WO2024077607A1 - 负极活性材料及其制备方法、以及包含其的二次电池及用电装置 - Google Patents

负极活性材料及其制备方法、以及包含其的二次电池及用电装置 Download PDF

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WO2024077607A1
WO2024077607A1 PCT/CN2022/125432 CN2022125432W WO2024077607A1 WO 2024077607 A1 WO2024077607 A1 WO 2024077607A1 CN 2022125432 W CN2022125432 W CN 2022125432W WO 2024077607 A1 WO2024077607 A1 WO 2024077607A1
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Prior art keywords
negative electrode
electrode active
active material
optionally
carbon
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PCT/CN2022/125432
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English (en)
French (fr)
Inventor
吴凯
王家政
吕子建
董晓斌
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2022/125432 priority Critical patent/WO2024077607A1/zh
Priority to JP2024571155A priority patent/JP2025518828A/ja
Priority to CN202280005900.8A priority patent/CN118202487B/zh
Priority to KR1020257004380A priority patent/KR20250038679A/ko
Priority to CN202512020581.6A priority patent/CN121748379A/zh
Priority to EP22961794.9A priority patent/EP4517870A4/en
Publication of WO2024077607A1 publication Critical patent/WO2024077607A1/zh
Priority to US19/023,551 priority patent/US20250158027A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/205—Preparation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/13—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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—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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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/387—Tin or alloys based on tin
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—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 belongs to the field of battery technology, and specifically relates to a negative electrode active material and a preparation method thereof, as well as a secondary battery and an electrical device containing the same.
  • the purpose of the present application is to provide a negative electrode active material and a preparation method thereof, as well as a secondary battery and an electrical device containing the same, wherein the negative electrode active material can take into account high specific capacity, high first coulombic efficiency, low volume expansion, high conductivity and good cycle stability.
  • the present application provides a negative electrode active material, comprising a carbon matrix and a filling material, wherein the graphitization degree of the carbon matrix is less than or equal to 87%, the carbon matrix comprises a plurality of pore structures, at least a portion of the filling material is located in the pore structure of the carbon matrix, and the filling material comprises one or more elements that can undergo an alloying reaction with Li.
  • the inventors of the present application have found in their research that by placing a filler material with a high specific capacity advantage in the pore structure of a carbon matrix with a low degree of graphitization (greater than 0 and less than or equal to 87%), the obtained negative electrode active material can take into account high specific capacity, high first coulombic efficiency, low volume expansion, high conductivity and good cycle stability, and the secondary battery can also take into account high energy density, high first coulombic efficiency and long cycle life.
  • the degree of graphitization of the carbon matrix of the present application is less than or equal to 87%.
  • the negative electrode active material provided by the present application can give full play to the advantages of high specific capacity of the filler material, and can also make up for the defects of poor conductivity and low first coulombic efficiency of the filler material; in addition, at least a part of the filler material is located in the pore structure of the carbon matrix, thereby reducing the volume expansion of the filler material through the carbon matrix.
  • the graphitization degree of the carbon matrix is 65%-87%, which is conducive to the negative electrode active material to better balance high specific capacity, high first coulombic efficiency, low volume expansion, high conductivity and good cycle stability.
  • the element capable of alloying with Li includes one or more of silicon, tin and germanium, which is beneficial for the negative electrode active material to have a high specific capacity advantage.
  • the filling material includes one or more of silicon-based materials, tin-based materials and germanium-based materials.
  • the silicon-based material includes one or more of elemental silicon, silicon oxide, silicon-carbon material, silicon-nitrogen compound and silicon alloy.
  • the tin-based material includes one or more of elemental tin, tin oxide, tin sulfide, tin phosphide, tin composite oxide, tin-carbon material and tin alloy material.
  • the germanium-based material includes one or more of elemental germanium, germanium oxide, germanium-carbon material, germanium alloy material and germanate.
  • the filling material includes a crystalline filling material and/or an amorphous filling material, and optionally includes a crystalline silicon-based material and/or an amorphous silicon-based material.
  • Silicon-based materials have the advantage of high specific capacity, which is conducive to improving the energy density of secondary batteries.
  • the grain size of the crystalline filling material is ⁇ 100nm, and can be 2nm-50nm.
  • the crystalline filling material has a suitable grain size, it can improve the initial coulombic efficiency of the secondary battery while avoiding a significant adverse effect on the cycle performance and storage performance of the secondary battery.
  • the filling material includes one or more of vapor-deposited silicon-based materials, tin-based materials and germanium-based materials, and optionally includes vapor-deposited silicon-based materials.
  • the negative electrode active material in the X-ray diffraction spectrum of the negative electrode active material measured by an X-ray diffractometer, includes a (002) crystal plane peak at 26.4° and a (111) crystal plane peak at 28.6°, and the ratio of the half-peak width of the (002) crystal plane peak to the half-peak width of the (111) crystal plane peak is 0.2-50, and can be 0.2-20.
  • the carbon matrix can have a suitable degree of graphitization, and the filling material can have a suitable grain size, which is beneficial for the negative electrode active material to have high specific capacity, high first coulomb efficiency, low volume expansion, high conductivity and good cycle stability.
  • At least a portion of the filler material is located in the pore structure of the carbon matrix, and there is a gap between the filler material and the carbon matrix.
  • the gap can be used as a space to accommodate the volume expansion of the filler material to buffer the stress generated during the expansion of the filler material, thereby further reducing the probability of particle breakage and pulverization.
  • the negative electrode active material further includes a coating layer, and the coating layer is located on at least part of the surface of the carbon matrix.
  • the coating layer can prevent the filler material from directly contacting the electrolyte, thereby reducing electrolyte side reactions, reducing active ion consumption, and improving the cycle performance of the secondary battery; at the same time, it can also improve the stability of the negative electrode slurry and avoid the reaction of the filler material with solvent water, etc., which increases the difficulty of processing the negative electrode slurry.
  • the coating layer can also play a role in buffering the volume expansion of the filler material, which is also conducive to improving the structural stability of the negative electrode active material and improving the electrochemical performance of the secondary battery.
  • the coating layer includes one or more of a carbon material, a conductive polymer, a metal oxide and a metal sulfide, and optionally includes a carbon material.
  • the thickness of the coating layer is ⁇ 100nm, and can be 10nm-100nm.
  • the integrity of the coating layer is higher, and the contact between the filling material and the electrolyte can be more effectively avoided, thereby helping to reduce the side reaction of the electrolyte, so that the negative electrode active material has high specific capacity, high initial coulombic efficiency and low volume expansion.
  • the negative electrode active material includes carbon and an element capable of alloying with Li.
  • the mass percentage of the carbon element in the negative electrode active material is 20wt%-80wt%, and can be optionally 30wt%-70wt%.
  • the mass percentage of the element capable of alloying with Li in the negative electrode active material is 20wt%-80wt%, and can be optionally 30wt%-70wt%.
  • the negative electrode active material When the content of carbon element and/or the element capable of alloying with Li in the negative electrode active material is within the above range, it is beneficial for the negative electrode active material to have both high specific capacity and high conductivity.
  • the negative electrode active material further includes other elements, and the other elements include one or more of oxygen, metal and nitrogen.
  • the sum of the mass percentages of the other elements in the negative electrode active material is less than or equal to 20 wt %, and may be less than or equal to 10 wt %.
  • the first coulombic efficiency of the carbon matrix is ⁇ 75%, and can be 75%-87%, which is beneficial to improve the first coulombic efficiency of the negative electrode active material.
  • the powder resistivity of the carbon matrix under a pressure of 16 MPa is ⁇ 5 ⁇ 10 -2 ⁇ ⁇ cm, and can be ⁇ 3.5 ⁇ 10 -2 ⁇ cm, which is beneficial to improving the conductivity of the negative electrode active material.
  • the BET specific surface area of the carbon matrix is 50m2 /g- 1000m2 /g, and can be 100m2 /g- 700m2 /g. This is conducive to the negative electrode active material having a suitable BET specific surface area, thereby reducing the surface activity of the negative electrode active material, reducing the interface side reaction, and reducing the SEI film formation consumption, thereby improving the first coulombic efficiency and cycle performance of the secondary battery.
  • the graphitization degree of the negative electrode active material is ⁇ 65%, and can be 65%-87%. This is conducive to the negative electrode active material to better balance high initial coulombic efficiency, high conductivity and good cycle stability.
  • the first coulombic efficiency of the negative electrode active material is ⁇ 92%, and can be 92%-95%, thereby reducing the irreversible consumption of active ions and improving the capacity performance and cycle performance of the secondary battery.
  • the volume particle size Dv50 of the negative electrode active material is 3 ⁇ m-50 ⁇ m, and can be optionally 5 ⁇ m-20 ⁇ m.
  • the volume particle size Dv90 of the negative electrode active material is ⁇ 60 ⁇ m, and can be optionally 20 ⁇ m-50 ⁇ m.
  • the diameter distance (Dv90-Dv10)/Dv50 of the negative electrode active material is 1.0-3.0, and can be optionally 1.0-2.0.
  • volume particle size Dv50, volume particle size Dv90 and diameter distance (Dv90-Dv10)/Dv50 of the negative electrode active material helps to reduce the surface activity of the negative electrode active material, reduce interfacial side reactions, reduce SEI film formation consumption, and is also beneficial to improve the active ion and electron transport performance, thereby further improving the cycle performance of the secondary battery.
  • the BET specific surface area of the negative electrode active material is 2m2 /g- 100m2 /g, and can be 2m2 /g- 30m2 /g.
  • the BET specific surface area of the negative electrode active material is within the above range, it is helpful to reduce surface activity, reduce interface side reactions, and reduce SEI film formation consumption, thereby improving the first coulombic efficiency and cycle performance of the secondary battery.
  • the powder resistivity of the negative electrode active material under a pressure of 16 MPa is ⁇ 5 ⁇ 10 -1 ⁇ cm, and can be ⁇ 2 ⁇ 10 -1 ⁇ cm.
  • the negative electrode active material has good conductivity, which is beneficial to improving the cycle performance and rate performance of the secondary battery.
  • the second aspect of the present application provides a method for preparing a negative electrode active material, comprising the following steps: step 1, providing a carbon matrix with a graphitization degree of less than or equal to 87%, optionally 65%-87%, and including multiple pore structures; step 2, dispersing a filler material into the pore structure of the carbon matrix to obtain a negative electrode active material, wherein the negative electrode active material includes a carbon matrix and a filler material, the carbon matrix includes multiple pore structures, at least a portion of the filler material is located in the pore structure of the carbon matrix, and the filler material includes one or more elements that can undergo an alloying reaction with Li, optionally, the element that can undergo an alloying reaction with Li includes one or more of silicon, tin and germanium.
  • the carbon matrix is prepared by the following method: placing a carbon source including a plurality of pore structures in a high temperature furnace, graphitizing the carbon source at 1600°C-2400°C in a protective gas atmosphere, and obtaining a carbon matrix after the graphitization treatment.
  • a carbon matrix having a graphitization degree of less than or equal to 87%, optionally 65%-87%, and including a plurality of pore structures can be obtained.
  • the holding time of the graphitization treatment is 1h-12h.
  • the carbon source includes one or more selected from hard carbon, petroleum coke, pitch coke, biomass carbon and resin carbon.
  • the micropores in the carbon source can be reduced and the dispersion uniformity of the subsequent filling material can be improved; on the other hand, the residual bonds on the surface of the carbon source can be removed, the content of oxygen-containing functional groups in the carbon source can be reduced, and the side reactions of the electrolyte can be reduced, which is beneficial to improving the first coulombic efficiency, conductivity and high-temperature performance of the obtained carbon matrix, thereby enabling the secondary battery to have good cycle performance.
  • the first coulombic efficiency of the carbon matrix is ⁇ 75%, and can be optionally 75%-87%.
  • the powder resistivity of the carbon matrix under a pressure of 16 MPa is ⁇ 5 ⁇ 10 -2 ⁇ cm, and can be optionally ⁇ 3.5 ⁇ 10 -2 ⁇ cm.
  • the BET specific surface area of the carbon matrix is 50 m 2 /g-1000 m 2 /g, and can be optionally 100 m 2 /g-700 m 2 /g.
  • the volume particle size Dv50 of the carbon matrix is 3 ⁇ m-50 ⁇ m, and can be optionally 5 ⁇ m-20 ⁇ m.
  • the process of dispersing the filling material into the pore structure of the carbon matrix includes a liquid deposition process and a vapor deposition process, and the vapor deposition process can be selected.
  • the vapor deposition process is conducive to better deposition and uniform dispersion of the filling material in the pore structure of the carbon matrix, and can avoid the problem of agglomeration of the filling material and/or the problem of large-scale deposition on the surface of the carbon matrix.
  • the vapor deposition process is relatively mature and easy to carry out industrial mass production.
  • the vapor deposition process includes a chemical vapor deposition process and a physical vapor deposition process, and the chemical vapor deposition process may be selected.
  • step 2 the step of dispersing the filler material into the pore structure of the carbon matrix comprises the following steps: placing the carbon matrix in a reaction furnace, introducing a first mixed gas containing a source of an element capable of alloying with Li, and depositing at a first temperature T 1 for a first time t 1 , and obtaining a negative electrode active material after completion.
  • the first mixed gas includes the source of the element capable of alloying with Li and a protective gas.
  • the volume proportion of the source of the element capable of alloying with Li in the first mixed gas is 10%-50%.
  • the first mixed gas further includes a carbon source gas.
  • the volume ratio of the source of the element capable of alloying with Li to the carbon source gas is greater than or equal to 0.5:1, and can be optionally (2-10):1.
  • the volume proportion of the carbon source gas in the first mixed gas is ⁇ 20%, and can be optionally 5%-20%.
  • the pressure in the reaction furnace is 200Pa-600Pa higher than the atmospheric pressure.
  • the total gas flow rate of the first mixed gas is 0.5 L/min-20 L/min.
  • the first temperature T1 is 400°C-1000°C.
  • the first time t1 is 1h-12h.
  • the composition ratio of the first mixed gas By adjusting at least one of the composition ratio of the first mixed gas, the total gas flow rate of the first mixed gas, the first temperature and the first time within the above-mentioned range, it is beneficial to deposit the filling material in the pore structure of the carbon matrix, and it is also beneficial to adjust the crystallinity and/or grain size of the filling material within a suitable range.
  • the method further comprises step 3: forming a coating layer on at least a portion of the surface of the negative electrode active material obtained in step 2, wherein the coating layer comprises one or more of a carbon material, a conductive polymer, a metal oxide and a metal sulfide.
  • the step of forming the coating layer includes the following steps: placing the negative electrode active material obtained in step 2 in a reaction furnace, introducing a second mixed gas containing a carbon source gas, and depositing at a second temperature T 2 for a second time t 2 to obtain a carbon-coated negative electrode active material.
  • the second mixed gas includes a carbon source gas and a protective gas.
  • a volume proportion V2 of the carbon source gas in the second mixed gas is 5%-50%.
  • the total gas flow rate of the second mixed gas is 0.5 L/min-20 L/min.
  • the second temperature T2 is 700°C-850°C.
  • the second time t2 is 1h-6h.
  • step 3 by adjusting at least one of the composition ratio of the second mixed gas, the total gas flow rate of the second mixed gas, the second temperature and the second time within the above range, it is beneficial to form a coating layer of appropriate thickness, thereby avoiding the coating layer being too thick and reducing the specific capacity of the negative electrode active material.
  • a third aspect of the present application provides a secondary battery, comprising a negative electrode plate, wherein the negative electrode plate comprises the negative electrode active material of the first aspect of the present application or the negative electrode active material prepared by the method of the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, comprising the secondary battery of the third aspect of the present application.
  • the inventors of the present application have found in their research that by placing a filler material with a high capacity advantage in the pore structure of a carbon matrix with a low degree of graphitization, the obtained negative electrode active material can have high capacity, high first coulomb efficiency, low volume expansion, high conductivity and good cycle stability, and the secondary battery can also have high energy density, high first coulomb efficiency and long cycle life.
  • the electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of a battery cell according to an embodiment of the present application.
  • FIG. 2 is an exploded schematic diagram of an embodiment of a battery cell of the present application.
  • FIG. 3 is a schematic diagram of an embodiment of a battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of a battery pack of the present application.
  • FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present application as a power source.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • the values of the parameters mentioned in this application can be measured by various test methods commonly used in the art, for example, they can be measured according to the test methods given in this application.
  • non-carbon materials such as silicon-based materials, tin-based materials and germanium-based materials
  • Silicon has a theoretical specific capacity of up to 4200mAh/g
  • tin has a theoretical specific capacity of up to 994mAh/g
  • germanium has a theoretical specific capacity of up to 1600mAh/g, which can significantly improve the energy density of secondary batteries.
  • non-carbon materials such as silicon-based materials, tin-based materials, and germanium-based materials, store energy by forming alloys through alloying reactions with metals (such as lithium, sodium, etc.), which leads to a huge volume effect during the charge and discharge process, which is easy to cause particle breakage and pulverization, and then leads to pulverization of the negative electrode film layer, which is easy to lose electrical contact with the current collector, resulting in the failure of the active ion deintercalation process to proceed smoothly, significantly increasing the irreversible capacity.
  • metals such as lithium, sodium, etc.
  • the huge volume effect will also cause the solid electrolyte interface (SEI) film on the surface of the negative electrode active material particles to be repeatedly destroyed and rebuilt, further increasing the irreversible consumption of active ions and ultimately affecting the capacity of the secondary battery; at the same time, as the charge and discharge process proceeds, the SEI film on the surface of the negative electrode active material particles becomes thicker and thicker, thereby increasing the impedance of the secondary battery. Furthermore, the unstable SEI film on the surface of the negative electrode active material particles will also cause the negative electrode active material to directly contact the electrolyte, thereby further increasing the interface side reactions and irreversible capacity.
