WO2023165415A1 - 一种负极活性材料及其制备方法和应用 - Google Patents

一种负极活性材料及其制备方法和应用 Download PDF

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WO2023165415A1
WO2023165415A1 PCT/CN2023/078030 CN2023078030W WO2023165415A1 WO 2023165415 A1 WO2023165415 A1 WO 2023165415A1 CN 2023078030 W CN2023078030 W CN 2023078030W WO 2023165415 A1 WO2023165415 A1 WO 2023165415A1
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active material
negative electrode
electrode active
silicon
carbon film
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PCT/CN2023/078030
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English (en)
French (fr)
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罗姝
王岑
李喆
查道松
张和宝
叶兰
赵双宇
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博赛利斯（南京）有限公司
博赛利斯（合肥）有限公司
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Publication of WO2023165415A1 publication Critical patent/WO2023165415A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—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
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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 battery field, in particular, to a negative electrode active material for a secondary battery, a preparation method thereof, an electrode and a battery.
  • silicon negative electrode active materials one is simple silicon (including nano-silicon, porous silicon, amorphous silicon, etc.) and its composite material with carbon materials; the other is silicon and other metals (such as iron, manganese, Nickel, chromium, cadmium, tin, copper, etc.), non-metallic (carbon, nitrogen, phosphorus, boron, etc.)
  • silicon and other metals such as iron, manganese, Nickel, chromium, cadmium, tin, copper, etc.
  • non-metallic carbon, nitrogen, phosphorus, boron, etc.
  • Siloxanes also have their own specific problems.
  • a thicker SEI film is often formed on the particle surface due to many side reactions with the electrolyte; at the same time, lithium silicate and lithium oxide and other substances that cannot be reversibly delithiated will be generated inside the particle, resulting in The irreversible loss of lithium ions within the battery.
  • the above two types of irreversible reactions lead to the low initial coulombic efficiency of lithium-ion batteries containing silicon-oxygen compound anodes, which limits the improvement of the energy density of the full battery.
  • silicon oxide compounds also suffer from low ionic and electronic conductivity, and low Coulombic efficiency during battery cycling.
  • the surface of silicon oxide particles has a significant performance on the stability of its electrochemical performance, including the interface reaction between the surface of silicon oxide particles and the electrolyte. stress stability, the susceptibility of the surface of silicon oxide particles to the precipitation of transition metals, etc.
  • the above-mentioned interface stability significantly affects the cycle life of the silicon-containing battery system, the charge-discharge and storage stability in a high-temperature environment, and the cell expansion. Due to the existence of side reactions at the interface, serious gas production may occur after the battery core has undergone multiple charge-discharge cycles or exposed to high-temperature environments, causing safety risks. Therefore, the preparation of silicon oxide particles with stable surface properties is one of the key issues that the industry urgently needs to solve.
  • the present invention provides a negative electrode active material, which includes negative electrode active material particles, the negative electrode active material particles include a silicon-based material inner core, and carbon covering the surface of the silicon-based material inner core film layer; the core of the silicon-based material contains a silicon oxide compound;
  • the ratio of the median particle diameter D 50 to the calculated particle diameter D c of the negative electrode active material satisfies: D 50 /D c ⁇ 10, preferably D 50 /D c ⁇ 5, more preferably D 50 /D c ⁇ 2.5.
  • the specific surface area S of the negative electrode active material is 0.1-15 m 2 /g, preferably 0.3-10 m 2 /g, more preferably 0.3-6 m 2 /g.
  • the median particle size D50 of the negative electrode active material is 0.2-20 ⁇ m, preferably 1-15 ⁇ m, more preferably 3-13 ⁇ m;
  • the particle size distribution span value of the negative electrode active material is A ⁇ 2.0, preferably ⁇ 1.5, further Preferably ⁇ 1.2.
  • the core of the silicon-based material further contains lithium element.
  • the content of lithium element in the negative electrode active material particles is 0.1-20wt%, preferably 2-18wt%, more preferably 4-15wt%.
  • the content of silicon in the negative electrode active material particles is 30-80wt%, preferably 35-65wt%, more preferably 40-65wt%.
  • the negative electrode active material particles also include elemental silicon nanoparticles, and the median diameter of the elemental silicon nanoparticles dispersed in the inner core of the silicon-based material is between 0.1-35 nm, preferably 0.5-20 nm, more preferably 1-15 nm.
  • the thickness of the carbon film layer is 0.001-5 ⁇ m, preferably 0.005-2 ⁇ m, more preferably 0.01-1 ⁇ m.
  • the mass proportion of the carbon film layer is 0.01-20 wt%, preferably 0.1-15 wt%, more preferably 1-12 wt%, of the total mass of the negative electrode active material particles.
  • the present invention also provides an electrode comprising the above-mentioned negative electrode active material.
  • the present invention also provides a battery comprising the above electrode.
  • the present invention also provides a method for preparing the above negative electrode active material, comprising:
  • a carbon film layer is coated on the surface of the silicon oxide compound particles.
  • the above method also includes:
  • Lithium doping is performed on the silicon oxide compound particles coated with the carbon film layer.
  • the negative electrode active material carbon film provided by the invention has fewer defects, higher interface stability in an electrochemical system, and has more excellent cycle stability, high temperature performance, and lower expansion and gas production.
  • Figure 1 is a flow chart of the preparation process provided by an embodiment of the present invention.
  • Fig. 2 is a flow chart of the preparation process provided by another embodiment of the present invention.
  • the present invention provides a negative electrode active material for batteries, which has negative electrode active material particles.
  • the negative electrode active material particles contain a silicon-based material inner core and a carbon film layer covering the surface of the silicon-based material inner core.
  • the silicon-based material inner core contains silicon-oxygen compound, and the silicon-based material inner core can be silicon-oxygen compound particles or silicon-oxygen compound particles intercalated with lithium, that is, the silicon-based material inner core can also include lithium element.
  • A (D 90 -D 10 )/D 50 , wherein, the particle diameter D 10 is the particle diameter at which the particle cumulative distribution is 10%, that is, the volume content of particles smaller than this particle diameter accounts for 10% of all particles; the median particle diameter D 50 is the particle size at which the cumulative distribution of particles is 50%, that is, 50% of the particles The particle size exceeds this value, and 50% of the particles are lower than this value; the particle size D90 is the particle size where the particle cumulative distribution is 90%, that is, the volume content of particles smaller than this particle size accounts for 90% of all particles.
  • the inventors of the present invention found in their research that the surface properties of the negative electrode active material particles used in batteries, especially their interface stability in the electrochemical system, have a significant correlation with the structure of the carbon film layer coated on the surface.
  • Common structural defects of the carbon film layer include pores, impurities in the carbon film layer, disorder of the crystal structure of the carbon layer, more carbon-hydrogen/carbon-oxygen/carbon-sulfur bonds, higher surface wrinkle, cracks, etc.
