WO2017101470A1 - 一种锂离子二次电池负极活性材料及制备方法、锂离子二次电池负极极片和锂离子二次电池 - Google Patents

一种锂离子二次电池负极活性材料及制备方法、锂离子二次电池负极极片和锂离子二次电池 Download PDF

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WO2017101470A1
WO2017101470A1 PCT/CN2016/094899 CN2016094899W WO2017101470A1 WO 2017101470 A1 WO2017101470 A1 WO 2017101470A1 CN 2016094899 W CN2016094899 W CN 2016094899W WO 2017101470 A1 WO2017101470 A1 WO 2017101470A1
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lithium ion
secondary battery
ion secondary
carbon
active material
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PCT/CN2016/094899
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English (en)
French (fr)
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梁家华
夏圣安
谢封超
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华为技术有限公司
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Priority to EP16874530.5A priority Critical patent/EP3382781B1/en
Publication of WO2017101470A1 publication Critical patent/WO2017101470A1/zh
Priority to US16/010,947 priority patent/US11569496B2/en
Priority to US18/147,618 priority patent/US20230197939A1/en
Priority to US18/147,609 priority patent/US20230170475A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/02—Amorphous compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C01P2002/54—Solid solutions containing elements as dopants one element only
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
    • 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
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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 present invention relates to the field of lithium ion secondary batteries, and in particular to a lithium ion secondary battery anode active material and a preparation method thereof, a lithium ion secondary battery negative electrode sheet and a lithium ion secondary battery.
  • the negative electrode material is one of the most critical materials for fast charging of lithium ion batteries, and the common carbon materials of common negative electrode materials have low current charging and discharging performance, thus affecting their rapid charging performance, especially at low temperature. ability. Therefore, in order to improve the user experience and improve the fast charge performance of lithium ion batteries, especially to achieve low temperature fast charge, it is necessary to provide a high energy density, high rate charge and discharge characteristics, especially lithium ions with fast charging ability at low temperature. Battery anode material.
  • the first aspect of the present invention provides a negative active material for a lithium ion secondary battery, which has high energy density, high rate of charge and discharge characteristics, and particularly fast charging capability at a low temperature to solve the existing ordinary carbon. Material high current charge and discharge performance is low, fast charging performance is poor, especially at low temperatures The problem of poor charging ability.
  • the present invention provides a negative active material for a lithium ion secondary battery, comprising a core of a carbon material and a coating layer formed on a surface of the core of the carbon material, the material of the coating layer comprising amorphous carbon And a doping element, the doping element comprising a nitrogen element.
  • the coating layer has a two-layer structure or a single-layer structure.
  • the cladding layer is a two-layer structure, and the cladding layer includes an amorphous carbon layer and a doped layer sequentially formed on a surface of the core material of the carbon material, wherein The doped layer is an outermost layer; or the cladding layer includes a doped layer and an amorphous carbon layer sequentially formed on a surface of the core material of the carbon material, wherein the amorphous carbon layer is an outermost layer, and the doping
  • the impurity layer contains a carbon element and the doping element.
  • the amorphous carbon layer has a thickness of 0.1 to 10 ⁇ m
  • the doped layer has a thickness of 0.1 to 10 ⁇ m.
  • the doping layer has a mass of 0.1 to 30% of the entire negative electrode active material, and the doping element has a mass of 0.1 to 30% of the mass of the doping layer.
  • the cladding layer is a single layer structure, and the doping element is dispersed in the amorphous carbon.
  • the coating layer has a single layer structure
  • the quality of the coating layer accounts for 0.1 to 30% of the entire negative electrode active material
  • the mass of the doping element accounts for 0.1 to 20% of the mass of the coating layer.
  • the coating layer has a thickness of 0.1 to 10 ⁇ m.
  • the amorphous carbon is a mixture of one or more of a pitch, an epoxy resin, and a phenol resin.
  • the amorphous carbon has a mass of 0.1 to 30% of the entire negative electrode active material.
  • the doping element further includes one or more of P, B, S, O, F, Cl, H elements.
  • the material of the core of the carbon material includes at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, hard carbon, soft carbon, graphene, carbon nanotubes, and carbon fibers.
  • a lithium ion secondary battery anode active material provided by the first aspect of the present invention has a carbon material as a core, and a doping element and an amorphous carbon coating layer are disposed on a surface thereof, wherein
  • the doping element can form lattice defects in the carbon layer, which not only can improve the cloud mobility of the electron cloud, but also reduce the anti-storage lithium barrier, increase the lithium-binding site, increase the layer spacing of the carbon material, and greatly improve
  • the lithium ion migration speed increases the lithium storage space and channel, thereby effectively improving the material capacity and fast charge performance; the amorphous carbon coating can greatly improve the low temperature fast charge performance of the negative electrode material.
  • the negative active material of the lithium ion secondary battery not only can increase the capacity of the carbon material, but also achieve a faster charging speed, especially a charging speed at a low temperature, thereby solving the current high-current charging of ordinary carbon materials.
  • the present invention provides a method for preparing a negative active material for a lithium ion secondary battery, comprising the steps of:
  • the anode active material of the lithium ion secondary battery is prepared by incubating at a temperature of ° C for 1 to 12 hours, and the anode active material of the lithium ion secondary battery includes a core of a carbon material and a coating formed on the surface of the core of the carbon material.
  • the layer, the material of the cladding layer includes amorphous carbon and a doping element, the doping element includes a nitrogen element, and the cladding layer is a single layer structure, and the doping element is dispersed in the amorphous carbon.
  • the present invention provides a method for preparing a negative active material for a lithium ion secondary battery, comprising the steps of:
  • Lithium ion II a secondary battery anode active material, the lithium ion secondary battery anode active material comprising a carbon material core and a coating layer formed on a surface of the carbon material core, the material of the coating layer comprising amorphous carbon and doping An element, the doping element includes a nitrogen element, the cladding layer is a two-layer structure, and the cladding layer includes an amorphous carbon layer and a doped layer sequentially formed on a surface of the core material of the carbon material, the doping The impurity layer contains a carbon element and the doping element.
  • the present invention provides a method for preparing a negative active material for a lithium ion secondary battery, comprising the steps of:
  • the secondary battery anode active material includes a core of a carbon material and a coating layer formed on a surface of the core of the carbon material, the material of the cladding layer including amorphous carbon and a doping element, the doping element including nitrogen element
  • the cladding layer is a two-layer structure, and the cladding layer includes a doped layer and an amorphous carbon layer sequentially formed on a surface of the core material of the carbon material, the doped layer containing a carbon element and the doping element.
  • the method for preparing a negative electrode active material for a lithium ion secondary battery provided by the invention has the advantages of simple process, low cost and suitable for expanding production.
  • the present invention provides a negative electrode tab for a lithium ion secondary battery, comprising a current collector and a lithium ion secondary battery anode active material coated on the current collector, the lithium ion secondary battery anode active
  • the material is as described in the first aspect of the invention.
  • the lithium ion secondary battery provided by the fifth aspect of the invention has a high capacity, a long service life and a good fast charge performance.
  • the present invention provides a lithium ion secondary battery comprising a lithium ion secondary battery negative electrode tab, a positive electrode tab, a separator, a nonaqueous electrolyte, and an outer casing, the lithium
  • the ion secondary battery negative electrode tab includes a current collector and a lithium ion secondary battery negative electrode active material coated on the current collector, the lithium ion secondary battery negative electrode active material being as described in the first aspect of the invention.
  • a lithium ion secondary battery provided by the sixth aspect of the invention has high capacity, long service life and good fast charge performance.