  • SEI solid electrolyte interface
  • silicon is also a semiconductor material with low intrinsic conductivity and poor electrical conductivity, which further deteriorates the electrochemical performance of the secondary battery.
  • the inventors of the present application have proposed a new type of negative electrode active material through extensive research, which can take into account high specific capacity, high first coulombic efficiency, low volume expansion, high conductivity and good cycle stability, and can also enable secondary batteries to take into account high energy density, high first coulombic efficiency and long cycle life.
  • a negative electrode active material in a first aspect of the embodiment of the present application, includes a carbon matrix and a filler material, wherein the graphitization degree of the carbon matrix is less than or equal to 87%, the carbon matrix includes a plurality of pore structures, at least a portion of the filler material is located in the pore structure of the carbon matrix, and the filler material includes one or more elements that can undergo an alloying reaction with Li.
  • the filling material includes one or more elements that can undergo alloying reaction with Li, thereby contributing a higher capacity to make up for the defect of low capacity of the carbon matrix.
  • it has a serious volume effect, which will affect the electrochemical performance.
  • the method currently used is to place it in a carbon matrix or natural graphite including multiple pore structures through a deposition process.
  • the carbon matrix including multiple pore structures currently used is mostly obtained by etching with a pore-forming agent, such as an alkaline solution, and the carbon matrix itself is non-graphitized carbon (or amorphous carbon), which has the defects of high irreversible capacity, low initial coulomb efficiency and poor conductivity; while natural graphite itself has a pore structure, so it can also be used as a substrate material for deposition, and has the advantage of excellent conductivity, but the irregular pore structure of natural graphite leads to poor dispersion uniformity of the filling material.
  • natural graphite also has the defects of poor structural stability, large volume expansion and poor cycle performance.
  • the methods currently used in the prior art cannot enable the obtained negative electrode active materials to have high specific capacity, high first coulombic efficiency, low volume expansion, high conductivity and good cycle stability.
  • the inventors of the present application have found in their research that by placing a filler material with a high specific capacity advantage in the pore structure of a carbon matrix with a low degree of graphitization (greater than 0 and less than or equal to 87%), the obtained negative electrode active material can take into account high specific capacity, high first coulombic efficiency, low volume expansion, high conductivity and good cycle stability, and the secondary battery can also take into account high energy density, high first coulombic efficiency and long cycle life.
  • the degree of graphitization of the carbon matrix of the present application is less than or equal to 87%.
  • the negative electrode active material provided by the present application can give full play to the advantages of high specific capacity of the filler material, and can also make up for the defects of poor conductivity and low first coulombic efficiency of the filler material; in addition, at least a part of the filler material is located in the pore structure of the carbon matrix, thereby reducing the volume expansion of the filler material through the carbon matrix.
  • the graphitization degree of the carbon matrix is less than or equal to 87%, for example, less than or equal to 85%, less than or equal to 80%, less than or equal to 75%, or less than or equal to 70%.
  • the graphitization degree of the carbon matrix is greater than 87%, the volume expansion of the carbon matrix during the charge and discharge process is large and the structural stability is poor, which will affect the cycle stability and cycle life of the negative electrode active material.
  • the graphitization degree of the carbon matrix is reduced and its structural stability is improved, which is beneficial to improving the cycle stability of the negative electrode active material and extending the cycle life of the secondary battery.
  • the graphitization degree of the carbon matrix should not be too low, because its first coulombic efficiency and conductivity are poor, which will lead to the improvement effect of the first coulombic efficiency and conductivity of the negative electrode active material becoming less obvious.
  • the graphitization degree of the carbon matrix can also be greater than or equal to 10%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, or greater than or equal to 65%.
  • the graphitization degree of the carbon matrix may be 40%-87%, 50%-87%, 60%-87%, 65%-87%, 65%-85%, 65%-82% or 65%-80%.
  • the negative electrode active material it is beneficial for the negative electrode active material to better balance high specific capacity, high first coulombic efficiency, low volume expansion, high conductivity and good cycle stability.
  • At least a portion of the filler material is located in the pore structure of the carbon matrix, and there is a gap between the filler material and the carbon matrix.
  • the gap can be used as a space to accommodate the volume expansion of the filler material to buffer the stress generated during the expansion of the filler material, thereby further reducing the probability of particle breakage and pulverization.
  • the element capable of alloying with Li comprises one or more of silicon, tin and germanium, which is advantageous for the negative electrode active material to have a high specific capacity advantage.
  • the filling material includes one or more of silicon-based materials, tin-based materials, and germanium-based materials, and optionally includes silicon-based materials.
  • silicon-based material refers to a compound containing silicon.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon material, silicon-nitrogen compound, and silicon alloy.
  • the term "tin-based material” refers to a compound containing the element tin.
  • the tin-based material may include one or more of elemental tin, tin oxide, tin sulfide, tin phosphide, tin composite oxide, tin-carbon material, and tin alloy material.
  • Tin composite oxide refers to a metal and/or non-metal oxide in which some glass phases are introduced into tin oxide.
  • germanium-based material refers to a compound containing germanium.
  • the germanium-based material may include one or more of single-element germanium, germanium oxide, germanium-carbon material, germanium alloy material, and germanate.
  • the filler material may include a crystalline filler material and/or an amorphous filler material.
  • the filling material includes crystalline silicon-based materials and/or amorphous silicon-based materials. Silicon-based materials have the advantage of high specific capacity, which is conducive to improving the energy density of secondary batteries.
  • the filling material includes crystalline single-substance silicon and/or amorphous single-substance silicon.
  • the grain size of the crystalline filling material is ⁇ 100nm, for example, ⁇ 80nm, ⁇ 70nm, ⁇ 60nm, ⁇ 50nm, ⁇ 40nm, ⁇ 30nm, ⁇ 20nm.
  • the grain size of the crystalline filling material is 2nm-50nm, 2nm-40nm, 2nm-30nm or 2nm-20nm.
  • the grain size of the crystalline filling material When the grain size of the crystalline filling material is large, it is beneficial to improve the first coulombic efficiency of the secondary battery, but it is not beneficial to the cycle performance and storage performance of the secondary battery. Therefore, when the crystalline filling material has a suitable grain size, it can not only improve the first coulombic efficiency of the secondary battery, but also avoid a significant adverse effect on the cycle performance and storage performance of the secondary battery.
  • the grain size of the crystalline filling material is well known in the art and can be measured using instruments and methods known in the art. For example, a high-resolution transmission electron microscope (HRTEM) can be used for testing and measurement.
  • HRTEM transmission electron microscope
  • the filling material can be obtained by a vapor deposition process.
  • the filling material may include one or more of a vapor-deposited silicon-based material, a tin-based material, and a germanium-based material.
  • the filling material includes a vapor-deposited silicon-based material.
  • the filling material includes vapor-deposited silicon.
  • the vapor deposition process includes a chemical vapor deposition process and a physical vapor deposition process, which can be a chemical vapor deposition process, for example, any one of a thermal chemical vapor deposition process, a plasma-enhanced chemical vapor deposition process, and a microwave plasma-assisted chemical vapor deposition process.
  • the vapor deposition process is conducive to better deposition and uniform dispersion of the filling material in the pore structure of the carbon matrix, and can avoid the problem of agglomeration of the filling material and/or the problem of large-scale deposition on the surface of the carbon matrix.
  • the vapor deposition process is relatively mature and easy to carry out industrial mass production.
  • the negative electrode active material in the X-ray diffraction spectrum of the negative electrode active material measured by an X-ray diffractometer, includes a (002) crystal plane peak at 26.4° and a (111) crystal plane peak at 28.6°, and the ratio of the half-peak width of the (002) crystal plane peak to the half-peak width of the (111) crystal plane peak is 0.2-50, for example, it can be 0.2, 0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or any range consisting of the above values.
  • the ratio of the half-peak width of the (002) crystal plane peak to the half-peak width of the (111) crystal plane peak is 0.2-20.
  • the half-width of the (002) crystal plane peak and the half-width of the (111) crystal plane peak can refer to JIS K 0131-1996.
  • the crystal cell parameters are calculated using an X-ray diffractometer (such as Bruker D8 Discover).
  • the center of gravity method is used to find the peak positions of C 002 and Si 111 of two parallel samples.
  • the test angle range can be 20°-80°.
  • the half-peak width of the (002) crystal plane peak can characterize the arrangement integrity of the (002) crystal plane in the carbon matrix
  • the half-peak width of the (111) crystal plane peak can characterize the content of elemental silicon in the filling material and the grain size of elemental silicon.
  • the negative electrode active material further includes a coating layer, and the coating layer is located on at least part of the surface of the carbon matrix.
  • the coating layer can prevent the filler material from directly contacting the electrolyte, thereby reducing electrolyte side reactions, reducing active ion consumption, and improving the cycle performance of the secondary battery; at the same time, it can also improve the stability of the negative electrode slurry and avoid the reaction of the filler material with solvent water, etc., which increases the difficulty of processing the negative electrode slurry.
  • the coating layer can also play a role in buffering the volume expansion of the filler material, which is also conducive to improving the structural stability of the negative electrode active material and improving the electrochemical performance of the secondary battery.
  • the coating layer includes one or more of a carbon material, a conductive polymer, a metal oxide, and a metal sulfide.
  • the carbon material includes one or more of hard carbon, soft carbon, graphene, carbon fiber and carbon nanotube.
  • the conductive polymer includes one or more of polyaniline, polypyrrole, and polythiophene.
  • the metal oxide includes one or more of iron oxide, zinc oxide, tin oxide, copper oxide and titanium oxide.
  • the metal sulfide includes one or more of tin sulfide, molybdenum sulfide, titanium sulfide, iron sulfide and copper sulfide.
  • the coating layer includes a carbon material.
  • the coating layer in addition to preventing the filler material from directly contacting the electrolyte and buffering the volume expansion of the filler material, the coating layer can also contribute part of the capacity and increase the specific capacity of the negative electrode active material.
  • the coating layer when the coating layer includes a carbon material, it also helps to improve the conductivity of the filler material, especially the silicon-based material, which is conducive to improving the capacity performance characteristics of the negative electrode active material.
  • the thickness of the coating layer is ⁇ 100nm, and can be optionally 10nm-100nm.
  • the integrity of the coating layer is higher, and the filling material can be more effectively prevented from contacting the electrolyte, which is beneficial to reduce the side reaction of the electrolyte, so that the negative electrode active material can take into account high specific capacity, high first coulomb efficiency and low volume expansion.
  • the thickness of the coating layer is greater than 100nm, the integrity of the coating layer is better, but the brittleness increases, and it is more likely to break and pulverize during repeated charge and discharge; in addition, the specific capacity of the negative electrode active material is reduced.
  • the negative electrode active material includes carbon and an element capable of alloying with Li.
  • the mass percentage of the carbon element in the negative electrode active material is 20wt%-80wt%, for example, it can be 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt% or any range of the above values.
  • the mass percentage of the carbon element in the negative electrode active material is 30wt%-70wt%.
  • the distribution area of the carbon element is not specifically limited, for example, it can be located in at least one of the carbon matrix, the filling material and the coating layer.
  • the mass percentage of the element capable of alloying with Li in the negative electrode active material is 20wt%-80wt%, for example, it can be 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt% or any range of the above values.
  • the mass percentage of the element capable of alloying with Li in the negative electrode active material is 30wt%-70wt%.
  • the element capable of alloying with Li includes silicon.
  • the negative electrode active material When the content of carbon element and/or the element capable of alloying with Li in the negative electrode active material is within the above range, it is beneficial for the negative electrode active material to have both high specific capacity and high conductivity.
  • the negative electrode active material includes other elements in addition to carbon and elements capable of alloying with Li, and the other elements include one or more of oxygen, metal and nitrogen.
  • the distribution area of the other elements is not specifically limited, for example, the other elements may be located in at least one of the coating layer, the filling material and the carbon matrix.
  • the sum of the mass percentages of the other elements in the negative electrode active material is less than or equal to 20 wt %, more optionally less than or equal to 10 wt %, or less than or equal to 5 wt %.
  • the first coulombic efficiency of the carbon matrix is ⁇ 75%, and can be 75%-87%, which is helpful to improve the first coulombic efficiency of the negative electrode active material.
  • the powder resistivity of the carbon matrix under a pressure of 16 MPa is ⁇ 5 ⁇ 10 -2 ⁇ cm, and can be ⁇ 3.5 ⁇ 10 -2 ⁇ cm, which is beneficial to improving the conductivity of the negative electrode active material.
  • the BET specific surface area of the carbon matrix is 50m2 /g- 1000m2 /g, and can be 100m2 /g- 700m2 /g. This is conducive to the negative electrode active material having a suitable BET specific surface area, thereby reducing the surface activity of the negative electrode active material, reducing interface side reactions, and reducing SEI film formation consumption, thereby improving the first coulombic efficiency and cycle performance of the secondary battery.
  • the graphitization degree of the negative electrode active material is ⁇ 65%, and can be 65%-87%. This helps the negative electrode active material to better balance high initial coulombic efficiency, high conductivity, and good cycle stability.
  • the first coulombic efficiency of the negative electrode active material is ⁇ 92%, and can be 92%-95%, thereby reducing the irreversible consumption of active ions and improving the capacity performance and cycle performance of the secondary battery.
  • the volume particle size Dv50 of the negative electrode active material is 3 ⁇ m-50 ⁇ m, and can be 5 ⁇ m-20 ⁇ m.
  • the volume particle size Dv90 of the negative electrode active material is ⁇ 60 ⁇ m, and can be optionally 20 ⁇ m-50 ⁇ m.
  • the diameter distance (Dv90-Dv10)/Dv50 of the negative electrode active material is 1.0-3.0, and can be 1.0-2.0.
  • volume particle size Dv50, volume particle size Dv90 and diameter distance (Dv90-Dv10)/Dv50 of the negative electrode active material helps to reduce the surface activity of the negative electrode active material, reduce interfacial side reactions, reduce SEI film formation consumption, and is also beneficial to improve the active ion and electron transport performance, thereby further improving the cycle performance of the secondary battery.
  • the BET specific surface area of the negative electrode active material is 2m2 /g- 100m2 /g, optionally 2m2 /g- 30m2 /g, 2m2 /g- 20m2 /g.
  • the BET specific surface area of the negative electrode active material is within the above range, it is helpful to reduce surface activity, reduce interface side reactions, and reduce SEI film formation consumption, thereby improving the first coulombic efficiency and cycle performance of the secondary battery.
  • the powder resistivity of the negative electrode active material under a pressure of 16 MPa is ⁇ 5 ⁇ 10 -1 ⁇ cm, and can be ⁇ 2 ⁇ 10 -1 ⁇ cm.
  • the negative electrode active material has good conductivity, which is beneficial to improving the cycle performance and rate performance of the secondary battery.
  • volume particle sizes Dv10, Dv50, and Dv90 of materials are well known in the art, and respectively represent the particle sizes corresponding to the cumulative volume distribution percentages of the materials reaching 10%, 50%, and 90%, and can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer with reference to GB/T 19077-2016.
  • the test instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.
  • the BET specific surface area of a material has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be tested by nitrogen adsorption specific surface area analysis test method according to GB/T 19587-2017 and calculated by BET (Brunauer Emmett Teller) method.
  • the nitrogen adsorption specific surface area analysis test can be performed by TRISTAR II 3020 specific surface area and porosity analyzer of Micromeritics, USA.
  • the powder resistivity of a material is a well-known meaning in the art and can be measured using instruments and methods known in the art.
  • a powder sample of a certain mass can be placed in a feeding cup of a resistivity tester, a certain pressure can be applied, and then data can be manually collected to record the powder resistivity test results of the sample under different pressures.
  • the test pressure can be 16MPa.
  • the graphitization degree of a material is a well-known meaning in the art and can be measured by instruments and methods well-known in the art.
  • a material e.g., negative electrode active material, carbon matrix, etc.
  • an X-ray diffractometer e.g., Bruker D8 Discover
  • the content of each element in the negative electrode active material can be measured by instruments and methods known in the art.
  • the carbon content can be tested with reference to GB/T 20123-2006/ISO 15350:2000, and the testing instrument can be an HCS-140 infrared carbon-sulfur analyzer.
  • the silicon content can be tested with reference to GB/T 20975.5-2020.
  • the tin content in the negative electrode active material can be tested with reference to GB/T 20975.10-2020.
  • the germanium content can be tested with reference to GB/T 20127.6-2006.
  • a second aspect of the embodiments of the present application provides a method for preparing a negative electrode active material, which can prepare the negative electrode active material of the first aspect of the embodiments of the present application.
  • the method comprises the following steps: step 1, providing a carbon matrix having a graphitization degree of less than or equal to 87%, optionally 65%-87%, and comprising a plurality of pore structures; step 2, dispersing a filler material into the pore structure of the carbon matrix, i.e., obtaining a negative electrode active material, wherein the negative electrode active material comprises a carbon matrix and a filler material, the carbon matrix comprises a plurality of pore structures, at least a portion of the filler material is located in the pore structure of the carbon matrix, and the filler material comprises one or more elements capable of alloying with Li, and optionally, the elements capable of alloying with Li comprise one or more of silicon, tin and germanium.
  • the carbon matrix is prepared by the following method: placing a carbon source including a plurality of pore structures in a high temperature furnace, graphitizing the carbon source under a protective gas atmosphere at 1600°C-2400°C, and obtaining a carbon matrix after completion.
