WO2024178595A1 - 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
WO2024178595A1
WO2024178595A1 PCT/CN2023/078666 CN2023078666W WO2024178595A1 WO 2024178595 A1 WO2024178595 A1 WO 2024178595A1 CN 2023078666 W CN2023078666 W CN 2023078666W WO 2024178595 A1 WO2024178595 A1 WO 2024178595A1
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Prior art keywords
negative electrode
silicon
electrode active
active material
based negative
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PCT/CN2023/078666
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English (en)
French (fr)
Inventor
苏颖薇
刘良彬
王家政
吕子建
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to KR1020257010191A priority Critical patent/KR20250055597A/ko
Priority to PCT/CN2023/078666 priority patent/WO2024178595A1/zh
Priority to EP23924570.7A priority patent/EP4583208A4/en
Priority to CN202380009176.0A priority patent/CN116868373B/zh
Priority to JP2025517054A priority patent/JP2025531349A/ja
Publication of WO2024178595A1 publication Critical patent/WO2024178595A1/zh
Priority to US19/098,502 priority patent/US20250230052A1/en
Anticipated expiration legal-status Critical
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    • 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • 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
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
    • 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
    • C01P2006/10—Solid density
    • 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
    • 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 one of the most promising negative electrode active materials due to their high capacity. As secondary batteries have made great progress, higher requirements have been placed on their electrochemical performance. Therefore, there is still a need for silicon-based negative electrode active materials with better performance in the field.
  • 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 phase containing an alkaline earth metal element, and the silicon-based negative electrode active material contains both K element and Fe element.
  • the silicon-based negative electrode active material contains a combination of K element and Fe element, and this specific combination improves the first coulombic efficiency and kinetic performance of the silicon-based negative electrode active material.
  • the combination of K element and Fe element achieves 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 used separately.
  • the presence of Fe element improves the conductivity of active ions and electrons in the process of embedding/extracting active ions (lithium ions) of the negative electrode active material, suppresses the increase of negative electrode impedance during the cycle, and improves the rate performance of the material.
  • the potassium silicate generated by the reaction of K element and silicon oxygen material is beneficial to improve the capacity of the negative electrode active material, thereby improving the first coulombic efficiency of the secondary battery. Therefore, the negative electrode active material of the present application is adopted, so that the secondary battery can have a higher first coulombic efficiency and better rate performance while having a higher energy density.
  • the content of the K element is greater than the content of the Fe element.
  • the K element and the Fe element exhibit unexpected synergistic effects, significantly improving the first coulombic efficiency and kinetic performance of the silicon-based negative electrode active material.
  • the mass ratio of the K element to the Fe element is greater than or equal to 8:1, and can be 10:1 to 36:1.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and kinetic performance.
  • the content of K element is 400 ppm or more, and can be 800 ppm to 2000 ppm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and kinetic performance.
  • the content of the Fe element is 500 ppm or less, and can be optionally 30 ppm to 400 ppm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and kinetic performance.
  • the volume average particle size D v 50 of the silicon-based negative electrode active material is 4 ⁇ m-10 ⁇ m, and can be 5 ⁇ m-8 ⁇ m.
  • the silicon-based negative electrode active material has improved kinetic performance.
  • the specific surface area of the silicon-based negative electrode active material is less than 6 m 2 /g, and can be 3 m 2 /g-5 m 2 /g. In the above solution, the silicon-based negative electrode active material has an improved first coulombic efficiency.
  • the powder volume resistivity of the silicon-based negative electrode active material under a pressure of 4 MPa is less than 6 ⁇ cm, and can be optionally 0.5 ⁇ cm-4.5 ⁇ cm.
  • the silicon-based negative electrode active material has improved kinetic properties.
  • the compaction density of the silicon-based negative electrode active material under a pressure of 49000 N 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 phase containing alkaline earth metal elements includes a silicate phase containing magnesium, and the half-peak width of the silicate phase containing magnesium is less than or equal to 0.50°.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and kinetic performance.
  • the silicate phase containing alkaline earth metal elements includes a silicate phase containing magnesium, and the grain size of the silicate phase containing magnesium is less than or equal to 21 nm.
  • the silicon-based negative electrode active material has improved capacity utilization and ion conductivity.
  • 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 raw material is heated to form a vapor, and then the vapor is cooled to form a deposit;
  • the sediment is pulverized to obtain a pulverized product.
  • the method for preparing a silicon-based negative electrode active material further comprises:
  • the pulverized 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.
  • K and Fe elements achieved an unexpected synergistic effect, and the technical effect achieved by their combination was significantly better than the simple addition of the two elements used separately.
  • Silicon-based negative electrode active materials have improved first coulombic efficiency
  • Silicon-based negative electrode active materials have improved kinetic properties
  • 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 a secondary battery according to an embodiment of the present application.
  • 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. It may also include steps (b) and (a) performed sequentially.
  • the reference that the method may further include step (c) indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • ppm parts per million means parts per million.
  • ppm refers to the mass of K element or Fe element in silicon-based negative electrode active material as a percentage of the mass of 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 positive electrode, negative electrode, diaphragm, and electrolyte.
  • the positive and negative electrodes are separated by a diaphragm to prevent short circuit, 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.
  • 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+, causing oxidation and reduction reactions at the positive and negative electrodes, respectively.
  • Sodium ions can be in the positive electrode and in the electrolyte.
  • the positive electrode and the negative electrode are both 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 phase containing an alkaline earth metal element, and the silicon-based negative electrode active material contains both K element and Fe element.
  • the silicon-based negative electrode active material contains a combination of K element and Fe element, 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 K element and Fe element 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 used.
