WO2024001605A1 - 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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WO2024001605A1
WO2024001605A1 PCT/CN2023/095292 CN2023095292W WO2024001605A1 WO 2024001605 A1 WO2024001605 A1 WO 2024001605A1 CN 2023095292 W CN2023095292 W CN 2023095292W WO 2024001605 A1 WO2024001605 A1 WO 2024001605A1
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porous carbon
carbon
negative electrode
pore structure
electrode material
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PCT/CN2023/095292
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English (en)
French (fr)
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肖称茂
何鹏
郭锷明
任建国
贺雪琴
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贝特瑞新材料集团股份有限公司
惠州市鼎元新能源科技有限公司
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Priority to EP23761411.0A priority Critical patent/EP4325602A1/en
Priority to KR1020237030803A priority patent/KR20240003438A/ko
Publication of WO2024001605A1 publication Critical patent/WO2024001605A1/zh

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    • 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
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    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • C—CHEMISTRY; METALLURGY
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    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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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
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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    • H—ELECTRICITY
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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
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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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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, 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
    • H—ELECTRICITY
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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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • H—ELECTRICITY
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of negative electrode materials, specifically, to negative electrode materials and preparation methods thereof, and lithium-ion batteries.
  • Silicon is the second most abundant element in the earth's crust and a common semiconductor material. It has become an indispensable and important technical foundation for modern high-tech society. Simple silicon has extensive and important applications in energy, semiconductors, organic silicon and metallurgical industries. Applications. At present, the anode materials of mature commercial lithium-ion batteries are mainly graphite-like carbon materials. However, the theoretical lithium storage capacity of carbon materials is only 372mAh/g, which cannot meet people's demand for high-energy-density materials. Silicon has great potential as an anode material for lithium-ion batteries. The high theoretical capacity (approximately 4200mAh/g) is ten times higher than that of commercial graphite and has great prospects in energy storage.
  • the silicon anode has a severe volume expansion effect during the cycle, causing the material to be pulverized and broken, and the battery cycle to decay rapidly. Therefore, developing an anode material with high capacity and good cycle performance is a technical problem in the field of lithium-ion batteries.
  • the purpose of this application is to provide a negative electrode material and a preparation method thereof, and a lithium-ion battery.
  • the negative electrode material of this application has high conductivity, can effectively suppress volume expansion, and improve the capacity performance and cycle of the negative electrode material. performance.
  • the present application provides a negative electrode material.
  • the negative electrode material includes an inner core and a coating layer provided on at least part of the surface of the inner core.
  • the inner core includes porous carbon and active materials filled in the porous carbon pore structure.
  • the porous carbon has a first pore structure with a pore diameter less than or equal to 2 nm and a second pore structure with a pore diameter greater than 2 nm, and the ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is greater than or equal to 40% , the filling rate of the second hole structure is greater than or equal to 95%.
  • the negative electrode material further includes an active material further distributed between the porous carbons.
  • the median particle diameter D1 of the porous carbon and the median particle diameter D2 of the active material satisfy: 0.4 ⁇ D1/D2 ⁇ 6.
  • the median particle diameter D1 of the porous carbon and the median particle diameter D2 of the active material satisfy: 0.5 ⁇ D1/D2 ⁇ 4.5.
  • the active material has a median particle size of 1 nm to 300 nm.
  • the morphology of the active material includes at least one of point-like, spherical, ellipsoidal and flake-like.
  • the active material includes at least one of Li, Na, K, Sn, Ge, Si, SiOx, Fe, Mg, Ti, Zn, Al, Ni, P and Cu, wherein ,0 ⁇ x ⁇ 2.
  • the porous carbon includes at least one of carbon black, ordered mesoporous carbon materials, and nanoporous carbon materials.
  • the porous carbon has a median particle size of 1 nm to 500 nm.
  • the core has a median particle size of 0.8 ⁇ m to 10 ⁇ m.
  • the cladding layer includes at least one of a carbon layer, a metal oxide layer, a polymer layer, and a nitride layer.
  • the material of the carbon layer includes at least one of soft carbon, crystalline carbon, amorphous carbon and hard carbon.
  • the material of the metal oxide layer includes at least one of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca and Zn oxides.
  • the material of the nitride layer includes at least one of silicon nitride, aluminum nitride, titanium nitride and tantalum nitride.
  • the thickness of the coating layer ranges from 10 nm to 500 nm.
  • the polymer layer is made of at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethylcellulose, polyimide and polyvinyl alcohol. A sort of.
  • the specific surface area of the negative electrode material is less than or equal to 10 m 2 /g.
  • the negative electrode material has a median particle size of 0.5 ⁇ m to 20 ⁇ m.
  • the porosity of the negative electrode material is less than or equal to 10%.
  • embodiments of the present application provide a method for preparing a negative electrode material, including the following steps:
  • Raw materials containing porous carbon and active materials are vacuum mixed to obtain a precursor, wherein the porous carbon has a first pore structure with a pore diameter less than or equal to 2 nm and a second pore structure with a pore diameter greater than 2 nm, and the pores of the first pore structure
  • the ratio of the volume to the total pore volume of the porous carbon is greater than or equal to 40%, the filling rate of the second pore structure is greater than or equal to 95%, and the vacuum degree of the vacuum mixing is less than or equal to 10 Pa;
  • the precursor is coated to obtain a negative electrode material.
  • the median particle diameter D1 of the porous carbon and the median particle diameter D2 of the active material satisfy: 0.4 ⁇ D1/D2 ⁇ 6.
  • the median particle diameter D1 of the porous carbon and the median particle diameter D2 of the active material satisfy: 0.5 ⁇ D1/D2 ⁇ 4.5.
  • the active material has a median particle size of 1 nm to 300 nm.
  • the active material includes at least one of Li, Na, K, Sn, Ge, Si, SiOx, Fe, Mg, Ti, Zn, Al, Ni, P and Cu, wherein ,0 ⁇ x ⁇ 2.
  • the porous carbon includes at least one of carbon black, ordered mesoporous carbon materials, and nanoporous carbon.
  • the porous carbon has a median particle size of 1 nm to 500 nm.
  • the mass ratio of the porous carbon and the active material is 40: (10-80).
  • the vacuum mixing of the raw materials containing porous carbon and active materials further includes the step of adding auxiliaries and solvents.
  • the auxiliary agent includes polyvinyl alcohol, n-octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecyl benzene sulfonate, n-eicosanoic acid, palmitic acid, myristanoic acid , at least one of undecanoic acid, fatty acid, cetyltrimethylamine bromide and polyvinylpyrrolidone.
  • the solvent includes phenol, methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerin, n-butanol, isobutanol, n-hexane, cyclohexane, acetic acid At least one of ethyl ester, chloroform, carbon tetrachloride, methyl acetate, acetone and pentanol.
  • the mass ratio of the auxiliary agent to the porous carbon is (0.05-3):100.
  • the mass ratio of the solvent to the porous carbon is 100: (15-55).
  • the vacuum mixing equipment includes a double star vacuum mixer, a planetary vacuum mixer, a planetary vacuum disperser, a ribbon vacuum mixer, a multifunctional vacuum mixer, a vacuum disperser and a vacuum emulsifier. at least one of the machines.
  • drying is performed after the vacuum mixing, and the vacuum mixing time ranges from 0.5h to 15h.
  • the vacuum mixing is followed by a drying process, and the temperature of the drying process is -50°C to 500°C.
  • the vacuum mixing is followed by a drying process, and the drying process lasts for 0.5 to 15 hours.
  • the vacuum mixing is followed by a drying process
  • the equipment for the drying process includes at least one of a rotary evaporator, a vacuum oven, a spray dryer, a heat treatment furnace, and a freeze dryer.
  • the step of coating the precursor to obtain the negative electrode material specifically includes: mixing the precursor and the coating material and performing heat treatment.
  • the cladding material includes at least one of carbon material, metal oxide material, polymer material and nitride material.
  • the carbon material includes at least one of soft carbon, hard carbon, crystalline carbon and amorphous carbon.
  • the metal oxide material includes at least one of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca, and Zn oxides.
  • the nitride material includes at least one of silicon nitride, aluminum nitride, titanium nitride, and tantalum nitride.
  • the coating material includes at least one of carbon material, metal oxide material, polymer material and nitride material
  • the polymer material includes polyaniline, polyacrylic acid, polyurethane, At least one of polydopamine, polyacrylamide, sodium carboxymethylcellulose, polyimide and polyvinyl alcohol.
  • the mass ratio of the negative electrode material to the coating material is 100: (5-100).
  • the temperature of the heat treatment is 400°C to 900°C.
  • the holding time of the heat treatment is 1 h to 12 h.
  • the heating rate of the heat treatment is 1°C/min to 15°C/min.
  • the heat treatment is performed in a protective atmosphere, including at least one of nitrogen, helium, neon, argon, and krypton.
  • the negative electrode material is mixed with the coating material and then heat treated. Including the steps of crushing and screening the resulting material.
  • the pulverizing equipment includes at least one of a mechanical pulverizer, a jet pulverizer, and a crusher.
  • the screen size of the screening ranges from 10 mesh to 800 mesh.
  • embodiments of the present application provide a lithium ion battery, including the negative electrode material described in the first aspect or the negative electrode material prepared by the preparation method described in the second aspect.
  • the core of the negative electrode material of this application includes porous carbon and active material.
  • the first pore structure of the porous carbon is micropores (average pore diameter is less than or equal to 2 nm).
  • the micropores with a volume ratio of greater than or equal to 40% can provide additional space for the expansion of the active material. The space effectively alleviates the volume expansion, thereby avoiding or reducing the pulverization of the negative electrode material due to huge volume changes and stress during the process of inserting and removing lithium.
  • the second pore structure of the porous carbon is a pore with a pore diameter greater than 2 nm.
  • the active material is filled in the second pore structure of the porous carbon, so that the filling rate of the second pore structure is greater than or equal to 95%, which can increase the material capacity while avoiding material-induced
  • an appropriate number of small pores should be retained in the negative electrode material to avoid pores with excessively large diameters.
  • the synergistic effect of the two pore structures enables the negative electrode material of this application to effectively suppress volume expansion and have rate performance. High, high capacity and good cycle performance.
  • the coating layer provided on at least part of the surface of the core in the negative electrode material of the present application can reduce the direct contact between the active material in the core and the electrolyte, reduce the occurrence of side reactions between the negative electrode material and the electrolyte, thereby improving the ratio of the negative electrode material Capacity; it can also suppress the volume expansion of the negative electrode material, improve the conductivity of the negative electrode material, and at the same time help improve the lithium ion transmission efficiency, improve the rate performance and cycle performance of the negative electrode material.
  • the preparation method of the negative electrode material of the present application obtains a precursor by vacuum mixing raw materials containing porous carbon and active materials, wherein the porous carbon raw materials include pore structures of two pore sizes, wherein the first pore structure of the porous carbon is micropores ( (pore diameter less than or equal to 2 nm), the second pore structure of porous carbon is a pore with a pore diameter greater than 2 nm.
  • This application uses vacuum mixing to fill the active material in the larger second pore structure of porous carbon, and in a vacuum of less than or equal to 10 Pa Under pressure, the filling rate of the second pore structure is greater than or equal to 95%, so as to avoid the problems of stress concentration and electrolyte penetration in the material due to the existence of the second pore structure.
  • the precursor is coated. On the one hand, it can prevent the electrolyte from entering the negative electrode material and causing side reactions that will reduce the first Coulombic efficiency and specific capacity. On the other hand, it can alleviate the volume expansion of the active material and reduce the volume expansion of the entire composite material. Reduce electrode swelling.
  • the preparation method of this application is simple. By selecting porous carbon with a specific pore structure and specific size, the active material is filled in the second pore structure inside the porous carbon, which can effectively suppress volume expansion and further improve the rate performance, specific capacity and capacity of the negative electrode material. Cycle performance.
  • Figure 1 is a schematic structural diagram of the negative electrode material of the present application.
  • Figure 2 is a schematic structural diagram of porous carbon with active substances distributed in the second pore structure of the present application
  • Figure 3 is a schematic diagram 2 of the structure of the negative electrode material of this application.
  • Figure 4 is a flow chart for the preparation of negative electrode materials of the present application.
  • Figure 5 is an SEM image of the negative electrode material prepared in Example 1 of the present application.
  • Figure 6 is an XRD pattern of the negative electrode material prepared in Example 1 of the present application.
  • Figure 7 is the first charge and discharge curve of the negative electrode material prepared in Example 1 of the present application.
  • Figure 8 is the cycle performance curve of the negative electrode material prepared in Example 1 of the present application.
  • Figure 1 Figure 2 and Figure 3: 1-kernel; 11-Porous carbon; 111-First hole structure; 112-Second hole structure; 12-Active substances; 2- Cladding.
  • the embodiment of the present application provides a negative electrode material.
  • the negative electrode material includes a core 1 and a coating layer 2 provided on at least part of the surface of the core 1.
  • the core 1 includes porous carbon 11 and a Active material 12 in the pore structure of porous carbon 11, wherein porous carbon 11 has a first pore structure 111 with a pore diameter less than or equal to 2 nm and a second pore structure 112 with a pore diameter greater than 2 nm.
