CN115084456B - Graphite composite material, preparation method thereof and lithium ion battery - Google Patents

Graphite composite material, preparation method thereof and lithium ion battery Download PDF

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CN115084456B
CN115084456B CN202110288786.1A CN202110288786A CN115084456B CN 115084456 B CN115084456 B CN 115084456B CN 202110288786 A CN202110288786 A CN 202110288786A CN 115084456 B CN115084456 B CN 115084456B
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graphite
carbon
particles
coating layer
composite material
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CN115084456A (en
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夏路
徐晓东
王为
任建国
贺雪琴
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BTR New Material Group Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes

Abstract

The application discloses a graphite composite material, a preparation method thereof and a lithium ion battery, wherein the graphite composite material is of a core-shell structure and comprises a secondary particle inner core and a second hard carbon coating layer formed on the surface of the secondary particle inner core; the secondary particles comprise primary particles and amorphous carbon, wherein the primary particles comprise graphite and a first hard carbon coating layer formed on the surface of the graphite; the first hard carbon cladding layer and the second hard carbon cladding layer comprise carbon framework materials. Namely, the technical scheme of the application can improve the quick charge performance of the graphite anode material while improving the capacitance of the graphite anode material.

Description

Graphite composite material, preparation method thereof and lithium ion battery
Technical Field
The application relates to the technical field of graphite cathode materials, in particular to a graphite composite material, a preparation method thereof and a lithium ion battery.
Background
The graphite anode material has the characteristics of high energy density, good cycle performance, mature preparation technology, low manufacturing cost and the like, and is widely applied to lithium ion batteries. Along with the increasing wide application fields of lithium ion batteries, higher and higher requirements are also put forward on graphite anode materials, so that the problem to be solved is to propose the graphite anode materials with high charge and discharge capacity and good quick charge performance.
The prior art discloses the following graphite anode materials: the preparation method comprises the steps of (1) crushing graphite raw material particles to a certain granularity, and carrying out kneading to realize granulation of secondary particles, so as to obtain a graphite negative electrode material through graphitization; the defect of the structure is that the capacity and the quick charge performance are difficult to be simultaneously achieved, and if the raw materials easy to graphitize are selected, the capacity can be ensured but the quick charge performance is poor; if the raw materials difficult to graphitize are selected, the quick charge performance is better but the capacity is lower. In the second graphite cathode material, the surface of the graphite is coated with a hard carbon layer or a soft carbon layer, and the surface coating can reduce interface impedance and improve quick charge performance. The defect that this kind of structure exists is that the cladding layer on surface can influence graphite capacity through graphitization treatment not, if the cladding is resin class hard carbon, can lead to the surface hard carbon cladding layer specific surface area too big, influence material coulomb efficiency for the first time, if the cladding is pitch class soft carbon, to the material quick charge performance promotion not like hard carbon.
When the negative electrode material is charged and discharged at a high rate, secondary particles are easy to deform and pulverize, a coating layer is unstable, the particle size is uneven, the lithium ion transmission capacity is poor, and the rate performance does not meet the requirements.
Disclosure of Invention
The application mainly aims to provide a graphite composite material, which aims to improve the capacitance of a graphite negative electrode material and the quick charge performance of the graphite negative electrode material.
In order to achieve the above purpose, the graphite composite material provided by the application has a core-shell structure, and comprises a secondary particle inner core and a second hard carbon coating layer formed on the surface of the secondary particle inner core;
the secondary particles comprise primary particles and amorphous carbon, wherein the primary particles comprise graphite and a first hard carbon coating layer formed on the surface of the graphite;
the first hard carbon cladding layer and the second hard carbon cladding layer comprise carbon framework materials.
Optionally, the carbon skeleton material is uniformly distributed in the first hard carbon coating layer and the second hard carbon coating layer;
and/or, based on 100% of the mass of the first hard carbon coating layer, the content of the carbon skeleton material uniformly distributed in the first hard carbon coating layer is 1% -10%;
and/or, the content of the carbon skeleton material uniformly distributed in the second hard carbon coating layer is 1-10% based on 100% of the mass of the second hard carbon coating layer.
Optionally, the graphite comprises at least one of artificial graphite and natural graphite;
and/or, the amorphous carbon comprises soft carbon;
and/or, the amorphous carbon is filled between the primary particles.
Optionally, the carbon skeleton material includes at least one of carbon nanotubes and carbon fibers.
The application also provides a preparation method of the graphite composite material, which comprises the following steps:
s10, uniformly dispersing a carbon skeleton material and a polymer in an organic solvent to obtain a polymer precursor;
s20, mixing and granulating graphite raw material particles and the polymer precursor to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles so as to obtain primary particle precursors;
s30, mixing the primary particle precursor with a carbon source, and carbonizing to obtain secondary particles;
and S40, mixing and granulating the secondary particles and the polymer precursor to form a second polymer precursor coating layer on the surfaces of the secondary particles, and graphitizing to obtain the graphite composite material.
Optionally, in step S10, the carbon skeleton material includes at least one of carbon nanotubes and carbon fibers; and/or the number of the groups of groups,
in step S10, the polymer includes at least one of phenolic resin, polypropylene resin and polyurethane; and/or the number of the groups of groups,
In step S10, the organic solvent includes at least one of ethanol and water; and/or the number of the groups of groups,
in the step S10, the solid content of the polymer precursor is 40% -60%.
Alternatively, the step S20 may specifically be:
s21, spraying the polymer precursor to the surfaces of graphite raw material particles;
s22, rolling the graphite raw material particles to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles;
s23, drying the graphite raw material particles with the first polymer precursor coating layer;
in step S21, the graphite raw material particles include at least one of natural graphite particles and soft carbon particles; and/or the number of the groups of groups,
in the step S22, the rolling speed of the graphite raw material particles is 5 r/min-30 r/min; and/or the number of the groups of groups,
in the step S23, the temperature of the drying treatment is 80-95 ℃ and the time is 20-40 min.
