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WO2023273726A1 - 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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WO2023273726A1
WO2023273726A1 PCT/CN2022/095217 CN2022095217W WO2023273726A1 WO 2023273726 A1 WO2023273726 A1 WO 2023273726A1 CN 2022095217 W CN2022095217 W CN 2022095217W WO 2023273726 A1 WO2023273726 A1 WO 2023273726A1
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Prior art keywords
aggregate
carbon
silicon
alloy
treatment
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PCT/CN2022/095217
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English (en)
French (fr)
Inventor
何鹏
肖称茂
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 KR1020227042923A priority Critical patent/KR20230009434A/ko
Priority to US18/006,720 priority patent/US20230275213A1/en
Priority to JP2022575676A priority patent/JP7683888B2/ja
Priority to EP22831549.5A priority patent/EP4170752A4/en
Publication of WO2023273726A1 publication Critical patent/WO2023273726A1/zh

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    • H—ELECTRICITY
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    • 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
    • H—ELECTRICITY
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    • 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
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    • 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
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H01M4/364—Composites as mixtures
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    • 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
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    • 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
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    • 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
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • H01M4/602—Polymers
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    • 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
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    • 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
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    • H01M4/00—Electrodes
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
    • 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 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 present disclosure provides a negative electrode material.
  • the negative electrode material includes aggregates, and the aggregates include active materials and carbon materials, wherein the porosity of the aggregates is ⁇ 10%, and the compressive hardness of the aggregates is ⁇ 100 MPa.
  • the active material includes at least one of silicon oxide, a non-metal element, a metal element, and an alloy of the metal element and silicon.
  • the metal element includes at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al and Cu.
  • the non-metal elemental substance includes at least one of Si and P.
  • the silicon oxide includes SiOx, where 0 ⁇ x ⁇ 2.
  • the alloy of the metal element and silicon includes silicon-lithium alloy, silicon-sodium alloy, silicon-potassium alloy, silicon-tin alloy, silicon-germanium alloy, ferrosilicon alloy, silicon-magnesium alloy, silicon-titanium alloy, silicon-zinc alloy, silicon At least one of aluminum alloy and silicon copper alloy.
  • the median diameter of the active material is 1 nm to 500 nm.
  • the carbon material includes at least one of amorphous carbon, crystalline carbon, and mesocarbon microspheres.
  • the amorphous carbon includes at least one of hard carbon and soft carbon.
  • the mass ratio of the active material to the carbon material is (30-70):(10-70).
  • the aggregate density satisfies the following relationship: ( ⁇ 1- ⁇ 2)/ ⁇ 2 ⁇ 5%, wherein ⁇ 1 is the test density of the aggregate, ⁇ 2 is the average density of the aggregate, and ⁇ 2 is each component in the aggregate The mass percentage in the aggregate * the sum of the values of the theoretical density of each component.
  • the aggregates further include metal oxides.
  • the metal oxide is distributed in the active material, and the carbon material is filled between the active material and the metal oxide.
  • pores there are pores between the active material and the metal oxide, and the carbon material is filled in the pores.
  • 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 active material to the metal oxide is (30-70):(1-20).
  • the aggregates further include a conductivity enhancer.
  • 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 sheets, conductive carbon fibers and graphene.
  • 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 mass ratio of the conductivity enhancer to the active material is (0.1 ⁇ 10):100.
  • the negative electrode material further includes a carbon layer covering at least part of the surface of the aggregate.
  • the coverage rate of the carbon layer on the surface of the aggregate is 1%-100%.
  • the material of the carbon layer includes amorphous carbon.
  • the carbon layer has a thickness of 10 nm to 1500 nm.
  • the median particle size of the negative electrode material is 0.5 ⁇ m to 30 ⁇ m.
  • the specific surface area of the negative electrode material is ⁇ 10m 2 /g.
  • the present disclosure provides a method for preparing a negative electrode material, comprising the following steps:
  • the precursor is densified to obtain an aggregate, the aggregate has a porosity ⁇ 10% and a compressive hardness ⁇ 100MPa.
  • the first carbon source includes sucrose, glucose, polyethylene, polyvinyl alcohol, polyethylene glycol, polyaniline, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyethylene oxide, At least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride and asphalt.
  • the active material includes at least one of silicon oxide, a non-metal element, a metal element, and an alloy of the metal element and silicon.
  • the metal element includes at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al and Cu.
  • the non-metal elemental substance includes at least one of Si and P.
  • the silicon oxide includes SiOx, where 0 ⁇ x ⁇ 2.
  • the alloy of the metal element and silicon includes silicon-lithium alloy, silicon-sodium alloy, silicon-potassium alloy, silicon-tin alloy, silicon-germanium alloy, ferrosilicon alloy, silicon-magnesium alloy, silicon-titanium alloy, silicon-zinc alloy, silicon At least one of aluminum alloy and silicon copper alloy.
  • the mass ratio of the active material to the first carbon source is (15-120):(10-50).
  • the solvent is an organic solvent.
  • the organic solvent includes an alcoholic solvent.
  • the alcohol solvent includes at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol and pentanol.
  • the mixture is dried to obtain the precursor.
  • the temperature of the drying treatment is 40°C-300°C, and the time of the drying treatment is 1h-15h.
  • the preparation method of the mixture specifically includes: ultrasonically treating the active material, the first carbon source and the solvent, and then grinding.
  • the time of the ultrasonic treatment is 15-45 minutes.
  • the time of the grinding treatment is 3-8 hours.
  • the mixture further includes metal oxides.
  • 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 active material, the metal oxide and the first carbon source is (15-120):(1-20):(10-50).
  • the mixture further includes a conductivity enhancer.
  • 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 sheets, conductive carbon fibers and graphene.
  • 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 mass ratio of the conductivity enhancer to the active material is (0.1 ⁇ 10):100.
  • additives are also included in the mixture.
  • the additive includes at least one of a surfactant and a coupling agent.
  • the surfactant includes octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecylbenzenesulfonate, n-eicosic acid, palmitic acid, myristic acid, undecanoic acid, At least one of hexaalkyltrimethylammonium bromide and polyvinylpyrrolidone.
  • the silane coupling agent includes ⁇ -aminopropyltriethoxysilane, ⁇ -glycidyloxypropyltrimethoxysilane and ⁇ -methacryloxypropyltrimethoxysilane at least one of the
  • the mass ratio of the active material, the metal oxide, the additive to the first carbon source is (15-120):(1-20):(1-10):(10 ⁇ 50).
  • the densification treatment includes: performing a fusion treatment on the precursor, and then performing a heat treatment.
  • the fusion treatment comprises mechanical fusion.
  • the rotation speed of the fusion machine used for the mechanical fusion is 500r/min-3000r/min.
  • the fusion machine used for the mechanical fusion has a gap width of 0.01 cm to 0.5 cm.
  • the duration of the mechanical fusion is at least 0.5 h.
  • the primary heat treatment includes a carbonization treatment.
  • the temperature of the primary carbonization treatment is 500° C. to 1200° C.
  • the time of the primary carbonization treatment is 1 h to 10 h.
  • the primary carbonization treatment is performed under a protective gas condition, and the protective gas includes at least one of nitrogen, helium, neon, argon and krypton.
  • the primary heat treatment further includes a secondary carbonization treatment, and the secondary carbonization treatment is performed after the fusion treatment.
  • the secondary carbonization treatment includes at least one of gas phase coating, solid phase coating and liquid phase coating.
  • the aggregates are carbon coated.
  • the carbon coating treatment includes: mixing the aggregate with a second carbon source, and then performing a second 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, At least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride and asphalt.
  • the mass ratio of the aggregate to the second carbon source is (10-100):(10-70).
  • the temperature of the second heat treatment is 600° C. to 1200° C.
  • the time of the second heat treatment is 1 h to 10 h.
  • the secondary heat treatment is performed under a protective gas condition, and the protective gas includes at least one of nitrogen, helium, neon, argon and krypton.
  • a lithium-ion battery comprising the above-mentioned negative-electrode material or the negative-electrode material prepared by the above-mentioned preparation method of the negative-electrode material.
  • Fig. 1 is the flow chart of the preparation method of the negative electrode material provided by the embodiment of the present disclosure
  • Example 2 is a scanning electron microscope (SEM) picture of the negative electrode material prepared in Example 1 of the present disclosure
  • Fig. 3 is the XRD pattern of the negative electrode material prepared in Example 1 of the present disclosure
  • FIG. 5 is a graph showing the cycle performance of the negative electrode material prepared in Example 1 of the present disclosure.
  • One embodiment provides a negative electrode material, which has excellent structural stability, effectively suppresses volume expansion of the negative electrode material, and improves battery cycle performance. Another embodiment provides a preparation method of the above-mentioned negative electrode material, which can reduce the preparation cost. Yet another embodiment provides a lithium ion battery.
  • the negative electrode material in one embodiment includes aggregates, and the aggregates include active materials and carbon materials, wherein the porosity of the aggregates is ⁇ 10%, and the compressive hardness of the aggregates is ⁇ 100 MPa.
  • the negative electrode material in the present embodiment includes aggregates, and the aggregates have a relatively low porosity, that is, their compactness is high. On the one hand, it helps to increase the energy density of the composite material. On the other hand, even if the carbon layer on the surface of the aggregate surface is destroyed by the high-density material, the electrolyte is not easy to penetrate into the aggregate, which is conducive to protecting the active material inside. Particles reduce the chance of contact between the electrolyte and the active material, which is conducive to the formation of a stable solid electrolyte film. Moreover, the highly dense aggregates have high compressive hardness, which can counteract the stress effect caused by expansion, improve the structural stability of the negative electrode material, effectively inhibit the volume expansion of the negative electrode material, reduce the expansion rate, and improve the battery cycle performance.
  • the porosity of the aggregate in this embodiment is ⁇ 10%, and the porosity of the aggregate can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%. , 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9% or 9.5%, etc., of course, can also be other values within the above range, which is not limited here. Understandably, 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 aggregates have a porosity ⁇ 5%. In one embodiment, the aggregates have a porosity ⁇ 3%.
  • the compressive hardness of the aggregate is ⁇ 100MPa, and the compressive hardness of the aggregate can be 100MPa, 200MPa, 250MPa, 300MPa, 400MPa, 450MPa, 500MPa, 600MPa, 750MPa, 800MPa, 900MPa, 1000MPa, 1150MPa, 1200MPa or 1250MPa, etc. Of course, other values within the above range may also be used, which are 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. In one embodiment, the compressive hardness of the aggregate is ⁇ 200 MPa. In one embodiment, the compressive hardness of the aggregate is ⁇ 400 MPa.
  • the active material refers to a material that can react with lithium to perform lithium intercalation and deintercalation.
  • the active material includes at least one of silicon oxide, non-metal element, metal element and alloy of metal element and silicon.
  • the metal element includes at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al and Cu.
  • the non-metal elemental substance includes at least one of Si and P.
  • the silicon oxide includes SiOx, where 0 ⁇ x ⁇ 2.
  • alloys of simple metals and silicon include silicon-lithium alloys, silicon-sodium alloys, silicon-potassium alloys, silicon-tin alloys, silicon-germanium alloys, silicon-iron alloys, silicon-magnesium alloys, silicon-titanium alloys, silicon-zinc alloys, silicon-aluminum alloys and at least one of silicon-copper alloys.
  • the active material has a median particle size of 1 nm to 500 nm. Specifically, it can be 1nm, 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 100nm, 200nm, 300nm, 400nm or 500nm, etc., or other values within the above range, which are not limited here. It has been found through multiple tests that the nanoscale active material particles have a strong structure and can inhibit the volume expansion of silicon. However, due to the large surface energy of the nano-scale active particles, they are prone to agglomeration during the charging and discharging process, and the particle size of the active material is too small, resulting in high production process costs.
  • the median diameter of the active material is 1 nm to 200 nm. In one embodiment, the median diameter of the active material is 1 nm to 100 nm.
  • the carbon material includes at least one of amorphous carbon, crystalline carbon, and mesocarbon microspheres.
  • the amorphous carbon includes at least one of hard carbon and soft carbon. Understandably, the carbon material can increase the conductivity of the aggregates and can reduce the porosity of the aggregates, allowing the aggregates to be denser.
  • the mass ratio of the active material to the carbon material is (30-70):(10-70).
  • the mass ratio of the active material to the carbon material is specifically 30:10, 30:40, 30:50, 30:70, 40:10, 40:50, 40:70, 50:30, 50:60, 60:10, 60:50, 70:10, 70:40, or 70:70, etc., of course, may also be other values within the above range, which are not limited here.
  • 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 test density of the aggregate 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 satisfies the following relational formula: ( ⁇ 1- ⁇ 2)/ ⁇ 2 ⁇ 5%, wherein, ⁇ 1 is the test density of the aggregate, ⁇ 2 is the average density of the aggregate, and ⁇ 2 is the aggregation of each component in the aggregate The sum of the mass percentage of the body * the theoretical density of each component.
  • ⁇ 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.
  • the aggregates also include metal oxides. Combining the metal oxide with the active material can reduce the expansion of the active material, improve the long-term cycle performance, and the aggregate has higher compressive hardness.
  • the metal oxide is distributed in the active material, and the carbon material is filled between the active material and the metal oxide.
  • the carbon material is filled between the active material and the metal oxide.
  • 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 Specifically, the metal oxide may be GeO 2 , SnO 2 , ZnO, TiO 2 , Fe 3 O 4 , MgO, SiO 2 , 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, compounding the metal oxide with the active material can reduce the expansion of the active material and improve the long-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 diameter perpendicular to the length direction of the elongated conductivity enhancer. 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.