  • FIG. 1 is a schematic structural view of a negative electrode active material of a lithium ion secondary battery according to an embodiment of the present invention
  • FIG. 2 is a SEM image of a negative electrode active material of a lithium ion secondary battery according to an embodiment of the present invention
  • FIG. 3 is a schematic structural view of an anode active material of a lithium ion secondary battery according to an embodiment of the present invention
  • FIG. 4 is a schematic structural view of a negative electrode active material of a lithium ion secondary battery according to an embodiment of the present invention
  • 5 is a comparison diagram of performance tests of the button battery of the first embodiment, the third embodiment, and the first embodiment;
  • FIG. 6 is a comparison diagram of performance tests of a button battery according to Embodiment 2 of the present invention and Comparative Example 1;
  • Example 8 is a comparison diagram of cycle performance of a negative electrode material of Comparative Example 1 and Comparative Example 2 under 1 C rapid charging at a low temperature of 10 ° C in a full battery according to Example 1 of the present invention.
  • the anode material is one of the key materials affecting its rapid charging performance.
  • the conventional common carbon anode materials have low current charging and discharging performance, poor fast charging performance, especially low temperature.
  • the capability of fast charging is not good. Therefore, in order to improve the user experience and improve the fast charging performance of the lithium ion battery, especially to achieve low temperature fast charging, the embodiment of the present invention provides a high energy density and high rate charge and discharge characteristics.
  • a lithium ion secondary battery negative active material having a rapid charging ability at a low temperature.
  • an embodiment of the present invention provides a negative active material for a lithium ion secondary battery, comprising a core of a carbon material and a coating layer formed on a surface of the core of the carbon material, the material of the coating layer comprising amorphous Carbon and a doping element, the doping element comprising a nitrogen element.
  • the coating layer may be a single layer structure or a double layer structure.
  • the cladding layer is a two-layer structure, and the cladding layer includes an amorphous carbon layer formed on a surface of a core of a carbon material, and a doped layer formed on a surface of the amorphous carbon layer.
  • the doped layer contains a carbon element and the doping element, and the doping element is uniformly distributed in the doped layer.
  • the cladding layer is a two-layer structure
  • the cladding layer includes a doped layer formed on a surface of the core of the carbon material, and an amorphous carbon layer formed on a surface of the doped layer
  • the doped layer contains a carbon element and the doping element, and the doping element is uniformly distributed in the doped layer.
  • the thickness of the amorphous carbon layer is 0.1-10 ⁇ m, and the thickness of the doped layer is 0.1-10 ⁇ m; the quality of the doped layer accounts for the whole 0.1 to 30%, preferably 0.5% to 10%, of the negative electrode active material; the mass of the doping element is 0.1 to 30%, preferably 1% to 15%, based on the mass of the doped layer.
  • the main element composition of the doped layer is a carbon element, and the source of the carbon element may be a nitrogen-containing compound such as pyrrole or pyridine, and the mass of the carbon element accounts for 70 to 99.9% of the mass of the doped layer, preferably.
  • the ground is 85% to 99%.
  • the doping element is uniformly distributed in the doped layer, taking nitrogen doping as an example, the doping element nitrogen element is partially derived from pyrrole or pyridine, and a part is obtained by further introducing a nitrogen-containing gas molecule doping, After doping, in the doped layer, the ring structure of the original pyridine and pyrrole is broken to form a hole structure, thereby improving the lithium storage ability and the conductivity of the negative electrode active material.
  • the cladding layer has a single layer structure, that is, the doping element is in the same layer as the amorphous carbon, and the doping element is dispersed in the amorphous carbon.
  • the thickness of the coating layer is 0.1 to 10 ⁇ m.
  • the quality of the coating layer is 0.1 to 30%, preferably 0.5% to 15%, of the entire negative electrode active material; and the mass of the doping element is 0.1 to 20% of the mass of the coating layer, preferably The ground is 0.2% to 10%.
  • the amorphous carbon may be a mixture of one or more of asphalt, epoxy resin, and phenolic resin.
  • the amorphous carbon has a mass of 0.1 to 30% of the entire negative active material. In a preferred embodiment of the present invention, the amorphous carbon has a mass of 0.2% to 10% of the entire negative active material.
  • the doping element further comprises one or more of P, B, S, O, F, Cl, H elements.
  • the material of the carbon material core comprises at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, hard carbon, soft carbon, graphene, carbon nanotubes, and carbon fibers.
  • the lithium ion secondary battery anode active material has a carbon material as a core, and a doping element and an amorphous carbon coating layer are disposed on the surface thereof, wherein
  • the doping element can form lattice defects in the carbon layer, which not only can improve the cloud mobility of the electron cloud, but also reduce the anti-storage lithium barrier, increase the lithium-binding site, increase the layer spacing of the carbon material, and greatly improve
  • the lithium ion migration speed increases the lithium storage space and channel, thereby effectively improving the material capacity and fast charge performance; the amorphous carbon coating can greatly improve the low temperature fast charge performance of the negative electrode material.
  • the negative active material of the lithium ion secondary battery provided by the embodiment of the invention can not only increase the capacity of the carbon material, but also achieve a faster charging speed, especially a charging speed at a low temperature, thereby solving the problem of the existing ordinary carbon material.
  • the embodiment of the invention further provides a method for preparing a negative active material for a lithium ion secondary battery, comprising the following steps:
  • the lithium ion secondary battery negative electrode active material is prepared by incubating at a temperature of ° C for 1 to 12 hours, and the lithium ion secondary battery negative electrode active material includes a carbon material core and is formed in the carbon material.
  • the material of the cladding layer comprising amorphous carbon and a doping element, the doping element comprising a nitrogen element, the cladding layer being a single layer structure, the doping element being dispersed in none Shaped in carbon.
  • the carbon material comprises at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, hard carbon, soft carbon, graphene, carbon nanotubes, and carbon fibers.
  • the amorphous carbon may be a mixture of one or more of asphalt, epoxy resin, and phenol resin.
  • the ionic liquid may be one of triphenylboron, 3-methyl-butylpyridine dicyanamide or 1-ethyl-3-methylimidazolium dicyanamide. The mass ratio of the added ionic liquid to the carbon material is 1:1 to 10:1.
  • the rate of the mixed gas of the organic small molecule containing the doping element and the inert carrier gas is 5 to 300 mL/min, and the volume ratio of the organic small molecule containing the doping element to the inert carrier gas is 1: 1-1:10.
  • the mixture may be kept at a temperature of 600 to 1000 ° C for 2 to 6 hours.
  • the doping element further comprises one or more of P, B, S, O, F, Cl, H elements.
  • the organic small molecule is a compound which can provide doping elements such as N, P, B, S, O, F, Cl, H, and the like.
  • the organic small molecule may include one of pyridine, pyrrole, and thiophene.
  • the mass of the amorphous carbon accounts for 0.1 to 30% of the entire negative electrode active material; in a preferred embodiment of the present invention, the mass of the amorphous carbon accounts for 0.2% to 10% of the entire negative active material. %.
  • the quality of the coating layer is 0.1 to 30%, preferably 0.5% to 15%, of the entire negative electrode active material; and the mass of the doping element is 0.1 to 20% of the mass of the coating layer, preferably The ground is 0.2% to 10%.
  • the embodiment of the present invention provides another method for preparing a negative active material for a lithium ion secondary battery, comprising the following steps:
  • a lithium ion secondary battery anode active material comprising a carbon material core and a coating layer formed on a surface of the carbon material core, the material of the coating layer comprising amorphous carbon
  • a doping element comprising a nitrogen element
  • the cladding layer being a two-layer structure
  • the cladding layer comprising an amorphous carbon layer and a doped layer sequentially formed on a surface of the core material of the carbon material
  • the doped layer contains a carbon element and the doping element.
  • the carbon material comprises at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, hard carbon, soft carbon, graphene, carbon nanotubes, and carbon fibers.
  • the amorphous carbon may be a mixture of one or more of asphalt, epoxy resin, and phenol resin.
  • the coating and carbonization treatment may specifically be: first coating treatment at 400-800 ° C for 2-6 hours, and then carbonization treatment at 800-1200 ° C for 2-6 hours.
  • the carbonization treatment is carried out in a protective gas atmosphere, which may be nitrogen.
  • the surfactant in the step (2), may be cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate or sodium carboxymethylcellulose.
  • the acid solution may be hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid.