  • the pore volume of the first pore structure 111 is the same as that of the porous carbon 11
  • the total pore volume ratio is greater than or equal to 40%, and the filling rate of the second pore structure 112 is greater than or equal to 95%.
  • the core 1 of the anode material of the present application includes porous carbon 11 and active material 12.
  • the porous carbon 11 includes a pore structure with two pore sizes, wherein the first pore structure 111 of the porous carbon 11 is a micropore (a pore size less than or equal to 2nm), micropores with a volume ratio of greater than or equal to 40% can provide additional space for the expansion of the active material 12 and effectively alleviate the volume expansion, thereby avoiding or reducing the negative electrode material due to huge volume changes and stress during the process of inserting and desorbing lithium. Chalking occurs.
  • the second pore structure 112 of the porous carbon 11 is a pore with a pore diameter greater than 2 nm.
  • the second pore structure can easily cause stress concentration and electrolyte penetration. Therefore, the second pore structure needs to be filled as much as possible.
  • the second pore structure 112 of the porous carbon 11 It is filled with active material 12, and the filling rate of the active material in the second pore structure 112 is greater than or equal to 95%, which can increase the material capacity while reducing stress concentration and electrolyte penetration problems caused by the second pore structure.
  • the negative electrode material Retain an appropriate number of small pores and reduce the occurrence of pores with excessively large diameters.
  • the synergistic effect of the two pore structures enables the anode material of the present application to effectively suppress volume expansion, and has the advantages of high rate performance, high capacity and good cycle performance.
  • the coating layer provided on at least part of the surface of the core in the negative electrode material of the present application can reduce the direct contact between the active material in the core and the electrolyte, and reduce side reactions between the negative electrode material and the electrolyte. , thereby increasing the specific capacity of the anode material; it can also suppress the volume expansion of the anode material, improve the conductivity of the anode material, and at the same time help improve the lithium ion transmission efficiency, improve the rate performance and cycle performance of the anode material.
  • the porous carbon 11 has a first pore structure 111 with a pore diameter less than or equal to 2 nm and a second pore structure 112 with a pore diameter greater than 2 nm.
  • the pore diameter of the first pore structure 111 can be 0.05nm, 0.07nm, 0.1nm, 0.3nm, 0.5nm, 0.8nm, 1nm, 1.5nm, 2nm, etc., and of course can also be other values within the above range. No limitation is made here.
  • the pore diameter of the second pore structure 112 can specifically be 2.5nm, 5nm, 10nm, 20nm, 100nm, 150nm, 200nm, 250nm, 300nm, etc. Of course, it can also be other values within the above range, which is not limited here.
  • the first pore structure 111 is a pore with a pore diameter less than or equal to 2 nm
  • the second pore structure 112 is a pore with a pore diameter greater than 2 nm.
  • the first pore structure 111 with a smaller pore diameter can effectively alleviate the volume expansion of the active material 12 , while reducing the expansion of the electrode film and improving the safety of the battery
  • the second pore structure 112 has a larger pore size than the first pore structure 111, and the second pore structure 112 with a larger pore diameter is filled with active material, which can Reduce stress concentration and electrolyte penetration caused by the second pore structure, while increasing the capacity of the negative electrode material.
  • the ratio of the pore volume of the first pore structure 111 to the total pore volume of the porous carbon 11 may specifically be 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., and of course it may also be within the above range. Other values of are not limited here. If the pore volume ratio of the first pore structure 111 is less than 40%, the volume expansion of silicon cannot be effectively alleviated. Preferably, the ratio of the pore volume of the first pore structure 111 to the total pore volume of the porous carbon 11 is greater than or equal to 45%.
  • the filling rate of the second hole structure 112 can be specifically 95%, 96%, 97%, 98%, 99%, etc., and of course it can also be other values within the above range, which is not limited here. If the filling rate of the second pore structure 112 is less than 95%, it will easily lead to stress concentration in the material and penetration of the electrolyte. It should be noted that the filling rate of the second pore structure 112 may refer to the filling rate of the active material 12 in the pores, or the filling rate of the coating material and the active material in the pores. Preferably, the filling rate of the active material 12 in the pores is The filling rate in the pores is beneficial to improving the capacity of the negative electrode material.
  • the negative electrode material also includes active material 12 distributed between the porous carbons 11 , that is, while the active material 12 is filled in the pore structure of the porous carbon 11 , the active material 12 is also distributed in the porous carbon 11 . between porous carbon 11 particles.
  • the median particle diameter D1 of the porous carbon 11 and the median particle diameter D2 of the active material 12 satisfy: 0.4 ⁇ D1/D2 ⁇ 6, for example, D1/D2 can be 0.4, 0.5, 1, 1.5, 2 , 2.5, 3, 3.5, 4, 4.5 and 6, etc. Of course, it can also be other values within the above range, which are not limited here.
  • D1/D2 can be 0.4, 0.5, 1, 1.5, 2 , 2.5, 3, 3.5, 4, 4.5 and 6, etc.
  • it can also be other values within the above range, which are not limited here.
  • the ratio of D1/D2 is greater than 6, that is, the particle size of the porous carbon 11 is much larger than the particle size of the active material 12. On the one hand, it will cause the binding between the porous carbon 11 and the active material 12 distributed between the porous carbon 11. On the other hand, the volume of porous carbon 11 in core 1 will exceed the volume of active material 12, causing the internal porosity of the material to increase, resulting in the inability to increase the capacity of the material.
  • the ratio of D1/D2 is less than 0.4, that is, the particle size of the active material 12 is much larger than the particle size of the porous carbon 11, direct contact between the active materials 12 is easy to occur, forming a "hard contact" between the active materials.
  • the median particle diameter D1 of the porous carbon and the median particle diameter D2 of the active material satisfy: 0.5 ⁇ D1/D2 ⁇ 4.5.
  • the distribution surface of C and active material elements is in a uniformly dispersed state.
  • the morphology of the active material includes at least one of point-like, spherical, ellipsoidal and flake-like.
  • the median particle diameter of the active material is 1 nm to 300 nm, specifically, it can be 1 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, etc., and of course it can also be other values within the above range. This is not limited.
  • the average particle diameter of the active material 12 is 5 nm to 200 nm, and further preferably, the average particle diameter of the active material is 5 nm to 80 nm.
  • the active material includes at least one of Li, Na, K, Sn, Ge, Si, SiOx, Fe, Mg, Ti, Zn, Al, Ni, P and Cu, where 0 ⁇ x ⁇ 2 . It can be understood that the active material distributed between the porous carbons 11 and the active material located in the second pore structure of the porous carbon 11 may be the same or different, or may be partially the same and partially different.
  • the core 1 when the active material located between the porous carbon 11 and the active material located in the second pore structure of the porous carbon 11 are silicon particles, then the core 1 includes porous carbon 11 and silicon particles, and the silicon particles and porous Carbon together forms the core, and the silicon particles and porous carbon are evenly distributed.
  • the silicon particles provide lithium storage capacity.
  • the porous carbon 11 can not only buffer the volume change of the silicon anode during charging and discharging, but also improve the conductivity of the silicon particles, thereby improving the battery's performance. magnification performance.
  • the porous carbon 11 has a first pore structure 111 and a second pore structure 112. The pore diameter of the first pore structure 111 is smaller than the pore diameter of the second pore structure 112.
  • the second pore structure 112 is filled with silicon particles, and the silicon particles are made of porous carbon. Wrapping, on the one hand, can improve the conductivity of silicon, and on the other hand, it can avoid the agglomeration of silicon particles.
  • the silicon particles are located between and inside the porous carbon 11, which can improve the conductivity of the negative electrode material and further improve The negative electrode material improves the rate performance while mitigating the volume expansion of nano-silicon.
  • the porous carbon 11 includes at least one of carbon black, ordered mesoporous carbon material (CMK), and nanoporous carbon material (NCP).
  • the median particle diameter of the porous carbon 11 is 1 nm to 500 nm, specifically, it can be 1 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc., and of course it can also be within the above range. Other values of are not limited here.
  • the median particle diameter of the porous carbon 11 is 5 nm to 200 nm, and further preferably, the median particle diameter of the porous carbon 11 is 5 nm to 150 nm.
  • the median particle diameter of the core 1 is 0.8 ⁇ m to 10 ⁇ m, specifically, it can be 0.8 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, and 10 ⁇ m, etc., and of course it can also be Other values within the above range are not limited here.
  • the cladding layer 2 includes at least one of a carbon layer, a metal oxide layer, a polymer layer, and a nitride layer.
  • the setting of the coating layer 2 can, on the one hand, reduce the side reaction caused by the electrolyte entering the anode material, resulting in the reduction of the first Coulombic efficiency and specific capacity. On the other hand, it can alleviate the volume expansion of silicon and reduce the overall composite energy consumption. The volume of the material expands and reduces the swelling of the electrode sheet.
  • the material of the carbon layer includes at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon.
  • the metal oxide layer is made of at least one oxide of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca and Zn.
  • the material of the nitride layer includes at least one of silicon nitride, aluminum nitride (AlN), titanium nitride (TiN), and tantalum nitride (TaN).
  • the material of the polymer layer includes at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethylcellulose, polyimide, and polyvinyl alcohol.
  • the thickness of the coating layer 2 is 10nm to 500nm, specifically, it can be 1nm, 10nm, 20nm, 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc., and of course it can also be other thicknesses within the above range. The value is not limited here. It can be understood that the coating layer 2 can reduce the contact between silicon and the electrolyte, reduce the formation of passivation film, and increase the reversible capacity of the battery.
  • Controlling the thickness of the coating layer 2 within the above range can increase the conductivity of the negative electrode material, suppress the volume expansion of the negative electrode material, and at the same time help improve the lithium ion transmission efficiency, and help improve the high-rate charge and discharge performance, cycle performance and its comprehensive performance.
  • the specific surface area of the negative electrode material is less than or equal to 10m 2 /g, specifically 1m 2 /g, 2m 2 /g, 3m 2 /g, 4m 2 /g, 5m 2 /g, 6m 2 /g , 7m 2 /g, 8m 2 /g, 9m 2 /g and 10m 2 /g, etc.
  • 10m 2 /g specifically 1m 2 /g, 2m 2 /g, 3m 2 /g, 4m 2 /g, 5m 2 /g, 6m 2 /g , 7m 2 /g, 8m 2 /g, 9m 2 /g and 10m 2 /g, etc.
  • controlling the specific surface area of the negative electrode material within the above range can suppress the volume expansion of the negative electrode material, which is beneficial to improving the cycle performance of the negative electrode material.
  • the median particle diameter of the negative electrode material is 0.5 ⁇ m to 20 ⁇ m, specifically, it can be 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 15 ⁇ m, 18 ⁇ m, and 20 ⁇ m, etc., and of course it can also be within the above range. Other values are not limited here.
  • the median particle diameter of the negative electrode material is 0.8 ⁇ m to 12 ⁇ m, and further preferably, the median particle diameter of the negative electrode material is 1 ⁇ m to 8 ⁇ m. It can be understood that controlling the median particle size of the negative electrode material within the above range is beneficial to improving the cycle performance of the negative electrode material.
  • the porosity of the negative electrode material is less than or equal to 10%, specifically, it can be 1%, 2%, 2.5%, 5%, 7%, 8.5%, 10%, etc., and of course it can also be other values within the above range. The value is not limited here.
  • the porosity of the negative electrode material is less than or equal to 5%, and further preferably, the porosity of the negative electrode material is less than or equal to 2.5%.
  • the porosity of the negative electrode material is too large, resulting in a reduction in the tap density of the material, which further leads to a reduction in the energy density of the material.
  • this application provides a preparation method for the above-mentioned negative electrode material, as shown in Figure 4, including the following steps:
  • the porous carbon has a first pore structure with a pore diameter less than or equal to 2 nm and a second pore structure with a pore diameter greater than 2 nm.
  • the pore volume of the first pore structure is equal to
  • the total pore volume ratio of the porous carbon is greater than or equal to 40%, the filling rate of the second pore structure is greater than or equal to 95%, and the vacuum degree of the vacuum mixing is less than or equal to 10 Pa;
  • the preparation method of the anode material of the present application obtains a precursor by vacuum mixing raw materials containing porous carbon and active materials, wherein the porous carbon raw materials include pore structures of two pore sizes, wherein the first of the porous carbon 11
  • the pore structure 111 is a micropore (a pore diameter is less than or equal to 2 nm), and the second pore structure 112 of the porous carbon 11 is a pore with a pore diameter greater than 2 nm.
  • This application uses vacuum mixing to fill the active material in the larger porous carbon.
  • the precursor is coated. On the one hand, it can prevent the electrolyte from entering the negative electrode material and causing side reactions that will reduce the first Coulombic efficiency and specific capacity. On the other hand, it can alleviate the volume expansion of the active material and reduce the volume expansion of the entire composite material. Reduce electrode swelling.
  • the preparation method of this application is simple. By selecting porous carbon with a specific pore structure and specific size, the active material is filled in the second pore structure 112 inside the porous carbon 11, which can effectively suppress the volume expansion and further improve the rate performance and ratio of the negative electrode material. capacity and cycle performance.