  • the above-mentioned structural defects may lead to an increase in the specific surface area of the negative electrode active material, an increase in side reactions with the electrolyte, and a stronger interaction with the transition metal dissolved in the positive electrode, making the cycle stability and high temperature stability of the negative electrode active material , expansion rate and other electrochemical performance deterioration. Due to the existence of side reactions at the interface, severe flatulence may occur after the battery core undergoes cycling or high temperature environment, causing safety risks.
  • the ratio of the median particle diameter D 50 and the calculated particle diameter D c of the negative electrode active material provided by the present invention satisfies: D 50 /D c ⁇ 15, at this moment, its carbon film layer defect is less, thus in the electrochemical system interface Higher stability, which has more excellent cycle stability, high temperature performance and lower expansion and gas production.
  • D 50 /D c ⁇ 10 preferably D 50 /D c ⁇ 5, more preferably D 50 /D c ⁇ 2.5.
  • the specific surface area S of the negative electrode active material is
  • 0.1-15m 2 /g preferably 0.3-10m 2 /g, more preferably 0.3-6m 2 /g.
  • the median diameter D 50 of the negative electrode active material is 0.2-20 ⁇ m, preferably 1-15 ⁇ m, more preferably 3-13 ⁇ m.
  • the particle size distribution span value A of the negative electrode active material is ⁇ 2.0, preferably ⁇ 1.5, more preferably ⁇ 1.2.
  • the silicon element content in the negative electrode active material particles can be 30-80wt%, preferably 35-65wt%, more preferably 40-65wt%, so that the material has a very high reversible capacity .
  • the lithium element content in the core of the silicon-based material can be 0.1-20wt%, preferably 2-18wt%, more preferably 4-15wt%.
  • the negative electrode active material particles also contain elemental nano-silicon. It can be uniformly dispersed in the inner core of the silicon-based material.
  • elemental nano-silicon may exist in the core of the silicon-based material in the form of nanoparticles, and its median particle size may be between 0.1-35 nm, preferably 0.5-20 nm, more preferably 1-15 nm.
  • the thickness of the carbon film layer may be between 0.001-5 ⁇ m, preferably between 0.005-2 ⁇ m, and more preferably between 0.01-1 ⁇ m.
  • the existence of the carbon film layer can effectively improve the conductivity of the particles, reduce the contact resistance between the particles in the negative electrode sheet, the negative electrode sheet and the current collector, thereby improving the lithium-deintercalation efficiency of the material, reducing the polarization of the lithium-ion battery and promoting its cyclic stability.
  • the mass proportion of the carbon film layer may be 0.01-20 wt%, preferably 0.1-15 wt%, more preferably 1-12 wt%, of the total mass of the negative electrode active material particles.
  • the negative electrode active material used in the battery provided by the present application has relatively stable surface characteristics, so it has high interface stability with the electrolyte, and has less interaction with the transition metal precipitated from the positive electrode.
  • the battery prepared by using the negative electrode active material has the advantages of stable cycle, excellent high temperature performance, low expansion and less gas production.
  • Fig. 1 is a flow chart of the preparation process of the negative electrode active material according to an exemplary embodiment of the present invention.
  • S101 Prepare silicon oxide particles.
  • the concrete process of preparation can adopt following steps to carry out:
  • the mixture of metal silicon powder and silicon dioxide powder is heated in the temperature range of 900° C. to 1600° C. in an inert gas atmosphere or under reduced pressure to generate silicon oxide gas.
  • the molar ratio of metal silicon powder and silicon dioxide powder is set in the range of 0.5-1.5.
  • the gas generated by the heating reaction of the raw materials will be deposited on the adsorption plate.
  • the temperature in the reaction furnace is lowered to below 100°C, the sediment is taken out, crushed and powdered using equipment such as a ball mill, jet mill, etc., to obtain silica compound particles.
  • the siloxane particles referred to in the present invention include silicon oxide (silicon monoxide and/or silicon dioxide) materials.
  • the silicon-oxygen stoichiometric ratio in the silicon-oxygen compound particles may be 1:0.4-1:2, optionally 1:0.6-1:1.5, further optionally 1: 0.8-1:1.2.
  • the structure of the carbon film layer on the particle surface has a great relationship with its preparation process. Different process parameters (such as carbon source type, coating temperature, atmosphere, air pressure, heating rate, carbon content, magnetic field, electric field, etc.) and different furnace structure designs
  • the carbon film layer obtained under the above method has significant structural differences, and the degree of defects is also significantly different.
  • the silicon oxide compound may be a silicon oxide compound that has not been disproportionated, or a silicon oxide compound that has undergone a disproportionation heat treatment.
  • the disproportionation heat treatment temperature may be 600-1100°C, optionally 700-1000°C, more preferably 800-1000°C.
  • the carbon film layer can be directly obtained by chemical vapor deposition (CVD).
  • the carbon source used in CVD is hydrocarbon gas, and the decomposition temperature of hydrocarbon gas may be 600-1100°C, preferably 700-1000°C, more preferably 800-1000°C.
  • the choice of carbon source, carbonization temperature, carbon source addition, gas ratio and flow rate all have a significant impact on the final carbon film structure.
  • the air pressure (vacuum degree), atmosphere ratio and unique airflow direction of the carbon film growth process it also has a significant impact on the structure of the carbon film.
  • a mixture of carbon source gas and inert gas or reducing gas (such as argon, nitrogen, helium, hydrogen, etc.) is fed in a certain proportion, and the quality of the obtained carbon film is better than that of pure carbon source gas.
  • controlling the volume ratio of the carbon source gas in the mixed gas is not higher than 90%, preferably not higher than 75%, more preferably not higher than 65%, which is conducive to obtaining better coating quality and better uniformity.
  • Carbon film layer is also greatly increase the uniformity of the carbon film layer, and obtain a carbon film layer with higher smoothness and density.
  • the carbon film layer can also be obtained by first carrying out carbon reaction coating and then carrying out heat treatment and carbonization in a non-oxidizing atmosphere.
  • the carbon reaction coating method can use mechanical fusion machine, VC mixer, coating kettle, Any one of spray drying, sand mill or high-speed dispersing machine, the solvent used for coating is water, methanol, ethanol, isopropanol, n-butanol, ethylene glycol, ether, acetone, N-methylpyrrolidone , methyl butanone, tetrahydrofuran, benzene, toluene, xylene, N,N-dimethylformamide, N,N-dimethylacetamide, and a combination of chloroform.
  • the carbon source may be one or a combination of coal tar pitch, petroleum pitch, polyvinyl alcohol, epoxy resin, polyacrylonitrile, polymethylmethacrylate, glucose, sucrose, polyacrylic acid, and polyvinylpyrrolidone.
  • the equipment used for heat treatment and carbonization can be any one of rotary furnace, ladle furnace, roller kiln, pusher kiln, atmosphere box furnace or tube furnace.
  • the heat treatment carbonization temperature can be 600-1100°C, preferably 700-1000°C, more preferably 800-1000°C, and the holding time is 0.5-24 hours.