  • the oxidizing agent may be ammonium persulfate, iron trichloride or iron sulfate.
  • the amount of the pyrrole monomer to be added may be determined according to the pre-doping concentration.
  • the specific operation of washing the black precipitate to neutrality and drying may be: sequentially washing with a 1 mol/L HCl solution and purified water to neutrality, and then drying at 80 ° C for 12 hours.
  • the mixed gas of the hydride containing the doping element and the inert carrier gas may be at a rate of 5 to 300 mL/min, and the hydride containing the doping element and the inert carrier gas The volume ratio can be from 1:1 to 1:10.
  • the hydride containing the doping element is a hydride which can provide doping elements such as N, P, B, S, O, F, Cl, H, and the like. Specifically, it may be, for example, NH 3 , N 2 H 4 .
  • the inert carrier gas may be nitrogen, argon, helium or the like.
  • the mixture is kept at a temperature of 600 to 1000 ° C for 2 to 6 hours.
  • the mass of the amorphous carbon accounts for 0.1 to 30% of the entire negative electrode active material; in a preferred embodiment of the present invention, the mass of the amorphous carbon accounts for 0.2% to 10% of the entire negative active material.
  • the doping element further includes one or more of P, B, S, O, F, Cl, H elements.
  • the amorphous carbon layer has a thickness of 0.1 to 10 ⁇ m
  • the doped layer has a thickness of 0.1 to 10 ⁇ m
  • the doped layer has a mass of 0.1 to 30%, preferably 0.5% to 10% of the entire negative electrode active material.
  • the mass of the doping element is 0.1 to 30%, preferably 1% to 15%, of the mass of the doped layer.
  • the embodiment of the present invention provides another method for preparing a negative active material for a lithium ion secondary battery, comprising the following steps:
  • the secondary battery anode active material includes a core of a carbon material and a coating layer formed on a surface of the core of the carbon material, the material of the cladding layer including amorphous carbon and a doping element, the doping element including nitrogen element
  • the cladding layer is a two-layer structure, and the cladding layer includes a doped layer and an amorphous carbon layer sequentially formed on a surface of the core material of the carbon material, the doped layer containing a carbon element and the doping element.
  • the carbon material comprises at least one of natural graphite, artificial graphite, expanded graphite, graphite oxide, hard carbon, soft carbon, graphene, carbon nanotubes, and carbon fibers.
  • the surfactant may be cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate or sodium carboxymethylcellulose.
  • the acid solution may be hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid.
  • the oxidizing agent may be super sulfur Ammonium acid, ferric chloride, iron sulfate.
  • the amount of the pyrrole monomer to be added depends on the pre-doping concentration.
  • the specific operation of washing the black precipitate to neutrality and drying may be: sequentially washing with a 1 mol/L HCl solution and purified water to neutrality, followed by drying at 80 ° C for 12 hours.
  • the rate of the mixed gas of the hydride containing the doping element and the inert carrier gas is 5 - 300 mL / min, and the volume of the hydride containing the doping element and the inert carrier gas The ratio is 1:1 - 1:10.
  • the hydride containing the doping element is a hydride which can provide doping elements such as N, P, B, S, O, F, Cl, H, and the like. Specifically, it may be, for example, NH 3 , N 2 H 4 .
  • the inert carrier gas may be nitrogen, argon, helium or the like.
  • the mixture is kept at a temperature of 600 to 1000 ° C for 2 to 6 hours.
  • the amorphous carbon may be a mixture of one or more of asphalt, epoxy resin, and phenol resin.
  • the coating and carbonization treatment are specifically: first coating treatment at 400-800 ° C for 2-6 hours, and then carbonization treatment at 800-1200 ° C for 2-6 hours.
  • the carbonization treatment is carried out in a protective gas atmosphere, which may be nitrogen.
  • the mass of the amorphous carbon accounts for 0.1 to 30% of the entire negative electrode active material; in a preferred embodiment of the present invention, the mass of the amorphous carbon accounts for 0.2% to 10% of the entire negative active material.
  • the doping element further includes one or more of P, B, S, O, F, Cl, H elements.
  • the amorphous carbon layer has a thickness of 0.1 to 10 ⁇ m
  • the doped layer has a thickness of 0.1 to 10 ⁇ m
  • the doped layer has a mass of 0.1 to 30%, preferably 0.5% to 10% of the entire negative electrode active material.
  • the mass of the doping element is 0.1 to 30%, preferably 1% to 15%, of the mass of the doped layer.
  • the method for preparing a negative electrode active material for a lithium ion secondary battery provided by the above embodiments of the present invention is simple in process, low in cost, and suitable for expanding production.
  • the embodiment of the invention further provides a lithium ion secondary battery negative electrode pole piece and a lithium ion secondary battery, which adopt the lithium ion secondary battery negative electrode active material provided by the above embodiments of the invention.
  • a method for preparing a negative electrode active material for a lithium ion secondary battery comprising the steps of:
  • the anode active material of the lithium ion secondary battery of the present embodiment includes an artificial graphite core 10 and a coating layer formed on the surface of the artificial graphite core 10, the coating layer having a two-layer structure and having an inner layer of no
  • the carbon layer 11 is shaped and the outer layer is an N-doped doped layer 12.
  • the thickness of the amorphous carbon layer is 3 ⁇ m
  • the thickness of the doped layer is 1 ⁇ m.
  • the mass content of the amorphous carbon is 3.9%
  • the mass content of the doped layer is 1%
  • the mass of the doping element accounts for 9% of the mass of the doped layer.
  • 2 is an SEM image of a negative electrode active material of a lithium ion secondary battery of the present embodiment. As can be seen from Figure 2, a coating layer is formed on the surface of the graphite.
  • a method for preparing a negative electrode active material for a lithium ion secondary battery comprising the steps of:
  • the black precipitate was washed three times with a 1 mol/L HCl solution, and then washed with purified water until the solution was colorless neutral.
  • the precipitate was then dried at 80 ° C for 12 hours to obtain a dried precipitate; the dried precipitate was placed in a reaction vessel, and N 2 H 4 was added to a volume of 10% N 2 H 4 /Ar. Mixing gas, sintering at 700 ° C for 6 hours to obtain N-doped layer coated artificial graphite;
  • FIG. 3 is a schematic view showing the structure of a negative electrode active material of a lithium ion secondary battery of the present embodiment. As can be seen from FIG.
  • the anode active material of the lithium ion secondary battery of the present embodiment includes an artificial graphite core 20, and a coating layer formed on the surface of the artificial graphite core 20, the coating layer having a two-layer structure and an inner layer of N
  • the doped doped layer 21 and the outer layer are an amorphous carbon layer 22.
  • the thickness of the amorphous carbon layer is 4.2 ⁇ m
  • the thickness of the doped layer is 1.3 ⁇ m.
  • the mass content of the amorphous carbon is 5.1%
  • the mass content of the doped layer is 1.2%
  • the mass of the doping element accounts for 11% of the mass of the doped layer.
  • a method for preparing a negative electrode active material for a lithium ion secondary battery comprising the steps of:
  • the negative electrode active material of the lithium ion secondary battery of the present embodiment includes an artificial graphite core 30, and a coating layer 31 formed on the surface of the artificial graphite core 30, the cladding layer 31 being a single layer structure, and the N element is uniform. Doped in amorphous carbon.
  • the thickness of the coating layer is 5 ⁇ m
  • the mass content of the amorphous carbon in the negative electrode active material is 6.5%
  • the mass of the doping element accounts for 5% of the mass of the coating layer.
  • a method for preparing a negative electrode active material for a lithium ion secondary battery comprising the steps of:
  • the dried precipitate was placed in an autoclave, into N 2 H 4 volume content of 20% N 2 H 4 / Ar mixed gas, sintering at 700 °C 6 hours to obtain a lithium ion secondary Secondary battery negative active material.
  • the thickness of the amorphous carbon layer is 8 um
  • the thickness of the doped layer is 2.1 um.
  • the mass content of the amorphous carbon is 11.2%
  • the mass content of the doped layer is 2.3%
  • the mass of the doping element accounts for 13% of the mass of the doped layer.