  • the potassium silicate generated by the reaction of K element and silicon dioxide is conducive to reducing the consumption of lithium in the first charge and discharge process, improving the capacity of the negative electrode active material, and thus improving the first coulombic efficiency of the secondary battery; at the same time, the Fe element improves the conductivity of active ions and electrons in the negative electrode active material during the embedding/extraction of active ions (lithium ions), and reduces the negative electrode impedance during the cycle, thereby effectively improving the rate performance of the battery.
  • Fe is coupled with K element, which can alleviate the expansion of the material to a certain extent while improving the ion conductivity. Therefore, the negative electrode active material of the present application enables the secondary battery to have a higher energy density while taking into account a higher first coulombic efficiency and better rate performance.
  • the silicon-based negative electrode active material includes a silicon-based negative electrode active material.
  • the silicon in the silicon-based negative electrode active material may exist in the form of multiple silicon phases including crystalline silicon.
  • the silicon phase may be uniformly distributed and embedded/buried in a matrix including the silicon-based negative electrode active material.
  • the silicon phase may be dispersed and uniformly distributed in the matrix.
  • the silicon phase is a group formed by assembling one or more silicon crystals, and there may be a single group or there may be two or more groups.
  • the K element and the Fe 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 K element and the Fe 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 silicon-based negative electrode active material has a composite structure in which one or more nanocrystals are dispersed in a silicon-oxygen material matrix.
  • the silicon-based negative electrode active material has a structure in which Si grains and silicate grains are dispersed in a silicon-oxygen material matrix.
  • the content of the K element is greater than the content of the Fe element.
  • the K element and the Fe element exhibit an unexpected synergistic effect, significantly improving the first coulombic efficiency and kinetic performance of the silicon-based negative electrode active material.
  • the silicon-based negative electrode material has a mass ratio of K to Fe greater than or equal to 8: 1. Within the above ratio range, the K element and the Fe element exhibit an unexpected synergistic effect, further significantly improving the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the silicon-based negative electrode material has a mass ratio of K to Fe of 10:1 to 36:1. Within this range, K and Fe elements exhibit unexpected synergistic effects, further significantly improving the first coulombic efficiency and kinetic performance of the negative electrode active materials.
  • the silicon-based negative electrode material has a mass ratio of K to Fe of 20: 1 to 32: 1. Within the above ratio range, the K element and the Fe element exhibit an unexpected synergistic effect, further significantly improving the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the mass ratio of the K element in the silicon-based negative electrode material to the Fe element may be 60:1 or less, optionally 50:1 or less, optionally 40:1 or less, optionally 30:1 or less, optionally 25:1 or less, optionally 20:1 or less, or 15:1 or less. In some embodiments, the mass ratio of the K element in the silicon-based negative electrode material to the Fe element may be greater than or equal to 8:1, optionally 10:1 or more, optionally 12:1 or more, optionally 13:1 or more, optionally 16:1 or more, or optionally 18:1 or more.
  • the mass ratio of the K element to the Fe element may be composed of any of the aforementioned upper and lower limit values. Within the above-mentioned ratio range, the K element and the Fe element exhibit unexpected synergistic effects, further significantly improving the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the mass ratio of the K element to the Fe element in the silicon-based negative electrode material can be selected as 21-26:1, or 21-27:1, or 20-27:1, or 20-32:1, or 13-32:1, or 13-34:1, or 13-54:1, or 16-54:1, or 16-30:1, or 18-25:1.
  • the content of K element in the silicon-based negative electrode material is 400 ppm or more.
  • K element and Fe element show unexpected synergistic effects, significantly improving the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the content of K element in the silicon-based negative electrode material is 800ppm to 2000ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and kinetic performance. Within the above content range, K element and Fe element show unexpected synergistic effects, significantly improving the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the content of K element in the silicon-based negative electrode material is 800ppm to 1800ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and kinetic performance. Within the above content range, K element and Fe element show unexpected synergistic effects, significantly improving the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the content of K element in the silicon-based negative electrode material is 1200ppm to 1600ppm K content. Based on this, the negative electrode active material has further improved first cycle efficiency and kinetic performance. Within the above content range, K element and Fe element show unexpected synergistic effects, significantly improving the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the upper limit of the content of K element can be selected from any one of 2000ppm, 1800ppm, 1600ppm, 1500ppm, 1400ppm, 1300ppm, 1200ppm, and 1000ppm; the lower limit of the content of K element can be selected from any one of 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, and 1200ppm. That is, the content of K element can be a range of any of the above upper and lower limit values. In the above content range, K and Fe show an unexpected synergistic effect, which significantly improves the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the content of K element in the silicon-based negative electrode material can be selected as 400ppm-1600ppm, 800ppm-1600ppm, 1300-1600ppm, 700-1400ppm, 800-1500ppm, 900-1600ppm, or 1000-1500ppm.
  • the content of Fe in the silicon-based negative electrode material is 500 ppm or less. Based on this, the negative electrode active material has further improved first cycle efficiency and kinetic performance.
  • the content of Fe element in the silicon-based negative electrode material is 30 ppm to 500 ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and kinetic performance.
  • the content of Fe element in the silicon-based negative electrode material is 30 ppm to 400 ppm. Based on this, the negative electrode active material has further improved first cycle efficiency and kinetic performance.
  • the upper limit of the content of the Fe element in the silicon-based negative electrode material can be selected from any one of 500ppm, 400ppm, 300ppm, 260ppm, 200ppm, 170ppm, 150ppm, 130ppm, 100ppm, 80ppm, and 60ppm;
  • the lower limit of the content of the Fe element can be selected from any one of 15ppm, 20ppm, 25ppm, 30ppm, 35ppm, 40ppm, 45ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm, and 100ppm; that is, the content of the Fe element can be composed of any of the above upper and lower limits.
  • the K element and the Fe element show unexpected synergistic effects, which significantly improve the first coulombic efficiency and kinetic performance of the negative electrode active material.