  • the graphitization treatment can be carried out at 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C or any range of the above values.
  • a carbon matrix having a graphitization degree of less than or equal to 87%, optionally 65%-87%, and including a plurality of pore structures can be obtained.
  • the obtained carbon matrix is still non-graphitized carbon (or amorphous carbon), which has a high irreversible capacity, low first coulombic efficiency and poor conductivity, which will affect the first coulombic efficiency and cycle performance of the secondary battery;
  • the graphitization temperature is too high, the obtained carbon matrix has a large volume expansion and poor structural stability during the charge and discharge process, which will affect the cycle stability of the negative electrode active material and the cycle performance of the secondary battery.
  • the heating rate of the high temperature furnace is below 10°C/min, for example, below 8°C/min, or below 5°C/min.
  • the holding time of the graphitization treatment is 1h-12h, for example, it can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or any range thereof.
  • the carbon source includes one or more selected from hard carbon, petroleum coke, pitch coke, biomass carbon and resin carbon.
  • the high temperature furnace is a graphitization furnace, such as any one of a box-type graphitization furnace, an Acheson graphitization furnace, a continuous graphitization furnace, and an inner string graphitization furnace.
  • the carbon source used to prepare the carbon matrix is of various types, has large reserves in nature, is inexpensive, and has a simple preparation process.
  • the carbon source including multiple pore structures can be directly purchased from the market, or prepared according to methods known in the art, for example, by etching with a pore-forming agent, such as an alkaline solution.
  • the micropores in the carbon source can be reduced and the dispersion uniformity of the subsequent filling material can be improved; on the other hand, the residual bonds on the surface of the carbon source can be removed, the content of oxygen-containing functional groups in the carbon source can be reduced, and the side reactions of the electrolyte can be reduced, which is beneficial to improving the first coulombic efficiency, conductivity and high-temperature performance of the obtained carbon matrix, thereby enabling the secondary battery to have good cycle performance.
  • the first coulombic efficiency of the carbon matrix is ⁇ 75%, and can be 75%-87%.
  • the powder resistivity of the carbon matrix under a pressure of 16 MPa is ⁇ 5 ⁇ 10 ⁇ 2 ⁇ cm, and can be optionally ⁇ 3.5 ⁇ 10 ⁇ 2 ⁇ cm.
  • the BET specific surface area of the carbon matrix is 50 m 2 /g-1000 m 2 /g, and optionally 100 m 2 /g-700 m 2 /g.
  • the volume particle size Dv50 of the carbon matrix is 3 ⁇ m-50 ⁇ m, and can be 5 ⁇ m-20 ⁇ m.
  • the process of dispersing the filling material into the pore structure of the carbon matrix includes a liquid deposition process and a vapor deposition process, and the vapor deposition process can be selected.
  • the vapor deposition process is conducive to better deposition and uniform dispersion of the filling material in the pore structure of the carbon matrix, and can avoid the problem of agglomeration of the filling material and/or the problem of large-scale deposition on the surface of the carbon matrix.
  • the vapor deposition process is relatively mature and easy to carry out industrial mass production.
  • the vapor deposition process includes a chemical vapor deposition process and a physical vapor deposition process, and can be more selectively a chemical vapor deposition process, for example, it can be any one of a thermal chemical vapor deposition process, a plasma enhanced chemical vapor deposition process, and a microwave plasma assisted chemical vapor deposition process.
  • step 2 the step of dispersing the filler material into the pore structure of the carbon matrix comprises the following steps: placing the carbon matrix in a reaction furnace, introducing a first mixed gas containing a source of an element capable of alloying with Li, and depositing at a first temperature T 1 for a first time t 1 , and obtaining a negative electrode active material after completion.
  • the first mixed gas includes a source of the element capable of alloying with Li and a protective gas.
  • the volume fraction of the source of the element capable of alloying reaction with Li in the first mixed gas is 10%-50%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or any range consisting of the above values.
  • the first mixed gas may further include a carbon source gas.
  • the volume ratio of the source of the element capable of alloying with Li to the carbon source gas is greater than or equal to 0.5:1, and can be optionally (2-10):1.
  • the volume ratio of the source of the element capable of alloying with Li to the carbon source gas is within the above range, it is beneficial for the negative electrode active material to have a high specific capacity.
  • the volume ratio of the two is too small, the content of carbon element in the obtained filling material is higher and the content of the element capable of alloying with Li is lower, which leads to the effect of improving the capacity of the negative electrode active material becoming less obvious.
  • the volume proportion of the carbon source gas in the first mixed gas is ⁇ 20%, and more optionally 5%-20%, which is beneficial for the negative electrode active material to have both high specific capacity and high conductivity.
  • the volume proportion of the protective gas in the first mixed gas is 30%-90%, for example, it can be 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or any range consisting of the above values.
  • the total gas flow rate of the first mixed gas may be 0.5 L/min-20 L/min.
  • it may be 1 L/min, 2 L/min, 3 L/min, 4 L/min, 5 L/min, 6 L/min, 7 L/min, 8 L/min, 9 L/min, 10 L/min, 12 L/min, 14 L/min, 16 L/min, 18 L/min, 20 L/min or any range thereof.
  • the pressure in the reaction furnace may be a slightly positive pressure, for example, 200Pa-600Pa higher than the atmospheric pressure, which is conducive to the smooth progress of the deposition process.
  • the reaction furnace includes but is not limited to any one of a deposition furnace, a rotary furnace, a tubular furnace, and a fluidized bed.
  • the first temperature T1 may be 400°C-1000°C, for example, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C or any range thereof.
  • the first time t1 may be 1h-12h, for example, it may be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or any range thereof.
  • the vapor deposition process by adjusting at least one of the composition ratio of the first mixed gas, the total gas flow rate of the first mixed gas, the first temperature and the first time within the above-mentioned range, it is beneficial to deposit the filling material in the pore structure of the carbon matrix, and it is also beneficial to adjust the crystallinity and/or grain size of the filling material within an appropriate range.
  • the method further comprises step 3: forming a coating layer on at least a portion of the surface of the negative electrode active material obtained in step 2, wherein the coating layer comprises one or more of a carbon material, a conductive polymer, a metal oxide and a metal sulfide.
  • the method of forming a coating layer on at least part of the surface of the negative electrode active material obtained in step 2 is not particularly limited and can be selected according to the composition of the coating layer, for example, any one of solid phase coating, liquid phase coating or gas phase coating can be used.
  • the step of forming the coating layer comprises the following steps: mixing the negative electrode active material obtained in step 2 with the coating material and subjecting the mixture to carbonization treatment.
  • the coating material comprises one or more of asphalt (e.g., coal tar, petroleum asphalt, etc.) and polymer materials.
  • the temperature of the carbonization treatment is 500°C-1000°C.
  • the step of forming the coating layer includes the following steps: placing the negative electrode active material obtained in step 2 in a reaction furnace, introducing a second mixed gas containing a carbon source gas, and depositing at a second temperature T 2 for a second time t 2 to obtain a carbon-coated negative electrode active material.
  • the second mixed gas includes a carbon source gas and a protective gas.
  • the volume proportion V2 of the carbon source gas in the second mixed gas is 5%-50%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or any range consisting of the above values.
  • the total gas flow rate of the second mixed gas is 0.5 L/min-20 L/min.
  • it can be 0.8 L/min, 1 L/min, 2 L/min, 3 L/min, 4 L/min, 5 L/min, 6 L/min, 7 L/min, 8 L/min, 9 L/min, 10 L/min, 12 L/min, 14 L/min, 16 L/min, 18 L/min, 20 L/min or any range thereof.
  • the second temperature T2 is 700°C-850°C, for example, it can be 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C or any range thereof.
  • the second time t2 is 1h-6h, for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h or any range thereof.
  • step 3 by adjusting at least one of the composition ratio of the second mixed gas, the total gas flow rate of the second mixed gas, the second temperature and the second time within the above range, it is beneficial to form a coating layer of appropriate thickness, thereby avoiding the coating layer being too thick and reducing the specific capacity of the negative electrode active material.
  • the term "protective gas” includes one or more of nitrogen and rare gases.
  • the rare gas may include one or more of argon, helium, etc.
  • source of an element capable of alloying with Li refers to a gas capable of forming the filling material of the present application, for example, may include one or more of a silicon source gas, a tin source gas and a germanium source gas.
  • the silicon source gas refers to a gas that can form the silicon-based material of the present application.
  • the silicon source gas includes but is not limited to monosilane (H 4 Si), disilane (H 6 Si 2 ), trisilane (H 8 Si 3 ), silicon tetrachloride (Cl 4 Si), trichlorosilane (Cl 3 HSi), dichlorosilane (Cl 2 H 2 Si), chlorosilane (ClH 3 Si), silicon tetrafluoride (F 4 Si), trifluorosilane (F 3 HSi), difluorosilane (F 2 H 2 Si), fluorosilane (FH 3 Si), hexachlorodisilane (Cl 6 Si 2 ), pentachlorodisilane (Cl 5 HSi 2 ), tetrachlorodisilane (Cl 4 H 2 Si 2 , including 1,1,2,2-tetrachlorodisilane and 1,1,1,2-tetrachlor
  • the tin source gas refers to a gas that can form the tin-based material of the present application.
  • the tin source gas includes but is not limited to one or more of methyl tin ( H4Sn ), Cl4Sn , Cl3HSn , Cl2H2Sn , ClH3Sn , F4Sn , F3HSn , F2H2Sn and FH3Sn .
  • the germanium source gas refers to a gas that can form the germanium-based material of the present application.
  • the germanium source gas includes but is not limited to one or more of germane (H 4 Ge), Cl 4 Ge and F 4 Ge.
  • carbon source gas refers to a gas that can form a carbon material.
  • the carbon source gas includes but is not limited to one or more of methane, ethane, propane, isopropane, butane, isobutane, ethylene, propylene, butene, acetylene, ethyl chloride, ethyl fluoride, difluoroethane, methyl chloride, methyl fluoride, difluoromethane, trifluoromethane, vinyl chloride, vinyl fluoride, difluoroethylene, methylamine, formaldehyde, benzene, toluene, xylene, styrene and phenol.
  • a third aspect of the embodiments of the present application provides a secondary battery.
  • the secondary battery mentioned in the embodiments or implementations of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.
  • the secondary battery mentioned in the present application may include a battery cell, a battery module or a battery pack, etc.
  • a battery cell is the smallest unit that makes up a secondary battery, which can realize the function of charging and discharging alone.
  • the present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape.
  • Figure 1 is a battery cell 5 of a square structure as an example.
  • the battery cell includes an electrode assembly, and the single cell may further include an outer packaging.
  • the electrode assembly may be made of a positive electrode sheet, a negative electrode sheet, and a separator, etc., by a winding process and/or a lamination process, and the outer packaging may be used to encapsulate the above-mentioned electrode assembly.
  • the outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.
  • battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 3, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. The multiple battery cells 5 can be further fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.
  • the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • Figures 4 and 5 are schematic diagrams of a battery pack 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery module 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • secondary batteries may include but are not limited to lithium-ion batteries, sodium-ion batteries, and the like.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode film layer includes the negative electrode active material of the first aspect of the embodiment of the present application or the negative electrode active material prepared by the method described in the second aspect of the embodiment of the present application. This enables the secondary battery to have both high energy density, high first coulomb efficiency and long cycle life.
  • the negative electrode film layer may further include other negative electrode active materials in addition to the above-mentioned negative electrode active materials.
  • the other negative electrode active materials include but are not limited to one or more of natural graphite, artificial graphite, soft carbon, hard carbon, elemental silicon, silicon oxide, silicon nitrogen complex, silicon alloy material, elemental tin, tin oxide, tin alloy material, and lithium titanate. The present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries may also be used.
  • the negative electrode film layer may further include a negative electrode conductive agent.
  • a negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode film layer may further include a negative electrode binder.
  • the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include other additives.
  • the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC-Na), a PTC thermistor material, and the like.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode plate described in the present application may also include a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode collector and the negative electrode film layer and disposed on the surface of the negative electrode collector; in some embodiments, the negative electrode plate described in the present application may also include a protective layer covering the surface of the negative electrode film layer.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material, and the positive electrode active material can be a positive electrode active material for a secondary battery known in the art.
  • the positive electrode active material may include one or more of a lithium transition metal oxide, a lithium phosphate containing an olivine structure, and their respective modified compounds.
  • lithium transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.
  • lithium phosphate containing an olivine structure may include one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for secondary batteries may also be used.
  • the positive electrode active material for the lithium ion battery may include one or more of a lithium transition metal oxide and a modified compound thereof of the general formula Li a Ni b Co c M d O e A f . 0.8 ⁇ a ⁇ 1.2, 0.5 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 1 ⁇ e ⁇ 2, 0 ⁇ f ⁇ 1, M includes one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more selected from N, F, S and Cl.
  • the positive electrode active material for a lithium ion battery may include one or more of LiCoO2 , LiNiO2 , LiMnO2 , LiMn2O4 , LiNi1/3Co1/ 3Mn1 / 3O2 ( NCM333 ) , LiNi0.5Co0.2Mn0.3O2 ( NCM523 ) , LiNi0.6Co0.2Mn0.2O2 ( NCM622 ) , LiNi0.8Co0.1Mn0.1O2 ( NCM811 ), LiNi0.85Co0.15Al0.05O2 , LiFePO4 and LiMnPO4 .
  • the positive electrode active material may include but is not limited to one or more of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.
  • the positive electrode active material for a sodium ion battery may include one or more of NaFeO2 , NaCoO2 , NaCrO2 , NaMnO2 , NaNiO2 , NaNi1 /2Ti1/ 2O2 , NaNi1/2Mn1/2O2, Na2/3Fe1 / 3Mn2 / 3O2 , NaNi1 / 3Co1 / 3Mn1 /3O2, NaFePO4 , NaMnPO4 , NaCoPO4 , Prussian blue-based materials, and materials of the general formula XpM'q ( PO4 ) rOxY3 -x .
  • X includes one or more selected from H + , Li + , Na + , K + and NH4 + , M ' is a transition metal cation, which can be selected from one or more selected from V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halogen anion, which can be selected from one or more selected from F, Cl and Br.
  • the modified compound of each positive electrode active material mentioned above may be a compound obtained by doping and/or surface coating the positive electrode active material.
  • the positive electrode film layer may further include a positive electrode conductive agent.
  • a positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode film layer may further include a positive electrode binder.
  • the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them uniformly.
  • the solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.
  • the present application has no specific restrictions on the type of the electrolyte, which can be selected according to needs.
  • the electrolyte can include one or more selected from solid electrolytes and liquid electrolytes (i.e., electrolytes).
  • the electrolyte is an electrolyte solution
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlorate
  • the electrolyte salt may include one or more of sodium hexafluorophosphate (NaPF 6 ), sodium tetrafluoroborate (NaBF 4 ), sodium perchlorate (NaClO 4 ), sodium hexafluoroarsenate (NaAsF 6 ), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO 2 F 2 ), sodium difluorobis(oxalatophosphate) (NaDFOP) and sodium tetrafluorooxalato
  • the solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sul
  • the electrolyte may further include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature power performance.
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the separator is arranged between the positive electrode plate and the negative electrode plate, and mainly plays the role of preventing the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.
  • the present application has no particular restrictions on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.
  • the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a secondary battery.
  • the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained.
  • Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module.
  • Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.
  • the present application also provides an electrical device, which includes the secondary battery of the present application.
  • the secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.
  • the electrical device may select a specific type of secondary battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.
  • Fig. 6 is a schematic diagram of an electric device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module can be used as a power source.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the electric device is usually required to be light and thin, and a battery cell may be used as a power source.
  • Step 1 1 kg of commercially available porous biomass carbon (BET surface area of 1545 m 2 /g, volume particle size Dv50 of about 6 ⁇ m, which can also be obtained by pore-forming agent) is selected and placed in a graphitization furnace. Under nitrogen protection conditions, the temperature is raised to 2400°C at a rate of 5°C/min for graphitization treatment, and kept at 2400°C for 2 hours. After the end, it is cooled to room temperature to obtain a carbon matrix with a graphitization degree of 87%, an initial coulomb efficiency of 85%, a powder resistivity of 5.5 ⁇ 10 -3 ⁇ cm, and a BET specific surface area of 100 m 2 /g.
  • BET surface area 1545 m 2 /g, volume particle size Dv50 of about 6 ⁇ m, which can also be obtained by pore-forming agent
  • Step 2 Place the above-mentioned carbon matrix as a substrate in a vapor deposition furnace, heat it to 500°C at a rate of 5°C/min, introduce the first mixed gas according to 20% monosilane + 80% nitrogen (volume ratio), the total gas flow rate is 5L/min, the pressure in the reactor is 200Pa higher than the atmospheric pressure, and the deposition reaction is 8h.
  • Step 3 Turn off the first mixed gas, then heat it to 800°C at a rate of 5°C/min, and introduce the second mixed gas according to 40% acetylene + 60% nitrogen (volume ratio).
  • the total gas flow rate is 0.8L/min.
  • the deposition reaction is carried out for 2h. After the reaction is completed, it is cooled, discharged, and sieved through a 325-mesh sieve to obtain the negative electrode active material.
  • the negative electrode active material prepared above is mixed evenly with the conductive agent conductive carbon black and carbon nanotubes, and the binder polyacrylic acid in a mass ratio of 95:1.9:0.1:3, added to the solvent deionized water, and stirred under the action of a fast mixer until the system is uniform to obtain a negative electrode slurry with a solid content of 45%; the negative electrode slurry is evenly coated on the negative electrode collector copper foil and dried at 85°C and cold pressed to obtain a negative electrode sheet.