  • CAB cetyltrimethylammonium bromide
  • N 4 H 4 /Ar mixed gas having a H 4 volume content of 10% was sintered at 700 ° C for 6 hours to obtain an N-doped composite negative electrode material.
  • Button cell fabrication The anode materials of Examples 1 to 4 and Comparative Examples 1 and 2 were separately mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 92:5:3 in N-methylpyrrolidone.
  • the foil current collector was vacuum dried at 120 ° C to obtain an electrode sheet, which was then assembled into a button cell in a glove box for testing.
  • the counter electrode was made of lithium metal, the diaphragm was celgard C2400, and the electrolyte was 1.3 M LiPF6 EC. PC and DEC (3:1:6 by volume) solution.
  • FIG. 5 is a test comparison diagram of a button battery according to Embodiment 1, Example 3 and Comparative Example 1
  • FIG. 6 is a test comparison diagram of the button battery according to Embodiment 2 of the present invention and Comparative Example 1. It can be seen from FIG. 5 and FIG. 6 that the charge-discharge curves and capacities of the negative electrode active materials of the two cladding layers of the first embodiment and the second embodiment are substantially different, and the capacity is completely uncoated with respect to the first comparative example.
  • graphite materials The coating layer of the third embodiment is a single-layer structure of the negative electrode active material, and its capacity is slightly lower than that of the first embodiment, but the capacity is still greatly improved compared with the first comparative example.
  • FIG. 7 is a comparison diagram of cycle performance of a negative electrode material of Comparative Example 1 and Comparative Example 2 under normal temperature 2C rapid charging in a full battery according to Example 1 of the present invention. It can be seen from FIG. 7 that the completely uncoated graphite negative electrode of Comparative Example 1 has substantially no capacity for 2C charging cycle, and has been attenuated to about 60% in less than 300 cycles; and the graphite negative electrode of the first embodiment of the present invention is completely It satisfies the 2C charging cycle, and can maintain a capacity of more than 90% in 500 cycles, and the capacity retention rate is better than that of Comparative Example 2.
  • FIG. 8 is a comparison diagram of cycle performance of a negative electrode material of Comparative Example 1 and Comparative Example 2 under 1 C rapid charging at a low temperature of 10 ° C in a full battery according to Example 1 of the present invention. It can be seen from Fig. 8 that the completely uncoated graphite anode battery of Comparative Example 1 cannot satisfy the 1C fast charging cycle at a low temperature of 10 ° C, and has been attenuated to about 60% in less than 20 cycles; The 1C fast charge cycle of the graphite anode at a low temperature of 10 ° C is also relatively poor. The capacity retention rate has been attenuated to 95% in less than 20 cycles. However, the graphite anode of the first embodiment of the present invention has a good 1C fast charge cycle performance at a low temperature of 10 ° C. The capacity retention rate still reached about 99% at 80 cycles.
  • the lithium ion battery anode active material provided by the embodiment of the present invention can achieve a normal temperature 2C fast charge and maintain a volume of more than 90% in 500 cycles, compared to a normal anode material having a charging capacity of about 0.5 C at a normal temperature; Compared with the comparative example 2, the low-temperature fast charging performance of the lithium ion battery anode active material provided by the embodiment of the invention is obviously improved.

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Abstract

