WO2024182969A1 - 硅基负极活性材料及其制备方法、二次电池及用电装置 - Google Patents

硅基负极活性材料及其制备方法、二次电池及用电装置 Download PDF

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WO2024182969A1
WO2024182969A1 PCT/CN2023/079821 CN2023079821W WO2024182969A1 WO 2024182969 A1 WO2024182969 A1 WO 2024182969A1 CN 2023079821 W CN2023079821 W CN 2023079821W WO 2024182969 A1 WO2024182969 A1 WO 2024182969A1
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negative electrode
silicon
electrode active
active material
based negative
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French (fr)
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郭晓鑫
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 EP23925694.4A priority Critical patent/EP4604202A4/en
Priority to CN202380009160.XA priority patent/CN116802836B/zh
Priority to PCT/CN2023/079821 priority patent/WO2024182969A1/zh
Priority to JP2025529717A priority patent/JP2025537894A/ja
Priority to KR1020257017251A priority patent/KR20250095699A/ko
Publication of WO2024182969A1 publication Critical patent/WO2024182969A1/zh
Priority to US19/210,739 priority patent/US20250276904A1/en
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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
    • C01B33/24—Alkaline-earth 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • 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
    • 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
    • H01M4/58—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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • 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
    • C01P2006/12—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 and a preparation method thereof, 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 anode active materials are considered to be promising secondary battery silicon-based anode active materials. With the rapid development of secondary batteries, higher requirements are placed on the first coulombic efficiency and cycle performance of silicon-based anode active materials.
  • the present application provides a novel silicon-based negative electrode active material and a preparation method thereof, a secondary battery and an electrical device, which are described below respectively.
  • the present application provides a silicon-based negative electrode active material, comprising Si and MSiO 3 , wherein M comprises one or more alkaline earth metal elements; in the XRD diffraction pattern of the silicon-based negative electrode active material, the diffraction angle 2 ⁇ has a first diffraction peak between 28°-28.6°, and the half-peak width of the first diffraction peak is ⁇ A ; the diffraction angle 2 ⁇ has a second diffraction peak between 31°-32°, and the half-peak width of the second diffraction peak is ⁇ B ; then the silicon-based negative electrode active material satisfies: 1.5 ⁇ A / ⁇ B ⁇ 5.0.
  • the negative electrode active material based on the above scheme takes into account both good first coulomb efficiency and cycle life.
  • the above performance improvement may be related to the size and distribution of Si grains and alkaline earth metal silicate grains in the silicon-based negative electrode active material.
  • the ratio of the half-peak width ⁇ A of the XRD diffraction peak to ⁇ B is 1-5:1
  • the position distribution of Si grains and alkaline earth metal silicate grains in the silicon-based negative electrode active material has an improved size distribution, and such a microstructure helps to alleviate the volume expansion problem of the silicon-based negative electrode active material during the cycle, thereby improving its electrochemical performance.
  • the ratio of ⁇ A to ⁇ B is too large, the first coulomb efficiency of the negative electrode active material is low, and when the ratio of ⁇ A to ⁇ B is too small, the cycle performance of the negative electrode active material is low.
  • the ratio of ⁇ A to ⁇ B is 2.0 ⁇ A / ⁇ B ⁇ 5.0, and can be 2.5 ⁇ A / ⁇ B ⁇ 4.0. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the grain size of the Si is smaller than the grain size of the MSiO 3. Based on this scheme, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the grain size of Si is less than or equal to 12nm, and can be 2nm-10nm; and/or, the grain size of MSiO3 is greater than or equal to 11nm, and can be 12nm-18nm. Based on this scheme, the silicon-based negative electrode active material shows a further improved cycle life.
  • the silicon-based negative electrode active material has a coating layer on at least part of its surface; optionally, the coating layer comprises one or more of a carbon material and an alkali metal ion conductor material. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the specific surface area of the silicon-based negative electrode active material is 4 m 2 /g or less, and may be 0.5-1.5 m 2 /g. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the volume average particle size Dv50 of the silicon-based negative electrode active material is 4-15 ⁇ m, and optionally 5-9 ⁇ m. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the particle size distribution of the silicon-based negative electrode active material (D V 90 - D V 10)/D V 50 is 0.5-3.0, and can be 0.8-1.3. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the content of Si element in the silicon-based negative electrode active material is 20-80 wt %, and optionally 30-60 wt %. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the total content of alkaline earth metal elements in the silicon-based negative electrode active material is 2-14 wt %, and optionally 2-10 wt %. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the Si:O molar ratio of the silicon-based negative electrode active material is 1:0.6-1:1.8, optionally 1:0.9-1:1.5;
  • M includes at least one of Mg, Ca, Be, Sr, and Ba. Based on this scheme, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the present application provides a method for preparing the above-mentioned silicon-based negative electrode active material, comprising the following steps:
  • the raw material is heated to a first temperature to form a vapor, and then the vapor is cooled to a second temperature to form a deposit;
  • the content of M element in the raw material is 7%-10%
  • the raw material is heated to a first temperature at a heating rate of less than 10°C/min;
  • the first temperature is 1100-1500°C
  • the second temperature is 800-1000°C.
  • the feedstock includes elemental silicon, silicon dioxide, and an alkaline earth metal source.
  • the first temperature is 1200-1400°C.
  • the second temperature is 800-900°C.
  • the vapor deposition is performed under an environment with an absolute pressure of 40 Pa or less.
  • the method for preparing a silicon-based negative electrode active material further comprises the following steps: coating the silicon-based negative electrode active material; optionally, the coating is a carbon material coating; more optionally, The carbon material coating treatment includes the following operations: placing the silicon-based negative electrode active material in a chamber containing a carbon source gas, heating it to 700-1000° C., and keeping it warm for 1-6 hours.
  • the present application provides a secondary battery, comprising a negative electrode, wherein the negative electrode comprises the above-mentioned silicon-based negative electrode active material.
  • the present application provides an electrical device, comprising the above-mentioned secondary battery.
  • Silicon-based negative electrode active materials have improved first coulombic efficiency
  • Silicon-based negative electrode active materials have improved cycle capacity retention
  • 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 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 special range.
  • the scope limited in this way can be to include end value or not include end value, and can be combined arbitrarily, that is, any lower limit can form a scope with any upper limit combination.
  • any lower limit can form a scope with any upper limit combination.
  • the scope of 60-120 and 80-110 is listed for a particular parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are listed the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.
  • the numerical range “ab” represents an abbreviation of any real number combination between a and b, where a and b are real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" have been listed in this document, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (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
  • 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.
  • Lithium-ion batteries are mainly composed of 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 soaks the positive and negative electrodes to ensure ion conduction.
  • Li + escapes from the positive electrode, passes through the separator through the electrolyte and embeds into the negative electrode, making the positive electrode in a high-potential sodium-poor state and the negative electrode in a low-potential sodium-rich state.
  • the discharge process is the opposite, with Li+ escaping from the negative electrode, passing through the separator through the electrolyte and embedding into the positive electrode material, making the positive electrode
  • 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+, causing oxidation and reduction reactions at the positive and negative electrodes respectively.
  • Lithium ions can reversibly migrate between the positive and negative electrodes in the electrolyte, and both the positive and negative electrodes are composed of insertion materials that allow lithium ions to be reversibly inserted and removed.
  • Secondary batteries are, for example, sodium ion batteries.
  • the composition of sodium ion batteries mainly includes a positive electrode, a negative electrode, a diaphragm, and an electrolyte.
  • the positive and negative electrodes are separated by a diaphragm to prevent short circuits, and the electrolyte infiltrates the positive and negative electrodes to ensure ion conduction.
  • Na + escapes from the positive electrode, passes through the diaphragm through the electrolyte and is embedded in the negative electrode, so that the positive electrode is in a high potential sodium-poor state, and the negative electrode is in a low potential sodium-rich state.
  • the discharge process is the opposite, Na+ escapes from the negative electrode, passes through the diaphragm through the electrolyte and is embedded in the positive electrode material, so that the positive electrode is restored to a sodium-rich state.
  • the same number of electrons are transferred through the external circuit during the charge and discharge process, and migrate between the positive and negative electrodes together with Na+, so that the positive and negative electrodes undergo oxidation and reduction reactions respectively.
  • Sodium ions can reversibly migrate between the positive and negative electrodes in the electrolyte, and both the positive and negative electrodes are composed of insertion materials that allow sodium ions to be reversibly inserted and removed.
  • the negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a silicon-based negative electrode active material, and the silicon-based negative electrode active material adopts the silicon-based negative electrode active material of the present application.