  • the aspect ratio of the metal oxide can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, etc., of course, can also be other values within the above range, which are not limited here. According to many experiments, it is found that 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, and the network structure formed by the two can be improved, thereby buffering the volume expansion change of the active material and improving cycle performance. .
  • the mass ratio of the active material to the metal oxide is (30-70):(1-20).
  • the mass ratio of the active material to the metal oxide is specifically 30:5, 30:15, 30:20, 40:5, 40:15, 40:20, 50:10, 50:20, 60:10, 60:25 Or 70:20, of course, it can also be other values within the above range, which is not limited here. Too high a metal oxide content will lead to a decrease in the first efficiency of the material, and too low a metal oxide content will lead to a decrease in the rigidity of the aggregate structure and a decrease in particle cycle stability.
  • the aggregate also includes a conductivity enhancer.
  • the conductivity enhancer can provide more transport channels for carriers, thereby enhancing the transport of carriers inside the material; on the other hand, it also has excellent mechanical properties, which can be used as a structural support to enhance the stability of the material. sex.
  • 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 conductivity enhancer has a conductivity of 10 0 S/m ⁇ 10 8 S/m.
  • the conductivity of the conductivity enhancer is specifically 10S/m, 100S/m, 1000S/m, 10 4 S/m, 10 5 S/m, 10 6 S/m or 10 7 S/m, of course it can also be within the above range Other values within are not limited here.
  • 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 elongated, the aspect ratio specifically refers to the ratio of the length of the conductivity enhancer particles to the particle diameter of the particles, where the particle diameter refers to the The maximum linear distance between two points on the periphery of the cross-section in the length direction; 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 conductive enhancer can be 2, 5, 10, 15, 20, 33, 50, 60, 70, 80, 90, 100, 150, 600, 780, 890, 1300, 1500, 2000, 3000, 4000, 5000, etc., of course, can also be other values within the above range, which are not limited here. According to many tests, it has been found that the conductivity enhancer with the 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 buffering the volume expansion change of the active material and improving cycle performance.
  • the mass ratio of the conductivity enhancer to the active material is (0.1 ⁇ 10):100.
  • the mass ratio of the conductivity enhancer to the active material is specifically 0.1:100, 0.5:100, 1:100, 2:100, 2.6:100, 3:100, 3.5:100, 4:100, 4.8:100, 6:100 , 7:100, 8.5:100 or 10:100 etc.
  • other values within the above range may also be used, which are not limited here.
  • the negative electrode material further includes a carbon layer coating at least part of the surface of the aggregate.
  • the surface of the aggregate may be partly or completely covered by the carbon layer.
  • the coverage rate of the carbon layer on the aggregate surface is 1%-100%. It should be noted that the coverage ratio in the present disclosure refers to the degree to which the surface of the aggregate is covered by the carbon layer. The coverage rate is specifically 1%, 5%, 10%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. Of course, other values within the above range may also be used, which are not limited here.
  • the material of the carbon layer includes amorphous carbon.
  • the carbon layer has a thickness of 10 nm to 1500 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 a passivation film, and increase the reversible capacity of the battery.
  • the thickness of the carbon layer is specifically 10nm, 50nm, 180nm, 200nm, 350nm, 400nm, 550nm, 700nm, 850nm, 900nm, 1050nm, 1200nm or 1500nm, etc. Of course, it can also be other values within the above range, which is not limited here .
  • the thickness of the carbon layer is 50nm-800nm. In one embodiment, the carbon layer has a thickness of 100 nm to 500 nm.
  • the median particle size of the negative electrode material is 0.5 ⁇ m ⁇ 30 ⁇ m.
  • the median particle size of the negative electrode material is specifically 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.
  • it can also be other values within the above range, which is not limited here . It can be understood that controlling the median 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 ⁇ 10 m 2 /g.
  • the specific surface area of the negative electrode material is specifically 0.5m 2 /g, 1m 2 /g, 2m 2 /g, 3m 2 /g, 5m 2 /g, 7m 2 /g, 8m 2 /g or 10m 2 /g, etc., Of course, other values within the above range may also be used, 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 median particle size mentioned in the present disclosure refers to the average particle size, 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 embodiments can be combined arbitrarily if there is no conflict with each other, for example, the compressive hardness, porosity and density of the aggregates are limited in combination.
  • the preparation method of the negative electrode material of one embodiment comprises the following steps:
  • Step S10 preparing a precursor from a mixture of the active material, the first carbon source and the solvent
  • Step S20 performing densification treatment on the precursor to obtain aggregates, the porosity of the aggregates is ⁇ 10% and the compressive hardness is ⁇ 100MPa;
  • step S30 the aggregates are subjected to carbon coating treatment to obtain negative electrode materials.
  • the preparation method of the negative electrode material provided by the present disclosure uses the densification treatment of the precursor to improve the compressive hardness of the negative electrode material, enhance the stability of the particle structure, and at the same time enhance the connection stability between the active material and the first carbon source , reducing the porosity; thus reducing the expansion rate of the negative electrode material and increasing the cycle stability.
  • Step S10 preparing a precursor from the mixture of the active material, the first carbon source and the solvent.
  • 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 active material refers to a material that can react with lithium to perform lithium intercalation and deintercalation.
  • the active material includes the active material including at least one of an alloy of a metal element and silicon, an oxide of silicon, a metal element and a non-metal element.
  • the metal element includes at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al and Cu.
  • the non-metal elemental substance includes at least one of Si and P.
  • the silicon oxide includes SiOx, where 0 ⁇ x ⁇ 2.
  • alloys of simple metals and silicon include silicon-lithium alloys, silicon-sodium alloys, silicon-potassium alloys, silicon-tin alloys, silicon-germanium alloys, silicon-iron alloys, silicon-magnesium alloys, silicon-titanium alloys, silicon-zinc alloys, silicon-aluminum alloys and at least one of silicon-copper alloys.
  • the mass ratio of the active material to the first carbon source is (15-120):(10-50).
  • the mass ratio of the active substance to the first carbon source is specifically 100:15.9, 100:21.9, 100:24.5, 100:9.5, 100:9.5, 100:9.5 or 100:9.5, etc., of course, it can also be the above Other values within the range are not limited here.
  • the mixing method of the mixture may include magnetic stirring, mechanical stirring, ultrasonic dispersion, grinding dispersion and the like. Grinding and dispersing is used to disperse active substances, avoid agglomeration of active substances, and disperse active substances into smaller nanoparticles.
  • the preparation method of the mixture specifically includes: ultrasonically treating the active material, the first carbon source and the solvent, and then grinding.
  • the time of ultrasonic treatment is 15-45 minutes.
  • the ultrasonic treatment time is specifically 20 min, 25 min, 30 min, 35 min or 40 min, etc., of course, it can also be other values within the above range, which is not limited here.
  • the grinding treatment time is 3-8 hours.
  • the grinding treatment time is specifically 4h, 5h, 6h or 7h, etc. Of course, it can also be other values within the above range, which is not limited here.
  • the ingredients can be mixed more evenly by grinding thoroughly.
  • the active material, the first carbon source and the solvent are mixed to obtain a precursor solution, and the precursor solution is subjected to wet ball milling, so that the particle size in the precursor solution reaches 1 nm to 500 nm.
  • the particle size in the precursor solution may specifically be 1nm, 5nm, 10nm, 15nm, 50nm, 100nm, 150nm, 200nm, 300nm, 400nm or 500nm, etc., which is not limited here.
  • the solvent includes an organic solvent.
  • the organic solvent includes an alcoholic solvent, specifically, the alcoholic solvent includes methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutanol, and pentanol at least one of the Adding each component into an organic solvent for wet ball milling can improve the mixing uniformity of the components and facilitate rapid drying.
  • the mixture is dried to obtain a precursor.
  • the temperature of the drying treatment is 40°C to 300°C, and the time of the drying treatment is 1h to 15h.
  • the drying temperature is specifically 50°C, 70°C, 100°C, 120°C, 150°C, 200°C, 220°C, 250°C, etc. Of course, it can also be other values within the above range, which are not limited here.
  • the drying time is specifically 1.5h, 2h, 2.5h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h or 14h, etc. Of course, it can also be other values within the above range, It is not limited here.
  • the drying treatment method can be, for example, furnace drying, freeze drying, stirring and evaporation to dryness, spray drying, etc. The drying treatment in this embodiment can remove the solvent in the precursor solution as much as possible.
  • metal oxides are also included in the mixture.
  • 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 Specifically, the metal oxide may be GeO 2 , SnO 2 , ZnO, TiO 2 , Fe 3 O 4 , MgO, SiO 2 , CuO or the like.
  • 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 particle to the particle diameter of the particle; when the metal oxide is flaky, the aspect ratio specifically refers to the The ratio of the length to width of an 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 or 22, etc., or it can be within the above range Other values within are not limited here.
  • the aspect ratio of the metal oxide is less than or equal to 2
  • the physical binding force between the metal oxide and the active material can be improved, and the network structure formed by the two can be improved, thereby Better buffer volume expansion changes of active substances and improve cycle performance.
  • the mass ratio of the active material, the metal oxide and the first carbon source is (15-120):(1-20):(10-50).
  • the mass ratio of active material, metal oxide and first carbon source can be 15:1:10, 20:3:25, 50:8:35, 60:9:38, 70:11:45, 90 :15:40, 100:9:15.9, 100:5:21.9, 100:2:24.5, 100:9:19.5, 100:9:19.5, 100:9:19.5, 100:11:19.5, 100:9.5 : 19.5, etc.
  • it can also be other values within the above range, which is not limited here.
  • a conductivity enhancer is also included in the mixture.
  • a conductivity enhancer is added in the step of mixing the active material, the first carbon source and the solvent.
  • 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 conductivity enhancer has a conductivity of 10 0 S/m ⁇ 10 8 S/m.
  • the conductivity of the conductivity enhancer can be 1S/m, 10S/m, 100S/m, 10 3 S/m, 10 4 S/m, 10 5 S/m, 10 8 S/m, etc. Of course, it can also be the above Other values within the range are not limited here.
  • the conductivity enhancer is in the form of flakes and/or strips. In some embodiments, the aspect ratio of the conductivity enhancer is 2-5000.
  • the aspect ratio of the conductive enhancer can be 2, 5, 10, 15, 20, 33, 50, 60, 70, 80, 90, 100, 150, 600, 780, 890, 1300, 1500, 2000, 3000, 4000, 5000, etc., of course, can also be other values within the above range, which are not limited here.
  • the mass ratio of the conductivity enhancer to the active material is (0.1 ⁇ 10):100. Specifically, the mass ratio of the conductivity enhancer to the active material is 0.1:100, 0.5:100, 1:100, 2:100, 2.6:100, 3:100, 3.5:100, 4:100, 4.8:100, 6 :100, 7:100, 8.5:100 or 10:100 etc.
  • the mass ratio of the conductivity enhancer to the active material is 0.1:100, 0.5:100, 1:100, 2:100, 2.6:100, 3:100, 3.5:100, 4:100, 4.8:100, 6 :100, 7:100, 8.5:100 or 10:100 etc.
  • other values within the above range may also be used, which are not limited here.
  • additives are also included in the mixture.
  • the additive in this embodiment can effectively enhance the connection stability of the active material and the carbon material, thereby forming a firm system.
  • the additive includes at least one of a surfactant and a coupling agent.
  • surfactants include, but are not limited to, octadecanoic acid, lauric acid, polyacrylic acid (PAA), sodium dodecylbenzenesulfonate (SDBS), n-eicosic acid, palmitic acid, tetradecane At least one of acid, undecanoic acid, cetyltrimethylammonium bromide and polyvinylpyrrolidone (PVP).
  • PAA polyacrylic acid
  • SDBS sodium dodecylbenzenesulfonate
  • PVP polyvinylpyrrolidone
  • silane coupling agents but not limited to ⁇ -aminopropyltriethoxysilane, ⁇ -glycidyloxypropyltrimethoxysilane and ⁇ -methacryloxypropyltrimethoxy at least one of silanes.
  • the mass ratio of the active material, the metal oxide, the additive and the first carbon source is (15-120):(1-20):(1-10):(10-50).
  • the mass ratio of the active material, the metal oxide, the additive and the first carbon source is specifically 100:9:5.9:15.9, 100:5:8:21.9, 100:2:5:24.5, 100:9:5:19.5, 100:9:11:19.5, 100:9:10.5:19.5, 100:11:5.5:19.5, 100:9.5:6.9:19.5, etc.
  • other values within the above range may also be used, which are not limited here.
  • Step S20 densifying the precursor to obtain an aggregate, the aggregate has a porosity ⁇ 10% and a compressive hardness ⁇ 100MPa.
  • the densification treatment includes performing a fusion treatment on the precursor and then performing a heat treatment.
  • the fusion treatment of the precursor is used to improve the compressive hardness of the negative electrode material, and then a heat treatment is performed to enhance the stability of the particle structure, and at the same time, it can enhance the connection stability between the active material and the first carbon source and reduce the porosity.
  • other methods can also be used for densification treatment, such as molding, isostatic pressing, impregnation and other processes, as long as the porosity of the aggregate is ⁇ 10% and the compressive hardness is ⁇ 100MPa.
  • 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 rotational speed of the fusion machine used for mechanical fusion is 500r/min-3000r/min, specifically 500r/min, 1000r/min, 1500r/min, 2000r/min, 2500r/min or 3000r/min, etc. etc.
