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WO2023040319A1 - 复合石墨材料及其制备方法、负极极片、二次电池、电池模块、电池包及用电装置 - Google Patents

复合石墨材料及其制备方法、负极极片、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023040319A1
WO2023040319A1 PCT/CN2022/093671 CN2022093671W WO2023040319A1 WO 2023040319 A1 WO2023040319 A1 WO 2023040319A1 CN 2022093671 W CN2022093671 W CN 2022093671W WO 2023040319 A1 WO2023040319 A1 WO 2023040319A1
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Prior art keywords
composite graphite
optionally
graphite material
negative electrode
carbon
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PCT/CN2022/093671
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English (en)
French (fr)
Inventor
康蒙
何立兵
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宁德时代新能源科技股份有限公司
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Priority to EP22868696.0A priority Critical patent/EP4228034B1/en
Priority to KR1020237016302A priority patent/KR20230088766A/ko
Priority to JP2023530727A priority patent/JP7626571B6/ja
Publication of WO2023040319A1 publication Critical patent/WO2023040319A1/zh
Priority to US18/466,006 priority patent/US20230416097A1/en

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    • 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
    • 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
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    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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    • C01B32/205—Preparation
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    • C01B32/225—Expansion; Exfoliation
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    • C01B32/21—After-treatment
    • C01B32/23—Oxidation
    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/10—Solid density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
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    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/10—Batteries in stationary systems, e.g. emergency power source in plant
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the application belongs to the field of battery technology, and in particular relates to a composite graphite material and a preparation method thereof, a negative electrode sheet, a secondary battery, a battery module, a battery pack and an electrical device.
  • Secondary batteries rely on active ions to reciprocate and deintercalate between the positive and negative electrodes for charging and discharging. It has the outstanding characteristics of high energy density, long cycle life, no pollution, and no memory effect. Therefore, secondary batteries, as clean energy, have been gradually popularized from electronic products to large-scale devices such as electric vehicles, in order to adapt to the sustainable development strategy of the environment and energy.
  • electric vehicles are generally charged at a smaller rate, which often requires a longer charging time, causing anxiety about the cruising range of consumers and limiting the use of electric vehicles. Rapid popularity.
  • the purpose of this application is to provide a composite graphite material and its preparation method, negative electrode sheet, secondary battery, battery module, battery pack and electrical device, aiming at making the secondary battery have high energy density, and also has Greatly improved fast charging performance and low temperature power performance.
  • the first aspect of the present application provides a composite graphite material
  • the composite graphite material includes a body particle and a coating layer on at least a part of the surface of the body particle, and the body particle is a secondary particle formed by gathering more than two primary particles
  • the bulk particles include artificial graphite
  • the coating layer includes amorphous carbon
  • the air oxidation temperature T 0 of the composite graphite material is 630°C to 730°C.
  • the air oxidation temperature T 0 is the temperature corresponding to the intersection of two tangent lines at two points on the thermogravimetric curve of the composite graphite material respectively corresponding to 500 ° C and T 1 temperature
  • the T 1 temperature is the temperature corresponding to the composite
  • the peak top temperature of the largest area peak in the differential thermogravimetric curve of graphite material, the thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis carried out under the following conditions: sample mass 10 ⁇ 0.05mg, purging The gas is air, the air flow rate is 60mL/min, the heating rate is 5°C/min, and the test temperature range is 35°C to 950°C.
  • the air oxidation temperature T 0 of the composite graphite material can accurately represent the temperature at which the composite graphite material begins to lose weight in air oxidation, and then can accurately reflect the end faces and the number of defects of the composite graphite material.
  • the air oxidation temperature T 0 of the composite graphite material is 630°C to 730°C. At this time, the composite graphite material contains a moderate number of end faces and defects, and the composite graphite material has good active ion and electron transport properties.
  • the active ions and electrons in the composite graphite The charge exchange speed on the surface of the material is fast, and the solid-phase transport capacity of active ions inside the composite graphite material is high, so the secondary battery can have greatly improved fast charging performance and low-temperature power performance while maintaining high energy density.
  • the air oxidation temperature T 0 of the composite graphite material is 660°C-710°C.
  • the air oxidation temperature T 0 of the composite graphite material is in an appropriate range, which can make the composite graphite material have more suitable end faces and defect numbers, further improve the transport performance of active ions and electrons, and improve the fast charging performance and low-temperature power of the secondary battery. performance.
  • the composite graphite material further includes a kinetic carbon material.
  • the kinetic carbon material is located at least part of the interface between primary particles and primary particles in the bulk particles.
  • the kinetic carbon material is located in the coating.
  • the kinetic carbon material is located at least part of the interface between primary particles and primary particles in the bulk particles and in the coating layer.
  • the dynamic carbon material raw material is selected from one or more of hard carbon, micro-expanded graphite, expanded graphite, and graphene, and the interlayer spacing d of the dynamic carbon material raw material (002) crystal plane 002 ⁇ 0.3358nm .
  • the interlayer distance d 002 of the (002) crystal plane of the kinetic carbon material raw material is 0.3359 nm ⁇ 0.3366 nm.
  • the kinetic carbon material obtained from the above dynamic carbon material raw material is uniformly distributed in the bulk particles and/or coating layer of the composite graphite material, it is conducive to the rapid insertion and extraction of active ions, thereby improving the transmission of active ions and electrons Performance, thereby improving the fast charging performance and low-temperature power performance of the secondary battery, without causing a loss in the energy density of the secondary battery.
  • the mass percentage of the kinetic carbon material is 1%-30%.
  • the mass percentage of the kinetic carbon material is 8%-15%.
  • the mass percentage of kinetic carbon material is in an appropriate range, which can make the composite graphite material have high active ion solid-phase transport capacity and high active ion and electronic charge exchange under the premise of high gram capacity. speed.
  • the interlayer distance d 002 of the (002) crystal plane of the composite graphite material is 0.3355 nm ⁇ 0.3364 nm.
  • the interlayer distance d 002 of the (002) crystal plane of the composite graphite material is 0.3356 nm ⁇ 0.3361 nm.
  • the composite graphite material has a relatively high layer spacing d 002 , which can improve the solid-phase transport capability of active ions in it, and improve the fast charging performance and low-temperature power performance of the secondary battery.
  • the volume average particle diameter Dv50 of the composite graphite material is 8.5 ⁇ m ⁇ 14.5 ⁇ m.
  • the volume average particle diameter Dv50 of the composite graphite material is 10 ⁇ m ⁇ 12 ⁇ m.
  • the composite graphite material can have better active ion and electron transport performance and fast charging performance, and the composite graphite material also has a higher powder compaction density.
  • the volume average particle diameter Dv50 of the bulk particles is 7.5 ⁇ m ⁇ 13.5 ⁇ m.
  • the volume average particle diameter Dv50 of the bulk particles is 9.0 ⁇ m ⁇ 11.5 ⁇ m.
  • the volume average particle diameter Dv50 of the bulk particles of the composite graphite material is within an appropriate range, and the composite graphite material can have a higher gram capacity on the premise of better active ion and electron transport performance.
  • the ratio of the volume average particle diameter Dv50 of the primary particles to the volume average particle diameter Dv50 of the secondary particles composed of them is 0.45 ⁇ 0.75.
  • the ratio of the volume average particle diameter Dv50 of the primary particles to the volume average particle diameter Dv50 of the secondary particles they consist of is 0.55-0.65. If the above ratio is in a suitable range, the bulk particles of the composite graphite material can have a better degree of secondary particles, which is conducive to improving the active ion and electron transport performance of the composite graphite material while making it have higher structural stability.
  • the mass percentage of amorphous carbon in the cladding layer is 1%-8%.
  • the mass percentage of amorphous carbon in the cladding layer is 2%-5%.
  • the composite graphite material can have high solid-phase transport capacity of active ions while having high gram capacity.
  • the powder compacted density of the composite graphite material under a force of 20000N is 1.45g/cm 3 -1.75g/cm 3 .
  • the powder compacted density of the composite graphite material under a force of 20000N is 1.55g/cm 3 -1.65g/cm 3 .
  • the powder compaction density of the composite graphite material is within an appropriate range, which can make the negative electrode film layer have a higher compaction density, and then the secondary battery has a higher energy density; in addition, the composite graphite material maintains the negative electrode film during the cycle.
  • the ability of the layer pore structure is stronger, and the electrolyte wettability of the negative electrode sheet is better, so it is also beneficial to improve the cycle performance of the secondary battery.
  • the second aspect of the present application provides a method for preparing a composite graphite material, including the step: S10, providing coke powder or coke powder added with kinetic carbon material raw material powder, and the coke powder or the added kinetic
  • the coke powder of the carbon material raw material powder is graphitized to obtain body particles, the body particles are secondary particles formed by the aggregation of two or more primary particles, and the body particles include artificial graphite;
  • S20 the body particles Mixing with an organic carbon source, or mixing the bulk particles with an organic carbon source and the kinetic carbon material raw material powder, forming a coating layer including amorphous carbon on at least a part of the surface of the bulk particles after carbonization treatment, to obtain The composite graphite material.
  • the kinetic carbon material raw material powder is added, and the dynamic carbon material raw material is selected from one or more of hard carbon, micro-expanded graphite, expanded graphite, and graphene.
  • the interlayer distance d 002 of the (002) crystal plane of the carbon material raw material is ⁇ 0.3358nm.
  • the air oxidation temperature T0 of the composite graphite material obtained is 630°C to 730°C, and the air oxidation temperature T0 is at two points on the thermogravimetric curve of the composite graphite material respectively corresponding to the temperature of 500°C and T1
  • the temperature corresponding to the intersection point of the two tangent lines, the T1 temperature is the peak temperature of the largest area peak in the differential thermogravimetric curve of the composite graphite material, and the thermogravimetric curve and the differential thermogravimetric curve can be passed
  • the thermogravimetric analysis was carried out under the following conditions: the sample mass was 10 ⁇ 0.05 mg, the purge gas was air and the air flow rate was 60 mL/min, the heating rate was 5 °C/min, and the test temperature range was 35 °C to 950 °C.
  • the preparation method of the composite graphite material of the present application is simple in operation, controllable in cost, and can be used for large-scale industrial production.
  • the method of the present application can obtain a composite graphite material with moderate content of end faces and defects, so that the secondary battery can have greatly improved fast charging performance and low-temperature power performance under the premise of high energy density.
  • the interlayer distance d 002 of the (002) crystal plane of the kinetic carbon material raw material is 0.3359 nm ⁇ 0.3366 nm.
  • the total mass percentage of the kinetic carbon material raw material powder added in steps S10 and S20 is 1%-30%.
  • the total mass percentage of the kinetic carbon material raw material powder added in steps S10 and S20 is 8%-15%.
  • the coke powder has a volume average particle diameter Dv50 of 6 ⁇ m to 12 ⁇ m.
  • the coke powder has a volume average particle diameter Dv50 of 8 ⁇ m ⁇ 10 ⁇ m.
  • the volume average particle diameter Dv50 of the kinetic carbon material raw material powder is 3 ⁇ m to 12 ⁇ m.
  • the volume average particle diameter Dv50 of the kinetic carbon material raw material powder is 4 ⁇ m ⁇ 9 ⁇ m.
  • the ratio of the volume average particle diameter Dv50 of the coke powder to the volume average particle diameter Dv50 of the kinetic carbon material raw material powder is 1.05 ⁇ 1.75.
  • the ratio of the volume average particle diameter Dv50 of the coke powder to the volume average particle diameter Dv50 of the kinetic carbon material raw material powder is 1.2 ⁇ 1.5.
  • the ratio of the volume average particle diameter Dv50 of the coke powder to the volume average particle diameter Dv50 of the dynamic carbon material raw material powder is in an appropriate range, which can make the bulk particles of the composite graphite material have a better degree of secondary particles.
  • the method further includes the step of: adding a binder in S10, mixing the binder with coke powder, granulating, and then performing graphitization treatment to obtain bulk particles, or
  • the binder is mixed with the coke powder added with the raw material powder of the kinetic carbon material, then granulated, and then graphitized to obtain bulk particles.
  • Adding a binder can make the bulk particles of the composite graphite material have a better degree of secondary particles, which is beneficial to improve the active ion and electron transport performance of the composite graphite material while making it have higher structural stability.
  • the mass percentage of the binder is 3%-12%.
  • the mass percentage of the binder is 5%-8%.
  • the binder is selected from asphalt.
  • the volume average particle diameter Dv50 of the particles obtained after granulation is 8 ⁇ m to 14 ⁇ m.
  • the volume average particle diameter Dv50 of the particles obtained after granulation is 9.5 ⁇ m ⁇ 12 ⁇ m.
  • the organic carbon source is selected from one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell.
  • the source of organic carbon is selected from petroleum pitch.
  • the amount of organic carbon source added is such that the mass percentage of amorphous carbon obtained after carbonization of the organic carbon source is 1%-8%.
  • the amount of the organic carbon source added is such that the mass percentage of the amorphous carbon obtained after the organic carbon source is carbonized is 2%-5%.
  • the added amount of the organic carbon source is in an appropriate range, so that the composite graphite material can have a high gram capacity and a high solid-phase transport capacity of active ions.
  • the third aspect of the present application provides a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes the composite according to the first aspect of the present application Graphite material, or a composite graphite material prepared according to the method of the second aspect of the present application.
  • the negative electrode film layer also includes additives, the additives are selected from one or more of hard carbon, micro-expanded graphite, expanded graphite, and graphene, and the interlayer distance d 002 of the additive (002) crystal plane ⁇ 0.3358nm.
  • additives have good active ion and electron transport performance, which can make the secondary battery have greatly improved fast charging performance and low-temperature power performance under the premise of high energy density.
  • the interlayer distance d 002 of the (002) crystal plane of the additive is 0.3359 nm ⁇ 0.3366 nm.
  • the mass percentage of the additive is 1%-20%.
  • the mass percentage of the additive is 3%-8%.
  • the secondary battery can have greatly improved fast charging performance and low-temperature power performance under the premise of high energy density.
  • the mass percentage of additives is within an appropriate range, the ability to maintain the pore structure of the negative electrode film layer during the cycle is better, the electrolyte wettability of the negative electrode sheet is better, and the secondary battery can also have a good cycle. performance.
  • a fourth aspect of the present application provides a secondary battery, which includes the negative electrode sheet of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery module, which includes the secondary battery of the fourth aspect of the present application.
  • a sixth aspect of the present application provides a battery pack, which includes one of the secondary battery of the fourth aspect of the present application and the battery module of the fifth aspect.
  • a seventh aspect of the present application provides an electric device, which includes at least one of the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect, and the battery pack of the sixth aspect.
  • the secondary battery of the present application can also have greatly improved fast charging performance and low-temperature power performance under the premise of high energy density.
  • the battery module, battery pack and electric device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • Fig. 1 is a schematic diagram of an embodiment of the composite graphite material of the present application.
  • Fig. 2 is a schematic diagram of another embodiment of the composite graphite material of the present application.
  • Fig. 3 is a schematic diagram of another embodiment of the composite graphite material of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 5 is an exploded schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 6 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 7 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 8 is an exploded view of FIG. 4 .
  • FIG. 9 is a schematic diagram of an embodiment of an electrical device in which a secondary battery is used as a power source of the present application.
  • Fig. 10 is the thermogravimetric curve and differential thermogravimetric curve of the composite graphite materials of Example 3 and Comparative Example 2.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined in any combination, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • micro-expanded graphite refers to graphite whose loose volume change (ie expansion ratio) before and after expansion is 80-200; graphite.
  • coke raw material refers to the component that can be processed to obtain “coke”, that is, the raw material used to prepare coke;
  • coke refers to the product obtained by coking the coke raw material, and
  • coke powder and " The composition of “coke” is exactly the same, and “coke powder” refers to “coke” that exists in the form of powder with a certain particle size.
  • kinetic carbon material raw material and “kinetic carbon material raw material powder” are completely consistent in composition
  • kinetic carbon material raw material powder refers to “kinetic carbon material powder” that exists in the form of powder with a certain particle size.
  • Material Raw Materials “Kinetic carbon material” refers to the product of “kinetic carbon material raw material” or “kinetic carbon material raw material powder” after graphitization and/or carbonization treatment.
  • amorphous carbon refers to a transition state carbon material with a low degree of graphitization and crystallization, which is approximately amorphous (or has no fixed shape and periodic structure).
  • amorphous carbon refers to the product after carbonization of organic carbon sources.
  • the key to improving the fast charging performance of secondary batteries is to improve the performance of negative electrode sheets and negative electrode active materials.
  • hard carbon is usually selected as the negative electrode active material, but the gram capacity and compaction density of hard carbon are low, and it is difficult for secondary batteries to have high energy density. The cruising range is greatly reduced.
  • graphite as an anode active material, a secondary battery can have a high energy density, but the secondary battery has poor fast charging performance and low-temperature power performance.
  • the inventor proposed a new type of composite graphite material, which can enable the secondary battery to have greatly improved fast charging performance and low-temperature power performance under the premise of high energy density.
  • the first aspect of the embodiment of the present application provides a composite graphite material
  • the composite graphite material includes a body particle and a coating layer on at least a part of the surface of the body particle, and the body particle is formed by agglomeration of two or more primary particles
  • the bulk particles include artificial graphite
  • the coating layer includes amorphous carbon
  • the air oxidation temperature T 0 of the composite graphite material is 630°C-730°C.
  • the air oxidation temperature T 0 is the temperature corresponding to the intersection of two tangent lines at two points on the thermogravimetric curve of the composite graphite material respectively corresponding to 500 ° C and T 1 temperature
  • the T 1 temperature is the temperature corresponding to the composite
  • the peak top temperature of the largest area peak in the differential thermogravimetric curve of graphite material, the thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis carried out under the following conditions: sample mass 10 ⁇ 0.05mg, purging The gas is air, the air flow rate is 60mL/min, the heating rate is 5°C/min, and the test temperature range is 35°C to 950°C.