  • Step S100 vacuum mixing raw materials containing porous carbon and active materials to obtain a precursor, wherein the porous carbon has a first pore structure and a second pore structure, the average pore diameter of the first pore structure is less than or equal to 2 nm, and the second pore structure has an average pore diameter of less than or equal to 2 nm.
  • the average pore diameter is greater than 2 nm
  • the ratio of the pore volume of the first pore structure to the total pore volume of the porous carbon is greater than or equal to 40%
  • the filling rate of the second pore structure is greater than or equal to 95%
  • the vacuum degree of vacuum mixing is less than or equal to 10 Pa.
  • the average pore diameter of the first pore structure 111 can be 0.05nm, 0.07nm, 0.1nm, 0.3nm, 0.5nm, 0.8nm, 1nm, 1.5nm, 2nm, etc., and of course can also be within the above range. Other values of are not limited here.
  • the porous carbon 11 has a first pore structure 111 with a pore diameter less than or equal to 2 nm and a second pore structure 112 with a pore diameter greater than 2 nm.
  • the average pore diameter of the second pore structure 112 may be 2.5 nm, 5 nm, 10 nm, or 20 nm. , 100nm, 150nm, 200nm, 250nm and 300nm, etc. Of course, it can also be other values within the above range, which are not limited here.
  • the first pore structure 111 is a pore with a pore diameter less than or equal to 2 nm
  • the second pore structure 112 is a pore with a pore diameter greater than 2 nm.
  • the first pore structure 111 with a smaller pore diameter can effectively alleviate the volume expansion of the active material 12 , while reducing the expansion of the electrode film and improving the safety of the battery;
  • the second pore structure 112 has a larger pore size than the first pore structure 111, and the second pore structure 112 with a larger pore diameter is filled with active material, which can Reducing the second pore structure 112 causes stress concentration and electrolyte penetration.
  • the ratio of the pore volume of the first pore structure 111 to the total pore volume of the porous carbon 11 may be 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., of course. It can also be other values within the above range, which is not limited here. If the pore volume ratio of the first pore structure 111 is less than 40%, the volume expansion of silicon cannot be effectively alleviated. Preferably, the ratio of the pore volume of the first pore structure 111 to the pore volume of the porous carbon 11 is greater than or equal to 45%.
  • this application controls the vacuum degree of vacuum mixing to be less than or equal to 10 Pa, so that the filling rate of the second pore structure 112 is greater than or equal to 95%.
  • the vacuum degree of vacuum mixing can specifically be 10 - 7 Pa, 10 -6 Pa, 10 -5 Pa, 10 -4 Pa, 10 -3 Pa, 10 -2 Pa, 10 Pa, etc. Of course, they can also be other values within the above range, which are not limited here.
  • This application controls the filling rate of the active material in the porous carbon through vacuum mixing processing, so that the active material can be filled into the second pore structure in the porous carbon as much as possible.
  • the vacuum degree is greater than 10 Pa, the vacuum degree is too low and the generated force will It is difficult to fill active materials into the corresponding pores, and the filling rate of the second pore structure will be reduced; if the vacuum degree is less than 10 -7 Pa, additional molecular pumps need to be configured, which increases additional costs.
  • the active material includes at least one of Li, Na, K, Sn, Ge, Si, SiOx, Fe, Mg, Ti, Zn, Al, Ni, P and Cu, where 0<x< 2.
  • the median particle diameter D1 of the porous carbon and the median particle diameter D2 of the active material satisfy 0.4 ⁇ D1/D2 ⁇ 6, for example, they can be 0.4, 0.5, 1, 1.5, 2, 2.5, 3, 3.5 , 4, 4.5, 5, 5.5 and 6, etc. Of course, it can also be other values within the above range, which are not limited here. It can be understood that when the ratio of the median particle diameter D1 of the porous carbon to the median particle diameter D2 of the active material is limited to the above range, the resulting precursor structure includes the porous carbon 11 and the active material filled in the pore structure of the porous carbon 11 12 and the active material 12 distributed between the porous carbon 11.
  • the porous carbon 11 can be evenly dispersed with the active material 12 to form a well-dispersed structure. There is no or only a small amount of direct contact between the active material and the active material. , most of them use porous carbon as a buffer layer for indirect contact, which can rely on the high-porosity porous carbon particle layer to buffer the volume expansion of the active material and reduce the powdering of the material. When the ratio of D1/D2 is greater than 6, that is, the particle size of the porous carbon 11 is much larger than the particle size of the active material 12. On the one hand, the binding property of the porous carbon 11 and the active material 12 distributed between the porous carbon 11 will change.
  • the volume of porous carbon 11 in core 1 will exceed the volume of active material 12, causing the internal porosity of the material to increase, resulting in the inability to increase the capacity of the material.
  • the ratio of D1/D2 is less than 0.4, that is, the particle size of the active material 12 is much larger than the particle size of the porous carbon 11, direct contact between the active materials 12 is easy to occur, forming a "hard contact" between the active materials.
  • the huge deformation produced easily causes the active material 12 to be pulverized and deformed, thus reducing the structural stability of the negative electrode material.
  • the median particle diameter D1 of the porous carbon and the median particle diameter D2 of the active material satisfy: 0.5 ⁇ D1/D2 ⁇ 4.5.
  • the median particle diameter of the active material is 1 nm to 300 nm, specifically, it can be 1 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, etc., and of course it can also be other values within the above range. This is not limited.
  • the median particle diameter of the active material is 5 nm to 200 nm, and further preferably, the median particle diameter of the active material is 5 nm to 80 nm.
  • the porous carbon includes at least one of carbon black, ordered mesoporous carbon materials, and nanoporous carbon materials.
  • the median particle diameter of the porous carbon is 1 nm to 500 nm, specifically, it can be 1 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc., and of course it can also be within the above range. Other values are not limited here.
  • the mass ratio of porous carbon to active material is 40: (10-80).
  • the mass ratio of porous carbon to active material and silicon material can be 40:10, 40:20, or 40:30. , 40:40, 40:50, 40:60, 40:70 and 40:80, etc.
  • it can also be other values within the above range, which are not limited here. Controlling the mass ratio of porous carbon and active material within the above range is conducive to obtaining a uniformly dispersed core material, and is conducive to improving the cycle performance and structural stability of the material.
  • the vacuum mixing equipment includes at least one of a double star vacuum mixer, a planetary vacuum mixer, a planetary vacuum disperser, a ribbon vacuum mixer, a multifunctional vacuum mixer, a vacuum disperser and a vacuum emulsifier. kind;
  • the vacuum mixing time is 0.5h to 15h, specifically, it can be 0.5h, 1h, 3h, 5h, 7h, 9h, 10h, 12h, 14h, 15h, etc., and of course it can also be other times within the above range. The value is not limited here.
  • the vacuum mixing of the raw materials containing porous carbon and active materials also includes the step of adding auxiliaries and solvents, that is, step S100 includes: placing porous carbon, active materials and auxiliaries in a solvent for vacuum mixing. , drying treatment to obtain the precursor.
  • auxiliary agents include polyvinyl alcohol, n-octadecanoic acid, lauric acid, polyacrylic acid, sodium dodecyl benzene sulfonate, n-eicosanoic acid, palmitic acid, myristanoic acid, undecanoic acid , fatty acid, cetyltrimethylamine bromide and at least one of polyvinylpyrrolidone.
  • the above-mentioned additives can modify the surface of the pore structure of the active material and porous carbon, thereby making it easier for the active material particles to penetrate into the pores of the porous carbon.
  • the solvent includes at least one of an organic solvent and a non-organic solvent
  • the organic solvent includes phenol, methanol, ethanol, ethylene glycol, propanol, isopropanol, glycerol, n-butanol, isobutyl
  • non-organic solvents include water, liquid ammonia, liquid carbon dioxide and liquid sulfur dioxide and ultrasonic acid At least one of the strong acids.
  • the mass ratio of the additive to the porous carbon is (0.05 ⁇ 3):100, specifically it can be 0.05:100, 0.1:100, 1:100, 2:100, 3:100, etc., of course it can also be It is other values within the above range and is not limited here.
  • the mass ratio of solvent to porous carbon is 100: (15-55), specifically 100:15, 100:20, 100:25, 100:30, 100:35, 100:40, 100 :50 and 100:55, etc.
  • it can also be other values within the above range, which are not limited here.
  • the raw materials including porous carbon and active material are vacuum mixed and then dried.
  • the temperature of the drying process is -50°C to 500°C, specifically -50°C, -40°C, -30°C, -20°C, 50°C, 100°C, 150°C, 200°C, 250°C ° C, 300 ° C, 350 ° C, 400 ° C, 450 ° C, 500 ° C, etc.
  • the drying process may be a low-temperature freeze-drying process or a high-temperature drying process.
  • the drying treatment time is 0.5h to 15h, specifically, it can be 0.5h, 1h, 3h, 5h, 7h, 9h, 10h, 12h, 14h, 15h, etc., and of course it can also be other times within the above range. The value is not limited here.
  • the equipment for drying treatment includes at least one of a rotary evaporator, a vacuum oven, a spray dryer, a heat treatment furnace and a freeze dryer.
  • coating the precursor specifically includes: mixing the precursor and the coating material and performing heat treatment to obtain a negative electrode material.
  • coating the coating material on the one hand, it can avoid the electrolyte entering the negative electrode material and causing side reactions, which will lead to the reduction of the first Coulombic efficiency and specific capacity.
  • it can alleviate the volume expansion of silicon, reduce the volume expansion of the entire composite material, and reduce The electrode pad swells.
  • the cladding material includes at least one of carbon materials, metal oxide materials, polymer materials, and nitride materials;
  • the carbon material includes at least one of soft carbon, hard carbon, crystalline carbon, and amorphous carbon.
  • the metal oxide material includes at least one of Sn, Ge, Fe, Si, Cu, Ti, Na, Mg, Al, Ca, and Zn oxides.
  • the nitride material includes at least one of silicon nitride, aluminum nitride, titanium nitride, and tantalum nitride.
  • the polymer material includes at least one of polyaniline, polyacrylic acid, polyurethane, polydopamine, polyacrylamide, sodium carboxymethylcellulose, polyimide, and polyvinyl alcohol.
  • the mass ratio of the precursor to the coating material is 100:(5-100), specifically it can be 100:5, 100:10, 100:20, 100:30, 100:40, 100:50, 100:60, 100:70, 100:80, 100:90 and 100:100, etc., of course it can also be the above Other values within the range are not limited here.
  • the mass ratio of the precursor to the coating material is less than 100:100, resulting in the thickness of the coating layer being too thin, which is not conducive to increasing the conductivity of the negative electrode material, and the volume expansion suppression performance of the negative electrode material is weak, resulting in poor cycle performance; precursor The mass ratio of the body to the coating material is greater than 100:5, resulting in the thickness of the coating layer being too thick, reducing the lithium ion transmission efficiency, and reducing the overall performance of the negative electrode material.
  • the heat treatment temperature is 400°C to 900°C, specifically, it can be 400, 500, 600, 700, 800, 900, etc., and of course it can also be other values within the above range, which is not limited here.
  • the heat treatment holding time is 1h to 12h, specifically, it can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc., and of course it can also be within the above range. Other values of are not limited here.
  • the heating rate of the heat treatment is 1°C/min to 15°C/min, specifically, it can be 1°C/min, 2°C/min, 3°C/min, 4°C/min, 5°C/min, 6°C/min. °C/min, 7°C/min, 8°C/min, 9°C/min, 10°C/min, 11°C/min, 12°C/min, 13°C/min, 14°C/min and 15°C/min, etc. Of course, it can also be other values within the above range, which is not limited here.
  • the heat treatment is performed in a protective atmosphere including at least one of nitrogen, helium, neon, argon, and krypton.
  • the heat treatment further includes the steps of crushing and screening the resulting material.
  • the pulverizing equipment includes at least one of a mechanical pulverizer, a jet pulverizer, and a crusher.
  • the screen size for screening is 10 mesh to 800 mesh, specifically 10 mesh, 50 mesh, 100 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh, 700 mesh and 800 mesh.
  • 10 mesh to 800 mesh specifically 10 mesh, 50 mesh, 100 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh, 700 mesh and 800 mesh.
  • it can also be other values within the above range, which is not limited here.
  • the present application provides a lithium ion battery, which includes the above negative electrode material or the negative electrode material prepared by the above preparation method.
  • porous carbon particles Screen nano silicon particles and porous carbon particles through BET tester testing and Malvern particle size analyzer to obtain nano silicon particles with a median diameter of 17 nm and porous carbon particles with a median diameter of 20 nm.
  • the porous carbon particles are specifically It is carbon black, and the volume proportion of porous carbon particles with pore diameters less than or equal to 2 nm (micropores) is 60%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon and nano-silicon particles distributed in the porous carbon pore structure.
  • the outer shell is a carbon coating layer, wherein the porous carbon has a first pore structure and a second pore structure. , the values of the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of porous carbon and the median particle size of nano-silicon particles are shown in Table 1.