  • the present application provides a silicon-based negative electrode active material, comprising Si and MSiO 3 , wherein M comprises one or more alkaline earth metal elements; in the XRD diffraction pattern of the silicon-based negative electrode active material, the diffraction angle 2 ⁇ has a first diffraction peak between 28°-28.6°, and the half-peak width of the first diffraction peak is ⁇ A ; the diffraction angle 2 ⁇ has a second diffraction peak between 31°-32°, and the half-peak width of the second diffraction peak is ⁇ B ; then the silicon-based negative electrode active material satisfies: 1.5 ⁇ A / ⁇ B ⁇ 5.0.
  • the silicon-based negative electrode active material based on the above scheme has an improved first coulombic efficiency and/or cycle life.
  • the above performance improvement may be related to the grain size and distribution of Si grains and MSiO3 grains in the silicon-based negative electrode active material.
  • the half-peak width of the XRD diffraction peak has a negatively correlated functional relationship with the grain size.
  • the present application finds that when the ratio of ⁇ A to ⁇ B is 1-5:1, Si grains and MSiO3 grains have improved grain size in the silicon-based negative electrode active material, and a more uniform position distribution.
  • Such a microstructure helps to alleviate the volume expansion problem of the silicon-based negative electrode active material during the cycle, thereby improving its electrochemical performance.
  • Si grains and MSiO3 grains show a mutually reinforcing synergistic effect, so that the silicon-based negative electrode active material has a good cycle life.
  • the ratio of ⁇ A to ⁇ B is less than 2 or greater than 4, it will lead to a large difference in the size of Si grains and MSiO3 grains, which reflects the uneven growth and distribution of Si grains and MSiO3 grains in the silicon-based negative electrode active material, resulting in poor electrochemical performance of the negative electrode active material.
  • the ratio of ⁇ A to ⁇ B is 2.0-2.2: 1, 2.2-2.4: 1, 2.4-2.6: 1, 2.6-2.8: 1, 2.8-3: 1, 3.0-3.2: 1, 3.2-3.4: 1, 3.4-3.6: 1, 3.6-3.8: 1, 3.8-4: 1, 4.0-4.2: 1, 4.2-4.4: 1, 4.4-4.6: 1, 4.6-4.8: 1 or 4.8-5: 1.
  • the silicon-based negative electrode active material shows a further improved cycle life.
  • the ratio of ⁇ A to ⁇ B is 2.0 ⁇ A / ⁇ B ⁇ 5.0, and can be 2.5 ⁇ A / ⁇ B ⁇ 4.0. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the ratio of ⁇ A to ⁇ B is 2.0-5.0:1 (e.g., 2.5-2.6:1, 2.6-2.8:1, 2.8-3:1, Based on this scheme, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the ratio of ⁇ A to ⁇ B is 2.5-4.0: 1 (e.g., 2.5-2.6: 1, 2.6-2.8: 1, 2.8-3: 1, 3-3.2: 1, 3.2-3.4: 1, 3.4-3.6: 1, 3.6-3.8: 1, 3.8-4.0: 1). Based on this scheme, the silicon-based negative electrode active material shows a further improved cycle life.
  • the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the value of ⁇ A is 1.0°-3.0° (e.g., 1.0°-1.2°, 1.2°-1.4°, 1.4°-1.6°, 1.6°-1.8°, 1.8°-2.0°, 2.0°-2.2°, 2.2°-2.4°, 2.4°-2.6°, 2.6°-2.8°, 2.8°-3.0°), and may be 1° ⁇ A ⁇ 2° (e.g., 1.0°-1.2°, 1.2°-1.4°, 1.4°-1.6°, 1.6°-1.8°, or 1.8°-2.0°).
  • the silicon-based negative electrode active material has a further improved energy cycle life.
  • the value of ⁇ B is 0.2°-1.0° (eg, 0.2°-0.4°, 0.4°-0.6°, 0.6°-0.8°, or 0.8°-1°). It may be 0.2° ⁇ A ⁇ 1.0°.
  • the silicon-based negative electrode active material has a further improved cycle life.
  • the grain size of the Si is smaller than the grain size of the MSiO 3. Based on this scheme, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the grain size of Si is less than or equal to 12 nm, and can be 2 nm to 10 nm. Based on this scheme, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the grain size is calculated by the half-peak width of the XRD diffraction peak according to the Debye-Scherrer formula. The half-peak width is negatively correlated with the grain size. The larger the half-peak width, the smaller the grain size.
  • the grain size of the MSiO 3 is greater than or equal to 11 nm, and can be selected as 12 nm-18 nm. Based on this scheme, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the grain size is calculated by the half-peak width of the XRD diffraction peak according to the Debye-Scherrer formula. The half-peak width and the grain size are negatively correlated. The larger the half-peak width, the smaller the grain size.
  • the intensity ratio of the first diffraction peak to the second diffraction peak is 1-5: 1, and can be 2-4: 1.
  • the silicon-based negative electrode active material has an improved cycle life.
  • the surface of the silicon-based composite has a coating layer; optionally, the coating layer includes one or more of a carbon material and an alkali metal ion conductor material. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the alkali metal ion conductor coating includes a lithium ion conductor and/or a sodium ion conductor.
  • the alkali metal ion conductor has an alkali metal ion conductivity of 0.01 ⁇ cm or greater.
  • the lithium ion conductor includes one or more of: Li 3 Fe 2 (PO 4 ) 3 , Li 3 Zr 2 Si 2 PO 4 , LiZr 2 (PO 4 ) 3 , LiTi 2 (PO 4 ) 3 , and Li 3 PO 4 .
  • the sodium ion conductor includes one or more of: Na- ⁇ -Al 2 O 3 , NASICON sodium ion Conductor, sodium sulfide ion conductor.
  • the surface (e.g., the entire surface) of the silicon-based negative electrode active material is covered with a coating layer.
  • the coating layer can further alleviate the volume expansion effect of the negative electrode active material and improve the cycle life of the material.
  • the coating layer also protects the negative electrode active material, inhibits the side reaction of the electrolyte on the surface of the material, and protects the surface of the material from being corroded by the electrolyte, so that the negative electrode active material has a higher capacity and the cycle life of the battery is further improved.
  • the material of the coating layer may include 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 include one or more of polyaniline, polyacetylene, polystyrene, polyacrylonitrile, polyvinyl chloride and polyethylene.
  • 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 surface of the material, and protects the surface of the material from being corroded by the electrolyte, so that the silicon-based negative electrode active material has a higher capacity and the cycle life of the battery is further improved.
  • the coating layer is a carbon material coating layer.
  • the carbon material may include one or more of mesophase microcarbon beads (MCMB), hydrocarbon compound pyrolysis carbon, hard carbon and soft carbon.
  • the weight proportion of carbon material in the silicon-based negative electrode active material can be 1.5-8wt%.
  • the silicon-based negative electrode active material has a further improved cycle life. Too low a carbon material content will result in insufficient stability and integrity of the coating layer, and the silicon-based negative electrode active material and the electrolyte cannot be effectively isolated. Too high a carbon material content will result in a decrease in the first coulombic efficiency.
  • the specific surface area of the silicon-based negative electrode active material is 4 m 2 /g or less, and may be 0.5-1.5 m 2 /g. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the silicon-based negative electrode active material has a BET specific surface area of 4 m 2 /g or less (e.g., 1-2 m 2 /g, 2-3 m 2 /g, 3-4 m 2 /g). Based on this solution, the silicon-based negative electrode active material exhibits improved cycle life. The above solution effectively avoids excessive loss of active lithium when the SEI film is formed on the surface of the silicon-based negative electrode active material, resulting in a lower initial efficiency.
  • the volume average particle size Dv50 of the silicon-based negative electrode active material is 4-15 ⁇ m, and optionally 5-9 ⁇ m. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the silicon-based negative electrode active material has a volume average particle size Dv50 of 4-15 ⁇ m (e.g., 4-5 ⁇ m, 5-6 ⁇ m, 6-7 ⁇ m, 7-8 ⁇ m, 8-9 ⁇ m, 9-10 ⁇ m, 10-11 ⁇ m, 11-12 ⁇ m, 12-13 ⁇ m, 13-14 ⁇ m or 14-15 ⁇ m). Based on this scheme, the silicon-based negative electrode active material exhibits an improved cycle life.
  • the silicon-based negative electrode active material of the above scheme has both good kinetics and first coulombic efficiency.