  • the air oxidation temperature T0 can be determined according to the thermogravimetric analysis including the following steps: the composite graphite material has a weighing mass of 10 ⁇ 0.05mg, the purge gas is air, the air flow rate is 60mL/min, and the heating rate is 5°C/min , The thermogravimetric test is carried out under the condition of the test temperature range of 35°C to 950°C, and the thermogravimetric curve (also called TG curve) and differential thermogravimetric curve (also called DTG curve) are obtained, and the maximum value read from the differential thermogravimetric curve
  • the peak top temperature T 1 of the area peak, and determine the intersection point of two tangent lines at the two points corresponding to 500 ° C and T 1 temperature respectively on the thermogravimetric curve, and the temperature corresponding to the intersection point on the thermogravimetric curve is The air oxidation temperature T 0 of the composite graphite material.
  • the inventor unexpectedly found that the temperature corresponding to the intersection of two tangent lines at two points on the thermogravimetric curve corresponding to 500°C and the peak temperature T 1 of the largest area peak, that is, the air oxidation temperature T 0 of graphite, can be accurately Indicates the temperature at which graphite air oxidation begins to lose weight, and then can accurately reflect the end faces and the number of defects of graphite.
  • the air oxidation temperature T0 of the composite graphite material in the first aspect of the present application is 630°C to 730°C.
  • the composite graphite material contains a moderate number of end faces and defects, and the composite graphite material has good active ion and electron transport properties, and the activity
  • the charge exchange speed of ions and electrons on the surface of the composite graphite material is relatively fast, and the solid-phase transport capacity of active ions inside the composite graphite material is high, so the secondary battery can have a greatly improved fast charging performance while maintaining a high energy density and low temperature power performance.
  • the inventor also found that the existing graphite layer spacing is small, and the number of end faces and defects is also small, and the air oxidation temperature T is very high, so it is difficult to make the secondary battery have better fast charging performance and low-temperature power performance. .
  • the air oxidation temperature T0 of the composite graphite material is 630°C to 730°C, 640°C to 730°C, 650°C to 730°C, 660°C to 730°C, 670°C to 730°C, 680°C to 730°C °C, 690°C ⁇ 730°C, 700°C ⁇ 730°C, 710°C ⁇ 730°C, 720°C ⁇ 730°C, 630°C ⁇ 720°C, 640°C ⁇ 720°C, 650°C ⁇ 720°C, 660°C ⁇ 720°C, 670°C ⁇ 720°C, 680°C ⁇ 720°C, 690°C ⁇ 720°C, 700°C ⁇ 720°C, 710°C ⁇ 720°C, 630°C ⁇ 710°C, 640°C ⁇ 710°C, 650°C ⁇ 710°C, 660°C ⁇ 710°C, 670°C ⁇ 710°C, 670°C ⁇
  • the air oxidation temperature T 0 of the composite graphite material is in an appropriate range, which can make the composite graphite material have more suitable end faces and defect numbers, further improve the transport performance of active ions and electrons, and improve the fast charging performance and low-temperature power of the secondary battery. performance.
  • the composite graphite material further includes a kinetic carbon material.
  • the kinetic carbon material is located at least part of the interface between primary particles and primary particles in the bulk particles.
  • the bulk particles of the negative electrode active material include artificial graphite primary particles and kinetic carbon materials between the primary particles.
  • the kinetic carbon material is located in the coating.
  • the coating layer includes both amorphous carbon and kinetic carbon materials.
  • the kinetic carbon material is located at least part of the interface between the primary particle and the primary particle in the bulk particle and in the coating layer.
  • the composite graphite material includes a body particle and a coating layer 102 on at least a part of the surface of the body particle, and the body particle is a secondary particle formed by agglomerating more than two primary particles 101 .
  • the kinetic carbon material 103 can be located at least part of the interface between the primary particle 101 and the primary particle 101 in the bulk particle; referring to Fig. 2, the kinetic carbon material 102 can also be located in the coating layer 102; referring to Fig. 3
  • the kinetic carbon material 103 can also be located in at least part of the interface between the primary particles 101 and the primary particles 101 in the bulk particles and in the coating layer 102 at the same time.
  • the mass percentage of the kinetic carbon material is 1%-30%.
  • the mass percentage of kinetic carbon materials is 3% to 30%, 3% to 25%, 3% to 20%, 3% to 15%, 5% to 30%, 5% to 25%, 5% ⁇ 20%, 5% ⁇ 15%, 8% ⁇ 30%, 8% ⁇ 25%, 8% ⁇ 20%, 8% ⁇ 15%, or 8% ⁇ 12%.
  • the mass percentage of the kinetic carbon material is the mass percentage of the kinetic carbon material located at least part of the interface between the primary particles and the primary particles in the bulk particle and the mass percentage of the kinetic carbon material located in the cladding layer. sum of content.
  • the mass percentage of kinetic carbon material is in an appropriate range, which can make the composite graphite material have high active ion solid-phase transport capacity and high active ion and electronic charge exchange under the premise of high gram capacity. Speed, and then the secondary battery has a greatly improved fast charging performance and low temperature power performance under the premise of high energy density.
  • the mass percentage of the kinetic carbon material is within an appropriate range, the ability to maintain the pore structure of the negative electrode film layer during the cycle is better, the electrolyte wettability of the negative electrode sheet is better, and the secondary battery can also have Good cycle performance.
  • the raw material of the kinetic carbon material is selected from one or more of hard carbon, micro-expanded graphite, expanded graphite, and graphene.
  • the gram capacity of the hard carbon below 1V is ⁇ 320mAh/g
  • the powder compacted density of the hard carbon under a force of 20000N is ⁇ 1.05g/cm 3 .
  • the kinetic carbon material raw material is selected from one or more of micro-expanded graphite and expanded graphite.
  • the kinetic carbon material raw material is selected from expanded graphite.
  • the interlayer spacing d 002 of the (002) crystal plane of the kinetic carbon material raw material is ⁇ 0.3358 nm.
  • the interlayer distance d 002 of the (002) crystal plane of the kinetic carbon material raw material is 0.3359 nm ⁇ 0.3366 nm.
  • the interlayer spacing d002 of the above-mentioned kinetic carbon material raw materials is greater than that of conventional graphite, and when the kinetic carbon material obtained therefrom is evenly distributed in the bulk particles and/or coating layers of the composite graphite material, it is conducive to the rapid insertion of active ions and extraction, thereby improving the transport performance of active ions and electrons, thereby improving the fast charging performance and low-temperature power performance of the secondary battery, without causing a loss in the energy density of the secondary battery.
  • the raw materials of the above-mentioned dynamic carbon materials also have high compression resistance, and have a strong ability to maintain the pore structure of the negative electrode film layer during the cycle, and the electrolyte wettability of the negative electrode sheet is better, so it is also conducive to improving the secondary battery. cycle performance.
  • the interlayer distance d 002 of the (002) crystal plane of the composite graphite material is 0.3355 nm to 0.3364 nm.
  • the interlayer distance d 002 of the (002) crystal plane of the composite graphite material is 0.3356 nm ⁇ 0.3361 nm.
  • the composite graphite material has a relatively high layer spacing d 002 , which can improve the solid-phase transport capability of active ions in it, and improve the fast charging performance and low-temperature power performance of the secondary battery.
  • the volume average particle diameter Dv50 of the composite graphite material is 8.5 ⁇ m ⁇ 14.5 ⁇ m.
  • the volume average particle diameter Dv50 of the composite graphite material is 10 ⁇ m ⁇ 12 ⁇ m.
  • the composite graphite material can have better active ion and electron transport performance and fast charging performance, and the composite graphite material also has a higher powder compaction density.
  • the volume average particle diameter Dv50 of the bulk particles is 7.5 ⁇ m ⁇ 13.5 ⁇ m.
  • the volume average particle diameter Dv50 of the bulk particles is 9.0 ⁇ m ⁇ 11.5 ⁇ m.
  • the volume average particle diameter Dv50 of the bulk particles of the composite graphite material is within an appropriate range, and the composite graphite material can have a higher gram capacity on the premise of better active ion and electron transport performance.
  • the ratio of the volume average particle diameter Dv50 of the primary particles to the volume average particle diameter Dv50 of the secondary particles (ie, the bulk particles) of the primary particles is 0.45 ⁇ 0.75.
  • the ratio of the volume average particle diameter Dv50 of the primary particles to the volume average particle diameter Dv50 of the secondary particles they consist of is 0.55 ⁇ 0.65.
  • the ratio of the volume average particle diameter Dv50 of the primary particles to the volume average particle diameter Dv50 of the secondary particles they consist of is within an appropriate range, and the bulk particles of the composite graphite material can have a good degree of secondary particles, which is conducive to improving the composite
  • the active ion and electron transport properties of graphite materials make it have high structural stability.
  • the bulk particles have a stronger ability to maintain the pore structure of the negative electrode film layer during the cycle, and the electrolyte wettability of the negative electrode sheet is better, so it is also conducive to improving the cycle performance of the secondary battery.
  • the mass percentage of amorphous carbon in the cladding layer is 1%-8%.
  • the mass percentage of amorphous carbon in the cladding layer is 2%-5%.
  • the composite graphite material can have high solid-phase transport capacity of active ions while having high gram capacity.
  • the composite graphite material includes bulk particles and a coating layer covering at least 80% of the surface of the bulk particles.
  • the composite graphite material includes bulk particles and a coating covering at least 90% of the surface of the bulk particles.
  • the powder compacted density of the composite graphite material under a force of 20000 N is 1.45 g/cm 3 to 1.75 g/cm 3 .
  • the powder compacted density of the composite graphite material under a force of 20000N is 1.55g/cm 3 -1.65g/cm 3 .
  • the negative electrode film layer can have a higher compacted density, and thus the secondary battery has a higher energy density.
  • the powder compaction density of the composite graphite material is within an appropriate range, and the ability to maintain the pore structure of the negative electrode film layer during the cycle is strong, and the electrolyte wettability of the negative electrode sheet is better, so it is also conducive to improving the cycle of the secondary battery performance.
  • the volume average particle diameter Dv50 of a material is a well-known meaning in the art, which means the particle diameter corresponding to when the cumulative volume distribution percentage of the material reaches 50%, which can be measured by instruments and methods known in the art. For example, it can be conveniently measured by laser particle size analyzer with reference to GB/T 19077-2016 particle size distribution laser diffraction method, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd., UK.
  • the interlayer distance d 002 of a material is a well-known meaning in the art, and can be measured with instruments and methods known in the art.
  • d 002 can be measured by using an X-ray powder diffractometer (for example, PANalytical X'pert PRO) with reference to JIS K 0131-1996 and JB/T 4220-2011.
  • the powder compacted density of a material is a well-known meaning in the art, and can be measured with instruments and methods known in the art. For example, it can be measured by an electronic pressure testing machine (such as UTM7305 type) with reference to the standard GB/T24533-2009.
  • An exemplary test method is as follows: Weigh 1g of material, add it to a mold with a bottom area of 1.327cm2 , pressurize to 2000kg (equivalent to 20000N), hold the pressure for 30s, then release the pressure and keep it for 10s, then record and calculate the material in Powder compaction density under 20000N force.
  • the gram capacity of a material is a meaning known in the art, and can be tested by methods known in the art.
  • An exemplary test method is as follows: the material to be tested, the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) are mixed with the solvent N-methylpyrrolidone (NMP) at a mass ratio of 91.6:1.8:6.6 Evenly, make a slurry; apply the prepared slurry on the copper foil current collector, dry it in an oven, and set it aside. A metal lithium sheet was used as the counter electrode, and a polyethylene (PE) film was used as the separator.
  • NMP solvent N-methylpyrrolidone
  • EC ethylene carbonate
  • EMC ethylmethyl carbonate
  • DEC diethyl carbonate
  • the concentration is 1mol/L.
  • a CR2430 button cell was assembled in an argon-protected glove box. After the resulting coin cell was left to stand for 12 hours, at 25°C, it was discharged at a constant current of 0.05C to 0.005V, and then it was discharged at a constant current of 50 ⁇ A to 0.005V at 25°C for 10 minutes. Then discharge to 0.005V at a constant current; then charge to 2V at a constant current of 0.1C, and record the charging capacity.
  • the ratio of charging capacity to material mass is the gram capacity of the material.
  • the second aspect of the embodiment of the present application provides a method for preparing a composite graphite material.
  • the method includes steps: S10, providing coke powder or coke powder added with dynamic carbon material raw material powder, and performing graphitization treatment on the coke powder or the coke powder added with dynamic carbon material raw material powder to obtain Body particles, the body particles are secondary particles formed by the aggregation of two or more primary particles, and the body particles include artificial graphite; S20, mixing the body particles with an organic carbon source, or mixing the body particles with an organic carbon source The carbon source is mixed with the raw material powder of the kinetic carbon material, and after carbonization treatment, a coating layer including amorphous carbon is formed on at least a part of the surface of the body particle, so as to obtain the composite graphite material.
  • the kinetic carbon material raw material powder is added, and the dynamic carbon material raw material is selected from one or more of hard carbon, micro-expanded graphite, expanded graphite, and graphene.
  • the interlayer distance d 002 of the (002) crystal plane of the carbon material raw material is ⁇ 0.3358nm.
  • the air oxidation temperature T of gained composite graphite material is 630 °C ⁇ 730 °C
  • described air oxidation temperature T 0 is corresponding to 500 °C and T 1 temperature at two points respectively on the thermogravimetric curve of described composite graphite material
  • the temperature corresponding to the intersection point of the two tangent lines, the T1 temperature is the peak temperature of the largest area peak in the differential thermogravimetric curve of the composite graphite material, and the thermogravimetric curve and the differential thermogravimetric curve can be passed through
  • the thermogravimetric analysis was carried out under the following conditions: the sample mass was 10 ⁇ 0.05 mg, the purge gas was air and the air flow rate was 60 mL/min, the heating rate was 5 °C/min, and the test temperature range was 35 °C to 950 °C.
  • the air oxidation temperature T 0 can be determined according to thermogravimetric analysis comprising the following steps: the composite graphite material is 10 ⁇ 0.05 mg in weight, the purge gas is air and the air flow rate is 60 mL/min, and the heating rate is 5 °C/min, and the test temperature range is 35 °C ⁇ 950 °C, the thermogravimetric test is carried out to obtain the thermogravimetric curve and differential thermogravimetric curve, read the peak temperature T 1 of the largest area peak from the differential thermogravimetric curve, and Determine the intersection point of two tangent lines at the two points respectively corresponding to the temperature of 500° C. and T 1 on the thermogravimetric curve, and the temperature corresponding to the intersection point on the thermogravimetric curve is the air oxidation temperature T 0 of the composite graphite material.
  • the preparation method of the composite graphite material of the present application is simple in operation, controllable in cost, and can be used for large-scale industrial production.
  • the method of the present application can obtain a composite graphite material with moderate content of end faces and defects, so that the secondary battery can have greatly improved fast charging performance and low-temperature power performance under the premise of high energy density.
  • the gram capacity of the hard carbon below 1V is ⁇ 320mAh/g
  • the powder compacted density of the hard carbon under a force of 20000N is ⁇ 1.05g/cm 3 .
  • the kinetic carbon material raw material is selected from one or more of micro-expanded graphite and expanded graphite.
  • the kinetic carbon material raw material is selected from expanded graphite.
  • the interlayer distance d 002 of the (002) crystal plane of the kinetic carbon material raw material is 0.3359 nm to 0.3366 nm.
  • the method for providing coke powder includes the steps of: coking coke raw materials to obtain coke, pulverizing, shaping and classifying the obtained coke to obtain coke powder.
  • coke is directly commercially available.
  • the coke raw material can be selected from one or more of petroleum-based raw materials and coal-based raw materials.
  • the petroleum-based raw material is selected from one or more of heavy oil, residual oil, and vacuum residual oil
  • the coal-based raw material is mainly selected from coal tar pitch.
  • Heavy oil, residual oil, and vacuum residual oil are usually produced in the petroleum refining process
  • coal tar pitch is usually produced in the coal dry distillation process.
  • the coke includes one or more of petroleum-based non-needle coke, petroleum-based needle coke, coal-based non-needle coke, and coal-based needle coke.
  • the coke includes one or more of petroleum-based non-needle coke (such as petroleum calcined coke, petroleum-based green coke) and petroleum-based needle coke.
  • coke includes petroleum-based green coke.
  • the coking treatment of the coke raw material is carried out in a delayed coker.
  • the delayed coking device includes a heating furnace and a coke tower.
  • the delayed coking process refers to that the coke raw material is first rapidly heated in the heating furnace to the required coking treatment temperature, and then enters the coke tower, and undergoes preheating, cold coking and other processes in the coke tower. Generate coke.
  • the coke can be crushed using equipment and methods known in the art, such as jet mills, mechanical mills, roller mills or other crushing equipment.
  • the morphology of coke powder obtained after crushing may include one or more of block, spherical and spherical-like.
  • the edges and corners of the coke powder are polished by shaping. The greater the degree of shaping, the closer the powder particles are to the spherical shape, which can increase the deintercalation active ion sites on the surface of the composite graphite material. Shaping treatment is also beneficial to the subsequent granulation process, so that the secondary particles in the obtained composite graphite material have higher structural stability.
  • the powder can be conditioned using equipment and methods known in the art, such as a sizing machine or other sizing equipment.
  • classification treatment can be carried out according to the needs to remove the too small particles and too large particles in the powder.
  • Coke powder with better particle size distribution can be obtained after classification treatment, which is convenient for the subsequent granulation and coating process.
  • Classification treatment can be carried out using equipment and methods known in the art, such as classifying sieves, gravity classifiers, centrifugal classifiers and the like.
  • the coke powder has a volume average particle diameter Dv50 of 6 ⁇ m ⁇ 12 ⁇ m.
  • the coke powder has a volume average particle diameter Dv50 of 8 ⁇ m ⁇ 10 ⁇ m.
  • the method for providing a kinetic carbon material raw material powder includes the steps of: crushing, shaping, and grading the kinetic carbon material raw material to obtain a kinetic carbon material raw material powder.