  • the content of Fe element in the silicon-based negative electrode material can be selected as 15-500ppm, 15-300ppm, 15-150ppm, 15-80ppm, 15-60ppm, 20-260ppm, 20-150ppm, 20-100ppm, 20-80ppm, 20-60ppm, 30-200ppm, 30-100ppm, 35-400ppm, 35-300ppm, 35-200ppm, 35-100ppm, 35-80ppm, 35-60ppm, 40-170ppm, 40-130ppm, 40-100ppm, 40-80ppm, 45-100ppm, 60-300ppm, 60-150ppm, 80-500ppm, 90-300ppm, 100-260ppm.
  • 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 kinetic performance.
  • the volume average particle size D v 50 of the silicon-based negative electrode active material can be selected to be 4 ⁇ m or more, and more preferably 5 ⁇ m or more, which can reduce the film-forming consumption of active ions in the negative electrode and reduce the side reaction of the electrolyte in the negative electrode, thereby reducing the non-first coulomb efficiency 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 less than 10 ⁇ m, and more preferably less than 8 ⁇ m, 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 6 m 2 /g, and can be 3 m 2 /g or less. 5m 2 /g. In the above scheme, 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 3m 2 /g-6m 2 /g.
  • the specific surface area can be selected to be 3m 2 /g or more, 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 6m 2 /g or less, 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 non-first coulomb efficiency 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 6 ⁇ cm, and can be optionally 0.5 ⁇ cm-4.5 ⁇ cm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and kinetic performance.
  • the powder volume resistivity of the silicon-based negative electrode active material under a pressure of 4MPa is less than 6 ⁇ cm, and more preferably less than 4.5 ⁇ 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, is conducive to improving the kinetic properties of the silicon-based negative electrode active material, and is conducive to reducing the negative electrode polarization phenomenon, thereby improving 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 49000 N 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 phase containing alkaline earth metal elements includes a silicate phase containing magnesium, and the half-peak width of the silicate phase containing magnesium is less than or equal to 0.50°.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and kinetic performance.
  • the silicate phase containing alkaline earth metal elements includes a silicate phase containing magnesium, and the grain size of the silicate phase containing magnesium is less than or equal to 21 nm.
  • the silicon-based negative electrode active material has improved first coulombic efficiency and kinetic performance.
  • the XRD spectrum of the silicon-based negative electrode active material has a first diffraction peak at a diffraction angle 2 ⁇ of 26°-30°, and the half-peak width of the first diffraction peak is 0.8°-3.2°; the position of the diffraction angle 2 ⁇ is 46°-50° has a second diffraction peak, and the half-peak width of the second diffraction peak is 1.0°-4.2°; the position of the diffraction angle 2 ⁇ is 54°-58° has a third diffraction peak, and the half-peak width of the third diffraction peak is 0.8°-4.5°.
  • the negative electrode active material has the above three diffraction peaks, and the half-peak width is within the above range, indicating that it has a good crystallite size and suitable crystallinity, so that the negative electrode active material has a higher capacity performance and first coulomb efficiency, and the negative electrode active material maintains a higher structural stability during the charge and discharge cycle, is not easy to break, and thus improves the cycle life of the battery.
  • 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.
  • the alkaline earth metal element includes one or more of Mg, Be, Ca, and Ba.
  • the silicon-based negative electrode active material exhibits improved first cycle efficiency and dynamic Mechanical properties.
  • the alkaline earth metal element includes Mg element.
  • the silicon-based negative electrode active materials all show improved first cycle efficiency and kinetic performance.
  • At least a portion of the surface of the silicon-based negative electrode active material has a coating layer.
  • At least a portion of the surface of the silicon-based negative electrode active material is covered with 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 pyrolysis 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, inhibits the side reaction of the electrolyte on the material surface, and protects the material surface from being corroded by the electrolyte, thereby enabling the silicon-based negative electrode active material to have a higher capacity and further improving the cycle life of the battery.
  • 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 sediment is pulverized to obtain a pulverized product.
  • the method for preparing a silicon-based negative electrode active material further comprises:
  • the pulverized 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.
  • the purity of the silicon element for example, is 3N or more, 4N or more, 5N or more, or 6N or more.
  • the K element in the raw material may come from the K element contained in silicon or silicon oxide itself, or may come from a potassium source added to the raw material.
  • the Fe element in the raw material may come from the Fe element contained in silicon alone or silicon oxide, or may come from an iron source added to the raw material.
  • the alkaline earth metal elements in the raw materials may come from the alkaline earth metal elements contained in silicon or silicon oxide, or may come from an alkaline earth metal source added to the raw materials.
  • the potassium source may be selected from one or more of potassium oxide, potassium hydroxide, potassium chloride and potassium silicate.
  • the iron source can be selected from one or more of metallic iron, iron alloys and iron compounds; wherein, The iron compound can be selected from one or more of iron oxide, iron sulfide, iron carbonate, iron hydroxide, iron acetate, iron oxalate, iron nitrate and iron sulfate.
  • the alkaline earth metal source can be selected from one or more of alkaline earth metal elements, alkaline earth metal alloys and alkaline earth metal compounds; wherein the alkaline earth metal compound can be selected from one or more of alkaline earth metal oxides, alkaline earth metal sulfides, alkaline earth metal carbonates, alkaline earth metal hydroxides, alkaline earth metal acetates, alkaline earth metal oxalates, alkaline earth metal nitrates and alkaline earth metal sulfates.
  • the raw material containing Si element, O element, K element, Fe element and alkaline earth metal element includes simple silicon, silicon dioxide, a potassium source, an iron source and an alkaline earth metal source.
  • the content of K element in the silicon oxide-based composite is adjusted by adjusting the type and amount of potassium source added in the raw material.