一种锂离子二次电池负极活性材料及其制备方法、锂离子二次电池负极极片以及锂离子二次电池，该负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素。该锂离子二次电池负极活性材料以碳素材料为内核，通过在其表面设置掺杂元素和无定形碳包覆层，从而具有长寿命、高容量、高倍率充放电特性和低成本的优势，该负极活性材料能够有效地提高电池充电速率，特别是低温下的快速充电能力。

Description

一种锂离子二次电池负极活性材料及制备方法、锂离子二次电池负极极片和锂离子二次电池
本申请要求了2015年12月18日提交中国专利局的，申请号201510964585.3，发明名称为“一种锂离子二次电池负极活性材料及制备方法、锂离子二次电池负极极片和锂离子二次电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及锂离子二次电池领域，特别是涉及一种锂离子二次电池负极活性材料及制备方法、锂离子二次电池负极极片和锂离子二次电池。
背景技术
目前，电子技术飞速发展，电子产品已成为了人类生活不可缺少的必需品，但电池能量密度的进步速度还远远跟不上电子技术的发展速度，因此成为电子产品的瓶颈之一。快速充电则是近1～2年备受关注、用户体验加倍提升的热门技术方向。
负极材料是锂离子电池实现快速充电的最关键材料之一，而现有常用的负极材料普通碳素材料，其大电流充放电性能低，因而影响其快速充电性能，特别是低温下快速充电的能力。因此，为了提升用户体验，提高锂离子电池的快充性能，特别是实现低温快充，有必要提供一种高能量密度、高倍率充放电特性良好，特别是低温下具有快速充电能力的锂离子电池负极材料。
发明内容
鉴于此，本发明第一方面提供了一种锂离子二次电池负极活性材料，其具有高能量密度、高倍率充放电特性良好，特别是低温下具有快速充电能力，以解决现有普通碳素材料大电流充放电性能低，快速充电性能差，特别是低温下快 速充电的能力不佳的问题。
第一方面，本发明提供了一种锂离子二次电池负极活性材料，包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素。
在本发明第一方面中，所述包覆层为双层结构或单层结构。
具体地，在本发明第一方面中，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的无定形碳层和掺杂层，其中所述掺杂层为最外层；或者所述包覆层包括依次形成于所述碳素材料内核表面的掺杂层和无定形碳层，其中所述无定形碳层为最外层，所述掺杂层包含碳元素和所述掺杂元素。所述无定形碳层的厚度为0.1～10μm，掺杂层的厚度为0.1～10μm。
当所述包覆层为双层结构时，所述掺杂层的质量占整个负极活性材料的0.1～30％，所述掺杂元素的质量占所述掺杂层质量的0.1～30％。
在本发明第一方面中，所述包覆层为单层结构，所述掺杂元素分散于无定形碳中。当所述包覆层为单层结构时，所述包覆层的质量占整个负极活性材料的0.1～30％，所述掺杂元素的质量占所述包覆层质量的0.1～20％。当所述掺杂元素与所述无定形碳同处一层，即所述包覆层为单层结构时，所述包覆层厚度为0.1～10μm。
在本发明第一方面中，所述无定形碳为沥青、环氧树脂、酚醛树脂中的一种或多种的混合。
在本发明第一方面中，所述无定形碳的质量占整个负极活性材料的0.1～30％。
在本发明第一方面中，所述掺杂元素还包括P、B、S、O、F、Cl、H元素中的一种或多种。
在本发明第一方面中，所述碳素材料内核的材料包括天然石墨、人造石墨、膨胀石墨、氧化石墨、硬碳、软碳、石墨烯、碳纳米管和碳纤维中的至少一种。
与现有技术相比，本发明第一方面提供的一种锂离子二次电池负极活性材料，以碳素材料为内核，通过在其表面设置掺杂元素和无定形碳包覆层，其中， 掺杂元素可在碳层中形成晶格缺陷，不仅可以提高电子云流动性，而且还能降低反储锂应势垒、增加储锂结合位点、增加碳素材料的层间距，大大地提高了锂离子迁移速度，提升储锂空间和通道，从而有效提高材料容量和快充性能；无定形碳包覆则可大大提高负极材料的低温快充性能。因此本发明提供的锂离子二次电池负极活性材料不但可以提高碳素材料的容量，还能达到更快的充电速度特别是低温下的充电速度，从而解决了现有普通碳素材料大电流充放电性能低，快速充电性能差，特别是低温下快速充电的能力不佳的问题。
第二方面，本发明提供了一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
将碳素材料、无定形碳原料与离子液体进行混合，获得混合物；将所述混合物放入反应釜内，通入含掺杂元素的有机小分子与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，即制得锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素，所述包覆层为单层结构，所述掺杂元素分散于无定形碳中。
第三方面，本发明提供了一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
(1)将碳素材料与无定形碳原料混合，在400～1200℃下进行包覆及炭化处理，得到无定形碳包覆的碳素负极材料；
(2)将上述所得碳素负极材料放入反应釜内，超声分散于第一混合溶液中，并加入氧化剂获得悬浊液；向所述悬浊液中加入吡咯单体得到第二混合溶液；将所述第二混合溶液于0-5℃下进行保温反应1-24h，获得黑色沉淀物，将所述黑色沉淀物洗涤至中性并进行干燥；所述第一混合溶液由表面活性剂溶解在酸溶液中制得，所述表面活性剂与所述酸溶液的摩尔比为1:2～1:10，所添加的氧化剂与所述吡咯单体摩尔比为1:0.5～1:5；
(3)将干燥后的黑色沉淀物放置在反应釜内，通入含掺杂元素的氢化物与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，即制得锂离子二 次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的无定形碳层和掺杂层，所述掺杂层包含碳元素和所述掺杂元素。
第四方面，本发明提供了一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
(1)将碳素材料放入反应釜内，超声分散于第一混合溶液中，并加入氧化剂获得悬浊液；向所述悬浊液中加入吡咯单体得到第二混合溶液；将所述第二混合溶液于0-5℃下进行保温反应1-24h，获得黑色沉淀物，将所述黑色沉淀物洗涤至中性并进行干燥；所述第一混合溶液由表面活性剂溶解在酸溶液中制得，所述表面活性剂与所述酸溶液的摩尔比为1:2～1:10，所添加的氧化剂与所述吡咯单体摩尔比为1:0.5～1:5；
(2)将干燥后的黑色沉淀物放置在反应釜内，通入含掺杂元素的氢化物与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，得到掺杂层包覆的负极材料；
(3)将上述所得掺杂层包覆的负极材料与无定形碳原料混合，在400～1200℃下进行包覆及炭化处理，即制得锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的掺杂层和无定形碳层，所述掺杂层包含碳元素和所述掺杂元素。
本发明上述提供的锂离子二次电池负极活性材料制备方法，工艺简单，成本低廉，适于扩大化生产。
第五方面，本发明提供了一种锂离子二次电池负极极片，包括集流体和涂覆在所述集流体上的锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料如本发明第一方面所述。
本发明第五方面提供的一种锂离子二次电池负极极片容量高，使用寿命长且快充性能良好。
第六方面，本发明提供了一种锂离子二次电池，所述锂离子二次电池由锂离子二次电池负极极片、正极极片、隔膜、非水电解液和外壳组成，所述锂离子二次电池负极极片包括集流体和涂覆在所述集流体上的锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料如本发明第一方面所述。
本发明第六方面提供的一种锂离子二次电池容量高，使用寿命长且快充性能良好。
本发明实施例的优点将会在下面的说明书中部分阐明，一部分根据说明书是显而易见的，或者可以通过本发明实施例的实施而获知。
附图说明
图1为本发明实施例一锂离子二次电池负极活性材料的结构示意图；
图2为本发明实施例一锂离子二次电池负极活性材料的SEM图；
图3为本发明实施例二锂离子二次电池负极活性材料的结构示意图；
图4为本发明实施例三锂离子二次电池负极活性材料的结构示意图；
图5为本发明实施例一、实施例三和对比例一的扣式电池的性能测试对比图；
图6为本发明实施例二和对比例一的扣式电池的性能测试对比图；
图7为本发明实施例一、对比例一、对比例二的负极材料在全电池中的常温2C快速充电下的循环性能对比图；
图8为本发明实施例一、对比例一、对比例二的负极材料在全电池中的低温10℃下1C快速充电下的循环性能对比图。
具体实施方式