  • the non-oxidizing atmosphere may be provided by at least one of the following gases: nitrogen, argon, hydrogen or helium.
  • the selection of carbon source, carbonization temperature, the amount of carbon source added, the heating rate, the design of heating and heat preservation procedures, the strength of mechanical stirring and the selection of coating equipment all have a great impact on the final carbon film.
  • Structure has a significant effect.
  • designing a heating program for multi-temperature section insulation is conducive to obtaining a carbon film-coated structure with better quality.
  • Selecting a suitable intermediate heat preservation program allows the carbon source compound to fully melt, have suitable fluidity, and perform a preliminary coking reaction, which is conducive to obtaining a more uniform and dense carbon film coating.
  • dynamic carbonization is preferred, that is, the material is dynamically stirred during the heating and heat preservation process, so as to promote the effective discharge of volatiles in the carbonization process of the carbon source, and it is also conducive to obtaining a more compact structure and fewer defects. Carbon film layer.
  • FIG. 2 shows a process flow for preparing negative electrode active materials according to another exemplary embodiment of the present invention. Include the following steps:
  • S201 Prepare silicon oxide particles.
  • the doping (intercalation of lithium element) of the silicon-oxygen compound particles can be done by means of electrochemical doping, liquid phase doping and thermal doping.
  • the doping atmosphere of the lithium element is a non-oxidizing atmosphere, and the non-oxidizing atmosphere is composed of at least one of nitrogen, argon, hydrogen or helium.
  • the method of inserting lithium element can be:
  • An electrochemical cell which includes four components of a bath, an anode electrode, a cathode electrode and a power supply, and the anode electrode and the cathode electrode are respectively connected to two ends of the power supply. Simultaneously, the anode electrode is connected to a lithium source, and the cathode electrode is connected to a container containing silicon oxide particles.
  • the bath is filled with an organic solvent, and the lithium source (anode electrode) and the container containing silicon oxide particles (cathode electrode) are immersed in the organic solvent. After the power is turned on, due to the occurrence of electrochemical reaction, lithium ions are intercalated into the silicon oxide compound structure to obtain lithium-doped modified silicon oxide compound particles.
  • organic solvent can adopt ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, propyl acetate, ethyl propionate Solvents such as ester, propyl propionate, dimethyl sulfoxide, etc.
  • the organic solvent also contains electrolyte lithium salt, such as lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), etc. can be used.
  • the above-mentioned lithium source can be lithium foil, or lithium compounds, such as lithium carbonate, lithium oxide, lithium hydroxide, lithium cobaltate, lithium iron phosphate, lithium manganate, lithium vanadium phosphate, lithium nickelate, etc.
  • the electron transfer catalyst includes biphenyl, naphthalene and the like.
  • the ether-based solvent includes methyl butyl ether, ethylene glycol butyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and the like.
  • the constant temperature reaction temperature is 25-200°C.
  • the non-oxidizing atmosphere is provided by at least one of the following gases: nitrogen, argon, hydrogen or helium.
  • the silicon oxide compound particles are uniformly mixed with the lithium-containing compound, and then heat-treated in a non-oxidizing atmosphere.
  • the lithium-containing compound includes lithium hydroxide, lithium carbonate, lithium oxide, lithium peroxide, lithium hydride, lithium nitrate, lithium acetate, lithium oxalate and the like.
  • the mixing method adopts any one of a high-speed disperser, a high-speed stirring mill, a ball mill, a conical mixer, a spiral mixer, a stirring mixer or a VC mixer.
  • the equipment used for the heat treatment is any one of a rotary furnace, a ladle furnace, a liner furnace, a roller kiln, a pusher kiln, an atmosphere box furnace or a tube furnace.
  • the temperature of the heat treatment is 400-850°C, preferably 550-800°C; the holding time is 1-12 hours; the heating rate is greater than 0.1°C per minute, less than or equal to 10°C per minute.
  • the non-oxidizing atmosphere is provided by at least one of the following gases: nitrogen, argon, hydrogen or helium.
  • the step of intercalating the lithium element is carried out after coating the carbon film layer, which can inhibit the growth of silicon crystal grains in the silicon oxide compound during heat treatment.
  • the nano-scale elemental silicon particles are evenly dispersed and fixed in the lithium silicate compound or silicon oxide matrix, which can effectively inhibit the expansion of silicon nanoparticles and prevent the silicon particles from gradually merging into larger particles during charging and discharging.
  • the size of the particles thereby reducing the expansion deformation of the battery during the cycle and reducing the electrical failure of the silicon material, so that the cycle expansion of the lithium-ion secondary battery using this material is small and the cycle is stable.
  • the step of coating the carbon film layer is carried out before intercalating the lithium element, which is beneficial to obtain a carbon film layer with better quality and more complete coating.
  • Homogenization and pole piece production take 30 parts of the above-mentioned negative electrode active material, 64 parts of artificial graphite, 2.5 parts of conductive additives, and 3.5 parts of binder, perform homogenization coating in an aqueous system, then dry and roll, A negative electrode sheet containing the negative electrode active material of the present application was obtained.
  • the discharge capacity is D1.
  • the discharge capacity of the cell before high-temperature storage is D0.
  • the capacity retention ratio D1/D0.
  • the high-temperature storage evaluation results of the full battery containing the negative active material are as follows: after 60 days of high-temperature storage at 60° C., the thermal expansion rate of the battery cell is 22.7%, and the battery cell has floating gas. The capacity retention rate after high temperature storage is 78.6%, and the capacity recovery rate is 86.3%.
  • silicon oxide particles are used as raw materials, and different carbon film coating processes are used, including adjusting the choice of carbon source, carbonization temperature, carbon source addition, and air pressure (vacuum degree) , atmosphere ratio, airflow direction, and heating rate, design of heating and heat preservation programs, strength of mechanical stirring, selection of equipment, etc., to obtain silicon oxide powders coated with different carbon films in Examples 1-9 to 1-17.
  • the powder, metal lithium strips and biphenyl were added into a sealable glass container, and then methyl butyl ether was added and stirred for reaction under an argon atmosphere. After the reaction is completed and dried, the obtained powder is placed in an argon atmosphere for heat treatment, and the temperature is raised to 680°C at a rate of 2°C per minute, and then kept for 10 hours, and then naturally cooled to obtain lithium-doped silicon oxide compound powder.
  • Example 1-16 Using the product of Example 1-16 as the raw material, it is similar to Example 2-1, but the heat treatment process after lithium doping is changed to: use a heating rate of 5°C per minute to raise the temperature to 720°C, and then keep it warm After 3 hours, the lithium-doped silicon-oxygen compound powder can be obtained after natural cooling.
  • Example 1-16 Using the product of Example 1-16 as the raw material, it is similar to Example 2-1, but the heat treatment process after doping with lithium is changed to: use a heating rate of 10°C per minute to raise the temperature to 720°C, then keep it warm for 6 hours, and then Lithium-doped silicon oxide powder can be obtained after natural cooling.
