WO2024125601A1 - 负极材料及其制备方法、锂离子电池 - Google Patents

负极材料及其制备方法、锂离子电池 Download PDF

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WO2024125601A1
WO2024125601A1 PCT/CN2023/138789 CN2023138789W WO2024125601A1 WO 2024125601 A1 WO2024125601 A1 WO 2024125601A1 CN 2023138789 W CN2023138789 W CN 2023138789W WO 2024125601 A1 WO2024125601 A1 WO 2024125601A1
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negative electrode
electrode material
metal
characteristic peak
silicon oxide
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PCT/CN2023/138789
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English (en)
French (fr)
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梁腾宇
庞春雷
石晓太
汪静伟
任建国
贺雪琴
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贝特瑞新材料集团股份有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • 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
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • 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
    • 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 technical field of negative electrode materials, and in particular, to a negative electrode material and a preparation method thereof, and a lithium ion battery.
  • Electric new energy vehicles are the future development direction of the automobile market, and their core components are lithium-ion batteries. As the market develops, the demand for high-capacity and high-density batteries is increasing. The use of new high-specific-capacity positive and negative electrode materials is one of the important methods to improve the energy density of batteries.
  • silicon-based negative electrode materials as one of the above-mentioned active materials, are generally considered to be the next generation of negative electrode materials. They have ultra-high theoretical specific capacity (4200mAh/g) and low delithiation potential ( ⁇ 0.5V). The voltage platform of silicon is slightly higher than that of graphite. It is difficult to cause surface lithium deposition during charging, and has better safety performance. It is highly praised. However, the silicon negative electrode has a drastic volume expansion effect during the cycle process, which causes the material to pulverize and break, and the battery cycle decays quickly.
  • metal M is used to remove part of the oxygen in the silicon-oxygen material system.
  • the reduction products of the silicon-oxygen material are SiO x , Si, and M silicides in sequence.
  • the formation of local M silicides releases a large amount of heat, which greatly increases the grain size of Si microcrystals, affecting the material's cycle performance and expansion rate.
  • the present application proposes a negative electrode material and a preparation method thereof, and a lithium-ion battery, which can reduce the volume expansion of the negative electrode material and improve the rate performance and cycle stability of the negative electrode material.
  • the present application provides a negative electrode material, the negative electrode material comprising an active substance, the active substance comprising silicon oxide and a compound of metal M, the compound of metal M comprising at least one of an oxide of metal M and a silicate of metal M, the metal M being selected from at least one of metals having an electronegativity ⁇ 1.8;
  • the gas production after 10 g of the negative electrode material is mixed with 10 mL of 1 mol/L hydrochloric acid is ⁇ 1 mL.
  • the silicon oxide includes silicon and oxygen, and an atomic ratio of the silicon to the oxygen is 0 to 2, excluding 0.
  • the general chemical formula of the silicon oxide is SiO x , wherein 0 ⁇ x ⁇ 2.
  • the metal M is selected from at least one of Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.
  • the metal M is Mg.
  • the silicon oxide contains Si crystallites, and the size of the Si crystallites is ⁇ 20 nm.
  • the pH of the negative electrode material is 8-14.
  • the specific surface area of the negative electrode material is ⁇ 30 m 2 /g.
  • the median particle size of the negative electrode material is 1 ⁇ m to 20 ⁇ m.
  • the Wadell sphericity ⁇ of the negative electrode material is 0.3 ⁇ 1.
  • the negative electrode material has a characteristic peak A, a characteristic peak B and/or a characteristic peak C, wherein characteristic peak A represents the characteristic peak of Si or SiO, characteristic peak B represents the characteristic peak of the oxide of metal M, and characteristic peak C represents the characteristic peak of the silicate of metal M; the characteristic peak of the silicide of metal M is recorded as characteristic peak D, and the peak height ratio of the strongest peak of characteristic peak D to the strongest peak of characteristic peak A is I, 0 ⁇ I ⁇ 0.05.
  • the present application provides a negative electrode material, the negative electrode material comprising an active substance, the active substance comprising silicon oxide and a compound of metal M, the compound of metal M comprising at least one of an oxide of metal M and a silicate of metal M, the metal M being selected from at least one of metals having an electronegativity ⁇ 1.8;
  • the negative electrode material has a characteristic peak A, a characteristic peak B and/or a characteristic peak C, wherein the characteristic peak A represents the characteristic peak of Si or the characteristic peak of SiO, the characteristic peak B represents the characteristic peak of the oxide of metal M, and the characteristic peak C represents the characteristic peak of the silicate of metal M; the characteristic peak of the silicide of metal M is recorded as characteristic peak D, and the peak height ratio of the strongest peak of characteristic peak D to the strongest peak of characteristic peak A is I, 0 ⁇ I ⁇ 0.05.
  • the silicon oxide includes silicon and oxygen, and an atomic ratio of the silicon to the oxygen is 0 to 2, excluding 0.
  • the general chemical formula of the silicon oxide is SiO x , wherein 0 ⁇ x ⁇ 2.
  • the metal M is selected from at least one of Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.
  • the metal M is Mg.
  • the silicon oxide contains Si crystallites, and the size of the Si crystallites is ⁇ 20 nm.
  • the pH of the negative electrode material is 8-14.
  • the specific surface area of the negative electrode material is ⁇ 30 m 2 /g.
  • the median particle size of the negative electrode material is 1 ⁇ m to 20 ⁇ m.
  • the Wadell sphericity ⁇ of the negative electrode material is 0.3 ⁇ 1.
  • the negative electrode material further includes a carbon material located on at least a portion of the surface of the active material.
  • the negative electrode material further includes a carbon material layer located on at least a portion of the surface of the active material, and the thickness of the carbon material layer is 10 nm to 500 nm.
  • the mass content of carbon in the negative electrode material is 1% to 40%.
  • the porosity of the negative electrode material is less than 20%.
  • the specific heat capacity of the negative electrode material is 0.2 J/(g.K) to 2.0 J/(g.K).
  • the negative electrode material has pores, wherein the volume proportion of micropores with a pore diameter of less than 2 nm in the total pore volume of all pores is 1% to 5%.
  • an embodiment of the present application further provides a method for preparing a negative electrode material, the method comprising the following steps:
  • the mixture containing the metal M raw material and the silicon oxygen raw material is subjected to a reduced pressure heating treatment to form M vapor and silicon oxygen raw material vapor, and the vapors are fully mixed for 1 min to 600 min, wherein the metal M is selected from at least one metal with an electronegativity of less than 1.8;
  • the mixed steam gas is cooled to obtain an active material;
  • the active material includes silicon oxide and a compound of metal M, and the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M.
  • the metal M raw material is selected from at least one of a metal M element and a metal M oxide.
  • the metal M is selected from at least one of Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.
  • the silicon oxygen raw material includes at least one of Si, a mixture of SiO y and SiO 2 , a mixture of SiO y and Si, and a mixture of Si and SiO 2 , wherein 0 ⁇ y ⁇ 2.
  • the molar amount of the metal M in the metal M raw material is n M
  • the molar amount of Si in the silicon oxide raw material is n Si
  • n M :n Si (0.2-1):1.
  • the silicon oxide includes silicon and oxygen, and the atomic ratio of the silicon and oxygen is 0 to 2, excluding zero.
  • the silicon oxide has a general chemical formula of SiO x , wherein 0 ⁇ x ⁇ 2.
  • the temperature of the reduced pressure heating treatment is 900°C to 2000°C.
  • the pressure of the reduced pressure heating treatment is 0.1Pa to 1000Pa.
  • the cooling process is performed at a temperature of 500°C to 900°C.
  • the pressure of the reduced pressure heating treatment is 0.1Pa to 1000Pa.
  • the method further comprises repeating step (1) to step (2), and controlling the total insulation time to be 1 h to 120 h.
  • the active material obtained by the cooling treatment is subjected to a carbon coating treatment to obtain a negative electrode material;
  • the carbon coating treatment includes at least one of solid phase carbon coating, liquid phase carbon coating and gas phase carbon coating.
  • the carbon coating treatment step specifically includes: heating the active material obtained by cooling treatment, introducing a protective gas and a carbon source gas, and thermally cracking the carbon source gas to obtain a negative electrode material.
  • the carbon source gas is a hydrocarbon
  • the carbon source gas includes at least one of methane, ethylene, acetylene, propyne, propylene, propane, toluene, benzene, styrene, and phenol.
  • the temperature of the thermal cracking is 600°C to 1000°C, and the time of the thermal cracking is 30 min to 24 h.
  • the carbon coating step specifically includes: carbonizing a mixture obtained by mixing the active material obtained by cooling with a solid carbon source to obtain a negative electrode material.
  • the carbonization treatment temperature is 500° C.-1000° C.
  • the carbonization treatment time is 30 min-24 h.
  • the solid carbon source includes at least one of sugars, esters, hydrocarbons, organic acids and high molecular polymers.
  • the solid carbon source includes polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, At least one of polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, asphalt, furfural resin, epoxy resin and phenolic resin.
  • the mass ratio of the solid carbon source to the active material is 5:(5-95).
  • the present application provides a battery, comprising the negative electrode material described in the first aspect and/or the second aspect or the negative electrode material prepared according to the third aspect.
  • the negative electrode material provided by the present application includes silicon oxide and a compound of metal M, the compound of metal M is dispersed in the silicon oxide, and the gas production after the negative electrode material is mixed with hydrochloric acid is ⁇ 1mL, that is, the compound of metal M includes oxide of metal M and/or silicate of metal M, and almost no silicide of M exists, which can effectively control the size of Si crystallites in silicon oxide, and the compound of metal M is dispersed in silicon oxide, that is, the compound of metal M can be embedded on silicon oxide particles, or embedded between silicon oxide particles, which can improve the rate performance and cycle stability of the negative electrode material.
  • the present application provides a method for preparing a negative electrode material, wherein a mixture of a silicon oxide raw material and a metal M raw material is subjected to a reduced pressure heating treatment at a high temperature to form M vapor and silicon oxide raw material vapor, and by allowing the vapors to be fully mixed, the local M vapor excess can be reduced, and the local silicon oxide raw material vapor can be reduced from being reduced to silicon element and metal M silicide, and then cooled to obtain a mixture of silicon oxide and metal M compounds, wherein the metal M compounds are dispersed in the silicon oxide, the metal M compounds can be embedded on the silicon oxide particles, or embedded between the silicon oxide particles, and the metal M compounds hardly exist in the form of silicide, which is beneficial to effectively control the size of Si microcrystals in the silicon oxide, so that the expansion rate of the negative electrode material is controlled, and it is beneficial to prepare a negative electrode material with a lower expansion rate and excellent cycle performance.
  • FIG1 is a schematic diagram of a process for preparing a negative electrode material according to an embodiment of the present application
  • FIG2 is a schematic diagram of a test state of gas production of a negative electrode material provided in an embodiment of the present application
  • FIG3 is an XRD diagram of silicon in the negative electrode material prepared in Example 1 of the present application.
  • FIG4 is an XRD diagram of MgSiO 3 in the negative electrode material prepared in Example 1 of the present application.
  • FIG5 is an XRD diagram of Mg 2 SiO 4 in the negative electrode material prepared in Example 1 of the present application.
  • FIG6 is a graph showing the specific heat capacity of the negative electrode material prepared in Example 1 of the present application.
  • metal M can be used to remove part of the oxygen in the silicon-oxygen material system.
  • the reduction products of the silicon-oxygen material are SiO x , Si, and M silicides in sequence.
  • the formation of local M silicides will release a lot of heat, causing the grain size of Si microcrystals to increase significantly.
  • due to the presence of a large amount of M silicides in the negative electrode material it means that there is a lot of free elemental silicon in the negative electrode material. After the electrolyte contacts the negative electrode material, a large amount of gas will be generated.
  • the grain size of Si microcrystals is large, which will cause excessive local expansion stress of the negative electrode material, which is easy to cause particle rupture or crushing.
