WO2022188818A1 - Matériau composite de graphite et son procédé de préparation, et batterie au lithium-ion - Google Patents

Matériau composite de graphite et son procédé de préparation, et batterie au lithium-ion Download PDF

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WO2022188818A1
WO2022188818A1 PCT/CN2022/079995 CN2022079995W WO2022188818A1 WO 2022188818 A1 WO2022188818 A1 WO 2022188818A1 CN 2022079995 W CN2022079995 W CN 2022079995W WO 2022188818 A1 WO2022188818 A1 WO 2022188818A1
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composite material
graphite
carbon
coating layer
graphite composite
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Chinese (zh)
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夏路
刘若琦
王为
任建国
贺雪琴
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贝特瑞新材料集团股份有限公司
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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

Definitions

  • the present disclosure relates to the technical field of graphite anode materials, in particular to a graphite composite material, a preparation method thereof and a lithium ion battery.
  • Graphite anode materials have the characteristics of high energy density, good cycle performance, mature preparation technology, and low manufacturing cost, and are widely used in lithium-ion batteries. With the increasing application of lithium-ion batteries, higher and higher requirements are also placed on graphite anode materials. Therefore, it has become an urgent problem to propose a graphite anode material with high charge-discharge capacity and good fast charge performance.
  • the present disclosure provides a graphite composite material, the graphite composite material has a core-shell structure, and the graphite composite material includes a secondary particle inner core and a second hard carbon coating layer coated on the surface of the secondary particle inner core;
  • the secondary particle core includes primary particles and amorphous carbon, and the primary particles include graphite and a first hard carbon coating layer coated on the surface of the graphite;
  • the first hard carbon coating layer and the second hard carbon coating layer include a carbon framework material.
  • the carbon framework material is uniformly distributed in the first hard carbon coating layer and the second hard carbon coating layer.
  • the content of the carbon framework material in the first hard carbon coating layer is 1% to 10%.
  • the content of the carbon framework material in the second hard carbon coating layer is 1% to 10%.
  • the graphite includes at least one of artificial graphite and natural graphite.
  • the amorphous carbon comprises soft carbon.
  • the amorphous carbon is filled between the primary particles.
  • the carbon framework material includes at least one of carbon nanotubes and carbon fibers.
  • the quantity of carbon framework material contained in the unit cross-sectional area of the first hard carbon coating layer is 2 pieces/ ⁇ m 2 to 5 pieces/ ⁇ m 2 .
  • the quantity of carbon framework material contained in the unit cross-sectional area of the second hard carbon coating layer is 2 pieces/ ⁇ m 2 to 5 pieces/ ⁇ m 2 .
  • the aspect ratio of the carbon framework material is 200-5000.
  • the hardness of the first hard carbon coating layer is 50N/mm 2 to 100N/mm 2 .
  • the hardness of the second hard carbon coating layer is 50N/mm 2 to 100N/mm 2 .
  • n is the first hard carbon
  • H is the hardness of the first hard carbon coating layer.
  • the electrical conductivity of the graphite composite material is 200 S/m ⁇ 400 S/m.
  • the median particle size D50 of the graphite composite material is 13 ⁇ m ⁇ 24 ⁇ m.
  • the particle size distribution (D90-D10)/D50 of the graphite composite material is 0.75-1.0.
  • the specific surface area of the graphite composite material is 0.8 m 2 /g ⁇ 2.0 m 2 /g.
  • the orientation degree I 004 /I 110 of the graphite composite material is 2.0-8.0.
  • the Raman ID/ IG of the graphite composite material is 1.0-2.0 .
  • the thickness of both the first hard carbon coating layer and the second hard carbon coating layer is 50 nm ⁇ 200 nm.
  • the present disclosure also provides a preparation method of the graphite composite material, comprising the following steps:
  • the secondary particles and the solution containing the carbon skeleton material and the polymer are mixed and granulated to form a second polymer precursor coating layer on the surface of the secondary particles, and the graphite composite material is obtained after graphitization.
  • the solution containing the carbon skeleton material and the polymer is prepared by dispersing the carbon skeleton material and the polymer uniformly in a solvent to obtain a solution containing the carbon skeleton material and the polymer.
  • the carbon framework 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 solvent includes at least one of organic solvent and water.
  • the solid content of the polymer precursor is 40%-60%.
  • the step of preparing the primary particle precursor is:
  • the graphite raw material particles formed with the first polymer precursor coating layer are dried.
  • the graphite raw material particles include at least one of natural graphite particles and soft carbon particles.
  • the tumbling speed of the graphite raw material particles is 5 r/min to 30 r/min.
  • the temperature of the drying treatment is 80°C to 95°C, and the time is 20 min to 40 min.
  • the step of preparing the secondary particles is:
  • Carbonizing the primary particle precursor to which the carbon source is bound is bound.
  • the carbon source includes easily graphitizable raw materials.
  • the carbon source includes pitch.
  • the tumbling speed of the primary particle precursor is 5 r/min to 30 r/min.
  • the temperature of the carbonization treatment is 450°C to 750°C, and the time is 1 h to 5 h.
  • the step of preparing the graphite composite material is:
  • the secondary particles formed with the second polymer precursor coating layer are graphitized.
  • the particle size of the secondary particles is 13 ⁇ m ⁇ 24 ⁇ m, and the particle size distribution (D90-D10)/D50 is 0.75 ⁇ 1.0.
  • the tumbling speed of the secondary particles ranges from 5 r/min to 30 r/min.
  • the temperature of the graphitization treatment is 2400° C. ⁇ 3000° C., and the time is 1 h ⁇ 6 h.
  • the present disclosure also provides a lithium-ion battery, the lithium-ion battery includes the above-mentioned graphite composite material; and/or, the lithium-ion battery includes the graphite composite material prepared by the above-mentioned preparation method.
  • FIG. 1 is a schematic structural diagram of some embodiments of the disclosed graphite composite material
  • Fig. 2 is the flow chart of the preparation method of the disclosed graphite composite material
  • FIG. 3 is a production process diagram of the preparation method of the disclosed graphite composite material.
  • a graphite composite material 100 has a core-shell structure, and the graphite composite material 100 includes a core of secondary particles 10 and is formed (coated) on the secondary particles 10 a second hard carbon coating layer 20 on the surface of the inner core;
  • the secondary particles 10 include primary particles 11 and amorphous carbon 12, and the primary particles 11 include graphite 111 and a first hard carbon coating layer 112 formed (coated) on the surface of the graphite 111;
  • the first hard carbon coating layer 112 and the second hard carbon coating layer 20 include a carbon framework material.
  • the graphite composite material 100 when used as the graphite negative electrode material, since the graphite 111 has the characteristics of high charge and discharge capacity, the charge and discharge capacity of the graphite negative electrode material is improved.
  • the second hard carbon coating layer 20 is coated on the surface of the inner core of the secondary particle 10, the secondary particle 10 includes the primary particle 11 and the amorphous carbon 12, and the first hard carbon coating layer 112 in the primary particle 11 is coated on graphite
  • the second hard carbon coating layer 20 and the first hard carbon coating layer 112 are formed by hard carbon material, and the hard carbon material has good fast charging performance, thereby improving the fast charging performance of the graphite negative electrode material.
  • the carbon nanotubes in the hard carbon coating can improve the electrical conductivity, stabilize the structure of the coating, and reduce the polarization internal resistance of the material. That is, the technical solution of the present disclosure can improve the fast charging performance of the graphite negative electrode material while improving the electric capacity of the graphite negative electrode material.