  • Example 1-16 Using the product of Example 1-16 as the raw material, it is similar to Example 2-1, but the heat treatment process after doping with lithium is changed to: use a heating rate of 10°C per minute to raise the temperature to 850°C, then keep it warm for 2 hours, and then Lithium-doped silicon oxide powder can be obtained after natural cooling.
  • lithium-containing compounds such as lithium oxide, lithium hydride, lithium hydroxide, lithium carbonate, etc.
  • place the mixed powder under an argon atmosphere for heat treatment and use 2°C
  • the heating rate per minute is raised to 400° C. for 3 hours, and then heated to 650° C. for 10 hours. After natural cooling, a lithium-containing silicon oxide compound coated with a carbon film is obtained.
  • Lithium-doped silicon oxide powder can be obtained after natural cooling.
  • Lithium-doped silicon oxide powder can be obtained after natural cooling.

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Abstract

本发明提供了一种负极活性材料及其制备方法和应用。其中，该负极活性材料，包含负极活性物质颗粒，负极活性物质颗粒包括硅基材料内核，以及覆盖硅基材料内核表面的碳膜层；硅基材料内核包含硅氧化合物；负极活性材料的中值粒径D50和计算粒径Dc的比值满足：D50/Dc≤15，其中计算粒径Dc＝7×A/S，A为负极活性材料的粒径分布跨度值，S为负极活性材料的比表面积。本发明提供的负极活性材料碳膜层缺陷较少、在电化学体系中界面稳定性较高，具有更加优异的循环稳定性、高温性能和较低的膨胀及产气。

Description

一种负极活性材料及其制备方法和应用 技术领域
本申请涉及电池领域，具体地，涉及一种用于二次电池的负极活性材料、其制备方法、电极以及电池。
背景技术
目前针对硅负极活性材料的开发主要有三种：一是单质硅(包括纳米硅、多孔硅、非晶硅等)及其同碳材料的复合材料；二是硅与其它金属(如铁、锰、镍、铬、镉、锡、铜等)、非金属(碳、氮、磷、硼等)成分组合而成的合金材料；三是硅氧化合物及其同碳材料的复合材料。然而第一、第二种材料由于单质硅自身的诸多原因，所得的电极材料的循环性能差，且容易粉化、容易与集流体分离。
硅氧化合物由于具有较多的非活性物质，导致其容量低于单质硅负极活性材料；然而同时，由于这些非活性组分的存在，硅在循环过程中的膨胀被非活性相有效抑制，因此其循环稳定性具有明显优势。
硅氧化合物也存在其特定的问题。该材料在首次嵌锂时，颗粒表面由于与电解液发生较多副反应，往往会生成较厚的SEI膜；同时，颗粒内部会生成硅酸锂和氧化锂等无法可逆脱锂的物质，造成电池内锂离子的不可逆损失。上述两类不可逆反应导致含硅氧化合物负极的锂离子电池首次库伦效率较低，从而限制了全电池能量密度的提升。此外，硅氧化合物还存在离子和电子导电率较低、电池循环过程中库伦效率较低等问题。
另一方面，大量的研究工作发现，硅氧化合物颗粒的表面对其电化学性能的稳定性具有显著的性能，其中包括硅氧颗粒表面与电解液的界面反 应稳定性，硅氧颗粒表面对于过渡金属析出的敏感性等。上述界面稳定性显著地影响含硅电池体系的循环寿命、在高温环境下的充放电以及存储稳定性、以及电芯膨胀等。由于界面副反应的存在，电芯在经历多次充放电循环或暴露高温环境后，还有可能发生严重的产气，引发安全风险。因此，制备具有稳定表面特性的硅氧化合物颗粒是行业急需解决的关键问题之一。
背景技术部分的内容仅仅是申请人所知晓的技术，并不代表本领域的现有技术。
发明内容
为了解决上述技术问题中的至少一个，本发明提供了一种负极活性材料，其包含负极活性物质颗粒，所述负极活性物质颗粒包括硅基材料内核，以及覆盖所述硅基材料内核表面的碳膜层；所述硅基材料内核包含硅氧化合物；
所述负极活性材料的中值粒径D50和计算粒径Dc的比值满足：D50/Dc≤15，其中所述计算粒径Dc＝7×A/S，A为所述负极活性材料的粒径分布跨度值，S为所述负极活性材料的比表面积。
在本发明的一些实施例中，所述负极活性材料的中值粒径D50和计算粒径Dc的比值满足：D50/Dc≤10，优选D50/Dc≤5，进一步优选D50/Dc≤2.5。
在本发明的一些实施例中，所述负极活性材料的比表面积S为0.1-15m2/g，优选为0.3-10m2/g，进一步优选为0.3-6m2/g。
在本发明的一些实施例中，所述负极活性材料的中值粒径D50为0.2-20μm，优选为1-15μm，进一步优选为3-13μm；
所述负极活性材料的粒径分布跨度值A≤2.0，优选为≤1.5，进一步 优选为≤1.2。
在本发明的一些实施例中，所述硅基材料内核还包含锂元素。
在本发明的一些实施例中，所述负极活性物质颗粒中的锂元素含量为0.1-20wt％，优选为2-18wt％，更优选为4-15wt％。
在本发明的一些实施例中，所述负极活性物质颗粒中的硅元素含量为30-80wt％，优选为35-65wt％，更优选为40-65wt％。
在本发明的一些实施例中，所述负极活性物质颗粒还包含有单质硅纳米颗粒，分散于所述硅基材料内核内的单质硅纳米颗粒的中值粒径在0.1-35nm之间，优选为0.5-20nm，进一步优选为1-15nm。
在本发明的一些实施例中，所述碳膜层的厚度为0.001-5μm，优选为0.005-2μm，更优选为0.01-1μm。
在本发明的一些实施例中，所述碳膜层的质量占比为所述负极活性物质颗粒总质量的0.01-20wt％，优选为0.1-15wt％，更优选为1-12wt％。
本发明还提供了一种电极，其包括上述负极活性材料。
