WO2024182919A1 - 硅基负极活性材料、二次电池及用电装置 - Google Patents

硅基负极活性材料、二次电池及用电装置 Download PDF

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Publication number
WO2024182919A1
WO2024182919A1 PCT/CN2023/079521 CN2023079521W WO2024182919A1 WO 2024182919 A1 WO2024182919 A1 WO 2024182919A1 CN 2023079521 W CN2023079521 W CN 2023079521W WO 2024182919 A1 WO2024182919 A1 WO 2024182919A1
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Prior art keywords
negative electrode
silicon
electrode active
active material
based negative
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PCT/CN2023/079521
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English (en)
French (fr)
Inventor
吕子建
王家政
邓静娴
刘良彬
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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/CN2023/079521 priority Critical patent/WO2024182919A1/zh
Priority to KR1020257012478A priority patent/KR20250073214A/ko
Priority to CN202380009158.2A priority patent/CN116888761B/zh
Priority to EP23925647.2A priority patent/EP4618189A4/en
Priority to JP2025522892A priority patent/JP2025535430A/ja
Publication of WO2024182919A1 publication Critical patent/WO2024182919A1/zh
Priority to US19/172,688 priority patent/US20250239609A1/en
Anticipated expiration legal-status Critical
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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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C01B33/32—Alkali metal silicates
    • C01B33/325—After-treatment, e.g. purification or stabilisation of solutions, granulation; Dissolution; Obtaining solid silicate, e.g. from a solution by spray-drying, flashing off water or adding a coagulant
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C01B33/32—Alkali metal silicates
    • 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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • 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
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • 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
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to a silicon-based negative electrode active material, a secondary battery and an electrical device.
  • secondary batteries are widely used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • Silicon-based materials are considered to be promising silicon-based negative electrode active materials for secondary batteries. As secondary batteries have made great progress, higher requirements have been put forward for their first coulombic efficiency, cycle performance, etc. Therefore, the field still needs silicon-based negative electrode active materials with better performance.
  • the present application provides a novel silicon-based negative electrode active material, a secondary battery and an electrical device, which are described below respectively.
  • the present application provides a silicon-based negative electrode active material, wherein the silicon-based negative electrode active material comprises a silicate containing an alkali metal element, and the silicon-based negative electrode active material contains both Al and Mg elements.
  • the silicon-based negative electrode active material contains a combination of Al and Mg elements, and this specific combination improves the first coulombic efficiency and cycle capacity retention rate of the silicon-based negative electrode active material.
  • the combination of Al and Mg elements has achieved an unexpected synergistic effect, and the technical effect achieved by the combination of the two is significantly better than the simple addition of the two separately.
  • Mg and Al elements can effectively improve the deintercalation ability of lithium ions and the conductivity of electrons in the silicon negative electrode, and can also reduce polarization and inhibit the increase of negative electrode impedance during the cycle; and magnesium elements can form a silicate structure with the oxygen-containing silicon part, effectively reducing lithium consumption.
  • the above factors work together to significantly improve the first coulombic efficiency and cycle capacity retention rate of silicon-based negative electrode active materials. Therefore, the use of the silicon-based negative electrode active material of the present application enables secondary batteries to simultaneously take into account higher cycle performance and first coulombic efficiency.
  • the content of the Al element is greater than the content of the Mg element.
  • the Al element and the Mg element exhibit unexpected synergistic effects, significantly improving the first coulombic efficiency and cycle capacity retention rate of the silicon-based negative electrode active material.
  • the mass ratio of the Al element to the Mg element is greater than or equal to 1.2:1, and can be optionally 5:1 to 20:1.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the content of the Al element is 400 ppm or more, and can be 800 ppm-2000 ppm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the content of the Mg element is 800 ppm or less, and can be 50 ppm to 500 ppm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the volume average particle size D v 50 of the silicon-based negative electrode active material is 4 ⁇ m-10 ⁇ m, and optionally 5 ⁇ m-8 ⁇ m.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the specific surface area of the silicon-based negative electrode active material is less than 3 m 2 /g, and can be 0.5 m 2 /g-2 m 2 /g.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the powder volume resistivity of the silicon-based negative electrode active material under a pressure of 4 MPa is less than 3 ⁇ cm, and can be optionally 0.5 ⁇ cm-1.5 ⁇ cm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the compaction density of the silicon-based negative electrode active material under a pressure of 5 tons is 1.4-1.8 g/cm 3 , and can be 1.5-1.7 g/cm 3 .
  • the silicon-based negative electrode active material has improved energy density.
  • the silicate containing alkali metal elements includes a silicate containing lithium, and the half-peak width of the XRD diffraction peak of the silicate containing lithium is less than or equal to 1.50°.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the silicate containing alkali metal elements includes a silicate containing lithium, and the grain size of the silicate containing lithium is less than or equal to 20 nm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • At least a portion of the surface of the silicon-based negative electrode active material has a coating layer.
  • the present application provides a method for preparing the silicon-based negative electrode active material as described in any one of the above items, comprising:
  • the product of the previous step is reacted with an alkali metal source to obtain an alkali metalated product.
  • the method for preparing a silicon-based negative electrode active material further comprises:
  • the alkali metalation product is subjected to coating treatment to obtain a product with a coating layer.
  • the heating temperature is 1100-1550°C.
  • the cooling temperature is 700-900°C.
  • the present application provides a secondary battery, comprising a negative electrode, wherein the negative electrode comprises any one of the silicon-based negative electrode active materials described above.
  • the present application provides an electrical device, comprising any of the secondary batteries described above.
  • Silicon-based negative electrode active materials have improved first coulombic efficiency
  • Silicon-based negative electrode active materials have improved cycle capacity retention
  • Silicon-based negative electrode active materials have higher energy density.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • “Scope” disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope limited in this way can be including end values or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope 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" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an 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 also include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps
  • the method may further comprise steps (a), (c) and (b), or may comprise 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).
  • ppm parts per million means parts per million.
  • ppm refers to the mass of Al or Mg in the silicon-based negative electrode active material as a percentage of the mass of the silicon-based negative electrode active material.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can continue to be used by recharging the active materials after the battery is discharged.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • active ions such as sodium ions
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.
  • the electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct active ions.
  • Secondary batteries are, for example, lithium-ion batteries.
  • the composition of lithium-ion batteries mainly includes a positive electrode, a negative electrode, a separator, and an electrolyte.
  • the positive and negative electrodes are separated by a separator to prevent short circuits, and the electrolyte infiltrates the positive and negative electrodes to ensure ion conduction.
  • Li + escapes from the positive electrode, passes through the separator through the electrolyte and is embedded in the negative electrode, so that the positive electrode is in a high potential sodium-poor state, and the negative electrode is in a low potential sodium-rich state.
  • the discharge process is the opposite, Li+ escapes from the negative electrode, passes through the separator through the electrolyte and is embedded in the positive electrode material, so that the positive electrode is restored to a sodium-rich state.
  • the same number of electrons are transferred through the external circuit during the charge and discharge process, and migrate between the positive and negative electrodes together with Li+, so that the positive and negative electrodes undergo oxidation and reduction reactions respectively.
  • Lithium ions can reversibly migrate between the positive and negative electrodes in the electrolyte, and both the positive and negative electrodes are composed of insertion materials that allow lithium ions to be reversibly inserted and removed.
  • Secondary batteries are, for example, sodium ion batteries.
  • the composition of sodium ion batteries mainly includes a positive electrode, a negative electrode, a diaphragm, and an electrolyte.
  • the positive and negative electrodes are separated by a diaphragm to prevent short circuits, and the electrolyte infiltrates the positive and negative electrodes to ensure ion conduction.
  • Na + escapes from the positive electrode, passes through the diaphragm through the electrolyte and is embedded in the negative electrode, so that the positive electrode is in a high potential sodium-poor state, and the negative electrode is in a low potential sodium-rich state.
  • the discharge process is the opposite, Na+ escapes from the negative electrode, passes through the diaphragm through the electrolyte and is embedded in the positive electrode material, so that the positive electrode is restored to a sodium-rich state.
  • the same number of electrons are transferred through the external circuit during the charge and discharge process, and migrate between the positive and negative electrodes together with Na+, so that the positive and negative electrodes undergo oxidation and reduction reactions respectively.
  • Sodium ions can reversibly migrate between the positive and negative electrodes in the electrolyte, and both the positive and negative electrodes are composed of insertion materials that allow sodium ions to be reversibly inserted and removed.
  • 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, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode active material of the present application is as follows: a silicon-based negative electrode active material, including a silicate containing an alkali metal element, and the silicon-based negative electrode active material contains both Al and Mg elements.
  • the silicon-based negative electrode active material contains a combination of Al and Mg elements, and this specific combination improves the first coulombic efficiency and cycle capacity retention rate of the silicon-based negative electrode active material.
  • the combination of Al and Mg elements has achieved an unexpected synergistic effect, and the technical effect achieved by the combination of the two is significantly better than the simple addition of the two separately.
  • Mg and Al elements can effectively improve the deintercalation ability of lithium ions and the conductivity of electrons in the silicon negative electrode, and can also reduce polarization and inhibit the increase of negative electrode impedance during the cycle; and magnesium elements can form a silicate structure with the oxygen-containing silicon part, effectively reducing lithium consumption.
  • the above factors work together to significantly improve the first coulombic efficiency and cycle capacity retention rate of silicon-based negative electrode active materials. Therefore, the use of the silicon-based negative electrode active material of the present application enables secondary batteries to simultaneously take into account higher cycle performance and first coulombic efficiency.
  • the silicon in the silicon-based negative electrode active material may exist in the form of multiple silicon phases including crystalline silicon. Specifically, the silicon phases may be uniformly distributed and embedded/buried in the matrix including the silicon-based negative electrode active material. In other words, the silicon phases may be dispersed and uniformly distributed in the matrix.
  • the silicate containing alkali metal elements includes a silicate containing lithium, and the half-peak width of the XRD diffraction peak of the silicate containing lithium is less than or equal to 1.50°.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the lithium-containing silicate includes at least one of Li 2 Si 2 O 5 , Li 2 SiO 3 .
  • the silicate containing alkali metal elements includes a silicate containing lithium, and the grain size of the silicate containing lithium is less than or equal to 20 nm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the alkali metal element includes one or more of Li, Na, and K.