Alternatively, the step S30 may specifically be:
s31, spraying a carbon source on the surface of the primary particle precursor;
s32, rolling the primary particle precursors to bond the primary particle precursors through the carbon source;
s33, carbonizing the primary particle precursor bonded with the carbon source;
In step S31, the carbon source includes pitch; and/or the number of the groups of groups,
in the step S32, the rolling speed of the primary particle precursor is 5 r/min-30 r/min; and/or the number of the groups of groups,
in the step S33, the carbonization treatment temperature is 450-750 ℃ and the time is 1-5 h.
Alternatively, the step S40 may specifically be:
s41, spraying the polymer precursor to the surface of the secondary particles;
s42, rolling the secondary particles to form a second polymer precursor coating layer on the surfaces of the secondary particles;
s43, graphitizing the secondary particles with the second polymer precursor coating layer formed;
in the step S41, the particle size of the secondary particles is 13-24 μm, and the particle size distribution is 0.75-1.0; and/or the number of the groups of groups,
in the step S42, the rolling speed of the secondary particles is 5 r/min-30 r/min; and/or in the step S43, the graphitization treatment is carried out at 2400-3000 ℃ for 1-6 h.
The application also provides a lithium ion battery, which comprises the graphite composite material; and/or the lithium ion battery comprises the graphite composite material prepared by the preparation method.
According to the technical scheme, when the graphite composite material is used as a graphite negative electrode material, the graphite has the characteristic of high charge-discharge capacity, so that the charge-discharge capacity of the graphite negative electrode material is improved. And, the second hard carbon coating coats on the surface of the secondary particle inner core, the secondary particle comprises primary particles and amorphous carbon, the first hard carbon coating coats on the surface of graphite in the primary particles, the second hard carbon coating and the first hard carbon coating are used as structures formed by hard carbon materials, and the hard carbon materials have good quick charging performance, so that the quick charging performance of the graphite negative electrode material is improved. Namely, the technical scheme of the application can improve the quick charge performance of the graphite anode material while improving the capacitance of the graphite anode material.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic view of a graphite composite material according to an embodiment of the present application;
FIG. 2 is a flow chart of a method of preparing a graphite composite material of the present application;
FIG. 3 is a production process diagram of a method for preparing a graphite composite material of the present application.
Description of the drawings:
reference numerals Name of the name Reference numerals Name of the name
100 Graphite composite material 112 First hard carbon coating layer
10 Secondary particles 12 Amorphous carbon
11 Primary particles 20 Second hard carbon coating layer
111 Graphite
The achievement of the objects, functional features and advantages of the present application will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the technical solutions in the embodiments of the present application will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Referring to fig. 1, in an embodiment of the present application, a graphite composite material 100 is a core-shell structure, and the graphite composite material 100 includes a secondary particle 10 core and a second hard carbon coating layer 20 formed on the surface of the secondary particle 10 core;
the secondary particles 10 include primary particles 11 and amorphous carbon 12, the primary particles 11 including graphite 111 and a first hard carbon coating layer 112 formed on the surface of the graphite 111;
the first hard carbon cladding 112 and the second hard carbon cladding 20 comprise carbon skeleton materials.
According to the technical scheme, when the graphite composite material 100 is used as a graphite negative electrode material, the graphite 111 has the characteristic of high charge-discharge capacity, so that the charge-discharge capacity of the graphite negative electrode material is improved. And, the second hard carbon coating layer 20 coats the surface of the inner core of the secondary particle 10, the secondary particle 10 comprises a primary particle 11 and amorphous carbon 12, a first hard carbon coating layer 112 in the primary particle 11 coats the surface of graphite 111, the second hard carbon coating layer 20 and the first hard carbon coating layer 112 are used as hard carbon material forming structures, and the hard carbon material has good quick charging performance, so that the quick charging performance of the graphite negative electrode material is improved. Namely, the technical scheme of the application can improve the quick charge performance of the graphite anode material while improving the capacitance of the graphite anode material.
It should be noted that the amorphous carbon 12 may be a structure formed by graphitizing soft carbon, and of course, the secondary particles 10 may include one primary particle 11 or may include a plurality of primary particles 11, and the plurality of primary particles 11 are contained in the amorphous carbon 12, so as to further increase the capacity of the prepared graphite composite material. In addition, the second hard carbon coating layer 20 coats the surface of the amorphous carbon 12, the hard carbon material has high conductivity, so that the polarization internal resistance in the charge and discharge process is effectively reduced, and the hard carbon coating layer can accelerate the lithium ion desolvation process in the charge process, so that lithium ions can be quickly intercalated into graphite, and the rate capability of the graphite cathode material can be greatly improved.
In one embodiment of the present application, the carbon skeleton material is uniformly distributed in the first hard carbon coating layer 112 and the second hard carbon coating layer 20. It should be noted that, according to the present application, the carbon skeleton material is uniformly distributed in the first hard carbon coating layer 112 and the second hard carbon coating layer 20, and the carbon skeleton material may be carbon nanotubes or carbon fibers, and the carbon skeleton material has high electrical conductivity, so that the polarization internal resistance in the charge and discharge process of the graphite composite material 100 is reduced, and the rate performance and the low-temperature charge and discharge performance of the graphite composite material 100 are ensured.
In an embodiment of the present application, the content of the carbon skeleton material uniformly distributed in the first hard carbon coating layer is 1% to 10% based on 100% of the mass of the first hard carbon coating layer 112. It should be noted that, by adjusting the content of the carbon skeleton material, the present application makes the formed first hard carbon coating layer 112 realize uniform coating on the surface of the graphite 111, and at the same time, further improves the electrical conductivity of the first hard carbon coating layer 112, and reduces the polarization internal resistance in the charge-discharge process of the graphite composite material 100, so as to ensure the rate capability and low-temperature charge-discharge capability of the graphite composite material 100.