本发明还提供了一种电池，其包括上述电极。
本发明还提供了一种制备上述负极活性材料的方法，包括：
准备硅氧化合物颗粒；以及
在所述硅氧化合物颗粒表面包覆碳膜层。
在本发明的一些实施例中，上述方法还包括：
对包覆有所述碳膜层的所述硅氧化合物颗粒进行锂掺杂。
本发明提供的负极活性材料碳膜层缺陷较少、在电化学体系中界面稳定性较高，具有更加优异的循环稳定性、高温性能和较低的膨胀及产气。
本发明的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本发明的实践了解到。
附图说明
图1为本发明一实施例提供的制备工艺流程图。
图2为本发明另一实施例提供的制备工艺流程图。
具体实施方式
以下结合附图和实施例，对本发明的具体实施方式进行更加详细的说明，以便能够更好地理解本发明的方案以及其各个方面的优点。然而，以下描述的具体实施方式和实施例仅是说明的目的，而不是对本发明的限制。
特别需要指出的是，所有类似的替换和改动对本领域技术人员来说是显而易见的，它们都被视为包括在本发明。本发明的方法及应用已经通过较佳实施例进行了描述，相关人员明显能在不脱离本发明内容、精神和范围内对本文所述的方法和应用进行改动或适当变更与组合，来实现和应用本发明技术。
【负极活性材料】
本发明提供了一种用于电池的负极活性材料，其具有负极活性物质颗粒。该负极活性物质颗粒含有硅基材料内核，以及覆盖硅基材料内核表面的碳膜层。硅基材料内核包含硅氧化合物，该硅基材料内核可为硅氧化合物颗粒或嵌有锂的硅氧化合物颗粒，即该硅基材料内核还可包含锂元素。
本发明提供的负极活性材料的中值粒径D50和计算粒径Dc的比值满足：D50/Dc≤15，其中计算粒径Dc＝7×A/S，A为所述负极活性材料的粒径分布跨度值，S为所述负极活性材料的比表面积。A＝(D90-D10)/D50，其中，粒径D10为颗粒累积分布为10％的粒径，即小于此粒径的颗粒体积含量占全部颗粒的10％；中值粒径D50为颗粒累积分布为50％的粒径，即有50％的颗 粒超过此值，有50％的颗粒低于此值；粒径D90为颗粒累积分布为90％的粒径，即小于此粒径的颗粒体积含量占全部颗粒的90％。
本发明发明人等在研究中发现，用于电池的负极活性物质颗粒的表面特性尤其是其在电化学体系中的界面稳定性，与其表面包覆的碳膜层结构具有显著的相关性。
常见的碳膜层结构缺陷包括碳膜层内的孔隙、杂质、碳层晶体结构的无序性、含有较多的碳氢/碳氧/碳硫键、表面褶皱度较高、裂纹等等。上述结构缺陷可能会导致负极活性材料的比表面积增大，与电解液的副反应增多，与正极溶出的过渡金属发生更强的相互作用，使得所述负极活性材料的循环稳定性、高温稳定性、膨胀率等电化学性能恶化。由于界面副反应的存在，电芯在经历循环或高温环境后，还有可能发生严重的胀气，引发安全风险。
本发明提供的负极活性材料的中值粒径D50和计算粒径Dc的比值满足：D50/Dc≤15，此时，其碳膜层缺陷较少，因而在电化学体系中界面稳定性较高，其具有更加优异的循环稳定性、高温性能和较低的膨胀及产气。
在本发明的一些实施例中，D50/Dc≤10，优选D50/Dc≤5，进一步优选D50/Dc≤2.5。该值越小，表明负极活性材料表面的碳膜层缺陷越小。
在本发明的一些实施例中，负极活性材料的比表面积S为
0.1-15m2/g，优选为0.3-10m2/g，进一步优选为0.3-6m2/g。
在本发明的一些实施例中，负极活性材料的中值粒径D50为0.2-20μm，优选为1-15μm，进一步优选为3-13μm。
在本发明的一些实施例中，负极活性材料的粒径分布跨度值A≤2.0，优选为≤1.5，进一步优选为≤1.2。
在本发明的一些实施例中，负极活性物质颗粒中的硅元素含量可为30-80wt％，优选为35-65wt％，进一步优选为40-65wt％，因此使得该材料具有很高的可逆容量。
在本发明的一些实施例中，硅基材料内核中的锂元素含量可为 0.1-20wt％，优选为2-18wt％，进一步优选为4-15wt％。
在本发明的一些实施例中，负极活性物质颗粒内还包含有单质纳米硅。其可以均匀分散于硅基材料内核内。其中，单质纳米硅可以以纳米颗粒的形式存在于硅基材料内核内，其中值粒径可在0.1-35nm之间，优选为0.5-20nm，更优选为1-15nm。该粒径范围内的颗粒在经历锂离子嵌入脱出的循环时，颗粒发生的膨胀较小且不易破裂，使得使用该材料的锂离子二次电池的循环膨胀小且循环稳定。
在本发明的一些实施例中，碳膜层厚度可在0.001-5μm之间，优选为0.005-2μm之间，进一步优选为0.01-1μm之间。碳膜层的存在可以有效提高颗粒的电导率，降低负极极片中颗粒之间、负极极片和集流体的接触电阻，从而提高材料的脱嵌锂效率，降低锂离子电池的极化并促进其循环稳定性。
在本发明的一些实施例中，碳膜层的质量占比可为负极活性物质颗粒的总质量的0.01-20wt％，优选为0.1-15wt％，更优选为1-12wt％。
本申请所提供用于电池的负极活性材料具有相对稳定的表面特性，因此其和电解液的界面稳定性较高，与正极析出的过渡金属的相互作用较少。利用该种负极活性材料制备的电池具有循环稳定、高温性能优异、膨胀较低及产气少等优势。
【负极活性材料的制备方法】
图1为本发明一示例性实施例的负极活性材料的制备工艺流程图。
S101：准备硅氧化合物颗粒。
制备的具体过程可采用如下步骤进行：
首先，在惰性气体氛围或者减压条件下，将金属硅粉末与二氧化硅粉末的混合物在900℃-1600℃的温度范围内加热，从而产生氧化硅气体。金属硅粉末和二氧化硅粉末的摩尔比设定在0.5-1.5的范围。由原料加热反应产生的气体会沉积在吸附板上。在将反应炉内温度降低到100℃以下时取出沉积物，使用球磨机、气流粉碎机等设备进行粉碎和粉末化，得到硅氧 化合物颗粒。
本发明中所指的硅氧化合物颗粒包括氧化硅(一氧化硅和/或二氧化硅)材料。在本发明的示例性实施例中，硅氧化合物颗粒中的硅氧化学计量比可为1:0.4-1:2，可选地为1:0.6-1:1.5，进一步可选地为1:0.8-1:1.2。当然，除硅氧之外还可以有其他微量的杂质元素。
S102：在硅氧化合物颗粒表面包覆碳膜层。
颗粒表面碳膜层的结构与其制备工艺有非常大的关系，不同工艺参数(如碳源种类、包覆温度、气氛、气压、升温速度、碳含量、磁场、电场等)和不同炉体结构设计下得到的碳膜层具有显著的结构差异，其缺陷的程度亦有明显的不同。
根据示例性实施例，硅氧化合物可以是未经歧化的硅氧化合物，也可以经过歧化热处理的硅氧化合物。其中，歧化热处理温度可为600-1100℃，可选地为700-1000℃，更优选为800-1000℃。