  • the electrolyte since the amorphous carbon inside the particle will shrink to generate pores and cracks during the graphitization process, the electrolyte will enter the particle core through the pores and cracks, and directly contact with the core particles, which will cause the composite material to cause excessive circulation during the cycle.
  • the electrochemical performance of the battery such as fast charge performance, 1C double charge retention rate and 50-cycle capacity retention rate
  • the first hard carbon coating layer 112 amorphous carbon in the graphite composite 100 of the present disclosure 12.
  • the structure of the second hard carbon coating layer 20 enables the graphite composite material 100 to effectively prevent the direct contact between the electrolyte and the primary particles 11, thereby effectively protecting the graphite composite material 100 from proper expansion and contraction during battery cycling.
  • the electrochemical properties of the graphite composite material 100 of the present disclosure such as fast charge performance, 1C double charge retention rate, and 50-cycle capacity retention rate, are improved.
  • the amorphous carbon 12 may be a structure formed by graphitization of soft carbon.
  • the secondary particles 10 may include one primary particle 11 , or may include a plurality of primary particles 11 . A plurality of primary particles 11 are contained within the amorphous carbon 12, thereby further increasing the capacity of the prepared graphite composite material.
  • the second hard carbon coating layer 20 coats the surface of the amorphous carbon 12, the hard carbon material has high electrical conductivity, effectively reduces the polarization internal resistance during charging and discharging, and the hard carbon
  • the coating layer can speed up the desolvation process of lithium ions during charging, so that lithium ions can be quickly embedded in graphite, thus greatly improving the fast charging performance of graphite anode materials.
  • the carbon framework material is uniformly distributed in the first hard carbon coating layer 112 and the second hard carbon coating layer 20.
  • the carbon skeleton material is evenly distributed in the first hard carbon coating layer 112 and the second hard carbon coating layer 20, and the carbon skeleton material can be carbon nanotubes, or carbon fiber, carbon skeleton material. It has high conductivity, thereby reducing the polarization internal resistance during the charging and discharging process of the graphite composite material 100, thereby ensuring the rate performance and low temperature charging and discharging performance of the graphite composite material 100.
  • the content of the carbon framework material in the first hard carbon coating layer is 1% to 10%, for example, 1% to 8%. %, 2%-10% or 2%-8%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.
  • the content of the carbon framework material uniformly distributed in the first hard carbon coating layer is 1% to 10%.
  • the first hard carbon coating layer 112 can be formed to uniformly coat the surface of the graphite 111, and at the same time, the first hard carbon coating layer 112 can be further improved.
  • the electrical conductivity of the graphite composite material 100 is high, which reduces the polarization internal resistance during the charging and discharging process of the graphite composite material 100, thereby ensuring the rate performance and low temperature charging and discharging performance of the graphite composite material 100.
  • the content of the carbon framework material in the second hard carbon coating layer is 1% to 10%, for example, 2% to 6%. %, 1%-9% or 2%-7%, such as 1%, 1.5%, 2.5%, 3.5%, 4.5%, 5.5%, 6.5%, 7.5%, 8.5%, 9.5%, 10%.
  • the content of the carbon framework material uniformly distributed in the second hard carbon coating layer is 1% to 10%.
  • the formed second hard carbon coating layer 20 further improves the second hard carbon coating layer 20 while achieving uniform coating on the surface of the secondary particles 10 .
  • the electrical conductivity of the graphite composite material 100 is high, which reduces the polarization internal resistance during the charging and discharging process of the graphite composite material 100, thereby ensuring the rate performance and low temperature charging and discharging performance of the graphite composite material.
  • the graphite 111 includes at least one of artificial graphite and natural graphite. It should be noted that the graphite 111 can be natural graphite or artificial graphite made by graphitization of soft carbon material. Both of the above two kinds of graphite have the characteristics of high charge and discharge capacity, which ensures the charge and discharge capacity of the graphite composite material 100 .
  • the amorphous carbon 12 includes soft carbon. It should be noted that the present disclosure coats the surface of the primary particles 11 with soft carbon, which reduces the defects on the surface of the primary particles 11 , and in the subsequent graphitization treatment, makes the prepared spherical particles more compact, thereby improving the vibration of the graphite composite material 100 . In terms of compaction and compaction performance, the more important point is that the volume expansion of the primary particles 11 can be suppressed during the high-temperature carbonization process, and the deformation of the secondary particles 10 during the graphitization process can be prevented.
  • amorphous carbon is filled between the primary particles 11 . In an embodiment of the present disclosure, the amorphous carbon is filled between primary particles. It should be noted that, since the second hard carbon coating layer 20 and the first hard carbon coating layer 112 have a turbostratic carbon structure, and the carbon atomic layer spacing is relatively large, in the embodiment of the present disclosure, the amorphous carbon 12 is sandwiched between Between the second hard carbon coating layer 20 and the first hard carbon coating layer 112 , in this way, lithium ions can be rapidly inserted and inserted, which improves the rate performance of the graphite composite material and the charge-discharge performance in a low temperature environment.
  • the carbon skeleton material is selected from at least one of carbon nanotubes and carbon fibers. It should be noted that carbon nanotubes and carbon fibers have high electrical conductivity, which improves the electrical conductivity of the hard carbon coating layer, thereby reducing the polarization internal resistance during the charging and discharging process of the graphite composite material, thereby ensuring the graphite composite material. Rate performance and low temperature charge-discharge performance.
  • the first hard carbon coating layer 112 is formed by carbonization of a mixture of carbon skeleton material and polymer.
  • the carbon skeleton material includes carbon nanotubes and carbon fibers, and carbon nanotubes and carbon fibers have high electrical conductivity, thereby reducing the polarization internal resistance during the charging and discharging process of the graphite composite material, thereby ensuring the graphite composite material 100. Rate performance and low temperature charge-discharge performance.
  • the polymer can be soluble in organic solvents, liquid at room temperature (about 15°C to 30°C), and carbon content ⁇ 15% (mass percent), such as resin-based polymers or polyurethane-based polymers.
  • the second hard carbon coating layer 20 is formed by carbonization of a mixture of carbon skeleton material and polymer.
  • the carbon skeleton material includes carbon nanotubes and carbon fibers. Carbon nanotubes and carbon fibers have high electrical conductivity, which improves the electrical conductivity of the hard carbon shell and reduces the polarization internal resistance during the charging and discharging process of the graphite composite material, thereby The rate performance and low-temperature charge-discharge performance of the graphite composite material 100 are guaranteed.
  • the polymer can be soluble in organic solvents, liquid at room temperature (about 15°C to 30°C), and carbon content ⁇ 15% (mass percent), such as resin polymers or polyurethane polymers.
  • 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, and the amorphous carbon 12 is formed by pitch graphitization.
  • the pitch Acting as a binder, the pitch has a certain fluidity, so that the pitch is filled in the defects of the second hard carbon coating layer 20 and the first hard carbon coating layer 112, reducing the specific surface area of the hard carbon coating layer and increasing the The granulation effect of the secondary particles 10 is improved, the secondary particles 10 are more spherical, the OI orientation of the material is reduced, and the high first efficiency, low expansion and rate performance of the graphite composite material are ensured.
  • the asphalt serves as a filling layer with little deformation, thereby improving the compactness of the graphite composite material 100, improving the material's vibrating and compacting properties, and improving its coating processability.
  • 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 is coated inside the amorphous carbon 12, thereby avoiding The volume expansion of the polymer used to form the first hard carbon coating layer 112 during the graphitization process prevents the prepared graphite composite material 100 from being deformed.
  • the amorphous carbon 12 is formed by graphitization of easily graphitizable raw materials.
