.

[0028] Alternatively, the feeding sequence can be adjusted, and the following kneading and mixing process can be used to prepare a thermoplastic liquid-solid slurry: First, heat the above raw materials A / B / C in a kneader at a temperature range of 110℃-190℃ and knead and mix them evenly; then, controllably cool the material temperature to 110℃-130℃; next, add peroxide crosslinking agent and co-crosslinking agent, and continue kneading and mixing for 10min-60min; finally, add graphite micropowder preheated to 110℃-130℃, and continue kneading and mixing for 30min-240min; this achieves partial chemical crosslinking between the polymers within the liquid-solid slurry, while the liquid-solid slurry retains its thermoplastic physical state.

[0029] Then the liquid-solid slurry is controlled to cool it, keeping the material temperature between 95℃ and 100℃, while the liquid-solid slurry material still maintains a thermoplastic physical state.

[0030] Step 3: The liquid-solid slurry is homogenized and emulsified in hot water to disperse into spheres.

[0031] Hot water is used as the medium, with the water temperature controlled between 95℃ and 100℃. 0.5-4 wt.% of a nonionic surfactant and 0.1-1.5 wt.% of a water-soluble polymer dispersant are pre-added to the hot water and dissolved uniformly. The aforementioned liquid-solid slurry material, which still retains thermoplasticity when cooled to the 95℃-100℃ temperature range, is then homogenized and emulsified. The nonionic surfactant includes one or a combination of polyoxyethylene-polyoxypropylene copolymer, fatty alcohol polyoxyethylene ether, and polyvinylpyrrolidone. The dispersant includes one or a combination of water-soluble polymers such as polyvinyl alcohol (PVA), hydroxypropyl methylcellulose (HEMC), hydroxyethyl cellulose (HEC), sodium carboxymethyl cellulose (CMC), and polyoxyethylene (PEO). Utilizing the high-speed shear dispersion function of the homogenizing emulsifier and the combined effect of the liquid-solid surface tension in the water-based emulsion, the aforementioned thermoplastic liquid-solid slurry is homogenized and emulsified in hot water, dispersing it into micron-sized spherical particles (Partly Cross-linking Spherical). Paticles (hereinafter referred to as PCSP) are uniformly distributed in water-based emulsions, with a solid content controlled between 25 wt.% and 55 wt.%.

[0032] Step 4: Thermostatic Pressing Crosslinking and Curing Treatment

[0033] The homogenized and uniformly emulsified water-based emulsion is placed inside a high-pressure container, and the PCSP within it undergoes thermo-isostatic pressure (HIP) crosslinking and curing treatment under high temperature and high pressure. The material temperature during treatment is between 135°C and 190°C. Compressed air, high-pressure oxygen, high-pressure nitrogen, or compressed air mixed with ozone (or a combination thereof) are pumped into the high-pressure container to adjust the internal environmental pressure (P1) to be at least 0.20 MPa to 1.20 MPa higher than the saturated vapor pressure (P0) of the hot water corresponding to the material temperature. The superheated water in the water-based emulsion, operating at high temperature and pressure, serves as the medium for transmitting the static pressure. The crosslinking and curing time is preferably controlled between 30 minutes and 6 hours. After HIP treatment, the PCSP in the water-based emulsion completes crosslinking and curing, preventing the formation of bubbles within the PCSP. The material is then further dried using either spray drying or a slow, stepped cooling and depressurization followed by drying in an atmospheric pressure oven to obtain crosslinked and cured spherical granular powder. Particles (hereinafter referred to as WCSP); After drying, the WCSP is subjected to another carbonization treatment and subsequent CVD surface sealing treatment in a loose or compacted physical state;