  • the present application provides a negative electrode material, the negative electrode material includes an active substance, the active substance includes silicon oxide and a compound of metal M, the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M, and the metal M is selected from at least one of metals with an electronegativity of ⁇ 1.8;
  • the gas production after 10g of negative electrode material is mixed with 10mL of 1mol/L hydrochloric acid is ⁇ 1mL.
  • the active material of the negative electrode material includes silicon oxide and a compound of metal M
  • the compound of metal M is dispersed in the silicon oxide
  • the gas production after the negative electrode material is mixed with hydrochloric acid is ⁇ 1mL
  • the compound of metal M includes oxide of metal M and/or silicate of metal M, and almost no M silicide exists, which can effectively control the size of Si crystallites in silicon oxide
  • the compound of metal M is dispersed in silicon oxide, that is, the compound of metal M can be embedded on silicon oxide particles, or embedded between silicon oxide particles, which can improve the rate performance and cycle stability of the negative electrode material.
  • silicon oxide includes silicon and oxygen
  • the atomic ratio of silicon to oxygen is 0 to 2, excluding 0.
  • the atomic ratio of silicon to oxygen can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 2, etc., which are not limited here.
  • the atomic ratio of silicon to oxygen is 0 to 1, excluding 0.
  • the chemical formula of silicon oxide is SiO x , wherein 0 ⁇ x ⁇ 2, and x can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 2, etc., which are not limited here.
  • the metal M is selected from at least one of Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.
  • the distribution surface of Si, O and metal M is in a uniform dispersion state.
  • Si, O and metal M are evenly distributed in the negative electrode material particles, which can effectively reduce the infiltration of air and other components into the primary particles and cause the active components to fail.
  • the structure and properties will not deteriorate during long-term storage, which is very suitable for lithium-ion batteries.
  • the main advantage of uniform dispersion is to ensure that the physicochemical state of the material is similar (i.e., silicate concentration, silicon grain size, etc.), so that the expansion and contraction of each part during the lithium insertion and extraction process are at the same level, and there will be no stress weak points caused by excessive local expansion, so that the material performance is better.
  • the metal M is magnesium
  • compounds of the metal M include MgO, MgSiO 3 and Mg 2 SiO 4.
  • the metal M is magnesium, the size of Si crystallites can be further reduced, thereby reducing the expansion of the negative electrode material.
  • the silicate of the metal M is uniformly distributed within the primary particles of the active material.
  • the silicate of metal M is lithium silicate
  • the lithium silicate includes at least one of Li 2 SiO 3 , Li 4 SiO 4 , Li 2 Si 2 O 5 , and Li 2 Si 3 O 7.
  • the lithium silicate is Li 2 Si 2 O 5 .
  • the negative electrode material has a characteristic peak A, a characteristic peak B and/or a characteristic peak C by X-ray diffraction analysis, wherein the characteristic peak A represents a Si characteristic peak (based on PDF card number 27-1402) or a SiO characteristic peak.
  • Characteristic peaks (based on PDF card number 30-1127), characteristic peak B represents the characteristic peak of the oxide of metal M, and characteristic peak C represents the characteristic peak of the silicate of metal M; the characteristic peak of the silicide of metal M is recorded as characteristic peak D, and the peak height ratio of the strongest peak of characteristic peak D to the strongest peak of characteristic peak A is I, 0 ⁇ I ⁇ 0.05.
  • the peak height ratio I may be 0.04, 0.03, 0.02, 0.01, 0.005, 0, etc.
  • the compound of metal M includes an oxide of metal M, and the oxide of metal M is uniformly distributed in the negative electrode material particles.
  • the silicon oxide contains Si crystallites, and the size of the Si crystallites is ⁇ 20 nm; specifically, the size of the Si crystallites in the silicon oxide can be 20 nm, 18 nm, 15 nm, 12 nm, 10 nm, 9.2 nm, 8 nm, 6.7 nm, 6 nm, 5 nm or 3 nm, etc., but is not limited to the listed values, and other values not listed in the numerical range are also applicable.
  • the size of the Si crystallites reflects the degree of disproportionation of the silicon oxide. The larger the size of the Si crystallites, the higher the degree of disproportionation.
  • silicon oxide contains Si crystallites, and the size of Si crystallites is ⁇ 10 nm, indicating that the volume of negative electrode Si grains is small, and the Si crystallites in silicon oxide are dispersedly distributed.
  • the compound with metal M will not release a large amount of heat to affect the size of Si crystallites, which can effectively reduce the expansion of negative electrode materials and improve cycle performance.
  • the pH value of the negative electrode material is 8-14, specifically 8, 9, 10, 10.5, 11, 11.5, 12, 13 or 14, etc., which are not limited here.
  • the pH value of the negative electrode material is 9-11.
  • the specific surface area of the negative electrode material is less than 30 m 2 /g, specifically 1.0 m 2 /g, 1.5 m 2 /g, 1.8 m 2 /g, 2.0 m 2 /g, 2.5 m 2 /g, 3.0 m 2 /g, 3.6 m 2 /g, 4.0 m 2 /g, 5 m 2 /g, 5.5 m 2 /g, 6.0 m 2 /g, 7.0 m 2 /g, 8.0 m 2 /g, 8.5 m 2 /g, 10.0 m 2 /g, 12.0 m 2 /g, 15.0 m 2 /g, 18.0 m 2 /g or 30.0 m 2 /g, but is not limited to the listed values, and other values not listed in the numerical range are also applicable.
  • the specific surface area of the negative electrode material is less than 10 m 2 /g.
  • the median particle size of the negative electrode material is 1 ⁇ m to 20 ⁇ m, specifically 1 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 6 ⁇ m, 8 ⁇ m, 9.5 ⁇ m, 10 ⁇ m, 12.5 ⁇ m, 15 ⁇ m or 20 ⁇ m, etc., which is not limited here.
  • the Wadell sphericity ⁇ of the negative electrode material 0.3 ⁇ 1; the Wadell sphericity may be 0.325, 0.43, 0.54, 0.65, 0.76, 0.87, 0.98, 0.99, etc. It is understandable that the Wadell sphericity of the negative electrode material particles is not limited to the listed values, and other values not listed in the numerical range are also applicable.
  • the negative electrode material further includes a carbon material located on at least a portion of the surface of the active material.
  • the negative electrode material further includes a carbon material layer located on at least a portion of the surface of the active material. It is understandable that the carbon material layer on the surface of the active material can reduce the breakage of material particles caused by repeated formation of the SEI film, which is beneficial to improving the cycle performance of the negative electrode material and reducing the volume expansion caused by the formation of the SEI film.
  • the thickness of the carbon material layer is 10 nm to 500 nm, more preferably 50 nm to 200 nm.
  • the thickness of the carbon material layer can be 10 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 200 nm, 300 nm, 400 nm or 500 nm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
  • the active material is dispersed in the carbon material, and the carbon material forms a conductive network for the active material.
  • the complex overcomes the disadvantage of poor conductivity of active materials (such as silicon oxide SiO x ) and is beneficial to the capacity development and cycle stability of silicon oxide.
  • the mass content of carbon element in the negative electrode material is 1% to 40%; specifically, it can be 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 28%, 35% or 40%, etc., and of course, it can also be other values within the above range, which is not limited here.
  • the negative electrode material may further include a coating layer located on the surface of the active material, wherein the coating layer contains a high molecular weight flexible polymer.
  • the negative electrode material has pores, wherein the volume of micropores with a pore size of ⁇ 2 nm accounts for 1% to 5% of the total pore volume of all pores, and specifically may be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., which are not limited here.
  • the presence of an appropriate amount of micropores can provide a buffer space for the volume expansion of the active material and reduce the particle breakage caused by excessive local stress.
  • the porosity of the negative electrode material is less than 20%.
  • the porosity of the negative electrode material can be 19.2%, 18%, 15%, 13%, 10%, 8%, 5%, 3% or 2%, etc. It is understood that the porosity of the negative electrode material is not limited to the listed values, and other values not listed within the numerical range are also applicable.
  • the specific heat capacity of the negative electrode material is 0.2 to 2.0 J/(g.K). If the specific heat capacity of the negative electrode material is too high or too low, it means that there are obvious impurities. By controlling the distribution uniformity of the metal M compound in the negative electrode material, the specific heat capacity of the material can be adjusted. When the negative electrode material contains a certain content of metal silicide, the specific heat capacity of the negative electrode material will increase, and the specific heat capacity will exceed 2.0 J/(g.K); or if the metal element content in the negative electrode material is high, the specific heat capacity will decrease.
  • the present application also provides a method for preparing a negative electrode material, as shown in FIG1 , the method comprises the following steps S100 to S200:
  • the mixed steam gas is cooled to obtain an active substance;
  • the active substance includes silicon oxide and a compound of metal M, and the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M.
  • a mixture of silicon oxide raw material and metal M raw material is subjected to reduced pressure heating treatment at high temperature to form M vapor and silicon oxide raw material vapor, and by allowing the vapor to be fully mixed, the local excess of M vapor can be reduced, and the local silicon oxide raw material vapor can be reduced from being reduced to silicon element and metal M silicide.
  • the mixture is cooled to obtain a mixture of silicon oxide and metal M compounds, wherein the metal M compounds are dispersed in the silicon oxide, the metal M compounds can be embedded on the silicon oxide particles, or embedded between the silicon oxide particles, and the metal M compounds hardly exist in the form of silicide, which is beneficial to effectively control the size of Si microcrystals in the silicon oxide, so that the expansion rate of the negative electrode material is controlled, and it is beneficial to prepare a negative electrode material with a lower expansion rate and excellent cycle performance.
  • a mixture containing a metal M raw material and a silicon oxygen raw material is subjected to a reduced pressure heating process to form M vapor and silicon oxygen raw material vapor, and the vapor is fully mixed for 1 min to 600 min, wherein the metal M is selected from at least one metal with an electronegativity less than 1.8.
  • the silicon oxygen raw material includes at least one of Si, a mixture of SiOy and SiO2 , a mixture of SiOy and Si, and a mixture of Si and SiO2 , wherein 0 ⁇ y ⁇ 2.
  • the metal M raw material is selected from at least one of a single metal and a metal oxide.
  • the metal M is selected from at least one of Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.
  • the molar amount of metal M in the metal M raw material is n M
  • the molar amount of Si in the silicon oxide raw material is n Si
  • n M :n Si (0.2-1):1, specifically 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, etc., and of course other values within the above range may also be used.
  • the silicate of metal M can be uniformly distributed in the primary particles of the active material.
  • the temperature of the heat treatment is 900° C. to 2000° C.
  • the temperature of the heat treatment may be 900° C., 1000° C., 1100° C., 1200° C., 1400° C., 1500° C., 1550° C., 1575° C., 1600° C., 1650° C., 1700° C., 1800° C., 1900° C., or 2000° C. It is understood that the above temperature is not limited to the listed values, and other values not listed within the numerical range are also applicable.
  • the reduced pressure heating treatment is performed in a vacuum furnace, and the vacuum furnace is preheated to 900° C. to 2000° C. before the mixture is added.
  • the gas pressure in the vacuum furnace is 0.1Pa to 1000Pa, and specifically may be 0.1Pa, 50Pa, 100Pa, 200Pa, 500Pa, 600Pa, 700Pa, 800Pa, 900Pa or 1000Pa, etc., which is not limited here.
  • the mixture is co-evaporated under reduced pressure and heating to form M vapor and silicon oxygen raw material vapor.
  • the vacuum furnace pipe port valve is closed to allow the steam gas to continue to stay in the vacuum furnace for 1min to 600min, which can be 1min, 5min, 10min, 30min, 60min, 90min, 120min, 150min, 300min, 360min, 420min or 600min, etc., which are not limited here.
  • the vacuum furnace is generally divided into a furnace tube and a cooling zone. In the prior art, it is commonly used that after the material is heated in the furnace tube, the steam formed immediately enters the cooling zone for cooling, while in the present application, the furnace tube port valve connects and closes the furnace tube and the cooling zone.
  • the raw materials of the reaction can be kept in a vapor state, and are always in a high-pressure environment. After sufficient mixing, the uniformity of the steam can be greatly improved, and the steam gas can be mixed more evenly.
  • the preferred residence time is 30min to 600min.