  • porous carbon particles Screen nano silicon particles and porous carbon particles through BET tester testing and Malvern particle size analyzer to obtain nano silicon particles with a median diameter of 50 nm and porous carbon particles with a median diameter of 40 nm.
  • the porous carbon particles are specifically It is carbon black, and the volume proportion of porous carbon particles with pore diameters less than or equal to 2 nm (micropores) is 45%.
  • the negative electrode material prepared in this Example has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles distributed in the porous carbon pore structure, and nano-silicon particles distributed in the porous carbon pore structure.
  • the nano-silicon particles between porous carbons have a carbon coating shell.
  • the porous carbon has a first pore structure and a second pore structure.
  • the second pore structure is filled with nano-silicon.
  • the volume ratio of the first pore structure is, The values of the filling rate of the second pore structure, the median particle size of the porous carbon, and the median particle size of the nanosilica particles are shown in Table 1.
  • the porous carbon particles are specifically Ketjen Black.
  • the volume proportion of porous carbon particles with pore diameters less than or equal to 2 nm (micropores) is 49%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles distributed in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbon.
  • the outer shell is a carbon coating layer, in which the porous The carbon has a first pore structure and a second pore structure, and the second pore structure is filled with nano-silicon.
  • the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of the porous carbon, and the nano-silicon particles The values of the median particle size are shown in Table 1.
  • the porous carbon particles are specifically MCM-41, and the volume proportion of the porous carbon particles with pore diameters less than or equal to 2 nm (micropores) is 55%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles distributed in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbon.
  • the outer shell is a carbon coating layer, in which the porous Carbon has a first pore structure and a second pore structure. The volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of porous carbon and the median particle size of nano-silicon particles are shown in Table 1 .
  • the porous carbon particles are specifically ordered mesoporous carbon (CMK-3), and the volume proportion of the porous carbon particles with pore diameters less than or equal to 2 nm (micropores) is 62%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles distributed in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbons.
  • the outer shell is a polymer coating layer, where,
  • the porous carbon has a first pore structure and a second pore structure. The volume proportion of the first pore structure, the filling rate of the second pore structure, the median particle size of the porous carbon, and the median particle size of the nano-silicon particles are shown in the table. 1.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, SiO particles distributed in the porous carbon pore structure, and SiO particles distributed between the porous carbon.
  • the outer shell is a carbon coating layer, in which the porous carbon has The values of the first pore structure and the second pore structure, the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of porous carbon, and the median particle size of SiO particles are shown in Table 1.
  • porous carbon particles Screen nano silicon particles and porous carbon particles through BET tester testing and Malvern particle size analyzer to obtain nano silicon particles with a median diameter of 50 nm and porous carbon particles with a median diameter of 40 nm.
  • the porous carbon particles are specifically It is carbon black, and the volume proportion of porous carbon particles with pore diameters less than or equal to 2 nm (micropores) is 45%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nanoparticles distributed in the porous carbon pore structure, and nanosilica particles distributed between the porous carbon.
  • the outer shell is a carbon coating layer, in which the porous carbon has The values of the first pore structure and the second pore structure, the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of porous carbon, and the median particle size of nanosilica particles are shown in Table 1.
  • step (2) the vacuum degree in step (2) is replaced by 10 -7 Pa.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbons.
  • the outer shell is a carbon coating layer, in which the porous carbon has The values of the first pore structure and the second pore structure, the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of porous carbon, and the median particle size of nanosilica particles are shown in Table 1.
  • step (2) the vacuum degree in step (2) is replaced with 10 Pa.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbons.
  • the outer shell is a carbon coating layer, in which the porous carbon has The values of the first pore structure and the second pore structure, the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of porous carbon, and the median particle size of nanosilica particles are shown in Table 1.
  • Example 2 Different from Example 2, the precursor and titanium oxide were mixed at a mass ratio of 50:35.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbon.
  • the outer shell is a titanium oxide coating layer, and the porous carbon is formed with The values of the first pore structure and the second pore structure, the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of porous carbon, and the median particle size of nanosilica particles are shown in Table 1.
  • Example 2 Different from Example 2, the precursor and silicon nitride were mixed at a mass ratio of 50:35.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles in the porous carbon pore structure, and nano-silicon particles distributed in the porous carbon pores.
  • the outer shell is a silicon nitride coating layer formed by porous carbon.
  • the median particle size of nano-silicon is 50 nm, and the median particle size of porous carbon particles is 250 nm.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles distributed in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbon.
  • the outer shell is a carbon coating layer, in which the porous The carbon has a first pore structure and a second pore structure, and the second pore structure is filled with nano-silicon.
  • the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of the porous carbon, and the nano-silicon particles The values of the median particle size are shown in Table 1.
  • the median particle size of nano-silicon is 50 nm, and the median particle size of porous carbon particles is 20 nm.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles distributed in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbon.
  • the outer shell is a carbon coating layer, in which the porous The carbon has a first pore structure and a second pore structure, and the second pore structure is filled with nano-silicon.
  • the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of the porous carbon, and the nano-silicon particles The values of the median particle size are shown in Table 1.
  • the porous carbon particles are specifically carbon black, and the volume proportion of the porous carbon particles with pore diameters less than or equal to 2 nm (micropores) is 40.1%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes porous carbon, nano-silicon particles distributed in the porous carbon pore structure, and nano-silicon particles distributed between the porous carbon.
  • the outer shell is a carbon coating layer, in which the porous The carbon has a first pore structure and a second pore structure, and the second pore structure is filled with nano-silicon.
  • the volume ratio of the first pore structure, the filling rate of the second pore structure, the median particle size of the porous carbon, and the nano-silicon particles The values of the median particle size are shown in Table 1.
  • step (2) Different from Example 1, the vacuum degree in step (2) is replaced with 10 -8 Pa.
  • Example 1 What is different from Example 1 is that the volume proportion of pores with a diameter of less than or equal to 2 nm (micropores) in the porous carbon particles is 30%.
  • step (2) Different from Example 1, the vacuum degree in step (2) is replaced with 15 Pa.
  • step (2) nano silicon: porous carbon particles: polyvinyl alcohol are mixed using a planetary mixer.
  • V1 of the second pore structure of the material Before etching the active material in the negative electrode material, test the volume V1 of the second pore structure of the material. After etching the silicon, test the volume of the second pore structure as V2. (V2-V1)/V2 is the second pore structure. The filling rate of active substances in the medium.
  • Micron Tristar3020 specific surface area and pore size analyzer to test the specific surface area of the negative electrode material. Weigh a certain mass of powder and completely degas it under vacuum heating. After removing the surface adsorbed matter, use the nitrogen adsorption method to absorb nitrogen. quantity, calculate the specific surface area of the particles.
  • Dissolve the negative electrode material, conductive agent and binder in water at a mass percentage of 94:1:5 and mix, control the solid content to 50%, apply it on the copper foil current collector, dry it in a vacuum, and prepare a negative electrode piece; then Combine the ternary positive electrode piece (lithium nickel cobalt manganate NCM523) prepared by traditional mature technology and 1 mol/L lithium hexafluorophosphate LiPF6/(ethylene carbonate EC+dimethyl carbonate DMC+ethyl methyl carbonate EMC) (v/v 1: 1:1)
  • the electrolyte, Celgard2400 separator, and casing are assembled using conventional production processes to assemble 18650 cylindrical single cells.
  • the charge and discharge test of the cylindrical battery was 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 and discharge voltage was limited to 2.75 ⁇ 4.2V.
  • the first reversible capacity, first cycle charging capacity and first cycle discharge capacity were obtained.
  • First-time Coulomb efficiency first-cycle discharge capacity/first-cycle charging capacity.
  • capacity retention rate remaining capacity/initial capacity*100%.
  • the active materials are evenly dispersed in the pores of the porous carbon, forming a well-dispersed structure, and there is no or only a small amount of direct contact between the active materials.
  • most of which use porous carbon as a buffer layer for indirect contact which can rely on the first pore structure with a high volume ratio of porous carbon to buffer the volume expansion of the active material, which is beneficial to improving the rate performance of the negative electrode material while mitigating the volume expansion of nano-silicon.
  • the active material is filled in the porous carbon so that the filling rate of the second pore structure of the porous carbon is greater than or equal to 95%, which can increase the capacity of the material while avoiding stress concentration and electrolyte penetration caused by the material.
  • the anode material of the present application can effectively suppress volume expansion while having good structural stability, and has the advantages of high rate performance, high capacity and good cycle performance.
  • Example 15 the vacuum degree of the vacuum treatment during the preparation process was less than 10 -7 Pa, which resulted in a decrease in the filling rate of the second pore structure and a decrease in the structural stability and capacity retention rate of the negative electrode material compared to Example 1.
  • Comparative Example 1 it can be seen that the volume proportion of the first pore structure in the porous carbon is too small, causing the negative electrode material to be unable to completely alleviate the volume expansion.
  • the vacuum degree of the vacuum treatment is greater than 10 Pa, which leads to a reduction in the filling rate of the second pore structure, thereby reducing the structural stability and capacity retention rate of the negative electrode material.
  • Comparative Example 3 it can be seen that when a conventional mixing method is used to prepare anode materials, the filling rate of the second pore structure is 45%, which is far less than 99.4% in Example 1, which causes stress concentration in the anode material and reduces the cycle performance of the material. , the expansion rate is large.