[0034] Step 5: First carbonization treatment

[0035] The aforementioned fully cross-linked and cured spherical WCSP powder, which is not easily agglomerated, is passed through a 200-mesh vibrating screen or subjected to airflow particle size separation. It is then subjected to a first carbonization treatment in a loosely packed or compacted natural stack. First, the material is heated to 190℃-230℃ in air, an oxidizing atmosphere, or an inert atmosphere. Within this temperature range, a pulsed high-pressure oxidation treatment is performed for 0-12 hours. The container is filled with high-pressure oxygen, compressed air, or compressed air mixed with ozone at a pressure between 0.60-1.6MPa. High pressure is maintained during each cycle. The peak time of the pulse is between 30 min and 2 h. Then, some of the internal gas is discharged and the pressure is reduced to 0.20-0.80 MPa. This cycle is repeated 0-N times. Then, under vacuum or an inert atmosphere with positive pressure, the material is heated stepwise to the highest carbonization temperature between 700-1200℃ and held for 2-6 hours. After the material cools down, a spherical powder semi-finished product with a hard carbon-graphite island structure with numerous nanoscale openings on the surface is obtained. At this time, the BET specific surface area of ​​the spherical powder semi-finished product is greater than 15 m² / g. Subsequent CVD surface sealing treatment is then performed.

[0036] Step 6: Surface sealing is achieved using CVD.

[0037] After the initial carbonization process described above, a carbon-source gas, such as methane or propane, is introduced into the material while it is in a fluidized state. Conventional CVD (chemical vapor deposition) is then used to achieve surface sealing. Alternatively, while the material is in a loose or compacted state, pulsed high-pressure chemical vapor deposition (PH-CVD) is used to achieve surface sealing. An inert gas with a pressure between 0.60 and 1.60 MPa is used as the carrier gas, and naphthenic oil liquid or other hydrocarbons are used as the carbon source. The nanoscale micropores distributed on the surface of the spherical powder semi-finished product formed after the initial carbonization adsorb the active gas polymer clusters formed after the thermal evaporation or thermal decomposition of the carbon source. Following subsequent high-temperature thermal decomposition, thermal condensation, and other complex physicochemical changes, an amorphous carbon coating layer is formed on the surface of the powder or inside the open micropores, achieving surface sealing, reducing the BET specific surface area, and improving the battery's initial efficiency. Pulsed high-pressure chemical vapor deposition (PH-CVD) The specific technical operation is as follows: With the material heating temperature between 200℃ and 600℃, pulsed high-pressure chemical vapor deposition employs multiple variable-pressure cycles: High-pressure pulse heat treatment is performed for 1-2 hours using an internal gas pressure between 0.60-1.60 MPa, followed by pressure reduction to a low-pressure range of 0.20-0.80 MPa. This pulsed pressure variation is repeated 6-20 times to achieve mass transfer and adsorption of active gas polymer clusters between powder gaps and on the powder surface. After a secondary carbonization treatment at a temperature range of 600℃-1600℃, amorphous carbon of pyrolytic carbon forms on the powder surface, achieving surface sealing and reducing the BET specific surface area of ​​the spherical powder. After cooling to below 300℃ and exiting the furnace, the material is passed through a 200-mesh vibrating screen or air classifier to remove magnetic impurities, resulting in a hard carbon-graphite island-structured spherical negative electrode material with a BET specific surface area less than or equal to 6 m². 2 / g.

[0038] The method of this invention has the following positive technical effects: In a thermoplastic physical state, a liquid-solid slurry with a certain viscosity, composed of partially chemically cross-linked modified asphalt hard carbon precursor and graphite micropowder, is homogenized and emulsified into spheres in hot water. This method has the advantages of low energy consumption, high production efficiency, and high material yield. The dispersed emulsion is then subjected to cross-linking and curing treatment using hot isostatic pressing to obtain chemically cross-linked and cured spherical powders. This avoids the defects of air bubbles easily generated in the powder during cross-linking reactions of semi-finished products under normal pressure, ensuring the structural and performance stability of the powder. It also avoids the problems associated with conventional methods. The asphalt coating process suffers from severe adhesion between powder particles after carbonization, necessitating crushing and resulting in structural damage. The spherical semi-finished product obtained after cross-linking and curing in this invention provides a material basis for subsequent carbonization at higher packing density and CVD surface sealing, as well as for improving the compaction density and rate capability of the finished anode material. The method of this invention lays the material processing foundation for improving the structural stability of composite powder anode materials and the initial efficiency and cycle life of batteries. The hard carbon-graphite island-structure spherical anode material of this invention exhibits good power characteristics when applied to lithium-ion batteries, balancing compaction density and energy density.