  • the Fe content in the silicon oxide-based composite is adjusted by one or more means such as mixing silicon oxide powders or metallic silicon powders with various Fe contents, adjusting the type and amount of the iron 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 K element and Fe element in the finally obtained silicon-based negative electrode active material can be increased accordingly.
  • the heating temperature is 1100-1550°C.
  • 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 K and Fe in the final silicon-based negative electrode active material accordingly.
  • reducing the pressure that is, increasing the vacuum degree, can increase the contents of K and Fe 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 meeting 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-classifier integrated machine.
  • the method for preparing a silicon-based negative electrode active material further comprises: coating the pulverized product to obtain a product having 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 pyrolysis 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, inhibits the side reaction of the electrolyte on the material surface, and protects the material surface from being corroded by the electrolyte, thereby enabling the silicon-based negative electrode active material to have a higher capacity and further improving the cycle life of the battery.
  • 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 alkaline earth metal source may be one or more of an alkaline earth metal element, an alkaline earth metal hydroxide, an alkaline earth metal carbonate, an alkaline earth metal nitrate, an alkaline earth metal amide, and an alkaline earth metal hydride.
  • the alkaline earth metal source may be one or more of metallic magnesium, magnesium hydroxide, magnesium carbonate, magnesium nitrate, magnesium amide, and magnesium 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.
  • a metal foil a copper foil may be used.
  • 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 mixing a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and Silver alloy, etc.) is formed on a polymer material substrate (such as 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 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 can all be obtained commercially.
  • 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 plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • the electrolyte salt is selected from sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate and sodium hexafluoroarsenate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • 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 schematic diagram of a secondary battery according to an embodiment of the present application
  • FIG2 is an exploded view of a secondary battery according to an embodiment of the present application.
  • the outer packaging of the secondary battery 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 are enclosed to form 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.
  • the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in any manner. Arranged in the battery box.
  • 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.
  • Silicon-based negative electrode active materials Silicon-based negative electrode active materials Silicon-based negative electrode active materials Silicon-based negative electrode active materials
  • the preparation method of the silicon-based negative electrode active material is summarized as follows:
  • the raw material composition comprises silicon element, silicon oxide, a potassium source (potassium carbonate), an iron source (ferric nitrate), and an alkaline earth metal source (metallic 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 alkaline earth metal in the raw material mixture is adaptively adjusted.
  • the contents of potassium source, iron source and iron source negative electrode active materials with various Fe and K 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 K and Fe elements in advance.
  • the contents of potassium source and iron source in the raw material mixture should be adaptively adjusted according to the composition of the target product of the sample.
  • silicon-based negative electrode active materials with various K and Fe 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 K and Fe elements in advance. At this time, the contents of potassium and iron 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 (hereinafter referred to as samples) were prepared, and these samples had different K contents and Fe contents. These samples had the following properties:
  • the 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 ⁇ 0.2%;
  • the molar ratio of silicon to oxygen in the silicon-based negative electrode active material is 1 ⁇ 0.1;
  • the content of Mg element is 7.5 ⁇ 0.5%.
  • the volume average particle size Dv50 of the negative electrode active material is 6.5 ⁇ 0.5 ⁇ m.
  • the specific surface area of the negative electrode active material is 5 ⁇ 0.2 m 2 /g.
  • the powder volume resistivity of the negative electrode active material under a pressure of 4MPa is 4 ⁇ 0.1 ⁇ cm
  • the compaction density of the silicon-based negative electrode active material under a pressure of 49000N is 1.6 ⁇ 0.1 g/cm 3 .
  • 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 mixture of the silicon-based negative electrode active material and artificial graphite prepared above (the mass ratio of the two is 15%:85%), the conductive agent carbon black (Super P), carbon nanotubes (CNTs), the binder styrene-butadiene rubber, and the thickener sodium carboxymethyl cellulose are fully stirred and mixed in an appropriate amount of solvent deionized water according to a weight ratio of 96.2%:0.7%:0.1%:1.8%:1.2% to form a negative electrode slurry.
  • the negative electrode slurry is coated on both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.
  • LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), conductive agent Super P, and binder polyvinylidene fluoride were mixed in a weight ratio of 96.5%:1.5%:2%, and an appropriate amount of solvent NMP was added and stirred evenly to obtain a positive electrode slurry.
  • the positive electrode slurry was coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, and fluoroethylene carbonate (FEC) is added, wherein the concentration of LiPF6 is 1 mol/L, and the mass proportion of FEC in the electrolyte is 6%.
  • a PE isolation film is used and placed in order with the positive electrode sheet and the negative electrode sheet prepared above, so that the isolation film is placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and then the electrode assembly is wound; the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and a secondary battery is obtained after vacuum packaging, standing, formation, aging and other processes.
  • the element content is a well-known meaning in the art and can be tested by 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 is determined using the ICAP-7000 inductively coupled plasma emission spectrometer (ICP-OES) of Thermo Fisher Scientific in the United States in accordance with EPA 6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectrometry".
  • ICP-OES inductively coupled plasma emission spectrometer
  • the specific test method is as follows: 0.5g of silicon-based negative electrode active material sample is microwave digested with 10mL nitric acid and 10mL hydrofluoric acid, and after digestion, it is added to a 50mL volumetric flask to make up the volume, and then the content of the target element is determined using 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 the nitrogen adsorption specific surface area analysis test method, and calculate it using the BET (Brunauer Emmett Teller) method.
  • the nitrogen adsorption specific surface area analysis test can be performed using the Tri Star II 3020 specific surface and pore analyzer from Micromeritics, USA.
  • the battery At 25°C, the battery is charged to 4.25V at 0.33C constant current, and then discharged at 1C constant current for 48 minutes to adjust the battery to 20% SOC.
  • the battery voltage at this time is recorded as U1; the battery is discharged at 3C constant current for 30 seconds, and the sampling point is 0.1 seconds.