  • the silicon-based negative electrode active materials all exhibit improved first cycle efficiency and cycle capacity retention.
  • the alkali metal element includes Li.
  • the silicon-based negative electrode active materials all show improved first cycle efficiency and cycle capacity retention.
  • the silicon-based negative electrode active material further contains at least one of silicon grains and silicon-oxygen material grains.
  • the Al element and the Mg element grow in the silicon-based negative electrode active material, for example, grow in it during the process of vapor deposition of the silicon-based negative electrode active material. In some embodiments, the Al element and the Mg element grow in the silicon-based negative electrode active material when they are vapor deposited together with the silicon-based negative electrode active material.
  • the content of Al in the silicon-based negative electrode active material is greater than that of Mg.
  • Al and Mg show unexpected synergistic effects, significantly improving the first coulombic efficiency and cycle capacity retention rate of the silicon-based negative electrode active material.
  • the silicon-based negative electrode active material has a mass ratio of Al to Mg of 1.2:1 or more. Within the above ratio range, the Al element and the Mg element exhibit an unexpected synergistic effect, further significantly improving the negative electrode activity. The first coulombic efficiency and cycle capacity retention of the material.
  • the silicon-based negative electrode active material has a mass ratio of Al to Mg of 1.2: 1 to 18: 1. Within the above ratio range, the Al element and the Mg element exhibit an unexpected synergistic effect, further significantly improving the first coulombic efficiency and cycle capacity retention rate of the negative electrode active material.
  • the silicon-based negative electrode active material has a mass ratio of Al to Mg of 2.2: 1 to 6: 1. Within the above ratio range, the Al element and the Mg element exhibit an unexpected synergistic effect, further significantly improving the first coulombic efficiency and cycle capacity retention rate of the negative electrode active material.
  • the silicon-based negative electrode active material has a mass ratio of Al to Mg of 5: 1 to 20: 1. Within the above ratio range, the Al element and the Mg element exhibit an unexpected synergistic effect, further significantly improving the first coulombic efficiency and cycle capacity retention rate of the negative electrode active material.
  • the mass ratio of the Al element to the Mg element in the silicon-based negative electrode active material may be 40:1 or less, 30:1 or less, 20:1 or less, 15:1 or less, 14:1 or less, 13:1 or less, or 12:1 or less. In some embodiments, the mass ratio of the Al element to the Mg element in the silicon-based negative electrode active material may be 1.2:1 or more, 2:1 or more, 3:1 or more, 4:1 or more, or 5:1 or more.
  • the mass ratio of the Al element to the Mg element may be composed of any of the aforementioned upper and lower limit values. Within the above-mentioned ratio range, the Al element and the Mg element exhibit unexpected synergistic effects, further significantly improving the first coulombic efficiency and cycle capacity retention rate of the negative electrode active material.
  • the mass ratio of the Al element to the Mg element in the silicon-based negative electrode active material can be 3-6:1, and can also be 2-6:1, can also be 2-7:1, can also be 2-8:1, can also be 2-10:1, can also be 2-12:1, can also be 2-14:1, can also be 2-16:1, can also be 2-18:1, can also be 1-18:1, can also be 1-20:1, can also be 1-30:1, can also be 1-40:1.
  • the content of Al in the silicon-based negative electrode active material is 400 ppm or more.
  • Al and Mg show unexpected synergistic effects, significantly improving the first coulombic efficiency and cycle capacity retention of the negative electrode active material.
  • the content of Al in the silicon-based negative electrode active material is 500ppm-2000ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and cycle capacity retention rate. Within the above content range, Al and Mg elements show unexpected synergistic effects, significantly improving the first coulombic efficiency and cycle capacity retention rate of the negative electrode active material.
  • the content of Al in the silicon-based negative electrode active material is 800ppm-2000ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and cycle capacity retention rate. Within the above content range, Al and Mg elements show unexpected synergistic effects, significantly improving the first coulombic efficiency and cycle capacity retention rate of the negative electrode active material.
  • the content of Al in the silicon-based negative electrode active material is 800ppm-1800ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and cycle capacity retention rate. Within the above content range, Al and Mg elements show unexpected synergistic effects, significantly improving the first coulombic efficiency and cycle capacity retention rate of the negative electrode active material.
  • the content of Al in the silicon-based negative electrode active material is 1100ppm-1500ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and cycle capacity retention rate. Within the above content range, Al and Mg elements show unexpected synergistic effects, significantly improving the first coulombic efficiency and cycle capacity retention rate of the negative electrode active material.
  • the upper limit of the content of the Al element in the silicon-based negative electrode active material can be selected from any one of 2300ppm, 2000ppm, 1900ppm, 1800ppm, 1700ppm, 1600ppm, 1500ppm, 1400ppm, 1300ppm, 1200ppm, and 1100ppm;
  • the lower limit of the content of the Al element can be selected from any one of 500ppm, 550ppm, 600ppm, 650ppm, 700ppm, 750ppm, 800ppm, 900ppm, and 1000ppm. That is, the content range of the Al element can be composed of any of the above upper and lower limits. Within the above content range, the Al element and the Mg element show unexpected synergistic effects, which significantly improve the first coulomb efficiency and cycle capacity retention rate of the negative electrode active material.
  • the content of Al element in the silicon-based negative electrode active material may be 1100-1500 ppm, 1100-1800 ppm, 800-1500 ppm, 800-1800 ppm, 800-2000 ppm, or 500-2000 ppm.
  • the content of Mg in the silicon-based negative electrode active material is 800 ppm or less. Based on this, the negative electrode active material has further improved first cycle efficiency and cycle capacity retention rate.
  • the content of Mg in the silicon-based negative electrode active material is 250ppm-500ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and cycle capacity retention rate.
  • the upper limit of the content of Mg in the silicon-based negative electrode active material can be selected from any one of 1000ppm, 900ppm, 800ppm, 700ppm, 600ppm, 500ppm, 400ppm, 300ppm, 200ppm, and 100ppm; the lower limit of the content of manganese can be selected from any one of 50ppm, 60ppm, 70ppm, 80ppm, and 90ppm; that is, the range of the content of manganese can be composed of any of the above upper and lower limits.
  • Al and Mg show unexpected synergistic effects, which significantly improve the first coulomb efficiency and cycle capacity retention rate of the negative electrode active material.
  • the content of Mg element in the silicon-based negative electrode active material may be 250-500 ppm, 250-650 ppm, 100-650 ppm, 100-800 ppm, 50-800 ppm, 50-600 ppm, 50-400 ppm, 50-300 ppm, 50-200 ppm.
  • the volume average particle size D v 50 of the silicon-based negative electrode active material is 4 ⁇ m-10 ⁇ m, and optionally 5 ⁇ m-8 ⁇ m.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the volume average particle size D v 50 of the silicon-based negative electrode active material may be 4 ⁇ m or more.
  • the average particle size D v 50 can be selected to be 5 ⁇ m or more, which can reduce the consumption of active ions in the negative electrode film formation and the side reaction of the electrolyte in the negative electrode, thereby reducing the irreversible capacity of the secondary battery and improving the cycle performance of the secondary battery; it can also reduce the amount of binder added in the negative electrode plate, which is beneficial to improving the energy density of the secondary battery.
  • the average particle size D v 50 can be selected to be 10 ⁇ m or less, and more preferably 8 ⁇ m or less, so that the migration path of active ions and electrons in the material particles is shorter, and the migration rate of ions and electrons is increased, thereby improving the kinetic performance of the secondary battery; it is also beneficial to prevent the silicon-based negative electrode active material from rupturing during the charge and discharge process, thereby improving the cycle performance of the secondary battery.
  • the specific surface area of the silicon-based negative electrode active material is less than 3 m 2 /g, and can be 0.5 m 2 /g-2 m 2 /g.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the specific surface area of the silicon-based negative electrode active material is 0.5m 2 /g-2m 2 /g.
  • the specific surface area can be selected to be above 0.5m 2 /g so that the surface of the material particles has more active sites, which can effectively improve the electrochemical performance of the silicon-based negative electrode active material and meet the requirements of the secondary battery for kinetic performance.
  • the specific surface area can be selected to be below 2m 2 /g, which is conducive to reducing the side reactions of the electrolyte at the negative electrode and can also reduce the film-forming consumption of active ions at the negative electrode, thereby reducing the irreversible capacity of the secondary battery and improving the cycle performance of the secondary battery.
  • the powder volume resistivity of the silicon-based negative electrode active material under a pressure of 4 MPa is less than 3 ⁇ cm, and can be optionally 0.5 ⁇ cm-1.5 ⁇ cm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and cycle capacity retention rate.
  • the powder volume resistivity of the silicon-based negative electrode active material under a pressure of 4MPa is less than 3 ⁇ cm, and more preferably less than 1.5 ⁇ cm.
  • the powder volume resistivity of the silicon-based negative electrode active material is within the above range, which can reduce the migration barrier of electrons inside the particles, improve the kinetic properties of the silicon-based negative electrode active material, and reduce the negative electrode polarization phenomenon, thereby increasing the cycle life of the secondary battery.
  • the powder volume resistivity can be reduced by surface treatment of the silicon-based negative electrode active material.
  • the compaction density of the silicon-based negative electrode active material under a pressure of 5 tons is 1.4-1.8 g/cm 3 , and can be 1.5-1.7 g/cm 3 .
  • the silicon-based negative electrode active material has improved energy density.
  • the silicon-based negative electrode material contains Si element and O element, and the molar ratio of O element to Si element is greater than 0 and less than 2, and can be selected as 0.2-1.8:1, or 0.3-1.7:1, or 0.4-1.6:1, or 0.6-1.5:1, or 0.7-1.4:1, or 0.8-1.3:1, or 0.9-1.2:1, or 1.0-1.1:1.
  • At least a portion of the surface of the silicon-based negative electrode active material has a coating layer.
  • the material of the coating layer includes one or more of a polymer, a carbon material, a metal material and a metal compound.
  • the coating layer includes one or more of a polymer coating layer, a carbon coating layer and a metal compound coating layer.
  • the polymer may be selected from one or more of polyaniline, polyacetylene, polystyrene, polyacrylonitrile, polyvinyl chloride and polyethylene.
  • the carbon material may include one or more of graphite, mesophase microcarbon beads (MCMB), hydrocarbon compound pyrolytic carbon, hard carbon and soft carbon, wherein the graphite may be one or more of natural graphite and artificial graphite.