  • the easily graphitizable raw material may be at least one of pitch, petroleum coke, anthracite, pitch coke, coal-based coke, resin, grease, alkane, alkene, alkyne, and aromatic hydrocarbon.
  • the pitch is selected from at least one of coal pitch, petroleum pitch, mesophase pitch, or modified pitch.
  • “easy graphitization raw material” mainly refers to a raw material of amorphous carbon that is easily converted into graphite at high temperature such as ⁇ 2000°C.
  • the soft carbon is graphitized from readily graphitizable raw materials.
  • the easily graphitizable raw material may be at least one of pitch, petroleum coke, anthracite, pitch coke, coal-based coke, resin, grease, alkane, alkene, alkyne, and aromatic hydrocarbon.
  • the resin may be selected from one of epoxy resins or phenolic resins.
  • the pitch is selected from at least one of coal pitch, petroleum pitch, mesophase pitch, or modified pitch.
  • the first hard carbon coating layer 112 is formed by carbonization of a mixture of carbon framework material and polymer; the second hard carbon coating layer 20 is formed by carbonization of a mixture of carbon framework material and polymer,
  • the carbon skeleton material includes at least one of nanofibers and carbon nanotubes.
  • the number of carbon framework materials contained in the unit cross-sectional area of the first hard carbon coating layer 112 is 2 pieces/ ⁇ m 2 to 5 pieces/ ⁇ m 2 , for example, 2 pieces/ ⁇ m 2 , 3 pieces/ ⁇ m 2 , 4 pieces/ ⁇ m 2 , 5 pieces/ ⁇ m 2 .
  • the amount of carbon framework material contained in the unit cross-sectional area of the second hard carbon coating layer 20 is 2 pieces/ ⁇ m 2 to 5 pieces/ ⁇ m 2 , for example, 2 pieces/ ⁇ m 2 , 3 pieces/ ⁇ m 2 , 4 pieces/ ⁇ m 2 , 5 pieces/ ⁇ m 2 .
  • the percentage of the interface (eg hard carbon cladding interface) of the carbon framework material (represented by A in the context of this disclosure), ie in the carbon framework material at the cladding interface, the carbon framework material's ability to increase the cladding strength and the The percentage of the effective contact area of toughness, which also characterizes the uniformity of the carbon skeleton in the polymer dispersion.
  • carbon skeleton materials such as carbon nanotubes or carbon fibers, when they are dispersed on the interface, the carbon skeleton material is mainly disordered between individuals. state, the carbon framework material can be embedded in the interface (for example, the aspect ratio of the carbon framework material is large) or dispersed on the interface as a whole (for example, the aspect ratio of the carbon framework material is small);
  • the range of A is 10% to 60%, the range of A may be, for example, 25% to 60%, 25% to 50% or 20% to 55%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%.
  • the range of A is selected in the range of 10%-60%, which can ensure the uniform dispersion of the carbon skeleton material, and at the same time can increase the strength and toughness of the coating layer, and improve the strength and conductivity of the material, thereby improving the battery fast charging capacity and cycle. performance.
  • a ⁇ 10% it means that the effective contact area of the carbon skeleton material to enhance the strength is small.
  • the content of the carbon skeleton material is too small and the dispersion is uneven, which will affect the strength and conductivity of the material, resulting in a decrease in the fast charging capacity and cycle performance of the battery.
  • a > 60% it means that the content of carbon skeleton material is too much, which means that the effective contact area of carbon skeleton material to enhance the strength is large at the same time, and at the same time, the material strength is too large and the specific surface area is too high, which will affect the energy density of the battery;
  • the difference between the percentage (A) of the interface of the carbon framework material (for example, the interface of the hard carbon coating layer), the number of carbon framework materials contained in the unit cross-sectional area of the hard carbon coating layer (n), and the hardness of the hard carbon coating layer can be represented by the following formula:
  • n is the quantity of the carbon skeleton material contained in the unit cross-sectional area of the hard carbon coating layer described above;
  • H represents the hardness of the corresponding hard carbon coating
  • 0.7 is the strength coefficient, indicating that the gain coefficient of the carbon skeleton to the frontal compressive strength of the shell is 0.7.
  • the amount of carbon framework material contained in a unit cross-sectional area, and H is the hardness of the first hard carbon coating layer.
  • the quantity of carbon framework material contained in the unit cross-sectional area of , H is the hardness of the second hard carbon coating layer.
  • n can be measured directly, or can be derived from the hardness ranges described below.
  • n derived from the above formula or the range of n in the above embodiment not only makes the carbon skeleton material evenly dispersed, but also effectively improves the electrical conductivity of the hard carbon coating layer, thereby ensuring the performance of the graphite composite material 100 Rate performance (such as 1C charge retention rate) and low-temperature charge-discharge performance; at the same time, this quantity can also satisfy the thickness and hardness of the corresponding carbon coating layer.
  • the aspect ratio of the carbon framework material is 200-5000, for example, it can be 300-5000, 200-4000 or 500-5000, such as 200, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 or 5000.
  • the aspect ratio of the carbon skeleton material of the present disclosure is within the above range, which can further ensure the high electronic conductivity and a certain coating layer strength of the carbon skeleton material, and further improve the fast charging and cycle performance of the material; at the same time, the carbon skeleton material can be further improved. Dispersion effect in polymer solution, thereby improving the cycling performance of graphite composites.
  • the aspect ratio of the carbon skeleton material is too small, the electronic conductivity of the carbon skeleton material will be too low and the strength of the coating layer will be too low, which will affect the fast charging and cycle performance of the graphite composite; if the aspect ratio is too large, it will affect the carbon
  • the dispersion effect of the skeleton material in the polymer solution is easy to agglomerate, which will lead to uneven strength of the coating layer, thus affecting the cycle performance of the graphite composite material.
  • the respective hardnesses of the first hard carbon coating layer 112 and the second hard carbon coating layer 20 may be 50 N/mm 2 to 100 N/mm 2 , for example, the hardness is 60 N/mm 2 to 60 N/mm 2 .
  • 100N/ mm2 , 65N/ mm2 ⁇ 90N/ mm2 or 65N/ mm2 ⁇ 85N/ mm2 such as 51N/ mm2 , 55N/ mm2 , 60N/ mm2 , 65N/ mm2 , 70N/ mm2 , 75N/mm 2 , 80N/mm 2 , 85N/mm 2 , 90N/mm 2 , 95N/mm 2 , 99N/mm 2 , 100N/mm 2 .
  • Both the first hard carbon coating layer 112 and the second hard carbon coating layer 20 of the present disclosure are within the above ranges, which can further improve the battery cycle performance of the composite material, the battery charging rate, and ensure the overall energy density of the battery. If the hardness of the coating layer is less than 50N/mm 2 , it is difficult for the coating layer to suppress the volume expansion of the particle core during the lithium intercalation process, and the particles are easily broken, resulting in poor battery cycle performance; if the hardness of the coating layer is greater than 100N /mm 2 , which means that the coating layer is too dense, which affects the penetration rate of the electrolyte, which will affect the charging rate of the battery.
  • the coating layer is too hard, which reduces the compaction density of the material and affects the overall energy density of the battery.
  • the solid content of the polymer precursor and the amount of carbon skeleton material contained in the unit cross-sectional area of the corresponding hard carbon coating layer are the main factors affecting the hardness of the coating layer.
