WO2023273782A1 - 负极材料及其制备方法、锂离子电池 - Google Patents

负极材料及其制备方法、锂离子电池 Download PDF

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WO2023273782A1
WO2023273782A1 PCT/CN2022/096668 CN2022096668W WO2023273782A1 WO 2023273782 A1 WO2023273782 A1 WO 2023273782A1 CN 2022096668 W CN2022096668 W CN 2022096668W WO 2023273782 A1 WO2023273782 A1 WO 2023273782A1
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Prior art keywords
aggregate
premix
carbon
precursor
negative electrode
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PCT/CN2022/096668
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English (en)
French (fr)
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肖称茂
何鹏
郭锷明
任建国
贺雪琴
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贝特瑞新材料集团股份有限公司
惠州市鼎元新能源科技有限公司
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Application filed by 贝特瑞新材料集团股份有限公司, 惠州市鼎元新能源科技有限公司 filed Critical 贝特瑞新材料集团股份有限公司
Priority to CN202280003853.3A priority Critical patent/CN115803913A/zh
Priority to KR1020227043162A priority patent/KR20230009947A/ko
Priority to EP22831603.0A priority patent/EP4170753A1/en
Priority to US18/006,354 priority patent/US20230261183A1/en
Priority to JP2022575678A priority patent/JP2023535258A/ja
Publication of WO2023273782A1 publication Critical patent/WO2023273782A1/zh

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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
    • H01M4/364—Composites as mixtures
    • 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
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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 disclosure belongs to the technical field of negative electrode materials for lithium ion batteries, and relates to a negative electrode material, a preparation method thereof, and a lithium ion battery.
  • the drop on the current collector makes the electrical contact between the negative electrode active material and the current collector lost, resulting in the deterioration of the electrochemical performance of the negative electrode material, such as capacity fading and decreased cycle stability, making it difficult for such negative electrode materials to be commercially applied.
  • the present disclosure provides a negative electrode material, including an aggregate, the aggregate includes an active material and a carbon material, and the mass percentage of the active material in the aggregate decreases gradually from the center of the aggregate to the surface .
  • the negative electrode material includes aggregates, and the aggregates include active materials and carbon materials, and the active material components in the core center of the aggregates account for more, and the carbon material components account for less, and the active material components far away from the core center
  • the proportion of the carbon material gradually decreases, and the proportion of the carbon material component increases. This change in the concentration of the active material helps to concentrate the high concentration of the active material in the center of the negative electrode material particles, and controls the expansion of the active material inside the aggregate.
  • the mass ratio of the active material to the carbon material gradually decreases from the center to the surface of the aggregate.
  • the total mass ratio of the active material to the carbon material is 0.5-8.
  • the total mass percentage of the active substance is 5%-90%.
  • the total mass percentage of the active substance is 5%-80%.
  • the mass percentage of the active substance on the surface of the aggregate is 2%-55%.
  • the mass ratio of the active material to the carbon material in the aggregate has a maximum value of E, a minimum value of F, and E-F ⁇ 0.5.
  • an energy spectrometer is used to perform an EDS point scanning test on any region from the surface to the center on the SEM section of the aggregate, and the mass ratio of the active material to the carbon material is defined as T, and for the region N times of tests are carried out, N ⁇ 10, wherein, A is the minimum value of T in the N test results, B is the maximum value of T in the N test results, and the distance from any point on the surface of the aggregate to the center is L 0 ⁇ m, the distance from the center of the test area to the center of the aggregate is L 1 ⁇ m, the T value at the center of the test area is defined as T 0 , and T 0 satisfies the relationship: T 0 ⁇ B-(BA)L 1 / L 0 .
  • the active material includes at least one of Li, Na, K, Sn, Ge, Si, SiO x , Fe, Mg, Ti, Zn, Al, Ni, P and Cu, wherein 0 ⁇ x ⁇ 2.
  • the median diameter of the active material is 1 nm to 300 nm.
  • the carbon materials include graphitic carbon materials and non-graphitic carbon materials.
  • the graphitic carbon material includes natural graphite and/or artificial graphite.
  • the artificial graphite includes mesocarbon microspheres.
  • the non-graphitic carbon material includes at least one of amorphous carbon, crystalline carbon, hard carbon, and soft carbon.
  • the aggregate further includes at least one of a metal oxide and a conductivity enhancer.
  • the general chemical formula of the metal oxide is M x O y , 0.2 ⁇ y/x ⁇ 3, wherein M includes Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca and at least one of Zn.
  • the metal oxide is in the form of flakes and/or strips.
  • the aspect ratio of the metal oxide is greater than 2.
  • the conductivity enhancer has a conductivity of 10 0 S/m ⁇ 10 8 S/m.
  • the conductivity enhancer is in the form of flakes and/or strips.
  • the aspect ratio of the conductivity enhancer is 2-5000.
  • the conductivity enhancer includes at least one of alloy material and conductive carbon.
  • the alloy material includes at least one of zinc alloy, aluminum alloy, copper alloy, silicon alloy, nickel alloy and titanium alloy.
  • the conductive carbon includes one of graphite fibers, carbon nanotubes, graphite flakes, conductive carbon fibers, and graphene.
  • the mass ratio of the metal oxide to the active material is 1 ⁇ 20:100.
  • the mass ratio of the conductivity enhancer to the active material is 0.01-20:100.
  • the negative electrode material further includes a carbon layer covering at least part of the surface of the aggregate.
  • the material of the carbon layer includes graphite and/or amorphous carbon.
  • the carbon layer has a thickness of 10 nm to 2000 nm.
  • the median particle size of the negative electrode material is 0.5 ⁇ m ⁇ 30 ⁇ m.
  • the specific surface area of the negative electrode material is ⁇ 10m 2 /g.
  • the aggregates have a porosity ⁇ 10%.
  • the compressive hardness of the aggregate is ⁇ 100 MPa.
  • the aggregate density satisfies the following relationship: ( ⁇ 1- ⁇ 2)/ ⁇ 2 ⁇ 5%, wherein, ⁇ 1 is the test density of the aggregate, and ⁇ 2 is the average density of the aggregate; the ⁇ 2 is the density of the aggregate The sum of the mass percentage of each component in the aggregate * the theoretical density of each component.
  • the present disclosure also provides a preparation method of negative electrode material, comprising the following steps:
  • each group of premixes at least includes an active material, a first carbon source and a solvent, and at least two groups of the active material in the premixes different mass percentages;
  • multiple premixes are obtained by mixing the active material, carbon source and solvent according to different proportions, and the aggregates obtained by mixing and heat-treating the multiple premixes, the From the particle surface to the particle center of the aggregate, the proportion of active material components gradually increases, which is beneficial to suppress the expansion rate of the negative electrode material, and the preparation process is simple and controllable.
  • the difference between the maximum mass percentage content and the minimum mass percentage content of the active substance is 20%-90%.
  • the active material includes at least one of Li, Na, K, Sn, Ge, Si, SiO x , Fe, Mg, Ti, Zn, Al, P, and Cu, wherein 0 ⁇ x ⁇ 2.
  • the first carbon source includes sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide , polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride and at least one of asphalt.
  • the solvent includes an organic solvent.
  • the organic solvent includes at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and pentanol.
  • At least one set of the premixes further includes at least one of additives, metal oxides and conductivity enhancers.
  • the additive includes at least one of a surfactant and a coupling agent.
  • the surfactant includes n-octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, n-eicosic acid, palmitic acid, myristic acid, undecanoic acid, At least one of cetyltrimethylammonium bromide and polyvinylpyrrolidone.
  • the coupling agent includes a silane coupling agent and/or a titanate coupling agent.
  • the silane coupling agent includes ⁇ -aminopropyltriethoxysilane, ⁇ -glycidyloxypropyltrimethoxysilane, ⁇ -methacryloxypropyltrimethoxy silane.
  • the general chemical formula of the metal oxide is M x O y , 0.2 ⁇ y/x ⁇ 3, wherein M includes Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca and at least one of Zn.
  • the metal oxide is in the form of flakes and/or strips.
  • the aspect ratio of the metal oxide is greater than 2.
  • the mass ratio of the metal oxide to the active material is 1 ⁇ 20:100.
  • the mass ratio of the conductivity enhancer to the active material is 0.01-20.
  • the conductivity enhancer has a conductivity of 10 0 S/m ⁇ 10 8 S/m.
  • the conductivity enhancer is in the form of flakes and/or strips.
  • the aspect ratio of the conductivity enhancer is 2-5000.
  • the conductivity enhancer includes at least one of alloy material and conductive carbon.
  • the alloy material includes at least one of zinc alloy, aluminum alloy, copper alloy, silicon alloy, nickel alloy and titanium alloy.
  • the conductive carbon includes one of graphite fibers, carbon nanotubes, graphite flakes, conductive carbon fibers, and graphene.
  • preparing the precursor further includes at least one of drying and dispersing the mixed pre-mixture.
  • the temperature of the drying treatment is 30° C. to 400° C., and the drying treatment time is 1 h to 15 h.
  • the dispersion treatment includes at least one of mechanical stirring, ultrasonic dispersion and grinding dispersion.
  • preparing the precursor further includes centrifuging the mixed pre-mixture.
  • the rotational speed of the centrifugation is 100 rpm to 3000 rpm, and the centrifugation time is 10 min to 60 min.
  • the at least two sets of premixes include a first premix and a second premix.
  • the mass ratio of the active material to the first carbon source in the first premix is (80-120):(1-20).
  • the mass ratio of the active material to the first carbon source in the second premix is (40-80):(1-30).
  • the mass percent content of the active substance in the first premix is greater or less than the mass percent content of the active substance in the second premix.
  • the step of preparing the precursor includes: mixing the first premix and the second premix to obtain the precursor.
  • the step of preparing the precursor is as follows: drying and dispersing the first premix; mixing the dispersed first premix and the second premix to obtain a mixture, and drying the mixture Mix with the third premix to prepare a precursor.
  • the mass ratio of the active substance to the additive is (80-120):(1-20).
  • the mass ratio of the active substance to the additive is (40-80):(1-10).
  • the step of mixing at least two sets of premixes to prepare the precursor includes mixing at least three sets of premixes to prepare the precursor.
  • the step of mixing the at least three sets of premixes includes sequentially mixing the premixes according to the mass percentage content of the active substance in the premixes from high to low.
  • the at least two sets of premixes also include a third premix.
  • the third premix is prepared by mixing the active material, the first carbon source in a mass ratio of (10-40):(10-40) and a solvent.
  • the mass percent content of the active substance in the second premix is greater than the mass percent content of the active substance in the third premix.
  • the step of preparing the precursor includes: sequentially mixing the first premix, the second premix, and the third premix to obtain the precursor.
  • the step of preparing the precursor is as follows: drying and dispersing the first premix; mixing the dispersed first premix and the second premix to obtain a mixture, and drying the mixture Mix with the third premix to prepare a precursor.
  • the mass ratio of the active substance to the additive is (10-40):(1-10).
  • the flow rate ratio of the first premix and the second premix is (1-15): 1.
  • the first premix is mixed with the second premix to obtain a mixture
  • the flow rate of the mixture and the third premix is mixed during the process of mixing the mixture with the third premix
  • the ratio is (1 ⁇ 15):1.
  • the precursor before the heat treatment of the precursor, it also includes densifying the precursor or the premix, so that the porosity of the aggregate is ⁇ 10% and the compressive hardness is ⁇ 100Mpa.
  • the densification treatment includes at least one of fusion treatment, kneading extrusion treatment, molding treatment, isostatic pressing treatment, and dipping treatment.
  • the fusion treatment is mechanical fusion.
  • the rotation speed of the fusion machine used for the mechanical fusion is 500r/min-3000r/min.
  • the fusion machine tool gap width used for the mechanical fusion is 0.01 cm to 0.5 cm.
  • the mechanofusion time is at least 0.5 h.
  • drying treatment is also included before the thermal treatment of the precursor.
  • the temperature of the drying treatment is 30°C-400°C, and the time of the drying treatment is 1h-15h.
  • the heat treatment temperature is 600° C. to 1200° C.
  • the heat treatment time is 1 h to 15 h.
  • a protective gas is passed through the heat treatment process.
  • the protective gas includes at least one of nitrogen, helium, neon, argon, and krypton.
  • the method further includes carbon coating the aggregate.
  • the step of carbon coating treatment includes: mixing the precursor and the second carbon source, and heat treatment.
  • the mass ratio of the precursor to the second carbon source is (30-100):(10-70).
  • the step of carbon coating treatment includes: mixing the aggregate with a second carbon source, and carbonization treatment.
  • the second carbon source includes sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide , polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride and at least one of asphalt.
  • the mass ratio of the aggregate to the second carbon source is (30-100):(10-70).
  • the temperature of the carbonization treatment is 600°C-1200°C, and the time of the carbonization treatment is 1h-15h.
  • the present disclosure further provides a negative electrode material, including an aggregate, the aggregate includes an active material and a carbon material, the carbon material is dispersed among the active materials, and the mass percentage of the aggregate is 100%. Calculated, the mass percentage of the active material on the surface of the aggregate is less than the mass percentage of the active material inside the aggregate.
  • the present disclosure also provides a lithium ion battery, which includes the negative electrode material or the negative electrode material prepared by the preparation method.
  • FIG. 1 is a schematic structural view of an anode material provided by an embodiment of the present disclosure
  • FIG. 2 is a schematic flow chart of a method for preparing an anode material provided by an embodiment of the present disclosure.
  • the negative electrode material of one embodiment, as shown in Figure 1, comprises aggregate 10, and aggregate 10 comprises active material and carbon material; Wherein, the mass percent content of active material in aggregate is from the center of aggregate to surface Gradually decreases.
  • the mass percentage of the active substance in the aggregate is measured by the following method:
  • an energy dispersive spectrometer was used to perform EDS point scanning, and the mass percentage of active substances in the aggregate at different positions was measured.
  • the negative electrode material of this embodiment includes aggregates, and the aggregates include active materials and carbon materials, and the number of active material particles in the center of the core of the aggregate is relatively large, and the number of active material particles far away from the center of the core gradually decreases, that is, the active material in the aggregate
  • the mass percentage content of ⁇ gradually decreases from the center of the aggregate to the surface.
  • the active material is distributed in the carbon material, preferably, the active material is dispersed in the carbon material with a certain concentration gradient.
  • the total mass percentage of active substances is 5% to 90% based on 100% mass percentage of aggregates.
  • the total mass percentage of the active substance is 5% to 80% based on the mass percentage of the aggregate as 100%; specifically, the mass percentage of the active substance can be 5%, 7%, 10%, 20%, 25%, 35%, 40%, 50%, 55%, 60%, 70%, 75%, 80%, etc.
  • the mass percentage of the active substance can be 5%, 7%, 10%, 20%, 25%, 35%, 40%, 50%, 55%, 60%, 70%, 75%, 80%, etc.
  • other values within the above range can also be used. This is not limited.
  • the mass ratio of active material to carbon material gradually decreases from the center of the aggregate to the surface
  • the mass percentage of the carbon material in the aggregate is tested according to the test method of the mass percentage of the active material in the aggregate, and the ratio between the two is the mass ratio of the active material to the carbon material.
  • this structure is more conducive to controlling the expansion of the active material inside the aggregate, avoiding the damage of the surface layer due to the expansion effect of the active material, and improving the stability of the SEI film on the surface of the negative electrode material. It has good surface and interface stability, reduces the expansion rate of the negative electrode material with the addition of active materials, thereby improving the cycle stability of the negative electrode material and improving the battery cycle performance.
  • the mass percentage of the active material on the aggregate surface is 2%-55%.
  • the mass percent content of the active substance on the aggregate surface can be 2%, 5%, 7.5%, 10%, 12.5%, 15%, 20%, 22.5%, 25%, 27.5%, 30%, 35% %, 40%, 45%, 50% or 55%, etc., of course, can also be other values within the above range, which are not limited here.
  • the mass percent content of the active substance on the surface of the aggregate is defined as: the mass percent content of the active substance at any point on the surface of the aggregate; the test method is: use an energy spectrometer to conduct EDS at any point on the edge of the SEM section of the aggregate Point scanning, test to obtain the mass percentage of active substances on the aggregate surface.
  • the mass ratio of the active material to the carbon material in the aggregate has a maximum value of E, a minimum value of F, and E-F ⁇ 0.5.
  • the aggregate structure formed within this range is more conducive to controlling the expansion of the active material inside the aggregate, avoiding the damage to the surface layer by the expansion effect of the active material, improving the stability of the SEI film on the surface of the negative electrode material, and having a good surface Interface stability, reducing the expansion rate of the negative electrode material with the addition of active materials, thereby improving the cycle stability of the negative electrode material and improving the battery cycle performance.
  • E-F Preferably, E-F ⁇ 2.
  • E-F may be 0.5, 0.8, 1, 1.5, 2, 2.1, 2.3, 2.5, 2.8, 3.0, 3.5, 4.0, 5.5, etc., which is not limited here.
  • the total mass ratio of the active material to the carbon material is 0.5-8.
  • the total mass ratio of the active material to the carbon material refers to the ratio of the total mass of the active material in the aggregate to the total mass of the carbon material.
  • the total mass ratio of the active material to the carbon material can be 0.5, 1, 1.5, 2, 2.6, 3, 3.9, 4, 4.8, 5, 5.3, 6, 6.7, 7.2 or 8, etc., of course, it can also be the above-mentioned Other values within the range are not limited here.
  • A is the minimum value of T value in N test results
  • B is the maximum value of T value in N test results (N ⁇ 10)
  • the distance from the aggregate surface to the center is L 0 ⁇ m
  • the center of the test area to The distance between the centers of the aggregates is L 1 ⁇ m
  • the T value of the central position of the test area is defined as T 0
  • T 0 satisfies the relationship: T 0 ⁇ B-(BA)L 1 /L 0 .
  • the aggregate material that satisfies this relationship has a more dense interior, stronger compressive stress, a more stable structure, and well gathers the active material at the inner core of the aggregate, which inhibits the negative electrode material from charging and discharging. swell.
  • the active material refers to a material that can react with lithium and can perform lithium intercalation and deintercalation, that is, a type of material that can increase the capacity of the negative electrode material.
  • the active material includes at least one of Li, Na, K, Sn, Ge, Si, SiO x , Fe, Mg, Ti, Zn, Al, P and Cu; wherein, 0 ⁇ x ⁇ 2.
  • the active material can be a metal element.
  • the active material can be specifically Si particles, Sn particles, Ge particles, and Al particles.
  • the active material can also be a silicon-lithium alloy, a silicon-magnesium alloy Etc.
  • the active material includes elemental particles or alloys thereof, or a combination of different active material materials.
  • the median diameter of the active material is 1 nm to 300 nm. Specifically, it can be 1nm, 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 100nm, 200nm or 300nm, etc. Of course, it can also be other values within the above range, which is not limited here.
  • Nano-scale active materials have high surface energy and are prone to agglomeration during charging and discharging. The particles have a strong structure and can inhibit the volume expansion of active materials.
  • the median diameter of the active material is 1 nm to 300 nm, more preferably 1 nm to 100 nm.
  • the carbon materials include graphitic carbon materials and non-graphitic carbon materials.
  • graphitic carbon materials include natural graphite and/or artificial graphite, wherein artificial graphite includes mesocarbon microspheres; said non-graphitic carbon materials include amorphous carbon, crystalline carbon, hard carbon and soft carbon. at least one of .
  • the technical solution provided by the present disclosure to suppress material expansion by concentrating the active material inside the aggregate can be applied to different carbon negative electrode materials.
  • the aggregate further includes at least one of a metal oxide, a conductivity enhancer.
  • the general chemical formula of the metal oxide is M x O y , 0.2 ⁇ y/x ⁇ 3, wherein M includes Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca or Zn At least one of; specifically, the metal oxide may be GeO 2 , SnO 2 , ZnO, TiO 2 , Fe 3 O 4 , MgO, CuO, and the like.
  • the volume expansion change rate of the selected metal oxide during the lithium intercalation process is lower than that of the active material. Therefore, combining metal oxides with active materials can reduce the expansion of active materials and improve long-term cycle performance.
  • the metal oxide is in the form of flakes and/or strips.