  • the particle size distribution of the silicon-based negative electrode active material (D V 90 - D V 10)/D V 50 is 0.5-3.0, and can be 0.8-1.3. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the silicon-based negative electrode active material has a (D V 90 - D V 10)/D V 50 ratio of 0.5-3.0:1 (e.g., 0.5-1:1, 1-1.5:1, 1.5-2:1, 2-2.5:1, or 2.5-3:1). It exhibits improved cycle life and especially improved dynamic performance.
  • the content of Si element in the silicon-based negative electrode active material is 20-80 wt %, and optionally 30-60 wt %. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the silicon-based negative electrode active material has an Si element content of 20-80wt% (e.g., 20-30wt%, 30-40wt%, 40-50wt%, 50-60wt%, 60-70wt% or 70-80wt%). Based on this scheme, the silicon-based negative electrode active material exhibits improved cycle life.
  • the total content of alkaline earth metal elements in the silicon-based negative electrode active material is 2-14 wt %, and optionally 2-10 wt %. Based on this solution, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • the silicon-based negative electrode active material has an alkaline earth metal element content of 2-14wt% (e.g., 2-3%, 3-4%, 4-5%, 5-6%, 6-7%, 7-8%, 8-9%, 9-10%, 10-11%, 11-12%, 12-13% or 13-14%). Based on this scheme, the silicon-based negative electrode active material shows an improved first coulombic efficiency.
  • the Si:O molar ratio of the silicon-based negative electrode active material is 1:0.6-1:1.8, and can be optionally 1:0.9-1:1.5.
  • the silicon-based negative electrode active material has a Si:O molar ratio of 1:0.6-1.8 (eg, 1:0.6-0.8, 1:0.8-1, 1:1-1.2, 1:1.2-1.4, 1:1.4-1.6, or 1:1.6-1.8). Based on this approach, the silicon-based negative electrode active material exhibits improved cycle life.
  • M includes at least one of Mg, Ca, Be, Sr, and Ba. Based on this scheme, the silicon-based negative electrode active material exhibits a further improved cycle life.
  • M includes Mg. Based on this scheme, the silicon-based negative electrode active material exhibits further improved cycle life.
  • the present application provides a method for preparing the above-mentioned silicon-based negative electrode active material, comprising the following steps:
  • the raw material is heated to a first temperature to form a vapor, and then the vapor is cooled to a second temperature to form a deposit;
  • the content of M element in the raw material is 7%-10%
  • the raw material is heated to a first temperature at a heating rate of less than 10°C/min;
  • the first temperature is 1100-1500°C
  • the second temperature is 800-1000°C.
  • the content of Mg element in the raw material is controlled within a preset range (7%-10%), a specific heating rate (8°C/min-15°C/min) is used, heating to a specific first temperature (1100°C-1500°C), and cooling to a specific second temperature (700°C-900°C) is adopted, which is beneficial to obtaining the silicon-based negative electrode active material of the present application.
  • a specific heating rate 8°C/min-15°C/min
  • heating to a specific first temperature (1100°C-1500°C
  • a specific second temperature 700°C-900°C
  • the content of the M element in the raw material is controlled within a preset range (8%-8.5%), a specific heating rate (8°C/min-12°C/min) is used, and the raw material is heated to a specific first temperature (1100°C-1300°C), and cooled to a specific second temperature (800°C-900°C), which is advantageous for obtaining a silicon-based negative electrode active material with a ratio of the half-peak width ⁇ A of the first diffraction peak to the half-peak width ⁇ B of the second diffraction peak of 1.0 ⁇ A / ⁇ B ⁇ 5.
  • the heating rate is too fast, the first temperature is too high, and the second temperature is too low, ⁇ A / ⁇ B will be too small. If the content of the M element is too low, the heating rate is too low, the first temperature is too low, and the second temperature is too high, ⁇ A / ⁇ B will be too large.
  • the feedstock includes elemental silicon, silicon dioxide, and an alkaline earth metal source.
  • the alkaline earth metal source includes one or more of a simple substance of the M element, a salt of the M element (eg, carbonate, nitrate, acetate, phosphate, oxalate, etc.), an oxide of the M element, and a hydroxide of the M element.
  • the source of Mg element includes one or more of Mg element, Mg element salt (such as carbonate, nitrate, acetate, phosphate, oxalate, etc.), Mg element oxide, and Mg element hydroxide.
  • Mg element salt such as carbonate, nitrate, acetate, phosphate, oxalate, etc.
  • silicon and silicon dioxide can be heated to form a silicon-oxygen gas containing Si and O elements, and further deposition can obtain a silicon-based negative electrode active material.
  • Silicon can be metallic silicon (also known as industrial silicon), polycrystalline silicon, or single crystal silicon commonly used in the art. The purity of silicon can be above 99.9%, above 99.99%, or above 99.999%.
  • the first temperature is 1100-1500° C.
  • each raw material can be gasified at the same time to generate a mixed silicon-oxygen vapor with uniform components, and the silicon element and the oxygen element are evenly distributed inside the deposited material. It is conducive to obtaining a silicon-based negative electrode active material with a ratio of ⁇ A to ⁇ B of 1-5:1.
  • the cooling temperature is 800-900° C.
  • the silicon-based negative electrode active material obtains a better crystallite size and suitable crystallinity, so that the silicon-based negative electrode active material has a higher first coulombic efficiency and cycle performance.
  • the vapor deposition is performed under an environment with an absolute pressure of 40 Pa or less. Based on this scheme, vapor can be formed faster in the step of vapor deposition.
  • the operation of crushing the sediment includes: according to the preset volume average particle size (Dv50) and specific surface area parameters of the product, the sediment is subjected to a coarse crushing-fine crushing-classification operation to obtain a product that meets the preset parameters.
  • the sediment can be crushed and classified by any method and equipment known in the art, such as a grinder, a jet mill-classifying integrated machine.
  • the alkali metalization reaction temperature of 450°C-800°C is conducive to obtaining a suitable alkali metalization degree of 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 temperature is lower than 500°C, the alkali metalization degree of the material may be insufficient, affecting the first coulombic efficiency of the material; when the temperature is higher than 800°C, the material may have an oversized grain size, affecting the cycle performance of the material.
  • the method for preparing a silicon-based negative electrode active material further comprises the following steps: coating the silicon-based negative electrode active material; optionally, the coating is a carbon material coating; more optionally, the carbon material coating comprises the following operations: placing the silicon-based negative electrode active material in a chamber containing a carbon source gas, adding Heat to 700-1000°C and keep warm for 1-6h.
  • a liquid phase coating method is used to coat the surface of the silicon-based negative electrode active material to form a coating layer.
  • 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 is formed on the surface of the silicon-based negative electrode active material by chemical vapor deposition, for example, a carbon source gas (such as a hydrocarbon compound gas) is introduced into a reactor containing the silicon-based negative electrode active material, and a heat treatment is performed to carbonize the carbon source gas to form a coating layer on the surface of the silicon-based negative electrode active material, thereby obtaining a silicon-based negative electrode active material having a coating layer on the surface.
  • a carbon source gas such as a hydrocarbon compound gas
  • the method for preparing the negative electrode active material further comprises the following step: coating the pulverized product.
  • the coating treatment includes a carbon coating treatment and/or an alkali metal ion conductor coating treatment.
  • the carbon coating process includes the following operations: placing the target to be coated in a deposition chamber containing a carbon source gas, heating the carbon source gas to carbonize and deposit, and forming a coating layer containing a carbon material.
  • the carbon source gas accounts for 5-15% of the total gas volume in the deposition chamber.
  • the deposition chamber may also contain a non-oxidizing gas, such as nitrogen or an inert gas.
  • the carbon source gas includes one or more of the following: acetylene, methane, ethylene, propane, ethane, propylene, propyne, toluene.
  • the alkali metal ion conductor coating process includes the following operations: placing the target to be coated in a chamber containing an alkali metal ion conductor forming source, heating to deposit the alkali metal ion conductor forming source, and forming a coating layer containing the alkali metal ion conductor coating.
  • the alkali metal ion conductor forming source refers to a substance that can form an alkali metal ion conductor after sintering.
  • the alkali metal ion conductor forming source includes, for example, alkali metal hydroxides and phosphates.
  • the alkali metal ion conductor forming source includes, for example, alkali metal hydroxides and ammonium hydrogen phosphate.
  • the heating temperature is 700-1000°C.
  • the heating time is 1-6 hours.
  • the heating temperature during the alkali metal ion conductor coating process is 600-800°C.
  • the heating time is 1-6 hours.