  • the mixed steam gas is cooled to obtain an active substance;
  • the active substance includes silicon oxide and a compound of metal M, and the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M.
  • the temperature of the cooling treatment is 500° C. to 900° C., specifically 500° C., 550° C., 600° C., 650° C., 700° C., 750° C., 800° C., 850° C. or 900° C. It is understood that the above temperature is not limited to the listed values, and other values not listed within the numerical range are also applicable.
  • the appearance of local metal elements is suppressed, that is, the formation of elemental Si and metal silicides is suppressed.
  • the active material obtained after cooling does not require traditional acid washing or water washing, and can directly proceed to subsequent carbon coating or secondary granulation processes.
  • the cooling process is performed in a cooling zone of a vacuum furnace, and the pressure in the cooling zone is 0.1 Pa to 1000Pa, specifically it can be 0.1Pa, 50Pa, 100Pa, 200Pa, 500Pa, 600Pa, 700Pa, 800Pa, 900Pa or 1000Pa, etc., which is not limited here.
  • steps S100 to S200 are repeated so that the silicon oxide raw material and the metal M raw material can be fully evaporated to form a mixed vapor gas, and then the metal M compound formed by cooling is dispersed in the silicon oxide.
  • steps (1) to (2) are repeated, and the total insulation time is controlled to be 1 h to 120 h; specifically, it can be 1 h, 5 h, 10 h, 15 h, 20 h, 30 h, 40 h, 50 h, 60 h, 120 h, etc., and of course, it can also be other values within the above range.
  • Repeating steps S100 to S200 is conducive to forming a more uniformly dispersed negative electrode material, and can also inhibit the formation of elemental Si and metal silicide.
  • silicon oxide includes silicon and oxygen
  • the atomic ratio of silicon to oxygen is 0 to 2, excluding 0.
  • the atomic ratio of silicon to oxygen can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 2, etc., which are not limited here.
  • the atomic ratio of silicon to oxygen is 0 to 1, excluding 0.
  • the chemical formula of silicon oxide is SiO x , wherein 0 ⁇ x ⁇ 2, and x can be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 2, etc., which are not limited here.
  • Another method for preparing a negative electrode material includes the following steps:
  • Step S300 carbon coating the active material obtained by cooling to obtain a negative electrode material.
  • the active material obtained by cooling treatment can be prepared by using steps S100 to S200.
  • the negative electrode material obtained by the preparation method comprises an active substance and a carbon material located on at least a part of the surface of the active substance, wherein the active substance comprises a compound of silicon oxide and metal M, wherein the chemical formula of the silicon oxide is SiO x , 0 ⁇ x ⁇ 2.
  • the carbon coating treatment is at least one of solid phase carbon coating, liquid phase carbon coating and gas phase carbon coating.
  • the step of carbon coating treatment specifically includes: heating the active material obtained by cooling treatment, introducing protective gas and carbon source gas, and thermally cracking the carbon source gas to obtain the negative electrode material.
  • the carbon source gas used for gas-phase carbon coating includes hydrocarbons.
  • the carbon source gas includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone, and benzene.
  • the chemical vapor deposition device includes at least one of a rotary chemical vapor deposition reactor, a plasma enhanced chemical vapor deposition reactor, a chemical vapor deposition tube furnace, and a fluidized bed.
  • the chemical vapor deposition device is at least one of a rotary furnace and a box furnace.
  • the temperature of thermal cracking is 600° C. to 1000° C.
  • the time of thermal cracking is 2 h to 20 h.
  • the carbon source gas is introduced under a protective gas.
  • the protective gas includes at least one of nitrogen, helium, neon, argon, krypton, and xenon.
  • the step of carbon coating treatment specifically includes: cooling the active material obtained by the cooling treatment and The mixture obtained by mixing the solid carbon source is carbonized to obtain the negative electrode material.
  • the solid carbon source includes at least one of sugars, esters, hydrocarbons, organic acids and high molecular polymers, and can be specifically at least one of polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, asphalt, furfural resin, epoxy resin and phenolic resin.
  • the cooling product and the carbon source can be mixed by VC mixing, fusion, ball milling, three-dimensional mixing, fluidized bed mixing, etc.
  • the mixing is performed in a fusion machine
  • the fusion time is 0.5h-2h
  • the rotation speed of the fusion machine is 500r/min-5000r/min.
  • the mass ratio of the solid carbon source to the active material is 5:(5-95).
  • the temperature of the carbonization treatment is 500° C.-1000° C.
  • the time of the carbonization treatment is 2 h-20 h.
  • the equipment used for solid phase carbon coating is at least one of a rotary kiln, a box furnace, a roller kiln, a tunnel kiln, and a push plate kiln.
  • the protective gas may be at least one of nitrogen, argon, helium, neon, krypton, and xenon.
  • the liquid phase carbon coating process specifically comprises mixing the cooled product with the carbon source uniformly, then placing it in a furnace, introducing a protective gas, and heat treating the mixture so that the carbon source is cracked and coated on the surface of the cooled product.
  • the carbon source used for liquid carbon coating is an organic carbon source, specifically low-temperature liquid asphalt, furfuryl alcohol, glycidyl methacrylate, triethylene glycol dimethacrylate, etc.
  • the protective gas may be at least one of nitrogen, argon, helium, neon, krypton, and xenon.
  • the heat treatment temperature is 600°C to 1000°C.
  • the method also includes: screening and demagnetizing the carbonized material to obtain a negative electrode material.
  • the screening method is any one of a fixed screen, a drum screen, a resonance screen, a roller screen, a vibrating screen and a chain screen, and the screening mesh number is 100 to 500 meshes.
  • the screening mesh number can be 100 mesh, 200 mesh, 250 mesh, 325 mesh, 400 mesh, 500 mesh, etc.
  • the screening mesh number is 250 mesh, and the particle size of the negative electrode material is controlled within the above range, which is beneficial to the improvement of the processing performance of the negative electrode material.
  • the demagnetization equipment is any one of a permanent magnetic drum magnetic separator, an electromagnetic iron remover and a pulsating high gradient magnetic separator.
  • the demagnetization is to ultimately control the magnetic substance content of the negative electrode material, reduce the discharge effect of the magnetic substance on the lithium-ion battery and the safety of the battery during use.
  • the present application also provides a battery using the negative electrode material provided in the above embodiment of the present application or the negative electrode material prepared by the method for preparing the negative electrode material provided in the above embodiment of the present application.
  • the battery may be a lithium ion battery or a sodium ion battery, etc., which is not limited here.
  • the battery provided in the embodiment of the present application has the advantages of excellent rate performance and low expansion.
  • the particle size test method refers to GB/T 19077-2016. It can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.
  • the monolayer adsorption amount of the sample is obtained based on the Brownauer-Etter-Taylor adsorption theory and its formula (BET formula), thereby calculating the specific surface area of the negative electrode material.
  • the negative electrode material particles were sectioned using a FIB-SEM device, and the average thickness of the carbon material layer was measured in the SEM.
  • the porosity of the negative electrode material particles was tested using the mercury injection method.
  • Thermogravimetric analysis was used to test the carbon content in the negative electrode material.
  • the specific heat capacity of the sample was tested using a NETZSCH DSC instrument at a test temperature of 0 to 130°C, a heating rate of 10°C/min, an N 2 atmosphere, and a sample amount of 13 mg.
  • the specific heat capacity value of the negative electrode material was obtained by testing.
  • the negative electrode material was made into sheets and tested using an X-ray diffraction analyzer. Angle range: 10-90°, scanning mode: step scan, select slit width 1.0, and set voltage 40kW and current 40mA. The measured data was analyzed using Jade 6.5 software, and the negative electrode material composition was confirmed by comparing the PDF card.
  • characteristic peaks can be observed in the ranges of 27.5° to 29.5°, 46.3° to 48.3°, and 55.0° to 57.0°; the Si (111) peak at 28.6° was fitted, and the half-peak width FWHM was obtained, and then the Scherrer formula was used to calculate the size of the Si crystallite.
  • the prepared negative electrode material, conductive carbon black and polyacrylic acid binder were dissolved in N-methylpyrrolidone at a mass percentage of 75:15:10, mixed, coated on a copper foil current collector, and vacuum dried to obtain a negative electrode sheet; a metal lithium sheet was used as a counter electrode and assembled into a button cell in an argon-filled glove box.
  • the charge and discharge test was carried out at a current density of 0.1C and a charge and discharge interval of 0.01-1.5V.
  • ternary positive electrode plate nickel cobalt manganese oxide NCM523
  • the cycle performance test uses a current of 30mA for constant current charge and discharge experiments, and the charge and discharge voltage is limited to 0 ⁇ 1.5V.
  • the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd. is used for testing.
  • the charge and discharge test was carried out in the charge and discharge range of 0.005V-1.5V.
  • First coulombic efficiency first cycle discharge capacity/first cycle charge capacity.
  • the cycle was repeated for 50 times.
  • the thickness of the electrode of the lithium-ion battery was measured with a micrometer and found to be H1.
  • the expansion rate after 50 cycles (H1-H0)/H0 ⁇ 100%.
  • capacity retention rate remaining capacity/initial capacity*100%.
  • a method for preparing a negative electrode material comprises the following steps:
  • the active material is placed in a high-temperature box furnace, methane gas is introduced under nitrogen protection, and carbon coating treatment is performed at 820° C. for 4 h.
  • the product is crushed and sieved to obtain the negative electrode material.
  • the negative electrode material prepared in this embodiment includes an active substance, which includes silicon oxide and a metal Li compound.
  • the metal Li compound includes Li 2 O, Li 2 SiO 3 and Li 4 SiO 4.
  • the specific surface area of the negative electrode material is 7.3 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, Li 2 O peak, Li 2 SiO 3 peak, and Li 4 SiO 4 peak.
  • the size of the Si microcrystal is 19.9 nm, and the pH value is 11.9.
  • the mass proportion of carbon element in the negative electrode material is 10%, as shown in Figure 6, the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 1.6%.
  • the negative electrode material has pores, among which the volume proportion of micropores with a pore diameter of ⁇ 2 nm in the total pore volume of all pores is 2.56%.
  • a method for preparing a negative electrode material comprises the following steps:
  • the negative electrode material prepared in this embodiment includes an active substance, which includes silicon oxide and a metal Al compound.
  • the metal Al compound includes Al 2 O 3 , Al 2 (SiO 3 ) 3 and Al 4 (SiO 4 ) 3 .
  • the specific surface area of the negative electrode material is 18.3 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO 3 peak, and Mg 2 SiO 4 peak.
  • the size of the Si microcrystal is 19.3 nm, and the pH value is 8.4.
  • the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 2.3%.
  • the negative electrode material has pores, wherein the volume of micropores with a pore diameter of less than 2 nm accounts for 4.11% of the total pore volume of all pores.
  • a method for preparing a negative electrode material comprises the following steps:
  • the active material is placed in a high-temperature box furnace, methane gas is introduced under nitrogen protection, and carbon coating treatment is performed at 950° C. for 4 h.
  • the product is crushed and sieved to obtain the negative electrode material.
  • the negative electrode material prepared in this embodiment includes active substances, and the active substances include silicon oxide and metal Mg compounds.
  • the metal Mg compounds include MgO, MgSiO 3 and Mg 2 SiO 4.
  • the specific surface area of the negative electrode material is 12.6 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO 3 peak, and Mg 2 SiO 4 peak.
  • the size of Si microcrystals is 15.1 nm, and the pH value is 11.2.
  • the mass proportion of carbon element in the negative electrode material is 10%, and the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 2.0%.
  • the negative electrode material has pores, wherein the volume proportion of micropores with a pore diameter of ⁇ 2 nm in the total pore volume of all pores is 3.23%.
  • Example 3 The difference from Example 3 is that the temperature of the vacuum furnace is 2000° C. and the pressure is 100 Pa.
  • the negative electrode material prepared in this embodiment includes active substances, and the active substances include silicon oxide and metal Mg compounds.
  • the metal Mg compounds include MgO, MgSiO 3 and Mg 2 SiO 4.