  • other values within the above range can also be used, which are not limited here.
  • the width of the tool gap of the fusion machine is 0.01cm ⁇ 0.5cm, which can be 0.01cm, 0.05cm, 0.1cm, 0.15cm, 0.2cm, 0.25cm, 0.3cm or 0.5cm, etc. Of course, it can also be other within the above range value, which is not limited here.
  • the time for mechanical fusion is at least 0.5h, specifically, it can be 0.5h, 0.8h, 0.9h, 1.0h, 1.5h or 2h, etc. Of course, it can also be other values within the above range, which is not limited here.
  • a heat treatment includes a carbonization treatment.
  • the mixture after the fusion treatment is sent into a high-temperature box furnace for a carbonization treatment, so that the first carbon source is carbonized, and the active material and the carbon material are closely connected together.
  • the method of the primary carbonization treatment may be, for example, normal-pressure firing, vacuum firing or hot-press firing.
  • the temperature of the primary carbonization treatment is 500° C. to 1200° C.
  • the time of the primary carbonization treatment is 1 h to 10 h.
  • the temperature of the primary carbonization treatment is specifically 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc.
  • the time for one carbonization treatment is specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 15 h, etc.
  • the heating rate of the primary carbonization treatment is 1° C./min to 30° C./min. Specifically, it can be 1°C/min, 5°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min or 30°C/min, etc. Of course, it can also be other values within the above range , is not limited here.
  • the heating rate of one heat treatment is 1° C./min ⁇ 15° C./min.
  • the primary carbonization treatment is performed under a protective gas condition, and the protective gas includes at least one of nitrogen, helium, neon, argon and krypton.
  • the primary heat treatment also includes a secondary carbonization treatment, and the secondary carbonization treatment is performed after the fusion treatment.
  • the secondary carbonization treatment is performed after the fusion treatment and before the primary carbonization treatment, or the secondary carbonization treatment is performed after the primary carbonization treatment. Secondary carbonization treatment can further reduce the porosity of the material.
  • the secondary carbonization treatment includes at least one of gas phase coating, solid phase coating and liquid phase coating.
  • the reaction temperature of solid phase coating is 500°C to 1200°C, specifically including but not limited to 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C °C, 1150 °C, etc.
  • the reaction time is 1h-12h, specifically including but not limited to 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, etc.
  • the reaction temperature of liquid phase coating is 500°C to 1200°C, specifically including but not limited to 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C °C, 1150 °C, etc.
  • the reaction time is 1h-12h, specifically including but not limited to 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, etc.
  • vapor coating includes chemical vapor deposition
  • the reaction temperature of chemical vapor deposition is 600°C to 1050°C, specifically 600°C, 700°C, 800°C, 850°C, 900°C, 950°C, 1000°C Or 1050°C, etc.
  • the chemical vapor deposition time is 0.5h to 2h, specifically 0.5h, 0.8h, 1.0h, 1.5h, 1.8h or 2h, etc., of course, it can also be other values within the above range, which is not limited here.
  • the reaction temperature of chemical vapor deposition is 800°C-1000°C.
  • the carbon source gas in the chemical vapor deposition process includes at least one of methane, ethylene, acetylene, benzene, toluene, xylene, styrene, and phenol.
  • step S30 the aggregates are subjected to carbon coating treatment to obtain negative electrode materials.
  • step S30 may be omitted.
  • the carbon coating treatment includes: mixing the aggregates with a second carbon source, and then performing a second 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 aggregate is 0.5 ⁇ m to 15 ⁇ m, specifically 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m or 15 ⁇ m, etc., of course it can also be are other values within the above range, and are not limited here. Controlling the particle size within the above range is conducive to obtaining products with high compressive hardness. The test found that the aggregate particles are too large, which will lead to low degree of densification, tight connection, and low compressive hardness.
  • the mass ratio of aggregates to the second carbon source is (10-100):(10-70). Specifically, the mass ratio of aggregates to the second carbon source is 10:20, 20:10, 100:25, 100:35, 100:45, 100:55, 100:65, etc., of course, it can also be within the above range Other values are not limited here.
  • the method of mixing the aggregates with the second carbon source may include magnetic stirring, mechanical stirring, ultrasonic dispersion, grinding dispersion, and the like.
  • the way of the secondary heat treatment can be normal pressure firing, vacuum firing or hot pressing firing, for example.
  • the temperature of the secondary heat treatment is 600°C to 1200°C, and the time of the secondary heat treatment is 1h to 10h.
  • the temperature of the secondary heat treatment is specifically 500°C, 600°C, 700°C, 800°C, 900°C, 1000° C., 1200° C., 1200° C., etc., of course, may also be other values within the above range, which are not limited here.
  • the time for the secondary heat treatment is specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 15 h, etc. Of course, it can also be other values within the above range, which is not limited here.
  • the heating rate during the secondary heat treatment is 1-30° C./min.
  • the temperature increase rate during the secondary heat treatment is 1 to 15° C./min.
  • the heating rate during the secondary 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./min, etc., of course, other values within the above range can also be used, which are not limited here.
  • the heating rate during one heat treatment is 1° C./min ⁇ 15° C./min.
  • the secondary heat treatment is performed under a protective gas condition, and the protective gas includes at least one of nitrogen, helium, neon, argon, and krypton.
  • the negative electrode material prepared by the above preparation method is coated with a carbon layer on the surface of the aggregate formed by the active material and carbon material, which can inhibit the expansion of the material during the cycle.
  • Its core structure aggregate has high compressive hardness and strong rigidity, which can effectively resist a certain volume expansion stress, which is conducive to maintaining the structural stability of the negative electrode material, thereby reducing the expansion rate and improving the battery cycle performance.
  • the aggregate has low porosity and high density, which is conducive to the formation of a stable solid electrolyte film, reduces the contact between the electrolyte and the active material, reduces the volume expansion of the material, and improves the cycle performance.
  • the present disclosure also provides a lithium ion battery, including the above-mentioned negative electrode material.
  • the speed of the fusion machine is 500r/min; the width of the tool gap of the fusion machine used for mechanical fusion is 0.05cm; the mechanical fusion time is 0.5h.
  • the fused material in a heat treatment furnace , and then pass nitrogen gas under the condition of 600° C., conduct a heat treatment, keep the temperature for 3 hours, and obtain aggregates.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include Si powder, SiO particles and carbon materials.
  • the mass ratio of silicon powder, SiO particles and carbon materials is 55.9:4.3: 39.8, the median particle size of the negative electrode material is 16 ⁇ m, the specific surface area is 5.2 m 2 /g, and the average thickness of the carbon layer is 166 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 5.5%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 330MPa. The difference between the test density of the aggregate and the average density of silicon powder, SiO particles and carbon material is 0.9%.
  • Figure 2 is a scanning electron microscope image of the negative electrode material prepared in Example 1, and there is a silicon peak in the X-ray diffraction pattern of Figure 3 .
  • Si powder with a median particle size of 80nm, GeO2 particles with an aspect ratio of 12, palmitic acid and polyvinylpyrrolidone were added to the propanol solution at a mass ratio of 40:1.8:8:21.9, and ultrasonically dispersed After 15 minutes to obtain a dispersion solution, the dispersion solution was placed in a ball mill to grind and disperse for 3 hours to obtain a precursor solution, and then dried at 190° C. for 3 hours to obtain a precursor.
  • the rotation speed of the fusion machine is 800r/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 that present embodiment makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises Si powder, GeO granule and carbon material, and the mass ratio of Si powder, GeO granule and carbon material is 63.3: 2.9:33.8.
  • the median particle size of the negative electrode material was 12 ⁇ m, the specific surface area was 3.2 m 2 /g, and the average thickness of the carbon layer was 154 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 4.9%.
  • the aggregate particles were tested by a nano-indenter, and the average compressive hardness of the aggregates was 540MPa. The difference between the test density of the aggregate and the average density of silicon powder, SiO particles and carbon materials in the aggregate is 2.09%.
  • the precursor is placed in the fusion machine, the rotation speed of the fusion machine is 600r/min; the width of the tool gap of the fusion machine is 0.3cm; the fusion time is 3h.
  • the fused material was placed in a heat treatment furnace, and then a heat treatment was performed at 900° C. by introducing nitrogen gas, and kept for 5 hours to obtain aggregates.
  • the negative electrode material that present embodiment makes comprises aggregate and is coated on the carbon layer of aggregate surface, and aggregate comprises Si powder, SnO granule and carbon material; Si powder, SnO
  • the mass ratio of particle and carbon material is 48.1: 2.3:49.6; the median particle size of the negative electrode material is 8.4 ⁇ m, the specific surface area is 4.2 m 2 /g, and the average thickness of the carbon layer is 79 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 6.5%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 116MPa. The difference between the tested density of the aggregate and the average density of Si powder, SnO2 particles and carbon material in the aggregate is 2.78%.
  • Si powder with a median particle size of 20nm, ZnO particles with an aspect ratio of 18, oleic acid and polyethylene glycol were added to the n-butanol solution at a mass ratio of 40:10.5:9:29.5, and ultrasonically dispersed
  • the dispersion solution was obtained in 45 minutes, and then the dispersion solution was ground and dispersed in a ball mill for 6 hours to obtain a precursor solution, and then dried at a temperature of 250° C. for 2.5 hours to obtain a precursor.
  • the precursor is placed in the fusion machine, the rotation speed of the fusion machine is 900r/min; the width of the tool gap of the fusion machine is 0.4cm; the mechanical fusion time is 3h.
  • the fused material was placed in a heat treatment furnace, and then a heat treatment was performed at 780° C. by introducing nitrogen gas, and kept for 8 hours to obtain aggregates.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include Si powder, ZnO particles and carbon materials, and the mass ratio of Si powder, ZnO particles and carbon materials is 51.3:13.5: 35.2.
  • the median particle diameter of the negative electrode material was 6.4 ⁇ m, the specific surface area was 3.2 m 2 /g, and the average thickness of the carbon layer was 155 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 8.5%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 556MPa. The difference between the test density of the aggregate and the average density of Si powder, ZnO particles and carbon materials in the aggregate is 3.98%.
  • the precursor is placed in the fusion machine, the speed of the fusion machine is 650r/min; the width of the fusion machine tool gap is 0.35cm; the fusion time is 2h, the fused material is placed in a heat treatment furnace, and then helium is introduced into the furnace Carry out a heat treatment at 600°C, keep it warm for 6 hours, then pulverize the heat-treated material and place it in a vapor deposition furnace.
  • the negative electrode material that present embodiment makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises Si powder, TiO granule and carbon material, and the mass ratio of Si powder, TiO granule and carbon material is 65.2: 7.3:27.5.
  • the median particle size of the negative electrode material was 6 ⁇ m, the specific surface area was 2.3 m 2 /g, and the average thickness of the carbon layer was 418 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 3.5%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 756MPa.
  • the difference between the test density of the aggregate and the average density of Si powder, TiO 2 particles and carbon materials in the aggregate is 4.38%.
  • the precursor is placed in the fusion machine, the rotation speed of the fusion machine is 800r/min; the width of the tool gap of the fusion machine is 0.2cm; the fusion time is 3h.
  • the negative electrode material that present embodiment makes comprises aggregate and the carbon layer that is coated on aggregate surface, and aggregate comprises Si powder, TiO granule and carbon material, Si powder, TiO
  • the mass ratio of particle and carbon material is 39.1: 14.5:46.4, the median particle size of the negative electrode material is 5.2 ⁇ m, the specific surface area is 1.3 m 2 /g, and the average thickness of the carbon layer is 511 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 1.5%.
  • the aggregate particles were tested by a nano-indenter, and the average compressive hardness of the aggregates was 356MPa.
  • the difference between the test density of the aggregate and the average density of Si powder, TiO 2 particles and carbon material is 1.58%.
  • the precursor is placed in the fusion machine, the rotation speed of the fusion machine is 900r/min; the width of the tool gap of the fusion machine is 0.3cm; the fusion time is 3h. Then put it in a vapor deposition furnace, and the temperature in the vapor deposition furnace is 1050°C, and acetylene gas is introduced into the vapor deposition furnace for 1 hour to form a carbon material and obtain an aggregate.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include Ge powder, ZnO particles and carbon materials; the mass ratio of the aggregates including Ge powders, ZnO particles and carbon materials is 65.3 :8:26.7.
  • the median particle size of the negative electrode material was 11.2 ⁇ m, the specific surface area was 3.3 m 2 /g, and the average thickness of the carbon layer was 310 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 3.2%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 446MPa. The difference between the test density of the aggregate and the average density of Ge powder, ZnO particles and carbon materials in the aggregate is 5.11%.
  • the precursor is placed in the fusion machine, the rotation speed of the fusion machine is 650r/min; the width of the tool gap of the fusion machine is 0.5cm; the fusion time is 3h.
  • the fused materials were placed in a heat treatment furnace, and then subjected to a heat treatment at 790° C. for 4 hours to obtain aggregates.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include Al powder, Fe3O4 particles and carbon materials, and the mass of Al powder, Fe3O4 particles and carbon materials The ratio is 59.6:5.96:34.44.
  • the median particle size of the negative electrode material was 16.2 ⁇ m, the specific surface area was 4.3 m 2 /g, and the average thickness of the carbon layer was 351 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 4.0%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 292MPa. The difference between the test density of the aggregate and the average density of Al powder, Fe 3 O 4 particles and carbon materials in the aggregate is 4.78%.