本发明中，碳膜层可通过化学气相沉积(CVD)的方式直接得到。CVD所采用的碳源为碳氢化合物气体，碳氢化合物气体的分解温度可以为600-1100℃，优选为700-1000℃，更优选为800-1000℃。在上述碳膜包覆过程中，碳源的选择、碳化温度、碳源的添加量、气体的比例和流速等都对最后碳膜的结构有显著的影响。此外，通过控制碳膜生长过程的气压(真空度)、气氛比例以及设计独特的气流方向，亦对碳膜的结构有明显的影响。优选地，按一定比例通入碳源气体和惰性气体或还原性气体(如氩气、氮气、氦气、氢气等)的混合物，其得到的碳膜质量优于仅通入纯碳源气体。进一步地，控制碳源气体在混合气中的体积占比不高于90％，优选不高于75％，更优选不高于65％，有利于得到包覆质量更好、均匀性更好的碳膜层。此外，降低碳膜生长过程的炉体气压，使其保持一定程度的负压(真空度)，亦能大大增加碳膜层的均匀性，得到平滑度和致密性更高的碳膜层。
碳膜层也可以通过先进行碳反应包覆再在非氧化气氛中进行热处理碳化的方法得到。碳反应包覆方法可以采用机械融合机、VC混合机、包覆釜、 喷雾干燥、砂磨机或高速分散机中的任意一种，包覆时选用的溶剂是水、甲醇、乙醇、异丙醇、正丁醇、乙二醇、乙醚、丙酮、N-甲基吡咯烷酮、甲基丁酮、四氢呋喃、苯、甲苯、二甲苯、N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、三氯甲烷中的一种或多种的组合。碳源可以是煤沥青、石油沥青、聚乙烯醇、环氧树脂、聚丙烯腈、聚甲基丙烯酸甲酯、葡萄糖、蔗糖、聚丙烯酸、聚乙烯吡咯烷酮中的一种或多种的组合。热处理碳化所用设备可以为回转炉、钢包炉、辊道窑、推板窑、气氛箱式炉或管式炉中的任意一种。热处理碳化的温度可以为600-1100℃，优选为700-1000℃，更优选为800-1000℃，保温时间为0.5-24小时。非氧化气氛可以由下述至少一种气体提供：氮气、氩气、氢气或氦气。在上述碳膜包覆过程中，碳源的选择、碳化温度、碳源的添加量、升温速度、升温和保温程序的设计、机械搅拌的强度及包覆设备的选择等都对最后碳膜的结构有显著的影响。优选地，设计多温段保温的升温程序有利于得到质量更好的碳膜包覆结构。选择合适的中间保温程序，使得碳源化合物可以充分地熔融，具有合适的流动性，并进行初步排焦反应，有利于得到更加均匀和致密的碳膜包覆层。此外，在热处理碳化过程中，优选动态碳化，即升温和保温的过程中使材料动态搅动，促使碳源碳化过程中的挥发分有效排出，亦有利于得到结构更为紧致、缺陷更少的碳膜层。
图2示出了本发明另一示例性实施例的负极活性材料的制备工艺流程。包括以下步骤：
S201：准备硅氧化合物颗粒。
S202：在硅氧化合物颗粒表面包覆碳膜层。
S203：对包覆有碳膜层的硅氧化合物颗粒进行锂掺杂。
本发明中，硅氧化合物颗粒的掺杂(嵌入锂元素)可采用电化学掺杂、液相掺杂和热掺杂等方式。锂元素的掺杂气氛为非氧化性气氛，该非氧化性气氛由氮气、氩气、氢气或氦气中的至少一种构成。
嵌入锂元素方法(锂掺杂改性法)可为：
1)电化学法
提供一个电化学池，其中包含浴槽、阳极电极、阴极电极和电源四个部件，而阳极电极和阴极电极分别连接电源的两端。同时，阳极电极接通锂源，而阴极电极接通包含有硅氧化合物颗粒的容器。在浴槽中填充满有机溶剂，使锂源(阳极电极)和包含有硅氧化合物颗粒的容器(阴极电极)浸没于有机溶剂中。接通电源后，由于电化学反应的发生，锂离子嵌入硅氧化合物结构中，得到锂掺杂改性的硅氧化合物颗粒。上述有机溶剂可采用碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、氟代碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、乙酸乙酯、乙酸丙酯、丙酸乙酯、丙酸丙酯、二甲基亚砜等溶剂。另外，该有机溶剂中还含有电解质锂盐，可采用六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、高氯酸锂(LiClO4)等。上述锂源(阳极电极)可采用锂箔，或锂化合物，如碳酸锂、氧化锂、氢氧化锂、钴酸锂、磷酸铁锂、锰酸锂、磷酸钒锂、镍酸锂等。
2)液相掺杂法
将金属锂、电子转移催化剂、硅氧化合物颗粒加入醚基溶剂中，在非氧化气氛中持续搅拌并加热保持恒温反应，直至溶液中的金属锂完全消失。在电子转移催化剂的作用下，金属锂可以溶解于醚基溶剂中，并形成锂离子的配位化合物，具有较低的还原电势，因此可与硅氧化合物发生反应，锂离子进入硅氧化合物结构中。所述电子转移催化剂包括联苯、萘等。所述醚基溶剂包括甲基丁基醚、乙二醇丁醚、四氢呋喃、乙二醇二甲醚等。所述恒温反应温度为25-200℃。所述非氧化性气氛由下述至少一种气体提供：氮气、氩气、氢气或氦气。
3)热掺杂法
将硅氧化合物颗粒与含锂化合物均匀混合，然后在非氧化气氛中进行热处理。所述含锂化合物包括氢氧化锂、碳酸锂、氧化锂、过氧化锂、氢化锂、硝酸锂、醋酸锂、草酸锂等。所述混合方法采用高速分散机、高速搅拌磨、球磨机、锥形混合机，螺旋混合机，搅拌式混合机或VC混合机中的任意一种。所述热处理所用设备为回转炉、钢包炉、内胆炉、辊道窑、推板窑、气氛箱式炉或管式炉中的任意一种。所述热处理的温度为400-850℃，优选为550-800℃；保温时间为1-12小时；升温速度大于0.1℃ 每分钟，小于等于10℃每分钟。所述非氧化性气氛由下述至少一种气体提供：氮气、氩气、氢气或氦气。
嵌入锂元素的步骤在包覆碳膜层之后进行，可以抑制热处理过程中硅氧化合物内硅晶粒的长大。由此，纳米级的单质硅颗粒均匀分散并被固定在硅酸锂化合物或者硅氧化合物基体内，可以有效抑制硅纳米颗粒的膨胀，并阻止硅颗粒在充放电过程中逐渐融并成更大尺寸的颗粒，从而降低电池在循环过程中的膨胀变形和减少硅材料的电学失效，使得使用该材料的锂离子二次电池的循环膨胀小且循环稳定。此外，包覆碳膜层的步骤在嵌入锂元素之前进行，有利于得到质量更好、包覆更完整的碳膜层。
同时，嵌入锂元素的过程会对硅氧化合物颗粒表面的碳膜层结构产生不同程度的影响。如果扩散过程温和可控，则其对颗粒表面的碳膜层结构影响微小；如果扩散过程相对激烈，则能够引发碳膜层结构的变化。【负极活性材料的表征方法】：
1、材料检测：采用以下设备对各个实施例及对比例所制备的负极活性材料进行表征：采用丹东百特BetterSize 2000型激光粒度仪测试负极活性材料的粒径分布。采用Hitachi SU8010型扫描电子显微镜(SEM)观察负极活性材料的表面形貌。采用Quantachrome Instruments的NOVA 4200e型比表面积测试仪测试负极活性材料的比表面积。其中比表面积的测试要求如下：用样品管称取样品，使用氮气，在相对压力p/p0＝0.05-0.3范围内，使用多点法测试样品的比表面积。
2、匀浆及极片制作：取上述负极活性材料30份，人造石墨64份，导电添加剂2.5份，粘结剂3.5份，在水性体系下进行匀浆涂布，然后烘干、碾压，得到含有本申请负极活性材料的负极极片。