  • the methods of crushing, shaping, and grading are the same as the crushing, shaping, and grading of the above-mentioned coke.
  • the volume average particle diameter Dv50 of the kinetic carbon material raw material powder is 3 ⁇ m ⁇ 12 ⁇ m.
  • the volume average particle diameter Dv50 of the kinetic carbon material raw material powder is 4 ⁇ m ⁇ 9 ⁇ m.
  • the ratio of the volume average particle diameter Dv50 of the coke powder to the volume average particle diameter Dv50 of the kinetic carbon material raw material powder is 1.05 ⁇ 1.75.
  • the ratio of the volume average particle diameter Dv50 of the coke powder to the volume average particle diameter Dv50 of the kinetic carbon material raw material powder is 1.2 ⁇ 1.5.
  • the ratio of the volume average particle diameter Dv50 of the coke powder to the volume average particle diameter Dv50 of the dynamic carbon material raw material powder is in an appropriate range, which can make the bulk particles of the composite graphite material have a better degree of secondary particles.
  • the mass ratio of coke powder to kinetic carbon material raw material powder is 1-20:99-80.
  • the mass ratio of coke powder to kinetic carbon material raw material is 3-12:97-88.
  • the mass ratio of coke powder to kinetic carbon material raw material powder is in an appropriate range, which is conducive to obtaining composite graphite materials with moderate end faces and defect content, so that the secondary battery can have a greatly improved fast charging under the premise of high energy density performance and low temperature power performance.
  • the total mass percentage of the kinetic carbon material raw material powder added in steps S10 and S20 is 1%-30%. For example, 3% to 30%, 3% to 25%, 3% to 20%, 3% to 15%, 5% to 30%, 5% to 25%, 5% to 20%, 5% to 15%, 8% to 30%, 8% to 25%, 8% to 20%, 8% to 15%, or 8% to 12%.
  • the method further includes the step of: adding a binder in S10.
  • the binder is mixed with the coke powder and then granulated, and then graphitized to obtain the bulk particles, or the binder is mixed with the coke powder added with the raw material powder of the kinetic carbon material, and then granulated, and then graphite Chemical treatment to obtain bulk particles.
  • Adding a binder can make the bulk particles of the composite graphite material have a better degree of secondary particles, which is beneficial to improve the active ion and electron transport performance of the composite graphite material while making it have higher structural stability.
  • the mass percentage of the binder is 3%-12%. Further optionally, the mass percentage of the binder is 5%-8%.
  • the content of the binder is in an appropriate range, excessive agglomeration of the particles can be avoided, so that the bulk particles of the composite graphite material have a better degree of secondary particles.
  • the binder is selected from asphalt.
  • the softening point of the pitch is above 200°C.
  • the pitch is selected from one or more of coal pitch and petroleum pitch.
  • the volume average particle diameter Dv50 of the particles obtained after granulation is 8 ⁇ m ⁇ 14 ⁇ m.
  • the volume average particle diameter Dv50 of the particles obtained after granulation is 9.5 ⁇ m to 12 ⁇ m.
  • Granulation can be performed using equipment and methods known in the art, such as a granulator.
  • a granulator usually consists of a stirred reactor and a module for temperature control of the reactor. By adjusting the stirring speed, heating rate, granulation temperature, cooling rate, etc. in the granulation process, the granulation degree and the structural strength of the granules can be regulated, and the volume average particle diameter of the bulk particles of the composite graphite material finally prepared can be Dv50 within the desired range.
  • the graphitization treatment temperature may be 2800°C-3200°C.
  • the graphitization treatment temperature may be 2900°C-3100°C.
  • the graphitization treatment can make the bulk particles have a suitable degree of graphitization, and then the composite graphite material has a higher gram capacity.
  • the graphitization treatment also makes the lattice expansion of the bulk particles lower during the deintercalation of active ions. It can effectively eliminate the defects of the bulk phase structure of the bulk particles, and improve the cycle performance of the secondary battery.
  • the graphitization treatment time is 10 days to 15 days.
  • the graphitization can be carried out using equipment and methods known in the art, such as a graphitization furnace, especially an Acheson graphitization furnace. After the graphitization treatment, a small amount of oversized particles formed by the agglomeration of the granulated product during the graphitization process can also be removed by sieving, which can prevent the oversized particles from affecting the processing performance of the composite graphite material, such as the stability of the negative electrode slurry properties, coating properties, etc.
  • the volume average particle diameter Dv50 of the obtained bulk particles is 7.5 ⁇ m ⁇ 13.5 ⁇ m.
  • the volume average particle diameter Dv50 of the obtained bulk particles is 9.0 ⁇ m ⁇ 11.5 ⁇ m.
  • the organic carbon source is selected from one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell.
  • the source of organic carbon is selected from petroleum pitch.
  • the softening point of the coal tar pitch and petroleum pitch is below 250°C.
  • the organic carbon source is added in an amount such that the mass percentage of amorphous carbon obtained after the organic carbon source is carbonized is 1%-8%.
  • the amount of the organic carbon source added is such that the mass percentage of the amorphous carbon obtained after the organic carbon source is carbonized is 2%-5%.
  • the added amount of the organic carbon source is in an appropriate range, so that the composite graphite material can have a high gram capacity and a high solid-phase transport capacity of active ions.
  • the carbonization treatment temperature is 700°C-1800°C.
  • the carbonization treatment temperature is 1000°C-1300°C.
  • the organic carbon source and optional kinetic carbon material raw material
  • a coating layer containing amorphous carbon can be formed on at least a part of the surface of the artificial graphite.
  • the carbonization treatment time is 1 h ⁇ 6 h.
  • the preparation method of the composite graphite material includes the step: S10, providing coke powder and kinetic carbon material raw material powder, mixing the binder with coke powder and kinetic carbon material raw material powder and then granulating, Then graphitization treatment is carried out to obtain bulk particles, which are secondary particles formed by the aggregation of more than two primary particles, and the bulk particles include artificial graphite; S20, mix the bulk particles with an organic carbon source, and carbonize After the treatment, a coating layer including amorphous carbon is formed on at least a part of the surface of the bulk particle to obtain a composite graphite material.
  • the preparation method of the composite graphite material includes the steps: S10, providing coke powder, mixing the binder with the coke powder, granulating, and then performing graphitization treatment to obtain bulk particles, the bulk Particles are secondary particles formed by the aggregation of two or more primary particles, and the bulk particles include artificial graphite; S20, mix the bulk particles with organic carbon sources and kinetic carbon material raw material powders, and after carbonization treatment, at least a part of the bulk particles A coating layer comprising amorphous carbon is formed on the surface to obtain a composite graphite material.
  • the preparation method of the composite graphite material includes the step: S10, providing coke powder and kinetic carbon material raw material powder, mixing the binder with coke powder and kinetic 30 carbon material raw material powder, and then granulating , and then carry out graphitization treatment to obtain body particles, the body particles are secondary particles formed by the aggregation of more than two primary particles, and the body particles include artificial graphite; S20, combine the body particles with organic carbon sources, kinetic The carbon material raw material powders are mixed, and after carbonization treatment, a coating layer including amorphous carbon is formed on at least a part of the surface of the body particles to obtain a composite graphite material.
  • the coke powder or the coke powder added with kinetic carbon material raw material powder is graphitized to obtain bulk particles, and the bulk particles are secondary particles formed by aggregation of more than two primary particles.
  • the coke powder obtained after crushing, shaping, etc. is mainly a single particle. From the appearance point of view, the coke powder is a primary particle (or primary particle);
  • the bulk particles obtained after graphitization treatment are agglomerates of a plurality of the above-mentioned primary particles, so from the appearance point of view, the bulk particles are secondary particles.
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active materials and continue to be used after the battery is discharged.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows active ions to pass through.
  • the electrolyte plays the role of conducting active ions between the positive pole piece and the negative pole piece.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector can be metal foil or composite current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the negative electrode film layer usually includes negative electrode active materials, optional binders, optional conductive agents and other optional additives.
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring them evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode active material may include one of the composite graphite material according to the first aspect of the embodiment of the present application and the composite graphite material prepared according to the method of the second aspect of the embodiment of the present application.
  • the negative active material may further include other negative active materials known in the art for secondary batteries.
  • other negative electrode active materials may include one or more of natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials.
  • the tin-based material may include one or more of simple tin, tin oxide, and tin alloy materials. The present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries may also be used. These other negative electrode active materials may be used alone or in combination of two or more.
  • the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylate sodium PAAS), polyacrylic acid One or more of acrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS).
  • other optional additives may include thickeners (eg, sodium carboxymethylcellulose CMC-Na), PTC thermistor materials, and the like.
  • the negative electrode film layer may further include additives.
  • additives, composite graphite materials, optional conductive agents, optional binders and other optional additives can be dispersed in the solvent and stirred evenly to form negative electrode slurry, and then the negative electrode slurry can be coated on On the negative electrode current collector, after drying and cold pressing, a negative electrode film layer is formed.
  • the additive is selected from one or more of hard carbon, micro-expanded graphite, expanded graphite, and graphene, and the interlayer distance d 002 of the (002) crystal plane of the additive is ⁇ 0.3358nm. These additives have good active ion and electron transport performance, which can make the secondary battery have greatly improved fast charging performance and low-temperature power performance under the premise of high energy density.
  • the gram capacity of the hard carbon below 1V is ⁇ 320mAh/g
  • the powder compacted density of the hard carbon under a force of 20000N is ⁇ 1.05g/cm 3 .
  • the additive is selected from one or more of micro-expanded graphite and expanded graphite.
  • the additive is chosen from expanded graphite.
  • the interlayer distance d 002 of the (002) crystal plane of the additive is 0.3359 nm ⁇ 0.3366 nm.
  • the mass percentage of the additive is 1%-20%.
  • the mass percentage of additives is 1%-20%, 1%-18%, 1%-15%, 1%-12%, 1%-10%, 1%-8%, 1%-5% , 2% to 20%, 2% to 18%, 2% to 15%, 2% to 12%, 2% to 10%, 2% to 8%, 2% to 5%, 3% to 20%, 3 % ⁇ 18%, 3% ⁇ 15%, 3% ⁇ 12%, 3% ⁇ 10%, 3% ⁇ 8%, or 3% ⁇ 5%.
  • the mass percentage of the additive is in an appropriate range, the secondary battery can have greatly improved fast charging performance and low-temperature power performance under the premise of high energy density.
  • the mass percentage of additives is within an appropriate range, the ability to maintain the pore structure of the negative electrode film layer during the cycle is better, the electrolyte wettability of the negative electrode sheet is better, and the secondary battery can also have a good cycle. performance.
  • the areal density of the negative electrode film layer is 0.035 kg/m 2 to 0.125 kg/m 2 .
  • the areal density of the negative electrode film layer is 0.078kg/m 2 -0.107kg/m 2 .
  • the areal density of the negative electrode film layer is within the above range, which can make the negative electrode sheet have a high reversible capacity and a low resistance to transporting active ions and electrons, thereby further improving the energy density of the secondary battery. Charging performance, low temperature power performance and cycle performance.
  • the negative electrode film layer has a compacted density of 1.2 g/cm 3 to 1.75 g/cm 3 .
  • the compacted density of the negative electrode film layer is 1.4g/cm 3 -1.6g/cm 3 .
  • the negative electrode sheet can have high reversible capacity, low cycle expansion and good dynamic performance, thereby further improving the energy density of the secondary battery. , fast charging performance, low temperature power performance and cycle performance.
  • the compacted density of the negative electrode film layer is a well-known meaning in the art, and can be tested by methods known in the art.
  • the compacted density of the negative electrode film layer areal density of the negative electrode film layer/thickness of the negative electrode film layer.
  • the thickness of the negative electrode film layer has a meaning known in the art, and can be tested by methods known in the art. For example, a spiral micrometer with 4-digit precision is used.
  • the porosity of the negative electrode film layer is 25%-45%.
  • the porosity of the negative electrode film layer is 28%-35%.
  • the porosity of the negative electrode film layer is within the above range, which can make the negative electrode sheet have suitable electrolyte wettability and good reaction interface, improve the charge and discharge performance of the negative electrode at a large rate, thereby improving the rapid charge performance of the secondary battery .
  • the negative electrode film layer can also have a suitable amount of electrolyte retention, so that the quality of the secondary battery is low, which is conducive to making the secondary battery have a high mass energy density.
  • the porosity of the negative electrode film layer has a meaning known in the art and can be measured by methods known in the art.
  • the test method is as follows: Take the negative electrode sheet coated on one side and cold pressed (if it is a negative electrode sheet coated on both sides, you can wipe off the negative electrode film on one side first), punch it into a small circle with a diameter of 14mm sheet sample; test the thickness of the negative electrode film (the thickness of the negative electrode sheet-the thickness of the negative electrode current collector); calculate the apparent volume V 1 of the negative electrode film layer according to the cylinder volume calculation formula; use an inert gas such as helium or nitrogen as a medium , using the gas displacement method, using a true density tester (such as Micromeritics AccuPyc II 1340 type) to measure the real volume of the negative pole piece, the test can refer to GB/T 24586-2009; the real volume of the negative pole piece minus the negative
  • the porosity of the negative electrode film layer (V 1 ⁇ V 2 )/V 1 ⁇ 100%. It is possible to take multiple (for example, 30) samples of the negative electrode sheet for testing, and take the average value of the results, thereby improving the accuracy of the test results.
  • the bonding force between the negative electrode film layer and the negative electrode current collector is 4.5N/m ⁇ 15N/m.
  • the bonding force between the negative electrode film layer and the negative electrode current collector is 8N/m ⁇ 12N/m.
  • the binding force between the negative electrode film layer and the negative electrode current collector is within the above range, the fast charging performance and cycle performance of the secondary battery can be improved.
  • the strong bonding force between the negative electrode film layer and the negative electrode current collector makes the negative electrode sheet have good electron conductivity, which is conducive to increasing the insertion speed of active ions.
  • the bonding force between the negative electrode film layer and the negative electrode current collector also reflects the ability of the negative electrode sheet to maintain bonding reliability during the cycle, which is conducive to maintaining good electronic conductivity of the secondary battery throughout the life cycle, thereby The cycle performance of the secondary battery can be further improved.
  • the binding force between the negative electrode film layer and the negative electrode current collector is a well-known meaning in the art, and can be measured by methods known in the art.
  • An exemplary test method is as follows: Cut the negative pole piece into a test sample with a length of 100 mm and a width of 10 mm; take a stainless steel plate with a width of 25 mm, stick double-sided adhesive tape (width 11 mm), and paste the test sample on the double-sided adhesive tape on the stainless steel plate , use a 2000g pressure roller to roll back and forth on its surface three times (300mm/min); bend the test sample 180 degrees, manually peel off the negative electrode film layer and negative electrode current collector of the test sample by 25mm, and fix the test sample on the testing machine (For example, INSTRON 336), keep the peeling surface consistent with the force line of the testing machine, and the testing machine peels continuously at 30mm/min, and the obtained peeling force curve takes the average value of the steady break as the peeling force F 0 .
  • the relevant parameters of the negative electrode film layer refer to the parameters of the single-sided negative electrode film layer. That is, when the negative electrode film layer is arranged on both surfaces of the negative electrode current collector, if the parameters of the negative electrode film layer on any one surface meet the parameter range of the present application, it is deemed to fall within the protection scope of the present application.
  • the negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer.
  • the negative electrode sheet described in the present application also includes a conductive primer layer (for example, made of a conductive agent and a binder) that is sandwiched between the negative electrode current collector and the negative electrode film layer and is arranged on the surface of the negative electrode current collector. composition).
  • the negative electrode sheet described in the present application further includes a protective layer covering the surface of the negative electrode film layer.
  • the positive electrode sheet includes a positive electrode collector and a positive electrode film layer disposed on at least one surface of the positive electrode collector and including a positive electrode active material.
  • the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • positive electrode active materials known in the art for secondary batteries can be used as the positive electrode active material.
  • the positive electrode active material may include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, lithium manganese iron phosphate
  • One or more of the composite materials with carbon and their respective modified compounds may be used. The present application is not limited to these materials, and other conventionally known materials that can be used as a secondary battery positive electrode active material may also be used.
  • the positive electrode active material may include one or more of the lithium transition metal oxide and its modified compound shown in formula 1,
  • M is selected from Mn, Al, Zr, Zn
  • Mn One or more of , Cu, Cr, Mg, Fe, V, Ti and B, and A is one or more of N, F, S and Cl.
  • the modified compounds of the above materials may be doping modification or surface coating modification of the positive electrode active material.
  • the positive electrode film layer generally includes a positive electrode active material, an optional binder, and an optional conductive agent.
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder and any other components in a solvent and stirring them uniformly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder used for the positive film layer may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoro One or more of propylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoro
  • fluorine-containing acrylate resin fluorine-containing acrylate resin
  • a metal foil or a composite current collector can be used as the positive electrode current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the secondary battery of the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • the electrolyte may be selected from at least one of solid electrolytes and liquid electrolytes (ie, electrolytic solutions).
  • the electrolyte is an electrolytic solution.
  • the electrolytic solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI ( Lithium bisfluorosulfonyl imide), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO One or more of 2 F 2 (lithium difluorophosphate), LiDFOP (lithium difluorooxalatephosphate) and LiTFOP (lithium tetrafluorooxalate
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC ), Dipropyl Carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Butylene Carbonate (BC), Fluoroethylene Carbonate (FEC), Methyl Formate (MF), Methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate ( One of MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone
  • EC ethylene carbonate
  • PC propylene carbonate
  • EMC diethyl carbonate
  • additives are optionally included in the electrolyte.
  • additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of batteries, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and battery low-temperature power performance. additives, etc.
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the separator is a multilayer composite film, the materials of each layer are the same or different.
  • the positive pole piece, the separator and the negative pole piece can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS) and the like.