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Abstract

一种负极材料及其制备方法、锂离子电池，负极材料包括内核（1）以及设置在内核（1）至少部分表面的包覆层（2），内核（1）包括多孔碳（11）和填充在多孔碳（11）孔结构中的活性物质（12），多孔碳（11）具有孔径小于等于2nm的第一孔结构（111）和孔径大于2nm的第二孔结构（112），第一孔结构（111）的孔体积与多孔碳（11）总的孔体积之比大于等于40%，第二孔结构（112）的填充率大于等于95%。

Description

负极材料及其制备方法、锂离子电池
本申请要求于2022年6月29日提交中国专利局，申请号为2022107575432、发明名称为“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
本申请涉及负极材料技术领域，具体地讲，尤其涉及负极材料及其制备方法、锂离子电池。
背景技术
硅是地壳中第二大含量元素，是一种常见的半导体材料，已经成为现代高科技社会不可或缺的重要技术基础，单质硅在能源、半导体、有机硅以及冶金工业等方面有着广泛而重要的应用。目前成熟商业锂离子电池的负极材料主要为石墨类碳材料，但碳材料的理论储锂容量仅为372mAh/g，无法满足人们对高能量密度材料的需求，硅作为锂离子电池负极材料具有很高的理论容量(约4200mAh/g)，高十倍于商业用石墨的容量，在能量存储方面具有非常大的前景。
目前，硅负极在循环过程中存在剧烈的体积膨胀效应，导致材料粉化、破碎，电池的循环衰减很快。因此，研发一种容量高、循环性能好的负极材料是锂离子电池领域的技术难题。
申请内容
针对现有技术存在的上述问题，本申请的目的在于提供一种负极材料及其制备方法、锂离子电池，本申请的负极材料导电性高、能够有效抑制体积膨胀，提高负极材料容量性能和循环性能。
第一方面，本申请提供一种负极材料，所述负极材料包括内核以及设置在所述内核至少部分表面的包覆层，所述内核包括多孔碳和填充在所述多孔碳孔结构中的活性物质，所述多孔碳具有孔径小于等于2nm的第一孔结构和孔径大于2nm的第二孔结构，所述第一孔结构的孔体积与所述多孔碳总的孔体积之比大于等于40％，所述第二孔结构的填充率大于等于95％。
在一些可选的实施方案中，所述负极材料还包括还分布在所述多孔碳之间的活性物质。
在一些可选的实施方案中，所述多孔碳的中值粒径D1与所述活性物质的中值粒径D2满足：0.4≤D1/D2≤6。
在一些可选的实施方案中，所述多孔碳的中值粒径D1与所述活性物质的中值粒径D2满足：0.5≤D1/D2≤4.5。
在一些可选的实施方案中，所述活性物质的中值粒径为1nm～300nm。
在一些可选的实施方案中，所述活性物质的形貌包括点状、球形、椭球形和片状中的至少一种。
在一些可选的实施方案中，所述活性物质包括Li、Na、K、Sn、Ge、Si、SiOx、Fe、Mg、Ti、Zn、Al、Ni、P和Cu中的至少一种，其中，0＜x＜2。
在一些可选的实施方案中，所述多孔碳包括炭黑、有序介孔碳材料和纳米多孔碳材料中的至少一种。
在一些可选的实施方案中，所述多孔碳的中值粒径为1nm～500nm。
在一些可选的实施方案中，所述内核的中值粒径为0.8μm～10μm。
在一些可选的实施方案中，所述包覆层包括碳层、金属氧化物层、聚合物层和氮化物层中的至少一种。
在一些可选的实施方案中，所述碳层的材质包括软碳、结晶碳、无定形碳和硬碳中的至少一种。
在一些可选的实施方案中，所述金属氧化物层的材质包括Sn、Ge、Fe、Si、Cu、Ti、Na、Mg、Al、Ca和Zn的氧化物中的至少一种。
在一些可选的实施方案中，所述氮化物层的材质包括氮化硅、氮化铝、氮化钛和氮化钽中的至少一种。
在一些可选的实施方案中，所述包覆层的厚度为10nm～500nm。
在一些可选的实施方案中，所述聚合物层的材质包括聚苯胺、聚丙烯酸、聚氨酯、聚多巴胺、聚丙烯酰胺、羧甲基纤维素钠、聚酰亚胺和聚乙烯醇中的至少一种。
在一些可选的实施方案中，所述负极材料的比表面积小于等于10m2/g。
在一些可选的实施方案中，所述负极材料的中值粒径为0.5μm～20μm。
在一些可选的实施方案中，所述负极材料的孔隙率小于等于10％。
第二方面，本申请实施例提供一种负极材料的制备方法，包括如下步骤：
将包含多孔碳和活性物质的原料进行真空混合得到前驱体，其中，所述多孔碳具有孔径小于等于2nm的第一孔结构和孔径大于2nm的第二孔结构，所述第一孔结构的孔体积与所述多孔碳总的孔体积之比大于等于40％，所述第二孔结构的填充率大于等于95％，所述真空混合的真空度小于等于10Pa；
将所述前驱体进行包覆处理得到负极材料。
在一些可选的实施方案中，所述多孔碳的中值粒径D1与活性物质的中值粒径D2满足：0.4≤D1/D2≤6。
在一些可选的实施方案中，所述多孔碳的中值粒径D1与所述活性物质的中值粒径D2满足：0.5≤D1/D2≤4.5。
在一些可选的实施方案中，所述活性物质的中值粒径为1nm～300nm。
在一些可选的实施方案中，所述活性物质包括Li、Na、K、Sn、Ge、Si、SiOx、Fe、Mg、Ti、Zn、Al、Ni、P和Cu中的至少一种，其中，0＜x＜2。
在一些可选的实施方案中，所述多孔碳包括炭黑、有序介孔碳材料和纳米多孔碳中的至少一种。
在一些可选的实施方案中，所述多孔碳的中值粒径为1nm～500nm。
在一些可选的实施方案中，所述多孔碳和所述活性物质的质量比为40：(10～80)。
在一些可选的实施方案中，所述将包含多孔碳和活性物质的原料进行真空混合之前还包括加入助剂和溶剂的步骤。
在一些可选的实施方案中，所述助剂包括聚乙烯醇、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、脂肪酸、十六烷基三甲基溴化胺和聚乙烯吡咯烷酮中的至少一种。
在一些可选的实施方案中，所述溶剂包括苯酚、甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇、正己烷、环己烷、乙酸乙酯、氯仿、四氯化碳、乙酸甲酯、丙酮和戊醇中的至少一种。
在一些可选的实施方案中，所述助剂与所述多孔碳的质量比为(0.05～3)：100。
在一些可选的实施方案中，所述溶剂与所述多孔碳的质量比为100：(15～55)。
在一些可选的实施方案中，所述真空混合的设备包括双星真空混合机、行星真空混合机、行星真空分散机、螺条式真空混合机、多功能真空混合机、真空分散机和真空乳化机中的至少一种。
在一些可选的实施方案中，所述真空混合之后还进行干燥处理，所述真空混合的时间为0.5h～15h。
在一些可选的实施方案中，所述真空混合之后还进行干燥处理，所述干燥处理的温度为-50℃～500℃。
在一些可选的实施方案中，所述真空混合之后还进行干燥处理，所述干燥处理的时间为0.5～15h。
在一些可选的实施方案中，所述真空混合之后还进行干燥处理，所述干燥处理的设备包括旋转蒸发仪、真空烘箱、喷雾干燥机、热处理炉和冷冻干燥机中的至少一种。
在一些可选的实施方案中，所述将所述前驱体进行包覆处理得到负极材料的步骤具体为：将所述前驱体与包覆材料混合进行热处理。
在一些可选的实施方案中，所述包覆材料包括碳材料、金属氧化物材料、聚合物材料和氮化物材料中的至少一种。
在一些可选的实施方案中所述碳材料包括软碳、硬碳、结晶碳和无定形碳中的至少一种。
在一些可选的实施方案中，所述金属氧化物材料包括Sn、Ge、Fe、Si、Cu、Ti、Na、Mg、Al、Ca及Zn的氧化物中的至少一种。
在一些可选的实施方案中，所述氮化物材料包括氮化硅、氮化铝、氮化钛和氮化钽中的至少一种。
在一些可选的实施方案中，所述包覆材料包括碳材料、金属氧化物材料、聚合物材料和氮化物材料中的至少一种，所述聚合物材料包括聚苯胺、聚丙烯酸、聚氨酯、聚多巴胺、聚丙烯酰胺、羧甲基纤维素钠、聚酰亚胺和聚乙烯醇中的至少一种。
在一些可选的实施方案中，所述负极材料与包覆材料的质量比为100:(5～100)。
在一些可选的实施方案中，所述热处理的温度为400℃～900℃。
在一些可选的实施方案中，所述热处理的保温时间为1h～12h。
在一些可选的实施方案中，所述热处理的升温速率为1℃/min～15℃/min。
在一些可选的实施方案中，所述热处理在保护性氛围下进行，所述保护性氛围包括氮气、氦气、氖气、氩气及氪气中的至少一种。
在一些可选的实施方案中，所述负极材料与包覆材料混合进行热处理之后还包 括对所得料进行粉碎和筛分的步骤。
在一些可选的实施方案中，所述粉碎的设备包括机械粉碎机、气流粉碎机和破碎机中的至少一种。
在一些可选的实施方案中，所述筛分的筛网尺寸为10目～800目。
第三方面，本申请实施例提供一种锂离子电池，包括第一方面所述的负极材料或第二方面所述的制备方法制备的负极材料。
本申请的技术方案至少具有以下有益的效果：
本申请负极材料的内核包括多孔碳和活性物质，多孔碳的第一孔结构为微孔(平均孔径小于等于2nm)，体积占比大于等于40％的微孔能够为活性物质的膨胀提供额外的空间，有效缓解体积膨胀，从而避免或减少了负极材料在嵌脱锂过程因巨大的体积变化和应力而发生粉化。多孔碳的第二孔结构为孔径大于2nm的孔，活性物质填充在多孔碳的第二孔结构中，使得第二孔结构的填充率大于等于95％，能够在提高材料容量的同时避免材料引起应力集中、电解液的渗透问题，负极材料中保留合适数量的小孔，避免出现孔径过大的孔，两种孔结构的协同作用使得本申请的负极材料能够有效的抑制体积膨胀，具备倍率性能高、容量高和循环性能好的优点。本申请负极材料中设置在内核至少部分表面的包覆层可以减少内核中的活性物质与电解液之间的直接接触，减少负极材料与电解液之间副反应的发生，从而提升负极材料的比容量；还可以抑制负极材料的体积膨胀，提高负极材料的导电性，同时有利于提高锂离子传输效率，提高负极材料的倍率性能和循环性能。
本申请负极材料的制备方法通过将包含多孔碳和活性物质的原料进行真空混合得到前驱体，其中，多孔碳原料包括两种孔径的孔结构，其中，多孔碳的第一孔结构为微孔(孔径小于等于2nm)，多孔碳的第二孔结构为孔径大于2nm的孔，本申请通过真空混合的方式使得活性物质填充在多孔碳较大的第二孔结构中，并在小于等于10Pa的真空压力下，使得第二孔结构的填充率大于等于95％，避免第二孔结构的存在使得材料产生应力集中、电解液的渗透问题。最后将前驱体进行包覆处理，一方面可以避免电解液进入负极材料内部发生副反应导致首次库伦效率和比容量降低，另一方面可以缓解活性物质的体积膨胀，降低整个复合材料的体积膨胀，减小电极片溶胀。本申请的制备方法简单，通过选择特定孔结构、特定尺寸的多孔碳使得活性物质填充在多孔碳内部的第二孔结构中，能够有效抑制体积膨胀，进一步提高负极材料的倍率性能、比容量和循环性能。
附图说明
下面结合附图和实施例对本申请进一步说明。
图1为本申请负极材料的结构示意图一；
图2为本申请第二孔结构内分布有活性物质的多孔碳的结构示意图；
图3为本申请负极材料的结构示意图二；
图4为本申请负极材料的制备流程图；
图5为本申请实施例1制备的负极材料的SEM图；
图6为本申请实施例1制备的负极材料的XRD图；
图7为本申请实施例1制备的负极材料的首次充放电曲线；
图8为本申请实施例1制备的负极材料的循环性能曲线。
图1、图2和图3中：
1-内核；
11-多孔碳；
111-第一孔结构；
112-第二孔结构；
12-活性物质；
2-包覆层。
具体实施方式
为了更好的理解本申请的技术方案，下面结合附图对本申请实施例进行详细描述。
应当明确，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其它实施例，都属于本申请保护的范围。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本申请。在本申请实施例和所附权利要求书中所使用的单数形式的“一种”、“所述”和“该”也旨在包括多数形式，除非上下文清楚地表示其它含义。
应当理解，本文中使用的术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
本申请实施例提供一种负极材料，如图1所示，负极材料包括内核1以及设置在内核1至少部分表面的包覆层2，如图2所示，内核1包括多孔碳11和填充在多孔碳11孔结构中的活性物质12，其中，多孔碳11具有孔径小于等于2nm的第一孔结构111和孔径大于2nm的第二孔结构112，第一孔结构111的孔体积与多孔碳11总的孔体积之比大于等于40％，第二孔结构112的填充率大于等于95％。
在上述方案中，本申请负极材料的内核1包括多孔碳11和活性物质12，多孔碳11包括两种孔径的孔结构，其中，多孔碳11的第一孔结构111为微孔(孔径小于等于2nm)，体积占比大于等于40％的微孔能够为活性物质12的膨胀提供额外的空间，有效缓解体积膨胀，从而避免或减少了负极材料在嵌脱锂过程因巨大的体积变化和应力而发生粉化。多孔碳11的第二孔结构112为孔径大于2nm的孔，第二孔结构容易引起应力集中、电解液渗透，因此需要把第二孔结构尽可能填充，在多孔碳11的第二孔结构112内填充有活性物质12，且第二孔结构112中的活性物质的填充率大于等于95％，能够在提高材料容量的同时减少第二孔结构引起应力集中、电解液的渗透问题，负极材料中保留合适数量的小孔，减少出现孔径过大的孔，两种孔结构的协同作用使得本申请的负极材料能够有效的抑制体积膨胀，具备倍率性能高、容量高和循环性能好的优点。本申请负极材料中设置在内核至少部分表面的包覆层可以减少内核中的活性物质与电解液之间的直接接触，减少负极材料与电解液之间副反应 的发生，从而提升负极材料的比容量；还可以抑制负极材料的体积膨胀，提高负极材料的导电性，同时有利于提高锂离子传输效率，提高负极材料的倍率性能和循环性能。
在一些实施方式中，多孔碳11具有孔径小于等于2nm的第一孔结构111和孔径大于2nm的第二孔结构112。具体地，第一孔结构111的孔径具体可以是0.05nm、0.07nm、0.1nm、0.3nm、0.5nm、0.8nm、1nm、1.5nm和2nm等，当然也可以是上述范围内的其他值，在此不做限定。第二孔结构112的孔径具体可以是2.5nm、5nm、10nm、20nm、100nm、150nm、200nm、250nm和300nm等，当然也可以是上述范围内的其他值，在此不做限定。