In an embodiment of the present application, the content of the carbon skeleton material uniformly distributed in the second hard carbon coating layer is 1% -10% based on 100% of the mass of the second hard carbon coating layer 20. Similarly, the content of the carbon skeleton material is regulated, so that the formed second hard carbon coating layer 20 can uniformly coat the surface of the secondary particles 10, the electric conductivity of the second hard carbon coating layer 20 is further improved, and the polarization internal resistance in the charging and discharging process of the graphite composite material 100 is reduced, thereby ensuring the multiplying power performance and the low-temperature charging and discharging performance of the graphite composite material.
In one embodiment of the present application, the graphite 111 includes at least one of artificial graphite and natural graphite. It should be noted that, the graphite 111 may be natural graphite or artificial graphite made by graphitizing soft carbon material, and both the above two kinds of graphite have the characteristic of high charge and discharge capacity, so as to ensure the charge and discharge capacity of the graphite composite material 100.
In one embodiment of the application, the amorphous carbon 12 comprises soft carbon. It should be noted that, the soft carbon is coated on the surface of the primary particles 11, so that the defect of the surface of the primary particles 11 is reduced, and the prepared spherical particles are more compact in the subsequent graphitization treatment, so that the compaction and compaction performance of the graphite composite material 100 are improved, and more importantly, the application can inhibit the volume expansion of the primary particles 11 in the high-temperature carbonization process and prevent the deformation of the secondary particles 10 in the graphitization process.
In one embodiment of the present application, the amorphous carbon is filled between the primary particles 11. It should be noted that, since the second hard carbon coating layer 20 and the first hard carbon coating layer 112 have a disordered carbon structure and a relatively large carbon atom layer spacing, in the embodiment of the application, the amorphous carbon 12 is sandwiched between the second hard carbon coating layer 20 and the first hard carbon coating layer 112, so that lithium ions can be quickly embedded and embedded, and the rate capability of the graphite composite material and the charge-discharge performance under a low-temperature environment are improved.
In an embodiment of the present application, the carbon skeleton material is at least one selected from carbon nanotubes and carbon fibers. It is to be noted that the carbon nanotubes and the carbon fibers have high electrical conductivity, so that the electrical conductivity of the hard carbon coating layer is improved, and the polarization internal resistance in the charge and discharge process of the graphite composite material is reduced, so that the rate performance and the low-temperature charge and discharge performance of the graphite composite material are ensured.
In one embodiment of the present application, the first hard carbon coating 112 is formed by carbonizing a mixture of a carbon skeleton material and a polymer. It should be noted that, the carbon skeleton material includes carbon nanotubes and carbon fibers, which have high electrical conductivity, so as to reduce the polarization internal resistance in the charge-discharge process of the graphite composite material, thereby ensuring the rate capability and the low-temperature charge-discharge capability of the graphite composite material 100.
In one embodiment of the present application, the second hard carbon coating 20 is formed by carbonizing a mixture of carbon skeleton material and polymer. It should be noted that, the carbon skeleton material includes carbon nanotubes and carbon fibers, which have high electrical conductivity, so that the electrical conductivity of the hard carbon shell is improved, and the polarization internal resistance in the charge-discharge process of the graphite composite material is reduced, thereby ensuring the rate capability and the low-temperature charge-discharge capability of the graphite composite material 100.
In one embodiment of the application, the amorphous carbon 12 is graphitized from pitch. It should be noted that, the amorphous carbon 12 is filled between the second hard carbon coating layer 20 and the first hard carbon coating layer 112, the amorphous carbon 12 is formed by asphalt graphitization, before asphalt graphitization, asphalt is used as a binder, and the asphalt has certain fluidity, so that the asphalt is filled in the defects of the second hard carbon coating layer 20 and the first hard carbon coating layer 112, the specific surface area of the hard carbon coating layer is reduced, the granulating effect of the secondary particles 10 is increased, the secondary particles 10 are more spherical, the orientation of the OI material is reduced, and the high first efficiency, the low expansibility and the multiplying power performance of the graphite composite material are ensured. In addition, asphalt is used as a filling layer to deform little in the subsequent graphitization treatment process, so that the compactness of the graphite composite material 100 is improved, the compaction and compaction performance of the material are improved, and the coating processability of the material is improved. More importantly, the amorphous carbon 12 coats the graphite 111 coated with the first hard carbon coating layer 112, so that the first hard carbon coating layer 112 coats the inside of the amorphous carbon 12, thereby avoiding volume expansion of the polymer forming the first hard carbon coating layer 112 in the graphitization treatment process and preventing deformation of the prepared graphite composite material 100.
Referring to fig. 2, in one embodiment of the present application, a method for preparing a graphite composite material includes the steps of: s10, uniformly dispersing a carbon skeleton material and a polymer in an organic solvent to obtain a polymer precursor; s20, mixing and granulating graphite raw material particles and the polymer precursor to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles so as to obtain primary particle precursors; s30, mixing the primary particle precursor with a carbon source, and carbonizing to obtain secondary particles; and S40, mixing and granulating the secondary particles and the polymer precursor to form a second polymer precursor coating layer on the surfaces of the secondary particles, and graphitizing to obtain the graphite composite material. The preparation of the primary particles can be realized by forming the first hard carbon coating layer on the surface of the graphite through high-temperature graphitization, the preparation of the secondary particles can be realized by forming soft carbon on the carbon source on the surface of the primary particles while graphitizing at high temperature, and the preparation of the graphite composite material can be realized by forming the second hard carbon coating layer on the surface of the secondary particles. The supplementary explanation shows that the graphitization degree of the secondary particles reaches more than 93% through graphitization treatment, so that the charge-discharge capacity of the graphite composite material is improved.