  • the metal compound may include one or more of Ti 5 Si 3 , Al 2 O 3 and TiO 2.
  • the coating layer can further alleviate the volume expansion effect of the silicon-based negative electrode active material and improve the cycle life of the material.
  • the coating layer also protects the silicon-based negative electrode active material, inhibiting the side effects of the electrolyte on the surface of the material. reaction, protecting the material surface from being corroded by the electrolyte, so that the silicon-based negative electrode active material has a higher capacity and the cycle life of the battery is further improved.
  • the present application provides a method for preparing the silicon-based negative electrode active material as described in any one of the above items, comprising:
  • the raw material is heated to form a vapor, and then the vapor is cooled to form a deposit;
  • the product of the previous step is reacted with an alkali metal source to obtain an alkali metalated product.
  • the method for preparing a silicon-based negative electrode active material further comprises:
  • the alkali metalation product is subjected to coating treatment to obtain a product with a coating layer.
  • the Si element in the raw material may be derived from silicon and silicon oxide
  • the O element in the raw material may be derived from silicon oxide.
  • the silicon element for example, includes metallic silicon.
  • Silicon oxide for example, includes one or more of silicon monoxide (SiO) and silicon dioxide (SiO 2 ).
  • Metallic silicon for example, is any metallic silicon or industrial silicon specified in the standard GB/T 2881-2014, for example, is any electronic grade polysilicon specified in GB/T 12963-2014, for example, is any solar grade polysilicon specified in GB/T 25074-2010.
  • the purity of the silicon element for example, is 3N or more, 4N or more, 5N or more, or 6N or more.
  • the Al element in the raw material may come from the Al element contained in silicon alone or silicon oxide, or may come from an aluminum source added to the raw material.
  • the Mg element in the raw material may come from the Mg element contained in silicon alone or silicon oxide, or may come from a magnesium source added to the raw material.
  • the alkali metal element in the raw material may come from the alkali metal element contained in silicon or silicon oxide itself, or may come from an alkali metal source added to the raw material.
  • the raw material contains an aluminum source.
  • the aluminum element in the raw material comes at least partially from an aluminum source.
  • the aluminum source can be selected from metallic aluminum, aluminum alloys, and aluminum compounds, and the aluminum compounds can be selected from one or more of aluminum oxides, aluminum sulfides, and aluminum hydroxides.
  • the aluminum source can be selected from one or more of metallic aluminum, aluminum nitrate, aluminum chloride, aluminum hydroxide, and aluminum silicate.
  • the raw material contains a magnesium source.
  • the Mg element in the raw material comes at least partially from the magnesium source.
  • the magnesium source can be selected from one or more of metallic magnesium and magnesium compounds; wherein the magnesium compound can be selected from one or more of magnesium oxide, magnesium carbonate, magnesium hydroxide, magnesium nitrate and magnesium sulfate.
  • the alkali metal source can be selected from one or more of alkali metal elements, alkali metal alloys and alkali metal compounds; wherein the alkali metal compound can be selected from one or more of alkali metal oxides, alkali metal sulfides, alkali metal carbonates, alkali metal hydroxides, alkali metal acetates, alkali metal oxalates, alkali metal nitrates and alkali metal sulfates.
  • the raw material containing Si element, O element, Al element, and Mg element includes simple silicon, silicon dioxide, an aluminum source, and a magnesium source.
  • the Al element in the negative electrode active material is adjusted by adjusting the type and amount of the aluminum source in the raw material. The content of nutrients.
  • the content of Mg in the negative electrode active material is adjusted by adjusting the type and amount of the magnesium source in the raw material.
  • the Al content in the negative electrode active material is adjusted by one or more means such as mixing silicon oxide powders or metallic silicon powders with various Al contents, adjusting the type and amount of the aluminum source, and the like.
  • the Mg content in the negative electrode active material is adjusted by one or more means such as mixing silicon oxide powders or metallic silicon powders with various Mg contents, adjusting the type and amount of the magnesium source, and the like.
  • the heating of the feedstock to form the vapor is performed in an inert atmosphere at normal or reduced pressure.
  • cooling the vapor-formed deposit is performed in an inert atmosphere at normal or reduced pressure.
  • the inert atmosphere can be a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, etc.
  • the absolute pressure of the inert atmosphere is normal pressure (1 standard atmospheric pressure) or reduced pressure (less than 1 standard atmospheric pressure).
  • the absolute pressure of the inert atmosphere is 10Pa-950Pa, and more preferably 20Pa-100Pa.
  • the contents of Al and Mg in the final silicon-based negative electrode active material can be increased accordingly.
  • the cooling temperature is 700-900°C.
  • the cooling temperature in the operation of cooling the vapor to form a deposit, can be adjusted to allow the deposit to obtain an appropriate crystal structure.
  • the cooling temperature is 850°C-1050°C, which is conducive to obtaining a better crystallite size and suitable crystallinity for the silicon-based negative electrode active material, so that the silicon-based negative electrode active material has a higher first coulombic efficiency and cycle performance.
  • the cooling temperature is lower than 800°C, the crystallinity of the material may be too low, affecting the first coulombic efficiency of the material; when the cooling temperature is higher than 1050°C, the crystallite size of the material may be too large, affecting the cycle performance of the material.
  • increasing the temperature can increase the contents of Al and Mg in the final silicon-based negative electrode active material accordingly.
  • reducing the pressure that is, increasing the vacuum degree, can increase the contents of Al and Mg in the final silicon-based negative electrode active material accordingly.
  • the operation of crushing the sediment includes: according to the preset volume average particle size (Dv50) and specific surface area parameters of the product, the sediment is subjected to a coarse crushing-fine crushing-classification operation to obtain a product that meets the preset parameters.
  • the sediment can be crushed and classified by any method and equipment known in the art, such as a grinder, a jet mill-classifying integrated machine.
  • the method for preparing a silicon-based negative electrode active material further comprises: coating the alkali metalization product to obtain a product having a coating layer.
  • the coating layer comprises one or more of a polymer, a carbon material, a metal material, and a metal compound.
  • the coating layer comprises one or more of a polymer coating layer, a carbon coating layer, and a metal compound coating layer.
  • the polymer can be selected from one or more of polyaniline, polyacetylene, polystyrene, polyacrylonitrile, polyvinyl chloride and polyethylene.
  • the carbon material can include one or more of graphite, mesophase microcarbon beads (MCMB), hydrocarbon compound pyrolysis carbon, hard carbon and soft carbon, wherein the graphite can be one or more of natural graphite and artificial graphite.
  • the metal compound can include one or more of Ti 5 Si 3 , Al 2 O 3 and TiO 2.
  • the coating layer can further alleviate the volume expansion effect of the silicon-based negative electrode active material and improve the cycle life of the material.
  • the coating layer also protects the silicon-based negative electrode active material, inhibits the side reaction of the electrolyte on the surface of the material, and protects the surface of the material from being corroded by the electrolyte, so that the silicon-based negative electrode active material has a higher capacity and the cycle life of the battery is further improved.
  • a coating layer is formed by coating the surface of the silicon-based negative electrode active material using a liquid phase coating method, for example, a polymer is dissolved in a certain solvent, and the polymer is fully stirred with the silicon-based negative electrode active material particles to mix evenly, and then the solvent is evaporated and removed, so that the polymer is evenly coated on the surface of the silicon-based negative electrode active material particles.
  • a liquid phase coating method for example, a polymer is dissolved in a certain solvent, and the polymer is fully stirred with the silicon-based negative electrode active material particles to mix evenly, and then the solvent is evaporated and removed, so that the polymer is evenly coated on the surface of the silicon-based negative electrode active material particles.
  • a coating treatment is performed on the surface of the silicon-based negative electrode active material by chemical vapor deposition to form a coating layer.
  • hydrocarbon compound gas is introduced into a reactor containing the silicon-based negative electrode active material, and heat treatment is performed under an inert atmosphere to carbonize the hydrocarbon compound to form a coating layer coated on the surface of the silicon-based negative electrode active material, thereby obtaining a silicon-based negative electrode active material with a coating layer on the surface.
  • the coating treatment includes a carbon coating treatment.
  • the carbon coating treatment includes the following operations: placing the pulverized product in a chamber containing a carbon source gas, heating it to 700-1000° C., and keeping it warm for 1-6 hours.
  • the coating treatment includes carbon coating treatment.
  • the carbon coating treatment includes the following operations: placing the pulverized product in a chamber containing a carbon source gas, heating to 800-900° C., and keeping the temperature for 2-5 hours.
  • the alkali metal source may be one or more of an alkali metal element, an alkali metal hydroxide, an alkali metal carbonate, an alkali metal nitrate, an alkali metal amide, and an alkali metal hydride.
  • the alkali metal source can be one or more of metallic lithium, lithium hydroxide, lithium carbonate, lithium nitrate, lithium amide, and lithium hydride.
  • 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 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 layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode film layer may also include silicon-based negative electrode active materials known in the art other than those in the present application, and those skilled in the art may choose according to actual needs.
  • it may include, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, other silicon-based materials and tin-based materials.
  • the other silicon-based materials may include one or more of elemental silicon, silicon-oxygen composites different from the present application, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may include one or more of elemental tin, tin oxide compounds, and tin alloys. These materials All materials can be obtained through commercial channels.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as silicon-based negative electrode active material, conductive agent, binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the positive electrode sheet generally 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 the positive electrode film layer includes 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 current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the positive electrode active material may employ a positive electrode active material for a secondary battery known in the art.
  • the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • an olivine-structured lithium-containing phosphate a lithium transition metal oxide
  • their respective modified compounds the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), and LiNi 0.8 Co 0.2 Mn 0.2 O 2 (also referred to as NCM 811 ), lithium
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • 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 or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • 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 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are battery packs 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 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • 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 may be used.
  • the preparation method of the negative electrode active material is summarized as follows:
  • the raw material composition comprises silicon, silicon oxide, an aluminum source (aluminum nitrate) and a magnesium source (metal magnesium);
  • the raw material composition is heated to 1300° C. to form a vapor by a vapor deposition method, and then the vapor is cooled to 900° C. to form a deposit;
  • the carbon-coated product is mixed with a lithium source (lithium amide) at a ratio of 100:30 (mass ratio), heated to 650° C., kept warm for 2 h, a lithiation reaction is carried out, and the product is collected to obtain a negative electrode active material.