[0039] By using the manufacturing method of this invention, replacing the aforementioned graphite micropowder with a composition of graphite micropowder and nano-silicon powder, it is possible to manufacture a lithium-ion battery anode material with a specific capacity greater than 400 mAh / g, higher energy density characteristics, and good rate performance. The resulting hard carbon-(graphite micropowder + nano-silicon) island-structured spherical anode material powder, wherein micron-sized graphite micropowder and nano-silicon are dispersed in an island-like manner within a hard carbon ocean matrix, and the product has a specific capacity greater than 400 mAh / g; the nano-silicon powder raw material... The particle size D90 is controlled to be less than 150 nanometers, and more preferably less than 120 nanometers. The nano-silicon powder is produced by vapor deposition condensation method, or by using hypereutectic aluminum-silicon alloy to quickly solidify by rapid cooling and spinning to control the primary precipitation size of silicon. Then, it is artificially aged at low temperature of 80℃-120℃ for 24 to 96 hours to control the precipitation and growth size of nano-silicon. After removing aluminum by acid washing with hydrochloric acid or dilute nitric acid, it is washed with pure water, floated, and dried to obtain nano-silicon powder with a particle size D90 of less than 120 nanometers.

[0040] To better illustrate the technical objectives, technical solutions, and beneficial effects of the present invention, further explanations are provided below in conjunction with specific embodiments.

[0041] Example 1: Hard carbon-graphite island-structured spherical anode material was prepared using the following manufacturing method:

[0042] Step 1: Preparation of graphite micropowder with high specific surface area

[0043] The graphite micro powder raw material is 4000 parts by weight, made of natural flake graphite; its average particle size D50 is between 4-5 micrometers, D90 is less than or equal to 10 micrometers, carbon content is greater than 99.93%, reversible specific capacity is greater than or equal to 363mAh / g, and BET specific surface area of ​​the graphite micro powder raw material is between 18-20 square meters / gram.

[0044] Step 2: Preparation of thermoplastic liquid-solid slurry

[0045] The modified bitumen (MP) comprises 6000 parts by weight, using the following raw materials:

[0046] Main raw material A: Medium-temperature asphalt with a softening point between 80℃ and 90℃ and a coking value greater than 45% is used; the weight percentage of main raw material A in (MP) raw materials is 57 wt.%;

[0047] Auxiliary raw material B: High-temperature asphalt with a softening point between 110℃ and 115℃ and a coking value greater than 52%; its weight percentage in (MP) raw materials is 15 wt.%.

[0048] Auxiliary raw material C: Styrene-butadiene rubber of grade YH-792E is used, with a styrene-butadiene structural ratio of 40:60, and its weight percentage in (MP) raw materials is 25 wt.%.

[0049] Auxiliary raw material D: The peroxide crosslinking agent is bis-tert-butyl peroxide dicumyl peroxide (BIPB); its weight percentage in (MP) raw material is 2 wt.%.

[0050] Auxiliary raw material E: is triallyl isocyanurate (TAIC); its weight percentage in (MP) raw material is 1 wt.%.

[0051] The above raw materials A / B / C are first heated in a vacuum kneader at a temperature range of 125-135℃ and kneaded and mixed evenly; the material temperature is then controlled to cool to 115-120℃, and then peroxide crosslinking agent and co-crosslinking agent are added, and kneading and mixing continues for 15 minutes; then graphite powder preheated to 120℃ is added, and kneading and mixing continues for 30 minutes; the liquid-solid slurry is then controlled to cool, and the material temperature is controlled between 97-99℃, so that the liquid-solid slurry material still maintains a thermoplastic physical state;

[0052] Step 3: The liquid-solid slurry is homogenized and emulsified in hot water to disperse into spheres.

[0053] Hot water is used as the medium, with the water temperature controlled between 97-99℃. 1.8 wt.% of a nonionic surfactant, specifically polyoxyethylene-polyoxypropylene copolymer L44 produced by Jiangsu Haian Petrochemical, is added to the hot water beforehand and dissolved evenly. 0.2 wt.% of a dispersant, specifically polyvinyl alcohol 17-88 produced by Beijing Organic Chemical Plant, is added and dissolved evenly. The liquid-solid slurry material, which still retains thermoplasticity when cooled to the 97-99℃ temperature range, is then homogenized and emulsified. Using a self-made specialized equipment for homogenizing and emulsifying asphalt, the thermoplastic liquid-solid slurry is homogenized and evenly dispersed in hot water to prepare an emulsion state in which spherical fine particles are uniformly distributed in the hot water.