  • the voltage at the end of discharge is recorded as U2.
  • 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 content ratio of K element and Fe element in the silicon-based negative electrode active material product, and the battery performance based on the above silicon-based negative electrode active materials as silicon-based negative electrode active materials. The following are discussed separately:
  • the raw silicon element used in the sample (D1) is metallic silicon 2 (Si ⁇ 99.9wt%, excluding K and Fe).
  • the K and Fe elements in the silicon-based negative electrode active materials can come from a variety of sources:
  • the K element in the silicon-based negative electrode active material can come from the raw material metal silicon;
  • the Fe element in the silicon-based negative electrode active material can come from the raw material metal silicon;
  • the K element in the silicon-based negative electrode active material can come from an additional added potassium source
  • the Fe element in the silicon-based negative electrode active material can come from an additionally added iron source.
  • Those skilled in the art can adaptively adjust the content of Fe and K elements in the raw materials according to the target chemical composition of the silicon-based negative electrode active material, and finally obtain a silicon oxide-based compound with a target chemical composition. If it is necessary to increase/decrease the K element content in the target silicon oxide-based compound, metal silicon (or silicon oxide) with a higher/lower K element content can be used, or the amount of potassium source added to the raw material can be increased/decreased. If it is necessary to increase/decrease the Fe element content in the target silicon oxide-based compound, metal silicon (or silicon oxide) with a higher/lower Fe element content can be used, or the amount of iron source added to the raw material can be increased/decreased.
  • the silicon-based negative electrode active material of comparative example D1 does not contain K and Fe elements, and its first coulombic efficiency value is 65.32%, and its DC internal resistance is 583.68m ⁇ .
  • the silicon-based negative electrode active materials of Examples E1-E16 contain both K and Fe elements, and their first coulombic efficiency values are higher, at 71.42%-76.32%; and their DC internal resistance values are lower, at 505.86-515.07m ⁇ , which is significantly improved compared with D1. It can be seen that the simultaneous presence of K and Fe elements brings about significant improvements in the first coulombic efficiency and kinetic performance.
  • the content of K element in the silicon-based negative electrode active material is 800 ppm or more, for example, 800 ppm to 1520 ppm, and the negative electrode active material exhibits improved first coulombic efficiency and improved kinetic performance.
  • the content of Fe in the silicon-based negative electrode active material is less than 100 ppm, for example, 35 ppm to 100 ppm.
  • the negative electrode active material exhibits improved first coulombic efficiency and improved kinetic performance.
  • the content of K element in the silicon-based negative electrode active material is between 1200 ppm and 1500 ppm, and the negative electrode active material exhibits improved first coulombic efficiency and kinetic performance.
  • the content of Fe in the silicon-based negative electrode active material is between 45 ppm and 64 ppm.
  • the negative electrode active material exhibits improved first coulombic efficiency and improved kinetic performance.

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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土金属元素的硅酸盐相，且所述硅基负极活性材料中同时含有K元素和Fe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。
硅基材料因其容量高被认为是具有前景的负极活性材料之一。由于二次电池取得了极大的发展，因此对其电化学性能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土金属元素的硅酸盐相，且所述硅基负极活性材料中同时含有K元素和Fe元素。
在以上方案中，硅基负极活性材料含有K元素和Fe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动力学性能。K元素和Fe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，含有Fe元素改善了负极活性材料在嵌入/脱出活性离子(锂离子)过程中活性离子及电子的传导性能，抑制循环过程中的负极阻抗增加，提高材料的倍率性能，同时K元素与硅氧材料反应生成的钾硅酸盐有利于提高负极活性材料的容量发挥，从而提高二次电池的首次库伦效率。因此，采用本申请的负极活性材料，使得二次电池能够在具有较高能量密度的前提下，同时兼顾较高的首次库伦效率及较好的倍率性能。