  • FIG. 4 shows a secondary battery 5 with a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and the side plates enclose to form a receiving cavity.
  • the housing 51 has an opening communicating with the receiving chamber, and the cover plate 53 is used to cover the opening to close the receiving chamber.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to requirements.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 6 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 is used to cover the lower box body 3 and forms a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a secondary battery.
  • the positive pole piece, the separator, and the negative pole piece can be formed into an electrode assembly through a winding process or a lamination process, and the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and after vacuum packaging, standing, Formation, shaping and other processes to obtain secondary batteries.
  • the embodiments of the present application also provide an electric device, the electric device includes at least one of the secondary battery, the battery module, or the battery pack of the present application.
  • the secondary battery, battery module or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric device can be, but not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electric device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 9 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module can be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • Dv50 volume average particle size
  • micro-expanded graphite (expansion factor: 180) with interlayer spacing d002 of 0.3363nm was pulverized, shaped and classified to obtain micro-expanded graphite powder with volume average particle diameter Dv50 of 7.5 ⁇ m.
  • the coke powder and micro-expanded graphite powder are mixed, and then mixed with the binder coal tar pitch, and then granulated.
  • the volume average particle diameter Dv50 of the obtained granules after granulation is about 13 ⁇ m.
  • Put the granulated product in a graphite crucible then place the graphite crucible in the Acheson graphitization furnace, fill the surroundings of the graphite crucible with resistance material, energize the current to flow through the resistance material to generate heat, and carry out graphitization treatment at about 3000°C , to obtain bulk particles.
  • the obtained bulk particles are mixed with organic carbon source petroleum pitch, and then carbonized in an orbital kiln.
  • the highest temperature zone is about 1150 ° C, and the running time in the highest temperature zone is about 4 hours, so as to form a coating layer on at least a part of the surface of the bulk particles.
  • a composite graphite material is obtained.
  • the mass percentage of the micro-expanded graphite powder added is 1%
  • the mass percentage of the binder added is 6%
  • the quality of the organic carbon source added is such that the organic
  • the mass percentage of amorphous carbon obtained after carbonization of the carbon source is 3%.
  • the composite graphite material prepared above is used as negative electrode active material and binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) and conductive agent carbon black (SuperP) by weight 96.2:1.8 :1.2:0.8 Fully stir and mix in an appropriate amount of solvent deionized water to form a uniform negative electrode slurry; evenly coat the negative electrode slurry on the surface of the negative electrode current collector copper foil, dry and cold press to obtain the negative electrode sheet .
  • the areal density of the negative electrode film layer is 0.097kg/m 2
  • the compacted density is 1.64g/cm 3 .
  • the positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), conductive agent carbon nanotube (CNT), conductive agent carbon black (Super P), binder polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:0.5 :0.9:1.1 Fully stir and mix in an appropriate amount of solvent NMP to form a uniform positive electrode slurry; evenly coat the positive electrode slurry on the surface of the positive electrode current collector aluminum foil, dry and cold press to obtain the positive electrode sheet.
  • the areal density of the positive electrode film layer is 0.178kg/m 2
  • the compacted density is 3.4g/cm 3 .
  • a porous polyethylene (PE) film is used as the separator.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the preparation method of the secondary battery is similar to that of Example 1, except that based on the total mass of the obtained composite graphite material, the mass percentage of the added micro-expanded graphite powder is 3%, and the mass percentage of the added binder is The content is 6%, and the mass of the added organic carbon source is such that the mass percentage of amorphous carbon obtained after the organic carbon source is carbonized is 3%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that based on the total mass of the obtained composite graphite material, the mass percentage of the added micro-expanded graphite powder is 8%, and the mass percentage of the added binder is The content is 6%, and the mass of the added organic carbon source is such that the mass percentage of amorphous carbon obtained after the organic carbon source is carbonized is 3%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that based on the total mass of the obtained composite graphite material, the mass percentage of the added micro-expanded graphite powder is 12%, and the mass percentage of the added binder is The content is 6%, and the mass of the added organic carbon source is such that the mass percentage of amorphous carbon obtained after the organic carbon source is carbonized is 3%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that based on the total mass of the obtained composite graphite material, the mass percentage of the added micro-expanded graphite powder is 20%, and the mass percentage of the added binder is The content is 6%, and the mass of the added organic carbon source is such that the mass percentage of amorphous carbon obtained after the organic carbon source is carbonized is 3%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that based on the total mass of the obtained composite graphite material, the mass percentage of the added micro-expanded graphite powder is 30%, and the mass percentage of the added binder is The content is 6%, and the mass of the added organic carbon source is such that the mass percentage of amorphous carbon obtained after the organic carbon source is carbonized is 3%.
  • the preparation method of the secondary battery is similar to that of Example 3, except that the micro-expanded graphite powder is replaced by hard carbon powder with an interlayer distance d 002 of 0.33615 nm and a volume average particle diameter Dv50 of 5.3 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 3, except that the micro-expanded graphite powder is replaced by expanded graphite powder with an interlayer distance d002 of 0.33638 nm and a volume average particle diameter Dv50 of 7.2 ⁇ m (expansion factor is 300).
  • the preparation method of the secondary battery is similar to that of Example 3, except that the micro-expanded graphite powder is replaced by graphene powder with an interlayer distance d 002 of 0.33620 nm and a volume average particle diameter Dv50 of 8.0 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the composite graphite material is prepared according to the following method.
  • Dv50 volume average particle size
  • micro-expanded graphite (expansion factor: 180) with interlayer spacing d002 of 0.3363nm was pulverized, shaped and classified to obtain micro-expanded graphite powder with volume average particle diameter Dv50 of 7.5 ⁇ m.
  • the coke powder is mixed with the binder coal tar pitch, and then granulated.
  • the volume average particle diameter Dv50 of the obtained granules after granulation is about 13 ⁇ m.
  • Put the granulated product in a graphite crucible then place the graphite crucible in the Acheson graphitization furnace, fill the surroundings of the graphite crucible with resistance material, energize the current to flow through the resistance material to generate heat, and carry out graphitization treatment at about 3000°C , to obtain bulk particles.
  • the obtained bulk particles are mixed with micro-expanded graphite powder and organic carbon source petroleum pitch, and then carbonized in an orbital kiln.
  • a coating layer is formed to obtain a composite graphite material.
  • the mass percentage of the micro-expanded graphite powder added is 8%
  • the mass percentage of the binder added is 6%
  • the quality of the organic carbon source added is such that the organic
  • the mass percentage of amorphous carbon obtained after carbonization of the carbon source is 3%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the composite graphite material is prepared according to the following method.
  • Dv50 volume average particle size
  • micro-expanded graphite (expansion factor: 180) with interlayer spacing d002 of 0.3363nm was pulverized, shaped and classified to obtain micro-expanded graphite powder with volume average particle diameter Dv50 of 7.5 ⁇ m.
  • the coke powder and micro-expanded graphite powder are mixed, and then mixed with the binder coal tar pitch, and then granulated.
  • the volume average particle diameter Dv50 of the obtained granules after granulation is about 13 ⁇ m.
  • Put the granulated product in a graphite crucible then place the graphite crucible in the Acheson graphitization furnace, fill the surroundings of the graphite crucible with resistance material, energize the current to flow through the resistance material to generate heat, and carry out graphitization treatment at about 3000°C , to obtain bulk particles.
  • the obtained bulk particles are mixed with micro-expanded graphite powder and organic carbon source petroleum pitch, and then carbonized in an orbital kiln.
  • a coating layer is formed to obtain a composite graphite material.
  • the total mass percentage of the micro-expanded graphite powder added twice is 10%
  • the mass percentage of the binder added is 6%
  • the mass of the organic carbon source added In order to make the mass percentage of amorphous carbon obtained after carbonization of the organic carbon source be 3%.
  • the preparation method of the secondary battery is similar to that of Example 3, except that the negative electrode sheet is prepared according to the following method.
  • the composite graphite material prepared above is used as negative electrode active material and binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) and conductive agent carbon black (SuperP) by weight 96.2:1.8 :1.2:0.8 mixed, then mixed with the above-mentioned micro-expanded graphite powder according to the mass ratio of 96:4, add an appropriate amount of solvent deionized water, fully stir and mix to form a uniform negative electrode slurry; evenly coat the negative electrode slurry on the negative electrode assembly On the surface of the fluid copper foil, after drying and cold pressing, a negative electrode sheet is obtained.
  • SBR styrene-butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • SuperP conductive agent carbon black
  • the preparation method of the secondary battery is similar to that of Example 10, except that the negative electrode sheet is prepared according to the following method.
  • the composite graphite material prepared above is used as negative electrode active material and binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) and conductive agent carbon black (Super P) by weight 96.2: After mixing 1.8:1.2:0.8, mix with the above-mentioned micro-expanded graphite powder at a mass ratio of 96:4, add an appropriate amount of solvent deionized water, stir and mix thoroughly to form a uniform negative electrode slurry; evenly coat the negative electrode slurry on the negative electrode On the surface of the current collector copper foil, after drying and cold pressing, the negative electrode sheet is obtained.
  • SBR styrene-butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • Super P conductive agent carbon black
  • the preparation method of the secondary battery is similar to that of Example 11, except that the negative electrode sheet is prepared according to the following method.
  • the composite graphite material prepared above is used as negative electrode active material and binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) and conductive agent carbon black (Super P) by weight 96.2: After mixing 1.8:1.2:0.8, mix with the above-mentioned micro-expanded graphite powder at a mass ratio of 96:4, add an appropriate amount of solvent deionized water, stir and mix thoroughly to form a uniform negative electrode slurry; evenly coat the negative electrode slurry on the negative electrode On the surface of the current collector copper foil, after drying and cold pressing, the negative electrode sheet is obtained.
  • SBR styrene-butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • Super P conductive agent carbon black
  • the preparation method of the secondary battery is similar to that of Example 1, except that the composite graphite material is prepared according to the following method.
  • Delayed coking treatment of petroleum residue at 490°C-510°C to obtain raw petroleum non-needle coke; crushing, shaping, and grading of raw coke to obtain coke powder with a volume average particle size Dv50 of 7.0 ⁇ m, and As the main raw material of composite graphite material.
  • micro-expanded graphite (expansion factor: 180) with interlayer distance d 002 of 0.3363nm was pulverized, shaped and classified to obtain micro-expanded graphite powder with volume average particle diameter Dv50 of 6.5 ⁇ m.
  • the coke powder and micro-expanded graphite powder are mixed, and then mixed with the binder coal tar pitch, and then granulated.
  • the volume average particle diameter Dv50 of the obtained granules after granulation is about 9 ⁇ m.
  • Put the granulated product in a graphite crucible then place the graphite crucible in the Acheson graphitization furnace, fill the surroundings of the graphite crucible with resistance material, energize the current to flow through the resistance material to generate heat, and carry out graphitization treatment at about 3000°C , to obtain bulk particles.
  • the obtained bulk particles are mixed with organic carbon source petroleum pitch, and then carbonized in an orbital kiln.
  • the highest temperature zone is about 1150 ° C, and the running time in the highest temperature zone is about 4 hours, so as to form a coating layer on at least a part of the surface of the bulk particles.
  • a composite graphite material is obtained.
  • the mass percentage of the micro-expanded graphite powder added is 20%
  • the mass percentage of the binder added is 6%
  • the quality of the organic carbon source added is such that the organic
  • the mass percentage of amorphous carbon obtained after carbonization of the carbon source is 3%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the composite graphite material is prepared according to the following method.
  • Delayed coking treatment of petroleum residue at 490°C-510°C to obtain petroleum non-needle coke raw coke; crushing, shaping, and classification of raw coke to obtain coke powder with a volume average particle diameter Dv50 of 11.5 ⁇ m, and As the main raw material of composite graphite material.
  • micro-expanded graphite (expansion factor: 180) with interlayer spacing d002 of 0.3363nm was pulverized, shaped and classified to obtain micro-expanded graphite powder with volume average particle diameter Dv50 of 7.5 ⁇ m.
  • Coke powder and micro-expanded graphite powder are mixed, then mixed with coal tar pitch as a binder, and then granulated.
  • the volume average particle diameter Dv50 of the obtained particles after granulation is about 14.5 ⁇ m.
  • Put the granulated product in a graphite crucible then place the graphite crucible in the Acheson graphitization furnace, fill the surroundings of the graphite crucible with resistance material, energize the current to flow through the resistance material to generate heat, and carry out graphitization treatment at about 3000°C , to obtain bulk particles.
  • the obtained bulk particles are mixed with organic carbon source petroleum pitch, and then carbonized in an orbital kiln.
  • the highest temperature zone is about 1150 ° C, and the running time in the highest temperature zone is about 4 hours, so as to form a coating layer on at least a part of the surface of the bulk particles.
  • a composite graphite material is obtained.
  • the mass percentage of the micro-expanded graphite powder added is 1%
  • the mass percentage of the binder added is 6%
  • the quality of the organic carbon source added is such that the organic
  • the mass percentage of amorphous carbon obtained after carbonization of the carbon source is 3%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that conventional artificial graphite without a coating layer is used as the negative electrode active material. Artificial graphite was prepared as follows.
  • Delayed coking treatment of petroleum residue at 490°C-510°C to obtain petroleum non-needle coke green coke; crushing, shaping, and classification of the green coke to obtain coke powder with a volume average particle size Dv50 of 9.5 ⁇ m.
  • the coke powder is mixed with the binder coal tar pitch, and then granulated.
  • the volume average particle diameter Dv50 of the obtained granules after granulation is about 13 ⁇ m.
  • Put the granulated product in a graphite crucible then place the graphite crucible in the Acheson graphitization furnace, fill the surroundings of the graphite crucible with resistance material, energize the current to flow through the resistance material to generate heat, and carry out graphitization treatment at about 3000°C , to obtain artificial graphite. Based on the total mass of the obtained artificial graphite, the mass percentage of the added binder is 6%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the composite graphite material is prepared according to the following method.
  • the coke powder is mixed with the binder coal tar pitch, and then granulated.
  • the volume average particle diameter Dv50 of the obtained granules after granulation is about 13 ⁇ m.
  • Put the granulated product in a graphite crucible then place the graphite crucible in the Acheson graphitization furnace, fill the surroundings of the graphite crucible with resistance material, energize the current to flow through the resistance material to generate heat, and carry out graphitization treatment at about 3000°C , to obtain bulk particles.
  • the obtained bulk particles are mixed with organic carbon source petroleum pitch and then carbonized in an orbital kiln.
  • the highest temperature zone is about 1150°C, and the running time in the highest temperature zone is about 4 hours to form a coating layer on at least a part of the surface of the bulk particles.
  • a composite graphite material is obtained.
  • the mass percentage of the binder added is 6%, and the quality of the organic carbon source added is such that the mass percentage of the amorphous carbon obtained after carbonization of the organic carbon source is 3%.
  • the Dv50 of the negative electrode active material, the compacted density of the powder, and the compacted density of the negative electrode film layer were tested according to the method described above in the specification.
  • the test was carried out with a NETZSCH STA 449 F3 synchronous thermal analyzer.
  • the heating rate is set to 10°C/min.
  • thermogravimetric curve TG
  • TCG differential thermogravimetric curve
  • a CR2430 button cell was assembled in an argon-protected glove box. After the resulting coin cell was left to stand for 12 hours, at 25°C, it was discharged at a constant current of 0.05C to 0.005V, and then it was discharged at a constant current of 50 ⁇ A to 0.005V at 25°C for 10 minutes. Then discharge to 0.005V at a constant current; then charge to 2V at a constant current of 0.1C, and record the charging capacity.
  • the ratio of the charging capacity to the mass of the composite graphite material is the gram capacity of the prepared composite graphite material.
  • the state of charge SOC of the secondary battery Charge rate (C) 0 ⁇ 10% 0.33 10% ⁇ 20% 5.2 20% ⁇ 30% 4.5 30% ⁇ 40% 4.2 40% ⁇ 50% 3.3 50% ⁇ 60% 2.6 60% ⁇ 70% 2 70% ⁇ 80% 1.5 80% ⁇ 100% 0.33
  • Table 2 shows the preparation parameters of the composite graphite materials of Examples 1-16 and Comparative Examples 1-2.
  • Table 3 shows the test results of Examples 1-16 and Comparative Examples 1-2.
  • the secondary battery can have a greatly improved fast charging performance under the premise of high energy density and low temperature power performance.
  • the high-rate cycle performance of the secondary battery is also significantly improved.
  • Fig. 10 is the thermogravimetric curve and differential thermogravimetric curve of the composite graphite materials prepared in Example 3 and Comparative Example 2. It can be seen from Figure 10 that the composite graphite material in Example 3 has a lower air oxidation temperature T 0 , and the composite graphite material contains a moderate number of end faces and defects, which can make the secondary battery maintain a high energy density. It has greatly improved fast charging performance and low temperature power performance.