[0054] Step 4: Thermostatic Pressing Crosslinking and Curing Treatment

[0055] The homogenized and uniformly emulsified water-based emulsion was placed into a high-pressure container. The PCSP in the container was subjected to thermal isostatic crosslinking treatment. The material temperature during the thermal isostatic crosslinking treatment was between 155°C and 160°C. High-temperature and high-pressure superheated water was used as the medium to transmit pressure. Compressed air was pumped into the high-pressure container to control the ambient pressure (P1) inside the high-pressure container between 1.10 and 1.20 MPa. The crosslinking time was controlled between 120 and 180 minutes. After the PCSP in the water-based emulsion was crosslinked and cured, the temperature and pressure were reduced in a stepwise manner, and the container was dried in an atmospheric pressure oven at 120°C to obtain crosslinked and cured spherical particle powder WCSP. The WCSP was then subjected to a carbonization treatment and subsequent pulse high-pressure CVD surface sealing treatment in a loose physical state.

[0056] Step 5: First carbonization treatment

[0057] The above-mentioned non-sticky spherical powder semi-finished product is passed through a 200-mesh vibrating screen, loosely packed into tooling, and placed in the furnace. First, the material is heated to 190℃-230℃ in a high-pressure oxidizing atmosphere and subjected to pulse high-pressure oxidation treatment for 8 hours within this temperature range. The container is filled with compressed air mixed with ozone at a pressure of 0.80MPa. In each cycle, the peak time of the high-pressure pulse is maintained for 55 minutes. Then, some of the internal gas is discharged, and the pressure inside the container is reduced to 0.40MPa. This cycle is repeated 8 times. Then, under the protection of nitrogen atmosphere, a carbonization treatment is carried out again. The material is heated to 350℃ at a heating rate of 1℃ / min and held for 3 hours; then heated to 460℃ at a heating rate of 1℃ / min and held for 3 hours; then heated to 600℃ at a heating rate of 2℃ / min and held for 2 hours; then heated to 900℃ at a heating rate of 5℃ / min and held for 3 hours. After the material cools to 200℃, the subsequent CVD sealing treatment is carried out.

[0058] Step 6: Surface sealing is achieved using polymer cluster pulsed high-pressure chemical vapor deposition.

[0059] Using nitrogen as the carrier gas and naphthenic oil liquid K4010 as the carbon source, pulsed high-pressure chemical vapor deposition (PCVD) was performed at a material heating temperature between 200-600℃, employing multiple variable-pressure cycles: high-pressure pulsed heat treatment for 2 hours at a pressure between 0.60-0.80 MPa, followed by depressurization to a low-pressure range of 0.30-0.40 MPa, repeated 10 times to achieve mass transfer and adsorption of active gas polymer clusters within powder gaps and on the powder surface; followed by... The powder was heated from 600℃ to 1250℃ at a heating rate of ℃ / min for a secondary carbonization treatment of 3 hours. This process formed amorphous carbon materials of pyrolytic carbon on the surface of the powder, achieving the technical objective of sealing pores and reducing the BET specific surface area, and further optimizing the microstructure of the hard carbon. After cooling to below 200℃ and removing from the furnace, airflow classification was used to remove magnetic foreign matter, resulting in a spherical hard carbon-graphite island structure composite anode material with an average particle size D50 between 10-12 micrometers and D90 less than 16 micrometers; the true density was 1.99 g / cm³. 3 The compacted density is greater than 1.35 g / cm³. 3 It has a reversible specific capacity of 360mAh / g and a BET specific surface area of ​​2.85m². 2 / g, initial coulombic efficiency greater than 90%, 5C / 1C charging capacity ratio greater than 95%.

[0060] Example 2: Using the same manufacturing method as in Example 1, a hard carbon-(graphite + nano-silicon) island-structured spherical anode material was prepared, with slight adjustments made to the raw material preparation step in the first step:

[0061] Step 1: Preparation of high specific surface area micro-fine graphite powder and nano-silicon powder

[0062] The fine graphite powder raw material is 3600 parts by weight, made of natural flake graphite; its average particle size D50 is between 4-5 micrometers, D90 is less than or equal to 10 micrometers, carbon content is greater than 99.93%, reversible specific capacity is greater than or equal to 363mAh / g, and the BET specific surface area of ​​the fine graphite powder raw material is between 18-20 square meters / gram.