  • Example 1 The difference between this example and Example 1 is that the mass ratio of Si powder with a median particle size of 100 nm, SiO particles with an aspect ratio of 22, lauric acid and phenolic resin in step 1) is 15:2:1.5:12.5 ;
  • the primary heat treatment temperature in step 2) is 1200°C.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include silicon powder, SiO particles and carbon materials.
  • the mass ratio of Si powder, SiO particles and carbon materials is 51.3:6.8: 41.9, the median particle size of the negative electrode material is 14.7 ⁇ m, the specific surface area is 3.2 m 2 /g, and the average thickness of the carbon layer is 378 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 3.5%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 380MPa. The difference between the test density of the aggregate and the average density of Si powder, SiO particles and carbon materials in the aggregate is 0.99%.
  • Example 1 The difference between this example and Example 1 is that the mass ratio of Si powder with a median particle size of 100 nm, SiO particles with an aspect ratio of 22, lauric acid and phenolic resin in step 1) is 120:15.5:5.9:45.9 ;
  • the secondary heat treatment temperature in step 3) is 600°C.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include silicon powder, SiO particles and carbon materials.
  • the mass ratio of silicon powder, SiO particles and carbon materials is 60.7:7.8: 31.5, the median particle size of the negative electrode material is 17.7 ⁇ m, the specific surface area is 6.1m 2 /g, and the average thickness of the carbon layer is 240nm; the aggregate particles are tested by mercury porosimetry, and the aggregate porosity is 4.8%;
  • the aggregate particles were tested with a nano-indenter, and the average compressive hardness of the aggregate was 160 MPa.
  • the difference between the test density of the aggregate and the average density of Si powder, SiO particles and carbon materials in the aggregate is 8.18%.
  • the median particle size in step 1) is that the mass ratio of Si powder of 100nm, SiO particles with aspect ratio of 22, CNT with diameter of 20nm, lauric acid and phenolic resin in step 1) is 60: 4.5:0.9:3.9:22.9; the rest of the parameters remain unchanged.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include silicon powder, SiO particles, CNTs, and carbon materials.
  • the mass ratio of Si powder, SiO particles, CNTs, and carbon materials is 60.7:5.8:1.9:31.6, the median particle size of the negative electrode material is 13.7 ⁇ m, the specific surface area is 5.1m 2 /g, and the average thickness of the carbon layer is 221nm;
  • the porosity is 7.8%.
  • the aggregate particle is tested by a nano-indenter, and the average compressive hardness of the aggregate is 375MPa. The difference between the test density of the aggregate and the average density of Si powder, SiO particles and carbon materials in the aggregate is 9.4%.
  • the negative electrode material prepared in this embodiment includes aggregates, and the aggregates include silicon powder, SiO particles and carbon materials.
  • the mass ratio of silicon powder, SiO particles and carbon materials is 55.9:4.3:39.8, and the median particle size of the negative electrode material is 14.9 ⁇ m, the specific surface area is 3.8m 2 /g.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 6.7%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 240MPa. The difference between the test density of the aggregate and the average density of Si powder, SiO particles and carbon materials in the aggregate is 0.9%.
  • the speed of the fusion machine is 500r/min; the fusion machine tool gap width used for the mechanical fusion is 0.05cm; the mechanical fusion time is 0.5h, and the fusion machine is placed In a heat treatment furnace, nitrogen gas was introduced to conduct a heat treatment at 600° C., and the temperature was kept for 3 hours to obtain the negative electrode material.
  • the negative electrode material prepared in this embodiment includes aggregates, the aggregates include Si powder and carbon material, the mass ratio of silicon powder to carbon material is 55.1:44.9, the median particle size of the negative electrode material is 14.6 ⁇ m, and the specific surface area is 4.7 m 2 /g; the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 5.8%; the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 195MPa. The difference between the test density of aggregates and the average density of silicon powder and carbon materials is 1.1%.
  • step 1) is different, and step 1) adds Si powder, lauric acid and phenolic resin with a median particle size of 100nm to 40% ethylene glycol according to a mass ratio of 60:5.9:45.
  • step 1) adds Si powder, lauric acid and phenolic resin with a median particle size of 100nm to 40% ethylene glycol according to a mass ratio of 60:5.9:45.
  • the alcohol solution ultrasonically disperse for 10 minutes to obtain a dispersion solution, and then place the dispersion solution in a ball mill to grind and disperse for 4 hours to obtain a precursor solution, and then perform drying treatment at a drying temperature of 190°C for 3 hours to obtain a precursor.
  • the negative electrode material prepared in this embodiment includes an aggregate and a carbon layer coated on the surface of the aggregate.
  • the aggregate includes Si powder and carbon material.
  • the mass ratio of silicon powder to carbon material is 45.9:54.1, and the median particle size of the negative electrode material is The diameter is 12.5 ⁇ m, the specific surface area is 3.1m 2 /g, and the average thickness of the carbon layer is 425nm; the aggregate particles are tested by mercury porosimetry, and the porosity of the aggregate is 4.9%; The particles were tested, and the average compressive hardness of the aggregates was 208MPa.
  • the difference between the measured density of the aggregate and the average density of silicon powder and carbon material is 0.6%.
  • step 1) Si powder, FeSi 2 , lauric acid and phenolic resin with a median particle size of 100 nm are added according to the mass ratio of 60:4.5:3.9:22.9 Put into 40% ethylene glycol solution, ultrasonically disperse for 10 minutes to obtain a dispersion solution, then place the dispersion solution in a ball mill to grind and disperse for 4 hours to obtain a precursor solution, and then perform drying treatment at a drying temperature of 190°C for 3 hours to obtain a precursor .
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include Si powder and carbon materials.
  • the mass ratio of silicon powder, FeSi and carbon materials is 55.3:4.2:40.5.
  • the median particle size of the material is 14.9 ⁇ m, the specific surface area is 4.9m 2 /g, and the average thickness of the carbon layer is 176nm; the aggregate particles are tested by mercury porosimetry, and the porosity of the aggregate is 5.3%.
  • the aggregate particles were tested by a trace instrument, and the average compressive hardness of the aggregate was 319MPa. The difference between the measured density of the aggregate and the average density of silicon powder and carbon material is 0.8%.
  • the negative electrode material was prepared in the same manner as in Example 1, except that no lauric acid was added.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include silicon powder, SiO particles and carbon materials.
  • the mass ratio of silicon powder, SiO particles and carbon materials is 55.9:4.2: 39.4, the median particle size of the negative electrode material is 15.8 ⁇ m, the specific surface area is 5.0 m 2 /g, and the average thickness of the carbon layer is 159 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 6.2%.
  • the aggregate particles were tested by a nano-indenter, and the average compressive hardness of the aggregates was 278MPa. The difference between the test density of the aggregate and the average density of silicon powder, SiO particles and carbon materials in the aggregate is 4.8%.
  • the negative electrode material was prepared in the same manner as in Example 1, except that the aspect ratio of SiO was 2.1.
  • the negative electrode material prepared in this embodiment includes aggregates and a carbon layer coated on the surface of the aggregates.
  • the aggregates include silicon powder, SiO particles and carbon materials.
  • the mass ratio of silicon powder, SiO particles and carbon materials is 55.4:4.3: 39.9, the median particle size of the negative electrode material is 17.8 ⁇ m, the specific surface area is 5.4 m 2 /g, and the average thickness of the carbon layer is 169 nm.
  • the aggregate particles were tested by mercury porosimetry, and the porosity of the aggregates was 6.0%.
  • the aggregate particles were tested by a nano-indentation instrument, and the average compressive hardness of the aggregates was 244MPa. The difference between the test density of the aggregate and the average density of silicon powder, SiO particles and carbon materials in the aggregate is 8.9%.
  • the negative electrode material was prepared in the same manner as in Example 1, except that fusion treatment was not performed.
  • the porosity of the aggregate is 22.4%
  • the average compressive hardness of the aggregate is 50.3 MPa
  • the difference between the tested density of the aggregate and the average density of silicon powder, SiO particles and carbon materials in the aggregate is 10.1%.
  • the electrochemical cycle performance is tested by the following method: the prepared silicon-carbon composite negative electrode material, conductive agent and binder are dissolved in a solvent and mixed in a mass percentage of 94:1:5, and the solid content is controlled at 50%.
  • the copper foil current collector vacuum-dried to obtain the negative electrode sheet; then the ternary positive electrode sheet prepared by the traditional mature process, 1mol/L LiPF6/ethylene carbonate+dimethyl carbonate+methyl ethyl carbonate
  • 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.
  • Porosity was measured by mercury intrusion porosimetry using a mercury porosimeter. The porosity is measured at least three times, and the arithmetic mean of the at least three times is used as the measurement result.
  • the compressive hardness is tested by a nano-indenter, and the indentation hardness test is carried out with a load of 0.6N and an indentation depth of 0.5 ⁇ m.
  • Test method for specific surface area use a McRae surface area analyzer to test the specific surface area of the negative electrode material.
  • Testing method of electrical conductivity use a powder resistivity tester to measure the electrical conductivity of the negative electrode material.
  • the expansion rate and cycle life of the negative electrode sheet made of the negative electrode material and first-time efficiency are both improved.
  • the aggregates with high compressive hardness in the negative electrode material enhance the stability of the structure, keep the structural stability during the expansion-shrinkage process as much as possible, and reduce the probability of the carbon layer being destroyed; at the same time, the aggregates have the characteristics of low porosity , even if the carbon layer on the surface is destroyed, it is difficult for the electrolyte to penetrate due to the surface tension of the aggregates, thereby improving the electrochemical performance.
  • Example 16 In the preparation process of the negative electrode material of Example 16, compared with Example 1, no additives are added, and the connection between the active particles, the carbon matrix and the metal oxide is less tight, so the obtained aggregates have lower compressive hardness. Swelling buffer inhibition weakened.
  • the present disclosure provides a negative electrode material, a preparation method thereof, and a lithium ion battery.
  • the negative electrode material has excellent structural stability, can effectively inhibit the volume expansion of the negative electrode material, and improve battery cycle performance, and the preparation method can reduce the preparation cost.