  • Both the composite graphite materials of Comparative Example 1 and Comparative Example 2 have a relatively high air oxidation temperature T 0 , the composite graphite materials contain fewer end faces and defects, and have poor kinetic performance. It is difficult for the secondary battery to charge and discharge at a high rate The low-temperature power performance of the secondary battery is also poor.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请公开了一种复合石墨材料及其制备方法、负极极片、二次电池、电池模块、电池包及用电装置。所述复合石墨材料包括本体颗粒以及位于本体颗粒至少一部分表面上的包覆层，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨，所述包覆层包括无定形碳，所述复合石墨材料的空气氧化温度T 0为630℃～730℃。本申请的复合石墨材料能使二次电池具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。

Description

复合石墨材料及其制备方法、负极极片、二次电池、电池模块、电池包及用电装置
相关申请的交叉引用
本申请要求享有于2021年09月15日提交的名称为“复合石墨材料及其制备方法、负极极片、二次电池”的中国专利申请202111079771.0的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请属于电池技术领域，尤其涉及一种复合石墨材料及其制备方法、负极极片、二次电池、电池模块、电池包及用电装置。
背景技术
二次电池依靠活性离子在正极和负极之间往复脱嵌来进行充电和放电，其具有能量密度高、循环寿命长，以及无污染、无记忆效应等突出特点。因此，二次电池作为清洁能源，已由电子产品逐渐普及到电动汽车等大型装置领域，以适应环境和能源的可持续发展战略。然而，与传统的燃油车能快速及时的加油相比，电动汽车一般是以较小的倍率充电，这常常需要较长的充电时间，给消费者造成了续航里程的焦虑，限制了电动汽车的快速普及。
发明内容
本申请的目的在于提供一种复合石墨材料及其制备方法、负极极片、二次电池、电池模块、电池包及用电装置，旨在使二次电池具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。
本申请第一方面提供一种复合石墨材料，所述复合石墨材料包括本体颗粒以及位于本体颗粒至少一部分表面上的包覆层，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨，所述包覆层包括无定形碳，所述复合石墨材料的空气氧化温度T 0为630℃～730℃。空气氧化温度T 0为在所述复合石墨材料的热重曲线上分别对应于500℃和T 1温度的两点处的两条切线的交点所对应的温度，所述T 1温度为所述复合石墨材料的微分热重曲线中最大面积峰的峰顶温度，所述热重曲线和所述微分热重曲线可通过在如下条件下进行的热重分析获得：样品质量10±0.05mg、吹扫气为空气且气流速率为60mL/min、升温速率为5℃/min、测试温度范围为35℃～950℃。
复合石墨材料的空气氧化温度T 0可以准确地表示复合石墨材料空气氧化开始失重时的温度，进而可以准确地反应出复合石墨材料的端面和缺陷数量。复合石墨材料的空气 氧化温度T 0为630℃～730℃，此时，复合石墨材料包含的端面和缺陷数量适中，复合石墨材料具有良好的活性离子和电子传输性能，活性离子和电子在复合石墨材料表面电荷交换速度较快，且活性离子在复合石墨材料内部固相传输能力较高，因此二次电池可在保持高能量密度的前提下，具有大幅提升的快速充电性能和低温功率性能。
在本申请的任意实施方式中，复合石墨材料的空气氧化温度T 0为660℃～710℃。复合石墨材料的空气氧化温度T 0在合适的范围内，可以使复合石墨材料具有更合适的端面和缺陷数量，进一步提升活性离子和电子传输性能，提升二次电池的快速充电性能和低温功率越性能。
在本申请的任意实施方式中，复合石墨材料还包括动力学碳材料。
在本申请的任意实施方式中，动力学碳材料位于本体颗粒中一次颗粒与一次颗粒之间的至少部分界面处。
在本申请的任意实施方式中，动力学碳材料位于包覆层中。
在本申请的任意实施方式中，动力学碳材料同时位于本体颗粒中一次颗粒与一次颗粒之间的至少部分界面处以及包覆层中。
在本申请的任意实施方式中，动力学碳材料原料选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种，动力学碳材料原料(002)晶面的层间距d 002≥0.3358nm。
可选地，动力学碳材料原料(002)晶面的层间距d 002为0.3359nm～0.3366nm。
当由上述动力学碳材料原料得到的动力学碳材料均匀分布在复合石墨材料的本体颗粒和/或包覆层中时，有利于活性离子的快速嵌入和脱出，从而提升活性离子和电子的传输性能，进而提升二次电池的快速充电性能和低温功率性能，并且不会带来二次电池能量密度的损失。
在本申请的任意实施方式中，基于复合石墨材料的总质量，动力学碳材料的质量百分含量为1％～30％。可选地，动力学碳材料的质量百分含量为8％～15％。动力学碳材料的质量百分含量在合适的范围内，可以使复合石墨材料在具有高克容量的前提下，还具有较高的活性离子固相传输能力以及较高的活性离子和电子电荷交换速度。
在本申请的任意实施方式中，复合石墨材料(002)晶面的层间距d 002为0.3355nm～0.3364nm。可选地，复合石墨材料(002)晶面的层间距d 002为0.3356nm～0.3361nm。复合石墨材料具有较高的层间距d 002，可以提升活性离子在其中的固相传输能力，提升二次电池的快速充电性能和低温功率性能。
在本申请的任意实施方式中，复合石墨材料的体积平均粒径Dv50为8.5μm～14.5μm。可选地，复合石墨材料的体积平均粒径Dv50为10μm～12μm。复合石墨材料的体积平均粒径Dv50在合适范围内，复合石墨材料能具有更好的活性离子和电子传输性能以及快速充电性能，同时复合石墨材料还具有较高的粉体压实密度。
在本申请的任意实施方式中，本体颗粒的体积平均粒径Dv50为7.5μm～13.5μm。可选地，本体颗粒的体积平均粒径Dv50为9.0μm～11.5μm。复合石墨材料的本体颗粒的体积平均粒径Dv50在合适范围内，复合石墨材料能在具有更好的活性离子和电子传输性能的前提下，还具有更高的克容量。
在本申请的任意实施方式中，一次颗粒的体积平均粒径Dv50与其所组成的二次颗粒的体积平均粒径Dv50的比值为0.45～0.75。可选地，一次颗粒的体积平均粒径Dv50与其 所组成的二次颗粒的体积平均粒径Dv50的比值为0.55～0.65。上述比值在合适的范围内，复合石墨材料的本体颗粒能具有较好的二次颗粒程度，有利于在提高复合石墨材料活性离子和电子传输性能的同时，使其具有较高的结构稳定性。
在本申请的任意实施方式中，基于复合石墨材料的总质量，包覆层中无定形碳的质量百分含量为1％～8％。可选地，包覆层中无定形碳的质量百分含量为2％～5％。无定形碳的含量在合适范围内，可以使复合石墨材料在具有高克容量的同时，还具有较高的活性离子固相传输能力。
在本申请的任意实施方式中，复合石墨材料在20000N作用力下的粉体压实密度为1.45g/cm 3～1.75g/cm 3。可选地，复合石墨材料在20000N作用力下的粉体压实密度为1.55g/cm 3～1.65g/cm 3。复合石墨材料的粉体压实密度在合适范围内，能使负极膜层具有较高的压实密度，进而二次电池具有较高的能量密度；此外，复合石墨材料在循环过程中维持负极膜层孔道结构的能力较强，负极极片的电解液浸润性更好，因此还有利于提升二次电池的循环性能。
本申请第二方面提供一种用于制备复合石墨材料的方法，包括步骤：S10，提供焦粉末或加有动力学碳材料原料粉末的焦粉末，对所述焦粉末或所述加有动力学碳材料原料粉末的焦粉末进行石墨化处理，以得到本体颗粒，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨；S20，将所述本体颗粒与有机碳源混合，或将所述本体颗粒与有机碳源和所述动力学碳材料原料粉末混合，经碳化处理后在本体颗粒至少一部分表面上形成包括无定形碳的包覆层，以获得所述复合石墨材料。在步骤S10和S20的至少之一中加入了所述动力学碳材料原料粉末，动力学碳材料原料选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种，动力学碳材料原料(002)晶面的层间距d 002≥0.3358nm。
所得的复合石墨材料的空气氧化温度T 0为630℃～730℃，所述空气氧化温度T 0为在所述复合石墨材料的热重曲线上分别对应于500℃和T 1温度的两点处的两条切线的交点所对应的温度，所述T 1温度为所述复合石墨材料的微分热重曲线中最大面积峰的峰顶温度，所述热重曲线和所述微分热重曲线可通过在如下条件下进行的热重分析获得：样品质量10±0.05mg、吹扫气为空气且气流速率为60mL/min、升温速率为5℃/min、测试温度范围为35℃～950℃。
本申请的复合石墨材料的制备方法操作简单、成本可控，可以进行大规模工业生产。本申请的方法可以获得端面和缺陷含量适中的复合石墨材料，进而二次电池可在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。
在本申请的任意实施方式中，动力学碳材料原料(002)晶面的层间距d 002为0.3359nm～0.3366nm。
在本申请的任意实施方式中，基于所获得的复合石墨材料的总质量，在步骤S10、S20加入的动力学碳材料原料粉末的总质量百分含量为1％～30％。可选地，在步骤S10、S20加入的动力学碳材料原料粉末的总质量百分含量为8％～15％。
在本申请的任意实施方式中，焦粉末的体积平均粒径Dv50为6μm～12μm。可选地，焦粉末的体积平均粒径Dv50为8μm～10μm。
在本申请的任意实施方式中，动力学碳材料原料粉末的体积平均粒径Dv50为3μm～12μm。可选地，动力学碳材料原料粉末的体积平均粒径Dv50为4μm～9μm。
在本申请的任意实施方式中，焦粉末的体积平均粒径Dv50与动力学碳材料原料粉末的体积平均粒径Dv50之比为1.05～1.75。可选地，焦粉末的体积平均粒径Dv50与动力学碳材料原料粉末的体积平均粒径Dv50之比为1.2～1.5。焦粉末的体积平均粒径Dv50与动力学碳材料原料粉末的体积平均粒径Dv50之比在合适的范围内，可以使复合石墨材料的本体颗粒具有较好的二次颗粒程度。
在本申请的任意实施方式中，所述方法还包括步骤：在S10中加入粘结剂，将粘结剂与焦粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒，或将粘结剂与加有动力学碳材料原料粉末的焦粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒。加入粘结剂可以使复合石墨材料的本体颗粒具有较好的二次颗粒程度，有利于在提高复合石墨材料活性离子和电子传输性能的同时，使其具有较高的结构稳定性。
在本申请的任意实施方式中，基于所获得的复合石墨材料的总质量，粘结剂的质量百分含量为3％～12％。可选地，粘结剂的质量百分含量为5％～8％。粘结剂的含量在合适的范围内，可以避免颗粒过度团聚，使复合石墨材料的本体颗粒具有较好的二次颗粒程度。
在本申请的任意实施方式中，粘结剂选自沥青。
在本申请的任意实施方式中，造粒后所获得的颗粒的体积平均粒径Dv50为8μm～14μm。可选地，造粒后所获得的颗粒的体积平均粒径Dv50为9.5μm～12μm。
在本申请的任意实施方式中，在S20中，有机碳源选自煤沥青、石油沥青、酚醛树脂、椰壳中的一种或几种。可选地，有机碳源选自石油沥青。
在本申请的任意实施方式中，基于所获得的复合石墨材料的总质量，有机碳源的加入量为使得有机碳源碳化后得到的无定形碳的质量百分含量为1％～8％。可选地，有机碳源的加入量为使得有机碳源碳化后得到的无定形碳的质量百分含量为2％～5％。有机碳源的加入量在合适范围内，可以使复合石墨材料在具有高克容量的同时，还具有较高的活性离子固相传输能力。
本申请第三方面提供一种负极极片，所述负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括根据本申请第一方面的复合石墨材料，或根据本申请第二方面的方法制备的复合石墨材料。
在本申请的任意实施方式中，负极膜层还包括添加剂，添加剂选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种，添加剂(002)晶面的层间距d 002≥0.3358nm。这些添加剂具有较好的活性离子和电子传输性能，可以使二次电池在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。
在本申请的任意实施方式中，添加剂(002)晶面的层间距d 002为0.3359nm～0.3366nm。
在本申请的任意实施方式中，基于负极膜层的总质量，添加剂的质量百分含量为1％～20％。可选地，添加剂的质量百分含量为3％～8％。添加剂的质量百分含量在合适的范围内，可以使二次电池在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。同时，添加剂的质量百分含量在合适的范围内，在循环过程中维持负 极膜层孔道结构的能力更好，负极极片的电解液浸润性更好，二次电池还可兼具良好的循环性能。
本申请第四方面提供一种二次电池，其包括本申请第三方面的负极极片。
本申请第五方面提供一种电池模块，其包括本申请第四方面的二次电池。
本申请第六方面提供一种电池包，其包括本申请第四方面的二次电池、第五方面的电池模块中的一种。
本申请第七方面提供一种用电装置，其包括本申请第四方面的二次电池、第五方面的电池模块、第六方面的电池包中的至少一种。
本申请的二次电池能在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的复合石墨材料的一实施方式的示意图。
图2是本申请的复合石墨材料的另一实施方式的示意图。
图3是本申请的复合石墨材料的又一实施方式的示意图。
图4是本申请的二次电池的一实施方式的示意图。
图5是本申请的二次电池的一实施方式的分解示意图。
图6是本申请的电池模块的一实施方式的示意图。
图7是本申请的电池包的一实施方式的示意图。
图8是图4的分解图。
图9是本申请的二次电池用作电源的用电装置的一实施方式的示意图。
图10是实施例3和对比例2的复合石墨材料的热重曲线和微分热重曲线图。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的复合石墨材料及其制备方法、负极极片、二次电池、电池模块、电池包及用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以 与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
在本申请中，“微膨胀石墨”是指膨胀前后松装体积变化(即膨胀倍数)为80～200的石墨；“膨胀石墨”是指膨胀前后松装体积变化(即膨胀倍数)＞200的石墨。
在本申请中，“焦原料”是指可以经处理得到“焦”的组分，即用于制备焦的原料；“焦”是指焦原料经焦化处理得到的产物，“焦粉末”与“焦”在组成上完全一致，“焦粉末”是指以一定颗粒尺寸的粉末形式存在的“焦”，“焦”经破碎等处理后得到“焦粉末”。
在本申请中，“动力学碳材料原料”和“动力学碳材料原料粉末”在组成上完全一致，“动力学碳材料原料粉末”是指以一定颗粒尺寸的粉末形式存在的“动力学碳材料原料”。“动力学碳材料”是指“动力学碳材料原料”或“动力学碳材料原料粉末”经石墨化处理和/或碳化处理后的产物。
在本申请中，“无定形碳”指石墨化晶化程度很低，近似非晶形态(或无固定形状和周期性的结构规律)的过渡态碳材料。在本申请中，“无定形碳”是指有机碳源碳化处理后的产物。
提升二次电池快速充电性能的关键在于提升负极极片以及负极活性材料的性能。现有技术为了提高二次电池的快速充电性能，通常采用的做法选择硬碳作为负极活性材料， 但是硬碳的克容量和压实密度较低，二次电池难以具有高能量密度，电动汽车的续航里程大幅缩减。使用石墨作为负极活性材料，二次电池可具有较高的能量密度，但是二次电池的快速充电性能和低温功率性能较差。
发明人经过大量研究，提出一种新型的复合石墨材料，其能使二次电池在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。
复合石墨材料
本申请实施方式的第一方面提供一种复合石墨材料，所述复合石墨材料包括本体颗粒以及位于本体颗粒至少一部分表面上的包覆层，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨，所述包覆层包括无定形碳，所述复合石墨材料的空气氧化温度T 0为630℃～730℃。空气氧化温度T 0为在所述复合石墨材料的热重曲线上分别对应于500℃和T 1温度的两点处的两条切线的交点所对应的温度，所述T 1温度为所述复合石墨材料的微分热重曲线中最大面积峰的峰顶温度，所述热重曲线和所述微分热重曲线可通过在如下条件下进行的热重分析获得：样品质量10±0.05mg、吹扫气为空气且气流速率为60mL/min、升温速率为5℃/min、测试温度范围为35℃～950℃。
空气氧化温度T 0可根据包括如下步骤的热重分析确定：将复合石墨材料在称重质量为10±0.05mg、吹扫气为空气且气流速率为60mL/min、升温速率为5℃/min、测试温度范围为35℃～950℃的条件下进行热重测试，得到热重曲线(也称为TG曲线)和微分热重曲线(也成为DTG曲线)，从微分热重曲线上读取最大面积峰的峰顶温度T 1，并在热重曲线上确定分别对应于500℃和T 1温度的两点处的两条切线的交点，该交点对应在所述热重曲线上的温度即为复合石墨材料的空气氧化温度T 0。
石墨的端面和缺陷数量越多，石墨中能够脱嵌活性离子的位点数量越多，二次电池的快速充电性能和低温功率性能越好。发明人意外发现，石墨的端面和缺陷数量与石墨空气氧化开始失重时的温度密切相关。石墨空气氧化开始失重时的温度越低，石墨的端面和缺陷数量越多，进而二次电池的快速充电性能和低温功率越性能越好。
发明人意外发现，热重曲线上分别对应于500℃和最大面积峰的峰顶温度T 1的两点处的两条切线的交点对应的温度，即石墨的空气氧化温度T 0，可以准确地表示石墨空气氧化开始失重时的温度，进而可以准确地反应出石墨的端面和缺陷数量。本申请第一方面的复合石墨材料的空气氧化温度T 0为630℃～730℃，此时，复合石墨材料包含的端面和缺陷数量适中，复合石墨材料具有良好的活性离子和电子传输性能，活性离子和电子在复合石墨材料表面电荷交换速度较快，且活性离子在复合石墨材料内部固相传输能力较高，因此二次电池可在保持高能量密度的前提下，具有大幅提升的快速充电性能和低温功率性能。发明人还发现，现有的石墨层间距较小，且端面和缺陷数量也较少，空气氧化温度T 0均很高，难以使二次电池的具有更好的快速充电性能和低温功率越性能。