  • the aspect ratio of the metal oxide is greater than 2. It should be noted that, when the metal oxide is elongated, the aspect ratio specifically refers to the ratio of the length of the metal oxide to the particle diameter, and the particle diameter here refers to the ratio perpendicular to the length direction of the elongated metal oxide. The maximum linear distance between two points on the periphery of the cross-section; when the metal oxide is in the form of flakes, the aspect ratio specifically refers to the ratio of the length to the width of the flake metal oxide. Specifically, the aspect ratio of the metal oxide can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 12, 15, 17, 18, 22, etc. Of course, it can also be Other values within the above range are not limited here. When the aspect ratio of the metal oxide is greater than 2, the physical binding force between the metal oxide and the active material can be improved, thereby improving the inhibition and buffering effect on the volume expansion of the active material, and improving the cycle performance of the negative electrode.
  • the mass ratio of the metal oxide to the active material is 1 ⁇ 20:100.
  • the mass ratio of the metal oxide to the active material can be 1:100, 1.5:100, 2:100, 3:100, 4.5:100, 5:100, 6:100, 7:100, 8:100, 9:100 and so on.
  • other values within the above range may also be used, which are not limited here.
  • the metal oxide and the active material are distributed in the aggregate, and the carbon material is filled between the active material and the metal oxide.
  • a conductivity enhancer is added to the aggregate, which can provide more transport channels for carriers on the one hand, thereby enhancing the transport of carriers inside the material; on the other hand, it also has Excellent mechanical properties, can be used as a structural support to enhance the stability of the material.
  • the mass ratio of the conductivity enhancer to the active material is 0.01 ⁇ 20:100. Specifically, it can be 0.01:100, 1:100, 2.5:100, 3:100, 5:100, 7.5:100, 10:100, 12.5:100, 15:100, 20:100 and so on. Of course, other values within the above range may also be used, which are not limited here.
  • the conductivity enhancer has a conductivity of 10 0 S/m ⁇ 10 8 S/m.
  • the conductivity of the conductivity enhancer may be 1 S/m, 10 S/m, 100 S/m, 10 3 S/m, 10 4 S/m, 10 5 S/m, 10 8 S/m and the like.
  • the conductivity enhancer is in the form of flakes and/or strips.
  • the aspect ratio of the conductivity enhancer is 2-5000. It should be noted that when the conductivity enhancer is strip-shaped, the aspect ratio specifically refers to the ratio of the length of the particle to the particle diameter of the particle, where the particle diameter refers to the length perpendicular to the length direction of the strip-shaped conductivity enhancer. The maximum linear distance between two points on the periphery of the section; when the metal oxide is in the form of a sheet, the aspect ratio specifically refers to the ratio of the length to the width of the sheet-shaped conductivity enhancer.
  • the aspect ratio of the conductivity enhancer can be 2, 30, 46, 150, 360, 670, 800, 900, 1500, 2000, 3000, 4000, 5000, etc., of course, it can also be other values within the above range , is not limited here.
  • the conductivity enhancer with an aspect ratio within this range has excellent mechanical properties, and can be used as a structural support to enhance the stability of the material, thereby improving the inhibition and buffering effect on the volume expansion of the active material, and improving the cycle performance of the negative electrode.
  • the conductivity enhancer includes alloy materials and their alloys and/or conductive carbon.
  • the alloy material includes at least one of zinc alloy, aluminum alloy, copper alloy, silicon alloy, nickel alloy and titanium alloy.
  • the conductive carbon includes one of graphite fibers, carbon nanotubes, graphite flakes, conductive carbon fibers, and graphene.
  • the porosity of the aggregate is ⁇ 10%, and the compressive hardness of the aggregate is ⁇ 100Mpa.
  • the porosity of the aggregate is low, that is, its compactness is high, which helps to increase the energy density of the composite material on the one hand, and on the other hand, even if the surface layer of the high-density material is damaged, the electrolyte is not easy to penetrate into it.
  • the highly dense aggregate has a high compressive hardness, which can hedge The stress effect brought by the expansion improves the structural stability of the negative electrode material, which can effectively inhibit the volume expansion of the negative electrode material and reduce its expansion rate, thereby improving the battery cycle performance.
  • the porosity of the aggregate is ⁇ 10%
  • the porosity of the aggregate may specifically be 10%, 9%, 9.5%, 8%, 8.5%, 7.5%, 7%, 6.5%, 6%, or 5% and so on, of course, can also be other values within the above range, which are not limited here.
  • the low porosity of the aggregates that is, their high density, is conducive to the formation of a stable solid electrolyte film and reduces the contact between the electrolyte and the active material.
  • the porosity of the aggregates is ⁇ 5%, more preferably, the porosity of the aggregates is ⁇ 3%.
  • the compressive hardness of the aggregate is ⁇ 100Mpa; the compressive hardness of the aggregate can be 100Mpa, 250Mpa, 300Mpa, 450Mpa, 500Mpa, 750Mpa, 900Mpa, 1150Mpa, 1200Mpa or 1250Mpa, etc., of course, it can also be other values within the above range , is not limited here. Because of its strong rigidity and strong particle structure stability, it can resist a certain volume expansion stress, thereby reducing expansion and improving battery cycle stability.
  • the compressive hardness of the aggregate is ⁇ 200Mpa, more preferably, the compressive hardness of the aggregate is ⁇ 400Mpa.
  • the aggregate density satisfies the following relationship: the difference between the tested density of aggregates and the average density of aggregates is ⁇ 5%. The closer the density of the aggregate particles is to the average density, the smaller the difference, indicating that the pores inside the particles are less and denser, which is conducive to the formation of a stable solid electrolyte film and reduces the contact between the electrolyte and the active material.
  • the aggregate density is calculated as follows: ( ⁇ 1- ⁇ 2)/ ⁇ 2 ⁇ 5%, where ⁇ 1 is the test density of the aggregate, and ⁇ 2 is the average density of the aggregate;
  • ⁇ 2 is the sum of the value of the mass percentage content of each component in the aggregate * the theoretical density of each component in the aggregate.
  • test density ⁇ 2 of the aggregates was obtained by the following method:
  • ⁇ 2 mass percentage of active material in the aggregate*theoretical density of active material+mass percentage of carbon material in the aggregate*carbon material theory density.
  • ⁇ 2 mass percentage of active materials in aggregates * theoretical density of active materials + mass percentage of metal oxides in aggregates * metal oxides Theoretical density + mass percentage of carbon material in the aggregate * theoretical density of carbon material.
  • ⁇ 2 mass percentage of active materials in aggregates%*theoretical density of active materials+mass percentage of metal oxides in aggregates Content*theoretical density of metal oxide+mass percentage of conductive enhancer in aggregate*theoretical density of conductive enhancer+mass percentage of carbon material in aggregate*theoretical density of carbon material.
  • the negative electrode material also includes a carbon layer 20 coated on at least part of the surface of the aggregate 10 , preferably, the carbon layer is distributed on the surface of the aggregate, and the carbon layer includes amorphous carbon.
  • the carbon layer has a thickness of 10 nm to 2000 nm. It can be understood that the carbon layer covering the surface of the aggregate can reduce the contact between the active material and the electrolyte, reduce the formation of passivation film, and improve the reversible capacity of the battery.
  • the thickness of the carbon layer can be 10nm, 50nm, 80nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 600nm, 1000nm, 1500nm or 2000nm, etc. Of course, it can also be other thicknesses within the above range. value, which is not limited here. If the carbon layer is too thick, the transmission efficiency of lithium ions will be reduced, which is not conducive to the high-rate charge and discharge of the material, and the overall performance of the negative electrode material will be reduced; if the carbon layer is too thin, it will not be conducive to increasing the conductivity of the negative electrode material and the volume expansion inhibition performance of the material is weak. Resulting in long cycle performance differentials.
  • the thickness of the carbon layer is 50nm-800nm; more preferably, the thickness of the carbon layer is 100nm-500nm.
  • the median particle size of the negative electrode material is 0.5 ⁇ m to 30 ⁇ m; specifically, it can be 0.5 ⁇ m, 1 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 13 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, 25 ⁇ m or 30 ⁇ m, etc., of course it can also be are other values within the above range, and are not limited here. It can be understood that controlling the average particle size of the negative electrode material within the above range is beneficial to the improvement of the cycle performance of the negative electrode material.
  • the specific surface area of the negative electrode material is ⁇ 10m 2 /g, specifically 10m 2 /g, 8m 2 /g, 7m 2 /g, 5m 2 /g, 3m 2 /g, 2m 2 /g , 1m 2 /g, or 0.5m 2 /g, etc., of course, can also be other values within the above range, which are not limited here. It can be understood that controlling the specific surface area of the negative electrode material within the above range is beneficial to suppress volume expansion and improve the cycle performance of the negative electrode material.
  • the specific surface area was measured by a McRae surface area tester.
  • the median particle size mentioned in the present disclosure refers to the average particle size, and its physical meaning is the particle size corresponding to when the cumulative particle size distribution percentage of the particles reaches 50%, which is tested by a Malvern particle size analyzer.
  • the Malvern Particle Size Analyzer uses the light scattering phenomenon of particles to comprehensively convert the particle size distribution of the measured particles according to the distribution of scattered light energy.
  • the negative electrode materials in the above-mentioned embodiments can be combined arbitrarily if there is no conflict with each other, for example, the specific surface area, the porosity of the aggregate, and the compressive strength are limited by combination.
  • the present disclosure provides a method for preparing an anode material, the method comprising the following steps:
  • Step S10 mixing at least two groups of premixes to prepare a precursor, wherein each group of premixes includes an active material, a first carbon source and a solvent, and the active material in the at least two groups of premixes The mass percentage content is different;
  • Step S20 heat-treating the precursor to carbonize the first carbon source to obtain aggregates.
  • the negative electrode material prepared in this embodiment includes aggregates, the aggregates include active materials and carbon materials, and the mass percentage of active materials in the aggregates gradually decreases from the center to the surface of the aggregates.
  • the premix includes an active material, a carbon source and a solvent, and the premix with different mass percentages of the active material is mixed and subjected to heat treatment to obtain the aggregate, the aggregate
  • the mass percentage of the active material in the aggregate gradually decreases from the center to the surface of the aggregate.
  • Step S10 mixing at least two groups of premixes to prepare a precursor, wherein each group of premixes includes an active material, a first carbon source and a solvent, and the active material in the at least two groups of premixes The mass percentages are different.
  • preparation steps of each group of premix are specifically obtained by mixing the active material, the first carbon source and the solvent.
  • the precursor can be obtained by mixing two sets of premixes; it can also be obtained by mixing at least three sets of premixes.
  • the step of mixing at least three sets of premixes includes mixing the premixes sequentially according to the mass percentage content of the active substances in the components from high to low; by configuring more than three sets of different active substances Concentration of the premix, each group of premixes are mixed in sequence according to the mass percentage of the active substance in the premix from high to low, as the high active substance content as the central core, and then mixed with the low concentration components in turn Agglomerates prepared by mixing and heat treatment, the proportion of the active material components gradually increases from the particle surface to the particle center of the aggregate.
  • the difference between the maximum mass percent content of the active substance and the minimum mass percent content is 20%-90%.
  • the difference between the maximum value of the mass percentage content of the active substance and the minimum value of the mass percentage content is 20%, 25%, 30%, 35%, 45%, 50%, 55%, 65%, 75% %, 80% or 90%; of course, it can also be other values within the above range, which is not limited here.
  • the active material includes at least one of Li, Na, K, Sn, Ge, Si, Fe, SiO x (0 ⁇ x ⁇ 2), Mg, Ti, Zn, Al, P, and Cu;
  • the active material can be a metal element.
  • the active material can be specifically Si particles, Sn particles, Ge particles, and Al particles; in other embodiments, the active material can also be a silicon-lithium alloy, a silicon-magnesium alloy Etc.
  • the active material includes elemental particles or alloys thereof, or a combination of different active material materials.
  • the first carbon source includes sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyethylene At least one of vinylidene fluoride, polyacrylonitrile, polyvinyl chloride, and asphalt.
  • the solvent includes an organic solvent.
  • the organic solvent includes at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and pentanol.
  • At least one set of the premixes further includes at least one of additives, metal oxides and conductivity enhancers.
  • At least one of additives, metal oxides and conductivity enhancers is added to at least one group of premixes in the step of preparing the precursor by mixing at least two groups of premixes.
  • additives when two sets of premixes are used to mix and prepare the precursor, at least one of additives, metal oxides and conductivity enhancers can be added to one set of premixes, or two sets can be added at the same time.
  • types of additives, metal oxides and conductivity enhancers in each group of premixes may be the same or different, and there is no limitation here.
  • the additive can effectively enhance the connection stability of the active material and the carbon material, thereby forming a firm system and reducing the expansion rate of the pole piece.
  • the additive includes at least one of a surfactant and a coupling agent.
  • Surfactants include octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, n-eicosic acid, palmitic acid, myristic acid, undecanoic acid, cetyltrimethyl bromide At least one of chemical amines and polyvinylpyrrolidone.
  • Coupling agents include silane coupling agents and/or titanate coupling agents.
  • Silane coupling agents include ⁇ -aminopropyltriethoxysilane, ⁇ -glycidoxypropyltrimethoxysilane, ⁇ -methacryloxypropyltrimethoxysilane.
  • the general chemical formula of the metal oxide is M x O y , 0.2 ⁇ y/x ⁇ 3, wherein M includes Sn, Ge, Fe, Cu, Ti, Na, Mg, Al, Ca and Zn at least one of the
  • the metal oxide is in the form of flakes and/or strips.
  • the aspect ratio of the metal oxide is greater than 2.
  • the mass ratio of the metal oxide to the active material is 1 ⁇ 20:100.
  • the mass ratio of the conductivity enhancer to the active material is 0.01 ⁇ 20:100.
  • the conductivity enhancer has a conductivity of 10 0 S/m ⁇ 10 8 S/m.
  • the conductivity enhancer is in the form of flakes and/or strips.
  • the aspect ratio of the conductivity enhancer is 2-5000.
  • the conductivity enhancer includes at least one of alloy material and conductive carbon.
  • the alloy material includes at least one of zinc alloy, aluminum alloy, copper alloy, silicon alloy, nickel alloy and titanium alloy.
  • the conductive carbon includes one of graphite fibers, carbon nanotubes, graphite flakes, conductive carbon fibers, and graphene.
  • the mixing method of the active material, the first carbon source and the solvent may include magnetic stirring, mechanical stirring, ultrasonic dispersion, grinding dispersion, etc. Agglomeration of the substance and the dispersion of the active substance into smaller nanoparticles can be achieved.
  • each group of premixes to prepare the precursor before mixing each group of premixes to prepare the precursor, it also includes performing wet ball milling on each group of premixes, so that the particle size of the active material particles reaches 1 nm to 300 nm.
  • the dispersion time of wet ball milling can be controlled within 0.5h-10h, and the components can be mixed more uniformly through sufficient grinding.
  • the individual sets of premixes are combined and then dried.
  • the temperature of the drying treatment is 30°C-400°C, and the time of the drying treatment is 1h-15h.
  • centrifugation is performed after mixing the premixes of each group.
  • the rotational speed of centrifugation is 100 rpm to 3000 rpm, for example, 100 rpm, 500 rpm, 1000 rpm, 2000 rpm or 3000 rpm, and the centrifugation time is 10 min to 60 min, for example, it may be 10 min, 20 min, 30 min, 40 min or 50 min.
  • it also includes densifying the precursor or premix, through which the connection between the active material and the carbon material can be effectively enhanced, the pores between each other can be reduced, and the densification can be improved, so that the prepared The porosity of aggregates is ⁇ 10%, and the compressive hardness of aggregates is ⁇ 100Mpa.
  • the densification treatment includes at least one of fusion treatment, kneading extrusion treatment, molding treatment, isostatic pressing treatment, and impregnation treatment.
  • fusion treatment kneading extrusion treatment
  • molding treatment isostatic pressing treatment
  • impregnation treatment impregnation treatment
  • the fusion treatment is mechanical fusion.
  • the connection between the active material and the carbon material can be effectively enhanced, the pores between them can be reduced, and the densification can be improved.
  • the rotation speed of the fusion machine is 500r/min to 3000r/min, specifically 500r/min, 1000r/min, 1500r/min, 2000r/min, 2500r/min or 3000r/min, etc.
  • the fusion machine tool gap width is 0.01cm ⁇ 0.5cm, specifically 0.01cm, 0.05cm, 0.1cm, 0.15cm, 0.2cm, 0.25cm, 0.3cm or 0.5cm, etc.; the fusion time is at least 0.5h, specifically It can be 0.5h, 0.8h, 0.9h, 1.0h, 1.5h or 2h, etc., which is not limited here.
  • the precursor of this embodiment can be prepared by mixing two premixes.
  • At least two sets of premixes include a first premix and a second premix.
  • the active material, the first carbon source are mixed according to the mass ratio of (80-120): (1-20) and the solvent to prepare the first premix; the active material, the first carbon source The second premix is prepared by mixing the mass ratio of (40-80):(1-30) with the solvent.
  • the mass ratio of the active substance to the first carbon source can be 100:12.9, 100:10.9, 100:12.9, 100:15.9, 100:11.9, 100:15.9, 100:22.9, etc. , of course, can also be other values within the above range, which is not limited here.
  • the mass ratio of the active substance to the first carbon source can be 60:22.9, 50:20.9, 67:12.9, 50:22.9, 70:21.9, 78:20.9, etc., of course it can also be are other values within the above range, and are not limited here.
  • the mass ratio of the active substance to the additive may be (80-120):(1-20); 100:12.9, 100:10.9, 100:12.9, 100:15.9, 100: 11.9, 100: 15.9, 100: 22.9, etc.
  • other values within the above range may also be used, which are not limited here.
  • the mass ratio of the active substance to the additive may be (40-80):(1-10); the mass ratio of the active substance to the carbon source may be 40:22.9, 50: 20.9, 45: 12.9, 55: 22.9, 60: 21.9, 70: 20.9, etc., of course, can also be other values within the above range, which are not limited here.
  • the mass percent content of the active substance in the first premix is greater than the mass percent content of the active substance in the second premix.
  • the step of preparing the precursor at this time includes: mixing the first premix and the second premix to obtain the precursor.
  • the flow rate ratio of the first premix and the second premix is (1-15):1; specifically, it can be 1:1, 3 :1, 5:1, 8:1, 10:1, 12:1, or 15:1, etc. Of course, other values within the above range may also be used, which are not limited here. It can be understood that the content of each component in the dispersed product and the second premix is different, and by controlling the addition ratio and flow rate of the two, it is beneficial to obtain aggregates with a concentration gradient.
  • the step of preparing the precursor specifically includes: drying and dispersing the first premix.
  • the drying temperature is 30°C to 400°C, specifically 30°C, 40°C, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 250°C, 280°C °C, 300 °C or 400 °C, etc.
  • the drying time is 1h to 15h, specifically 1h, 3h, 5h, 7h, 9h, 10h, 12h or 15h, etc.
  • the drying method can be, for example, oven drying , freeze-drying, stirring and evaporating to dryness, spray drying, etc., the drying treatment in this embodiment can remove the solvent in the precursor solution as much as possible.
  • the dispersion is grinding dispersion
  • the dispersion time is 0.5-9h, specifically 0.5h, 1.5h, 2.5h, 3.5h, 4.5h, 5.5h, 7.5h or 9h, etc., in this embodiment Grinding and dispersing, controlling the particle size after dispersion, as the core.
  • the dispersed product and the second premix are mixed and dried to obtain a precursor.
  • the flow rate ratio of the dispersed product to the second premix is (1 ⁇ 15):1.
  • the dispersed product and the second premix are also centrifuged.
  • the centrifugation time is 30 min to 60 min, specifically, it can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, etc. Of course, it can also be other values within the above range.
  • mixing the dispersed product with the second premix further includes drying.
  • the temperature of the drying treatment is 30°C to 400°C, specifically 30°C, 40°C, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 250°C, 280°C, 300°C or 400°C, etc.
  • the drying time is 1h to 15h, specifically 1h, 3h, 5h, 7h, 9h, 10h, 12h or 15h, etc.
  • the drying method can be, for example, oven drying Drying, freeze drying, stirring and evaporating to dryness, spray drying, etc., the drying treatment in this embodiment can remove the solvent in the precursor solution as much as possible.
  • the dried precursor may be subjected to densification treatment, the densification treatment includes fusion treatment, and the fusion treatment is mechanical fusion.
  • the connection of active materials and carbon materials can be effectively enhanced, the pores between them can be reduced, and the densification can be improved.