  • the electrical conductivity of the graphite composite material 100 is 200S/m ⁇ 400S/m, such as 2300S/m ⁇ 400S/m, 200S/m ⁇ 3600S/m, or 280S/m ⁇ 320S/m, such as 200S/m, 220S/m, 240S/m, 260S/m, 280S/m, 300S/m, 320S/m, 340S/m, 360S/m, 380S/m, 400S/m;
  • the electrical conductivity of the graphite composite material 100 of the present disclosure is within the above range, the charge-discharge capacity of the composite material can be further improved, and the 1C double charge retention rate can be improved. If the electrical conductivity is too low, the 1C double charge retention rate will be reduced. If the electrical conductivity is too large, it means that the carbon skeleton material is covered too much (that is, the hard carbon coating layer is too thick), which will affect the battery capacity and decrease the first Coulomb efficiency.
  • the median particle size D50 of the graphite composite material 100 is 13 ⁇ m ⁇ 24 ⁇ m, and the particle size distribution (D90-D10)/D50 is 0.75 ⁇ 1.0.
  • the median particle size of the graphite composite material 100 is within the above range, which can further ensure higher first Coulomb efficiency and fast charging performance of the material. If the median particle size of the material is too large, it will increase the migration distance of Li+ in the material and affect the fast charging performance of the material; if the particle size is too small, the specific surface area of the product will be larger, and the compaction density of the material will decrease, causing the battery The energy density drops.
  • the specific surface area of the graphite composite material 100 is 0.8 m 2 /g ⁇ 2.0 m 2 /g.
  • the specific surface area of the graphite composite material 100 is within the above range, which can further ensure higher first coulombic efficiency and 1C double charge retention rate. If the specific surface area is too large, the first coulomb efficiency will be reduced, and if the specific surface area is too small, the 1C double charge retention rate will be maintained. rate is poor.
  • the graphite composite material 100 has a peak area ratio of the orientation degree I 004 /I 110 of 2.0 to 8.0 at a compaction density of 1.0 g/cm 3 to 2.0 g/cm 3 .
  • the orientation degree of the graphite composite material 100 is within the above range, which can further ensure a higher 1C double charge retention rate and a 50-cycle capacity retention rate. If the orientation is too large, it is easy to cause the material expansion rate to be too large, and thus the 50-cycle capacity retention rate.
  • the size of the graphite raw material particles and the degree of granulation are the main factors affecting the degree of orientation of the graphite composite material 100 .
  • the Raman ID/ IG of the graphite composite material 100 is 1.0 ⁇ 2.0 .
  • the thickness of both the first hard carbon coating layer 112 and the second hard carbon coating layer 20 is 50 nm ⁇ 200 nm.
  • the battery cycle performance of the material can be further ensured and the 1C double charge retention rate of the material can be improved.
  • the thickness of the graphite composite material 100 is too thin, it is difficult for the coating layer to suppress the volume expansion of the particle core during the lithium intercalation process, and the particles are easily broken, resulting in poor battery cycle performance; if the coating layer is too thick, the coating If the coating is too dense, it affects the penetration rate of the electrolyte, thereby affecting the 1C double charge retention rate of the material. At the same time, if the coating is too thick, the compaction density of the material is reduced, which affects the overall energy density of the battery.
  • the solid content of the polymer precursor and the treatment time are the main factors affecting the hardness of the coating layer.
  • a method for preparing a graphite composite material includes the following steps: S10, dispersing the carbon skeleton material and the polymer uniformly in a solvent to obtain a polymer precursor (that is, containing solution of carbon framework material and polymer); S20, mixing and granulating graphite raw material particles and polymer precursors to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles to obtain primary particle precursors; S30, granulating The primary particle precursor and the carbon source are mixed, and the secondary particles are obtained after carbonization; S40, the secondary particles and the polymer precursor are mixed and granulated to form a coating layer of the second polymer precursor on the surface of the secondary particles, and after graphitization A graphite composite material is obtained.
  • a polymer precursor that is, containing solution of carbon framework material and polymer
  • S20 mixing and granulating graphite raw material particles and polymer precursors to form a first polymer precursor coating layer on the surfaces of the graphite raw material particles to obtain
  • the present disclosure can form a first hard carbon coating layer on the surface of graphite to realize the preparation of primary particles through high-temperature graphitization, and at the same time of high-temperature graphitization, the carbon source on the surface of the primary particles forms soft carbon to realize secondary particles and the second hard carbon coating layer is formed on the surface of the secondary particles, so as to realize the preparation of the graphite composite material. It is added that through the graphitization treatment, the degree of graphitization of the secondary particles reaches more than 93%, which improves the charge-discharge capacity of the graphite composite.
  • the solution containing the carbon skeleton material and the polymer is prepared by dispersing the carbon skeleton material and the polymer uniformly in a solvent to obtain a solution containing the carbon skeleton material and the polymer.
  • the carbon framework 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 solvent includes at least one of an organic solvent and water.
  • the carbon skeleton material and the polymer are uniformly dispersed in an organic solvent to obtain a solution containing the carbon skeleton material and the polymer.
  • the organic solvent includes at least one of ethanol and water.
  • the solid content of the polymer precursor is 40%-60%, for example, the solid content is 40%-50%, 50%-60% or 45%-60%, such as 40%, 42% , 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%.
  • the carbon skeleton material and the polymer are added to the organic solution and stirred to disperse the carbon skeleton material and the polymer in the organic solvent.
  • the carbon framework material may be carbon nanotubes and carbon fibers.
  • the lengths of the carbon nanotubes and carbon fibers are 100 nm-300 nm, and the diameters are 5 nm-10 nm.
  • the mass ratio of the carbon skeleton material to the polymer is (1-10):(90-99).
  • the organic solvent may be ethanol, as long as it can achieve dissolution or dispersion of the carbon skeleton material and the polymer.
  • the solid content of the mixed solution of the carbon skeleton material and the polymer is 40% to 60%.
  • Embodiments of the present disclosure use a mixture of a carbon framework material and a polymer to prepare the first hard carbon coating layer and the second hard carbon coating layer, so that the first hard carbon coating layer and the second hard carbon coating layer are in graphite After the high temperature treatment, the hard carbon structure can still be maintained, and the ultra-high temperature of the graphitization process can greatly reduce the specific surface area of the graphite composite material, avoiding the disadvantages of excessive side reactions and large irreversible capacity for the first time due to excessive specific surface area. , which improves the coulombic efficiency of the first charge and discharge of the graphite anode material.
  • step S20 may be: S21, spraying the polymer precursor onto the surface of the graphite raw material particles; S22, rolling the graphite raw material particles to form a first polymer precursor coating layer on the surface of the graphite raw material particle; S23, drying the graphite raw material particles formed with the first polymer precursor coating layer.
  • the tumbling speed of the graphite feedstock particles is 5 r/min to 30 r/min, such as 10 r/min to 30 r/min, 15 r/min to 30 r/min, or 5 r/min to 25 r/min, such as 5 r/min , 8r/min, 10r/min, 12r/min, 15r/min, 17r/min, 20r/min, 22r/min, 25r/min, 27r/min, 30r/min.
  • the drying temperature ranges from 80°C to 95°C, such as 80°C, 82°C, 85°C, 87°C, 90°C, 92°C, and 95°C; the drying time ranges from 20min to 40min. Times such as 20min, 22min, 25min, 27min, 30min, 32min, 35min, 37min, 40min.
  • tumbling may refer to the term “tumbling”, referring to the rolling, turning and/or spinning of particles.
  • tumbling can be the rolling forward and reciprocating motion of the graphite raw material in a circular shape along the circular furnace wall.
  • the polymer precursor is transferred to a coating device, the coating device is a drum spray coating device, the drum rotation speed of the coating device is adjusted to be 5r/min-30r/min, and the polymerization is carried out through a two-fluid nozzle.
  • the precursor is sprayed onto the surface of the tumbling graphite raw material particles, and dried under hot air.