在一些实施方式中，复合石墨材料的空气氧化温度T 0为630℃～730℃，640℃～730℃，650℃～730℃，660℃～730℃，670℃～730℃，680℃～730℃，690℃～730℃，700℃～730℃，710℃～730℃，720℃～730℃，630℃～720℃，640℃～720℃，650℃～720℃，660℃～720℃，670℃～720℃，680℃～720℃，690℃～720℃，700℃～720℃，710℃～720℃，630℃～710℃，640℃～710℃，650℃～710℃，660℃～710℃，670℃～710℃，680℃～710℃，690℃～710℃，700℃～710℃，630℃～700℃，640℃～700℃，650℃～700℃，660℃～700℃，670℃～700℃， 680℃～700℃，690℃～700℃，630℃～690℃，640℃～690℃，650℃～690℃，660℃～690℃，670℃～690℃，680℃～690℃，630℃～680℃，640℃～680℃，650℃～680℃，660℃～680℃，或670℃～680℃。
复合石墨材料的空气氧化温度T 0在合适的范围内，可以使复合石墨材料具有更合适的端面和缺陷数量，进一步提升活性离子和电子传输性能，提升二次电池的快速充电性能和低温功率越性能。
在一些实施方式中，所述复合石墨材料还包括动力学碳材料在一些实施方式中，动力学碳材料位于本体颗粒中一次颗粒与一次颗粒之间的至少部分界面处。此时，负极活性材料的本体颗粒包括人造石墨一次颗粒以及位于一次颗粒之间的动力学碳材料。
在一些实施方式中，动力学碳材料位于包覆层中。此时，所述包覆层同时包括无定形碳和动力学碳材料。
在一些实施方式中，动力学碳材料同时位于本体颗粒中一次颗粒与一次颗粒之间的至少部分界面处以及包覆层中。
图1至图3是本申请的复合石墨材料的不同实施方式的示意图。参照图1至图3，复合石墨材料包括本体颗粒以及位于本体颗粒至少一部分表面上的包覆层102，所述本体颗粒为两个以上一次颗粒101聚集而成的二次颗粒。参考图1，动力学碳材料103可位于本体颗粒中一次颗粒101与一次颗粒101之间的至少部分界面处；参考图2，动力学碳材料102还可位于包覆层102中；参考图3，动力学碳材料103还可同时位于本体颗粒中一次颗粒101与一次颗粒101之间的至少部分界面处以及包覆层102中。
在一些实施方式中，基于复合石墨材料的总质量，动力学碳材料的质量百分含量为1％～30％。例如，动力学碳材料的质量百分含量为3％～30％，3％～25％，3％～20％，3％～15％，5％～30％，5％～25％，5％～20％，5％～15％，8％～30％，8％～25％，8％～20％，8％～15％，或8％～12％。动力学碳材料的质量百分含量为位于本体颗粒中一次颗粒与一次颗粒之间的至少部分界面处的动力学碳材料的质量百分含量与位于包覆层中的动力学碳材料的质量百分含量之和。
动力学碳材料的质量百分含量在合适的范围内，可以使复合石墨材料在具有高克容量的前提下，还具有较高的活性离子固相传输能力以及较高的活性离子和电子电荷交换速度，进而二次电池在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。同时，动力学碳材料的质量百分含量在合适的范围内，在循环过程中维持负极膜层孔道结构的能力更好，负极极片的电解液浸润性更好，二次电池还可兼具良好的循环性能。
在一些实施方式中，动力学碳材料原料选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种。
可选地，硬碳在1V以下的克容量≥320mAh/g，且硬碳在20000N作用力下的粉体压实密度≥1.05g/cm 3。
可选地，动力学碳材料原料选自微膨胀石墨、膨胀石墨中的一种或几种。特别地，动力学碳材料原料选自膨胀石墨。
在一些实施方式中，动力学碳材料原料(002)晶面的层间距d 002≥0.3358nm。可选地，动力学碳材料原料(002)晶面的层间距d 002为0.3359nm～0.3366nm。
上述动力学碳材料原料的层间距d 002均大于常规石墨，当由其得到的动力学碳材料均匀分布在复合石墨材料的本体颗粒和/或包覆层中时，有利于活性离子的快速嵌入和脱出，从而提升活性离子和电子的传输性能，进而提升二次电池的快速充电性能和低温功率性能，并且不会带来二次电池能量密度的损失。
上述动力学碳材料原料还具有较高的抗压性能，在循环过程中维持负极膜层孔道结构的能力较强，负极极片的电解液浸润性更好，因此还有利于提升二次电池的循环性能。
在一些实施方式中，复合石墨材料(002)晶面的层间距d 002为0.3355nm～0.3364nm。可选地，复合石墨材料(002)晶面的层间距d 002为0.3356nm～0.3361nm。
复合石墨材料具有较高的层间距d 002，可以提升活性离子在其中的固相传输能力，提升二次电池的快速充电性能和低温功率性能。
在一些实施方式中，复合石墨材料的体积平均粒径Dv50为8.5μm～14.5μm。可选地，复合石墨材料的体积平均粒径Dv50为10μm～12μm。
复合石墨材料的体积平均粒径Dv50在合适范围内，复合石墨材料能具有更好的活性离子和电子传输性能以及快速充电性能，同时复合石墨材料还具有较高的粉体压实密度。
在一些实施方式中，本体颗粒的体积平均粒径Dv50为7.5μm～13.5μm。可选地，本体颗粒的体积平均粒径Dv50为9.0μm～11.5μm。
复合石墨材料的本体颗粒的体积平均粒径Dv50在合适范围内，复合石墨材料能在具有更好的活性离子和电子传输性能的前提下，还具有更高的克容量。
在一些实施方式中，一次颗粒的体积平均粒径Dv50与其所组成的二次颗粒(即本体颗粒)的体积平均粒径Dv50的比值为0.45～0.75。可选地，一次颗粒的体积平均粒径Dv50与其所组成的二次颗粒的体积平均粒径Dv50的比值为0.55～0.65。
一次颗粒的体积平均粒径Dv50与其所组成的二次颗粒的体积平均粒径Dv50的比值在合适的范围内，复合石墨材料的本体颗粒能具有较好的二次颗粒程度，有利于在提高复合石墨材料活性离子和电子传输性能的同时，使其具有较高的结构稳定性。同时本体颗粒在循环过程中维持负极膜层孔道结构的能力较强，负极极片的电解液浸润性更好，因此还有利于提升二次电池的循环性能。
在一些实施方式中，基于复合石墨材料的总质量，包覆层中无定形碳的质量百分含量为1％～8％。可选地，包覆层中无定形碳的质量百分含量为2％～5％。
无定形碳的含量在合适范围内，可以使复合石墨材料在具有高克容量的同时，还具有较高的活性离子固相传输能力。
在一些实施方式中，本体颗粒表面至少一部分被包覆层包覆。可选地，复合石墨材料包括本体颗粒以及包覆在本体颗粒表面至少80％的包覆层。特别地，复合石墨材料包括本体颗粒和包覆在本体颗粒表面至少90％的包覆层。
在一些实施方式中，复合石墨材料在20000N作用力下的粉体压实密度为1.45g/cm 3～1.75g/cm 3。可选地，复合石墨材料在20000N作用力下的粉体压实密度为1.55g/cm 3～1.65g/cm 3。
复合石墨材料的粉体压实密度在合适范围内，能使负极膜层具有较高的压实密度，进而二次电池具有较高的能量密度。复合石墨材料的粉体压实密度在合适范围内，在循环过程中维持负极膜层孔道结构的能力较强，负极极片的电解液浸润性更好，因此还有利于提升二次电池的循环性能。
在本申请中，材料的体积平均粒径Dv50为本领域公知的含义，其表示材料累计体积分布百分数达到50％时所对应的粒径，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在本申请中，材料的层间距d 002为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参考JIS K 0131-1996、JB/T 4220-2011，使用X射线粉末衍射仪(例如PANalytical X’pert PRO)测出d 002。
在本申请中，材料的粉体压实密度为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以参照标准GB/T24533-2009，通过电子压力试验机(例如UTM7305型)测定。示例性测试方法如下：称取1g材料，加入底面积为1.327cm 2的模具中，加压至2000kg(相当于20000N)，保压30s，然后卸压，保持10s，然后记录并计算得到材料在20000N作用力下的粉体压实密度。
在本申请中，材料的克容量为本领域公知的含义，可以采用本领域已知的方法测试。示例性测试方法如下：将待测材料、导电剂炭黑(Super P)、粘结剂聚偏氟乙烯(PVDF)按质量比91.6:1.8:6.6与溶剂N-甲基吡咯烷酮(NMP)中混合均匀，制成浆料；将制备好的浆料涂覆于铜箔集流体上，于烘箱中干燥后备用。以金属锂片为对电极，聚乙烯(PE)薄膜作为隔离膜。将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，LiPF 6的浓度为1mol/L。在氩气保护的手套箱组装成CR2430型扣式电池。将所得扣式电池静置12小时后，在25℃下，以0.05C恒流放电至0.005V，静置10分钟，以50μA的电流再恒流放电至0.005V，静置10分钟，以10μA再恒流放电至0.005V；然后以0.1C恒流充电至2V，记录充电容量。充电容量与材料质量的比值即为该材料的克容量。
复合石墨材料的制备方法
本申请实施方式的第二方面提供了一种用于制备复合石墨材料的方法。所述方法包括步骤：S10，提供焦粉末或加有动力学碳材料原料粉末的焦粉末，对所述焦粉末或所述加有动力学碳材料原料粉末的焦粉末进行石墨化处理，以得到本体颗粒，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨；S20，将所述本体颗粒与有机碳源混合，或将所述本体颗粒与有机碳源和所述动力学碳材料原料粉末混合，经碳化处理后在本体颗粒至少一部分表面上形成包括无定形碳的包覆层，以获得所述复合石墨材料。
在步骤S10和S20的至少之一中加入了所述动力学碳材料原料粉末，动力学碳材料原料选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种，动力学碳材料原料(002)晶面的层间距d 002≥0.3358nm。
所得复合石墨材料的空气氧化温度T 0为630℃～730℃，所述空气氧化温度T 0为在所述复合石墨材料的热重曲线上分别对应于500℃和T 1温度的两点处的两条切线的交点所对 应的温度，所述T 1温度为所述复合石墨材料的微分热重曲线中最大面积峰的峰顶温度，所述热重曲线和所述微分热重曲线可通过在如下条件下进行的热重分析获得：样品质量10±0.05mg、吹扫气为空气且气流速率为60mL/min、升温速率为5℃/min、测试温度范围为35℃～950℃。
具体地，空气氧化温度T 0可根据包括如下步骤的热重分析确定：将复合石墨材料在称重质量为10±0.05mg、吹扫气为空气且气流速率为60mL/min、升温速率为5℃/min、测试温度范围为35℃～950℃的条件下进行热重测试，得到热重曲线和微分热重曲线，从微分热重曲线上读取最大面积峰的峰顶温度T 1，并在热重曲线上确定分别对应于500℃和T 1温度的两点处的两条切线的交点，该交点对应在所述热重曲线上的温度即为复合石墨材料的空气氧化温度T 0。
本申请的复合石墨材料的制备方法操作简单、成本可控，可以进行大规模工业生产。
本申请的方法可以获得端面和缺陷含量适中的复合石墨材料，进而二次电池可在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。
在一些实施方式中，硬碳在1V以下的克容量≥320mAh/g，且硬碳在20000N作用力下的粉体压实密度≥1.05g/cm 3。
在一些实施方式中，动力学碳材料原料选自微膨胀石墨、膨胀石墨中的一种或几种。可选地，动力学碳材料原料选自膨胀石墨。
在一些实施方式中，动力学碳材料原料(002)晶面的层间距d 002为0.3359nm～0.3366nm。
在一些实施方式中，提供焦粉末的方法包括步骤：将焦原料焦化处理得到焦，对得到的焦进行粉碎、整形、分级处理，获得焦粉末。
在一些实施方式中，焦可以直接商购获得。
可选地，所述焦原料可选自石油系原料、煤系原料中的一种或几种。作为示例，石油系原料选自重油、渣油、减压渣油中的一种或几种，煤系原料主要选自煤沥青。重油、渣油、减压渣油通常是在石油炼油工艺产生，煤沥青通常是在煤干馏工艺产生。
在一些实施方式中，焦包括石油系非针状焦、石油系针状焦、煤系非针状焦、煤系针状焦中的一种或几种。可选地，焦包括石油系非针状焦(例如石油煅后焦、石油系生焦)、石油系针状焦中的一种或几种。特别地，焦包括石油系生焦。采用合适的焦能使所制备的复合石墨材料具有合适数量的端面和缺陷，进而具有较好的活性离子和电子传输性能以及较高的结构稳定性，因此能提高二次电池的快速充电性能、低温功率性能和循环性能。
可选地，焦原料的焦化处理在延迟焦化装置中进行。延迟焦化装置包括加热炉和焦炭塔，延迟焦化工艺是指将焦原料先在加热炉中快速加热到所需焦化处理温度，然后进入焦炭塔，并在焦炭塔中经过预热、冷焦等工艺生成焦。
可以采用本领域已知的设备和方法对焦进行破碎，例如气流磨、机械磨、辊压磨或其他破碎设备。
破碎后所得焦粉末的形貌可包括块状、球状和类球状中的一种或几种。破碎完成后，再通过整形以便将焦粉末的棱角打磨。整形程度越大，粉末颗粒越接近球形，这样能增 加复合石墨材料表面的脱嵌活性离子位点。整形处理还有利于后续的造粒工艺，使所得复合石墨材料中的二次颗粒具有较高的结构稳定性。
可以采用本领域已知的设备和方法对焦粉末进行整形处理，例如整形机或其他整形设备。
破碎和整形过程中常常会产生较多的过小颗粒，有时还会存在过大颗粒，因而可根据需求进行分级处理，以除去粉末中的过小颗粒和过大颗粒。分级处理后能得到具有较好的粒径分布的焦粉末，以便于后续的造粒和包覆工艺。分级处理可以采用本领域已知的设备和方法进行，例如分级筛、重力分级机、离心分级机等。
在一些实施方式中，焦粉末的体积平均粒径Dv50为6μm～12μm。可选地，焦粉末的体积平均粒径Dv50为8μm～10μm。
在一些实施方式中，提供动力学碳材料原料粉末的方法包括步骤：对动力学碳材料原料进行粉碎、整形、分级处理，得到动力学碳材料原料粉末。粉碎、整形、分级处理的方法与上述焦的粉碎、整形、分级相同。
在一些实施方式中，动力学碳材料原料粉末的体积平均粒径Dv50为3μm～12μm。可选地，动力学碳材料原料粉末的体积平均粒径Dv50为4μm～9μm。
在一些实施方式中，焦粉末的体积平均粒径Dv50与动力学碳材料原料粉末的体积平均粒径Dv50之比为1.05～1.75。可选地，焦粉末的体积平均粒径Dv50与动力学碳材料原料粉末的体积平均粒径Dv50之比为1.2～1.5。焦粉末的体积平均粒径Dv50与动力学碳材料原料粉末的体积平均粒径Dv50之比在合适的范围内，可以使复合石墨材料的本体颗粒具有较好的二次颗粒程度。
在一些实施方式中，在加有动力学碳材料原料粉末的焦粉末中，焦粉末与动力学碳材料原料粉末的质量比为1～20:99～80。可选地，焦粉末与动力学碳材料原料的质量比为3～12:97～88。焦粉末与动力学碳材料原料粉末的质量比在合适范围内，有利于获得端面和缺陷含量适中复合石墨材料，进而二次电池可在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。
在一些实施方式中，基于所获得的复合石墨材料的总质量，在步骤S10、S20加入的动力学碳材料原料粉末的总质量百分含量为1％～30％。例如，3％～30％，3％～25％，3％～20％，3％～15％，5％～30％，5％～25％，5％～20％，5％～15％，8％～30％，8％～25％，8％～20％，8％～15％，或8％～12％。
在一些实施方式中，所述方法还包括步骤：在S10中加入粘结剂。将粘结剂与焦粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒，或将粘结剂与加有动力学碳材料原料粉末的焦粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒。
加入粘结剂可以使复合石墨材料的本体颗粒具有较好的二次颗粒程度，有利于在提高复合石墨材料活性离子和电子传输性能的同时，使其具有较高的结构稳定性。
可选地，基于所获得的复合石墨材料的总质量，粘结剂的质量百分含量为3％～12％。进一步可选地，粘结剂的质量百分含量为5％～8％。粘结剂的含量在合适的范围内，可以避免颗粒过度团聚，使复合石墨材料的本体颗粒具有较好的二次颗粒程度。
可选地，所述粘结剂选自沥青。可选地，所述沥青的软化点为200℃以上。
可选地，所述沥青选自煤沥青、石油沥青中的一种或几种。
可选地，造粒后所获得的颗粒的体积平均粒径Dv50为8μm～14μm。特别地，造粒后所获得的颗粒的体积平均粒径Dv50为9.5μm～12μm。
可以采用本领域已知的设备和方法进行造粒，例如造粒机。造粒机通常包括搅拌反应釜和对反应釜进行温度控制的模块。通过调控造粒过程中的搅拌转速、升温速率、造粒温度、降温速率等，能调控造粒程度和颗粒的结构强度，能使最终制备得到的复合石墨材料的本体颗粒的体积平均粒径Dv50在所需范围内。
在一些实施方式中，在S10中，石墨化处理温度可为2800℃～3200℃。可选地，石墨化处理温度可为2900℃～3100℃。石墨化处理可以使本体颗粒具有合适的石墨化度，进而复合石墨材料具有较高的克容量，石墨化处理还使本体颗粒在脱嵌活性离子过程中的晶格膨胀较低，石墨化处理还能有效消除本体颗粒的体相结构缺陷，提高二次电池的循环性能。
在一些实施方式中，在S10中，石墨化处理时间为10天～15天。
可以采用本领域已知的设备和方法进行石墨化，例如石墨化炉，特别地采用艾奇逊石墨化炉。在石墨化处理结束后，还可以通过筛分除去造粒产物在石墨化处理过程中团聚形成的少量过大颗粒，这样可以防止过大颗粒影响复合石墨材料的加工性能，如负极浆料的稳定性、涂布性能等。
在一些实施方式中，在S10中，所得到本体颗粒的体积平均粒径Dv50为7.5μm～13.5μm。可选地，所得到本体颗粒的体积平均粒径Dv50为9.0μm～11.5μm。
在一些实施方式中，在S20中，有机碳源选自煤沥青、石油沥青、酚醛树脂、椰壳中的一种或几种。可选地，有机碳源选自石油沥青。可选地，所述煤沥青、石油沥青的软化点为250℃以下。
在一些实施方式中，基于所获得的复合石墨材料的总质量，有机碳源的加入量为使得有机碳源碳化后得到的无定形碳的质量百分含量为1％～8％。可选地，有机碳源的加入量为使得有机碳源碳化后得到的无定形碳的质量百分含量为2％～5％。有机碳源的加入量在合适范围内，可以使复合石墨材料在具有高克容量的同时，还具有较高的活性离子固相传输能力。
在一些实施方式中，在S20中，碳化处理温度为700℃～1800℃。可选地，碳化处理温度为1000℃～1300℃。碳化处理温度在合适的范围内，可使有机碳源(以及可选的动力学碳材料原料)碳化，并在人造石墨的至少一部分表面形成包含无定形碳的包覆层。
在一些实施方式中，在S20中，碳化处理时间为1h～6h。
在一些实施方式中，所述复合石墨材料的制备方法包括步骤：S10，提供焦粉末和动力学碳材料原料粉末，将粘结剂与焦粉末、动力学碳材料原料粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨；S20，将本体颗粒与有机碳源混合，经碳化处理后在本体颗粒至少一部分表面上形成包括无定形碳的包覆层，得到复合石墨材料。
在一些实施方式中，所述复合石墨材料的制备方法包括步骤：S10，提供焦粉末，将粘结剂与焦粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨；S20，将本体颗 粒与有机碳源、动力学碳材料原料粉末混合，经碳化处理后在本体颗粒至少一部分表面上形成包括无定形碳的包覆层，得到复合石墨材料。
在一些实施方式中，所述复合石墨材料的制备方法包括步骤：S10，提供焦粉末和动力学碳材料原料粉末，将粘结剂与焦粉末、动力学30碳材料原料粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨；S20，将本体颗粒与有机碳源、动力学碳材料原料粉末混合，经碳化处理后在本体颗粒至少一部分表面上形成包括无定形碳的包覆层，得到复合石墨材料。