  • the speed of the fusion machine is 500r/min ⁇ 3000r/min, which can be 500r/min, 1000r/min, 1500r/min, 2000r/min, 2500r/min or 3000r/min, etc. 0.01cm ⁇ 0.5cm, specifically 0.01cm, 0.05cm, 0.1cm, 0.15cm, 0.2cm, 0.25cm, 0.3cm or 0.5cm, etc.; the fusion time is at least 0.5h, specifically 0.5h, 0.8 h, 0.9h, 1.0h, 1.5h or 2h, etc., are not limited here.
  • the precursor of this embodiment may be prepared by mixing three groups of premixes.
  • a third premix may also be included; the operations of the first premix, the second premix and mixing in this embodiment are the same as above, It will not be described in detail here.
  • the active material, the first carbon source are mixed at a mass ratio of (10-40): (10-40) and a solvent to prepare a third premix; specifically, the active material and the first carbon source
  • the mass ratio can be 30:22.9, 30:20.9, 35:12.9, 50:22.9, 30:21.9, 20:20.9, etc.
  • it can also be other values within the above range, which is not limited here.
  • the mass percent content of the active substance in the second premix is greater than the mass percent content of the active substance in the third premix.
  • the mass ratio of the active substance to the additive is (10-40):(1-10); specifically, the mass ratio of the active substance to the additive can be 30:5.5, 30 : 3.5, 35: 5.5, 20: 5.5, 10: 8.5, 20: 4.5, etc.
  • the mass ratio of the active substance to the additive can be 30:5.5, 30 : 3.5, 35: 5.5, 20: 5.5, 10: 8.5, 20: 4.5, etc.
  • other values within the above range may also be used, which are not limited here.
  • the step of preparing the precursor includes: mixing the first premix with the second premix and the third premix in sequence to obtain the precursor; specifically, first configuring three groups of components with different concentrations, of which the first The active substance content is the highest in the premix, and the active substance content is the lowest in the third premix; then the first premix is used as the central core of the high active substance content, and the second premix and the third premix with low concentrations are sequentially combined.
  • the mixture is mixed; the final heat treatment is used to obtain aggregates, and the proportion of active material components in the aggregates gradually increases from the surface of the particles to the center of the particles.
  • the flow rate ratio of the first premix and the second premix is (1-15):1
  • the mixed mixture of the first premix and the second premix is mixed with the third premix
  • the mixing flow rate ratio is (1-15):1.
  • the step of preparing the precursor is as follows: drying and dispersing the first premix; mixing the dispersed first premix and the second premix to obtain a mixture, and drying the mixture with the third The premix is mixed to prepare a precursor.
  • the flow rate ratio of the mixture to the third premix is (1-15):1; specifically, it can be 1:1, 3:1, 5:1, 8:1, 10 :1, 12:1, or 15:1, etc.
  • the flow rate ratio of the mixture to the third premix is (1-15):1; specifically, it can be 1:1, 3:1, 5:1, 8:1, 10 :1, 12:1, or 15:1, etc.
  • other values within the above range may also be used, which are not limited here.
  • the mixture and the third premix also need to be centrifuged.
  • the centrifugation time is 30 min to 60 min, specifically, it can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, etc., of course, it can also be other values within the above range.
  • drying is further included after mixing the mixture with the third premix.
  • the temperature of the drying treatment is 30°C to 400°C, specifically 30°C, 40°C, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 250°C, 280°C, 300°C or 400°C, etc.
  • the drying time is 1h to 15h, specifically, it can be 1h, 3h, 5h, 7h, 9h, 10h, 12h or 15h, etc.
  • the drying method can be, for example, oven drying Drying, freeze drying, stirring and evaporating to dryness, spray drying, etc., the drying treatment in this embodiment can remove the solvent in the precursor solution as much as possible.
  • the dried precursor may be subjected to densification treatment, the densification treatment includes fusion treatment, and the fusion treatment is mechanical fusion.
  • the connection of active materials and carbon materials can be effectively enhanced, the pores between them can be reduced, and the densification can be improved.
  • the speed of the fusion machine is 500r/min ⁇ 3000r/min, which can be 500r/min, 1000r/min, 1500r/min, 2000r/min, 2500r/min or 3000r/min, etc. 0.01cm ⁇ 0.5cm, specifically 0.01cm, 0.05cm, 0.1cm, 0.15cm, 0.2cm, 0.25cm, 0.3cm or 0.5cm, etc.; the fusion time is at least 0.5h, specifically 0.5h, 0.8 h, 0.9h, 1.0h, 1.5h or 2h, etc., are not limited here.
  • Step S20 heat-treating the precursor to carbonize the first carbon source to obtain aggregates.
  • the heat treatment may be, for example, vacuum sintering, hot pressing sintering or normal pressure sintering.
  • the heat treatment temperature is 400°C to 1200°C, for example, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1200°C, 1200°C, etc.
  • the heat treatment temperature is 600°C to 1000°C.
  • the heat treatment time is 1 h to 15 h, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, etc.
  • the heating rate during heat treatment is 1°C/min to 30°C/min, specifically 1°C/min, 5°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min or 30°C °C/min etc.
  • the heating rate during the heat treatment is 1° C./min to 15° C./min.
  • a protective gas is used in the heat treatment process, and the protective gas includes at least one of nitrogen, helium, neon, argon and krypton.
  • a step of carbon coating the aggregate is also included.
  • the step of carbon coating treatment includes: mixing the precursor and the second carbon source, and heat treatment.
  • the second carbon source includes sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, polyethylene glycol, At least one of vinylidene fluoride, polyacrylonitrile, polyvinyl chloride and asphalt.
  • the particle size of the precursor is 0.5 ⁇ m to 20 ⁇ m, specifically, it can be 0.5 ⁇ m, 1 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 13 ⁇ m, 15 ⁇ m, 18 ⁇ m or 20 ⁇ m, etc. Of course, it can also be other particles within the above range. value, which is not limited here. It can be understood that controlling the average particle size of the negative electrode material within the above range is beneficial to the improvement of the cycle performance of the negative electrode material.
  • the mass ratio of the precursor to the second carbon source is (30-100):(10-70); specifically, the mass ratio of the precursor to the third carbon source is 100:25, 100:35 , 100:45, 100:55, 100:65, etc., of course, can also be other values within the above range, which are not limited here.
  • the mixing method may include magnetic stirring, mechanical stirring, ultrasonic dispersion, grinding dispersion, and the like.
  • the step of carbon coating treatment includes mixing the aggregates with a second carbon source, and carbonizing the aggregates to form carbon on the surface of the aggregates. Floor.
  • the temperature of the carbonization treatment is 400°C-1200°C, such as 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1200°C, 1200°C, etc.
  • the heat treatment temperature is 600°C to 1000°C.
  • the time for the carbonization treatment is 1 h to 15 h, for example, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, etc.
  • the heating rate during the carbonization treatment is 1°C/min to 30°C/min, specifically 1°C/min, 5°C/min, 10°C/min, 15°C/min, 20°C/min , 25°C/min or 30°C/min, etc.
  • the heating rate during the heat treatment is 1° C./min to 15° C./min.
  • a protective gas is passed through the carbonization process, and the protective gas includes at least one of nitrogen, helium, neon, argon, and krypton.
  • the negative electrode material in this embodiment may not be coated with carbon, and is not limited to the above two methods of carbon coating.
  • the negative electrode material prepared by the above preparation method includes aggregates, the aggregates include active materials and carbon materials, and the mass percentage of active materials in the aggregates gradually decreases from the center to the surface of the aggregates.
  • This structure helps to control the expansion of the active material inside the aggregate, avoiding the damage of the carbon layer on the surface due to the expansion effect of the active material, improving the stability of the SEI film on the surface of the negative electrode material, and having good surface interface stability, thus Improve the cycle stability of the material and reduce the expansion rate.
  • the present disclosure further provides a negative electrode material, including an aggregate, the aggregate includes an active material and a carbon material, and the carbon material is dispersed among the active materials, and the mass percentage of the aggregate is 100%, and the surface of the aggregate is The mass percentage of the active material is less than the mass percentage of the active material inside the aggregate.
  • the present disclosure also provides a lithium ion battery, which includes the above negative electrode material.
  • the negative electrode material prepared in this embodiment includes aggregates and carbon layers coated on the surface of the aggregates.
  • the aggregates include nano-silicon and amorphous carbon, and the amorphous carbon is dispersed between nano-silicons. 61%, the mass percentage of nano-silicon on the aggregate surface is 45%, and the total mass ratio of nano-silicon to amorphous carbon is 1.56.
  • the mass percentage of nano-silicon in the aggregate decreases by 26.2% from the center of the aggregate to the surface, and the mass ratio of nano-silicon to amorphous carbon decreases by 2.2 from the center of the aggregate to the surface; the value of E-F in this embodiment is 2.2.
  • the energy dispersive spectrometer was used to scan the points, and the mass percentages of active substances in the aggregate at three different positions were measured to be 71.2%, 61.0% and 45.0%, respectively.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the central position satisfies the following relationship within 80 measurements : T 0 ⁇ 3.2-2.2L 1 /L 0 .
  • the median particle diameter of the negative electrode material was 14 ⁇ m, and the specific surface area was 4.2 m 2 /g.
  • the aggregate particles were tested by mercury intrusion porosimetry, and the porosity of the aggregate was 2.9%.
  • the negative electrode material prepared in this embodiment includes aggregates and carbon layers coated on the surface of the aggregates.
  • the aggregates include nano-silicon and amorphous carbon, and the amorphous carbon is dispersed between nano-silicons. 55%, the mass percentage of nano-silicon on the aggregate surface is 31%, and the total mass ratio of nano-silicon to amorphous carbon is 1.22.
  • the mass percentage of nano-silicon in the aggregate decreases by 30.4% from the center to the surface of the aggregate, the mass ratio of nano-silicon to amorphous carbon decreases by 1.05 from the center to the surface of the aggregate, and the value of E-F in this embodiment is 1.05.
  • the energy dispersive spectrometer was used for point scanning, and the mass percentages of active substances in the aggregate at four different positions were measured to be 61.4%, 55.3%, 47.4% and 33.0%, respectively.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the central position satisfies the following relationship within 80 measurements : T 0 ⁇ 1.5-1.05L 1 /L 0 .
  • the median diameter of the negative electrode material was 11.8 ⁇ m, and the specific surface area was 4.2 m 2 /g.
  • the third precursor is mechanically fused, the rotation speed of the fusion machine is 500r/min; the width of the tool gap of the fusion machine is 0.15cm; the fusion time is 1.5h.
  • the fused material was placed in a heat treatment furnace, then nitrogen gas was introduced, the temperature was raised to 900° C. for a heat treatment, and the temperature was kept for 3 hours to obtain aggregates.
  • the negative electrode material prepared in this embodiment includes aggregates and carbon layers coated on the surface of the aggregates.
  • the aggregates include nano-silicon and amorphous carbon, and the amorphous carbon is dispersed between nano-silicons. 46%, the mass percentage of nano-silicon on the aggregate surface is 27%, and the total mass ratio of nano-silicon to amorphous carbon is 0.85.
  • the mass percentage of nano-silicon in the aggregate decreases by 29% from the center to the surface of the aggregate, the mass ratio of nano-silicon to amorphous carbon decreases by 0.9 from the center to the surface of the aggregate, and the value of E-F in this embodiment is 0.9.
  • the energy dispersive spectrometer was used to perform point scanning, and the mass percentages of active substances in the aggregate at four different positions were measured to be 56.0%, 46.3%, 33.4% and 27.0%, respectively.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the central position, the T 0 measured within 100 times satisfies the following relationship: T 0 ⁇ 1.26-0.9L 1 /L 0 .
  • the median particle size of the negative electrode material is 11 ⁇ m, and the specific surface area is 2.2m 2 /g.
  • the aggregate particles are tested by mercury porosimetry, and the porosity of the aggregate is 3.3%.
  • the aggregate particles are tested by a nano-indentation instrument , the average compressive hardness of the aggregate obtained is 151Mpa, and the difference between the test density of the aggregate and the average density of nano-silicon and amorphous carbon in the aggregate is 1.5%.
  • Nano-silicon with a median particle size of 50nm, oleic acid and glucose were added to the isopropanol solution at a mass ratio of 15:3.5:12.9, ultrasonicated for 40 minutes, and then ground and dispersed in a ball mill for 2 hours to obtain the second premix.
  • the third precursor is mechanically fused, the rotation speed of the fusion machine is 400r/min; the width of the tool gap of the fusion machine is 0.25cm; the fusion time is 1.5h.
  • the fused material was placed in a heat treatment furnace, then nitrogen gas was introduced, the temperature was raised to 920° C. for a heat treatment, and the temperature was kept for 3 hours to obtain aggregates.
  • the negative electrode material prepared in this embodiment includes aggregates and carbon layers coated on the surface of the aggregates.
  • the aggregates include nano-silicon and amorphous carbon, and the amorphous carbon is dispersed between nano-silicons. 51%, the mass percentage of nano-silicon on the aggregate surface is 43%, and the total mass ratio of nano-silicon to amorphous carbon is 1.17.
  • the mass percentage of nano-silicon in the aggregate decreases by 11.5% from the center of the aggregate to the surface, the mass ratio of nano-silicon to amorphous carbon decreases by 0.5 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 0.5.
  • the energy dispersive spectrometer was used to perform point scanning, and the mass percentages of active substances in the aggregate at four different positions were measured to be 54.5%, 50.3%, 46.4% and 43.0%, respectively.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the central position, the T 0 measured within 90 times satisfies the following relationship: T 0 ⁇ 1.32-0.5L 1 /L 0 .
  • the median particle size of the negative electrode material is 5.2 ⁇ m, and the specific surface area is 4.2m 2 /g.
  • the aggregate particles are tested by mercury porosimetry, and the porosity of the aggregates is 3.9%.
  • the aggregate particles are tested by a nanoindenter. The test shows that the average compressive hardness of the aggregate is 165Mpa, and the difference between the tested density of the aggregate and the average density of nano-silicon and amorphous carbon in the aggregate is 1.1%.
  • nano-silicon, stearic acid and sucrose with a median particle size of 20nm are added to the ethylene glycol solution according to the mass ratio of 50:5.5:22.9, ultrasonicated for 10min, and then ground and dispersed in a ball mill for 2 hours to obtain the second preliminary Mixture; nano-silicon, stearic acid and sucrose with a median particle size of 20nm are added to the ethylene glycol solution in a mass ratio of 30:3.5:22.9, ultrasonicated for 10 minutes, and then ground and dispersed in a ball mill for 2 hours to obtain the third premix things.
  • the second precursor and the third premix are passed into the mixing equipment, and the flow rate ratio of the second precursor and the third premix is controlled to be 6:2, and then dried at 450°C for 4 hours to obtain the third Precursor.
  • the negative electrode material prepared in this embodiment includes aggregates and carbon layers coated on the surface of the aggregates.
  • the aggregates include nano-silicon and amorphous carbon, and the amorphous carbon is dispersed between nano-silicons. 69%, the mass percentage of nano-silicon on the aggregate surface is 54%, and the total mass ratio of nano-silicon to amorphous carbon is 2.22.
  • the mass percentage of nano-silicon in the aggregate decreases by 21.2% from the center of the aggregate to the surface, the mass ratio of nano-silicon to amorphous carbon decreases by 1.86 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 1.86.
  • the energy dispersive spectrometer was used to perform point scanning, and the mass percentages of active substances in the aggregate at three different positions were measured to be 75.2%, 66.3% and 54.0%, respectively.
  • the median particle size of the negative electrode material was 18 ⁇ m, and the specific surface area was 3.2 m 2 /g.
  • nano-tin, polyvinylpyrrolidone and fructose with a median particle size of 100nm to the ethylene glycol solution at a mass ratio of 100:4:11.9, ultrasonicate for 10 minutes, and then grind and disperse in a ball mill for 5 hours to obtain the first premix
  • nano-tin, polyvinylpyrrolidone and fructose with a median particle size of 100nm were added to the ethylene glycol solution at a mass ratio of 45:8.5:21.9, ultrasonicated for 10 minutes, and then ground and dispersed in a ball mill for 2 hours to obtain the second premix things.
  • the negative electrode material that the present embodiment makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises nano-tin and amorphous carbon, and amorphous carbon is dispersed between nano-tin, and nano-tin accounts for the mass of aggregate 66%, the mass percentage of nano-tin on the aggregate surface is 47.5%, and the total mass ratio of nano-tin to amorphous carbon is 3.04.
  • the mass percentage of nano-tin in the aggregate decreases by 32.2% from the center of the aggregate to the surface, the mass ratio of nano-tin to amorphous carbon decreases by 3.04 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 3.04.
  • the energy dispersive spectrometer was used to perform point scanning, and the mass percentages of active substances in the aggregate at four different positions were measured to be 79.7%, 66.3%, 55.4% and 47.5%, respectively.
  • the median particle size of the negative electrode material was 3.9 ⁇ m, and the specific surface area was 4.5 m 2 /g.
  • the third precursor is mechanically fused, the rotation speed of the fusion machine is 550r/min; the width of the tool gap of the fusion machine is 0.15cm; the fusion time is 3h.
  • the fused material was placed in a heat treatment furnace, and then nitrogen gas was introduced, and the temperature was raised to 800° C. for a heat treatment, and the temperature was kept for 3 hours to obtain aggregates.
  • the negative electrode material prepared in this embodiment comprises aggregates and carbon layers coated on the surface of the aggregates.
  • the aggregates include nano-germanium and amorphous carbon, and the amorphous carbon is dispersed between nano-germaniums. 54%, the mass percentage of nano-germanium on the aggregate surface is 38%, and the total mass ratio of nano-germanium to amorphous carbon is 1.17.
  • the mass percentage of nano-germanium in the aggregate decreases by 31.4% from the center of the aggregate to the surface, the mass ratio of nano-germanium to amorphous carbon decreases by 1.31 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 1.31.
  • the energy spectrometer is used for point scanning, and the mass percentages of active substances in the aggregate at six different positions are measured to be 69.5%, 60.3%, 55.7%, 50.4%, and 45.4%, respectively. and 38.0%.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the central position, the T 0 measured within 80 times satisfies the following relationship: T 0 ⁇ 2.26-1.31L 1 /L 0 .
  • the median particle size of the negative electrode material is 13.9 ⁇ m, and the specific surface area is 2.9m 2 /g; the aggregate particles are tested by mercury porosimetry, and the porosity of the aggregates is 4.9%; the aggregate particles are tested by a nanoindentation instrument The test shows that the average compressive hardness of the aggregate is 138Mpa, and the difference between the tested density of the aggregate and the average density of nano-germanium and amorphous carbon in the aggregate is 1.7%.
  • the negative electrode material prepared in this embodiment includes aggregates and carbon layers coated on the surface of the aggregates.
  • the aggregates include nano-aluminum and amorphous carbon, and nano-aluminum accounts for 49% of the mass of the aggregates.
  • the amount of nano-aluminum on the surface of the aggregates is The mass percentage is 33%, and the total mass ratio of nanometer aluminum to amorphous carbon is 0.96.
  • the mass percentage of nano-aluminum in the aggregate decreases by 12.02% from the center of the aggregate to the surface, the mass ratio of nano-aluminum to amorphous carbon decreases by 2.0 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 2.0.
  • the energy spectrometer is used for point scanning, and the mass percentages of the active substances in the aggregate at five different positions are measured to be 45.02%, 41.3%, 38.5%, 35.6% and 33.0%. .
  • the median diameter of the negative electrode material was 17.9 ⁇ m, and the specific surface area was 1.95 m 2 /g.
  • Example 1 The difference between this example and Example 1 is that the precursor is not coated with carbon; that is, in step (3), the precursor is placed in a high-temperature box furnace, nitrogen is introduced, and after heat treatment at 950°C for 3 hours, it is pulverized and sieving through a 500-mesh sieve to obtain the negative electrode material.
  • the negative electrode material that present embodiment makes comprises aggregate, and aggregate comprises nano-silicon and amorphous carbon, and nano-silicon accounts for 65% of the mass of aggregate, and the mass percent content of nano-silicon on aggregate surface is 53%, and nano-silicon
  • the total mass ratio to amorphous carbon is 1.86.
  • the mass percentage of nano-silicon in the aggregate decreases by 16.7% from the center of the aggregate to the surface
  • the mass ratio of nano-silicon to amorphous carbon decreases by 1.18 from the center of the aggregate to the surface
  • the value of E-F in this embodiment is 1.18.
  • test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • T For the T value at the center position, T within 75 measurements meets the following relationship: T ⁇ 2.37-1.18L 1 /L 0 .