  • a lithium source lithium amide
  • negative electrode active materials with various Mg contents and Al contents can be obtained. It should be understood that, affected by the purity of silicon and silicon dioxide, some silicon and silicon dioxide contain a certain amount of Al and Mg elements in advance. At this time, the content of the aluminum source and the magnesium source in the raw material mixture should be adaptively adjusted according to the composition of the target product of the sample.
  • a plurality of negative electrode active material samples (hereinafter referred to as samples) were prepared, and these samples had different Mg contents and Al contents, as shown in Table 1.
  • the examples shown in Table 1 include Examples 1-11 (E1-E12) and Comparative Examples 1-3 (D1-D3).
  • silicon-based negative electrode active materials with various Al and Mg content can be obtained. It should be understood that, affected by the purity of silicon and silicon dioxide, some silicon and silicon dioxide contain a certain amount of Al and Mg in advance. At this time, the contents of the aluminum and magnesium sources in the raw material mixture should be adaptively adjusted according to the composition of the target product of the sample.
  • samples silicon-based negative electrode active material samples. There are different Al and Mg contents. These samples have the following properties:
  • the silicon-based negative electrode active material is a silicon-based negative electrode active material with a carbon coating layer, wherein the content of the carbon coating layer accounts for 4.2 ⁇ 1%, and the balance is the silicon-based negative electrode active material;
  • the content of the Li element is 7.5 ⁇ 0.5%.
  • Al element content is shown in Table 1.
  • the volume average particle size Dv50 of the silicon-based negative electrode active material is 6.5 ⁇ 0.5 ⁇ m.
  • the specific surface area of the silicon-based negative electrode active material is 1.75 ⁇ 0.25 m 2 /g.
  • the powder volume resistivity of the silicon-based negative electrode active material under a pressure of 4MPa is 1 ⁇ 0.1 ⁇ cm.
  • the silicon-based negative electrode active material contains Li 2 SiO 3 and Li 2 Si 2 O 5 , and the half-peak width of the XRD diffraction peak of Li 2 SiO 3 is 0.6° ⁇ 0.2°, and the grain size is 15 ⁇ 2 nm; the half-peak width of the XRD diffraction peak of Li 2 Si 2 O 5 is 1.0° ⁇ 0.1°, and the grain size is 8 ⁇ 2 nm.
  • Table 1 shows silicon-based negative electrode active material samples with different Al and Mg content.
  • Isolation film polyethylene (PE) film.
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte, and fluoroethylene carbonate (FEC) was added, wherein the concentration of LiPF6 was 1 mol/L, and the mass proportion of FEC in the electrolyte was 6%.
  • button cell stack the above-mentioned negative electrode sheet, separator, and metal lithium sheet in order, add the above-mentioned electrolyte, and obtain a button cell.
  • the element content has a well-known meaning in the art and can be tested using methods known in the art.
  • the silicon-based negative electrode active material can be digested with reference to EPA-3052-1996 "Microwave Acid Digestion of Silicates", and then the content of the target element can be determined using the ICAP-7000 Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) from Thermo Fisher Scientific in the United States in accordance with EPA 6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectrometry”.
  • the specific test method is as follows: Use 10mL nitric acid and 10mL hydrofluoric acid to perform microwave digestion on a 0.5g sample of silicon-based negative electrode active material. After digestion, the solution was added to a 50 mL volumetric flask and then the content of the target element was determined using an ICAP-7000 ICP-OES.
  • the element content is well known in the art and can be tested by methods known in the art.
  • the carbon content in the silicon-based negative electrode active material 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 oxygen content can refer to JY/T 017-1996 General Rules for Element Analyzer Methods, and the test instrument can be Elementar's rapid OXY cube oxygen analyzer.
  • the volume resistivity of a material is a well-known meaning in the art and can be measured using instruments and methods well-known in the art.
  • the four-probe method can be used to test the powder volume resistivity of the silicon-based negative electrode active material of the present application under a pressure of 4 MPa.
  • the testing method comprises: adding the powder of the silicon-based negative electrode active material of the present application to a sample table, applying a pressure of 4 MPa to the powder by a press, and after the pressure stabilizes, reading the powder volume resistivity of the silicon-based negative electrode active material under a pressure of 4 MPa by a resistivity meter.
  • the Dv10, Dv50 and Dv90 of a material are well known in the art and can be tested by methods known in the art.
  • the standard GB/T 19077-2016 can be referred to and measured using a laser particle size analyzer (such as Malvern Master Size 3000).
  • Dv10, Dv50, and Dv90 are as follows: the particle sizes corresponding to the cumulative volume distribution percentages of silicon-based negative electrode active materials reaching 10%, 50%, and 90%, respectively.
  • the specific surface area of a material has a well-known meaning in the art and can be measured by instruments and methods well-known in the art. For example, refer to GB/T 19587-2017 Gas Adsorption BET Method for Determining the Specific Surface Area of Solids Standard, use nitrogen adsorption specific surface area analysis test method, and calculate by BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by Tri StarII3020 specific surface and pore analyzer from Micromeritics, USA.
  • Table 1 shows the ingredients and composition of the raw materials of the silicon-based negative electrode active materials of some embodiments of the present application, the content and weight ratio of Al and Mg in the silicon-based negative electrode active material products, and the battery performance based on the above silicon-based negative electrode active materials as negative electrode active materials. The following are discussed separately:
  • the raw silicon element used in samples (D1-D3) is metallic silicon 2 (Si ⁇ 99.9wt%, excluding Al and Mg).
  • the Al and Mg elements in the silicon-based negative electrode active materials can come from a variety of sources:
  • the Al element in the silicon-based negative electrode active material can come from the raw material metal silicon;
  • the Mg element in the silicon-based negative electrode active material can come from the raw material metal silicon;
  • the Al element in the silicon-based negative electrode active material can come from an additionally added aluminum source
  • the Mg element in the silicon-based negative electrode active material can come from an additionally added magnesium source.
  • Those skilled in the art can adaptively adjust the content of Mg and Al in the raw materials according to the target chemical composition of the silicon-based negative electrode active material, and finally obtain a silicon-based negative electrode active material with a target chemical composition. If it is necessary to increase/decrease the Al content in the target silicon-based negative electrode active material, metal silicon (or silicon oxide) with a higher/lower Al content can be used, or the additional aluminum source added to the raw material can be increased/decreased. If it is necessary to increase/decrease the Mg content in the target silicon-based negative electrode active material, metal silicon (or silicon oxide) with a higher/lower Mg content can be used, or the additional magnesium source added to the raw material can be increased/decreased.
  • Example E1 Comparative Examples D1, D2 and D3:
  • the silicon-based negative electrode active material of Comparative Example D1 does not contain Mg and Al elements, and its IC+CR value is 152.2%.
  • the silicon-based negative electrode active material of comparative example D2 contains 1500 ppm of Al element but no Mg element, and its IC+CR value is 160.0%, which is only increased by 7.8% compared with D1.
  • the silicon-based negative electrode active material of Example D3 contains 500 ppm of Mg element but no Al element, and its IC+CR value is 155.3%, which is only increased by 3.1% compared with D1.
  • Example E12 the weight ratio of Al/Mg is 0.8:1 (less than 1), and the IC+CR value of the negative electrode active material is only 162.5%.
  • Example E11 the weight ratio of Al/Mg is 1.2:1 to 40:1 (greater than 1), and the IC+CR value of the negative electrode active material is 164.5%-175.9%, which is better than Example E12.
  • the content of Al element in the silicon-based negative electrode active material is 500 ppm or more, for example, 500 ppm-2000 ppm, and the negative electrode active material exhibits improved first coulombic efficiency and cycle capacity retention performance.
  • the content of Al element in the silicon-based negative electrode active material is 500 ppm or more, for example, 800 ppm-2000 ppm, and the negative electrode active material exhibits improved first coulombic efficiency and cycle capacity retention performance.
  • the content of Mg in the silicon-based negative electrode active material is less than 800 ppm, for example, 50 ppm to 800 ppm.
  • the negative electrode active material exhibits improved first coulombic efficiency and cycle capacity retention performance.
  • the above experimental data show that when the silicon-based negative electrode active material contains Mg or Al alone, the performance of the first coulombic efficiency and the cycle capacity retention rate is usually only improved unilaterally, and the improvement is not significant.
  • the silicon-based negative electrode active material contains a combination of Mg and Al elements, the negative electrode active material shows a double improvement in the first coulombic efficiency and the cycle capacity retention rate, and the improvement is particularly significant, which shows that the Mg and Al elements have achieved an unexpected synergistic effect.