In an embodiment of the present application, in step S10, the carbon skeleton material includes at least one of carbon nanotubes and carbon fibers, the polymer includes at least one of phenolic resin, polypropylene resin and polyurethane, the organic solvent includes at least one of ethanol and water, and the solid content of the polymer precursor is 40% -60%. In this embodiment, a carbon skeleton material and a polymer are added to an organic solution and stirred so that the carbon skeleton material and the polymer are dispersed in the organic solvent. The carbon skeleton material can be carbon nano tubes and carbon fibers, the length of the carbon nano tubes and the carbon fibers is 100-300 nm, the pipe diameter is 5-10 nm, the mass ratio of the carbon skeleton material to the polymer is (1-10) (90-99), the polymer can be phenolic resin, polypropylene resin, polyurethane and the like, the organic solvent can be ethanol or water as long as the dissolution or dispersion of the carbon skeleton material and the polymer can be realized, and the solid content of the mixed solution of the carbon skeleton material and the polymer is 40-60%. The application is not limited to this, and the dosage of the carbon skeleton material and the polymer can be adjusted according to the needs, which are all within the protection scope of the embodiment of the application. According to the embodiment of the application, the first hard carbon coating layer and the second hard carbon coating layer are prepared by adopting the mixture of the carbon framework material and the polymer, so that the first hard carbon coating layer and the second hard carbon coating layer can maintain a hard carbon structure after graphitization high-temperature treatment, the specific surface area of the graphite composite material can be greatly reduced by the ultrahigh temperature in the graphitization process, the defects of excessive side reaction and high irreversible capacity for the first time caused by the overlarge specific surface area are avoided, and the first charge-discharge coulomb efficiency of the graphite anode material is improved.
In an embodiment of the present application, the step S20 may specifically be: s21, spraying the polymer precursor to the surfaces of graphite raw material particles; s22, rolling the graphite raw material particles to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles; s23, drying the graphite raw material particles with the first polymer precursor coating layer. More specifically, the polymer precursor is transferred into coating equipment, the coating equipment is roller spray coating equipment, the roller rotating speed of the coating equipment is regulated to be 5-30 r/min, the polymer precursor is sprayed to the surface of the rolled graphite raw material particles through a two-fluid nozzle, drying treatment is carried out under hot air, the drying treatment temperature is 80-95 ℃, and the coating treatment time is 20-40 min. It should be noted that, the present application can properly adjust the coating time according to the rotation speed of the drum, so long as the polymer precursor is uniformly coated on the surface of the graphite raw material particles, and of course, other coating devices can be adopted in the present application, and the present application is not limited thereto, and the above is within the scope of the present application. It should be noted that the graphite raw material particles may be natural graphite particles or soft carbon particles, and the soft carbon particles include petroleum coke, needle coke, carbon fiber, anthracite, carbon microsphere, and the like, and of course, the needle coke includes oil-based needle coke and coal-based needle coke, which are not limited in the scope of the embodiments of the present application.
Additionally, before the step S21, the method further includes pulverizing the graphite raw material to obtain graphite raw material particles. Specifically, the graphite raw material is added into a crusher, the crusher is utilized to crush the graphite raw material, so as to obtain crushed materials with the granularity smaller than 5mm, the crushed materials are mechanically crushed until the granularity D10:3-8 mu m, D50:5-12 mu m, D90:12-18 mu m and Dmax less than 30 mu m are obtained, and graphite raw material particles are obtained, so that after graphitization treatment, the first hard carbon coating layer is uniformly coated on the graphite surface formed by the graphite raw material particles, and the charge and discharge performance of the prepared graphite negative electrode material is ensured.
In an embodiment of the present application, the step S30 may specifically be: s31, spraying a carbon source on the surface of the primary particle precursor; s32, rolling the primary particle precursors to bond the primary particle precursors through the carbon source; s33, carbonizing the primary particle precursor bonded with the carbon source. The carbon source is asphalt, the temperature of the materials in the roller is increased to 150-250 ℃, the molten asphalt is sprayed on the surface of the primary particle precursor through a two-fluid nozzle, the rotating speed of the roller is adjusted to 5-30 r/min, the spraying flow of the asphalt is 80-120 mL/min, the spraying time is 10-30 min, after stopping spraying, the rotating speed of the roller is adjusted to 20-40 r/min, meanwhile, the temperature of the materials in the roller is increased to 450-750 ℃ for 2-8 h, the materials are kept for 1-5 h, the secondary particles are obtained after cooling, the particle size D50 of the secondary particles is 13-24 mu m, and the particle size distribution Span is 0.75-1.0. According to the embodiment of the application, the asphalt is sprayed onto the surface of the primary particle precursor after being melted, so that the dosage proportion of the asphalt is reduced, the granulating effect is increased, the consistency of secondary particle granulation is improved, the orientation of the secondary particles OI is lower, and the lithium intercalation expansion degree of the prepared graphite composite material is reduced on the premise that the primary particle precursor is fully coated by the asphalt.
In an embodiment of the present application, the step S40 may specifically be: s41, spraying the polymer precursor to the surface of the secondary particles; s42, rolling the secondary particles to form a second polymer precursor coating layer on the surfaces of the secondary particles; s43, graphitizing the secondary particles with the second polymer precursor coating layer. The rotating speed of the roller is adjusted to 5 r/min-30 r/min, the polymer precursor is sprayed on the surface of the rolled secondary particles through a two-fluid nozzle at the speed of 30-80 mL/min, the spraying coating treatment time is 20-40 min, the secondary particles sprayed with the polymer precursor are put into a graphitization furnace for high-temperature graphitization, the graphitization furnace is an inner furnace or an Acheson furnace, the graphitization temperature is 2400-3000 ℃, and the graphitization time is 1-6 h, so that the graphite composite material is obtained. According to the embodiment of the application, the graphitization condition can be adjusted according to the actual situation, the embodiment of the application is not limited to the graphitization condition, and the graphitization condition is within the protection scope of the embodiment of the application.