  • the median particle size of the negative electrode material is 9.6 ⁇ m, and the specific surface area is 5.2m 2 /g.
  • the aggregate particles are tested by mercury porosimetry, and the porosity of the aggregates is 2.1%.
  • the aggregate particles are tested by a nanoindentation instrument. The test shows that the average compressive hardness of the aggregate is 149Mpa. The difference between the measured density of the aggregates and the average density of nano-aluminum and amorphous carbon in the aggregates was 1.8%.
  • the difference between this embodiment and Example 2 is that the first premix and the second premix in step 1) are different; 22 SiO, polyvinylpyrrolidone and polyvinyl chloride were added to the ethylene glycol solution at a mass ratio of 80:3:2:2.5, ultrasonicated for 10 minutes, and then ground and dispersed in a ball mill for 2 hours to obtain the first premix; the median particle size Nano-silicon with a diameter of 100nm, SiO with an aspect ratio of 22, polyvinylpyrrolidone and polyvinyl chloride were added to the ethylene glycol solution at a mass ratio of 55:1.5:1:2.9, ultrasonicated for 10 minutes, and then ground and dispersed in a ball mill for 2 hours to obtain the first Two premixes.
  • the negative electrode material that present embodiment makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises nano-Si, SiO and amorphous carbon, and nano-silicon accounts for 58% of the mass of aggregate, and nano-silicon and amorphous
  • the total mass ratio of carbon was 1.49.
  • the mass percentage of nano-silicon in the aggregate decreases by 20.9% from the center of the aggregate to the surface, the mass ratio of nano-silicon to amorphous carbon decreases by 1.23 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 1.23.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the central position, the T 0 measured within 93 times satisfies the following relationship: T 0 ⁇ 2.13-1.23L 1 /L 0 .
  • the median particle size of the negative electrode material is 13 ⁇ m, and the specific surface area is 3.8m 2 /g.
  • the aggregate particles are tested by mercury porosimetry, and the porosity of the aggregate is 6.9%.
  • the aggregate particles are tested by a nano-indentation instrument , the average compressive hardness of the aggregate is 258Mpa; the difference between the test density of the aggregate and the average density of nano-Si, SiO particles and carbon materials in the aggregate is 1.2%.
  • step 1) is: the median particle diameter is 100nm nano silicon, the aspect ratio 15 NiSi alloy, polyvinylpyrrolidone and polyvinyl chloride were added to the ethylene glycol solution at a mass ratio of 100:4.5:2:2.5, ultrasonicated for 10 minutes, and then ground and dispersed in a ball mill for 2 hours to obtain the first premix; Nano-silicon with a diameter of 100nm, NiSi alloy with an aspect ratio of 15, polyvinylpyrrolidone and polyvinyl chloride were added to the ethylene glycol solution at a mass ratio of 45:1:2.9, ultrasonicated for 10min, and then ground and dispersed in a ball mill for 2h to obtain the first Two premixes.
  • the negative electrode material that present embodiment makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises nano-silicon, NiSi alloy and amorphous carbon, and nano-silicon accounts for 55% of the mass of aggregate, and nano-silicon is gathered
  • the mass percentage of the body surface is 42.8%, and the total mass ratio of nano-silicon to amorphous carbon is 1.35.
  • the mass percentage of nano-silicon in the aggregate decreases by 24% from the center of the aggregate to the surface, the mass ratio of nano-silicon to amorphous carbon decreases by 0.92 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 0.92.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the center position, T 0 measured within 55 times satisfies the following relationship: 1.1 ⁇ T ⁇ 2.02, and T 0 ⁇ 2.02-0.92L 1 /L 0 .
  • the median particle diameter of the negative electrode material was 11.6 ⁇ m, and the specific surface area was 4.1 m 2 /g.
  • the aggregate particles are tested by mercury intrusion method, and the porosity of the aggregate is 2.5%; the aggregate particles are tested by a nano-indentation instrument, and the average compressive hardness of the aggregate is 378Mpa; the test density of the aggregate and the aggregation
  • the average density difference between nano-Si, NiSi alloy and carbon material in the body is 0.8%.
  • step 1 is: nano-silicon, TiO 2 , FeSi 2 , polyvinylpyrrolidone and polyvinyl chloride were added to the ethylene glycol solution at a mass ratio of 100:3:3.5:2:30, ultrasonicated for 10 minutes, and then ground and dispersed in a ball mill for 2 hours to obtain the first premix; Nano-silicon with a diameter of 100 nm, polyvinylpyrrolidone and polyvinyl chloride were added to the ethylene glycol solution at a mass ratio of 65:1:22.9, ultrasonicated for 10 minutes, and then ground and dispersed in a ball mill for 2 hours to obtain the second premix.
  • the negative electrode material that present embodiment makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises nano-silicon and amorphous carbon, and nano-silicon accounts for 45% of the mass of aggregate, and nano-silicon is on the surface of aggregate.
  • the mass percentage is 37.5%, and the total mass ratio of nano-silicon to amorphous carbon is 0.98.
  • the mass percentage of nano-silicon in the aggregate decreases by 14.2% from the center of the aggregate to the surface, the mass ratio of nano-silicon to amorphous carbon decreases by 0.85 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 0.85.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the central position, the T 0 measured within 100 times satisfies the following relationship: and T 0 ⁇ 1.45-0.85L1/L0.
  • the median particle size of the negative electrode material is 12.5 ⁇ m, and the specific surface area is 5.1m 2 /g.
  • the aggregate particles are tested by mercury porosimetry, and the porosity of the aggregates is 4.4%.
  • the aggregate particles are tested by a nanoindenter. The test shows that the average compressive hardness of the aggregate is 498Mpa; the difference between the tested density of the aggregate and the average density of nano-Si, NiSi alloy and carbon material in the aggregate is 0.85%.
  • the negative electrode material was prepared in the same manner as in Example 3, except that no additives were added.
  • the negative electrode material that present embodiment makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises nano-silicon and amorphous carbon, and nano-silicon accounts for 46% of the mass of aggregate, and nano-silicon is on the surface of aggregate.
  • the mass percentage is 27%, and the total mass ratio of nano-silicon to amorphous carbon is 0.85.
  • the mass percentage of nano-silicon in the aggregate decreases by 28.5% from the center of the aggregate to the surface, the mass ratio of nano-silicon to amorphous carbon decreases by 0.88 from the center of the aggregate to the surface, and the value of E-F in this embodiment is 0.88.
  • the test area is a square area of 2 ⁇ m ⁇ 2 ⁇ m.
  • the ratio of the mass percentage of nano-silicon to the mass percentage of amorphous carbon is defined as T, and any test area is counted.
  • the T 0 value at the central position, the T 0 measured within 55 times satisfies the following relationship: T 0 ⁇ 1.29-0.88L 1 /L 0 .
  • the median particle size of the negative electrode material was 10.4 ⁇ m, and the specific surface area was 2.8 m 2 /g.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregate was 3.9%; the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregate was 98Mpa.
  • the average density difference between nano-silicon and carbon materials in the body is 2.6%.
  • the negative electrode material that this comparative example makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises nano-silicon and amorphous carbon, and amorphous carbon is dispersed between nano-silicon, and nano-silicon accounts for the mass of aggregate 60%, the ratio of the mass percent of nano-silicon to amorphous carbon is 1.5.
  • the energy spectrometer is used for point scanning, and the mass percentages of active substances in the aggregate at 4 different positions are measured to be 61.0%, 59.3%, 60.4%, 58.8% and 61.4%, respectively. .
  • the median diameter of the negative electrode material was 12.8 ⁇ m, and the specific surface area was 3.2 m 2 /g.
  • the charge-discharge test of the lithium-ion battery is carried out on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd., under normal temperature conditions, 0.2C constant current charge and discharge, and the charge-discharge voltage is limited to 2.75 ⁇ 4.2V, get the first reversible capacity, the first cycle charge capacity and the first cycle discharge capacity.
  • the first coulombic efficiency the discharge capacity of the first cycle / the charge capacity of the first cycle.
  • the negative electrode materials prepared in Examples 1 to 13 include aggregates, wherein the aggregates include active materials and carbon materials, and the active material components in the core center of the aggregates account for a large proportion, and the carbon material group
  • the proportion of active material components is small, the proportion of active material components far away from the center of the core gradually decreases, and the proportion of carbon material components gradually increases.
  • This structure helps to control the expansion of active material within the aggregate and avoid the expansion effect of active material on the surface.
  • the destruction of the carbon layer improves the stability of the SEI film on the surface of the negative electrode material, and has good surface interface stability, thereby improving the cycle stability of the material and reducing the expansion rate.
  • the flow rate ratio of the first premix and the second premix is too small, that is, the first premix with high active material concentration and the second premix with low active material concentration
  • the mixing of the active material reduces the gradient range of the active material component content, that is, the T value distribution range is narrowed, and the concentration gradient difference is narrowed, which is not conducive to controlling the expansion of the active material inside the aggregate, resulting in a slight decrease in the cycle retention rate and electrode expansion to raise efficiency.