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Abstract

本申请提供一种硅基负极活性材料，所述硅基负极活性材料包括含碱金属元素的硅酸盐，且所述硅基负极活性材料中同时含有Al元素和Mg元素。

Description

硅基负极活性材料、二次电池及用电装置 技术领域
本申请涉及电池技术领域，尤其涉及一种硅基负极活性材料、二次电池及用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、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。
硅基材料被认为是具有前景的二次电池硅基负极活性材料。由于二次电池取得了极大的发展，因此对其首次库伦效率、循环性能等也提出了更高的要求。因此，本领域仍需要性能更好的硅基负极活性材料
发明内容
鉴于上述课题，本申请提供一种新型硅基负极活性材料、二次电池及用电装置，下面分别描述。
在第一方面，本申请提供一种硅基负极活性材料，所述硅基负极活性材料包括含碱金属元素的硅酸盐，且所述硅基负极活性材料中同时含有Al元素和Mg元素。
在以上方案中，硅基负极活性材料含有Al元素和Mg元素组合，该特定组合改善了硅基负极活性材料的首次库伦效率和循环容量保持率。Al元素和Mg元素的组合取得了预料不到的协同作用，二者联合取得的技术效果显著优于二者分别使用的简单加和。不受以下理论的限制，Mg元素和Al元素可以有效改善硅负极锂离子的脱嵌能力及电子的传导性能，还能减小极化现象，抑制循环过程中的负极阻抗增加；且镁元素可与含氧硅部分生成硅酸盐结构，有效减小锂耗。以上因素共同作用，显著改善了硅基负极活性材料的首次库伦效率和循环容量保持率。因此，采用本申请的硅基负极活性材料，使得二次电池能够同时兼顾较高的循环性能、首次库伦效率。
在一些实施方案中，所述Al元素的含量大于Mg元素的含量。在上述比例范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了硅基负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述Al元素和所述Mg元素的质量比大于等于1.2:1；可选为5:1至20:1。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述Al元素的含量为400ppm以上，可选为800ppm-2000ppm。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述Mg元素的含量为800ppm以下，可选为50ppm-500ppm。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料的体积平均粒径Dv50为4μm-10μm，可选为5μm-8μm。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料的比表面积为3m2/g以下，可选为0.5m2/g-2m2/g。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料在4MPa压力下的粉体体积电阻率为3Ω·cm以下，可选为0.5Ω·cm-1.5Ω·cm。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料在5吨压力下的压实密度为1.4-1.8g/cm3，可选为1.5-1.7g/cm3。在上述方案中，硅基负极活性材料具有改善的能量密度。
在一些实施方案中，所述含碱金属元素的硅酸盐包括含锂的硅酸盐，且所述含锂的硅酸盐的XRD衍射峰的半峰宽小于等于1.50°。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述含碱金属元素的硅酸盐包括含锂的硅酸盐，且所述含锂的硅酸盐的晶粒尺寸小于等于20nm。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料的至少部分表面具有包覆层。
在第二方面，本申请提供上述任一项所述的硅基负极活性材料的制备方法，包括
提供含有Si元素、O元素、Mg元素和Al元素的原料；
采用气相沉积方法，加热所述原料形成蒸气，然后冷却所述蒸气形成沉积物；
将沉积物粉碎，获得粉碎产物；
使上一步产物与碱金属源反应，获得碱金属化产物。
在一些实施方案中，硅基负极活性材料的制备方法还包括：
对碱金属化产物进行包覆处理，获得有包覆层的产物。
在一些实施方案中，在加热所述原料形成蒸气的操作中，加热的温度为1100-1550℃。
在一些实施方案中，在冷却所述蒸气形成沉积物的操作中，冷却的温度为700-900℃。
在第三方面，本申请提供一种二次电池，包括负极，所述负极包括上述任一项所述的硅基负极活性材料。
在第四方面，本申请提供一种用电装置，包括上述任一项所述的二次电池。
有益效果
本申请一个或多个实施方式具有以下一项或多项有益效果：
(1)Al元素和Mg元素取得了预料不到的协同作用，二者联合取得的技术效果显著优于二者分别使用的简单加和。
(2)硅基负极活性材料具有改善的首次库伦效率；
(3)硅基负极活性材料具有改善的循环容量保持率；
(4)硅基负极活性材料具有较高的能量密度。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
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硅基负极活性材料及其制造方法、正极极片、负极极片、二次电池、电池模块、电池包和装置的实施方式。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。
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)。
在本文中，ppm(parts per million)是百万分比。但ppm用于描述Al元素或Mg元素的含量时，其是指硅基负极活性材料中Al元素或Mg元素的质量占硅基负极活性材料的质量的百万分比。
[二次电池]
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性离子(例如钠离子)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
二次电池例如是锂离子电池。锂离子电池的构成主要包括正极、负极、隔膜、电解液。正负极之间由隔膜隔开以防止短路，电解液浸润正负极以确保离子导通。充电时，Li+从正极脱出，经电解液穿过隔膜嵌入负极，使正极处于高电势的贫钠态，负极处于低电势的富钠态。放电过程与之相反，Li+从负极脱出，经由电解液穿过隔膜嵌入正极材料中，使正极恢复到富钠态。为保持电荷的平衡，充放电过程中有相同数量的电子经外电路传递，与Li+一起在正负极间迁移，使正负极分别发生氧化和还原反应。锂离子在电解液中可以在正极与负极之间可逆地迁移，正极和负极均由允许锂离子可逆地插入和脱出的插入型材料构成。
二次电池例如是钠离子电池。钠离子电池的构成主要包括正极、负极、隔膜、电解液。正负极之间由隔膜隔开以防止短路，电解液浸润正负极以确保离子导通。充电时，Na+从正极脱出，经电解液穿过隔膜嵌入负极，使正极处于高电势的贫钠态，负极处于低电势的富钠态。放电过程与之相反，Na+从负极脱出，经由电解液穿过隔膜嵌入正极材料中，使正极恢复到富钠态。为保持电荷的平衡，充放电过程中有相同数量的电子经外电路传递，与Na+一起在正负极间迁移，使正负极分别发生氧化和还原反应。钠离子在电解液中可以在正极与负极之间可逆地迁移，正极和负极均由允许钠离子可逆地插入和脱出的插入型材料构成。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
本申请的负极活性材料如下：硅基负极活性材料，包括含碱金属元素的硅酸盐，且所述硅基负极活性材料中同时含有Al元素和Mg元素。
在以上方案中，硅基负极活性材料含有Al元素和Mg元素组合，该特定组合改善了硅基负极活性材料的首次库伦效率和循环容量保持率。Al元素和Mg元素的组合取得了预料不到的协同作用，二者联合取得的技术效果显著优于二者分别使用的简单加和。不受以下理论的限制，Mg元素和Al元素可以有效改善硅负极锂离子的脱嵌能力及电子的传导性能，还能减小极化现象，抑制循环过程中的负极阻抗增加；且镁元素可与含氧硅部分生成硅酸盐结构，有效减小锂耗。以上因素共同作用，显著改善了硅基负极活性材料的首次库伦效率和循环容量保持率。因此，采用本申请的硅基负极活性材料，使得二次电池能够同时兼顾较高的循环性能、首次库伦效率。
在一些实施方案中，硅基负极活性材料中的硅可以以包括结晶硅在内的多个硅相的形式存在。具体地，硅相可以均匀地分布并且嵌入/埋入包括硅基负极活性材料的基质中。换句话说，硅相可以分散并且均匀地分布在基质中。
在一些实施方案中，所述含碱金属元素的硅酸盐包括含锂的硅酸盐，且所述含锂的硅酸盐的XRD衍射峰的半峰宽小于等于1.50°。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，含锂的硅酸盐包括Li2Si2O5、Li2SiO3中的至少一种。
在一些实施方案中，所述含碱金属元素的硅酸盐包括含锂的硅酸盐，且所述含锂的硅酸盐的晶粒尺寸小于等于20nm。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述碱金属元素包括Li元素、Na元素、K元素中的一种或多种。在以上实施方案中，硅基负极活性材料均表现出改善的首次循环效率和循环容量保持率。
在一些实施方案中，所述碱金属元素包括Li元素。在以上实施方案中，硅基负极活性材料均表现出改善的首次循环效率和循环容量保持率。
在一些实施方案中，硅基负极活性材料还含有硅晶粒、硅氧材料晶粒中的至少一种。
在一些实施方案中，Al元素和Mg元素生长在硅基负极活性材料中，例如在气相沉积硅基负极活性材料的过程中生长在其中。在一些实施方案中，Al元素和Mg元素在与硅基负极活性材料共同气相沉积时生长在硅基负极活性材料中。
在一些实施方案中，所述硅基负极活性材料中Al元素的含量大于Mg元素的含量。在上述比例范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了硅基负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，硅基负极活性材料具有1.2:1以上的Al和Mg的质量比。在上述比例范围内，Al元素和Mg元素表现出预料不到的协同作用，进一步显著改善了负极活性 材料的首次库伦效率和循环容量保持率。
在一些实施方案中，硅基负极活性材料具有1.2:1至18:1的Al和Mg的质量比。在上述比例范围内，Al元素和Mg元素表现出预料不到的协同作用，进一步显著改善了负极活性材料的首次库伦效率和循环容量保持率。
一些实施方案中，硅基负极活性材料具有2.2:1至6:1的Al和Mg的质量比。在上述比例范围内，Al元素和Mg元素表现出预料不到的协同作用，进一步显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料具有5:1至20:1的Al和Mg的质量比。在上述比例范围内，Al元素和Mg元素表现出预料不到的协同作用，进一步显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，硅基负极活性材料中的Al元素与所述Mg元素的质量比可以为40:1以下、30:1以下、20:1以下、15:1以下、14:1以下、13:1以下、12:1以下。在一些实施方案中，硅基负极活性材料中的Al元素与所述Mg元素的质量比可以为1.2:1以上、2:1以上、3:1以上、4:1以上、5:1以上。Al元素与所述Mg元素的质量比可以是由前述任意上、下限数值组成。在上述比例范围内，Al元素和Mg元素表现出预料不到的协同作用，进一步显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，硅基负极活性材料中的Al元素与所述Mg元素的质量比可以为3-6:1，还可选为2-6:1，还可选为2-7:1，还可选为2-8:1，还可选为2-10:1，还可选为2-12:1，还可选为2-14:1，还可选为2-16:1，还可选为2-18:1，还可选为1-18:1，还可选为1-20:1，还可选为1-30:1，还可选为1-40:1。