以下所述是本发明实施例的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明实施例原理的前提下，还可以做出若干改进 和润饰，这些改进和润饰也视为本发明实施例的保护范围。
目前，在锂离子电池中，负极材料是影响其实现快速充电性能的关键材料之一，然而现有常用的普通碳素负极材料，其大电流充放电性能低，快速充电性能差，特别是低温下快速充电的能力不佳，因此，为了提升用户体验，提高锂离子电池的快充性能，特别是实现低温快充，本发明实施例提供了一种具有高能量密度、高倍率充放电特性良好，特别是低温下具有快速充电能力的锂离子二次电池负极活性材料。
具体地，本发明实施例提供了一种锂离子二次电池负极活性材料，包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素。
本发明实施方式中，所述包覆层可为单层结构或双层结构。
本发明第一实施方式中，所述包覆层为双层结构，所述包覆层包括形成于碳素材料内核表面的无定形碳层，以及形成于无定形碳层表面的掺杂层，所述掺杂层包含碳元素和所述掺杂元素，所述掺杂元素均匀分布在掺杂层中。
本发明第二实施方式中，所述包覆层为双层结构，所述包覆层包括形成于所述碳素材料内核表面的掺杂层，以及形成于掺杂层表面的无定形碳层，所述掺杂层包含碳元素和所述掺杂元素，所述掺杂元素均匀分布在掺杂层中。
本发明实施方式中，当所述包覆层为双层结构时，所述无定形碳层的厚度为0.1～10μm，掺杂层的厚度为0.1～10μm；所述掺杂层的质量占整个负极活性材料的0.1～30％，较佳地为0.5％～10％；所述掺杂元素的质量占所述掺杂层质量的0.1～30％，较佳地为1％～15％。所述掺杂层的主要元素组成为碳元素，所述碳元素的来源可以是吡咯或者吡啶等含氮化合物，所述碳元素的质量占所述掺杂层质量的70～99.9％，较佳地为85％～99％。所述掺杂元素均匀分布在掺杂层中，以氮掺杂为例，所述掺杂元素氮元素部分来源于吡咯或者吡啶，还有一部分可通过进一步引入含氮气体分子掺杂获得，经掺杂后，最终在所述掺杂层中，原有吡啶和吡咯的环状结构被打破，形成空穴结构，从而提高了负极活性材料的储锂能力和导电能力。
本发明第三实施方式中，所述包覆层为单层结构，即所述掺杂元素与所述无定形碳同处一层，所述掺杂元素分散于无定形碳中。此时，所述包覆层厚度为0.1～10μm。所述包覆层的质量占整个负极活性材料的0.1～30％，较佳地为0.5％～15％；所述掺杂元素的质量占所述包覆层质量的0.1～20％，较佳地为0.2％～10％。
本发明实施方式中，所述无定形碳可以是沥青、环氧树脂、酚醛树脂中的一种或多种的混合。所述无定形碳的质量占整个负极活性材料的0.1～30％；本发明一优选实施方式中，所述无定形碳的质量占整个负极活性材料的0.2％～10％。
本发明实施方式中，所述掺杂元素还包括P、B、S、O、F、Cl、H元素中的一种或多种。
本发明实施方式中，所述碳素材料内核的材料包括天然石墨、人造石墨、膨胀石墨、氧化石墨、硬碳、软碳、石墨烯、碳纳米管和碳纤维中的至少一种。
与现有技术相比，本发明实施例上述提供的一种锂离子二次电池负极活性材料，以碳素材料为内核，通过在其表面设置掺杂元素和无定形碳包覆层，其中，掺杂元素可在碳层中形成晶格缺陷，不仅可以提高电子云流动性，而且还能降低反储锂应势垒、增加储锂结合位点、增加碳素材料的层间距，大大地提高了锂离子迁移速度，提升储锂空间和通道，从而有效提高材料容量和快充性能；无定形碳包覆则可大大提高负极材料的低温快充性能。因此本发明实施例提供的锂离子二次电池负极活性材料不但可以提高碳素材料的容量，还能达到更快的充电速度特别是低温下的充电速度，从而解决了现有普通碳素材料大电流充放电性能低，快速充电性能差，特别是低温下快速充电的能力不佳的问题。
相应地，本发明实施例还提供了一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
将碳素材料、无定形碳原料与离子液体进行混合，获得混合物；将所述混合物放入反应釜内，通入含掺杂元素的有机小分子与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，即制得锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内 核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素，所述包覆层为单层结构，所述掺杂元素分散于无定形碳中。
本发明实施方式中，所述碳素材料包括天然石墨、人造石墨、膨胀石墨、氧化石墨、硬碳、软碳、石墨烯、碳纳米管和碳纤维中的至少一种。所述无定形碳可以是沥青、环氧树脂、酚醛树脂中的一种或多种的混合。所述离子液体可以为三苯基硼、3-甲基-丁基吡啶二氰胺盐或1-乙基-3-甲基咪唑二氰胺中的一种。其中，加入的离子液体与碳素材料质量比为1:1～10:1。
本发明实施方式中，通入含掺杂元素的有机小分子与惰性载气的混合气体的速率为5-300mL/min，含掺杂元素的有机小分子与惰性载气的体积比为1:1-1:10。本发明优选实施方式中，通入混合气体后，可在600～1000℃温度下保温2～6小时。
本发明实施方式中，所述掺杂元素还包括P、B、S、O、F、Cl、H元素中的一种或多种。所述有机小分子为可提供N、P、B、S、O、F、Cl、H等掺杂元素的化合物。具体地，所述有机小分子可包括吡啶、吡咯、噻吩中的一种。
本发明该实施方式中，所述无定形碳的质量占整个负极活性材料的0.1～30％；本发明一优选实施方式中，所述无定形碳的质量占整个负极活性材料的0.2％～10％。所述包覆层的质量占整个负极活性材料的0.1～30％，较佳地为0.5％～15％；所述掺杂元素的质量占所述包覆层质量的0.1～20％，较佳地为0.2％～10％。
相应地，本发明实施例提供了另一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
(1)将碳素材料与无定形碳原料混合，在400～1200℃下进行包覆及炭化处理，得到无定形碳包覆的碳素负极材料；
(2)将上述所得碳素负极材料放入反应釜内，超声分散于第一混合溶液中，并加入氧化剂获得悬浊液；向所述悬浊液中加入吡咯单体得到第二混合溶液；将所述第二混合溶液于0-5℃下进行保温反应1-24h，获得黑色沉淀物，将所述黑色沉淀物洗涤至中性并进行干燥；所述第一混合溶液由表面活性剂溶解在酸 溶液中制得，所述表面活性剂与所述酸溶液的摩尔比为1:2～1:10，所添加的氧化剂与所述吡咯单体摩尔比为1:0.5～1:5；
(3)将干燥后的黑色沉淀物放置在反应釜内，通入含掺杂元素的氢化物与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，即制得锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的无定形碳层和掺杂层，所述掺杂层包含碳元素和所述掺杂元素。
本发明实施方式中，步骤(1)中，所述碳素材料包括天然石墨、人造石墨、膨胀石墨、氧化石墨、硬碳、软碳、石墨烯、碳纳米管和碳纤维中的至少一种。所述无定形碳可以是沥青、环氧树脂、酚醛树脂中的一种或多种的混合。其中，包覆及炭化处理具体可以为：先在400-800℃下包覆处理2-6小时，再在800-1200℃下炭化处理2-6小时。所述炭化处理在保护气体气氛中进行，该保护气体可以是氮气。
本发明实施方式中，步骤(2)中，所述表面活性剂可以为十六烷基三甲基溴化铵、十二烷基苯磺酸钠、羧甲基纤维素钠。所述酸溶液可以为盐酸、硫酸、硝酸、磷酸。所述氧化剂可以为过硫酸铵、三氯化铁、硫酸铁。其中，吡咯单体的加入量可根据预掺杂浓度而定。其中，将所述黑色沉淀物洗涤至中性并进行干燥的具体操作可以是：依次采用1mol/L的HCl溶液和纯净水进行洗涤至中性，再于80℃下干燥12小时。
本发明实施方式中，步骤(3)中，通入含掺杂元素的氢化物与惰性载气的混合气体的速率可以为5-300mL/min，含掺杂元素的氢化物与惰性载气的体积比可以为1:1-1:10。所述含掺杂元素的氢化物为可提供N、P、B、S、O、F、Cl、H等掺杂元素的氢化物。具体地，例如可以是NH3，N2H4。所述惰性载气可以是氮气、氩气、氦气等。本发明优选实施方式中，通入混合气体后，在600～1000℃温度下保温2～6小时。
本发明实施方式中，所述无定形碳的质量占整个负极活性材料的0.1～30％；本发明一优选实施方式中，所述无定形碳的质量占整个负极活性材料的0.2％～10％。所述掺杂元素还包括P、B、S、O、F、Cl、H元素中的一种或多种。所述无定形碳层的厚度为0.1～10μm，掺杂层的厚度为0.1～10μm；所述掺杂层的质量占整个负极活性材料的0.1～30％，较佳地为0.5％～10％；所述掺杂元素的质量占所述掺杂层质量的0.1～30％，较佳地为1％～15％。
相应地，本发明实施例提供了另一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