  • Example 8 The carbon source precursor glucose in Example 8 was added too much, so that the proportion of the active material in the final negative electrode material was reduced, and the first coulombic efficiency and cycle capacity retention rate of the negative electrode material decreased.
  • the active material containing the metal oxide and the conductivity enhancer has higher compressive hardness, the cycle capacity retention rate of the negative electrode material is higher, and the volume expansion rate is lower.
  • the second premix is not configured, only the first premix exists, and the content ratio of the active material to the carbon material component in the obtained aggregate particles is single, that is, the distribution range of the active material is Tends to concentrate, the percentage content of the active material does not show the law of gradually decreasing from the center to the surface, and the law that the surface is smaller than the inside, which is not conducive to suppressing the expansion rate of the negative electrode material.
  • the present disclosure provides a negative electrode material, a preparation method thereof, and a lithium ion battery, wherein the negative electrode material includes an aggregate, and the aggregate includes an active material and a carbon material; the active material in the aggregate The mass percentage gradually decreases from the center of the aggregate to the surface.
  • the negative electrode material provided by the present disclosure can effectively suppress volume expansion of the negative electrode material and improve battery cycle performance.

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Abstract

本公开涉及负极材料领域，提供负极材料及其制备方法、锂离子电池，其中，负极材料包括聚集体，所述聚集体包括活性物质和碳材料；所述活性物质在所述聚集体中的质量百分含量由所述聚集体的中心到表面逐渐降低。本公开提供的负极材料能够有效抑制负极材料体积膨胀，提升电池循环性能。

Description

负极材料及其制备方法、锂离子电池
相关申请的交叉引用
本申请要求于2021年06月30日提交中国专利局的申请号为202110736759.6、名称为“负极材料及其制备方法、锂离子电池”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
本公开属于锂离子电池负极材料技术领域，本公开涉及一种负极材料及其制备方法、锂离子电池。
背景技术
现有的锂离子电池由于具备能量密度大、输出功率高、循环寿命长和环境污染小等优点而被广泛应用于电动汽车以及消费类电子产品中。为了提高电池能量密度，在负极材料中添加活性物质的研究和开发日趋成熟，例如硅负极材料。但是添加了活性物质以后的负极材料在脱嵌锂的过程中体积膨胀较大，特别是硅负极材料在脱嵌锂过程中体积膨胀可以达到300％以上，在充放电过程中会粉化并从集流体上掉落，使得负极活性材料与集流体之间失掉电接触，导致负极材料电化学性能变差，例如容量衰减、循环稳定性下降，导致此类负极材料难以得到商业应用。
因此，如何抑制负极材料的体积膨胀、提高负极材料的循环稳定性是目前急需解决的问题。
发明内容
本公开提供了一种负极材料，包括聚集体，所述聚集体包括活性物质和碳材料，所述活性物质在所述聚集体中的质量百分含量由所述聚集体的中心到表面逐渐降低。
在上述方案中，负极材料包括聚集体，聚集体包括活性物质和碳材料，且处于聚集体内核中心的活性物质组分占比较多，碳材料组分占比较少，远离内核中心的活性物质组分占比逐渐减少，碳材料组分占比增加，这种活性物质的浓度变化有助于将高浓度的活性物质集中在负极材料颗粒的中心位置，将活性物质的膨胀控制在聚集体内部，避免活性物质的膨胀效应对表面的碳层的破坏，提高负极材料表面的SEI膜的稳定性，具备良好的界面稳定性，降低添加活性物质的负极材料的体积膨胀率，从而提高负极材料的循环稳定性能，提升电池循环性能。
在一些实施方式中，所述活性物质与所述碳材料的质量比由所述聚集体的中心到表面逐渐降低。
在一些实施方式中，所述活性物质与所述碳材料的总质量比为0.5～8。
在一些实施方式中，以聚集体的质量百分含量为100％计，所述活性物质的总的质量百分含量为5％～90％。
在一些实施方式中，以聚集体的质量百分含量为100％计，所述活性物质的总的质量百分含量为5％～80％。
在一些实施方式中，所述活性物质在所述聚集体表面的质量百分含量为2％～55％。
在一些实施方式中，所述聚集体中所述活性物质与所述碳材料的质量比的最大值为E，最小值为F，E-F≥0.5。
在一些实施方式中，对所述聚集体SEM切面上自表面至中心的任一区域使用能谱仪进行EDS点扫描测试，所述活性物质与所述碳材料的质量比定义为T，对区域内进行N次测试，N≥10，其中，A为N次测试结果中T的最小值，B为N次测试结果中T的最大值，所述聚集体表面任意一点至中心的距离为L 0μm，测试区域的中心至所述聚集体的中心的距离为L 1μm，所述测试区域中心位置的T值定义为T 0，T 0满足关系：T 0≤B-(B-A)L 1/L 0。
在一些实施方式中，所述活性物质包括Li、Na、K、Sn、Ge、Si、SiO x、Fe、Mg、Ti、Zn、Al、Ni、P及Cu中的至少一种，其中，0＜x＜2。
在一些实施方式中，所述活性物质的中值粒径为1nm～300nm。
在一些实施方式中，所述碳材料包括石墨类碳材料和非石墨类碳材料。
在一些实施方式中，所述石墨类碳材料包括天然石墨和/或人造石墨。
在一些实施方式中，所述人造石墨包括中间相碳微球。
在一些实施方式中，所述非石墨类碳材料包括无定形碳、结晶碳、硬碳和软碳中的至少一种。
在一些实施方式中，所述聚集体还包括金属氧化物及导电增强剂中的至少一种。
在一些实施方式中，所述金属氧化物的化学通式为M xO y，0.2≤y/x≤3，其中，M包括Sn、Ge、Fe、Cu、Ti、Na、Mg、Al、Ca及Zn中的至少一种。
在一些实施方式中，所述金属氧化物呈片状和/或长条状。
在一些实施方式中，所述金属氧化物的长径比大于2。
在一些实施方式中，所述导电增强剂的电导率为10 0S/m～10 8S/m。
在一些实施方式中，所述导电增强剂呈片状和/或长条状。
在一些实施方式中，所述导电增强剂的长径比为2～5000。
在一些实施方式中，所述导电增强剂包括合金材料及导电碳中的至少一种。
在一些实施方式中，所述合金材料包括锌合金、铝合金、铜合金、硅合金、镍合金和钛合金中的至少一种。
在一些实施方式中，所述导电碳包括石墨纤维、碳纳米管、石墨片、导电碳纤维和石墨烯中的一种。
在一些实施方式中，所述金属氧化物与活性物质的质量比为1～20：100。
在一些实施方式中，所述导电增强剂与活性物质的质量比为0.01～20：100。
在一些实施方式中，所述负极材料还包括包覆于所述聚集体的至少部分表面的碳层。
在一些实施方式中，所述碳层的材料包括石墨和/或无定形碳。
在一些实施方式中，所述碳层的厚度为10nm～2000nm。
在一些实施方式中，所述负极材料的中值粒径为0.5μm～30μm。
在一些实施方式中，所述负极材料的比表面积≤10m 2/g。
在一些实施方式中，所述聚集体的孔隙率≤10％。
在一些实施方式中，所述聚集体的耐压硬度≥100Mpa。
在一些实施方式中，所述聚集体密度满足以下关系：(ρ1-ρ2)/ρ2≤5％，其中，ρ1为聚集体的测试密度，ρ2为聚集体的平均密度；所述ρ2为聚集体中各组分在聚集体中的质量百分含量*各组分的理论密度的值的总和。
本公开还提供了一种负极材料的制备方法，包括以下步骤：
将至少两组预混物混合制备前驱体，其中，每组所述预混物均至少包含活性物质、第一碳源及溶剂，且至少有两组所述预混物中所述活性物质的质量百分含量不同；及
对所述前驱体热处理，使所述第一碳源碳化，得到聚集体。
在上述方案中，本公开所提供的制备方法，通过将活性物质、碳源和溶剂按照不同的配比混合得到多个预混物，多个预混物混合、热处理制得的聚集体，该聚集体从颗粒表面至颗粒中心，活性物质组分占比逐渐增多，有利于抑制负极材料的膨胀率，并且制备过程简单可控。
在一些实施方式中，所述至少两组预混物中，所述活性物质的质量百分含量最大值与质量百分含量最小值的差值为20％～90％。
在一些实施方式中，所述活性物质包括Li、Na、K、Sn、Ge、Si、SiO x、Fe、Mg、Ti、Zn、Al、P及Cu中的至少一种，其中，0＜x＜2。
在一些实施方式中，所述第一碳源包括蔗糖、葡萄糖、聚乙烯、聚乙烯醇、聚乙二醇、聚苯胺、环氧树脂、酚醛树脂、糠醛树脂、丙烯酸树脂、聚环氧乙烷、聚偏氟乙烯、聚丙烯腈、聚氯乙烯和沥青中的至少一种。
在一些实施方式中，所述溶剂包括有机溶剂。
在一些实施方式中，所述有机溶剂包括甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇及戊醇中的至少一种。
在一些实施方式中，至少一组所述预混物中还包括添加剂、金属氧化物及导电增强剂中的至少一种。
在一些实施方式中，所述添加剂包括表面活性剂和偶联剂中的至少一种。
在一些实施方式中，所述表面活性剂包括正十八酸、月桂酸、聚丙烯酸、十二烷基苯磺酸钠、正二十酸、棕榈酸、十四烷酸、十一烷酸、十六烷基三甲基溴化胺及聚乙烯吡咯烷酮中的至少一种。
在一些实施方式中，所述偶联剂包括硅烷偶联剂和/或钛酸酯偶联剂。
在一些实施方式中，所述硅烷偶联剂包括γ-氨丙基三乙氧基硅烷、γ-缩水甘油醚氧丙基三甲氧基硅烷、γ-甲基丙烯酰氧基丙基三甲氧基硅烷。
在一些实施方式中，所述金属氧化物的化学通式为M xO y，0.2≤y/x≤3，其中，M包括Sn、Ge、Fe、Cu、Ti、Na、Mg、Al、Ca及Zn中的至少一种。
在一些实施方式中，所述金属氧化物呈片状和/或长条状。
在一些实施方式中，所述金属氧化物的长径比大于2。
在一些实施方式中，所述金属氧化物与活性物质的质量比为1～20：100。
在一些实施方式中，所述导电增强剂与活性物质的质量比为0.01～20。
在一些实施方式中，所述导电增强剂的电导率为10 0S/m～10 8S/m。
在一些实施方式中，所述导电增强剂呈片状和/或长条状。
在一些实施方式中，所述导电增强剂的长径比为2～5000。
在一些实施方式中，所述导电增强剂包括合金材料及导电碳中的至少一种。
在一些实施方式中，所述合金材料包括锌合金、铝合金、铜合金、硅合金、镍合金和钛合金中的至少一种。
在一些实施方式中，所述导电碳包括石墨纤维、碳纳米管、石墨片、导电碳纤维和石墨烯中的一种。
在一些实施方式中，制备所述前驱体还包括将混合后的预混合物进行干燥处理、分散处理中的至少一种。
在一些实施方式中，所述干燥处理的温度为30℃～400℃，干燥处理的时间为1h～15h。
在一些实施方式中，所述分散处理包括机械搅拌、超声分散及研磨分散中的至少一种。
在一些实施方式中，制备所述前驱体还包括将混合后的预混合物进行离心处理。
在一些实施方式中，所述离心处理的转速为100rpm～3000rpm，所述离心处理时间为10min～60min。
在一些实施方式中，所述至少两组预混物包括第一预混物、第二预混物。
在一些实施方式中，所述第一预混物中所述活性物质与所述第一碳源的质量比为(80～120)：(1～20)。
在一些实施方式中，所述第二预混物中所述活性物质与所述第一碳源的质量比为(40～80)：(1～30)。
在一些实施方式中，所述第一预混物中的活性物质的质量百分含量大于或小于所述第二预混物中的活性物质质量百分含量。
在一些实施方式中，制备所述前驱体的步骤包括：将所述第一预混物和第二预混物混合，得到所述前驱体。
在一些实施方式中，制备所述前驱体的步骤具体为：将第一预混物进行干燥，分散；将分散后的第一预混物和第二预混物混合得到混合物，将混合物干燥后与第三预混物混合制备得到前驱体。
在一些实施方式中，所述第一预混物中，所述活性物质与所述添加剂的质量比为(80～120)：(1～20)。
在一些实施方式中，所述第二预混物中，所述活性物质与所述添加剂的质量比为(40～80)：(1～10)。
在一些实施方式中，所述至少两组预混物混合制备前驱体步骤包括至少三组预混物混合制备所述前驱体。
在一些实施方式中，所述至少三组预混物混合的步骤包括将所述预混物按照活性物质在所述预混物中的质量百分含量由高至低顺序依次混合。
在一些实施方式中，所述至少两组预混物还包括第三预混物。
在一些实施方式中，将所述活性物质、所述第一碳源按质量比为(10～40)：(10～40)和溶剂混合制备得到所述第三预混物。
在一些实施方式中，所述第二预混物中的活性物质质量百分含量大于所述第三预混物中的活性物质质量百分含量。
在一些实施方式中，制备所述前驱体的步骤包括：将所述第一预混物依次与第二预混物、第三预混物混合，得到所述前驱体。
在一些实施方式中，制备所述前驱体的步骤具体为：将第一预混物进行干燥，分散；将分散后的第一预混物和第二预混物混合得到混合物，将混合物干燥后与第三预混物混合制备得到前驱体。
在一些实施方式中，所述第三预混物中，所述活性物质与所述添加剂的质量比为(10～40)：(1～10)。
在一些实施方式中，所述将第一预混物与第二预混物进行混合过程中，所述第一预混物与所述第二预混物的流速比为(1～15):1。
在一些实施方式中，将所述第一预混物与第二预混物混合得到混合物，将所述混合物与第三 预混物混合过程中，所述混合物与第三预混物混合的流速比为(1～15):1。
在一些实施方式中，所述前驱体进行热处理之前，还包括对所述前驱体或对所述预混物进行密实化处理，使得所述的聚集体的孔隙率≤10％且耐压硬度≥100Mpa。
在一些实施方式中，所述密实化处理包括融合处理、混捏挤压处理、模压处理、等静压处理、及浸渍处理中的至少一种。
在一些实施方式中，所述的融合处理为机械融合。
在一些实施方式中，所述机械融合所用的融合机的转速为500r/min～3000r/min。
在一些实施方式中，所述机械融合所用的融合机刀具间隙宽度为0.01cm～0.5cm。
在一些实施方式中，所述机械融合时间至少为0.5h。
在一些实施方式中，所述对前驱体热处理前还包括干燥处理。
在一些实施方式中，所述干燥处理的温度为30℃～400℃，所述干燥处理的时间为1h～15h。
在一些实施方式中，所述热处理温度为600℃～1200℃，所述热处理的时间为1h～15h。
在一些实施方式中，所述热处理过程通有保护性气体。
在一些实施方式中，所述保护性气体包括氮气、氦气、氖气、氩气及氪气中的至少一种。
在一些实施方式中，所述方法还包括对所述聚集体进行碳包覆处理。
在一些实施方式中，所述碳包覆处理的步骤包括：将前驱体与第二碳源进行混合、热处理。
在一些实施方式中，所述前驱体与所述第二碳源的质量比为(30～100)：(10～70)。
在一些实施方式中，所述碳包覆处理的步骤包括：将所述聚集体与第二碳源混合、碳化处理。
在一些实施方式中，所述第二碳源包括蔗糖、葡萄糖、聚乙烯、聚乙烯醇、聚乙二醇、聚苯胺、环氧树脂、酚醛树脂、糠醛树脂、丙烯酸树脂、聚环氧乙烷、聚偏氟乙烯、聚丙烯腈、聚氯乙烯及沥青中的至少一种。
在一些实施方式中，所述聚集体与所述第二碳源的质量比为(30～100)：(10～70)。
在一些实施方式中，所述碳化处理的温度为600℃～1200℃，所述碳化处理的时间为1h～15h。
本公开又提供了一种负极材料，包括聚集体，所述聚集体包括活性物质和碳材料，所述碳材料分散于所述活性物质之间，且以聚集体的质量百分含量为100％计，所述聚集体表面的所述活性物质的质量百分含量小于所述聚集体内部的所述活性物质的质量百分含量。
本公开还提供了一种锂离子电池，所述锂离子电池包括所述的负极材料或所述的制备方法制得的负极材料。
附图说明
图1为本公开实施例提供的负极材料的结构示意图；
图2为本公开实施例提供的负极材料的制备方法的流程示意图。
具体实施方式
以下所述是本公开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，在不脱离本公开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公开实施例的保护范围。
一实施方式的负极材料，如图1所示，负极材料包括聚集体10，聚集体10包括活性物质和碳材料；其中，活性物质在聚集体中的质量百分含量由聚集体的中心到表面逐渐降低。
从聚集体的中心到表面，活性物质在聚集体中的质量百分含量通过以下方法测得：
从聚集体的SEM切面中心到表面使用能谱仪进行EDS点扫描，测得不同位置活性物质在聚集体中的质量百分含量。
本实施方式的负极材料包括聚集体，聚集体包括活性物质和碳材料，且处于聚集体内核中心的活性物质粒子数较多，远离内核中心的活性物质粒子逐渐降低，即活性物质在聚集体中的质量百分含量由聚集体的中心到表面逐渐降低，这种结构有助于将活性物质的膨胀控制在聚集体内部，避免活性物质膨胀效应对表面碳层的破坏，提高负极材料表面的SEI膜的稳定性，具备良好的表面界面稳定性，降低添加活性物质的负极材料的膨胀率，从而提高负极材料的循环稳定性能，提升电池循环性能。
具体地，在聚集体中，活性物质分布于碳材料中，优选地，活性物质以一定的浓度梯度分散在碳材料中。
在一些实施方式中，以聚集体的质量百分含量为100％计，活性物质的总的质量百分含量为 5％～90％。
在一些实施方式中，以聚集体的质量百分含量为100％计，活性物质的总的质量百分含量为5％～80％；具体地，活性物质的质量百分含量可以为5％、7％、10％、20％、25％、35％、40％、50％、55％、60％、70％、75％、80％等等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，活性物质与碳材料的质量比由聚集体的中心到表面逐渐降低；
按照活性物质在聚集体中的质量百分含量的测试方法测试碳材料在聚集体中的质量百分含量，二者的比值即为活性物质和碳材料的质量比。
此聚集体结构，处于聚集体内核中心的活性物质粒子数较多，碳材料组分较少，远离内核中心的活性物质粒子逐渐降低，碳材料组分增加，即活性物质与碳材料的质量比由聚集体的中心到表面逐渐降低，这种结构更有助于将活性物质的膨胀控制在聚集体内部，避免活性物质膨胀效应对表面层的破坏，提高负极材料表面的SEI膜的稳定性，具备良好的表面界面稳定性，降低添加活性物质的负极材料的膨胀率，从而提高负极材料的循环稳定性能，提升电池循环性能。
在一些实施方式中，活性物质在聚集体表面的质量百分含量为2％～55％。具体地，活性物质在聚集体表面的质量百分含量可以为2％、5％、7.5％、10％、12.5％、15％、20％、22.5％、25％、27.5％、30％、35％、40％、45％、50％或55％等等，当然也可以是上述范围内的其他值，在此不做限定。
活性物质在聚集体表面的质量百分含量的定义为：聚集体表面任意一点上，活性物质的质量百分含量；测试方法为：在聚集体的SEM切面边缘上任意一点使用能谱仪进行EDS点扫描，测试得到活性物质在聚集体表面的质量百分含量。
在一些实施方式中，聚集体中活性物质与碳材料的质量比的最大值为E，最小值为F，E-F≥0.5。此范围内的形成的聚集体结构更有助于将活性物质的膨胀控制在聚集体内部，避免活性物质膨胀效应对表面层的破坏，提高负极材料表面的SEI膜的稳定性，具备良好的表面界面稳定性，降低添加活性物质的负极材料的膨胀率，从而提高负极材料的循环稳定性能，提升电池循环性能。优选地，E-F≥2。
可选地，E-F可以是0.5、0.8、1、1.5、2、2.1、2.3、2.5、2.8、3.0、3.5、4.0、5.5等等，在此不做限定。
在一些实施方式中，所述活性物质与所述碳材料的总质量比为0.5～8。该实施方式中，所述活性物质与所述碳材料的总质量比指的是：所述聚集体中所述活性物质的总质量与所述碳材料的总质量之比。具体地，活性物质与碳材料的总质量比可以为0.5、1、1.5、2、2.6、3、3.9、4、4.8、5、5.3、6、6.7、7.2或8等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，请继续参阅图1，对聚集体SEM切面上自表面至中心的各个区域使用能谱仪进行EDS点扫描测试，所述活性物质与所述碳材料的质量比定义为T，对区域内进行N次测试，N≥10。其中，A为N次测试结果中T值的最小值，B为N次(N≥10)测试结果中T值的最大值，聚集体表面至中心的距离为L 0μm，测试区域的中心至聚集体的中心的距离为L 1μm，测试区域中心位置的T值定义为T 0，T 0满足关系：T 0≤B-(B-A)L 1/L 0。满足该关系的聚集体材料，内部更加密实化，耐压应力更强，具备更加稳定的结构，并且很好地将活性物质聚集在聚集体的内部核心位置，抑制了充放电过程中负极材料的膨胀。
在一些实施方式中，活性物质指的是可以与锂反应，可以进行脱嵌锂的物质，即可以提高负极材料容量的一类材料。
具体地，活性物质包括Li、Na、K、Sn、Ge、Si、SiO x、Fe、Mg、Ti、Zn、Al、P及Cu中的至少一种；其中，0＜x＜2。
活性物质可以是金属单质，在一些实施方式中，活性物质具体可以是Si颗粒、Sn颗粒、Ge颗粒、Al颗粒，在另外的一些实施方式中，活性物质也可以是硅锂合金、硅镁合金等，当然，需要说明的是，在一些情况下，活性物质包括单质颗粒或其合金，或者是不同活性物质材料的组合物。
在一些实施方式中，活性物质的中值粒径为1nm～300nm。具体可以是1nm、5nm、10nm、15nm、20nm、30nm、40nm、50nm、100nm、200nm或300nm等等，当然也可以是上述范围内的其他值，在此不做限定。纳米级的活性物质，其表面能高，在充放电过程中容易发生团聚，颗粒的结构性强，可以抑制活性物质体积的膨胀。但由于纳米级活性物质粒径越小，有表面能越大，在充放电过程中容易发生团聚，并且活性物质的粒径过小，生产工艺成本高。优选地，活性物质的中值粒径为1nm～300nm，更优选为1nm～100nm。
在一些实施方式中，碳材料包括石墨类碳材料和非石墨类碳材料。