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a proper amount of solvent NMP at a mass ratio of 97:1:2 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode sheet is obtained.
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed evenly in a volume ratio of 20:20:60 as an organic solvent, then LiPF6 is dissolved in the above organic solvent, and fluoroethylene carbonate (FEC) is added.
  • the concentration of LiPF6 in the electrolyte is 1 mol/L, and the mass percentage of FEC is 5wt%.
  • Preparation of secondary batteries stack and wind the positive electrode sheet, separator, and negative electrode sheet in order to obtain an electrode assembly; place the electrode assembly in an outer package, inject electrolyte after drying, and obtain a secondary battery through vacuum packaging, standing, formation, shaping and other processes.
  • the negative electrode active material prepared above was mixed with the conductive agent conductive carbon black and the binder polyacrylic acid in a mass ratio of 8:1:1, added to the solvent deionized water, and stirred under the action of a rapid mixer until the system was uniform to obtain a negative electrode slurry with a solid content of 45%; the negative electrode slurry was evenly coated on the negative electrode current collector copper foil and dried and cold pressed at 85°C to obtain an electrode sheet.
  • a metal lithium sheet was used as the counter electrode, a Celgard 2400 isolation membrane was used, and the same electrolyte as in the preparation of the secondary battery was injected to assemble a button battery.
  • the preparation method of the secondary battery and button battery is similar to that of Example 1, except that the preparation process parameters of the negative electrode active material are adjusted, as shown in Table 1 for details.
  • the preparation methods of the secondary battery and button cell are similar to those of Example 1, except that crystalline silicon coated with amorphous carbon is used as the negative electrode active material, and the coating layer thickness is 80 nm.
  • Step 1 Provide crystalline silicon particles with a volume particle size Dv50 of 500 nm.
  • Step 2 Place the above-mentioned crystalline silicon particles into a rotary furnace, introduce a mixed gas of 40% acetylene + 60% nitrogen (volume ratio) with a total gas flow rate of 0.8 L/min, and perform the deposition reaction at 800°C for 2 hours. After the reaction is completed, cool and discharge the material to obtain amorphous carbon-coated crystalline silicon material.
  • the preparation method of the secondary battery and button battery is similar to that of Example 1, except that the preparation process parameters of the negative electrode active material are adjusted.
  • Step 1 Mechanically crush, classify, spheroidize and purify the flake graphite to obtain natural spherical graphite.
  • Step 2 Select 1 kg of natural spherical graphite as the substrate and place it in a vapor deposition furnace. Heat it to 500°C at a rate of 5°C/min, introduce the first mixed gas of 20% monosilane + 80% nitrogen (volume ratio), and the total gas flow rate is 5L/min. The pressure in the reactor is 200Pa higher than the atmospheric pressure, and the deposition reaction is carried out for 8 hours.
  • Step 3 Turn off the first mixed gas, then heat it to 800°C at a rate of 5°C/min, and introduce the second mixed gas according to 40% acetylene + 60% nitrogen (volume ratio).
  • the total gas flow rate is 0.8L/min.
  • the deposition reaction is carried out for 2h. After the reaction is completed, it is cooled, discharged, and sieved through a 325-mesh sieve to obtain the negative electrode active material.
  • the preparation method of the secondary battery and button battery is similar to that of Example 1, except that the preparation process parameters of the negative electrode active material are adjusted, as shown in Table 1 for details.
  • the preparation methods of the secondary battery and button battery are similar to those of Example 1, except that the preparation process parameters of the negative electrode active material are adjusted.
  • Step 1 Select 1 kg of porous biomass carbon directly as the carbon matrix without graphitization treatment.
  • Step 2 Place the above-mentioned carbon matrix as a substrate in a vapor deposition furnace, heat it to 500°C at a rate of 5°C/min, introduce the first mixed gas according to 20% monosilane + 80% nitrogen (volume ratio), the total gas flow rate is 5L/min, the pressure in the reactor is 200Pa higher than the atmospheric pressure, and the deposition reaction is 8h.
  • Step 3 Turn off the first mixed gas, then heat it to 800°C at a rate of 5°C/min, and introduce the second mixed gas according to 40% acetylene + 60% nitrogen (volume ratio).
  • the total gas flow rate is 0.8L/min.
  • the deposition reaction is carried out for 2h. After the reaction is completed, it is cooled, discharged, and sieved through a 325-mesh sieve to obtain the negative electrode active material.
  • the test instrument can be a Bruker D8 Discover X-ray diffractometer.
  • the carbon matrix prepared above was mixed with the conductive agent conductive carbon black and the binder polyacrylic acid in a mass ratio of 8:1:1, and then added to the solvent deionized water, and stirred under the action of a rapid mixer until the system was uniform, to obtain a negative electrode slurry with a solid content of 45%; the negative electrode slurry was evenly coated on the negative electrode current collector copper foil and dried and cold pressed at 85°C to obtain an electrode sheet.
  • a metal lithium sheet was used as the counter electrode, a Celgard 2400 isolation membrane was used, and the same electrolyte as in the above Example 1 was injected to assemble a button battery.
  • the button battery After the button battery was left to stand for 4 hours, it was placed in a blue electric test cabinet and discharged at a constant current of 0.05C to 5mV. After standing for 10 minutes, it was discharged at a constant current of 50 ⁇ A to 5mV, and the total discharge capacity of the button battery was recorded; then after the button battery was left to stand for 10 minutes, it was charged at a constant current of 0.1C to 2.0V, and the charging capacity of the button battery was recorded.
  • the first coulomb efficiency of the carbon matrix charging capacity/total discharge capacity.
  • test pressure can be 16MPa.
  • the nitrogen adsorption specific surface area analysis test method is used for testing, and the specific surface area of the carbon matrix is calculated by the BET (Brunauer Emmett Teller) method.
  • the test instrument can be the TRISTAR II 3020 specific surface area and porosity analyzer of Micromeritics, USA.
  • Dual Beam FIB-SEM was used to cut samples from the middle area of the negative electrode active material particles, and then high resolution transmission electron microscopy (HRTEM) was used to test the grain size of the filling material.
  • HRTEM high resolution transmission electron microscopy
  • the testing instrument can be HCS-140 infrared carbon-sulfur analyzer.
  • GB/T 20975.5-2020 to test the silicon content in the negative electrode active material.
  • GB/T 20975.10-2020 to test the tin content in the negative electrode active material.
  • GB/T 20127.6-2006 to test the germanium content in the negative electrode active material.
  • the crystal unit cell parameters are calculated by X-ray diffractometer, and the peak positions of C 002 and Si 111 of two parallel samples are obtained by the center of gravity method.
  • the test angle range can be 20°-80°. From the X-ray diffraction spectrum of the negative electrode active material, the half-peak width of the (002) crystal plane peak at 26.4° and the half-peak width of the (111) crystal plane peak at 28.6° are obtained.
  • the test instrument can be a Bruker D8 Discover X-ray diffractometer.
  • the button cells prepared in the above embodiments and comparative examples were placed in a blue electric test cabinet after being left to stand for 4 hours, and discharged to 5mV at a constant current of 0.05C. After being left to stand for 10 minutes, they were discharged to 5mV at a constant current of 50 ⁇ A. The total discharge capacity of the button cell was recorded as the lithium insertion capacity. Then, after the button cell was left to stand for 10 minutes, it was charged to 2V at a constant current of 0.1C. The charging capacity of the button cell was recorded as the lithium removal capacity.
  • the first coulomb efficiency of the negative electrode active material lithium removal capacity/lithium insertion capacity.
  • the secondary battery prepared above is fully charged at 0.5C and then fully discharged at 1C. This is a cycle charge and discharge process.
  • the discharge capacity at this time is recorded as the initial discharge capacity.
  • the secondary battery is subjected to a cycle charge and discharge test according to the above method, and the discharge capacity after each cycle is recorded until the discharge capacity of the secondary battery decays to 80% of the initial discharge capacity.
  • the number of cycles at this time is used to characterize the cycle performance of the secondary battery. The higher the number of cycles of the secondary battery, the better the cycle performance.