(1)将碳素材料放入反应釜内，超声分散于第一混合溶液中，并加入氧化剂获得悬浊液；向所述悬浊液中加入吡咯单体得到第二混合溶液；将所述第二混合溶液于0-5℃下进行保温反应1-24h，获得黑色沉淀物，将所述黑色沉淀物洗涤至中性并进行干燥；所述第一混合溶液由表面活性剂溶解在酸溶液中制得，所述表面活性剂与所述酸溶液的摩尔比为1:2～1:10，所添加的氧化剂与所述吡咯单体摩尔比为1:0.5～1:5；
(2)将干燥后的黑色沉淀物放置在反应釜内，通入含掺杂元素的氢化物与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，得到掺杂层包覆的负极材料；
(3)将上述所得掺杂层包覆的负极材料与无定形碳原料混合，在400～1200℃下进行包覆及炭化处理，即制得锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的掺杂层和无定形碳层，所述掺杂层包含碳元素和所述掺杂元素。
本发明实施方式中，步骤(1)中，所述碳素材料包括天然石墨、人造石墨、膨胀石墨、氧化石墨、硬碳、软碳、石墨烯、碳纳米管和碳纤维中的至少一种。所述表面活性剂可以为十六烷基三甲基溴化铵、十二烷基苯磺酸钠、羧甲基纤维素钠。所述酸溶液可以为盐酸、硫酸、硝酸、磷酸。所述氧化剂可以为过硫 酸铵、三氯化铁、硫酸铁。吡咯单体的加入量根据预掺杂浓度而定。将所述黑色沉淀物洗涤至中性并进行干燥的具体操作可以是：依次采用1mol/L的HCl溶液和纯净水进行洗涤至中性，再于80℃下干燥12小时。
本发明实施方式中，步骤(2)中，通入含掺杂元素的氢化物与惰性载气的混合气体的速率为5-300mL/min，含掺杂元素的氢化物与惰性载气的体积比为1:1-1:10。所述含掺杂元素的氢化物为可提供N、P、B、S、O、F、Cl、H等掺杂元素的氢化物。具体地，例如可以是NH3，N2H4。所述惰性载气可以是氮气、氩气、氦气等。本发明优选实施方式中，通入混合气体后，在600～1000℃温度下保温2～6小时。
本发明实施方式中，步骤(3)中，所述无定形碳可以是沥青、环氧树脂、酚醛树脂中的一种或多种的混合。其中，包覆及炭化处理具体为：先在400-800℃下包覆处理2-6小时，再在800-1200℃下炭化处理2-6小时。所述炭化处理在保护气体气氛中进行，该保护气体可以是氮气。
本发明实施方式中，所述无定形碳的质量占整个负极活性材料的0.1～30％；本发明一优选实施方式中，所述无定形碳的质量占整个负极活性材料的0.2％～10％。所述掺杂元素还包括P、B、S、O、F、Cl、H元素中的一种或多种。所述无定形碳层的厚度为0.1～10μm，掺杂层的厚度为0.1～10μm；所述掺杂层的质量占整个负极活性材料的0.1～30％，较佳地为0.5％～10％；所述掺杂元素的质量占所述掺杂层质量的0.1～30％，较佳地为1％～15％。
本发明实施例上述提供的锂离子二次电池负极活性材料制备方法，工艺简单，成本低廉，适于扩大化生产。
本发明实施例还提供了一种锂离子二次电池负极极片和一种锂离子二次电池，采用本发明上述实施例提供的锂离子二次电池负极活性材料。
下面分多个实施例对本发明实施例进行进一步的说明。其中，本发明实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例一
一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
(1)称取3.0kg人造石墨和粉碎至0.1mm以下的石油沥青0.3kg，酚醛树脂0.02kg，搅拌均匀放入到反应釜中，在500℃进行加热包覆处理2小时，然后再通氮气保护，在1000℃进行炭化处理4小时，之后将反应产物冷却至室温，得到无定形碳包覆的人造石墨；
(2)将十六烷基三甲基溴化铵(CTAB，0.5kg)溶解在冰水浴的HCl(8L，1mol/L)溶液中得到第一混合溶液，取上述所得无定形碳包覆的人造石墨2.0kg加入到上述第一混合溶液中，超声分散30分钟，然后将过硫酸铵(APS，0.8kg)加入其中，立刻形成白色的悬浊液，搅拌0.5小时后，再加入0.5L吡咯单体得到第二混合溶液，将该第二混合溶液在4℃下保温反应24小时后过滤，得到黑色沉淀物，将该黑色沉淀物用1mol/L的HCl溶液洗涤三次，再用纯净水洗涤至溶液呈无色中性，接着把沉淀物在80℃下干燥12小时，得到干燥后的沉淀物；
(3)最后将干燥后的沉淀物放置在反应釜中，通入N2H4体积含量为10％的N2H4/Ar混合气体，在700℃下烧结6小时，即得到锂离子二次电池负极活性材料。
图1为本实施例锂离子二次电池负极活性材料的结构示意图。从图1可知，本实施例锂离子二次电池负极活性材料包括人造石墨内核10，以及形成在人造石墨内核10表面的包覆层，所述包覆层为双层结构，其内层为无定形碳层11、外层为N掺杂的掺杂层12。本实施例中，无定形碳层的厚度为3μm，掺杂层的厚度为1μm。所述负极活性材料中，无定形碳的质量含量为3.9％，掺杂层的质量含量为1％，掺杂元素的质量占掺杂层质量的9％。图2为本实施例锂离子二次电池负极活性材料的SEM图。由图2可见，石墨表面上形成了包覆层。
实施例二
一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
(1)将十六烷基三甲基溴化铵(CTAB，0.5kg)溶解在冰水浴的HCl(8L，1mol/L)溶液中得到第一混合溶液，取人造石墨2.0kg加入到上述第一混合溶 液中，超声分散30分钟，然后将过硫酸铵(APS，0.8kg)加入其中，立刻形成白色的悬浊液，搅拌0.5小时后，再加入0.5L吡咯单体得到第二混合溶液，将该第二混合溶液在4℃下保温反应24小时后过滤，得到黑色沉淀物，将该黑色沉淀物用1mol/L的HCl溶液洗涤三次，再用纯净水洗涤至溶液呈无色中性，接着把沉淀物在80℃下干燥12小时，得到干燥后的沉淀物；再将干燥后的沉淀物放置在反应釜中，通入N2H4体积含量为10％的N2H4/Ar混合气体，在700℃下烧结6小时即可得到N掺杂层包覆的人造石墨；
(2)称取1.5kg上述制备的N掺杂层包覆的人造石墨和粉碎至0.1mm以下的石油沥青0.15g，酚醛树脂0.01kg，搅拌均匀放入到反应釜中，在500℃进行加热包覆处理2小时，然后再通氮气保护在800℃进行炭化处理4小时，之后将反应产物冷却至室温，得到锂离子二次电池负极活性材料。图3为本实施例锂离子二次电池负极活性材料的结构示意图。从图3可知，本实施例锂离子二次电池负极活性材料包括人造石墨内核20，以及形成在人造石墨内核20表面的包覆层，所述包覆层为双层结构，其内层为N掺杂的掺杂层21、外层为无定形碳层22。本实施例中，无定形碳层的厚度为4.2μm，掺杂层的厚度为1.3μm。所述负极活性材料中，无定形碳的质量含量为5.1％，掺杂层的质量含量为1.2％，掺杂元素的质量占掺杂层质量的11％。
实施例三
一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
在干燥气氛下，将2.0kg人造石墨、3.0kg三苯基硼、0.1kg沥青、0.1g酚醛树脂混合，搅拌2h混合均匀后得到混合物，将混合物转入到反应釜内，通入NH3体积含量为30％的NH3/Ar混合气体，流量控制为50mL/min，以2℃/min的升温速率将反应釜内升温至800℃并保温6小时，随后冷却至室温，即可得到锂离子二次电池负极活性材料。图4为本实施例锂离子二次电池负极活性材料的结构示意图。从图4可知，本实施例锂离子二次电池负极活性材料包括人造石墨内核30，以及形成在人造石墨内核30表面的包覆层31，所述包覆层31为 单层结构，N元素均匀掺杂在无定形碳中。本实施例中，包覆层的厚度为5μm，所述负极活性材料中，无定形碳的质量含量为6.5％，掺杂元素的质量占包覆层质量的5％。
实施例四
一种锂离子二次电池负极活性材料的制备方法，包括以下步骤：
(1)称取3.0kg天然石墨和粉碎至0.1mm以下的石油沥青0.6kg，环氧树脂0.2kg，搅拌均匀放入到反应釜中，在600℃进行加热包覆处理2小时，然后再通氮气保护在1000℃下进行炭化处理4小时，之后将反应产物冷却至室温，得到无定形碳包覆的天然石墨；
(2)将十六烷基三甲基溴化铵(CTAB，0.8kg)溶解在冰水浴的HCl(10L，1mol/L)溶液中得到第一混合溶液，取上述所得无定形碳包覆的人造石墨2.0kg加入到上述第一混合溶液中，超声分散30分钟，然后将过硫酸铵(APS，1.0kg)加入其中，立刻形成白色的悬浊液，搅拌0.5小时后，再加入1.0L吡咯单体得到第二混合溶液，将该第二混合溶液在4℃下保温反应24小时后过滤，得到黑色沉淀物，将该黑色沉淀物用1mol/L的HCl溶液洗涤三次，再用纯净水洗涤至溶液呈无色中性，接着把沉淀物在80℃下干燥12小时，得到干燥后的沉淀物；
(3)最后将干燥后的沉淀物放置在反应釜中，通入N2H4体积含量为20％的N2H4/Ar混合气体，在700℃下烧结6小时，即得到锂离子二次电池负极活性材料。本实施例中，无定形碳层的厚度为8um，掺杂层的厚度为2.1um。所述负极活性材料中，无定形碳的质量含量为11.2％，掺杂层的质量含量为2.3％，掺杂元素的质量占掺杂层质量的13％。