  • the carbon coating treatment includes the following operations: placing the crushed product in a deposition chamber containing a carbon source gas, heating the temperature to 450-800° C. at a heating rate of less than 5° C./min, and keeping the temperature for 3-10 hours.
  • the negative electrode current collector has two surfaces opposite to each other in its own 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 forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base (such as polypropylene (PP), polyethylene terephthalate (PET), It is formed on a substrate such as 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 further optionally include a binder.
  • the binder may include 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, 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 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 film layer may also include negative electrode active materials known in the art other than the present application, and those skilled in the art may select 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 sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as silicon-based negative electrode active materials, conductive agents, binders 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 by the following method: The positive electrode active material, conductive agent, 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 includes sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium hexafluoroarsenate.
  • the solvent may include 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, 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 may include glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinyl chloride. At least one of difluoroethylene.
  • the isolation film can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation film is a multi-layer composite film, 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 shows a secondary battery 5 of a square structure as an example.
  • the outer packaging of the secondary battery 5 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, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, Energy storage systems, etc., but not limited to these.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the silicon-based composite can be understood as a composite structure in which a plurality of nanocrystals are dispersed in a silicon oxide matrix, such as a structure in which Si grains and MSiO 3 grains are dispersed in a silicon oxide material.
  • M includes one or more alkaline earth metal elements, and in the following examples, M includes Mg).
  • the silicon-based negative electrode active material is also coated with a Li 3 PO 4 coating layer and a carbon material coating layer.
  • the raw material composition is heated to a first temperature at a preset heating rate to form a vapor containing Si, Mg and O elements. (See Table 1 for the heating rate and the first temperature)
  • the sediment is coarsely crushed, finely crushed and classified to obtain a crushed product.
  • the crushed product is carbon-coated by using a vapor deposition device.
  • the carbon source gas used is a mixture of acetylene and nitrogen (20% by volume of acetylene and 80% by volume of nitrogen). It is heat treated at 800°C for 2h to form a coating layer containing carbon material.
  • the XRD spectrum of the sample has a first diffraction peak (between 28° and 28.6°) corresponding to the Si (111) crystal plane.
  • the half-peak width of the first diffraction peak is ⁇ A °, the intensity is IA , and the grain size of the corresponding Si grain is D A ;
  • the XRD spectrum of the sample has a second diffraction peak (between 31-32°) corresponding to the MSiO 3 (310) crystal plane (M includes Mg), the half-peak width of the second diffraction peak is ⁇ B °, the intensity is 1 B , and the grain size of the corresponding MSiO 3 grains is DB ;
  • the negative electrode active material has a coating layer, the coating layer contains a carbon material, wherein the content of the carbon material in the negative electrode active material is within 5wt%, and the content of Li 3 PO 4 in the negative electrode active material is 0.5wt%;
  • the silicon-based negative electrode active material has a Mg content of 8.0 ⁇ 1%
  • the silicon-based negative electrode active material has a Si content of 56 ⁇ 4%
  • the silicon-based negative electrode active material has a BET specific surface area of 1.3 ⁇ 0.05 M/g;
  • the silicon-based negative electrode active material has a volume average particle size D V 50 of 6.0 ⁇ 1 ⁇ m;
  • the silicon-based negative electrode active material has a (D V 90 - D V 10)/D V 50 ratio of 1.05 ⁇ 0.05;
  • the half-peak width and the crystal size are well-known in the art and can be tested by methods known in the art.
  • the XRD pattern of the sample can be tested according to the JIS/K0131-1996 test standard
  • the corresponding diffraction peak of the target crystal can be located according to the XRD pattern of the sample
  • the half-peak width and peak height can be determined based on the diffraction peak.
  • Half peak width is the peak width at half the height of the XRD diffraction peak. That is, the distance in degrees between the two points where a straight line parallel to the bottom of the peak passes through the midpoint of the peak height and intersects the two sides of the peak.
  • Peak height refers to the peak height of the diffraction peak (peak ordinate).
  • the standard card data with PDF number 01-075-0589 can be used to identify the first diffraction peak corresponding to the (111) crystal plane of Si grains, and the diffraction angle 2 ⁇ of the first diffraction peak is between 26-26.8°.
  • the standard card data with PDF number 00-035-0610 can be used to identify the second diffraction peak corresponding to the (310) crystal plane of the MgSiO 3 grain, and the diffraction angle 2 ⁇ of the second diffraction peak is between 31-32°.
  • Grain size calculation The half-peak width ⁇ and diffraction angle ⁇ of the diffraction peaks of Si (111) crystal plane and MSiO 3 (310) crystal plane were measured respectively, and substituted into the Debye-Scherrer formula to calculate and obtain the corresponding grain size.
  • the Debye-Scherrer formula is as follows:
  • ⁇ --half-maximum width of the diffraction peak unit: °
  • ⁇ --diffraction angle unit: degree
  • the grain size is calculated from the half-peak width of the XRD diffraction peak.
  • the half-peak width is negatively correlated with the grain size. The larger the half-peak width, the smaller the grain size.
  • the element content is well known in the art and can be tested by methods known in the art.
  • Spectroscopic testing Inductively coupled plasma, ICP determines the content of alkaline earth metal elements and silicon elements. The details are as follows: Take the sample to be tested and digest it with aqua regia and hydrofluoric acid HF, and then test the content of total alkaline earth metal elements (such as lithium) and silicon elements in the solution after digestion.
  • the specific surface area of a material is a well-known meaning in the art and can be tested by methods known in the art. For example, it can be tested by nitrogen adsorption specific surface area analysis test method according to GB/T 19587-2017 and calculated by BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.
  • 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 the silicon-based negative electrode active material reaching 10%, 50% and 90% respectively.
  • negative electrode sheet The silicon-based negative electrode active material prepared above is thoroughly stirred and mixed with the conductive agent Super-P (conductive carbon black) and the binder PAA (polyacrylic acid) in a mass ratio of 85:5:10 in an appropriate amount of deionized water to form a uniform negative electrode slurry; the negative electrode slurry is coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.
  • the conductive agent Super-P conductive carbon black
  • PAA polyacrylic acid
  • Separation film polyethylene (PE) film.
  • 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%.
  • Assembly of 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 battery Under normal temperature conditions, the battery was left to stand for 3 hours, then discharged at a constant current of 0.05C to a voltage of 0.005V, and further discharged at a constant current of 50 ⁇ A to a voltage of 0.005V, and the capacity at this time was recorded as the first lithium insertion capacity (C 2 ). After standing for 5 minutes, the battery was charged at a rate of 0.1C to a voltage of 2V, and the capacity at this time was recorded as the first lithium removal capacity (C 1 ).
  • Material initial efficiency (%) (initial lithium removal capacity C 1 / initial lithium insertion capacity C 2 )*100%
  • the positive electrode active material LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), conductive carbon black and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a proper amount of N-methylpyrrolidone (NMP) solvent in a weight ratio of 93:2:5 to form a uniform positive electrode slurry; the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying and other processes, a positive electrode sheet is obtained.
  • NMP N-methylpyrrolidone
  • the silicon-based negative electrode active material silicon-oxygen composite material
  • conductive carbon black thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber latex (SBR) are fully stirred and mixed in a proper amount of deionized water at a weight ratio of 96.5:1.0:1.0:1.5 to form a uniform negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying and other processes, a negative electrode sheet is obtained.
  • CMC thickener sodium carboxymethyl cellulose
  • SBR binder styrene-butadiene rubber latex
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol/L.
  • the positive electrode sheet, PP isolation film, and negative electrode sheet are stacked in sequence, then wound into a battery cell and loaded into a packaging shell, the above-mentioned electrolyte is injected into the battery cell, and then the secondary battery is obtained through sealing, standing, hot and cold pressing, and formation processes.
  • the secondary battery prepared in the embodiment and the comparative example is charged at a constant current of 1C to a charge cut-off voltage V1, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage V2, left to stand for 5 minutes.
  • This is a charge and discharge cycle.
  • the battery is subjected to a cyclic charge and discharge test according to this method until the battery capacity decays to 80%. The number of cycles at this time is the cycle life of the battery.
  • the content of Mg in the raw material is controlled within a preset range (7%-10%), a specific heating rate (8-15°C/min) is used, and the raw material is heated to a specific first temperature (1100°C-1500°C), and cooled to a specific second temperature (700°C-900°C), which is advantageous for obtaining a silicon-based negative electrode active material having a ratio of the half-peak width ⁇ A of the first diffraction peak to the half-peak width ⁇ B of the second diffraction peak of 1.0 ⁇ A / ⁇ B ⁇ 5.