  • the specific surface area of the negative electrode material is 15.5 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO 3 peak, and Mg 2 SiO 4 peak.
  • the size of Si microcrystals is 9.9 nm, and the pH value is 10.8.
  • the mass proportion of carbon in the negative electrode material is 10%, and the specific heat capacity of the negative electrode material is 0.2-2.0 J/(gK); the porosity of the negative electrode material is 3.5%.
  • the negative electrode material has pores, among which the micropores with a pore size of ⁇ 2 nm account for the total of all pores. The volume share of the pore volume is 1.34%.
  • Example 3 The difference from Example 3 is that the temperature of the vacuum furnace is 900° C. and the pressure is 10 Pa.
  • the negative electrode material prepared in this embodiment includes active substances, and the active substances include silicon oxide and metal Mg compounds.
  • the metal Mg compounds include MgO, MgSiO 3 and Mg 2 SiO 4.
  • the specific surface area of the negative electrode material is 4.3 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO 3 peak, and Mg 2 SiO 4 peak.
  • the size of Si microcrystals is 6.5 nm, and the pH value is 13.1.
  • the mass proportion of carbon element in the negative electrode material is 10%, and the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 1.3%.
  • the negative electrode material has pores, wherein the volume proportion of micropores with a pore diameter of ⁇ 2 nm in the total pore volume of all pores is 1.40%.
  • Example 3 The difference from Example 3 is that the silicon oxygen raw materials input are SiO 2 and Si;
  • the negative electrode material prepared in this embodiment includes active substances, and the active substances include silicon oxide and metal Mg compounds.
  • the metal Mg compounds include MgO, MgSiO 3 and Mg 2 SiO 4.
  • the specific surface area of the negative electrode material is 7.6 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO 3 peak, and Mg 2 SiO 4 peak.
  • the size of Si microcrystals is 19.1 nm, and the pH value is 11.5.
  • the mass proportion of carbon element in the negative electrode material is 10%, and the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 2.4%.
  • the negative electrode material has pores, wherein the volume proportion of micropores with a pore diameter of ⁇ 2 nm in the total pore volume of all pores is 2.95%.
  • the negative electrode material prepared in this embodiment includes active substances, and the active substances include silicon oxide and metal Ca compounds.
  • the metal Ca compounds include CaO, CaSiO 3 and Ca 2 SiO 4.
  • the specific surface area of the negative electrode material is 9.0 m 2 /g. X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, CaO peak, CaSiO 3 peak, Ca 2 SiO 4 peak, the size of Si microcrystals is 15.5 nm, and the pH value is 13.0.
  • the mass proportion of carbon element in the negative electrode material is 10%, and the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 2.2%.
  • the negative electrode material has pores, wherein the volume proportion of micropores with a pore diameter of ⁇ 2 nm in the total pore volume of all pores is 4.01%.
  • the negative electrode material prepared in this embodiment includes active substances, and the active substances include silicon oxide, CaO, CaSiO 3 , Ca 2 SiO 4 , MgO, MgSiO 3 and Mg 2 SiO 4.
  • the specific surface area of the negative electrode material is 9.8 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, CaO peak, CaSiO 3 peak, Ca 2 SiO 4 peak, MgO peak, MgSiO 3 peak and Mg 2 SiO 4 peak.
  • the size of Si microcrystals is 15.0 nm, and the pH value is 12.7.
  • the mass proportion of carbon element in the negative electrode material is 10%, and the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 2.7%.
  • the negative electrode material has pores, wherein the volume proportion of micropores with a pore diameter of ⁇ 2 nm in the total pore volume of all pores is 4.89%.
  • Example 3 The difference from Example 3 is that (2) the valve at the furnace tube port is closed, and the gas pressure in the furnace tube and the cooling zone is pumped down to 1000 Pa, so that the evaporated gas stays in the furnace for 600 min.
  • the negative electrode material prepared in this embodiment includes active substances, and the active substances include silicon oxide and metal Mg compounds.
  • the metal Mg compounds include MgO, MgSiO 3 and Mg 2 SiO 4.
  • the specific surface area of the negative electrode material is 15.6 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO 3 peak, and Mg 2 SiO 4 peak.
  • the size of Si microcrystals is 17.0 nm, and the pH value is 11.7.
  • the mass proportion of carbon element in the negative electrode material is 10%, and the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 2.3%.
  • the negative electrode material has pores, wherein the volume proportion of micropores with a pore diameter of ⁇ 2 nm in the total pore volume of all pores is 2.49%.
  • Example 3 The difference from Example 3 is that (2) the valve at the furnace tube port is closed, and the gas pressure in the furnace tube and the cooling zone is pumped down to 1000 Pa, so that the evaporated gas stays in the furnace for 1 minute.
  • the negative electrode material prepared in this embodiment includes active substances, and the active substances include silicon oxide and metal Mg compounds.
  • the metal Mg compounds include MgO, MgSiO 3 and Mg 2 SiO 4.
  • the specific surface area of the negative electrode material is 11.3 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO 3 peak, and Mg 2 SiO 4 peak.
  • the size of Si microcrystals is 13.5 nm, and the pH value is 10.9.
  • the mass proportion of carbon element in the negative electrode material is 10%, and the specific heat capacity of the negative electrode material is 0.2-2.0 J/(g.K); the porosity of the negative electrode material is 1.8%.
  • the negative electrode material has pores, wherein the volume proportion of micropores with a pore diameter of ⁇ 2 nm in the total pore volume of all pores is 4.93%.
  • a method for preparing a negative electrode material comprises the following steps:
  • the acid-washed active material is placed in a high-temperature box furnace, methane gas is introduced under nitrogen protection, and carbon coating treatment is performed at 950° C. for 4 h.
  • the product is crushed and sieved to obtain the negative electrode material.
  • the negative electrode material prepared in this embodiment includes an active substance, and the active substance includes a compound of silicon oxide and metal Mg.
  • the specific surface area of the negative electrode material is 25.3 m 2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgSiO 3 peaks, and there is no Mg 2 Si peak.