在一些实施方式中，石墨类碳材料包括天然石墨和/或人造石墨，其中人造石墨包括中间相碳 微球；所述非石墨类碳材料包括无定形碳、结晶碳、硬碳和软碳中的至少一种。
具体地，本公开所提供的通过将活性物质集中在聚集体内部以抑制材料膨胀的技术方案，可以适用于不同的碳负极材料。
在一些实施方式中，聚集体还包括金属氧化物、导电增强剂中的至少一种。
在一些实施方式中，金属氧化物的化学通式为M xO y，0.2≤y/x≤3，其中，M包括Sn、Ge、Fe、Cu、Ti、Na、Mg、Al、Ca或Zn中的至少一种；具体地，金属氧化物可以是GeO 2、SnO 2、ZnO、TiO 2、Fe 3O 4、MgO、CuO等等。选取的金属氧化物在嵌锂过程的体积膨胀变化率低于活性物质。因此，将金属氧化物与活性物质进行复合，可以降低活性物质的膨胀，提升长循环性能。
在一些实施方式中，金属氧化物呈片状和/或长条状。
在一些实施方式中，金属氧化物的长径比值大于2。需要说明的是，当金属氧化物为长条状时，长径比具体是指金属氧化物的长度与的粒径的比值，这里的粒径指的是垂直于长条状金属氧化物长度方向的截面周缘上的两点之间的最大直线距离；当金属氧化物为片状时，长径比具体是指片状金属氧化物的长度与宽度的比值。具体地，金属氧化物的长径比值可以是2、2.5、3、3.5、4、4.5、5、6、7、8、9、12、15、17、18、22等等，当然也可以是上述范围内的其他值，在此不做限定。金属氧化物的长径比大于2时，可以提升金属氧化物与活性物质的物理结合力，从而提高对活性物质体积膨胀的抑制和缓冲作用，提升负极的循环性能。
在一些实施方式中，金属氧化物与活性物质的质量比为1～20：100。具体地，金属氧化物与活性物质的质量比可以为1：100、1.5：100、2：100、3：100、4.5：100、5：100、6：100、7：100、8：100、9：100等等。当然也可以是上述范围内的其他值，在此不做限定。
在聚集体中，金属氧化物与活性物质分布于聚集体中，活性物质和金属氧化物之间填充有碳材料。
在一些实施方式中，聚集体中加入导电增强剂，该导电增强剂一方面可以提供更多的载流子的传输通道，进而增强载流子在材料内部的传输；另一方面，同时还具备优异的机械性能，可以作为结构的支撑体增强材料的稳定性。
在一些实施方式中，导电增强剂与活性物质的质量比为0.01～20：100。具体可以为0.01：100、1：100、2.5：100、3：100、5：100、7.5：100、10：100、12.5：100、15：100、20：100等等。当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，导电增强剂的电导率为10 0S/m～10 8S/m。具体地，导电增强剂的电导率可以为1S/m、10S/m、100S/m、10 3S/m、10 4S/m、10 5S/m、10 8S/m等。
在一些实施方式中，导电增强剂呈片状和/或长条状。
在一些实施方式中，导电增强剂的长径比为2～5000。需要说明的是，当导电增强剂为长条状时，长径比具体是指颗粒的长度与颗粒的粒径的比值，这里的粒径指的是垂直于长条状导电增强剂长度方向的截面周缘上的两点之间的最大直线距离；当金属氧化物为片状时，长径比具体是指片状导电增强剂的长度与宽度的比值。具体地，导电增强剂的长径比值可以是2、30、46、150、360、670、800、900、1500、2000、3000、4000、5000等等，当然也可以是上述范围内的其他值，在此不做限定。长径比在该范围内的导电增强剂，具有较优异的机械性能，可以作为结构的支撑体增强材料的稳定性，从而提高对活性物质体积膨胀的抑制和缓冲作用，提升负极的循环性能。
具体地，导电增强剂包括合金材料及其合金和/或导电碳。
在一些实施方式中，所述合金材料包括锌合金、铝合金、铜合金、硅合金、镍合金和钛合金中的至少一种。
在一些实施方式中，所述导电碳包括石墨纤维、碳纳米管、石墨片、导电碳纤维和石墨烯中的一种。
在一些实施方式中，聚集体的孔隙率≤10％，聚集体的耐压硬度≥100Mpa。
此时，聚集体的孔隙率较低，即其密实度很高，一方面有助于提高复合材料的能量密度，另一方面高密实度的材料即使表层被破坏，电解液也不容易渗透进聚集体内部，有利于保护内部的活性物质颗粒，减少电解液与活性物质的接触几率，从而有利于形成稳定的固体电解质膜；并且高密实化的聚集体具有较高的耐压硬度，能够对冲膨胀所带来的应力效应，提高负极材料的结构稳定性，可以有效抑制负极材料体积膨胀，降低其膨胀率，从而提升电池循环性能。
在一些实施方式中，聚集体的孔隙率≤10％，聚集体的孔隙率具体可以是10％、9％、9.5％、8％、8.5％、7.5％、7％、6.5％、6％或5％等等，当然也可以是上述范围内的其它值，在此不做限定。可以理解地，聚集体的孔隙率较低，即其密实度很高，有利于形成稳定的固体电解质膜，减少电解液与活性物质的接触。优选地，所述聚集体的孔隙率≤5％，更优选地，所述聚集体的孔隙率≤3％。
聚集体的耐压硬度≥100Mpa；聚集体的耐压硬度具体可以是100Mpa、250Mpa、300Mpa、450Mpa、 500Mpa、750Mpa、900Mpa、1150Mpa、1200Mpa或1250Mpa等等，当然也可以是上述范围内的其它值，在此不做限定。因为其具有较强的刚性，粒子结构稳定性强，可以抵御一定的体积膨胀应力，从而降低膨胀，提升电池循环稳定性。优选地，聚集体的耐压硬度≥200Mpa，更优选地，聚集体的耐压硬度≥400Mpa。
在一些实施方式中，所述聚集体密度满足以下关系：聚集体的测试密度与聚集体的平均密度的差值≤5％。聚集体颗粒的密度与平均密度越接近，相差越小，说明颗粒内部的孔隙越少，越密实，有利于形成稳定的固体电解质膜，减少电解液与活性物质的接触。
具体地，聚集体密度计算如下：(ρ1-ρ2)/ρ2≤5％，其中ρ1为聚集体的测试密度，ρ2为聚集体的平均密度；
其中，ρ2为聚集体中各组分在聚集体的质量百分含量*各组分的理论密度的值的总和。
采用以下方法得到聚集体的测试密度ρ2：
称取空瓶的质量m，注满蒸馏水，称取此时的质量为m1；然后将瓶子清洗，干燥，在一定量的聚集体加入到比重瓶中，记录此时的总体质量为m2，然后加入蒸馏水，注满比重瓶，称取质量m3，比重瓶的体积V1＝(m1-m)/ρ1，活性物质的体积V2＝(m2-m3)/ρ1,活性物质的测试密度ρ2＝(m3-m)/(V-V1)，ρ1是蒸馏水的密度。
具体的示例中，当聚集体包括活性物质和碳材料时，ρ2＝活性物质在聚集体中的质量百分含量*活性物质理论密度+碳材料在聚集体中的质量百分含量*碳材料理论密度。
当聚集体包括活性物质、金属氧化物和碳材料时，ρ2＝活性物质在聚集体中的质量百分含量*活性物质理论密度+金属氧化物在聚集体中的质量百分含量*金属氧化物理论密度+碳材料在聚集体中的质量百分含量*碳材料理论密度。
当聚集体包括活性物质、金属氧化物、导电增强剂和碳材料时，ρ2＝活性物质在聚集体中的质量百分含量％*活性物质理论密度+金属氧化物在聚集体中的质量百分含量*金属氧化物理论密度+导电增强剂在聚集体中的质量百分含量*导电增强剂的理论密度+碳材料在聚集体中的质量百分含量*碳材料理论密度。
进一步地，负极材料还包括包覆于所述聚集体10的至少部分表面的碳层20，优选地，碳层分布于聚集体的表面，碳层包括无定形碳。
在一些实施方式中，碳层的厚度为10nm至2000nm。可以理解地，包覆聚集体表面的碳层能够减少活性物质与电解液接触，减少钝化膜生成，提升电池可逆电容量。
具体地，碳层的厚度可以是10nm、50nm、80nm、100nm、150nm、200nm、250nm、300nm、350nm、400nm、450nm、600nm、1000nm、1500nm或2000nm等等，当然也可以是上述范围内的其他值，在此不做限定。碳层过厚，锂离子传输效率降低，不利于材料大倍率充放电，降低负极材料的综合性能；碳层过薄，不利于增加负极材料的导电性且对材料的体积膨胀抑制性能较弱，导致长循环性能价差。优选地，碳层的厚度为50nm～800nm；更优选地，碳层的厚度为100nm～500nm。
在一些实施方式中，负极材料的中值粒径为0.5μm～30μm；具体可以是0.5μm、1μm、5μm、8μm、10μm、13μm、15μm、18μm、20μm、25μm或30μm等等，当然也可以是上述范围内的其他值，在此不做限定。可以理解地，负极材料的平均粒径控制在上述范围内，有利于负极材料循环性能的提升。
在一些实施方式中，负极材料的比表面积为≤10m 2/g，具体可以是10m 2/g、8m 2/g、7m 2/g、5m 2/g、3m 2/g、2m 2/g、1m 2/g或0.5m 2/g等等，当然也可以是上述范围内的其他值，在此不做限定。可以理解地，负极材料的比表面积控制在上述范围内，有利于抑制体积膨胀，有利于负极材料循环性能的提升。比表面积通过麦克比表面积测试仪测得。
本公开中所述中值粒径指的是平均粒径，其物理意义是颗粒的累计粒度分布百分数达到50％时所对应的粒径，通过马尔文粒度仪测试。马尔文粒度仪利用颗粒对光的散射现象，根据散射光能的分布综合换算出被测颗粒的粒径分布。
需要说明的是，上述各个实施方式的负极材料在不相互矛盾的情况下，可以任意进行组合，比如比表面积与聚集体的孔隙率、耐压强度进行组合限定等。
另一方面，本公开提供一种负极材料的制备方法，方法包括以下步骤：
步骤S10，将至少两组预混物混合制备前驱体，其中，每组所述预混物均包含活性物质、第一碳源及溶剂，且所述至少两组预混物中所述活性物质的质量百分含量不同；
步骤S20，对前驱体热处理，使所述第一碳源碳化，得到聚集体。
该实施方式制备得到的负极材料，包括聚集体，聚集体包括活性物质和碳材料，活性物质在所述聚集体中的质量百分含量由所述聚集体的中心到表面逐渐降低。
该实施方式的制备方法，所述预混物包括活性物质、碳源和溶剂，将活性物质质量百分含量 不同的所述预混物进行混合，经过热处理制得所述聚集体，该聚集体中的活性物质的质量百分含量由聚集体的中心到表面逐渐降低，这种结构有助于将活性物质的膨胀控制在聚集体内部，避免活性物质膨胀效应对表面的碳层的破坏，提高负极材料表面的SEI膜的稳定性，具备良好的表面界面稳定性，从而提高材料的循环稳定性能，降低膨胀率，并且制备过程简单可控。
以下结合实施例具体介绍本公开的制备方法：
步骤S10，将至少两组预混物混合制备前驱体，其中，每组所述预混物均包含活性物质、第一碳源及溶剂，且所述至少两组预混物中所述活性物质的质量百分含量不同。
可以理解地，每组预混物制备步骤具体为：将活性物质、第一碳源及溶剂混合得到。
在一些实施方式中，前驱体可以为两组预混物混合得到；也可以为至少三组预混物混合得到。
在一些实施方式中，至少三组预混物混合的步骤包括将预混物按照活性物质在所述组分中的质量百分含量由高至低顺序依次混合；通过配置三组以上不同活性物质含量浓度的预混物，将各组预混物按照活性物质在预混物中的质量百分含量由高至低顺序依次混合，作为高活性物质含量为中心内核，然后依次与低浓度组分混合，热处理制得的聚集体，该聚集体从颗粒表面至颗粒中心，活性物质组分占比逐渐增多。
在一些实施方式中，至少两组预混物中，活性物质的质量百分含量的最大值与质量百分含量的最小值的差值为20％～90％。具体地，活性物质的质量百分含量的最大值与质量百分含量的最小值的差值为20％、25％、30％、35％、45％、50％、55％、65％、75％、80％或90％；当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，活性物质包括Li、Na、K、Sn、Ge、Si、Fe、SiO x(0＜x＜2)、Mg、Ti、Zn、Al、P及Cu中的至少一种；活性物质可以是金属单质，在一些实施方式中，活性物质具体可以是Si颗粒、Sn颗粒、Ge颗粒、Al颗粒；在另外的一些实施方式中，活性物质也可以是硅锂合金、硅镁合金等，当然，需要说明的是，在一些情况下，活性物质包括单质颗粒或其合金，或者是不同活性物质材料的组合物。
在一些实施方式中，第一碳源包括蔗糖、葡萄糖、聚乙烯、聚乙烯醇、聚乙二醇、聚苯胺、环氧树脂、酚醛树脂、糠醛树脂、丙烯酸树脂、聚环氧乙烷、聚偏氟乙烯、聚丙烯腈、聚氯乙烯、沥青中的至少一种。
在一些实施方式中，溶剂包括有机溶剂。
在一些实施方式中，有机溶剂包括甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇及戊醇中的至少一种。
在一些实施方式中，至少一组所述预混物中还包括添加剂、金属氧化物及导电增强剂中的至少一种。
在一些实施方式中，至少两组预混物混合制备前驱体步骤中的至少一组预混物还加入了添加剂、金属氧化物及导电增强剂中的至少一种。
可以理解地，当采用两组预混物进行混合制备前驱体时，可以在其中一组预混物中加入添加剂、金属氧化物及导电增强剂中的至少一种，也可以两组同时加入，且每组预混物中的添加剂、金属氧化物及导电增强剂种类可以相同也可以不同，在此不做限制。
其中，添加剂可以有效增强活性物质与碳材料的连接稳定性，从而形成牢固的体系，降低极片膨胀率。
在一些实施方式中，添加剂包括表面活性剂、偶联剂中的至少一种。
表面活性剂包括正十八酸、月桂酸、聚丙烯酸、十二烷基苯磺酸钠、正二十酸、棕榈酸、十四烷酸、十一烷酸、十六烷基三甲基溴化胺及聚乙烯吡咯烷酮中的至少一种。
偶联剂包括硅烷偶联剂和/或钛酸酯偶联剂。硅烷偶联剂包括γ-氨丙基三乙氧基硅烷、γ-缩水甘油醚氧丙基三甲氧基硅烷、γ-甲基丙烯酰氧基丙基三甲氧基硅烷。
在一些实施方式中，金属氧化物的化学通式为M xO y，0.2≤y/x≤3，其中，M包括Sn、Ge、Fe、Cu、Ti、Na、Mg、Al、Ca及Zn中的至少一种。
在一些实施方式中，金属氧化物呈片状和/或长条状。
在一些实施方式中，金属氧化物的长径比大于2。
在一些实施方式中，金属氧化物与活性物质的质量比为1～20：100。
在一些实施方式中，导电增强剂与活性物质的质量比为0.01～20：100。
在一些实施方式中，导电增强剂的电导率为10 0S/m～10 8S/m。
在一些实施方式中，导电增强剂呈片状和/或长条状。
在一些实施方式中，导电增强剂的长径比为2～5000。
在一些实施方式中，导电增强剂包括合金材料及导电碳中的至少一种。
在一些实施方式中，所述合金材料包括锌合金、铝合金、铜合金、硅合金、镍合金和钛合金中的至少一种。
在一些实施方式中，所述导电碳包括石墨纤维、碳纳米管、石墨片、导电碳纤维和石墨烯中的一种。
在一些实施方式中，活性物质、第一碳源及溶剂混合方式可以包括磁力搅拌、机械搅拌、超声分散、研磨分散等等，优选地，采用研磨分散，从而使得活性物质能够分散开，避免活性物质团聚在一起，并且可以使得活性物质分散为较小的纳米颗粒。
具体地，每组预混物进行混合制备前驱体之前，还包括将各组预混物进行湿法球磨，使得活性物质颗粒粒径达到1nm～300nm。
在一些实施方式中，湿法球磨分散时间可以控制在0.5h～10h，通过充分研磨可以使得组分混合更加均匀。
在一些实施方式中，将各组预混物混合之后进行干燥处理。
在一些实施方式中，干燥处理的温度为30℃～400℃，干燥处理的时间为1h～15h。
在一些实施方式中，各组预混物混合后还进行离心处理。
在一些实施方式中，离心处理的转速为100rpm～3000rpm，例如可以为100rpm、500rpm、1000rpm、2000rpm或3000rpm，离心处理时间为10min～60min，例如可以为10min、20min、30min、40min或50min。通过将混合溶液进行旋转离心，从而有利于形成聚集体。
在一些实施方式中，还包括对前驱体或预混物进行密实化处理，通过密实化处理可以有效增强活性物质、碳材料的连接，减少彼此之间的孔隙，提高密实化，以使得制备得到的聚集体的孔隙率≤10％，聚集体的耐压硬度≥100Mpa。
在一些实施方式中，密实化处理包括融合处理、混捏挤压处理、模压处理、等静压处理、及浸渍处理中的至少一种。当然不限于上述方法，只要能使得聚集体的孔隙率≤10％且耐压硬度≥100MPa即可。
在一些实施方式中，融合处理为机械融合。通过融合处理，可以有效增强活性物质与碳材料的连接，减少彼此之间的孔隙，提高密实化。
在一些实施方式中，融合时，融合机的转速为500r/min～3000r/min，具体可以是500r/min、1000r/min、1500r/min、2000r/min、2500r/min或3000r/min等等，融合机刀具间隙宽度为0.01cm～0.5cm，具体可以是0.01cm、0.05cm、0.1cm、0.15cm、0.2cm、0.25cm、0.3cm或0.5cm等等；融合时间至少为0.5h，具体可以是0.5h、0.8h、0.9h、1.0h、1.5h或2h等等，在此不做限定。
在一些实施方式中，本实施方式的前驱体可以包括两种预混物混合制备得到。
具体地，至少两组预混物包括第一预混物、第二预混物。
在一些实施方式中，将活性物质、第一碳源按照质量比为(80～120)：(1～20)和溶剂混合制备得到所述第一预混物；将活性物质、第一碳源按照质量比为(40～80)：(1～30)和溶剂混合制备得到所述第二预混物。
具体地，第一预混物中，活性物质与第一碳源的质量比可以是100：12.9、100：10.9、100：12.9、100：15.9、100：11.9、100：15.9、100：22.9等，当然也可以是上述范围内的其它值，在此不做限定。
具体地，第二预混物中，活性物质与第一碳源的质量比可以是60：22.9、50：20.9、67：12.9、50：22.9、70：21.9、78：20.9等，当然也可以是上述范围内的其它值，在此不做限定。
在一些实施方式中，第一预混物中，活性物质与添加剂的质量比可以为(80～120)：(1～20)；100：12.9、100：10.9、100：12.9、100：15.9、100：11.9、100：15.9、100：22.9等，当然也可以是上述范围内的其它值，在此不做限定。
在一些实施方式中，第二预混物中，活性物质与添加剂的质量比可以为(40～80)：(1～10)；活性物质与碳源的质量比可以是40：22.9、50：20.9、45：12.9、55：22.9、60：21.9、70：20.9等，当然也可以是上述范围内的其它值，在此不做限定。
在一些实施方式中，第一预混物中的活性物质的质量百分含量大于第二预混物中的活性物质质量百分含量。
具体地，此时制备前驱体的步骤包括：将第一预混物和第二预混物混合，得到前驱体。
将第一预混物与第二预混物进行混合过程中，第一预混物与所述第二预混物的流速比为(1～15):1；具体可以是1：1、3：1、5：1、8：1、10：1、12：1或15：1等等，当然也可以是上述范围内的其它值，在此不做限定。可以理解地，分散后的产品和第二预混物中的各组分含量不同，通过控制二者的添加比例和加入流速，有利于获得具有浓度梯度的聚集体。
更进一步地，制备前驱体步骤具体为：将第一预混物进行干燥，分散。
在一些实施方式中，干燥的温度为30℃～400℃，具体可以是30℃、40℃、50℃、80℃、100℃、120℃、150℃、180℃、200℃、250℃、280℃、300℃或400℃等等，干燥处理的时间为1h～15h，具体可以是1h、3h、5h、7h、9h、10h、12h或15h等等，干燥处理方式例如可以是炉内烘干、冷冻干燥、搅拌蒸干、喷雾干燥等，本实施例中的干燥处理可以尽可能地将前驱体溶液中的溶剂去除。
在一些实施方式中，分散为研磨分散，分散时间为0.5-9h，具体可以是0.5h、1.5h、2.5h、3.5h、4.5h、5.5h、7.5h或9h等等，本实施例中的研磨分散，控制分散后的粒度大小，作为内核。
将分散后的产品和第二预混物混合，干燥，得到前驱体。
在一些实施方式中，在混合过程中，分散后的产品与第二预混物的流速比为(1～15)：1。
在一些实施方式中，此混合过程中，还对分散后的产品与第二预混物进行离心处理。离心处理时间为30min～60min，具体可以是30min、35min、40min、45min、50min、55min或60min等等，当然也可以是上述范围内的其他值。通过将混合溶液进行旋转离心，从而有利于形成聚集体。
在一些实施方式中，将分散后的产品与第二预混物混合后还包括干燥处理。
在一些实施方式中，干燥处理的温度为30℃～400℃，具体可以是30℃、40℃、50℃、80℃、100℃、120℃、150℃、180℃、200℃、250℃、280℃、300℃或400℃等等，干燥处理的时间为1h～15h，具体可以是1h、3h、5h、7h、9h、10h、12h或15h等等，干燥处理方式例如可以是炉内烘干、冷冻干燥、搅拌蒸干、喷雾干燥等，本实施例中的干燥处理可以尽可能地将前驱体溶液中的溶剂去除。
在一些实施方式中，干燥后的前驱体可以进行密实化处理，密实化处理包括融合处理，所述融合处理为机械融合。通过融合处理，可以有效增强活性物质、碳材料的连接，减少彼此之间的孔隙，提高密实化。
融合时，融合机的转速为500r/min～3000r/min，具体可以是500r/min、1000r/min、1500r/min、2000r/min、2500r/min或3000r/min等等，融合机刀具间隙宽度为0.01cm～0.5cm，具体可以是0.01cm、0.05cm、0.1cm、0.15cm、0.2cm、0.25cm、0.3cm或0.5cm等等；融合时间至少为0.5h，具体可以是0.5h、0.8h、0.9h、1.0h、1.5h或2h等等，在此不做限定。
在一些实施方式中，本实施方式的前驱体可以包括三组预混物混合制备得到。
具体地，除了上述第一预混物、第二预混物外还可包括第三预混物；本实施方式的第一预混物、第二预混物以及混合等操作均与上述相同，在此不做详细描述。
在一些实施方式中，将活性物质、第一碳源按质量比为(10～40)：(10～40)和溶剂混合制备得到第三预混物；具体地，活性物质与第一碳源的质量比可以是30：22.9、30：20.9、35：12.9、50：22.9、30：21.9、20：20.9等，当然也可以是上述范围内的其它值，在此不做限定。
其中，第二预混物中的活性物质质量百分含量大于第三预混物中的活性物质质量百分含量。
在一些实施方式中，第三预混物中，活性物质与添加剂的质量比为(10～40)：(1～10)；具体地，活性物质与添加剂的质量比可以是30：5.5、30：3.5、35：5.5、20：5.5、10：8.5、20：4.5等，当然也可以是上述范围内的其它值，在此不做限定。
其中，制备前驱体的步骤包括：将第一预混物依次与第二预混物、第三预混物混合，得到前驱体；具体地，首先配置三组不同浓度的组分，其中第一预混物中活性物质含量最高，第三预混物中活性物质含量最低；然后将第一预混物作为高活性物质含量的中心内核，依次与低浓度的第二预混物、第三预混物混合；最后热处理制得聚集体，该聚集体从颗粒表面至颗粒中心，活性物质组分占比逐渐增多。
在一些实施方式中，第一预混物与第二预混物的流速比为(1～15):1，第一预混物和第二预混物混合后的混合物与第三预混物混合的流速比为(1～15):1。
进一步地，制备所述前驱体的步骤具体为：将第一预混物进行干燥，分散；将分散后的第一预混物和第二预混物混合得到混合物，将混合物干燥后与第三预混物混合制备得到前驱体。
在一些实施方式中，在混合过程中，混合物与第三预混物的流速比为(1～15)：1；具体可以是1：1、3：1、5：1、8：1、10：1、12：1或15：1等等，当然也可以是上述范围内的其它值，在此不做限定。
在一些实施方式中，此混合过程中，还需要对混合物与第三预混物进行离心处理。离心处理时间为30min～60min，具体可以是30min、35min、40min、45min、50min、55min或60min等等，当然也可以是上述范围内的其他值。通过将混合溶液进行旋转离心，从而有利于形成聚集体。
在一些实施方式中，将混合物与第三预混物混合后还包括干燥处理。
在一些实施方式中，干燥处理的温度为30℃～400℃，具体可以是30℃、40℃、50℃、80℃、100℃、120℃、150℃、180℃、200℃、250℃、280℃、300℃或400℃等等，干燥处理的时间为1h～15h， 具体可以是1h、3h、5h、7h、9h、10h、12h或15h等等，干燥处理方式例如可以是炉内烘干、冷冻干燥、搅拌蒸干、喷雾干燥等，本实施例中的干燥处理可以尽可能地将前驱体溶液中的溶剂去除。
在一些实施方式中，干燥后的前驱体可以进行密实化处理，密实化处理包括融合处理，所述融合处理为机械融合。通过融合处理，可以有效增强活性物质、碳材料的连接，减少彼此之间的孔隙，提高密实化。