  • the ⁇ A: ⁇ B value of sample D1 is 0.9 ( ⁇ 1.5), its first coulombic efficiency is only 83.4%, and the battery capacity retention rate decays to 80% after 450 cycles at 25°C.
  • the ⁇ A: ⁇ B value of sample D2 is 5.5 (>5.0), its first coulombic efficiency is only 78%, and the battery capacity retention rate decays to 80% after 680 cycles at 25°C.

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Abstract

一种硅基负极活性材料，包括Si和MSiO 3，其中，M包括一种或多种碱土金属元素；在所述硅基负极活性材料的XRD衍射图谱中，衍射角2θ在26°-26.8°之间具有第一衍射峰，所述第一衍射峰的半峰宽为β A；衍射角2θ在31°-32°之间具有第二衍射峰，所述第二衍射峰的半峰宽为β B；则所述硅基负极活性材料满足：1.5≤β A/β B≤5.0。

Description

硅基负极活性材料及其制备方法、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及其制备方法、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。
硅基负极活性材料被认为是具有前景的二次电池硅基负极活性材料。随着二次电池的快速发展，对硅基负极活性材料的首次库伦效率和循环性能提出了更高的要求。
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及其制备方法、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，包括Si和MSiO3，其中，M包括一种或多种碱土金属元素；在所述硅基负极活性材料的XRD衍射图谱中，衍射角2θ在28°-28.6°之间具有第一衍射峰，所述第一衍射峰的半峰宽为βA；衍射角2θ在31°-32°之间具有第二衍射峰，所述第二衍射峰的半峰宽为βB；则所述硅基负极活性材料满足：1.5≤βA/βB≤5.0。
基于上述方案的负极活性材料兼顾较好的首次库伦效率和循环寿命。尽管机理尚不十分明确，但上述性能改进可能与硅基负极活性材料中Si晶粒和含碱土金属硅酸盐晶粒的尺寸和分布有关。当XRD衍射峰的半峰宽βA与βB的比值为1-5:1时，Si晶粒和含碱土金属硅酸盐晶粒在硅基负极活性材料中具有改善的尺寸分布的位置分布，这样的微观结构有助于缓解硅基负极活性材料在循环过程中的体积膨胀问题，进而改善其电化学性能。当βA与βB的比值过大，负极活性材料的首次库伦效率偏低，当βA与βB的比值过小，负极活性材料的循环性能偏低。
在一些实施方案中，βA与βB的比值为2.0≤βA/βB≤5.0，可选为2.5≤βA/βB≤4.0。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，1°≤βA≤3°，可选为1°≤βA≤2°。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，0.2°≤βB≤1.0°，可选为0.3°≤βB≤0.5°。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述Si的晶粒尺寸小于所述MSiO3的晶粒尺寸。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述Si的晶粒尺寸小于等于12nm，可选为2nm-10nm；和/或，所述MSiO3的晶粒尺寸大于等于11nm，可选为12nm-18nm。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
根据权利要求1-6任一项所述的硅基负极活性材料，所述硅氧基复合物的至少部分表面具有包覆层；可选地，所述包覆层包括碳材料和碱金属离子导体材料中的一种或多种。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料的比表面积为4m2/g以下，可选为0.5-1.5m2/g。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
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4-15μm，可选为5-9μm。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料的粒度分布(DV90-DV10)/DV50为0.5-3.0，可选为0.8-1.3。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料中Si元素的含量为20-80wt％，可选为30-60wt％。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料中碱土金属元素的总含量为2-14wt％，可选为2-10wt％。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料的Si:O摩尔比1:0.6-1:1.8，可选为1:0.9-1:1.5；
在一些实施方案中，M包括Mg、Ca、Be、Sr、Ba中的至少一种。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在第二方面，本申请提供上述硅基负极活性材料的制备方法，包括以下步骤：
提供含有Si元素、O元素和M元素的的原料，M包括一种或多种碱土金属元素；
利用气相沉积技术，将所述原料加热至第一温度形成蒸气，然后将所述蒸气冷却至第二温度形成沉积物；
将沉积物粉碎，获得粉碎产物；
其中，所述原料中M元素的含量为7％-10％；
其中，以10℃/min以下的升温速度将所述原料加热至第一温度；
其中，所述第一温度为1100-1500℃；
其中，所述第二温度为800-1000℃。
在一些实施方案中，所述原料包括硅单质、二氧化硅和碱土金属源。
在一些实施方案中，执行气相沉积时，第一温度为1200-1400℃。
在一些实施方案中，执行气相沉积时，第二温度为800-900℃。
在一些实施方案中，在绝对压力为40Pa以下的环境下执行气相沉积。
在一些实施方案中，硅基负极活性材料的制备方法方法还包括以下步骤：对所述硅基负极活性材料进行包覆处理；可选地，所述包覆处理是碳材料包覆处理；更可选地，所述 碳材料包覆处理包括以下操作：将所述硅基负极活性材料置于含有碳源气体的腔室内，加热至700-1000℃，保温1-6h。
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
(1)硅基负极活性材料具有改善的首次库伦效率；
(2)硅基负极活性材料具有改善的循环容量保持率；
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用于描述元素的含量时，其是指硅基负极活性材料中元素的质量占硅基负极活性材料的质量的百万分比。
术语“包括”“包含”“含有”是指开放式地涵盖目标对象或步骤，即不排除还含有其它的对象或步骤。“包括”“包含”“含有”一个对象，意味着该对象以大于零的含量存在，例如1-10％、10-20％、20-30％、30-40％、40-50％、50-60％、60-70％、70-80％、80-90％、90-100％。在一个不特定的例子中，“包括”“包含”“含有”一个对象涵盖由该对象本身构成的情况。
[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，所述负极膜层包括硅基负极活性材料，硅基负极活性材料采用本申请的硅基负极活性材料。
在第一方面，本申请提供一种硅基负极活性材料，包括Si和MSiO3，其中，M包括一种或多种碱土金属元素；在所述硅基负极活性材料的XRD衍射图谱中，衍射角2θ在28°-28.6°之间具有第一衍射峰，所述第一衍射峰的半峰宽为βA；衍射角2θ在31°-32°之间具有第二衍射峰，所述第二衍射峰的半峰宽为βB；则所述硅基负极活性材料满足：1.5≤βA/βB≤5.0。
基于上述方案的硅基负极活性材料具有改善的首次库伦效率和/或循环寿命。尽管机理尚不十分明确，但上述性能改进可能与硅基负极活性材料中Si晶粒和MSiO3晶粒的晶粒尺寸和分布有关。XRD衍射峰的半峰宽与晶粒尺寸具有负相关的函数关系，本申请发现，当βA与βB的比值为1-5:1时，Si晶粒和MSiO3晶粒在硅基负极活性材料中具有改善的晶粒尺寸，以及更均匀的的位置分布，这样的微观结构有助于缓解硅基负极活性材料在循环过程中的体积膨胀问题，进而改善其电化学性能。当βA与βB的比值为1-5:1时，Si晶粒和MSiO3晶粒表现出相互促进的协同作用，使得硅基负极活性材料具有较好的循环寿命。当βA与βB的比值小于2或大于4会导致Si晶粒和MSiO3晶粒的尺寸差异悬殊，这反映了Si晶粒和MSiO3晶粒在硅基负极活性材料中的生长和分布不均匀，结果导致负极活性材料的电化学性能不佳。