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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，聚集体包括活性物质和碳材料；其中，聚集体的孔隙率≤10％，聚集体的耐压硬度≥100Mpa。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29日提交中国专利局的申请号为202110727563.0、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，硅负极材料的研究和开发日趋成熟。但是负极材料脱嵌锂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，导致电化学性能变差，容量衰减、循环稳定性下降，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
本公开提供一种负极材料，所述负极材料包括聚集体，聚集体包括活性物质和碳材料，其中，所述聚集体的孔隙率≤10％，所述聚集体的耐压硬度≥100MPa。
一些实施方式中，所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种。
一些实施方式中，所述金属单质包括Li、Na、K、Sn、Ge、Fe、Mg、Ti、Zn、Al和Cu中的至少一种。
一些实施方式中，所述非金属单质包括Si和P中的至少一种。
一些实施方式中，所述硅的氧化物包括SiOx，其中，0<x≤2。
一些实施方式中，所述金属单质与硅的合金包括硅锂合金、硅钠合金、硅钾合金、硅锡合金、硅锗合金、硅铁合金、硅镁合金、硅钛合金、硅锌合金、硅铝合金和硅铜合金中的至少一种。
一些实施方式中，所述活性物质的中值粒径为1nm至500nm。
一些实施方式中，所述碳材料包括无定形碳、结晶碳和中间相碳微球中的至少一种。
一些实施方式中，所述无定形碳包括硬碳和软碳中的至少一种。
一些实施方式中，所述活性物质与所述碳材料的质量比为(30～70):(10～70)。
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，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。
一些实施方式中，所述聚集体还包括金属氧化物。
一些实施方式中，所述金属氧化物分布于所述活性物质中，所述活性物质和所述金属氧化物之间填充有所述碳材料。
一些实施方式中，所述活性物质与所述金属氧化物之间具有孔隙，所述孔隙中填充有所述碳材料。
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和Zn中的至少一种。
一些实施方式中，所述金属氧化物呈片状和/或长条状。
一些实施方式中，所述金属氧化物的长径比大于2。
一些实施方式中，所述活性物质和所述金属氧化物的质量比为(30～70):(1～20)。
一些实施方式中，所述聚集体还包括导电增强剂。
一些实施方式中，所述导电增强剂包括合金材料和导电碳中的至少一种。
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。
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。
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。
一些实施方式中，所述导电增强剂呈片状和/或长条状。
一些实施方式中，所述导电增强剂的长径比为2～5000。
一些实施方式中，所述导电增强剂与所述活性物质的质量比为(0.1～10):100。
一些实施方式中，所述负极材料还包括包覆在所述聚集体的至少部分表面的碳层。
一些实施方式中，所述聚集体表面的所述碳层的包覆率为1％～100％。
一些实施方式中，所述碳层的材料包括无定形碳。
一些实施方式中，所述碳层的厚度为10nm至1500nm。
一些实施方式中，所述负极材料的中值粒径为0.5μm～30μm。
一些实施方式中，所述负极材料的比表面积≤10m 2/g。
本公开提供一种负极材料的制备方法，包括以下步骤：
采用包含活性物质、第一碳源和溶剂的混合物制备前驱体；及
对所述前驱体进行密实化处理得到聚集体，所述聚集体的孔隙率≤10％且耐压硬度≥100MPa。
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。
一些实施方式中，所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种。
一些实施方式中，所述金属单质包括Li、Na、K、Sn、Ge、Fe、Mg、Ti、Zn、Al和Cu中的至少一种。
一些实施方式中，所述非金属单质包括Si和P中的至少一种。
一些实施方式中，所述硅的氧化物包括SiOx，其中，0<x≤2。
一些实施方式中，所述金属单质与硅的合金包括硅锂合金、硅钠合金、硅钾合金、硅锡合金、硅锗合金、硅铁合金、硅镁合金、硅钛合金、硅锌合金、硅铝合金和硅铜合金中的至少一种。
一些实施方式中，所述活性物质与所述第一碳源的质量比为(15～120):(10～50)。
一些实施方式中，所述溶剂为有机溶剂。
一些实施方式中，所述有机溶剂包括醇类溶剂。
一些实施方式中，所述醇类溶剂包括甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇和戊醇中的至少一种。
一些实施方式中，所述混合物经过干燥处理得到所述前驱体。
一些实施方式中，所述干燥处理的温度为40℃～300℃，所述干燥处理的时间为1h～15h。
一些实施方式中，所述混合物的制备方法具体包括：将所述活性物质、所述第一碳源和所述溶剂进行超声处理，再进行研磨处理。
一些实施方式中，所述超声处理的时间为15～45min。
一些实施方式中，所述研磨处理的时间为3～8h。
一些实施方式中，所述混合物中还包括金属氧化物。
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。
一些实施方式中，所述金属氧化物呈片状和/或长条状。
一些实施方式中，所述金属氧化物的长径比大于2。
一些实施方式中，所述活性物质、所述金属氧化物与第一碳源的质量比为(15～120):(1～20):(10～50)。
一些实施方式中，所述混合物中还包括导电增强剂。
一些实施方式中，所述导电增强剂包括合金材料和导电碳中的至少一种。
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。
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。
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。
一些实施方式中，所述导电增强剂呈片状和/或长条状。
一些实施方式中，所述导电增强剂的长径比为2～5000。
一些实施方式中，所述导电增强剂与所述活性物质的质量比为(0.1～10):100。
一些实施方式中，所述混合物中还包括添加剂。
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。
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和聚乙烯吡咯烷酮中的至少一种。
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和γ-甲基丙烯酰氧基丙基三甲氧基硅烷中的至少一种。
一些实施方式中，所述活性物质、所述金属氧化物、所述添加剂与所述第一碳源的质量比为(15～120):(1～20):(1～10):(10～50)。
一些实施方式中，所述密实化处理包括：将所述前驱体进行融合处理，再进行一次热处理。
一些实施方式中，所述融合处理包括机械融合。
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。
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。
一些实施方式中，所述机械融合的时间至少为0.5h。
一些实施方式中，所述一次热处理包括一次碳化处理。
一些实施方式中，所述一次碳化处理的温度为500℃～1200℃，所述一次碳化处理的时间为1h～10h。
一些实施方式中，所述一次碳化处理在保护性气体条件下进行，所述保护性气体包括氮气、氦气、氖气、氩气和氪气中的至少一种。
一些实施方式中，所述一次热处理还包括二次碳化处理，所述二次碳化处理在融合处理之后进行。
一些实施方式中，所述二次碳化处理包括气相包覆、固相包覆和液相包覆中的至少一种。
一些实施方式中，对所述聚集体进行碳包覆处理。
一些实施方式中，所述碳包覆处理包括：将所述聚集体与第二碳源进行混合，再进行二次热处理。
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。
一些实施方式中，所述聚集体与所述第二碳源的质量比为(10～100):(10～70)。
一些实施方式中，所述二次热处理的温度为600℃～1200℃，所述二次热处理的时间为1h～10h。
一些实施方式中，所述二次热处理在保护性气体条件下进行，所述保护性气体包括氮气、氦气、氖气、氩气和氪气中的至少一种。
一种锂离子电池，所述锂离子电池包括如上所述的负极材料或如上所述的负极材料的制备方法制得的负极材料。
附图说明
为了更清楚地说明本公开实施方式的技术方案，下面将对实施方式中所需要使用的附图作简单地介绍，应当理解，以下附图仅示例地表征本公开的实施方式，图中尺寸比例与实施方式的真 实比例并不能直接对应，同时以下附图仅示出了本公开的某些实施方式，因此不应被看作是对范围的限定。
图1为本公开实施例提供的负极材料的制备方法流程图；
图2为本公开实施例1制备的负极材料的扫描电子显微镜(SEM)图片；
图3为本公开实施例1制备的负极材料的XRD图；
图4为本公开实施例1制备的负极材料的首次充放电曲线图；
图5为本公开实施例1制备的负极材料的循环性能曲线图。
实施方式
发明内容中实施方式的优点将会在下面的说明书实施方式部分阐明，一部分根据说明书是显而易见的，或者可以通过本公开实施例的部分实施例而获得。
下面结合附图并通过一些实施方式来进一步说明本公开的技术方案。
为了使本公开的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本公开进行进一步详细说明。应当理解，此处所描述的实施例仅仅用以解释本公开，并不用于限定本公开。此外，下面所描述的本公开各个实施方式中所涉及的技术特征只要彼此之间未构成冲突就可以相互组合。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。
一实施方式提供了一种负极材料，具有优异的结构稳定性，有效抑制负极材料体积膨胀，提升电池循环性能。另一实施方式提供了上述负极材料的制备方法，该制备方法可降低制备成本。又一实施方式提供了锂离子电池。
一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，其中，聚集体的孔隙率≤10％，聚集体的耐压硬度≥100MPa。
本实施方式的负极材料包括聚集体，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的聚集体表面的碳层被破坏，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，降低膨胀率，提升电池循环性能。
本实施方式的聚集体的孔隙率≤10％，聚集体的孔隙率具体可以是1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％、5.5％、6％、6.5％、7％、7.5％、8％、8.5％、9％或9.5％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。在一种实施方式中，聚集体的孔隙率≤5％。在一种实施方式中，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、200MPa、250MPa、300MPa、400MPa、450MPa、500MPa、600MPa、750MPa、800MPa、900MPa、1000MPa、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。在一种实施方式中，聚集体的耐压硬度≥200MPa。在一种实施方式中，聚集体的耐压硬度≥400MPa。
一些实施方式中，活性物质指的是可以与锂反应，进行脱嵌锂的物质。活性物质包括硅的氧化物、非金属单质、金属单质及金属单质与硅的合金中的至少一种。
一些实施方式中，金属单质包括Li、Na、K、Sn、Ge、Fe、Mg、Ti、Zn、Al和Cu中的至少一种。
一些实施方式中，非金属单质包括Si和P中的至少一种。
一些实施方式中，硅的氧化物包括SiOx，其中，0<x≤2。
一些实施方式中，金属单质与硅的合金包括硅锂合金、硅钠合金、硅钾合金、硅锡合金、硅锗合金、硅铁合金、硅镁合金、硅钛合金、硅锌合金、硅铝合金和硅铜合金中的至少一种。
一些实施方式中，活性物质的中值粒径为1nm至500nm。具体可以是1nm、5nm、10nm、15nm、 20nm、30nm、40nm、50nm、100nm、200nm、300nm、400nm或500nm等，也可以是上述范围内的其他值，在此不做限定。通过多次试验发现，纳米级的活性物质颗粒的结构性强，可以抑制硅体积膨胀。但由于纳米级活性粒子有较大的表面能，在充放电过程中容易发生团聚，而且活性物质的粒径过小，生产工艺成本高。在一种实施方式中，活性物质的中值粒径为1nm～200nm。在一种实施方式中，活性物质的中值粒径为1nm～100nm。
一些实施方式中，碳材料包括无定形碳、结晶碳和中间相碳微球中的至少一种。一些实施方式中，无定形碳包括硬碳和软碳中的至少一种。可以理解地，碳材料可以提高聚集体的导电性，并且可以减少聚集体的孔隙率，使得聚集体能够更加密实。
在一些实施方式中，活性物质与碳材料的质量比为(30～70):(10～70)。活性物质与碳材料的质量比具体为30:10、30:40、30:50、30:70、40:10、40:50、40:70、50:30、50:60、60:10、60:50、70:10、70:40或70:70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，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％。聚集体的测试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，聚集体密度满足如下关系式：(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，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。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。
一些实施方式中，聚集体还包括金属氧化物。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，且聚集体有更高的耐压硬度。在一种实施方式中，当聚集体还包括金属氧化物时，聚集体的耐压硬度≥150MPa，进一步地，聚集体的耐压硬度≥200MPa，更进一步地，聚集体的耐压硬度≥400MPa。需要说明的是，此时聚集体的平均密度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锂*碳材料理论密度。
一些实施方式中，在聚集体中，金属氧化物分布于活性物质中，活性物质和金属氧化物之间填充有碳材料。具体地，活性物质与金属氧化物之间具有孔隙，孔隙中填充有碳材料。可以理解地，通过活性物质与金属氧化物形成的孔隙结构，使得碳材料填充孔隙内，可以提高聚集体的结构稳定性，可以抵御一定的体积膨胀应力，降低膨胀。
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和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、SiO 2、CuO等等。本技术方案中，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、10、11、12、13、14、15、16、17、18、19、20、21、22等等，当然也可以是上述范围内的其他值，在此不做限定。根据多次试验发现，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，改善两者形成的网络结构，从而缓冲活性物质的体积膨胀变化，提升循环性能。
在一些实施方式中，活性物质和金属氧化物的质量比为(30～70):(1～20)。活性物质和金属氧化物的质量比具体为30:5、30:15、30:20、40:5、40:15、40:20、50:10、50:20、60:10、60:25或70:20，当然也可以是上述范围内的其他值，在此不做限定。金属氧化物含量过高，导致材料的首次效率下降，金属氧化物含量过低，会导致其对聚集体结构的刚性下降，颗粒循环稳定性下降。
在一些实施方式中，聚集体还包括导电增强剂。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，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。
在一种实施方式中，聚集体的耐压硬度≥150Mpa。在一种实施方式中，聚集体的耐压硬度≥200Mpa。在一种实施方式中，聚集体的耐压硬度≥400Mpa。需要说明的是，此时聚集体的平均密度ρ2＝活性物质在聚集体的质量百分含量*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+导电增加剂的质量百分含量*导电增强剂的理论密度。
在一些实施方式中，导电增强剂包括合金材料和导电碳中的至少一种。
一些实施方式中，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。
一些实施方式中，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，导电增强剂的电导率为10 0S/m～10 8S/m。导电增强剂的电导率具体为10S/m、100S/m、1000S/m、10 4S/m、10 5S/m、10 6S/m或10 7S/m，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，长径比具体是指导电增强剂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、5、10、15、20、33、50、60、70、80、90、100、150、600、780、890、1300、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。根据多次试验发现，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，从而缓冲活性物质的体积膨胀变化，提升循环性能。