  • the size of Si microcrystals is 20.9 nm, and the pH value is 7.7.
  • a method for preparing a negative electrode material comprises the following steps:
  • the active material is placed in a high-temperature box furnace, methane gas is introduced under nitrogen protection, and carbon coating treatment is performed at 950° C. for 4 h.
  • the product is crushed and sieved to obtain the negative electrode material.
  • the specific surface area of the negative electrode material prepared in this comparative example is 15.9m2 /g.
  • X-ray diffraction analysis shows that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO3 peak, Mg2SiO4 peak and a small amount of Mg2Si peak, the size of Si microcrystal grains is 25.6nm, and the pH value is 13.0.
  • the peak height ratio I of the strongest peak of Mg2Si peak to the strongest peak of Si characteristic peak is 0.1.
  • the negative electrode materials prepared in Examples 1 to 11 include active materials, and the metal M compounds in the active materials contain almost no metal M silicides.
  • the gas production of the negative electrode materials is less than 1 mL. This is because the mixture of the prepared silicon oxide raw material and the metal M raw material is subjected to a reduced pressure heating treatment at a high temperature to form M vapor and silicon oxide raw material vapor, and by allowing the vapor to be fully mixed, the local M vapor excess can be reduced, and the local silicon oxide raw material can be reduced from being reduced to silicon element and metal M silicide; the size of Si crystallites in silicon oxide can be effectively controlled, and the rate performance and cycle stability of the negative electrode material can be improved.
  • the negative electrode material of Example 2 is not subjected to carbon coating treatment, and the specific surface area of the negative electrode material is large. The side reactions between the negative electrode material and the electrolyte increase during the cycle process, resulting in a slight decrease in the rate performance and cycle performance of the battery.
  • Example 11 has undergone a pickling process to remove the silicide of M, the pickling process does not reduce the size of the larger Si grains that have been produced before pickling, which reduces the cycle life of the material and increases the expansion rate. At the same time, the pickling process will also result in a larger specific surface area due to the removal of substances, resulting in more irreversible Li 4 SiO 4 and Li 2 O and SEI film generated during the first lithium insertion, and the first capacity and the first Coulomb efficiency are both reduced. It can also be seen from the specific heat capacity that the specific heat capacity after pickling is lower than 0.2 J/(gK), indicating that the negative electrode material contains materials with low specific heat capacity, which comes from the local elemental Si produced by the inadequate mixing of gases during the evaporation process.

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Abstract

一种负极材料及其制备方法、锂离子电池，负极材料包括活性物质，活性物质包括硅氧化物及金属M的化合物，金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种，金属M选自电负性＜1.8的金属中的至少一种；10g负极材料与10mL的浓度为1mol/L盐酸混合后的产气量≤1mL。能降负极材料的体积膨胀，提高负极材料的倍率性能和循环稳定性。

Description

负极材料及其制备方法、锂离子电池
本申请要求于2022年12月16提交国家知识产权局，申请号为202211627204.9、申请名称为“负极材料及其制备方法、锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及负极材料技术领域，具体地讲，涉及一种负极材料及其制备方法、锂离子电池。
背景技术
电动化的新能源汽车是汽车市场未来发展方向，其核心部件是锂离子电池。随着市场发展，对高容量密度的电池需要越来越高，采用新型高比容正负极材料是提高电池的能量密度的重要方法之一。
越来越多的金属、氧化物、金属合金等新材料作为活性材料被应用于负极材料中以不断探索提高电池的能量密度的各种方式。以硅基负极材料为例，硅基负极材料作为上述活性材料中的一种，被普遍认为是下一代的负极材料，其超高的理论比容量(4200mAh/g)和较低的脱锂电位(<0.5V)，且硅的电压平台略高于石墨，在充电时难引起表面析锂，安全性能更好等优点使其备受好评。但是硅负极在循环过程中存在剧烈的体积膨胀效应，导致材料粉化、破碎，电池的循环衰减很快。
现有技术中，会通过金属M来脱除硅氧材料体系中的部分氧，硅氧材料的还原产物依次为SiOx、Si、M的硅化物，局部的M的硅化物的生成会放出大量热，使得Si微晶的晶粒尺寸大幅上升，影响材料的循环性能及膨胀率。
因此，如何抑制负极材料的体积膨胀，提高循环稳定性是目前急需解决的问题。
申请内容
本申请提出一种负极材料及其制备方法、锂离子电池，能降负极材料的体积膨胀，提高负极材料的倍率性能和循环稳定性。
第一方面，本申请提供一种负极材料，所述负极材料包括活性物质，所述活性物质包括硅氧化物及金属M的化合物，所述金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种，所述金属M选自电负性<1.8的金属中的至少一种；
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量≤1mL。
在一些实施方式中，所述硅氧化物包括硅元素和氧元素，所述硅元素和所述氧元素的原子比为0～2，且不包括0。
在一些实施方式中，所述硅氧化物的化学通式为SiOx，其中0＜x≤2。
在一些实施方式中，所述金属M选自Li、K、Na、Mg、Ca、Al、La、Zn、Ti和Mn中的至少一种。
在一些实施方式中，所述金属M为Mg。
在一些实施方式中，所述硅氧化物中含有Si微晶，所述Si微晶的尺寸≤20nm。
在一些实施方式中，所述负极材料的pH为8～14。
在一些实施方式中，所述负极材料的比表面积≤30m2/g。
在一些实施方式中，所述负极材料的中值粒径为1μm～20μm。
在一些实施方式中，所述负极材料的wadell球形度Φ，0.3＜Φ＜1。
在一些实施方式中，采用X射线衍射分析，所述负极材料具有特征峰A、特征峰B和/或特征峰C，其中，特征峰A表示Si特征峰或SiO特征峰，特征峰B表示金属M的氧化物特征峰，特征峰C表示金属M的硅酸盐特征峰；将金属M的硅化物的特征峰记为特征峰D，且特征峰D的最强峰与特征峰A的最强峰的峰高比值为I，0≤I＜0.05。
第二方面，本申请提供一种负极材料，所述负极材料包括活性物质，所述活性物质包括硅氧化物及金属M的化合物，所述金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种，所述金属M选自电负性<1.8的金属中的至少一种；
采用X射线衍射分析，所述负极材料具有特征峰A、特征峰B和/或特征峰C，其中，特征峰A表示Si特征峰或SiO特征峰，特征峰B表示金属M的氧化物特征峰，特征峰C表示金属M的硅酸盐特征峰；将金属M的硅化物的特征峰记为特征峰D，且特征峰D的最强峰与特征峰A的最强峰的峰高比值为I，0≤I＜0.05。
在一些实施方式中，所述硅氧化物包括硅元素和氧元素，所述硅元素和所述氧元素的原子比为0～2，且不包括0。
在一些实施方式中，所述硅氧化物的化学通式为SiOx，其中0＜x≤2。
在一些实施方式中，所述金属M选自Li、K、Na、Mg、Ca、Al、La、Zn、Ti和Mn中的至少一种。
在一些实施方式中，所述金属M为Mg。
在一些实施方式中，所述硅氧化物中含有Si微晶，所述Si微晶的尺寸≤20nm。
在一些实施方式中，所述负极材料的pH为8～14。
在一些实施方式中，所述负极材料的比表面积≤30m2/g。
在一些实施方式中，所述负极材料的中值粒径为1μm～20μm。
在一些实施方式中，所述负极材料的wadell球形度Φ，0.3＜Φ＜1。
在一些实施方式中，所述负极材料还包括位于所述活性物质至少部分表面的碳材料。
在一些实施方式中，所述负极材料还包括位于所述活性物质至少部分表面的碳材料层，所述碳材料层的厚度为10nm～500nm。
在一些实施方式中，所述负极材料中的碳元素的质量含量为1％～40％。
在一些实施方式中，所述负极材料的孔隙率＜20％。
在一些实施方式中，所述负极材料的比热容为0.2J/(g.K)～2.0J/(g.K)。
在一些实施方式中，所述负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为1％～5％。
第三方面，本申请实施例还提供一种负极材料的制备方法，所述方法包括以下步骤：
将包含金属M原料与硅氧原料的混合物进行减压加热处理，形成M蒸气及硅氧原料蒸气，并使得蒸气充分混合1min～600min，其中，所述金属M选自电负性<1.8的金属中的至少一种；
混合后的蒸气气体进行冷却处理，得到活性物质；所述活性物质包括硅氧化物及金属M的化合物，所述金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种。
在一些实施方式中，所述金属M原料选自金属M单质、金属M的氧化物中的至少一种。
在一些实施方式中，所述金属M选自Li、K、Na、Mg、Ca、Al、La、Zn、Ti和Mn中的至少一种。
在一些实施方式中，所述硅氧原料包括Si、SiOy和SiO2的混合物、SiOy和Si的混合物、Si和SiO2的混合物中的至少一种，其中，0＜y＜2。
在一些实施方式中，所述金属M原料中的金属M的摩尔量为nM，所述硅氧原料中的Si的摩尔量为nSi，且nM：nSi＝(0.2～1)：1。
在一些实施方式中，所述硅氧化物包括硅元素和氧元素，所述硅元素和氧元素的原子比为0～2，且不包括0。
在一些实施方式中，所述硅氧化物的化学通式为SiOx，其中0＜x≤2。
在一些实施方式中，所述减压加热处理的温度为900℃～2000℃。
在一些实施方式中，所述减压加热处理的气压为0.1Pa～1000Pa。
在一些实施方式中，所述冷却处理的温度为500℃～900℃。
在一些实施方式中，所述减压加热处理的气压为0.1Pa～1000Pa。
在一些实施方式中，所述方法还包括重复步骤(1)至步骤(2)，并控制总保温时间为1h～120h。
在一些实施方式中，将冷却处理得到的活性物质进行碳包覆处理，得到负极材料；所述碳包覆处理包括固相碳包覆、液相碳包覆及气相碳包覆中的至少一种。
在一些实施方式中，所述碳包覆处理的步骤具体包括：将冷却处理得到的活性物质加热后，通入保护性气体及碳源气体，所述碳源气体进行热裂解，得到负极材料。
在一些实施方式中，所述碳源气体为烃类。
在一些实施方式中，所述碳源气体包括甲烷、乙烯、乙炔、丙炔、丙烯、丙烷、甲苯、苯、苯乙烯和苯酚中的至少一种。
在一些实施方式中，所述热裂解的温度为600℃～1000℃，热裂解的时间为30min-24h。
在一些实施方式中，所述碳包覆处理的步骤具体包括：将冷却处理得到的活性物质与固相碳源混合得到的混合物进行碳化处理，得到负极材料。
在一些实施方式中，所述碳化处理的温度500℃-1000℃，碳化处理的时间为30min-24h。
在一些实施方式中，所述固相碳源包括糖类、酯类、烃类、有机酸和高分子聚合物中的至少一种。
在一些实施方式中，所述固相碳源包括聚氯乙烯、聚乙烯醇缩丁醛、聚丙烯腈、 聚丙烯酸、聚乙二醇、聚吡咯、聚苯胺、蔗糖、葡萄糖、麦芽糖、柠檬酸、沥青、糠醛树脂、环氧树脂和酚醛树脂中的至少一种。