The surface of the graphite raw material particles and the surface of the secondary particles are coated with polymer precursors containing carbon skeleton materials and polymers, and the polymer precursors are converted into hard carbon coating layers similar to a reinforced cement concrete structure after graphitization, wherein the carbon skeleton materials serve as skeletons in the second hard carbon coating layer and the first hard carbon coating layer, so that the mechanical strength, young modulus and electric conductivity of the second hard carbon coating layer and the first hard carbon coating layer are effectively improved, and the graphite composite material with a spherical structure is stably stacked, so that the long-term cycle performance of the graphite anode material is improved. In addition, the embodiment of the application adopts different components as the coating agent, thereby realizing the coating, pelleting and one-step coating of graphite raw material particles, greatly shortening the manufacturing period of the graphite cathode material, reducing the production cost and being convenient for large-scale production.
The application also provides a lithium ion battery, which comprises the graphite composite material; and/or the lithium ion battery comprises the graphite composite material prepared by the preparation method. When the graphite composite material is used as a graphite negative electrode material, the graphite has the characteristic of high charge and discharge capacity, so that the charge and discharge capacity of the graphite negative electrode material is improved. And, the second hard carbon coating coats on the surface of the secondary particle inner core, the secondary particle comprises primary particles and amorphous carbon, the first hard carbon coating coats on the surface of graphite in the primary particles, the second hard carbon coating and the first hard carbon coating are used as structures formed by hard carbon materials, and the hard carbon materials have good quick charging performance, so that the quick charging performance of the graphite negative electrode material is improved. Namely, the technical scheme of the application can improve the quick charge performance of the graphite anode material while improving the capacitance of the graphite anode material.
The technical scheme of the application is further described below with reference to specific embodiments. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the application.
The preparation process of the graphite composite material in examples 1 to 6 of the present application is shown in fig. 3.
Example 1
Firstly, coarsely crushing an oil needle coke raw material by using a crusher to obtain crushed materials with the granularity smaller than 5mm, and crushing the crushed materials by using a mechanical mill until the granularity is as follows: d10 is 4-6 um, D50 is 7-8 um, D90 is 14-16 um, dmax is less than graphite raw material particle of 28um, carbon nano tube and phenolic resin are respectively added into ethanol according to the mass ratio of 1:19, the solid content is controlled to be 45%, and stirring is carried out to dissolve the carbon nano tube and the phenolic resin in the ethanol, thus obtaining the mixed solution of the carbon nano tube and the phenolic resin;
transferring graphite raw material particles into a roller spray coating device, wherein the rotating speed of the roller is 15r/min, spraying a mixed solution of carbon nano tube and phenolic resin on the surfaces of the rolled graphite raw material particles at a speed of 50mL/min through a two-fluid nozzle, drying the particles at a temperature of 90 ℃ under hot air, and coating for 30min to obtain primary particle precursors;
step three, raising the temperature of the materials in the roller to 200 ℃, spraying molten asphalt on the surface of a primary particle precursor through a two-fluid nozzle, adjusting the rotating speed of the roller to 15r/min, adjusting the spraying flow of the asphalt to 100mL/min, adjusting the rotating speed of the roller to 30r/min after stopping spraying, simultaneously raising the temperature of the materials in the roller to 600 ℃ for 4h, preserving heat for 2h, cooling to obtain secondary particles, wherein the particle size D50 of the secondary particles is 18um, and the particle size distribution Span is 0.8;
And fourthly, regulating the rotating speed of the roller to 15r/min, spraying the mixed solution of the carbon nano tube and the phenolic resin on the surface of the rolling spherical secondary particles at the speed of 50mL/min through a two-fluid nozzle, drying the mixed solution at the temperature of 90 ℃ under hot air, carrying out high-temperature graphitization on the obtained secondary particles coated with the carbon nano tube and the phenolic resin for 30min, wherein the graphitization furnace is an Acheson furnace, and the graphitization temperature is 2800-3000 ℃ and the graphitization time is 2-4 h, thus obtaining the graphite composite material.
Example 2
Firstly, coarsely crushing coal needle coke raw materials by using a crusher to obtain crushed materials with the granularity smaller than 5mm, and crushing the crushed materials by using a mechanical mill until the granularity is as follows: d10 is 4-6 um, D50 is 6-7 um, D90 is 13-15 um, dmax is less than graphite raw material particle of 28um, carbon nano tube and polyacrylonitrile are added into ethanol according to mass ratio of 7:93, solid content is controlled to be 50%, stirring is carried out to dissolve carbon nano tube and polyacrylonitrile into ethanol, and mixed solution of carbon nano tube and polyacrylonitrile is obtained;
transferring graphite raw material particles into a roller spray coating device, wherein the rotating speed of the roller is 18r/min, spraying a carbon nano tube-polyacrylonitrile mixed solution on the surfaces of the rolled graphite raw material particles at a speed of 60mL/min through a two-fluid nozzle, drying the graphite raw material particles at a temperature of 95 ℃ under hot air, and coating for 35min to obtain primary particle precursors;
Step three, raising the temperature of the materials in the roller to 250 ℃, spraying molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the rotating speed of the roller to 20r/min, enabling the asphalt spraying flow to be 90mL/min, enabling the spraying time to be 30min, adjusting the rotating speed of the roller to 30r/min after stopping spraying, raising the temperature of the materials in the roller to 650 ℃ for 5h, preserving heat for 3h, cooling to obtain secondary particles, enabling the particle size D50 of the secondary particles to be 16um, and enabling the particle size distribution Span to be 0.85;
and fourthly, regulating the rotating speed of the roller to 18r/min, spraying the mixed solution of the carbon nano tube and the polyacrylonitrile on the surface of the rolling spherical secondary particles at the speed of 60mL/min through a two-fluid nozzle, drying the mixed solution at the temperature of 95 ℃ under hot air, and carrying out high-temperature graphitization on the secondary particles coated with the carbon nano tube and the polyacrylonitrile for 35min, wherein a graphitization furnace is an Acheson furnace, the graphitization temperature is 2800 ℃, and the graphitization time is 3h, so that the graphite composite material is obtained.