在一些实施方案中，βA与βB的比值为2.0-2.2:1、2.2-2.4:1、2.4-2.6:1、2.6-2.8:1、2.8-3:1、3.0-3.2:1、3.2-3.4:1、3.4-3.6:1、3.6-3.8:1、3.8-4:1、4.0-4.2:1、4.2-4.4:1、4.4-4.6:1、4.6-4.8:1或4.8-5:1。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，βA与βB的比值为2.0≤βA/βB≤5.0，可选为2.5≤βA/βB≤4.0。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，βA与βB的比值为2.0-5.0:1(例如2.5-2.6:1、2.6-2.8:1、2.8-3:1、 3-3.2:1、3.2-3.4:1、3.4-3.6:1、3.6-3.8:1、3.8-4:1)。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，βA与βB的比值为2.5-4.0:1(例如2.5-2.6:1、2.6-2.8:1、2.8-3:1、3-3.2:1、3.2-3.4:1、3.4-3.6:1、3.6-3.8:1、3.8-4.0:1)。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，1°≤βA≤3°，可选为1°≤βA≤2°。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，0.2°≤βB≤1.0°，可选为0.3°≤βB≤0.5°。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，βA的值为1.0°-3.0°(例如1.0°-1.2°、1.2°-1.4°、1.4°-1.6°、1.6°-1.8°、1.8°-2.0°、2.0°-2.2°、2.2°-2.4°、2.4°-2.6°、2.6°-2.8°、2.8°-3.0°)，可选为1°≤βA≤2°(例如1.0°-1.2°、1.2°-1.4°、1.4°-1.6°、1.6°-1.8°或1.8°-2.0°)。在此方案中，硅基负极活性材料具有进一步改善的能循环寿命。
在一些实施方案中，βB的值为0.2°-1.0°(例如0.2°-0.4°、0.4°-0.6°、0.6°-0.8°或0.8°-1°)。可选为0.2°≤βA≤1.0°在此方案中，硅基负极活性材料具有进一步改善的循环寿命。
在一些实施方案中，所述Si的晶粒尺寸小于所述MSiO3的晶粒尺寸。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述Si的晶粒尺寸小于等于12nm，可选为2nm-10nm；。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。晶粒尺寸是由XRD衍射峰的半峰宽根据Debye-Scherrer公式计算得出，半峰宽和晶粒大小成负相关，半峰宽越大则晶粒尺寸越小。
在一些实施方案中，所述MSiO3的晶粒尺寸大于等于11nm，可选为12nm-18nm。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。晶粒尺寸是由XRD衍射峰的半峰宽根据Debye-Scherrer公式计算得出，半峰宽和晶粒大小成负相关，半峰宽越大则晶粒尺寸越小。
在一些实施方案中，所述第一衍射峰和第二衍射峰的强度比为1-5：1，可选为2-4：1。在此方案中，硅基负极活性材料具有改善的循环寿命。
在一些实施方案中，所述硅氧基复合物的至少部分表面具有包覆层；可选地，所述包覆层包括碳材料和碱金属离子导体材料中的一种或多种。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，碱金属离子导体包覆层包括锂离子导体和/或钠离子导体。
在一些实施方案中，碱金属离子导体具有0.01Ω·cm以上的碱金属离子电导率。
在一些实施方案中，锂离子导体包括以下一种或多种：Li3Fe2(PO4)3、Li3Zr2Si2PO4、LiZr2(PO4)3、LiTi2(PO4)3和Li3PO4。
在一些实施方案中，钠离子导体包括一些一种或多种：Na-β-Al2O3，NASICON钠离子 导体、硫化物钠离子导体。
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(例如全部表面)覆有包覆层。所述包覆层能够使得所述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，包覆层的材料可以包括聚合物、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，所述聚合物可以包括聚苯胺、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，所述包覆层是碳材料包覆层。在上述方案中，所述碳材料可以包括中间相微碳球(MCMB)、烃类化合物热解碳、硬碳及软碳中的一种或几种。
在一些实施方案中，碳材料在所述硅基负极活性材料中的重量占比可以为1.5-8wt％。在此方案中，硅基负极活性材料具有进一步改善的循环寿命。碳材料含量过低会导致包覆层的稳定性和完整性不足，不能有效地隔离硅基负极活性材料以及电解液。碳材料含量过高会导致导致首次库伦效率的降低。
在一些实施方案中，所述硅基负极活性材料的比表面积为4m2/g以下，可选为0.5-1.5m2/g。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料具有4m2/g以下(例如1-2m2/g、2-3m2/g、3-4m2/g)的BET比表面积。基于此方案，硅基负极活性材料表现出改善的循环寿命。上述方案有效避免了硅基负极活性材料表面SEI膜形成时对活性锂的过多损耗，造成首效较低。
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4-15μm，可选为5-9μm。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料具有4-15μm(例如4-5μm、5-6μm、6-7μm、7-8μm、8-9μm、9-10μm、10-11μm、11-12μm、12-13μm、13-14μm或14-15μm)的体积平均粒径Dv50。基于此方案，硅基负极活性材料表现出改善的循环寿命。上述方案的硅基负极活性材料兼具较好的动力学和首次库伦效率。
在一些实施方案中，所述硅基负极活性材料的粒度分布(DV90-DV10)/DV50为0.5-3.0，可选为0.8-1.3。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料具有0.5-3.0:1(例如0.5-1:1、1-1.5:1、1.5-2:1、2-2.5:1或2.5-3:1)的(DV90-DV10)/DV50比值。基于此方案，硅基负极活性材料表 现出改善的循环寿命，尤其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中Si元素的含量为20-80wt％，可选为30-60wt％。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料具有20-80wt％(例如20-30wt％、30-40wt％、40-50wt％、50-60wt％、60-70wt％或70-80wt％)的Si元素含量。基于此方案，硅基负极活性材料表现出改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料中碱土金属元素的总含量为2-14wt％，可选为2-10wt％。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，所述硅基负极活性材料具有2-14wt％(例如2-3％、3-4％、4-5％、5-6％、6-7％、7-8％、8-9％、9-10％、10-11％、11-12％、12-13％或13-14％)的碱土金属元素含量。基于此方案，硅基负极活性材料表现出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的Si:O摩尔比1:0.6-1:1.8，可选为1:0.9-1:1.5。
在一些实施方案中，所述硅基负极活性材料具有1:0.6-1.8(例如1:0.6-0.8、1:0.8-1、1:1-1.2、1:1.2-1.4、1:1.4-1.6或1:1.6-1.8)的Si:O摩尔比。基于此方案，硅基负极活性材料表现出改善的循环寿命。
在一些实施方案中，M包括Mg、Ca、Be、Sr、Ba中的至少一种。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在一些实施方案中，M包括Mg。基于此方案，硅基负极活性材料表现出进一步改善的循环寿命。
在第二方面，本申请提供上述硅基负极活性材料的制备方法，包括以下步骤：
提供含有Si元素、O元素和M元素的的原料，M包括一种或多种碱金属元素；
利用气相沉积技术，将所述原料加热至第一温度形成蒸气，然后将所述蒸气冷却至第二温度形成沉积物；
将沉积物粉碎，获得粉碎产物；
其中，所述原料中M元素的含量为7％-10％，
其中，以10℃/min以下的升温速度将所述原料加热至第一温度；
其中，所述第一温度为1100-1500℃；
其中，所述第二温度为800-1000℃。
在上述方案中，将原料中Mg元素的含量控制在预设范围内(7％-10％)，采用特定的升温速度(8℃/min-15℃/min)，加热至特定的第一温度(1100℃-1500℃)，冷却至特定的第二温度(700℃-900℃)，对获得本申请硅基负极活性材料是有利的。一般情况下，升温速率越大，半峰宽越大；热处理温度越高、时间越长，半峰宽越小。本领域的技术人员可以在上述各参数范围内通过有限次试验，获得本申请的硅基负极活性材料。基于此方案，制备获得的硅基负极活性材料表现出改善的首次库伦效率和/或循环寿命。
在上述方案中，将原料中M元素的含量控制在预设范围内(8％-8.5％)，采用特定的升温速度(8℃/min-12℃/min)，加热至特定的第一温度(1100℃-1300℃)，冷却至特定的第二温度(800℃-900℃)，对于获得第一衍射峰半峰宽βA和第二衍射峰的半峰宽βB比值为1.0≤βA/βB≤5的硅基负极活性材料是有利的。M元素的含量过高、升温速度过快、第一温度过高、第二温度过低，会导致βA/βB偏小。M元素的含量过低、升温速度过低、第一温度过低、第二温度过高，会导致βA/βB偏大。
在一些实施方案中，所述原料包括硅单质、二氧化硅和碱土金属源。