在一些实施方式中，导电增强剂与活性物质的质量比为(0.1～10):100。导电增强剂与活性物质的质量比具体为0.1:100、0.5:100、1:100、2:100、2.6:100、3:100、3.5:100、4:100、4.8:100、6:100、7:100、8.5:100或10:100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，负极材料还包括包覆在聚集体的至少部分表面的碳层。需要说明的是，聚集体的表面可部分或者全部被碳层所包覆。在一些实施方式中，聚集体表面的碳层的包覆率为1％～100％。需要说明的是，本公开中的包覆率是指聚集体表面被碳层所包覆的程度。包覆率具体为1％、5％、10％、20％、25％、30％、35％、40％、45％、50％、55％、60％、65％、70％、75％、80％、85％、90％或95％。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，碳层的材料包括无定形碳。
在一些实施方式中，碳层的厚度为10nm至1500nm。可以理解地，包覆所述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。碳层的厚度具体是10nm、50nm、180nm、200nm、350nm、400nm、550nm、700nm、850nm、900nm、1050nm、1200nm或1500nm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，碳占比过高，不利于获得高比容量的复合材料；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。在一种实施方式中，碳层的厚度为50nm～800nm。在一种实施方式中，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。负极材料的中值粒径具体为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，负极材料的中值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。负极材料的比表面积具体为0.5m 2/g、1m 2/g、2m 2/g、3m 2/g、5m 2/g、7m 2/g、8m 2/g或10m 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。
本公开中所述中值粒径指的是平均粒径，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，比如聚集体的耐压硬度、孔隙率与密度进行组合限定等。
一实施方式的负极材料的制备方法，包括以下步骤：
步骤S10，将活性物质、第一碳源和溶剂的混合物制备前驱体；
步骤S20，对前驱体进行密实化处理得到聚集体，聚集体的孔隙率≤10％且耐压硬度≥100MPa；
步骤S30，将聚集体进行碳包覆处理，得到负极材料。
本公开提供的负极材料的制备方法，利用对前驱体进行密实化处理，提高负极材料的耐压硬度，增强颗粒结构的稳定性，同时可以增强活性物质与第一碳源之间的连接稳定性，降低孔隙率；从而使得负极材料的膨胀率降低，循环稳定性增高。
以下结合实施例具体介绍本公开的制备方法：
步骤S10，将活性物质、第一碳源和溶剂的混合物制备前驱体。
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、聚氯乙烯和沥青中的至少一种。
一些实施方式中，活性物质指的是可以与锂反应，进行脱嵌锂的物质。活性物质包括活性物质包括金属单质与硅的合金、硅的氧化物、金属单质和非金属单质中的至少一种。一些实施方式中，金属单质包括Li、Na、K、Sn、Ge、Fe、Mg、Ti、Zn、Al和Cu中的至少一种。一些实施方式中，非金属单质包括Si和P中的至少一种。一些实施方式中，硅的氧化物包括SiOx，其中，0<x≤2。一些实施方式中，金属单质与硅的合金包括硅锂合金、硅钠合金、硅钾合金、硅锡合金、硅锗合金、硅铁合金、硅镁合金、硅钛合金、硅锌合金、硅铝合金和硅铜合金中的至少一种。
一些实施方式中，活性物质与第一碳源的质量比为(15～120):(10～50)。活性物质与第一碳源的质量比具体为100:15.9、100:21.9、100:24.5、100:9.5、100:9.5、100:9.5、100:9.5或100:9.5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，混合物的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。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。
一些实施方式中，混合物的制备方法具体包括：将活性物质、第一碳源和溶剂进行超声处理，再进行研磨处理。一些实施方式中，超声处理的时间为15～45min。超声处理的时间具体为20min、25min、30min、35min或40min等，当然也可以是上述范围内的其它值，在此不做限定。一些实施方式中，研磨处理的时间为3～8h。研磨处理的时间具体为4h、5h、6h或7h等，当然也可以是上述范围内的其它值，在此不做限定。通过充分研磨可以使得组分混合更加均匀。
具体地，将活性物质、第一碳源和溶剂混合，得到前驱体溶液，并将前驱体溶液进行湿法球磨，使得前驱体溶液中的颗粒粒径达到1nm～500nm。前驱体溶液中的颗粒粒径具体可以是1nm、5nm、10nm、15nm、50nm、100nm、150nm、200nm、300nm、400nm或500nm等，在此不做限定。
在一些实施方式中，溶剂包括有机溶剂。一些实施方式中，所述有机溶剂包括醇类溶剂，具体地，醇类溶剂包括甲醇、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。将各个组分加入有机溶剂中进行湿法球磨，可以提高组分混合均匀度，并且有利于快速干燥。
在一些实施方式中，混合物经过干燥处理得到前驱体。在一些实施方式中，干燥处理的温度为40℃～300℃，干燥处理的时间为1h～15h。干燥处理的温度具体为50℃、70℃、100℃、120℃、150℃、200℃、220℃、250℃等，当然也可以是上述范围内的其它值，在此不做限定。干燥处理的时间具体为1.5h、2h、2.5h、3h、4h、5h、6h、7h、8h、9h、10h、11h、12h、13h或14h等，当然也可以是上述范围内的其它值，在此不做限定。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，混合物中还包括金属氧化物。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。金属氧化物具体可以是GeO 2、SnO 2、ZnO、TiO 2、Fe 3O 4、MgO、SiO 2、CuO等。
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。需要说明的是，当金属氧化物为长条状时，长径比具体是指颗粒的长度与颗粒的粒径的比值；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或22等，也可以是上述范围内的其他值，在此不做限定。根据多次试验发现，金属氧化物的长径比小于等于2时，通过控制金属氧化物的长径比，可以提升金属氧化物与活性物质的物理结合力，改善两者形成的网络结构，从而更好的缓冲活性物质的体积膨胀变化，提升循环性能。
在一些实施方式中，活性物质、金属氧化物与第一碳源的质量比为(15～120):(1～20):(10～50)。具体地，活性物质、金属氧化物与第一碳源的质量比可以是15:1:10、20:3:25、50:8:35、60:9:38、70:11:45、90:15:40、100:9:15.9、100:5:21.9、100:2:24.5、100:9:19.5、100:9:19.5、100:9:19.5、100:11:19.5、100:9.5:19.5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，混合物中还包括导电增强剂。
在一种实施方式中，将活性物质、第一碳源和溶剂混合的步骤中加入导电增强剂。在一些实施方式中，导电增强剂包括合金材料和导电碳中的至少一种。
在一些实施方式中，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，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，导电增强剂的电导率为10 0S/m～10 8S/m。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，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，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。具体地，导电增强剂的长径比值可以是2、5、10、15、20、33、50、60、70、80、90、100、150、600、780、890、1300、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。
在一些实施方式中，导电增强剂与活性物质的质量比为(0.1～10):100。具体地，导电增强剂与活性物质的质量比为0.1:100、0.5:100、1:100、2:100、2.6:100、3:100、3.5:100、4:100、4.8:100、6:100、7:100、8.5:100或10:100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，混合物中还包括添加剂。该实施方式中的添加剂，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。在一些实施方式中，添加剂包括表面活性剂和偶联剂中的至少一种。经试验发现，采用上述种类的添加剂能够有效增强活性物质与碳材料的连接稳定性，以形成牢固的体系，降低孔隙率，从而使得负极材料的膨胀率降低，循环稳定性增高。
在一些实施方式中，表面活性剂包括但不限于正十八酸、月桂酸、聚丙烯酸(PAA)、十二烷基苯磺酸钠(SDBS)、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(PVP)中的至少一种。
在一些实施方式中，硅烷偶联剂但不限于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和γ-甲基丙烯酰氧基丙基三甲氧基硅烷中的至少一种。
在一些实施方式中，活性物质、金属氧化物、添加剂与第一碳源的质量比为(15～120):(1～20):(1～10):(10～50)。活性物质、金属氧化物、添加剂与第一碳源的质量比具体为100:9:5.9:15.9、100:5:8:21.9、100:2:5:24.5、100:9:5:19.5、100:9:11:19.5、100:9:10.5:19.5、100:11:5.5:19.5、100:9.5:6.9:19.5等，当然也可以是上述范围内的其它值，在此不做限定。
步骤S20，对前驱体进行密实化处理得到聚集体，聚集体的孔隙率≤10％且耐压硬度≥100MPa。
在一些实施方式中，密实化处理包括对前驱体进行融合处理，再进行一次热处理。利用对前驱体进行融合处理，提高负极材料的耐压硬度，再进行一次热处理，增强颗粒结构的稳定性，同时可以增强活性物质与第一碳源之间的连接稳定性，降低孔隙率。当然，在其他的实施方式中，还可以采用其他方法进行密实化处理，比如模压、等静压、浸渍等工艺，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，机械融合所用的融合机的转速为500r/min～3000r/min，具体可以是500r/min、1000r/min、1500r/min、2000r/min、2500r/min或3000r/min等等，当然也可以是上述范围内的其它值，在此不做限定。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，当然也可以是上述范围内的其它值，在此不做限定。机械融合的时间至少为0.5h，具体可以是0.5h、0.8h、0.9h、1.0h、1.5h或2h等等，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，一次热处理包括一次碳化处理。
在一些实施方式中，将融合处理后的混合物送入高温箱式炉内进行一次碳化处理，使得第一碳源进行碳化，将活性物质、碳材料紧密连接在一起。一次碳化处理的方式例如可以是常压烧成、真空烧成或者热压烧成。
在一些实施方式中，一次碳化处理的温度为500℃～1200℃，一次碳化处理的时间为1h～10h。一次碳化处理的温度具体为500℃、600℃、700℃、800℃、900℃、1000℃、1100℃、1200℃等，当然也可以是上述范围内的其它值，在此不做限定。一次碳化处理的时间具体为1h、2h、3h、4h、5h、6h、7h、8h、9h或15h等，当然也可以是上述范围内的其它值，在此不做限定。
一次碳化处理的升温速率为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，当然也可以是上述范围内的其它值，在此不做限定。
在一种实施方式中，一次热处理的升温速率为1℃/min～15℃/min。
在一些实施方式中，一次碳化处理在保护性气体条件下进行，保护性气体包括氮气、氦气、氖气、氩气和氪气中的至少一种。
在一些实施方式中，一次热处理还包括二次碳化处理，二次碳化处理在融合处理之后进行。在融合处理后及一次碳化处理前进行二次碳化处理，或者在一次碳化处理后进行二次碳化处理。二次碳化处理可以进一步降低材料的孔隙率。
在一些实施方式中，二次碳化处理包括气相包覆、固相包覆和液相包覆中的至少一种。一些实施方式中，固相包覆的反应温度为500℃～1200℃，具体包括但不限于为600℃、700℃、800℃、850℃、900℃、950℃、1000℃、1050℃、1100℃、1150℃等，反应时间为1h～12h，具体包括但不限于为2h、3h、4h、5h、6h、7h、8h、9h、10h、11h等。一些实施方式中，液相包覆的反应温度为500℃～1200℃，具体包括但不限于为600℃、700℃、800℃、850℃、900℃、950℃、1000℃、1050℃、1100℃、1150℃等，反应时间为1h～12h，具体包括但不限于为2h、3h、4h、5h、6h、7h、8h、9h、10h、11h等。
在一些实施方式中，气相包覆包括化学气相沉积，化学气相沉积的反应温度为600℃～1050℃，具体可以是600℃、700℃、800℃、850℃、900℃、950℃、1000℃或1050℃等，当然也可以是上述范围内的其它值，在此不做限定。化学气相沉积时间为0.5h～2h，具体可以是0.5h、0.8h、1.0h、1.5h、1.8h或2h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，通过化学气相沉积，碳源气体裂解时分解成为零维的单个碳原子自由基或一维的较短碳链，互相堆叠会更紧密，更有利于形成密实结构的聚集体，有利于材料导电网络的完整及结构的稳定性，有利于提高负极材料的循环稳定性。
在一种实施方式中，化学气相沉积的反应温度为800℃～1000℃。
在一些实施方式中，化学气相沉积过程中的碳源气体包括甲烷、乙烯、乙炔、苯、甲苯、二甲苯、苯乙烯和苯酚中的至少一种。
步骤S30，将聚集体进行碳包覆处理，得到负极材料。
需要说明的是，本实施方式的负极材料可以不进行碳包覆，此时，步骤S30可以省略。
在一些实施方式中，碳包覆处理包括：将聚集体与第二碳源进行混合，再进行二次热处理。
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，聚集体的粒径为0.5μm～15μm，具体可以是0.5μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、10μm、12μm或15μm等等，当然也可以是上述范围内的其他值，在此不做限定。将粒径控制在上述范围内，有利于获得高耐压硬度的产品。试验发现聚集体的颗粒过大，会导致密实化程度低，连接紧密，耐压硬度小。
在一些实施方式中，聚集体与第二碳源的质量比为(10～100):(10～70)。具体地，聚集体与第二碳源的质量比为10:20、20:10、100:25、100:35、100:45、100:55、100:65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，聚集体与第二碳源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，二次热处理的方式例如可以常压烧成、真空烧成或者热压烧成。
在一些实施方式中，二次热处理的温度为600℃～1200℃，二次热处理的时间为1h～10h.二次热处理的温度具体为500℃、600℃、700℃、800℃、900℃、1000℃、1200℃、1200℃等，当然也可以是上述范围内的其他值，在此不做限定。二次热处理的时间具体为1h、2h、3h、4h、5h、6h、7h、8h、9h或15h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，二次热处理时的升温速率为1～30℃/min。例如可以是，优选地，二次热处理时的升温速率为1～15℃/min。二次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，当然也可以是上述范围内的其他值，在此不做限定。
在一种实施方式中，一次热处理时的升温速率为1℃/min～15℃/min。
在一些实施方式中，二次热处理在保护性气体条件下进行，保护性气体包括氮气、氦气、氖气、氩气和氪气中的至少一种。
在本方案中，采用上述制备方法制得的负极材料，在活性物质及碳材料形成的聚集体的表面包覆碳层，可以抑制材料在循环过程中的膨胀。其核结构聚集体具有较高的耐压硬度，具有较强的刚性，可以有效抵御一定的体积膨胀的应力，有利于保持负极材料结构稳定性，从而降低膨胀率，提升电池循环性能。聚集体具有低孔隙率，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，降低材料体积膨胀，提升循环性能。
本公开还提供一种锂离子电池，包括上述的负极材料。