  • the drying temperature is 80°C to 95°C, and the coating treatment time is 20min to 40min. It should be noted that the present disclosure can appropriately adjust the coating treatment time according to the rotation speed of the drum, as long as the uniform coating of the polymer precursor on the surface of the graphite raw material particles is ensured.
  • the present disclosure can also adopt other coating equipment, such as Fluid bed coaters, press coating equipment, etc., the present disclosure is not limited thereto, and the above are all within the protection scope of the present disclosure.
  • the graphite raw material particles may be natural graphite particles or soft carbon particles.
  • the soft carbon particles include petroleum coke, needle coke, carbon fiber, anthracite, carbon microspheres, and the like.
  • needle coke includes oil-based needle coke and coal-based needle coke, the above embodiments of the present disclosure are not limited thereto, and the above are all within the protection scope of the embodiments of the present disclosure.
  • the method before step S21, further includes pulverizing the graphite raw material to obtain graphite raw material particles.
  • the particle size distribution of the graphite raw material particles is: D10: 3-8 ⁇ m, D50: 5-12 ⁇ m, D90: 12-18 ⁇ m, D max ⁇ 30 ⁇ m, and the particle diameters in the particle size distribution are all median diameters.
  • the graphite raw material is added to a crusher, and the graphite raw material is pulverized by the crusher to obtain a crushed material with a particle size of less than 5 mm, and the crushed material is then mechanically ground to a particle size of D10:3-8 ⁇ m, D50: 5 ⁇ 12 ⁇ m, D90: 12 ⁇ 18 ⁇ m, D max ⁇ 30 ⁇ m, to obtain graphite raw material particles, in this way, after graphitization treatment, the first hard carbon coating layer is uniformly coated on the graphite surface formed by the graphite raw material particles, thereby The charge-discharge performance of the prepared graphite anode material is guaranteed.
  • step S30 may be: S31, spray the carbon source on the surface of the primary particle precursor; S32, roll the primary particle precursor to bond the primary particle precursors through the carbon source; S33, carbonize The carbon source-bonded primary particle precursor is processed.
  • the carbon source is a graphitizable feedstock.
  • the easily graphitizable raw material may be at least one of pitch, petroleum coke, anthracite, pitch coke, coal-based coke, resin, grease, alkane, alkene, alkyne, and aromatic hydrocarbon.
  • the resin may be selected from one of epoxy resins or phenolic resins.
  • the pitch is selected from at least one of coal pitch, petroleum pitch, mesophase pitch, or modified pitch.
  • the carbon source is pitch.
  • the equipment used for the preparation can be selected such as a drum furnace and a rotary furnace.
  • the tumbling speed of the primary particle precursor is 5r/min to 30r/min, such as 5r/min, 12r/min, 15r/min, 18r/min, 20r/min, 22r/min, 25r/min , 28r/min, 30r/min.
  • the temperature of the carbonization treatment is 450°C to 750°C, such as 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C; and the time is 1h to 5h, such as 1h, 1.5h , 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h.
  • step S30 is performed in a drum furnace, the temperature of the material in the drum is raised to 150°C-250°C, the molten asphalt is sprayed on the surface of the primary particle precursor through a two-fluid nozzle, and the drum rotational speed is adjusted to 5r/min ⁇ 30r/min, the asphalt spraying flow is 80mL/min ⁇ 120mL/min, and the spraying time is 10min ⁇ 30min.
  • the drum speed adjust the drum speed to 20r/min ⁇ 40r/min, and at the same time, the material in the drum is 2h ⁇ 8h liters. to 450°C ⁇ 750°C, keep the temperature for 1h ⁇ 5h, and cool down to obtain secondary particles.
  • the median particle diameter D50 of the prepared secondary particles is 13 ⁇ m ⁇ 24 ⁇ m, and the particle size distribution Span is 0.75 ⁇ 1.0.
  • the asphalt is melted and then sprayed onto the surface of the primary particle precursor, thereby reducing the proportion of the amount of asphalt used, increasing the granulation effect, and improving the The consistency of the granulation of the secondary particles makes the OI orientation of the secondary particles lower and reduces the expansion degree of lithium intercalation of the prepared graphite composites.
  • step S40 may be: S41, spraying the polymer precursor onto the surface of the secondary particles; S42, rolling the secondary particles to form a second polymer precursor coating layer on the surface of the secondary particles; S43, graphitizing the secondary particles formed with the coating layer of the second polymer precursor.
  • the median particle size of the secondary particles is 13 ⁇ m to 24 ⁇ m, such as 13 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, 22 ⁇ m, 24 ⁇ m; the particle size distribution (D90-D10)/D50 is 0.75 to 1.0, such as 0.75, 0.8 , 0.85, 0.9, 0.95, 1.
  • the tumbling speed of the secondary particles is 5 r/min to 30 r/min, such as 5 r/min, 8 r/min, 10 r/min, 15 r/min, 20 r/min, 25 r/min, 30 r/min.
  • the graphitization temperature is 2400°C to 3000°C, such as 2500°C to 3000°C, 2400°C to 2600°C, or 2500°C to 2900°C; the graphitization time is 1h to 6h, such as 1h, 2h, 3h, 4h, 5h, 6h.
  • the equipment used for the preparation can be selected such as coating equipment, fluidized bed coater, press coating equipment and the like.
  • step S40 is carried out in the coating equipment, the rotation speed of the drum is adjusted to 5r/min ⁇ 30r/min, and the polymer precursor is sprayed on the tumbling two-fluid nozzle at a speed of 30mL/min ⁇ 80mL/min through a two-fluid nozzle
  • the spray coating treatment time is 20min to 40min, and the secondary particles sprayed with the polymer precursor are put into a graphitization furnace for high-temperature graphitization.
  • the graphitization furnace is an inner string furnace or an Acheson furnace.
  • the graphitization temperature is 2400°C ⁇ 3000°C, and the graphitization time is 1h ⁇ 6h to obtain the graphite composite material.
  • the embodiments of the present disclosure can adjust the graphitization conditions according to the actual situation, and the embodiments of the present disclosure are not limited thereto, and the above are all within the protection scope of the embodiments of the present disclosure.
  • the surface of the graphite raw material particles and the surface of the secondary particles are coated with a polymer precursor containing a carbon framework material and a polymer, and the polymer precursor is converted into a hard carbon coating similar to a reinforced cement concrete structure after graphitization.
  • layer wherein the carbon skeleton material acts as a skeleton in both the second hard carbon coating layer and the first hard carbon coating layer, effectively increasing the mechanical strength of the second hard carbon coating layer and the first hard carbon coating layer,
  • the Young's modulus and conductance are beneficial to the stable accumulation of the graphite composite material into a spherical structure, thereby improving the long-term cycle performance of the graphite anode material.
  • the coating, granulation and coating of the graphite raw material particles can be achieved in one step, which greatly shortens the manufacturing cycle of the graphite negative electrode material and reduces the The production cost is convenient for large-scale production.
  • the present disclosure also provides a lithium-ion battery, where the lithium-ion battery includes the above-mentioned graphite composite material; and/or, the lithium-ion battery includes the graphite composite material prepared by the above-mentioned preparation method.
  • the graphite composite material is used as the graphite negative electrode material, the charge and discharge capacity of the graphite negative electrode material is improved due to the high charge and discharge capacity of graphite.