本申请的多孔碳中，第一孔结构111为孔径小于等于2nm的孔，第二孔结构112为孔径大于2nm的孔，孔径较小的第一孔结构111能够有效缓解活性物质12的体积膨胀，同时减少电极膜的膨胀，提高电池的安全性；第二孔结构112相对第一孔结构111而言，孔的尺寸更大，孔径较大的第二孔结构112内填充有活性物质，能够减少第二孔结构引起应力集中和电解液的渗透，同时提高负极材料的容量。
第一孔结构111的孔体积与多孔碳11的总孔体积之比具体可以是40％、45％、50％、55％、60％、65％和70％等，当然也可以是上述范围内的其他值，在此不做限定。第一孔结构111的孔体积占比若小于40％，则无法有效缓解硅的体积膨胀，优选地，第一孔结构111的孔体积与多孔碳11总的孔体积之比大于等于45％。
第二孔结构112的填充率具体可以是95％、96％、97％、98％和99％等，当然也可以是上述范围内的其他值，在此不做限定。若第二孔结构112的填充率小于95％，则会容易导致材料引起应力集中、电解液的渗透问题。需要说明的是，第二孔结构112的填充率指的可以是活性物质12在孔中的填充率，也可以是包覆层材料和活性物质共同在孔中的填充率，优选为活性物质在孔中的填充率，有利于提高负极材料的容量。
在一些实施方式中，如图3所示，负极材料还包括分布在多孔碳11之间的活性物质12，即活性物质12填充在多孔碳11的孔结构内的同时，活性物质12还分布在多孔碳11颗粒之间。
在一些实施方式中，多孔碳11的中值粒径D1与活性物质12的中值粒径D2满足：0.4≤D1/D2≤6，例如D1/D2可以是0.4、0.5、1、1.5、2、2.5、3、3.5、4、4.5和6等，当然也可以是上述范围内的其他值，在此不做限定。将多孔碳11的中值粒径D1与活性物质12的中值粒径D2满足：0.4≤D1/D2≤6，能够获得活性物质12与多孔碳11结合良好的内核结构。当0.4≤D1/D2≤1时，大部分的活性物质12分布在均匀分布在多孔碳11之间，以多孔碳11作为缓冲层而间接接触；当1≤D1/D2≤6时，大部分的活性物质12填充在多孔碳11的孔结构内，少部分的活性物质12会均匀分布在多孔碳11之间，这样分布的活性物质，可以大幅减少活性物质12与活性物质12之间的直接接触。因此，控制D1/D2的比例，可以依托具有高孔隙率的多孔碳来缓冲活性物质12的体积膨胀，避免活性物质12之间的直接接触，同时减少负极材料的粉化。当D1/D2的比值大于6时，即多孔碳11的粒径远大于活性物质12的粒径，一方面，会导致多孔碳11与分布在多孔碳11之间的活性物质12的结合性 变差；另一方面，内核1中多孔碳11的体积会超过活性物质12的体积，造成材料内部孔隙率增加，导致材料的容量无法提升。当D1/D2的比值小于0.4时，即活性物质12的粒径远大于多孔碳11的粒径，活性物质12之间容易产生直接接触，形成活性物质与活性物质之间的“硬接触”，在脱嵌锂过程中，产生的巨大形变容易造成活性物质12的粉化、变形，从而降低负极材料的结构稳定性。优选地，多孔碳的中值粒径D1与活性物质的中值粒径D2满足：0.5≤D1/D2≤4.5。
利用X射线扫描负极材料内核的SEM切面获得的元素分布谱图中，C、活性物质元素的分布面为均匀弥散状态。
在一些实施方式中，活性物质的形貌包括点状、球形、椭球形和片状中的至少一种。
在一些实施方式中，活性物质的中值粒径为1nm～300nm，具体可以是1nm、10nm、20nm、50nm、80nm、100nm、200nm和300nm等，当然也可以是上述范围内的其他值，在此不做限定。优选地，活性物质12的平均粒径为5nm～200nm，进一步优选地，活性物质的平均粒径为5nm～80nm。
在一些实施方式中，活性物质包括Li、Na、K、Sn、Ge、Si、SiOx、Fe、Mg、Ti、Zn、Al、Ni、P和Cu中至少一种，其中，0＜x＜2。可以理解的，分布在多孔碳11之间的活性物质和位于多孔碳11第二孔结构中的活性物质可以是相同的，也可以是不同的，还可以是部分相同，部分不同。
在一些实施方式中，当位于多孔碳11之间的活性物质和位于多孔碳11第二孔结构中的活性物质均为硅粒子时，则内核1包括多孔碳11和硅颗粒，硅颗粒与多孔碳共同组成内核，且硅颗粒与多孔碳均匀分布，硅颗粒提供储锂容量，多孔碳11既能缓冲充放电过程中硅负极的体积变化，又能改善硅颗粒的导电性，从而提高电池的倍率性能。多孔碳11具有第一孔结构111和第二孔结构112，其中，第一孔结构111的孔径小于第二孔结构112的孔径，第二孔结构112内填充有硅颗粒，硅颗粒采用多孔碳包裹，一方面可以提高硅的导电性，另一方面能够避免硅颗粒发生团聚，本实施例的负极材料中，硅颗粒位于多孔碳11之间及内部，能够提高负极材料的导电性、进一步提高负极材料倍率性能的同时缓解纳米硅的体积膨胀。
在一些实施方式中，多孔碳11包括炭黑、有序介孔碳材料(CMK)和纳米多孔碳材料(NCP)中的至少一种。
在一些实施方式中，多孔碳11的中值粒径为1nm～500nm，具体可以是1nm、10nm、20nm、50nm、80nm、100nm、200nm、300nm、400nm和500nm等，当然也可以是上述范围内的其他值，在此不做限定。优选地，多孔碳11的中值粒径为5nm～200nm，进一步优选地，多孔碳11的中值粒径为5nm～150nm。
在一些实施方式中，内核1的中值粒径为0.8μm～10μm，具体可以是0.8μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm和10μm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，包覆层2包括碳层、金属氧化物层、聚合物层和氮化物层中的至少一种。包覆层2的设置，一方面可以减少电解液进入负极材料内部发生副反应导致首次库伦效率和比容量降低，另一方面可以缓解硅的体积膨胀，降低整个复合 材料的体积膨胀，减小电极片溶胀。
在一些实施方式中，碳层的材质包括软碳、硬碳、结晶碳、无定形碳中的至少一种。
在一些实施方式中，金属氧化物层的材质包括Sn、Ge、Fe、Si、Cu、Ti、Na、Mg、Al、Ca和Zn的氧化物中的至少一种。
在一些实施方式中，氮化物层的材质包括氮化硅、氮化铝(AlN)、氮化钛(TiN)和氮化钽(TaN)中的至少一种。
在一些实施方式中，聚合物层的材质包括聚苯胺、聚丙烯酸、聚氨酯、聚多巴胺、聚丙烯酰胺、羧甲基纤维素钠、聚酰亚胺和聚乙烯醇中的至少一种。
在一些实施方式中，包覆层2的厚度为10nm～500nm，具体可以是1nm、10nm、20nm、50nm、80nm、100nm、200nm、300nm、400nm和500nm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，包覆层2能够减少硅与电解液接触，减少钝化膜生成，提升电池的可逆电容量。控制包覆层2的厚度在上述范围内，可以增加负极材料的导电性，抑制负极材料的体积膨胀，同时有利于提高锂离子传输效率，有利于提高负极材料大倍率充放电性能、循环性能及其综合性能。
在一些实施方式中，负极材料的比表面积小于等于10m2/g，具体可以是1m2/g、2m2/g、3m2/g、4m2/g、5m2/g、6m2/g、7m2/g、8m2/g、9m2/g和10m2/g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，将负极材料的比表面积控制在上述范围内，能够抑制负极材料的体积膨胀，有利于负极材料循环性能的提升。
在一些实施方式中，负极材料的中值粒径为0.5μm～20μm，具体可以是0.5μm、1μm、3μm、5μm、8μm、10μm、15μm、18μm和20μm等，当然也可以是上述范围内的其他值，在此不做限定。优选地，负极材料的中值粒径为0.8μm～12μm，进一步优选地，负极材料的中值粒径为1μm～8μm。可以理解，将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，负极材料的孔隙率小于等于10％，具体可以是1％、2％、2.5％、5％、7％、8.5％和10％等，当然也可以是上述范围内的其他值，在此不做限定。优选地，负极材料的孔隙率小于等于5％，进一步优选地，负极材料的孔隙率小于等于2.5％。负极材料的孔隙率太大，导致材料的振实密度降低，进一步导致材料的能量密度降低。
第二方面，本申请提供上述负极材料的制备方法，如图4所示，包括以下步骤：
S100、将包含多孔碳和活性物质的原料进行真空混合得到前驱体，其中，多孔碳具有孔径小于等于2nm的第一孔结构和孔径大于2nm的第二孔结构，第一孔结构的孔体积与多孔碳总的孔体积之比大于等于40％，所述第二孔结构的填充率大于等于95％，真空混合的真空度小于等于10Pa；
S200、将前驱体进行包覆处理得到负极材料。
在上述方案中，本申请负极材料的制备方法通过将包含多孔碳和活性物质的原料进行真空混合得到前驱体，其中，多孔碳原料包括两种孔径的孔结构，其中，多孔碳11的第一孔结构111为微孔(孔径小于等于2nm)，多孔碳11的第二孔结构112为孔径大于2nm的孔，本申请通过真空混合的方式使得活性物质填充在多孔碳较大 的第二孔结构112中，并在小于等于10Pa的真空压力下，使得第二孔结构112的填充率大于等于95％，避免第二孔结构112的存在使得材料产生应力集中、电解液的渗透问题。最后将前驱体进行包覆处理，一方面可以避免电解液进入负极材料内部发生副反应导致首次库伦效率和比容量降低，另一方面可以缓解活性物质的体积膨胀，降低整个复合材料的体积膨胀，减小电极片溶胀。本申请的制备方法简单，通过选择特定孔结构、特定尺寸的多孔碳使得活性物质填充在多孔碳11内部的第二孔结构112中，能够有效抑制体积膨胀，进一步提高负极材料的倍率性能、比容量和循环性能。
以下结合实施例具体介绍本申请的制备方法：
步骤S100、将包含多孔碳和活性物质的原料进行真空混合得到前驱体，其中，多孔碳具有第一孔结构和第二孔结构，第一孔结构的平均孔径小于等于2nm，第二孔结构的平均孔径大于2nm，第一孔结构的孔体积与多孔碳总的孔体积之比大于等于40％，第二孔结构的填充率大于等于95％，真空混合的真空度小于等于10Pa。
在一些实施方式中，第一孔结构111的平均孔径具体可以是0.05nm、0.07nm、0.1nm、0.3nm、0.5nm、0.8nm、1nm、1.5nm和2nm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，多孔碳11具有孔径小于等于2nm的第一孔结构111和孔径大于2nm的第二孔结构112，第二孔结构112的平均孔径具体可以是2.5nm、5nm、10nm、20nm、100nm、150nm、200nm、250nm和300nm等，当然也可以是上述范围内的其他值，在此不做限定。
本申请的多孔碳中，第一孔结构111为孔径小于等于2nm的孔，第二孔结构112为孔径大于2nm的孔，孔径较小的第一孔结构111能够有效缓解活性物质12的体积膨胀，同时减少电极膜的膨胀，提高电池的安全性；第二孔结构112相对第一孔结构111而言，孔的尺寸更大，孔径较大的第二孔结构112内填充有活性物质，能够减少第二孔结构112引起应力集中和电解液的渗透。
在一些实施方式中，第一孔结构111的孔体积与多孔碳11总的孔体积之比具体可以是40％、45％、50％、55％、60％、65％和70％等，当然也可以是上述范围内的其他值，在此不做限定。第一孔结构111的孔体积占比小于40％，则无法有效缓解硅的体积膨胀，优选地，第一孔结构111的孔体积与多孔碳总11的孔体积之比大于等于45％。
在一些实施方式中，本申请通过控制真空混合的真空度小于等于10Pa，使得第二孔结构112的填充率大于等于95％，本申请中真空混合的真空度具体可以是10- 7Pa、10-6Pa、10-5Pa、10-4Pa、10-3Pa、10-2Pa和10Pa等，当然也可以是上述范围内的其他值，在此不做限定。本申请通过真空混合处理控制活性物质在多孔碳中的填充率，使得活性物质尽可能的填充到多孔碳中的第二孔结构中，真空度大于10Pa，则真空度太低，产生的作用力难以将活性物质填充到相应的孔隙里面，第二孔结构的填充率会降低；真空度小于10-7Pa，则需要配置额外的分子泵，增加额外的成本。
在一些实施方式中，活性物质包括Li、Na、K、Sn、Ge、Si、SiOx、Fe、Mg、Ti、Zn、Al、Ni、P和Cu中的至少一种，其中，0＜x＜2。
在一些实施方式中，多孔碳的中值粒径D1与活性物质的中值粒径D2满足0.4≤D1/D2≤6，例如可以是0.4、0.5、1、1.5、2、2.5、3、3.5、4、4.5、5、5.5和6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，将多孔碳的中值粒径D1与活性物质的中值粒径D2的比值限定上述范围内，得到的前驱体结构包括多孔碳11、填充在多孔碳11的孔结构内的活性物质12及分布在多孔碳11之间的活性物质12，多孔碳11可以很好与活性物质12均匀分散，形成分散良好的结构体，活性物质与活性物质之间不存在或者只存在少量的直接接触，大部分是以多孔碳作为缓冲层而间接接触，可以依托高孔隙率的多孔碳粒子层缓冲活性物质的体积膨胀，同时减少材料的粉化。当D1/D2的比值大于6时，即多孔碳11的粒径远大于活性物质12的粒径，一方面，会导致多孔碳11与分布在多孔碳11之间的活性物质12的结合性变差；另一方面，内核1中多孔碳11的体积会超过活性物质12的体积，造成材料内部孔隙率增加，导致材料的容量无法提升。当D1/D2的比值小于0.4时，即活性物质12的粒径远大于多孔碳11的粒径，活性物质12之间容易产生直接接触，形成活性物质与活性物质之间的“硬接触”，在脱嵌锂过程中，产生的巨大形变容易造成活性物质12的粉化、变形，从而降低负极材料的结构稳定性。优选地，多孔碳的中值粒径D1与活性物质的中值粒径D2满足：0.5≤D1/D2≤4.5。
在一些实施方式中，活性物质的中值粒径为1nm～300nm，具体可以是1nm、10nm、20nm、50nm、80nm、100nm、200nm和300nm等，当然也可以是上述范围内的其他值，在此不做限定。优选地，活性物质的中值粒径为5nm～200nm，进一步优选地，活性物质的中值粒径为5nm～80nm。