  • Comparative Example 1 uses carbon-coated crystalline silicon as the negative electrode active material. Crystalline silicon has a huge volume effect, while the carbon layer on the surface has limited protective effect on crystalline silicon, and the carbon layer will break after multiple charge and discharge, which will lead to repeated destruction and reconstruction of the SEI film, increasing the irreversible consumption of active ions; and as the number of charge and discharge increases, the thickness of the SEI film also increases, and then the impedance of the secondary battery will also increase. Therefore, the cycle performance of the secondary battery prepared in Comparative Example 1 is very poor.
  • Comparative Example 2 uses natural spherical graphite as the carbon matrix.
  • Natural spherical graphite itself has a pore structure and can be used as a deposition base material. It also has the advantage of excellent conductivity.
  • the pore structure of natural spherical graphite is irregular, which results in poor uniformity in the dispersion of the filling material.
  • natural spherical graphite also has the defects of poor structural stability and large volume expansion, which results in poor cycle performance of the secondary battery, and the secondary battery cannot have high energy density, high first coulomb efficiency and long cycle life.
  • Comparative Example 4 directly uses porous biomass carbon that has not been graphitized as the carbon matrix.
  • the carbon matrix at this time is non-graphitized carbon, which has the defects of high irreversible capacity, low first coulombic efficiency and poor conductivity.
  • the negative electrode active material prepared from it has low first coulombic efficiency and very poor conductivity, and thus the secondary battery cannot have high energy density, high first coulombic efficiency and long cycle life.

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Abstract

本申请提供一种负极活性材料及其制备方法、以及包含其的二次电池及用电装置，所述负极活性材料包括碳基体以及填充材料，所述碳基体的石墨化度为小于等于87％，所述碳基体包括多个孔结构，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料包括能与Li发生合金化反应的元素中的一种或几种。本申请提供的负极活性材料能兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性。

Description

负极活性材料及其制备方法、以及包含其的二次电池及用电装置 技术领域
本申请属于电池技术领域，具体涉及一种负极活性材料及其制备方法、以及包含其的二次电池及用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。在二次电池高速发展过程中人们对其能量密度提出了更高的要求，以石墨为代表的碳基材料是二次电池最常用的负极活性材料，但是其容量发挥已接近理论比容量。非碳类材料，例如硅基材料、锡基材料和锗基材料等，由于具有高理论比容量而引起人们广泛关注，但是这类负极活性材料存在普遍体积膨胀大、首次库伦效率低和/或导电性差的缺陷。
发明内容
本申请的目的在于提供一种负极活性材料及其制备方法、以及包含其的二次电池及用电装置，所述负极活性材料能兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性。
本申请第一方面提供一种负极活性材料，包括碳基体以及填充材料，其中，所述碳基体的石墨化度为小于等于87％，所述碳基体包括多个孔结构，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料包括能与Li发生合金化反应的元素中的一种或几种。
本申请的发明人在研究中发现，通过将具有高比容量优势的填充材料设置在具有低石墨化度(大于0且小于等于87％)的碳基体的孔结构中，能够使获得的负极活性材料兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性，并且还能使二次电池兼顾高能量密度、高首次库伦效率和长循环寿命。本申请的碳基体的石墨化度为小于等于87％，与通过造孔剂造孔得到的碳基体相比，具有导电性高和首次库伦效率高的优势，与天然石墨相比，具有体积膨胀小和循环稳定性高的优势。因此，本申请提供的负极活性材料能充分发挥填充材料高比容量的优势，还能弥补填充材料导电性差、首次库伦效率低的缺陷；此外，填充材料的至少一部分位于碳基体的孔结构中，由此通过碳基体还可以降低填充材料的体积膨胀。
在本申请的任意实施方式中，所述碳基体的石墨化度为65％-87％。由此，有利于负极活性材料更好地兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性。
在本申请的任意实施方式中，所述能与Li发生合金化反应的元素包括硅元素、锡元 素和锗元素中的一种或几种。由此有利于负极活性材料具有高比容量优势。
在本申请的任意实施方式中，所述填充材料包括硅基材料、锡基材料和锗基材料中的一种或几种。
在本申请的任意实施方式中，所述硅基材料包括单质硅、硅氧化物、硅碳材料、硅氮复合物和硅合金中的一种或几种。
在本申请的任意实施方式中，所述锡基材料包括单质锡、锡氧化物、锡硫化物、锡磷化物、锡复合氧化物、锡碳材料和锡合金材料中的一种或几种。
在本申请的任意实施方式中，所述锗基材料包括单质锗、锗氧化物、锗碳材料、锗合金材料和锗酸盐中的一种或几种。
在本申请的任意实施方式中，所述填充材料包括晶态的填充材料和/或非晶态的填充材料，可选地包括晶态的硅基材料和/或非晶态的硅基材料。硅基材料具有高比容量优势，有利于提高二次电池的能量密度。
在本申请的任意实施方式中，所述晶态的填充材料的晶粒尺寸为≤100nm，可选为2nm-50nm。当晶态的填充材料具有合适的晶粒尺寸时，既能提升二次电池的首次库伦效率，同时又能避免对二次电池的循环性能和存储性能产生较大不利影响。
在本申请的任意实施方式中，所述填充材料包括气相沉积的硅基材料、锡基材料和锗基材料中的一种或几种，可选地包括气相沉积硅基材料。
在本申请的任意实施方式中，在所述负极活性材料通过X射线衍射仪测定的X射线衍射谱图中，所述负极活性材料包括在26.4°处的(002)晶面峰和在28.6°处的(111)晶面峰，并且(002)晶面峰的半峰宽与(111)晶面峰的半峰宽的比值为0.2-50，可选为0.2-20。通过控制(002)晶面峰的半峰宽与(111)晶面峰的半峰宽在合适的范围内，可以使碳基体具有合适的石墨化度，并且使填充材料具有合适的晶粒尺寸，从而有利于负极活性材料兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性。
在本申请的任意实施方式中，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料与所述碳基体之间具有空隙。当填充材料与碳基体之间具有空隙时，该部分孔隙可以作为容纳填充材料体积膨胀的空间，以缓冲填充材料膨胀过程中产生的应力，由此能够进一步降低颗粒破碎、粉化的概率。
在本申请的任意实施方式中，所述负极活性材料还包括包覆层，所述包覆层位于所述碳基体的至少部分表面。包覆层可以阻止填充材料与电解液直接接触，从而能够减少电解液副反应、降低活性离子消耗，提高二次电池的循环性能；同时还可以提升负极浆料的稳定性，避免填充材料与溶剂水等反应而导致负极浆料加工难度增加。此外，包覆层还可以起到缓冲填充材料体积膨胀的作用，由此还有利于改善负极活性材料的结构稳定性，提升二次电池的电化学性能。
在本申请的任意实施方式中，所述包覆层包括碳材料、导电聚合物、金属氧化物和金属硫化物中的一种或几种，可选地包括碳材料。
在本申请的任意实施方式中，所述包覆层的厚度为≤100nm，可选为10nm-100nm。包覆层的厚度在上述范围内时，包覆层的完整性更高，能更有效地避免填充材料与电解液接触，从而有利于减少电解液副反应，使负极活性材料兼顾高比容量、高首次库伦效 率和低体积膨胀。
在本申请的任意实施方式中，所述负极活性材料包括碳元素和能与Li发生合金化反应的元素。
在本申请的任意实施方式中，所述负极活性材料中的所述碳元素的质量百分含量为20wt％-80wt％，可选为30wt％-70wt％。
在本申请的任意实施方式中，所述负极活性材料中的所述能与Li发生合金化反应的元素的质量百分含量为20wt％-80wt％，可选为30wt％-70wt％。
当负极活性材料中的碳元素和/或能与Li发生合金化反应的元素的含量在上述范围内时，有利于负极活性材料兼顾高比容量和高导电性。
在本申请的任意实施方式中，所述负极活性材料还包括其他元素，所述其他元素包括氧元素、金属元素和氮元素中的一种或几种。
在本申请的任意实施方式中，所述负极活性材料中的所述其他元素的质量百分含量之和为小于等于20wt％，可选为小于等于10wt％。
在本申请的任意实施方式中，所述碳基体的首次库伦效率为≥75％，可选为75％-87％。由此有利于提升负极活性材料的首次库伦效率。
在本申请的任意实施方式中，所述碳基体在16MPa压力下的粉末电阻率为≤5×10 - 2Ω·cm，可选为≤3.5×10 -2Ω·cm。由此有利于提升负极活性材料的导电性。
在本申请的任意实施方式中，所述碳基体的BET比表面积为50m 2/g-1000m 2/g，可选为100m 2/g-700m 2/g。由此有利于负极活性材料具有合适的BET比表面积，从而能够降低负极活性材料表面活性、减少界面副反应、降低SEI膜成膜消耗，进而能够提升二次电池的首次库伦效率和循环性能。
在本申请的任意实施方式中，所述负极活性材料的石墨化度为≥65％，可选为65％-87％。由此，有利于负极活性材料更好地兼顾高首次库伦效率、高导电性以及良好的循环稳定性。
在本申请的任意实施方式中，所述负极活性材料的首次库伦效率为≥92％，可选为92％-95％。由此能够减少活性离子的不可逆消耗，提升二次电池的容量发挥特性和循环性能。
在本申请的任意实施方式中，所述负极活性材料的体积粒径Dv50为3μm-50μm，可选为5μm-20μm。
在本申请的任意实施方式中，所述负极活性材料的体积粒径Dv90为≤60μm，可选为20μm-50μm。
在本申请的任意实施方式中，所述负极活性材料的径距(Dv90-Dv10)/Dv50为1.0-3.0，可选为1.0-2.0。
负极活性材料的体积粒径Dv50、体积粒径Dv90以及径距(Dv90-Dv10)/Dv50中的至少一者在上述范围内时，有助于降低负极活性材料的表面活性、减少界面副反应、降低SEI膜成膜消耗，还有利于提升活性离子和电子传输性能，从而能够进一步提升二次电池的循环性能。
在本申请的任意实施方式中，所述负极活性材料的BET比表面积为2m 2/g-100m 2/g，可选为2m 2/g-30m 2/g。负极活性材料的BET比表面积在上述范围内时，有助于降低表面活 性、减少界面副反应、降低SEI膜成膜消耗，从而能够提升二次电池的首次库伦效率和循环性能。
在本申请的任意实施方式中，所述负极活性材料在16MPa压力下的粉末电阻率为≤5×10 -1Ω·cm，可选为≤2×10 -1Ω·cm。由此负极活性材料具有良好的导电性，有利于提升二次电池的循环性能和倍率性能。
本申请第二方面提供一种负极活性材料的制备方法，包括如下步骤：步骤1，提供石墨化度为小于等于87％，可选为65％-87％，且包括多个孔结构的碳基体；步骤2，将填充材料分散至所述碳基体的孔结构中，即得到负极活性材料，其中，所述负极活性材料包括碳基体以及填充材料，所述碳基体包括多个孔结构，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料包括能与Li发生合金化反应的元素中的一种或几种，可选地，所述能与Li发生合金化反应的元素包括硅元素、锡元素和锗元素中的一种或几种。
在本申请的任意实施方式中，在步骤1中，所述碳基体通过以下方法制备：将包括多个孔结构的碳源置于高温炉中，在保护气体气氛、1600℃-2400℃下进行石墨化处理，结束后即得到碳基体。由此能够得到石墨化度为小于等于87％，可选为65％-87％，且包括多个孔结构的碳基体。
在本申请的任意实施方式中，所述石墨化处理的保温时间为1h-12h。
在本申请的任意实施方式中，所述碳源包括选自硬碳、石油焦、沥青焦、生物质碳和树脂碳中的一种或几种。
通过将包括多个孔结构的碳源在一定温度下进行石墨化处理，一方面能够减少碳源中的微孔，提高后续填充材料的分散均匀性，另一方面能够去除碳源表面的残键，减少碳源中含氧官能团的含量，减少电解液副反应，从而有利于提升所获得的碳基体的首次库伦效率、导电性以及高温性能，进而能够使二次电池具有良好的循环性能。
在本申请的任意实施方式中，在步骤1中，所述碳基体的首次库伦效率为≥75％，可选为75％-87％。
在本申请的任意实施方式中，在步骤1中，所述碳基体在16MPa压力下的粉末电阻率为≤5×10 -2Ω·cm，可选为≤3.5×10 -2Ω·cm。
在本申请的任意实施方式中，在步骤1中，所述碳基体的BET比表面积为50m 2/g-1000m 2/g，可选为100m 2/g-700m 2/g。
在本申请的任意实施方式中，在步骤1中，所述碳基体的体积粒径Dv50为3μm-50μm，可选为5μm-20μm。
在本申请的任意实施方式中，在步骤2中，将填充材料分散至所述碳基体的孔结构中的工艺包括液相沉积工艺和气相沉积工艺，可选为气相沉积工艺。与液相沉积工艺相比，气相沉积工艺有利于将填充材料更好地沉积并均匀分散在碳基体的孔结构中，并可以避免填充材料出现团聚问题和/或大量沉积在碳基体表面的问题。此外，气相沉积工艺发展比较成熟，易于进行工业化量产。
在本申请的任意实施方式中，所述气相沉积工艺包括化学气相沉积工艺和物理气相沉积工艺，可选为化学气相沉积工艺。
在本申请的任意实施方式中，在步骤2中，将填充材料分散至所述碳基体的孔结构中 的步骤包括如下步骤：将所述碳基体置于反应炉内，通入含有能与Li发生合金化反应的元素的源的第一混合气并在第一温度T 1下沉积第一时间t 1，结束后即得到负极活性材料。
在本申请的任意实施方式中，所述第一混合气包括所述能与Li发生合金化反应的元素的源和保护气体，可选地，所述第一混合气中的所述能与Li发生合金化反应的元素的源的体积占比为10％-50％。
在本申请的任意实施方式中，所述第一混合气还进一步包括碳源气体。
在本申请的任意实施方式中，所述能与Li发生合金化反应的元素的源与所述碳源气体的体积比为大于等于0.5:1，可选为(2-10):1。
在本申请的任意实施方式中，所述第一混合气中的所述碳源气体的体积占比为≤20％，可选为5％-20％。
在本申请的任意实施方式中，所述反应炉内的压力为高于大气压200Pa-600Pa。
在本申请的任意实施方式中，所述第一混合气的总气体流量为0.5L/min-20L/min。
在本申请的任意实施方式中，所述第一温度T 1为400℃-1000℃。
在本申请的任意实施方式中，所述第一时间t 1为1h-12h。
通过调节第一混合气的组成比例、第一混合气的总气体流量、第一温度和第一时间等中的至少一者在上述范围内，有利于在碳基体的孔结构中沉积填充材料，同时还有利于调节填充材料的结晶度和/或晶粒尺寸在合适范围内。
在本申请的任意实施方式中，所述方法还包括步骤3：在步骤2所获得的负极活性材料的至少部分表面形成包覆层，所述包覆层包括碳材料、导电聚合物、金属氧化物和金属硫化物中的一种或几种。
在本申请的任意实施方式中，所述形成包覆层的步骤包括以下步骤：将步骤2所获得的负极活性材料置于反应炉内，通入含有碳源气体的第二混合气，并在第二温度T 2下沉积第二时间t 2，结束后得到碳包覆的负极活性材料。
在本申请的任意实施方式中，所述第二混合气包括碳源气体和保护气体，可选地，所述第二混合气中的所述碳源气体的体积占比V 2为5％-50％。
在本申请的任意实施方式中，所述第二混合气的总气体流量为0.5L/min-20L/min。
在本申请的任意实施方式中，所述第二温度T 2为700℃-850℃。
在本申请的任意实施方式中，所述第二时间t 2为1h-6h。
在步骤3中，通过调节第二混合气的组成比例、第二混合气的总气体流量、第二温度和第二时间等中的至少一者在上述范围内，有利于形成合适厚度的包覆层，避免包覆层过厚而降低负极活性材料的比容量。
本申请第三方面提供一种二次电池，包括负极极片，所述负极极片包括本申请第一方面的负极活性材料或通过本申请第二方面的方法制备得到的负极活性材料。
本申请第四方面提供一种用电装置，包括本申请第三方面的二次电池。
本申请的发明人在研究中发现，通过将具有高容量优势的填充材料设置在具有低石墨化度的碳基体的孔结构中，能够使获得的负极活性材料兼顾高容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性，并且还能使二次电池兼顾高能量密度、高首次库伦效率和长循环寿命。本申请的用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的电池单体的一实施方式的示意图。
图2是本申请的电池单体的一实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
在附图中，附图未必按照实际的比例绘制。附图标记说明如下：1电池包，2上箱体，3下箱体，4电池模块，5电池单体，51壳体，52电极组件，53盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的负极活性材料及其制备方法、以及包含其的二次电池及用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案，并且这样的技术方案应被认为包含在本申请的公开内容中。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案，并且这样的技术方案应被认为包含在本申请的公开内容中。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步 骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
如果没有特别的说明，在本申请中，术语“第一”、“第二”等是用于区别不同对象，而不是用于描述特定顺序或主次关系。
在本申请中，术语“多个”、“几个”、“多种”、“几种”是指两个或两种以上。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。
除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测试方法进行测定，例如，可以按照本申请给出的测试方法进行测定。
为了满足对二次电池能量密度的更高要求，非碳类材料，例如硅基材料、锡基材料和锗基材料等，由于具有高理论比容量而引起人们广泛关注。硅具有高达4200mAh/g的理论比容量，锡具有高达994mAh/g的理论比容量，锗具有高达1600mAh/g的理论比容量，由此可以显著提高二次电池的能量密度。
但是，与石墨储能机理不同，非碳类材料，例如硅基材料、锡基材料和锗基材料等，是通过与金属(例如锂、钠等)发生合金化反应形成合金而进行储能，由此导致在充放电过程中存在巨大的体积效应，易造成颗粒破碎、粉化，进而导致负极膜层出现粉化问题，容易与集流体失去电接触，导致活性离子的脱嵌过程不能顺利进行，显著增加不可逆容量。此外，巨大的体积效应还会导致负极活性材料颗粒表面的固态电解质界面(SEI)膜反复破坏与重建，进一步增加了活性离子的不可逆消耗，最终影响二次电池的容量；同时，随着充放电过程的进行，负极活性材料颗粒表面的SEI膜越来越厚，由此使得二次电池的阻抗不断增加。再者，负极活性材料颗粒表面不稳定的SEI膜还会使得负极活性材料与电解液直接接触，由此进一步增加界面副反应和不可逆容量。