[0063] 400 parts by weight of nano-silicon powder were obtained by using hypereutectic aluminum-silicon alloy A187-13Si. The material was first solidified by water-cooled copper roller rapid cooling and spinning process to obtain a strip with a thickness of 0.03 mm. Then, the strip was artificially aged at 95℃ for 60 hours to control the precipitation and growth size of nano-silicon. After removing aluminum by acid washing with hydrochloric acid or dilute nitric acid, the strip was washed with pure water, floated, and dried to obtain nano-silicon powder with a particle size D90 between 80-110 nanometers.

[0064] The remaining processing steps are the same as in Example 1, yielding a spherical hard carbon-(graphite + nano-silicon) island-structured composite anode material with an average particle size D50 between 10-12 micrometers and D90 less than 16 micrometers; the true density is 2.01 g / cm³. 3 The compacted density is greater than 1.38 g / cm³. 3 It has a reversible specific capacity of 490mAh / g and a BET specific surface area of ​​3.87m². 2 / g, initial coulombic efficiency greater than 87%, 5C / 1C charging capacity ratio greater than 92%.

Claims

1. A method for manufacturing a hard carbon-graphite island-structured spherical anode material, characterized in that, The hard carbon component acts as the ocean within the spherical anode material with an island structure, serving as a complete, interconnected carrier or coating layer. The graphite powder, acting as the islands within the island structure, is dispersed within the ocean matrix of the hard carbon component. The precursor for the hard carbon component is modified bitumen (MP) and manufactured using a water-based homogeneous emulsification dispersion into spheres followed by thermostatic crosslinking and curing. (MP) possesses the following technical characteristics: it enables controllable chemical crosslinking, has a thermoplastic processing window, and can chemically crosslink and cure at higher temperatures to obtain non-agglomerated spherical particle semi-finished products. After initial melting, (MP) forms a low-viscosity liquid melt, which, along with the graphite powder... During the kneading and mixing process, even if some chemical cross-linking reaction occurs, the material retains thermoplasticity, ensuring that it is dispersed into a uniform liquid-solid slurry. Furthermore, hot water can be used to homogenize the liquid-solid slurry into micron-sized spherical particles (hereinafter referred to as PCSP), which are uniformly distributed in the water-based emulsion. The homogenized water-based emulsion is then placed into a high-pressure vessel, where the PCSP undergoes thermostatic cross-linking curing under high temperature and pressure. The thermostatic cross-linking curing process uses a material temperature between 135℃ and 190℃, achieved by pumping compressed air into the high-pressure vessel. Oxygen, high-pressure nitrogen, or compressed air mixed with ozone, or a combination thereof, are used to control the ambient pressure (P1) inside the high-pressure vessel to be at least 0.20 MPa to 1.20 MPa higher than the saturated vapor pressure (P0) of the hot water corresponding to the material temperature. The superheated water in the water-based emulsion, operating at high temperature and pressure, is used as the medium to transfer static pressure. The cross-linking and curing time is controlled between 10 minutes and 6 hours. After treatment, the PCSP in the water-based emulsion is sufficiently cross-linked and cured, preventing the formation of bubbles in the PCSP. Further spray drying or slow, stepped cooling and depressurization of the material followed by drying in an atmospheric pressure oven yields the cross-linked and cured product. Spherical carbon-graphite island-structured spherical anode material (hereinafter referred to as WCSP) is produced. The WCSP is then subjected to a second carbonization treatment and subsequent pulsed high-pressure CVD surface sealing treatment in a loosely packed or compacted physical state. The modified asphalt component after cross-linking and curing is transformed into a marine component dominated by hard carbon structure. Graphite micropowder is distributed in an island-like distribution within the marine matrix of the hard carbon component. After cooling to below 300℃ and exiting the furnace, the material is passed through a 200-mesh vibrating sieve or air classifier to remove magnetic impurities, resulting in a finished product of hard carbon-graphite island-structured spherical anode material with both power characteristics and high energy density. Its average particle size D50 is between 7-15 micrometers, and its true density is greater than or equal to 1.85 g / cm³. 3 The compacted density is greater than or equal to 1.35 g / cm³. 3 First-time coulombic efficiency greater than or equal to 85%, reversible specific capacity greater than or equal to 350 mAh / g, and BET specific surface area less than or equal to 6 m². 2 / g, 5C / 1C charging capacity ratio greater than 90%.