融合时，融合机的转速为500r/min～3000r/min，具体可以是500r/min、1000r/min、1500r/min、2000r/min、2500r/min或3000r/min等等，融合机刀具间隙宽度为0.01cm～0.5cm，具体可以是0.01cm、0.05cm、0.1cm、0.15cm、0.2cm、0.25cm、0.3cm或0.5cm等等；融合时间至少为0.5h，具体可以是0.5h、0.8h、0.9h、1.0h、1.5h或2h等等，在此不做限定。
步骤S20，将前驱体进行热处理，使所述第一碳源碳化，得到聚集体。
在一些实施方式中，热处理的方式例如可以是真空烧结、热压烧结或者常压烧结。热处理的温度为400℃～1200℃，例如可以是500℃、600℃、700℃、800℃、900℃、1000℃、1200℃、1200℃等。优选地，热处理的温度为600℃～1000℃。
在一些实施方式中，热处理的时间1h～15h，例如可以是1h、2h、3h、4h、5h、6h、7h、8h、9h等。
热处理时的升温速率为1℃/min～30℃/min，具体可以是1℃/min、5℃/min、10℃/min、15℃/min、20℃/min、25℃/min或30℃/min等等。例如可以是，优选地，热处理时的升温速率为1℃/min～15℃/min。
热处理过程通有保护性气体，保护性气体包括氮气、氦气、氖气、氩气及氪气中的至少一种。
在一些实施方式中，还包括将聚集体进行碳包覆处理的步骤。
在一些实施方式中，碳包覆处理的步骤包括：将前驱体与第二碳源进行混合、热处理。
在一些实施方式中，第二碳源包括蔗糖、葡萄糖、聚乙烯、聚乙烯醇、聚乙二醇、聚苯胺、环氧树脂、酚醛树脂、糠醛树脂、丙烯酸树脂、聚环氧乙烷、聚偏氟乙烯、聚丙烯腈、聚氯乙烯及沥青中的至少一种。
在一些实施方式中，前驱体的粒径为0.5μm～20μm，具体可以是0.5μm、1μm、5μm、8μm、10μm、13μm、15μm、18μm或20μm等等，当然也可以是上述范围内的其他值，在此不做限定。可以理解地，负极材料的平均粒径控制在上述范围内，有利于负极材料循环性能的提升。
在一些实施方式中，前驱体与第二碳源的质量比为(30～100)：(10～70)；具体地，前驱体与第三碳源的质量比为100:25、100:35、100:45、100:55、100:65等等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，混合方式可以包括磁力搅拌、机械搅拌、超声分散、研磨分散等等。
在一些实施方式中，还可以采用其他方式对聚集体进行碳包覆，具体地，碳包覆处理的步骤包括将聚集体与第二碳源混合、碳化处理，以在聚集体的表面形成碳层。
在一些实施方式中，碳化处理的温度为400℃～1200℃，例如可以是500℃、600℃、700℃、800℃、900℃、1000℃、1200℃、1200℃等。优选地，热处理的温度为600℃～1000℃。
在一些实施方式中，碳化处理的时间1h～15h，例如可以是1h、2h、3h、4h、5h、6h、7h、8h、9h等。
在一些实施方式中，碳化处理时的升温速率为1℃/min～30℃/min，具体可以是1℃/min、5℃/min、10℃/min、15℃/min、20℃/min、25℃/min或30℃/min等等。例如可以是，优选地，热处理时的升温速率为1℃/min～15℃/min。
在一些实施方式中，碳化处理过程通有保护性气体，保护性气体包括氮气、氦气、氖气、氩气及氪气中的至少一种。
需要说明的是，本实施方式的负极材料可以不进行碳包覆，且不限于上述两种碳包覆的方法。
在本方案中，采用上述制备方法制得的负极材料包括聚集体，聚集体包括活性物质和碳材料，活性物质在聚集体中的质量百分含量由所述聚集体的中心到表面逐渐降低。这种结构有助于将活性物质的膨胀控制在聚集体内部，避免活性物质膨胀效应对表面的碳层的破坏，提高负极材料表面的SEI膜的稳定性，具备良好的表面界面稳定性，从而提高材料的循环稳定性能，降低膨胀率。
本公开又提供了一种负极材料，包括聚集体，聚集体包括活性物质和碳材料，碳材料分散于活性物质之间，且以聚集体的质量百分含量为100％计，聚集体表面的活性物质的质量百分含量小于聚集体内部的所述活性物质的质量百分含量。
本公开还提供一种锂离子电池，锂离子电池包括上述负极材料。
本领域的技术人员将理解，以上描述的锂离子电池的制备方法仅是实施例。在不背离本公开 公开的内容的基础上，可以采用本领域常用的其他方法。
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1
本实施例的负极材料的制备方法包括以下步骤：
(1)将中值粒径为100nm的纳米硅、聚乙烯吡咯烷酮和聚氯乙烯按照质量比100：9：12.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第一预混物；将中值粒径为100nm的纳米硅、聚乙烯吡咯烷酮和聚氯乙烯按照质量比60：5.5：22.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第二预混物。
(2)将第一预混物和第二预混物通入混合设备中，控制第一预混物与第二预混物的流速比例为8：2，然后进行旋转离心30min，之后在190℃进行干燥处理5h后获得前驱体。
(3)将前驱体与葡萄糖按照质量比50：55的比例进行混合，随后将混合后的物料放置到高温箱式炉中，通入氮气，在850℃条件下热处理3h后，进行粉碎、通过500目筛过筛，获得负极材料。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅和无定形碳，无定形碳分散于纳米硅之间，纳米硅占聚集体的质量的61％，纳米硅在聚集体表面的质量百分含量为45％，纳米硅与无定形碳的总质比为1.56。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少26.2％，纳米硅与无定形碳的质量比值由聚集体的中心到表面减少2.2；本实施例E-F的值为2.2。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得3个不同位置活性物质在聚集体中的质量百分含量分别为71.2％、61.0％和45.0％。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得80次内T 0满足以下关系：T 0≤3.2-2.2L 1/L 0。
负极材料的中值粒径为14μm，比表面积为4.2m 2/g。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为2.9％。
实施例2
本实施例的负极材料的制备方法包括以下步骤：
(1)将中值粒径为100nm的纳米硅、聚乙烯吡咯烷酮和聚氯乙烯按照质量比100：9：12.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第一预混物；将中值粒径为100nm的纳米硅、聚乙烯吡咯烷酮和聚氯乙烯按照质量比60：5.5：22.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第二预混物；将中值粒径为100nm的纳米硅、聚乙烯吡咯烷酮和聚氯乙烯按照质量比20：2.5：22.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第三预混物。
(2)将第一预混物290℃进行干燥处理3h，获得第一前驱体，然后对第一前驱体加入乙醇溶剂中进行研磨分散，分散时间为8h，获得第一前驱体分散液体；第一前驱体分散液体和第二预混物通入混合设备中，控制第一预混物与第二预混物的流速比例为8：2，然后进行旋转离心30min，之后在190℃进行干燥处理5h后获得第二前驱体。
(3)第二前驱体和第三预混物通入混合设备中，控制第二前驱体与第二预混物的流速比例为2：2，之后在150℃进行干燥处理4h后获得第三前驱体。
(4)将第三前驱体与葡萄糖按照质量比50：55的比例进行混合，随后将混合后的物料放置到高温箱式炉中，通入氮气，在850℃条件下热处理3h后，进行粉碎、通过500目筛过筛，获得负极材料。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅和无定形碳，无定形碳分散于纳米硅之间，纳米硅占聚集体的质量的55％，纳米硅在聚集体表面的质量百分含量为31％，纳米硅与无定形碳的总质量比为1.22。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少30.4％，纳米硅与无定形碳质量比值由聚集体的中心到表面减少1.05，本实施例E-F的值为1.05。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得4个不同位置活性物质在聚集体中的质量百分含量分别为61.4％、55.3％、47.4％和33.0％。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得80次内T 0满足以下关系：T 0≤1.5-1.05L 1/L 0。
负极材料的中值粒径为11.8μm，比表面积为4.2m 2/g。
实施例3
本实施例的负极材料的制备方法包括以下步骤：
(1)将中值粒径为70nm的纳米硅、丙烯酸和葡萄糖按照质量比100：4.9：10.9加入到乙醇溶液中，超声10min，之后在球磨机研磨分散3小时得到第一预混物；将中值粒径为70nm的纳米硅、丙烯酸和葡萄糖按照质量比70：3.5：20.9加入到乙醇溶液中，超声10min，之后在球磨机研磨分散2小时得到第二预混物；将中值粒径为70nm的纳米硅、丙烯酸和葡萄糖按照质量比30：1.5：20.9加入到乙醇溶液中，超声30min，之后在球磨机研磨分散2小时得到第三预混物。
(2)将第一预混物160℃进行干燥处理2h，获得第一前驱体，然后对第一前驱体加入乙二醇溶剂中进行研磨分散，分散时间为4h，获得第一前驱体分散液体；第一前驱体分散液体和第二预混物通入混合设备中，控制第一预混物与第二预混物的流速比例为8：2，然后进行旋转离心30min，之后在180℃进行干燥处理5h后获得第二前驱体。
(3)第二前驱体和第三预混物通入混合设备中，控制第二前驱体与第三预混物的流速比例为4：2，之后在250℃进行干燥处理4h后获得第三前驱体。
(4)将第三前驱体进行机械融合，融合机的转速为500r/min；融合机刀具间隙宽度为0.15cm；融合时间为1.5h。将融合后的物料置于热处理炉中，然后通入氮气，升温至900℃进行一次热处理，保温3h，获得聚集体。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅和无定形碳，无定形碳分散于纳米硅之间，纳米硅占聚集体的质量的46％，纳米硅在聚集体表面的质量百分含量为27％，纳米硅与无定形碳的总质量比为0.85。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少29％，纳米硅与无定形碳质量比值由聚集体的中心到表面减少0.9，本实施例E-F的值为0.9。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得4个不同位置活性物质在聚集体中的质量百分含量分别为56.0％、46.3％、33.4％和27.0％。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得100次内的T 0满足以下关系：T 0≤1.26-0.9L 1/L 0。
负极材料的中值粒径为11μm，比表面积为2.2m 2/g，采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为3.3％；采用纳米压痕仪对聚集体颗粒进行测试，得到聚集体的耐压硬度平均为151Mpa，聚集体的测试密度与聚集体中的纳米硅及无定形碳的平均密度差为1.5％。
实施例4
本实施例的负极材料的制备方法包括以下步骤：
(1)将中值粒径为50nm的纳米硅、油酸和葡萄糖按照质量比100：5：12.9加入到异丙醇溶液中，超声10min，之后在球磨机研磨分散4小时得到第一预混物；将中值粒径为50nm的纳米硅、油酸和葡萄糖按照质量比65：5.5：12.9加入到异丙醇溶液中，超声10min，之后在球磨机研磨分散2小时得到第二预混物。将中值粒径为50nm的纳米硅、油酸和葡萄糖按照质量比15：3.5：12.9加入到异丙醇溶液中，超声40min，之后在球磨机研磨分散2小时得到第二预混物。
(2)将第一预混物在360℃进行干燥处理2h，获得第一前驱体，然后对第一前驱体加入乙二醇溶剂中进行研磨分散，分散时间为7h，获得第一前驱体分散液体；第一前驱体分散液体和第二预混物通入混合设备中，控制第一预混物与第二预混物的流速比例为5：3，然后进行旋转离心30min，之后在180℃进行干燥处理5h后获得第二前驱体。
(3)第二前驱体和第三预混物通入混合设备中，控制第一预混物与第二预混物的流速比例为4：5，之后在250℃进行干燥处理4h后获得第三前驱体。
(4)将第三前驱体进行机械融合，融合机的转速为400r/min；融合机刀具间隙宽度为0.25cm；融合时间为1.5h。将融合后的物料置于热处理炉中，然后通入氮气，升温至920℃进行一次热处理，保温3h，获得聚集体。
(5)将聚集体与酚醛树脂按照质量比100：25的比例进行混合，随后将混合后的物料放置到高温箱式炉中，通入氮气，在1050℃条件下热处理2h后，进行粉碎、通过500目筛过筛，获得负极材料。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅和无定形碳，无定形碳分散于纳米硅之间，纳米硅占聚集体的质量的51％，纳米硅在聚集体表面的质量百分含量为43％，纳米硅与无定形碳的总质量比为1.17。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少11.5％，纳米硅与无定形碳质量比值由聚集体的中心到表面减少0.5，本实施例E-F的值为0.5。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得4个不同位置活性物质在聚集体中的质量百分含量分别为54.5％、50.3％、46.4％和43.0％。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得90次内的T 0满足以下关系：T 0≤1.32-0.5L 1/L 0。
负极材料的中值粒径为5.2μm，比表面积为4.2m 2/g，采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为3.9％；采用纳米压痕仪对聚集体颗粒进行测试，得到聚集体的耐压硬度平均为165Mpa，聚集体的测试密度与聚集体中的纳米硅及无定形碳的平均密度差为1.1％。
实施例5
本实施例的负极材料的制备方法包括以下步骤：
(1)将中值粒径为20nm的纳米硅、硬脂酸和柠檬酸按照质量比100：1.9：15.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2小时得到第一预混物；同时将中值粒径为20nm的纳米硅、硬脂酸和蔗糖按照质量比50：5.5：22.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2小时得到第二预混物；将中值粒径为20nm的纳米硅、硬脂酸和蔗糖按照质量比30：3.5：22.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2小时得到第三预混物。
(2)将第一预混物在140℃进行干燥处理6h，获得第一前驱体，然后对第一前驱体加入乙二醇溶剂中进行研磨分散，分散时间为8h，获得第一前驱体分散液体；第一前驱体分散液体和第二预混物通入混合设备中，控制第一预混物与第二预混物的流速比例为3：3，然后进行旋转离心30min，之后在280℃进行干燥处理5h后获得第二前驱体。
(3)第二前驱体和第三预混物通入混合设备中，控制第二前驱体和第三预混物的流速比例为6：2，之后在450℃进行干燥处理4h后获得第三前驱体。
(4)将第三前驱体与葡萄糖按照质量比100：35的比例进行混合，随后将混合后的物料放置到高温箱式炉中，通入氮气，在750℃条件下热处理3h后，进行粉碎、通过500目筛过筛，获得负极材料。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅和无定形碳，无定形碳分散于纳米硅之间，纳米硅占聚集体的质量的69％，纳米硅在聚集体表面的质量百分含量为54％，纳米硅与无定形碳的总质量比为2.22。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少21.2％，纳米硅与无定形碳质量比值由聚集体的中心到表面减少1.86，本实施例E-F的值为1.86。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得3个不同位置活性物质在聚集体中的质量百分含量分别为75.2％、66.3％和54.0％。
负极材料的中值粒径为18μm，比表面积为3.2m 2/g。
实施例6
本实施例的负极材料的制备方法包括以下步骤：
(1)将中值粒径为100nm的纳米锡、聚乙烯吡咯烷酮和果糖按照质量比100：4：11.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散5小时得到第一预混物；同时将中值粒径为100nm的纳米锡、聚乙烯吡咯烷酮和果糖按照质量比45：8.5：21.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2小时得到第二预混物。
(2)将第一前驱体溶液和第二前驱体溶液通入混合设备中，控制第一预混物与第二预混物的流速比例为4：6，然后进行旋转离心30min，之后在300℃进行干燥处理4h后获得前驱体。
(3)将前驱体与葡萄糖按照质量比100：45的比例进行混合，随后将混合后的物料放置到高温箱式炉中，通入氮气，在750℃条件下热处理3h后，进行粉碎、通过500目筛过筛，获得负极材料。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米锡和无定形碳，无定形碳分散于纳米锡之间，纳米锡占聚集体的质量的66％，纳米锡在聚集体表面的质量百分含量为47.5％，纳米锡与无定形碳的总质量比为3.04。纳米锡在聚集体中的质量百分含量由聚集体的中心到表面减少32.2％，纳米锡与无定形碳质量比值由聚集体的中心到表面减少3.04，本实施例E-F的值为3.04。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得4个不同位置活性物质在聚集体中的质量百分含量分别为79.7％、66.3％、55.4％和47.5％。
负极材料的中值粒径为3.9μm，比表面积为4.5m 2/g。
实施例7
本实施例的负极材料的制备方法包括以下步骤：
(1)将中值粒径为100nm的纳米锗、十二烷基苯磺酸钠和酚醛树脂按照质量比100：3.5：15.9加入到乙醇溶液中，超声10min，之后在球磨机研磨分散2小时得到第一预混物；同时将中值粒径为100nm的纳米锗、十二烷基苯磺酸钠和聚氯乙烯按照质量比50：4.5：20.9加入到乙醇溶液中，超声10min，之后在球磨机研磨分散6小时得到第二预混物；将中值粒径为100nm的纳米锗、十二烷基苯磺酸钠和聚氯乙烯按照质量比20：1.5：20.9加入到乙醇溶液中，超声40min，之后在球磨机研磨分散6小时得到第二预混物。
(2)将第一预混物在120℃进行干燥处理5h，获得第一前驱体，然后对第一前驱体加入丁醇溶剂中进行研磨分散，分散时间为6h，获得第一前驱体分散液体；第一前驱体分散液体和第二预混物通入混合设备中，控制第一预混物与第二预混物的流速比例为9：3，之后在280℃进行干燥处理5h后获得第二前驱体。
(3)第二前驱体和第三预混物通入混合设备中，控制第二前驱体与第三预混物的流速比例为8：2，之后在350℃进行干燥处理4h后获得第三前驱体。
(4)将第三前驱体进行机械融合，融合机的转速为550r/min；融合机刀具间隙宽度为0.15cm；融合时间为3h。将融合后的物料置于热处理炉中，然后通入氮气，升温至800℃进行一次热处理，保温3h，获得聚集体。
(3)将聚集体与葡萄糖按照质量比100：65的比例进行混合，随后将混合后的物料放置到高温箱式炉中，通入氮气，在950℃条件下热处理3h后，进行粉碎、通过500目筛过筛，获得负极材料。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米锗和无定形碳，无定形碳分散于纳米锗之间，纳米锗占聚集体的质量的54％，纳米锗在聚集体表面的质量百分含量为38％，纳米锗与无定形碳的总质量比为1.17。纳米锗在聚集体中的质量百分含量由聚集体的中心到表面减少31.4％，纳米锗与无定形碳的质量比值由聚集体的中心到表面减少1.31，本实施例E-F的值为1.31。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得6个不同位置活性物质在聚集体中的质量百分含量分别为69.5％、60.3％、55.7％、50.4％、45.4％和38.0％。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得80次内的T 0满足以下关系：T 0≤2.26-1.31L 1/L 0。
负极材料的中值粒径为13.9μm，比表面积为2.9m 2/g；采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为4.9％；采用纳米压痕仪对聚集体颗粒进行测试，得到聚集体的耐压硬度平均为138Mpa，聚集体的测试密度与聚集体中的纳米锗及无定形碳的平均密度差为1.7％。
实施例8
本实施例的负极材料的制备方法包括以下步骤：
(1)将中值粒径为100nm的纳米铝、聚丙烯酰胺和柠檬酸按照质量比100：7.9：22.9加入到丙醇溶液中，超声10min，之后在球磨机研磨分散8小时得到第一预混物；将中值粒径为100nm的纳米铝、聚丙烯酰胺和柠檬酸按照质量比48：3.5：12.9加入到丙醇溶液中，超声10min，之后在球磨机研磨分散5小时得到第二预混物；同时将中值粒径为100nm的纳米铝、聚丙烯酰胺和柠檬酸按照质量比22：2.5：12.9加入到丙醇溶液中，超声10min，之后在球磨机研磨分散5小时得到第三预混物。
(2)将第一预混物在220℃进行干燥处理5h，获得第一前驱体，然后对第一前驱体加入正戊醇溶剂中进行研磨分散，分散时间为2h，获得第一前驱体分散液体；第一前驱体分散液体和第二预混物通入混合设备中，控制第一预混物与第二预混物的流速比例为9：9，之后在280℃进行干燥处理4h后获得第二前驱体。
(3)第二前驱体和第三预混物通入混合设备中，控制第二前驱体和第三预混物的流速比例为8：5，之后在350℃进行干燥处理2h后获得第三前驱体。
(4)将第三前驱体与葡萄糖按照质量比100：55的比例进行混合，随后将混合后的物料放置到高温箱式炉中，通入氮气，在950℃条件下热处理4h后，进行粉碎、通过500目筛过筛，获得负极材料。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米铝和无定形碳，纳米铝占聚集体的质量的49％，纳米铝在聚集体表面的质量百分含量为33％，纳米铝与无定形碳的总质量比为0.96。纳米铝在聚集体中的质量百分含量由聚集体的中心到表面减少12.02％，纳米铝与无定形碳的质量比值由聚集体的中心到表面减少2.0，本实施例E-F的值为2.0。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得5个不同位置活性物质在聚集 体中的质量百分含量分别为45.02％、41.3％、38.5％、35.6％和33.0％。
负极材料的中值粒径为17.9μm，比表面积为1.95m 2/g。
实施例9