因此，上述非碳类材料作为负极活性材料使用时通常存在不可逆容量高、首次库伦效率低和体积膨胀大的缺陷，由此导致二次电池的实际容量损失大且循环寿命差。此外，硅还是一种半导体材料，其本征电导率较低、导电性较差，由此导致二次电池的电化学性能进一步变差。
鉴于此，本申请的发明人通过大量研究提出一种新型的负极活性材料，其能兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性，并且还能使二次电池兼顾高能量密度、高首次库伦效率和长循环寿命。
负极活性材料
本申请实施方式第一方面提供一种负极活性材料。所述负极活性材料包括碳基体以 及填充材料，所述碳基体的石墨化度为小于等于87％，所述碳基体包括多个孔结构，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料包括能与Li发生合金化反应的元素中的一种或几种。
填充材料包括能与Li发生合金化反应的元素中的一种或几种，由此可以贡献较高的容量，弥补碳基体容量低的缺陷，但是其存在严重的体积效应，会影响电化学性能的发挥。
在现有技术的研究中，为了克服填充材料体积膨胀大的缺陷，目前采用的方法是将其通过沉积等工艺设置在包括多个孔结构的碳基体或者天然石墨中。但是，目前采用的包括多个孔结构的碳基体多是通过造孔剂，例如碱性溶液刻蚀造孔得到，碳基体本身为非石墨化碳(或者无定形碳)，由此存在不可逆容量高、首次库伦效率低和导电性差的缺陷；而天然石墨本身具有孔结构，由此也可以作为沉积的基底材料，并且具有导电性优良的优势，但是天然石墨孔结构不规则导致填充材料分散均匀性很差，此外，天然石墨还存在结构稳定性差、体积膨胀大和循环性能差的缺陷。
因此，目前现有技术采用的方法并不能使获得的负极活性材料兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性。
本申请的发明人在研究中发现，通过将具有高比容量优势的填充材料设置在具有低石墨化度(大于0且小于等于87％)的碳基体的孔结构中，能够使获得的负极活性材料兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性，并且还能使二次电池兼顾高能量密度、高首次库伦效率和长循环寿命。本申请的碳基体的石墨化度为小于等于87％，与上述通过造孔剂造孔得到的碳基体相比，具有导电性高和首次库伦效率高的优势，与天然石墨相比，具有体积膨胀小和循环稳定性高的优势。因此，本申请提供的负极活性材料能充分发挥填充材料高比容量的优势，还能弥补填充材料导电性差、首次库伦效率低的缺陷；此外，填充材料的至少一部分位于碳基体的孔结构中，由此通过碳基体还可以降低填充材料的体积膨胀。
在本申请中，所述碳基体的石墨化度为小于等于87％，例如可以小于等于85％，小于等于80％，小于等于75％，小于等于70％。当碳基体的石墨化度大于87％时，碳基体在充放电过程中的体积膨胀大、结构稳定性差，由此会影响负极活性材料的循环稳定性和循环寿命。碳基体的石墨化度降低，其结构稳定性提升，有利于提升负极活性材料的循环稳定性，延长二次电池的循环寿命。
本申请的发明人在进一步研究中还注意到，碳基体的石墨化度也不宜太低，此时其首次库伦效率和导电性较差，由此会导致对负极活性材料的首次库伦效率和导电性的改善效果变得不明显。例如，所述碳基体的石墨化度还可为大于等于10％，大于等于20％，大于等于30％，大于等于40％，大于等于45％，大于等于50％，大于等于55％，大于等于60％，大于等于65％。
在一些实施例中，所述碳基体的石墨化度可为40％-87％，50％-87％，60％-87％，65％-87％，65％-85％，65％-82％或65％-80％。由此，有利于负极活性材料更好地兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性。
在一些实施例中，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料与所述碳基体之间具有空隙。当填充材料与碳基体之间具有空隙时，该部分 孔隙可以作为容纳填充材料体积膨胀的空间，以缓冲填充材料膨胀过程中产生的应力，由此能够进一步降低颗粒破碎、粉化的概率。
在一些实施例中，可选地，所述能与Li发生合金化反应的元素包括硅元素、锡元素和锗元素中的一种或几种。由此有利于负极活性材料具有高比容量优势。
在一些实施例中，所述填充材料包括硅基材料、锡基材料和锗基材料中的一种或几种，可选地包括硅基材料。
在本申请的中，术语“硅基材料”是指包含硅元素的化合物。在一些实施例中，所述硅基材料可包括单质硅、硅氧化物、硅碳材料、硅氮复合物和硅合金中的一种或几种。
在本申请的中，术语“锡基材料”是指包含锡元素的化合物。在一些实施例中，所述锡基材料可包括单质锡、锡氧化物、锡硫化物、锡磷化物、锡复合氧化物、锡碳材料和锡合金材料中的一种或几种。锡复合氧化物是指在锡氧化物中引入了一些玻璃相的金属和/或非金属氧化物。
在本申请的中，术语“锗基材料”是指包含锗元素的化合物。在一些实施例中，所述锗基材料可包括单质锗、锗氧化物、锗碳材料、锗合金材料和锗酸盐中的一种或几种。
在一些实施例中，所述填充材料可包括晶态的填充材料和/或非晶态的填充材料。
在一些实施例中，所述填充材料包括晶态的硅基材料和/或非晶态的硅基材料。硅基材料具有高比容量优势，有利于提高二次电池的能量密度。可选地，所述填充材料包括晶态的单质硅和/或非晶态的单质硅。
在一些实施例中，所述晶态的填充材料的晶粒尺寸为≤100nm，例如可以为≤80nm，≤70nm，≤60nm，≤50nm，≤40nm，≤30nm，≤20nm。可选地，所述晶态的填充材料的晶粒尺寸为2nm-50nm，2nm-40nm，2nm-30nm或2nm-20nm。
晶态的填充材料的晶粒尺寸较大时，有利于提升二次电池的首次库伦效率但是对于二次电池的循环性能和存储性能不利。因此，当晶态的填充材料具有合适的晶粒尺寸时，既能提升二次电池的首次库伦效率，同时又能避免对二次电池的循环性能和存储性能产生较大不利影响。
晶态的填充材料的晶粒尺寸为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以采用高分辨透射电镜(High Resolution Transmission Electron Microscope，HRTEM)进行测试和量取。
在一些实施例中，所述填充材料可通过气相沉积工艺得到。例如，所述填充材料可包括气相沉积的硅基材料、锡基材料和锗基材料中的一种或几种，可选地，所述填充材料包括气相沉积硅基材料，更可选地，所述填充材料包括气相沉积硅。所述气相沉积工艺包括化学气相沉积工艺和物理气相沉积工艺，可选为化学气相沉积工艺，例如可以为热化学气相沉积工艺、等离子体增强化学气相沉积工艺、微波等离子体辅助化学气相沉积工艺中的任一种。与液相沉积工艺相比，气相沉积工艺有利于将填充材料更好地沉积并均匀分散在碳基体的孔结构中，并可以避免填充材料出现团聚问题和/或大量沉积在碳基体表面的问题。此外，气相沉积工艺发展比较成熟，易于进行工业化量产。
在一些实施例中，在所述负极活性材料通过X射线衍射仪测定的X射线衍射谱图中， 所述负极活性材料包括在26.4°处的(002)晶面峰和在28.6°处的(111)晶面峰，并且(002)晶面峰的半峰宽与(111)晶面峰的半峰宽的比值为0.2-50，例如可以为0.2，0.5，1，2，5，10，15，20，25，30，35，40，45，50或以上任何数值所组成的范围。可选地，(002)晶面峰的半峰宽与(111)晶面峰的半峰宽的比值为0.2-20。
(002)晶面峰的半峰宽和(111)晶面峰的半峰宽可以参照JIS K 0131-1996，采用X射线衍射仪(如Bruker D8 Discover)计算晶体晶胞参数，采用重心法寻峰获取2个平行样的C 002和Si 111峰位，测试角度范围可为20°-80°。
(002)晶面峰的半峰宽可以表征碳基体中(002)晶面的排列完整性，(111)晶面峰的半峰宽可以表征填充材料中单质硅的含量以及单质硅的晶粒尺寸。通过控制(002)晶面峰的半峰宽与(111)晶面峰的半峰宽在合适的范围内，可以使碳基体具有合适的石墨化度，并且使填充材料具有合适的晶粒尺寸，从而有利于负极活性材料兼顾高比容量、高首次库伦效率、低体积膨胀、高导电性以及良好的循环稳定性。
在一些实施例中，所述负极活性材料还包括包覆层，所述包覆层位于所述碳基体的至少部分表面。包覆层可以阻止填充材料与电解液直接接触，从而能够减少电解液副反应、降低活性离子消耗，提高二次电池的循环性能；同时还可以提升负极浆料的稳定性，避免填充材料与溶剂水等反应而导致负极浆料加工难度增加。此外，包覆层还可以起到缓冲填充材料体积膨胀的作用，由此还有利于改善负极活性材料的结构稳定性，提升二次电池的电化学性能。
在一些实施例中，可选地，所述包覆层包括碳材料、导电聚合物、金属氧化物和金属硫化物中的一种或几种。
在一些实施例中，所述碳材料包括硬碳、软碳、石墨烯、碳纤维和碳纳米管中的一种或几种。
在一些实施例中，所述导电聚合物包括聚苯胺、聚吡咯和聚噻吩中的一种或几种。
在一些实施例中，所述金属氧化物包括氧化铁、氧化锌、氧化锡、氧化铜和氧化钛中的一种或几种。
在一些实施例中，所述金属硫化物包括硫化锡、硫化钼、硫化钛、硫化铁和硫化铜中的一种或几种。
在一些实施例中，所述包覆层包括碳材料。由此，包覆层除了可以阻止填充材料与电解液直接接触、缓冲填充材料的体积膨胀之外，还可以贡献部分容量，提高负极活性材料的比容量。此外，包覆层包括碳材料时，还有助于提升填充材料，特别是硅基材料的导电性，进而有利于改善负极活性材料的容量发挥特性。
在一些实施例中，所述包覆层的厚度为≤100nm，可选为10nm-100nm。包覆层的厚度在上述范围内时，包覆层的完整性更高，能更有效地避免填充材料与电解液接触，从而有利于减少电解液副反应，使负极活性材料兼顾高比容量、高首次库伦效率和低体积膨胀。包覆层的厚度大于100nm时，包覆层的完整性更好，但是脆性增加，反复充放电过程中更易出现破碎、粉化；此外，负极活性材料的比容量降低。
在一些实施例中，所述负极活性材料包括碳元素和能与Li发生合金化反应的元素。
在一些实施例中，所述负极活性材料中的所述碳元素的质量百分含量为20wt％-80wt％，例如可以为20wt％，25wt％，30wt％，35wt％，40wt％，45wt％，50wt％， 55wt％，60wt％，65wt％，70wt％，75wt％，80wt％或以上任何数值组成的范围。可选地，所述负极活性材料中碳元素的质量百分含量为30wt％-70wt％。所述碳元素的分布区域不受具体限制，例如可以位于所述碳基体、所述填充材料和所述包覆层中的至少一者中。
在一些实施例中，所述负极活性材料中的所述能与Li发生合金化反应的元素的质量百分含量为20wt％-80wt％，例如可以为20wt％，25wt％，30wt％，35wt％，40wt％，45wt％，50wt％，55wt％，60wt％，65wt％，70wt％，75wt％，80wt％或以上任何数值组成的范围。可选地，所述负极活性材料中的所述能与Li发生合金化反应的元素的质量百分含量为30wt％-70wt％。可选地，所述能与Li发生合金化反应的元素包括硅元素。
当负极活性材料中的碳元素和/或能与Li发生合金化反应的元素的含量在上述范围内时，有利于负极活性材料兼顾高比容量和高导电性。
在一些实施例中，所述负极活性材料除包括碳元素和能与Li发生合金化反应的元素之外，还包括其他元素，所述其他元素包括氧元素、金属元素和氮元素中的一种或几种。所述其他元素的分布区域不受具体限制，例如可以位于所述包覆层、所述填充材料和所述碳基体中的至少一者中。
在一些实施例中，可选地，所述负极活性材料中的所述其他元素的质量百分含量之和为小于等于20wt％，更可选为小于等于10wt％，小于等于5wt％。
在一些实施例中，所述碳基体的首次库伦效率为≥75％，可选为75％-87％。由此有利于提升负极活性材料的首次库伦效率。
在一些实施例中，所述碳基体在16MPa压力下的粉末电阻率为≤5×10 -2Ω·cm，可选为≤3.5×10 -2Ω·cm。由此有利于提升负极活性材料的导电性。
在一些实施例中，所述碳基体的BET比表面积为50m 2/g-1000m 2/g，可选为100m 2/g-700m 2/g。由此有利于负极活性材料具有合适的BET比表面积，从而能够降低负极活性材料表面活性、减少界面副反应、降低SEI膜成膜消耗，进而能够提升二次电池的首次库伦效率和循环性能。
在一些实施例中，所述负极活性材料的石墨化度为≥65％，可选为65％-87％。由此，有利于负极活性材料更好地兼顾高首次库伦效率、高导电性以及良好的循环稳定性。
在一些实施例中，所述负极活性材料的首次库伦效率为≥92％，可选为92％-95％。由此能够减少活性离子的不可逆消耗，提升二次电池的容量发挥特性和循环性能。
在一些实施例中，所述负极活性材料的体积粒径Dv50为3μm-50μm，可选为5μm-20μm。
在一些实施例中，所述负极活性材料的体积粒径Dv90为≤60μm，可选为20μm-50μm。
在一些实施例中，所述负极活性材料的径距(Dv90-Dv10)/Dv50为1.0-3.0，可选为1.0-2.0。
负极活性材料的体积粒径Dv50、体积粒径Dv90以及径距(Dv90-Dv10)/Dv50中的至少一者在上述范围内时，有助于降低负极活性材料的表面活性、减少界面副反应、降低SEI膜成膜消耗，还有利于提升活性离子和电子传输性能，从而能够进一步提升二次电池的循环性能。
在一些实施例中，所述负极活性材料的BET比表面积为2m 2/g-100m 2/g，可选为2m 2/g-30m 2/g，2m 2/g-20m 2/g。负极活性材料的BET比表面积在上述范围内时，有助于降低表面活性、减少界面副反应、降低SEI膜成膜消耗，从而能够提升二次电池的首次库伦效率和循环性能。
在一些实施例中，所述负极活性材料在16MPa压力下的粉末电阻率为≤5×10 -1Ω·cm，可选为≤2×10 -1Ω·cm。由此负极活性材料具有良好的导电性，有利于提升二次电池的循环性能和倍率性能。
在本申请中，材料(例如负极活性材料、碳基体等)的体积粒径Dv10、Dv50、Dv90为本领域公知的含义，其分别表示材料累计体积分布百分数达到10％、50％、90％时所对应的粒径，可以用本领域已知的仪器及方法进行测定。例如可以参照GB/T 19077-2016，采用激光粒度分析仪方便地测定。测试仪器可以为英国马尔文仪器有限公司的Mastersizer3000型激光粒度分析仪。
在本申请中，材料(例如负极活性材料、碳基体等)的BET比表面积为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出，氮气吸附比表面积分析测试可以通过美国Micromeritics公司的TRISTAR II 3020型比表面积与孔隙度分析仪进行。
在本申请中，材料(例如负极活性材料、碳基体等)的粉末电阻率为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以将一定质量的粉末样品置于电阻率测试仪的加料杯中，施加一定压力，然后手动采集数据，记录样品在不同压力下的粉末电阻率测试结果。在本申请中，测试压力可为16MPa。
在本申请中，材料(例如负极活性材料、碳基体等)的石墨化度为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参照JIS K 0131-1996，采用X射线衍射仪(如Bruker D8 Discover)得到(002)晶面的层间距d 002，然后根据公式g＝(0.3440-d 002)/(0.3440-0.3354)×100％计算得出材料的石墨化度。
在本申请中，负极活性材料中各元素的含量可以用本领域公知的仪器及方法进行测定。例如，碳元素含量可以参照GB/T 20123-2006/ISO 15350:2000进行测试，测试仪器可以为HCS-140型红外碳硫分析仪。硅元素含量可以参照GB/T 20975.5-2020进行测试。负极活性材料中锡元素含量可以参照GB/T 20975.10-2020进行测试。锗元素含量可以参照GB/T 20127.6-2006进行测试。
制备方法
本申请实施方式第二方面提供一种负极活性材料的制备方法，其能制备本申请实施方式第一方面的负极活性材料。
所述方法包括如下步骤：步骤1，提供石墨化度为小于等于87％，可选为65％-87％，且包括多个孔结构的碳基体；步骤2，将填充材料分散至所述碳基体的孔结构中，即得到负极活性材料，其中，所述负极活性材料包括碳基体以及填充材料，所述碳基体包括多个孔结构，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料包括能与Li发生合金化反应的元素中的一种或几种，可选地，所述能与Li发生合金化反应的元素包括硅元素、锡元素和锗元素中的一种或几种。
在一些实施例中，在步骤1中，所述碳基体通过以下方法制备：将包括多个孔结构的碳源置于高温炉中，在保护气体气氛、1600℃-2400℃下进行石墨化处理，结束后即得到碳基体。例如，可以在1600℃，1700℃，1800℃，1900℃，2000℃，2100℃，2200℃，2300℃，2400℃或以上任何数值组成的范围内进行石墨化处理。由此能够得到石墨化度为小于等于87％，可选为65％-87％，且包括多个孔结构的碳基体。
石墨化温度过低时，所获得的碳基体仍为非石墨化碳(或无定形碳)，其不可逆容量高、首次库伦效率低且导电性差，由此会影响二次电池的首次库伦效率和循环性能；石墨化温度过高时，所获得的碳基体在充放电过程中的体积膨胀大、结构稳定性差，由此会影响负极活性材料的循环稳定性和二次电池的循环性能。
在一些实施例中，可选地，所述高温炉的升温速率为10℃/min以下，例如为8℃/min以下，5℃/min以下。
在一些实施例中，可选地，所述石墨化处理的保温时间为1h-12h，例如可以为1h，2h，3h，4h，5h，6h，7h，8h，9h，10h，11h，12h或以上任何数值组成的范围。
在一些实施例中，可选地，所述碳源包括选自硬碳、石油焦、沥青焦、生物质碳和树脂碳中的一种或几种。
在一些实施例中，可选地，所述高温炉为石墨化炉，例如箱式石墨化炉、艾奇逊石墨化炉、连续式石墨化炉和内串石墨化炉中的任一种。
在步骤1中，用于制备所述碳基体的碳源种类多、自然界储量大、价格低廉，并且所述碳基体的制备工艺简单。所述包括多个孔结构的碳源可以直接市购获得，或者按照本领域公知的方法制备获得，例如可以通过造孔剂，例如碱性溶液刻蚀造孔获得。
通过将包括多个孔结构的碳源在一定温度下进行石墨化处理，一方面能够减少碳源中的微孔，提高后续填充材料的分散均匀性，另一方面能够去除碳源表面的残键，减少碳源中含氧官能团的含量，减少电解液副反应，从而有利于提升所获得的碳基体的首次库伦效率、导电性以及高温性能，进而能够使二次电池具有良好的循环性能。
在一些实施例中，在步骤1中，所述碳基体的首次库伦效率为≥75％，可选为75％-87％。
在一些实施例中，在步骤1中，所述碳基体在16MPa压力下的粉末电阻率为≤5×10 - 2Ω·cm，可选为≤3.5×10 -2Ω·cm。
在一些实施例中，在步骤1中，所述碳基体的BET比表面积为50m 2/g-1000m 2/g，可选为100m 2/g-700m 2/g。
在一些实施例中，在步骤1中，所述碳基体的体积粒径Dv50为3μm-50μm，可选为5μm-20μm。
在一些实施例中，在步骤2中，将填充材料分散至所述碳基体的孔结构中的工艺包括液相沉积工艺和气相沉积工艺，可选为气相沉积工艺。与液相沉积工艺相比，气相沉积工艺有利于将填充材料更好地沉积并均匀分散在碳基体的孔结构中，并可以避免填充材料出现团聚问题和/或大量沉积在碳基体表面的问题。此外，气相沉积工艺发展比较成熟，易于进行工业化量产。
在一些实施例中，可选地，所述气相沉积工艺包括化学气相沉积工艺和物理气相沉积工艺，更可选为化学气相沉积工艺，例如可以为热化学气相沉积工艺、等离子体增强 化学气相沉积工艺、微波等离子体辅助化学气相沉积工艺中的任一种。
在一些实施例中，在步骤2中，将填充材料分散至所述碳基体的孔结构中的步骤包括如下步骤：将所述碳基体置于反应炉内，通入含有能与Li发生合金化反应的元素的源的第一混合气并在第一温度T 1下沉积第一时间t 1，结束后即得到负极活性材料。
在一些实施例中，可选地，所述第一混合气包括所述能与Li发生合金化反应的元素的源和保护气体。
在一些实施例中，可选地，所述第一混合气中的所述能与Li发生合金化反应的元素的源的体积占比为10％-50％，例如可以为10％，15％，20％，25％，30％，35％，40％，45％，50％或以上任何数值组成的范围。
在一些实施例中，所述第一混合气还可以包括碳源气体。
在一些实施例中，可选地，所述能与Li发生合金化反应的元素的源与所述碳源气体的体积比为大于等于0.5:1，可选为(2-10):1。所述能与Li发生合金化反应的元素的源与所述碳源气体的体积比在上述范围内时，有利于负极活性材料具有高比容量。二者的体积比过小时，所获得的填充材料中的碳元素的含量较高、能与Li发生合金化反应的元素的含量较低，进而导致对负极活性材料容量的提升效果变得不明显。
在一些实施例中，可选地，所述第一混合气中的所述碳源气体的体积占比为≤20％，更可选为5％-20％。此时有利于负极活性材料兼顾高比容量和高导电性。
在一些实施例中，可选地，所述第一混合气中的所述保护气体的体积占比为30％-90％，例如可以为35％，40％，45％，50％，55％，60％，65％，70％，75％，80％，85％，90％或以上任何数值组成的范围。
在一些实施例中，所述第一混合气的总气体流量可为0.5L/min-20L/min。例如可以为1L/min，2L/min，3L/min，4L/min，5L/min，6L/min，7L/min，8L/min，9L/min，10L/min，12L/min，14L/min，16L/min，18L/min，20L/min或以上任何数值组成的范围。
在一些实施例中，所述反应炉内的压力可为微正压，例如可为高于大气压200Pa-600Pa，由此有利于沉积工艺顺利进行。