Example 3
Step one, coarse crushing of petroleum coke raw materials by using a crusher to obtain crushed materials with granularity smaller than 5mm, and crushing to obtain the crushed materials with granularity of: d10 is 5-7 um, D50 is 8-9 um, D90 is 15-17 um, dmax is less than graphite raw material particle of 28um, adding carbon nano tube and polyurethane into ethanol according to mass ratio of 2:23, controlling solid content to 55%, stirring to dissolve carbon nano tube and polyurethane in ethanol, obtaining carbon nano tube-polyurethane mixed solution;
Transferring graphite raw material particles into a roller spray coating device, wherein the rotating speed of the roller is 18r/min, spraying a carbon nano tube-polyurethane mixed solution on the surfaces of the rolled graphite raw material particles at a speed of 55mL/min through a two-fluid nozzle, drying the particles at a temperature of 90 ℃ under hot air, and coating for 40min to obtain primary particle precursors;
step three, raising the temperature of the materials in the roller to 250 ℃, spraying molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the rotating speed of the roller to 30r/min, adjusting the spraying flow of the asphalt to 90mL/min, adjusting the rotating speed of the roller to 40r/min after stopping spraying, simultaneously raising the temperature of the materials in the roller to 650 ℃ for 5h, preserving heat for 3h, cooling to obtain secondary particles, wherein the particle size D50 of the secondary particles is 19um, and the particle size distribution Span is 0.75;
and fourthly, regulating the rotating speed of the roller to 18r/min, spraying the mixed solution of the carbon nano tube and the polyurethane on the surface of the rolling spherical secondary particles at the speed of 60mL/min through a two-fluid nozzle, drying the mixed solution at the temperature of 90 ℃ under hot air, and carrying out high-temperature graphitization on the secondary particles coated with the carbon nano tube and the polyurethane for 40min by spraying coating treatment, wherein a graphitization furnace is an Acheson furnace, the graphitization temperature is 2900 ℃, and the graphitization time is 4h, so that the graphite composite material is obtained.
Example 4
Step one, coarse crushing of petroleum coke raw materials by using a crusher to obtain crushed materials with granularity smaller than 5mm, and crushing to obtain the crushed materials with granularity of: d10 is 3-4 um, D50 is 5-7 um, D90 is 12-15 um, dmax is less than graphite raw material particle of 25um, adding carbon fiber and polyvinyl alcohol into ethanol according to mass ratio of 2:23, controlling solid content to 55%, stirring to dissolve carbon fiber and polyvinyl alcohol in ethanol, obtaining carbon fiber-polyvinyl alcohol mixed solution;
transferring graphite raw material particles into a roller spray coating device, wherein the rotating speed of the roller is 18r/min, spraying a carbon fiber-polyvinyl alcohol mixed solution on the surfaces of the rolled graphite raw material particles at a speed of 55mL/min through a two-fluid nozzle, drying the particles at a temperature of 90 ℃ under hot air, and coating for 40min to obtain primary particle precursors;
step three, raising the temperature of the materials in the roller to 250 ℃, spraying molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the rotating speed of the roller to 30r/min, adjusting the spraying flow of the asphalt to 90mL/min, adjusting the rotating speed of the roller to 40r/min after stopping spraying, simultaneously raising the temperature of the materials in the roller to 650 ℃ for 5h, preserving heat for 3h, cooling to obtain secondary particles, wherein the particle size D50 of the secondary particles is 15um, and the particle size distribution Span is 0.85;
And fourthly, regulating the rotating speed of the roller to 18r/min, spraying the mixed solution of the carbon fiber and the polyvinyl alcohol on the surface of the rolling spherical secondary particles at the speed of 60mL/min through a two-fluid nozzle, drying the mixed solution at the temperature of 90 ℃ under hot air, carrying out high-temperature graphitization on the secondary particles coated with the carbon fiber and the polyvinyl alcohol for 40min, wherein a graphitization furnace is an Acheson furnace, the graphitization temperature is 2900 ℃, and the graphitization time is 4h, so that the graphite composite material is obtained.
Example 5
Step one, coarse crushing of petroleum coke raw materials by using a crusher to obtain crushed materials with granularity smaller than 5mm, and crushing to obtain the crushed materials with granularity of: d10 is 3-4 um, D50 is 5-7 um, D90 is 12-15 um, dmax is smaller than graphite raw material particles of 25um, carbon nano tube and polyurethane are respectively added into ethanol according to the mass ratio of 1:99, the solid content is controlled to be 55%, and stirring is carried out to dissolve the carbon nano tube and polyurethane in the ethanol, thus obtaining a mixed solution of the carbon nano tube and the polyurethane;
transferring graphite raw material particles into a roller spray coating device, wherein the rotating speed of the roller is 18r/min, spraying a carbon nano tube-polyurethane mixed solution on the surfaces of the rolled graphite raw material particles at a speed of 55mL/min through a two-fluid nozzle, drying the particles at a temperature of 90 ℃ under hot air, and coating for 40min to obtain primary particle precursors;
Step three, raising the temperature of the materials in the roller to 250 ℃, spraying molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the rotating speed of the roller to 30r/min, adjusting the spraying flow of the asphalt to 90mL/min, adjusting the rotating speed of the roller to 40r/min after stopping spraying, simultaneously raising the temperature of the materials in the roller to 650 ℃ for 5h, preserving heat for 3h, cooling to obtain secondary particles, wherein the particle size D50 of the secondary particles is 16um, and the particle size distribution Span is 0.85;
and fourthly, regulating the rotating speed of the roller to 18r/min, spraying the mixed solution of the carbon nano tube and the polyurethane on the surface of the rolling spherical secondary particles at the speed of 60mL/min through a two-fluid nozzle, drying the mixed solution at the temperature of 90 ℃ under hot air, and carrying out high-temperature graphitization on the secondary particles coated with the carbon nano tube and the polyurethane for 40min by spraying coating treatment, wherein a graphitization furnace is an Acheson furnace, the graphitization temperature is 2900 ℃, and the graphitization time is 4h, so that the graphite composite material is obtained.