在一些实施方案中，所述硅基负极活性材料中Al元素的含量为400ppm以上。在上述含量范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Al元素的含量为500ppm-2000ppm。基于此，负极活性材料具有进一步改善的首次循环效率和循环容量保持率。在上述含量范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Al元素的含量为800ppm-2000ppm。基于此，负极活性材料具有进一步改善的首次循环效率和循环容量保持率。在上述含量范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Al元素的含量为800ppm-1800ppm。基于此，负极活性材料具有进一步改善的首次循环效率和循环容量保持率。在上述含量范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Al元素的含量为1100ppm-1500ppm。基于此，负极活性材料具有进一步改善的首次循环效率和循环容量保持率。在上述含量范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Al元素的含量上限值可以选自2300ppm、2000ppm、1900ppm、1800ppm、1700ppm、1600ppm、1500ppm、1400ppm、1300ppm、1200ppm、1100ppm中的任意一个数值；所述Al元素的含量下限值可以选自500ppm、550ppm、600ppm、650ppm、700ppm、750ppm、800ppm、900ppm、1000ppm中的任意一个数值。即Al元素的含量的范围可以是由前述任意上、下限数值组成。在上述含量范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Al元素的含量可选为1100-1500ppm，可选为1100-1800ppm，可选为800-1500ppm，可选为800-1800ppm，可选为800-2000ppm，可选为500-2000ppm。
在一些实施方案中，所述硅基负极活性材料中Mg元素的含量为800ppm以下。基于此，负极活性材料具有进一步改善的首次循环效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Mg元素的含量为50ppm-500ppm。基于此，负极活性材料具有进一步改善的首次循环效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Mg元素的含量为100ppm-650ppm。基于此，负极活性材料具有进一步改善的首次循环效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Mg元素的含量为250ppm-500ppm。基于此，负极活性材料具有进一步改善的首次循环效率和循环容量保持率。
在一些实施方案中，硅基负极活性材料中Mg元素的含量上限值可以选自1000ppm、900ppm、800ppm、700ppm、600ppm、500ppm、400ppm、300ppm、200ppm、100ppm中的任意一个数值；所述锰元素的含量下限值可以选自50ppm、60ppm、70ppm、80ppm、90ppm中的任意一个数值；即所述锰元素的含量的范围可以是由前述任意上下限数值组成。在上述含量范围内，Al元素和Mg元素表现出预料不到的协同作用，显著改善了负极活性材料的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料中Mg元素的含量可选为250-500ppm，250-650ppm，100-650ppm，100-800ppm，50-800ppm，50-600ppm，50-400ppm，50-300ppm，50-200ppm。
在一些实施方案中，所述硅基负极活性材料的体积平均粒径Dv50为4μm-10μm，可选为5μm-8μm。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料的体积平均粒径Dv50可选为4μm以上， 更可选为5μm以上，能够减少活性离子在负极的成膜消耗，以及减少电解液在负极的副反应，从而降低二次电池的不可逆容量，提高二次电池的循环性能；还能够减少负极极片中粘结剂的添加量，有利于提高二次电池的能量密度。平均粒径Dv50可选为10μm以下，更可选为8μm以下，使得活性离子和电子在材料颗粒中的迁移路径较短，提高离子和电子的迁移速率，从而提高二次电池的动力学性能；还有利于防止硅基负极活性材料在充放电过程中发生破裂，进而提高二次电池的循环性能。
在一些实施方案中，所述硅基负极活性材料的比表面积为3m2/g以下，可选为0.5m2/g-2m2/g。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料的比表面积为0.5m2/g-2m2/g。比表面积可选为0.5m2/g以上可以使材料颗粒的表面具有较多的活性位点，能够有效提高硅基负极活性材料的电化学性能，满足二次电池对动力学性能的要求。比表面积可选为2m2/g以下，有利于减少电解液在负极的副反应，还能够减少活性离子在负极的成膜消耗，从而降低二次电池的不可逆容量，提高二次电池的循环性能。
在一些实施方案中，所述硅基负极活性材料在4MPa压力下的粉体体积电阻率为3Ω·cm以下，可选为0.5Ω·cm-1.5Ω·cm。在上述方案中，硅基负极活性材料具有改善的首次库伦效率和循环容量保持率。
在一些实施方案中，所述硅基负极活性材料在4MPa压力下的粉体体积电阻率为3Ω·cm以下，更可选为1.5Ω·cm以下。所述硅基负极活性材料的粉体体积电阻率在上述范围内，能够降低电子在颗粒内部的迁移阻碍，有利于改善硅基负极活性材料的动力学性能，并有利于降低负极极化现象，从而提升二次电池的循环寿命。可以通过对硅基负极活性材料进行表面处理降低粉体体积电阻率。
在一些实施方案中，所述硅基负极活性材料在5吨压力下的压实密度为1.4-1.8g/cm3，可选为1.5-1.7g/cm3。在上述方案中，硅基负极活性材料具有改善的能量密度。
在一些实施方案中，所述硅基负极材料含有Si元素和O元素，O元素和Si元素的摩尔比大于0且小于2，可选为0.2-1.8:1，还可选为0.3-1.7:1，还可选为0.4-1.6:1，还可选为0.6-1.5:1，还可选为0.7-1.4:1，还可选为0.8-1.3:1，还可选为0.9-1.2:1，还可选为1.0-1.1:1。
在一些实施方案中，所述硅基负极活性材料的至少部分表面具有包覆层。
在一些实施方案中，包覆层的材料包括聚合物、碳材料、金属材料及金属化合物中的一种或几种。例如，包覆层包括聚合物包覆层、碳包覆层及金属化合物包覆层中的一种或几种。可选地，所述聚合物可以选自聚苯胺、聚乙炔、聚苯乙烯、聚丙烯腈、聚氯乙烯及聚乙烯中的一种或几种。可选地，所述碳材料可以包括石墨、中间相微碳球(MCMB)、烃类化合物热解碳、硬碳及软碳中的一种或几种，其中石墨可以是天然石墨及人造石墨中的一种或几种。可选地，所述金属化合物可以包括Ti5Si3、Al2O3及TiO2中的一种或几种。所述包覆层能够使得所述硅基负极活性材料的体积膨胀效应进一步得到缓解，提高材料的循环寿命。同时，包覆层还对硅基负极活性材料起到保护作用，抑制电解液在材料表面的副 反应，保护材料表面不被电解液侵蚀，从而使硅基负极活性材料具有较高的容量发挥，使电池的循环寿命得到进一步提高。
在第二方面，本申请提供上述任一项所述的硅基负极活性材料的制备方法，包括
提供含有Si元素、O元素、Mg元素和Al元素的原料；
采用气相沉积方法，加热所述原料形成蒸气，然后冷却所述蒸气形成沉积物；
将沉积物粉碎，获得粉碎产物；
使上一步产物与碱金属源反应，获得碱金属化产物。
在一些实施方案中，硅基负极活性材料的制备方法还包括：
对碱金属化产物进行包覆处理，获得有包覆层的产物。
在一些实施方案中，所述原料中的Si元素可以来源于硅单质和硅氧化物，所述原料中的O元素可以来源于硅氧化物。其中，硅单质例如包括金属硅。硅氧化物例如包括氧化亚硅(SiO)、二氧化硅(SiO2)中的一种或几种。金属硅例如是标准GB/T 2881-2014中规定的任一种金属硅或工业硅，例如是GB/T 12963-2014中规定的任一种电子级多晶硅，例如是GB/T 25074-2010中规定的任一项太阳能级多晶硅。硅单质的纯度例如为3N以上、4N以上、5N以上或6N以上。
在一些实施方案中，原料中的Al元素可以来自于硅单质或硅氧化物中本身含有的Al元素，也可以来自于原料添加的铝源。
在一些实施方案中，原料中的Mg元素可以来自于硅单质或硅氧化物中本身含有的Mg元素，也可以来自于原料中添加的镁源。
在一些实施方案中，原料中的碱金属元素可以来自于硅单质或硅氧化物中本身含有的碱金属元素，也可以来自于原料中添加的碱金属源。
在一些实施方案中，原料中含有铝源。原料中的铝元素至少部分地来自铝源。铝源可以选自金属铝、铝合金、铝化合物，铝化合物可以选自铝的氧化物、铝的硫化物、铝的氢氧化物中的一种或几种。可选地，铝源可以选自金属铝、硝酸铝、氯化铝、氢氧化铝以及硅酸铝中的一种或几种。
在一些实施方案中，原料含有镁源。原料中的Mg元素至少部分地来自镁源。镁源可以选自金属镁及镁化合物中的一种或几种；其中，镁化合物可以选自镁的氧化物、镁的碳酸盐、镁的氢氧化物、镁的硝酸盐及镁的硫酸盐中的一种或几种。
在一些实施方案中，碱金属源可以选自碱金属单质、碱金属合金及碱金属化合物中的一种或几种；其中，碱金属化合物可以选自碱金属的氧化物、碱金属的硫化物、碱金属的碳酸盐、碱金属的氢氧化物、碱金属的醋酸盐、碱金属的草酸盐、碱金属的硝酸盐及碱金属的硫酸盐中的一种或几种。
在一些实施方案中，含有Si元素、O元素、Al元素和Mg元素的原料包括硅单质、二氧化硅、铝源和镁源。
在一些实施方案中，通过调整原料中铝源的种类和加入量来调整负极活性材料中Al元 素的含量。
在一些实施方案中，通过调整原料中镁源的种类和加入量来调整负极活性材料中Mg元素的含量。
在一些实施方案中，通过混合多种Al元素含量的硅氧化物粉末或金属硅粉末、以及调整铝源的种类及加入量等一种或几种手段，来调整负极活性材料中Al元素的含量。
在一些实施方案中，通过混合多种Mg元素含量的硅氧化物粉末或金属硅粉末、以及调整镁源的种类及加入量等一种或几种手段，来调整负极活性材料中Mg元素的含量。
在一些实施方案中，加热原料形成蒸气的操作在常压或减压下的惰性气氛中实施。
在一些实施方案中，冷却所述蒸气形成沉积物的操作在常压或减压下的惰性气氛中实施。
在上述制备方法中，所述惰性气氛可以是氮气气氛、氩气气氛、氦气气氛等。可选地，惰性气氛的绝对压力为常压(1个标准大气压)或减压(小于1个标准大气压)。可选地，所述惰性气氛的绝对压力为10Pa-950Pa，更可选为20Pa-100Pa。
在一些实施方案中，在上述惰性气氛压力的范围内，通过降低压力(即提高真空度)，能够使最终得到的硅基负极活性材料中Al元素和Mg元素的含量相应地增加。
在一些实施方案中，在加热所述原料形成蒸气的操作中，加热的温度为1100-1550℃。
在一些实施方案中，在冷却所述蒸气形成沉积物的操作中，冷却的温度为700-900℃。
在一些实施方案中，在冷却所述蒸气形成沉积物的操作中，可以通过调整冷却的温度来使沉积物获得适当的晶体结构。可选地，所述冷却的温度为850℃-1050℃，这有利于使硅基负极活性材料获得较好的微晶尺寸及适宜的结晶性，从而使硅基负极活性材料具有较高的首次库伦效率及循环性能。当冷却的温度低于800℃，可能会导致材料的结晶性过低，影响材料的首次库伦效率；当冷却的温度高于1050℃时，可能会导致材料的微晶尺寸过大，影响材料的循环性能。
在一些实施方案中，在上述加热温度范围内，升高温度，能够使最终得到的硅基负极活性材料中Al元素和Mg元素的含量相应地增加。
在一些实施方案中，在上述惰性气氛压力的范围内，降低压力，即提高真空度，能够使最终得到的硅基负极活性材料中Al元素和Mg元素的含量相应地增加。