2. The method for manufacturing the hard carbon-graphite island-structured spherical anode material according to claim 1, characterized in that, The process includes the following steps: Step 1: Preparation of graphite micropowder with high specific surface area The raw materials for graphite micron powder include natural or artificial graphite, with an average particle size D50 between 2 and 8 micrometers, preferably natural graphite micron powder with an average particle size D50 between 3 and 6 micrometers. The particle size D90 of the graphite micron powder raw materials is controlled to be less than or equal to 14 micrometers, the carbon content is greater than 99.9%, and the true density is greater than or equal to 2.20 g / cm³. 3 The reversible specific capacity is greater than or equal to 350 mAh / g. In order to improve the interfacial adhesion strength between the hard carbon component and the graphite powder surface, in addition to the above-mentioned particle size control technology measures, for graphite powder raw materials with low specific surface area, pulse high pressure carbon dioxide vapor phase etching is used to increase the specific surface area of ​​graphite powder. That is, pulse high pressure carbon dioxide gas with a peak pressure between 0.50-1.00 MPa is used to perform surface vapor phase etching treatment on graphite powder raw materials in a loose or compacted state in a high temperature range between 760-830℃. Micropores are created on the surface of graphite powder raw materials through the Bourdelle reaction. After vapor phase etching treatment, the BET specific surface area of ​​graphite powder increases by more than 20%. It is used to prepare the fine graphite powder before the liquid-solid slurry below, and its BET specific surface area is controlled to be greater than 12 m² / g. Step 2: Preparation of thermoplastic liquid-solid slurry The thermoplastic liquid-solid slurry uses a partially cross-linked modified bitumen (MP) melt as the liquid phase component. The present invention delays the cross-linking and curing process after homogeneous emulsification into spheres by controlling the thermal decomposition kinetics of the peroxide cross-linking agent therein. The above-mentioned graphite micro powder with high specific surface area is used as the solid phase component. The modified bitumen (MP) used in this product is made from the following raw materials: Main raw material A: Medium-temperature asphalt with a softening point between 75℃ and 95℃ and a coking value greater than 40% is used; the weight percentage of main raw material A in (MP) raw materials is greater than or equal to 40 wt.%; Auxiliary raw material B: As a melt strength modifier, it is a high-temperature asphalt with a relatively high molecular weight, a softening point between 100℃ and 180℃, and a coking value greater than 50%; the weight percentage of auxiliary raw material B in (MP) raw material is between 0-30 wt.%. Auxiliary raw material C: As a viscosity modifier and participating in chemical crosslinking, it is one or a combination thereof, including naphthenic oil, coal tar, ethylene tar, vacuum residue, naphthalene pitch, ethylene-vinyl acetate (EVA) copolymer with a melting point between 55-90℃, and styrene-butadiene rubber (SBR); the weight percentage of auxiliary raw material C in the (MP) raw material is between 10-35 wt.%. Auxiliary raw material D: Utilizes a peroxide crosslinking agent, exhibiting controllable thermal decomposition kinetics, with a 1-minute half-life temperature greater than 165℃, a 1-hour half-life temperature greater than 130℃, and a 10-hour half-life temperature between 110-125℃; including one or a combination of dicumyl peroxide (DCP), bis-tert-butyldicumyl peroxide (BIPB), and 2,5-dimethyl-2,5-di-tert-butylperoxide (BIPB); Auxiliary raw material D constitutes 1.0-4.0 wt.% of the (MP) raw material. Auxiliary raw material E: Small molecule crosslinking agents with olefin polyfunctional groups that have grafting and bridging functions, including triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), vinyltriethoxysilane (A1522), etc.; The weight percentage of auxiliary raw material E in (MP) raw material is between 0-8.0 wt.