在一些实施方案中，碱土金属源包括M元素单质、M元素的盐(例如碳酸盐、硝酸盐、醋酸盐、磷酸盐、草酸盐等)、M元素的氧化物、M元素的氢氧化物中的一种或多种。
在一些实施方案中，Mg元素源包括Mg元素单质、Mg元素的盐(例如碳酸盐、硝酸盐、醋酸盐、磷酸盐、草酸盐等)、Mg元素的氧化物、Mg元素的氢氧化物中的一种或多种。
在一些实施方案中，硅单质和二氧化硅被加热后能够形成含有Si元素和O元素的硅氧气体，进一步沉积能够获得硅基负极活性材料。硅单质可以采用本领域通用的金属硅(也称工业硅)、多晶硅、单晶硅。硅单质的纯度可以为99.9％以上，99.99％以上，99.999％以上。
在一些实施方案中，执行气相沉积时，第一温度为1100-1500℃。在上述方案中，各原料能够同时气化生成组分均匀的混合硅氧蒸气，沉积获得的材料内部硅元素和氧元素分布均匀。有利于获得βA与βB的比值为1-5:1的硅基负极活性材料。
在一些实施方案中，执行气相沉积时，冷却温度为800-900℃。在上述方案中，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。
在一些实施方案中，在绝对压力为40Pa以下的环境下执行气相沉积。基于此方案，能够在气相沉积的步骤中较快地形成蒸气。
在一些上述方案中，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，450℃-800℃碱金属化反应温度有利于使硅基负极活性材料获得适宜的碱金属化程度，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。当温度低于500℃，可能会导致材料的碱金属化程度不够，影响材料的首次库伦效率；当温度高于800℃时，可能会导致材料的具有尺寸过大的晶粒尺寸，影响材料的循环性能。
在一些实施方案中，硅基负极活性材料的制备方法方法还包括以下步骤：对所述硅基负极活性材料进行包覆处理；可选地，所述包覆处理是碳材料包覆处理；更可选地，所述碳材料包覆处理包括以下操作：将所述硅基负极活性材料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，采用液相包覆法在硅基负极活性材料的表面进行包覆，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，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碳源气体(如烃类化合物气体)，进行热处理，使碳源气体碳化，形成包覆于硅基负极活性材料表面的包覆层，得到表面有包覆层的硅基负极活性材料。
在一些实施方案中，负极活性材料的制备方法还包括以下步骤：对粉碎产物进行包覆处理。
在一些实施方案中，所述包覆处理包括碳包覆处理和/或碱金属离子导体包覆处理。
在一些实施方案中，所述碳包覆处理包括以下操作：将待包覆目标置于含有碳源气体的沉积腔室内，加热使碳源气体碳化沉积，形成含有碳材料都包覆层。
在一些实施方案中，碳源气体占沉积腔室内总气体体积的5～15％。沉积腔室内还可以含有非氧化性气体，例如氮气或惰性气体。
在一些实施方案中，碳源气体包括以下一种或多种：乙炔、甲烷、乙烯、丙烷、乙烷、丙烯、丙炔、甲苯烷。
在一些实施方案中，所述碱金属离子导体包覆处理包括一些操作：将待包覆目标置于含有碱金属离子导体形成源的腔室中，加热使碱金属离子导体形成源沉积，形成含有碱金属离子导体包覆的包覆层。
在一些实施方案中，碱金属离子导体形成源是指经烧结后能够形成碱金属离子导体的物质。碱金属离子导体形成源例如包括碱金属氢氧化物和磷酸盐。碱金属离子导体形成源例如包括碱金属氢氧化物和磷酸氢铵。
在一些实施方案中，所述碳包覆处理中，加热的温度为700-1000℃。
在一些实施方案中，所述碳包覆处理中，加热的时间为1-6h。
在一些实施方案中，所述碱金属离子导体包覆处理中，加热的温度为600-800℃。
在一些实施方案中，所述碳包覆处理中，加热的时间为1-6h。
在一些实施方案中，所述碳包覆处理包括以下操作：将破碎产物置于含有碳源气体的沉积腔室内，以5℃/min以下的升温速度升温至450-800℃，保温3-10h。
在一些实施方案中，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，负极膜层还可选地包括粘结剂。作为示例，粘结剂可包括丁苯橡胶(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，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，负极膜层还可以包括除本申请以外的本领域已知的负极活性材料，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，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，电解质盐包括高氯酸钠，六氟磷酸钠，四氟硼酸钠及六氟砷酸钠。
在一些实施方式中，溶剂可包括碳酸亚乙酯、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，隔离膜的材质可包括玻璃纤维、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示出作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2示出的二次电池5的分解图，二次电池5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。
1.硅基负极活性材料的组成
以下实施例提供硅基负极活性材料。在以下实施例中，硅基复合物可以理解为是一种多种纳米晶分散在硅氧化物基体中的复合结构，例如Si晶粒和MSiO3晶粒分散在硅氧材料中的结构。(M包括一种或多种碱土金属元素，在以下实施例中M包括Mg)。硅基负极活性材料上还覆有Li3PO4包覆层和碳材料包覆层。
2.硅基负极活性材料的制备方法
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)将金属硅粉末(硅元素含量为99.8％)30g、二氧化硅(SiO2)粉末60g及金属镁混合，得到原料(原料中Mg元素的含量参见表1)。
2)在绝对压力为20Pa的氦气气氛中，以预设升温速度将原料组合物加热至第一温度，形成含有Si元素、Mg元素和O元素的蒸气。(升温速度和第一温度参见表1)
3)在绝对压力为20Pa的氦气气氛中，将所述蒸气冷却至沉积温度，使蒸气沉积，得到沉积物。(沉积温度参见表1)
4)对沉积物进行粗破-细碎-分级，得到破碎产物。
5)在常压条件下，采用气相沉积设备对破碎产物进行碳包覆处理，所用碳源气体为乙炔和氮气的混合气(乙炔体积20％，氮气80体积％)，在800℃热处理2h，形成含有碳材料的包覆层。
6)将具有碳包覆层的产物(2g)、LiOH(0.17mol)和(NH4)2HPO4(0.17mol)研磨混合均匀，将混合物放入热处理设备(如CVD回转炉)，在氮气气氛下，在700℃热处理2h，形成含有Li3PO4的包覆层，即获得产品负极活性材料。
按照上述方法，制备了多个硅基负极活性材料样品(以下简称样品)，这些样品各自具有表1示出的彼此区别的特征参数：
(1)样品的XRD图谱具有对应Si(111)晶面的第一衍射峰(28-28.6°之间)，第一衍射峰的半峰宽为βA°，强度为IA，对应Si晶粒的晶粒尺寸为DA；
(2)样品的XRD图谱具有对应MSiO3(310)晶面(M包括Mg)的第二衍射峰(31-32°之间)，第二衍射峰的半峰宽为βB°，强度为IB，对应MSiO3晶粒的晶粒尺寸为DB；
除上述特征参数之外，这些样品的其它参数基本相同，这些相同的参数如下：
a)负极活性材料具有包覆层，包覆层含有碳材料，其中，碳材料在负极活性材料中的含量为5wt％以内，Li3PO4在负极活性材料中的含量为0.5wt％；
b)硅基负极活性材料具有8.0±1％的Mg元素含量；
c)硅基负极活性材料具有56±4％的Si含量；
d)硅基负极活性材料中硅元素和氧元素的摩尔比为x＝1.0±0.1；
e)硅基负极活性材料具有1.3±0.05M/g的BET比表面积；
f)硅基负极活性材料具有6.0±1μm的体积平均粒径DV50；
g)所述硅基负极活性材料具有1.05±0.05的(DV90-DV10)/DV50比值；
h)第一衍射峰和第二衍射峰的峰强度比值为IA:IB＝3.5：1。
下面将上述硅基负极活性材料组装为扣式电池，并进行电化学性能分析。
二、分析检测方法
2.1半峰宽及晶粒尺寸
半峰宽及晶粒尺寸为本领域公知的含义，可采用本领域已知的方法测试。例如，可以依据JIS/K0131-1996测试标准测试样品的XRD图，根据样品的XRD图定位目标晶体的对应的衍射峰，基于衍射峰确定半峰宽和峰高。
半峰宽是XRD衍射峰高一半处的峰宽度。即通过峰高的中点作平行于峰底的直线，此直线与峰两侧相交两点之间的以单位°计的距离。
峰高是指衍射峰的峰值高度(峰值纵坐标)。
PDF编号为01-075-0589的标准卡片数据可用于识别对应Si晶粒(111)晶面的第一衍射峰，第一射峰的衍射角2θ在26-26.8°之间。
PDF编号为00-035-0610的标准卡片数据可用于识别对应MgSiO3晶粒(310)晶面的二衍射峰，第二衍射峰的衍射角2θ在31-32°之间。
晶粒尺寸计算：分别测量Si(111)晶面、MSiO3(310)晶面衍射峰的半峰宽β和衍射角θ，代入Debye-Scherrer公式计算，得到相应的晶粒尺寸。
Debye-Scherrer公式如下：
Dhkl＝kλ/βcosθ
Dhkl--晶粒尺寸，单位：nm；k--Scherrer常数，k＝0.89；λ--入射X射线波长，λ＝0.15406nm；
β--衍射峰的半高峰宽，单位°；θ--衍射角，单位：度。
晶粒尺寸晶粒大小是由XRD衍射峰的半峰宽计算得出，半峰宽和晶粒大小成负相关，半峰宽越大则晶粒尺寸越小。
以上参数测试结果如表1所示。
2.2碱土金属元素、硅元素含量的测试