  • the second hard carbon coating layer is coated on the surface of the inner core of the secondary particles, the secondary particles include primary particles and amorphous carbon, and the first hard carbon coating layer is coated on the surface of the graphite in the primary particles, and the second hard carbon coating is
  • the coating layer and the first hard carbon coating layer are formed by the hard carbon material, and the hard carbon material has good fast charging performance, thereby improving the fast charging performance of the graphite negative electrode material. That is, the technical solution of the present disclosure can improve the fast charging performance of the graphite negative electrode material while improving the electric capacity of the graphite negative electrode material.
  • the prior art discloses the following graphite negative electrode materials: the first graphite negative electrode material, the graphite raw material particles are pulverized to a certain particle size, the granulation of secondary particles is realized by kneading, and the graphite negative electrode material is obtained by graphitization; the defects of this structure exist It is difficult to take into account the capacity and fast charging performance. If you choose easy graphitization raw materials, the capacity can be guaranteed but the fast charging performance is poor; if you choose difficult graphitization raw materials, the fast charging performance is good but the capacity is low.
  • the second type of graphite anode material coats the graphite surface with a hard carbon layer or a soft carbon layer. Although the surface coating can reduce the interface impedance and improve the fast charging performance.
  • the disadvantage of this structure is that it has not undergone graphitization treatment, and the coating layer on the surface will affect the graphite capacity. If the coating is pitch-based soft carbon, the fast charging performance of the material is not as good as that of hard carbon.
  • the secondary particles are easily deformed and pulverized, the coating layer is unstable, the particle size is uneven, the lithium ion transmission ability is poor, and the rate performance does not meet the requirements.
  • the present disclosure provides a graphite composite material, which aims to improve the fast charging performance of the graphite negative electrode material while improving the electric capacity of the graphite negative electrode material.
  • the charge and discharge capacity of the graphite negative electrode material is improved because the graphite has the characteristics of high charge and discharge capacity.
  • the second hard carbon coating layer is coated on the surface of the inner core of the secondary particles, the secondary particles include primary particles and amorphous carbon, and the first hard carbon coating layer is coated on the surface of the graphite in the primary particles, and the second hard carbon coating is The coating layer and the first hard carbon coating layer are formed by the hard carbon material, and the hard carbon material has good fast charging performance, thereby improving the fast charging performance of the graphite negative electrode material. That is, the technical solution of the present disclosure can improve the fast charging performance of the graphite negative electrode material while improving the electric capacity of the graphite negative electrode material.
  • Step 1 use a crusher to roughly crush the oil-based needle coke raw material to obtain crushed material with a particle size of less than 5 mm, and then use a mechanical mill to pulverize to a particle size of: D10: 4-6 ⁇ m, D50: 7-8 ⁇ m, D90: 14-16 ⁇ m, D max ⁇ 28 ⁇ m graphite raw material particles, carbon nanotubes and phenolic resin were added to ethanol at a mass ratio of 1:19, the solid content was controlled to be 45%, and stirred to dissolve the carbon nanotubes and phenolic resin in ethanol to obtain Carbon nanotube-phenolic resin mixture, wherein the average aspect ratio of carbon nanotubes is 3125;
  • step 2 the graphite raw material particles are transferred to the drum spray coating equipment, and the rotating speed of the drum is 15r/min, and the mixed solution of carbon nanotube-phenolic resin is sprayed on the surface of the tumbling graphite raw material particles at a speed of 50 mL/min through a two-fluid nozzle. , and dried under hot air at 90°C, and the coating treatment time was 30min to obtain the primary particle precursor;
  • Step 3 raising the temperature of the material in the drum to 200°C, spraying the molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the drum speed to 15r/min, the asphalt spraying flow rate to 100mL/min, and the spraying time to 20min. After stopping spraying, adjust the rotation speed of the drum to 30r/min, and at the same time raise the material in the drum to 600°C for 4h, keep the temperature for 2h, and cool down to obtain secondary particles.
  • the median particle size D50 of the secondary particles is 18 ⁇ m, and the particle size distribution Span is 0.8;
  • Step 4 adjust the rotating speed of the drum to 15r/min, spray the mixture of carbon nanotube-phenolic resin on the surface of the tumbling spherical secondary particles at a speed of 50mL/min through a two-fluid nozzle, and dry it under hot air at 90°C, spray
  • the coating treatment time is 30min, and the obtained secondary particles coated with carbon nanotube-phenolic resin are subjected to high-temperature graphitization. 2h ⁇ 4h, the graphite composite material is obtained.
  • the graphite composite material has a core-shell structure, which includes a secondary particle inner core and a second hard carbon coating on the surface of the secondary particle inner core (from step 4 carbon nanotube-phenolic resin preparation);
  • the secondary particles include primary particles (that is, the precursor of the primary particles in step 2) and amorphous carbon (obtained from the molten pitch in step 3), and the primary particles include graphite and the first hard carbon coated on the surface of the graphite Coating layer (formed by carbon nanotube-phenolic resin preparation in step 1); carbon nanotubes are uniformly distributed in the first hard carbon coating layer and the second hard carbon coating layer.
  • Step 1 use a crusher to roughly crush the coal-based needle coke raw material to obtain crushed material with a particle size of less than 5 mm, and then use a mechanical mill to pulverize to a particle size of: D10: 4-6 ⁇ m, D50: 6-7 ⁇ m, D90: 13-15 ⁇ m, D max ⁇ 28 ⁇ m graphite raw material particles, carbon nanotubes and polyacrylonitrile were added to ethanol in a mass ratio of 7:93, the solid content was controlled to 50%, and stirred to dissolve carbon nanotubes and polyacrylonitrile in ethanol , to obtain a mixture of carbon nanotubes-polyacrylonitrile, wherein the average aspect ratio of carbon nanotubes is 714;
  • Step 2 the graphite raw material particles are transferred to the drum spray coating equipment, the drum rotation speed is 18r/min, and the carbon nanotube-polyacrylonitrile mixed solution is sprayed on the tumbling graphite raw material particles at a speed of 60 mL/min through a two-fluid nozzle.
  • the surface was dried under hot air at 95°C, and the coating treatment time was 35min to obtain the primary particle precursor;
  • Step 3 raising the temperature of the material in the drum to 250°C, spraying the molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the drum speed to 20r/min, the asphalt spraying flow rate to 90mL/min, and the spraying time to 30min, After stopping spraying, adjust the rotation speed of the drum to 30r/min, and at the same time raise the material in the drum to 650°C for 5h, keep the temperature for 3h, and cool down to obtain secondary particles.
  • the median particle size D50 of the secondary particles is 16 ⁇ m, and the particle size distribution Span is 0.85;
  • Step 4 adjust the rotating speed of the drum to 18r/min, spray the mixture of carbon nanotube-polyacrylonitrile at a speed of 60mL/min on the surface of the tumbling spherical secondary particles through a two-fluid nozzle, and dry it under hot air at 95°C,
  • the spray coating treatment time is 35min, and the secondary particles coated with carbon nanotube-polyacrylonitrile are subjected to high temperature graphitization. composite material.
  • the graphite composite material obtained in this example is similar in structure to Example 1, and the material composition of Example 1 is different in that the second hard carbon coating layer is prepared from carbon nanotube-polyacrylonitrile in step 4; The carbon coating layer is formed by preparing carbon nanotubes-polyacrylonitrile in step one.