Example 6
Firstly, coarsely crushing coal needle coke raw materials by using a crusher to obtain crushed materials with the granularity smaller than 5mm, and crushing the crushed materials by using a mechanical mill until the granularity is as follows: d10 is 3-4 um, D50 is 5-7 um, D90 is 12-15 um, dmax is less than graphite raw material particle of 25um, carbon nano tube and phenolic resin are added into ethanol according to mass ratio of 1:9, solid content is controlled to be 55%, stirring is carried out to dissolve carbon nano tube and phenolic resin into ethanol, and mixed solution of carbon nano tube-phenolic resin is obtained;
Transferring graphite raw material particles into a roller spray coating device, wherein the rotating speed of the roller is 18r/min, spraying a mixed solution of carbon nano tube and phenolic resin on the surfaces of the rolled graphite raw material particles at a speed of 55mL/min through a two-fluid nozzle, drying the particles at a temperature of 90 ℃ under hot air, and coating for 40min to obtain primary particle precursors;
step three, raising the temperature of the materials in the roller to 250 ℃, spraying molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the rotating speed of the roller to 30r/min, adjusting the spraying flow of the asphalt to 90mL/min, adjusting the rotating speed of the roller to 40r/min after stopping spraying, simultaneously raising the temperature of the materials in the roller to 650 ℃ for 5h, preserving heat for 3h, cooling to obtain secondary particles, wherein the particle size D50 of the secondary particles is 19um, and the particle size distribution Span is 0.75;
and fourthly, regulating the rotating speed of the roller to 18r/min, spraying the mixed solution of the carbon nano tube and the phenolic resin on the surface of the rolling spherical secondary particles at the speed of 60mL/min through a two-fluid nozzle, drying the mixed solution at the temperature of 90 ℃ under hot air, and carrying out high-temperature graphitization on the secondary particles coated with the carbon nano tube and the phenolic resin for 40min by spraying coating treatment, wherein a graphitization furnace is an inner channeling furnace, the graphitization temperature is 2900 ℃, and the graphitization time is 4h, so that the graphite composite material is obtained.
Comparative example 1
Coarsely crushing the oily needle coke raw material by using a crusher to obtain crushed materials with the granularity smaller than 5mm, and crushing the crushed materials by using a mechanical mill until the granularity is as follows: d10:5um, D50:9 um, D90:917um, dmax < 25 um;
weighing graphite raw material particles and molten asphalt according to a mass ratio of 22:3, mixing the graphite raw material particles and the molten asphalt for 30min, and then putting the mixture into a heating reaction kettle for granulating, wherein the reaction kettle is a heating stirring reaction kettle, and the heating conditions are as follows: heating to 650 ℃ for 4h at normal temperature, preserving heat for 2h, cooling, and stirring at a speed of 15r/min and N in the whole reaction process 2 The flow rate is 4L/min; granulating to obtain the granularity of secondary particles: d10 is 8 μm, D50 is 18 μm, D90 is 28 μm, and Dmax is 33 μm;
and (3) graphitizing the secondary particles for 3 hours, wherein the graphitizing furnace is an inner series furnace, the graphitizing temperature is 2900 ℃, and the graphite composite material is obtained after graphitizing.
Comparative example 2
The difference from example 1 is that step three and step four are not performed.
Comparative example 3
The difference from example 1 is that step four is not performed.
Performance test: the graphite composite materials obtained in each example and comparative example of the present application were used as a negative electrode active material according to the following: conductive carbon black: CMC: sbr=95.3:1.5:1.4:1.8, and the coated surface density was 6.5±0.1mg/cm 2 Vacuum drying at 90 ℃ to obtain a negative electrode plate, and rolling the negative electrode plate until the compaction density is 1.65+/-0.02 g/cc; the anode piece, the lithium piece and the electrolyte (LiPF of 1mol/L 6 EC: emc=1:1) and Celgard2400 separator assembled into 2016 type coin cell: performing multiplying power and cycle test on the obtained battery at the temperature of 25+/-2 ℃ under the conditions of: (1) placing the temperature of 0.1C to 0.01V, and keeping constant pressure for 5 hours; 0.1C to 1.5V; (2) 0.2C is put to 0.01V, and the constant pressure is 0.01C;0.2C to 1.5V; (3) 0.2C is put to 0.01V, and the constant pressure is 0.01C;2C to 1.5V and 0.2C to 1.5V; (4) 0.2C is put to 0.01V, and the constant pressure is 0.01C;0.2C to 1.5V; (5) 1C is put to 0.01V, and the constant pressure is 0.01C;0.2C to 1.5V; (6) 2C to 0.01V; the cycle test conditions were: charging and discharging at 0.2C multiplying power, and the voltage interval is 0.01V-1.5V. The first week charge specific capacity, first week efficiency and 50 week snap cycle stability were respectively tested, and 1C (CC/0.2c cc+cv) double charge and 50 week capacity retention were calculated, with the test results shown below:
according to the table, the comparative analysis with comparative examples 1 to 3 shows that the graphite composite materials prepared in examples 1 to 6 of the present application have good capacity retention rate, and the quick charge performance of the graphite negative electrode material is improved. Moreover, as can be seen from comparison analysis of comparative examples 1, 2 and 3, the arrangement of the second hard carbon coating layer and the first hard carbon coating layer in the embodiment of the application reduces internal resistance in the charge and discharge process, and is favorable for rapid intercalation and intercalation of lithium ions, so that the graphite negative electrode material has good capacity retention rate.