对比例一
将完全未作表面处理的普通人造石墨作为对比例一的负极材料。
对比例二
将十六烷基三甲基溴化铵(CTAB，15g)溶解在冰水浴的HCl(240mL，1 mol/L)溶液中，将20g人造石墨放入上述溶液中，超声分散30分钟，然后将过硫酸铵(APS，26g)加入其中，立刻形成白色的悬浊液，搅拌0.5小时后，再加入16mL吡咯单体，在4℃下保温反应24小时后过滤，将得到的黑色沉淀物用1mol/L的HCl溶液洗涤三次，再用纯净水洗涤至溶液呈无色中性，接着把沉淀物在80℃下干燥12小时，最后将干燥后的沉淀物放置在反应釜中，通入N2H4体积含量为10％的N2H4/Ar混合气体，在700℃下烧结6小时即可得到N掺杂的复合负极材料。
电化学性能测试样品制作：
扣式电池制作：分别将实施例一至四及对比例一和二的负极材料与导电炭黑、聚偏二氟乙烯按照质量比92：5：3在N-甲基吡咯烷酮中混合均匀涂于铜箔集流体上，120℃真空烘干，得到电极片，然后在手套箱中组装成扣式电池进行测试，其中，对电极采用锂金属，隔膜为celgard C2400，电解液为1.3M LiPF6的EC、PC和DEC(体积比为3:1:6)溶液。
全电池制作：用钴酸锂做正极，分别以实施例一至四及对比例一和二的负极材料作为锂离子电池负极，电解液为1mol/L LiPF6/EC+PC+DEC+EMC(体积比1:0.3:1:1)，隔膜为PP/PE/PP三层隔膜，厚度为16μm，制作成3Ah左右的软包电池，用于测试材料的全电池性能。
效果实施例
为对本发明实施例技术方案带来的有益效果进行有力支持，特提供以下性能测试：
1、容量及充放电性能测试
图5为本发明实施例一、实施例三和对比例一的扣式电池的测试对比图，图6为本发明实施例二和对比例一的扣式电池的测试对比图。从图5和图6可见，实施例一和实施例二的两种包覆层结构的负极活性材料的充放电曲线和容量基本无很大差别，且容量相对对比例一的完全未包覆的石墨材料有很大的提 升；实施例三的包覆层为单层结构的负极活性材料，其容量比实施例一略低，但与对比例一相比容量仍有很大提升。
2、常温快充循环性能测试
图7为本发明实施例一、对比例一、对比例二的负极材料在全电池中的常温2C快速充电下的循环性能对比图。从图7可见，对比例一的完全未包覆的石墨负极电池基本不具备2C充电循环的能力，在不到300循环容量已经衰减至60％左右；而本发明实施例一的石墨负极完全可满足2C充电循环，在500次循环还能保持90％以上的容量，容量保持率优于对比例二。
3、低温快充循环性能测试
图8为本发明实施例一、对比例一、对比例二的负极材料在全电池中的低温10℃下1C快速充电下的循环性能对比图。从图8可见，对比例一的完全未包覆的石墨负极电池无法满足低温10℃下1C快速充电循环，在不到20循环容量已经衰减至60％左右；对比例二中单纯N掺杂的石墨负极的低温10℃下1C快速充电循环也相对稍差，不到20循环其容量保持率已经衰减到95％；而本发明实施例一的石墨负极低温10℃下1C快速充电循环性能良好，在80次循环时容量保持率仍达到99％左右。
因此，相对于普通的负极材料的常温0.5C左右的充电能力，本发明实施例提供的锂离子电池负极活性材料可以实现常温2C快充，在500次循环还能保持90％以上的容量；且相对于对比例二，本发明实施例提供的锂离子电池负极活性材料的低温快速充电性能有很明显的提升。

Claims (15)

  1. 一种锂离子二次电池负极活性材料，其特征在于，所述负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素。
  2. 如权利要求1所述的锂离子二次电池负极活性材料，其特征在于，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的无定形碳层和掺杂层，所述掺杂层包含碳元素和所述掺杂元素，其中，所述掺杂层为最外层。
  3. 如权利要求1所述的锂离子二次电池负极活性材料，其特征在于，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的掺杂层和无定形碳层，所述掺杂层包含碳元素和所述掺杂元素，其中所述无定形碳层为最外层。
  4. 如权利要求2或3所述的锂离子二次电池负极活性材料，其特征在于，当所述包覆层为双层结构时，所述掺杂层的质量占整个负极活性材料的0.1～30％，所述掺杂元素的质量占所述掺杂层质量的0.1～30％。
  5. 如权利要求1所述的锂离子二次电池负极活性材料，其特征在于，所述包覆层为单层结构，所述掺杂元素分散于所述无定形碳中。
  6. 如权利要求5所述的锂离子二次电池负极活性材料，其特征在于，所述包覆层的质量占整个负极活性材料的0.1～30％，所述掺杂元素的质量占所述包覆层质量的0.1～20％。
  7. 如权利要求1-6任一项所述的锂离子二次电池负极活性材料，其特征在于，所述无定形碳为沥青、环氧树脂、酚醛树脂中的一种或多种的混合。
  8. 如权利要求1-7任一项所述的锂离子二次电池负极活性材料，其特征在于，所述无定形碳的质量占整个负极活性材料的0.1～30％。
  9. 如权利要求1-8任一项所述的锂离子二次电池负极活性材料，其特征在于，所述掺杂元素还包括P、B、S、O、F、Cl、H元素中的一种或多种。
  10. 如权利要求1-9任一项所述的锂离子二次电池负极活性材料，其特征在于，所述碳素材料内核的材料包括天然石墨、人造石墨、膨胀石墨、氧化石墨、硬碳、软碳、石墨烯、碳纳米管和碳纤维中的至少一种。
  11. 一种锂离子二次电池负极活性材料的制备方法，其特征在于，包括以下步骤：
    将碳素材料、无定形碳原料与离子液体进行混合，获得混合物；将所述混合物放入反应釜内，通入含掺杂元素的有机小分子与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，即制得锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素，所述包覆层为单层结构，所述掺杂元素分散于无定形碳中。
  12. 一种锂离子二次电池负极活性材料的制备方法，其特征在于，包括以下步骤：
    (1)将碳素材料与无定形碳原料混合，在400～1200℃下进行包覆及炭化处理，得到无定形碳包覆的碳素负极材料；
    (2)将上述所得碳素负极材料放入反应釜内，超声分散于第一混合溶液中，并加入氧化剂获得悬浊液；向所述悬浊液中加入吡咯单体得到第二混合溶液；将所述第二混合溶液于0-5℃下进行保温反应1-24h，获得黑色沉淀物，将所述黑色沉淀物洗涤至中性并进行干燥；所述第一混合溶液由表面活性剂溶解在酸 溶液中制得；
    (3)将干燥后的黑色沉淀物放置在反应釜内，通入含掺杂元素的氢化物与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，即制得锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括氮元素，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的无定形碳层和掺杂层，所述掺杂层包含碳元素和所述掺杂元素。
  13. 一种锂离子二次电池负极活性材料的制备方法，其特征在于，包括以下步骤：
    (1)将碳素材料放入反应釜内，超声分散于第一混合溶液中，并加入氧化剂获得悬浊液；向所述悬浊液中加入吡咯单体得到第二混合溶液；将所述第二混合溶液于0-5℃下进行保温反应1-24h，获得黑色沉淀物，将所述黑色沉淀物洗涤至中性并进行干燥；所述第一混合溶液由表面活性剂溶解在酸溶液中制得，所述表面活性剂与所述酸溶液的摩尔比为1:2～1:10，所添加的氧化剂与所述吡咯单体摩尔比为1:0.5～1:5；
    (2)将干燥后的黑色沉淀物放置在反应釜内，通入含掺杂元素的氢化物与惰性载气的混合气体，在500-1200℃的温度下保温1-12小时，得到掺杂层包覆的负极材料；
    (3)将上述所得掺杂层包覆的负极材料与无定形碳原料混合，在400～1200℃下进行包覆及炭化处理，即制得锂离子二次电池负极活性材料，所述锂离子二次电池负极活性材料包括碳素材料内核以及形成在所述碳素材料内核表面的包覆层，所述包覆层的材料包括无定形碳和掺杂元素，所述掺杂元素包括 氮元素，所述包覆层为双层结构，所述包覆层包括依次形成于所述碳素材料内核表面的掺杂层和无定形碳层，所述掺杂层包含碳元素和所述掺杂元素。
  14. 一种锂离子二次电池负极极片，其特征在于，所述锂离子二次电池负极极片包括集流体和涂覆在所述集流体上的权1-10任一项所述的锂离子二次电池负极活性材料。
  15. 一种锂离子二次电池，其特征在于，所述锂离子二次电池由锂离子二次电池负极极片、正极极片、隔膜、非水电解液和外壳组成，所述锂离子二次电池负极极片包括集流体和涂覆在所述集流体上的权1-10任一项所述的锂离子二次电池负极活性材料。
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