在一些实施例中，所述反应炉包括但不限于沉积炉、回转炉、管式炉和流化床中的任一种。
在一些实施例中，所述第一温度T 1可为400℃-1000℃，例如可以为400℃，450℃，500℃，550℃，600℃，650℃，700℃，750℃，800℃，850℃，900℃，950℃，1000℃或以上任何数值组成的范围。
在一些实施例中，所述第一时间t 1可为1h-12h，例如可以为1h，2h，3h，4h，5h，6h，7h，8h，9h，10h，11h，12h或以上任何数值组成的范围。
在气相沉积工艺中，通过调节第一混合气的组成比例、第一混合气的总气体流量、第一温度和第一时间等中的至少一者在上述范围内，有利于在碳基体的孔结构中沉积填充材料，同时还有利于调节填充材料的结晶度和/或晶粒尺寸在合适范围内。
在一些实施例中，所述方法还包括步骤3：在步骤2所获得的负极活性材料的至少部分表面形成包覆层，所述包覆层包括碳材料、导电聚合物、金属氧化物和金属硫化物中的一种或几种。
在步骤2所获得的负极活性材料的至少部分表面形成包覆层的方法不受具体的限制， 可以根据包覆层的组成进行选择，例如可以采用固相包覆、液相包覆或气相包覆中的任一种。
在一些实施例中，所述形成包覆层的步骤包括以下步骤：将步骤2所获得的负极活性材料与包覆材料混合后经碳化处理得到。可选地，所述包覆材料包括沥青(例如煤沥青、石油沥青等)和高分子材料中的一种或几种。可选地，所述碳化处理的温度为500℃-1000℃。
在一些实施例中，所述形成包覆层的步骤包括以下步骤：将步骤2所获得的负极活性材料置于反应炉内，通入含有碳源气体的第二混合气，并在第二温度T 2下沉积第二时间t 2，结束后得到碳包覆的负极活性材料。
在一些实施例中，所述第二混合气包括碳源气体和保护气体，可选地，所述第二混合气中的所述碳源气体的体积占比V 2为5％-50％，例如可以为5％，10％，15％，20％，25％，30％，35％，40％，45％，50％或以上任何数值组成的范围。
在一些实施例中，所述第二混合气的总气体流量为0.5L/min-20L/min。例如可以为0.8L/min，1L/min，2L/min，3L/min，4L/min，5L/min，6L/min，7L/min，8L/min，9L/min，10L/min，12L/min，14L/min，16L/min，18L/min，20L/min或以上任何数值组成的范围。
在一些实施例中，所述第二温度T 2为700℃-850℃，例如可以为700℃，710℃，720℃，730℃，740℃，750℃，760℃，770℃，780℃，790℃，800℃，810℃，820℃，830℃，840℃，850℃或以上任何数值组成的范围。
在一些实施例中，所述第二时间t 2为1h-6h，例如可以为1h，1.5h，2h，2.5h，3h，3.5h，4h，4.5h，5h，5.5h，6h或以上任何数值组成的范围。
在步骤3中，通过调节第二混合气的组成比例、第二混合气的总气体流量、第二温度和第二时间等中的至少一者在上述范围内，有利于形成合适厚度的包覆层，避免包覆层过厚而降低负极活性材料的比容量。
在本申请中，术语“保护气体”包括氮气和稀有气体中的一种或几种，可选地，所述稀有气体可包括氩气、氦气等中的一种或几种。
在本申请中，术语“能与Li发生合金化反应的元素的源”是指能够形成本申请的填充材料的气体，例如可以包括硅源气体、锡源气体和锗源气体中的一种或几种。
硅源气体是指能够形成本申请的硅基材料的气体，可选地，所述硅源气体包括但不限于甲硅烷(H 4Si)、乙硅烷(H 6Si 2)、丙硅烷(H 8Si 3)、四氯化硅(Cl 4Si)、三氯硅烷(Cl 3HSi)、二氯硅烷(Cl 2H 2Si)、氯硅烷(ClH 3Si)、四氟化硅(F 4Si)、三氟硅烷(F 3HSi)、二氟硅烷(F 2H 2Si)、氟硅烷(FH 3Si)、六氯二硅烷(Cl 6Si 2)、五氯二硅烷(Cl 5HSi 2)、四氯二硅烷(Cl 4H 2Si 2，包括1,1,2,2-四氯二硅烷、1,1,1,2-四氯二硅烷)、三氯二硅烷(Cl 3H 3Si 2，包括1,1,2-三氯二硅烷、1,1,1-三氯二硅烷)、二氯二硅烷(Cl 2H 4Si 2，包括1,1-二氯二硅烷、1,2-二氯二硅烷)、一氯二硅烷(ClH 5Si 2)、六氟二硅烷(F 6Si 2)、五氟二硅烷(F 5HSi 2)、1,1,2,2-四氟二硅烷(F 4H 2Si 2)、1,1,1-三氟二硅烷(F 3H 3Si 2)、二氟二硅烷(F 2H 4Si 2，包括1,1-二氟二硅烷、1,2-二氟二硅烷)、一氟二硅烷(FH 5Si 2)、甲基硅烷、乙基硅烷、二甲基硅烷、三甲基硅烷、四甲基硅烷、甲基二硅烷、二甲基二硅烷、三甲基二硅烷、四甲基二硅烷、六甲基硅烷、甲基三氯硅烷、甲基 氯硅烷、氯乙基硅烷、二氯二甲基硅烷和二氯二乙基硅烷中的一种或几种。
锡源气体是指能够形成本申请的锡基材料的气体，可选地，所述锡源气体包括但不限于甲锡烷(H 4Sn)、Cl 4Sn、Cl 3HSn、Cl 2H 2Sn、ClH 3Sn、F 4Sn、F 3HSn、F 2H 2Sn和FH 3Sn中的一种或几种。
锗源气体是指能够形成本申请的锗基材料的气体，可选地，所述锗源气体包括但不限于甲锗烷(H 4Ge)、Cl 4Ge和F 4Ge中的一种或几种。
在本申请中，“碳源气体”是指能够形成碳材料的气体，可选地，所述碳源气体包括但不限于甲烷、乙烷、丙烷、异丙烷、丁烷、异丁烷、乙烯、丙烯、丁烯、乙炔、氯乙烷、氟乙烷、二氟乙烷、氯甲烷、氟甲烷、二氟甲烷、三氟甲烷、氯乙烯、氟乙烯、二氟乙烯、甲胺、甲醛、苯、甲苯、二甲苯、苯乙烯和苯酚中的一种或几种。
如果没有特别的说明，在本申请的制备方法中所使用的各原料及其仪器等均可以通过市购获得。
二次电池
本申请实施方式第三方面提供一种二次电池。
本申请的实施例或实施方式中所提到的二次电池是指包括一个或多个电池单体以提供更高的电压和容量的单一的物理模块。例如，本申请中所提到的二次电池可以包括电池单体、电池模块或电池包等。电池单体是组成二次电池的最小单元，其独自能够实现充放电的功能。本申请对电池单体的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的电池单体5。
在一些实施例中，电池单体包括电极组件，单体电池还可包括外包装。电极组件可通过卷绕工艺和/或叠片工艺由正极极片、负极极片以及隔离膜等制成，外包装可用于封装上述电极组件。外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)和聚丁二酸丁二醇酯(PBS)中的一种或几种。
在一些实施例中，如图2所示，外包装可包括壳体51和盖板53。壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。电极组件52封装于所述容纳腔。电池单体5所含电极组件52的数量可以为一个或多个，可根据需求来调节。
在本申请的一些实施例中，电池单体可以组装成电池模块，电池模块所含电池单体的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。图3是作为一个示例的电池模块4的示意图。如图3所示，在电池模块4中，多个电池单体5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电池单体5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个电池单体5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4 的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
本申请对二次电池种类没有特别的限制，例如，二次电池可以包括但不限于锂离子电池、钠离子电池等。
[负极极片]
在一些实施例中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面且包括负极活性材料的负极膜层。例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层设置在所述负极集流体的两个相对表面中的任意一者或两者上。
在一些实施例中，所述负极膜层包括本申请实施方式第一方面的负极活性材料或通过本申请实施方式第二方面所述的方法制备得到的负极活性材料。由此能使二次电池兼顾高能量密度、高首次库伦效率和长循环寿命。在一些实施例中，所述负极膜层还可以进一步包括除了上述负极活性材料以外的其他负极活性材料。在一些实施例中，所述其他负极活性材料包括但不限于天然石墨、人造石墨、软碳、硬碳、单质硅、硅氧化物、硅氮复合物、硅合金材料、单质锡、锡氧化物、锡合金材料、和钛酸锂中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的传统公知的材料。
在一些实施例中，所述负极膜层还可选地包括负极导电剂。本申请对所述负极导电剂的种类没有特别的限制，作为示例，所述负极导电剂可包括超导碳、导电石墨、乙炔黑、碳黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或几种。
在一些实施例中，所述负极膜层还可选地包括负极粘结剂。本申请对所述负极粘结剂的种类没有特别的限制，作为示例，所述负极粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或几种。
在一些实施例中，所述负极膜层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC-Na)、PTC热敏电阻材料等。
在一些实施例中，所述负极集流体可采用金属箔片或复合集流体。作为所述金属箔片的示例，可采用铜箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铜、铜合金、镍、镍合金、钛、钛合金、银和银合金中的一种或几种。作为示例，所述高分子材料基层可包括聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)和聚乙烯(PE)中的一种或几种。
所述负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。所述负极浆料通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
所述负极极片并不排除除了所述负极膜层之外的其他附加功能层。例如，在一些实施例中，本申请所述的负极极片还可以包括夹在所述负极集流体和所述负极膜层之间、设置于所述负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)；在一些实施 例中，本申请所述的负极极片还可以包括覆盖在所述负极膜层表面的保护层。
[正极极片]
在一些实施例中，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面且包括正极活性材料的正极膜层。例如，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极膜层设置于所述正极集流体的两个相对表面中的任意一者或两者上。
所述正极膜层包括正极活性材料，所述正极活性材料可采用本领域公知的用于二次电池的正极活性材料。
当本申请的二次电池为锂离子电池时，所述正极活性材料可包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物的示例可包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其各自的改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池正极活性材料的传统公知的材料。
在一些实施例中，为了进一步提高二次电池的能量密度，用于锂离子电池的正极活性材料可以包括通式为Li aNi bCo cM dO eA f的锂过渡金属氧化物及其改性化合物中的一种或几种。0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，1≤e≤2，0≤f≤1，M包括选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti和B中的一种或几种，A包括选自N、F、S和Cl中的一种或几种。
作为示例，用于锂离子电池的正极活性材料可包括LiCoO 2、LiNiO 2、LiMnO 2、LiMn 2O 4、LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、LiNi 0.85Co 0.15Al 0.05O 2、LiFePO 4和LiMnPO 4中的一种或几种。
当本申请的二次电池为钠离子电池时，所述正极活性材料可包括但不限于含钠过渡金属氧化物、聚阴离子材料(如磷酸盐、氟磷酸盐、焦磷酸盐、硫酸盐等)、普鲁士蓝类材料中的一种或几种。
作为示例，用于钠离子电池的正极活性材料可包括NaFeO 2、NaCoO 2、NaCrO 2、NaMnO 2、NaNiO 2、NaNi 1/2Ti 1/2O 2、NaNi 1/2Mn 1/2O 2、Na 2/3Fe 1/3Mn 2/3O 2、NaNi 1/3Co 1/3Mn 1/3O 2、NaFePO 4、NaMnPO 4、NaCoPO 4、普鲁士蓝类材料和通式为X pM’ q(PO 4) rO xY 3-x的材料中的一种或几种。在通式X pM’ q(PO 4) rO xY 3-x中，0＜p≤4，0＜q≤2，1≤r≤3，0≤x≤2，X包括选自H +、Li +、Na +、K +和NH 4 +中的一种或几种，M’为过渡金属阳离子，可选为包括选自V、Ti、Mn、Fe、Co、Ni、Cu和Zn中的一种或几种，Y为卤素阴离子，可选为包括选自F、Cl和Br中的一种或几种。
在本申请中，上述各正极活性材料的改性化合物可以是对所述正极活性材料进行掺杂改性和/或表面包覆改性。
在一些实施例中，所述正极膜层还可选地包括正极导电剂。本申请对所述正极导电剂的种类没有特别的限制，作为示例，所述正极导电剂包括超导碳、导电石墨、乙炔黑、 碳黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或几种。
在一些实施例中，所述正极膜层还可选地包括正极粘结剂。本申请对所述正极粘结剂的种类没有特别的限制，作为示例，所述正极粘结剂可包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物和含氟丙烯酸酯类树脂中的一种或几种。
在一些实施例中，所述正极集流体可采用金属箔片或复合集流体。作为所述金属箔片的示例，可采用铝箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铝、铝合金、镍、镍合金、钛、钛合金、银和银合金中的一种或几种。作为示例，所述高分子材料基层可包括聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)和聚乙烯(PE)中的一种或几种。
所述正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
[电解质]
电解质在正极极片和负极极片之间起到传导活性离子的作用。本申请对所述电解质的种类没有具体的限制，可根据需求进行选择。例如，所述电解质可以包括选自固态电解质及液态电解质(即电解液)中的一种或几种。
在一些实施例中，所述电解质采用电解液，所述电解液包括电解质盐和溶剂。
当本申请的二次电池为锂离子电池时，作为示例，所述电解质盐可包括六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)和四氟草酸磷酸锂(LiTFOP)中的一种或几种。
当本申请的二次电池为钠离子电池，特别地，为钠离子二次电池时，所述电解质盐可包括六氟磷酸钠(NaPF 6)、四氟硼酸钠(NaBF 4)、高氯酸钠(NaClO 4)、六氟砷酸钠(NaAsF 6)、双氟磺酰亚胺钠(NaFSI)、双三氟甲磺酰亚胺钠(NaTFSI)、三氟甲磺酸钠(NaTFS)、二氟草酸硼酸钠(NaDFOB)、二草酸硼酸钠(NaBOB)、二氟磷酸钠(NaPO 2F 2)、二氟二草酸磷酸钠(NaDFOP)和四氟草酸磷酸钠(NaTFOP)中的一种或几种。
所述溶剂的种类不受具体的限制，可根据实际需求进行选择。在一些实施例中，作为示例，所述溶剂可包括碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)和二乙砜(ESE)中的一种或几种。
在一些实施例中，所述电解液中还可选地包括添加剂。例如，所述添加剂可以包括 负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温功率性能的添加剂等。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。所述隔离膜设置在所述正极极片和所述负极极片之间，主要起到防止正极和负极短路的作用，同时可以使活性离子通过。本申请对所述隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施例中，所述隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯和聚偏二氟乙烯中的一种或几种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
[制备方法]
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到电池单体。多个电池单体还可以进一步经由串联或并联或混联组成电池模块。多个电池模块还可以经由串联或并联或混联形成电池包。在一些实施例中，多个电池单体还可以直接组成电池包。
用电装置
本申请实施方式还提供一种用电装置，所述用电装置包括本申请的二次电池。所述二次电池可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以但不限于是移动设备(例如手机、平板电脑、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述用电装置可以根据其使用需求来选择二次电池的具体类型，例如电池单体、电池模块或电池包。
图6是作为一个示例的用电装置的示意图。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包或电池模块作为电源。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用电池单体作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
(1)负极活性材料的制备
步骤1：选取1kg市售多孔生物质碳(BET表面积为1545m 2/g、体积粒径Dv50为约6μm，也可以通过造孔剂造孔获得)置于石墨化炉内，在氮气保护条件下以5℃/min的速率升温至2400℃进行石墨化处理，并在2400℃下保温2h，结束后冷却至室温获得石墨化度为87％、首次库伦效率为85％、粉末电阻率为5.5×10 -3Ω·cm、BET比表面积为100m 2/g的碳基体。
步骤2：将上述碳基体作为基底置于气相沉积炉内，以5℃/min的速率升温至500℃，按照20％甲硅烷+80％氮气(体积比)通入第一混合气，总气体流量为5L/min，反应炉内的压力为高于大气压200Pa，沉积反应8h。
步骤3：关闭第一混合气，再以5℃/min的速率升温至800℃，按照40％乙炔+60％氮气(体积比)通入第二混合气，总气体流量为0.8L/min，沉积反应2h，结束后冷却、出料、过325目筛，得到负极活性材料。
(2)二次电池(全电池)的制备
负极极片的制备：将上述制备的负极活性材料与导电剂导电碳黑和碳纳米管、粘结剂聚丙烯酸按照质量比95:1.9:0.1:3混合均匀后，加入至溶剂去离子水中，在快速搅拌机作用下搅拌至体系呈均一状，获得固含量为45％的负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上并在85℃下烘干、冷压后得到负极极片。
正极极片的制备：将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、导电剂碳黑(Super P)、粘结剂聚偏氟乙烯(PVDF)按质量比97:1:2在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片。
电解液的制备：将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)按照体积比20:20:60混合均匀作为有机溶剂，然后将LiPF 6溶解在上述有机溶剂中，并加入氟代碳酸乙烯酯(FEC)，电解液中LiPF 6的浓度为1mol/L，FEC的质量百分含量为5wt％。
隔离膜的制备：采用Celgard 2400隔离膜。
二次电池的制备：将正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件置于外包装中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
(3)扣式电池(半电池)的制备
将上述制备的负极活性材料与导电剂导电碳黑、粘结剂聚丙烯酸按照质量比8:1:1混合均匀后，加入至溶剂去离子水中，在快速搅拌机作用下搅拌至体系呈均一状，获得固含量为45％的负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上并在85℃下烘干、冷压后得到电极极片。以金属锂片作为对电极，采用Celgard 2400隔离膜，并注入与上述制备二次电池时相同的电解液，组装得到扣式电池。
实施例2-24
二次电池和扣式电池的制备方法与实施例1类似，不同之处在于调整了负极活性材料的制备工艺参数，具体详见表1。