实施例
以下为本公开典型但非限制性实施例：
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Si粉、长径比为22的SiO颗粒、月桂酸和酚醛树脂按照质量比60:4.5:3.9:22.9加入到40％乙二醇溶液中，超声分散10min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液，然后进行干燥处理，干燥温度190℃，时间3h，获得前驱体。
(2)将前驱体放置融合机中，融合机的转速为500r/min；机械融合所用的融合机刀具间隙宽度为0.05cm；机械融合时间为0.5h.将融合后的物料置于热处理炉中，然后通入氮气在600℃条件下，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30:45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1000℃条件下二次热处理，保温6h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Si粉、SiO颗粒及碳材料，硅粉、SiO颗粒与碳材料的质量比为55.9:4.3:39.8，负极材料的中值粒径为16μm，比表面积为5.2m 2/g，碳层的平均厚度为166nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为5.5％；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330MPa。聚集体的测试密度与硅粉、SiO颗粒及碳材料的平均密度差为0.9％。
如图2为实施例1制得的负极材料的扫描电子显微镜图，图3的X射线衍射图谱中存在硅峰峰位。
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80nm的Si粉、长径比为12的GeO 2颗粒、棕榈酸和聚乙烯吡咯烷酮按照质量比为40:1.8:8:21.9加入到丙醇溶液中，超声分散15min得到分散溶液，再将分散溶液置于球磨机中研磨分散3小时，得到前驱体溶液，然后进行干燥190℃，时间3h，获得前驱体。
(2)将前驱体放置融合机中，融合机的转速为800r/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。
(3)将聚集体与蔗糖按照质量比20:45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900℃条件下二次热处理，保温5h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Si粉、GeO 2颗粒及碳材料，Si粉、GeO 2颗粒与碳材料的质量比为63.3:2.9:33.8。负极材料的中值粒径为12μm，比表面积为3.2m 2/g，碳层的平均厚度为154nm。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540MPa。聚集体的测试密度与聚集体中的硅粉、SiO颗粒及碳材料的平均密度差为2.09％。
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50nm的Si粉、长径比为6的SnO 2颗粒、亚油酸和聚乙烯按照质量比20:1:5:24.5加入到40％乙醇溶液中，超声分散25min得到分散溶液，再将分散溶液置于球磨机中研磨分散8小时，得到前驱体溶液，然后进行干燥处理，干燥温度为200℃，时间为3h，获得前驱体。
(2)前驱体放置融合机中，融合机的转速为600r/min；融合机刀具间隙宽度为0.3cm；融合时间为3h。将融合后的物料置于热处理炉中，然后通入氮气在900℃条件下进行一次热处理，保温5h，获得聚集体。
(3)将聚集体与沥青按照质量比30:55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℃条件下二次热处理，保温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Si粉、SnO 2颗粒和碳材料；Si粉、SnO 2颗粒与碳材料的质量比为48.1:2.3:49.6；负极材料的中值粒径为8.4μm，比表面积为4.2m 2/g，碳层的平均厚度为79nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为6.5％；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116MPa。聚集体的测试密度与聚集体中的Si粉、SnO 2颗粒和碳材料平均密度差为2.78％。
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20nm的Si粉、长径比为18的ZnO颗粒、油酸和聚乙二醇按照质量比40:10.5:9:29.5加入到正丁醇溶液中，超声分散45min得到分散溶液，再将分散溶液置于球磨机中研磨分散6小时，得到前驱体溶液，然后进行干燥处理，干燥温度250℃，时间为2.5h，获得前驱体。
(2)前驱体放置融合机中，融合机的转速为900r/min；融合机刀具间隙宽度为0.4cm；所述机械融合时间为3h。将融合后的物料置于热处理炉中，然后通入氮气在780℃条件下进行一次热处理，保温8h，获得聚集体。
(3)将聚集体与沥青按照质量比40:45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950℃条件下二次热处理，保温6h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Si粉、ZnO颗粒及碳材料，Si粉、ZnO颗粒与碳材料的质量比为51.3:13.5:35.2。负极材料的中值粒径为6.4μm，比表面积为3.2m 2/g，碳层的平均厚度为155nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为8.5％；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556MPa。聚集体的测试密度与聚集体中的Si粉、ZnO颗粒及碳材料的平均密度差为3.98％。
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50nm的Si粉、长径比为18的TiO 2颗粒、癸酸和沥青按照质量比80:9:10:9.5加入到乙二醇溶液中，超声分散45min得到分散溶液，再将分散溶液置于球磨机中研磨分散6小时，得到前驱体溶液，然后进行干燥处理，干燥温度为150℃，时间为5h，获得前驱体。
(2)前驱体放置融合机中，融合机的转速为650r/min；融合机刀具间隙宽度为0.35cm；融合时间为2h，将融合后的物料置于热处理炉中，然后通入氦气在600℃条件下进行一次热处理，保温6h，然后将热处理后的材料粉碎，置于气相沉积炉内，气相沉积炉内温度为1000℃，通入甲烷 沉积1.5h形成碳材料，获得聚集体。
(3)将聚集体与沥青按照质量比50:35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920℃条件下二次热处理，保温5h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Si粉、TiO 2颗粒及碳材料，Si粉、TiO 2颗粒与碳材料的质量比为65.2:7.3:27.5。负极材料的中值粒径为6μm，比表面积为2.3m 2/g，碳层的平均厚度为418nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为3.5％；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756MPa。聚集体的测试密度与聚集体中的Si粉、TiO 2颗粒及碳材料的平均密度差为4.38％。
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50nm的Si粉、长径比为17的TiO 2颗粒、癸酸和沥青按照质量比22:8:10:16.5加入到乙二醇溶液中，超声分散45min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液，然后进行干燥处理，获得前驱体。
(2)前驱体放置融合机中，融合机的转速为800r/min；融合机刀具间隙宽度为0.2cm；融合时间为3h。将融合后的物料置于热处理炉中，然后通入氦气在770℃条件下进行一次热处理，保温5h，然后将热处理后的材料粉碎，置于气相沉积炉，气相沉积炉内温度为900℃，通入乙炔气体，进行沉积0.5h形成碳材料，获得聚集体。
(3)将聚集体与沥青按照质量比35:50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920℃条件下二次热处理，保温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Si粉、TiO 2颗粒及碳材料，Si粉、TiO 2颗粒与碳材料的质量比为39.1:14.5:46.4，负极材料的中值粒径为5.2μm，比表面积为1.3m 2/g，碳层的平均厚度为511nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为1.5％；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356MPa。聚集体的测试密度与Si粉、TiO 2颗粒及碳材料的平均密度差为1.58％。
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Ge粉、长径比为8的ZnO颗粒、油酸和果糖按照质量比90:11:5.5:18.9加入到乙二醇溶液中，超声分散45min得到分散溶液，再将分散溶液置于球磨机中研磨分散8小时，得到前驱体溶液，然后进行干燥处理，干燥温度190℃，时间为3h，获得前驱体。
(2)前驱体放置融合机中，融合机的转速为900r/min；融合机刀具间隙宽度为0.3cm；融合时间为3h。然后置于气相沉积炉，气相沉积炉内温度为1050℃通入乙炔气体，进行沉积1h形成碳材料，获得聚集体。
(3)将聚集体与沥青按照质量比45:40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1020℃条件下二次热处理，保温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Ge粉、ZnO颗粒及碳材料；聚集体包括Ge粉、ZnO颗粒与碳材料的质量比为65.3:8:26.7。负极材料的中值粒径为11.2μm，比表面积为3.3m 2/g，碳层的平均厚度为310nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为3.2％；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446MPa。聚集体的测试密度与聚集体中的Ge粉、ZnO颗粒及碳材料的平均密度差为5.11％。
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120nm的Al粉、长径比为18的Fe 3O 4颗粒、月桂酸和沥青按照质量比20:2:6.9:10加入到40％乙醇溶液中，超声分散45min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液，然后进行干燥处理，干燥温度200℃，时间为3h，获得前驱体。
(2)前驱体放置融合机中，融合机的转速为650r/min；融合机刀具间隙宽度为0.5cm；融合时间为3h。将融合后的物料置于热处理炉中，然后在790℃条件下进行一次热处理，保温4h，获得聚集体。
(3)将聚集体与沥青按照质量比100:45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820℃条件下二次热处理，保温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Al粉、Fe 3O 4颗粒及碳材料，Al粉、Fe 3O 4颗粒与碳材料的质量比为59.6:5.96:34.44。负极材料的中值粒径为16.2μm，比表面积为4.3m 2/g，碳层的平均厚度为351nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为4.0％；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292MPa。聚集体的测试密度与聚集体中的Al粉、Fe 3O 4颗粒及碳材料的平均密度差为4.78％。
实施例9
本实施例与实施例1区别在于，步骤1)中的中值粒径为100nm的Si粉、长径比为22的SiO颗粒、月桂酸和酚醛树脂的质量比为15:2:1.5:12.5；步骤2)中的一次热处理温度为1200℃。
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，聚集体包括硅粉、SiO颗粒及碳材料，Si粉、SiO颗粒与碳材料的质量比为51.3:6.8:41.9，负极材料的中值粒径为14.7μm，比表面积为3.2m 2/g，碳层的平均厚度为378nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为3.5％；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380MPa。聚集体的测试密度与聚集体中的Si粉、SiO颗粒及碳材料的平均密度差为0.99％。
实施例10
本实施例与实施例1区别在于，步骤1)中的中值粒径为100nm的Si粉、长径比为22的SiO颗粒、月桂酸和酚醛树脂的质量比为120:15.5:5.9:45.9；步骤3)中的二次热处理温度为600℃。
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，聚集体包括硅粉、SiO颗粒及碳材料，硅粉、SiO颗粒与碳材料的质量比为60.7:7.8:31.5，负极材料的中值粒径为17.7μm，比表面积为6.1m 2/g，碳层的平均厚度为240nm；采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为4.8％；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160MPa。聚集体的测试密度与聚集体中的Si粉、SiO颗粒及碳材料的平均密度差为8.18％。
实施例11
本实施例与实施例1区别在于，步骤1)中的中值粒径为100nm的Si粉、长径比为22的SiO颗粒、直径20nm的CNT、月桂酸和酚醛树脂的质量比为60:4.5:0.9:3.9:22.9；其余参数保持不变。
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，聚集体包括硅粉、SiO颗粒、CNT及碳材料，Si粉、SiO颗粒、CNT与碳材料的质量比为60.7:5.8:1.9:31.6，负极材料的中值粒径为13.7μm，比表面积为5.1m 2/g，碳层的平均厚度为221nm；采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为7.8％；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375MPa。聚集体的测试密度与聚集体中的Si粉、SiO颗粒及碳材料平均密度差为9.4％。
实施例12
本实施例与实施例1区别在于，不进行步骤3)中的碳包覆处理步骤。
本实施例制得的负极材料包括聚集体，聚集体包括硅粉、SiO颗粒及碳材料，硅粉、SiO颗粒与碳材料的质量比为55.9:4.3:39.8，负极材料的中值粒径为14.9μm，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6.7％；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240MPa。聚集体的测试密度与聚集中的Si粉、SiO颗粒及碳材料的平均密度差为0.9％。
实施例13
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Si粉、月桂酸和酚醛树脂按照质量比60:3.9:22.9加入到40％乙二醇溶液中，超声分散10min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液，然后进行干燥处理，干燥温度190℃，时间3h，获得前驱体。
(2)将前驱体放置融合机中，融合机的转速为500r/min；所述机械融合所用的融合机刀具间隙宽度为0.05cm；所述机械融合时间为0.5h，将融合后的物料置于热处理炉中，然后通入氮气在 600℃条件下，进行一次热处理，保温3h，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Si粉及碳材料，硅粉与碳材料的质量比为55.1:44.9，负极材料的中值粒径为14.6μm，比表面积为4.7m 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5.8％；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195MPa。聚集体的测试密度与硅粉、碳材料的平均密度差为1.1％。
实施例14
本实施例与实施例1的区别在于，步骤1)的不同，步骤1)将中值粒径为100nm的Si粉、月桂酸和酚醛树脂按照质量比60:5.9:45加入到40％乙二醇溶液中，超声分散10min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液，然后进行干燥处理，干燥温度190℃，时间3h，获得前驱体。
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Si粉及碳材料，硅粉与碳材料的质量比为45.9:54.1，负极材料的中值粒径为12.5μm，比表面积为3.1m 2/g，碳层的平均厚度为425nm；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208MPa。聚集体的测试密度与硅粉及碳材料的平均密度差为0.6％。
实施例15
本实施例与实施例1的区别在于，步骤1)的不同，步骤1)将中值粒径为100nm的Si粉、FeSi 2、月桂酸和酚醛树脂按照质量比60:4.5:3.9:22.9加入到40％乙二醇溶液中，超声分散10min得到分散溶液，再将分散溶液置于球磨机中研磨分散4小时，得到前驱体溶液，然后进行干燥处理，干燥温度190℃，时间3h，获得前驱体。