%. The raw materials A / B / C are first heated in a kneader at a temperature range of 115℃-190℃ to ensure uniform kneading and mixing. Then, graphite powder preheated to 110℃-190℃ is added, and kneading and mixing continues for 30min-120min. The material temperature is then controlled to 110℃-130℃. Next, peroxide crosslinking agent and co-crosslinking agent are added, and kneading continues for 20min-240min. The free radicals generated during the thermal decomposition of the peroxide crosslinking agent and the above raw materials are used to generate a three-dimensional structure of CC crosslinks through free radical addition reaction or double bond addition reaction. Alternatively, the highly active oxides formed after peroxide decomposition can undergo addition reaction with the above hydrocarbon polymer raw materials through hydrogen abstraction to generate free radicals, thereby achieving partial chemical crosslinking reaction between the polymers inside (MP), while the liquid-solid slurry still maintains a thermoplastic physical state. Alternatively, the feeding sequence can be adjusted, and the following kneading and mixing process can be used to prepare a thermoplastic liquid-solid slurry: First, heat the above raw materials A / B / C in a kneader at a temperature range of 110℃-190℃ and knead and mix them evenly; then, controllably cool the material temperature to 110℃-130℃; next, add peroxide crosslinking agent and co-crosslinking agent, and continue kneading and mixing for 10min-60min; finally, add graphite micropowder preheated to 110℃-130℃, and continue kneading and mixing for 30min-240min; this achieves partial chemical crosslinking between the polymers within the liquid-solid slurry, while the liquid-solid slurry retains its thermoplastic physical state. Then the liquid-solid slurry is controlled to cool it, keeping the material temperature between 95-100℃, while the liquid-solid slurry material still maintains a thermoplastic physical state; Step 3: The liquid-solid slurry is homogenized and emulsified in hot water to disperse into spheres. Hot water is used as the medium, with the water temperature controlled between 95-100℃. 0.5-4 wt.% of a nonionic surfactant and 0.1-1.5 wt.% of a water-soluble polymer dispersant are pre-added to the hot water and dissolved uniformly. The aforementioned liquid-solid slurry material, which still retains thermoplasticity even after cooling to the 95-100℃ temperature range, is then homogenized and emulsified. The nonionic surfactant includes one or a combination of polyoxyethylene-polyoxypropylene copolymer, fatty alcohol polyoxyethylene ether, and polyvinylpyrrolidone. The dispersant includes one or a combination of water-soluble polymers such as polyvinyl alcohol (PVA), hydroxypropyl methylcellulose (HEMC), hydroxyethyl cellulose (HEC), sodium carboxymethyl cellulose (CMC), and polyoxyethylene (PEO). Utilizing the high-speed shear dispersion function of the homogenizing emulsifier and the combined effect of the liquid-solid surface tension in the water-based emulsion, the aforementioned thermoplastic liquid-solid slurry is homogenized and emulsified in hot water, dispersing it into micron-sized spherical particles (Partly Cross-linking Spherical). Paticles (hereinafter referred to as PCSP) are uniformly distributed in water-based emulsions, with a solid content controlled between 25 wt.% and 55 wt.%. Step 4: Thermostatic Pressing Crosslinking and Curing Treatment The homogenized and uniformly emulsified water-based emulsion was placed inside a high-pressure container, and the PCSP within it underwent thermo-isostatic pressure (HIP) crosslinking and curing treatment under high temperature and high pressure. The material temperature was maintained between 135°C and 190°C. Compressed air, high-pressure oxygen, high-pressure nitrogen, or compressed air mixed with ozone (or a combination thereof) were pumped into the high-pressure container to adjust the internal environmental pressure (P1) to be at least 0.20 MPa to 1.20 MPa higher than the saturated vapor pressure (P0) of the hot water corresponding to the material temperature. The superheated water in the water-based emulsion under high temperature and pressure was used as the medium to transfer the static pressure. The crosslinking and curing time was controlled between 30 minutes and 6 hours. After HIP treatment, the PCSP in the water-based emulsion was completely crosslinked and cured, preventing the formation of bubbles within the PCSP. The material was then further dried using either spray drying or a slow, stepped cooling and depressurization followed by drying in an atmospheric pressure oven to obtain crosslinked and cured spherical granular powder. Particles (hereinafter referred to as WCSP); After drying, the WCSP is subjected to another carbonization treatment and subsequent CVD surface sealing treatment in a loose or compacted physical state; Step 5: First carbonization treatment The aforementioned fully cross-linked and cured spherical WCSP powder, which is not easily agglomerated, is passed through a 200-mesh vibrating screen or subjected to airflow particle size separation. It is then subjected to a first carbonization treatment in a loosely packed or compacted natural stacked state. First, under the protection of air, an oxidizing atmosphere, or an inert atmosphere, the material is heated to 190℃-230℃. Within this temperature range, a pulsed high-pressure oxidation treatment