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。例如，可以采用发射 光谱测试(Inductively coupled plasma，ICP)测定碱土金属元素及硅元素的含量。具体如下：取待测样品用王水和氢氟酸HF对样品进行消解，取消解后的溶液测试总碱土金属元素(如锂元素)、硅元素的含量。
2.3 BET比表面积测试
材料的比表面积为本领域公知的含义，可采用本领域已知的方法测试。例如可以参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出，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 3020型比表面积孔径分析测试仪进行。
2.4粒径测试
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。
其中，Dv10、Dv50、Dv90的物理定义如下：所述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首次库伦效率
(1)扣式电池的制备
负极极片的制备：将上述制备的硅基负极活性材料与导电剂Super-P(导电炭黑)、粘结剂PAA(聚丙烯酸)按85:5:10的质量比在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。
对电极：金属锂片。
隔离膜：聚乙烯(PE)薄膜。
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％。
扣式电池的组装：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。
(2)首次库伦效率测试
常温条件下，将电池静置3h，之后以0.05C恒流放电至电压为0.005V，进一步以50μA恒流放电电至电压为0.005V，记录此时容量为首次嵌锂容量(C2)。静置5分钟，然后以0.1C倍率充电至电压为2V，记录此时容量为首次脱锂容量(C1)。
材料首效(％)＝(首次脱锂容量C1/首次嵌锂容量C2)*100％
以上参数测试结果如表1所示。
2.8材料循环寿命测试
(1)全电池的制备
1、正极极片的制备
将正极活性材料LiNi1/3Co1/3Mn1/3O2(NCM333)、导电炭黑、粘结剂聚偏二氟乙烯(PVDF)按93：2：5的重量比在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料；将正极浆料涂覆于正极集流体的表面上，经烘干等工序后，得到正极极片。
2、负极极片的制备
将硅基负极活性材料(硅氧复合材料)、导电炭黑、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶乳液(SBR)按96.5：1.0：1.0：1.5重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上，经烘干等工序后，得到负极极片。
3、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)按照按体积比1:1:1进行混合得到有机溶剂，接着将充分干燥的锂盐LiPF6溶解于混合后的有机溶剂中，配制成浓度为1mol/L的电解液。
4、全电池的制备
将正极极片、PP隔离膜、负极极片依次层叠设置，然后卷绕成电芯并装入包装外壳中，将上述电解液注入到电芯中，之后经过密封、静置、热冷压、化成等工序，得到二次电池。
(2)25℃循环性能测试
25℃下，将实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压V1，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至放电截止电压V2，静置5min，此为一个充放电循环。按照此方法对电池进行循环充放电测试，直至电池容量衰减至80％。此时的循环圈数即为电池的循环寿命。
以上参数测试结果如表1所示。
三、结果与讨论
如表1所示，样品E1-E10的制备过程中，将原料中Mg元素的含量控制在预设范围内(7％-10％)，采用特定的升温速度(8-15℃/min)，加热至特定的第一温度(1100℃-1500℃)，冷却至特定的第二温度(700℃-900℃)，对于获得第一衍射峰半峰宽βA和第二衍射峰的半峰宽βB比值为1.0≤βA/βB≤5的硅基负极活性材料是有利的。相比之下，样品D1的工艺参数不在上述范围，如第一温度为1050℃，仅能获得βA/βB＝0.9的硅基负极活性材料。样品D2的工艺参数不在上述范围，如沉积温度为650℃，仅能获得βA/βB＝5.5的硅基负极活性材料。
如样品E1-E9所示，它们的βA:βB值为1.5-5:1，电池的首次库伦效率为81％以上，25℃循环580周以上电池容量保持率衰减到80％。
如样品E3-E9所示，它们的βA:βB值为2.5-5:1，电池的首次库伦效率为83.9％以上，25℃循环700电池容量保持率衰减到80％。
如样品E3-E7所示，它们的βA:βB值为2.5-4:1，电池的首次库伦效率为82％以上，25℃循环700周以上电池容量保持率衰减到80％。
作为对照，样品D1的βA:βB值为0.9(＜1.5)，它的首次库伦效率为仅为83.4％，25℃循环450周后电池容量保持率衰减到80％。
作为对照，样品D2的βA:βB值为5.5(＞5.0)，它的首次库伦效率为仅为78％，25℃循环680周后电池容量保持率衰减到80％。
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 (14)

  1. 一种硅基负极活性材料，包括Si和MSiO3，其中，M包括一种或多种碱土金属元素；在所述硅基负极活性材料的XRD衍射图谱中，衍射角2θ在26°-26.8°之间具有第一衍射峰，所述第一衍射峰的半峰宽为βA；衍射角2θ在31°-32°之间具有第二衍射峰，所述第二衍射峰的半峰宽为βB；则所述硅基负极活性材料满足：1.5≤βA/βB≤5.0。
  2. 根据权利要求1所述的硅基负极活性材料，其中，βA与βB的比值为2.0≤βA/βB≤5.0，可选为2.5≤βA/βB≤4.0。
  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，1°≤βA≤3°，可选为1°≤βA≤2°。
  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，0.2°≤βB≤1.0°，可选为0.3°≤βB≤0.5°。
  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Si的晶粒尺寸小于所述MSiO3的晶粒尺寸。
  6. 根据权利要求1-5任一项所述的硅基负极活性材料，其中，
    所述Si的晶粒尺寸小于等于12nm，可选为2nm-10nm；和/或，
    所述MSiO3的晶粒尺寸大于等于11nm，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，所述第一衍射峰和第二衍射峰的强度比为1-5:1，可选为2-4:1。
  8. 根据权利要求1-7任一项所述的硅基负极活性材料，所述硅氧基复合物的至少部分表面具有包覆层；可选地，所述包覆层包括碳材料和碱金属离子导体材料中的一种或多种。
  9. 根据权利要求1-8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：
    a)所述硅基负极活性材料的比表面积为4m2/g以下，可选为0.5-1.5m2/g；
    b)所述硅基负极活性材料的体积平均粒径Dv50为4-15μm，可选为5-9μm；
    c)所述硅基负极活性材料的粒度分布(DV90-DV10)/DV50为0.5-3.0，可选为0.8-1.3；
    d)所述硅基负极活性材料中Si元素的含量为20-80wt％，可选为30-60wt％；
    e)所述硅基负极活性材料中碱土金属元素的总含量为2-14wt％，可选为2-10wt％；
    f)所述硅基负极活性材料的Si:O摩尔比1:0.6-1:1.8，可选为1:0.9-1:1.5；
    g)M包括Mg、Ca、Be、Sr、Ba中的至少一种。
  10. 权利要求1-9任一项所述的硅基负极活性材料的制备方法，包括以下步骤：
    提供含有Si元素、O元素和M元素的的原料，M包括一种或多种碱金属元素；
    利用气相沉积技术，将所述原料加热至第一温度形成蒸气，然后将所述蒸气冷却至第二温度形成沉积物；
    将沉积物粉碎，获得粉碎产物；
    其中，所述原料中M元素的含量为7-10％，
    其中，以10℃/min以下的升温速度将所述原料加热至第一温度；
    其中，所述第一温度为1100-1500℃；
    其中，所述第二温度为800-1000℃。
  11. 根据权利要求10所述的方法，其具有以下一项或多项特征：
    (1)所述原料包括硅单质、二氧化硅和碱土金属源；
    (2)执行气相沉积时，第一温度为1200-1400℃；
    (3)执行气相沉积时，第二温度为800-900℃；
    (4)在绝对压力为40Pa以下的环境下执行气相沉积。
  12. 根据权利要求10或11所述的方法，还包括以下步骤：对所述硅基负极活性材料进行包覆处理；可选地，所述包覆处理是碳材料包覆处理；更可选地，所述碳材料包覆处理包括以下操作：将所述硅基负极活性材料置于含有碳源气体的腔室内，加热至700-1000℃，保温1-6h。
  13. 一种二次电池，包括负极，所述负极包括权利要求1-9任一项所述的硅基负极活性材料。
  14. 一种用电装置，包括根据权利要求13所述的二次电池。
PCT/CN2023/079821 2023-03-06 2023-03-06 硅基负极活性材料及其制备方法、二次电池及用电装置 Ceased WO2024182969A1 (zh)

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