  • Step 1 use a crusher to roughly crush the raw material of petroleum coke to obtain crushed material with a particle size of less than 5 mm, and then use a mechanical mill to pulverize to a particle size of: D10: 5-7 ⁇ m, D50: 8-9 ⁇ m, D90: 15-17 ⁇ m, D max ⁇ 28 ⁇ m graphite raw material particles, carbon nanotubes and polyurethane were added to ethanol at a mass ratio of 2:23, the solid content was controlled to 55%, and the carbon nanotubes and polyurethane were stirred to dissolve in ethanol to obtain carbon nanotube-polyurethane
  • the mixed solution wherein the average aspect ratio of carbon nanotubes is 2836;
  • Step 2 the graphite raw material particles are transferred to the drum spray coating equipment, the drum rotation speed is 18r/min, and the carbon nanotube-polyurethane mixed solution is sprayed on the surface of the tumbling graphite raw material particles at a speed of 55mL/min through a two-fluid nozzle, And dried under hot air at 90°C, the coating treatment time is 40min, and the primary particle precursor is obtained;
  • Step 3 raising the temperature of the material in the drum to 250°C, spraying the molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the drum rotation speed to 30r/min, the asphalt spraying flow rate to 90mL/min, and the spraying time to 30min. After stopping spraying, adjust the rotation speed of the drum to 40r/min, and at the same time raise the material in the drum to 650°C for 5h, keep the temperature for 3h, and cool down to obtain secondary particles.
  • the median particle size D50 of the secondary particles is 19 ⁇ m, and the particle size distribution Span is 0.75;
  • Step 4 Adjust the rotating speed of the drum to 18r/min, spray the carbon nanotube-polyurethane mixture on the surface of the tumbling spherical secondary particles at a speed of 60mL/min through a two-fluid nozzle, and dry it under hot air at 90°C.
  • the coating treatment time is 40min, and the carbon nanotube-polyurethane-coated secondary particles are subjected to high-temperature graphitization.
  • the graphitization furnace is an Acheson furnace, the graphitization temperature is 2900°C, and the graphitization time is 4h to obtain a graphite composite material.
  • the graphite composite material obtained in this example is similar in structure to Example 1, and the material composition of Example 1 is different in that the second hard carbon coating layer is prepared from carbon nanotube-polyurethane in step 4; The coating is formed by the carbon nanotube-polyurethane preparation in step one.
  • Step 1 use a crusher to coarsely crush the petroleum coke raw material to obtain crushed material with a particle size of less than 5mm, and then use a mechanical mill to pulverize to a particle size of: D10: 3 ⁇ 4 ⁇ m, D50: 5 ⁇ 7 ⁇ m, D90: 12 ⁇ 15 ⁇ m, D max ⁇ 25 ⁇ m graphite raw material particles, carbon fiber and polyvinyl alcohol were added to ethanol at a mass ratio of 2:23, and the solid content was controlled to 55%, and stirred to dissolve carbon fiber and polyvinyl alcohol in ethanol to obtain carbon fiber-polyvinyl alcohol
  • the mixed solution in which the average aspect ratio of carbon fiber is 480;
  • Step 2 the graphite raw material particles are transferred to the drum spray coating equipment, the drum rotation speed is 18r/min, and the mixed solution of carbon fiber-polyvinyl alcohol is sprayed on the surface of the tumbling graphite raw material particles at a speed of 55mL/min through a two-fluid nozzle, And dried under hot air at 90°C, the coating treatment time is 40min, and the primary particle precursor is obtained;
  • Step 3 raising the temperature of the material in the drum to 250°C, spraying the molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the drum rotation speed to 30r/min, the asphalt spraying flow rate to 90mL/min, and the spraying time to 30min. After stopping spraying, adjust the rotation speed of the drum to 40r/min, and at the same time raise the material in the drum to 650°C for 5h, keep the temperature for 3h, and cool down to obtain secondary particles.
  • the median particle size D50 of the secondary particles is 15 ⁇ m, and the particle size distribution Span is 0.85;
  • Step 4 adjust the rotating speed of the drum to 18r/min, spray the mixture of carbon fiber-polyvinyl alcohol on the surface of the tumbling spherical secondary particles at a speed of 60mL/min through a two-fluid nozzle, and dry it under hot air at 90 ° C, spray the bag.
  • the coating treatment time is 40min, and the carbon fiber-polyvinyl alcohol-coated secondary particles are subjected to high temperature graphitization.
  • the graphitization furnace is an Acheson furnace, the graphitization temperature is 2900°C, and the graphitization time is 4h to obtain a graphite composite material.
  • the graphite composite material obtained in this example is similar in structure to Example 1, and the material composition of Example 1 is different in that the second hard carbon coating layer is prepared from step 4 carbon fiber-polyvinyl alcohol; the first hard carbon coating layer is formed.
  • the cladding layer is formed by carbon fiber-polyvinyl alcohol preparation in step 1; the carbon fibers are uniformly distributed in the first hard carbon cladding layer and the second hard carbon cladding layer.
  • Step 1 use a crusher to coarsely crush the petroleum coke raw material to obtain crushed material with a particle size of less than 5mm, and then use a mechanical mill to pulverize to a particle size of: D10: 3 ⁇ 4 ⁇ m, D50: 5 ⁇ 7 ⁇ m, D90: 12 ⁇ 15 ⁇ m, D max ⁇ 25 ⁇ m graphite raw material particles, carbon nanotubes and polyurethane were added to ethanol at a mass ratio of 1:99, and the solid content was controlled to 55%, and stirred to dissolve carbon nanotubes and polyurethane in ethanol to obtain carbon nanotube-polyurethane
  • the mixed solution wherein the average aspect ratio of carbon nanotubes is 3128;
  • Step 2 the graphite raw material particles are transferred to the drum spray coating equipment, the drum rotation speed is 18r/min, and the carbon nanotube-polyurethane mixed solution is sprayed on the surface of the tumbling graphite raw material particles at a speed of 55mL/min through a two-fluid nozzle, And dried under hot air at 90°C, the coating treatment time is 40min, and the primary particle precursor is obtained;
  • Step 3 raising the temperature of the material in the drum to 250°C, spraying the molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the drum rotation speed to 30r/min, the asphalt spraying flow rate to 90mL/min, and the spraying time to 30min. After stopping spraying, adjust the rotation speed of the drum to 40r/min, and at the same time raise the material in the drum to 650°C for 5h, keep the temperature for 3h, and cool down to obtain secondary particles.
  • the median particle size D50 of the secondary particles is 16 ⁇ m, and the particle size distribution Span is 0.85;
  • Step 4 Adjust the rotating speed of the drum to 18r/min, spray the carbon nanotube-polyurethane mixture on the surface of the tumbling spherical secondary particles at a speed of 60mL/min through a two-fluid nozzle, and dry it under hot air at 90°C.
  • the coating treatment time is 40min, and the carbon nanotube-polyurethane-coated secondary particles are subjected to high-temperature graphitization.
  • the graphitization furnace is an Acheson furnace, the graphitization temperature is 2900°C, and the graphitization time is 4h to obtain a graphite composite material.
  • the graphite composite material obtained in this example is similar in structure to Example 1, and the material composition of Example 1 is different in that the second hard carbon coating layer is prepared from carbon nanotube-polyurethane in step 4; The coating is formed by the carbon nanotube-polyurethane preparation in step one.