在一些实施方式中，多孔碳包括炭黑、有序介孔碳材料和纳米多孔碳材料中的至少一种。
在一些实施方式中，多孔碳的中值粒径为1nm～500nm，具体可以是1nm、10nm、20nm、50nm、80nm、100nm、200nm、300nm、400nm和500nm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，多孔碳和活性物质的质量比为40：(10～80)，具体地，多孔碳和活性物质和硅材料的质量比可以是40：10、40：20、40：30、40：40、40：50、40：60、40：70和40：80等，当然也可以是上述范围内的其他值，在此不做限定。将多孔碳和活性物质质量比控制在上述范围内，有利于得到分散均匀的内核材料，有利于提高材料的循环性能和结构稳定性。
在一些实施方式中，真空混合的设备包括双星真空混合机、行星真空混合机、行星真空分散机、螺条式真空混合机、多功能真空混合机、真空分散机和真空乳化机中的至少一种；
在一些实施方式中，真空混合的时间为0.5h～15h，具体可以是0.5h、1h、3h、5h、7h、9h、10h、12h、14h和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，将包含多孔碳和活性物质的原料进行真空混合之前还包括加入助剂和溶剂的步骤，即步骤S100包括：将多孔碳、活性物质和助剂置于溶剂中进行真空混合、干燥处理得到前驱体。
在一些实施方式中，助剂包括聚乙烯醇、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、脂肪酸、十六烷基三甲基溴化胺及聚乙烯吡咯烷酮中的至少一种。上述助剂可以通过对活性物质和多孔碳的孔结构表面进行修饰，从而促使活性物质颗粒更加容易渗透进入到多孔碳的孔内。
在一些实施方式中，溶剂包括有机溶剂和非有机溶剂中的至少一种，有机溶剂包括苯酚、甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇、正己烷、环己烷、乙酸乙酯、氯仿、四氯化碳、乙酸甲酯、丙酮和戊醇中的至少一种；非有机溶剂包括水、液氨、液态二氧化碳与液态二氧化硫和超强酸中的至少一种。
在一些实施方式中，助剂与多孔碳的质量比为(0.05～3)：100，具体可以是0.05：100、0.1：100、1：100、2：100和3：100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，溶剂与多孔碳的质量比为100：(15～55)，具体可以是100：15、100：20、100：25、100：30、100：35、100：40、100：50和100：55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，将包含多孔碳和活性物质的原料进行真空混合之后进行干燥处理。
在一些实施方式中，干燥处理的温度为-50℃～500℃，具体可以是-50℃、-40℃、-30℃、-20℃、50℃、100℃、150℃、200℃、250℃、300℃、350℃、400℃、450℃和500℃等，当然也可以是上述范围内的其他值，在此不做限定。可以理解的，干燥处理可以是低温冷冻干燥处理，也可以是高温干燥处理。
在一些实施方式中，干燥处理的时间为0.5h～15h，具体可以是0.5h、1h、3h、5h、7h、9h、10h、12h、14h和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，干燥处理的设备包括旋转蒸发仪、真空烘箱、喷雾干燥机、热处理炉和冷冻干燥机中的至少一种。
在一些实施方式中，将前驱体进行包覆处理具体包括：将前驱体与包覆材料混合进行热处理得到负极材料。通过包覆材料的包覆，一方面可以避免电解液进入负极材料内部发生副反应导致首次库伦效率和比容量降低，另一方面可以缓解硅的体积膨胀，降低整个复合材料的体积膨胀，减小电极片溶胀。
在一些实施方式中，包覆材料包括碳材料、金属氧化物材料、聚合物材料和氮化物材料中的至少一种；
在一些实施方式中，碳材料包括软碳、硬碳、结晶碳和无定形碳中的至少一种。
在一些实施方式中，金属氧化物材料包括Sn、Ge、Fe、Si、Cu、Ti、Na、Mg、Al、Ca及Zn的氧化物中的至少一种。
在一些实施方式中，氮化物材料包括氮化硅、氮化铝、氮化钛和氮化钽中的至少一种。
在一些实施方式中，聚合物材料包括聚苯胺、聚丙烯酸、聚氨酯、聚多巴胺、聚丙烯酰胺、羧甲基纤维素钠、聚酰亚胺和聚乙烯醇中的至少一种。
在一些实施方式中，前驱体与包覆材料的质量比为100:(5～100)，具体可以是 100:5、100:10、100:20、100:30、100:40、100:50、100:60、100:70、100:80、100:90和100:100等，当然也可以是上述范围内的其他值，在此不做限定。前驱体与包覆材料的质量比小于100：100，导致包覆层的厚度太薄，不利于增加负极材料的导电性，且对负极材料的体积膨胀抑制性能较弱，导致循环性能差；前驱体与包覆材料的质量比大于100：5，导致包覆层的厚度太厚，锂离子传输效率降低，降低负极材料的综合性能。
在一些实施方式中，热处理的温度为400℃～900℃，具体可以是400、500、600、700、800和900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，热处理的保温时间为1h～12h，具体可以是1h、2h、3h、4h、5h、6h、7h、8h、9h、10h、11h和12h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，热处理的升温速率为1℃/min～15℃/min，具体可以是1℃/min、2℃/min、3℃/min、4℃/min、5℃/min、6℃/min、7℃/min、8℃/min、9℃/min、10℃/min、11℃/min、12℃/min、13℃/min、14℃/min和15℃/min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，热处理在保护性氛围下进行，保护性氛围包括氮气、氦气、氖气、氩气和氪气中的至少一种。
在一些实施方式中，热处理之后还包括对所得料进行粉碎和筛分的步骤。
在一些实施方式中，粉碎的设备包括机械粉碎机、气流粉碎机和破碎机中的至少一种。
在一些实施方式中，筛分的筛网尺寸为10目～800目，具体可以是10目、50目、100目、200目、300目、400目、500目、600目、700目和800目，当然也可以是上述范围内的其他值，在此不做限定。
第三方面，本申请提供一种锂离子电池，锂离子电池包含上述负极材料或上述制备方法制备的负极材料。
本领域的技术人员将理解，以上描述的锂离子电池的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例1
(1)通过BET测试仪测试和马尔文粒度仪对纳米硅粒子、多孔碳粒子进行筛选，获得中值粒径为17nm纳米硅以及中值粒径20nm的多孔碳粒子，其中，多孔碳粒子具体为炭黑，多孔碳粒子中孔径小于等于2nm(微孔)的体积占比为60％。
(2)将筛选的纳米硅粒子：多孔碳粒子：聚乙烯醇按照质量比50：25：25置于苯酚中，然后在行星式真空球磨机中控制真空度为0.1Pa，球磨2h，在120℃旋转蒸干获得前驱体。
(3)将前驱体与酚醛树脂按照质量比50:45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℃条件下热处理，保温4h。
(4)对获得的样品进行粉碎、筛分，然后分级，获得负极材料。
本实施例制备的负极材料为核壳结构，内核包括多孔碳和分布在多孔碳孔结构中的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
如图6所示，为本实施例1制备的负极材料的XRD图，从图6可见，产物中存在硅峰峰位。
如图7所示，为本实施例1制备的负极材料的首次充放电曲线，由图7可见，该材料首次充放电容量较高，首次库伦效率也较高。
如图8所示，为本实施例1制备的负极材料的循环性能曲线图，由图8可见，该实施例制备的负极材料具有优异的循环性能，循环100周容量保持率为92.1％。
实施例2
(1)通过BET测试仪测试和马尔文粒度仪对纳米硅粒子、多孔碳粒子进行筛选，获得中值粒径为50nm纳米硅以及中值粒径40nm的多孔碳粒子，其中，多孔碳粒子具体为炭黑，多孔碳粒子中孔径小于等于2nm(微孔)的体积占比为45％。
(2)将筛选的纳米硅粒子：多孔碳粒子：聚乙烯醇按照质量比50：25：25置于苯酚中，然后在行星式真空球磨机中控制真空度为0.1Pa，球磨2h，在120℃旋转蒸干获得前驱体。
(3)将前驱体与酚醛树脂按照质量比50:45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℃条件下热处理，保温4h。
(4)对获得的样品进行粉碎、筛分，然后分级，获得负极材料。
如图5所示，为本实施例1制备的负极材料的SEM图，本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第二孔结构内填充有纳米硅，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例3
(1)通过BET测试仪测试和马尔文粒度仪对纳米硅粒子、多孔碳粒子进行筛选，获得中值粒径为30nm纳米硅以及中值粒径50nm的多孔碳粒子。多孔碳粒子具体为科琴黑。多孔碳粒子中孔径小于等于2nm(微孔)的体积占比为49％。
(2)将筛选的纳米硅粒子：多孔碳粒子：聚乙烯醇按照质量比50：35：22置于异丙醇中，然后在双星真空混合机控制真空度为0.01Pa，混合4h，在150℃旋转蒸干获得前驱体。
(3)将前驱体与蔗糖按照质量比50:55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℃条件下热处理，保温3h。
(4)对获得的样品进行粉碎、筛分，然后分级，获得所述的负极材料。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第二孔结构内填充有纳米硅，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例4
(1)通过BET测试仪测试和马尔文粒度仪对纳米硅粒子、多孔碳粒子进行筛选，获得中值粒径为20nm纳米硅以及中值粒径30nm的多孔碳粒子。多孔碳粒子具体为MCM-41，多孔碳粒子中孔径小于等于2nm(微孔)的体积占比为55％。
(2)将筛选的纳米硅粒子、多孔碳粒子、聚乙烯醇按照质量比50：31：18置于丁醇中，然后在真空分散机控制真空度为10-5Pa，混合5h，在220℃旋转蒸干获得前驱体。
(3)将前驱体与葡萄糖按照质量比50:45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780℃条件下热处理，保温5h。
(4)对获得的样品进行粉碎、筛分，然后分级，获得所述的负极材料。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例5
(1)通过BET测试仪测试和马尔文粒度仪对纳米硅粒子、多孔碳粒子进行筛选，获得中值粒径为60nm纳米硅以及中值粒径80nm的多孔碳粒子。多孔碳粒子具体为有序介孔碳(CMK-3)，多孔碳粒子中孔径小于等于2nm(微孔)的体积占比为62％。
(2)将筛选的纳米硅粒子：多孔碳粒子：聚乙烯醇按照质量比40：25：25置于苯酚中，然后在螺条式真空混合机中控制真空度为1.5Pa，混合2h，在120℃旋转蒸干获得前驱体。
(3)将前驱体与聚乙烯胺混合，350℃下进行热处理。
(4)对获得的样品进行粉碎、筛分，然后分级，获得所述的负极材料。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为聚合物包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例6
(1)通过BET测试仪测试和马尔文粒度仪对SiO粒子、多孔碳粒子进行筛选，获得中值粒径为25nmSiO粒子以及中值粒径20nm的多孔碳粒子。多孔碳粒子具体为NCP。多孔碳粒子微孔体积占比为70％。
(2)将筛选的SiO粒子：多孔碳粒子：聚乙烯醇按照质量比30：25：15置于苯酚中，然后在真空搅拌机中控制真空度为3Pa，混合8h，在150℃旋转蒸干获得前驱体。
(3)将前驱体与沥青按照质量比30:25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980℃条件下热处理，保温3h。
(4)对获得的样品进行粉碎、筛分，然后分级，获得所述的负极材料。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中的SiO颗粒和分布在多孔碳之间的SiO颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及SiO颗粒的中值粒径的数值见表1。
实施例7
(1)通过BET测试仪测试和马尔文粒度仪对纳米硅粒子、多孔碳粒子进行筛选，获得中值粒径为50nm纳米硅和中值粒径40nm的多孔碳粒子，其中，多孔碳粒子具体为炭黑，多孔碳粒子中孔径小于等于2nm(微孔)的体积占比为45％。
(2)将筛选的纳米硅粒子：多孔碳粒子：聚乙烯醇按照质量比30：25：15置于苯酚中，然后在真空搅拌机中控制真空度为5Pa，混合8h，在150℃旋转蒸干获得前驱体。
(3)将前驱体与沥青按照质量比30:25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980℃条件下热处理，保温3h。
(4)对获得的样品进行粉碎、筛分，然后分级，获得所述的负极材料。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中纳米颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例8