在一些实施方式中，所述固相碳源与所述活性物质的质量比为5：(5～95)。
第四方面，本申请提供一种电池，包括第一方面和/或第二方面所述的负极材料或根据第三方面制备得到的负极材料。
本申请的技术方案至少具有以下有益的效果：
首先，本申请提供的负极材料，负极材料的活性物质包括硅氧化物及金属M的化合物，金属M的化合物弥散分布在硅氧化物中，且负极材料与盐酸混合后的产气量≤1mL，即金属M的化合物包括金属M的氧化物和/或金属M的硅酸盐，而几乎没有以M的硅化物的形式存在，可以有效控制硅氧化物中的Si微晶的尺寸，金属M的化合物弥散分布在硅氧化物中，即金属M的化合物可以嵌设于硅氧化物颗粒上，或嵌设于硅氧化物颗粒之间，可以提高负极材料的倍率性能及循环稳定性。
本申请提供的负极材料的制备方法，将制备硅氧原料与金属M原料的混合物在高温下进减压加热处理，形成M蒸气及硅氧原料蒸气，并通过让蒸气充分混合，可以减少局部M蒸气过量，减少局部的硅氧原料蒸气被还原成硅单质及金属M的硅化物，然后冷却得到硅氧化物与金属M的化合物的混合物，其中，金属M的化合物弥散分布在硅氧化物中，金属M的化合物可以嵌设于硅氧化物颗粒上，或嵌设于硅氧化物颗粒之间，金属M的化合物几乎不以硅化物的形式存在，有利于有效控制硅氧化物中的Si微晶的尺寸，使得负极材料的膨胀率得到控制，有利于制备得到具有较低的膨胀率和优异的循环性能的负极材料。
附图说明
图1为本申请实施例提供的负极材料的制备方法的流程示意图；
图2为本申请实施例提供的负极材料的产气量的测试状态示意图；
图3为本申请实施例1制备的负极材料中的硅的XRD图；
图4为本申请实施例1制备的负极材料中的MgSiO3的XRD图；
图5为本申请实施例1制备的负极材料中的Mg2SiO4的XRD图；
图6为本申请实施例1制备的负极材料的比热容曲线图。
具体实施方式
以下所述是本申请实施例的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请实施例原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本申请实施例的保护范围。
通常，可以利用金属M来脱除硅氧材料体系中的部分氧，硅氧材料的还原产物依次为SiOx、Si、M的硅化物，局部的M的硅化物的生成会放出大量热，使得Si微晶的晶粒尺寸大幅上升；并且，由于负极材料中大量的M的硅化物的存在，说明负极材料中存在很多游离单质硅，在电解液与负极材料接触后，会产生大量的气体；且Si微晶的晶粒尺寸较大，会导致负极材料局部膨胀应力过大，容易导致颗粒破裂或粉碎， 影响材料的循环性能及膨胀率。目前，可采用酸洗去除材料中的M的硅化物，但是酸洗处理不能改变Si微晶的尺寸大小，酸洗过程中容易起火发生安全隐患，M的硅化物的烧结产物SiO2混入负极材料中，还会降低负极材料的比容量，可见通过酸洗来控制负极材料中的M的硅化物的含量是事倍功半的，耗时耗力，还提高生产成本。
本申请提供了一种负极材料，负极材料包括活性物质，活性物质包括硅氧化物及金属M的化合物，金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种，金属M选自电负性<1.8的金属中的至少一种；
10g负极材料与10mL的浓度为1mol/L盐酸混合后的产气量≤1mL。
在上述方案中，负极材料的活性物质包括硅氧化物及金属M的化合物，金属M的化合物弥散分布在硅氧化物中，且负极材料与盐酸混合后的产气量≤1mL，即金属M的化合物包括金属M的氧化物和/或金属M的硅酸盐，而几乎没有以M的硅化物的形式存在，可以有效控制硅氧化物中的Si微晶的尺寸，金属M的化合物弥散分布在硅氧化物中，即金属M的化合物可以嵌设于硅氧化物颗粒上，或嵌设于硅氧化物颗粒之间，可以提高负极材料的倍率性能及循环稳定性。
在一些实施方式中，硅氧化物包括硅元素和氧元素，硅元素和氧元素的原子比为0～2，且不包括0。硅元素和氧元素的原子比具体可以是0.05、0.11、0.21、0.26、0.31、0.41、0.51、0.59、0.61、0.69、0.71、0.74、0.76、0.79、0.89、0.99、1、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9和2等，在此不做限定。优选地，硅元素和氧元素的原子比为0～1，且不包括0。
在一些实施方式中，硅氧化物的化学通式为SiOx，其中，0＜x≤2，x具体可以是0.05、0.11、0.21、0.26、0.31、0.41、0.51、0.59、0.61、0.69、0.71、0.74、0.76、0.79、0.89、0.99、1、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9和2等，在此不做限定。优选地，0<x<1。
在一些实施方式中，金属M选自Li、K、Na、Mg、Ca、Al、La、Zn、Ti和Mn中的至少一种。
在一些实施方式中，利用X射线扫描负极材料颗粒的SEM切面获得的元素分布谱图中，Si、O以及金属M的分布面为均匀弥散状态。在负极材料中，Si、O和金属M均匀分布于负极材料颗粒内，可有效减少空气等成分渗入到一次颗粒内部而导致活性成分失效，长期存放结构和性质不会劣化，非常适合用于锂离子电池。均匀弥散的主要优点是保证材料内部各处的物化状态类似(即硅酸盐浓度、硅晶粒尺寸等)，这样在脱嵌锂过程中各处的膨胀收缩均处于相同的水平，不会出现局部膨胀过大而带来的应力薄弱点，从而使得材料性能发挥更优。
在一些实施方式中，金属M为镁，金属M的化合物包括MgO、MgSiO3及Mg2SiO4。当金属M为镁时，可以进一步降低Si微晶尺寸，降低负极材料的膨胀。
在一些实施方式中，金属M的硅酸盐均匀分布于活性物质的一次颗粒内。
在一些实施方式中，金属M的硅酸盐为硅酸锂，硅酸锂包括Li2SiO3、Li4SiO4、Li2Si2O5、Li2Si3O7中的至少一种。优选地，硅酸锂为Li2Si2O5。
在一些实施方式中，采用X射线衍射分析，负极材料具有特征峰A、特征峰B和/或特征峰C，其中，特征峰A表示Si特征峰(基于PDF卡片编号27-1402)或SiO特 征峰(基于PDF卡片编号30-1127)，特征峰B表示金属M的氧化物特征峰，特征峰C表示金属M的硅酸盐特征峰；将金属M的硅化物的特征峰记为特征峰D，且特征峰D的最强峰与特征峰A的最强峰的峰高比值为I，0≤I＜0.05。
具体地，峰高比I可以是0.04、0.03、0.02、0.01、0.005、0等，优选地，峰高比0≤I＜0.01。当峰高比I为0时，确认负极材料不存在金属M的硅化物。
在一些实施方式中，金属M的化合物包括金属M的氧化物，金属M的氧化物均匀分布于负极材料颗粒内。
在一些实施方式中，硅氧化物中含有Si微晶，Si微晶尺寸≤20nm；具体地，硅氧化物中的Si微晶尺寸可以为20nm、18nm、15nm、12nm、10nm、9.2nm、8nm、6.7nm、6nm、5nm或3nm等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。Si微晶的大小反映了硅氧化物歧化程度，Si微晶尺寸越大，说明歧化程度越高，硅氧原料反应后会生成大量Si晶粒和SiO2，从而带来单质Si所导致的更大体积膨胀和SiO2无容量所导致的容量降低等问题，不利于表现出硅氧材料本身的优异性能。
在一些实施方式中，硅氧化物中含有Si微晶，Si微晶尺寸≤10nm，说明负极Si晶粒的体积较小，硅氧化物中的Si微晶弥散分布，与金属M的化合物不会放出大量热影响Si微晶的尺寸，能有效降低负极材料膨胀，提升循环性能。
在一些实施方式中，负极材料的pH为8～14，具体可以是8、9、10、10.5、11、11.5、12、13或14等，在此不做限定。优选地，负极材料的pH值为9～11。
在一些实施方式中，负极材料的比表面积小于30m2/g，具体可以为1.0m2/g、1.5m2/g、1.8m2/g、2.0m2/g、2.5m2/g、3.0m2/g、3.6m2/g、4.0m2/g、5m2/g、5.5m2/g、6.0m2/g、7.0m2/g、8.0m2/g、8.5m2/g、10.0m2/g、12.0m2/g、15.0m2/g、18.0m2/g或30.0m2/g，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。优选地，负极材料的比表面积小于10m2/g。
在一些实施方式中，负极材料的中值粒径为1μm～20μm，具体可以是1μm、2μm、2.5μm、3.5μm、4μm、6μm、8μm、9.5μm、10μm、12.5μm、15μm或20μm等，在此不做限定。
在一些实施方式中，负极材料的wadell球形度Φ，0.3＜Φ＜1；wadell球形度可以为0.325、0.43、0.54、0.65、0.76、0.87、0.98、0.99等。可以理解地，负极材料颗粒的wadell球形度不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一些实施方式中，负极材料还包括位于活性物质至少部分表面的碳材料。
在一些实施方式中，负极材料还包括位于活性物质至少部分表面的碳材料层。可以理解地，活性物质表面的碳材料层能够减少SEI膜反复生成导致材料颗粒破碎，有利于提升负极材料的循环性能并降低由于SEI膜生成所导致的体积膨胀。
在一些实施方式中，碳材料层的厚度为10nm～500nm，进一步优选为50nm～200nm。具体地，碳材料层的厚度可以为10nm、50nm、80nm、100nm、120nm、150nm、200nm、300nm、400nm或500nm，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一些实施方式中，活性物质分散于碳材料中，碳材料为活性物质构建了导电网 络，克服了活性物质(例如硅氧化物SiOx)导电性差的缺点，有利于硅氧化物的容量发挥以及循环稳定。
在一些实施方式中，负极材料中的碳元素的质量含量为1％～40％；具体可以是2％、5％、8％、10％、12％、15％、18％、20％、25％、28％、35％或40％等，当然也可以是上述范围内的其它值，在此不做限定。
在一些实施方式中，负极材料还可以包括位于活性物质表面的包覆层，包覆层含有高分子柔性聚合物。
在一些实施方式中，负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为1％～5％，具体可以是1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％等，在此不做限定。适量的微孔的存在，可以给活性物质的体积膨胀提供缓冲空间，减少由于局部应力过大导致的颗粒破碎。
在一些实施方式中，负极材料的孔隙率＜20％。孔隙率越小，有利于保持结构稳定性，有利于负极材料的容量发挥及循环稳定性。具体地，负极材料的孔隙率可以为19.2％、18％、15％、13％、10％、8％、5％、3％或2％等。可以理解的是，负极材料的孔隙率并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一些实施方式中，负极材料的比热容为0.2～2.0J/(g.K)。负极材料比热容过高或过低，说明都存在明显的杂质。通过控制负极材料中金属M的化合物的分布均匀度，能够调节材料的比热容。负极材料中含有一定含量的金属硅化物时，负极材料的比热容会升高，比热容会突破2.0J/(g.K)；或者负极材料中的金属单质含量高，比热容会降低。
本申请还提供一种负极材料的制备方法，如图1所示，方法包括以下步骤S100～S200：
S100，将包含金属M原料与硅氧原料的混合物进行减压加热处理，形成M蒸气及硅氧原料蒸气，并使得蒸气充分混合1min～600min，其中，金属M选自电负性<1.8的金属中的至少一种；
S200，混合后的蒸气气体进行冷却处理，得到活性物质；活性物质包括硅氧化物及金属M的化合物，金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种。
在上述方案中，将制备硅氧原料与金属M原料的混合物在高温下进减压加热处理，形成M蒸气及硅氧原料蒸气，并通过让蒸气充分混合，可以减少局部M蒸气过量，减少局部的硅氧原料蒸气被还原成硅单质及金属M的硅化物，然后冷却得到硅氧化物与金属M的化合物的混合物，其中，金属M的化合物弥散分布在硅氧化物中，金属M的化合物可以嵌设于硅氧化物颗粒上，或嵌设于硅氧化物颗粒之间，金属M的化合物几乎不以硅化物的形式存在，有利于有效控制硅氧化物中的Si微晶的尺寸，使得负极材料的膨胀率得到控制，有利于制备得到具有较低的膨胀率和优异的循环性能的负极材料。
以下具体介绍本方案：
S100，将包含金属M原料与硅氧原料的混合物进行减压加热处理，形成M蒸气 及硅氧原料蒸气，并使得蒸气充分混合1min～600min，其中，金属M选自电负性<1.8的金属中的至少一种。
在一些实施方式中，硅氧原料包括Si、SiOy和SiO2的混合物、SiOy和Si的混合物、Si和SiO2的混合物中的至少一种，其中，0＜y＜2。
在一些实施方式中，金属M原料选自金属单质、金属氧化物中的至少一种。
在一些实施方式中，金属M选自Li、K、Na、Mg、Ca、Al、La、Zn、Ti和Mn中的至少一种。
在一些实施方式中，金属M原料中的金属M的摩尔量为nM，硅氧原料中的Si的摩尔量为nSi，且nM：nSi＝(0.2～1)：1，具体可以是0.2:1、0.3:1、0.4:1、0.5:1、0.6:1、0.7:1、0.8:1、0.9:1或1:1等，当然也可以是上述范围内的其他值。通过控制金属M的摩尔量与硅的摩尔量的比值，使得金属M的硅酸盐能够均匀分布于活性物质的一次颗粒内。
在一些实施方式中，加热处理的温度为900℃～2000℃。具体地，加热处理的温度可以为900℃、1000℃、1100℃、1200℃、1400℃、1500℃、1550℃、1575℃、1600℃、1650℃、1700℃、1800℃、1900℃或2000℃。可以理解地，上述温度并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一些实施方式中，减压加热处理在真空炉内进行，在投入混合物前，先将真空炉预热至900℃～2000℃。
在一些实施方式中，真空炉内的气压为0.1Pa～1000Pa，具体可以是0.1Pa、50Pa、100Pa、200Pa、500Pa、600Pa、700Pa、800Pa、900Pa或1000Pa等，在此不做限定。
在一些实施方式中，混合物在减压加热作用下共蒸发形成M蒸气及硅氧原料蒸气，此时关闭真空炉炉管口阀门令蒸气气体在真空炉内继续停留1min～600min，具体可以是1min、5min、10min、30min、60min、90min、120min、150min、300min、360min、420min或600min等，在此不做限定。真空炉一般分为炉管和冷却区，现有技术中，常用的是材料在炉管加热后，形成的蒸气立即进入冷却区冷却，而本申请中，炉管口阀门连通和封闭炉管和冷却区，通过关闭炉管口阀门使得蒸汽在炉管内停留，可以让反应的原料保持蒸气状态，并且一直处于高压的环境中，充分混合后蒸气的均匀度能够大幅提升，蒸气气体能够混合地更加均匀。优选停留时间为30min～600min。
S200，混合后的蒸气气体进行冷却处理，得到活性物质；活性物质包括硅氧化物及金属M的化合物，金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种。
在一些实施方式中，冷却处理的温度为500℃～900℃，具体可以是500℃、550℃、600℃、650℃、700℃、750℃、800℃、850℃或900℃。可以理解地，上述温度并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一些实施方式中，由于蒸气气体已充分混合，抑制了局部金属单质的出现，也就是抑制了单质Si以及金属硅化物的形成，冷却后得到的活性物质不需要传统的酸洗或水洗，可以直接进行后续的碳包覆或二次造粒工序。