The foregoing description of the preferred embodiments of the present application should not be construed as limiting the scope of the application, but rather should be understood to cover all modifications, equivalent arrangements, or direct/indirect applications of the present application in other relevant fields of technology.

Claims (10)

1. The graphite composite material is characterized by being of a core-shell structure, and comprises a secondary particle inner core and a second hard carbon coating layer formed on the surface of the secondary particle inner core;
the secondary particles comprise primary particles and amorphous carbon, wherein the primary particles comprise graphite and a first hard carbon coating layer formed on the surface of the graphite;
the first hard carbon coating layer and the second hard carbon coating layer comprise carbon framework materials;
the graphite composite material is prepared by the following preparation method:
s10, uniformly dispersing a carbon skeleton material and a polymer in an organic solvent to obtain a polymer precursor;
s20, mixing and granulating graphite raw material particles and the polymer precursor to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles so as to obtain primary particle precursors;
S30, mixing the primary particle precursor with a carbon source, and carbonizing to obtain secondary particles;
and S40, mixing and granulating the secondary particles and the polymer precursor to form a second polymer precursor coating layer on the surfaces of the secondary particles, and graphitizing to obtain the graphite composite material.
2. The graphite composite material of claim 1, wherein the carbon skeleton material is uniformly distributed in the first hard carbon cladding layer and the second hard carbon cladding layer;
and/or, based on 100% of the mass of the first hard carbon coating layer, the content of the carbon skeleton material uniformly distributed in the first hard carbon coating layer is 1% -10%;
and/or, the content of the carbon skeleton material uniformly distributed in the second hard carbon coating layer is 1-10% based on 100% of the mass of the second hard carbon coating layer.
3. The graphite composite material of claim 1, wherein the graphite comprises at least one of artificial graphite and natural graphite;
and/or, the amorphous carbon comprises soft carbon;
and/or, the amorphous carbon is filled between the primary particles.
4. The graphite composite material of claim 1, wherein the carbon skeleton material comprises at least one of carbon nanotubes and carbon fibers.
5. The preparation method of the graphite composite material is characterized by comprising the following steps of:
s10, uniformly dispersing a carbon skeleton material and a polymer in an organic solvent to obtain a polymer precursor;
s20, mixing and granulating graphite raw material particles and the polymer precursor to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles so as to obtain primary particle precursors;
s30, mixing the primary particle precursor with a carbon source, and carbonizing to obtain secondary particles;
and S40, mixing and granulating the secondary particles and the polymer precursor to form a second polymer precursor coating layer on the surfaces of the secondary particles, and graphitizing to obtain the graphite composite material.
6. The method of preparing a graphite composite material as set forth in claim 5, wherein in step S10, the carbon skeleton material includes at least one of carbon nanotubes and carbon fibers; and/or the number of the groups of groups,
in step S10, the polymer includes at least one of phenolic resin, polypropylene resin and polyurethane; and/or the number of the groups of groups,
in step S10, the organic solvent includes at least one of ethanol and water; and/or the number of the groups of groups,
in the step S10, the solid content of the polymer precursor is 40% -60%.
7. The method for preparing a graphite composite material as claimed in claim 5, wherein said step S20 comprises:
s21, spraying the polymer precursor to the surfaces of graphite raw material particles;
s22, rolling the graphite raw material particles to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles;
s23, drying the graphite raw material particles with the first polymer precursor coating layer;
in step S21, the graphite raw material particles include at least one of natural graphite particles and soft carbon particles; and/or the number of the groups of groups,
in the step S22, the rolling speed of the graphite raw material particles is 5 r/min-30 r/min; and/or the number of the groups of groups,
in the step S23, the temperature of the drying treatment is 80-95 ℃ and the time is 20-40 min.
8. The method of preparing a graphite composite material as claimed in claim 5, wherein said step S30 comprises:
s31, spraying a carbon source on the surface of the primary particle precursor;
s32, rolling the primary particle precursors to bond the primary particle precursors through the carbon source;
s33, carbonizing the primary particle precursor bonded with the carbon source;
In step S31, the carbon source includes pitch; and/or the number of the groups of groups,
in the step S32, the rolling speed of the primary particle precursor is 5 r/min-30 r/min; and/or the number of the groups of groups,
in the step S33, the carbonization treatment temperature is 450-750 ℃ and the carbonization treatment time is 1-5 h.
9. The method of preparing a graphite composite material as claimed in claim 5, wherein said step S40 comprises:
s41, spraying the polymer precursor to the surface of the secondary particles;
s42, rolling the secondary particles to form a second polymer precursor coating layer on the surfaces of the secondary particles;
s43, graphitizing the secondary particles with the second polymer precursor coating layer formed;
in the step S41, the particle size of the secondary particles is 13-24 μm, and the particle size distribution is 0.75-1.0; and/or the number of the groups of groups,
in the step S42, the rolling speed of the secondary particles is 5 r/min-30 r/min; and/or the number of the groups of groups,
in the step S43, the graphitization treatment is carried out at 2400-3000 ℃ for 1-6 h.
10. A lithium ion battery, characterized in that it comprises the graphite composite material according to any one of claims 1 to 4; and/or the lithium ion battery comprises the graphite composite material prepared by the preparation method of claims 5 to 9.
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