对比例1
二次电池和扣式电池的制备方法与实施例1类似，不同之处在于采用无定形碳包覆的 晶体硅作为负极活性材料，包覆层厚度为80nm。
步骤1：提供体积粒径Dv50为500nm的晶体硅颗粒。
步骤2：将上述晶体硅颗粒放入回转炉中，按照40％乙炔+60％氮气(体积比)通入混合气，总气体流量为0.8L/min，在800℃下沉积反应2h，结束后冷却、出料，获得无定形碳包覆的晶体硅材料。
对比例2
二次电池和扣式电池的制备方法与实施例1类似，不同之处在于调整了负极活性材料的制备工艺参数。
步骤1：将鳞片石墨进行机械粉碎、分级、球化、纯化处理，获得天然球形石墨。
步骤2：选取1kg天然球形石墨作为基底置于气相沉积炉内，以5℃/min的速率升温至500℃，按照20％甲硅烷+80％氮气(体积比)通入第一混合气，总气体流量为5L/min，反应炉内的压力为高于大气压200Pa，沉积反应8h。
步骤3：关闭第一混合气，再以5℃/min的速率升温至800℃，按照40％乙炔+60％氮气(体积比)通入第二混合气，总气体流量为0.8L/min，沉积反应2h，结束后冷却、出料、过325目筛，得到负极活性材料。
对比例3
二次电池和扣式电池的制备方法与实施例1类似，不同之处在于调整了负极活性材料的制备工艺参数，具体详见表1。
对比例4
二次电池和扣式电池的制备方法与实施例1类似，不同之处在于调整了负极活性材料的制备工艺参数。
步骤1：选取1kg多孔生物质碳直接作为碳基体，不进行石墨化处理。
步骤2：将上述碳基体作为基底置于气相沉积炉内，以5℃/min的速率升温至500℃，按照20％甲硅烷+80％氮气(体积比)通入第一混合气，总气体流量为5L/min，反应炉内的压力为高于大气压200Pa，沉积反应8h。
步骤3：关闭第一混合气，再以5℃/min的速率升温至800℃，按照40％乙炔+60％氮气(体积比)通入第二混合气，总气体流量为0.8L/min，沉积反应2h，结束后冷却、出料、过325目筛，得到负极活性材料。
测试部分
(1)碳基体和负极活性材料的石墨化度测试
参照JIS K 0131-1996，采用X射线衍射仪得到(002)晶面的层间距d 002，然后根据公式g＝(0.3440-d 002)/(0.3440-0.3354)×100％计算得出碳基体和负极活性材料的石墨化度。测试仪器可以采用Bruker D8 Discover X射线衍射仪。
(2)碳基体的首次库伦效率测试
将上述制备的碳基体与导电剂导电碳黑、粘结剂聚丙烯酸按照质量比8:1:1混合均匀后，加入至溶剂去离子水中，在快速搅拌机作用下搅拌至体系呈均一状，获得固含量为45％的负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上并在85℃下烘干、冷压后得到电极极片。以金属锂片作为对电极，采用Celgard 2400隔离膜，并注入与上述实施例1相同的电解液，组装得到扣式电池。
将扣式电池静置4h后放置于蓝电测试柜，以0.05C恒流放电至5mV，静置10min后，以50μA恒流放电至5mV，记录扣式电池的总放电容量；然后将扣式电池静置10min后，以0.1C恒流充电至2.0V，记录扣式电池的充电容量。碳基体的首次库伦效率＝充电容量/总放电容量。
(3)碳基体和负极活性材料的粉末电阻率测试
将一定质量的碳基体和负极活性材料粉末样品置于电阻率测试仪的加料杯中，施加一定压力，然后手动采集数据，记录样品在不同压力下的粉末电阻率测试结果。在本申请中，测试压力可为16MPa。
(4)碳基体的比表面积测试
参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出碳基体的比表面积。测试仪器可以采用美国Micromeritics公司的TRISTAR II 3020型比表面积与孔隙度分析仪。
(5)填充材料的晶粒尺寸测试
采用双束聚焦离子束-透射电镜(Dual Beam FIB-SEM)从负极活性材料颗粒中间区域截取样品，然后通过高分辨透射电镜(High Resolution Transmission Electron Microscope，HRTEM)测试填充材料的晶粒尺寸。
(6)负极活性材料中各元素的含量测试
参照GB/T 20123-2006/ISO 15350:2000测试负极活性材料中碳元素含量，测试仪器可以为HCS-140型红外碳硫分析仪。参照GB/T 20975.5-2020测试负极活性材料中硅元素含量。参照GB/T 20975.10-2020测试负极活性材料中锡元素含量。参照GB/T 20127.6-2006测试负极活性材料中锗元素含量。
(7)负极活性材料的X射线衍射谱图测试
参照JIS K 0131-1996，采用X射线衍射仪计算晶体晶胞参数，采用重心法寻峰获取2个平行样的C 002和Si 111峰位，测试角度范围可为20°-80°。从负极活性材料的X射线衍射谱图中，得到26.4°处的(002)晶面峰和28.6°处的(111)晶面峰的半峰宽。测试仪器可以采用Bruker D8 Discover X射线衍射仪。
(8)负极活性材料的首次库伦效率测试
将上述各实施例和对比例制备的扣式电池静置4h后放置于蓝电测试柜，以0.05C恒流放电至5mV，静置10min后，以50μA恒流放电至5mV，记录扣式电池的总放电容量即为嵌锂容量；然后将扣式电池静置10min后，以0.1C恒流充电至2V，记录扣式电池的充电容量即为脱锂容量。负极活性材料的首次库伦效率＝脱锂容量/嵌锂容量。
(9)二次电池的循环性能测试
在25℃下，将上述制备的二次电池以0.5C满充后再以1C满放，此为一个循环充放电过程，记录此时的放电容量，即为初始放电容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量，直至二次电池的放电容量衰减为初始放电容量的80％，用此时的循环圈数表征二次电池的循环性能。二次电池的循环圈数越高，循环性能越好。
表1
Figure PCTCN2022125432-appb-000001
Figure PCTCN2022125432-appb-000002
综合表2测试结果可知，将具有高比容量优势的填充材料，例如硅基材料、锡基材料、锗基材料等，设置在石墨化度为小于等于87％的碳基体的孔结构中，能够使获得的负极活性材料兼顾高比容量、高首次库伦效率、高导电性以及良好的循环稳定性，进而能使二次电池兼顾高能量密度、高首次库伦效率以及长循环寿命。综合实施例1-7的测试结果还可知，当碳基体的石墨化度为65％-87％时，制备的负极活性材料的导电性更好且首次库伦效率更高，可达到92％以上，并且二次电池还可具有更长的循环寿命。
本申请提供的负极活性材料中，填充材料的至少一部分位于碳基体的孔结构中，由此通过碳基体还可以降低填充材料的体积膨胀。对比例1采用碳包覆的晶体硅作为负极活性材料，晶体硅具有巨大的体积效应，而表面的碳层对晶体硅保护作用有限，并且在多次充放电后碳层即会出现破裂，进而导致SEI膜反复破坏与重建，增加了活性离子的不可逆消耗；并且随着充放电次数增加，SEI膜厚度也不断增加，进而二次电池的阻抗也会不断增加。因此，对比例1制备的二次电池的循环性能很差。
对比例2采用天然球形石墨作为碳基体，天然球形石墨本身具有孔结构，可以作为沉积的基底材料，并且具有导电性优良的优势，但是天然球形石墨的孔结构不规则，由此导致填充材料分散均匀性很差，此外天然球形石墨还存在结构稳定性差和体积膨胀大的缺陷，由此导致二次电池的循环性能很差，不能使二次电池兼顾高能量密度、高首次库伦效率以及长循环寿命。
对比例3在步骤1中对多孔生物质碳进行石墨化处理时的温度高于2400℃时，并且所获得的碳基体的石墨化度过高，此时制备的负极活性材料在充放电过程中的体积膨胀大且结构稳定性差，由此导致二次电池的循环性能很差，不能使二次电池兼顾高能量密度、高首次库伦效率以及长循环寿命。
对比例4直接采用未进行石墨化处理的多孔生物质碳作为碳基体，此时的碳基体为非石墨化碳，存在不可逆容量高、首次库伦效率低和导电性差的缺陷，由其制备的负极活性材料的首次库伦效率低且导电性很差，由此也不能使二次电池兼顾高能量密度、高首次库伦效率以及长循环寿命。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。
Figure PCTCN2022125432-appb-000003
Figure PCTCN2022125432-appb-000004

Claims (21)

  1. 一种负极活性材料，包括碳基体以及填充材料，其中，所述碳基体的石墨化度为小于等于87％，可选为65％-87％，所述碳基体包括多个孔结构，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料包括能与Li发生合金化反应的元素中的一种或几种，可选地，所述能与Li发生合金化反应的元素包括硅元素、锡元素和锗元素中的一种或几种。
  2. 根据权利要求1所述的负极活性材料，其中，所述填充材料包括硅基材料、锡基材料和锗基材料中的一种或几种，
    可选地，所述硅基材料包括单质硅、硅氧化物、硅碳材料、硅氮复合物和硅合金中的一种或几种；
    可选地，所述锡基材料包括单质锡、锡氧化物、锡硫化物、锡磷化物、锡复合氧化物、锡碳材料和锡合金材料中的一种或几种；
    可选地，所述锗基材料包括单质锗、锗氧化物、锗碳材料、锗合金材料和锗酸盐中的一种或几种。
  3. 根据权利要求1或2所述的负极活性材料，其中，所述填充材料包括晶态的填充材料和/或非晶态的填充材料，可选地包括晶态的硅基材料和/或非晶态的硅基材料，
    可选地，所述晶态的填充材料的晶粒尺寸为≤100nm，可选为2nm-50nm。
  4. 根据权利要求1-3任一项所述的负极活性材料，其中，所述填充材料包括气相沉积的硅基材料、锡基材料和锗基材料中的一种或几种，可选地包括气相沉积硅基材料。
  5. 根据权利要求1-4任一项所述的负极活性材料，其中，在所述负极活性材料通过X射线衍射仪测定的X射线衍射谱图中，所述负极活性材料包括在26.4°处的(002)晶面峰和在28.6°处的(111)晶面峰，并且(002)晶面峰的半峰宽与(111)晶面峰的半峰宽的比值为0.2-50，可选为0.2-20。
  6. 根据权利要求1-5任一项所述的负极活性材料，其中，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料与所述碳基体之间具有空隙。
  7. 根据权利要求1-6任一项所述的负极活性材料，其中，所述负极活性材料还包括包覆层，所述包覆层位于所述碳基体的至少部分表面，
    可选地，所述包覆层包括碳材料、导电聚合物、金属氧化物和金属硫化物中的一种或几种，更可选地包括碳材料；
    可选地，所述包覆层的厚度为≤100nm，更可选为10nm-100nm。
  8. 根据权利要求1-7任一项所述的负极活性材料，其中，所述负极活性材料包括碳元素和能与Li发生合金化反应的元素，
    可选地，所述负极活性材料中的所述碳元素的质量百分含量为20wt％-80wt％，更可选为30wt％-70wt％；
    可选地，所述负极活性材料中的所述能与Li发生合金化反应的元素的质量百分含量为20wt％-80wt％，更可选为30wt％-70wt％。
  9. 根据权利要求8所述的负极活性材料，其中，所述负极活性材料还包括其他元素，所述其他元素包括氧元素、金属元素和氮元素中的一种或几种，
    可选地，所述负极活性材料中的所述其他元素的质量百分含量之和为小于等于20wt％，更可选为小于等于10wt％。
  10. 根据权利要求1-9任一项所述的负极活性材料，其中，所述碳基体满足如下中的至少一者：
    (1)所述碳基体的首次库伦效率为≥75％，可选为75％-87％；
    (2)所述碳基体在16MPa压力下的粉末电阻率为≤5×10 -2Ω·cm，可选为≤3.5×10 - 2Ω·cm；
    (3)所述碳基体的BET比表面积为50m 2/g-1000m 2/g，可选为100m 2/g-700m 2/g。
  11. 根据权利要求1-10任一项所述的负极活性材料，其中，所述负极活性材料满足如下中的至少一者：
    (1)所述负极活性材料的石墨化度为≥65％，可选为65％-87％；
    (2)所述负极活性材料的首次库伦效率为≥92％，可选为92％-95％；
    (3)所述负极活性材料的体积粒径Dv50为3μm-50μm，可选为5μm-20μm；
    (4)所述负极活性材料的体积粒径Dv90为≤60μm，可选为20μm-50μm；
    (5)所述负极活性材料的径距(Dv90-Dv10)/Dv50为1.0-3.0，可选为1.0-2.0；
    (6)所述负极活性材料的BET比表面积为2m 2/g-100m 2/g，可选为2m 2/g-30m 2/g；
    (7)所述负极活性材料在16MPa压力下的粉末电阻率为≤5×10 -1Ω·cm，可选为≤2×10 -1Ω·cm。
  12. 一种负极活性材料的制备方法，包括如下步骤：步骤1，提供石墨化度为小于等于87％，可选为65％-87％，且包括多个孔结构的碳基体；步骤2，将填充材料分散至所述碳基体的孔结构中，即得到负极活性材料，其中，所述负极活性材料包括碳基体以及填充材料，所述碳基体包括多个孔结构，所述填充材料的至少一部分位于所述碳基体的孔结构中，并且所述填充材料包括能与Li发生合金化反应的元素中的一种或几种，可选地，所述能与Li发生合金化反应的元素包括硅元素、锡元素和锗元素中的一种或几种。
  13. 根据权利要求12所述的方法，其中，在步骤1中，所述碳基体通过以下方法制备：将包括多个孔结构的碳源置于高温炉中，在保护气体气氛、1600℃-2400℃下进行石墨化处理，结束后即得到碳基体，
    可选地，所述石墨化处理的保温时间为1h-12h；
    可选地，所述碳源包括选自硬碳、石油焦、沥青焦、生物质碳和树脂碳中的一种或几种。
  14. 根据权利要求12或13所述的方法，其中，在步骤1中，所述碳基体满足如下中的至少一者：
    (1)所述碳基体的首次库伦效率为≥75％，可选为75％-87％；
    (2)所述碳基体在16MPa压力下的粉末电阻率为≤5×10 -2Ω·cm，可选为≤3.5×10 - 2Ω·cm；
    (3)所述碳基体的BET比表面积为50m 2/g-1000m 2/g，可选为100m 2/g-700m 2/g；
    (4)所述碳基体的体积粒径Dv50为3μm-50μm，可选为5μm-20μm。
  15. 根据权利要求12-14任一项所述的方法，其中，在步骤2中，将填充材料分散至所述碳基体的孔结构中的工艺包括液相沉积工艺和气相沉积工艺，可选为气相沉积工 艺，
    可选地，所述气相沉积工艺包括化学气相沉积工艺和物理气相沉积工艺，更可选为化学气相沉积工艺。
  16. 根据权利要求15所述的方法，其中，在步骤2中，将填充材料分散至所述碳基体的孔结构中的步骤包括如下步骤：将所述碳基体置于反应炉内，通入含有能与Li发生合金化反应的元素的源的第一混合气并在第一温度T 1下沉积第一时间t 1，结束后即得到负极活性材料，
    可选地，所述第一混合气包括所述能与Li发生合金化反应的元素的源和保护气体，更可选地，所述第一混合气中的所述能与Li发生合金化反应的元素的源的体积占比为10％-50％；
    可选地，所述反应炉内的压力为高于大气压200Pa-600Pa；
    可选地，所述第一混合气的总气体流量为0.5L/min-20L/min；
    可选地，所述第一温度T 1为400℃-1000℃；
    可选地，所述第一时间t 1为1h-12h。
  17. 根据权利要求16所述的方法，其中，所述第一混合气还包括碳源气体，
    可选地，所述能与Li发生合金化反应的元素的源与所述碳源气体的体积比为大于等于0.5:1，可选为(2-10):1；
    可选地，所述第一混合气中的所述碳源气体的体积占比为≤20％，更可选为5％-20％。
  18. 根据权利要求12-17任一项所述的方法，还包括步骤3：在步骤2所获得的负极活性材料的至少部分表面形成包覆层，所述包覆层包括碳材料、导电聚合物、金属氧化物和金属硫化物中的一种或几种。
  19. 根据权利要求18所述的方法，其中，所述形成包覆层的步骤包括以下步骤：将步骤2所获得的负极活性材料置于反应炉内，通入含有碳源气体的第二混合气，并在第二温度T 2下沉积第二时间t 2，结束后得到碳包覆的负极活性材料，
    可选地，所述第二混合气包括碳源气体和保护气体，更可选地，所述第二混合气中的所述碳源气体的体积占比V 2为5％-50％；
    可选地，所述第二混合气的总气体流量为0.5L/min-20L/min；
    可选地，所述第二温度T 2为700℃-850℃；
    可选地，所述第二时间t 2为1h-6h。
  20. 一种二次电池，包括负极极片，所述负极极片包括权利要求1-11任一项所述的负极活性材料或通过权利要求12-19任一项所述的方法制备得到的负极活性材料。
  21. 一种用电装置，包括权利要求20所述的二次电池。
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN121709588A (zh) * 2026-02-13 2026-03-20 兰溪致德新能源材料有限公司 负极材料及其制备方法以及负极和二次电池

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5888430A (en) * 1996-03-14 1999-03-30 Kabushiki Kaisha Toyota Chuo Kenkyusho Graphite composite and method for producing the same
CN104269521A (zh) * 2014-10-20 2015-01-07 洛阳月星新能源科技有限公司 一种锂离子电池用碳/硅/块状石墨负极材料、制备方法及锂离子电池
CN109301225A (zh) * 2018-10-16 2019-02-01 周昊宸 一种具有石墨化度、孔径双梯度结构的石墨负极材料及其制备和应用
CN114127985A (zh) * 2021-03-31 2022-03-01 宁德新能源科技有限公司 一种负极极片、包含该负极极片的电化学装置和电子装置
CN114520313A (zh) * 2020-11-20 2022-05-20 华为技术有限公司 一种硅碳复合材料及其制备方法和应用
CN114759157A (zh) * 2022-04-29 2022-07-15 欣旺达电动汽车电池有限公司 一种负极极片及其制备方法、锂二次电池

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102479948B (zh) * 2010-11-30 2015-12-02 比亚迪股份有限公司 一种锂离子电池的负极活性材料及其制备方法以及一种锂离子电池
CN103199252B (zh) * 2013-03-08 2015-10-28 深圳市贝特瑞新能源材料股份有限公司 锂离子电池用硅碳负极材料及其制备方法
CN119419246A (zh) * 2015-08-28 2025-02-11 14集团技术公司 具有极其持久的锂嵌入的新型材料及其制造方法
CN116364877A (zh) * 2019-07-29 2023-06-30 宁德时代新能源科技股份有限公司 负极活性材料及二次电池
JP2022515938A (ja) * 2019-12-06 2022-02-24 リブエナジー カンパニー リミテッド 二次電池用電極活物質、これを含む電極および二次電池、並びに電極活物質の製造方法
CN115699368A (zh) * 2020-05-28 2023-02-03 昭和电工株式会社 锂离子二次电池用负极材料及其用途
WO2022193123A1 (zh) * 2021-03-16 2022-09-22 宁德新能源科技有限公司 负极材料及其制备方法, 电化学装置及电子装置

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5888430A (en) * 1996-03-14 1999-03-30 Kabushiki Kaisha Toyota Chuo Kenkyusho Graphite composite and method for producing the same
CN104269521A (zh) * 2014-10-20 2015-01-07 洛阳月星新能源科技有限公司 一种锂离子电池用碳/硅/块状石墨负极材料、制备方法及锂离子电池
CN109301225A (zh) * 2018-10-16 2019-02-01 周昊宸 一种具有石墨化度、孔径双梯度结构的石墨负极材料及其制备和应用
CN114520313A (zh) * 2020-11-20 2022-05-20 华为技术有限公司 一种硅碳复合材料及其制备方法和应用
CN114127985A (zh) * 2021-03-31 2022-03-01 宁德新能源科技有限公司 一种负极极片、包含该负极极片的电化学装置和电子装置
CN114759157A (zh) * 2022-04-29 2022-07-15 欣旺达电动汽车电池有限公司 一种负极极片及其制备方法、锂二次电池

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4517870A4 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2025241601A1 (zh) * 2024-05-20 2025-11-27 华为技术有限公司 负极材料及其制备方法、负极、电池、电子设备及储能设备
WO2025255710A1 (zh) * 2024-06-11 2025-12-18 中国科学院深圳先进技术研究院 一种电池碳基正极材料、制备方法及双离子电池

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