在一些实施方式中，在真空炉的冷却区进行冷却处理，冷却区内的气压为0.1Pa～ 1000Pa，具体可以是0.1Pa、50Pa、100Pa、200Pa、500Pa、600Pa、700Pa、800Pa、900Pa或1000Pa等，在此不做限定。
在一些实施方式中，重复进行步骤S100～步骤S200，从而使得硅氧原料与金属M原料能够充分蒸发形成混合后的蒸气气体，进而使得冷却形成的金属M的化合物弥散分布在硅氧化物中。
在一些实施方式中，重复步骤(1)至步骤(2)，并控制总保温时间为1h～120h；具体可以是1h、5h、10h、15h、20h、30h、40h、50h、60h、120h等，当然也可以是上述范围内的其他值，重复步骤S100～S200，有利于形成弥散状态更均匀的负极材料，也能够抑制单质Si以及金属硅化物的形成。
在一些实施方式中，硅氧化物包括硅元素和氧元素，硅元素和氧元素的原子比为0～2，且不包括0。硅元素和氧元素的原子比具体可以是0.05、0.11、0.21、0.26、0.31、0.41、0.51、0.59、0.61、0.69、0.71、0.74、0.76、0.79、0.89、0.99、1、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9和2等，在此不做限定。优选地，硅元素和氧元素的原子比为0～1，且不包括0。
在一些实施方式中，硅氧化物的化学通式为SiOx，其中，0＜x≤2，x具体可以是0.05、0.11、0.21、0.26、0.31、0.41、0.51、0.59、0.61、0.69、0.71、0.74、0.76、0.79、0.89、0.99、1、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9和2等，在此不做限定。优选地，0<x<1。
另一实施方式的负极材料的制备方法，包括以下步骤：
步骤S300，将冷却处理得到的活性物质进行碳包覆处理，得到负极材料。
其中，冷却处理得到的活性物质可采用步骤S100～步骤S200制备。
该制备方法得到的负极材料包括活性物质以及位于活性物质至少部分表面的碳材料，活性物质包括硅氧化物及金属M的化合物，其中，硅氧化物的化学通式为SiOx，0＜x≤2。
在一实施方式中，碳包覆处理具体为固相碳包覆、液相碳包覆及气相碳包覆中的至少一种。
具体地，碳包覆处理的步骤具体包括：将冷却处理得到的活性物质加热后，通入保护性气体及碳源气体，碳源气体进行热裂解，得到负极材料。
在一些实施方式中，气相碳包覆所用的碳源气体包括烃类。
在一些实施方式中，碳源气体包括甲烷、乙炔、乙烯、乙烷、丙烷、丙烯、丙炔、丙酮和苯中的至少一种。
在一些实施方式中，化学气相沉积装置包括回转式化学气相沉积反应炉、等离子增强化学气相沉积反应炉、化学气相沉积管式炉和流化床中的至少一种。具体地，化学气相沉积装置为回转炉和箱式炉中的至少一种。
在一些实施方式中，热裂解的温度为600℃～1000℃，热裂解的时间为2h～20h。
在一些实施方式中，在保护性气体下通入碳源气体。
在一些实施方式中，保护性气体包括氮气、氦气、氖气、氩气、氪气和氙气中的至少一种。
在一些实施方式中，碳包覆处理的步骤具体包括：将冷却处理得到的活性物质与 固相碳源混合得到的混合物进行碳化处理，得到负极材料。
在一些实施方式中，固相碳源包括糖类、酯类、烃类、有机酸和高分子聚合物中的至少一种。具体可以是聚氯乙烯、聚乙烯醇缩丁醛、聚丙烯腈、聚丙烯酸、聚乙二醇、聚吡咯、聚苯胺、蔗糖、葡萄糖、麦芽糖、柠檬酸、沥青、糠醛树脂、环氧树脂和酚醛树脂中的至少一种。
在一些实施方式中，冷却后的产物与碳源的混合方式，可为VC混合、融合、球磨、三维混合、流化床混合等。
在一些实施方式中，混合在融合机中进行，融合时间为0.5h-2h，融合机转速为500r/min～5000r/min。
在一些实施方式中，固相碳源与活性物质的质量比为5：(5～95)。
在一些实施方式中，碳化处理的温度500℃-1000℃，碳化处理的时间为2h-20h。
在一些实施方式中，固相碳包覆所用设备为回转炉、箱式炉、辊道窑、隧道窑、推板窑中的至少一种。
在一些实施方式中，保护性气体可为氮气、氩气、氦气、氖气、氪气及氙气中的至少一种。
液相碳包覆过程具体为将冷却后的产物与碳源混合均匀，然后置于炉中，通入保护性气体，热处理使碳源裂解包覆在冷却后的产物表面。
在一些实施方式中，液相碳包覆所用的碳源为有机碳源，具体可以为低温液相沥青、糠醇、甲基丙烯酸缩水甘油酯、三乙二醇二甲基丙烯酸酯等。
在一些实施方式中，保护性气体可为氮气、氩气、氦气、氖气、氪气及氙气中的至少一种。
在一些实施方式中，热处理温度为600℃～1000℃。
进一步地，方法还包括：将碳化处理后的物料进行筛分和除磁处理，得到负极材料。
在一些实施方式中，筛分的方式为固定筛、滚筒筛、共振筛、滚轴筛、振动筛和链条筛中任意一种，筛分的目数为100～500目，具体地，筛分的目数可以是100目、200目、250目、325目、400目、500目等，优选地，筛分的目数为250目，负极材料的粒径控制在上述范围内，有利于负极材料加工性能的提升。
在一些实施方式中，除磁的设备为永磁筒式磁选机、电磁除铁机和脉动高梯度磁选机中任意一种，除磁是为了最终控制负极材料的磁性物质含量，减少磁性物质对锂离子电池的放电效果以及电池在使用过程中的安全性。
本申请实施例还提供了一种电池，采用本申请上述实施例提供的负极材料或采用本申请上述实施例提供的负极材料的制备方法制得的负极材料。电池可以是锂离子电池或钠离子电池等，在此不做限定。本申请实施例提供的电池具有优异倍率性能以及低膨胀的优点。
测试方法：
1)负极材料的粒径：
颗粒粒度测试方法参照GB/T 19077-2016。可以用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 3000型激光粒度分析仪。
2)负极材料比表面积的测试方法：
在恒温低温下，测定不同相对压力时的气体在固体表面的吸附量后，基于布朗诺尔-埃特-泰勒吸附理论及其公式(BET公式)求得试样单分子层吸附量，从而计算出负极材料的比表面积。
3)负极材料pH测试：
取10g负极材料，加入10g水，搅拌30min后，取上清液测得负极材料的pH值。
4)碳材料层厚度的测试方法：
通过FIB-SEM设备对负极材料颗粒进行切面处理，在SEM中测量得到碳材料层平均厚度。
5)负极材料的孔隙率的测试方法：
采用压汞法对负极材料颗粒的孔隙率进行测试。
6)负极材料中碳的质量含量的测试方法：
采用热重分析法测试负极材料中碳的质量含量。
7)负极材料的比热容的测试方法：
使用耐驰的DSC仪测试样品的比热容，测试温度为0～130℃，升温速率10°C/min，气氛N2，样品量13mg，测试得到负极材料的比热容值。
8)负极材料中的XRD测试方法：
将负极材料制成片，使用X射线衍射分析仪进行测试。角度范围：10～90°，扫描模式：步进扫描，选择狭缝宽度1.0，并设置电压40kW，电流40mA。测得数据使用Jade 6.5软件进行分析，通过比对PDF卡片来确认负极材料成分。
通过X射线衍射分析仪表征，在27.5°～29.5°范围、46.3°～48.3°范围、55.0°～57.0°范围内均能观察到特征峰；并对28.6°的Si(111)峰进行拟合，得到的半峰宽FWHM后，再使用谢勒公式计算Si微晶的尺寸。
将负极材料加入至HCl和HNO3的混合酸溶液中，然后搅拌、分离液相及烘干，再使用上述的方法进行X射线衍射分析仪表征确认是否仍有除Si、SiO、SiO2的特征峰外的杂峰。若有杂峰存在，则重复进行酸处理，若无，则用氧氮氢分析仪测试负极材料的氧含量，再根据公式x＝28*氧含量/(16-16*氧含量)得到x的值。
9)负极材料中的产气量的测试方法：
如图2所示，将10g负极材料与10mL 1mol/L盐酸分别封装于分隔式液体包装袋的两端，用排水法测量其体积V1。然后将包装袋的中间分隔撕开，将负极材料与盐酸充分混合后常温静置24h，再次用相同方法测量其体积V2；V2与V1的差值为负极材料的产气量。
10)扣式电池测试
将制得的负极材料、导电炭黑和聚丙烯酸粘结剂按质量百分比75：15：10将他们溶解在N甲基吡咯烷酮中混合，涂覆于铜箔集流体上，真空烘干、制得负极极片；以金属锂片作为对电极，在充满氩气的手套箱中组装成扣式电池完成。在0.1C的电流密度下，按充放电区间为0.01-1.5V进行充放电测试。
11)电化学性能测试
将制得的负极材料、与石墨按10:90的比例混合得到负极活性材料，再将负极活性材料与羧甲基纤维素钠CMC、粘结剂丁苯橡胶SBR、导电剂Super-P、导电剂KS-6按照92:2:2:2的质量比混合后调成负极浆料，涂覆在铜箔上，并经真空干燥、辊压，制备成负极极片；然后将传统成熟工艺制备的三元正极极片(镍钴锰酸锂NCM523)、1mol/L的LiPF6/碳酸乙烯酯+碳酸二甲酯+碳酸甲乙酯(v/v＝1:1:1)电解液、Celgard2400隔膜、外壳采用常规生产工艺组装成CR2016模拟电池。循环性能测试使用30mA的电流进行恒流充放电实验，充放电电压限制在0～1.5V。采用武汉金诺电子有限公司LAND电池测试系统测试。在0.1C的电流密度下，按充放电区间为0.005V-1.5V进行充放电测试。
首次库伦效率＝首圈放电容量/首圈充电容量。
重复循环50周，利用千分尺测量锂离子电池此时极片的厚度为H1，循环50圈后膨胀率＝(H1-H0)/H0×100％。
重复100周循环，记录放电容量，作为锂离子电池的剩余容量；容量保持率＝剩余容量/初始容量*100％。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例1
一种负极材料的制备方法，包括以下步骤：
(1)将100kg Li锭，900kg SiO粉，nLi：nSi＝0.2：1，投入1600℃的真空炉中；
(2)关闭炉管口阀门，将炉管及冷却区的气压均抽至1000Pa，使蒸发出来的气体在炉内停留60min；
(3)打开炉管口阀门，使蒸发出来的气体通往冷却区，冷却区温度为900℃，冷凝成SiOx(0＜x≤2)；
(4)重复步骤(2)～(3)，总共保温10h，得到活性物质；
(5)将活性物质置于高温箱式炉中，在氮气保护下通入甲烷气体，在820℃条件下碳包覆处理4h，产物经粉碎、筛分，得到负极材料。
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Li的化合物，金属Li的化合物包括Li2O、Li2SiO3及Li4SiO4，负极材料的比表面积为7.3m2/g，如图3～图5所示，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、、Li2O峰、Li2SiO3峰、Li4SiO4峰，Si微晶晶粒的尺寸为19.9nm，pH值为11.9。
负极材料中的碳元素的质量占比为10％，如图6所示，负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为1.6％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为2.56％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.1mL。
实施例2
一种负极材料的制备方法，包括以下步骤：
(1)将100kg Al锭，900kg SiO粉，nAl：nSi＝0.19：1，投入1600℃的真空炉中；
(2)关闭炉管口阀门，将炉管及冷却区的气压均抽至1000Pa，使蒸发出来的气体在炉内停留60min；
(3)打开炉管口阀门，使蒸发出来的气体通往冷却区，并冷凝成SiOx(0＜x≤2)；
(4)重复步骤(2)～(3)，总共保温10h，得到活性物质；
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Al的化合物，金属Al的化合物包括Al2O3、Al2(SiO3)3及Al4(SiO4)3，负极材料的比表面积为18.3m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgO峰、MgSiO3峰、Mg2SiO4峰，Si微晶晶粒的尺寸为19.3nm，pH值为8.4。
负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为2.3％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为4.11％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.7mL。
实施例3
一种负极材料的制备方法，包括以下步骤：
(1)将100kg Mg锭，900kg SiO粉，nMg：nSi＝0.73：1，投入1600℃的真空炉中；
(2)关闭炉管口阀门，将炉管及冷却区的气压均抽至1000Pa，使蒸发出来的气体在炉内停留60min；
(3)打开炉管口阀门，使蒸发出来的气体通往冷却区，冷却区温度为900℃，冷凝成SiOx(0＜x≤2)；
(4)重复步骤(2)～(3)，总共保温10h，得到活性物质。
(5)将活性物质置于高温箱式炉中，在氮气保护下通入甲烷气体，在950℃条件下碳包覆处理4h，产物经粉碎、筛分，得到负极材料。
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Mg的化合物，金属Mg的化合物包括MgO、MgSiO3及Mg2SiO4，负极材料的比表面积为12.6m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgO峰、MgSiO3峰、Mg2SiO4峰，Si微晶晶粒的尺寸为15.1nm，pH值为11.2。
负极材料中的碳元素的质量占比为10％，且负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为2.0％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为3.23％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.9mL。
实施例4
与实施例3的区别在于，真空炉的温度为2000℃，压力为100Pa。
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Mg的化合物，金属Mg的化合物包括MgO、MgSiO3及Mg2SiO4，负极材料的比表面积为15.5m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgO峰、MgSiO3峰、Mg2SiO4峰，Si微晶晶粒的尺寸为9.9nm，pH值为10.8。
负极材料中的碳元素的质量占比为10％，且负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为3.5％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总 孔体积中的体积占比为1.34％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.1mL。
实施例5
与实施例3的区别在于，真空炉的温度为900℃，压力为10Pa。
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Mg的化合物，金属Mg的化合物包括MgO、MgSiO3及Mg2SiO4，负极材料的比表面积为4.3m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgO峰、MgSiO3峰、Mg2SiO4峰，Si微晶晶粒的尺寸为6.5nm，pH值为13.1。