在一些实施方案中，将沉积物粉碎的操作包括：根据预设的产物的体积平均粒径(Dv50)和比表面积参数，对沉积物进行粗破-细碎-分级的操作，得到符合预设参数的产物。在一些实施方案中，可以采用本领域已知的任意方法和设备对沉积物进行破碎分级处理，例如研磨机，气流粉碎-分级一体机。
在一些实施方案中，制备硅基负极活性材料的方法还包括：对碱金属化产物进行包覆处理，获得有包覆层的产物的操作。
在一些实施方案中，包覆层的材料包括聚合物、碳材料、金属材料及金属化合物中的一种或几种。例如，包覆层包括聚合物包覆层、碳包覆层及金属化合物包覆层中的一种或 几种。可选地，所述聚合物可以选自聚苯胺、聚乙炔、聚苯乙烯、聚丙烯腈、聚氯乙烯及聚乙烯中的一种或几种。可选地，所述碳材料可以包括石墨、中间相微碳球(MCMB)、烃类化合物热解碳、硬碳及软碳中的一种或几种，其中石墨可以是天然石墨及人造石墨中的一种或几种。可选地，所述金属化合物可以包括Ti5Si3、Al2O3及TiO2中的一种或几种。所述包覆层能够使得所述硅基负极活性材料的体积膨胀效应进一步得到缓解，提高材料的循环寿命。同时，包覆层还对硅基负极活性材料起到保护作用，抑制电解液在材料表面的副反应，保护材料表面不被电解液侵蚀，从而使硅基负极活性材料具有较高的容量发挥，使电池的循环寿命得到进一步提高。
在一些实施方案中，采用液相包覆法在硅基负极活性材料的表面进行包覆处理，形成包覆层。例如将聚合物溶解在一定的溶剂中，与硅基负极活性材料颗粒充分搅拌，混合均匀，随后将溶剂蒸发除去，使聚合物均匀包覆在硅基负极活性材料颗粒表面。
在一些实施方案中，采用化学气相沉积法在硅基负极活性材料表面进行包覆处理，形成包覆层。例如向装有硅基负极活性材料的反应炉内引入烃类化合物气体，在惰性气氛下进行热处理，使烃类化合物碳化，形成包覆于硅基负极活性材料表面的包覆层，得到表面覆有包覆层的硅基负极活性材料。
在一些实施方案中，所述包覆处理包括碳包覆处理。可选地，所述碳包覆处理包括以下操作：将粉碎产物置于含有碳源气体的腔室内，加热至700-1000℃，保温1-6h。
在一些实施方案中，所述包覆处理包括碳包覆处理。可选地，所述碳包覆处理包括以下操作：将粉碎产物置于含有碳源气体的腔室内，加热至800-900℃，保温2-5h。
在一些实施方案中，所述碱金属源可以是碱金属单质、碱金属氢氧化物、碱金属碳酸盐、碱金属硝酸盐、氨基化碱金属、氢化碱金属中的一种或几种。
在一些实施方案中，所述碱金属源可以是金属锂、氢氧化锂、碳酸锂、硝酸锂、氨基锂、氢化锂中的一种或几种。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(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)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极膜层还可以包括除本申请以外的本领域已知的硅基负极活性材料，本领域技术人员可以根据实际需求进行选择。作为示例，可以包括但不限于，人造石墨、天然石墨、硬碳、软碳、其它硅基材料和锡基材料中的一种或几种。所述其它硅基材料可包括单质硅、与本申请不同的硅氧复合物、硅碳复合物、硅氮复合物、硅合金中的一种或几种。所述锡基材料可包括单质锡、锡氧化合物、锡合金中的一种或几种。这些材 料均可以通过商业途径获得。
在一些实施方式中，负极膜层还可选地包括粘结剂。作为示例，粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如硅基负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[正极极片]
在一些实施方式中，正极极片通常包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(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)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(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-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[正极活性材料]
在一些实施方式中，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。
作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO2)、锂镍氧化物(如LiNiO2)、锂锰氧化物(如LiMnO2、LiMn2O4)、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(如LiNi1/3Co1/3Mn1/3O2(也可以简称为NCM333)、LiNi0.5Co0.2Mn0.3O2(也可以简称为NCM523)、LiNi0.5Co0.25Mn0.25O2(也可以简称为NCM211)、LiNi0.6Co0.2Mn0.2O2(也可以简称为NCM622)、LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi0.85Co0.15Al0.05O2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO4)、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中的至少一种。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，电解质为液态的，且包括电解质盐和溶剂。
在一些实施方式中，电解质盐选自高氯酸钠，六氟磷酸钠，四氟硼酸钠及六氟砷酸钠。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。作为示例，添加剂可以包括负极成膜添加剂、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、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对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。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池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。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，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能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池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二次电池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，多个二次电池5容纳于该容纳空间。
在一些实施方式中，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为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，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能够盖设于下箱体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。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包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。所述用电装置可以包括移动设备(例如手机、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，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。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二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而 不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
1.硅基负极活性材料的制备方法
1.1概述
在以下具体实施方式中，负极活性材料的制备方法概述如下：
1)提供含有Si元素、O元素、Mg元素和Al元素的蒸气，对蒸气进行冷却以获得沉积物
2)将沉积物粉碎，获得粉碎产物；
3)对粉碎产物进行碳包覆处理，获得碳包覆的产物；
4)使碳包覆的产物与锂源发生锂化反应，收集产物，即获得负极活性材料。
1.2详述
在以下具体实施方式中，负极活性材料的制备方法详细描述如下：
1)按照目标产物中Al元素和Mg元素的含量提供原料组合物，原料组合物包括硅单质、硅氧化物、铝源(硝酸铝)和镁源(金属镁)；
2)在绝对压力为30Pa的氦气气氛中，用气相沉积的方法，将原料组合物加热至1300℃形成蒸气，再将蒸气冷却至900℃形成沉积物；
3)收集沉积物，粉碎成粉末；
4)将粉末置于气相沉积设备的反应腔中，在反应腔中通入有碳源气体(乙炔)和氮气的混合气，乙炔占比20体积％，加热至750℃，保持2h，获得碳包覆的产物；
5)将碳包覆的产物与锂源(氨基化锂)按照100：30(质量比)混合，加热至650℃，保温2h，进行锂化反应，收集产物，即获得负极活性材料。
在以上制备方法中，根据目标产物的组成，通过适应性地调整原料混合物中铝源和镁源的含量，就能够获得各种Mg含量和Al含量的负极活性材料。应当理解的是，受硅单质和二氧化硅纯度的影响，一些硅单质和二氧化硅中预先含有一定量的Al元素和Mg元素，此时，应根据样品的目标产物的成分组成适应性地调整原料混合物中铝源和镁源的含量。
按照上述方法，制备获得了多个负极活性材料样品(以下简称样品)，这些样品具有不同的Mg含量和Al含量，详细如表1所示。表1示出的例子中，包括实施例1-11(E1-E12)和对比例1-3(D1-D3)。
在以上制备方法中，根据目标产物的组成，通过适应性地调整原料混合物中碱金属源、铝源和镁源的含量，就能够获得各种Al元素含量和Mg元素含量的硅基负极活性材料。应当理解的是，受硅单质和二氧化硅纯度的影响，一些硅单质和二氧化硅中预先含有一定量的Al元素和Mg元素，此时，应根据样品的目标产物的成分组成适应性地调整原料混合物中铝源和镁源的含量。
按照上述方法，制备获得了多种硅基负极活性材料样品(以下简称样品)，这些样品具 有不同的Al元素含量和Mg元素含量。这些样品具有以下性质：
1)硅基负极活性材料为具有碳包覆层的硅基负极活性材料，其中，碳包覆层的含量占比为4.2±1％，余量为硅基负极活性材料；
2)硅基负极活性材料的O元素和Si元素的摩尔比为1±0.1:1；
3)基于100％的硅基负极活性材料，Li元素的含量为7.5±0.5％。
4)基于100％的硅基负极活性材料，Al元素含量如表1所示。
5)基于100％的硅基负极活性材料，Mg元素含量如表1所示。
6)硅基负极活性材料的体积平均粒径Dv50为6.5±0.5μm。
7)硅基负极活性材料的比表面积为1.75±0.25m2/g。
8)硅基负极活性材料在4MPa压力下的粉体体积电阻率为1±0.1Ω·cm。
9)硅基负极活性材料在5吨压力下的压实密度为1.6±0.1g/cm3
10)硅基负极活性材料含有Li2SiO3和Li2Si2O5，且Li2SiO3的XRD衍射峰的半峰宽为0.6°±0.2°，晶粒尺寸为15±2nm；Li2Si2O5的XRD衍射峰的半峰宽为1.0°±0.1°，晶粒尺寸为8±2nm。
表1示出了不同Al元素含量和Mg元素含量的硅基负极活性材料样品。
扣式电池的制备