在本申请的制备方法中，对焦粉末或加有动力学碳材料原料粉末的焦粉末进行石墨化处理后得到本体颗粒，且本体颗粒为两个以上一次颗粒聚集而成的二次颗粒。经粉碎、整形等处理后所得到焦粉末以单一颗粒为主，从形貌上看，焦粉末是一次颗粒(或一次粒子)；焦粉末或加有动力学碳材料原料粉末的焦粉末经造粒、石墨化处理后所得到本体颗粒是多个上述一次颗粒的团聚体，因此从形貌上看，本体颗粒是二次颗粒。
在本申请的制备方法中，通过调节焦粉末的体积平均粒径Dv50及其加入量、动力学碳材料原料粉末的体积平均粒径Dv50及其加入量、粘结剂加入量、有机碳源加入量等，可以得到具有不同空气氧化温度T 0的复合石墨材料。
二次电池
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜以及电解质。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解质在正极极片和负极极片之间起到传导活性离子的作用。
[负极极片]
在本申请的二次电池中，负极极片包括负极集流体以及设置在负极集流体至少一个表面的负极膜层。例如，负极集流体具有在自身厚度方向相对的两个表面，负极膜层设置在负极集流体的两个相对表面中的任意一者或两者上。
负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铜、铜合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等。
负极膜层通常包含负极活性材料、可选的粘结剂、可选的导电剂以及其他可选的助剂。负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料涂通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
在一些实施方式中，负极活性材料可包括本申请实施方式第一方面的复合石墨材料、根据本申请实施方式第二方面的方法制备的复合石墨材料中的一种。
在一些实施方式中，负极活性材料还可包括本领域公知的用于二次电池的其它负极活性材料。作为示例，其它负极活性材料可包括天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的一种或几种。锡基材料可包括单质锡、锡氧化物、锡合金材料中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的其它传统公知的材料。这些其它负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中一种或几种。在一些实施方式中，粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、羧甲基壳聚糖(CMCS)中的一种或几种。在一些实施方式中，其他可选的助剂可包括增稠剂(例如，羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
在一些实施方式中，所述负极膜层还可包括添加剂。此时，可将添加剂、复合石墨材料、可选的导电剂、可选的粘结剂以及其他可选的助剂分散于溶剂中并搅拌均匀形成负极浆料，再将负极浆料涂布在负极集流体上，经干燥、冷压，形成负极膜层。添加剂选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种，添加剂(002)晶面的层间距d 002≥0.3358nm。这些添加剂具有较好的活性离子和电子传输性能，可以使二次电池在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。
可选地，硬碳在1V以下的克容量≥320mAh/g，且硬碳在20000N作用力下的粉体压实密度≥1.05g/cm 3。
可选地，添加剂选自微膨胀石墨、膨胀石墨中的一种或几种。特别地，添加剂选自膨胀石墨。
可选地，添加剂(002)晶面的层间距d 002为0.3359nm～0.3366nm。
可选地，基于负极膜层的总质量，添加剂的质量百分含量为1％～20％。例如，添加剂的质量百分含量为1％～20％，1％～18％，1％～15％，1％～12％，1％～10％，1％～8％，1％～5％，2％～20％，2％～18％，2％～15％，2％～12％，2％～10％，2％～8％，2％～5％，3％～20％，3％～18％，3％～15％，3％～12％，3％～10％，3％～8％，或3％～5％。添加剂的质量百分含量在合适的范围内，可以使二次电池在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。同时，添加剂的质量百分含量在合适的范围内，在循环过程中维持负极膜层孔道结构的能力更好，负极极片的电解液浸润性更好，二次电池还可兼具良好的循环性能。
在一些实施方式中，负极膜层的面密度为0.035kg/m 2～0.125kg/m 2。可选地，负极膜层的面密度为0.078kg/m 2～0.107kg/m 2。
负极膜层的面密度在上述范围内，能使负极极片在具有较高的可逆容量的同时，还具有较低的传输活性离子和电子的阻抗，从而进一步改善二次电池的能量密度、快速充电性能、低温功率性能和循环性能。
在本申请中，负极膜层的面密度为本领域公知的含义，可采用本领域已知的方法进行测试。例如取单面涂布且经冷压后的负极极片(若是双面涂布的负极极片，可先擦拭 掉其中一面的负极膜层)，冲切成面积为S 1的小圆片，称其重量，记录为M 1。然后将上述称重后的负极极片的负极膜层擦拭掉，称量负极集流体的重量，记录为M 0。负极膜层的面密度＝(M 1-M 0)/S 1。
在一些实施方式中，负极膜层的压实密度为1.2g/cm 3～1.75g/cm 3。可选地，负极膜层的压实密度为1.4g/cm 3～1.6g/cm 3。
负极膜层的压实密度在上述范围内，能使负极极片在具有较高的可逆容量的同时，还具有较低的循环膨胀和良好的动力学性能，从而进一步改善二次电池的能量密度、快速充电性能、低温功率性能和循环性能。
在本申请中，负极膜层的压实密度为本领域公知的含义，可采用本领域已知的方法进行测试。负极膜层的压实密度＝负极膜层的面密度/负极膜层的厚度。在本申请中，负极膜层的厚度为本领域公知的含义，可采用本领域已知的方法进行测试。例如采用4位精度的螺旋测微仪。
在一些实施方式中，负极膜层的孔隙率为25％～45％。可选地，负极膜层的孔隙率为28％～35％。
负极膜层的孔隙率在上述范围内，能使负极极片具有适宜的电解液浸润性和良好的反应界面，提高负极在大倍率下的充放电性能，从而能提高二次电池的快速充电性能。同时，负极膜层还能具有适宜的电解液保持量，使得二次电池的质量较低，从而有利于使二次电池具有较高的质量能量密度。
在本申请中，负极膜层的孔隙率为本领域公知的含义，可以用本领域已知的方法进行测定。例如可参考GB/T24586-2009，采用气体置换法测量。测试方法如下：取单面涂布且经冷压后的负极极片(若是双面涂布的负极极片，可先擦拭掉其中一面的负极膜层)，冲切成直径为14mm的小圆片样品；测试负极膜层的厚度(负极极片的厚度-负极集流体的厚度)；按照圆柱体积计算公式，计算负极膜层的表观体积V 1；使用惰性气体如氦气或氮气作为介质，采用气体置换法，利用真密度测试仪(如Micromeritics AccuPyc II 1340型)测得负极极片的真实体积，测试可参考GB/T 24586-2009；负极极片的真实体积减去负极集流体的体积，得到负极膜层的真实体积V 2。负极膜层的孔隙率＝(V 1-V 2)/V 1×100％。可取多片(如30片)负极极片样品进行测试，结果取平均值，由此可提高测试结果的准确性。
在一些实施方式中，负极膜层与负极集流体之间的粘结力为4.5N/m～15N/m。可选地，负极膜层与负极集流体之间的粘结力为8N/m～12N/m。
负极膜层与负极集流体之间的粘结力在上述范围内，可提高二次电池的快速充电性能和循环性能。负极膜层与负极集流体之间的粘结力较大，使得负极极片具有良好的电子传导能力，这有利于提升活性离子的嵌入速度。并且，负极膜层与负极集流体之间的粘结力还体现了负极极片在循环过程中维持粘接可靠性的能力，有利于二次电池在全生命周期保持良好的电子传导能力，从而能进一步改善二次电池的循环性能。
在本申请中，负极膜层与负极集流体之间的粘结力为本领域公知的含义，可以用本领域已知的方法进行测定。示例性测试方法如下：将负极极片裁成长100mm、宽10mm的测试样品；取一条宽度25mm的不锈钢板，贴双面胶(宽度11mm)，将测试样品粘贴在不锈钢板上的双面胶上，用2000g压辊在其表面来回滚压三次(300mm/min)；将测 试样品180度弯折，手动将测试样品的负极膜层与负极集流体剥开25mm，将该测试样品固定在试验机(例如INSTRON 336)上，使剥离面与试验机力线保持一致，试验机以30mm/min连续剥离，得到的剥离力曲线，取平稳断的均值作为剥离力F 0。负极膜层与集流体之间的粘结力＝F 0/测试样品的宽度。
在本申请中，负极膜层的相关参数均指的是单面负极膜层的参数。也就是，当负极膜层设置在负极集流体两个表面上时，其中任意一个表面上的负极膜层的参数满足本申请的参数范围，即认为落入本申请的保护范围内。
本申请的二次电池中，负极极片并不排除除了负极膜层之外的其他附加功能层。例如在某些实施方式中，本申请所述的负极极片还包括夹在负极集流体和负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请所述的负极极片还包括覆盖在负极膜层表面的保护层。
[正极极片]
本申请的二次电池中，正极极片包括正极集流体以及设置在正极集流体至少一个表面且包括正极活性材料的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极膜层设置于正极集流体的两个相对表面中的任意一者或两者上。
本申请的二次电池中，正极活性材料可采用本领域公知的用于二次电池的正极活性材料。例如，正极活性材料可包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池正极活性材料的传统公知的材料。
在一些实施方式中，为了进一步提高二次电池的能量密度，正极活性材料可以包括式1所示的锂过渡金属氧化物及其改性化合物中的一种或几种，
Li aNi bCo cM dO eA f  式1，
式1中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，1≤e≤2，0≤f≤1，M选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种，A选自N、F、S及Cl中的一种或几种。
在本申请中，上述各材料的改性化合物可以是对正极活性材料进行掺杂改性或表面包覆改性。
本申请的二次电池中，正极膜层通常包含正极活性材料以及可选的粘结剂和可选的导电剂。正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。作为示例，用于正极膜层的粘结剂可包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、含氟丙烯酸酯树脂中的一种或几种。
在本申请的二次电池中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等。
[电解质]
本申请的二次电池对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。
在一些实施方式中，电解质采用电解液。电解液包括电解质盐和溶剂。
本申请对电解质盐的种类没有具体的限制，可根据需求进行选择。在一些实施方式中，作为示例，电解质盐可选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或几种。
本申请对溶剂的种类没有具体的限制，可根据需求进行选择。在一些实施方式中，作为示例，溶剂可选自碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，电解液中还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温功率性能的添加剂等。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。在一些实施方式中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施方式中，正极极片、隔离膜和负极极片可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图4是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图5，外包装可包括壳体51和盖板53。壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图6是作为一个示例的电池模块4。参照图6，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图7和图8是作为一个示例的电池包1。参照图7和图8，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
本申请的二次电池的制备方法是公知的。在一些实施方式中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
用电装置
本申请实施方式还提供一种用电装置，所述用电装置包括本申请的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图9是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通 常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
复合石墨材料的制备
将石油渣油在490℃～510℃条件下延迟焦化处理，得到石油非针状焦生焦；对生焦进行粉碎、整形、分级处理，得到体积平均粒径Dv50为9.5μm的焦粉末，以作为复合石墨材料的主体原料。
对层间距d 002为0.3363nm的微膨胀石墨(膨胀倍数为180)进行粉碎、整形、分级处理，得到体积平均粒径Dv50为7.5μm的微膨胀石墨粉末。
将焦粉末和微膨胀石墨粉末混合，再与粘结剂煤沥青混合，然后进行造粒，造粒后所获得的颗粒的体积平均粒径Dv50约为13μm。将造粒产物置于石墨坩埚中，然后将石墨坩埚置于艾奇逊石墨化炉，向石墨坩埚周围填入电阻料，通电使电流流经电阻料产生热能，在3000℃左右进行石墨化处理，得到本体颗粒。
将所获得的本体颗粒与有机碳源石油沥青混合后在轨道窑内进行碳化处理，最高温区约1150℃，最高温区运行时间约4h，以在本体颗粒至少一部分表面上形成包覆层，得到复合石墨材料。
基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为1％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
负极极片的制备
将上述制备的复合石墨材料作为负极活性材料与粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)以及导电剂炭黑(SuperP)按重量比96.2:1.8:1.2:0.8在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。负极膜层的面密度为0.097kg/m 2，压实密度为1.64g/cm 3。
正极极片的制备
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、导电剂碳纳米管(CNT)、导电剂炭黑(Super P)、粘结剂聚偏氟乙烯(PVDF)按重量比97.5:0.5:0.9:1.1在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片。正极膜层的面密度为0.178kg/m 2，压实密度为3.4g/cm 3。
隔离膜
采用多孔聚乙烯(PE)膜作为隔离膜。
电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，得到有机溶剂；将LiPF 6均匀溶解在上述有机溶剂中得到电解液，LiPF 6的浓度为1mol/L。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装中，加入上述电解液，经封装、静置、化成、老化等工序后，得到二次电池。
实施例2
二次电池的制备方法与实施例1类似，不同的是基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为3％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
实施例3
二次电池的制备方法与实施例1类似，不同的是基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为8％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
实施例4
二次电池的制备方法与实施例1类似，不同的是基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为12％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
实施例5
二次电池的制备方法与实施例1类似，不同的是基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为20％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
实施例6
二次电池的制备方法与实施例1类似，不同的是基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为30％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
实施例7
二次电池的制备方法与实施例3类似，不同的是使用层间距d 002为0.33615nm、体积平均粒径Dv50为5.3μm的硬碳粉末替代微膨胀石墨粉末。
实施例8
二次电池的制备方法与实施例3类似，不同的是使用层间距d 002为0.33638nm、体积平均粒径Dv50为7.2μm的膨胀石墨粉末(膨胀倍数为300)替代微膨胀石墨粉末。
实施例9
二次电池的制备方法与实施例3类似，不同的是使用层间距d 002为0.33620nm、体积平均粒径Dv50为8.0μm的石墨烯粉末替代微膨胀石墨粉末。
实施例10
二次电池的制备方法与实施例1类似，不同的是复合石墨材料按照下述方法制备。
将石油渣油在490℃～510℃条件下延迟焦化处理，得到石油非针状焦生焦；对生焦进行粉碎、整形、分级处理，得到体积平均粒径Dv50为9.5μm的焦粉末，以作为复合石墨材料的主体原料。
对层间距d 002为0.3363nm的微膨胀石墨(膨胀倍数为180)进行粉碎、整形、分级处理，得到体积平均粒径Dv50为7.5μm的微膨胀石墨粉末。
将焦粉末与粘结剂煤沥青混合，然后进行造粒，造粒后所获得的颗粒的体积平均粒径Dv50约为13μm。将造粒产物置于石墨坩埚中，然后将石墨坩埚置于艾奇逊石墨化炉，向石墨坩埚周围填入电阻料，通电使电流流经电阻料产生热能，在3000℃左右进行石墨化处理，得到本体颗粒。
将所获得的本体颗粒与微膨胀石墨粉末、有机碳源石油沥青混合后在轨道窑内进行碳化处理，最高温区约1150℃，最高温区运行时间约4h，以在本体颗粒至少一部分表面上形成包覆层，得到复合石墨材料。
基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为8％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