负极材料中的碳元素的质量占比为10％，且负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为1.3％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为1.40％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.1mL。
实施例6
与实施例3的区别在于，投入的硅氧原料为SiO2和Si；
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Mg的化合物，金属Mg的化合物包括MgO、MgSiO3及Mg2SiO4，负极材料的比表面积为7.6m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgO峰、MgSiO3峰、Mg2SiO4峰，Si微晶晶粒的尺寸为19.1nm，pH值为11.5。
负极材料中的碳元素的质量占比为10％，且负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为2.4％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为2.95％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.7mL。
实施例7
与实施例3的区别在于，投入的金属M原料为投入的金属M原料为CaO和Si，nCa：nSi＝0.73：1。
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Ca的化合物，金属Ca的化合物包括CaO、CaSiO3及Ca2SiO4，负极材料的比表面积为9.0m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、CaO峰、CaSiO3峰、Ca2SiO4峰，Si微晶晶粒的尺寸为15.5nm，pH值为13.0。
负极材料中的碳元素的质量占比为10％，且负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为2.2％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为4.01％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.7mL。
实施例8
与实施例1的区别在于，投入的金属M原料为MgO、CaO和Si，nMg+Ca：nSi＝0.2： 1；
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物、CaO、CaSiO3、Ca2SiO4、MgO、MgSiO3及Mg2SiO4，负极材料的比表面积为9.8m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、CaO峰、CaSiO3峰、Ca2SiO4峰、MgO峰、MgSiO3峰及Mg2SiO4峰，Si微晶晶粒的尺寸为15.0nm，pH值为12.7。
负极材料中的碳元素的质量占比为10％，且负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为2.7％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为4.89％。
10g所述活性物质与10mL的浓度为1mol/L盐酸混合后的产气量为0.6mL。
实施例9
与实施例3的区别在于，(2)关闭炉管口阀门，将炉管及冷却区的气压均抽至1000Pa，使蒸发出来的气体在炉内停留600min。
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Mg的化合物，金属Mg的化合物包括MgO、MgSiO3及Mg2SiO4，负极材料的比表面积为15.6m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgO峰、MgSiO3峰、Mg2SiO4峰，Si微晶晶粒的尺寸为17.0nm，pH值为11.7。
负极材料中的碳元素的质量占比为10％，且负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为2.3％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为2.49％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.3mL。
实施例10
与实施例3的区别在于，(2)关闭炉管口阀门，将炉管及冷却区的气压均抽至1000Pa，使蒸发出来的气体在炉内停留1min。
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Mg的化合物，金属Mg的化合物包括MgO、MgSiO3及Mg2SiO4，负极材料的比表面积为11.3m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgO峰、MgSiO3峰、Mg2SiO4峰，Si微晶晶粒的尺寸为13.5nm，pH值为10.9。
负极材料中的碳元素的质量占比为10％，且负极材料的比热容为0.2～2.0J/(g.K)；负极材料的孔隙率为1.8％。负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为4.93％。
10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量为0.9mL。
实施例11
一种负极材料的制备方法，包括以下步骤：
(1)将100kg Mg锭，900kg SiO粉，投入1600℃的真空炉中；
(2)将炉管及冷却区的气压均抽至1000Pa，使蒸发出来的气体立刻通往冷却区，并冷凝成SiOx(0＜x≤2)，总反应时间10h，得到活性物质。
(3)将1mol/L盐酸缓慢加入至活性物质中，并不断搅拌。直至继续加入盐酸也不再产生气泡时，将滤液过滤，将滤渣在80℃氮气氛保护下烘干，得到酸洗后的活性物质。
(4)将酸洗后活性物质置于高温箱式炉中，在氮气保护下通入甲烷气体，在950℃条件下碳包覆处理4h，产物经粉碎、筛分，得到负极材料。
本实施例制得的负极材料包括活性物质，所述活性物质包括硅氧化物及金属Mg的化合物，负极材料的比表面积为25.3m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgSiO3峰，不存在Mg2Si峰，Si微晶晶粒的尺寸为20.9nm，pH值为7.7。
对比例1
一种负极材料的制备方法，包括以下步骤：
(1)将100kg Mg锭，900kg SiO粉，投入1600℃的真空炉中；
(2)将炉管及冷却区的气压均抽至1000Pa，使蒸发出来的气体立刻通往冷却区，并冷凝成SiOx(0＜x≤2)，总反应时间10h，得到活性物质。
(3)将活性物质置于高温箱式炉中，在氮气保护下通入甲烷气体，在950℃条件下碳包覆处理4h，产物经粉碎、筛分，得到负极材料。
本对比例制得的负极材料的比表面积为15.9m2/g，采用X射线衍射分析发现，负极材料具有特征峰对应Si或SiO、MgO峰、MgSiO3峰、Mg2SiO4峰及少量Mg2Si峰，Si微晶晶粒的尺寸为25.6nm，pH值为13.0。其中，Mg2Si峰的最强峰与Si特征峰的最强峰的峰高比I为0.1。
对实施例以及对比例制得负极材料进行性能测试，上述性能测试的结果如表1：
表1.性能测试结果汇总表

根据表1的数据可知，实施例1～11制得的负极材料包括活性物质，活性物质中的金属M的化合物中几乎不含有金属M的硅化物，负极材料的产气量均低于1mL，这是因为通过将制备硅氧原料与金属M原料的混合物在高温下进减压加热处理，形成M蒸气及硅氧原料蒸气，并通过让蒸气充分混合，可以减少局部M蒸气过量，减少局部硅氧原料被还原成硅单质及金属M的硅化物；可以有效控制硅氧化物中的Si微晶的尺寸，提高负极材料的倍率性能及循环稳定性。
实施例2的负极材料未进行碳包覆处理，负极材料的比表面积较大，负极材料在循环过程中与电解液之间的副反应增多，使得电池的倍率性能、循环性能略有下降。
实施例11虽然经历了酸洗过程，去除了M的硅化物，但酸洗过程并不会使酸洗前已产生的较大Si晶粒尺寸不会因此而下降，使材料的循环寿命下降，膨胀率增大。同时酸洗过程还会出现因为物质去除而造成的较大比表面积，导致首次嵌锂时生成更多的不可逆的Li4SiO4和Li2O以及SEI膜，首次容量和首次库仑效率均下降。从比热容还可以看出，酸洗后比热容低于0.2J/(g.K)，说明负极材料中含有低比热容的材料，此来源于蒸发过程气体未充分混合而产生的局部单质Si，此部分在酸洗中无法去除，会造成材料的循环寿命下降，膨胀率增大。由此可见，通过酸洗来去除合成产生的M的硅化物，性能远不及本申请在蒸发时将气体充分混合来防止M的硅化物的产生。
对比例1在制备过程中，将蒸发出来的气体立刻通往冷却区，并冷凝成硅氧化物，蒸发出来的气体未充分混合，导致局部的M的硅化物的生成，同时放出大量热使得Si晶粒尺寸大幅上升，负极材料的循环性能下降及膨胀率上升。
本申请虽然以较佳实施例公开如上，但并不是用来限定权利要求，任何本领域技术人员在不脱离本申请构思的前提下，都可以做出若干可能的变动和修改，因此本申请的保护范围应当以本申请权利要求所界定的范围为准。

Claims (15)

  1. 一种负极材料，其特征在于，所述负极材料包括活性物质，所述活性物质包括硅氧化物及金属M的化合物，所述金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种，所述金属M选自电负性<1.8的金属中的至少一种；
    10g所述负极材料与10mL的浓度为1mol/L盐酸混合后的产气量≤1mL。
  2. 根据权利要求1所述的负极材料，其特征在于，所述硅氧化物包括硅元素和氧元素，所述硅元素和所述氧元素的原子比为0～2，且不包括0。
  3. 根据权利要求1所述的负极材料，其特征在于，所述硅氧化物的化学通式为SiOx，其中0＜x≤2。
  4. 根据权利要求1～3任一项所述的负极材料，其特征在于，满足以下特征(1)至(7)中的至少一种：
    (1)所述金属M选自Li、K、Na、Mg、Ca、Al、La、Zn、Ti和Mn中的至少一种；
    (2)所述金属M为Mg；
    (3)所述硅氧化物中含有Si微晶，所述Si微晶的尺寸≤20nm；
    (4)所述负极材料的pH为8～14；
    (5)所述负极材料的比表面积≤30m2/g；
    (6)所述负极材料的中值粒径为1μm～20μm；
    (7)所述负极材料的wadell球形度Φ，0.3＜Φ＜1。
  5. 根据权利要求1～4任一项所述的负极材料，其特征在于，采用X射线衍射分析，所述负极材料具有特征峰A、特征峰B和/或特征峰C，其中，特征峰A表示Si特征峰或SiO特征峰，特征峰B表示金属M的氧化物特征峰，特征峰C表示金属M的硅酸盐特征峰；将金属M的硅化物的特征峰记为特征峰D，且特征峰D的最强峰与特征峰A的最强峰的峰高比值为I，0≤I＜0.05。
  6. 一种负极材料，其特征在于，所述负极材料包括活性物质，所述活性物质包括硅氧化物及金属M的化合物，所述金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种，所述金属M选自电负性<1.8的金属中的至少一种；
    采用X射线衍射分析，所述负极材料具有特征峰A、特征峰B和/或特征峰C，其中，特征峰A表示Si特征峰或SiO特征峰，特征峰B表示金属M的氧化物特征峰，特征峰C表示金属M的硅酸盐特征峰；将金属M的硅化物的特征峰记为特征峰D，且特征峰D的最强峰与特征峰A的最强峰的峰高比值为I，0≤I＜0.05。
  7. 根据权利要求6所述的负极材料，其特征在于，所述硅氧化物包括硅元素和氧元素，所述硅元素和氧元素的原子比为0～2，且不包括0。
  8. 根据权利要求6所述的负极材料，其特征在于，所述硅氧化物的化学通式为SiOx，其中0＜x≤2。
  9. 根据权利要求6～8任一项所述的负极材料，其特征在于，满足以下特征(1)至(7)中的至少一种：
    (1)所述金属M选自Li、K、Na、Mg、Ca、Al、La、Zn、Ti和Mn中的至少 一种；
    (2)所述金属M为Mg；
    (3)所述硅氧化物中含有Si微晶，所述Si微晶的尺寸≤20nm；
    (4)所述负极材料的pH为8～14；
    (5)所述负极材料的比表面积≤30m2/g；
    (6)所述负极材料的中值粒径为1μm～20μm；
    (7)所述负极材料的wadell球形度Φ，0.3＜Φ＜1。
  10. 根据权利要求1～8任一项所述的负极材料，其特征在于，满足以下特征(1)至(4)中的至少一种：
    (1)所述负极材料还包括位于所述活性物质至少部分表面的碳材料；
    (2)所述负极材料还包括位于所述活性物质至少部分表面的碳材料层，所述碳材料层的厚度为10nm～500nm；
    (3)所述负极材料中的碳元素的质量含量为1％～40％；
    (4)所述负极材料的孔隙率＜20％。
  11. 根据权利要求1～10任一项所述的负极材料，其特征在于，所述负极材料的比热容为0.2J/(g.K)～2.0J/(g.K)。
  12. 根据权利要求1～11任一项所述的负极材料，其特征在于，所述负极材料具有孔，其中，孔径<2nm的微孔在所有孔的总孔体积中的体积占比为1％～5％。
  13. 一种负极材料的制备方法，其特征在于，所述方法包括以下步骤：
    将包含金属M原料与硅氧原料的混合物进行减压加热处理，形成M蒸气及硅氧原料蒸气，并使得蒸气充分混合1min～600min，其中，所述金属M选自电负性<1.8的金属中的至少一种；
    混合后的蒸气气体进行冷却处理，得到活性物质；所述活性物质包括硅氧化物及金属M的化合物，所述金属M的化合物包括金属M的氧化物、金属M的硅酸盐中的至少一种。
  14. 根据权利要求13所述的制备方法，其特征在于，包含以下特征(1)至(10)中的至少一种：
    (1)所述金属M原料选自金属M单质及含金属M的氧化物中的至少一种；
    (2)所述金属M选自Li、K、Na、Mg、Ca、Al、La、Zn、Ti和Mn中的至少一种；
    (3)所述硅氧原料包括Si、SiOy和SiO2的混合物、SiOy和Si的混合物、Si和SiO2的混合物中的至少一种，其中，0＜y＜2；
    (4)所述金属M原料中的金属M的摩尔量为nM，所述硅氧原料中的Si的摩尔量为nSi，且nM：nSi＝(0.2～1)：1；
    (5)所述减压加热处理的温度为900℃～2000℃；
    (6)所述减压加热处理的气压为0.1Pa～1000Pa；
    (7)所述冷却处理的温度为500℃～900℃；
    (8)所述减压加热处理的气压为0.1Pa～1000Pa；
    (9)所述硅氧化物包括硅元素和氧元素，所述硅元素和氧元素的原子比为0～2， 且不包括0；
    (10)所述硅氧化物的化学通式为SiOx，其中0＜x≤2。
  15. 一种电池，其特征在于，包括如权利要求1～12任一项的负极材料或如权利要求13～14任一项的制备方法制得的负极材料。
PCT/CN2023/138789 2022-12-16 2023-12-14 负极材料及其制备方法、锂离子电池 WO2024125601A1 (zh)

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