本实施例与实施例1的区别在于，前驱体不进行碳包覆；即步骤(3)将前驱体放置到高温箱式炉中，通入氮气，在950℃条件下热处理3h后，进行粉碎、通过500目筛过筛，获得负极材料。
本实施例制得的负极材料包括聚集体，聚集体包括纳米硅和无定形碳，纳米硅占聚集体的质量的65％，纳米硅在聚集体表面的质量百分含量为53％，纳米硅与无定形碳的总质量比为1.86。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少16.7％，纳米硅与无定形碳的质量比值由聚集体的中心到表面减少1.18，本实施例E-F的值为1.18。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T值，测得75次内的T满足以下关系：T≤2.37-1.18L 1/L 0。
负极材料的中值粒径为9.6μm，比表面积为5.2m 2/g，采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为2.1％；采用纳米压痕仪对聚集体颗粒进行测试，得到聚集体的耐压硬度平均为149Mpa。聚集体的测试密度与聚集体中的纳米铝及无定形碳的平均密度差为1.8％。
实施例10
本实施例与实施例2的区别在于，步骤1)中的第一预混物、第二预混物的不同；步骤1)为：将中值粒径为100nm的纳米Si、长径比为22的SiO、聚乙烯吡咯烷酮和聚氯乙烯按照质量比80：3：2：2.5加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第一预混物；将中值粒径为100nm的纳米硅、长径比为22的SiO、聚乙烯吡咯烷酮和聚氯乙烯按照质量比55：1.5：1：2.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第二预混物。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米Si、SiO和无定形碳，纳米硅占聚集体的质量的58％，纳米硅与无定形碳的总质量比为1.49。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少20.9％，纳米硅与无定形碳的质量比值由聚集体的中心到表面减少1.23，本实施例E-F的值为1.23。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得93次内的T 0满足以下关系：T 0≤2.13-1.23L 1/L 0。
负极材料的中值粒径为13μm，比表面积为3.8m 2/g，采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为6.9％；采用纳米压痕仪对聚集体颗粒进行测试，得到聚集体的耐压硬度平均为258Mpa；聚集体的测试密度与聚集体中的纳米Si、SiO颗粒及碳材料的平均密度差为1.2％。
实施例11
本实施例与实施例2的区别在于，步骤1)中的第一预混物、第二预混物的不同；步骤1)为：将中值粒径为100nm的纳米硅、长径比为15的NiSi合金、聚乙烯吡咯烷酮和聚氯乙烯按照质量比100：4.5:2：2.5加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第一预混物；将中值粒径为100nm的纳米硅、长径比为15的NiSi合金、聚乙烯吡咯烷酮和聚氯乙烯按照质量比45：1：2.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第二预混物。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅、NiSi合金和无定形碳，纳米硅占聚集体的质量的55％，纳米硅在聚集体表面的质量百分含量为42.8％，纳米硅与无定形碳的总质量比为1.35。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少24％，纳米硅与无定形碳的质量比值由聚集体的中心到表面减少0.92，本实施例E-F的值为0.92。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得55次内的T 0满足以下关系：1.1≤T≤2.02，且T 0≤2.02-0.92L 1/L 0。
负极材料的中值粒径为11.6μm，比表面积为4.1m 2/g。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为2.5％；采用纳米压痕仪对聚集体颗粒进行测试，得到聚集体的耐压硬度平均为378Mpa；聚集体的测试密度与聚集体中的纳米Si、NiSi合金及碳材料的平均密度差为0.8％。
实施例12
本实施例与实施例1的区别在于，步骤1)中的第一预混物、第二预混物的不同；步骤(1)为：将中值粒径为100nm的纳米硅、TiO 2、FeSi 2、聚乙烯吡咯烷酮和聚氯乙烯按照质量比100：3：3.5：2：30加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第一预混物；将中值粒径为100nm的纳米硅、聚乙烯吡咯烷酮和聚氯乙烯按照质量比65：1：22.9加入到乙二醇溶液中， 超声10min，之后在球磨机研磨分散2h得到第二预混物。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅和无定形碳，纳米硅占聚集体的质量的45％，纳米硅在聚集体表面的质量百分含量为37.5％，纳米硅与无定形碳的总质量比为0.98。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少14.2％，纳米硅与无定形碳的质量比值由聚集体的中心到表面减少0.85，本实施例E-F的值为0.85。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得100次内的T 0满足以下关系：且T 0≤1.45-0.85L1/L0。
负极材料的中值粒径为12.5μm，比表面积为5.1m 2/g，采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为4.4％；采用纳米压痕仪对聚集体颗粒进行测试，得到聚集体的耐压硬度平均为498Mpa；聚集体的测试密度与聚集体中的纳米Si、NiSi合金及碳材料的平均密度差为0.85％。
实施例13
按照与实施例3基本相同的方法制备负极材料，区别在于：未添加添加剂。
本实施例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅和无定形碳，纳米硅占聚集体的质量的46％，纳米硅在聚集体表面的质量百分含量为27％，纳米硅与无定形碳的总质量比为0.85。纳米硅在聚集体中的质量百分含量由聚集体的中心到表面减少28.5％，纳米硅与无定形碳的质量比值由聚集体的中心到表面减少0.88，本实施例E-F的值为0.88。
在聚集体颗粒内部取任意多个区域进行测试，测试区域为2μm×2μm的方形区域，将纳米硅的质量百分含量与无定形碳的质量百分含量的比值定义为T，统计任意测试区域中心位置的T 0值，测得55次内的T 0满足以下关系：T 0≤1.29-0.88L 1/L 0。
负极材料的中值粒径为10.4μm，比表面积为2.8m 2/g。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为3.9％；采用纳米压痕仪对聚集体颗粒进行测试，得到聚集体的耐压硬度平均为98Mpa，聚集体的测试密度与聚集体中的纳米硅及碳材料的平均密度差为2.6％。
对比例1
按照与实施例2基本相同的方法制备负极材料，区别在于只含有第一预混物；
(1)将中值粒径为100nm的纳米硅、聚乙烯吡咯烷酮和聚氯乙烯按照质量比100：9：12.9加入到乙二醇溶液中，超声10min，之后在球磨机研磨分散2h得到第一预混物。
(2)将第一预混物290℃进行干燥处理3h，获得第一前驱体，然后对第一前驱体加入乙醇溶剂中进行研磨分散，分散时间为8h，获得第一前驱体分散液体，之后在150℃进行干燥处理4h后获得第一前驱体。
(4)将第一前驱体与葡萄糖按照质量比50：55的比例进行混合，随后将混合后的物料放置到高温箱式炉中，通入氮气，在850℃条件下热处理3h后，进行粉碎、通过500目筛过筛，获得负极材料。
本对比例制得的负极材料包括聚集体及包覆于聚集体表面的碳层，聚集体包括纳米硅和无定形碳，无定型碳分散于纳米硅之间，纳米硅占聚集体的质量的60％，纳米硅与无定形碳的质量百分含量的比值为1.5。
从聚集体的SEM切面中心到表面使用能谱仪进行点扫描，测得4个不同位置活性物质在聚集体中的质量百分含量分别为61.0％、59.3％、60.4％、58.8％和61.4％。
负极材料的中值粒径为12.8μm，比表面积为3.2m 2/g。
测试方法
采用以下方法测试电化学循环性能：将制得的负极材料、导电剂和粘结剂按质量百分比94：1：5将他们溶解在溶剂中混合，控制固含量在50％，涂覆于铜箔集流体上，真空烘干、制得负极极片；然后将传统成熟工艺制备的三元正极极片、1mol/L的LiPF6/碳酸乙烯酯+碳酸二甲酯+甲基乙基碳酸酯(v/v＝1:1:1)电解液、Celgard2400隔膜、外壳采用常规生产工艺得到锂离子电池。利用千分尺测量锂离子电池的极片初始厚度为H0，锂离子电池的充放电测试在武汉金诺电子有限公司LAND电池测试***上，在常温条件，0.2C恒流充放电，充放电电压限制在2.75～4.2V，得到首次可逆容量、首圈充电容量和首圈放电容量。首次库伦效率＝首圈放电容量/首圈充电容量。
重复循环50周，利用千分尺测量锂离子电池此时极片的厚度为H 1，循环50圈后膨胀率＝(H 1-H 0)/H 0×100％。
重复100周循环，记录放电容量，作为锂离子电池的剩余容量；容量保持率＝剩余容量/初始容量*100％。上述性能测试的结果如下：
表1.性能比对结果表
Figure PCTCN2022096668-appb-000001
如表1所示，实施例1至13制得的负极材料，包括聚集体，其中，聚集体包括活性物质和碳材料，且处于聚集体内核中心的活性物质组分占比较多，碳材料组分占比较少，远离内核中心的活性物质组分占逐渐减少，碳材料组分占比逐渐增加，这种结构有助于将活性物质的膨胀控制在聚集体内部，避免活性物质膨胀效应对表面的碳层的破坏，提高负极材料表面的SEI膜的稳定性，具备良好的表面界面稳定性，从而提高材料的循环稳定性能，降低膨胀率。
其中，实施例6的负极材料在制备过程中，第一预混物与第二预混物流速比值过小，即活性物质浓度高的第一预混物与活性物质浓度低的第二预混物混合，缩小了活性物质组分含量的梯度范围，即T值分布范围缩小，浓度梯度差异缩小，不利于将活性物质的膨胀控制在聚集体内部，导致循环保持率略有下降，极片膨胀效率提高。
实施例8中的碳源前驱体葡萄糖的加入含量过多，使得最终制得负极材料中的活性物质占比减少，负极材料的首次库伦效率以及循环容量保持率下降。
实施例10～12中，含有金属氧化物以及导电增强剂的活性物质材料，拥有更高的耐压硬度，负极材料的循环容量保持率更高，体积膨胀率更低。
实施例13的负极材料在制备过程中，未添加添加剂，活性物质与碳材料聚体稳定性差，导致极片膨胀率提高。
对比例1的负极材料在制备过程中，未配置第二预混物，只存在第一预混物，制得的聚集体颗粒内部活性物质与碳材料组分含量比例单一，即活性物质分布范围趋于集中，活性物质的百分含量没有表现出从中心到表面逐渐降低的规律，以及表面小于内部的规律，不利于抑制负极材料的膨胀率。
本公开虽然以较佳实施例公开如上，但并不是用来限定权利要求，任何本领域技术人员在不脱离本公开构思的前提下，都可以做出若干可能的变动和修改，因此本公开的保护范围应当以本公开权利要求所界定的范围为准。
工业实用性
综上所述，本公开提供了负极材料及其制备方法、锂离子电池，其中，负极材料包括聚集体，所述聚集体包括活性物质和碳材料；所述活性物质在所述聚集体中的质量百分含量由所述聚集体的中心到表面逐渐降低。本公开提供的负极材料能够有效抑制负极材料体积膨胀，提升电池循环性能。

Claims (11)

  1. 一种负极材料，其特征在于，包括聚集体，所述聚集体包括活性物质和碳材料，所述活性物质在所述聚集体中的质量百分含量由所述聚集体的中心到表面逐渐降低。
  2. 根据权利要求1所述的负极材料，其中，包含以下特征(1)至(7)中的至少一种：
    (1)所述活性物质与所述碳材料的质量比由所述聚集体的中心到表面逐渐降低；
    (2)所述活性物质与所述碳材料的总质量比为0.5～8；
    (3)以聚集体的质量百分含量为100％计，所述活性物质的质量百分含量为5％～90％；
    (4)以聚集体的质量百分含量为100％计，所述活性物质的质量百分含量为5％～80％；
    (5)所述活性物质在聚集体表面的质量百分含量为2％～55％；
    (6)所述聚集体中所述活性物质与所述碳材料的质量比的最大值为E，最小值为F，E-F≥0.5；
    (7)对所述聚集体SEM切面上自表面至中心的任一区域使用能谱仪进行EDS点扫描测试，所述活性物质与所述碳材料的质量比定义为T，对区域内进行N次测试，N≥10，其中，A为N次测试结果中T的最小值，B为N次测试结果中T的最大值，所述聚集体表面任意一点至中心的距离为L 0μm，测试区域的中心至所述聚集体的中心的距离为L 1μm，所述测试区域中心位置的T值定义为T 0，T 0满足关系：T≤B-(B-A)L 1/L 0。
  3. 根据权利要求1或2所述的负极材料，其中，包含以下特征(1)至(6)中的至少一种：
    (1)所述活性物质包括Li、Na、K、Sn、Ge、Si、SiO x、Fe、Mg、Ti、Zn、Al、Ni、P及Cu中的至少一种，其中，0＜x＜2；
    (2)所述活性物质的中值粒径为1nm～300nm；
    (3)所述碳材料包括石墨类碳材料和非石墨类碳材料；
    (4)所述石墨类碳材料包括天然石墨和/或人造石墨；
    (5)所述人造石墨包括中间相碳微球；
    (6)所述非石墨类碳材料包括无定形碳、结晶碳、硬碳和软碳中的至少一种。
  4. 根据权利要求1～3任一项所述的负极材料，其中，包含以下特征(1)至(12)中的至少一种：
    (1)所述聚集体还包括金属氧化物及导电增强剂中的至少一种；
    (2)所述金属氧化物的化学通式为M xO y，0.2≤y/x≤3，其中，M包括Sn、Ge、Fe、Cu、Ti、Na、Mg、Al、Ca及Zn中的至少一种；
    (3)所述金属氧化物呈片状和/或长条状；
    (4)所述金属氧化物的长径比大于2；
    (5)所述导电增强剂的电导率为10 0S/m～10 8S/m；
    (6)所述导电增强剂呈片状和/或长条状；
    (7)所述导电增强剂的长径比为2～5000；
    (8)所述导电增强剂包括合金材料及导电碳中的至少一种；
    (9)所述金属氧化物与活性物质的质量比为1～20：100；
    (10)所述导电增强剂与活性物质的质量比为0.01～20：100；
    (11)所述合金材料包括锌合金、铝合金、铜合金、硅合金、镍合金和钛合金中的至少一种；
    (12)所述导电碳包括石墨纤维、碳纳米管、石墨片、导电碳纤维和石墨烯中的一种。
  5. 根据权利要求1～4任一项所述的负极材料，其中，包含以下特征(1)至(8)中的至少一种：
    (1)所述负极材料还包括包覆于所述聚集体的至少部分表面的碳层；
    (2)所述碳层的材料包括石墨和/或无定形碳；
    (3)所述碳层的厚度为10nm～2000nm；
    (4)所述负极材料的中值粒径为0.5μm～30μm；
    (5)所述负极材料的比表面积≤10m 2/g；
    (6)所述聚集体的孔隙率≤10％；
    (7)所述聚集体的耐压硬度≥100Mpa；
    (8)所述聚集体密度满足以下关系：(ρ1-ρ2)/ρ2≤5％，其中，ρ1为聚集体的测试密度，ρ2为聚集体的平均密度；所述ρ2为聚集体中各组分在聚集体中的质量百分含量*各组分的理论密度的值的总和。
  6. 一种负极材料的制备方法，其中，包括以下步骤：
    将至少两组预混物混合制备前驱体，其中，每组所述预混物均包含活性物质、第一碳源及溶剂，且至少有两组所述预混物中所述活性物质的质量百分含量不同；及
    对所述前驱体热处理，使所述第一碳源碳化，得到聚集体。
  7. 根据权利要求6的制备方法，其中，包括以下特征(1)至(26)中的至少一种：
    (1)所述至少两组预混物中，所述活性物质的质量百分含量最大值与质量百分含量最小值的差值为20％～90％；
    (2)所述活性物质包括Li、Na、K、Sn、Ge、Si、SiO x、Fe、Mg、Ti、Zn、Al、P及Cu中的至少一种，其中，0＜x＜2；
    (3)所述第一碳源包括蔗糖、葡萄糖、聚乙烯、聚乙烯醇、聚乙二醇、聚苯胺、环氧树脂、酚醛树脂、糠醛树脂、丙烯酸树脂、聚环氧乙烷、聚偏氟乙烯、聚丙烯腈、聚氯乙烯和沥青中的至少一种；
    (4)所述溶剂包括有机溶剂；
    (5)所述有机溶剂包括甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇及戊醇中的至少一种；
    (6)至少一组所述预混物中还包括添加剂、金属氧化物及导电增强剂中的至少一种；
    (7)所述添加剂包括表面活性剂和偶联剂中的至少一种；
    (8)所述表面活性剂包括正十八酸、月桂酸、聚丙烯酸、十二烷基苯磺酸钠、正二十酸、棕榈酸、十四烷酸、十一烷酸、十六烷基三甲基溴化胺及聚乙烯吡咯烷酮中的至少一种；
    (9)所述偶联剂包括硅烷偶联剂和/或钛酸酯偶联剂；
    (10)所述硅烷偶联剂包括γ-氨丙基三乙氧基硅烷、γ-缩水甘油醚氧丙基三甲氧基硅烷、γ-甲基丙烯酰氧基丙基三甲氧基硅烷；
    (11)所述金属氧化物的化学通式为M xO y，0.2≤y/x≤3，其中，M包括Sn、Ge、Fe、Cu、Ti、Na、Mg、Al、Ca及Zn中的至少一种；
    (12)所述金属氧化物呈片状和/或长条状；
    (13)所述金属氧化物的长径比大于2；
    (14)所述金属氧化物与活性物质的质量比为1～20：100；
    (15)所述导电增强剂与活性物质的质量比为0.01～20；
    (16)所述导电增强剂的电导率为10 0S/m～10 8S/m；
    (17)所述导电增强剂呈片状和/或长条状；
    (18)所述导电增强剂的长径比为2～5000；
    (19)所述导电增强剂包括合金材料及导电碳中的至少一种；
    (20)制备所述前驱体还包括将混合后的预混合物进行干燥处理、分散处理中的至少一种；
    (21)所述干燥处理的温度为30℃～400℃，干燥处理的时间为1h～15h；
    (22)所述分散处理包括机械搅拌、超声分散及研磨分散中的至少一种；
    (23)制备所述前驱体还包括将混合后的预混合物进行离心处理；
    (24)所述离心处理的转速为100rpm～3000rpm，所述离心处理时间为10min～60min；
    (25)所述合金材料包括锌合金、铝合金、铜合金、硅合金、镍合金和钛合金中的至少一种；
    (26)所述导电碳包括石墨纤维、碳纳米管、石墨片、导电碳纤维和石墨烯中的一种。
  8. 根据权利要求6或7所述的制备方法，其中，包括以下特征(1)至(18)中的至少一种：
    (1)所述至少两组预混物包括第一预混物、第二预混物；
    (2)所述第一预混物中所述活性物质与所述第一碳源的质量比为(80～120)：(1～20)；
    (3)所述第二预混物中所述活性物质与所述第一碳源的质量比为(40～80)：(1～30)；
    (4)所述第一预混物中的活性物质的质量百分含量大于或小于所述第二预混物中的活性物质质量百分含量；
    (5)制备所述前驱体的步骤包括：将所述第一预混物和第二预混物混合，得到所述前驱体；
    (6)制备所述前驱体的步骤具体为：将所述第一预混物进行干燥、分散，将分散后的固体颗粒和第二预混物混合、干燥，得到所述前驱体，并且所述第一预混物中的活性物质的质量百分含量大于所述第二预混物中的活性物质质量百分含量；
    (7)所述第一预混物中，所述活性物质与所述添加剂的质量比为(80～120)：(1～20)；
    (8)所述第二预混物中，所述活性物质与所述添加剂的质量比为(40～80)：(1～10)；
    (9)所述至少两组预混物混合制备前驱体步骤包括至少三组预混物混合制备所述前驱体；
    (10)所述至少三组预混物混合的步骤包括将所述预混物按照活性物质在所述预混物中的质量百分含量由高至低顺序依次混合；
    (11)所述至少两组预混物还包括第三预混物；
    (12)将所述活性物质、所述第一碳源按质量比为(10～40)：(10～40)和溶剂混合制备得到所述第三预混物；
    (13)所述第二预混物中的活性物质质量百分含量大于所述第三预混物中的活性物质质量百分含量；
    (14)制备所述前驱体的步骤包括：将所述第一预混物依次与第二预混物、第三预混物混合，得到所述前驱体；
    (15)制备所述前驱体的步骤具体为：将第一预混物进行干燥，分散；将分散后的第一预混物和第二预混物混合得到混合物，将混合物干燥后与第三预混物混合制备得到前驱体；
    (16)所述第三预混物中，所述活性物质与所述添加剂的质量比为(10～40)：(1～10)；
    (17)所述将第一预混物与第二预混物进行混合过程中，所述第一预混物与所述第二预混物的流速比为(1～15):1；
    (18)将所述第一预混物与第二预混物混合得到混合物，将所述混合物与第三预混物混合过程中，所述混合物与第三预混物混合的流速比为(1～15):1。
  9. 根据权利要求6-8任一项所述的制备方法，其中，包括以下特征(1)至(18)中的至少一种：
    (1)所述前驱体进行热处理之前，还包括对所述前驱体或对所述预混物进行密实化处理，使得所述的聚集体的孔隙率≤10％且耐压硬度≥100Mpa；
    (2)所述密实化处理包括融合处理、混捏挤压处理、模压处理、等静压处理、及浸渍处理中的至少一种；
    (3)所述的融合处理为机械融合；
    (4)所述机械融合所用的融合机的转速为500r/min～3000r/min；
    (5)所述机械融合所用的融合机刀具间隙宽度为0.01cm～0.5cm；
    (6)所述机械融合时间至少为0.5h；
    (7)所述对前驱体热处理前还包括干燥处理；
    (8)所述干燥处理的温度为30℃～400℃，所述干燥处理的时间为1h～15h；
    (9)所述热处理温度为600℃～1200℃，所述热处理的时间为1h～15h；
    (10)所述热处理过程通有保护性气体；
    (11)所述保护性气体包括氮气、氦气、氖气、氩气及氪气中的至少一种；
    (12)所述方法还包括对所述聚集体进行碳包覆处理；
    (13)所述碳包覆处理的步骤包括：将前驱体与第二碳源进行混合、热处理；
    (14)所述前驱体与所述第二碳源的质量比为(30～100)：(10～70)；
    (15)所述碳包覆处理的步骤包括：将所述聚集体与第二碳源混合、碳化处理；
    (16)所述第二碳源包括蔗糖、葡萄糖、聚乙烯、聚乙烯醇、聚乙二醇、聚苯胺、环氧树脂、酚醛树脂、糠醛树脂、丙烯酸树脂、聚环氧乙烷、聚偏氟乙烯、聚丙烯腈、聚氯乙烯及沥青中的至少一种；
    (17)所述聚集体与所述第二碳源的质量比为(30～100)：(10～70)；
    (18)所述碳化处理的温度为600℃～1200℃，所述碳化处理的时间为1h～15h。
  10. 一种负极材料，其特征在于，包括聚集体，所述聚集体包括活性物质和碳材料，所述碳材料分散于所述活性物质之间，且以聚集体的质量百分含量为100％计，所述聚集体表面的所述活性物质的质量百分含量小于所述聚集体内部的所述活性物质的质量百分含量。
  11. 一种锂离子电池，所述锂离子电池包括根据权利要求1-5或权利要求10任一项所述的负极材料、或根据权利要求6-9任一项所述的制备方法制得的负极材料。
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