is performed for 0-12 hours. The container is filled with high-pressure oxygen, compressed air, or compressed air mixed with ozone at a pressure between 0.60-1.6MPa. During each cycle, the pressure is maintained at a high level. The peak time of the pulse is between 30 min and 2 h. Then, some of the internal gas is discharged and the pressure is reduced to 0.20-0.80 MPa. This cycle is repeated 0-N times. Then, under vacuum or an inert atmosphere with positive pressure, the material is heated stepwise to the highest carbonization temperature between 700-1200℃ and held for 2-6 hours. After the material cools down, a spherical powder semi-finished product with a hard carbon-graphite island structure with numerous nanoscale openings on the surface is obtained. At this time, the BET specific surface area of ​​the spherical powder semi-finished product is greater than 15 m² / g. Subsequent CVD surface sealing treatment is then performed. Step 6: Surface sealing is achieved using CVD. After the initial carbonization process described above, a carbon-source gas, such as methane or propane, is introduced into the material while it is in a fluidized state. Conventional CVD (chemical vapor deposition) is then used to achieve surface sealing. Alternatively, while the material is in a loose or compacted state, pulsed high-pressure chemical vapor deposition (PH-CVD) is used to achieve surface sealing. An inert gas with a pressure between 0.60 and 1.60 MPa is used as the carrier gas, and naphthenic oil liquid or other hydrocarbons are used as the carbon source. The nanoscale micropores distributed on the surface of the spherical powder semi-finished product formed after the initial carbonization adsorb the active gas polymer clusters formed after the thermal evaporation or thermal decomposition of the carbon source. Following subsequent high-temperature thermal decomposition, thermal condensation, and other complex physicochemical changes, an amorphous carbon coating layer is formed on the surface of the powder or inside the open micropores, achieving surface sealing, reducing the BET specific surface area, and improving the battery's initial efficiency. Pulsed high-pressure chemical vapor deposition (PH-CVD) The specific technical operation is as follows: With the material heating temperature between 200℃ and 600℃, pulsed high-pressure chemical vapor deposition employs multiple variable-pressure cycles: High-pressure pulse heat treatment is performed for 1-2 hours using an internal gas pressure between 0.60-1.60 MPa, followed by pressure reduction to a low-pressure range of 0.20-0.80 MPa. This pulsed pressure variation is repeated 6-20 times to achieve mass transfer and adsorption of active gas polymer clusters between powder gaps and on the powder surface. After a secondary carbonization treatment at a temperature range of 600℃-1600℃, amorphous carbon of pyrolytic carbon forms on the powder surface, achieving surface sealing and reducing the BET specific surface area of ​​the spherical powder. After cooling to below 300℃ and exiting the furnace, the material is passed through a 200-mesh vibrating screen or air classifier to remove magnetic impurities, resulting in a hard carbon-graphite island-structured spherical negative electrode material with a BET specific surface area less than or equal to 6 m². 2 / g.

3. The method for manufacturing the hard carbon-graphite island-structured spherical anode material according to claim 1, characterized in that, The graphite micropowder in claims 1 and 2 is replaced by a combination of graphite micropowder and nano-silicon powder to manufacture a lithium-ion battery anode material with a specific capacity greater than 400 mAh / g, higher energy density characteristics, and rate capability. The particle size D90 of the nano-silicon powder raw material is controlled to be less than 120 nanometers, and the nano-silicon powder is produced by vapor deposition condensation; or a hypereutectic aluminum-silicon alloy is used to control the primary precipitation size of silicon through rapid solidification by quenching and spinning, followed by artificial time at a low temperature of 80℃-120℃. The precipitation and growth size of nano-silicon are controlled within 24 to 96 hours. After removing aluminum by acid washing with hydrochloric acid or dilute nitric acid, the nano-silicon powder with a particle size D90 of less than 120 nanometers is obtained by washing with pure water, flotation, and drying. Using the manufacturing methods of claims 1 and 2, a hard carbon-(graphite micropowder + nano-silicon) island structure spherical anode material is obtained, wherein the micron-sized graphite micropowder and nano-silicon are dispersed in an island-like manner in the hard carbon ocean matrix, and the specific capacity of the product is greater than 400 mAh / g.