实施例11
二次电池的制备方法与实施例1类似，不同的是复合石墨材料按照下述方法制备。
将石油渣油在490℃～510℃条件下延迟焦化处理，得到石油非针状焦生焦；对生焦进行粉碎、整形、分级处理，得到体积平均粒径Dv50为9.5μm的焦粉末，以作为复合石墨材料的主体原料。
对层间距d 002为0.3363nm的微膨胀石墨(膨胀倍数为180)进行粉碎、整形、分级处理，得到体积平均粒径Dv50为7.5μm的微膨胀石墨粉末。
将焦粉末和微膨胀石墨粉末混合，再与粘结剂煤沥青混合，然后进行造粒，造粒后所获得的颗粒的体积平均粒径Dv50约为13μm。将造粒产物置于石墨坩埚中，然后将石墨坩埚置于艾奇逊石墨化炉，向石墨坩埚周围填入电阻料，通电使电流流经电阻料产生热能，在3000℃左右进行石墨化处理，得到本体颗粒。
将所获得的本体颗粒与微膨胀石墨粉末、有机碳源石油沥青混合后在轨道窑内进行碳化处理，最高温区约1150℃，最高温区运行时间约4h，以在本体颗粒至少一部分表面上形成包覆层，得到复合石墨材料。
基于所获得的复合石墨材料的总质量，两次加入的微膨胀石墨粉末的总质量百分含量为10％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
实施例12
二次电池的制备方法与实施例3类似，不同的是负极极片按照下述方法制备。
将上述制备的复合石墨材料作为负极活性材料与粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)以及导电剂炭黑(SuperP)按重量比96.2:1.8:1.2:0.8混合后，再与上述微膨胀石墨粉末按质量比96:4混合，加入适量的溶剂去离子水，充分搅拌混合形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。
实施例13
二次电池的制备方法与实施例10类似，不同的是负极极片按照下述方法制备。
将上述制备的复合石墨材料作为负极活性材料与粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)以及导电剂炭黑(Super P)按重量比96.2:1.8:1.2:0.8混合后，再与上述微膨胀石墨粉末按质量比96:4混合，加入适量的溶剂去离子水，充分搅拌混合形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。
实施例14
二次电池的制备方法与实施例11类似，不同的是负极极片按照下述方法制备。
将上述制备的复合石墨材料作为负极活性材料与粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)以及导电剂炭黑(Super P)按重量比96.2:1.8:1.2:0.8混合后，再与上述微膨胀石墨粉末按质量比96:4混合，加入适量的溶剂去离子水，充分搅拌混合形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。
实施例15
二次电池的制备方法与实施例1类似，不同的是复合石墨材料按照下述方法制备。
将石油渣油在490℃～510℃条件下延迟焦化处理，得到石油非针状焦生焦；对生焦进行粉碎、整形、分级处理，得到体积平均粒径Dv50为7.0μm的焦粉末，以作为复合石墨材料的主体原料。
对层间距d 002为0.3363nm的微膨胀石墨(膨胀倍数为180)进行粉碎、整形、分级处理，得到体积平均粒径Dv50为6.5μm的微膨胀石墨粉末。
将焦粉末和微膨胀石墨粉末混合，再与粘结剂煤沥青混合，然后进行造粒，造粒后所获得的颗粒的体积平均粒径Dv50约为9μm。将造粒产物置于石墨坩埚中，然后将石墨坩埚置于艾奇逊石墨化炉，向石墨坩埚周围填入电阻料，通电使电流流经电阻料产生热能，在3000℃左右进行石墨化处理，得到本体颗粒。
将所获得的本体颗粒与有机碳源石油沥青混合后在轨道窑内进行碳化处理，最高温区约1150℃，最高温区运行时间约4h，以在本体颗粒至少一部分表面上形成包覆层，得到复合石墨材料。
基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为20％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
实施例16
二次电池的制备方法与实施例1类似，不同的是复合石墨材料按照下述方法制备。
将石油渣油在490℃～510℃条件下延迟焦化处理，得到石油非针状焦生焦；对生焦进行粉碎、整形、分级处理，得到体积平均粒径Dv50为11.5μm的焦粉末，以作为复合石墨材料的主体原料。
对层间距d 002为0.3363nm的微膨胀石墨(膨胀倍数为180)进行粉碎、整形、分级处理，得到体积平均粒径Dv50为7.5μm的微膨胀石墨粉末。
将焦粉末和微膨胀石墨粉末混合，再与粘结剂煤沥青混合，然后进行造粒，造粒后所获得的颗粒的体积平均粒径Dv50约为14.5μm。将造粒产物置于石墨坩埚中，然后将石墨坩埚置于艾奇逊石墨化炉，向石墨坩埚周围填入电阻料，通电使电流流经电阻料产生热能，在3000℃左右进行石墨化处理，得到本体颗粒。
将所获得的本体颗粒与有机碳源石油沥青混合后在轨道窑内进行碳化处理，最高温区约1150℃，最高温区运行时间约4h，以在本体颗粒至少一部分表面上形成包覆层，得到复合石墨材料。
基于所获得的复合石墨材料的总质量，加入的微膨胀石墨粉末的质量百分含量为1％，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
对比例1
二次电池的制备方法与实施例1类似，不同的是使用常规无包覆层的人造石墨作为负极活性材料。人造石墨按照下述方法制备。
将石油渣油在490℃～510℃条件下延迟焦化处理，得到石油非针状焦生焦；对生焦进行粉碎、整形、分级处理，得到体积平均粒径Dv50为9.5μm焦粉末。
将焦粉末与粘结剂煤沥青混合，然后进行造粒，造粒后所获得的颗粒的体积平均粒径Dv50约为13μm。将造粒产物置于石墨坩埚中，然后将石墨坩埚置于艾奇逊石墨化炉，向石墨坩埚周围填入电阻料，通电使电流流经电阻料产生热能，在3000℃左右进行石墨化处理，得到人造石墨。基于所获得的人造石墨的总质量，加入的粘结剂的质量百分含量为6％。
对比例2
二次电池的制备方法与实施例1类似，不同的是复合石墨材料按照下述方法制备。
将石油渣油在490℃～510℃条件下延迟焦化处理，得到石油非针状焦生焦；对生焦进行粉碎、整形、分级处理，得到体积平均粒径Dv50为9.5μm焦粉末，以作为复合石墨材料的主体原料。
将焦粉末与粘结剂煤沥青混合，然后进行造粒，造粒后所获得的颗粒的体积平均粒径Dv50约为13μm。将造粒产物置于石墨坩埚中，然后将石墨坩埚置于艾奇逊石墨化炉，向石墨坩埚周围填入电阻料，通电使电流流经电阻料产生热能，在3000℃左右进行石墨化处理，得到本体颗粒。
将所得到的本体颗粒与有机碳源石油沥青混合后在轨道窑内进行碳化处理，最高温区约1150℃，最高温区运行时间约4h，以在本体颗粒至少一部分表面上形成包覆层，得到复合石墨材料。
基于所获得的复合石墨材料的总质量，加入的粘结剂的质量百分含量为6％，加入的有机碳源的质量为使得有机碳源碳化后得到的无定形碳的质量百分含量为3％。
测试部分
负极活性材料的Dv50和粉体压实密度、负极膜层的压实密度的测试按照说明书上述记载的方法进行测试。
(1)复合石墨材料空气氧化温度T 0测试
使用德国耐驰STA 449 F3同步热分析仪进行测试。首先称取10±0.05mg复合石墨材 料样品于平底Al 2O 3坩埚中，不盖盖子；设置仪器参数：吹扫气为空气且气流速率设置为60mL/min，保护气为氮气且气流速率设置为20mL/min；设置升温速率为5℃/min，测试温度范围为35℃～950℃。在温度低于500℃时，由于该阶段无特征峰，可以进行快速升温，例如升温速率设置为10℃/min。
热重测试结束后得到复合石墨材料的热重曲线(TG)和微分热重曲线(DTG)，从微分热重曲线上读取最大面积峰的峰顶温度T 1，并在热重曲线上确定分别对应于500℃和T 1温度的两点处的两条切线的交点，该交点对应在所述热重曲线上的温度即为复合石墨材料的空气氧化温度T 0。
(2)复合石墨材料克容量测试
将复合石墨材料、导电剂炭黑(SuperP)、粘结剂聚偏氟乙烯(PVDF)按质量比91.6:1.8:6.6与溶剂N-甲基吡咯烷酮(NMP)中混合均匀，制成浆料；将制备好的浆料涂覆于铜箔集流体上，于烘箱中干燥后备用。以金属锂片为对电极，聚乙烯(PE)薄膜作为隔离膜。将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，LiPF 6的浓度为1mol/L。在氩气保护的手套箱组装成CR2430型扣式电池。将所得扣式电池静置12小时后，在25℃下，以0.05C恒流放电至0.005V，静置10分钟，以50μA的电流再恒流放电至0.005V，静置10分钟，以10μA再恒流放电至0.005V；然后以0.1C恒流充电至2V，记录充电容量。充电容量与复合石墨材料质量的比值即为所制备复合石墨材料的克容量。
(3)二次电池快速充电性能测试
25℃下，将二次电池以0.33C恒流充电至充电截止电压4.4V，之后恒压充电至电流为0.05C，静置5min，再以0.33C恒流放电至放电截止电压2.8V，记录其实际容量为C0。
然后将二次电池依次以0.5C0、1C0、1.5C0、2C0、2.5C0、3C0、3.5C0、4C0、4.5C0恒流充电至全电池充电截止电压4.4V或者0V负极截止电位(以先达到者为准)，每次充电完成后需以1C0放电至全电池放电截止电压2.8V，记录不同充电倍率下充电至10％、20％、30％……80％SOC(State of Charge，荷电状态)时所对应的负极电位，绘制出不同SOC态下的倍率-负极电位曲线，线性拟合后得出不同SOC态下负极电位为0V时所对应的充电倍率，该充电倍率即为该SOC态下的充电窗口，分别记为C10％SOC、C20％SOC、C30％SOC、C40％SOC、C50％SOC、C60％SOC、C70％SOC、C80％SOC，根据公式(60/C20％SOC+60/C30％SOC+60/C40％SOC+60/C50％SOC+60/C60％SOC+60/C70％SOC+60/C80％SOC)×10％计算得到该二次电池从10％SOC充电至80％SOC的充电时间T(min)。该时间越短，则代表二次电池的快速充电性能越优秀。
(4)二次电池循环寿命测试
25℃下，将二次电池以0.33C恒流充电至充电截止电压4.4V，之后恒压充电至电流为0.05C，静置5min，再以0.33C恒流放电至放电截止电压2.8V，记录其初始容量为C0。然后按照表1所述策略进行充电，0.33C放电，记录每次循环的放电容量Cn，直至循环容量保持率(即Cn/C0×100％)为80％，记录循环圈数。循环圈数越多，则代表二次电池的循环寿命越高。
表1
二次电池的荷电状态SOC 充电倍率(C)
0～10％ 0.33
10％～20％ 5.2
20％～30％ 4.5
30％～40％ 4.2
40％～50％ 3.3
50％～60％ 2.6
60％～70％ 2
70％～80％ 1.5
80％～100％ 0.33
(5)二次电池低温功率性能测试
25℃下，将二次电池以0.33C恒流充电至充电截止电压4.4V，之后恒压充电至电流为0.05C，静置5min，再以0.33C恒流放电至放电截止电压2.8V，记录其初始能量为P0。再将上述二次电池以0.33C恒流充电至充电截止电压4.4V，之后恒压充电至电流为0.05C，静置5min，调节恒温箱温度为-30℃，静置3h，然后再以0.33C恒流放电至放电截止电压2.5V，记录此时的能量P1。P1/P0即为二次电池的放电能量保持率。
表2给出实施例1～16和对比例1～2的复合石墨材料的制备参数。
表3给出实施例1～16和对比例1～2的测试结果。
表2
Figure PCTCN2022093671-appb-000001
Figure PCTCN2022093671-appb-000002
表3
Figure PCTCN2022093671-appb-000003
从表3的测试结果可以看出，当复合石墨材料的空气氧化温度T 0为630℃～730℃时，能使二次电池在具有高能量密度的前提下，还具有大幅提升的快速充电性能和低温功率性能。此外，二次电池的大倍率循环性能也明显改善。
图10是实施例3和对比例2制备的复合石墨材料的热重曲线和微分热重曲线图。从图10可以看出，实施例3的复合石墨材料具有较低的空气氧化温度T 0，进而复合石墨材料包含的端面和缺陷数量适中，可以使二次电池在保持高能量密度的前提下，具有大幅提升的快速充电性能和低温功率性能。
对比例1和对比例2的复合石墨材料均具有较高的空气氧化温度T 0，复合石墨材料包含的端面和缺陷数量较少、动力学性能较差，二次电池难以在大倍率充放电条件下使用，且二次电池的低温功率性能也较差。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (16)

  1. 一种复合石墨材料，包括本体颗粒以及位于本体颗粒至少一部分表面上的包覆层，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨，所述包覆层包括无定形碳，
    其中，
    所述复合石墨材料的空气氧化温度T 0为630℃～730℃，可选地为660℃～710℃，
    所述空气氧化温度T 0为在所述复合石墨材料的热重曲线上分别对应于500℃和T 1温度的两点处的两条切线的交点所对应的温度，所述T 1温度为所述复合石墨材料的微分热重曲线中最大面积峰的峰顶温度，所述热重曲线和所述微分热重曲线可通过在如下条件下进行的热重分析获得：样品质量10±0.05mg、吹扫气为空气且气流速率为60mL/min、升温速率为5℃/min、测试温度范围为35℃～950℃。
  2. 根据权利要求1所述的复合石墨材料，其中，所述复合石墨材料还包括动力学碳材料，
    可选地，所述动力学碳材料位于所述本体颗粒中一次颗粒与一次颗粒之间的至少部分界面处，和/或位于所述包覆层中；
    可选地，基于所述复合石墨材料的总质量，所述动力学碳材料的质量百分含量为1％～30％，进一步可选地为8％～15％。
  3. 根据权利要求2所述的复合石墨材料，其中，所述动力学碳材料原料选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种，所述动力学碳材料原料(002)晶面的层间距d 002≥0.3358nm，可选地为0.3359nm～0.3366nm。
  4. 根据权利要求1-3中任一项所述的复合石墨材料，其中，
    所述复合石墨材料(002)晶面的层间距d 002为0.3355nm～0.3364nm，可选0.3356nm～0.3361nm；和/或，
    所述复合石墨材料的体积平均粒径Dv50为8.5μm～14.5μm，可选地为10μm～12μm；和/或，
    所述本体颗粒的体积平均粒径Dv50为7.5μm～13.5μm，可选地为9.0μm～11.5μm；和/或，
    所述复合石墨材料在20000N作用力下的粉体压实密度为1.45g/cm 3～1.75g/cm 3，可选地为1.55g/cm 3～1.65g/cm 3。
  5. 根据权利要求1-4中任一项所述的复合石墨材料，其中，所述一次颗粒的体积平均粒径Dv50与其所组成的二次颗粒的体积平均粒径Dv50的比值为0.45～0.75，可选地为0.55～0.65。
  6. 根据权利要求1-5中任一项所述的复合石墨材料，其中，基于所述复合石墨材料的总质量，所述包覆层中无定形碳的质量百分含量为1％～8％，可选地为2％～5％。
  7. 一种用于制备复合石墨材料的方法，包括步骤：
    S10，提供焦粉末或加有动力学碳材料原料粉末的焦粉末，对所述焦粉末或所述加有动力学碳材料原料粉末的焦粉末进行石墨化处理，以得到本体颗粒，所述本体颗粒为两个以上一次颗粒聚集而成的二次颗粒，所述本体颗粒包括人造石墨；
    S20，将所述本体颗粒与有机碳源混合，或将所述本体颗粒与有机碳源和所述动力学碳材料原料粉末混合，经碳化处理后在本体颗粒至少一部分表面上形成包括无定形碳的包覆层，以获得所述复合石墨材料，
    其中，在步骤S10和S20的至少之一中加入了所述动力学碳材料原料粉末，动力学碳材料原料选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种，动力学碳材料原料(002)晶面的层间距d 002≥0.3358nm，可选地，d 002为0.3359nm～0.3366nm，
    所获得的复合石墨材料的空气氧化温度T 0为630℃～730℃，所述空气氧化温度T 0为在所述复合石墨材料的热重曲线上分别对应于500℃和T 1温度的两点处的两条切线的交点所对应的温度，所述T 1温度为所述复合石墨材料的微分热重曲线中最大面积峰的峰顶温度，所述热重曲线和所述微分热重曲线可通过在如下条件下进行的热重分析获得：样品质量10±0.05mg、吹扫气为空气且气流速率为60mL/min、升温速率为5℃/min、测试温度范围为35℃～950℃。
  8. 根据权利要求7所述的方法，其中，基于所获得的复合石墨材料的总质量，在步骤S10、S20加入的动力学碳材料原料粉末的总质量百分含量为1％～30％，可选地为8％～15％。
  9. 根据权利要求7-8中任一项所述的方法，其中，
    焦粉末的体积平均粒径Dv50为6μm～12μm，可选地为8μm～10μm；和/或，
    动力学碳材料原料粉末的体积平均粒径Dv50为3μm～12μm，可选地为4μm～9μm；
    可选地，焦粉末的体积平均粒径Dv50与动力学碳材料原料粉末的体积平均粒径Dv50之比为1.05～1.75，进一步可选为1.2～1.5。
  10. 根据权利要求7-9中任一项所述的方法，还包括步骤：在S10中加入粘结剂，将粘结剂与焦粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒，或将粘结剂与加有动力学碳材料原料粉末的焦粉末混合后进行造粒，再进行石墨化处理，以得到本体颗粒；
    可选地，基于所获得的复合石墨材料的总质量，所述粘结剂的质量百分含量为3％～12％，进一步可选为5％～8％；
    可选地，所述粘结剂选自沥青；
    可选地，造粒后所获得的颗粒的体积平均粒径Dv50为8μm～14μm，进一步可选为9.5μm～12μm。
  11. 根据权利要求7-10中任一项所述的方法，其中，在S20中，所述有机碳源选自煤沥青、石油沥青、酚醛树脂、椰壳中的一种或几种，可选地为石油沥青；
    可选地，基于所获得的复合石墨材料的总质量，所述有机碳源的加入量为使得有机碳源碳化后得到的无定形碳的质量百分含量为1％～8％，可选地为2％～5％。
  12. 一种负极极片，包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，其中，所述负极膜层包括根据权利要求1-6任一项所述的复合石墨材料，或根据权利要求7-11中任一项所述的方法制备的复合石墨材料，
    可选地，所述负极膜层还包括添加剂，所述添加剂选自硬碳、微膨胀石墨、膨胀石墨、石墨烯中的一种或几种，所述添加剂(002)晶面的层间距d 002≥0.3358nm，可选地为0.3359nm～0.3366nm；
    可选地，基于负极膜层的总质量，添加剂的质量百分含量为1％～20％，进一步可选为3％～8％。
  13. 一种二次电池，包括根据权利要求12所述的负极极片。
  14. 一种电池模块，包括根据权利要求13所述的二次电池。
  15. 一种电池包，包括根据权利要求13所述的二次电池、根据权利要求14所述的电池模块中的一种。
  16. 一种用电装置，包括根据权利要求13所述的二次电池、根据权利要求14所述的电池模块、根据权利要求15所述的电池包中的至少一种。
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