与实施例2不同的是，步骤(2)替换真空度为10-7Pa。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例9
与实施例2不同的是，步骤(2)替换真空度为10Pa。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例10
与实施例2不同的是，将前驱体与氧化钛按照质量比50:35进行混合。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为氧化钛包覆层，多孔碳形成有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例11
与实施例2不同的是，将前驱体与氮化硅按照质量比50:35进行混合。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、多孔碳孔结构中的纳米硅颗粒和分布在多孔碳孔隙中的纳米硅颗粒，外壳为氮化硅包覆层，多孔碳形成有第一孔结构和第二孔结构，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例12
与实施例2不同的是，纳米硅中值粒径为50nm，多孔碳粒子中值粒径大小为250nm。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第二孔结构内填充有纳米硅，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例13
与实施例2不同的是，纳米硅中值粒径为50nm，多孔碳粒子中值粒径大小为20nm。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第二孔结构内填充有纳米硅，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例14
与实施例2不同的是，多孔碳粒子具体为炭黑，多孔碳粒子中孔径小于等于2nm(微孔)的体积占比为40.1％。
本实施例制备的负极材料为核壳结构，内核包括多孔碳、分布在多孔碳孔结构中的纳米硅颗粒和分布在多孔碳之间的纳米硅颗粒，外壳为碳包覆层，其中，多孔碳具有第一孔结构和第二孔结构，第二孔结构内填充有纳米硅，第一孔结构的体积占比、第二孔结构的填充率、多孔碳的中值粒径以及纳米硅颗粒的中值粒径的数值见表1。
实施例15
与实施例1不同的是，步骤(2)替换真空度为10-8Pa。
对比例1
与实施例1不同的是，多孔碳粒子中孔径小于等于2nm(微孔)的体积占比为30％。
对比例2
与实施例1不同的是，步骤(2)替换真空度为15Pa。
对比例3
与实施例1不同的是，步骤(2)中纳米硅：多孔碳粒子：聚乙烯醇采用行星混合机进行混合处理。
性能测试
1、采用氢氟酸溶液将负极材料内核中的硅刻蚀掉，使用BET孔隙分布测试孔结构的孔容大小，计算多孔碳的第一孔结构和第二孔结构的孔体积占多孔碳中孔体积比。
2、将负极材料中的活性物质刻蚀之前测试材料第二孔结构的体积V1，刻蚀硅后再测试第二孔结构的体积为V2，(V2-V1)/V2即为第二孔结构中活性物质的填充率。
3、使用马尔文粒度仪测试材料的中值粒径。
4、在扫描电镜下观察200个碳材料和活性物质颗粒，使用Nano measure统计出两种物质的中值粒径。
5、采用麦克Tristar3020型比表面积与孔径分析仪对负极材料进行比表面积测试，称取一定质量粉末，在真空加热状态下进行完全脱气，去除表面吸附质后，使用氮气吸附法，通过吸附氮气量，计算出颗粒的比表面积。
6、采用微孔孔径分布方法测试负极材料的孔容，孔容为ΔV；测试负极材料的真密度P，计算得到负极材料的孔隙率＝ΔV/(ΔV+1/P)。
7、采用以下方法测试电化学性能：
将负极材料、导电剂和粘结剂按质量百分比94：1：5溶解在水中混合，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(镍钴锰酸锂NCM523)、1mol/L的六氟磷酸锂LiPF6/(碳酸乙烯酯EC+碳酸二甲酯DMC+碳酸甲乙酯EMC)(v/v＝1:1:1)电解液、Celgard2400隔膜、外壳采用常规生产工艺装配18650圆柱单体电池。圆柱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％。
30周极片膨胀率(％)测定：将负极材料混合石墨，配成固定容量(450mAh/g)，涂布成极片，测试极片的厚度d1，然后组装成扣式电池测试，循环30周后，拆卸电池，再次测试极片厚度d2。极片膨胀率＝(d2-d1)/d1*100％。
测试结果见表1。
表1.各实施例和对比例的性能测试数据
根据表1数据可知：本申请实施例1～13制备的负极材料中，活性物质均匀分散在多孔碳的孔隙中，形成分散良好的结构体，活性物质之间不存在或者只存在少量的直接接触，大部分是以多孔碳作为缓冲层而间接接触，可以依托多孔碳高体积占比的第一孔结构缓冲活性物质的体积膨胀，有利于提高负极材料倍率性能的同时缓解纳米硅的体积膨胀。此外，活性物质填充在多孔碳中使得多孔碳的第二孔结构的填充率大于等于95％，能够提高材料容量的同时避免材料引起应力集中、电解液的渗透， 本申请的负极材料，能够有效的抑制体积膨胀的同时具有良好的结构稳定性，具备倍率性能高、容量高和循环性能好的优点。
实施例15在制备过程中真空处理的真空度小于10-7Pa，导致第二孔结构的填充率降低，负极材料的结构稳定性和容量保持率相比于实施例1有所下降。
根据对比例1可知：多孔碳中第一孔结构的体积占比太小，导致负极材料无法完全缓解体积膨胀。
根据对比例2可知：真空处理的真空度大于10Pa，导致第二孔结构的填充率降低，从而降低负极材料的结构稳定性和容量保持率。
根据对比例3可知：采用常规的混合方法制备负极材料，第二孔结构的填充率为45％，远远小于实施例1的99.4％，导致负极材料容易产生应力集中，导致材料的循环性能降低，膨胀率较大。
申请人声明，本申请通过上述实施例来说明本申请的详细工艺设备和工艺流程，但本申请并不局限于上述详细工艺设备和工艺流程，即不意味着本申请必须依赖上述详细工艺设备和工艺流程才能实施。所属技术领域的技术人员应该明了，对本申请的任何改进，对本申请产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本申请的保护范围和公开范围之内。

Claims (10)

  1. 一种负极材料，其特征在于，所述负极材料包括内核以及设置在所述内核至少部分表面的包覆层，所述内核包括多孔碳和填充在所述多孔碳孔结构中的活性物质，所述多孔碳具有孔径小于等于2nm的第一孔结构和孔径大于2nm的第二孔结构，所述第一孔结构的孔体积与所述多孔碳总的孔体积之比大于等于40％，所述第二孔结构的填充率大于等于95％。
  2. 根据权利要求1所述的负极材料，其特征在于，所述负极材料包括如下特征(1)～(9)中的至少一种：
    (1)所述负极材料还包含分布在所述多孔碳之间的活性物质；
    (2)所述多孔碳的中值粒径D1与所述活性物质的中值粒径D2满足：0.4≤D1/D2≤6；
    (3)所述多孔碳的中值粒径D1与所述活性物质的中值粒径D2满足：0.5≤D1/D2≤4.5；
    (4)所述活性物质的中值粒径为1nm～300nm；
    (5)所述活性物质的形貌包括点状、球形、椭球形和片状中的至少一种；
    (6)所述活性物质包括Li、Na、K、Sn、Ge、Si、SiOx、Fe、Mg、Ti、Zn、Al、Ni、P和Cu中的至少一种，其中，0＜x＜2；
    (7)所述多孔碳材料包括炭黑、有序介孔碳材料和纳米多孔碳材料中的至少一种；
    (8)所述多孔碳的中值粒径为1nm～500nm；
    (9)所述内核的中值粒径为0.8μm～10μm。
  3. 根据权利要求1所述的负极材料，其特征在于，所述包覆层包括碳层、金属氧化物层、聚合物层和氮化物层中的至少一种，所述包覆层包括如下特征(1)～(5)中的至少一种：
    (1)所述碳层的材质包括软碳、结晶碳、无定形碳和硬碳中的至少一种；
    (2)所述金属氧化物层的材质包括Sn、Ge、Fe、Si、Cu、Ti、Na、Mg、Al、Ca和Zn的氧化物中的至少一种；
    (3)所述氮化物层的材质包括氮化硅、氮化铝、氮化钛和氮化钽中的至少一种；
    (4)所述聚合物层的材质包括聚苯胺、聚丙烯酸、聚氨酯、聚多巴胺、聚丙烯酰胺、羧甲基纤维素钠、聚酰亚胺和聚乙烯醇中的至少一种；
    (5)所述包覆层的厚度为10nm～500nm。
  4. 根据权利要求1所述的负极材料，其特征在于，所述负极材料包括如下特征(1)～(3)中的至少一种：
    (1)所述负极材料的比表面积小于等于10m2/g；
    (2)所述负极材料的中值粒径为0.5μm～20μm；
    (3)所述负极材料的孔隙率小于等于10％。
  5. 一种负极材料的制备方法，其特征在于，包括如下步骤：
    将包含多孔碳和活性物质的原料进行真空混合得到前驱体，其中，所述多孔碳具有孔径小于等于2nm的第一孔结构和孔径大于2nm的第二孔结构，所述第一孔结构 的孔体积与所述多孔碳总的孔体积之比大于等于40％，所述第二孔结构的填充率大于等于95％，所述真空混合的真空度小于等于10Pa；
    将所述前驱体进行包覆处理得到负极材料。
  6. 根据权利要求5所述的制备方法，其特征在于，所述方法包括如下特征(1)～(7)中的至少一种：
    (1)所述多孔碳的中值粒径D1与活性物质的中值粒径D2满足：0.4≤D1/D2≤6；
    (2)所述多孔碳的中值粒径D1与所述活性物质的中值粒径D2满足：0.5≤D1/D2≤4.5；
    (3)所述活性物质的中值粒径为1nm～300nm；
    (4)所述活性物质包括Li、Na、K、Sn、Ge、Si、SiOx、Fe、Mg、Ti、Zn、Al、Ni、P和Cu中的至少一种，其中，0＜x＜2；
    (5)所述多孔碳包括炭黑、有序介孔碳材料和纳米多孔碳材料中的至少一种；
    (6)所述多孔碳的中值粒径为1nm～500nm；
    (7)所述多孔碳和所述活性物质的质量比为40：(10～80)。
  7. 根据权利要求5所述的制备方法，其特征在于，所述将包含多孔碳和活性物质的原料中还包括助剂和溶剂，所述方法包括如下特征(1)～(4)中的至少一种：
    (1)所述助剂包括聚乙烯醇、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、脂肪酸、十六烷基三甲基溴化胺和聚乙烯吡咯烷酮中的至少一种；
    (2)所述溶剂包括苯酚、甲醇、乙醇、乙二醇、丙醇、异丙醇、丙三醇、正丁醇、异丁醇、正己烷、环己烷、乙酸乙酯、氯仿、四氯化碳、乙酸甲酯、丙酮和戊醇中的至少一种；
    (3)所述助剂与所述多孔碳的质量比为(0.05～3)：100；
    (4)所述溶剂与所述多孔碳的质量比为100：(15～55)。
  8. 根据权利要求7所述的制备方法，其特征在于，所述方法包括如下特征(1)～(5)中的至少一种：
    (1)所述真空混合的设备包括双星真空混合机、行星真空混合机、行星真空分散机、螺条式真空混合机、多功能真空混合机、真空分散机和真空乳化机中的至少一种；
    (2)所述真空混合的时间为0.5h～15h；
    (3)所述真空混合之后还进行干燥处理，所述干燥处理的温度为-50℃～500℃；
    (4)所述真空混合之后还进行干燥处理，所述干燥处理的时间为0.5～15h；
    (5)所述真空混合之后还进行干燥处理，所述干燥处理的设备包括旋转蒸发仪、真空烘箱、喷雾干燥机、热处理炉和冷冻干燥机中的至少一种。
  9. 根据权利要求5所述的制备方法，其特征在于，所述将所述前驱体进行包覆处理得到负极材料的步骤具体为：将所述前驱体与包覆材料混合进行热处理，所述方法包括如下特征(1)～(13)中的至少一种：
    (1)所述包覆材料包括碳材料、金属氧化物、聚合物材料和氮化物中的至少一 种；
    (2)所述包覆材料包括碳材料、金属氧化物材料、聚合物材料和氮化物材料中的至少一种，所述碳材料包括软碳、硬碳、结晶碳和无定形碳中的至少一种；
    (3)所述包覆材料包括碳材料、金属氧化物材料、聚合物材料和氮化物材料中的至少一种，所述金属氧化物材料包括Sn、Ge、Fe、Si、Cu、Ti、Na、Mg、Al、Ca及Zn的氧化物中的至少一种；
    (4)所述包覆材料包括碳材料、金属氧化物材料、聚合物材料和氮化物材料中的至少一种，所述聚合物材料包括聚苯胺、聚丙烯酸、聚氨酯、聚多巴胺、聚丙烯酰胺、羧甲基纤维素钠、聚酰亚胺和聚乙烯醇中的至少一种；
    (5)所述包覆材料包括碳材料、金属氧化物材料和氮化物材料中的至少一种，所述氮化物材料包括氮化硅、氮化铝、氮化钛和氮化钽中的至少一种；
    (6)所述前驱体与包覆材料的质量比为100:(5～100)；
    (7)所述热处理的温度为400℃～900℃；
    (8)所述热处理的保温时间为1h～12h；
    (9)所述热处理的升温速率为1℃/min～15℃/min；
    (10)所述热处理在保护性氛围下进行，所述保护性氛围包括氮气、氦气、氖气、氩气及氪气中的至少一种；
    (11)所述前驱体与包覆材料混合进行热处理之后还包括对所得料进行粉碎和筛分的步骤；
    (12)所述前驱体与包覆材料混合进行热处理之后还包括对所得料进行粉碎和筛分的步骤，所述粉碎的设备包括机械粉碎机、气流粉碎机和破碎机中的至少一种；
    (13)所述前驱体与包覆材料混合进行热处理之后还包括对所得料进行粉碎和筛分的步骤，所述筛分的筛网尺寸为10目～800目。
  10. 一种锂离子电池，其特征在于，包括权利要求1～4任一项所述的负极材料或权利要求5～9任一项所述的制备方法制备的负极材料。
PCT/CN2023/095292 2022-06-29 2023-05-19 负极材料及其制备方法、锂离子电池 WO2024001605A1 (zh)

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