在一些实施方案中，所述K元素的含量大于Fe元素的含量。在上述比例范围内，K元素和Fe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动力学性能。
在一些实施方案中，所述K元素和所述Fe元素的质量比大于等于8:1；可选为10:1至36:1。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动力学性能。
在一些实施方案中，所述K元素的含量为400ppm以上，可选为800ppm至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动力学性能。
在一些实施方案中，所述Fe元素的含量为500ppm以下，可选为30ppm至400ppm。 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动力学性能。
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动力学性能。
在一些实施方案中，所述硅基负极活性材料的比表面积为6m2/g以下，可选为3m2/g-5m2/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。
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6Ω·cm以下，可选为0.5Ω·cm-4.5Ω·cm。在上述方案中，硅基负极活性材料具有改善的动力学性能。
在一些实施方案中，所述硅基负极活性材料在49000N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，所述含碱土金属元素的硅酸盐相包括含镁的硅酸盐相，且所述含镁的硅酸盐相的半峰宽小于等于0.50°。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动力学性能。
在一些实施方案中，所述含碱土金属元素的硅酸盐相包括含镁的硅酸盐相，且所述含镁的硅酸盐相的晶粒尺寸小于等于21nm。在上述方案中，硅基负极活性材料具有改善的容量发挥和导离子率。
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、K元素、Fe元素和碱土金属元素的原料；
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。
在一些实施方案中，硅基负极活性材料的制备方法还包括：
对粉碎产物进行包覆处理，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)K元素和Fe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动力学性能；
(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是本申请一实施方式的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K元素或Fe元素的含量时，其是指硅基负极活性材料中K元素或Fe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，包括含碱土金属元素的硅酸盐相，且所述硅基负极活性材料中同时含有K元素和Fe元素。
在以上方案中，硅基负极活性材料含有K元素和Fe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。K元素和Fe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，K元素与二氧化硅反应生成的钾硅酸盐，有利于减少首次充放电过程对锂的消耗，提高负极活性材料的容量发挥，从而提高二次电池的首次库伦效率；同时，Fe元素改善了负极活性材料在嵌入/脱出活性离子(锂离子)过程中活性离子及电子的传导性能，降低循环过程中的负极阻抗，从而有效改善电池的倍率性能，Fe与K元素耦合，在提高离子传导率的同时能一定程度缓解材料内部的膨胀。因此，采用本申请的负极活性材料，使得二次电池能够在具有较高能量密度的前提下，同时兼顾较高的首次库伦效率和较好的倍率性能。
在一些实施方案中，硅基负极活性材料包括硅基负极活性材料。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。硅相是通过一个或多个硅晶体组装而形成的基团，可以存在单个基团或者可以存在两个或更多个基团。
在一些实施方案中，K元素和Fe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，K元素和Fe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，在一些实施方案中，硅基负极活性材料具有一种或多种纳米晶分散在硅氧材料基体中的复合结构。硅基负极活性材料例如具有Si晶粒和硅酸盐晶粒分散在硅氧材料基体的结构。
在一些实施方案中，所述K元素的含量大于Fe元素的含量。在上述比例范围内，K元素和Fe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动力学性能。
在一些实施方案中，硅基负极材料具有大于等于8:1的K和Fe的质量比。在上述比例范围内，K元素和Fe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动力学性能。
在一些实施方案中，硅基负极材料具有10:1至36:1的K和Fe的质量比。在上述比例 范围内，K元素和Fe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动力学性能。
在一些实施方案中，所述硅基负极材料具有20:1至32:1的K和Fe的质量比。在上述比例范围内，K元素和Fe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动力学性能。
在一些实施方案中，硅基负极材料中的K元素与所述Fe元素的质量比可以为60:1以下，可选为50:1以下、可选为40:1以下、可选为30:1以下、可选为25:1以下、可选为20:1以下、15:1以下。在一些实施方案中，硅基负极材料中的K元素与所述Fe元素的质量比可以为大于等于8:1、可选为10:1以上、可选为12:1以上、可选为13:1以上、可选为16:1以上、可选为18:1以上。K元素与所述Fe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，K元素和Fe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动力学性能。
在一些实施方案中，硅基负极材料中的K元素与所述Fe元素的质量比可选为21-26:1，还可选为21-27:1，还可选为20-27:1，还可选为20-32:1，还可选为13-32:1，还可选为13-34:1，还可选为13-54:1，还可选为16-54:1，还可选为16-30:1，还可选为18-25:1。
在一些实施方案中，所述硅基负极材料中K元素的含量为400ppm以上。在上述含量范围内，K元素和Fe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动力学性能。
在一些实施方案中，所述硅基负极材料中K元素的含量为800ppm至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动力学性能。在上述含量范围内，K元素和Fe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动力学性能。
在一些实施方案中，所述硅基负极材料中K元素的含量为800ppm至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动力学性能。在上述含量范围内，K元素和Fe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动力学性能。
在一些实施方案中，所述硅基负极材料中K元素的含量为具有1200ppm至1600ppm的K含量。基于此，负极活性材料具有进一步改善的首次循环效率和动力学性能。在上述含量范围内，K元素和Fe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动力学性能。
在一些实施方案中，K元素的含量上限值可以选自2000ppm、1800ppm、1600ppm、1500ppm、1400ppm、1300ppm、1200ppm、1000ppm中的任意一个数值；所述K元素的含量下限值可以选自400ppm、500ppm、600ppm、700ppm、800ppm、900ppm、1000ppm、1200ppm中的任意一个数值。即K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，K元素和Fe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动力学性能。
在一些实施方案中，所述硅基负极材料中K元素的含量为的含量可选为400ppm-1600ppm、800ppm-1600ppm、1300-1600ppm、还可选为700-1400ppm、还可选为800-1500ppm、还可选为900-1600ppm、还可选为1000-1500ppm。
在一些实施方案中，所述硅基负极材料中Fe元素的含量为500ppm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动力学性能。
在一些实施方案中，所述硅基负极材料中Fe元素的含量为30ppm至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动力学性能。
在一些实施方案中，所述硅基负极材料中Fe元素的含量为30ppm至400ppm。基于此，负极活性材料具有进一步改善的首次循环效率和动力学性能。