3、全电池评估：将各实施例及对比例所制备获得负极活性材料的负极片经过分切、真空烘烤、与配对的三元正极片和隔膜一起进行卷绕并装进相应大小的铝塑壳中，注入一定量电解液并除气封口，化成后得到一个约 3.2Ah的锂离子全电池。该全电池做了60℃下满电存储60天的实验，测试了该体系在经过高温满电存储后的热态膨胀率、容量保持率和容量回复率，用于评测该体系的高温存储稳定性。其中热态膨胀率的测试方法为：待电芯在60℃下满电存储60天后，将电芯取出并立刻测试电芯的厚度为d，其中电芯的初始半电状态的厚度为d0，所述热态膨胀率＝(d-d0)/d0。然后将该电芯冷却后，放置于新威电池测试系统上进行放电测试，放电容量为D1，该电芯在做高温存储前的放电容量为D0，所述容量保持率＝D1/D0。然后再将该电芯进行一次充电-放电循环，放电容量为D2，所述容量回复率＝D2/D0。
下面结合具体实施例对本申请做进一步说明。
实施例1-1
将1000g中值粒径为6μm的硅氧化合物颗粒(硅氧原子比为1:1)和低温煤沥青粉末在包覆釜内干法混合均匀后，边搅拌边加入2000g二甲基甲酰胺，将混合粉末在二甲基甲酰胺中分散均匀。随后加热包覆釜至340℃并保持恒温搅拌3小时，得到煤沥青包覆的硅氧化合物材料。将上述材料在氮气氛围下静态加热至680℃并保持4小时使煤沥青碳化。将冷却后得到的材料过500目筛网，得到碳膜包覆的硅氧化合物粉末。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为7wt％。
上述步骤得到负极活性材料的比表面积S＝15m2/g，产品的中值粒径D50为10.64μm，粒径分布跨度值为A＝1.52，根据比表面积估算的计算粒径Dc＝0.71μm，因此中值粒径D50和计算粒径Dc的比值为15。
取上述负极活性材料30份、人造石墨64份、导电添加剂3.5份、粘结剂2.5份，在水性体系下进行匀浆涂布，然后烘干、碾压，得到含硅负极极片。
在本实施例中，含有该负极活性材料的全电池高温存储评测结果为：60℃下满电高温存储60天后，电芯的热态膨胀率为22.7％，电芯有浮气， 经过高温存储后的容量保持率为78.6％，容量回复率为86.3％。
实施例1-2
和实施例1-1的工艺过程类似，仅将煤沥青的碳化温度调整为780℃，碳含量仍然为7wt％。
性能参数请见表1。
实施例1-3
将1000g中值粒径为9μm的硅氧化合物颗粒和中温煤沥青粉末在VC反应釜内干法混合均匀后，然后直接加热至720℃并保持恒温搅拌4小时，使煤沥青原位碳化。将冷却后得到的材料过500目筛网，得到碳膜包覆的硅氧化合物粉末。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为7wt％。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
实施例1-4
将1000g中值粒径为8μm的硅氧化合物颗粒和高温煤沥青粉末在VC反应釜内干法混合均匀后，然后加热至450℃恒温搅拌3小时，使煤沥青具有充分的流动性以实现均匀包覆，然后再升温至780℃保温5小时进行碳化，碳化过程中仍保持充分搅拌，促使沥青碳化过程中的挥发分有效排出，得到结构更为紧致的碳膜层。将冷却后得到的材料过500目筛网，得到碳膜包覆的硅氧化合物粉末。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为6wt％。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
实施例1-5
称取1000克中值粒径为7μm的硅氧化合物颗粒，置于CVD炉中。以甲烷为碳源，在800℃下进行包覆反应，其中甲烷和氩气的流量比例为1:1，得到包覆有碳膜层的硅氧化合物颗粒。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为5wt％。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
实施例1-6
称取1000克中值粒径为10μm的硅氧化合物颗粒，置于CVD炉中。以甲烷为碳源，在800℃下进行包覆反应，其中甲烷和氩气的流量比例为2:1，得到包覆有碳膜层的硅氧化合物颗粒。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为7wt％。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
实施例1-7
称取1000克中值粒径为6μm的硅氧化合物颗粒，置于CVD炉中。以甲烷为碳源，在800℃下进行低压包覆反应，其中甲烷和氩气的流量比例为2:1。低压CVD反应虽然生产效率较低，但能大大增加碳膜层的均匀性，得到平滑度和致密性更高、缺陷更少的碳膜层。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为7wt％。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
实施例1-8
称取1000克中值粒径为5μm的硅氧化合物颗粒，置于CVD炉中。以甲烷为碳源，在800℃下进行包覆反应，其中甲烷和氩气的流量比例为0.6:1，得到包覆有碳膜层的硅氧化合物颗粒。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为6wt％。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
实施例1-9至1-17
类似于实施例1-1至1-8，以硅氧化合物颗粒为原料，采用不同的碳膜包覆工艺，包括调整碳源的选择、碳化温度、碳源的添加量、气压(真空度)、气氛比例、气流方向，以及升温速度、升温和保温程序的设计、机械搅拌的强度、设备的选择等，得到实施例1-9至1-17的不同碳膜包覆的硅氧化合物粉末。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
对比例1-1
将1000g硅氧化合物颗粒和蔗糖在包覆釜内干法混合均匀后，然后加热至200℃恒温搅拌3小时，然后再升温至500℃保温5小时进行碳化。将冷却后得到的材料过500目筛网，得到碳膜包覆的硅氧化合物粉末。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为10wt％。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
对比例1-2
将1000g硅氧化合物颗粒和蔗糖在包覆釜内干法混合均匀后，然后加热至180℃恒温搅拌3小时，然后再升温至400℃保温8小时进行碳化。将冷却后得到的材料过500目筛网，得到碳膜包覆的硅氧化合物粉末。对所述碳膜包覆的硅氧化合物粉末进行碳含量测试，碳含量为8wt％。