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Si粉及碳材料，硅粉、FeSi 2与碳材料的质量比为55.3:4.2:40.5，负极材料的中值粒径为14.9μm，比表面积为4.9m 2/g，碳层的平均厚度为176nm；采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为5.3％；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319MPa。聚集体的测试密度与硅粉及碳材料的平均密度差为0.8％。
实施例16
按照与实施例1基本相同的方法制备负极材料，区别在于：未添加月桂酸。
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，聚集体包括硅粉、SiO颗粒及碳材料，硅粉、SiO颗粒与碳材料的质量比为55.9:4.2:39.4，负极材料的中值粒径为15.8μm，比表面积为5.0m 2/g，碳层的平均厚度为159nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为6.2％；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278MPa。聚集体的测试密度与聚集中的硅粉、SiO颗粒及碳材料的平均密度差为4.8％。
实施例17
按照与实施例1基本相同的方法制备负极材料，区别在于：SiO长径比为2.1。
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，聚集体包括硅粉、SiO颗粒及碳材料，硅粉、SiO颗粒与碳材料的质量比为55.4:4.3:39.9，负极材料的中值粒径为17.8μm，比表面积为5.4m 2/g，碳层的平均厚度为169nm。采用压汞法对聚集体颗粒进行测试，聚集体的孔隙率为6.0％；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244MPa。聚集体的测试密度与聚集中的硅粉、SiO颗粒及碳材料的平均密度差为8.9％。
对比例1
按照与实施例1基本相同的方法制备负极材料，区别在于：未进行融合处理。
本对比例中聚集体的孔隙率为22.4％，聚集体的耐压硬度平均为50.3MPa，聚集体的测试密度与聚集中的硅粉、SiO颗粒及碳材料的平均密度差为10.1％。
测试方法
(1)扣式电池测试
采用以下方法测试电化学循环性能：将制得的硅碳复合负极材料、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装配得到锂离子 扣式电池。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电池测试系统上，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H1，循环50圈后膨胀率＝(H1-H0)/H0×100％。
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％。
(2)聚集体的孔隙率测试：
使用压汞仪通过压汞法测定孔隙率。孔隙率至少测定三次，采用至少三次的算术平均作为测定结果。
(3)聚集体的耐压硬度测试：
耐压硬度通过纳米压痕仪测试，采用载荷0.6N，压痕深度0.5μm的方法进行压痕硬度测试。
(4)比表面积的测试方法：使用麦克比表面积分析仪测试负极材料的比表面积。
(5)电导率的测试方法：使用粉末电阻率测试仪负极材料的电导率。
上述性能测试的结果如下：
表1性能比对结果表
Figure PCTCN2022095217-appb-000001
Figure PCTCN2022095217-appb-000002
如表1所示，实施例1至17制得的负极材料，其中，聚集体的孔隙率≤10％，且耐压硬度≥100MPa，由该负极材料制造的负极极片的膨胀率、循环寿命和首次效率均得到改善。这是由于负极材料中高耐压硬度的聚集体，增强了结构的稳定性，尽可能保持膨胀-收缩过程中的结构稳定性，减少碳层被破坏的概率；同时，聚集体具有低孔隙率特点，即便表面的碳层被破坏，由于聚集体表面张力的因素，电解液也难以渗透进去，从而提升了电化学性能。
实施例16的负极材料在制备过程中，相对于实施例1，未添加添加剂，活性颗粒与碳基质、金属氧化物之间的连接更不紧密，因此获得聚集体的耐压硬度更低，对膨胀缓冲抑制作用减弱。
对比例1的负极材料在制备过程中，未进行融合处理，使得前驱体难以形成高耐压硬度的聚集体，孔隙率过高。在长循环过程中，由于体积膨胀容易表面碳层结构，进而破坏内核结构，电解液容易渗透到颗粒内部，形成厚SEI膜，消耗大量的活性锂离子，其循环容量保持率仅为80.1％，相较于实施例1的循环容量保持率94.1％，明显下降，且极片膨胀率为49.2％，相较于实施例的极片膨胀率35.3％，也明显提高。由此可见，通过融合处理，可以提高聚集体的耐压硬度，可以有效提高电池循环性能，抑制膨胀。
工业实用性
综上所述，本公开提供了一种负极材料及其制备方法、锂离子电池。该负极材料具有优异的结构稳定性，能有效抑制负极材料体积膨胀，提升电池循环性能，该制备方法可降低制备成本。

Claims (13)

  1. 一种负极材料，其特征在于，所述负极材料包括聚集体，聚集体包括活性物质和碳材料，其中，所述聚集体的孔隙率≤10％，所述聚集体的耐压硬度≥100MPa。
  2. 根据权利要求1所述的负极材料，其特征在于，包含以下特征(1)至(10)中的至少一种：
    (1)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种；
    (2)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种，所述金属单质包括Li、Na、K、Sn、Ge、Fe、Mg、Ti、Zn、Al和Cu中的至少一种；
    (3)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种，所述非金属单质包括Si和P中的至少一种；
    (4)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种，所述硅的氧化物包括SiOx，其中，0<x≤2；
    (5)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种，所述金属单质与硅的合金包括硅锂合金、硅钠合金、硅钾合金、硅锡合金、硅锗合金、硅铁合金、硅镁合金、硅钛合金、硅锌合金、硅铝合金和硅铜合金中的至少一种；
    (6)所述活性物质的中值粒径为1nm至500nm；
    (7)所述碳材料包括无定形碳、结晶碳和中间相碳微球中的至少一种；
    (8)所述碳材料包括无定形碳、结晶碳和中间相碳微球中的至少一种，所述无定形碳包括硬碳和软碳中的至少一种；
    (9)所述活性物质与所述碳材料的质量比为(30～70):(10～70)；
    (10)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，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。
  3. 根据权利要求2所述的负极材料，其特征在于，包含以下特征(1)至(7)中的至少一种：
    (1)所述聚集体还包括金属氧化物；
    (2)所述聚集体还包括金属氧化物，所述金属氧化物分布于活性物质中，所述活性物质和所述金属氧化物之间填充有所述碳材料；
    (3)所述聚集体还包括金属氧化物，所述活性物质与所述金属氧化物之间具有孔隙，所述孔隙中填充有所述碳材料；
    (4)所述聚集体还包括金属氧化物，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和Zn中的至少一种；
    (5)所述聚集体还包括金属氧化物，所述金属氧化物呈片状和/或长条状；
    (6)所述聚集体还包括金属氧化物，所述金属氧化物的长径比大于2；
    (7)所述聚集体还包括金属氧化物，所述活性物质和所述金属氧化物的质量比为(30～70):(1～20)。
  4. 根据权利要求1～3中任一项所述的负极材料，其特征在于，包含以下特征(1)至(8)中的至少一种：
    (1)所述聚集体还包括导电增强剂；
    (2)所述聚集体还包括导电增强剂，所述导电增强剂包括合金材料和导电碳中的至少一种；
    (3)所述聚集体还包括导电增强剂，所述导电增强剂包括合金材料和导电碳中的至少一种，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；
    (4)所述聚集体还包括导电增强剂，所述导电增强剂包括合金材料和导电碳中的至少一种，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)所述聚集体还包括导电增强剂，所述导电增强剂的电导率为10 0S/m～10 8S/m；
    (6)所述聚集体还包括导电增强剂，所述导电增强剂呈片状和/或长条状；
    (7)所述聚集体还包括导电增强剂，所述导电增强剂的长径比为2～5000；
    (8)所述聚集体还包括导电增强剂，所述导电增强剂与所述活性物质的质量比为(0.1～10):100。
  5. 根据权利要求1～4中任一项所述的负极材料，其特征在于，包含以下特征(1)至(6)中的至少一种：
    (1)所述负极材料还包括包覆在所述聚集体的至少部分表面的碳层；
    (2)所述负极材料还包括包覆在所述聚集体的至少部分表面的碳层，所述聚集体表面的所述碳层的包覆率为1％～100％；
    (3)所述负极材料还包括包覆在所述聚集体的至少部分表面的碳层，所述碳层的材料包括无定形碳；
    (4)所述负极材料还包括包覆在所述聚集体的至少部分表面的碳层，所述碳层的厚度为10nm至1500nm；
    (5)所述负极材料的中值粒径为0.5μm～30μm；
    (6)所述负极材料的比表面积≤10m 2/g。
  6. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    采用包含活性物质、第一碳源和溶剂的混合物制备前驱体；及
    对所述前驱体进行密实化处理得到聚集体，所述聚集体的孔隙率≤10％且耐压硬度≥100MPa。
  7. 根据权利要求6所述的负极材料的制备方法，其特征在于，包括以下特征(1)至(15)中的至少一种：
    (1)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；
    (2)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种；
    (3)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种，所述金属单质包括Li、Na、K、Sn、Ge、Fe、Mg、Ti、Zn、Al和Cu中的至少一种；
    (4)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种，所述非金属单质包括Si和P中的至少一种；
    (5)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种，所述硅的氧化物包括SiOx，其中，0<x≤2；
    (6)所述活性物质包括硅的氧化物、非金属单质、金属单质及所述金属单质与硅的合金中的至少一种，所述金属单质与硅的合金包括硅锂合金、硅钠合金、硅钾合金、硅锡合金、硅锗合金、硅铁合金、硅镁合金、硅钛合金、硅锌合金、硅铝合金和硅铜合金中的至少一种；
    (7)所述活性物质与所述第一碳源的质量比为(15～120):(10～50)；
    (8)所述溶剂为有机溶剂；
    (9)所述溶剂为有机溶剂，所述有机溶剂包括醇类溶剂；
    (10)所述溶剂为有机溶剂，所述有机溶剂包括醇类溶剂，所述醇类溶剂包括甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇和戊醇中的至少一种；
    (11)所述混合物经过干燥处理得到所述前驱体；
    (12)所述混合物经过干燥处理得到所述前驱体，所述干燥处理的温度为40℃～300℃，所述干燥处理的时间为1h～15h；
    (13)所述混合物的制备方法具体包括：将所述活性物质、所述第一碳源和所述溶剂进行超声处理，再进行研磨处理；
    (14)所述混合物的制备方法具体包括：将所述活性物质、所述第一碳源和所述溶剂进行超声处理，再进行研磨处理，所述超声处理的时间为15～45min；
    (15)所述混合物的制备方法具体包括：将所述活性物质、所述第一碳源和所述溶剂进行超声处理，再进行研磨处理，所述研磨处理的时间为3～8h。
  8. 根据权利要求6或7所述的负极材料的制备方法，其特征在于，包括以下特征(1)至(5)中的至少一种：
    (1)所述混合物中还包括金属氧化物；
    (2)所述混合物中还包括金属氧化物，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和Zn中的至少一种；
    (3)所述混合物中还包括金属氧化物，所述金属氧化物呈片状和/或长条状；
    (4)所述混合物中还包括金属氧化物，所述金属氧化物的长径比大于2；
    (5)所述混合物中还包括金属氧化物，所述活性物质、所述金属氧化物与所述第一碳源的质 量比为(15～120):(1～20):(10～50)。
  9. 根据权利要求6～8中任一项的负极材料的制备方法，其特征在于，包括以下特征(1)至(8)中的至少一种：
    (1)所述混合物中还包括导电增强剂；
    (2)所述混合物中还包括导电增强剂，所述导电增强剂包括合金材料和导电碳中的至少一种；
    (3)所述混合物中还包括导电增强剂，所述导电增强剂包括合金材料和导电碳中的至少一种，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；
    (4)所述混合物中还包括导电增强剂，所述导电增强剂包括合金材料和导电碳中的至少一种，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)所述混合物中还包括导电增强剂，所述导电增强剂的电导率为10 0S/m～10 8S/m；
    (6)所述混合物中还包括导电增强剂，所述导电增强剂呈片状和/或长条状；
    (7)所述混合物中还包括导电增强剂，所述导电增强剂的长径比为2～5000；
    (8)所述混合物中还包括导电增强剂，所述导电增强剂与所述活性物质的质量比为(0.1～10):100。
  10. 根据权利要求6～9中任一项的负极材料的制备方法，其特征在于，包括以下特征(1)至(5)中的至少一种：
    (1)所述混合物中还包括添加剂；
    (2)所述混合物中还包括添加剂，所述添加剂包括表面活性剂和偶联剂中的至少一种；
    (3)所述混合物中还包括添加剂，所述添加剂包括表面活性剂和偶联剂中的至少一种，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和聚乙烯吡咯烷酮中的至少一种；
    (4)所述混合物中还包括添加剂，所述添加剂包括表面活性剂和偶联剂中的至少一种，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和γ-甲基丙烯酰氧基丙基三甲氧基硅烷中的至少一种；
    (5)所述混合物中还包括添加剂，所述活性物质、所述金属氧化物、所述添加剂与所述第一碳源的质量比为(15～120):(1～20):(1～10):(10～50)。
  11. 根据权利要求6～10中任一项的负极材料的制备方法，其特征在于，包括以下特征(1)至(14)中的至少一种：
    (1)所述密实化处理包括：将所述前驱体进行融合处理，再进行一次热处理；
    (2)所述密实化处理包括：将所述前驱体进行融合处理，再进行一次热处理，所述融合处理包括机械融合；
    (3)所述密实化处理包括：将所述前驱体进行融合处理，再进行一次热处理，所述融合处理包括机械融合，所述机械融合所用的融合机的转速为500r/min～3000r/min；
    (4)所述密实化处理包括：将所述前驱体进行融合处理，再进行一次热处理，所述融合处理包括机械融合，所述机械融合所用的融合机刀具间隙宽度为0.01cm～0.5cm；
    (5)所述密实化处理包括：将所述前驱体进行融合处理，再进行一次热处理，所述融合处理包括机械融合，所述机械融合的时间至少为0.5h；
    (6)所述一次热处理包括一次碳化处理；
    (7)所述一次热处理包括一次碳化处理，所述一次碳化处理的温度为500℃～1200℃，所述一次碳化处理的时间为1h～10h；
    (8)所述一次热处理包括一次碳化处理，所述一次碳化处理在保护性气体条件下进行，所述保护性气体包括氮气、氦气、氖气、氩气和氪气中的至少一种；
    (9)所述一次热处理包括一次碳化处理，所述一次热处理还包括二次碳化处理，所述二次碳化处理在所述融合处理之后进行；
    (10)所述一次热处理包括一次碳化处理，所述一次热处理还包括二次碳化处理，所述二次碳化处理包括气相包覆、固相包覆和液相包覆中的至少一种。
  12. 根据权利要求6～11中任一项的负极材料的制备方法，其特征在于，包括以下特征(1)至(6)中的至少一种：
    (1)对所述聚集体进行碳包覆处理；
    (2)对所述聚集体进行碳包覆处理，所述碳包覆处理包括：将所述聚集体与第二碳源进行混合，再进行二次热处理；
    (3)对所述聚集体进行碳包覆处理，所述碳包覆处理包括：将所述聚集体与第二碳源进行混合，再进行二次热处理，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；
    (4)对所述聚集体进行碳包覆处理，所述碳包覆处理包括：将所述聚集体与第二碳源进行混合，再进行二次热处理，所述聚集体与所述第二碳源的质量比为(10～100):(10～70)；
    (5)对所述聚集体进行碳包覆处理，所述碳包覆处理包括：将所述聚集体与第二碳源进行混合，再进行二次热处理，所述二次热处理的温度为600℃～1200℃，所述二次热处理的时间为1h～10h；
    (6)对所述聚集体进行碳包覆处理，所述碳包覆处理包括：将所述聚集体与第二碳源进行混合，再进行二次热处理，所述二次热处理在保护性气体条件下进行，所述保护性气体包括氮气、氦气、氖气、氩气和氪气中的至少一种。
  13. 一种锂离子电池，其特征在于，所述锂离子电池包括权利要求1至5中任一项所述的负极材料或权利要求6至12中任一项所述的负极材料的制备方法制得的负极材料。
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