  • Step 1 use a crusher to roughly crush the coal-based needle coke raw material to obtain crushed material with a particle size of less than 5 mm, and then use a mechanical mill to pulverize to a particle size of: D10: 3-4 ⁇ m, D50: 5-7 ⁇ m, D90: 12-15 ⁇ m, D max ⁇ 25 ⁇ m graphite raw material particles, carbon nanotubes and phenolic resin were added to ethanol at a mass ratio of 1:9, the solid content was controlled to 55%, and stirred to dissolve the carbon nanotubes and phenolic resin in ethanol to obtain Carbon nanotube-phenolic resin mixture, wherein the average aspect ratio of carbon nanotubes is 3800;
  • step 2 the graphite raw material particles are transferred to the drum spray coating equipment, and the rotating speed of the drum is 18r/min, and the mixed solution of carbon nanotube-phenolic resin is sprayed on the surface of the tumbling graphite raw material particles at a speed of 55mL/min through a two-fluid nozzle. , and dried under hot air at 90°C, and the coating treatment time was 40min to obtain the primary particle precursor;
  • Step 3 raising the temperature of the material in the drum to 250°C, spraying the molten asphalt on the surface of the primary particle precursor through a two-fluid nozzle, adjusting the drum rotation speed to 30r/min, the asphalt spraying flow rate to 90mL/min, and the spraying time to 30min. After stopping spraying, adjust the rotation speed of the drum to 40r/min, and at the same time raise the material in the drum to 650°C for 5h, keep the temperature for 3h, and cool down to obtain secondary particles.
  • the median particle size D50 of the secondary particles is 19 ⁇ m, and the particle size distribution Span is 0.75;
  • Step 4 adjust the rotating speed of the drum to 18r/min, spray the mixture of carbon nanotube-phenolic resin on the surface of the tumbling spherical secondary particles at a speed of 60mL/min through a two-fluid nozzle, and dry it under hot air at 90°C.
  • the coating treatment time is 40min, and the carbon nanotube-phenolic resin-coated secondary particles are graphitized at high temperature.
  • the structure of the graphite composite material obtained in this example is similar to that of Example 1.
  • Example 1 The difference from Example 1 is that the solid content of the polymer (ie, the polymer precursor) in the control step 1 is 35%.
  • the structure of the graphite composite material obtained in this example is similar to that of Example 1.
  • Example 1 The difference from Example 1 is that the solid content of the polymer (ie, the polymer precursor) in the control step 1 is 65%.
  • the structure of the graphite composite material obtained in this example is similar to that of Example 1.
  • the reaction kettle is a heating and stirring reaction kettle, and the heating conditions are: 4h normal temperature temperature to 650°C, keep the temperature for 2h, then cool down and cool down, the stirring speed of the whole reaction process is 15r/min, and the N 2 flow rate is 4L/min; the particle size of the secondary particles obtained after granulation: D10 is 8 ⁇ m, D50 is 18 ⁇ m, D90 is 28 ⁇ m, Dmax is 33 ⁇ m;
  • the secondary particles are subjected to graphitization treatment for 3 hours, the graphitization furnace is an inner string furnace, and the graphitization temperature is 2900° C. After the graphitization treatment, a graphite composite material is obtained.
  • the graphite composite material obtained in this comparative example only includes graphite and amorphous carbon formed on the surface of the graphite.
  • Example 1 The difference from Example 1 is that Step 3 and Step 4 are not performed.
  • the graphite composite material obtained in this comparative example only includes graphite and a first hard carbon coating layer (formed by carbon nanotube-phenolic resin preparation in step 1) coated on the surface of the graphite.
  • step 4 is not performed.
  • the graphite composite material obtained in this example only includes the core of secondary particles, and the structure of the secondary particles is the same as that of the embodiment.
  • the particle size analysis laser diffraction method was used to measure.
  • the measurement was performed using a Macbee 3020 instrument using the gas adsorption BET method.
  • the Renishaw inVia Raman instrument was used for measurement using the Map image acquisition method.
  • the hardness is measured. It should be noted that in the embodiment of the present disclosure, the hardness of the first hard carbon coating layer and the second hard carbon coating layer are the same or similar. . Under the high-resolution microscope (Dynamic Ultra Micro Hardness Tester DUH-211S from Shimadzu, Japan), under the action of the load force P of the nano-indenter, the indenter presses a circular indentation on the surface of the particle.
  • the test was carried out under the microscope of Hitachi SU9000 ultra-high-resolution emission scanning electron microscope.
  • the rate test conditions are: 10.1C to 0.01V, constant voltage for 5h; 0.1C to 1.5V; 20.2C to 0.01V, constant voltage 0.01C ; 0.2C to 1.5V; 30.2C to 0.01V, constant voltage 0.01C; 2C to 1.5V, 0.2C to 1.5V; 40.2C to 0.01V, constant voltage 0.01C; 0.2C to charge 51C to 0.01V, constant voltage 0.01C; 0.2C to 1.5V; 62C to 0.01V; cycle test conditions: 0.2C rate charge and discharge, voltage range 0.01V ⁇ 1.5V.
  • the first-week charging specific capacity, the first-week efficiency, and the 50-week derating cycle stability were respectively tested, and the 1C (CC/0.2C CC+CV) double charge and 50-week capacity retention rate were calculated.
  • the test results are shown in Table 2 below:
  • Examples 1 to 6 of the present disclosure show that in Comparative Examples 1, 2 and 3 there is also an amorphous carbon (that is, formed from molten pitch) structure, and Comparative Examples 1 and 2
  • the amorphous carbon in the composite materials prepared by and 3 will generate holes due to shrinkage during the cycle of the battery, so that there will be gaps and holes inside the composite material, so the electrolyte will enter the particle core through the holes and cracks, directly with the core particles. contact, resulting in excessive expansion and shrinkage of the composite during cycling, thereby reducing the electrochemical performance of the battery, such as fast charge performance, 1C double charge retention, 50-cycle capacity retention, and -20°C low-temperature discharge capacity retention.
  • the present disclosure due to the existence of the first hard carbon coating layer on the primary particles of the composite material, the direct contact between the electrolyte and the primary particles is prevented, thereby effectively protecting the material in the battery cycle process. Therefore, the electrochemical performance of the composite material of the present disclosure is improved, thereby further ensuring the high capacity retention rate and excellent fast charging performance of the graphite negative electrode material.
  • the thickness and hardness of the hard carbon coating layer of the materials prepared in the examples of the present disclosure are within the scope of the present disclosure, It can further ensure that the material avoids volume expansion during the charging and discharging process, thereby further improving the cycle performance of the material, such as the 50-cycle capacity retention rate.
  • the thickness and hardness of the hard carbon coating layer of the materials prepared in the examples of the present disclosure can ensure a higher energy density of the battery and effectively improve the battery's performance. Gram capacity and first coulombic efficiency.
  • the graphite composite material provided by the present disclosure is used as a graphite negative electrode material, since graphite has the characteristics of high charge and discharge capacity, the charge and discharge capacity of the graphite negative electrode material is improved.
  • the hard carbon material in the graphite composite material of the present disclosure has good fast charging performance, thereby improving the fast charging performance of the graphite negative electrode material. That is, the technical solution of the present disclosure can improve the fast charging performance of the graphite negative electrode material while improving the electric capacity of the graphite negative electrode material, and has excellent application value.

Abstract

La présente divulgation concerne un matériau composite de graphite et son procédé de préparation, et une batterie au lithium-ion. Le matériau composite de graphite est d'une structure cœur-écorce, et comprend un cœur de particule secondaire et une seconde couche de revêtement de carbone dur formée sur la surface du cœur de particule secondaire ; une particule secondaire comprend une particule primaire et du carbone amorphe, et la particule primaire comprend du graphite et une première couche de revêtement de carbone dur formée sur la surface du graphite ; et la première couche de revêtement en carbone dur et la seconde couche de revêtement en carbone dur comprennent respectivement un matériau à squelette carboné. À savoir, la solution technique de la présente divulgation peut améliorer les performances de charge rapide d'un matériau d'électrode négative en graphite tout en augmentant la capacité du matériau d'électrode négative en graphite.
PCT/CN2022/079995 2021-03-10 2022-03-09 Matériau composite de graphite et son procédé de préparation, et batterie au lithium-ion WO2022188818A1 (fr)

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