性能参数和使用该负极活性材料的电芯的高温存储性能如表1所示。
表1

从表1可知，负极活性材料的中值粒径D50和计算粒径Dc的比值D50/Dc越小，负极活性材料的高温稳定性越好，膨胀越小，且越不容易产气。
进一步地，从表1可知，不同工艺参数(如碳源种类、包覆温度、气氛、气压、升温速度、碳含量、升温保温程序、机械搅拌等)和不同炉体结构设计下得到的碳膜层具有显著的结构差异，其缺陷的程度亦有明显的不同。
实施例2-1
以实施例1-16的负极活性材料作为原料，将该粉末、金属锂带和联苯加入一个可密封玻璃容器中，然后加入甲基丁基醚并在氩气气氛下搅拌反应。反应结束并烘干后，将得到的粉末置于氩气氛围下进行热处理，采用2℃每分钟的升温速度升温至680℃，然后保温10小时，随后自然冷却后可得到锂掺杂的硅氧化合物粉末。
性能参数和使用该负极活性材料的电芯的高温存储性能如表2所示。
实施例2-2
以实施例1-16的产品作为原料，类似于实施例2-1，但将锂掺杂后的热处理工艺改为：采用5℃每分钟的升温速度升温至720℃，然后保温 3小时，随后自然冷却后可得到锂掺杂的硅氧化合物粉末。
性能参数和使用该负极活性材料的电芯的高温存储性能如表2所示。
实施例2-3
以实施例1-16的产品作为原料，类似于实施例2-1，但将锂掺杂后的热处理工艺改为：采用10℃每分钟的升温速度升温至720℃，然后保温6小时，随后自然冷却后可得到锂掺杂的硅氧化合物粉末。
性能参数和使用该负极活性材料的电芯的高温存储性能如表2所示。
实施例2-4
以实施例1-16的产品作为原料，类似于实施例2-1，但将锂掺杂后的热处理工艺改为：采用10℃每分钟的升温速度升温至850℃，然后保温2小时，随后自然冷却后可得到锂掺杂的硅氧化合物粉末。
性能参数和使用该负极活性材料的电芯的高温存储性能如表2所示。
实施例2-5
以实施例1-10的产品为原料，取上述颗粒混合含锂化合物(如氧化锂、氢化锂、氢氧化锂、碳酸锂等)，将混合粉末置于氩气氛围下进行热处理，采用2℃每分钟的升温速度升温至400℃保温3小时，然后再升温至650℃保温10小时，自然冷却后得到包覆碳膜的含锂硅氧化合物。
性能参数和使用该负极活性材料的电芯的高温存储性能如表2所示。
实施例2-6
以实施例1-10的产品作为原料，类似于实施例2-5，但将锂掺杂后的热处理工艺改为：采用5℃每分钟的升温速度直接升温至700℃，然后保温6小时，随后自然冷却后可得到锂掺杂的硅氧化合物粉末。
性能参数和使用该负极活性材料的电芯的高温存储性能如表2所示。
实施例2-7
以实施例1-10的产品作为原料，类似于实施例2-5，但将锂掺杂后的热处理工艺改为：采用10℃每分钟的升温速度直接升温至820℃，然后保温2小时，随后自然冷却后可得到锂掺杂的硅氧化合物粉末。
性能参数和使用该负极活性材料的电芯的高温存储性能如表2所示。
表2
结合表1和表2的数据可知，嵌入锂元素的过程会对硅氧化合物颗粒表面的碳膜层结构产生不同程度的影响。如果扩散过程温和可控，则其对颗粒表面的碳膜层结构影响微小。如果扩散过程相对激烈，则能够引发碳膜层结构的变化，使得该材料的界面稳定性降低，导致使用该负 极活性材料的电池的高温存储性能下降，膨胀增大。
显然，上述实施例仅仅是为清楚地说明本发明所作的举例，而并非对实施方式的限定。对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式的变化或变动。这里无需也无法对所有的实施方式予以穷举。而由此所引申出的显而易见的变化或变动仍处于本发明的保护范围之中。

Claims (14)

  1. 一种负极活性材料，包含负极活性物质颗粒，其特征在于，所述负极活性物质颗粒包括硅基材料内核，以及覆盖所述硅基材料内核表面的碳膜层；所述硅基材料内核包含硅氧化合物；
    所述负极活性材料的中值粒径D50和计算粒径Dc的比值满足：D50/Dc≤15，其中所述计算粒径Dc＝7×A/S，A为所述负极活性材料的粒径分布跨度值，S为所述负极活性材料的比表面积。
  2. 根据权利要求1所述的负极活性材料，其特征在于，所述负极活性材料的中值粒径D50和计算粒径Dc的比值满足：D50/Dc≤10，优选D50/Dc≤5，进一步优选D50/Dc≤2.5。
  3. 根据权利要求1所述的负极活性材料，其特征在于，
    所述负极活性材料的比表面积S为0.1-15m2/g，优选为0.3-10m2/g，进一步优选为0.3-6m2/g。
  4. 根据权利要求1所述的负极活性材料，其特征在于，
    所述负极活性材料的中值粒径D50为0.2-20μm，优选为1-15μm，进一步优选为3-13μm；
    所述负极活性材料的粒径分布跨度值A≤2.0，优选为≤1.5，进一步优选为≤1.2。
  5. 根据权利要求1所述的负极活性材料，其特征在于，所述硅基材料 内核还包含锂元素。
  6. 根据权利要求5所述的负极活性材料，其特征在于，所述负极活性物质颗粒中的锂元素含量为0.1-20wt％，优选为2-18wt％，更优选为4-15wt％。
  7. 根据权利要求1所述的负极活性材料，其特征在于，
    所述负极活性物质颗粒中的硅元素含量为30-80wt％，优选为35-65wt％，更优选为40-65wt％。
  8. 根据权利要求1所述的负极活性材料，其特征在于，所述负极活性物质颗粒还包含有单质硅纳米颗粒，分散于所述硅基材料内核内的单质硅纳米颗粒的中值粒径在0.1-35nm之间，优选为0.5-20nm，进一步优选为1-15nm。
  9. 根据权利要求1所述的负极活性材料，其特征在于，所述碳膜层的厚度为0.001-5μm，优选为0.005-2μm，更优选为0.01-1μm。
  10. 根据权利要求1所述的负极活性材料，所述碳膜层的质量占比为所述负极活性物质颗粒总质量的0.01-20wt％，优选为0.1-15wt％，更优选为1-12wt％。
  11. 一种电极，其特征在于，包括如权利要求1-10中任一所述的负极活性材料。
  12. 一种电池，其特征在于，包括如权利要求11所述的电极。
  13. 一种制备如权利要求1所述的负极活性材料的方法，其特征在于，包括：
    准备硅氧化合物颗粒；以及
    在所述硅氧化合物颗粒表面包覆碳膜层。
  14. 根据权利要求13所述的方法，其特征在于，还包括：
    对包覆有所述碳膜层的所述硅氧化合物颗粒进行锂掺杂。
PCT/CN2023/078030 2022-03-02 2023-02-24 一种负极活性材料及其制备方法和应用 WO2023165415A1 (zh)

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