(1)负极极片的制备：将上述制备的硅基负极活性材料与导电剂Super-P(导电炭黑)、粘结剂PAA(聚丙烯酸)按85:5:10的质量比在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。
(2)对电极：金属锂片。
(3)隔离膜：聚乙烯(PE)薄膜。
(4)电解液的制备：将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)体积比1:1:1混合，然后将LiPF6均匀溶解在上述溶液中得到电解液，并加入氟代碳酸乙烯酯(FEC)，其中LiPF6的浓度为1mol/L，FEC在电解液中的质量占比为6％。
(5)扣式电池的制备：将上述负极极片、隔离膜、金属锂片对电极按顺序叠片，加入上述电解液，得到扣式电池。
二、分析检测方法
2.1、元素分析(例如K，P，Si及碱金属元素等)
元素含量为本领域公知的含义，可采用本领域已知的方法测试。可以参考EPA-3052-1996《硅酸盐的微波酸式消解法》将硅基负极活性材料消解，然后依据EPA 6010D-2014《电感耦合等离子体原子发射光谱法》，采用美国赛默飞世尔科技(Thermo Fisher Scientific)公司的ICAP-7000型电感耦合等离子发射光谱仪(ICP-OES)测定目标元素的含量。具体测试方法如下：采用10mL硝酸和10mL氢氟酸将0.5g硅基负极活性材料样品进行微波消解， 消解后加入50mL容量瓶中定容，之后采用ICAP-7000型ICP-OES测定目标元素的含量。
2.2、元素分析(氧元素、碳元素)
元素含量为本领域公知的含义，可采用本领域已知的方法测试。硅基负极活性材料中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。
氧元素含量可以参照JY/T 017-1996元素分析仪方法通则，测试仪器可以采用Elementar公司的rapid OXY cube氧元素分析仪。
2.3、体积电阻率
材料的体积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，例如可以采用四探针法测试本申请硅基负极活性材料在4MPa压力下的粉体体积电阻率，测试方法包括：将本申请硅基负极活性材料粉体加入样品台中，通过压力机对粉体施加4MPa的压力，待压力稳定后，通过电阻率仪读取硅基负极活性材料在4MPa压力下的粉体体积电阻率。
2.4压实密度
材料的压实密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GB/T24533-2009标准，通过电子压力试验机进行，如UTM7305型电子压力试验机。准确称取样品1g左右，加入底面积为1.327cm2的模具中，采用加压装置向样品施加5吨压力并在这一压力下保持30秒后再卸去压力，随后测量样品的高度即可通过公式ρ＝m/(1.327×h)得到材料的压实密度。式中，ρ表示材料的压实密度，m表示样品的质量，h表示样品在被施加5吨压力并在这一压力下保持30秒后再卸去压力后的高度。
2.4、粉末粒径分析
材料的Dv10、Dv50、Dv90为本领域公知的含义，可以采用本领域已知的方法测试。例如可以参照标准GB/T 19077-2016，使用激光粒度分析仪(如Malvern Master Size 3000)测定。
Dv10、Dv50、Dv90的物理定义如下：硅基负极活性材料累计体积分布百分数分别达到10％、50％、90％时所对应的粒径。
2.5、比表面积分析
材料的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，例如参照GB/T 19587-2017气体吸附BET法测定固态物质比表面积标准，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，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri StarⅡ3020型比表面与孔隙分析仪进行。
2.6、电池性能测试
(1)首次库伦效率和循环容量保持率
在25℃、常压环境下，将扣式电池以0.1C倍率恒流放电至0.005V，然后再以0.04C 恒流放电至0.005V，之后静置5min，记录此时的放电容量，即为第1圈嵌锂容量；再以0.1C倍率恒流充电至1.5V，再静置5min，此为一个循环充放电过程，记录此时的充电容量，即为第1圈脱锂容量。将扣式电池按照上述方法进行30次循环充放电测试，记录每次的脱锂容量。
首次库伦效率(％)＝第1圈脱锂容量/第1圈嵌锂容量×100％
循环容量保持率(％)＝第30圈脱锂容量/第1圈脱锂容量×100％

三、结果与讨论
表1示出了本申请一些实施例的硅基负极活性材料的原料的成分和组成、硅基负极活性材料产物中Al元素和Mg元素的含量和重量比，以及基于上述硅基负极活性材料作为负极活性材料的电池性能。下面分别讨论：
(1)关于原料的组成
样品(E1-E12)采用的原料硅单质为金属硅1(Si≥99.9wt％，Al＝300ppm，Mg＝20ppm)。
样品(D1-D3)采用的原料硅单质为金属硅2(Si≥99.9wt％，不含Al和Mg)。
从表2中可以看出，硅基负极活性材料中的Al元素和Mg元素可以来自于多种来源：
a)硅基负极活性材料中的Al元素可以来自于原料金属硅；
b)硅基负极活性材料中的Mg元素可以来自于原料金属硅；
c)硅基负极活性材料中的Al元素可以来自于额外添加的铝源；
d)硅基负极活性材料中的Mg元素可以来自于额外添加的镁源。
本领域技术人员可以根据硅基负极活性材料的目标化学成分，适应性地调整原料中Mg元素和Al元素的含量，最终获得具有目标化学成分的硅基负极活性材料。如果需要增加/降低目标硅基负极活性材料中的Al元素含量，可以采用Al元素含量更高/更低的金属硅(或氧化硅)，也可以增加/降低原料中额外添加的铝源。如果需要增加/降低目标硅基负极活性材料中的Mg元素含量，可以采用Mg元素含量更高/更低的金属硅(或氧化硅)，也可以增加/降低原料中额外添加的镁源。
(2)关于Mg和Al的协同作用
表2的实验数据证实了本申请的负极活性材料中Al和Mg的组合取得了预料不到的协同作用。
下面结合实施例E1，对比例D1、D2和D3详细分析：
对比例D1的硅基负极活性材料不含Mg元素和Al元素，其IC+CR值为152.2％。
对比例D2的硅基负极活性材料中含有1500ppm的Al元素，但不含Mg元素，其IC+CR值为160.0％，与D1相比仅增加了7.8％。
实施例D3的硅基负极活性材料中含有500ppm的Mg元素，但不含Al元素，其IC+CR值为155.3％，与D1相比仅增加了3.1％。
实施例E1的硅基负极活性材料中同时含有1500ppm的Al元素和300ppm的Mg元素，其IC+CR值为175.9％，与D1相比增加了23.7％，增加幅度远远大于单独添加Al或Mg带来性能提升之简单加和(即7.8％+3.1％＝10.9％)。因此，上述实验证据证实了Al和Mg的结合确实带来的预料不到的协同作用。
(3)关于硅基负极活性材料中Al/Mg的重量比
表2的实验数据还证实了Al/Mg的重量比大于1时，负极活性材料性能有显著提升。
实施例E12中Al/Mg的重量比的重量比为0.8:1(小于1)，负极活性材料的IC+CR值仅为162.5％。
实施例E1-E11中Al/Mg的重量比为1.2:1至40:1(大于1)，负极活性材料的IC+CR值为164.5％-175.9％，优于实施例E12
以上实验数据说明，硅基负极活性材料中的Al含量大于Mg含量时，硅基负极活性材料表现出更为显著的首次库伦效率和循环容量保持率性能改善
(4)关于硅基负极活性材料中Al/Mg的比值
如实施例E1-E9所示，当Al/Mg的重量比为1.2:1至18:1时，负极活性材料的IC+CR值为167.4％-175.9％，表现出进一步改善的首次库伦效率和循环容量保持率性能改善。
如实施例E1-E6所示，当Al/Mg的重量比为2.8:1至18:1时，负极活性材料的IC+CR值为169.8％-175.9％，表现出进一步改善的首次库伦效率和循环容量保持率性能改善。
(5)关于硅基负极活性材料中的Al元素含量和Mg元素含量
如实施例E1至E12所示，硅基负极活性材料中Al元素的含量为500ppm以上，例如在500ppm-2000ppm，负极活性材料表现出改善的首次库伦效率和循环容量保持率性能改善。
如实施例E1至E12所示，硅基负极活性材料中Al元素的含量为500ppm以上，例如在800ppm-2000ppm，负极活性材料表现出改善的首次库伦效率和循环容量保持率性能改善。
如实施例E1至E12所示，硅基负极活性材料中Mg元素的含量为800ppm以下，例如在50ppm-800ppm。负极活性材料表现出改善的首次库伦效率和循环容量保持率性能改善。
以上实验数据说明，硅基负极活性材料中单独含有Mg元素或Al元素时，首次库伦效率和循环容量保持率的性能通常仅有单方面的提升，而且提升幅度并不显著。当硅基负极活性材料含有Mg元素和Al元素的组合时，负极活性材料表现出首次库伦效率和循环容量保持率的双重提升，而是提升幅度特别显著，这说明Mg元素和Al元素取得了预料不到的协同作用。
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。

Claims (12)

  1. 一种硅基负极活性材料，所述硅基负极活性材料包括含碱金属元素的硅酸盐，且所述硅基负极活性材料中同时含有Al元素和Mg元素。
  2. 根据权利要求1所述的硅基负极活性材料，其中，所述Al元素的含量大于Mg元素的含量。
  3. 根据权利要求1-2任一项所述的硅基负极活性材料，其中，所述Al元素和所述Mg元素的质量比大于等于1.2:1；可选为5:1至20:1。
  4. 根据权利要求1-3任一项所述的硅基负极活性材料，其中，所述Al元素的含量为400ppm以上，可选为800ppm-2000ppm。
  5. 根据权利要求1-4任一项所述的硅基负极活性材料，其中，所述Mg元素的含量为800ppm以下，可选为50ppm-500ppm。
  6. 根据权利要求1-5任一项所述的硅基负极活性材料，其具有以下一项或多项特征：
    (1)所述硅基负极活性材料的体积平均粒径Dv50为4μm-10μm，可选为5μm-8μm；
    (2)所述硅基负极活性材料的比表面积为3m2/g以下，可选为0.5m2/g-2m2/g；
    (3)所述硅基负极活性材料在4MPa压力下的粉体体积电阻率为3Ω·cm以下，可选为0.5Ω·cm-1.5Ω·cm；
    (4)所述硅基负极活性材料在5吨压力下的压实密度为1.4-1.8g/cm3，可选为1.5-1.7g/cm3；
    (5)所述含碱金属元素的硅酸盐包括含锂的硅酸盐，且所述含锂的硅酸盐的XRD衍射峰的半峰宽小于等于1.50°；
    (6)所述含碱金属元素的硅酸盐包括含锂的硅酸盐，且所述含锂的硅酸盐的晶粒尺寸小于等于20nm。
  7. 根据权利要求1-6任一项所述的硅基负极活性材料，所述硅基负极活性材料的至少部分表面具有包覆层。
  8. 权利要求1-7任一项所述的硅基负极活性材料的制备方法，包括
    提供含有Si元素、O元素、Mg元素和Al元素的原料；
    采用气相沉积方法，加热所述原料形成蒸气，然后冷却所述蒸气形成沉积物；
    将沉积物粉碎，获得粉碎产物；
    使上一步产物与碱金属源反应，获得碱金属化产物。
  9. 根据权利要求8所述的方法，还包括：
    对碱金属化产物进行包覆处理，获得有包覆层的产物。
  10. 根据权利要求8-9任一项所述的方法，其具有以下一项或多项特征：
    (1)在加热所述原料形成蒸气的操作中，加热的温度为1100-1550℃；
    (2)在冷却所述蒸气形成沉积物的操作中，冷却的温度为700-900℃。
  11. 一种二次电池，包括负极，所述负极包括权利要求1-7任一项所述的硅基负极活性材料。
  12. 一种用电装置，包括根据权利要求11所述的二次电池。
PCT/CN2023/079521 2023-03-03 2023-03-03 硅基负极活性材料、二次电池及用电装置 Ceased WO2024182919A1 (zh)

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