在一些实施方案中，硅基负极材料中Fe元素的含量上限值可以选自500ppm、400ppm、300ppm、260ppm、200ppm、170ppm、150ppm、130ppm、100ppm、80ppm、60ppm中的任意一个数值；所述Fe元素的含量下限值可以选自15ppm、20ppm、25ppm、30ppm、35ppm、40ppm、45ppm、50ppm、60ppm、70ppm、80ppm、90ppm、100ppm中的任意一个数值；即所述Fe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，K元素和Fe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动力学性能。
在一些实施方案中，所述硅基负极材料中Fe元素的含量可选为15-500ppm、15-300ppm、15-150ppm、15-80ppm、15-60ppm、20-260ppm、20-150ppm、20-100ppm、20-80ppm、20-60ppm、30-200ppm、30-100ppm、35-400ppm、35-300ppm、35-200ppm、35-100ppm、35-80ppm、35-60ppm、40-170ppm、40-130ppm、40-100ppm、40-80ppm、45-100ppm、60-300ppm、60-150ppm、80-500ppm、90-300ppm、100-260ppm。
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动力学性能。
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首次库伦效率，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6m2/g以下，可选为3m2/g- 5m2/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3m2/g-6m2/g。比表面积可选为3m2/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6m2/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首次库伦效率，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6Ω·cm以下，可选为0.5Ω·cm-4.5Ω·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动力学性能。
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6Ω·cm以下，更可选为4.5Ω·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49000N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，所述含碱土金属元素的硅酸盐相包括含镁的硅酸盐相，且所述含镁的硅酸盐相的半峰宽小于等于0.50°。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动力学性能。
在一些实施方案中，所述含碱土金属元素的硅酸盐相包括含镁的硅酸盐相，且所述含镁的硅酸盐相的晶粒尺寸小于等于21nm。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动力学性能。
在一些实施方案中，所述硅基负极活性材料的XRD图谱在衍射角2θ为26°-30°的位置具有第一衍射峰，所述第一衍射峰的半峰宽为0.8°-3.2°；衍射角2θ为46°-50°的位置具有第二衍射峰，所述第二衍射峰的半峰宽为1.0°-4.2°；衍射角2θ为54°-58°的位置具有第三衍射峰，所述第三衍射峰的半峰宽为0.8°-4.5°。在上述方案中，负极活性材料具有上述3个衍射峰，且半峰宽在上述范围内，表明其具有较好的微晶尺寸及适宜的结晶性，使得负极活性材料具有较高的容量性能和首次库伦效率，并使负极活性材料在充放电循环过程中保持较高的结构稳定性，不易发生破裂，进而提升电池的循环寿命。
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，所述碱土金属元素包括Mg元素、Be元素、Ca元素、Ba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动 力学性能。
在一些实施方案中，所述碱土金属元素包括Mg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动力学性能。
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，所述硅基负极活性材料的至少部分表面覆有包覆层。
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、K元素、Fe元素和碱土金属元素的原料；
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。
在一些实施方案中，硅基负极活性材料的制备方法还包括：
对粉碎产物进行包覆处理，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。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K元素可以来自于硅单质或硅氧化物中本身含有的K元素，也可以来自于原料添加的钾源。
在一些实施方案中，原料中的Fe元素可以来自于硅单质或硅氧化物中本身含有的Fe元素，也可以来自于原料中添加的铁源。
在一些实施方案中，原料中的碱土金属元素可以来自于硅单质或硅氧化物中本身含有的碱土金属元素，也可以来自于原料中添加的碱土金属源。
在一些实施方案中，钾源可以选自钾的氧化物、氢氧化钾、氯化钾及硅酸钾中的一种或几种。
在一些实施方案中，铁源可以选自金属铁、铁合金及铁化合物中的一种或几种；其中， 铁化合物可以选自铁的氧化物、铁的硫化物、铁的碳酸盐、铁的氢氧化物、铁的醋酸盐、铁的草酸盐、铁的硝酸盐及铁的硫酸盐中的一种或几种。
在一些实施方案中，碱土金属源可以选自碱土金属单质、碱土金属合金及碱土金属化合物中的一种或几种；其中，碱土金属化合物可以选自碱土金属的氧化物、碱土金属的硫化物、碱土金属的碳酸盐、碱土金属的氢氧化物、碱土金属的醋酸盐、碱土金属的草酸盐、碱土金属的硝酸盐及碱土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、K元素、Fe元素和碱土金属元素的原料包括硅单质、二氧化硅、钾源、铁源和碱土金属源。
在一些实施方案中，通过调整原料中钾源的种类和加入量来调整氧化硅基复合体中K元素的含量。
在一些实施方案中，通过混合多种Fe含量的硅氧化物粉末或金属硅粉末、以及调整铁源的种类及加入量等一种或几种手段，来调整氧化硅基复合体中Fe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K元素和Fe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K元素和Fe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K元素和Fe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：对粉碎产物进行包覆处理，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，所述碱土金属源可以是碱土金属单质、碱土金属氢氧化物、碱土金属碳酸盐、碱土金属硝酸盐、氨基化碱土金属、氢化碱土金属中的一种或几种。
在一些实施方案中，所述碱土金属源可以是金属镁、氢氧化镁、碳酸镁、硝酸镁、氨基镁、氢化镁中的一种或几种。
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是本申请一实施方式的二次电池的示意图，图2是本申请一实施方式的的二次电池的分解图。
在一些实施方式中，参照图2，二次电池的外包装可包括壳体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。
硅基负极活性材料硅基负极活性材料硅基负极活性材料
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，硅基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、K元素、Fe元素和Mg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。
1.2详述
在以下具体实施方式中，硅基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K元素、Fe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、钾源(碳酸钾)、铁源(硝酸铁)和碱土金属源(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，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碱土金属 源、钾源和铁源的含量，就能够获得各种Fe含量和K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K元素和Fe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钾源和铁源的含量。
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土金属源、钾源和铁源的含量，就能够获得各种K含量和Fe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K元素和Fe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钾源和铁源的含量。
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K含量和Fe含量。这些样品具有以下性质：
1)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±0.2％；
2)硅基负极活性材料中硅元素和氧元素的摩尔比为1±0.1；
3)基于100％的硅基负极活性材料，Mg元素的含量为7.5±0.5％。
4)基于100％的硅基负极活性材料，K的含量如表1所示。
5)基于100％的硅基负极活性材料，Fe的含量如表1所示。
6)负极活性材料的体积平均粒径Dv50为6.5±0.5μm。
7)负极活性材料的比表面积为5±0.2m2/g。
8)负极活性材料在4MPa压力下的粉体体积电阻率为4±0.1Ω·cm；
9)所述硅基负极活性材料在49000N压力下的压实密度为1.6±0.1g/cm3。
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)、粘结剂丁苯橡胶按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。
全电池的制备
将上述制备的硅基负极活性材料与人造石墨的混合物(二者的质量比为15％：85％)、导电剂炭黑(Super P)、碳纳米管(CNTs)、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按照重量比96.2％:0.7％:0.1％:1.8％:1.2％在适量的溶剂去离子水中充分搅拌混合，形成负极浆料。将负极浆料涂布在负极集流体铜箔的两个表面上，经干燥、冷压后，获得负极极片。
将LiNi0.8Co0.1Mn0.1O2(NCM811)、导电剂Super P、粘结剂聚偏氟乙烯按照重量比96.5％:1.5％:2％混合，加入适量溶剂NMP，搅拌均匀，获得正极浆料。将正极浆料涂布在正极集流体铝箔的两个表面上，经干燥、冷压后，获得正极极片。
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％。
采用PE隔离膜，与上述制备的正极极片和负极极片按顺序放好，使隔离膜处于正极极片和负极极片中间起到隔离作用，之后卷绕得到电极组件；将电极组件置于外包装中，干燥后注入电解液，经过真空封装、静置、化成、老化等工序，得到二次电池。
二、分析检测方法
2.1、元素分析(例如K，Fe，Si及碱土金属元素等)
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49000N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49000N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 Star Ⅱ 3020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
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％
(2)电池的直流电阻DCR
在25℃下，将电池以0.33C恒流充电至4.25V，再以1C恒流放电48分钟，以调整电池至20％SOC，此时电池的电压记为U1；将电池以3C恒流放电30秒，采用0.1秒采点，放电末期电压记为U2。用电池20％SOC时的放电DCR表示电池的初始DCR，电池的初始DCR＝(U1-U2)/3C。

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K元素和Fe元素的含量和含量比，以及基于上述硅基负极活性材料作为硅基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-E16)采用的原料硅单质为金属硅1(Si≥99.9wt％，K＝200ppm，Fe＝20ppm)。
样品(D1)采用的原料硅单质为金属硅2(Si≥99.9wt％，不含K和Fe)。
从表1中可以看出，硅基负极活性材料中的K元素和Fe元素可以来自于多种来源：
a)硅基负极活性材料中的K元素可以来自于原料金属硅；
b)硅基负极活性材料中的Fe元素可以来自于原料金属硅；
c)硅基负极活性材料中的K元素可以来自于额外添加的钾源；
d)硅基负极活性材料中的Fe元素可以来自于额外添加的铁源。
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Fe元素和K元素的含量，最终获得具有目标化学成分的氧化硅基化合物。如果需要增加/降低目标氧化硅基化合物中的K元素含量，可以采用K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钾源添加量。如果需要增加/降低目标氧化硅基化合物中的Fe元素含量，可以采用Fe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铁源添加量。
(2)同时含有K元素和Fe元素带来显著的首次库伦效率和动力学性能提高
对比例D1的硅基负极活性材料中不含K元素和Fe元素，其首次库伦效率值为65.32％，直流内阻为583.68mΩ。实施例E1-E16的硅基负极活性材料中同时含有K元素和Fe元素，其首次库伦效率值更高，为71.42％-76.32％；直流内阻值更低，为505.86-515.07mΩ，与D1相比有显著提高。可见，同时含有K元素和Fe元素带来显著的首次库伦效率和动力学性能提高。
(3)关于硅基负极活性材料中K/Fe的比值
如实施例E2-E14所示，当K/Fe的重量比为10至36:1时，负极活性材料的首次库伦效率值为值为71.76％-76.32％，直流内阻值为505.86mΩ-515.07mΩ，表现出进一步改善的首次库伦效率和动力学性能。
如实施例E3-E14所示，当K/Fe的重量比为12:1至36:1时，负极活性材料的首次库伦效率值为值为71.82％-76.32％，直流内阻值为505.856mΩ-515.072mΩ，表现出进一步改善的首次库伦效率和动力学性能。
如实施例E6-E13所示，当K/Fe的重量比为20:1至32:1时，负极活性材料的首次库伦效率值为值为73.23％-76.32％，直流内阻值为510.976mΩ-514.56mΩ，表现出进一步改善的首次库伦效率和动力学性能。
(5)关于硅基负极活性材料中的K元素含量和Fe元素含量
如实施例E1至E16所示，硅基负极活性材料中K元素的含量为800ppm以上，例如在800ppm至1520ppm，负极活性材料表现出改善的首次库伦效率和动力学性能性能改善。
如实施例E1至E16所示，硅基负极活性材料中Fe元素的含量为100ppm以下，例如在35ppm至100ppm。负极活性材料表现出改善的首次库伦效率和动力学性能性能改善。
如实施例E6至E13所示，硅基负极活性材料中K元素的含量在1200ppm至1500ppm，负极活性材料表现出改善的首次库伦效率和动力学性能性能改善。
如实施例E6至E13所示，硅基负极活性材料中Fe元素的含量在45ppm至64ppm。负极活性材料表现出改善的首次库伦效率和动力学性能性能改善。
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土金属元素的硅酸盐，且所述硅基负极活性材料中同时含有K元素和Fe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K元素的含量大于Fe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K元素和所述Fe元素的质量比大于等于8:1；可选为10:1至36:1。
  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K元素的含量为400ppm以上，可选为800ppm至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Fe元素的含量为500ppm以下，可选为30ppm至400ppm。
  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6m2/g以下，可选为3m2/g-5m2/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6Ω·cm以下，可选为0.5Ω·cm-4.5Ω·cm；
    (4)所述硅基负极活性材料在49000N压力下的压实密度为1.4-1.8g/cm3，可选为1.5-1.7g/cm3；
    (5)所述含碱土金属元素的硅酸盐相包括含镁的硅酸盐，且所述含镁的硅酸盐的半峰宽小于等于0.60°，可选为0.35°-0.55°；
    (6)所述含碱土金属元素的硅酸盐包括含镁的硅酸盐，且所述含镁的硅酸盐的晶粒尺寸小于等于21nm，可选为12nm-18nm。
  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、K元素、Fe元素和碱土金属元素的原料；
    ·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。
  9. 根据权利要求8所述的方法，还包括：
    对粉碎产物进行包覆处理，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/CN2023/078666 2023-02-28 2023-02-28 硅基负极活性材料、二次电池及用电装置 Ceased WO2024178595A1 (zh)

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